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The corrosion and preservation of iron a 

3 1924 004 109 124 

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Published by the 

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Corrosion and Preservation 




ALLERTON S. CUSHMAN, A.M., Ph.D. (Harvard) 

Assistant Director and Chemist in charge of Physical and Chemical Investigations, Office of Public 

Roads, U. S. Department of Agriculture; Chairman, Committee U on Corrosion of Iron, and 

member of Committee E on Preservative Coatings, American Society for Testing 

Materials; Member of Iron and Steel Institute of Great Britain ; and Associate, 

American Society of Civil Engineers 



Director, Scientific Section, Paint Manufacturers' Association of the United States; Member of 

Committee E on Preservative Coatings, American Society for Testing Materials; 

Life Member, Master House Painters' and Decorators' Association of 

Pennsylvania; Honorary Member, Master Car and Locomotive 

Painters' Association of the United States and Canada 





- & 

Copzjright, 1910, by the McGraw-Hill Book Company 



T&e Plimpton Press Norwood Mass. U.S.A* 












It has been found a difficult matter to bring a work of this 
kind up to date. New material, which touches directly, or in- 
directly, on the corrosion and preservation of iron and steel, 
is appearing almost daily in the technical press of the world. 
The authors have made the effort to include or mention the results 
of all recent investigations and original researches touching on 
the subject which have appeared up to the time of going to press, 
even if to some extent the systematic arrangement of the work 
has had to suffer by frequent insertions. Although a consider- 
able space is given to the description and results of the researches 
of one of the authors working in a Government laboratory, no 
material is included from this source that has not already been 
printed in official bulletins for free distribution to all persons 
desiring it. While the book is written mainly to elucidate the 
electrolytic theory of corrosion (which some one has humorously 
referred to as "The New Thought" in the protection problem), 
it is nevertheless hoped that it will be found useful and suggestive 
even to those to whom the theory does not especially appeal. 


It has been found a difficult matter to bring a work of this 
kind up to date. New material, which touches directly, or in- 
directly, on the corrosion and preservation of iron and steel, 
is appearing almost daily in the technical press of the world. 
The authors have made the effort to include or mention the results 
of all recent investigations and original researches touching on 
the subject which have appeared up to the time of going to press, 
even if to some extent the systematic arrangement of the work 
has had to surfer by frequent insertions. Although a consider- 
able space is given to the description and results of the researches 
of one of the authors working in a Government laboratory, no 
material is included from this source that has not already been 
printed in official bulletins for free distribution to all persons 
desiring it. While the book is written mainly to elucidate the 
electrolytic theory of corrosion (which some one has humorously 
referred to as "The New Thought" in the protection problem), 
it is nevertheless hoped that it will be found useful and suggestive 
even to those to whom the theory does not especially appeal. 



Introduction. — The Object of the Work xvii 


The Importance of the Corrosion Problem . . 1 

Contending Statements as to Rust Resistance of Different Types 

of Metal . ... . 2 

Corrosion and Conservation . . . 4 

Three Phases in the Problem of Preservation . 6 

Discussion Aroused by the Electrolytic Theory of Corrosion 6 
Influence of Various other Elements Contained in Manufac- 
tured Iron . . . .9 

Problems Confronting Manufacturers of Structural Material . 10 

Local Conditions Affecting Corrosion . 11 
Working Knowledge Necessary to the Understanding of the 

Corrosion Problem . . ... 12 


Water as an Universal Solvent . . . 14 

Solution Pressure . . 14 

Osmotic Pressure 15 

Relations between Osmotic Pressure and Gas Pressure . 17 

The Theory of Electrolytic Dissociation .... 18 

Hydrolysis . ... 20 

Electrolysis . . 21 

Modes of Ion Formation . ... 22 

Oxidation and Reduction . 24 
Electrolysis and Polarization . . 26 
The Passive State of the Metals 28 
The Electro-Chemical Series of the Metals ... 30 
The Theory of Indicators . 31 
Phenol-phthalein as an Indicator of the Presence of Elec- 
trolysis . . . .... 32 

Colloids and Crystalloids . . 33 

Electro-Chemical Properties of Colloids .... 33 

Conclusion of the Chapter . 34 




The Three Theories which have been Advanced to Explain 

Corrosion . 35 

The Carbonic-Acid Theory .... .... 35 

Corrosion Occurs when Carbonic Acid is Absent ... 36 

The Peroxide Theory op Corrosion . 39 

The Electrolytic Theory ... .40 

Pure Water as a Solvent of Iron ... .41 

Rusting of Iron Primarily Due to Attack of Hydrogen Ions 44 
Brief Explanation of Corrosion of Iron from Standpoint of 

Electrolytic Theory ... 44 

Development and Use of Ferroxyl Reagent 48 
Ferroxyl Indicator Shows that Solution Tension of Iron Varies 

at Different Points on the Surface 49 

Preparation of Ferroxyl Mounts . . 50 

Ferroxyl Indicator Rational Proof of Electrolytic Theory 51 

Varied Rust Formation in Different Samples . 51 


Two Distinct Effects in Rust Formation . . 56 

Practical Application of Electrolytic Theory . . 58 

Modern Steels Seem more Corrodible than the Old . 65 

Chemical Purity an Aid in Resisting Corrosion 67 

Difficulties Introduced by Improper Heat Treatment . 68 

The Carbon Constituents of Steel . . . 72 

Influence of Iron-Carbon Constituents on Corrosion . . 75 

Possible Effect of Assembling Metals of Various Carbon Types 76 

Effect on Corrosion of other Constituents in Steels 78 

Various Factors which Modify the Effect of Impurities . . 80 
Problem of Confining Structural Metals of Different Chemical 

Constitution . ..... 80 

Conclusions Based on Measurements of Potential Differences . 82 

Effect of Heat Treatment, Tempering, Stresses, Strains, etc. 83 
Relative Stability and Solubility of Strained and Annealed 

Metals . . 85 
The Influence of Quenching and Reheating Soft, Mild Steel on 

its Solubility . . . .88 

Influences of Wire-Drawing and Subsequent Annealing 91 

Cold- Working Increases Solubility of Mild Steel . 92 

Relation Between the Acid Test and Resistance to Corrosion 97 

Probably no Reliable Acceleration Test Possible . . 99 

Efficient Annealing Essential to a Rust Resistant Metal . 99 
Effect of the Rusting Medium, Electrolytes, Natural Waters, 

etc . 99 




Highly Alkaline Solutions Prohibit Corrosion .... 100 

Natural Waters may Contain Inhibitive Impurites 100 

Dissolved Oxygen a Stimulator ... .... 101 

Relative Corrosion in Fresh Water and in Sewage . . . 102 

Non-Corrosion of Deeply Immersed or Buried Iron 104 

"Busy" Iron Does not Rust 107 

Application of Electrolytic Theory to Special Corrosion Prob- 
lems . ... ... 109 



The Use of the Word "Inhibition" ... .110 

Hydroxyl Ions as Inhibitors . . 110 

Passivity of Chromated Iron . Ill 

Bichromate Solutions do not Attack Iron Free from Manganese . 112 

Experiment with Bichromate to Induce Passivity 113 
Inhibitive Power of Pigments Containing Certain Oxidizing 

Agents . 113 
Solution System with Two Contending Forces, Inhibitive and 

Stimulative . 113 
Practical Bearing of Alkaline Solution on Corrosion 115 
Stimulative Action of Certain Paint Films Acting as Depolar- 
izers .... . 116 
Wounds on Steel Surface Stimulate Rusting 120 
Mill-Scale, a Stimulator . 121 
Various Inhibitive Expedients which have been Tried 121 
Passivity Maintained by Plunging Electrodes into Neutral or 

Alkaline Solution . . 122 

Rusting Caused by Escaped Currents 123 

Factors Causing Stimulation or Inhibition . 123 

Factors which Inhibit Corrosion 124 


Different Phases of the Protection Problem 125 

Protection with Zinc 126 

Methods of Applying Zinc Coating 127 

Hot Dip Method of Galvanizing 128 

The Weight of the Zinc Coating . . . 130 

The Preece or Copper Suplhate Dip Test . 130 

Standard Solution 131 

Cleaning of Samples . 131 

Apparatus . 132 

Test 132 


Specified Dips. . 133 

(a) Coating 133 

(6) Cleaning . . . 133 

(c) Solution . 133 

{d) Quantity of Solution ... ... 134 

(e) Samples . . .... 134 

(/) Test . . . ... 134 

(g) Rejection . ... 135 

Objections to the Standard Copper Sulphate Test . . . 135 

Walker's Contribution to the Testing of Galvanized Coatings . 137 
Walker's Desiderata for a New Test for Determining the 

Durability or Resistance to Corrosion. . . . 138 

Walker's Test for Detecting Pin Holes, Cracks. . 139 
Walker & Campbell's Test for Determining the Combined Effect 

of Imperfections . . .... 139 

First, Thickness of Coating . .... 140 

Second, Purity of Zinc . . . ... 141 

Third, Flexibility of the Zinc Coating 141 
Circumstances Affecting the Weight of the Zinc Coating and the 

Corrosion op Fence Wire . 142 

The Electrolytic or Cold Method of Galvanizing 144 

The Vapor Deposition Process . . . 146 

Tests of Galvanized Wire . . 148 

Preservation with Tin . 152 

Preservation with Copper, Lead, and other Metals and 

Alloys . 155 

Processing after Manufacture . . . 157 

Unprotected Steel 160 

Corrosion of Boilers 160 

Special Cases Met with in the Preservation of Iron . . 162 


Testing Pigments in Water Suspension . ... 164 

Effect of Impurities and Other Factors Governing Nature of 

Pigments . ... 166 

Electrical Conductivity of Paint Films . . . 169 

Water-Shedding and Excluding Properties of Pigments . 171 

Moisture Penetration Tests of Paint Films .... 172 

Industrial Application of the Theory of Inhibitors . . . 174 

Thompson's Work on Solubility of Paint Films 178 


Steel Test-Panels at Atlantic City . 180 



Pickling and Preparation op Plates .... . 180 

Fence Erection and Preparation for Work 181 

Method Followed in Painting Plates . . . . 181 

Vehicles Used and Reasons for Avoidance of Japan Driers 182 

Testing Effect of Various Prime Coats . ... 186 

Combination Formulas Tested .... . 186 

Drawing Conclusions from Results of Field Tests . . . 187 

Inspection of Painted Surfaces . . 188 

Other Field Tests and Their Value . 196 

Tests on Preservative Coatings Carried on under the Supervision 

of Committee "E," American Society for Testing Material 199 

Tests of Paint Coatings Disigned to Resist Sea Air 201 


The Importance of the Special Design of Paint Formulae . . 206 
Galvanized Iron and Modern Methods Used on its Decoration 

and Preservation . . . 206 

Painting of Tinned Surfaces . 207 

Bituminous Coatings and their Application for the Protection of 

Iron . . ... . 208 

Regarding the Use of Coal Tar 209 

Tar Paints . ... .211 

Paper Paints and Paper Preservations .... 215 

Painting Metals Subject to Marine Growths 215 

Painting Steel Cars . . .... . 216 

Paints for Locomotives and Fenders ... . 217 

Protection of Iron in Tunnel Work . . 218" 

Painting Train Sheds ... 218 

Paint Protection for Water Tanks 219 

Painting Steel Railroad Ties . . 219 

Inhibitive Pigments for Railways Equipment in General . 221 

The Preservation of Steel Mine Timbers . 221 

Painting of Steel Mine Timbers ... . 224 

Painting of Field Wire Fence . . 227 

Prime Coatings for Structural Metal . 229 

The Use of Oil as a Shop or Prime Coating . . . 231 

Paint Coatings Used at Panama . . . 235 

Painting Various Municipal Accessories, etc. . . 236 

Painting Refrigerating Machinery . 237 

Ornamental Iron Work Protection . .... 238 


The Testing and Design of Paints . 239 

General Directions in Regard to Testing 239 

Laboratory Acceleration Tests . . ... 241 



Design of Protective and Inhibitive Paint Coatings 

Inhibitive Paint Formulas 

Wire Fence Paint 

Condenser Paint 

Paint for Iron Piping 

Formula Labeling 



The Requisites of Protective Coatings 

Meaning and Cause of Hiding Power 


Stable and Chemically Active Pigments 

Spreading Value 

Effect of Gases on Paints 

Paint Coat Strengtheners and Preventatives to Settling 

Excluding Properties and Elasticity 

Working Properties of Paints .... 

Description of Pigments in General Use for Painting Iron 

Basic Carbonate (White Lead) 

Zinc Oxide 

Basic Sulphate — White Lead (Sublimed White Lead) 

Sublimed Blue Lead 

Lithopone . 

Zinc Lead White 

Leaded Zinc . 

Barium Sulphate (Barytes) 

Gypsum (Calcium Sulphate) . 

Mangesium Silicate (Asbestine and Talcose) 

Whiting (Calcium Carbonate) 

Aluminium Silicate (China Clay) 



Red Lead 

Orange Mineral 

Artificial Iron Oxides 

Venetians Reds 

Metallic Brown 

Indian Red 

Ochre, Sienna and Umber 

Graphitic Pigments .... 



Carbon Black 

Vine Black and Willow Charcoal 

Mineral Black Pigments 

Orange Chrome Yellow 




Medium Chrome Yellow . . 267 

American Vermilion . 267 

Lemon Chrome Yellow 267 

Barium Chromate . ... .... ... 267 

Zinc Chromate .... . 267 

Zinc and Barium Chromate . . 268 

Chrome Green (Blue Tone) . 268 

Chrome Green (Yellow Tone) . . ... 268 

Chrome Green (Oxide) . 268 

Prussian Blue . . . 268 

Ultramarine Blue . 269 


Linseed Oil . 271 

Chemical Characteristics of, .Linseed Oil 272 

Boiled Oil . . 273 

Chinese Wood Oil . 273 

Soya Bean Oil . . 274 

The Use op Driers . . . 275 

Turpentine . . . 275 

Paraffins Spirits . . 276 

Benzol . . . 276 

Lacquers and their Application . . 277 

Varnishes . .... . 278 


The Corrosion of Water Jackets of Copper Blast Furnaces . 279 

Discussion . . ... . . . . 280 

The Corrosion of Water Jackets of Copper Blast Furnaces . 288 

Appendix B. — Bibliography . 301 



In the preparation of this work it has been the aim of the 
authors to present as simply as possible the results of the more 
recent researches on the corrosion and preservation of iron and 
steel. The results of these researches have led to the electro- 
lytic theory of corrosion, which it is safe to say is now provision- 
ally accepted by almost all of the authorities on the subject. 
Friend, 1 who has appeared in several papers in opposition to the 
electrolytic theory, now very recently states that he is not an 
adherent of the carbonic acid theory, but rather of the general 
"acid theory" of corrosion. He agrees, however, that the acid 
theory is in harmony with the electrolytic theory of ionization. 
The question at issue, therefore, involves a distinction and not a 

The electrolytic action which can be demonstrated taking 
place when iron rusts in contact with water should not be con- 
fused with the rapid destruction of steel in the neighborhood of 
escaped currents from high potential circuits used for electric 
lighting or power lines. As a matter of fact, the phenomena do 
not differ except that in one case there is an external source of 
energy at work, whereas in the other the energy of electro-chem- 
ical action is due to the slow combustion or oxidation of iron. 
In order to avoid confusion of terms and ideas, it has been pro- 
posed that we should speak of the underlying electro-chemical 
cause of corrosion as autogenous electrolysis, while another sug- 
gestion is that the shorter term, autoelectrolysis, should be adopted. 
There is no reason why these terms should not come into general 
use, but the fact remains that they have not yet done so; the 
authors have therefore held to the electrolytic explanation of 
corrosion, without the introduction of these or other new terms. 

1 See Electro-Chem. and Met. Industry VII., 11, 489, Nov., 1909. Also 
Jour. Iron and Steel Inst. 77, 5, 1908. 


In the authors' opinion corrosion must be considered an electro- 
chemical phenomenon, and therefore a special effort has been 
made to treat the subject in such a manner as to render it intelli- 
gible to technologists, even if they are not thoroughly grounded 
in the underlying principles of physical chemistry. 

In the chapter on the theory of solutions an explanation is 
given of the fundamental electro-chemical principles, without 
an understanding of which no discussion of the corrosion problem 
from this point of view is possible. It is hoped that this exposi- 
tion of the subject will be found helpful by manufacturers, 
engineers, metallurgists, and, in short, by all persons to whom 
the rapid rusting and decay of iron is a matter of anxious solici- 
tude. Wherever citations from other authors have seemed to 
strengthen the development of the subject both as to theory and 
as to fact, these have been freely made with the fullest credit to 
the authority quoted. It has been remarked that the omission 
by some of the prominent workers in this field, to mention in 
their publications the contributions of others, has been the cause 
of confusion in the minds of investigators who have had occasion 
to review and discuss the problem. A considerable body of 
material has been included which has been already previously 
published by the authors from time to time in bulletins and 
papers before technical societies. The object of the insertion of 
this matter here is to better support the general argument and to 
preserve it in a more permanent and concrete form. So much 
has been claimed in regard to the relative rust resistance of iron 
and steel that it has seemed best to include names of both types 
of metal in the general title of the book. There are, however, 
many places in a general discussion in which the word "iron" 
can be used in its general sense, and whenever it has been 
possible without leading to confusion this has been done. 

The purely metallurgical problem of the manufacture of 
highly rust-resistant metal has been touched on lightly, as the 
subject is one on which much difference of opinion exists and 
little consistent information is available. It is hoped that neither 
the defenders of Bessemer and open-hearth steels, nor those who 
believe in puddled and charcoal irons, will find any biased opin- 
ions set forth in the succeeding pages. 

The tendency to rust is a characteristic inherent in the element 
known as iron, and will in all probability never be entirely over- 


come. Nevertheless, it is perfectly well known that there is 
the greatest variability both in the manner and rapidity with 
which different specimens and types of this metal and its alloys 
suffer from corrosion. Before substantial advance in the manu- 
facture of resistant types and in the protection of all types can 
be made, a thorough understanding of the mechanism of corro- 
sion and the function of protective coatings must be obtained. 

The demand of the engineer and architect for the most 
advanced knowledge regarding protective coatings for iron comes 
as a result of the failure of many types of paint now in use. 
Technical literature is replete with information regarding the 
protection of iron, but probably the most remarkable advance in 
knowledge of this subject has taken place during the last few 
years, and almost wholly as a result of a well-planned series of 
investigations recently undertaken by a number of independent 
workers. The aim of the authors is to present the latest de- 
velopments on this phase of the subject in a general way so that 
the underlying principles which govern corrosion can be applied 
by each investigator to his own particular problem. 

So diverse a subject as the corrosion and preservation of 
iron would become encyclopedic, if the attempt were made to 
take up every phase in detail, or to abstract the literature of the 
subject from the technical and scientific journals of the world. 
The protection of boiler tubes presents a very different problem 
from the protection of bridge structures, and yet the same main 
principles can be applied to the consideration of each case. It 
is this point that the authors have had in mind, and while a num- 
ber of specific cases of corrosion are presented and discussed the 
main object has been to treat the subject in a general way. For 
this reason no separate chapters are included on special phases 
of the problem, such for instance as the corrosion of boilers, the 
corrosion of fence wire, or the corrosion of ships' bottoms. All 
these subjects, as well as many other special cases of corrosion, 
are, however, brought up and treated as special instances to 
which the general discussion applies. On this account those 
readers who propose to use this work as a reference book in special 
cases of inquiry will depend upon the index to the volume rather 
than upon chapter headings to guide them. 

That much of the work which has been done along different 
lines in the past in the effort to supply adequate protection for 


iron and steel has been unsatisfactory requires no proof. Unfor- 
tunately, much of this work has been based on purely empirical 
knowledge of the subject, that is to say, it has depended on indi- 
vidual experience or observation without due regard to science 
and theory. Thus, for instance, we find one engineer experi- 
menting with red lead as a prime coating material, and reaching 
a conclusion favorable to its use, while another engineer as a 
result of his own observation arrives at a quite contrary opinion. 
The case comes up for discussion before an engineering or tech- 
nical society and adherents to the two sides of the argument are 
not wanting to carry it on to indefinite lengths. The old ques- 
tion in regard to who is to decide when doctors disagree applies 
quite as well to such a case as this, and less learned people are 
perplexed by the violent controversies between those who are 
supposed to be expert. A more scientific acquaintance with 
the technology of protective coatings from the standpoint of 
recent investigations would at once suggest that red lead, like 
other protective agents, is not a standard substance, and that 
material from different sources might or might not contain stimu- 
lative or accelerative impurities or properties. This same empiri- 
cism may be noted in numerous other phases of the protection 
problem, as in the steel versus iron controversy, or in the rival 
processes for galvanizing and tinning. A theory serves the pur- 
pose of a well-articulated skeleton, to which may be attached 
the sinews and muscles represented by observed facts. If most 
of the results of experiment and observation find their natural 
and prepared points of attachment the theory is, to say the least, 
useful as a working mechanism, even if some observations are 
found difficult to fit in. As a matter of fact the recent electro- 
chemical theory of corrosion presents few if any difficulties which 
require to be explained away, while on the other hand, it furnishes 
a rational explanation for many previously unexplained occur- 
rences and phenomena. 

In presenting and developing the electro-chemical explanation 
of corrosion the authors' hope is to put into the hands of tech- 
nologists generally a working theory which will be both suggestive 
and practically useful. 




Importance of the Corrosion Problem. — The importance to 
the human race of arresting the rapid decay of structural iron 
has never been denied. It is almost impossible to find a volume 
of transactions of an engineering or learned technical society for 
years past that does not include papers and discussions on this 
all-important subject. The different theories that have been 
formed to account for the effects produced have been numerous, 
and the suggested treatment and methods for protection, without 
end. As Sang in a recent resume of the whole subject aptly puts 
it: 1 "The decay of iron and steel by corrosion, if natural agencies 
are allowed to act on them, is far more rapid than that of wood 
and other materials of construction. Steel is being used more 
and more every day for buildings and other permanent struc- 
tures and therefore on the prevention of this decay depends the 
permanency of these works and the safety of future generations. 
Were it not for iron and steel, the erection of large works of engi- 
neering would be impossible and their very size and consequent 
high cost, representing as it does a large sum of human energy — 
which is after all the only true foundation for wealth — make 
it a duty to preserve them from decay. 

"On a structure like the Forth bridge a number of men are 
kept at work, cleaning rust-spots and repainting. The wise 
course of preserving such structures for the use of our descend- 
ants is not generally followed, and it is only when accidents like 
the one at Charing Cross Station in London take place, that 
interest is revived, for a time, in the question. Wood, in referring 
to the roof of a gas-works in New York City which collapsed for 
lack of attention, forecasted a similar fate, sooner or later, for 

1 Proc. Eng. Soc. West. Pa., Vol. XXIV, 10, 493. 


structures like the viaducts of the elevated railway of the same 
city, which almost casual observation will show are repainted 
over the rust without cleaning. 

"On account of this necessity of combating corrosion, it is 
imperative that engineers arrange the design so that every part 
of structural works be readily accessible for frequent inspection. 
It has been truly said that ' wrought iron is not only a bad but a 
dangerous material if neglected'; this is equally true of steel." 

Contending Statements as to Rust Resistance of Different Types 
of Metal. — No attempt will be made in this work to decide 
between contending statements as to the relative rust resistance 
of wrought iron, charcoal iron, and the various types of steel. 
The authors are satisfied to reiterate their previously published 
opinion that there is great variation in each type of metal in rust 
resistance and that in this respect there are good and bad irons 
just as there are good and bad steels. If this is true, and a mass 
of evidence seems to support the statement, it is useless for manu- 
facturers of the different types, through their agents, to engage 
in endless polemical debates over the comparative excellence 
of their respective products. The proper control of unavoidable 
impurities, their homogeneous distribution and a careful heat 
treatment, particularly as far as the annealing processes are 
concerned, will improve the rust-resistant quality of metal, whether 
it is called iron or steel, and regardless of the method by which 
it is made. 

It is now very generally admitted as the result of recent 
researches by a number of investigators that a state of stress or 
strain in a metal invites rapid corrosion, as will also a burnt 
condition of the metal leading to high porosity and the presence 
of occluded gas and blow holes. Sang says in regard to this 
point: 1 " Carelessness of manufacture, which tends to heterogene- 
ousness, is an invitation to corrosion and in itself goes far to 
explain why modern steel, which is tortured into shape at such 
a high speed that the molecules are not permitted to readjust 
themselves, is said to be more corrodible than the metals pro- 
duced a generation ago; in those days iron and steel were pro- 
duced in small quantities, without the addition of other metals, 
and were rolled slowly and allowed to cool naturally. The inter- 
nal strains due to mechanical treatment are not to be confounded 
iProc. Eng. Soc. West. Pa., Vol. XXIV, 10, 511. 


with the unevennesses in the distribution of the impurities due 
to segregation in cooling; these mechanically induced strains are 
really equivalent to straining the metal beyond the elastic limit 
which, as will be seen later, makes it more corrodible. More- 
over, the tonnage-craze, from which the quality of product in so 
many industries is to-day suffering, is causing to be placed on the 
market a great mass of material, only a small proportion of which 
is properly inspected, which is not in proper condition to do its 
work: — rails and axles which fail in service and steel skeletons 
for high buildings which may carry in them the germs of destruc- 
tion and death." With this summing up the authors are in 
complete accord and no further space in this work will be given 
to the discussion of the comparative merits of iron versus steel in 
the resistance to corrosion. 1 

That the old, largely hand-worked metal of about thirty 
years ago is superior in rust-resisting quality to the usual 
modern steel and iron is attested by the recorded evidence of a 
large number of observers. Many citations could be given to 
prove this and the examination of the discussions of numerous 
papers before engineering and technical societies seldom fail to 
bring out evidence of the very general belief in the superiority 
of the older product. A more detailed discussion of this subject 
must be postponed to a later chapter. The accompanying illus- 
tration (Fig. 1) showing a contrast between two nails is interest- 
ing though not unusual. Sample A is a forged nail that was 
used in the old Masonic Hall in Richmond, Va., and was prob- 
ably driven in 1807. It was in service about one hundred years 
and for a large portion of that time was freely exposed to the 
weather, as the old clapboarding rotted away. The illustration 
shows that even the thin edges of the forged head are still sharp 
and uncorroded. Sample B is an ordinary modern nail after six 
months' exposure in a wooden gutter on a roof at Washington, D. C. 
No thoughtful person supposes that it would be practically 
possible to return to the earlier laborious methods of iron manu- 
facture, in order to produce metal highly resistant to corrosion. 
The modern problem must be solved by modern economic methods, 

1 For a full discussion of this subject by advocates of various types of metal 
the reader is referred to the Transactions of The American Society for Testing 
Materials, for years 1906-7-8, also to Transactions American Institute of 
Mining Engineers for 1905. 


and there is no reason to suppose that great improvement will 
not be made in the quality of both iron and steel, as soon as the 
principles governing the rate and kind of corrosion which takes 
place on different types and kinds of iron are thoroughly estab- 
lished. These principles will be brought out in detail in suc- 
ceeding chapters. 

Fig 1. — Showing the relative cor- 
rosion of a modern steel nail and 
an old forged nail. 

Corrosion and Conservation. — No discussion of the corrosion 
problem is complete without reference to its bearing upon the 
conservation of natural resources. In the introduction to an 
address before a recent meeting of the Iron and Steel Institute 
of Great Britain,- one of the authors called attention to the im- 
portance of this phase of the problem in the following words: 
"It is significant of the present age that the tendency of thought 
among all nations is toward conservation of natural resources. 
Increasing consumption of the world's supplies and constant 
decay of materials menace the future of the human race. It is 
evident that carbon, from which we derive energy, and iron, 
which provides the principal means of applying energy, are the 
materials which should particularly engage the attention of those 


who are studying the problems of conservation. The annual 
production of pig iron in the United States alone grew from 
about 14,000,000 tons in 1900 to about 26,000,000 tons in 1907, 
and while for the year 1908, owing to industrial conditions, it 
decreased to about 16,000,000 tons, it seems sure to again show 
an increase in the near future. How much of the enormous and 
constantly increasing world's production of iron and steel is 
wasted for lack of adequate preservation? Where will the growth 
of demand stop, and how many years will the world's ore supply 
stand the drain upon it? These are questions of vast importance, 
the answers to which can only be vaguely guessed. One thing 
seems certain, namely, that civilization must learn to conserve 
more efficiently its stores of iron and steel already manufactured, 
and seek methods to prevent the almost resistless tendency of 
iron to return to its lethargic union with oxygen, from which it 
was won only by tjie consumption of vast quantities of the ever 
dwindling coal supply. It is not generally realized that about 
four tons of coal or its equivalent is used in preparing one ton of 
finished steel from the ore. The world's store of gold is not 
subject to loss by corrosion, but suffers to some extent from 
attrition, owing to the softness of the metal. If steel could by 
any means whatsoever be ennobled and thus protected from the 
inevitable decay due to corrosion, future conditions for all pos- 
sible years to come could be viewed with complacency. There 
exists at Delhi, India, an iron monument that, since the dim 
beginning of history, has been exposed to the weather without 
rust or decay, and yet this column has been provided with no 
protective coating, other than that which the atmosphere has 
itself formed upon it. Could we to-day, with all our boasted 
knowledge and our great pneumatic processes, build its like? 
It is probable that we could not, and yet an art is not necessarily 
lost forever. It is simply a question whether or not it is worth 
our while to rediscover it." 

The President of the Iron and Steel Institute in discussing this 
paper stated in his remarks that no doubt this was a phase of 
the subject which was most prominently before the world at the 
present time, and that nothing could be more valuable to the 
iron industry at large than that the question of the preservation 
of the metal which they were engaged in manufacturing should 
be investigated and solved. 


These citations serve to bring out the great importance of 
the corrosion problem and show the earnest attention that is 
being given to it by metallurgists and learned bodies. 

Three Phases in the Problem of Preservation. — One of the 
writers has in previous papers 1 referred to the fact that the 
problem of the preservation of iron has three distinct phases. 
The first phase has to do with the manufacture of a metal highly 
resistant to corrosion, such as is represented by the iron column of 
Delhi, Fig. 2, or the splendid examples of hand-forged metal that 
have come down to us from past centuries, and with which we may 
contrast the pitted, lacelike condition of specimens of modern 
steel after only a few years' exposure to the atmosphere. The 
illustration, Fig. 3, shows the condition of certain members taken 
from a signal bridge on an American railroad. 2 The structures 
were about twelve years old and exhibited great differences in 
the rate of corrosion of different members. This point will be 
discussed more fully later on, but the photographic reproduction 
serves to illustrate very forcibly the lacelike condition assumed by 
metal undergoing rapid corrosion. 

The second phase of the subject concerns the general subject 
of protective coatings, which may consist of other metals, such 
as zinc, tin, copper, and lead, or of oil paints, varnishes, lacquers, 
and bituminous materials, or, finally, the production of a higher 
oxide on the surface, as in the Bower-Barf, Wells, and Speller 
processes. The third phase includes the interesting study of the 
passive condition which iron is capable of assuming, and the 
possibility of maintaining the surface in such an ennobled con- 
dition, either by the use of inhibitive pigments in paint com- 
pounds, or by the use of electric currents as described later on. 

Discussion Aroused by the Electrolytic Theory of Corrosion. — 
Many discussions 3 have arisen in regard to the several rival 

1 U. S. Dept. Agr., Office of Public Roads, Bui. 30, 1907; Trans. Am. Soc. for 
Testing Materials, 1907, 7, 209; Trans. Am. Electro-Chem. Soc, 1907, 12, 403. 

2 Samples and information furnished by Mr. J. P. Snow, Bridge Engineer, 
Boston and Maine R. R. 

J Am. Soc. Mech. Eng., Trans. 1894, 15, 998; ibid., 1895, 16, 350, 663; Zts. 
Elektrochemie, 1903, 9, 442; Treadwell and Hall, Analytical Chem., 1907, 
p. 92; Manchester Lit. Phil. Mem., 1871, 5, 104; Jour. Iron and Steel Inst., 
1888, 129-131; Proc. Chem. Soc. (Lond.), 1906, 22, 101; Jour. Chem. Soc. 
(Lond.), 1905, 87, pt. 2, 1548; Jour. Am. Chem. Soc, 1903, 25, 394; The 
Analyst, 1905, 30, 232; Trans. Chem. Soc. (Lond.), 1906, 98, 1356. 


theories of corrosion, but the evidence which has been collected 
in numerous recent researches appears to the authors to prove 


Fig. 2. — The Iron Column of Kutab Minar Delhi, India, erected 900 b.c. 

beyond argument that the corrosion of iron, like that of other 
metals, is an electro-chemical phenomenon. Some confusion 
has arisen in regard to this contention which the authors take 



this occasion to explain. H. M. Howe, an eminent authority, 
has stated: 1 "Electrolytic action surely hastens corrosion very 
greatly, and in practice it may well be true that nearly the whole 
of corrosion is electrolytic. But imagine the case of absolutely 
pure iron, without stress or slip planes, immersed in pure water 
containing dissolved oxygen. Will not the iron go into solution 
till the solution tension is reached, and will not the iron so dis- 
solved oxidize, precipitate, and leave room for more iron to dis- 
solve? It seems to me in this and like ways corrosion may go 
on without electrolysis. If so, then electrolysis is an aggravator 
and hastener of corrosion, but not essential to it." 

Every one interested in the subject who will read the succeed- 
ing chapter on the Theory of Solutions will understand that iron 
which is pushed into solution by its solution tension immediately 
ionizes and assumes an electric charge and that probably iron is 
never in such a quiescent condition that some polarization does 
not take place. The further discussion of this point as well as 
the consideration of the effect of outside or extraneous currents 
of electricity in effecting corrosion must be postponed to a later 

Influence of Various other Elements Contained in Manufac- 
tured Iron. — In considering the corrosion of iron it is important 
to remember that iron is a metal which readily combines with or 
dissolves nearly all the other elements. With possibly one or 
two exceptions, there are no elements that do not either dissolve 
in or combine readily with iron. It is also unique in the fact 
that very small quantities of impurities suffice to entirely change 
its physical characteristics. On account of this fact metallurgists 
scrutinize the hundredth of a per cent, of some of the principal 
impurities that are generally associated with this metal. This 
is particularly true, for instance, of the element phosphorus. 
It is so important to modern metallurgy that the amount of 
phosphorus should be controlled in certain forms of steel that 
an animated discussion is going on at the present time between 
certain interests as to the control of the amount of phosphorus 
that steel shall carry, and the question at issue amounts to no 
more than a few hundredths of one per cent. 

Manganese is also an element which is nearly always asso- 
ciated in modern metallurgy with iron and steel. Manganese 
1 Trans. Am. Soc. for Testing Materials, VIII, 278, 1908. 


decreases the electrical conductivity of iron, and as the percentage 
of manganese, starting from zero, rises, the electrical resistance 
increases up to a certain specific maximum. It will be seen that 
if the presence of manganese in iron raises the electrical resistance, 
any variation in the distribution of the manganese means that 
there will not be a constant electrical conductivity throughout 
its mass, or on any given surface. There is abundant evidence 
to show that manganese associates itself to a considerable extent 
with sulphur when both these impurities are present in steel. 1 
That manganese sulphide shows a difference of electrical potential 
against iron is also well known. One who is familiar with the 
methods of modern metallurgy knows that the manganese is 
added for certain specific purposes, not as a rule quantitatively, 
but in accordance with the views of the iron master who has con- 
trol of the mill or furnace. Moreover, the manganese is usually 
added by throwing lumps of ferromanganese into the molten 
metal, either in the furnace itself or in the ladle into which it 
has been poured. Chemists know the extreme care that has to 
be taken in order to get uniform mixtures of substances in the 
course of chemical operations. On the large scale on which 
metallurgical processes are conducted, even if it were possible 
to take great care in the mixing, it still happens that when iron 
is cooled from the molten state segregation takes place — that is to 
say, the impurities, although they may have been thoroughly 
mixed in the molten mass, do not remain homogeneously dis- 
tributed after the metal is cooled. 

For these reasons we must remember that in studying iron 
and steel from the standpoint of their stability, under the con- 
ditions of service, we are not dealing with homogeneous pure 

Problems Confronting Manufacturers of Structural Materials. — 
If we consider the results of recent experimentation along the 
lines of the three phases as indicated above, we find that con- 
siderable progress has been made in the course of the last few 
years. Many leading manufacturers of iron and steel have been 
paying special attention to the careful control of impurities, and 
the heat treatment of their products, as well as to the equally 
important problem of evolving rust-resistant metallic coatings 
in the various processes of galvanizing with zinc and special 
iFay, Proc. Am. Soc. Test. Mat., VIII, 74 (1908). 


alloys. 1 The condition of maintained passivity which has come 
to be known as "inhibition" is especially a problem for the paint 
manufacturer and will be dealt with in detail in later chapters 
of this book. 

One phase of the corrosion problem which is of the utmost 
importance and which has been discussed with anxious foreboding 
is the possible corrosion of steel embedded in concrete. The 
consensus of opinion among engineers and investigators of the 
corrosion problem appears to be that concrete furnishes ample 
protection to steel embedded in it, except in certain cases in 
which infiltrating or percolating waters find a way through the 
concrete, washing away the free alkali present in the form of 
lime or calcium hydroxide. The reasonableness of this explana- 
tion will appear later on. 

Local Conditions Affecting Corrosion. — It is quite apparent 
that the corrosion problem has increased steadily with the growth 
of civilization, for the waste gases of combustion pollute the atmos- 
phere and the water with which iron may come in contact, 
and besides this there are many stray electric currents escaped 
from high potential circuits which undoubtedly aid in the work 
of destruction. H. M. Howe, in making a plea for modern steel, 
has said: 2 "The fact that steel has come into wide use simul- 
taneously with a great increase in the sulphurous acid in our city 
air and of strong electric currents in our city ground may well 
lead the practical man, be he hasty or cautious, into inferring 
that the rapid corrosion of to-day is certainly due to the new 
material of to-day, steel, whereas, in fact, it may be wholly due 
to the new conditions of to-day, sulphurous acid and electrolysis." 

While the above statements are perfectly true they do not 
furnish a complete and satisfactory explanation of the whole 
problem. Take the interesting case of the steel light-ship, U. S. 
Light-Vessel No. 71, built in 1897, which was anchored at Dia- 
mond Shoal off Cape Hatteras for eleven years, and was towed 
in at the expiration of that time so that 8400 four-inch bolts 

1 Since the writing of this paragraph, patents have been granted for a 
process of producing exceptionally pure iron in basic open-hearth furnaces 
which is claimed to be slagless, degasified and easily workable. Since the 
effort to produce this type of metal was originally suggested by one of the 
authors it is proper to record here its successful accomplishment on a com- 
mercial scale. 

2 Proc. Am. Soc. Testing Materials, 1906, VII, 155. 


which were destroyed by accelerated electrolytic action could be 
replaced. 1 In such a case as this serious damage occurred after 
eleven years, due to electrolytic corrosion, although the material 
was subjected to no stray currents or sulphurous acid gases. 
Probably not all the bolts were in actual contact with salt water, 
although the general saltiness of the atmosphere undoubtedly 
stimulated the action. The condition of the destroyed bolts is 
well shown in the illustration,. Fig. 4. The discussion of this and 
similar cases of corrosion will be postponed to a later chapter. 

Fig. 4. — Showing the corroded condition of bolts taken from the U. S. 
Light-Vessel, No. 71. 

The Working Knowledge Necessary to the Understanding of the 
Corrosion Problem. — It is not possible to make an intelligent 
study of the problem of corrosion without at least a working 
acquaintance with the principles of the new knowledge in physics 
and chemistry which has gone so far to elucidate and explain 
many heretofore obscure phenomena. It is, however, the opinion 

1 Information and specimens furnished by A. B. Johnson, Supt. Light- 
house Establishment, 5th District, Dept. Commerce and Labor, also by 
Robt. L. Russell, Commander, U. S. N. 


of the authors that the groundwork for a proper understanding 
can be acquired by any person with some technical knowledge 
and experience, even if chemistry, and more particularly physi- 
cal chemistry, has never before engaged his attention. To this 
end the following chapter on the theory of solutions has been 
included. In the treatment of this chapter the effort has been 
made to present in the simplest possible way the underlying 
principles which enter into the corrosion problems in their most 
recent and modern aspects. The new theories which attempt 
to explain corrosion have hitherto been presented mainly before 
learned technical bodies, and in the columns of the highly scien- 
tific and technical press. It is the earnest hope of the authors 
that a careful perusal and study of the following chapter will 
enable any intelligent person who may be interested in the prob- 
lem to understand the discussions and data presented in the 
succeeding chapters. 



Water a Universal Solvent. — Water is the universal solvent, 
and it is doubtful if there is a form of matter in existence which 
is not to some extent dissolved, disintegrated, or otherwise changed 
by it in the course of time. The action of water is not, however, 
to be considered as universally destructive, for it is the medium 
by means of which, and in which, synthesis as well as decomposi- 
tion takes place in nature. Whether the action of water is to 
be considered as destructive or constructive depends therefore 
on the point of view. For instance, the immense bodies of iron 
ore on which we must always depend for our supplies of iron 
were undoubtedly originally formed under the action of water, 
and now once more water carries on the attack on our finished 
iron and steel, which has been laboriously smelted and reduced 
from the ore at the expense of vast quantities of free carbon. 
To the layman iron is an insoluble substance as far as water 
alone is concerned, but as has been pointed out, when we speak 
of a substance as being insoluble, we may be merely employing 
a relative term. If the water is impure, that is to say, if it already 
contains slight amounts of dissolved substances, its action on any 
given body is modified. Whether the solvent action is stimu- 
lated or inhibited depends upon the nature of the case. 

Solution Pressure. — Leaving aside substances usually classed 
as insoluble, we will for the present consider only those which 
have a decided and appreciable solubility in pure water. Such a 
body, when immersed or brought into contact with water, tends 
to pass into solution; that is to say, its molecules or atoms (de- 
pending upon whether the substance in question is a compound 
or a simple element) tend to distribute themselves equi-spatially 
among the molecules of the solvent. The driving force which 
produces this tendency, and which is known as solution tension 
or solution pressure, is exactly analogous to the pressure exerted 
by a gas or vapor confined in a vessel, as for instance, in the 



case of steam in a boiler. But just as the rising steam pressure 
in the boiler will tend to resist the evaporation of the remainder 
of the water, the growing number of free particles entering the 
solution will produce a back pressure which tends to resist the 
entrance of more. This back pressure acting against solution 
tension is called osmotic pressure, and the class of phenomena 
which it produces is known as osmosis. It is at once apparent that 
for any given substance at a given temperature, its maximum 
solubility would be reached just as soon as the solution pres- 
sure and the osmotic pressure were equal. It is also apparent 
that any outside cause operating on the system, which tended 
constantly to lower the osmotic pressure, would allow more and 
more of the substance to enter into solution so that the action 
would become continuous, provided the supply of solvent and 
solute was maintained. This point is an important one in this 
discussion, inasmuch as it has a direct bearing on the corrosion 
of iron. 

Osmotic 'Pressure. — The existence of osmotic pressure was 
first recognized by the Abbe Nollet about the middle of the eight- 
eenth century. He used animal membranes for demonstrating 
the pressure. A glass tube closed at one end with animal parch- 
ment was filled with alcohol and plunged into a vessel of water. 
The alcohol tended to dissolve or diffuse into the water and the 
water into the alcohol, but alcohol cannot pass rapidly through a 
parchment diaphragm, whereas water can. The consequence was 
that the level of liquid rose in the tube, revealing the existence of 
osmotic pressure. Diaphragms which allow the passage of water 
molecules but resist the passage of substances soluble in water 
are known as semi-permeable membranes. Traube in 1867 dis- 
covered that by depositing a film of a gelatinous preparation of 
copper ferrocyanide in a suitable manner very good artificial 
semi-permeable membranes could be formed. This method of 
measurement has been improved and developed by Pfeffer in 
Germany and later by Morse in the United States. The copper 
ferrocyanide is now by an ingenious process deposited as a film 
inside the walls of a clay cylinder to the top of which the 
manometer tube for measuring the pressure is luted. It is only 
necessary here to bring out the fact that osmotic pressures and 
therefore solution pressures represent values of very considerable 
magnitude. This is best shown by results obtained by Pfeffer 


working with dilute solutions of cane sugar. Here again the 
water passes through the semi-permeable film while the sugar 
molecules are stopped so that the pressure can be recorded in 
the manometer tube in barometric readings. 

Pfeffer's results, which were taken at about 14° Centigrade, 
are as follows: 

C = Concentration of 

Solution in Per Cent. 

P = Osmotic Pressure 
in Centimeters of mercury 

P'= Osmotic Pressure 
in Inches of mercury 

P"= Osmotic Pressure 
in Atmospheres 

1 per cent. 




2 per cent. 




4 per cent. 




6 per cent. 




It will be seen from this that the osmotic pressure exerted by a 
six per cent, solution of sugar is equal to about four atmospheres, 
or reduced to ordinary terms sixty pounds to the square inch. 
Sugar, of course, is a very soluble substance and its solution 
pressure is high, but that even the more insoluble substances 
have solution pressures of definite and appreciable magnitude 
is incontestable. 

If a strip or rod of polished steel is plunged into a clear glass 
cylinder containing distilled water and placed so that it can be 
observed in a strong light, it will be seen that in the course of a 
few minutes delicate festoons of a whitish brown substance are 
clouding the sharp edge or outline of the steel specimen and fall- 
ing away from the surface. This phenomenon furnishes evidence 
to the eye that the iron has a direct solution pressure, for the 
whitish brown substance which is forming is a hydrated oxide 
or so-called hydroxide of iron, and cannot be formed unless iron 
first passes into solution. Careful observation of this simple 
experiment will bring out another point which has an important 
bearing on our subject. It will be noted that the festoons of 
hydroxide do not appear at all points of the polished surface, 
but seem to segregate at certain points or areas, leaving others 
still bright and unattacked. This observation furnishes the first 
indication that the solution tension of iron is not the same at all 
points on the surface. This fact is important to the considera- 
tion of the corrosion of iron, and will be taken up again after the 
principles governing solutions in general have been presented. 



It has been found possible to illustrate the uneven solution ten- 
sion of steel rods immersed in water and very dilute electrolytes. 
A photographic representation of the appearance of three polished 
steel rods after a few hours' immersion is shown in Fig. 5. 

Fig. 5. — Showing the unequal solution tension and rusting of three steel 
rods immersed in fresh water, sea water, and dilute sodium nitrate. 

Relations between Osmotic Pressure and Gas Pressure. — Pfef- 
fer's object in carrying out his researches was to study the role 
played by osmosis in certain physiological processes, such for 
instance as the swelling and bursting of seeds, and the movement 
of sap in plants. It was reserved for Van't HofT to make the 
wonderful observations and deductions which, published in an 
epoch-making paper in 1887 * was destined to become the foun- 
iZeit. Phys. Chem., 1, 481. 


dation of a new chemistry. The law of Boyle for gases points 
out that the pressure of a gas varies directly with its concentra- 
tion, and the general gas law is simply expressed by the formula, 
PV = RT, where P is the pressure, V the volume, T the tempera- 
ture, reckoned from the absolute zero ( — 273° Centigrade), and 
R a constant. Using Pfeffer's results, Van't Hoff pointed out 
that the osmotic pressure of a solution of cane sugar is exactly equal 
to the gas pressure of a gas having the same number of molecules in 
a given volume, when the temperature is the same in both cases. 
This is a surprising generalization, and especially so when we con- 
sider the different conditions under which gas molecules and the 
molecules of a dissolved substance are acting. Nevertheless, still 
greater surprises were in store, for Van't Hoff further pointed 
out that while one class of substances which were chiefly organic 
in their nature conformed with the gas law, another class in which 
could be included the acids, bases, and salts of inorganic chemistry 
gave osmotic pressures in dilute solutions, in many instances about 
twice as high as they ought to if they were in conformation with the 
generalization. It was at this point that Arrhenius, a Swedish 
physicist, in 1881 made his great contribution to the dawning science 
of physical chemistry. Arrhenius developed the discussion of 
Van't Hoff's deductions as follows l : If a gas shows a deviation from 
the gas law, as many of them do at high temperatures, we explain 
this by supposing that the molecules of the gas which are com- 
posed of two associated atoms (as, for instance, hydrochloric acid, 
which would be expressed molecularly by the symbol H — CI), 
break down at certain critical temperatures into simple atoms, thus 
providing twice as many free particles in a unit space. Arrhe- 
nius then proposed to apply the theory of dissociation to the mole- 
cules of inorganic substances in solution and inquire whether 
they were not split up on entering solution into constituent par- 
ticles, or, as he called them, ions. 

The Theory of Electrolytic Dissociation. — The theory of elec- 
trolytic dissociation, as it is stated at the present time, holds 
that when acids, bases, and salts are dissolved in water to form 
dilute solution, they break down or dissociate into ions. Ions 
are atoms or groups of atoms carrying in relation to their masses 
enormous charges of static electricity. The reason why these 
charges are not apparent in the molecule is because they are of 
^eit. Phys. Chem., 1, 631. 


necessity always equal and of opposite sign. These dissociation 
reactions are simply expressed as follows: 

Acid: hydrochloric HC1 = H + CI 

Base: sodium hydroxide NaOH — Na + OH 

Salt: sodium chloride NaCl = Na + CI 

or to give more complex examples: 

Acid: sulphuric H 2 S0 4 = H • H + S 4 

+ + — — 

Base: calcic hydroxide Ca(OH) 2 = Ca + OH • OH 

+ + 

Salt: calcic sulphate CaS0 4 = Ca + S0 4 

The positive hydrogen ion is the distinctive characteristic of all 
acids in solution, just as the negative hydroxyl ion (OH) is the 
characteristic of all bases in solution. Hydrogen, in spite of the 
fact that it occurs and is generally known as a gas, belongs to 
the type of elements which are called metals. 

This subject can be more clearly set forth by quoting from a 
recent excellent text-book on physical chemistry: 1 

"Each compound dissociates into a positively charged part 
called a cat-ion, and a negatively charged part, an an-ion. These 
ions may be charged atoms as the above cations, or groups of 
atoms as the anion OH. The cations are usually simple atoms 
charged with positive electricity. The cation of all acids is hydro- 
gen; the nature of the anion varies with the nature of the acid. 
It may be chlorine, bromine, the N0 3 group, S0 4 , etc. The 
anion of bases is the group (OH); the cation varies with the 
nature of the base. It may be potassium, barium, ammonium, 
etc. The anions and cations of salts both vary with the nature 
of the salt. They depend upon the nature of the acid and the 
base which have combined to form the salt. 

"It was stated that hydrogen is the cation into which all 
acids dissociate. It may be added that this is the characteristic 
ion of all acids, and whenever it is present we have acid proper- 
ties. Further, we never have acid properties unless there are 
hydrogen ions present. The same may be said of the hydroxyl 
ions into which bases dissociate. This is the characteristic ion 
of bases. 

1 Jones, Elements of Physical Chemistry, MacMillan (1909), pp. 211-212. 


"It has been repeatedly urged that the theory claims that a 
compound like potassium chloride dissociates into potassium and 
chlorine, and since neither potassium nor chlorine can remain in 
the presence of water under ordinary conditions without acting 
upon it, the theory is self-evidently wrong. This objection, like 
so many others, is based upon an imperfect understanding of the 
theory. No one has ever claimed that a compound like potas- 
sium chloride dissociates in the presence of water yielding atomic 
or molecular potassium, having the properties of ordinary potas- 
sium. The products of dissociation are a potassium ion and a 
chlorine ion, and the potassium ion is a potassium atom charged 
with a unit of positive electricity. There is no reason whatever for 
supposing any close agreement between the general properties of 
a potassium atom and those of a potassium atom charged with 
electricity. About the only property which we would expect to 
remain unchanged is that of mass, and the mass of an atom is 
not changed by charging it. The properties of atoms are doubt- 
less very closely connected with the energy relations which obtain 
in or upon the atom. When we change these fundamentally, 
as by adding an electrical charge, we would expect fundamental 
changes in properties; and such are the facts. It can be safely 
stated that whatever may be the ultimate fate of the theory of 
electrolytic dissociation, it will never suffer seriously from any 
such objection as that just referred to." 

Hydrolysis. — We have now familiarized ourselves with the 
principles of electrolytic dissociation in which certain substances 
in solution are broken down into constituent ions. We shall 
now have to consider a different form of dissociation in which ions 
and electrical charges are only indirectly concerned, but which 
has a bearing on many of the problems of the corrosion and pres- 
ervation of iron. It has long been known that compounds which 
are formed by association of a weak acid with a strong base- 
forming element have an alkaline reaction in solution, while 
conversely a compound made up of a strong acid with a weak 
base will tend to show an acid reaction. Thus, nearly all car- 
bonates of strong bases, such as potassium, sodium, calcium, and 
barium, are alkaline, whereas nearly all the salts of very weak 
bases, such as aluminum, are acid in reaction, if they exist at all. 1 

1 Aluminum carbonate cannot exist at all. Both the acid and base being 
weak, hydrolysis takes place with the formation of aluminum hydroxide. 


The explanation of the hydrolysis is best given by writing 
the chemical reactions as follows: 

Sodium Carbonate Water Sodic Hydrate Carbonic Acid 

(1) Na 2 C0 3 + 2HOH = 2NaOH + H 2 C0 3 

Aluminum Sulphate Water Aluminum Hydrate Sulphuric Acid 

(2) Al,(SCg 3 + 6HOH = 2A1(0H) 3 + 3H 2 S0 4 

In the first reaction sodium hydrate is highly dissociated, car- 
bonic acid very slightly dissociated into ions, so that the alkaline 
reaction due to hydroxyl ions predominates. 

In the second reaction aluminum hydroxide is not dissociated, 
while sulphuric acid is highly dissociated, so that the acid reaction 
due to the hydrogen ions is produced. 

Between these two extremes we meet with a very great num- 
ber of cases of hydrolysis, the principles of which should be under- 
stood by all manufacturers of protective paint compounds. In 
many cases salts and compounds which do not immediately 
hydrolyze when dissolved in water, will undergo slow decom- 
position under the action of acid gases and moisture in the 
atmosphere, and hydrolytic products will be formed. An under- 
standing of these points will frequently explain the stimulative 
corrosion effects produced hy certain types of pigments. 

Electrolysis. — The phenomenon known as electrolysis takes 
place whenever a current of electricity passes through a solution 
capable of conducting the current. Such a solution is known as 
a conductor of the second class to distinguish it from an ordinary 
conductor like a metallic wire, which is of the first class. A 
solution of sugar will not conduct a current of electricity while 
a 1 solution of salt will readily do so. This difference in behavior 
is accounted for by the fact that the salt is dissociated into ions 
while the sugar is not. A substance which in solution will con- 
duct electricity is known as an electrolyte. The phenomenon of 
electrolysis shows that when a current is passed through a solution 
of an electrolyte, there is a mechanical movement of the ions 
towards the electrodes. Thus, if a current is passed through a 
solution of hydrochloric acid the positive hydrogen ions will 
proceed to the negative electrode where they will plate out after 
giving up their electrical charges. Having now assumed the 
atomic or gaseous condition, the hydrogen escapes from the sys- 
tem in the form of minute bubbles. While this action is occur- 


ring at the negative pole an equivalent amount of chlorine is 
being plated out and disengaged at the positive pole. 

It is not necessary that an outside or external source of elec- 
tricity should be at work before electrolysis can take place. If 
two strips of dissimilar metal are plunged part way into a solution 
and connected by a wire, or by any other means, across the top 
a current will flow around the circuit. This current is generated 
at the expense of the more electro-positive metal in the couple. 
The electro-positive element rapidly shoots off positive ions into 
the solution, thereby leaving itself negatively charged so that it 
invariably appears as the negative pole in the circuit. Even 
two steel needles from the same package are sufficiently dissimilar 
to show a slight difference of potential when coupled in such a 
way, and one will be protected while the other suffers accelerated 
corrosion. From the standpoint of the electrolytic theory all iron 
and steel must be thought of as a composite structure, as though, 
indeed, it was compounded of more or less well consolidated bundles 
of more or less homogeneous needles or units. This statement 
contains the crux of the whole electrolytic explanation of corro- 
sion and will be further developed in another chapter. 

Modes of Ion Formation. — Jones describes the various modes 
of ion formation very clearly in the following paragraphs: 1 

"From what has been said thus far, the impression might be 
gained that ions can be formed from molecules in only one way 
■ — the molecules breaking down directly into an equivalent num- 
ber of anions and cations. This is one way in which ions are 
formed, and the way with which we are most familiar, since it 
occurs most frequently. The following examples illustrate this 
mode of ion formation: 

(1) HC1 = H 4- CI, H 2 S0 4 = H + H + S0 4 

NaOH = Na + OH, Ba(OH) 2 = Ba + OH + OH 
KN0 3 = K + N0 3 , K,S0 4 = K + K + S0 4 

Another method by which an ion can be formed, is for an atom 
to take the charge from an ion, converting it into an atom, the 
original atom becoming an ion. Thus, when a bar of zinc is 
dipped into a solution of copper salt, the copper which was present 

1 Jones, Elements of Physical Chemistry, loc. cit., pp. 419-421. 


in the solution as an ion gives up its two charges to an atom of 
zinc, becoming an atom; while the zinc, having received the 
charges, becomes an ion. This is the well-known precipitation of 
copper from a solution, by zinc. We will call this the second 
mode of ion formation. 

(2) Cu + S0 4 + Zn = Zn + SO, + Cu. 

"All that occurs is a transference of electricity from the copper 
to the zinc. This is exactly analogous to what takes place when- 
ever one metal replaces another, as it is said, from its salts. 

"The replacement of the hydrogen ion from acids by a metal 
like zinc is an illustration of the same mode of ion formation. 

2HC1 + Zn = Zn + CI + CI + H 2 . 

What takes place here is simply the transference of the electrical 
charge from the hydrogen which does not hold its charge firmly, 
to the zinc which holds its charge much more firmly than the 
hydrogen, and, therefore, takes the charge from the hydrogen. 

"This is typical of the reaction of acids on metals in general; 
and is probably typical of substitution in general. The work of 
Thomson makes it highly probable that when substitution takes 
place in organic compounds, the entering atom or group takes 
the charge away from the atom or group displaced. The sub- 
stituting atom or group always has the same charge that the 
substituted atom or group had when in the compound. The 
entire act of substitution is essentially an electrical act, and not a 
chemical act } as that term is usually understood. This is true 
whether we are dealing with the substitution of the hydrogen 
ions of an acid by a metal, or with substitution in organic com- 

"Another method of ion formation is where an atom of one 
substance passes over into a cation, at the same time that an 
atom of another substance passes over into an anion. When 
gold is dipped into chlorine water, both the gold and chlorine 
are in the atomic or molecular condition. But under these con- 
ditions the gold can become a cation, and the chlorine can form 
anions. This we will term the third method of ion formation. 

(3) Au + CI + CI + CI = + Au + + CI + CI + CI. 


This is usually expressed by saying that gold dissolves in chlorine 

"The fourth and last method by which ions are formed is 
where an atom passes over into an ion, at the same time convert- 
ing an ion already present into one with a different quantity of 
electricity upon it. Thus, chlorine brought in contact with 
ferrous chloride in solution forms an anion, at the same time 
converting the ferrous ion into a ferric ion. 

(4) Fe + C1 + CI + CI = + Fe+ CI + CI + CI. 

This is an example of what has so frequently been called in chem- 
istry, oxidation. The reverse phenomenon is, of course, what 
has been termed reduction. In this sense oxidation is simply 
increasing the number of charges carried by an ion, and reduction 
is diminishing the number of such charges. 

"These four methods of ion formation, which have been so 
clearly pointed out by Ostwald, 1 include all the cases which are 
known. If we study them carefully and apply them to chemical 
reactions, we shall see that they throw much light on many 
problems in chemistry, the meaning of which has hitherto been 
concealed in darkness.' 1 

Oxidation and Reduction. — The true nature of the processes 
known as oxidation and reduction, as set forth above, should be 
thoroughly understood by every student of the problem of corro- 
sion. By valence the chemist means the combining power of a 
given atom for other atoms, though as has been shown it may 
be considered as an expression for the measure of the electrical 
state of the ion. Many of the elements have only one known 
valence state or combining value, as for instance, hydrogen, 
which is always univalent and unites with one other univalent 
atom to form a compound as in hydrochloric acid (HC1). Biv- 
alent elements like calcium unite with two univalent atoms, as 
in calcic chloride (CaCl 2 ). Iron i§ typical of a number of other 
elements in that it can occur in, two states of valence, viz., the 
ferrous condition in which it is bivalent as in FeCl 2 , and the ferric 
condition in which it is trivalent, as in FeCl 3 . Every change from 
the lower to the higher state is known as oxidation, and every 
change from the higher to the lower is conversely a reduction. 

1 See Lehrb. d. Allg. Chem., II, 7S6. 


A neutral solution of ferrous chloride exposed to the air rusts 
just as surely as does a moist piece of metallic iron, and it is 
probable that both actions are due to ionic changes dependent 
upon the electrical states of the reacting ions. 

It is characteristic of ferrous ions that they are in an unstable 
condition, and in the presence of the oxygen in the atmosphere 
are changed to the ferric state. A solution of ferrous chloride 
contains ferrous ions and chlorine ions and may be written thus: 

FeCl 2 ^ Fe + CI CI 

If we admit no more chlorine ions to the system, as the change 
from the ferrous to ferric states goes on hydrolysis takes place 
and finally in the course of time a reddish rust consisting of 
ferric hydroxide will make its appearance. 

Fe + CI CI + 2 + 3HOH — 

Fe(OH) 3 + HH + CI CI + 2H 2 

Ferric 1 hydroxide is an insoluble compound so that when it is 
formed it drops out of solution. This action of dropping out 
of solution is known to chemists as precipitation, and the result 
of such action is called a precipitate. It is at once evident that 
such a precipitation removes a certain amount of material from 
the solution system, and thereby alters the equilibrium between 
solution pressure and osmotic pressure, as has- been previously 

Now if we apply these same principles to the discussion of 
the simple system represented by the immersion of a piece of 
iron in pure water, the rust which forms can be easily and simply 
accounted for. Iron has a definite solution tension in pure water, 
especially at certain points on its surface, which are electro-posi- 
tive to other points or areas. 3 The iron here enters the solution 
as positive ferrous ions, the corresponding negative charges being 
assumed by hydroxyls. But immediately the oxygen of the air 

1 As a matter of fact ferric hydroxide cannot be properly expressed by a 
chemical formula such as Fe(OH)3. It appears as a colloidal precipitate 
of indefinite composition as far as the amount of water associated with it 
is concerned. It would be more appropriately written as Fe 2 3 xH 2 but, for 
the purpose of the present discussion this point may be overlooked. 

2 Compare p. 17 and illustration, Fig. 5. 


changes the ferrous ions to the ferric condition resulting in the 
hydrolytic formation of the insoluble ferric hydroxide or rust. 
The more detailed discussion of the electrolysis which takes place 
will be taken up in a later chapter. 

Electrolysis and Polarization. — When a metal electrode is 
immersed in an electrolyte it tends to dissolve, or in other words, 
to pass from the atomic to the ionic condition. This is known 
as electrolytic solution pressure. As the atom of metal passes 
into solution it assumes a positive charge of electricity which it 
must take from some source. If the electrolyte contains positive 
hydrogen ions, that is to say, if the electrolyte is acid, the enter- 
ing metallic ions will acquire their charges by exchange with 
hydrogen, which immediately leaves the system in the form of 
minute gaseous bubbles. If the electrolyte is neutral the metallic 
ions take their positive charges from the electrode which is thereby 
left negatively charged. In almost neutral media a combination 
of the two results may take place, the hydrogen being disengaged 
too slowly to be visible. 

Such a state of affairs leads to a polarization effect first 
described by Helmholtz 1 and called by him an electrical double 
layer. The positively charged metallic ions cannot escape or 
free themselves from the negatively charged surface, although 
there is sufficient pressure to prevent the reneutralization of the 
charges. This effect polarizes the surface, which for practical 
purposes may be considered as plated with positive ions. Walker 2 
describes this phenomenon in the following words: 

" Every metal when placed in water, or under such conditions 
that a film of water may condense upon it, tends to dissolve in 
the water, or, in other words, to pass from its atomic or metallic 
condition into its ionic condition. This escaping tendency of 
the metals varies from that shown by sodium or potassium, 
which is so great as to cause instant and rapid decomposition 
of the metal and water, to gold or platinum where such tendency 
to dissolve is zero. Between these two extremes we find the 
other common metals, including thereunder the element hydro- 
gen, which may be considered as a metal. As the atom of metal 
passes into the water, it assumes a positive charge of electricity, 
leaving the metallic mass from which it separated charged nega- 

1 Wied. Ann., 7, 337 (1879). 

2 Jour. Iron & Steel Inst., I, 70 (1909). 


tively; this property or escaping tendency of the metal is termed 
its solution pressure. It is obvious, however, that this action 
dan continue for only a short time; owing to the fact that the 
mass of metal and solution are of opposite polarity, the electro- 
lytic tension becomes so great that no more atoms can escape 
to the ionic state, and the solvent action ceases. This condition 
was first described by Helmholtz, and called by him an electro- 
lytic double layer. If now there be in the water ions of another 
metal which has a smaller solution pressure than the one under 
consideration, the action as above described will be reversed 
and the ion with the less solution pressure will pass back to the 
metallic state, plating out on the first metal and giving up its 
charge of electricity. At this point the first metal will be charged 
positively, and the solution in the immediate vicinity negative, 
and there will tend to be set up a second electrolytic double layer 
opposite in polarity to the first. The result is, a current of elec- 
tricity flows from the metal to the solution at the point where 
the metal passes into solution, through the solution to the metal 
at the point where the ions of the second metal are plating out, 
and back through the first metal to the starting-point again. 
The electrolytic double layers are thus destroyed, an electric 
current passes, and the solvent action of the water on the first 
metal continues. 

"This phenomenon and its relation to the corrosion of iron 
are clearly exemplified in the well-known Daniel or gravity cell. 

"In the case of pure iron in water a perfectly analogous con- 
dition is found to exist. Water itself is dissociated to a small 
but perfectly definite extent into its ions, hydrogen (H), and 
hydroxyl (OH). When a strip of pure iron comes into contact 
with water, it sends into the water iron atoms in the form of 
positively charged ions. Hydrogen as a metal has a much smaller 
solution pressure than iron, and hence an equivalent number of 
hydrogen ions plate out on the iron strip (leaving the free hydroxyl 
ions with their negative charges to balance the iron ions with 
their positive charges), and an electric current flows from the 
iron by means of the iron ions to the solution, and by means of 
the hydrogens from the solution back to the iron again, thus 
completing the circuit. But here comes an important break in 
the analogy of the film of copper in the Daniel cell. Deposited 
copper is a good conductor of the current, and offers no resistance 


to its flow from the solution to the iron on which it is attached. 
The reverse is true of the deposited hydrogen; here we have a 
high insulator — a film of gas which offers a great resistance to 
the flow of the current. Hence, although in the case of the iron 
strip in water all the conditions for continuous solution are pres- 
ent, owing to the resistance offered by the deposited hydrogen 
film (called polarization) the action must cease. 

"Just as in the case of iron in a copper sulphate solution the 
rapidity of the action depended upon the number of copper ions 
present in the solution, so here the solution of the iron, in the 
first instance, depends upon the number of the hydrogen ions 
present. This number of hydrogen ions, or the concentration 
of these ions, is increased by the addition of any acid. So weak 
an acid as carbonic increases the number, but to a relatively 
small amount; while a strong acid, like hydrochloric or sulphuric, 
adds to the number to such an extent that the solvent action 
becomes violent, and the deposited hydrogen comes off as a stream 
of gas." 

The Passive State of the Metals. 1 — It is well known that 
under certain conditions iron and some other metals assume a 
condition in which they no longer have all the properties they 
usually possess. Iron which has been dipped in certain strong 
oxidizing agents no longer exhibits a solution pressure when dipped 
into dilute electrolytes, and comports itself as though it were a 
noble metal. This was first noticed by Keir, a British chemist, 
as early as 1790. 2 He found that specimens of bright steel which 
had been dipped into strong fuming nitric acid became passive 
and were no longer soluble even in dilute acid, or able to exchange 
places with copper when dipped into a dilute solution of copper 
sulphate. Other strong oxidizing agents, especially chromic 
acid and its soluble salts, have been found to induce this condi- 
tion of passivity on the surface of iron. This fact has been made 
the subject of special study by one of the authors, the results of 
which will be detailed in a later chapter. Since the phenomenon 
of passivity is produced only by strong oxidizing agents or by 
galvanic contact which causes oxygen to separate on the sur- 
face of the iron, it was explained by Faraday, Wiederman, and 

1 For the bibliography and an excellent discussion of the passive state see 
Byers Jour. Am. Chem. Soc, 1908, 30, 1718. 

2 Phil. Trans., London, 1790, 359. 


others 1 as due to a thin oxide film. Another explanation is that 
the passivity of iron is due to a polarization effect produced by 
the separation and retention of oxygen on the surface of the metal. 

Keir 2 observed that polished iron which had been immersed 
in red fuming nitric acid was altered in some manner so that its 
power of precipitating silver and copper from their solutions was 
inhibited, and this occurred, in the discoverer's own words, "with- 
out the least diminution of metallic splendour or change of color." 
Mugdan 3 discussed the passivity acquired by iron which was 
immersed in fuming nitric or sulphuric acids and concluded that 
it was not due to the formation of an oxide film, but was a true 
passivity in the sense of an ennobling (Veredlung) of the metal, 
accompanied by a low electrical potential. Jones 4 has discussed 
the subject in the following words: "A number of attempts have 
been made to explain the passivity of the metals. Faraday 5 
and Schonbein explained the passivity in the case of iron, as due 
to the formation of a layer of oxide on the surface of the metal. 
This was natural when we consider that iron is rendered passive 
by strong oxidizing agents, and loses its passivity when heated 
in a reducing gas. 

"The oxide layer theory of passivity is now regarded as 
untenable, since the passive state has been brought about under 
conditions where oxidation is impossible; and further, has been 
destroyed under conditions where any layer of oxide if formed 
would not be disturbed. 

"The same fate has befallen the theory that passivity is due 
to the formation of a protective layer of gas over the surface 
of the metal. The two views of passivity that have acquired 
the greatest prominence are those of Finkelstein 6 and Hittorf. 7 
According to the former, active iron is bivalent and passive iron 
trivalent. This conclusion was based upon the difference in 
potential between iron electrodes and the iron salt in which they 
were immersed. The potential difference depends upon whether 
the iron salt is in the ferrous or in the ferric conditions. 

1 Dammer's Anorg. Chem., 1893, V. 3, p. 294. 

2 Ibid. 

3 Ztschr. Elektrochemie, 1903, 9, 454. 

4 Jones, EL Phys. Chem., p. 441. 

6 Phil. Mag. (3), 9, 53 (1836); 10, 175 (1837). 
c Ztschr. Phys. Chem., 39, 91 (1901). 

7 Ibid., 30, 481 (1899); 34, 385 (1900). 


"Hittorf also points out that in the case of chromium the 
passive condition corresponds to the highest valence, and the 
active to the lower valence. He thinks that we have to do with 
two allotropic modifications of the elements, one of which is 
active and the other not." 

In spite of these various explanations of the interesting and 
extraordinary phenomenon of passivity, its fundamental cause 
is not thoroughly understood and is still an open question. It 
is possible that plating out of oxygen and a change of valence 
of the surface ions takes place simultaneously. Whatever the 
cause, however, the condition of passivity has an important 
bearing on the problem of the protection of iron and steel, and 
will be taken up for further discussion later on. 

The Electro-chemical Series of the Metals. — If a strip of iron 
is plunged into a solution of a salt of copper, iron will go into 
solution and copper will plate out. This is because iron is electro- 
positive to copper, or, in other words, iron has a higher solution 
pressure than copper. The copper ions in solution give up their 
positive charges of electricity to the iron, which in turn assumes 
the ionic condition. If now a strip of iron is plunged into a 
solution of a salt of zinc no such phenomenon takes place because 
iron is electro-negative to zinc, and it is only when a strip of zinc 
is plunged into a solution of an iron salt that exchange can take 
place. If two metals are connected together in metallic contact 
to form a couple and are then plunged into a dilute solution of 
an electrolyte, the more electro-positive metal will dissolve and 
oxidize (rust), while the more electro-negative will be practically 
speaking unacted on. In the meantime current will flow around 
the circuit. This is the underlying principle of all galvanic action 
and explains the action of all primary batteries. In the following 
list a number of the more familiar metals are put down in the order 
of their diminishing solution tensions, and this may be termed a 

tension series. 

Magnesium Nickel 

Zinc Lead 

Aluminum Copper 

Cadmium Tin 

Iron Antimony 

A metal anywhere in the above series will tend to precipitate, 
from a solution of its salts, a metal lower in the series. Thus 


zinc and iron will precipitate copper. A metal at any point 
when coupled with another lower in the series and plunged into 
a corroding medium will throw off positive ions into solution, 
and thereby become the negative pole. Zinc is the negative 
pole in almost all the common types of primary batteries. It 
is apparent from this that if metals which stand below iron 
are successfully used as protective coatings it is because they have 
very low solution tensions. It is equally apparent why pinholes 
or cracks in a tin or copper coating will result in more rapid cor- 
rosion of the exposed portions of the iron. These points must 
await further discussion in a later chapter; it should at once be 
stated, however, that the electro-chemical state of a metal may 
be considerably modified by the presence of other metals which 
may be alloyed with it. This is an important point which is 
often overlooked in connection with the problem of protecting 
iron from corrosion. Thus zinc which is strongly electro-positive 
to iron is much used as a protective coating. There are, however, 
certain alloys of zinc with iron, which are said to be electro- 
negative to iron, and as these alloys may be formed in the spelter 
baths of the hot dip process, much of the zinc coating which is 
turned out in metallurgical processes may have quite the opposite 
effect from the one desired. 

The Theory of Indicators. 1 — Certain substances usually of an 
organic type when dissolved in water are observed to change 
color when the reaction changes. Thus, a solution of litmus, 
which shows red in an acid solution, will change to blue in an 
alkaline solution. The color change is dependent upon the degree 
and state of the electrolytic dissociation of the compounds. Sub- 
stances which undergo these delicate changes are known as 
indicators. The only one of these which will be referred to in this 
work is phenolphthalein, and for the benefit of many persons 
who are interested in the corrosion problem, but who are not 
familiar with the theory of indicators, the following explanation 
is included. Phenolphthalein shows the presence of hydroxyl 
ions in a solution by the formation of a pink color, thus indicating 

1 It is fair to state that the explanation of the action of indicators based on 
the theory of electrolytic dissociation is not universally accepted by chemists. 
The principle, however, remains the same, even if a better explanation can be 
advanced, for the pink color developed by phenolphthalein will always furnish 
a sensitive indication of the negative pole in an electrolytic circuit. 


an alkaline reaction. Phthalic acid was first prepared by Laurent 
in 1836, by the oxidation of naphthalene, and was first called 
naphthalinic acid. It was afterwards shown that the compound 
was not directly related to the naphthalene structure, and Laurent 
changed the name to phthalic acid, the derivatives of which 
became known later as phthaleins. Phenolphthalein is a prod- 
uct which is formed by the condensation of two molecules of 
phenol or carbolic acid with the anhydride of phthalic acid. It 
is in its nature so weak an acid that it is not dissociated in solu- 
tion, and as the molecule is colorless no color is seen when it is 
added to a perfectly neutral solution. If, however, an alkali is 
added the corresponding salt of the weak acid is formed, which 
immediately dissociates with the formation of a colorless metallic 
cation, and the strongly rose-colored organic anion. Thus all 
hydroxides of basic elements will show the pink color in solution, 
even when present in only the slightest excess. On this account 
phenolphthalein is an exceedingly delicate indicator of the pres- 
ence of hydroxyl ions. 

Phenolphthalein as an Indicator of the Presence of Electrolysis. 
— As hydroxyl ions are always found in more or less excess around 
the negative pole of a galvanic circuit after the positive hydrogen 
ions have neutralized their charges and disappeared, phenol- 
phthalein can be used as an indicator of the existence of a negative 
pole. In order to show the sensibility of this substance for indi- 
cating an excess of hydroxyl ions by the development of a distinct 
pink color, the following simple experiment has been described: 1 

Five hundred and fifty c.c. of distilled water containing 1 c.c. 
of phenolphthalein indicator was boiled down in a Jena flask to 
500 c.c. One one-hundredth normal potassium hydroxide solu- 
tion was then run into the quickly cooled water from a burette. 
It was thus found that about 1 c.c. of one one-hundredth normal 
potassium hydroxide was the limit of the quantity necessary to 
produce a distinctly visible pink color; 1 c.c. of one one-hundredth 
normal potassium hydroxide contains 0.00017 gram of hydroxyl. 
This quantity in 500 c.c. of water represents a concentration of 
about 0.35 part of hydroxyl per million. 

This experiment shows how extremely delicate the phenol- 
phthalein test is as an indicator of the presence of hydroxyl 
ions, and hence of the negative pole in an electrolytic circuit. 
1 Cushman, Bull. 30, Office Public Roads, U. S. Dept. Agr. 


Colloids and Crystalloids. — Before closing this chapter on 
solutions, a brief reference should be made to the condition of 
substances as they precipitate out of solution, as a general knowl- 
edge of the subject will be of assistance in the design and prepara- 
tion of inhibitive compounds. The action of colloids under the 
effects of electrolysis will also be found later to have a bearing 
on the corrosion problem. 

Electro-Chemical Properties of Colloids. — Whenever substances 
suddenly precipitate out of solution they appear either in a finely 
crystalline condition in which they are denominated crystalloids, 
or in a gummy, gelatinous, more or less coagulated condition, as 
the case may be, in which we define them as colloids, or colloidal 
precipitates. It will not be necessary here to give a full descrip- 
tion of the properties of colloids in general, as this information 
can be obtained from any complete text-book on physical chem- 
istry. The points that particularly interest us in this work are 
the peculiar absorbent powers of colloidal precipitates and their 
electro-chemical properties. Many colloidal precipitates are 
-dried and used as pigments, and such substances not only absorb 
considerable quantities of water, but also absorb and carry down 
with them impurities from the mother liquors or solutions from 
which they were precipitated. 

There seems to be satisfactory evidence that colloidal pre- 
cipitates in suspension in an electrolyte carry electrical charges 
just as ions do. This is shown by the fact that the colloidal 
particles when suspended in a solution migrate to the electrodes 
under the influence of electrolysis. Colloidal ferric hydroxide, 
which although not exactly is essentially similar to all freshly 
formed iron rust, moves with the current to the cathode, this 
peculiarity it shares with all basic hydroxides. Acid hydroxides 
like precipitated silicic acid move in the opposite direction. The 
ferric hydroxide is therefore charged positively and the silicic 
acid negatively. This property appears to be a general one for 
all colloidal suspensions, and seems, under certain conditions, to 
give them the tendency of absorbing from the solution ions of 
opposite sign. According to Jones, two theories have been pro- 
posed to account for the electrification of the colloid particles. 
According to one of these theories, the particles of the colloidal 
precipitates assume the charge of one sign while the surrounding 
water takes on the charge of the other sign. This explanation 


does not seem to be in accord with the observed facts, and the 
more probable theory is that from every colloidal aggregate there 
split off either positive or negative ions, leaving the residue of 
the aggregate carrying the opposite charge. Thus, basic hydrox- 
ides would split off hydroxyl ions, and the residue be charged 
positively; in the same way silicic acid would split off hydrogen 
ions, leaving the colloidal residue charged negatively. 1 

This absorbent tendency of colloidal precipitates, both for 
water and salts, as well as their electro-chemical properties, 
should be thoroughly understood by paint technologists who are 
studying the protection of iron and steel. The explanation of 
the stimulating effects produced by certain pigments which are 
theoretically inhibitors is usually furnished by these colloidal 
absorptions which take place in the course of manufacture of 
the pigments. 

Conclusion of the Chapter. — It is hoped that a careful reading 
and study of this chapter by metallurgists and others interested 
in the special problems with which this book deals will lead to a 
clearer understanding of the discussion and data which is included 
in succeeding chapters. It is not necessary that the reader should 
be a chemist in order to understand the explanations which have 
been presented, and it is hoped that those who have never studied 
even the rudiments of chemistry and electrical action will have 
been introduced to theories which are further developed in suc- 
ceeding chapters. In conclusion, the authors desire to state 
that they are conversant with the interesting generalizations 
of Kahlenberg 2 and his school, who do not accept the theory of 
solutions, and who have brought strong arguments, based on ex- 
perimental evidence, to bear against it. Nevertheless, the theory 
has been and still is a useful one whatever its ultimate fate may 
be; the authors are strong in the conviction that the theory of 
solutions expresses fundamental truth even if it must eventually 
be modified in form. 

1 Jones, El. Phys. Chem., p. 283. 

2 See Science, XXXI, 785, 41. 



The Three Theories which have been Advanced to Explain Cor- 
rosion. — Three separate theories which, though they all more 
or less overlap, nevertheless involve distinctly different reactions, 
have been advanced and strenuously defended in the effort to 
furnish an explanation for the rusting of iron. These may be 
stated as the carbonic-acid, the hydrogen-peroxide, and the 
electrolytic theories. 

Before any distinct progress can be made in the manufacture 
of metal that shall be more than ordinarily resistant to corrosion, 
it is of great importance that the underlying causes of oxidation 
should be clearly understood. It is the object of this chapter to 
discuss the different theories and to present certain evidence 
which bears directly upon the subject. 

The Carbonic-acid Theory. 1 — The carbonic-acid theory is the 
one which until recently was most generally held. The theory 
presumed that without the interaction of carbonic or some other 
acid the oxidation, or better, the hydroxylation, of iron cannot 
take place. The theory is best set forth in the words of a text- 
book recently published. 2 

"The process of rusting is a cyclical one, and three factors 
play an important part: (1) An acid, (2) water, (3) oxygen. 
The process of rusting is always started by an acid (even the weak 
carbonic acid suffices); the acid changes the metal to a ferrous 
salt with evolution of hydrogen: 

2Fe + 2H 2 C0 3 = 2FeC0 3 + 2H 2 . 

"Water and oxygen now act upon the ferrous salt, causing the 
iron in this salt to separate out as ferric hydroxide, setting free the 
same amount of acid which was used in forming the ferrous salt : 
2FeC0 3 + 5H 2 + = 2Fe(OH) 3 + 2H 2 C0 3 . 

1 The best presentment of the general acid theory is due to Friend, Jour. 
Iron and Steel Inst., 77, 5, 1908. 

2 Treadwell and Hall, Analytical Chemistry, 1907, p. 92. 



"The acid which is set free again acts upon the metal, form- 
ing more ferrous salt, which is again decomposed, forming more 
rust. A very small amount of acid, therefore, suffices to rust 
a large amount of iron. If the acid is lacking, the iron will not 
rust. If we desire to prevent this rusting, we must neutralize the 
acid, e.g. } add milk of lime. Iron remains bright under an alkali." 

Corrosion Occurs when Carbonic Acid is Absent. — Although 
the above explanation is sufficiently plausible, and in spite of the 
fact that carbonic acid, as well as other acids, does act a part in 
the ordinary rusting of iron, it will presently be shown that iron 
readily oxidises, not only when carbonic acid is entirely absent, 
but also in dilute alkaline solutions. It is only when the hydroxyl 
ions supplied by an alkaline solution have reached a certain con- 
centration that rusting is entirely prohibited. 

The carbonic-acid theory was founded originally on the inves- 
tigations of Crace Calvert, 1 as interpreted by Crum Brown. 2 It 
has also more recently been vigorously defended by Moody, 3 
who insists that with water and oxygen quite free from carbonic 
acid iron cannot rust. This view is, however, not shared by 
Dunstan, Jowatt, and Goulding, 4 or by Whitney 5 or Cribb, 6 all 
of whom give experimental evidence to show that rusting takes 
place rapidly in the absence of carbonic acid, provided liquid 
water and oxygen ar6 present. The experiment of Dunstan and 
his coworkers was so carefully carried out that there seems to be 
no doubt that if carbonic acid plays any role whatever it is an 
unimportant one, and that rusting can go on with extreme rapidity 
in its absence. 

In order to confirm this conclusion the following experiment 
was made by one of the writers : 

The Jena glass flasks A, B, and the beaker C, shown in Fig. 6, 
were nearly filled with freshly distilled water and boiled vigor- 
ously for one-half hour. While the boiling was still proceeding 
bright polished strips of charcoal iron and steel were slipped into 
flasks A and B, and the rubber stoppers, which had been previously 

1 Manchester Lit. Phil. Mem., 1871, 5, 104. 

2 Jour. Iron and Steel Inst., 1S88, 129-131. 
3 Proc. Chem. Soc. (bond.), 1906, 22, 101. 

A Jour. Chem. Soc. (bond.), 1905, 87, pt. 2, 1548. 
5 Jour. Am. Chem. Soc, 1903, 25, 394. 
°The Analyst, 1905, 30, 232. 



cleaned by prolonged boiling in pure water, tightly inserted. 
After boiling for fifteen minutes longer the clamp at the end of 
tube D was opened for a moment and the back pressure allowed 
to drive any last traces of air from the tube. After tightly clos- 
ing the clamp again, the lamps under flasks A and B were removed 
while the water in C was still kept boiling. Boiled water imme- 
diately sucked back until the whole apparatus was completely 
filled, no trace of air being present. At all events, no slightest 
trace of rust appeared on the bright metal strips when kept 
indefinitely under this boiled water. Pure oxygen from a cylin- 

Fig. 6. — Apparatus to show the action on iron of 
pure water and oxygen. 

der was now washed perfectly free from last traces of carbonic 
acid by passing the gas through a train of wash bottles containing 
caustic potash,- barium hydroxide, and lime water. On allowing 
this carefully purified oxygen to enter at D and bubble through 
the system of flasks, rust appeared on the bright metal surfaces 
in five minutes or less and in one hour had become deep and heavy. 
The action, just as in Dunstan's experiments, did not take place 
evenly all over the surface, but in patches, which had the appear- 
ance of a more or less regular pattern following the physical 
structure of the metal. This experiment has been frequently 
repeated, with every possible precaution to avoid the entrance 
of even the smallest trace of carbonic acid. On numerous occa- 
sions a few drops of phenolphthalein indicator was added to the 
boiling water in the three flasks, and invariably a pink color 


developed, proceeding from the metallic surfaces. This effect 
will be discussed at length further on and is mentioned at this 
place as contributory evidence that carbonic acid is not neces- 
sarily present, as Moody believes, before any reaction between 
iron, water, and oxygen can take place. 

If pure, dry carbonic acid gas, freed from oxygen by passing 
through several wash bottles containing pyrogallic acid dissolved 
in sodium bicarbonate solution, was substituted for the pure 
oxygen gas and allowed to enter through tube D, no perceptible 
action took place on a bright piece of steel after several hours, 
although there can be no doubt that iron passed to a slight extent 
into solution as ferrous carbonate. Finally, if pure oxygen was 
allowed to enter at the same time and mingle with the carbonic 
acid, corrosion began in a short time. There was, however, a 
difference in the appearance of the rust that was formed with 
and without the interaction of carbonic acid. In the presence 
of carbonic acid the characteristic blue-green gradually changing 
to the red color peculiar to rust was observed. This appearance 
invariably accompanies the early stage of attack when iron is 
rusting in the presence of carbonic acid. In the experiments in 
which pure oxygen alone was permitted to enter the apparatus 
the blue-green initial stage of oxidation was never observed, the 
red ferric hydroxide making its appearance from the first, as it 
usually does, in normal cases of atmospheric rusting of bright 
iron surfaces. 1 

It may be doubted whether it is possible to boil out all car- 
bonic acid from the water contained in the apparatus shown in 
Fig. 6. Granting that this is the case in regard to last traces, 
it is easily shown that the hydrogen ions which would be supplied 
by a minute quantity of carbonic acid are of no more importance 
than the hydrogen ions supplied by the normal dissociation of 
pure water, and that the assumption that carbonic acid must be 
present is quite unnecessary. Whitney 2 shows this very clearly 
in the following paragraph: 

1 Statements frequently appear in discussions of the corrosion problem 
in regard to the importance of analyses of various samples of iron rust. As 
a matter of fact little can be learned from such analyses. The ferroso-ferric 
hydroxides, carbonates, etc., that are formed are of indefinite composition and 
their chemical constitution throws little if any light on the mechanism of 
the corrosion reactions. 

2 Jour. Am. Chem. Soc, 1903, 25, 397. 


"Assuming the laws of Henry and Dalton to apply to the 
solubility of carbonic acid gas in water, also that the solubility 
of the pure gas under ordinary pressure is one volume for one 
volume of water (which is correct at 15° C), and, finally, that the 
normal content of carbonic acid in the atmosphere is 2 parts 
in 10,000 by volume, we should expect water in equilibrium with 
air containing this concentration of carbonic acid to contain 
0.0002 volume carbon dioxide per volume of water. This corre- 
sponds to a concentration of the carbonic acid equal to 0.00001 
mol per liter, or 0.00002 normal. From the dissociation constant 
3040 X 10- 10 determined by Walker, 1 it follows that the first 
hydrogen of the acid is 16 per cent, dissociated at this concentra- 
tion. From this it follows that 10,000,000 liters of water contain- 
ing carbonic acid in equilibrium with ordinary air at 15° contains 
16 grams of hydrogen ions, or only 16 times as many as perfectly 
pure water contains. At the boiling temperature the carbon 
dioxide dissolved would probably yield a concentration of hydro- 
gen ions even less than in pure water, for not only is the solubility 
of the gas greatly diminished, but the dissociation of water is 
greatly increased by rise of temperature. Moreover, the dis- 
tilling water would rapidly reduce the concentration of any car- 
bonic acid capable of dissolving in water at 100° C." 

The carbonic acid theory does not furnish a complete explana- 
tion of the phenomenon of corrosion, but it does express partial 
truth inasmuch as hydrogen ions must be present before the attack 
on the surface of iron can be made. The fact as brought out in 
the previous paragraph that even pure water provides a sufficient 
number of hydrogen ions to start the action shows that the role 
of carbonic acid is only contributory and not the sole cause. 

The Peroxide Theory of Corrosion. — The peroxide theory of 
corrosion has not been found in accordance with observed facts, 
but it will be briefly stated here for the sake of completeness. 
This theory is based on the well-known scheme of oxidation 
processes advanced by Traube. 2 Thus the chemical reactions 
concerned in the formation of iron rust should be written: 

Fe + 2 + H 2 = FeO + H 2 2 

2FeO + H 2 2 = Fe 2 2 (OH) 2 = Fe 2 3 , H 2 

1 Zts. Phys. Chem., 1900, 32, 137. 
2 Ber. d. chem. Ges., 18, 1881. 


The excess of hydrogen peroxide immediately reacts with the 
iron, forming a further quantity of rust: 

Fe + H 2 2 = FeO + H. 2 
2FeO + H 2 2 = Fe 2 2 (OH) 2 = Fe 2 3; H 2 

One of the arguments which was used by its supporters to 
strengthen the theory was the seemingly extraordinary but now 
well-known fact that iron cannot rust in solutions of certain 
strong oxidizing agents, such as chromic acid and its salts. As 
chromic acid is known to destroy hydrogen peroxide, the explana- 
tion on first thought seems reasonable. The theory also seemed 
to derive some confirmation from the fact that delicate tests for 
hydrogen peroxide have beeen obtained during the slow oxida- 
tion of zinc and some other metals. On the other hand, in the 
case of iron these same delicate tests obstinately refuse to reveal 
even its transitory presence during the ordinary process of rust- 
ing. The theory has been criticised by Divers, 1 Moody, 2 and 
Cribb, 3 — the first named having pointed out that it is not ten- 
able to argue that, because such substances as chromic acid and 
alkalis gradually destroy hydrogen peroxide, they must prevent 
its formation. For instance, ferrous sulphate is oxidized by free 
chlorine, but it does not prevent manganese dioxide and hydro- 
chloric acid from reacting when brought together in its presence. 
Moreover, if the formation of hydrogen peroxide was a necessary 
stage in the rusting of iron, and this is inhibited by certain sub- 
stances which destroy hydrogen peroxide, why is not the inhibi- 
tion extended to strong reducing agents generally? The theory 
is an interesting and suggestive one, but in the author's opinion 
is not supported by the facts. 

The Electrolytic Theory. — From the standpoint of the modern 
theory of solutions, all reactions which take place in the wet 
way are attended with certain readjustments of the electrical 
states of the reacting ions. The electrolytic theory of rusting 
assumes that before iron can oxidize in the wet way it must first 
pass into solution as a ferrous ion. The subject has been interest- 
ingly treated by Whitney, 4 who discussed it from the standpoint 

1 Proc. Chem. Soc. (Lond.), 1905, U, 251. 

2 Jour. Chem. Soc. (Lond.), 1906, 89, 90, 720. 

3 Analyst, 1905, 30, 225. 
- hoc. cit., p. 38. 


of Nernst's conception of the source of electro-motive force 
between a metal and a solution. When a strip of metallic iron is 
placed in a solution of copper sulphate, iron passes into solu- 
tion and copper is deposited, this change being of course accom- 
panied by a transfer of electrical charge from the ions of copper 
to those of iron. Hydrogen acts as a metal and is electrolytic ally 
classed with copper in relation to iron. If, therefore, we immerse 
a strip of iron in a solution containing hydrogen ions, an exactly 
similar reaction will take place, iron will go into solution, and 
hydrogen will pass from the electrically charged or ionic to the 
atomic or gaseous condition. In such a system the solution of 
the iron, and, therefore, its subsequent oxidation, must be accom- 
panied by a "precipitation" or setting free of hydrogen. It is 
very well known that solutions of ferrous salts as well as freshly 
precipitated ferrous hydroxide are rapidly oxidized by the free 
oxygen of the air to the ferric conditions, so that if the electrolytic 
theory can account for the original solution of the iron the explana- 
tion of rusting becomes an exceedingly simple one. 

Pure Water a Solvent of Iron. — As iron has been shown by 
Whitney, Dunstan, and one of the authors, to rust in the presence 
of pure water and oxygen alone, the electrolytic theory as a funda- 
mental cause of the wet oxidation of iron must stand or fall on 
the determination of one crucial question, viz.: Does iron pass 
into solution, even to the slightest extent, in pure water? If 
iron does dissolve, the electrolytic theory is so far satisfactory; 
if it does not dissolve, we must conclude that the oxygen finds 
some way of directly attacking the metal. 

Almost every one will admit that in the case of impure iron, 
with its unhomogeneous physical and chemical constitution, elec- 
trolysis will supervene, but it must be remembered that we are 
now concerned with the underlying cause of the wet oxidation or 
hydroxylation of iron, regardless of its state of chemical purity. 

According to the dissociation theory, even the purest water 
contains free hydrogen ions to the extent of about 1 gram in 
10,000,000 liters. If iron dissolves in the purest water it should 
be by interchange with hydrogen, and as Whitney 1 has pointed 
out, pure water is to this extent an acid. In order to get experi- 
mental evidence on this crucial point, Whitney describes the 
following experiment: 

1 hoc. Hi., p. 38. 


"A clean bottle was steamed out for a time to remove soluble 
alkali from the glass and was then filled with pure distilled water, 
which was kept boiling by passing steam through it for fifteen 
minutes. While still boiling, a bright piece of iron was placed 
in the bottle. A stopper (in some cases rubber and in others 
cork) carrying a tube open in a capillary several inches above the 
stopper was inserted into the bottle and firmly fastened in place, 
the water being kept boiling. Finally, the glass capillary was 
heated hot by means of a blowpipe and sealed by squeezing the 
walls together. The bottle was then allowed to cool to a tempera- 
ture of about 80° C, and the neck of the bottle was finally covered 
with paraffin to prevent leaking. It was thought that in this way 
the oxygen, carbonic acid, and other gases in the water were 
completely removed. Bottles containing iron and sealed in this 
manner have stood without any visible change for weeks. In 
some cases a little air was subsequently admitted to bottles 
which had stood in this way with the iron apparently unaffected, 
and within a few minutes the water became cloudy and assumed 
a yellow color. Ordinary rust rapidly deposited upon the glass 
and in spots upon the metal. In fifteen or twenty minutes the 
production of rust throughout the bottle was perfectly evident. 
It seemed plain from the rapidity of formation of oxide and its 
precipitation on the glass that the iron had dissolved in the water 
before the addition of the air, and that the latter simply per- 
mitted the formation of the insoluble oxide." 

In order to obtain more light on the subject one of the writers 
devised the following experiment, which is sufficiently simple to 
be repeated by any one without encountering any difficulties 
whatever. The apparatus used is shown in Fig. 7. 

The two clean Jena glass flasks A and B are three-quarters 
filled with pure freshly distilled water. Two drops of an alcoholic 
solution of phenolphthalein indicator (1 gram in 100 c.c. pure 
alcohol) are added to the water in each of the flasks. The beaker 
C is more capacious than the flasks A and B. The flasks D and E 
are used in each experiment as blanks to check the results obtained. 
After connecting up as shown, the water in each vessel is simul- 
taneously boiled very vigorously until about one-quarter is 
boiled off. The rubber stopper in A is then lifted, and clean, 
polished strips of iron quickly slipped in. The stopper is again 
tightly inserted and the boiling continued for about fifteen minutes. 



The lamps under A and E are then extinguished, while the water 
in B, C, and D continues to boil. As soon as flasks A and E 
have sucked back boiling water so that they are completely filled, 
the lamps under flasks B and D are also extinguished. When B 
is quite full, flasks A and B are quickly cooled by surrounding 
them with cold water. The valve at F is then closed. By this 
means the bright specimens are immersed in water practically 
free from air, oxygen, or carbonic acid, and may be kept under 
observation for any desired length of time. This experiment 
has been repeated a great number of times with different samples 
of iron and steel, and no rusting has ever been observed unless 
air was allowed to enter. 

Fig. 7. — Apparatus to determine the extent of the solubility of iron 

in pure water. 

It has been shown that the electrolytic theory of the wet 
oxidation of iron is based on the premise that iron must first 
go into solution, an equivalent amount of hydrogen being set 
free. The resulting ferrous hydroxide in solution betrays its 
presence by producing a pink coloration with the phenolphthalein 
indicator. In every experiment made the pink color was seen, 
although in some cases the color developed slowly and only after 
the lapse of a number of hours. That the color was not due to 
the action of the water on the Jena glass was shown by the fact 
that no color appeared on the blank side of the experiments. 

Since it was thought that some doubt might be felt whether 
even the small amount of phenolphthalein present could attack 
the iron, the experiment was repeated with iron and boiled water 


alone, but the results invariably showed that a small amount of 
iron had dissolved. In view of the ease with which these experi- 
ments can be confirmed, it would seem needless to yield more 
space to this phase of the discussion. It appears to the writer 
to be demonstrated that Whitney was right in his assertion that 
iron goes into solution up to a certain maximum concentration 
in pure water, without the aid of oxygen, carbonic acid, or other 
reacting substances. 

Rusting of Iron Primarily due to Attack by Hydrogen Ions. — 
This point established, it becomes apparent that the rusting of 
iron is primarily due, not to attack by oxygen } but by hydrogen ions. 
Absolute confirmation of this view will be given later on. 

In order that rust should be formed iron must go into solution 
and hydrogen must be given off in the presence of oxygen or cer- 
tain oxidizing agents. This presumes electrolytic action, as every 
iron ion that appears at a certain spot demands the disappearance 
of a hydrogen ion at another, with a consequent formation of 
gaseous hydrogen. The gaseous hydrogen is rarely visible in the 
process of rusting, owing to the rather high solubility and great 
diffusive power of this element. Substances which increase the 
concentration of hydrogen ions, such as acids and acid salts, 
stimulate corrosion, while substances which increase the con- 
centration of hydroxyl ions inhibit it. Chromic acid and its salts 
inhibit corrosion by producing a polarizing or dampening effect 
which prevents the solution of iron and the separation of hydro- 
gen. This will be more fully discussed later on. 

Brief Explanation of Corrosion of Iron, from Standpoint of 
Electrolytic Theory. — From the standpoint of the electrolytic 
theory, the explanation of the corrosion of iron is not complicated, 
and so far has been found in accordance with all the facts. Briefly 
stated, the explanation is as follows: Iron has a certain solution 
tension, even when the iron is chemically pure and the solvent 
pure water. The solution tension is modified by impurities or 
additional substances contained in the metal and in the solvent. 
The effect of the slightest segregation in the metal, or even unequal 
stresses and strains in the surface, will throw the surface out of 
equilibrium, and the solution tension will be greater at some points 
than at others. The points or nodes of maximum solution 
pressure will be electro-positive to those of mimimum pressure, 
and a current will flow, provided the surface points are in contact, 


through a conducting film. If the film is water, or is in any way 
moist, the higher its conductivity the faster iron will pass into 
solution in the electro-positive areas, and the faster corrosion 
proceeds. Positive hydrogen ions migrate to the negative areas, 
negative hydroxyls to the positives. As explained in a previous 
chapter, by a hydrogen ion is meant a dissociated hydrogen atom 

carrying its equivalent static electrical charge, which may be 

represented by the symbol H. The hydroxyl ion is written OH. 

Water, which may be expressed by the symbol HOH, is made up 

+ - 

of the dissociation products H and OH. An acid like hydro- 

chloric acid (HC1) dissociates into H and CI. An acid is always 
highly dissociated in solution, while water itself is only slightly 
dissociated. This explains why the presence of an acid increases 
the concentration of the hydrogen ions. Ionization always takes 
place in every solution of an inorganic compound, and even the 

purest water is slightly dissociated into its constituent ions H 

and OH. The more ionized a solution is, the higher its electrical 
conductivity, and the more rapid the damage to the underlying 

If the concentration of the hydrogen ions is sufficiently high, 
which, as has been shown, is only the same as saying if the solu- 
tion is sufficiently acid, the hydrogen ions will exchange their 
electrostatic charges with the iron atoms sweeping into solution, 
and gaseous hydrogen is seen escaping from the system. This 
takes place whenever iron is dissolved in an acid. If, however, 
as is usual in ordinary rusting, the acidity is not high enough to 
produce this result, the hydrogen ions will polarize to a great 
extent around the positive nodes without accomplishing a complete 
exchange, and the so-called electrical double layer of Helmholtz 
will be formed. 1 This polarization effect resists and slows down 
the action. Nevertheless, although it cannot be seen, some 
exchange takes place and iron slowly pushes through, as is shown 
by the development of the blue nodes in the ferroxyl test. For 
every exchange of static charge between iron and hydrogen at the 
positive node, a corresponding negative hydroxyl ion appears at 
the negative node which is shown in pink with the ferroxyl indica- 

1 Wied. Ann., 1879, 7, 337. 


tor. In other words, as fast as the iron sweeps into solution the 
concentration of ferrous hydroxide grows, but the ferrous reaction 
appears in one place and the hydroxyl in another. It is now that 
the oxygen of the atmosphere dissolved in the solution takes up 
its work, the ferrous ions are oxidized to the insoluble ferric 
condition, which results in the precipitation of rust, and the 
action of hydrolysis proceeds. The formation of the insoluble 
ferroso-ferric carbonates and hydroxides, changing to the red 
ferric hydroxide known as rust, is familiar to every one. 

W. H. Walker puts into the following words a very similar 
explanation of the action which takes place: 1 

"Every metal when placed in water, or under such conditions 
that a film of water may condense upon it, tends to dissolve in 
the water, or, in other words, to pass from its atomic or metallic 
condition into its ionic condition. This escaping tendency of the 
metals varies from that shown by sodium or potassium, which is 
so great as to cause instant and rapid decomposition of the metal 
and water, to gold or platinum where such tendency to dissolve 
is zero. Between these two extremes we find the other common 
metals, including thereunder the element hydrogen, which may be 
considered as a metal. As the atom of metal passes into the 
water, it assumes a positive charge of electricity, leaving the 
metallic mass from which it separated charged negatively; this 
property or escaping tendency of the metal is termed its solution 
pressure. It is obvious, however, that this action can continue 
for only a short time; owing to the fact that the mass of metal 
and solution are of opposite polarity, the electrolytic tension 
becomes so great that no more atoms can escape to the ionic 
state, and the solvent action ceases. This condition was first 
described by Helmholtz, and called by him an electrolytic double 
layer. If now there be in the water ions of another metal which 
has a smaller solution pressure than the one under consideration, 
the action as above described will be reversed and the ion with 
the less solution pressure will pass back to the metallic state, 
plating out on the first metal and giving up its charge of electricity. 
At this point the first metal will be charged positively, and the 
solution in the immediate vicinity negative, and there will tend 
to be set up a second electrolytic double layer opposite in polarity 
to the first. The result is, a current of electricity flows from the 
1 Jour. Iron and Steel Inst., 1, 70 (1909). 


metal to the solution at the point where the metal passes into 
solution, through the solution to the metal at the point where the 
ions of the second metal are plating out, and back through the 
first metal to the starting-point again. The electrolytic double 
layers are thus destroyed, an electric current passes, and the sol- 
vent action of the water on the first metal continues. 

"This phenomenon and its relation to the corrosion of iron 
are clearly exemplified in the well-known Daniel or gravity cell. 
In the case of pure iron in water a perfectly analogous con- 
dition is found to exist. Water itself is dissociated to a small 
but perfectly definite extent into its ions, hydrogen (H) and 
hydroxyl (OH). When a strip of pure iron comes into contact 
with water, it sends into the water iron atoms in the form of 
positively charged ions. Hydrogen as a metal has a much smaller 
solution pressure than iron, and hence an equivalent number of 
hydrogen ions plate out on the iron strip (leaving the free hy- 
droxyl ions with their negative charges to balance the iron ions 
with their positive charges), and an electric current flows from 
the iron by means of the iron ions to the solution, and by means 
of the hydrogens from the solution back to the iron again, thus 
completing the circuit. But here comes an important break in 
the analogy of the film of copper in the Daniel cell. Deposited 
copper is a good conductor of the current, and offers no resistance 
to its flow from the solution' to the iron on which it is attached. 
The reverse is true of the deposited hydrogen; here we have a 
high insulator — a film of gas which offers a great resistance to 
the flow of the current. Hence, although in the case of the iron 
strip in water all the conditions for continuous solution are present, 
owing to the resistance offered by the deposited hydrogen film 
(called polarization) the action must cease. 

" Just as in the case of iron in a copper sulphate solution, the 
rapidity of the action depended upon the number of copper ions 
present in the solution, so here the solution of the iron, in the 
first instance, depends upon the number of the hydrogen ions 
present. This number of hydrogen ions, or the concentration of 
these ions, is increased by the addition of any acid. So weak an 
acid as carbonic increases the number, but to a relatively small 
amount; while a strong acid, like hydrochloric or sulphuric, adds 
to the number to such an extent that the solvent action becomes 
violent, and the deposited hydrogen comes off as a stream of gas. 


" Since the presence of the polarizing film of hydrogen arrests 
the further solution of the iron, it is obvious that in order for 
the reaction to proceed this hydrogen must be removed. The 
destruction of the hydrogen film in ordinary corrosion is accom- 
plished by the oxygen of the atmosphere, which is dissolved in 
the water. The action here taking place is a simple union of the 
hydrogen on the iron and the oxygen dissolved from the air, 
with the re-formation of water. It follows from this that any 
substance which dissolves or reacts with hydrogen should acceler- 
ate corrosion. This is found to be in fact the case.' 5 

Development and Use of Ferroxyl Reagent. — It is a matter of 
common observation that iron usually corrodes rapidly at cer- 
tain weak points, the effect produced being known as pitting. 
That this effect can best be explained by the electrolytic theory 
there can be no doubt, and it was in the effort to obtain an actual 
demonstration that the now well-known "ferroxyl" reagent was 
evolved. 1 Early in his investigations one of the authors observed 
that whenever a specimen of iron or steel is immersed in water 
or a dilute neutral solution of an electrolyte to which a sufficient 
quantity of phenolphthalein indicator has been added, a pink 
color is developed. If the solution is allowed to stand perfectly 
quiet, it will be noticed that the pink color is confined to certain 
spots or nodes on the surface. The pink color of the indicator is a 
proof of the presence of hydroxyl ion's, and thus indicates the nega- 
tive poles. It may be added that some specimens of steel exhibit 
this phenomenon much more quickly and distinctly than others. 

Since phenolphthalein shows only the nodes where solution 
of iron and subsequent oxidation does not take place, Walker 2 
suggested the addition of a trace of potassium ferricyanide to the 
reacting solution, in order to furnish an indicator for the ferrous 
ions whose appearance marks the positive poles. If iron goes into 
solution, ferrous ions must appear, which, with ferricyanide, 
form the well-known TurnbulPs blue compound. Walker further 
showed that if the reagent is stiffened with gelatin or agar-agar, 
diffusion is prevented and the effects produced are preserved. 
For this combined reagent, which indicates at one and the same 
time the appearance of hydroxyl and ferrous ions at opposite 

1 Announced in a paper before the American Soc. Testing Materials, 
June 21, 1907. 

2 Jour. Am. Chem. Soc., 29, 1257, October, 1907. 


poles, one of the authors has suggested for the sake of brevity 
the name "ferroxyl." If the reagent has been properly prepared, 
the color effects are strong and beautiful. In the course of a few 
days the maximum degree of beauty in the colors is obtained, after 
which a gradual deterioration sets in, although the effects can be 
preserved for a long time by flooding the jelly with alcohol. 

In the pink zones, as would naturally be expected, the iron 
remains quite bright as long as the pink color persists. In the 
blue zones the iron passes into solution and continually oxidizes, 
with a resulting formation of rust. Even the purest iron develops 
the nodes in the ferroxyl indicator, but impure and badly segre- 
gated metal develops the colors with greater rapidity and with 
bolder outlines. This result would of course be expected, as in 
pure iron the formation of poles would be conditioned by a 
much more delicate equilibrium than in impure iron, where varia- 
tions in concentration of the dissolved impurities would stimulate 
the electrolytic effects. Even so-called chemically pure iron 
contains small quantities of dissolved gases, and it is not improb- 
able that even slight variations in the physical homogeneity of 
pure iron will occasion the electrolytic effects which are made 
visible by this delicate reagent. 

Ferroxyl Indicator shows that Solution Tension of Iron Varies 
at Different Points on the Surface. — It should be remembered 
that the electrolytic action indicated by the ferroxyl tests is con- 
ditioned by a very delicate equilibrium. In order to decompose 
water by the electric current a very much higher difference of 
potential is needed than ever exists between points on the surface 
of a piece of corroding iron or steel, however badly segregated it 
may be. The entire value of the ferroxyl test consists in the fact 
that it indicates in a very delicate way that the solution tension 
of iron is higher at certain points on the surface than it is at 
others. Or, in other words, that certain surface points are, be 
it ever so slightly, electro-positive to others. 

The very delicacy of the test shows that it must be carried 
out with precise care. If a sewing needle is taken and rubbed 
with the finger at one end and then placed in the reagent and 
left there, it will be noticed that where the fingers had come in 
contact with the steel, the slight trace of sodium chloride from 
the fingers will cause corrosion to commence and continue. 1 
1 See Stead, Jour. Iron and Steel Inst., 1, 97 (1909). 


Bresch 1 in a short review of the new theory of corrosion has 
made use of a graphic method to show the action which takes 
place when a piece of iron is immersed in the ferroxyl reagent. 
This diagram, which is self-explanatory, is shown in Fig. 8. 

Ferroxyl Reagent 

Fig. 8. — Diagrammatic explanation of action in ferroxyl indicator. 

Preparation of Ferroxyl Mounts. — The ferroxyl mounts are 
prepared as follows: A lj per cent, solution of agar-agar is first 
made by dissolving a weighed quantity of powdered agar in the 
requisite amount of water. This solution is boiled for one hour, 
fresh water being added to replace that lost by evaporation. It 
is then filtered while hot and 2 c.c. of standard phenolphthalein 
indicator added to every 100 c.c. solution, after which it is brought 
to a perfectly neutral condition by titration with a tenth-normal 
solution of potassium hydroxide (KOH) or hydrochloric acid 
(HC1), as the case may be. The addition of 7 c.c. of a 1 per cent, 
solution of potassium ferricyanide to every 100 c.c. of solution is 
then made, and the ferroxyl reagent, while still hot, is ready to use. 
Enough of the reagent should be poured into a Petri dish to just 
cover the bottom, and the dish floated in cold water until the agar 
has jellied. A clean sample of iron is then placed on this bed of 
jelly and covered with the hot solution. After the final addition 
of agar the dish should not be moved until thoroughly cool. 
While the colors sometimes show up immediately, they usually 
require from twelve to twenty-four hours to attain "their most 
perfect development. The mounts may be preserved for many 
months by keeping the surface of the agar covered with alcohol. 
1 La Nature, Nov. 13, 1909, p. 373. 



Ferroxyl Indicator Rational Proof of Electrolytic Theory. — 
These effects which are produced in the ferroxyl indicator con- 
stitute a visible demonstration of electrolytic action taking 
place on the surface of iron and causing rapid corrosion at the 
positive nodes. 

The ferroxyl test in the hands of a number of investigators 
has brought out with clearness a considerable body of evidence 
to show that the electrolytic theory is in accord with observed 
facts when iron is undergoing corrosion. Some of the best re- 
sults obtained are shown in Figs. 9, 10, 11, 12, and 13. 

Fig. 9. — Showing some results obtained in the ferroxyl test. (Cushman.) 

Varied Rust Formation in Different Samples. — It has been 
noted by a number of investigators that different samples of iron 
and steel do not rust in the same way when subjected to the 
action of water and air. While some samples show localized 


electrolytic action, as indicated by deep pitting, others become 
covered with a more or less homogeneous coating of hydroxide, 
which shows little or no tendency to localize in spots or nodes. 
The question naturally arises: In what respect do these two 

Fig. 10. — Showing a number of iron and steel objects immersed in the 
ferroxyl jelly. (Cushman.) 

methods of rust formation differ? A close inspection of Fig. 13 
is suggestive if not conclusive of the answer in this respect. The 
photographic reproduction exhibits an effect which is frequently 
observed in the ferroxyl tests. When the colors first developed, 
two dark blue nodes formed at the opposite ends of the test piece, 



with a large pink area in the center, where for a time the metal 
remained quite bright. Very shortly, however, the poles changed, 
and the pink central area disappeared and gave way to a large 
blue node which enveloped three-quarters of the test piece, with 

Fig. 11. — Steel wire nails in ferroxyl jelly. (Cushman.) 

a small opposed pinkish spot. Again and again a reversal and 
change of poles took place, and at least five such changes are 
clearly shown in Fig. 13. As a result of this action the metal 
strip was rapidly covered over its entire surface with the same 
superficial, loosely adherent coating of hydroxide, which is 


obtained in many cases when certain samples of iron and steel 
are allowed to rust under a layer of water. It is presumable that 
as the surface of the metal is eaten into by the solution of the iron 
at the positive poles, a new condition of equilibrium occurs, 

Fig. 12. — Steel nails in ferroxyl reagent. (Walker.) 

resulting in changes and even reversals of the positive and nega- 
tive nodes. This would indicate that in the case of metals which 
suffer from local action or pitting the segregation conditions are 
of a different nature from those which exist in the case of metals 
which rust more evenly. A rough analogy may be drawn by 



imagining an imperfect mixture of black and white sand, the 
respective grains of which may lie in streaks, spots, and layers, 
or may tend to arrange themselves in some more or less uniform 
relation to each other. The best demonstration that the rusting 

Fig. 13. — Strip of steel in ferroxyl 
reagent, showing frequent shifting of 
poles. (Cushman.) 

and corrosion of iron and steel in all its forms is essentially an 
electrolytic phenomenon is afforded by the fact that it has not 
as yet been possible to find a specimen of such purity that no 
trace of positive and negative nodes will be formed in the ferroxyl 



Two Distinct Effects in Rust Formation. — We may now apply 
the electrolytic theory to the actual results obtained in the ordi- 
nary rusting of iron. If a section of rolled metal, such as sheet 
or plate, is immersed in water, according to the electrolytic theory, 
rusting must take place with the establishment of positive and 
negative spots or areas. At the positive points iron will pass 
into solution and be rapidly oxidized to the loose colloidal form 
of ferric hydroxide which is characteristic of rust formed under 
these conditions. It is a well-known fact that colloidal ferric 
hydroxide will move or migrate to the negative pole if subjected 
to electrolysis. 1 We may therefore consider the possibility of 
two separate effects that may be produced, viz., when a positive 
center is surrounded by a negative area, and vice versa. These 
two conditions may be graphically represented by the two circles 
A and B shown in Fig. 14. 

Fig. 14. — Diagram illustrating the electrolytic action 
on the surfaces of iron and steel. 

Now, as rusting proceeds we should expect in the case of A 
that the ferric hydroxide would be piled up in a crater formation, 
while the metal is eaten out at the center. In the case of B 
the effect would be reversed, and while the metal would be attacked 
in the surrounding area the hydroxide would be piled up in a 

1 See page 33. 



cone at the center. That this is precisely what is taking place 
whenever a sheet of metal rusts under water a low-power micro- 
scope very clearly shows. In Figs. 15, 16, 17, and 18 the writer 
has succeeded in showing the existence of both the craters and 
cones as they formed on the surface of a piece of wrought-iron 
boiler plate. In Fig. 15 a typical crater surrounding the point 
of pitting is shown, while in Fig. 16 an excellent example of the 

Fig. 15. — Formation of crater with pitting effect in 
center. (Enlarged 45 diameters.) 

cone appears. Both are photomicrographs magnified about 45 
diameters. The source of light was on the right in each case, 
and the shadows indicate the crater and cone formation, which 
is so clearly discernible under the microscope. Figs. 17 and 18 
are from photographs of the rusted metal, showing the craters 
and cones as they appeared with very low magnification. 

Fig. 19 shows the surfaces of strips of Bessemer steel (s), 
puddled wrought iron (z), and charcoal iron (c), prepared in the 
following manner: The respective samples were turned off in a 
lathe to a bright, smooth finish; they were then immersed under 
a thin layer of the ferroxyl reagent and allowed to stand quietly 


for several days. At the end of this time the surfaces were wiped 
clean. The electrolytic effects, which had been active on all 
three metals, are very well illustrated. The light portions show 
the negative areas, where little or no rusting took place, while the 
dark spots and areas show the special points of attack, with 
the pitting effects. The etching is not, of course, deep in the 

Fig. 16. — Formation of cone with pitting effect in sur- 
rounding area. (Enlarged 45 diameters.) 

case of any of the three samples, and should not be understood 
as showing the relative rate of corrosion of the different types of 
metal. The specimens simply serve as a demonstration that the 
rusting in each case has been accompanied by electrolysis. 

In Fig. 20 is shown a photograph of the actual pitting of a 
boiler tube, which failed, after eighteen months' service, in a 
water-tube type of marine boiler. The conclusion that pitting was 
due to electrolysis seems justified by comparing this photograph 
with those shown in Figs. 17 and 18. 

Practical Application of Electrolytic Theory. — The evidence 
advanced in the preceding pages appears to the writers to confirm 
the conclusion that the whole subject of the corrosion of iron is 



an electro-chemical one, which can be readily explained under 
the modern theory of solutions. It is an undeniable fact that 
some irons and steels suffer corrosion very much more rapidly 
than others, and the underlying causes for these differences con- 
stitute one of the important problems of modern metallurgy. 

Fig. 17. — Photographic representation of rust-spots 
formed on the surface of iron. 

Although the discussions brought forward up to this point 
are mainly theoretical in their nature, it is quite apparent that 
they also have an indirect practical bearing. Before advance 
can be made in overcoming the difficulties in the way of manu- 
facturing iron which shall have the maximum resistance to 
corrosion, as well as the preservation of the metal under the 
conditions of service, the underlying causes must be thoroughly 


understood. If we accept the electro-chemical explanation of the 
corrosion of iron, there can be no doubt that conditions which 
inhibit electrolytic effects also inhibit corrosion, and vice versa. 
The purer the iron in respect to certain other metals which differ 
electro-chemically from iron, and the more carefully lack of 
homogeneity and bad segregation are guarded against, the less 

Fig. 18. — Photographic representation of rust-spots 
formed on the surface of iron. 

likely are the electrolytic effects to become serious. These points 
constitute the essential problems which confront the manufac- 
turer who desires to make a product which shall have a high 
resistance to corrosion. The user and consumer, however, are 
interested in the protection of the various types of merchantable 
iron and steel which are available under market conditions at 


Fig. 19. — Strips of Bessemer steel (s), puddled wrought iron (z), and char- 
coal iron (c) after immersion in ferroxyl indicator. 

Fig. 20. — Actual pitting of tube in water-tube type of marine boiler. 


the present time. In short, protective coatings and palliative 
methods of treatment are in greater demand to-day than ever 
before. From the standpoint of the electrolytic theory many 
suggestions for experiment under the conditions of service present 

Walker has used the ferroxyl indicator to illustrate the appli- 
cation of the electrolytic theory to practical problems. This 
author states : x 

"When a piece of iron is placed in ordinary water, exposed 
to the air, it will dissolve or rust. If now there be placed in the 
water with this piece of iron a piece of platinum, the solvent or 
corroding action of the water will not be changed. The oxygen 
is present in the solution as before, and the iron ions as they 
separate from the metallic iron are being oxidized and precipi- 
tated as rust. If now the platinum and iron be electrically con- 
nected, a marked increase in the rate of the solution or corrosion 
of the iron is noticed. No chemical condition has been changed; 
the difference lies in the fact that there is now an electrical contact 
between the iron and the platinum, and the platinum furnishes 
a surface on which the hydrogen can deposit, and on which, by 
virtue of its catalysing action, the hydrogen will be rapidly 
oxidized by the dissolved oxygen, and thus removed from the 
sphere of action. This is shown in Fig. 21. A piece of platinum 
wire is seen in the center of the plate. A nail is also seen corrod- 
ing at the ends and setting free hydrogen in the center. A second 
nail is connected with a platinum wire. The red of the phenol- 
phthalein is seen around this wire, while the nail is corroding 
very much faster than the unconnected nail. 

"Another example is found in the action of zinc in water 
containing an electrolyte. If a strip of zinc and a piece of iron 
be placed in water containing a very little salt, the iron will cor- 
rode rapidly, while the zinc will be but slightly attacked. The 
usual explanation for this phenomenon is that the zinc protects 
itself with an adherent film of zinc oxide or hydroxide, while the 
iron produces a non-adherent voluminous hydroxide, which does 
not protect. If now instead of being separated the two strips 
of metal be placed so as to touch each other, the iron no longer 
corrodes, but the zinc very rapidly passes into solution. This 
action is shown in Fig. 22. A piece of zinc is seen at the center, 
1 Jour. Iron and Steel Inst., 1909, I. 



corroding slightly from the ends, and showing the red due to 
the separating hydrogen ions at the center. Zinc ferricyanide 
is white, and hence the same reagent demonstrates the separation 
of zinc ions just as it does the iron ions in the plates already con- 
sidered, in which the positive poles are shown in blue. The 
nail which has been connected to another piece of zinc is not 
corroding, but is protected by the separating hydrogen. The 
zinc thus connected, however, is seen to be rapidly dissolving." 

Fig. 21. — A piece of platinum wire is seen in the center of 
the plate. Shows the action of the electro-negative 
metal, platinum, stimulating the corrosion of iron. 

This point which is so beautifully illustrated here has a 
most interesting bearing on the galvanizing problem. It will 
at once be seen that the zinc coating which is applied to steel in 
the galvanizing processes has a double function to fulfil. In 
the first place it is designed to keep the surface of the steel from 
coming into contact with water and the atmosphere, and secondly 
it enacts the heroic role of self-sacrifice to the protection of the 
iron whenever water and oxygen finally succeed in breaking 


through. The practical applications of this theoretical treatment 
of the subject must await detailed presentation in a succeeding 

Walker's next demonstration, as illustrated in Fig. 23, shows 
the opposite tendency at work. In this case a piece of mill-scale 
is shown in the center, and in addition to this the effect produced 

Fig. 22, — A piece of zinc is shown in the center. Shows 
the protective action of the electro-positive metal, zinc, on 
the corrosion of iron. (Walker.) 

by connecting a fragment of mill-scale to a piece of steel. The 
mill-scale, which consists of the magnetic oxide of iron, is electro- 
negative to the iron, and is therefore acting a part directly oppo- 
site to that of the zinc in the preceding illustration. That is to say, 
instead of retarding the corrosion of the iron at its own expense, 
it is stimulating the attack made upon it by the electrolyte. 

These as well as many other observations and experiments, 
based upon the electrolytic theory, have a direct bearing upon 
many of the practical problems met with in the manufacture 
and use of iron and steel. These problems, as they affect the 
resistance to corrosion, will be discussed in the following order: 


(1) Effect of purity and chemical constitution of the metal. 

(2) Effect of heat treatment, annealing, tempering, condition 
of surface, etc. 

(3) Effect of state of purity of the rusting medium, electro- 
lytes, natural water, the atmosphere. 

Fig. 23. — A piece of mill scale is shown in the center. Shows 
the stimulated corrosion of iron affected by contact with the 
electro-negative magnetic oxide of iron. (Walker.) 

Modern Steels seem more Corrodible than the Old. — A mass of 
evidence appears to show that the old slowly fabricated irons of 
thirty years ago are much more resistant to corrosion than modern 
steels. Sang, in summing up from the opinions" of a number of 
authorities, discusses this phase of the subject as follows: 1 

"From a theoretical standpoint, steel, being negative to iron, 
should be the least corrodible of the two. As a general thing, 
results of tests between iron and steel have, in the past, resulted 
in favor of the iron; in most cases, the experimenters were un- 
doubtedly looking for the defeat of the new material, steel, and 
their state of mind helped them to find it. There are, however, 

iProc. Eng. Soc. West. Pa., XXIV, 10, p. 514. 


a large and ever-increasing number of contrary observations 
recorded, especially where the tests have been carried out on a 
large commercial scale, and with qualities of recent manufacture. 
The opinion one is led to form from a careful examination of 
recorded observations is in agreement with that of Ewing Mathe- 
son, 1 namely, that properly protected steel and iron rust to about 
the same extent, the steel doing so more uniformly; this is, of 
course, subject to the variations of structure already referred to, 
and those of chemical composition, especially as regards metallic 
impurities, which will be considered later. 

"A most important paper was presented before the Institute 
of Civil Engineers in 1881 by David Phillips, 2 'On the compara- 
tive endurance of iron and mild steel when exposed to corrosive 
influences 7 ; excellent tables are given, and the general conclu- 
sions favor iron. A distinction must here be made between the 
cast and wrought metal; cast iron will not rust as readily as 
wrought iron, unless the skin is removed, in which case it will 
rust faster. 

"It must be borne in mind, as a limitation to all results ad- 
duced, that while the initial rusting may be greater with either 
material, iron or steel, the rates of progression may be different 
and may bring about a complete reversal in the final result; in 
material which rusted faster at first may outlive the other. This 
is especially apt to be the case with forged, rolled, and drawn 
metals. Future tests should, therefore, either be carried out to 
destruction, as advocated by Howe, or else to the point at which 
failure of the material in service would result from loss of useful 
area." Again in another paragraph Sang 3 very truly says: 

"Carelessness of manufacture, which tends to heterogeneous- 
ness, is an invitation to corrosion, and in itself goes far to explain 
why modern steel, which is tortured into shape at such a high 
speed that the molecules are not permitted to readjust them- 
selves, is said to be more corrodible than the metals produced a 
generation ago; in those days iron and steel were produced in 
small quantities, without the addition of other metals, and were 
rolled slowly and allowed to cool naturally. The internal strains 
due to mechanical treatment are not to be confounded with the 

1 Proc. Inst. C. E., Vol. 69 (1882), p. 1. 
2 Proc. Inst. C. E., Vol. 65 (1881), p. 73. 
3 Proc. Eng. Soc. West. Pa., XXIV, 10, p. 511. 


unevennesses in the distribution of the impurities due to segrega- 
tion in cooling; these mechanically induced strains are really 
equivalent to straining the metal beyond the elastic limit, which, 
as will be seen later, makes it more corrodible. Moreover, the 
tonnage-craze, from which the quality of product in so many 
industries is to-day suffering, is causing to be placed on the market 
a great mass of material, only a small proportion of which is 
properly inspected, which is not in proper condition to do its 
work — rails and axles which fail in service and steel skeletons 
for high buidlings which may carry in them the germs of destruc- 
tion and death." 

Chemical Purity an Aid in Resisting Corrosion. — While wish- 
ing to avoid taking sides in the more or less heated controversy 
that has gone on for many years between the advocates of differ- 
ent types of metal, the authors are of the opinion that, other 
things being equal, the approach to chemical purity, whether the 
metal is classed as iron or steel, should lead to added resistance 
to corrosion. Indeed, it is impossible to accept the electrolytic 
theory without reaching this conclusion, for it follows naturally 
that the presence of impurities invites segregation in the structure 
of the metal with inevitable surface differences of potential and 
stimulated electrolytic action. All authorities who accept the 
electrolytic theory agree on this point. Walker says on this 

"Since before the iron can form rust it must first pass into 
solution, and in so doing cause an electric current to flow from 
the iron at that point to the iron at some other point, any cir- 
cumstance which will aid the flow of this current will accelerate 
the solution of the iron. In other words, any differences in poten- 
tial which may exist upon the surface of the iron will in itself 
cause a flow of electricity which will result in a solvent action on 
the iron. Such differences of potential inevitably result from a 
segregation or uneven distribution of any impurities which the 
iron or steel may contain. /Hence we should expect that the 
speed of corrosion would increase in accordance with the per- 
centage of impurities present, and it should decrease in accord- 
ance with the care bestowed upon the iron or steel during its 
manufacture to prevent a segregation of these impurities. The 
simplest way, of course, to insure an absence of segregation is to 
eliminate altogether those materials not needed in the iron. It 


has been found that a steel made under such conditions that the 
total impurities are reduced to not over five hundredths of 1 per 
cent. (0.05 per cent.) resists corrosion to an extent equal to the 
iron of our forefathers. The steel companies have been slow to 
accept this general proposition, but it is gratifying to know that 
material of this purity may now be obtained on the open market." 

Difficulties Introduced by Improper Heat Treatment, etc. — To 
sum up this phase of the subject we may say that, other things 
being equal, the electrolytic theory points to the fact that the 
purer and least segregated metals should be most resistant to 
corrosion. At the same time it should not be forgotten that it 
is always possible to leave the frying-pan for the fire, and that in 
the effort to arrive at chemical purity in the processes of manu- 
facture the metal may have come to harm by burning, gas occlu- 
sion, or faulty heat treatment. It is also true that in the effort 
to reach chemical purity the physical characteristics may be 
changed, to the damage of the metal produced. Unfortunately, 
analysts do not as a rule consider the question of occluded gas, 
and yet this factor undoubtedly has much to do with resistance 
to corrosion. Sang * has collected a mass of information from 
the literature of the subject bearing on this point. This author 
says, " Occluded gases must next claim attention. Graham found 
that iron cooled in hydrogen absorbed 46 per cent, of its volume. 
John Perry in 1872 2 detected the presence of hydrogen in steeL 
Ledebur found 0.0017 per cent, of hydrogen in a soft open-hearth 
steel. These observations are of interest because, hydrogen 
being negative to iron, it will, as already stated, promote its solu- 
tion and corrosion. The electrolytic activity of hydrogen was 
pointed out by Roberts- Austen. 3 

" According to Lenz, 45 per cent, of the absorbed gases in 
iron may be hydrogen, the balance being carbonic dioxide, car- 
bonic oxide, and nitrogen in about equal proportions. According 
to F. C. G. Muller, 4 about 67.8 to 90.3 per cent, of the gas in steel 
is purely hydrogen. 

"It is a well-known fact that iron or steel containing occluded 
hydrogen, due to pickling in acids, is hardened to a considerable 

i Proc. Eng. Soc. West. Pa., XXIV, 10, p. 504. 

2 Jour. Iron and Steel Inst., Yr. 1872, p. 240. 

3 Fifth Report, Alloys Research Comm., Inst. Mech. Engrs., 1889. 
4 Deuts. Chem. Gesell., Vol. XII (1878), p. 11. 


extent, and is readily oxidized while in that condition; thorough 
washing and neutralizing of the acid will not correct the hardness 
nor the readiness to oxidize. Gas occlusion by this method may, 
normally, reach 12 times the volume of the iron, proving that 
most of it must be alloyed or in a liquid or solid state. The 
greater proportion of this absorbed gas is hydrogen, and it must, 
necessarily, be as impure as that which rises in the pickling vats, 
containing, therefore, hydrogen sulphide, arsenide, etc. 

"On the other hand, electrolytically produced iron, which is 
quite difficult to corrode, is hardened to a considerable extent 
by the absorption of hydrogen during its deposition. The hard- 
ness of electrolytic iron is 5.5 as against 4.5 for ordinary iron. 
According to Cailletet/ electrolytic iron will hold as much as 
250 times its own volume of hydrogen, and the alloy containing 
0.028 per cent, (by weight) of hydrogen will scratch glass. This 
absorbed hydrogen must be relatively pure, and while this may 
preclude electro-chemical activity among the gases themselves, 
it can hardly have much bearing on the difference of behavior 
between it and pickled iron, when exposed to corroding agencies. 

"The hydrogen contained in pickled iron can be almost 
entirely baked out of it at a low temperature ; not so with the 
hydrogen absorbed electrolytically. This tends to show that in 
the pickled iron the gas is not so permanently or stably combined 
— if combined at all — as in electrolytic iron. Furthermore, 
the great volume of the gas taken in by the electrolytic iron 
shows that a very large percentage must exist in solution as an 
alloy with the iron. The coexistence of three states of matter 
has been supported by Graham, Wiedermann, and Spring. While 
there may be just as much free dissociated hydrogen contained 
in the pores of both classes of iron, and the tendency to rust from 
that cause may be the same, yet the larger amount of hydrogen- 
iron alloy in the electrolytic iron may resist corrosion much better 
than iron alone. The quality of resistivity to corrosion is inti- 
mately connected with the rise in electrical conductivity which 
is brought about by the chemical union of hydrogen with metals. 
Hot iron when quenched in water absorbs hydrogen, and Richards 
and Behr 2 have found that the electrode potential was raised by 
0.15 volt, the nature of the gas being apparently the same as that 

1 C. R., Vol. LXXX (1875), p. 319. 

2 T. W. Richards & G. E. Behr Jr., Zeits. Phys. Chem., March 5, 1907. 


which is absorbed in the presence of nascent hydrogen, and there- 
fore by electrolysis. The hydrogen taken up by finely powdered 
iron reduced at a low temperature was not found to affect the 
e.m.f . ; we may infer that the physical conditions attending 
the production of this iron were insufficiently powerful to cause the 
alloying on which the change of e.m.f. seems to depend. Dr. 
Steinmetz finds that electrolytic iron has a very high hysteresis 
loss, but attributes it to occluded nitrogen. 1 

"From an examination of all these facts, it would appear 
that the increase of potential due to the alloyed hydrogen in 
electrolytic iron overcomes the effect, as an electro-negative 
catalyzer or otherwise, of hydrogen in a free ionic state only. In 
all classes of iron the hydrogen exists in both conditions, free 
and combined, just as carbon does in pig iron, but the proportion 
of hydrogen-iron alloy in electrolytic iron is very much greater 
than in the other metals. Hydrogen, like carbon, when present 
in a free state will by contact action promote corrosion; like car- 
bon also, when chemically combined with the iron it will resist 
corrosion, but if the alloy is unevenly distributed the pure iron 
in contact with the alloy will be attacked. 

"According to Roberts-Austen, silicon, manganese, and alu- 
minium prevent the escape of hydrogen from iron; Ledebur 
claims, 2 however, that brittleness after pickling, due to hydrogen, is 
greater if the combined carbon is high, while silicon has the reverse 
effect; he is in accord, therefore, with Troost and Hautefeuille, 3 who 
claim that silicon diminishes absorption. These seemingly oppo- 
site statements may be reconciled by assuming that while silicon 
may reduce the absorption of hydrogen, it will also retard its 
subsequent removal, just as non-conductors which absorb heat 
with great difficulty will, on that very account, retain it the easier. 
Manganese is said 4 to greatly increase the absorption of the gas 
while diminishing that of carbonic oxide, which is, in any case, 
very slight. Manganiferous pig iron retains more gas than does 
ordinary pig. 

1 For u, discussion of the important influence of nitrogen on the physical 
characteristics of steel, see Giesen, The Special Steels 'in Theory and Practice, 
Carnegie Scholarship Memoirs, Iron and Steel Institute, I (1909). See also 
Stromeyer, Jour. Iron and Steel Inst., I (1909). 

2 Mitt. Kon. Tech. Versuchsanstalten, Ber. Yr. 1890. Suppl., I, 1907. 

3 An. Ch. & Ph., 5e S., Vol. VII, p. 1155. 

4 An. Ch. & Ph., 5e S., Vol. VIII, p. 1155. 


"Pressure applied during the solidification of metals — as, 
for instance, in the Whitworth process — prevents the escape of 
the gases. They can be driven out by heating, preferably in 
vacuo, or locally by machining or drilling; the combination is, 
therefore, not a very close one. To drive the gases out of pig 
iron, a temperature of 800° C. is sufficient. Malleable iron con- 
tains more carbonic oxide than hydrogen, and it is retained with 
greater energy. Steel is said to absorb somewhat less than cast 
iron, and wrought iron less than cast iron; these differences are, 
in great measure, no doubt, functions of the porosity. 

" Occluded gases, and especially hydrogen, must not be lost 
sight of when dealing with the problem of corrosion. Hydrogen 
is the lightest, and, therefore, kinetically the most active of ele- 
ments; it is, in a way, a sort of universal catalyzing 'daemon/ 
an extravagant statement to the ear, perhaps, but with some 
merit of suggestiveness; all chemical reactions take place in the 
presence of hydrogen, and it is the only element of which this 
is true. Hydrogen, which seems to form the main ejection from 
the sun, and may be regarded as closest to the primordial element 
from which, according to recent well-grounded theories, all other 
elements may proceed, is unique in many of its properties; it 
seems to stand apart from the other elements in many ways. 
These differences are, in many cases, attributable to the great 
activity of its molecules in proportion to their mass, hence, for 
instance, the distinct character of its curve representing the 
value of pv under different pressures. 

"The diffusion through a finely porous material, which gives 
rise to dissociation, is similar to, if not identical with, osmosis; 
in osmosis the porous membrane causes dissociation resulting in 
chemical effects which are the basis of important reactions, and, 
among others, of organic growth and life. 

"Hydrogen will pass through platinum and red-hot iron. 
(Ste. Claire-Deville) and its ready dissociation, which was demon- 
strated in Winklemann's important study of its diffusion through 
palladium/ suggests a belief in its breakdown, under conditions 
of common occurrence, into free and active atoms, ready to take 
the first opportunity offered of entering into a combination. The 
condition of most common occurrence is, as we have seen, the 
contact of dissimilar substances. The occlusion of free hydrogen 
1 An. Phys. Chem. Wied., Vol. 6, p. 104, and Vol. 8, p. 388. 


in coal-dust, wheat-dust, zinc-dust, and other dusts, will go far 
to account for their detonation by spontaneous oxidation. These 
dusts act in the same way as does spongy platinum on certain 
gases which it ignites by simple contact. A porous material like 
iron or steel should have a similar effect, but its action would be 
slow and progressive instead of sudden; instead of spontaneous 
oxidation we get slow oxidation, rusting. 

"We thus have additional reason to Relieve that free disso- 
ciated hydrogen ions, generated by the electro-chemical action on 
moisture of iron in contact with its impurities or other substances 
exterior to itself, induces by catalytic excitation, or an electrical 
effect of its contact with the iron, the solution of that iron as 
free ferrous ions which unite with free oxygen to form rust." 

It will be seen from the above citations that the occurrence 
of gases in steel is a matter of great importance which has not 
received the attention from manufacturers that it deserves. 
That the resistance to corrosion is influenced by occluded gases 
is highly probable. The authors are glad to take this occasion 
to recommend to manufacturers who are aiming at the produc- 
tion of pure irons, that this subject be given more careful study 
in the future. Baker 1 has recently published a valuable paper 
on gases occluded in steel, with an account of methods for esti- 
mating them. 

The Carbon Constituents of Steel. — It is not the authors' inten- 
tion to include in this work instruction in the metallography of 
steel. For full information on this subject the special works 
should be consulted. In view, however, of the possible influence 
of the carbon compounds in iron on the electrolytic effects which 
are observed, a brief reference to the general substance is here 
included. The microscopic examination of almost any steel when 
properly mounted and prepared will show that the structure is 
not by any means homogeneous, but that it contains recogniza- 
ble constituents. Specimens of pure iron, when properly polished 
and etched, exhibit a peculiar coarse-grained structure under the 
microscope to which the name ferrite has been given. As the 
percentage of carbon rises in steel various peculiar and character- 
istic structures make their appearance, corresponding to certain 
definite compounds, solid solutions, and eutectics. It does not 
follow that all these structures are different substances, as they 

1 Iron and Steel Inst., Carnegie Scholarship Memoirs, Vol. I, 1909. 


may be allotropic modifications or phases of one and the same 
substance. Carbon in steel does not exist in the free state, as it 
does in cast iron, but it combines with iron forming the carbide of 
iron, Fe 3 C. This carbide appears as dark areas of peculiar and 
characteristic appearance to which the name cementite has been 
given, because it occurs abundantly in steel, treated by the cemen- 
tation process. When examined under a high magnification car- 
bon steels show patches that exhibit a pearly luster, owing to a 
finely lamellar structure. This constituent has been called pearl- 
ite, and is now known to consist of a banded structure of cement- 
ite and ferrite, in definite proportions, not being a compound, but 
simply an intimate mixture. There are a number of other con- 
stituents which correspond to different quantities and conditions 
of the combined carbon in hardened steel. To these such names 
as austenite, martensite, troostite, osmondite, and sorbite have 
been given in honor of eminent metallographists. 

Austenite is produced by quenching high carbon steel in ice 
water from a temperature above 1050° C. It is not often met 
with, and is probably of little importance in any discussion on 
corrosive tendency. 

Martensite is defined as the constituent that confers hardness 
on steel. It is characterized by a finely interlaced structure, 
and is found only in hardened steels. 

In regard to troostite and sorbite little is known; they make 
their appearance when steel is subjected to definite quenching 
and tempering processes. Osmondite is a name which has re- 
cently been proposed to define a characteristic transition point 
that occurs in the tempering of quenched steels. 1 

According to Campbell, 2 "Pearlite is an 'eutectic alloy,' a 
term which may possibly not be familiar to all readers. An 
eutectic alloy is formed by the simultaneous crystallization of 
different metals in a liquid mixture, as for example, a mixture of 
copper and silver. These metals form an alloy in the propor- 
tions of 72 per cent, silver and 28 per cent, copper at a tempera- 
ture of 770° C. (1418° P.), and if a melted mixture of these two 
metals contain any different proportion than this, and if it be 
allowed to cool, the element in excess of this proportion crystal- 
lizes out, the crystals remaining uniformly distributed through- 

1 Heyn and Bauer, Jour. Iron and Steel Inst., 1, 112 (1909). 

2 Manufacture and Properties of Iron and Steel, Campbell, p. 298. 


out the molten mass. When the critical point of 770° C. is 
reached, the alloy of 72 silver and 28 copper becomes solid, and 
entrains the innumerable crystals of the excess element which 
have separated from the mother liquid. A little consideration 
will show that under the microscope the element solidifying first 
and the eutectic alloy will occupy areas exactly proportional to 
the original constitution. 

"In steel at high temperatures the same conditions exist as 
in the mass of silver and copper just described, save that the 
elements are in what is called 'solid solution/ martensite at the 
lowest critical point going through a transition into ferrite and 
cementite. The element in excess separates by itself, and when 
the proper relation has been established the ferrite and cementite 
crystallize together in most intimate mixture to form pearlite. 
As stated previously, the excess of cementite or ferrite begins to 
form by itself at the upper critical point, a small amount being 
found in steel quenched just below this, and at the second point 
this amount is increased, but this excess is always small except 
in the case of low carbon steel. 

"The foregoing argument may be summarized as stated by 
Sauveur : 

"(1) All unhardened steels are composed of pearlite alone, 
or of pearlite associated with ferrite or cementite. 

"(2) Without taking into consideration austenite and troos- 
tite, hardened steel is composed of martensite alone, or of mar- 
tensite associated with ferrite or cementite. 

" (3) Ferrite and cementite cannot exist together in the same 
piece of steel. 

" (4) The presence of the lamellar variety of pearlite is almost 
certain proof that the steel has been annealed. 

"Following the proposition that ferrite is iron free from carbon, 
and that cementite is a compound represented by the formula, Fe 3 C, 
it is evident that in very low steels, say ranging from .02 to .10 car- 
bon, the structure will be almost entirely ferrite, and that in steel 
of 2.00 per cent, carbon there will be an excess of cementite. There 
will therefore be one point of carbon content at which the compo- 
nent ferrite and cementite will both be satisfied, which is to say 
that the original proportion will be that of the eutectic alloy. This 
occurs in a pure steel containing about .80 per cent, of carbon, the 
micro-structure of this grade showing no ferrite or cementite." 


Influence of Iron-Carbon Constituents on Corrosion. — The influ- 
ence of the quantity and condition of the contained carbon of a 
steel on the tendency to corrosion opens up a most interesting 
field of inquiry, in which unfortunately the information is meager, 
and to a considerable degree contradictory. A vast amount of 
theorizing has been done on this point alone, and the literature 
of the subject abounds with statements in regard to the influence 
of carbon which are certainly based on insufficient evidence. 
Howe believes in a mechanical protection afforded by carbon 
as rusting proceeds. This authority has stated: 1 

"As steel is gradually corroded away, more and more of its 
surface should come to be composed of cementite, and this fact 
should tend to retard the corrosion of steel, because cementite 
should protect the underlying free iron or ferrite." 

And again: "The cementite is in such extremely minute 
microscopic plates that the eating away of a very small quantity 
of the iron from above them ought to bring very nearly the full 
proportion of this cementite to the surface." 

Sang claims that, 2 "Carbon, insomuch as it will allow harden- 
ing, will act as a protection, provided it is combined with the 
iron and uniformly distributed; high-carbon steel is less corrodible 
than mild steel or iron." 

There can be little doubt that maximum density in steel 
will contribute toward maximum resistance to corrosion provided 
segregation has not taken place, but in the authors' opinion it has 
not yet been proved that the majority of high-carbon steels in 
general use are less corrodible than mild steel or iron. This sub- 
ject can, however, best be discussed under another heading, on 
the effect of heat treatment and tempering. 

It is quite certain that more information is needed on the 
influence of carbon and the iron-carbon constituents on the cor- 
rosion problem. Munroe 3 observed a number of years ago that 
in a case of corrosion of a cold-chisel with a soft shank and hard- 
ened cutting edge, the soft part was eaten away while the hard- 
ened edge had been protected. This observation has been many 
times confirmed until we may feel sure that in some cases soft 
iron (ferrite) is electro-positive to hardened steel (cementite) so 

1 Trans. Am. Soc. Testing Materials, 1906. 

2 Proc. Eng. Soc. West. Pa., XXIV, 10, p. 528. 

3 Jour. Franklin Inst. 1883, 302. 


that in contact in a corroding medium the latter will be protected 
at the expense of the former type. Sauveur states, as quoted 
above, that ferrite and cementite cannot exist together in the 
same piece of steel. This would seem to indicate that differences 
of potential in the same piece of steel would not be occasioned 
from this cause. Sauveur, of course, does not refer to the inti- 
mate mixture of ferrite and cementite known as pearlite, but in 
this case the structure is too definite and intimately mixed to 
lead to local electrolytic couples. 

Possible Effect of Assembling Metals of Varying Carbon Types. 
— The association of steel and iron of different carbon content 
in structural work, is a question of the highest importance which 
has not received as much attention from engineers as it deserves. 
In this connection we may recur to the case already cited of the 
Diamond Shoal Light-vessel, in which in eleven years 8400 four- 
inch iron bolts were destroyed and had to be renewed. 1 In this 
and similar cases the more electro-positive metal is rapidly 
destroyed owing to the stimulated electrolysis, which is induced 
by the coupling of different types of metal. 

Sang treats this subject as follows: 2 "Some tests were made 
in 1882 by J. Farquharson 3 on six plates of iron and six of steel; 
these were immersed for six months in Portsmouth Harbor, six 
of each separately, the other six as connected couples; in this 
way the comparative corrosion of the iron and steel was obtained, 
and also the increase of corrosion due to galvanic action between 
steel and iron. The following table gives the losses observed 
in ounces and grains: 

(a) Steel) in contact (0-427 

Iron [ (7-417 

^ S teel l separate (3-340 

Iron ) l (3-327 

(<) Steel) incontact (0-297 

Iron f (7-770 

(d) EE?}-*"* [tS 

w Ep™ {JS5 

1 See illustration (Fig. 4) and description p. 11. 
a Proc. Eng. Soc. West. Pa., XXIV, 10, p. 520. 
3 Trans. Inst. Nav. Arch., vol. 3 (1882), p. 143. 


(/) ?n ■*— it 


"These results, which were confirmed by Mr. W. Denny, 
from his experience in the case of the steamship Ravenna, are 
interesting to analyze. They show that in two cases only did 
the steel corrode to a greater extent than the iron, but the differ- 
ence is so slight that for all practical purposes it can be said that 
the steel and iron of the experiments (ship-plates) were equally 
affected. They also confirm the theory that the combination 
of steel and iron, which is quite frequent in practice, is detri- 
mental to the iron, but protects the steel which is the negative 
partner. They also throw light on previous observations, and 
lead to the conclusion that good homogeneous iron and steel 
are about equally corrodible." 

Mr. J. P. Snow, Chief Engineer of the Boston and Maine Rail- 
road, has called attention to a very significant case of corrosion in 
connection with the destruction of some railroad signal bridges 
erected in 1894, and removed and scrapped in 1902. These struc- 
tures were built at the time that steel was fast displacing puddled 
iron as bridge material. The result was that the bridges were 
built from stock material which was partly steel and partly 
wrought iron. The particular point of interest in this case lies 
in the fact that while some of the members of the bridge struc- 
tures rusted to the point of destruction in eight years, others 
were in practically as good condition as on the day they were 
erected. This is clearly shown in the illustration, page 8, which 
is from a photograph of these bridge members. The specimen 
shown in the middle has suffered only very slight superficial 
rusting, while those shown on either side have gone to the point 
of destruction. Tests carried on by Snow and examinations made 
by one of us appeared to indicate that the badly rusted parts 
were steel and the unrusted portion wrought iron. On first 
thought this observation would appear to indicate that wrought 
iron was far superior to steel as material for such structures. In 
the light of the electrolytic theory and of the other evidence that 
has been given, it appears highly probable that the steel in this 
case was electro-positive to the iron, which resulted in the pro- 
tection of one metal at the expense of the other. 1 From this 

1 It should be noted that the equilibrium which decides which metal will 
be positive to the other is a delicate one and is determined by a number of 
factors, which may or may not be known. 


point of view the steel is no more to be condemned for having 
failed than the iron for having been the destructive agent. With 
the results of recent investigations to guide them, it is not prob- 
able that engineers will permit the assembling of different types 
of metal in one and the same structure, without first considering 
the probable effect on its life. 

Effect on Corrosion of Other Constituents in Steel. — We have 
now to consider the influence on corrosion of the other usual 
impurities found in steel, such as manganese, phosphorus, sul- 
phur, and silicon. From the standpoint of the electrolytic theory 
there are several reasons why the presence of manganese in steel 
should invite corrosion. Manganese decreases the electrical con- 
ductivity of iron, and as the percentage of manganese, starting 
from zero, rises, the electrical resistance increases up to a certain 
specific maximum. It will be seen that if the presence of man- 
ganese in iron raises the electrical resistance, any variation in 
the distribution of the manganese means that there will not be 
a constant electrical conductivity throughout its mass, or on 
any given surface. There is abundant evidence to show that 
manganese associates itself to a considerable extent with sulphur 
when both these impurities are present in steel. 1 That man- 
ganese sulphide shows a difference of electrical potential against 
iron is also well known. These theoretical reasons which indicate 
that manganese should stimulate the corrosion of steel, provided 
it is not perfectly homogeneously distributed in the iron, appear 
to be justified by a number of reliable observers among whom 
may be mentioned Dudley, 2 Drown, 3 Abel/ and Reynolds. 5 
Huntley 6 deals with the corrosion of boiler steel, and gives 
details of a case of pitting in a boiler. Each pit was found to 
be the center of a blister, and the blister contained a slightly 
acid solution of ferrous sulphate, while the boiler water was 
alkaline with caustic soda. The solid matter in the envelope of 
the blister, which consisted of a mixture of iron oxides, acted as 
a semi-permeable membrane, keeping apart the ferrous sulphate 
within and the caustic soda outside the blister. The theory 
advanced is that the particles of manganese sulphide, segregated 

1 Fay and Howard, Trans. Am. Soc. Testing Mat., 1908, 8, 74. 

2 Trans. Am. Inst. Mining Eng'rs, 1905. Disc. Roe's paper. 

3 Ibid. * Proc. Inst. C. E., 1881. 

b Ibid. 6 Jour. Soc. Chem. Ind., 28, pp. 339-340. 


in the steel, were oxidized by the oxygen dissolved in the boiler 
water to sulphuric acid and an oxide of manganese, the acid then 
acting locally on the surface of the boiler plate in the vicinity 
of the particles of manganese sulphide. The pitting of the boiler 
plate was prevented by adding sodium arsenite to the boiler 
water, the reagent taking up the dissolved oxygen. 

It should be noted that the above discussion refers to man- 
ganese when it occurs as an impurity in steel in amounts not 
exceeding about 1 per cent. Very high manganese steels are 
said to be unusually resistant to corrosion. It must be remem- 
bered, however, that in the latter case we are not dealing with 
steel at all, but with one or more special alloys in which stable 
eutectics are probably formed. These special manganese alloys 
would then fall in line with many others which are very well 
known to be highly resistant to corrosion. Among these resistant 
alloy steels that have been noted we may mention nickel, 1 
chromium, vanadium, tungsten, and silicon. More systematic 
investigation of this subject is needed. 

Phosphorus has been claimed to render iron more resist- 
ant to corrosion, but actual information in the literature of 
the subject is too meager to found an opinion on. Sang 2 says: 
" Phosphorus and silicon both appear to retard corrosion, and 
this effect may, as in the case of carbon, have some connec- 
tion with their hardening qualities, or cold-shortening power. 
If, however, they are present in patches, like the oft-occurring 
phosphide eutectics, the softer parts, through contact action with 
the parts rich in phosphorus and silicon, will be destroyed all 
the more rapidly. Some authors have claimed that these two 
elements increase corrosion, but there is no evidence to support 
the contention apart from the case of uneven distribution which 
will make any of the impurities rust promoters to a greater or 
lesser extent. The fact that common iron does not rust as rap- 
idly as the better grades has been attributed by some to the greater 
percentage of phosphorus in the former." 

Sulphur is usually present in steels in very small quantities, 
and probably affects the rate of corrosion mainly by increasing 
segregation, as in the case of manganese sulphide already cited. 

Silicon in small quantities like manganese may increase 

1 Unger, Proc. Eng. Soc. of West. Pa., 24, 10, 549. 

2 Ibid., page 259. 


the tendency to corrosion. In larger quantities from 10 to 
20 per cent., the solubility in acids as well as the tendency to 
rust is checked. Jouve * has called attention to the fact that 
iron containing 20 per cent, of silicon is not attacked by acids, 
and therefore such material theoretically should not be subject 
to rust. One of the authors has confirmed this deduction by 
experiment, and found that iron containing more than 10 per 
cent, of silicon is almost incorrodible. Unfortunately, such a 
metal is not easily workable and has peculiar properties. Since 
silicon is much like carbon, chemically speaking, it would seem 
as if it might be worked into the surface of steel by modifications 
of some of the processes used for case-hardening with carbon. 

Various Factors ivhich Modify Effect of Impurities. — It will 
be readily understood that even if there were much more data 
available than we have it would be quite impossible to accurately 
state the influence that any given impurity will have upon the 
corrosiveness of iron. Not only will much depend upon the 
quantity, distribution, and condition of the impurity, but the 
balanced effect produced by other impurities is an ever present 
factor in a heterogeneous equilibrium. The discussion and 
citations given in preceding paragraphs have been included only 
inasmuch as they have a bearing on the electrolytic theory of cor- 
rosion. But even as the interior structure of a metal influences its 
tendency to corrode, its use in connection with other types of 
metal in construction work becomes a matter of even greater 
importance. This has been pointed out in regard to iron of vary- 
ing carbon contents. 

Problem of Combining Structural Metals of Different Chemical 
Constitution. — If two metallic elements are joined in a structure 
the more electro-positive one will be corroded rapidly, while the 
more electro-negative will be protected. It therefore follows 
that even if a complete knowledge of the chemical constitution 
and interior structure of a metal was in our hands, unexpected 
results might still be met with under service conditions. A 
case in point is shown by the work of Preuss. 2 

In order to study the influence of electrolysis, a number of 
nickel steel rivets and iron rivets were driven through several 
plates of mild steel, and immersed for two months in a brine 

1 Engineer, 190S, 106, 397. 

2 Iron and Steel Inst., Carnegie Scholarship Memoirs, I, 1909, p. 81. 


corresponding to sea-water. The loss in weight sustained by the 
nickel steel rivets, as compared with the loss sustained by the 
rivets of iron, was in the proportion of 11 to 6. As the nickel 
steel was essentially more uncorrodible than the iron, we see in 
this a reversal of resistibility which only a complete understanding 
of the principles of electrolysis can explain. Sang cites the work 
of Mallet which is interesting in this connection. 1 

"The effects of electrolytic action are clearly demonstrated 
by the results secured by Mallet in a series of experiments which 
he undertook in order to ascertain the 'amount of corrosion in 
equal times in clear sea-water of a unit surface of wrought-iron 
plate, exposed in electro-chemical contact with an equal surface 
of the following metals electro-negative to it, as compared with 
the corrosion of the same surface of the same iron exposed alone 
for the same length of time; 7 

Relative Corrosion 

Iron plate alone 8.63 per cent. 

In contact with: Brass (Cu 2 + Zn) . . . 29.64 

Copper 42.79 

Lead 47.90 

Gun-metal (Bronze). 56.39 

Tin 74.71 

"In connection with the above table, the valuable fact is 
mentioned that the brass alloys of composition, Cu 8 + Zn 17 to 
Cu 8 + Zn 18 , are without galvanic action on iron in sea-water. 
This explains the incorrodibility of the alloy of iron, copper, 
zinc (and sometimes tin), which is known as Delta metal, and 
which, tested in conjunction with wrought iron and steel, showed 
remarkable resistance under test, as follows: 

Wrought Iron Steel Delta Metal 

Loss 45.9 45.45 1.2 per cent. 

"The first copper-zinc alloy for the special purpose of resist- 
ing the action of sea-water was patented in 1832 by Muntz. 
Muntz metal is used for bolts, valves, etc., and for sheathing 
ships; its composition is 2 parts zinc to 3 parts copper. Tobin 
bronze is similar to Delta metal, but contains tin and lead." 

Walker has used the ferroxyl test to give some very pretty 
illustrations of the protection of the electro-negative element 

1 Proc. Eng. Soc. West. Pa., XXIV, 10, p. 521. 


in an electrolytic couple. This is shown in Fig 21, where iron 
is suffering from stimulated corrosion owing to its being in 
connection with the more electro-negative metal platinum, while 
in Fig. 22, the reverse action is taking place, the iron being 
protected by contact with the more electro-positive metal zinc. 
In Fig. 23 the accelerating effect of the electro-negative mill- 
scale or magnetic oxide is shown. 

Conclusions Based on Measurements of Potential Differ- 
ences. — In view of the fact that differences of potential are 
known to exist not only between metals of different types, but 
also on the surface of more or less homogeneous pieces of 
iron, it is natural that a number of experimenters should have 
attempted to measure them. Unfortunately, these attempts 
have led to results of little or no value. As a matter of fact the 
equilibrium is so delicate that the slightest disturbance has an 
influence on the electric potential, which is always subject to 
change owing to more or less obscure causes over which little or 
no control can be exercised. 1 Some experimenters have made 
elaborate series of potential measurements which have led them 
to conclusions, without apparently understanding that the meas- 
urements were in reality nothing but haphazard results, which 
should not be interpreted as leading to definite conclusions. In 
many cases such results have been largely effected by the poten- 
tials of the contact points between the metals under examination 
and the take-off wires of the measuring instruments. Walker's 2 
ingenious method of adapting the potentiometer to the measure- 
ments of potential differences on the surface of iron was published 
some years ago, but this authority has since concluded that even 
these carefully made measurements cannot be used either to 
support or refute the electrolytic theory of corrosion. In the 
hands of nearly all investigators the efforts to establish definite 
polarity between samples of steel of different chemical analysis 
have led to confusing and unintelligible results. In one investi- 
gation which came under the notice of one of the authors, the 
effort was being made to measure the difference of potential 

1 Compare: Punga, Mitteilungen aus dem Material Prufiingsamt zu Gros- 
Lichterfelde West, 1908; See also Prenss, Iron and Steel Inst., Carnegie 
Memoirs 1909, I, 82. 

2 Walker, Cedarholm and Bent. Jour. Am. Chem. Soc, XXIX, 9, 1263 


between two steel wires. One wire contained .50 carbon and .81 
manganese, the other .50 carbon and .40 manganese. These 
were cleaned and polished and after being connected with an 
astatic galvanometer were plunged part way into a very dilute 
acid electrolyte. The galvanometer needle deflected 15° to the 
right, indicating that the low manganese was electro-positive to 
the high manganese wire. In another test of the same samples, 
made after the wires had slightly corroded, the needle deflected 
60° to the left, indicating that now the low manganese was strongly 
electro-negative to the higher manganese wire. In experiments 
made by one of the authors in which steel electrodes have been 
connected with a battery current of very low e.m.f. and amper- 
age and plunged into ferroxyl indicator, blue spots have been 
seen to form underneath the pink envelope on the negative 
electrode. Such an appearance serves as an ocular demonstra- 
tion of the delicacy of the equilibrium since it is thus shown that 
a negative member in an electrolytic couple can develop a super- 
imposed polarity of its own. The same effect can be seen by 
close inspection of Fig. 11, page 53, although in this case the 
pink zones are not being controlled or demarked by an external 
current. In calling attention to these anomalous effects, the 
authors merely wish to suggest that the results obtained from 
delicate measurements of polarity should be used with caution 
in drawing conclusions. 

Effect of Heat Treatment, Tempering, Stresses, Strains, etc. — 
The effect of heat treatment probably has as much to do with 
the resistance tendency to corrosion as any other factor to the 
problem. Under the special caption of heat treatment we may 
include all effects produced by rolling, whether hot or cold, as- 
well as surface stresses and strains. This subject has been 
-investigated by a number of authorities. Andrews 1 has published 
a paper on tests of steel under tensile, torsional, and flexional 
strains, and found that the unstrained parts were electro-positive 
to strained parts. Hambuechen, 2 following more or less closely 
the method of Andrews, arrived at a diametrically opposite result, 
and concluded that the strained metal was electro-positive, and 
hence would corrode more rapidly. Both of these investigations 
were unsatisfactory, and have been criticized by Walker and 

iProc. Inst. C. E. (1894), 355. 

2 Bull. Univ. Wisconsin, Engineering Series 8 (1900). 


Dill. 1 Richards and Behr 2 included some interesting experiments 
upon the effect of strain upon the potential of iron. No definite 
conclusion was reached, but it was clearly indicated that if poten- 
tial differences exist, the equilibrium that governs them is an 
extremely delicate one. Walker and Dill 3 were led to believe that 
although the potential differences were small, the strained metal 
had a slightly less tendency to corrode than the same metal 
unstrained. Burgess 4 has concluded that test pieces that have 
been deformed by straining beyond the elastic limit show a meas- 
urable difference of potential. That the potential equilibrium is a 
delicate one is again indicated by the fact that Burgess's strained 
parts corroded faster than the unstrained. This observation is 
confirmed by a great number of ferroxyl tests in which the 
deformed or strained portion of a specimen is usually electro-posi- 
tive and shows up in blue. It is for this reason that the heads 
and points of wire nails are usually electro-positive to the middle 
portion in ferroxyl tests. This is not invariably the case, how- 
ever, as may be seen in Fig. 10. The exception to the general 
rule only serves to show that strains set up in the cold-drawing 
of the wire from which the nails are fabricated has reversed 
the polarity. 

It appears to the authors that these apparently contradictory 
results arrived at by different experimenters may be best explained 
by the extreme delicacy of the equilibrium which governs the 
polarity. That iron has a definite solution pressure has already 
been shown. If for any reason, however obscure, the solution 
tension is to any extent greater at one point on a given surface 
than at another, that point will be to some extent electro-positive 
to the other. Whether these points retain the polarity or whether 
' it is actually reversed depends upon the nature of the given case, 
in which determinative causes may be at work which it is impos- 
sible to predicate. 

Sang 5 makes the following observations in reference to this 
subject: "Some years ago Witkowski found that in a strained 

1 Proc. Am. Soc. Testing Materials, VII, 230. 

2 Publications Carnegie Institution, Washington .(1906). 

3 hoc. cit., p. 237. 

4 Trans. Am. Elec. Chem. Soc, 1908.- 

6 Proc. Eng. Soc. West. Pa., XXIV, 10, p. 513. 
Trans. Roy. Soc. Edin., vol. XXX (1881), p. 413. 


metal there is an increase of electrical resistance in the direction 
of the strain. All these observations go to prove the claim that 
mechanical treatment, by setting up uneven strains in different 
parts of finished pieces, will create variations of potential which 
will promote rusting. Whatever the composition of the different 
inner parts of the metal may be, and apart from any action 
which may be due to difference of composition, if there is a differ- 
ence of molecular aggregation, it will promote the rusting of one 
or other of those parts. Action, power, everything knowable, 
depends on difference of potential, and any chemical or physical 
difference between two portions of matter in contact must give 
rise to a difference of potential and a flow of electricity. 

"If straining a metal below its elastic limit by exteriorly 
applied mechanical means will make it electro-negative to the 
same metal unstrained, the strains set up by chilling or hardening 
should have a like effect; the metal should resist corrosion to a 
greater extent and promote the corrosion of more positive metals 
in contact with it. This is found to be the case. Eighty years 
ago Daniel observed that a certain steel was dissolved by hydro- 
chloric acid five times as rapidly when unhardened as when hard- 
ened; this is an indication of what we may expect with the agents 
of corrosion. What becomes of the energy of a coiled watch 
spring when it is dissolved in acid? This is supposed to be one of 
the many unsolved mysteries of science. The energy of the coiled 
watch spring is indicated by a slight shift of its potential towards 
the negative end of the electro-chemical scale, resulting in an 
increase of e.m.f . ; when the spring is put in acid, the energy is 
expended in retarding the action of the acid, and is equivalent to 
a drop of temperature which would restrain chemical action. The 
energy of the spring, as increased e.m.f., counteracts the energy 
of the acid, is expended and disappears as work of a negative 

Relative Stability and Solubility of Strained and Annealed 
Metals. — A most interesting paper by Heyn and Bauer 1 on the 
influence of heat treatment on the solubility of steel in sulphuric 
acid throws much light on the effect of such treatment on the 
resistance character and stability of steels. This paper should 
be carefully studied by all who are interested in the manufacture 
of rust-resistant steel, for it very clearly shows the relative sta- 
1 Jour. Iron and Steel Inst., 1, May, 1909. 


bility of strained and annealed metals. In view of the importance 
of this work and its direct bearing on the subject under discussion, 
the following citations from these authors are worthy of record. 

"In the experiments a tool steel with the following com- 
position was first used: 

Per cent. 

Carbon 0.95 

Silicon 0.35 

Manganese 0.17 

Phosphorus .- 0.012 

Sulphur - 0.024 

It was in the form of a square forged bar of a cross-section 
25 X 25 millimeters. From this bar sections of a thickness of 6 
millimeters were cut and subjected to the following treatment: 

(a) Heated to 900° C, and quenched in water at 14° to 18° C, untreated 







(h) In the original forged state. 

(i) Heated to 900° C. and allowed to cool slowly. 

reheated at 100° C. 

at 200° C. 
at 275° to 305° C. 
at 405° to 415° C. 

at 500° C. 
at 600° to 640° C. 

"The high quenching temperature of 900° C. was chosen for 
the reason that with a small test-piece pure martensite is obtained 
by quenching in cold water and observing the necessary precau- 
tions. At lower temperatures those constituents indicating the 
transition to troostite occur in addition to martensite, and mark 
the observation. After the treatment as described above, the 
sections of an area of 25 X 25 millimeters were polished and 
immersed with the polished surface uppermost in 1 per cent, sul- 
phuric acid. The weight before immersion, and the loss in weight 
at the end of twenty-four, forty-eight, and seventy-two hours 
respectively, were determined. In Fig. 24 the tempering tem- 
peratures are taken as abscissae and the respective losses in weight 
as ordinates. 1 The letters attached to the ordinates refer to 
the kind of treatment given in the foregoing table. For the sake 

1 For more detailed information see E. Heyn and O. Bauer, "On the 
Structure of Quenched and Tempered Tool-steel," etc. (Communications 
of Royal Inst, for Testing Materials at Gross-Lichterfelde, 1906, p. 29.) 



of clearness the separate values are omitted, and only the average 
values of several experiments are given. 

"The shape of the curve in Fig. 24 reveals some startling 
features. According to the opinions hitherto prevailing, and still 
held by some, the transition of the martensite of hardened steel 
into the pearlite of annealed steel is continuous throughout the 
intermediate states of tempering. This would lead one to sup- 
















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400 500 600 



Fig. 24. — Tool steel in various states of heat-treatment. Solubility in 
one per cent, sulphuric acid. (Heyn and Bauer.) 

pose that the curve of solubility in dilute sulphuric acid, instead 
of showing any sharply denned peaks, would form a line indi- 
cating the gradual transition from the solubility of martensite 
to that of pearlite. The curve, however, runs up to a sharply 
defined maximum at a temperature of 400° C. The simplest 
and most obvious explanation of this phenomenon is as follows: 
The transition of the martensite from the unstable phase below 
700° C. into the stable phase of pearlite, due to tempering, does 
not proceed directly, but indirectly through an intermediate 


metastable form, to which the name osmondite has been given 
by the authors in honor of the celebrated investigator Osmond. 
Osmondite is the most soluble of all the forms intermediate 
between martensite and pearlite. As the tempering temperature 
gradually increases, the martensite first gradually changes into 
osmondite, until at 400° C. the whole mass consists of this alone. 
In order to prevent confusion in nomenclature, the term troostite 
has been hitherto retained by the authors for the designation of 
the intermediate states between martensite and osmondite, and 
for the stages intermediate between osmondite and pearlite they 
have continued to use the term sorbite. If the tempering tem- 
perature is raised above 400° .C. there again occurs a gradual 
transition from the readily soluble osmondite to the less easily 
soluble pearlite. Such transitions from a preliminary condition 
to a stable final condition, through one or more less stable inter- 
mediate conditions, are of not infrequent occurrence in physical 
and chemical processes. As an instance may be mentioned the 
combustion of hydrogen, which, according to Nernst, 1 is not 
burnt direct to water, but proceeds indirectly through the medium 
of the less stable peroxide. 

"Another remarkable point in Fig. 24 is the lowest value for 
the solubility at a tempering temperature of 100° C, which differs 
little from that of untempered steel. The variation lies, however, 
within the margin of error for the process, so that whether still 
another metastable intermediate form occurs is not yet proved." 

Similar work carried out on a sample of pure mild steel is 
recorded by Heyn and Bauer as follows: 

" The Influence of Quenching and Reheating Soft Mild Steel 
upon its Solubility. 

"For the experiments a very low carbon mild steel was 
used, of the following composition: 

Per Cent. 

Carbon 0.07 

Silicon 0.06 

Manganese 0.10 

Phosphorus 0.01 

Sulphur 0.019 

Copper 0.015 

The material was in the form of a rolled square bar 25 X 25 milli- 
1 Zeitschrift fur Elktrochemie, 1905, Vol. II, p. 713. 



meters in cross-section. From this bar were cut transverse sec- 
tions 23 X 23 X 6 millimeters, which were polished bright on 
an emery wheel. Near one corner a hole was bored, by which 
the small plates were suspended on glass hooks in the dilute 
sulphuric acid. 

"The test-pieces were quenched from a temperature of 1000° 
to 1030° C, since mild low carbon steel first becomes homogeneous 







t^0. 2 



• Series 1. of Experiments 
1 1 



o Series 2 of Experiments 


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^V o 


At End of 

72 Hours 









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At End of 48 Hours 


° ^^^ '■ 

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'i ,-^" < 



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rH r 1 


300 400 500 600 



Fig. 25. — Mild steel, carbon .07 per cent., quenched at 1000 degrees to 
1030 degrees centigrade in water at 18 degrees centigrade; tempered for 
two hours at if) degrees centigrade. (Heyn and Bauer.) 

from 900° upwards. The duration of reheating was two hours, 
and it was effected at the temperatures t given in Fig. 25. As a 
rule, at the end of the two hours the specimens at t° were quenched 
in water for the purpose of suddenly interrupting the tempering 
effect. Only the specimens reheated at 700° were first cooled 
slowly to 690°, that is, below the critical temperature 700°, and 


then quenched, otherwise a new quenching effect would have 
been added. The samples reheated at 900° were cooled quite 
slowly to the temperature of the room. 

"The loss in weight in 1 per cent, sulphuric acid was deter- 
mined in two series of experiments (I and II) , which were carried 
out independently of one another. The Roman numerals against 
the numbers of the test-pieces in the table indicate to which 
series the particular experiment belongs. 

"The test-pieces were suspended by means of glass hooks on 
glass rods, the hooks being passed through the holes. They 
were entirely immersed in the acid without being in contact 
with each other. The quantity of attacking liquid was 2500 
cubic centimeters for every ten to eleven test-pieces. The fol- 
lowing are the numbers of the test-pieces which were placed 
together in the respective vessels: 

Series I. — Test-pieces 

Vessel A Nos. 1, 3, 5, 7, 9, 11, 13, 15, 17, 52 

Vessel B Nos. 2, 4, 6, 8, 10, 12, 13, 16, 18, 53 

Series II. — Test-pieces 

Vessel A Nos. 19, 22, 27, 30, 38, 41, 44, 54, 57, 60, 62 

Vessel B Nos. 20, 23, 28, 34, 35, 39, 42, 50, 55, 58, 63 

The two series of experiments I and II were undertaken at differ- 
ent times. In each series the test-pieces in both vessels A and B 
were exposed to the action of the acid at the same time and in 
the same room. The results of the two series are, however, not 
immediately comparable, because the temperatures were not 
observed; nevertheless they have been amalgamated for the sake 
of clearness in Fig. 25. The losses in weight, in grams, at the 
end of twenty-four, forty-eight, and seventy-two hours' immer- 
sion in the acid, have been entered in the diagram. In the curve 
the points relating to Series I are marked thus, #, and those 
relating to Series II, thus O. The tempering heats are taken as 
abscissae, and the losses in weight as ordinates. 

"A maximum degree of solubility is plainly noticeable between 
the reheating temperatures 300° and 400°, which again corre- 
spond to osmondite. Thus this intermediate constituent, even 
with so low a carbon content as 0.07 per cent., still shows its 
special characteristic of greatest susceptibility to attack by the 
acid. "On comparing Fig. 25 with Fig. 24, it will be observed 



that in the case of the hard steel the solubility of the test-piece, 
with a degree of temper = (martensite), is lower than that 
of the slowly cooled steel with degree of temper = 1 (pearlite). 
With the mild steel, on the other hand, the solubility of the 
untempered test-piece is greater than that of the fully annealed 
one. This is no matter for surprise, since it is not possible with 
mild low carbon steel, however suddenly quite small samples 
may be quenched, to obtain martensite — that is, the degree 
of temper = 0." 

Influence of Wire-drawing and Subsequent Annealing. — The 
work of Heyn and Bauer on the influence of wire-drawing and 
subsequent annealing is particularly suggestive. For the details 
of this work the original should be referred to. Some of the 
conclusions reached are as follows: 

"1. By cold-drawing the wire, the solubility of the mild steel 
is increased. It rises rapidly until the ratio of elongation N = 4 
is reached, but drawing beyond that point produces compara- 
tively little further increase of the solubility. 




Fig. 26. — Influence of heating- on the solubility of cold-drawn, hard wire. 
(Heyn and Bauer.) 

"2. In the case of the harder wire, the curves of relative 
solubility for the different periods of attack lie nearer to each 
other than those of the softer wire, as may be seen from a 
comparison of Figs. 26 and 27. This means that the relative 


loss of weight of the softer material is less during the first 
period of attack than that of the harder material, but that 
as the period of attack is prolonged, the loss of weight increases 
more rapidly in the softer than in the harder steel wire. 

Fig. 27. — Influence of heating on the solubility of cold-drawn, soft wire. 
(Heyn and Bauer.) 

"3. After annealing the wires drawn from the same mild 
steel material, the degree of solubility is immediately no longer 
affected by the cold-drawing of the wire, however far this may 
have been carried. Wire-drawing, therefore, produces no change 
in the material which cannot be removed by annealing. 

"4. The heating of the cold-drawn wire involves a decrease 
in the degree of solubility (Figs. 26 and 27). The decrease in 
solubility is plainly noticeable even after heating to 100°." 

Cold-working Increases Solubility of Mild Steel. — The solu- 
bility of mild steel is shown to be increased by cold-working, 
irrespective of whether the cold-working has been effected by 
stretching or compression. Part of this effect is shown in Fig. 28. 
The investigators considered the solubility of iron from the electro- 
chemical point of view, and are led to assume that iron exists in 
some allotropic form induced by cold-drawing. They say: 

"It has to be further investigated whether iron, with reference 
to the increase of its solubility by cold-working, occupies an 
exceptional position with respect to all other metals, or whether 
there are other metals which behave in the same manner. If 
the former is the case, then the increase in solubility of cold- 
worked iron can only be attributed to the presence of a more 
readily soluble allotropic form of the iron, which is produced 
by cold-working. 



"Since the degree of cold-working does not require to be the same 
in all parts of the cold-drawn wire, one might then expect to find 
at different parts of it different quantities of the more soluble 
modification of the iron. This would explain why the surface 
of the drawn wire, on being subjected to the solubility test, 
becomes roughened, while the same wire after annealing preserves 
its smooth surface under the acid attack. The difference in the 
solubility might be accentuated if the galvanic effect differed of the 
parts subjected to varying degrees of cold-working. Investigations 
upon the electric potentials of cold-drawn and annealed wire in 

t 500 


5$ 3 

> w 



uj O 




Hours Att 





2 4 6 


Fig 28. — Influence of cold-drawing on the solubility 
of mild steel wire. (Heyn and Bauer.) 

contact with acid and solutions containing Fe ions were not 
undertaken by the authors. On the other hand, the differences 
of potential in distilled water were measured, and were found to 
be considerable, as appears from Fig. 29. 

It cannot, however, be concluded from these figures that the 
potentials peculiar to the cold-drawn and annealed wire neces- 
sarily differ from each other, since what is measured in water 
is not the actual potential of the iron, but the potential of an 
oxygen electrode formed on the iron, which certainly does differ 
considerably as between cold-drawn wire and annealed wire. 
The oxygen electrode formed on the cold-drawn wire appears 
more electro-positive than that on the annealed wire, which 


indicates that during the experiments the drawn wire consumed 
more oxygen, that is, it rusted sooner than the annealed wire. 1 









Fig. 29. — Electric potential drop between a cold-drawn hard wire 
and the same wire after annealing. Measured in distilled waters 
at 17 to 18 degrees C. The cold-drawn wire is poorer in quality 
than the annealed. (Heyn and Bauer.) 

"Pairs of wires were prepared as follows: Apiece of wire 100 
millimeters long in the original cold-drawn state marked u was 


Fig. 30. — Pairs of wires connected together for 
rusting test. (Heyn and Bauer.) 

attached as shown in Fig. 30, by means of platinum wire to 
another piece of wire marked g, annealed for half an hour at 900° C. 

1 E. Heyn and O. Bauer. "Uber den Angriff des Eisens, etc." "Mit- 
teilungen aus dem Koniglichen Materialprufungsamtes." Gross-Lichterfelde, 
Nos. 1 and 2, 1908. 


These pairs were supported at their free ends on glass rods, and 
completely immersed in distilled water of about the warmth of 
the room. At the end of twenty-two and forty-nine days the 
losses in weight of the single wires due to rusting were ascertained, 
and in all cases it was found that the cold-drawn annealed wire 
was more strongly attacked than the annealed wire, the propor- 
tion being from 103: 100 to 108: 100. Whether this proportion 
remains unaltered or is reversed under a long exposure is not yet 
determined, but such a possibility is by no means precluded. 

"100-millimeter lengths of the 'same kind of steel wires were 
then attached together in pairs in the same manner in order to see 
whether the attack on iron by dilute sulphuric acid (1 per cent.) 
was affected when cold-drawn and annealed wires were in metal- 
lic contact with each other. It appears that the strength of 
the sulphuric acid attack on the cold-drawn wire is increased by 
1.19 to 3.3 times. Therefore if the degree of cold-working differs 
in different places in the same wire, the wire will be attacked 
unevenly, owing to the contact of the unequally worked parts, 
and moreover the attack on the most heavily worked will proceed 
quickest. This is the explanation of the furrow and rough- 
nesses on the surface of the drawn wires after an acid attack, 
and the smooth nature of the surfaces of the wire annealed before 

"On the basis of the foregoing considerations on elastic and 
plastic change of form, the state of a cold-drawn wire might be 
compared with that of a structure produced in the following 
manner. Imagine a pressure cylinder filled with a thick fluid 
mass, for instance, pitch, and that mixed with this is a great 
number of small cylindrical helical springs. Pressure is then 
applied to the mixture, and it is forced out of the cylinder through 
a round hole. The pitch undergoes a purely plastic change of 
form, but the helical springs suffer an elastic change of form. 
As soon as the pressure from outside the mold ceases the springs 
have the tendency to return to their state of equilibrium, that 
is, to their unstrained state, but they are partly prevented by 
the mass of pitch surrounding them. Consequently they remain 
partially under stress, and the amount of this stress may vary in 
different parts of the mass. If one can imagine a similar condi- 
tion with respect to cold-drawn wire, it is intelligible why the 
amount of the elastic stresses varies so greatly at different parts." 


The Acid Test as a Measure of Corrosion Resistance. — This 
interesting discussion opens up the important question of the 
use of an acid test as a measure of corrosion resistance. This 
test has been much used by some manufacturers who believe it 
to be reliable as an accelerated method for measuring the sta- 
bility and hence the corrosion resistance of their products. The 
applicability of the acid test is absolutely denied by some author- 
ities/ and is treated with caution by others. 2 Committee U of 
the American Society for Testing Materials has reported that the 
acid test should not be used to decide the relative resistance to 
corrosion of different types of iron and steel, but since it seemed 
necessary that investigators should use the test in the same way, 
the following tentative suggestions for carrying it out were made : 

Samples to be tested are first stamped with suitable marks 
for identification, and are then accurately machined to a standard 
size, 2 inches in length, I inch in width, and -±q inch in thickness. 

The samples should be cut longitudinally in the direction in 
which the metal was rolled. A hole J inch in diameter is drilled 
in each sample about 1 inch from one of the ends. 

Samples are polished first with No. 00 emery paper, and 
finally with flour emery. The polishing should be done as much 
as possible, so that the polish marks run at right angles to the 
direction in which the metal was rolled. After polishing, the 
test pieces should not be handled with the fingers or allowed to 
come in contact with dirt or grease of any kind. 

The test-pieces should then be weighed carefully to four deci- 
mal places on a chemical balance, and are then strung on a glass 
rod with a double reverse right-angle bend at each end, which 
will allow the pieces to be suspended in a relatively large beaker 
or other suitable dish, so that their upper edges will be submerged 
to i inch below the surface of the liquid. The glass rod should 
be only slightly less than i inch in diameter, and the distance 
between any two adjacent test-pieces when suspended in the 
acid should not be less than i inch. 

The acid should be exactly 20 per cent. H 2 S0 4 (1.144 specific 
gravity at 15° C). 

The test-pieces are immersed in this acid for one hour, an 
approximately sustained temperature of 15° C. being maintained 

1 Saniter, Jour. Iron and Steel Inst., LXXIX (1909), p. 98. 

2 Speller, Proc.Eng. Soc. West. Pa., 24, 10, 541, Jan. 1909. Sang., Ibid. 


by any suitable cooling device, such as a large outside container 
of cold water. 

At the end of exactly one hour's immersion the test-pieces 
are quickly removed from the acid, well rinsed with running 
water, wiped as dry as possible and kept for one hour in a desic- 
cator over sulphuric acid before weighing. 

The results should be recorded as actual and not as percentage 

Note 1. — It has been shown that the corrosion of the sample is 
not directly proportional to the area exposed. Hence it is essential 
in making comparative tests that a standard size be adopted. 

Note 2. — Should the samples for investigation be less than 
tV inch in thickness, the other dimensions should be adhered to 
as closely as possible. 

Note 3. — The physical condition of the surface of the sample 
is found to materially affect the rapidity of its solution. It is 
therefore desirable to finish all samples in the same way. 

Note 4. — The strength of sulphuric acid chosen is that 
concentration which contains approximately the maximum num- 
ber of hydrogen ions, and which experiments have shown to be 
the most suitable. 

Note 5. — It is necessary that the samples be suspended in 
a reasonably large body of acid in order that the ferrous sulphate 
formed by the reaction may sink to the bottom or be otherwise dissi- 
pated through the solution, so that the concentration of the acid in 
the immediate vicinity of the samples be not materially changed. 

Note 6. — The greatest care should be taken to employ only 
chemically pure sulphuric acid. It has been shown that very 
minute traces of arsenic, for example, seriously retard the rapidity 
with which iron is dissolved. 

The Relation between the Acid Test and Resistance to Corrosion. 
— The authors of this work are not willing to state that the sta- 
bility of a steel as measured by an acid test bears no relation to 
its long-time resistance to corrosion. Nevertheless the test has 
not shown itself reliable when used to distinguish between the 
rust-resistant qualities of samples of different types of iron and 
steel. The authors are in complete agreement with the following 
opinion of Heyn and Bauer: 1 

"It is quite apparent that the chemical composition of iron 
1 Jour. Iron and Steel Inst., 1, 1909, p. 185. 


must considerably affect the solubility in dilute sulphuric acid, 
and that the influence of the composition may equal or exceed 
in magnitude the influence described in the previous sections. 
It must therefore again be specially emphasized that the com- 
parative tests of which particulars have been given only apply 
as regards their results, subject to the elimination of the influence 
of the chemical composition as an unknown variable. The whole 
of the solubility tests lead to relative results only, and the abso- 
lute degree of solubility has no special value. Only the relative 
values of the solubilities of the same material in various states 
of treatment are to be regarded as useful in throwing light upon 
the present state of the metal. But it is unsafe to draw from the 
behavior of one metal conclusions as to the behavior of another, 
even though their chemical compositions may be very similar, since 
it is always possible that such substances as are not determined in 
the course of analysis exercise an effect upon the solubility." 

To the above may be added the now well-known fact that 
very slight amounts of certain impurities in the acid used produce 
wide variations in the quantity of iron dissolved in unit time. 
Very small quantities of arsenic contained as an impurity in the 
acid will check the solubility of iron to an extraordinary degree, 1 
and this is probably true of many other sometimes unknown and 
unsuspected impurities. This fact is readily accounted for by 
the electro-chemical theory of corrosion. As has been previously 
explained, corrosion is a surface action and solution in acid 
depends upon the rapid depolarization and disengagement of 
hydrogen from the surface. This depolarization is easily affected 
one way or the other by impurities in the metal, and also in the elec- 
trolyte which provides the attack. It is not to be expected that 
the rapid attack furnished by a dilute acid will be comparable 
to the slow rusting of iron under the conditions of service. In 
the former case depolarization and solution go on rapidly, whereas 
in the latter case the difference of potential between positive 
and negative points and nodes on the surface is stubbornly main- 
tained for long periods of time. Unfortunately the same con- 
siderations must apply to all the acceleration tests that have 
been proposed and used by engineers and metallurgists, such as 
aerated brines and natural waters through which air and car- 
bonic acid are bubbled. 

1 Burgess, Electro-Chem. and Met. Ind., IV, 384. 


Probably No Reliable Acceleration Test Possible. — Owing to 
the nature of corrosion it is probably true that no perfectly 
reliable acceleration test for corrosion resistance can be devised. 
Corrosion, in the natural process of rust formation, that is to 
say, in very slightly acid media, is a question of comparatively 
slow growth under special conditions, and any effort to hasten 
the action changes all the conditions of equilibrium, producing 
an entirely different order of phenomena. 

Nevertheless, evidence has been brought out in the preceding 
paragraph to show that stresses and strains as the result of cold 
rolling or imperfect annealing of steel will affect not only the 
degree of solubility in acid, but also the tendency to maintain 
differences of surface potential affecting the rapidity of corrosion. 
In view of this it is probable that when its limitations are under- 
stood and its results properly interpreted, the acid test will be 
useful in the hands of competent investigators. 

Efficient Annealing Essential to a Rust-Resistant Metal. — A 
careful reading of the preceding paragraphs should show that in 
order to produce the most rust-resistant steel, it is not sufficient to 
work towards purity of the metal and homogeneous structure, 
but also efficient annealing as the last stage in the preparation 
of the product is absolutely essential. Recent work would appear 
to show that the annealing temperature necessary to remove the 
stressed condition is not high, provided sufficient time is allowed 
for equilibrium to be reached.. 

Effect of the Rusting Medium, Electrolytes, Natural Waters, etc. 
— In regard to two points all investigators are agreed, and as 
these furnish some common ground it is interesting to record 
them. Iron cannot rust in air or oxygen unless water is present, 
and on the other hand it cannot rust in water unless oxygen is 
present. The products of the combustion of coal, consisting, as 
they do, largely of carbonic and sulphurous acids, aggravate the 
corrosion problem for railway engineers, and in the neighborhood 
of large cities. It follows from what has been written in the 
previous paragraphs that any acid in the atmosphere or the water 
by which iron is environed will increase corrosion. In very damp 
climates the conditions are aggravated, and on the Isthmus of 
Panama they are said to be particularly bad. Natural waters 
do not all behave in the same way, some making a much more 
rapid attack on iron and steel than others. Sea-water, as is well 


known, stimulates corrosion, as do also all acid mine waters. 
These results are easily explained by the electrolytic theory of 
corrosion. Provided that the dissolved ions do not actually 
inhibit the action, all dissolved salts which increase the electrical 
conductivity of the medium result in stimulated galvanic action 
and supply hydrogen ions. In some cases, however, it has been 
noted that brackish waters from rivers in which sewage flows is 
less active in promoting the pitting of boiler tubes than much 
purer waters. This fact merely serves to emphasize the conclu- 
sion that the speed of the action is functioned by the electroytic 
solution pressure of the iron, and that in some cases the effect 
of dissolved impurities may be inhibitive instead of stimulative. 

Highly Alkaline Solutions Prohibit Corrosion. — Iron does not 
rust in alkaline solutions which contain an excess of hydroxyl ions, 
that is to say, if the alkalinity is high enough, but in dilute alkaline 
solutions rusting goes on in a dangerous fashion, the tendency to pit 
being accentuated. This action is incompatible with the theory 
that free acid is necessary to induce rusting, but is explained by 
the electro-chemical theory. Hydrogen and hydroxyl ions can exist 
in a solution at the same time to a considerable extent only when 
they are separated or held apart by potential differences, and there- 
fore in the rusting of iron the concentration of hydroxyl ions, or, 
in other words, the alkalinity, must reach a certain value before 
rusting is entirely prohibited. This is because, owing to the very 
slight dissociation of water, an excess of hydroxyl ions would be 
incompatible with the presence of free hydrogen ions. 1 

Natural Waters May Contain Inhibitive Impurities. — In addir 
tion to hydroxyl ions there are many other impurities that may 
exist in natural waters to inhibit corrosion. It has already been 
stated that iron cannot rust in water unless oxygen is present, 
for although the first cause of corrosion is due to the electrolytic 
exchange between iron and the hydrogen ions, the presence of 
oxygen is absolutely necessary for the action to proceed. Walker 
develops the point as follows : 2 

1 After this paragraph was written the authors' attention was called to 
the fact that iron has a considerable solution tension in strong boiling alkaline 
solutions, but in such a case the equilibrium is reversed and the metal acts 
the part of a negative radical in conjunction with oxygen. This point is at 
present being investigated. Sec also Zincite, Chem. Zeit., 12, 355. 

-Trans. Am. Electro. -Chem. Soc, XIV, 175 (1908). 


"Since oxygen is necessary to insure the continuous removal 
of the hydrogen film, it is obvious that if no oxygen be allowed 
to reach the iron through the water, no corrosion can take place. 
This fact teaches us much regarding the corrosion of boiler shells 
and tubes. Pitting may be entirely avoided if the air be removed 
from the free water before its introduction into the boiler. This 
may best be done by the employment of an open feed-water heater, 
or, what is better still, a feed-water heater connected to the dry 
vacuum pumps of the condenser. If such treatment is not pos- 
sible, the air may be removed from the feed water by drawing 
the water through a closed box containing scrap iron; the oxygen 
in the water is used up in corroding the scrap iron instead of the 
boiler tubes. Or, the oxygen in the water may be absorbed by 
feeding into the boiler with the water a very small quantity of 
an alkaline solution of a tannin material. Such a solution of 
alkaline tannate will break up under the pressure and tempera- 
ture of the boiler, with the formation of a pyrogallate of the 
alkali, and this rapidly absorbs the oxygen. Soda ash, or rather 
alkali, is of course useful, but not because of its effect upon the 
oxygen content, but because, as has already been explained, 
corrosion is inhibited by thus decreasing the hydrogen ion con- 
centration of the water." 

Dissolved Oxygen a Stimulator. — A theory must inevitably 
be judged according to whether or not it furnishes a satisfactory 
explanation of observed facts. A subject so complex as the 
corrosion of iron furnishes many examples of recorded facts that 
appear on first thought to completely contradict each other in 
the light of the electrolytic theory. Such discrepancies, however, 
usually find a rational and simple explanation. The particular 
point under discussion furnishes a good example of just such a 
case. On first thought it would be assumed that the purer the 
water and the lower the electrical conductivity, the less will be 
the tendency to rapid corrosion. If it were possible to deal only 
with absolutely pure waters, this conclusion would undoubtedly 
be justified. Natural waters are, however, only more or less 
pure, so that the conditions necessary for corrosion to take place 
are always present, as far as this factor alone is concerned. When 
we further consider, however, that dissolved oxygen is a necessary 
and important factor in the corrosion problem, we get new light 
on the subject. Every sanitary engineer knows that the measure 


of dissolved oxygen is a strong indication of the purity of a water 
supply. In sewage-laden natural waters, dissolved oxygen does 
not exist to any great extent, as the oxygen is fixed in oxidizing 
the organic matter present. The fact that certain impure waters 
have been found to be excellent boiler waters, thus finds a simple 
explanation under the electrolytic theory. It would not, of course, 
be safe to conclude that contaminated waters are less corrosive 
than pure waters, for this is far from being the truth. If two 
forces are present at the same time, acting in opposite directions, 
and if these forces are unknown and variable, it is impossible to 
tell what the resultant will be except by experiment under all 
the possible conditions. In the case in point, the impurity of 
the water should tend to increase the electrolytic action, but the 
absence of dissolved oxygen counteracts this tendency. 

Relative Corrosion in Fresh Water and in Sewage. — In con- 
nection with what has been said above, Howe and Lodge's 1 
exposure tests on wrought and cast iron plates are most interest- 
ing. These tests were carried out for the purpose of studying 
the efficiency of various protective coatings, but incidentally 
they serve to show the relative amount of corrosion which took 
place in fresh water and sewage. 

Loss of Weight of Wrought and Cast Iron with Different Pro- 
tective Coatings and under Different Conditions, in Pounds 
per Square Foot of Surface per Annum. 

Wrought-Iron Sheets (No. 32 Gauge, Black.) 

Protective Coatings 

Exposed to the Weather 


Immersed in — 



New York 

Fresh Water 






gain, .002.0 

gain, .000.4 

gain, .000.3 






Black, i.e. unprotected 









^owe, Metallurgy of Steel, 2d Ed. I, 372. 



Cast-Iron Plates. 

Protective Coatings 

Exposed to the Weather 

Immersed in — 



New York 

Fresh Water 



"& paraffined 

gain, .004.0 

gain, .003.1 

gain, .003.1 

gain, .005.5 


gain, .002.8 





Black, i.e. unprotected 

gain, .003.4 
" .004.0 
" .006.3 




gain, .002.9 





A single sheet of No. 23-gaged refined wrought iron was cut 
into plates 6 in. by 12 in., and others 6 in. by 6 in. Of the 6 in. 
by 12 in. pieces some were exposed without treatment of any 
kind, the scale left on; others were tinned; still others were gal- 
vanized by the Rhode Island Tool Company. Of the 6 in. by 
6 in. plates some were Bower-Barffed by the Yale and Towne 
Company, others were Barffed by the Pratt and Cady Company, 
still others were nickel-plated and copper-plated, in each case 
after pickling. The cast-iron pieces were skin-bearing plates, 
4 in. by 3.5 in. by 0.187 in., presented by Professor George W. 
Maynard. These were subsequently given the coatings indicated, 
their original skin being retained in all cases. 

One set of the pieces thus prepared was exposed on the roof 
of a dwelling house in the Eastern Townships of the Province of 
Quebec, Canada, by Mr. E. C. Hale, of Sherbrook, Canada; a 
second was similarly exposed in a village in Rensselaer County, 
New York State; a third was immersed in the Chestnut Hill 
(Boston) Reservoir, by Mr. Desmond FitzGerald, of Boston; a 
fourth was immersed in the Boston main sewer, near the pumping 
station, by Mr. H. H. Carter, of Boston. 

In each of the conditions of exposure the wrought-iron pieces 
were in one open wooden crate, the cast-iron ones in a second, 
the corners of the pieces (and in the case of the 6 in. by 12 in. 
wrought-iron pieces a small space in the middle of the long sides) 
alone being in contact with the crate; and care was taken that 
the specimens should not touch each other or any other metallic 


substance. Though exposed nearly a year, including autumn, 
winter, and spring, at the end of the experiments the gummed 
labels still adhered to twelve out of the twenty-six specimens 
exposed in Canada and in New York. 

The cast iron lost about as much as the wrought iron; the 
loss was about the same in fresh water and in sewage. Comparing 
the different conditions of exposure, immersion, of course, greatly 
accelerated rusting. Thus, in ten out of the fourteen sets of 
cases the pieces immersed in fresh water lost at least twenty 
times as much as those exposed to the weather in New York. 
The loss in sewage is slightly greater than in fresh water on the 
unprotected specimens, but in seven out of the fourteen cases 
the loss in fresh water equals or exceeds that in sewage, a result 
that was found difficult to explain before the electrolytic theory 
of corrosion was developed. 

Non-Corrosion of Deeply Immersed or Buried Iron. — If it be 
admitted as a fact that both hydrogen ions and free oxygen are 
necessary to promote the corrosion of iron under the electrolytic 
theory, many curious instances which have been recorded of resist- 
ance to corrosion of iron which has been deeply immersed in water 
or buried deep in the earth are explained. If the zone of dissolved 
and active oxygen has been passed the zone of corrosion has like- 
wise been passed, and the problem resolves itself into one of deter- 
mining the limits of penetration of active oxygen. These conclu- 
sions should be considered in all cases where, as on the Isthmus of 
Panama, deep piling in engineering construction is contemplated. 

Wemlinger 1 has collected some interesting data on this sub- 
ject which we include here. "It has been stated that steel sheet- 
piling has often been used as a part of permanent structures, and 
the question naturally arises: What is the life of the steel sheet- 
piling embedded in the ground? In order to be able to fully 
answer this question, it is necessary to consider the various con- 
ditions that affect the durability of iron or steel in this case, such 
as the nature of the soil and the composition of the metal itself." 

"In the first place, it must be remembered that iron or steel 
will not corrode in air unless moisture is present, nor will it cor- 
rode in water unless air is present. 2 Deep down in the ground the 

1 Engineering-Contracting, XXXI, 20, 407. 

2 Compare Cushman, Corrosion of Iron, Bull. 30, Office Public Roads, U. S. 
Dept. Agr. 


amount of air dissolved in the water is almost nil, and it is only 
near the surface that the ground-water contains free air and 
carbonic dioxide carried down from the upper layers. 

11 There is every logical reason to believe that steel embedded 
in the ground or left in contact with standing water will be pre- 
served indefinitely. However, it is appreciated that, no matter 
how much such evidence may be in favor of this conclusion, 
practical experience will have greater influence. It is fortunate 
that we can point to actual cases that seem to confirm the logical 
reasoning. There is in the possession of one of the New York Gas 
Companies quite a number of different articles of iron and steel 
that have been unearthed from time to time while excavating for 
laying gas pipes. Among these are arms and implements that 
were found in lower New York, and proved to have been origi- 
nally in the possession of British soldiers. Inasmuch as the British 
troops sailed away from New York on November 25, 1783, it 
follows that the articles are now at least 125 years old. While 
pretty well rusted, these things are by no means entirely destroyed 
as would be expected. As a matter of fact, it is believed that 
most of the rusting occurred before the implements were com- 
pletely embedded, and it is obvious that for some time these 
articles must have been lying very near the surface, if not alto- 
gether exposed. 

"I have also seen a piece of gas pipe 2 in. in diameter that 
was taken up after it has been in the ground for twenty years. 
This is in such excellent condition that it is impossible to detect 
any effect of corrosion. The original mill-scale is intact, and, in 
fact, the appearance of the pipe is such that, except for the thin 
coating of earthy matter, it has all the appearance of a pipe 
fresh from the mill. It is the most remarkable evidence of the 
durability of iron or steel embedded in the ground that I have 
ever seen. 

"At a meeting of the Engineers' Society of Western Pennsyl- 
vania, held recently, during which the question of corrosion was 
fully discussed, Mr. R. B. Woodworth made the following remarks: 

"'It may be interesting to state that I have in my possession 
a piece of iron that was put into the Mississippi River in the 
year 1863, and that is to-day in as good condition as when it was 
put in. It was painted with some kind of red paint which looks 
very much like red oxide of iron, and the paint is just as good 


to-day apparently as it was the day it was put in. The con- 
ditions there must have been extremely favorable to its preser- 
vation. The water of the Mississippi River at that point is 
probably pure and the iron was buried in the Mississippi River 
silt, sand or gravel, so as to be protected from exposure to 
atmospheric conditions, and as a consequence there was nothing 
to make corrosion. 

"'I have also a theory that so far as our own rivers are con- 
cerned, although they do carry a great deal of free acid, yet when 
the steel is placed sufficiently below the river-bed as to get the 
advantage of the filtering action of the sand and gravel, we do 
not have to do with an acid-laden condition, but rather with the 
condition of practically pure water free from contact with air, 
and I think we have every assurance to believe that the life of 
steel under such circumstances will be indefinite. I was told 
by the engineers who have charge of the construction of the Black 
Rock Lock at Buffalo, that the waters of the lake are not con- 
sidered in any way dangerous, and that steel of ordinary com- 
mercial quality in such installations may be expected to last 
for any reasonable length of time.' 

"Further evidence of the durability of iron and steel embedded 
in the ground is found in the Proceedings of the American Society 
of Civil Engineers, Nos. 6 and 7, for the year 1907. At the Annual 
Convention held at Mexico City, July 10, 1907, among various 
subjects for discussion was the following: Will iron or steel, used 
in foundations, independently or in combination with other 
materials, last indefinitely when in direct or indirect contact 
with water? 

"The most interesting contribution to this discussion was, 
undoubtedly, that submitted by Mr. John F. O'Rourke, the well- 
known foundation engineer and contractor. Mr. O'Rourke stated 

"'Iron and steel used in foundations, apart from conditions 
where electrolysis may occur, last indefinitely when in direct or 
indirect contact with water, provided the water remains un- 
changed. The reason for this is obvious. Water attacks iron 
or steel, on account of the oxygen it contains, and, if this is a 
proportionately small quantity, the amount of oxygen contained 
in wet concrete or ground is negligible, and, having once been 
exhausted, the metal remains unharmed and protected. 


"'The writer has seen many cases where immersion in stand- 
ing water has been a matter of years, and in every case the effect 
upon the metal has been no greater than if it had stood for the 
same length of time in linseed oil. In one case bolts on the inside 
of cast-iron cylinders, filled with concrete, were exposed to the 
salt water in the Harlem River for more than thirty years, and 
when removed were found to be without rust. In another case, 
a pipe was immersed for ten years in an artesian well, the water 
in which had not been pumped for ten or fifteen years, and no 
corrosion of this inside pipe had taken place, the scale was still as 
fresh as when the pipe was new, and the tool-marks of the pipe- 
coupling apparatus were still perfectly fresh. 

" ' Similar results came under the writer's observation in 
reference to the condition of rods and nails found in wood founda- 
tions where the surrounding material was impervious to air, and 
in one case which came under his observation, at the time of the 
removal of the old elevated railroad columns in Greenwich Street, 
New York City, prior to making way for the new structure in 
1878, the bottom part of these columns and the bolts in the 
masonry were found intact, the corrosion gradually increasing 
until near the surface, where the material was almost entirely 
destroyed by rust. This experience with both wood and iron, 
where the renewal of the oxygen in the surrounding water was 
prevented, has been uniformly that of finding the material per- 
fectly preserved, so that, in the writer's practice, he does not 
hesitate to advise the use of either material under conditions 
where a fresh supply of oxygen is excluded.' " 

"Busy" Iron does not Rust. — We have now to consider the 
well-known fact that in rapidly moving waters corrosion does 
not take place so rapidly and dangerously as when the conditions 
are comparatively quiescent provided dissolved oxygen is present 
in both cases. This has been a matter of record by pipe-line 
engineers, who have noted that their dangerous corrosion in 
buried pipes always takes place from the outside in, and not from 
the inside, out 1 . It follows that if the electrolytic explanation of 
corrosion is correct,- undisturbed and comparatively quiescent 
conditions are most favorable to the action. Differences of 
potential establish themselves, as the ferroxyl indicator shows 
at specific points and nodes. If the conditions are continually 
1 Gaines, Engineering News; also Thomson, Com. Eng. XLII, 67 (1908). 


changing on the surface, it is presumable that the points. of 
potential difference will not be maintained, but, on the contrary, 
will never remain long enough in one spot to produce deep 
rusting. It may safely be said that dangerous corrosion is 
localized electrolytic action. In a pipe-line as in many another 
case of structural steel, if the corrosion effect was distributed, 
little damage would accrue, but as a chain is no stronger than 
its weakest link, so a pipe-line, a boiler tube, or a bridge member 
can fail and endanger human life only because it has given way 
at some specific point. One of the authors of this work observed 
a number of years ago that busy iron does not rust, and explained 
this observation by the fact that frequent and recurrent vibra- 
tion was sufficient to break up specific points of potential 
difference on the surface. Sang's observations on this point are 
interesting in this connection: 1 

"The case of steel rails is an interesting one, showing, as it 
does, the effect of vibration on rusting. A rail which has been 
in service, but has been laid to one side, will rust all over, but 
especially at the ends where the vibration of the fish-plates has 
removed the mill-scale, and on the smooth top of the head. On 
the other hand, a quite remarkable fact, which has been univer- 
sally confirmed and can be easily observed by any one, is that a 
rail while in service will not rust nearly as rapidly as one which 
is" lying out of service. The rusting takes place in proportion to 
the service, and lines over which fast trains pass frequently, 
causing much vibration, will practically not rust at all, whereas 
the rails of turnouts or sidings, which undergo less service, and 
that of a slow nature, will rust to a certain extent. One observer 
(J. M. Heppel) has reported the case of some rails at Madras, 
India, which lost three pounds to the yard lying in the yard exposed 
to the sea air, while the rails in service near by were not percep- 
tibly affected. The top of a rail is compressed and smoothed down 
in service by the grinding of wheel tires, for there is always a 
certain amount of slip, especially during acceleration and retarda- 
tion. Galvanic action between the smooth head of the rail and 
the rest of it has been suggested to explain- this immunity from 
rust, but it is not at all likely that the foot would owe its pro- 
tection to the thin stratum of denser metal so far removed from 
it. If that dense skin on the top of the rail were not crushed 
1 Proc. Eng. Soc. West. Pa., XXIV, 10, p. 523. 


beyond its elastic limit, it would, on the contrary, tend to acceler- 
ate the corrosion of the steel in contact with it. The real reason 
for this difference of behavior seems to lie in the observed fact 
that oxidation is apparently arrested, or at least greatly retarded, 
by vibration. 1 Explanation seems to stop at this point, but a 
simple theory can be built on the assumption that the vibration 
causes a shedding of the rust as soon as it is formed on the spots 
that are not protected by mill-scale, and there is, therefore, no 
acceleration of the action due to the accumulation of spongy 
and electro-negative rust. The average speed of corrosion of a 
vibrating body would be that of the formation of a first film of 
rust. Most of the actual rust on rails is probably due to the 
rapid evaporation of rain on the surface. In the case of rails in 
service, the first film of rust would be confined to bare spots and 
cracks in the mill-scale, and the vibration would prevent its 
working its way under the mill-scale as would happen if the rail 
were at rest. The top of the rail being denser might be expected 
to resist corrosion better when the rail is out of use; such is not 
the case, however. The surface has not only been subjected to 
hammering and crushing, but also to abrasion and rolling, and it 
has become short and crackeled and sometimes exfoliated; once 
laid aside, the smooth top of an old rail rusts very rapidly." 

Application of the Electrolytic Theory to Special Corrosion 
Problems. — There are many applications of the electrolytic 
theory to special corrosion problems that might be properly 
included in this chapter. These will, however, be considered 
separately in the second portion of the book which is specially 
devoted to the preservation of iron and steel. In addition to 
this, much of the material given in this chapter might properly 
be presented in the next chapter, in which the specific bearing 
of the electrolytic theory on the stimulation and inhibition of 
corrosion are dealt with. In treating a complex problem of this 
kind, the arrangement of the material is not a simple matter, 
but it is hoped that enough has been said to make what follows 
quite clear to the reader. 

1 Edwin Clark: Proc. Soc. C. E., Yr. 1868, p. 554. 



Use of the Word "Inhibition." — The word "inhibition" in 
relation to the corrosion problem was first used by one of the 
authors, 1 to mean the restriction or repression of corrosion, and 
not its complete prohibition. As Sang 2 points out: "The pro- 
tective effect is, sooner or later, overcome, and clearly indicates 
that inhibition furnishes something to the iron, be it substance 
or physical state, which under the attacks of corrosive agencies 
is slowly expended until destroyed or brought below the safe 
limit of protection." Inhibitory treatments have the effect of 
rendering iron passive, but the passive condition is not the stable 
condition, so that there must be a continual tendency at work 
which causes the return to the normal surface condition. The 
passive state of the metals has already been described in a previous 
chapter and it will now be necessary to discuss the subject from 
the standpoint of the protection of iron. 

Hydroxyl Ions as Inhibitors. — All substances in solution which 
contain hydrogen ions, such as acids, stimulate the corrosion of 
iron. This is also true of salts of strong acids and weak bases, 
which, though perfectly stable in a dry condition, hydrolyze in 
solution to an acid reaction; or which, though neutral in fresh 
solutions, undergo slow decomposition under the action of light, 
with the formation of acid salts or free acid. With certain excep- 
tions, salts which are perfectly neutral in solution do not prevent 
oxidation but appear to aid it by increasing the electrolytic action. 
All substances which develop hydroxyl ions in solution, such as 
the alkalis or salts of strong bases with weak acids, to a certain 
extent inhibit, and, if the concentration is high enough, abso- 
lutely prohibit, the rusting of iron. 3 

Bushman Bull., Office Public Roads, U. S. Dept. Agr. (1907). 

2 hoc cit., p. 536. 

3 Under exceptional conditions this statement may require modification. 
In this connection see note, p. 100. 



Under the electrolytic theory the explanation of the pro- 
tection afforded by hydroxyl ions is a simple one. Owing to 
the small dissociation of water, hydrogen ions cannot exist in a 
solution in which the hydroxyl ions are in excess. As hydrogen 
ions cannot exist or be locally formed in sufficiently strong alka- 
line solutions, no attack is made upon the iron, which remains 
permanently unaltered. If, however, the concentration of the 
hydroxyl ions is not sufficiently great, electrolysis can go on 
with an apparent stimulation of the pitting effects similar to 
that produced by perfectly neutral electrolytes, such as sodium 

Bichromate Solutions as Inhibitors. — As has already been 
noted, solutions of chromic acid and potassium bichromate 
inhibit the rusting of iron. In order to determine the concentra- 
tion necessary to produce complete protection, a number of 
polished strips of two different samples of steel were immersed 
in bichromate solutions of increasing concentration, contained 
in tubes which were left quite open to the air. There were twelve 
tubes in each series, ranging by regular dilutions from tenth- 
normal down to ten-thousandth normal. At the end of two 
months the last four tubes showed graded rusting with accumu- 
lation of ferric hydroxide. No rusting had occurred in any of 
the solutions above tube No. 8, which contained six-hundred-and- 
fortieth normal bichromate, a strength corresponding to about 
8 parts of the salt in 100,000 parts of water, or about 2 pounds 
to 3,000 gallons. Since solutions of bichromate do not hydrolize 
with an alkaline reaction, but on the contrary are usually slightly 
acid, some other explanation must be found for this remarkable 
phenomenon. On first thought it would seem a paradox that a 
strong oxidizing agent should have the effect of preventing the 
oxidation of iron, and yet this is precisely the case. If, however, 
the initial cause of rusting is the hydrogen ion, it is possible to 
believe that under certain conditions oxygen would prove the 
most effective of all inhibitors. 1 

Passivity of Chromated Iron, — One of the authors has ob- 
served that if a rod or strip of bright iron or steel is- immersed 
for a few hours in a strong (5 to 10 per cent.) solution of potas- 
sium bichromate, and is then removed and thoroughly washed, 
that a certain change has been produced on the surface of the 
1 See explanation of passivity, p. 28. 


metal. The surface may be thoroughly washed and wiped 
with a clean cloth without disturbing this new surface condition. 
No visible change has been effected, for the polished surfaces 
examined under the microscope appear to be untouched. If, how- 
ever, the polished strips are immersed in water it will be found 
that rusting is inhibited. An ordinary untreated polished speci- 
men of steel will show rusting in a few minutes when immersed 
in the ordinary distilled water of the laboratory. Chromated 
specimens will stand immersion for varying lengths of time before 
rust appears, but the induced passivity gradually disappears. 

The passivity which iron has acquired can be much more 
strikingly shown, however, than by the rusting effect produced 
by air and water. If a piece of polished steel is dipped into a 
1 per cent, solution of copper sulphate, a 10-second immersion 
is sufficient to plate it with a distinctly visible coating of copper 
which cannot be wiped off. 1 A similar polished strip of steel 
which has been soaked over night in a concentrated solution of 
bichromate and subsequently well washed and wiped will stand 
from six to ten 10-second immersions in 1 per cent, copper sul- 
phate before a permanent coating of copper is deposited. Even 
a momentary plunging of the metal into the bichromate will 
induce a certain passivity, but the maximum effect appears to 
require a more prolonged contact with the solution. 

Bichromate Solutions do not Attack Iron Free from Manganese. 
— Moody 2 asserts that potassium bichromate prevents the for- 
mation of rust, owing to the fact that it slowly dissolves iron and 
its hydroxides. He observed that the addition of ammonia to 
solutions of chromic acid and its salts which had been allowed to 
act on iron produced precipitates of hydroxide. This point has 
been carefully investigated by the authors, with the following 
results: Iron which is free from manganese is not attacked by 
solutions of bichromate, even if boiled for days in a flask fitted 
with a return condenser. Manganese is, however, readily soluble 
in bichromate solutions, and therefore iron rich in manganese 
yields a sufficient amount to the solvent tiction to produce 
a small amount of brownish manganese hydroxide when the 
bichromate solution is poured off, made slightly ammoniacal, and 

1 This experiment has failed in hands of certain experimenters who have 
not been careful to use the copper sulphate solution as dilute as directed. 
' Proc. Chem'. Soc. (Lond.), 1906,- 22, 15. 


allowed to stand. If metallic manganese is boiled in bichromate 
solutions it dissolves readily, and subsequent addition of ammonia 
produces an abundant precipitate of brown manganese hydroxide. 

Experiment with Bichromate to Induce Passivity. — In order to 
show beyond doubt that a passive condition is induced by 
immersing iron in a strong solution of bichromate the following 
experiment was made: Two polished steel electrodes were pre- 
pared and chromated by immersion for a number of hours in a 
strong solution of potassium bichromate. The prepared elec- 
trodes were then thrust tightly through a rubber stopper which 
closed the Jena flask A, which was then filled with pure freshly 
boiled distilled water in the manner shown in Fig. 7. The 
electrodes were then attached to the poles of a primary battery 
at about two volts potential. At the end of half an hour although 
the potential was not. sufficient to disengage bubbles of gas and no 
visible change had occurred, the electrode which was connected 
to the zinc pole of the battery had lost its passivity, the other 
retaining it. 

Inhibitive Power of Pigments Containing Certain Oxidizing 
Agents. — Wood 1 in 1895 commented on the power of paints and 
pigments containing certain oxidizing agents, notably potassium 
bichromate and lead chromate, to form on iron and steel surfaces a 
thin coating of oxide which so effectually protects the metallic 
surfaces from corrosion that after the removal of the paint the 
metal still resists atmospheric effects for a long time, as well as 
the stronger effect of immersion in sea-water or acidulated waters 
and sulphurous and other vapors. This action, Wood adds, is 
very obscure and not thoroughly understood; but the fact remains, 
and extended experiments in this field only demonstrate its pres- 
ence and usefulness. 

Solution System with Two Contending Forces, Inhibitive and 
Stimulative. — It has been already pointed out in a previous 
chapter that in many cases a stimulative and an inhibitive tend- 
ency may be at work at one and the same time. This assertion 
is well brought out by the following experiment in which an 
inhibitor and stimulator are literally "pitted' 7 against one an- 
other. Samples of bright steel wire were immersed in 100 cubic 
centimeters of a very dilute one-thousandth normal solution of 
potassium bichromate in a series of shallow dishes. The wire- 
1 Am. Soc. Mech. Ens- Trans., 1895, 16, 671. 


test pieces were suspended in the solution so that they did not 
come in direct contact with the glass surfaces of the dishes. This 
precaution should never be omitted in experiments of this kind, 
as owing to the absorption of air by glass, rusting is always stimu- 
lated at the point of contact between glass and iron. The first 
dish was left as a blank, the second received one drop equal to 
sV cubic centimeter of a dilute tenth-normal copper sulphate 
solution. The third dish received two drops of the solution, 
and so on, each dish getting an increased amount of copper sul- 
phate until twenty-five dishes had been prepared. 

Now it is apparent that we have in this system two contending 
forces at work. Iron has a higher solution tension than copper, 
and therefore tends to pass into solution, the copper tending to 
plate out on the iron. Chromate ions, on the other hand, put 
the surface of iron in a condition in which it cannot pass into 
solution. In the solution system iron-chromate-copper we have 
an equilibrium to be decided between two contending forces 
acting in opposite directions. It was interesting and instructive 
to note the results of this struggle, which was known to be going 
on, although the actual conflict could not be watched. In the 
first dish, in which no copper was present, no corrosion took place; 
in the second, also, no action was visible; in the third, however, 
minute specks of iron rust appeared. These were larger and 
more frequent in the immediately succeeding dishes, the test- 
pieces showing rust tuberculation with the well-known pitting 
effect. As the middle of the series of dishes was approached, 
both iron rust and precipitated copper began to appear side by 
side on the surface of the iron, and from thereon in the series 
more and more copper separated, while less and less rust formed, 
until in the end dishes copper and iron were changing places 
evenly over the surface without apparent hindrance. These 
experiments, and others of a similar nature, were repeated many 
times with the same results, and there seems to be no escape from 
at least the following two conclusions to which they obviously 

(1) If the surface of iron is subject to the action of two con- 
tending influences, one tending to stimulate corrosion and the 
other to inhibit it, the result will be a breaking down of the defen- 
sive action of the inhibitor at the weakest points, thus localizing 
the action and leading to pitting effects. 


(2) While the concentration of an inhibitor may be strong 
enough to prevent the electrolytic exchange between atom and 
ion, it must be still stronger to prevent entirely the solution of 
iron and the subsequent oxidation which leads to the formation 
of rust-spots. 

Practical Bearing of Alkaline Solutions on Corrosion. — In 
the opinion of the authors these observations have a direct bear- 
ing on, if they do not actually explain, many of the practical 
problems of corrosion. It is well known that if sufficiently alka- 
line, solutions inhibit and in some cases actually prohibit corro- 
sion. If the concentration of the hydroxyl ions is not sufficiently 
high, however, local electrolysis goes on in the slightly alkaline 
medium and the tendency to pit is actually stimulated, as was 
noted by Cribb 1 in an extended investigation. Pennock 2 has 
shown that concentrated ammonia solutions not only do not rust 
clean iron but prevent its rusting in the presence of corrosive 
agents, and yet dilute ammoniacal liquors appear to stimulate 
corrosion. It is a curious fact, however, that iron is to some 
extent soluble in strong boiling solution of ammonia, although 
there is no apparent action in -the cold. This phenomenon is 
now being investigated. 

One of the authors has suggested that pipe lines trenched 
with lime or limed soil should be to some extent protected, 
but it is still a question whether or not the tendency to pit 
would not be stimulated. Knudson 3 has called attention to 
an interesting case of the stimulated corrosion of the bottom 
of oil tanks. In the process of purifying oils it is customary 
to treat them with sulphuric acid and after washing to neutralize 
the residual acid with a slight excess of caustic soda. The 
slightly alkaline liquors containing sodic sulphate which remain 
and settle to the bottom naturally stimulate corrosion to a very 
high degree. The natural cure for this difficulty which suggests 
itself would be in increasing the alkalinity of the oil lees until 
the prohibition point was reached. It might also be possible 
to use an excess of potassium bichromate for this purpose 
provided it was found that this oxidizing agent did not react 
with the oil. 

1 Analyst, 30, 225, also Engineering, 81, 32. 

' l Jour. Am. Chem. Soc, 24, 377. 

3 Trans. Am. Electro-chem. Soc, XIV, 189 (1908). 


Stimulative Action of Certain Paint Films Acting as Depolar- 
izers. — Walker 1 has shown that the effort to protect the interior 
of tinned cans by the application of a lacquer made from a high- 
grade copal linseed oil varnish only led to stimulated corrosion 
in the form of pit holes. This unexpected result Walker was 
enabled to explain satisfactorily by means of the electrolytic 
theory. It appears that the varnish acted as a depolarizer by 
absorption of hydrogen, and therefore at every scratch or imper- 
fection in the lacquer a stimulated pitting effect was operative. 
Walker, at the suggestion of one of the authors, has also applied 
this same reasoning to the general subject of protective paint 
coatings, with interesting results. Walker's method of investi- 
gation and conclusions are quoted in the following paragraphs: 

"To show that the corrosion of the iron occasioned by the 
lacquer film is accompanied by the flow of an electric current 
through the external circuit, the following experiment was tried: 
A U-tube with a KC1 solution and an agar plug, carefully boiled 
out, the whole under an atmosphere of hydrogen, contained two 
iron electrodes, the one bare and the other covered with a linoxy- 
lin film. An electrometer was inserted into the external circuit 
and the current flow measured as shown in the table below. It 
was found undesirable to use a silver voltameter for the exces- 
sively small currents employed and resort was had to a modifica- 
tion of Ostwald's Bromide Voltameter. This voltameter was 
used for all measurements made, after the first, which was done 
with the silver nitrate instrument. 

"Deposit obtained from current due to depolarization by two 
different linoxylin films: 

Time in 

Deposit of 
Mgs. Bromine 

Deposit Mgs. 
per Hour 

Film No. 1 

Film No. 2 










"These figures prove beyond doubt that the corrosion of the 
iron on the unlacquered side is due to the flow of an electric 
current through the external circuit from the lacquered surface. 
1 Jour. Ind. and Eng. Chem., I, II, 754. 


"These experimental facts seem to allow of but one explana- 
tion, namely, that the films in question are porous in their nature, 
allowing the electrolyte to penetrate them to the surface of the 
metal beneath, that some of these films, due to their unsaturated 
state, are capable of absorbing nascent hydrogen and in this way 
acting as depolarizers, and that aside from this, all the porous 
films allow the penetration through them to the surface beneath 
of any depolarizer that may exist in the solution, thus rendering 
the coated surface cathodic and concentrating the solvent action 
at the exposed part of the metal. 

"The reason for the failure of the fruit cans mentioned at the 
beginning of this article is now easily understood. While the 
lacquer film applied to the uncut sheet was probably a perfect 
one, still, in the process of making the can, this film was ruptured 
at many points. Thus the die stamping out the head of the can 
broke the film at the place where the tin was bent; the mandrel, 
on which the body of the can was formed, scratched the sides in 
long parallel lines upon the removal of the can, and the burning 
of the joints destroyed the lacquer in their immediate neighbor- 
hood. When the fruit was introduced into the can, the depolar- 
izing action of the lacquer itself, coupled with that of the small 
amount of air left in the can in packing, threw the protected 
areas into the cathodic state, concentrating the solution of the 
metal at the exposed points, dissolving in this way both tin and 
iron, and maintaining this corrosion until both the air was con- 
sumed and the unsaturated state of the lacquer was completely 
relieved. Before this point was reached, however, the corrosion 
had gone far enough to seriously damage the fruit and even in 
many cases to puncture the can. This action is entirely independ- 
ent of any possible imperfections in the tin plate. The remedy 
would be to find a lacquer impervious to the solution, or if that 
prove impracticable to at least furnish one which will not act 
as a hydrogen depolarizer. A non-porous lacquer it has as yet 
proven impossible to find; a saturated one can be made by suffi- 
ciently baking any ordinary varnish, but there still remains work to 
be done to develop this into a satisfactory solution of the problem. 
"It is self-evident, however, that the importance of these 
phenomena is by no means limited to the problem of lacquering 
fruit cans. The majority of protective coatings for iron contain 
linseed oil or some one of the various substances found by our 


experiments to be either unsaturated, or porous, or both; and so 
soon as a piece of metal painted with these substances comes in 
contact with water after the abrasion of the paint film at any 
point, all the conditions for corrosion as above outlined are ful- 
filled, and we may be sure that corrosion at the exposed point 
will be accelerated by the presence of such films in its neighbor- 
hood. It is true that the porosity of these films is reduced to a 
minimum by the use of the best obtainable loading materials, 
such for instance as certain pigments of ordinary linseed paints, 
the bituminous bodies of asphalt or coal tar paints, etc., and that 
these paints offer in consequence a much greater electrical resist- 
ance to the flow of the current than otherwise. One must not 
forget, however, that the insertion of such a resistance to the 
current flow can only reduce the rate of the reaction, and in no 
way influence its tendency or driving force. The exposure of 
such films to the air for a long period of time finally entirely satu- 
rates them, but this again does not affect their porosity and con- 
sequently does not preclude the possibility of acceleration of 
corrosion at the exposed point due to the depolarizing action of 
air through the film. These facts make clear the reason for the 
rapid deterioration and pitting of the iron or steel surface at 
points laid bare by the breaking down of many paint films, and 
show why it is so exceedingly important that a metal surface 
should be clean and bright before the application of a paint. 

"If a paint or lacquer film be intact, despite the fact of its 
porosity, corrosion does not seem to take place at once beneath 
its surface. Thus an iron can, carefully painted with a high- 
grade varnish and filled with cold 5 per cent, sulphuric acid, 
showed a test for iron with ferricyanide first after twenty-four 
hours. If heated on the water bath, however, a test could be 
obtained in slightly over one hour, but even then the action was 
not severe. It may perhaps be that the electrolyte does not 
find sufficient continuous surface beneath the film to allow of a 
ready separation into cathodic and anodic areas. At any rate, 
corrosion does not readily take place if the film be intact, but the 
surface below the film does easily become cathodic if an exposed 
area in the neighborhood can act as an anode. This cathodic 
liberation of hydrogen loosens the film from the metal in some 
way not yet clearly understood and likewise softens it. The 
resistance of a film diminishes quite rapidly in this way, and it 


soon becomes weak and rotten and easily removable from the iron. 
It is easy to see how, especially with rough usage, exposed points 
in a painted steel surface rapidly grow in size. 

"A few of the common commercial paints and paint-making 
materials were examined, using the following apparatus: A glass 
U-tube of one inch tubing with six inch arms and eight inches in 
length over all, contains 200 c.c. of normal KC1. The electrodes 
are of commercial soft iron wire, 0.044' diameter, carefully 
cleaned with emery. The bare electrode is 25 cm. long and 
the lacquered one 100 cm. The electrode is coated by dipping 
in the paint to be examined, the excess removed by rapid twirling 
and then dried. The water about the cathode is kept saturated 
with oxygen by bubbling air through it. The depolarization 
current is measured by the use of the bromide voltameter 
already mentioned. The bromide deposited is proportional to 
the time, up to a point when the film gives way. This point of 
disintegration is different for different films and two quantities 
can in general be measured, (1) the initial rate of depolarization 
and (2) the time of rupture. 

Paint film Corrosion in mgs. Bromide per hour. 

''Durable metal coating" 0.70 

"Copal linseed oil lacquer" 0.76 

"Cosmos" (coal tar) 0.34 

Graphite 1.87 

Carbon black 2.4 

Lampblack 2.3 

. Zinc chromate 0.11 x 

Barytes 1.2 

Zinc oxide 0.078 2 

Graphite (baked) 0.078 

White lead 0.10 3 

Linoxylin 0.31 

Paraffine 0.00 

"This second factor is somewhat difficult to obtain because 
our voltameter measures not current but total amount of electric- 
ity passed, and it is frequently, if not usually, impossible to tell 
at exactly what point the increase in current began. In the above 
table is the average of the data obtained. It is evident that 
the electricity measured by the bromine deposited is the resultant 

1 Broke down in 36 hours, but not badly. 

2 Still perfect after 71 hours. 

3 Broke down in 30 hours. 


of a number of factors acting at the same time. A comprehensive 
study of the relationship between such data and the value of 
various paints as a protective coating for iron is now in progress." 

It is interesting to note at this place, that this work furnishes 
a striking corroboration of the stimulative and inhibitive effects 
of certain pigments which had already been indicated by one of 
the authors, in a series of preliminary tests carried out on the 
inhibitive power of certain pigments. This work will be presented 
in detail in a later chapter. 

Wounds on Steel Surface Stimulate Rusting. — A considerable 
body of evidence has been brought forward from time to time to 
show that in addition to the segregation of impurities in steel, 
the presence of scratches, sand pitholes, and, in fact, all indenta- 
tions or wounds on the surface of steel, will stimulate rusting by 
becoming centers of corrosion. 1 Such marks or indentations are 
almost invariably electro-positive to surrounding areas, and the 
depolarization which results in the rapid disengagement of hydro- 
gen at these spots leads to stimulated pitting. This effect can 
be very prettily shown by means of the ferroxyl indicator. In 
the illustration shown in Fig. 31 a freshly polished steel plate has 
had the word £i Rust ,J carved upon its surface with a cutting tool. 
On immersion in the ferroxyl indicator the general surface has 
come out in red while the carved letters appeared in blue. This 
cause of stimulated pitting is probably very generally active on 
all surfaces of iron and steel which from the nature of their ser- 
vice cannot be treated with any form of protective coating. 
Boiler tubes furnish the best example of stimulated corrosion 
effects from this cause. The remedy should lie in truing up of all 
active contact surfaces even to the point of polishing if necessary. 
There are times when a sound boiler tube is of vastly more 
importance than a polished gun barrel, and when the added cost 
of preparing the boiler tubes would be insignificant in comparison 
with the danger of blow-outs from pitting. The above fact 
brought out by experimental investigation is also attested by the 
results of practical observation and experience. It has long been 
known in the Bureau of Steam Engineering of the U. S. Navy 
Department 2 that indentations such as sandpits, or injuries on 
the water surfaces of boilers, always become centers of corrosion 

Bushman, Proc. Am. Soc. Testing Materials, VIII, 605 (1908). 
2 Proc. Am. Soc. Testing Materials, VIII, 244 (1908). 


and pitting, and inspection has been as thorough as possible to 
guard against this danger. 

Mill-scale a Stimulator. — It has already been shown in a pre- 
vious chapter that mill-scale consisting of the black magnetic 
oxide of iron is electro-negative to the metal, and this acts inevi- 
tably as a common cause of stimulation of corrosion, whenever the 
coating of mill-scale is discontinuous on the surface. This point 
is now so well and generally understood that pickling and sand- 
blasting are often resorted to in order to obtain clean surfaces of 
metal, before protective coatings are applied. 

Fig. 31. — Showing the effect produced in the ferroxyl indicator by 
cutting the surface of a polished steel plate. (Cushman.) 

Various Inhibitive Expedients which have been Tried. — Almost 
all efforts to inhibit the corrosion of iron depend either upon 
producing and maintaining a passive condition of the surface or 
on maintaining a sufficiently alkaline medium in contact with the 
surface of the metal. Chromic acid and its more or less soluble 
salt furnish the principal chemical means of producing passivity. 
It has long been known that, if iron is made the anode in an elec- 
trolytic circuit, it will not rust, provided the quantity of current 


passing is sufficient to protect it. Various expedients based on 
this fact have been suggested or tried in order to inhibit corro- 
sion. Among these should be mentioned the insertion of zincs 
in boilers, and the use of zinc-corroding plates in connection with 
steel structures. Zinc, as has been shown, is electro-positive to 
iron, and when the two metals are in contact and wet with a 
corroding medium zinc will pass into solution and the iron will 
be protected. The sphere of influence of the zinc does not, how- 
ver, extend far from the point of contact between the two metals 

i< i [ 


' -jffE*rv^ 

Wm$?y : - 




*& .... . 


■'.■:. . ■ . ■ 

Fig. 32. — Illustrating the protection on the surface of the steel in the 
immediate neighborhood of a button of zinc soldered into the steel. The 
sphere of influence of the zinc is shown to be proscribed. (Cushman.) 

so that iron can begin to rust in places long before all the zinc 
is destroyed. This can easily be shown by soldering a button 
of zinc into the machined surface of a plate of steel and immersing 
the whole either in water or in the ferroxyl indicator. This is 
very well shown in Fig. 32. In general it may be said that even 
if the sphere of influence of the zinc was wider, the idea of burning 
up zinc in order to protect steel does not commend itself. 

Passivity Maintained by Plunging Electrodes into Neutral or 
Alkaline Solution. — If two iron electrodes are plunged into a 


neutral or alkaline solution and an electric current of sufficient 
density be passed through the circuit the pole where the oxygen 
disengages becomes passive, and while it is maintained in this 
condition rusting is inhibited or actually prohibited. Just as 
in the case of passivity induced by solutions of chromic acid and 
its salts, this passive condition is maintained to some extent after 
the removal of the cathode plate from the circuit. This action 
has been studied by a number of experimenters including the 
authors. Toch 1 has made a very recent contribution to the sub- 
ject, the details of which are not yet available. 

Rusting Caused by Escaped Currents. — It is very generally 
known that extraneous escaped currents from high-potential 
light and power circuits do great damage to structural iron and 
water mains, especially in the larger cities. There is a vast 
literature on this subject, much of which is cited in Appendix B. 
No effort will be made here to abstract the available information, 
as this phase of the subject constitutes a special problem on which 
a separate volume might be written. In a general wa} r it may be 
stated that the best preventive measures against this cause of 
rust stimulation are more judicious bonding of the rails carrying 
return currents and the use of effective feeders on the electric 
circuits, the maintenance of a negative condition of the struc- 
tural material or pipe lines, or their more thorough isolation and 
insulation. For more detailed information on this phase of the 
subject the original literature should be referred to. 

Factors Causing Stimulation or Inhibition . — The effort has 
been made in this brief chapter to set forth the principal factors 
which enter into the stimulation or inhibition of corrosion. Some 
of these factors, such as contact action in the air and in water, 
had already been treated in previous chapters, but may be con- 
veniently summarized here in the following list : 

Factors which Stimulate Corrosion 

(1) Impure and segregated metal. ' Unhomogeneous or burnt 
metal which may contain blow-holes. 

(2) Cold rolled or improperly annealed metal which may 
maintain an uneven, stressed, or strained condition. 

(3) Contact action, in which different types of iron and steel 
are used in one and the same structure. 

1 Proc. Am. Electro-chem. Soc. (1909). 


(4) The presence of hydrogen ions from any source whatsoever 
that may be brought in contact with the surface, in water or 
other electrolytes in the presence of oxygen. 

(5) The concentration of active oxygen that is present in the 
wetting medium. 

(6) The presence of electrolytes generally in the wetting 
medium. Even hydroxyl ions and other inhibitors may appear 
as stimulators if in insufficient concentration. 

(7) The stimulating or depolarizing effects of certain coatings 
applied to iron and steel with the object of protecting the metal. 

(8) The effect of indentations, scratches or other injuries 
which become centers of corrosion. 

(9) The effect of extraneous or stray currents escaped from 
high-potential circuits. 

Factors which Inhibit Corrosion 

(1) In most cases the reverse of the conditions which stimu- 
late corrosion. 

(2) Contact with certain substances in solution, such as 
chromic acid and its soluble salts which produce a passive con- 

(3) Alkaline solutions of all kinds in which the concentration 
of hydroxyl ions is sufficiently high. But this protection may be 
overcome and the equilibrium conditions reversed in very strong 
boiling alkaline solutions. 

(4) Contact with more electro-positive metals. 

(5) Electrolysis under certain specific conditions. 




The Different Phases of the Protection Problem. — No purely 
scientific discussion of the corrosion problem will be considered 
complete unless it also describes the more recent efforts to attain 
efficient protection of the numerous forms of iron and steel which 
enter into common use. This phase of the problem may be 
conveniently considered under three main heads: (1) Protective 
coatings of other metals and alloys. (2) Magnetic oxide sur- 
faces. (3) Paint coatings, including linseed oil paints, varnishes, 
lacquers, bitumens, and cements. 

The protection of iron is presumably a problem which in the 
ease of its solution varies directly with the rust-resisting character 
of the metal to be preserved. Progress in the manufacture of 
more rust-resistant metal must keep pace with an added efficiency 
in the methods of protection. That there is much still to be 
accomplished along both these lines is attested, not only by the 
complaints of innumerable consumers, but also by the records of 
the proceedings of engineering and other learned bodies and by the 
technical and scientific press. 

Metallurgists are exhibiting a growing tendency to look upon 
the structure of iron and steel as an aggregate in the same sense 
that geologists consider crystalline rock structures to have re- 
sulted from the more or less gradual cooling of molten magmas. 
From this point of view, careful study and control of the heat 
treatments which steel receives in the course of its manufacture 
is of the utmost importance if constancy of chemical constitution 
and physical character is to be developed. Upon just such 
factors as these resistance to corrosion will be found dependent. 
The mill man's purposes are often expedited by turning a stream 
of cold water upon red-hot piles of freshly shaped forms. How 
many mill men, however, have ever given consideration to the 
structural changes produced in the metal by such sudden quench- 



ing? Even subsequent annealing unless properly done will not 
restore the original homogeneous and quiescent conditions in 
the structure of the steel as the classic researches of Heyn and 
Bauer previously quoted very clearly show. The authors would 
earnestly recommend to manufacturers who desire to produce 
rust-resistant iron, that every step in the heat treatment which 
the metal receives from the furnace to the finished shape be 
studied with reference to its possible effect upon the final product. 

One way to attain homogeneity in the metal is to eliminate 
all the impurities and thus produce a practically pure iron. This 
has to a very considerable extent been accomplished on a com- 
mercial scale within the last few years, and metal of this type is 
now on the market. Every metallurgist knows that steel which 
is free from manganese is difficult to roll, and that special care 
is necessary in order to shape it successfully. Even if the 
influence of manganese as one of the many factors which control 
resistance to corrosion is denied, it is none the less probable that 
a metal which from its very nature must receive careful and even 
heat treatment, will be more resistant than one which will permit 
itself to be carelessly and rapidly pushed through the mill. 

Until the last few years, the methods of protection have been 
carried out mainly on an empirical basis. When iron had been 
coated with any substance which was believed to furnish a fairly 
good and durable waterproof surface it was considered that 
nothing more could be done. Of course, serious efforts were made 
to improve the physical character of the coatings as to their 
water or acid resisting qualities, but little or no attention was 
paid to the possible electrolytic effects produced, for indeed the 
fundamental causes of corrosion were not understood. For this 
reason many of the so-called protective coatings were actually 
stimulating the very kind of corrosion that they were designed to 

Protection with Zinc. — In any discussions of the use of other 
metals for the protection of iron, zinc must take the front rank. 
Zinc is the most electro-positive metal which can be practically 
used for coating iron and is from this point of view better suited 
for the purpose of providing an inhibitive coating than any other. 
On the other hand the solution tension of zinc is high 1 and its 
power of protecting iron is accomplished mainly at the expense 
1 Davies, Jour. Soc. Chem. Ind., 18, 102. 


of its own destruction. For this reason zinc must be considered 
at the very best as an inhibitor rather than as a prohibitor of 
corrosion, and the day must inevitably arrive when even the best 
of zinc coatings will fail. There is reason to believe, however, 
that the last word on the protection by zinc has not been spoken 
and that the methods of galvanizing may be so improved as to 
lengthen the life of the coatings by many years. It is probable 
that more than half of all the zinc produced is used for the pur- 
pose of protecting iron and steel. Burgess 1 has well said that 
the efficiency of the zinc coating varies greatly with the purity 
of the metal, its thickness, continuity, and methods of application, 
though the degree to which these various factors affect the effi- 
.ciency seems to have received little attention, if one may judge by 
published data. As a matter of fact the electrolytic theory of 
corrosion has opened up a number of questions which bear directly 
upon the efficiency of zinc coatings, and the answers to which, 
when they are available, will constitute new and valuable data 
on the subject. These points will be brought out in the following 

Methods of Applying Zinc Coatings, — There are only three 
processes in general use for coating iron with zinc," although the 
methods of application under the three processes may vary to a 
considerable extent in practice. These methods are well known 
as the hot dip, the "cold" or electrolytic, and the vapor or Sherard- 
izing processes. It is not necessary here to give a detailed account 
of the technology of these several methods, as it is assumed that 
the reader is either already familiar with the main and well- 
known details of the technology of zinc coating or can easily 
become so by referring to any standard work on the metallurgy 
of iron and steel. The principal effort that will be made here 
will be to apply the most recent theories and results of investi- 
gation to the problem of securing greater longevity for the pro- 
tected iron. An examination of the literature of the subject as 
given in Appendix B will reveal the fact that many claims and 
counter claims have been put forward and vigorously defended 
in the effort to show that one or other of the processes is the more 
efficient or superior. Thus one author 2 states: "The zinc applied 
by the hot method usually contains lead, tin and iron. It has 

1 Electro-chem. and Met. Ind., Ill, 1, 17 (1905). 

2 Cowper-Coles, quoted by Burgess, loc. cit. 


been found that iron above 3 per cent, makes the zinc too brittle 
to bend. Lead up to 1 per cent, is harmless, but above 1.5 per 
cent, will not dissolve and the excess collects (segregates) and 
forms weak spots. On the other hand zinc applied by the elec- 
tric process is very pure and it is found to resist the corroding 
action of a solution of copper sulphate very much better than hot 
galvanized iron." 

This statement indeed brings out some of the disadvantages 
of the hot-dip process, although by no means all of them; on the 
other hand, it does not refer to those which argue against the 
cold process. As a matter of fact it is probably true of the three 
methods of applying zinc that each will find its special field of 
usefulness, and that each will be found to have certain advan- 
tages and disadvantages. Further than this, it is quite certain 
that all the processes are at the present time more or less imper- 
fect and are therefore subject to improvement as time goes on. 
These processes will now be criticised from the standpoint of the 
electrolytic theory as it applies to the corrosion and preservation 
of iron and steel. 

The Hot-dip Method of Galvanizing. — In the hot-dip method 
the iron to be galvanized is dipped or drawn through a molten 
bath of spelter, which necessarily becomes more and more alloyed 
with iron up to the point where a definite eutectic alloy of iron 
and zinc crystallizes out, and being heavier than the molten 
magma falls to the bottom of the bath. This separated alloy 
is technically known as dross and is occasionally raked out of the 
bath and thus partially removed. The layer of partly oxidized 
zinc and impurities which forms on top of the bath is scum, and 
this also is removed from time to time. It will be seen that even 
if the original spelter was pure zinc, it would not remain so in the 
bath, as it would soon become contaminated by the iron which is 
immersed in it as well as by other impurities which might acci- 
dentally find their way in. As a matter of fact, however, the 
original spelter contains a certain amount of impurity in the form 
of lead, cadmium, iron, and other materials, and is therefore really 
an alloy to begin with. Burgess 1 truly remarks on this subject: 
"Such an alloy will dissolve very readily in an acid solution, 
owing to local action, which is set up between the different metals. 
This results in a more rapid corrosion than where a single metal 

1 hoc. tit. 


is immersed in a corroding solution." In other words, all that 
has been said in previous chapters in regard to the accelerated 
corrosion of impure and segregated iron applies equally to zinc. 
Not only is the solution tension of zinc alloyed with iron and other 
impurities greater than that of pure zinc, but even its electro- 
chemical relation to iron is said to change so that it may appear 
electro-negative instead of electro-positive. These facts will 
always operate against the efficiency of zinc coatings applied 
by the hot-dip process, but nevertheless, with proper care, im- 
provement in the results obtained should still be attainable. 
It is common practice in the hot-dip process to pass the iron or 
steel to be coated through a hydrochloric acid fluxing bath just 
before it enters the spelter bath. In many cases zinc chloride or 
ammonium chloride, "sal ammoniac," is used in conjunction 
with hydrochloric acid. Certainly no more corrosive mixture 
than this could be applied to the surface of iron, and it is equally 
certain that small portions of these acid products become included 
in the zinc coatings. One of the authors has dissolved a number 
of samples of hot-dip galvanized coatings in pure dilute nitric 
acid and never failed to get slight white precipitates with silver 
nitrate, proving the presence of chlorine ions. In some of the 
foreign practice much more attention is given to the control of 
the acidity of the fluxing bath than is usual in this country, and 
this fact undoubtedly is contributory to higher rust-resistant 
qualities. For this reason the authors have suggested the sub- 
stitution of alkaline fluxing and soldering solutions. Adopting 
the suggestion, experiments have been carried out in a prominent 
wire mill, on the use of a flux made by dissolving zinc oxide in a 
fairly strong solution of caustic soda. No trouble was experi- 
enced in getting heavy coatings of zinc on the wire with this flux, 
but occasional black spots appeared which interfered with the 
general efficiency of the coating and which have not as yet been 
explained. It is therefore not now certain whether a practical 
substitute for the acid flux can be found. 

All galvanized wire manufacturers have been to some extent 
troubled by the appearance on their finished products of a whitish 
efflorescence which often appears in little spots on the surface 
and which is technically spoken of as "mold." This appearance 
is undoubtedly due to zinc oxide which, formed as the result of 
electrolysis, marks a preliminary step to the final failure of the 


coating. The fact that chlorides included between the iron and the 
zinc will stimulate such an effect even if it is not the sole cause 
cannot be contested. The system Fe — FeCb — ZnCl 2 — Zn is 
a galvanic couple which, however well it may justify the name of 
"galvanized" iron, would certainly tend to hasten corrosion. If 
a practical galvanizing pan could be devised in which the zinc 
was melted and maintained in a molten condition out of contact 
with the air or in an atmosphere of inert gas, better results would 
be obtained. The excessive amount of scum which forms on top 
of the spelter bath dirties the coating and prevents the forma- 
tion of an even and homogeneous layer of zinc. 

The Weight of the Zinc Coating. — In addition to the purity, 
density, and homogeneity of the zinc coating, insufficient thickness 
is also a contributory cause of rapid corrosion, especially in the 
case of galvanized wire. Thin coatings of zinc are to some extent 
porous, a condition which leads naturally to electrolytic destruc- 
tion of the zinc. By increasing the thickness of the coating the 
pores are gradually filled up so that less opportunity exists for 
centers of corrosion to form. The method which is in most 
general use for determining the thickness of a zinc coating is the 
well-known copper sulphate test. The test depends upon the 
fact that if zinc is dipped into a strong solution of a copper salt 
it goes into solution and copper comes out. As soon as the zinc 
is removed from the iron the copper begins to plate out slowly 
on the iron and can be easily seen. The difference of solution 
pressure is much greater as between zinc and copper than as be- 
tween iron and copper. The consequence of this is that copper 
replaces the zinc so rapidly that it makes a crumbly deposit 
easily wiped off. The copper iron exchange on the other hand 
takes place so slowly that the copper plates on the surface of the 
iron so that it cannot be wiped. The appearance of copper 
plate is therefore an indication that the zinc is gone. 

The Preece or Copper Sulphate Dip Test, — This test which 
is known as the Preece Test is only an approximate method for 
determining the thickness of a zinc coating and cannot be inter- 
preted as a measure of the life of the coating or its resistance to 
corrosion under the conditions of service. A difficulty in carrying 
out the test has been found because there is no sharp point in the 
reaction which indicates the exact point when all the zinc is gone. 

This point is denned by the Chief Engineer of the Western 


Electric Company as follows: "The standard color of a bright 
metallic copper deposit on a sample will be denned as the one 
obtained by taking a piece of the same class of sample and im- 
mersing in .hydrochloric acid until the action ceases, after which 
the sample is immediately washed and wiped dry, and immersed 
in the standard copper sulphate solution for not over a minute, 
then removed, washed, and wiped dry. The copper deposit 
thus obtained will be the bright metallic copper deposit referred 
to in the specification. These standards should be made every 
test day. The specific gravity of the standard solution will be 
determined by a standard 6-inch hydrometer with only one 
mark on the scale which indicates 1.186 specific gravity at 65° F. 
In reading these hydrometers the following must be observed: 
(a) Clean and dry hydrometer before placing in standard solu- 
tion, (b) Depress the hydrometer so that the solution wets the 
tube at least \ in. above the 1.186 mark, (c) Sight just under 
level of solution to see if the 1.186 mark is on the solution level 
outside of the capillary." 

The American Steel and Wire Company have adopted the 
following instructions for carrying out the copper sulphate test, 
which has been found useful in maintaining a standard weight of 
zinc coating on wire : 

Standard Solution. — The standard solution of copper sul- 
phate shall consist of commercial copper sulphate crystals dis- 
solved in cold water about in the proportion of 36 parts by weight 
of crystals to 100 parts by weight of water. The solution shall 
be neutralized by addition of an excess of chemically pure cupric 
oxide (CuO). The presence of an excess of cupric oxide will be 
shown by a sediment of this reagent at the bottom of the contain- 
ing vessel. The neutralized solution should be filtered before using. 
This solution shall have a specific gravity of 1.186 at 65° F. 

Small differences in the density of the solution may be cor- 
rected by adding water or copper sulphate crystals according as 
the solution is too heavy or too light, but if the solution is not 
nearly correct or has become dirty or impaired for any reason it 
must be thrown out and a fresh supply obtained. 

Cleaning of Samples. — Samples must be cleansed thoroughly 
of oil and dirt by dipping in benzine or gasoline, then thoroughly 
rinsing in clean water and wiping dry with clean white cotton 
waste before making the test. 


Apparatus. — The apparatus required for the test is as follows: 
1 Fahrenheit thermometer with large scale to read up to 
at least 80° F. 

1 Specific gravity hydrometer. 

1 Hydrometer cylinder 3 in. by 15 in. 

2 Jars for washing samples. 

4 Glass test jars 2 in. in diameter and 5 in. in height. 

1 Copper or galvanized sheet steel box equipped with run- 
ning water and waste pipe connection and with a rack for holding 
thermometer and a tray over part of the box through which test 
jars may be immersed in the water to maintain constant tempera- 
ture. White cotton waste free from grease. Benzine or gasoline. 

The place for testing should be clean and with good natural 
light. A cupboard should be provided for the apparatus in which 
it can be placed when not in use and there should be both hot and 
cold running water connections. For tests in summer time ice 
may sometimes be required, but this should seldom be necessary 
as the cold water supply is nearly always lower than the testing 

Test. — Fill one of the glass test jars with standard solution 
to a mark one inch from the top. The temperature of the solu- 
tion must not be lower than 65° nor higher than 70° F. at any 
time during the test, and the water used for washing samples 
must be the same. 

Not more than seven wires shall be simultaneously immersed 
in one jar, and they must be grouped together but must be well 
separated so as to permit the action of the solution to be uniform 
on all immersed portions of the samples. The ends outside of 
the solution must not be grouped together. The ends inside jar 
are likely to touch, but this is not objected to, as indications on 
the lower inch of the samples are disregarded, as stated below. 
After each complete test of seven wires or less the solution must 
be thrown away and fresh solution taken for the next set. 

The specified dip must be made on each sample and the periods 
of time accurately observed. After each dip the samples must be 
immediately rinsed in water having a temperature within the speci- 
fied limits of the solution temperature, thoroughly cleaned with 
soft cotton waste (not with a brush) and wiped dry. Samples 
must be dry at the time of immersion. For an extended series of 
tests the wash water should be frequently renewed, for obvious 


reasons, and in order to maintain the proper temperature of the 
wash water the jars should be placed in the same tray as the test 

Specified Dips. — The standard method of making a test is as 
follows, using a "two-minute" immersion test for the purpose of 
illustration : 

The cleansed, washed and dried samples are immersed in fresh 
standard solution, within the temperature limits of 65° to 70° F., 
for exactly one minute. They are then removed, rinsed in water, 
of the proper temperature, and wiped with cotton waste so as to 
remove the dark deposit which forms, and until they are dry. 
They are then immersed again in the same solution for exactly 
one minute, removed, rinsed and wiped as above. Samples so 
treated should show no trace of metallic copper on the steel more 
than one inch from the end, although they may be black, indicat- 
ing nearly complete removal of zinc. If they do show copper on 
the steel they will be considered to have failed on the test and will 
be so marked in the record book. Occasionally copper deposits 
on the zinc, without removing the latter, and can be scratched 
off without destroying the zinc coating. Such cases, after the 
second immersion, are not counted as failures. 

The engineering department of the American Telephone and 
Telegraph Company have adopted the following test specifica- 
tions for galvanized iron and steel wire: 

These specifications give in detail the test to be applied to 
galvanized material. All specimens shall be capable of with- 
standing these tests. 

(a) Coating. — The galvanizing shall consist of a continuous 
coating of pure zinc of uniform thickness, and so applied that it 
adheres firmly to the surface of the iron and steel. The finished 
product shall be smooth. 

(b) Cleaning. — The samples shall be cleaned before testing, 
first with carbona, benzine or turpentine, and cotton waste (not 
with a brush), and then thoroughly rinsed in clean water and wiped 
dry with clean cotton waste. 

The samples shall be clean and dry before each immersion in 
the solution. 

(c) Solution. — The standard solution of copper sulphate shall 
consist of commercial copper sulphate crystals dissolved in cold 
water, about in the proportion of 36 parts, by weight, of crystals 


to 100 parts, by weight, of water. The solution shall be neutral- 
ized by the addition of an excess of chemically pure cupric oxide 
(CuO). The presence of an excess of cupric oxide will be shown 
by the sediment of this reagent at the bottom of the containing 

The neutralized solution shall be filtered before using by 
passing through filter paper. The filtered solution shall have a 
specific gravity of 1.186 at 65° F. (reading the scale at the level 
of the solution) at the beginning of each test. In case the fil- 
tered solution is high in specific gravity, clean water shall be added 
to reduce the specific gravity to 1.186 at 65° F. In case the 
filtered solution is low in specific gravity, filtered solution of a 
higher specific gravity shall be added to make the specific gravity 
1.186 at 65° F. 

As soon as the stronger solution is taken from the vessel 
containing the unfiltered neutralized stock solution, additional 
crystals and water must be added to the stock solution. An 
excess of cupric oxide shall always be kept in the unfiltered stock 

(d) Quantity of Solution. — Wire samples shall be tested in a 
glass jar of at least two (2) inches inside diameter. The jar with- 
out the wire samples shall be filled with standard solution to a 
depth of at least four (4) inches. Hardware samples shall be 
tested in a glass or earthenware jar containing at least one-half (i) 
pint of standard solution for each hardware sample. 

Solution shall not be used for more than one series of four 

(e) Samples. — Not more than seven wires shall be simultane- 
ously immersed, and not more than one sample of galvanized 
material other than wire shall be immersed, in the specified quan- 
tity of solution. 

The samples shall not be grouped or twisted together, but 
shall be well separated so as to permit the action of the solution 
to be uniform upon all immersed portions of the samples. 

(/) Test. — Clean and dry samples shall be immersed in the 
required quantity of standard solution in accordance with the 
following cycle of immersions. 

The temperature of the solution shall be maintained between 
62 and 68° F. at all times during the following test: 

First : Immerse for one minute, wash and wipe dry. 


Second : Immerse for one minute, wash and wipe dry. 

Third : Immerse for one minute, wash and wipe dry. 

Fourth : Immerse for one minute, wash and wipe dry. 

After each immersion the samples shall be immediately washed 
in clean water having a temperature between 62 and 68° F. and 
wiped dry with cotton waste. 

In the case of No. 14 galvanized iron or steel wire, the time 
of the fourth immersion shall be reduced to one-half minute. 

(g) Rejection. — If after the test described in section "F" 
there should be a bright metallic copper deposit upon the samples, 
the lot represented by the samples shall be rejected. 

Copper deposits on zinc or within one inch of the cut end shall 
not be considered causes for rejection. 

In case of a failure of only one wire in a group of seven wires 
immersed together, or if there is a reasonable doubt as to the 
copper deposit, two check tests shall be made on these seven 
wires and the lot reported in accordance with the majority of 
the sets of tests. 

Note. — The equipment necessary for the test herein out- 
lined is as follows : 

Commercial copper sulphate crystals. 

Chemically pure cupric oxide (CuO). 

Running water. 

Warm water or ice as per needs. 

Carbona, benzine, or turpentine. 

Glass jars at least 2 inches inside diameter by at least 4£ 
inches high. 

Glass or earthenware jars for hardware samples. 

Vessel for washing samples. 

Tray for holding jars of stock solution. 

Jars, bottles, and porcelain basket for stock solution. 

Cotton waste. 

Hydrometer cylinder 3 inches in diameter by 15 inches high. 

Thermometer with large Fahrenheit scale correct at 62 and 68°. 

Hydrometer correct at 1.186 at 65° F. 

Filter paper. 

Objections to the Standard Copper Sulphate Test — In the 
authors' opinion there are grave objections to the copper sul- 
phate test as carried out under either of the above specifications. 
The attack on the zinc coating which is made by the copper 


sulphate is most active when the wire is first immersed in the solu- 
tion and slows down to almost zero toward the end of the immer- 
sion. This slowing effect is of course due to the growing accumu- 
lation of deposited copper on the surface of the zinc. After the 
wire is withdrawn and wiped at the, end of one minute the action 
starts off rapidly again on the section immersion only to again slow 
down as before. The consequence of this action is that it is quite 
usual to find a sample that will stand a three-minute immersion 
without failure, whereas an additional one second plunge after 
wiping will suffice to completely plate the surface with adherent 
copper. It follows from this that the test as carried out is not giving 
the copper sulphate an opportunity to exert its maximum effect 
throughout the period of the test. In order to obviate this difficulty 
one of the authors carries out the test under the following specifica- 
tions which have been found to yield fairly concordant results: 1 
The clean wire sample is immersed with a quick motion in the 
copper solution, and at the end of exactly five seconds quickly 
withdrawn and at once dipped into pure water and wiped. The 
immersion should be timed with a stop-watch if possible. As 
long as no copper is visible plated out on the iron, the five-second 
immersions are repeated until the copper deposit which begins 
to form wipes off with difficulty. At this point a series of rapid 
two-second immersions are made, with alternate wipings, until a 
bright metallic copper surface, which cannot be wiped off the wire, 
appears. The total time of immersion in minutes and fractions 
of a minute is taken as an indication of the percentage of zinc 
carried by the wire. Thus, if 150 seconds' immersion were neces- 
sary to reach the end point, the weight of the galvanizing would 
be called 2.5 per cent. It must be remembered that although the 
results of this test are approximate only, their value depends 
entirely upon careful accuracy in following out the directions. 

It will readily be seen that the authors' method of making the 
test will give much lower results than those obtained under the com- 
mercial specifications given above. On the other hand, the results 
will be more accurate and more comparable. One great objection, 
however, to the more accurate method is that so much more time 
is consumed in carrying it out. In a wire mill in which samples 
are being tested from every bundle of wire made, this is a serious 

1 Cushman in appendix to Farmers' Bull., 239, U. S. Dept. Agr. 


Walker has very recently published some interesting and 
valuable data on the testing of galvanized coatings. He criticises 
the copper sulphate test in the following words : 

Walker's 1 Contribution to the Testing of Galvanized Coatings. — 
"When the copper sulphate reaction is used in testing galvanized 
iron it is assumed that the speed of solution of the zinc is a direct 
function of the time of immersion, and by the number of one- 
minute immersions necessary to dissolve the zinc from the iron 
and to deposit a film of bright copper thereon, the thickness of 
the zinc can be estimated. It will be seen that this method meas- 
ures the thickness of the coating only at its thinnest point, and 
that the assumption is made that no bright copper will be formed 
until the iron base is reached. To appreciate the limitations of 
this test, it is but necessary to note the structure of the three 
classes of zinc-coated iron." 

"Apolished oblique section of ordinary hot-galvanized iron etched 
with iodine reveals three distinct layers. First, a coating of zinc, 
which varies in thickness in accordance with the temperature of the 
zinc and the amount of squeezing or wiping applied to the article 
before the zinc solidifies; second, a distinct layer of a zinc-iron alloy, 
termed alloy B, which varies in thickness with the temperature of 
the zinc bath and length of time the iron was subjected to it; third, 
the iron base itself. Between the zinc and alloy B there is generally 
a second alloy, alloy A, which is a thin, discontinuous layer, richer 
in zinc than alloy B, and between the iron and alloy B is a third 
alloy, relatively unimportant, which is very rich in iron, alloy C. 

"The structure of wet-galvanized iron is comparatively simple, 
the layer being practically pure zinc." 

"Sherardized iron, on the other hand, presents a relatively 
complex structure. The metallic zinc penetrates the iron, form- 
ing deep layers of the alloys B and C, and in place of alloy A 
there occur$ a number of compounds, as yet unidentified. Upon 
the surface there is generally a layer of relatively pure zinc, 
although frequently the process is carried to the point where only 
a deep layer of alloys is formed. When examined under the micro- 
scope this alloy is seen to be covered with deep cracks or fissures 
as though the alloy in forming had contracted. It is thus apparent 
that in testing galvanized iron made by these different processes 
we are dealing with three very different materials." 
1 Electro-chem. and Met. Ind., VII. 10. 440. 


Walker's Desiderata for a New Test for Determining Durability 
or Resistance to Corrosion. — " It is the present purpose to treat 
of zinc-coated iron with regard only to its durability or resistance 
to corrosion, and not to its tensile strength. From this stand- 
point a test should, if possible, indicate the following: 

(1) The uniformity and thickness of the zinc coating; 

(2) the continuity of the coating with reference to pin holes; 

(3) the purity of the zinc, and 

(4) the toughness and ductility of the coating. 

The corrosion of pure zinc in water is very slow. If, however, 
the zinc is in electrical contact with any material upon which the 
hydrogen can be liberated, the corrosion of the zinc is relatively 
rapid. The iron-zinc alloy B, and the iron itself, are both sur- 
faces on which this depolarization action can take place, and, 
hence, so long as neither the iron nor the alloy is exposed, other 
things being equal, the zinc coating will not corrode. The impor- 
tance, therefore, of maintaining a uniform coating of metallic zinc 
upon the iron can be appreciated. 

To determine whether the ratio of the time of immersion 
required to produce a bright copper surface was in reality a 
measure of the thickness of the zinc coating, samples of galvanized 
sheets were obtained and tested. The weight of zinc per square 
inch area was determined by dissolving the zinc from the sheets 
without attacking the iron-zinc alloy. This can readily be 
accomplished by heating the galvanized sample, together with a 
piece of metallic iron, in boiling caustic soda until the generation 
of the hydrogen ceases. As might be expected, the ratio between 
the time of immersion required to show the presence of bright 
adherent copper and the amount of zinc present per unit area 
depends upon the uniformity with which the coating of zinc is 
spread upon the iron base. In the case of 14 pieces of galvanized 
sheet iron, for example, the average ratio found was 23, while 
the greatest variation in either direction was but 20. This test, 
therefore, so far as indicating the uniformity of the coating and 
measuring the thickness of the zinc are concerned, is fairly satis- 
factory; but alloy B is always indicated as iron, and hence, when 
the test is applied to sherardized articles, very erroneous and mis- 
leading results may be obtained. 

The presence of the channels or pin holes caused by the free 
iron surface coming in contact with the zinc and causing it to pass 


into solution cannot be detected by the copper-sulphate method, 
as these pin holes down through the zinc to the iron fill up with 
black, spongy copper and cover up the bright copper spot at the 

The purity of the zinc cannot be determined, as the bright 
copper particles precipitated by this method are so small that they 
are lost in the mass of black, spongy copper. 

Finally, the fourth factor, the toughness or the ductility of 
the coating, cannot be determined, due to the same tendency of 
the spongy copper to cover up the bright copper deposits, which 
indicate cracks extending down through the zinc coating to the 
alloy or iron underneath." 

Walker's Test for Detecting Pin Holes and Cracks, — "The rela- 
tion between the presence of pin holes in the zinc surface and 
cracks due to a brittle coating and the durability of the structure 
as a whole has not heretofore been studied, largely because no 
method of detecting these imperfections has been available. The 
following phenomenon serves as a basis for such a test. If a piece 
of zinc be placed in a strong solution of caustic soda heated to about 
100° C. no action is noticeable. If now the zinc be touched with 
a piece of iron, hydrogen is liberated in great volume from the 
iron. Small cracks in the zinc coating may be easily detected 
in the same way." 

"Ordinary hot-galvanized ware is generally very free from 
imperfections of this kind, while wet-galvanized ware, on the 
other hand, is frequently very porous, generating hydrogen at 
numberless small points over its entire surface. Theoretically, 
the best electroplated surface should be that carrying the greatest 
weight of zinc per unit area, deposited at the slowest rate. That 
is, the lower the current density at the cathode in plating, the less 
porous will be the deposited metal, and the thicker this dense 
deposit is the better protection will it be. A great many tests 
on electroplated zinc-coated iron were made, the samples varying 
in both these particulars. In every case, those deposited most 
rapidly were the most porous, and the results showed that the 
time of plating was more important than the weight of zinc per 
unit area, although there was a minimum below which it was not 
safe to go." 

Walker and Campbell's Test for Determining the Combined 
Effect of Imperfections.— "As the rapidity of hydrogen generat : on 


from zinc is a function of the presence of an alloy of zinc and iron, 
hence the more impure the zinc coating, the more rapid will be 
its solution in acid. Accordingly, the impurity of the zinc, the 
presence of pin holes and cracks, and the thinness of coating, are 
all factors which act in an accumulative way to increase the rate 
at which hydrogen is generated when the zinc surface is exposed 
to acid. This method has been developed by Mr. Charles L. 
Campbell in his thesis for the B. S. degree at the Massachusetts 
Institute of Technology, and found to give very concordant 
results. The apparatus employed may take any convenient 
form, it being but necessary to expose a known area of the zinc 
coating to a standard acid solution under uniform conditions and 
to measure the hydrogen generated per minute. In almost every 
case a sharp maximum is reached, giving the resultant of all the 
different factors which make for rapid dissolution of the zinc. 
Thus, in a series of wet-galvanized sheets, those electroplated for 
15 minutes reached a maximum of 7 cu. cm. in 3 minutes; those 
plated for 30 minutes a maximum of 14 cu. cm. in 10 minutes, 
while those plated for 45 minutes showed a rather poor maximum 
of 6 cu. cm. in 30 minutes. In many samples of sherardized pro- 
duct there were two maxima on the curve showing the amount of 
hydrogen generated per minute. This indicates that there is first 
an action between the outside zinc coating and the iron-zinc alloy, 
and later a well-defined action between the alloy and the iron." 

"Service tests with galvanized iron are of necessity very slow 
at best, and the relation of the above phenomenon to the real 
durability of the material can be determined only after a number 
of years. Something can, however, be learned by the study of 
ware which has already been exposed for sufficient time to 
determine its durability. Most of the material available for the 
purpose was in the form of fence wire ; from a study of these the 
following conclusions are drawn": 

First, Thickness of Coating, — "In every instance where a very 
durable fence was found, the coating of zinc proved to be relatively 
very thick. On the other hand, the wire fences which showed 
marked corrosion in from one to two years proved to have almost 
no zinc on the iron, the zinc color being due to a layer of alloy 
alone. It is doubtless true that the purity of the iron used in 
the wire itself plays an important part in determining the ulti- 
mate durability of a fence, yet in the opinion of the writer the 


thickness of the zinc coating calls for more immediate attention. 
The modern method of close mechanical wiping the wire as it 
emerges from the zinc bath produces too often a wire covered not 
with zinc but only a thin layer of electro-negative iron-zinc alloy, 
which affords but little protection to the iron. To produce a 
wire with a liberal coating of zinc would, of course, cost more, 
both on account of the extra zinc and on account of a somewhat 
smaller production per machine." 

Second, Purity of Zinc. — "It is probably a necessary conse- 
quence of hot galvanizing that the zinc becomes somewhat con- 
taminated with dissolved iron. It is apparent that this should 
be kept at a minimum in order that the coating should be of maxi- 
mum durability." 

Third, Flexibility of the Zinc Coating. — " The important objec- 
tion to placing a thick coating of zinc upon wire used for fencing 
is that such a coating cracks off when running through the machine. 
This objection applies only to those wires which are subjected to 
very sharp bends or turns. It is possible that by passing the zinc- 
coated wire through dies or under grooved rolls that the crystal- 
line condition of the zinc could be destroyed and the flexibility 
and ductility materially increased." 

Walker sums up his results as follows: 

1. "The copper sulphate immersion test is of value in deter- 
mining the uniformity of coating and relatively the thickness of 
coating in hot and in wet-galvanizing products; but it is worth- 
less in the case of sherardized products, and gives no idea of other 
important factors involved in the durability of the structure. 

2. By immersing a galvanized product in hot, strong caustic 
soda, the presence of any unprotected iron may easily be detected, 
however small such area may be. 

3. The weight of zinc per unit area apart from the zinc-iron 
alloy may be analytically determined by dissolving the zinc from 
the plate through treatment with hot caustic soda while in con- 
tact with metallic iron. 

4. Theoretically, the rate at which hydrogen is evolved when 
the galvanized product is immersed in dilute acid should indicate 
its relative durability; inferior products should reach a maximum 
in a few minutes compared with a much longer time for better 

5. In the very important matter of fencing wire, while the 


purity of the iron used is of consequence, a more immediate 
necessity is a heavier coating of zinc on the wire. 

6. The flexibility of a zinc-coated wire may possibly be 
increased by mechanically working the wire in rolls or dies, to 
destroy crystallization in the zinc coating." 

The authors desire to record here that the conclusions reached 
by Walker are in complete accord with their own opinions, as will 
appear in the following paragraphs which were written before 
Professor Walker's publication was available. 

Circumstances Affecting the Weight of the Zinc Coating and the 
Corrosion of Fence Wire. — Galvanized sheet metal from different 
sources show generally less variation than wire in the weight of 
zinc carried. The reason for this is perfectly obvious: the sheets- 
leave the spelter bath through light rollers and are set aside to 
cool. The rate of cooling affects the size of the " spangled''' 
crystalline structure of the zinc coating, but generally no effort 
is made to thin or smooth the zinc surface. Wire, on the other 
hand, is either smoothed or actually wiped as it leaves the spelter 
bath. This fact has an important bearing on the durability of 
wire galvanized by the hot-dip process. Telegraph, telephone, 
and in fact all straight-line wires which are not designed to be 
fabricated into any form of woven wire, are usually smoothed by 
drawing through a loose bed of damp charcoal or sand. Such 
wires can easily, and should always, be made to stand four- 
minute immersion in the copper sulphate test, this is sometimes. 
held to mean that the wire carries about 4 per cent, of zinc. This 
represents about the practical limit of the quantity of zinc that iron 
in any form can be made to carry in a smooth coating. If the coating 
is unsmoothed the zinc will to some extent collect in lumps and 
nodules which add to the cost without increasing the efficiency 
of the coating. The American market demands a form of wire 
fencing which for various reasons is not used to any extent in 
Europe. This is the woven wire or fabricated fence, so many 
types of which are in common use in this country. In the usuaL 
practice, wire for these fences is galvanized before the weaving 
or welding process of fabrication is begun, and if the coating of 
zinc is thick, it is liable to crack in the bends formed by the weav- 
ing machines. If a welding process is used too thick a coating 
of zinc interferes with the formation of strong bonds at the joints. 
For this reason it is customary to wipe the galvanized wire for 


fabricated fences as it issues from the spelter bath with asbestos 
wipers. The result of this treatment is that this type of wire 
generally will not stand more than two-minute immersions in the 
copper sulphate test, and trie authors have tested many. samples 
that would not stand even this length of time. Undoubtedly 
this is one of the principal contributory causes of the rapid corro- 
sion of woven-wire fences. 

It is well known to every one familiar with the process of gal- 
vanizing wire that it is not possible to get as heavy a coating of 
zinc on light-gage wires of small diameter as on heavier wires. 
It would therefore be unreasonable, even if unwiped wire could be 
used in fabricated fencing, to expect a number 14 gage wire to 
stand the copper sulphate test as long as a number 9 or 7 gage 
wire. The only cure for the fence problem will consist in the 
public demand for fences fabricated of heavy gage wire carrying 
the maximum weight of zinc consistent with the practical possi- 
bility of its manufacture. In the authors' opinion no wire of 
lighter gage than number 9 should ever be used in a fence if 
durability is an important consideration. From an economical 
point of view, it is cheaper to cut down the number of wires in a 
fence rather than to lighten their gage and weight. The authors 
would further suggest that the slight crackling of the zinc coating 
at the bends of wire or other flexible material should no longer 
be considered as objectionable, as it has been in the past. In the 
effort to reduce this tendency to crack the galvanizers have been 
tempted to wipe closer and closer, until in some of the modern 
practice almost no zinc is left at all. Cracking at sharp bends as a 
matter of fact is a good test of honest galvanizing and shows that 
at least a fairly heavy coating of zinc has been applied. Zinc is 
electro-positive to iron and when the two metals are in contact 
and wet with a corroding solution, zinc will be destroyed and iron 
will be protected. The extension of the sphere of influence of the 
protecting zinc will depend upon the severity of the attack. The 
more corrosive the action, the larger the protected area, but the 
more rapid the destruction of the zinc. This can easily be shown 
by soldering a button of zinc to a steel plate and immersing the 
whole in water or various corroding solutions. The appearance 
of such an experiment is shown in Fig. 32. From this point of 
view a heavily zinc-coated wire, even with slight cracks at the 
bends, should be preferred to a very light-coated wire which 


exhibits a smooth appearance to the eye. The test wire fences 
which are about to be described show that after fourteen months' 
exposure to the Pittsburg atmosphere the cut-off ends of the 
galvanized wires are all bright and free from any appearance of 
rust, although, of course, no zinc covers the cross-section of the 
cut-off ends. Since this is the case, slight cracking of the super- 
ficial coating of galvanized material should not be made the 
"bugaboo" of the honest galvanizer. It will often be noted that 
the cut ends of galvanized iron will rust in a warehouse if under 
cover, and will remain bright for long periods when exposed to 
more corrosive influences in the open. This apparently contra- 
dictory observation is accounted for by what has been said above. 
If the attack is very slight, such as is produced by condensed 
moisture from the atmosphere, the protective electrolytic action 
of the zinc does not come into play, leaving the iron to slowly 
coat itself with a superficial layer of hydroxide. Under the more 
severe outdoor conditions, however, the zinc continues to protect 
the iron in its neighborhood as long as it lasts. 

Summary of possible improvements in the hot-dip process: 

(1) Careful annealing of the wire and avoidance of stresses 
and strains. 

(2) Use of purer spelter and more careful attention to the 
drossing and scumming of the spelter bath. 

(3) Control of the acidity of the fluxing or soldering bath, with 
the possibility of substitution of an alkaline or inert fluid. 

(4) Development of methods for obtaining heavier coatings 
of zinc, with the possibility of devising a practical method for 
galvanizing wire fences after they are fabricated. 

The Electrolytic or Cold Method of Galvanizing. — Since it is 
possible by means of the electric current to deposit a coating of 
zinc on iron which is practically free from other metallic impuri- 
ties, it would seem that this method has some advantages over 
the hot-dip method. The fact that it has found and is maintain- 
ing a place in large industrial processes is the best indication 
that for certain purposes the method is successful. Like the 
hot-dip process, however, the cold electrolytic process has its 
weak points and is open to criticism. Burgess, 1 after an extended 
investigation, formed a favorable opinion of electro-galvanized 
material, but speaks of some of the disadvantages of the process 
1 Electro-chem. and Met. Ind., Ill, 1, 22. 


as follows: "It is seen that to obtain the best quality of coating 
the disadvantages of the electrical method are brought out, 
the principal one of which is the great length of time required to 
apply the deposit. This can be remedied only by the use of high 
current densities, and with solutions at present available it seems 
impracticable to run the density beyond 18 or 20 amperes per 
square foot on account of the liberation of hydrogen and unde- 
sirable physical quality of the deposit produced. In the tests 
made, 14.4 amperes per square foot was taken as best represent- 
ing practical conditions where a cold, unagitated solution is used. 
With this current density the metal may be deposited with a 
current efficiency of nearly 100 per cent. 

" A serious limitation upon the electrolytic process as at present 
applied is that after the coating has reached a certain thickness 
there is a tendency for it to become rough and crystalline, and 
this tendency makes it extremely difficult to apply a coating 
having more zinc than 30 grams per square foot." 

In another place the same investigator says: "A great diffi- 
culty lies in securing an even distribution of current over the object 
being plated, as demonstrated on corrugated sheet iron and other 
irregularly shaped articles. This causes, also, greater thickness 
and roughness around the edges. 

"The tests of durability show that the best results are attained 
with solutions operated as nearly neutral as possible, and that the 
addition of free acid, which seems desirable for keeping a clear 
solution, not only decreases the current efficiency, but also materi- 
ally reduces the efficiency of the zinc as a protection. 

"There seems, therefore, abundant opportunity for improve- 
ment in zinc-plating solutions, even though present methods are 
giving good results industrially. Such improvements may come 
through the discovery of new compositions for the bath which will 
enable higher current densities to be used, thicker deposits to 
be obtained, and greater stability and uniformity of operation 
acquired. Circulation has been suggested as an improvement, 
and it is to be expected that the advantages which efficient agita- 
tion gives in copper depositions may also be realized with zinc- 
plating vats. 

"The adherence of zinc coatings to iron is frequently ascribed 
to an alloying which is supposed to take place. The tests for 
adherence indicate that no such alloying occurs, either with hot or 


electrolytic galvanizing, since the tenacity with which the coatings 
adhere is far less than would be expected if alloying existed." 

Although it is true that the electro-galvanizing process pro- 
vides a method of obtaining a closely adherent coating of zinc 
which is not likely to be alloyed with other metals, evidence col- 
lected by the authors tends to show that material protected by 
this method is no more resistant to corrosion than that coated 
by hot dipping. Mowry 1 has claimed as the result of experi- 
ment that electrolytic coatings are inferior to those made by the 
hot-dip method. The difficulty seems to be, as has already been 
pointed out, that certain impurities from the electrolytic bath 
are included in the deposited zinc and become accelerators 
of corrosion. The Trunkhahn 2 system of electro-galvanizing 
attempts to surmount this difficulty by avoiding an acid bath, 
and by keeping the electrolyte saturated with nascent hydrogen 
by a special method which it is claimed prevents oxidation of the 
coating, renders it more dense, and prevents the occlusion of cor- 
rosion-stimulating impurities from the electrolyte. The authors 
have not been able up to the present time to determine to what 
extent the claims made for this system of electro-galvanizing are 
justified as far as the durability of the coatings are concerned. 

The Vapor Deposition Process. — The Cowper-Coles 3 method 
of vapor galvanizing which is known as Sherardizing is a develop- 
ment of recent years. There is a considerable literature on the 
subject as shown in Appendix B which should be consulted for 
full information. 4 "Vapor galvanizing is distinctive from all 
other forms of galvanizing inasmuch as the vapor of zinc is 
employed for coating metal surfaces instead of dipping them into 
molten zinc or into an aqueous solution through which a current 
of electricity is passed. Two forms of vapor galvanizing are 
practised, namely the 'zinc dust process' and the 'molten zinc 
vapor process.' In the first process the zinc dust and the iron 
articles to be coated are placed in an air-tight iron drum, which is 
heated in a gas-fired furnace to obtain a temperature within the 
drum of about 600° F. The length of time at which the drum is 
kept at that temperature depends on the thickness of the coat 

1 Mowry, Iron Age, 77, 352. 

2 See Dingler's Polytech. Jour., 320, 47, 1 (1905). 

3 J. Soc. Chem. Ind., 28, 399-403. 
" Chem. Abs., 3, 23, 2792. 


required. The drums are emptied over an iron grid, which retains 
the zinc-coated article and allows the zinc dust to collect into a 
receptacle in order to use it over again for charging the drums. 
The coating is distributed evenly and is alloyed with the iron 
surface. According to claims made, the alloy is non-corrosive and 
does not rust even when the zinc surface has been removed by 
abrasion. The advantages of vapor galvanizing are said to be 
that it is cheaper than the ordinary hot galvanizing, forms a bet- 
ter protection, and at the same time enables screw threads and 
machine work to be coated with an even distribution of zinc, so 
that the parts fit together properly. In the 'molten zinc process' 
the materials to be coated are placed in a cage or hollow drum 
which is slowly rotated inside an outer cylinder, composed of 
wrought iron, to ensure an even coating. The metallic zinc is 
heated by means of gas, or any other suitable means, to a tempera- 
ture sufficiently high to volatilize the zinc at the same time that 
hydrogen or any other gaseous reducing agent is forced into the 
apparatus. A modification of the vapor process is applied to the 
inlaying and decorating of metallic . surfaces which surpasses all 
other methods in artistic effects. Furthermore it has the advan- 
tage that a number of metals may be blended together, which 
hitherto has been impossible, and alloys of many tints and colors 
can be obtained in one operation." 

Sherardized material has not been available in this country 
for a sufficient time for complete tests of durability to be made. 
The vapor deposition process avoids some of the above-mentioned 
difficulties of the other two methods, but it is by no means cer- 
tain that it does not introduce other undesirable factors. Although 
zinc is electro-positive to iron, certain alloys of zinc and iron are 
said to be electro-negative and have in addition to this a higher 
solution pressure than pure zinc. If these alloys are formed in 
this process the main purpose of using zinc as a protective agent 
is defeated. On the other hand, the dry process can be used for 
galvanizing articles that have fine interstices, such as the threads 
of pipe fittings, etc., so that while it may not prove to be efficient 
for wire and some other special forms of iron, it will probably have 
a distinct field of usefulness. 1 The results of durability tests of 

1 Since the above paragraph was written Sang has described his Electro- 
Cementizing process for wire. This is a modified form of the vapor deposition 
method. See Proc. Elec. Chem. Soc, XVI, 257. 


sherardized material will be watched with interest. One curious fact 
that has been noted in connection with exposure tests on sherardized 
material is the peculiar black sooty color that is assumed by the 
exposed surfaces. After once acquiring the black surface, sherar- 
dized articles appear to be very resistant to corrosion. 

Tests of Galvanized Wire. 1 — At the request of one of the writers 
a number of interesting tests have recently been undertaken for 
the purpose of ascertaining the relative resistance to corrosion 
of steel wires of varying chemical composition, and also to show 
the relative value of protective coatings. 

With these ends in view twelve samples of galvanized steel 
wire were manufactured by the American Steel and Wire Com- 
pany. They have been put up in the form of fence and exposed 
to the action of the weather on the grounds of Carnegie 
Technical School at Pittsburg (Fig. 33). These twelve samples 
fall into three groups, which will be described in the order in which 
they were made. 

The first sample was a wire of the following composition: 

Per Cent. 

Carbon 0.66 

Manganese 84 

Sulphur 028 

Phosphorus 016 

This was made by the basic open-hearth method. The ingots 
were cast July 23, 1908, and were reheated and rolled into billets 
the same day. On the following day they were again heated to 
redness and rolled into A-inch rods. One billet was taken at 
random from the lot for the purpose of this test. The rod after 
cooling was cleaned by immersion in hot dilute sulphuric acid, 
then rinsed with water and dipped into milk of lime. After drying, 
the rod was drawn cold into 9-gage wire. It was then galvanized 
by passing it through a furnace in which it was heated to dull 
redness, and then into a bath of hydrochloric acid containing zinc 
chloride, and lastly into a bath of molten zinc. This wire was not 
wiped; that is to say, it was allowed to retain as much zinc as 

1 The expenses of these tests were incurred by the American Steel and 
Wire Co., and the fences were mounted on the grounds of the Carnegie Tech- 
nical School at Shenley Park, Pittsburg. The tests have been placed under 
the general supervision of Committee U of the American Society for Testing 
Materials. A description of them is included here as the intention is to keep 
them in place for a number of years until final failure occurs. 


would adhere to it. This sample was designated C-l, and it is 
purposed to test it against any of the low-carbon, low-manganese 
wires to be described later, and which may for this purpose be 
regarded as C-2. 

The second group consists of six samples of "American" style, 
8-strand fabricated fencing, 45 inches high. The object of this 
group is to determine the effect, if any, of segregation of the 


impurities in the iron. Therefore the six samples were taken 
from the same heat. The steel was made at the same mill and 
on the same day as sample C-l, but by the Bessemer process, 
and was cast in six ingots. As these ingots were rolled, two billets 
were taken from the top of the first ingot, two billets from the 
middle of the first ingot, and two from the bottom of the first 
ingot. These three pairs of billets were marked, respectively, 
A-l, A-2, and A-3. Similarly, from the last ingot of the heat 
two billets were taken from the top, two from the middle, and two 
from the bottom. These three pairs of billets were marked, 
respectively, B-l, B-2, and B-3. These were all rolled hot into 
rods, and after cooling and cleaning, in the manner described 
above, were drawn into wire. The six samples were each divided 
into three portions. About half of each sample was drawn into 
11-gage wire, a quarter of each sample into 9-gage wire, and the 
remaining quarter into 12-gage wire. This was because these 
three sizes of wire are all used in making the standard "Ameri- 
can" fence, the 9-gage for the top and bottom horizontal strands, 
the 11-gage for the intermediate strands, and the 12-gage for the 
vertical connecting wires. Immediately after being drawn the 
wire was galvanized in the same manner as described for sample 
C-l, except that on emerging from the molten zinc it was wiped 
by a mechanical device which left a thin, smooth coating of zinc 
on the steel. A separate piece of fencing about 300 feet in length 
was then woven from each of the samples. These six pieces of 
fencing then represented the top, middle, and bottom of the first 
and last ingots of the heat, respectively. The samples were not 
analyzed separately, but an analysis of the heat as a whole showed 
percentages as follows: 

Per Cent 

Carbon ;■> 0.09 

Manganese 55 

Sulphur 045 

Phosphorus 092 

The third group consists of five samples of basic open-hearth 
steel showing increasing amounts of manganese from 0.07 per 
cent, to 0.37 per cent. These were all made in one furnace, 
between August 18 and August 22, 1908. The process of manu- 
facture throughout was identical with that employed on the 
sample designated C-l, except that the wire was wiped during 



the process of galvanizing. These five samples were ail drawn 
to 11-gage and are designated by their "heat numbers," which 
axe given here together with the analyses. 

Analysis of Five Samples Forming the Third Group. 

Heat Numbers 





Per Cent. 

Per Cent. 

Per Cent. 

Per Cent. 


























All the wire described above was shipped to Pittsburg, Penn- 
sylvania, and between September 23 and September 26, 1908, was 
put up in the grounds of the Carnegie Technical Schools. The 
site assigned for this purpose is a level strip of ground at the 
bottom of a deep and narrow natural depression to the north of 
the quadrangle of school buildings. Because of this location none 
of the wire will be exposed to the action of wind, but all will 
show the effects of fog and dampness, which are very prevalent 
in this hollow. 

The fence was put up in an extremely substantial manner. 
The posts are 2 by 8 inches, dressed oak; the corner posts are 8 
by 8 inches, sunk 3 feet in the ground. The lower ends were 
painted with a mixture of benzine and asphalt, and the portion 
above ground with ordinary lead paint. The post holes were 
filled in with concrete. 

There are four parallel lines of posts, as shown in Fig. 33, 
3 feet apart and 275 feet long. These lines run almost due east 
and west. The one farthest north is called row No. 1, the next 
row No. 2, the next row No. 3, and the line farthest south No. 4. 
The arrangement of the wire on these posts is as follows : 

On the north side of row No. 1 is placed sample A-l. 

On the south side of row No. 1 is placed sample A-2. 

On the north side of row No. 2 is placed sample A-3. 

On the south side of row No. 2 is placed sample B- 1. 

On the north side of row No. 3 is placed sample B-2. 

On the south side of row No. 3 is placed sample B-3. 


On the north side of row No. 4 at the top are 8 strands of 8119. 

On the north side of row No. 4 at the middle are 8 strands 
of C-l. 

On the north side of row No. 4 at the bottom are 8 strands of 

On the south side of row No. 4 at the top are 8 strands of 8122. 

On the south side of row No. 4 at the middle are 8 strands of 

On the south side of row No. 4 at the bottom are 8 strands 
of 8120. 

In the first three rows the posts are 15 feet apart, in the fourth 
row 30 feet apart. The wire was all stretched as tightly as possible 
to prevent sagging, and none of it is less than 1 foot above the 

In addition to the test fences described above, a number of 
panels have been mounted on either side of the original rows 
in order to test different methods of providing protective coat- 
ings for ordinary steel wire fences. One panel of American style 
woven-wire fence is galvanized by the cold or electroplating 
process; another panel is made of double galvanized wire carrying 
about the same weight of zinc as is usually specified for telegraph 
wire. This galvanizing has been done by a special adaptation 
and variation of the ordinary hot-dip process, and has not been 
subjected to the acid bath before galvanizing. A third panel is 
coated with zinc by the Sherardizing process. A number of 
panels, in part galvanized by the ordinary hot-dip process, and 
in part ungalvanized, have been protected by painting with vari- 
ous protective paint coatings. The formulae of these stimulative 
and inhibitive paints will be published in a special report. All 
of these extra panels have been mounted in exactly the same 
manner and side by side with the samples already described in 
the foregoing, and the tests should in the course of time yield 
results of great value. A key to the arrangement of all the panels 
is shown in Fig. 34. 

Preservation with Tin. — Roofing, cans, and tinned utensils 
of all kinds depend for their preservation on a metal coating 
which, though not electro-positive to iron, has such a low solution 
tension that it is known to be practically incorrodible. The 
principal difficulty encountered in the use of this metal is that it 
seems impossible to apply it economically to the surface of steel 


aod Aiaioos nvoiubwv 

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so that pinholes shall not exist in the coating. Walker has shown 
this by an ingenious modification of the ferroxyl test. 1 A slightly 
acid solution of gelatin containing a small amount of potassium 
ferricyanide is flooded, while hot, upon the surface of the tin 
plate to be tested. The gelatin becomes hard upon cooling, and 
in a very short time every pinhole on the tin surface is marked 
by a spot of Turnbuli's blue. The results obtained by Walker 
are illustrated in Figs. 35 and 36. They are made even more 

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Fig. 35. — Showing Walker's method of determining pin holes in tin 


interesting by comparison with the actual corrosion of a tin plate 
under service conditions shown in Fig. 37. After the number 
and position of the pinholes is known, it becomes possible to study 
ways and means of eradicating them. Hot rolling and ageing of 
the plates under pressure are among the solutions that have been 
suggested in the hope that the pinholes will disappear. 

The passage of the Food and Drugs Act of 1906 has had a 
curious and interesting bearing on the tin-plate industry in its 
application to canned goods. Artificial coloring matter is debarred 
by this law, and it was found that the natural color of preserved 
food-stuff is reduced and destroyed by the action of the tin. In 

1 Jour. Iron and Steel Inst., 1, 79 (1909). 


the effort to meet this difficulty the can manufacturers sought to 
use less tin, and also to lacquer the tin plate so as to prevent its 
contact with the fruit and vegetable juices. The formation of 
pinholes has gone on rapidly, however, so that it is not an unusual 
occurrence to find tinned preserves discharging their juices in 
tiny streams through small holes resulting from rapid corrosion. 
Walker's more recent researches on this subject have already 
been described in a previous chapter. 


. ' 








. • 



' ". 

Fig. 36. — Showing Walker's method of determining pinholes in tin 


Preservation with Copper, Lead, and other Metals and Alloys. — 
It is possible to make copper-coated steel, but this makes an 
efficient and rust-resistant material only when the coating is 
thorough and homogeneous. Methods are being developed to 
extend the use of copper for this purpose, and it is now applied 
to wire as well as to sheet and plate metal. If the cost is not 
a prohibitive factor, there would seem to be no reason why steel 
protected in this way should not come into more general use. 
It follows, however, from the electrolytic theory of corrosion that 
if openings in the copper coating occur so that water can pene- 
trate to the point of contact, the corrosion of the iron will go on 
very rapidly. Tassin, 1 speaking for the new metallurgical product 
1 Jour. Industrial Chem., 1, 9, 670. 


known as copper-clad steel, makes the following claims: " Copper 
and steel in the presence of moisture form a galvanic couple, and 
the corrosion of the steel proceeds with great rapidity. The resist- 
ance to corrosion of copper-clad so far as the copper coating is 
concerned is, of course, the same as that of copper. But, in 

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•lli 1 


■■;■■■ '■■ ■ ■."■/' ■' ' 

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Fig. 37. — Charcoal iron tinned plate, showing the corrosion lines. 

view of the marked galvanic action set up between copper and 
steel, it would be assumed that corrosion would quickly occur at 
the exposed ends, and be a constant factor so long as an elec- 
trolyte was present. This supposition is not so, at least in 
the presence of fresh or salt water. Test samples placed in 
water, through which a current of air has been allowed to bubble 


continuously for three months, demonstrated that after a certain 
period of time, somewhere between 15 and 40 days, corrosion 
practically ceases, as shown by taking the loss in weight of the 
tests at varying periods. It is believed that this stopping of 
corrosion is a result of the following conditions : 

"After a certain amount of rust has been formed, it appears 
that a thin film of copper mixed with some copper oxide is plated 
out or deposited between the iron oxide and the unattacked steel, 
and that this film will act as a preservative coat as long as it 
remains intact. If broken, further oxidation sets up and the 
process simply repeats itself. While it is true that the corrosion 
on the end of a wire is not a factor in its life, yet the corrosion 
of the end of a relatively large diameter may become very serious. 
If the above observations hold true on larger sizes (so far it has 
not been tried on sizes above f in.) it will have quite a bearing 
on material suitable for marine work. Tests along this line are 
now being carried out, and the evidence to date points to a con- 
firmation of the observations made on the smaller sizes." 

Lead has to some extent been used for covering iron, and for 
certain purposes this material is useful. It is doubtful, however, 
whether the application of lead for this purpose will find a very 
wide field of usefulness. Terne plate covered with an alloy of 
lead and tin is, of course, extensively used. There have been 
many complaints recorded in regard to the rapid -corrosion of 
this material, to which much that has been said in previous 
paragraphs of this book about other forms of protection will 

Many other alloys have been proposed and experimented with 
for the protection of iron. In more recent work the effort is 
made to change the electro-negative character of lead or tin by 
producing electro-positive alloys of these metals that will have 
the proper physical characteristics to warrant their use as pro- 
tective coatings. Among these may be mentioned an alloy of 
lead and antimony, and of tin with antimony and aluminum. 
None of these special alloys have as yet come into very general 

Processing after Manufacture. — A number of metallurgical 
processes, which depend upon the production of a fully oxidized 
surface on iron and steel, have been in use for a number of years 
and are too well-known to require description. Among these are 


the Bower-Barf and Wells methods of producing a surface of 
magnetic oxide. If perfectly coherent and homogeneous such a 
surface is, of course, unrustible. The protection of the metal 
depending as it does upon a coating that is strongly electro- 
negative to iron, it follows- that any manipulation or accident 
that injures the continuity of the covering surface must neces- 
sarily lead to accelerated and deep corrosion. This fact together 
with certain other practical difficulties has confined the use of 
these processes to special cases where protection from corrosion 
is a matter of prime importance. It is claimed for the process 
that it is specially valuable for builders' hardware, domestic 
articles, wrought-iron grilling, railings, and the better class of 
scroll and fancy work. It has also been used for pipe of various 
kinds, and can be used on general structural material of a rigid 
nature. It could not, of course, be used with wire or flexible forms, 
owing to the brittle nature of the magnetic oxide. 

The well-known Russia iron, which is in common use for stove- 
pipes, locomotive casings, etc., depends upon a similar oxide 
coating. When taken care of, iron treated in this way will last 
for many years without failure from corrosion. 

Sang 1 in an article on the inoxidation processes for protecting 
iron and steel gives the following information: In the Barf 
process the articles to be coated are heated to 1000° and steam 
superheated to 538° is injected into the coating chamber. In 
the Bower process, producer gas rich in carbon monoxide is said 
to reduce the red oxide obtained by air treatment or by subject- 
ing the work to acid fumes. In the Bower-Barf process the articles 
to be coated are heated in a closed retort to 871°, after which 
superheated steam is injected which forms a coating of the black 
magnetic oxide. The operations are repeated alternately until 
a sufficient depth of oxidation is obtained. The cost of treatment 
is expensive and ranges from $5 to $20 per ton. It is claimed 
that enamel will hold tenaciously to iron so treated and that paint 
can be applied without trouble. The coatings are said to resist 
acid fumes better than galvanized iron; they are not affected by 
solutions of copper sulphate. This method has been used to 
some extent for coating pipes in order to make them withstand 
corrosion. A modification of the Bower-Barf is the Wells process, 
which consists of introducing the steam and carbon monoxide at 
1 Electro-chemical Metallurgical Industry, 7, 351-3. 


the same time. In Gesner's process, a compound of hydrogen, 
iron, and carbon is said to be deposited on the iron. Steam at 
low pressure is introduced through a red-hot pipe into the coat- 
ing retort, which is kept at a temperature of 538° to 649°, while 
some hydrocarbon gas is allowed to enter slowly. By this means 
the higher oxide of iron is reduced and the surface carbonated. 
The charge for so treating small articles is said to range from 4 
to 7 cents per pound, and for large pieces about 1 cent per pound. 
The Dewees Wood's process is similar to Gesner's process. Ruf- 
fington employs potassium nitrate in his method for oxidizing 
the surface of the iron. Claudius uses a solution of a manganese 
compound for the production of durable black coatings or patina. 
Hydraesfer's process is essentially similar to Gesner's, but requires 
only one furnace operation. 

A number of electric processes have been proposed, both for 
oxidizing the surface of steel and also for producing a passive 
condition of the surface. One of the authors called attention 
to the possibility of the use of electric currents in producing a 
passive condition some years ago. Meritens' method uses a bath 
of distilled water at a temperature of 70° to 80° and applies a 
weak current. The nascent oxygen which is given off in the 
presence of the hydrogen occluded in the metal produces a film 
of black oxide of iron. It is, however, impossible to produce a 
deep coating unless a sufficient amount of hydrogen is present 
in the iron, and on this account it is generally necessary to run 
the article first as cathode in order to enable it to absorb hydro- 
gen. Lately Toch has been investigating the use of electric 
currents to produce a more or less lasting passive condition of 
the surface. This work has not yet been published in detail, but 
it is understood to consist in making the iron to be treated an 
electrode in an alkaline solution using a current of large amperage 
at low potential. Krassa x works in a hot caustic soda solution 
and makes the iron the anode. Strong currents make the anode 
passive at once, while weak ones cover it with a black coating 
of Fe 3 4 . To get active iron again the specimens must be boiled 
for a long time. Further work along these lines will be watched 
with interest. 

Several other methods have been proposed from time to time 
for processing after manufacture in order to make the surface 
1 Zeit, Electro Chem., 15, 490. 


resistant to corrosion. The Coslet process is said to consist in 
immersing the iron in a hot, phosphorized solution containing 
an iron compound. The surface, it is claimed, is converted into 
a ferroso-ferric phosphate, which is to some extent resistant to 
corrosion. Jouve * has called attention to the fact that iron 
containing 10 per cent, of silicon is not attacked by acids, and, 
therefore, such material should theoretically be unrustible. The 
authors have confirmed this deduction by experiment, and found 
that iron containing 10 per cent, of silicon is almost incorrodible. 
Unfortunately, such a metal is not workable, and has peculiar 
properties. Since silicon is much like carbon, chemically speak- 
ing, it would seem as if it might be worked into the surface of 
steel by modifications of some of the processes used for case- 
hardening with carbon. 

Unprotected Steel. — A large proportion of the iron and steel 
which is in use cannot, from the very nature of the service to 
which it is put, be protected from corrosion. To this class belong 
rails, heavy chains, implements, boiler tubes, etc. The only hope 
of meeting this particular phase of the problem consists in the 
improvement of metallurgical processes, to the end that perfectly 
homogeneous metal, as free as possible from segregation, may be 
manufactured. It is well known that some of the alloyed steels, 
such as nickel steel, are very highly resistant to corrosion. The 
same thing is probably true of the chromium, vanadium, and chro- 
mium-vanadium steels. Unfortunately, such materials are too 
costly to be used on a large scale, although there is always the possi- 
bility that some alio} 7- or combination will be discovered which will 
be at the same time comparatively inexpensive and incorrodible. 

The Corrosion of Boilers. — One of the most important phases 
of the technical preservation problem is the necesssity for pre- 
venting the pitting of boilers and boiler tubes. In a bulletin 
published some years ago, one of the authors 2 stated that the 
pitting of boiler tubes was probably due to electrolysis, and it 
was shown that Wood had reached the same conclusion in 1894. 
Wood 3 said: "That there is a continual electrical action of a most 
complex character present in all boilers under steam can scarcely 

1 Engineer, 1908, Vol. CVI, p. 397. 

2 The Corrosion of Iron. Bui. 30, Office of Public Roads, U. S. Dept. 
Agr. (1897). 

3 Am. Soc. Mech. Eng. Trans. (1894), 15, 998. 


be doubted, and the same action, but less apparent, is possibly- 
present in all constructions of iron when the different members 
formed of iron and steel of various compositions, made by different 
processes after various torturing methods of manufacture to bring 
them to the desired shape, are assembled and put into duty under 
strains and conditions foreign to their nature. It would be strange 
indeed did not some electrical energy manifest itself and call for 
some palliative if not protective means of arresting decay." 

Recently Burgess 1 without reference to previous authorities 
has reached the same conclusion. Burgess describes an investi- 
gation which shows the importance of electrolytic action in boiler 
corrosion, and states that if electrolytic action were entirely 
absent or could be entirely neutralized, there would be practi- 
cally no internal corrosion. Iron may itself set up electrolytic 
couples even if it is not segregated owing to physical strains 
occasioned by previous heat treatment. Burgess suggests as a 
possible remedy the use of an external iron bar maintained as an 
anode by a current from a dynamo, the negative pole of which is 
connected to the boiler. This suggestion had been made many 
times before 2 in connection with boiler tubes and also for the 
protection of pipe lines; it has not, however, as far as the authors 
are aware, been very generally adopted. 

The expedient of using metallic zinc in boilers to overcome 
local electrolytic effects in the iron by producing a still greater 
electrolytic effect at the almost exclusive expense of the more 
positive zinc is well known and has been in use for a long time. 
Great difficulty has, however, been experienced in maintaining 
good metallic contacts between sufficiently large surfaces of the 
two metals under the conditions which maintain in a boiler; 
moreover, as has been previously shown, the protective action 
of zinc takes place only in a restricted area. 

The most practical method for protecting boiler tubes depends 
upon the exclusion of oxygen from the feed water. It has been 
shown that oxygen plays an important contributing role in the 
electrolytic corrosion of iron. In order to remove this action, 
the use of pyrogallol, amidol, tannic acid, and other reducing 
agents has been proposed, but far more practical ways than this 
are known. Feed-water heaters in which all the dissolved gases 

2 Jour. Western Soc. Eng., 14, 375. 

2 See Cushman in Journal Iron and Steel Inst,, 1 (1909), 37, 


may be removed are not difficult to design, and if these were 
made a necessary adjunct of all boilers there would be fewer cases 
of boiler-tube corrosion to cope with. 

Special Cases Met with in the Preservation of Iron. — In the 
opinion of the authors the most interesting and significant dis- 
cussion of recent date on a special corrosion problem is to be 
found in the Transactions of the American Institute of Mining 
Engineers for the years 1907 and 1908. The special significance 
of this discussion lies in the fact that it exhibits the more or less 
divergent opinions of a number of engineers and experts of wide 
experience. We find in it the views of engineers who are con- 
sidering their problems in the light of the electrolytic explanation 
of corrosion, as well as the opinions of those who refuse to consider 
that any form of electrolysis is a factor. 

Theories are manifestly of little value unless they can come to 
the aid of those who are charged with the great industrial prob- 
lems of the world, and it is in the court of practical experience 
that a working theory must be tried and either proved or found 
wanting. At the same time it frequently happens that an engi- 
neer will at first consider as "new-fangled" or " fanciful" a new 
theory only because he has not fully grasped its meaning or 
recognized its application to his problem. The authors have 
thought it best to include the entire discussion in an appendix 1 
as its re-reading will undoubtedly stimulate thought. Indeed, the 
problems discussed should be reviewed in the light of the modern 
theories and explanations of corrosion. 

As has been pointed out, the technical preservation of iron 
and steel presents a great number of separate problems, each one 
of which requires special consideration and different treatment. 
As an instance of this, it may be stated that the cases of wire, 
of ships' bottoms and boiler tubes involve special difficulties, in 
which the environment and conditions of service are so different 
as almost to constitute three separate problems. Nevertheless, 
the same underlying principles apply to the general problem of 
the corrosion of iron in all its phases. It has been the object 
of the authors to make these principles clear in the foregoing 
pages. The protection of the great bulk of finished iron and steel 
must inevitably remain a paint problem, and to the consideration 
of this the remaining portion of this book will be devoted. 
1 Appendix A, p. 279. 



The many theories which have attempted to explain the 
rusting of iron, during the last century, have stimulated a large 
amount of original research on the relation of various pigments 
to the corrosion problem. In the course of the investigations 
undertaken, the subject of protective coatings for iron and steel 
was naturally brought into prominence and received a consider- 
able amount of attention. The study of protective coatings 
for iron has led many paint manufacturers, as well as scientific 
investigators, to make a closer study of the causes of corrosion. 
It is evident that the electro-chemical explanation of corrosion 
must have a direct bearing on paint problems. 

In the course of researches carried on by one of the authors 
upon the corrosion of iron, it was found that certain substances 
in contact with iron possessed the property of exciting electrical 
action and stimulating corrosion, while still other substances 
exhibited a tendency to inhibit or prevent corrosion. Bichro- 
mates of soda and potash were found to be the most eminent 
examples of the so-called "inhibitives," and it was found that 
as long as steel or iron remained in contact with these salts, even 
in fairly dilute solution, rusting could not take place. This 
naturally suggested the preparation and use of slightly soluble 
chromates as pigments. It was found that the chromic acid salts 
could be precipitated with certain other compounds to produce 
chromates applicable as pigments. A series of these compounds 
were prepared and tested; but it soon became apparent that 
while some afforded protection to steel, others did not. The raw 
materials used, the method of preparation, the amount and 
character of the contained impurities, together with other factors, 
had a marked influence upon the efficiency of these compounds. 
It was even found that a series of chrome salts, all of which theo- 
retically should have possessed inhibitive value, were in many 
cases actually stimulative. 

Testing Pigments in Water Suspension. — The results obtained 



from these investigations led to a series of experiments, first 
suggested by Thompson, in which the effort was made to determine 
the relative inhibitive value of a number of typical pigments for 
application to iron. A series of fifty of the most important pig- 
ments used in the manufacture of paints was therefore procured 
and submitted to test. The apparatus in which these pigments 
were tested consisted of a series of eight-ounce bottles, into each of 
which was placed a measured amount of pigment, afterward adding 
the same amount of distilled water to each bottle. Into each bottle 
was then placed a strip of steel, numbered and carefully weighed. 
The bottles were then connected up in series by the use of rubber 
stoppers and bent glass tubing, through which a constant current 
of washed air was passed for a period of three weeks. At the 
end of this time the train of bottles was disconnected, the steel 
plates removed, washed off, carefully brushed with a tooth brush, 
to remove any extraneous or adherent pigment particles, and 
afterward dried and carefully reweighed. A loss in weight repre- 
sented the amount of iron which was removed by corrosion. 
From the results obtained it was possible to tentatively divide 
the pigments into three groups. 1 The pigments which caused 
the most active corrosion were termed "rust stimulators/' those 
which showed the least action were termed "rust inhibitors/' 
while those which were found to be intermediate in the group 
were called "inerts." 2 The results were charted, Fig. 38, show- 
ing the position of each pigment tested, and the results proved 
so interesting that it was decided by Committees "E" and "U" 
of the American Society for Testing Materials to carry on a sup- 
plementary series of experiments. A considerable quantity of 
pigments similar to those used in the first test were collected in 
the open market, and samples of each, from the original package, 
were put in cans, carefully marked, stamped, and forwarded to 
members of the Committee, who had volunteered to repeat the 
work. A series of small plates of steel of the same size, cut from 
the same sheet of metal, and all stamped with numbers running 
from 1 to 50, were also supplied to each investigator. A descrip- 
tion of the apparatus used for the test was also sent to the mem- 
bers of the Committee. 

1 See Cushman, The Inhibitive Power of Certain Pigments on the Corrosion 
of Iron and Steel. Proc. Am. Soc. Testing Materials, VIII, 605 (1908). 

2 Some objection was made to this use of the word ( inert" and the joint 
Sub-committee of Committees U and E, Am. Soc. Testing Materials, 
adopted the word ( 'indeterminate." 

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The results obtained by the various investigators, working 
independently and in different laboratories, were afterwards 
compared at a special sub-committee meeting, called for the 
purpose. The agreement between the results obtained by the 
several investigators corroborated the results of the original work, 
and appeared to indicate that the theory of inhibitives should 
have some practical application. 

Effect of Impurities and Other Factors Governing Nature of 
Pigments. — Since this work was done, so much progress has 
been made following this line of investigation that it now seems 
possible for certain rules to be formulated in regard to the 
inhibitive value of various pigments. Not only the nature of the 
pigment itself, but also the quantity and kind of impurities 
contained in it, decide in which one of the three groups a given 
material must be classed. The solubility of the pigment, and the 
ease with which it is ionized when brought into contact with 
water, are also important considerations. If the pigment is of a 
basic nature, and therefore tends to increase the number of 
hydroxyl ions in solution, it is sure to be in the inhibitive list, 
provided the concentration of the hydroxyl ions is sufficiently 
high to furnish protection. If the pigment is acid in nature, or 
contains any free acid which is easily hydrolized, it is quite 
certain to appear in the stimulative group. 

The question naturally arises as to whether a pigment which 
has been shown to possess active stimulative properties may be 
mixed with a pigment possessing inhibitive values, and in this 
manner become inert or non-stimulative. This depends largely 
upon the percentage of inhibitive pigment added. In some cases 
the addition of a large quantity of inhibitive pigment would be 
of little value, as the following statement already published by 
one of the authors illustrates: 1 "If the surface of iron is subjected 
to the action of two contending influences, one tending to stimu- 
late corrosion, and the other to inhibit it, the result will be a break- 
ing down of the defensive action of the inhibitor at the weakest 
points, thus localizing the action and leading to pitting effects. " 

It is interesting to note that the two samples of Prussian 
blue which were included in the tests described in a previous 
paragraph showed widely divergent results, one proving to be an 
inhibitor and the other a stimulator of corrosion. As a matter of 
fact, these two samples of Prussian blue were prepared by different 
1 Proc. Am. Soc. Testing Materials, 1908, VIII, 606. 


methods. In one, acid impurities were sure to have been included. 
As has been already pointed out in a previous chapter, it is impossi- 
ble to throw down a colloidal precipitate from a solution without 
the inclusion of ions and salts from the mother liquors. The 
methods of manufacture used in these two Prussian blues served 
as an advance indication that one would appear in the stimulative, 
and the other in the inhibitive class, and they were so marked. 
The fact that the result of experiment brought out this relation 
presents additional evidence in support of the general theory. 

Fig. 39. — Apparatus used in testing inhibition value of pigments. 

It is well known that a good working theory should enable 
an investigator to predict to some extent in advance what the 
results of experiment should show. Thus with the theory of 
periodicity of atomic weights in hand, Mendeleeff was enabled 
to predict the existence of unknown elements which were subse- 
quently discovered. Although it is not claimed that the obser- 
vations in regard to the Prussian blues are of the same order 
of magnitude as the predictions of Mendeleeff, nevertheless the 
results obtained are none the less suggestive. 1 

The results of these tests are given below. The apparatus 
used in their determination is illustrated in Fig. 39. 

1 It is of course not yet shown that the relative durability of paint coat- 
ings under service conditions will agree with these results, but the authors 
think that the point made is none the less interesting. 


Chart of Findings of Members of Committees "E"and "T7", American 
Society for Testing Materials. Loss of Steel in Grams in Tests 
Carried Out on Pigments to Ascertain Their Value as Rust 



No. 1 
20 days 





































Zinc Chromate 

Zinc and Barium Chromate . . . 

Zinc and Lead Chromate 

Zinc Oxide 

Zinc Lead White 

Barium Chromate 

Ultramarine Blue 

Chrome Green (blue tone) 
Prussian Blue (Inhibitive) 


Willow Charcoal 


Dutch Process White Lead .... 
Quick Process White Lead .... 

Calcium Sulphate 

Prince's Metallic Brown 

Orange Mineral French 

Calcium Carbonate (Whiting). . 

Sublimed Blue Lead 

Lemon Chrome Yellow 

Orange Chrome Yellow 

Medium Chrome Yellow 

Chrome Green 

Venetian Red 

Bone Black 


Keystone Filler 

Orange Mineral (American) . . . 


China Clay 

Calcium Carbonate Precipitated 

Red Lead 

Prussian Blue (Neutral) 

Indian Red 

American Vermilion 

Sublimed White Lead 


Naples Yellow 


No. 2 

7-£ days 















































































No. 2 

10 days 







































W. H. 
No. 1 













































Chart of Findings, etc. — Continued 



Prussian Blue (Stimulative) 

Mineral Black 


Natural Graphite 

Bright Red Oxide 

Acheson Graphite 


Carbonith White 

Carbon Black 

Precipitated Blanc Fixe 
Lamp Black 

Gardner Cush- 

No. 1 
20 days 


10 days 





P. H. 
No. 2 

74 days 




No. 2 
10 days 




No. 1 






Classification of Pigments Based on Results of Tests. 


Indeterminates 1 


Zinc Lead Chromate 

White Lead (quick process, 


Zinc Oxide 

Basic Carbonate) 

Precipitated Barium 

Zinc Chromate 

Sublimed White Lead (Basic 

Sulphate (Blanc 

Zinc and Barium 




Sublimed Blue Lead 


Zinc Lead White 


Bright Red Oxide 

Prussian Blue (In- 

Orange Mineral (American) 

Carbon Black 


Red Lead 

Graphite No. 2 

Chrome Green (Blue 


Barium Sulphate 


Venetian Red 


White Lead (Dutch 

Prince's Metallic Brown 

Graphite No. 1 


Calcium Carbonate (Whiting) 

Prussian Blue (Stim- 

Ultramarine Blue 

Calcium Carbonate (Precipi- 


Willow Charcoal 

Calcium Sulphate 
China Clay 

American Vermilion 
Medium Chrome Yellow 

1 See note, page 164. 

Electrical Conductivity of Paint Films. — Certain objections to 
the foregoing tests have been made on the ground that they 
were made in water solutions in which the pigments were sus- 


pended. It was claimed that pigments which might stimulate 
or cause corrosion in the presence of water would have no such 
action when enveloped in an oil medium. It was said that the 
oil acted as an envelope for the pigment particles, and being 
in itself a non-conductor of electricity should prevent electrolytic 
action taking place upon iron. While this criticism is worthy 
of the most careful consideration, it appeared to the authors 
that the objectors had not paid attention to the well-known fact 
that linseed oil films have the power of absorbing both water 
and carbonic acid. For this reason the oil film cannot be con- 
sidered a non-conductor of electricity, and must depend to a 
large extent upon the pigmentary substances with which it is 
reinforced. In order to get further data on this interesting sub- 
ject, the following experiments were carried on by one of the 

A series of glass slides such as are used in microscopic work 
were painted with a number of separate pigments ground in 
linseed oil. After the paint films were thoroughly dry, small 
strips of copper were attached to the opposite ends of the paint 
films, and these were in turn attached to the wires of an ordinary 
dry cell, a galvanometer being included in the circuit in order to 
measure the current passing through. It was found that abso- 
lutely no current could pass a perfectly dry paint film, and the 
galvanometer needle remained in its original position, at zero. 
The glass slides were then removed from the apparatus and im- 
mersed in water for four hours, during which time the films were 
inevitably penetrated to some extent by water. The action of 
rain and weather exposure upon painted metal surfaces in the 
open of course produces a similar result. The slides were then 
removed from the water and, after being carefully wiped, again 
inserted in the apparatus and tests made to determine whether 
any passage of current took place. It was found that those 
pigments which are naturally good conductors of electricity per- 
mitted to a slight extent the passage of current, which was shown 
by the deflection of the galvanometer needle. Those pigments, 
on the other hand, which are not good conductors of electricity, 
permitted so little current to pass that the needle remained prac- 
tically stationary. The pigments referred to as being conductors 
of electricity, which were used, belong in the carbonaceous group, 
and appeared in the stimulative class, as may be seen by reference 


to the foregoing table. These "experiments seem to indicate that 
when iron is painted with the so-called stimulators of corrosion, if 
for any reason water finds its way into the oil film, electrolysis, with, 
the resulting current flow, is able to take place, and is sure to 
cause active corrosion of the steel surfaces to which such pigments 
are applied. On the other hand, it appears to the authors that 
it is not unreasonable to conclude that the use of insulating pig- 
ments which prevent the flow of current, even when the film of 
lynoxyn, in which they are enveloped, is to some extent damaged, 
will tend to check the corrosion of painted metal surfaces. 

If. the immunity from rust, of painted surfaces, depends mainly 
upon the inhibitive properties of the pigments with which the 
steel is coated, it is fair to believe that this immunity from attack 
will be reinforced by providing that the principal base content 
of the pigment shall be a good non-conductor of electricity. In 
addition to the nature of the pigment, the character of the vehicle 
must also be considered. Inhibitives in liquid form may be in- 
corporated with the vehicle, and thus a double protective effect 
produced. The use of a paint inhibitive in both pigment and 
vehicle antagonizes the forces that cause corrosion, and the 
greater the inhibitive value of the pigment and the vehicle, the 
greater will be the defensive action working against the factors 
which produce corrosion and rapid decay. 

Water-shedding and Excluding Properties of Pigments. — A 
careful study of the nature of paint films has shown that some 
pigments produce and lend peculiar properties to the oil in which 
they are enveloped, which give to the resulting films an excluding 
or a water-shedding nature. An excluding paint is one that has 
the property of excluding and preventing the admittance of 
water to the underlying metal, thus protecting the steel from 
the water, which is the essential medium in which corrosion can 
alone take place. A water-shedding paint is one which, because 
of its peculiar physical character, appears to show a certain 
inability to become wetted. Plates painted with pigments of 
the latter class dry very soon after rains, while paints made of 
another type of pigments retain upon the surface drops of rain 
which tend to be absorbed by the paint coating and ultimately 
work through to the metal. The porosity which is generally 
noted in every dried paint film may be prevented by the use of 
gums, so that a coating is formed which is a good excluder, but 


such coatings are not always the best water shedders. The size of 
particle of the various pigments used, and their adaptability for 
filling the pores of the film, is an extremely important considera- 
tion in the composition of a paint which will form films, both 
excluding and water-shedding. Linseed oil when used by itself, 
will be found to possess neither excluding nor moisture-shedding 
properties. The film will soon become tacky, and show a peculiar 
blistered appearance, which indicates the spots where moisture 
has penetrated, and results in the formation of a soft, easily 
disintegrated film. 

It would appear from the conductivity experiments which 
have been described in a previous paragraph that the carbona- 
ceous pigments, which sometimes are good excluders, often fail 
to serve their purpose in the end, for the unctuous nature which 
has given them their water-shedding value sooner or later dis- 
appears, and the ultimate break-down of the coating admits 

That other authorities have accepted this explanation of the 
authors is shown in part by the following citation from Toch: 1 
"It is universally admitted that the presence of water is necessary 
before corrosion can take place, since this is the medium which 
contains or supplies the hydrogen ions which are necessary for 
interchange with the iron. Thus, in order to prevent rusting, 
you must either exclude water entirely, or have some substance 
present which will prevent the formation of the hydrogen ions. 
The only way in which this problem can be solved is by the appli- 
cation of a paint which will either protect the surface by being 
absolutely impervious to water, and therefore resistant to the 
hydrolizing action, or one which contains in itself either as a 
part of the vehicle or pigment some substance which can pro- 
duce the passive state." 

Moisture Penetration Tests of Paint Films. — The penetration 
of moisture into and through paint films is evidently to some 
extent dependent upon the peculiar nature of the pigments con- 
tained in the paint. Some paint films have the power of pre- 
venting the admission of water, while others containing different 
pigments seem to easily permit the entrance of moisture. A 
series of tests were designed by one of the authors, to determine 
the water-excluding power of a number of typical pigments, 
1 Trans. Amer. Electro-chem. Soc. XIV, 1908. 210. 


when ground in oil and made into films. It has not been found 
possible up to the present time to devise a method of making 
films of absolutely even gauge. In the test which is about to 
be described there may have occurred a very slight difference 
in the thickness of the films. 

A series of small glass bottles with wide mouths, holding about 
two ounces, were half filled with concentrated sulphuric acid, 
and paint films were tightly sealed over the mouths of the bottles, 
using Canada balsam. The bottles were then carefully labeled, 
numbered, accurately weighed on chemical balances, finally 
exposed to air saturated with moisture and kept at constant 
temperature under a large glass receptacle. The bottles were 
removed from the receptacle every week and weighed. The 
increase in weight, due to the amount of moisture which had 
penetrated the films, and which had been taken up by the sul- 
phuric acid, owing to its hygroscopic nature, was thus determined. 

In another series of bottles, lumps of calcium chloride were 
substituted for the sulphuric acid. The results obtained from 
these tests corresponded to those of the former series, and led 
to the conclusion that linseed oil films are undoubtedly porous, 
and also that certain pigments have the property of reducing 
this porosity to a greater extent than others. 

As has been pointed out, however, this test cannot be used 
as an accurate measure of relative permeability, owing to the 
difficulty of making films of definite and constant thickness. 
The following table gives the results of the test: 


Figures Given Express Gain in Weight, e.g., Water Absorbed 

7 days 

14 days 

21 days 

28 days 

35 days 

49 days 

Iron Oxides (with 2 per cent. Zinc 
Chromate and 2 per cent. Gum) 

White Lead, D. D 

White Lead and Zinc Oxide 

China Clay 


Zinc Oxide, Barytes and Blanc Fixe 

Zinc Lead White 

Red Lead 

Basic Sulphate' — 'White Lead 









7 days 

14 days 

21 days 

28 days 

35 days 

49 days 

Zinc Oxide and Whiting 

Zinc Chromate 

Barytes and Zinc Oxide 

Zinc Oxide 

Calcium Sulphate 

American Vermilion 

White Lead, Barytes and Blanc Fixe 


Willow Charcoal 


Carbon Black 

Lead and Zinc Chromate 

Chinese Blue (Stimulative) 

Venetian Red 

Natural Graphite 

Medium Chrome Yellow 

Bright Red Oxide 

Barium and Zinc Chromate ....... 


Prussian Blue (Inhibitive) 

Raw Linseed Oil 


Blanc Fixe 







The pigments appear in this table in the diminishing order 
of their excluding values. 

The action of a high-grade gum, in sealing up the pores and 
filling the interstices of a vehicle, is also indicated by this test. 
It will be found that iron oxide used alone appears about half- 
way down the list, while iron oxide, containing 2 per cent, of 
gum in addition to the linseed oil, was found to be an excellent 
excluder. The apparatus used is shown in Fig. 40. 

Industrial Application of the Theory of Inhibitors. — That the 
manufacturer is rapidly coming to the realization of the value 
of the new theory of rust inhibition, as outlined in the preceding 
chapters, and is adapting it to commercial practice, is shown by 
the change that has been made in the formulas of several pro- 
tective paints now on the market. Heckel 1 has said: "Out of 

Railway Age Gazette. 


this mass of tentatively accepted facts has developed a provisional 
theory along which the more advanced manufacturers are now 
engaged in working out a new mode of procedure in the painting 
of steel. 

"The theory is that rust-stimulating pigments should never 
be placed in contact with the steel surface, but that an inhibitive 
priming coat should always intervene. This inhibitive coating 
may be suitably compounded of the chromes, zinc oxide, white 

Fig. 40.— Apparatus for Testing Permeability of PaintFilms. 

lead, red lead, willow charcoal, etc., among the inhibitors, or of 
any of the neutral or indeterminate pigments reinforced with a 
small proportion of the stronger inhibitors, such as zinc chrome, 
zinc oxide, zinc and lead chrome, etc. 

"Over this priming coat the air — and moisture — excluding 
coats can then be safely applied; these coats being designed for 
protection only, with regard to inhibitive qualities/!. 

Commenting on the action of gums in rendering paint films 
less porous, Perry states: 1 "Turning, therefore, to the conserva- 

1 Coatings for Conservation of Structural Materials. Bulletin No 14 
Scien. Soc, Paint Mfrs. As/n. of U.S. 


tion of structural iron and steel, and to its rust inhibition through 
particular coatings, we have the problem of choosing the proper 
materials for manufacturing a paint which will both exclude the 
agencies of rusting, and which, when moisture and gases do 
penetrate the coating, will inhibit the iron from rusting; and we 
also have the problem of giving to the chemist, engineer, and 
architect some simple method of determining whether any given 
paint is, in at least rough measure, harmful, safe, or beneficial. 

"In the case of structural steel we have a condition of the 
surface to be protected, essentially different from the conditions 
existing with lumber. Lumber, no matter how well kiln dried, 
invariably has some moisture in its structure. It has been abso- 
lutely demonstrated, and all technical men acquainted with the 
subject are agreed, that linseed oil, when dried to a coat of linoxyn, 
has voids or pores in it. The paint manufacturer uses a com- 
bination of pigments which largely fill these voids, but the most 
carefully prepared coat of paint for lumber, when the vehicle is 
linseed oil, without the addition of varnish, is always somewhat 
porous, and the moisture has some opportunity to pass out with- 
out blistering, etc. 

"In the case of structural steel we have no moisture in the 
structural material to contend with, 1 as we have with lumber, 
and therefore we can safely add varnish gums in solution to the 
linseed oil, thus producing a more nearly water-proof coat to 
the agencies of decay. The action of the gum, diffused throughout 
the linseed oil by solution, is to help to fill up or fuse together 
the pores or voids, or, in other words, to render the linoxyn film 
more resistant to the entrance of moisture through the paint 
coating to the structural material. This is the conclusion reached 
from the standpoint of technical research, and practical experi- 
ence has also demonstrated that those coatings which have been 
proved the best protection for steel have invariably contained a 
vehicle in which some gum or varnish material has been present." 
In the above connection, Toch's 2 views on the subject of the 

1 With this statement the authors are not in complete agreement, as it 
has been contended that more or less moisture is always absorbed on the sur- 
face of iron and furnishes one of the many difficulties met with in the attempt 
to provide a perfect coating on iron. This point has been discussed in 
another chapter. 

2 M. Toch. The Chemistry and Technology of Mixed Paints, p. 87. D. 
Van Nostrand Co., New York, 1907. 


physical characteristics of linseed oil films, and the part they 
play in corrosion, should be added: "There are questions in 
regard to the physical and chemical characteristics of linseed oil 
on which there has been considerable discussion and naturally 
a difference of opinion. The first is whether linseed oil dries in 
a porous film, and the second is whether linseed oil while drying 
goes through a breathing process and absorbs oxygen, and gives 
off carbonic acid and water." With reference to the porosity of 
the dry film of linseed oil, the same authority has stated: 1 "In 
a paper before the American Chemical Society on March 20, 
1903, I gave it as my opinion that a dried film of linseed oil is 
not porous, excepting for the air bubbles which may be bedded 
in it, but that any dried film of linseed oil subjected to moisture 
forms with it a semi-solid solution, and the moisture is carried 
through the oil onto the surface of the metal. We then have 
two materials which, beyond a doubt, have sufficient inherent 
defects to produce oxidation under the proper conditions, and 
granted that the percentage of carbon dioxide in the air of the 
tunnel is not beyond the normal, the fact that carbon dioxide, 
together with moisture, would cause this progressive oxidation is 
sufficient warrant for the discontinuance of paints that are not 
moisture and gas proof. Lewkowitsch demonstrated in his Can- 
ton lectures that the fats and fatty oils hydrolized with water 
alone, and linseed oil is hydrolized to a remarkable degree in eight 
hours when subjected to steam. It can, therefore, be inferred 
that water would act on linseed oil without the presence of an 
alkali, and calcium hydroxide added to water simply hastens the 
hydrolysis, by acting as a catalyzer. This, then, bears out my 
previous assertion that a film of linseed oil (linoxyn) and water 
combine to form a semi-solid solution similar in every respect to 
soap, and inasmuch as we have lime, lead, iron, and similar bases 
present in many paints, it is almost beyond question that these 
materials aid in the saponification of oil and water." 

In summing up the discussion of the possible porosity of 
paint films as presented above, the authors can only reiterate 
that the results of their experiments appear to them to furnish 
actual proof of the permeability of paint films by moisture. 
Whether or not the result is due to porosity must depend upon 

1 Journal of the Society of Chemical Industry (May 31, 1905), "New Paint 
Conditions Existing in the New York Subway." 


just what is meant by that term. The formation of a solid or 
semi-solid solution must be dependent on the existence of molec- 
ular interstitial spaces. Whether spaces of these orders of mag- 
nitude should be called pores is quite beside the question as the 
final result is the same in either case. 

Thompson's Work on Solubility of Paint Films. — That the 
solubility in water of various paint coatings must also be taken 
into consideration, as well as the inhibitive and excluding proper- 
ties, seems to be indicated by the work of Thompson. 1 In a series 
of tests of oil films immersed in water, Thompson found that 
calcium sulphate was dissolved in great quantity from films 
containing this pigment. Thompson's method of conducting the 
solubility tests, as described by him, is as follows: "The paint 
is coated on antiseptic gauze in the following manner: Strips of 
gauze 2 in. wide and about 15 in. long are dipped in the paint for 
about 13 in., then drawn through a wringer consisting of two 
test tubes (J by 6 in.) drawn together by elastic bands. Gauze 
having these dimensions weighs about 1.25 grams. The weight 
of each piece of gauze is previously obtained, and after it has 
been dipped in the paint it is placed on a clock glass. The 
clock glass and its contents are then weighed, from which, by 
deducting the weight of the clock glass and any adhering paint, 
we obtain the amount of paint which has been placed on the 
gauze. This gauze is then hung up to dry for about ten days 
with a tared clock glass under it, so that paint drippings may 
be caught and weighed and deducted from the amount of paint 
taken. After ten days the gauze and paint are weighed, and if 
desired the percentage gain in weight may be calculated. The 
painted gauze is then placed in a 150 c.c. beaker and covered 
with about 130 c.c of distilled water. After 24 hours this water 
is poured off and evaporated and another 130 c.c. of water is 
placed on the gauze. The water poured off is placed in a tarred 
vessel, so that after evaporation to dryness the amount dissolved 
can be determined by weighing. This dissolved matter can then 
be analyzed for pigment constituents or treated with nitric acid, 
and carefully ignited and weighed. The treatment with water 
can be repeated as often as may be desirable, and, if it is thought 
best, the extract from several treatments can be combined and 

1 G. W. Thompson. Certain Solubility Tests on Protective Coatings. 
Froc. Amer. Soc. Testing Materials, 1908, Vol. VIII, p. 601. 


treated as one." The results obtained by this test have brought 
out some interesting points. It has shown, for instance, that in 
paints compounded of different pigments, some of these may be 
dissolved out by the action of water. As a specific instance of 
this, the case of Venetian red may be cited, which contains a 
large percentage of calcium sulphate. Such a pigment would 
prove dangerous to use on iron or steel, on account of the solubility 
of the calcium sulphate. 

The tables previously presented in this chapter, in which is 
given the list of inhibitive pigments, and also the list of excluding 
pigments, should prove of great value to the manufacturer in 
aiding him to select the best materials for the composition of 
paints for the protection of iron, and it is hoped that the tests 
described will be given full consideration in conjunction with the 
more practical field tests which are now being conducted. 

The architect and the engineer are constantly clamoring for 
protection for the enormous structural work under their super- 
vision. More attention than ever is being paid to recent investi- 
gations on the subject of paints, and better materials for painting 
purposes are being insisted on. It is fair to believe that those 
in charge of engineering work will demand in the future vital 
improvements in steel protecting compounds, based on modern 
knowledge of the problem. As has been previously pointed out, 
the day of empiricism in the selection of protective coatings has 
passed, and the subject must now be considered from the stand- 
point of scientific investigation based upon a satisfactory working 
theory. The treatment of steel surfaces by the metallurgist, 
either by physical or chemical means, may soon be developed to 
such an extent that metal will be made almost non-corrodible, 
but until such a day comes there will be an immense demand for 
protective coatings that will protect, and too much attention 
and study cannot be given to the subject. 



Steel Test Panels at Atlantic City. — The results obtained by 
recent investigators on the inhibitive value of pigments, as de- 
scribed in the previous chapter, suggested the erection of a series 
of steel panels on which could be tested the same range of pig- 
ments under the practical conditions of service in the open. The 
Paint Manufacturers Association of the United States offered 
to erect the panels, and place them under the supervision and 
inspection of Committee "U" of the American Society for Testing 
Materials. It was decided to erect the panels near Atlantic City, 
N. J., and the work was commenced during the fall of 1908, at 
this place. In order to broaden the test, and furnish data in regard 
to the durability of the various paint films when placed on differ- 
ent types of metal, three kinds of steel were used on the panels. 

The following table shows the analyses of the three grades of 
metal tested: 


Open Hearth 









Extra Mild 
Open Hearth 

Sulphur . . . 
Manganese . 




trace only 

Pickling and Preparation of Plates. — The three types of metal 
selected for the test were rolled to billets, the middle of which 
were selected, and worked up into plates 24 in. wide, 36 in. high, 
and i in. in diameter — approximately 11 gauge. A number of 
plates of each of the metals selected, in all 450, were pickled in 
10 per cent, sulphuric acid, kept at 180 to 200° F., in order to 
remove the mill-scale. The plates were then washed in water, 
and later in a 10 per cent, solution of caustic soda. Finally the 
plates were again washed in water and wiped dry. They were 

1 This metal is called "Ingot Iron' ; by the manufacturers. 


then packed in boxes containing dry lime, in order to prevent 
superficial corrosion. By this method the plates were secured 
in perfect condition, the surfaces being smooth and free from 
scale. Upon these pickled plates, paints were applied with a 
definite spreading rate of 900 sq. ft. per gallon. The unpickled 
plates, coated with mill-scale, were painted with the same paints, 
but without adopting any special spreading rate, thus following 
more closely the ordinary method of painting structural steel. 
A few extra plates of special Bessemer steel and Swedish charcoal 
iron were also included in the test, some of which were painted, 
while others were exposed without any protective coating. Plates 
of the three types of metal already mentioned were also exposed 
unpainted, both in the black and pickled condition. 

Fence Erection and Preparation for Work. — The fences which 
were erected for the holding of the plates were constructed of 
yellow pine, the posts being set deeply in the ground and properly 
braced. The framework of the fence was open, with a ledge 
upon the lateral girders, upon which the plates might rest, and 
to which the plates were secured by the use of steel buttons. 
After the framework had been erected, painted, and made ready 
for the placement of the panels, a small shed was built upon the 
ground, and the materials for the field test placed therein. The 
steel plates were unpacked from the boxes in which they were 
shipped, brushed off, and stacked up ready for painting. Small 
benches were erected, and the accessories of the work, such as 
cans, brushes, pots, balances, etc., were placed in position. 

Method Followed in Painting Plates. — A frame resting upon 
the work bench served to hold the plates in a lateral position 
while being painted, room being allowed beneath the plate for 
the operator to place his hands in order to lift the plates from 
the under surface, after the painting had been finished. 

A pickled plate having been placed upon the framework, 
everything was in readiness for the work. The specific gravity 
and weight per gallon of the paint to be applied was determined, 
and the amount, in grams, to be applied to each individual panel 
was calculated according to the following formula: 
Spreading rate sq. ft. in plate grams paint in gal. 

900 sq. ft. : 6 : : 4500 : x 

The reciprocal of x being the number of grams of paint to be 
applied to the panel. 


An enamel cup was then filled with the paint and a brush 
well stirred within. The cup, paint, and brush were placed upon 
the balances and accurately weighed in grams. After most of 
the paint had been applied to the panel, cross-brushing of the 
panel was continued until the pot with brush and paint exactly 
counterbalanced the deducted weight. The painted panel was 
then set in a rack, in a horizontal position, to dry. 

A period of eight days elapsed between the drying of each 
coat. The greatest care was taken in the painting of the edges 
of the plates, and the racks for containing the plates after they 
were painted were so constructed that the paint would not be 
abraded while sliding the plates back and forth. The working 
properties of each paint, and the appearance of the surface of 
each plate after painting were carefully noted and included in 
the report. No reductions were made to any of the paints applied 
except in three cases, where the viscosity was so great that it was 
necessary to add a small amount of pure spirits of turpentine. 
The amount of paint was proportionately increased in such cases, 
so that the evaporation of the turpentine would leave upon the 
plate the amount of paint originally intended. 

The appearance of the completed series of test panels is shown 
in Fig. 41. 

Vehicles Used and Reasons for Avoidance of Japan Driers. — 
The pigments used were selected with the view to securing as 
nearly as possible purity and strength, and as already noted were 
out of the same lots used in making the preliminary laboratory 
tests on inhibitives. They were ground in a vehicle composed 
of two parts of raw linseed oil and one part of pure boiled oil. 
Paint is generally caused to dry rapidly by the use of japans or 
driers. These materials contain a large amount of metallic 
oxides which might have some effect in either exciting or retard- 
ing corrosion. To prevent the introduction of such a factor, 
these materials were not used in the test. The boiled oil, with 
its small precentage of metallic oxides, was sufficient, however, 
to cause the paints to dry in a short time after they were spread. 

The table on page 184 gives the number of pounds of pigment 
to a gallon of oil, used in the manufacture of the pigment paints 
for this test. The formula for determining the amount is as fol- 

Sp. Gr. of pigment X 3 = lbs. pigment to gal. oil 



The excessive amount of oil required to grind pigments Nos. 
19 and 21 made it necessary to introduce a percentage of barytes 
(barytes requiring very little oil), in order to form paints which 
would contain relative amounts of oil. 




Sp. Gr. of 

Weight of 

Pigment to 

Gal. Oil 

Weight of 

per Gal. 



















Dutch Process White Lead 

Quick " " " 

Zinc Oxide 

Sublimed White Lead 

Blue Lead 


Zinc Lead White 

American Orange Mineral 

Red Lead 

Bright Red Oxide 

Venetian Red 

Prince's Metallic Brown 

Natural Graphite 

Acheson Graphite 

( Lampblack 

( Barytes 

Willow Charcoal 

J Gas Carbon Black 

\ Natural Barytes 

French Yellow Ochre 

Natural Barytes 

Precipitated Barytes (Blanc Fixe) . . 

Calcium Carbonate (Whiting) 

Calcium Carbonate Precipitated 

Calcium Sulphate (Gypsum) 

China Clay (Kaolin) 

Asbestine (Silicate of Magnesium) . . 
American Vermilion (Chrome Scarlet) 

Medium Chrome Yellow 

Zinc Chromate 

Zinc and Barium Chromate 

Chrome Green (Blue tone) 

Prussian Blue (Stimulative) 

Prussian Blue (Inhibitive) 

Ultramarine Blue 

Zinc and Lead Chromate 

Magnetic Black Oxide 
































































Note. — The oil used in grinding all these pigments and 
used throughout the test was composed of two parts raw linseed 
oil and one part boiled linseed oil. The specific gravity of this 
mixture was .937. 

Data of application of each pigment was accurately made 
during the tests. There is given herewith the data on four of 
the pigments applied. 

No. 2, Quick Process White Lead: 

Sp. Gr. of Pigment 6.78 

Lbs. to Gallon Oil 20.34 

Sp. Gr. of Paint as Received 2.47 

Wt. of Paint per Gallon 20.56 

Grams to Panel 62 

Condition of Paint Good 

Working Properties Works easy 

Drying 24 hours all coats 

1 Coat Oct. 26 T 60 B 29.94 W fair 

2 Coat Nov. 3 T 54 B 30.23 W clear 

3 Coat, Nov. 7 T 52 B 29.66 W cloudy 

No. 9, Orange Mineral (American) : 

Sp. Gr. of Pigment 8.97 

Lbs. to Gallon Oil 26.91 

Sp. Gr. of Paint as Received. . . 2.97 

Wt. of Paint per Gallon 24.74 

Grams to Panel 74.7 

Condition of Paint Good 

Working Properties Smooth — no brush marks. 

Drying Good 

1 Coat Oct. 28 T 58 B 30.01 W cloudy 

2 Coat Nov. 4 T 65 B 29.61 W cloudy 

3 Coat Nov. 9 T 58 B 29.91 W clear 

No. 14, Venetian Red: 

Sp. Gr. of Pigment 3.1 

Pigment to Gal. Oil 9.30 

Sp. Gr. of Paints Received .... 1.52 

Wt. of Gallon Paint 12.6 

Grams to Panel 38 

Condition Good Smooth Paint 

Working Properties Smooth — no brush marks. 

Drying Good on all coats 

1 Coat Oct. 29 T 56 B 29.82 W cloudy 

2 Coat Nov. 4 T 65 B 29.61 W cloudy 

3 Coat Nov. 9 T 65 B 29.91 W clear 


No. 19, Lampblack: 

Sp. Gr. of Pigment 1.82 

Lbs. to Gallon Oil: Lampblack ... 1.82 

Barytes 8.92 

Sp. Gr. of Paint as Received 1.60 

Wt. per Gallon Paint 13.32 

Grams to Panel 40.2 

Condition Good 

Working Properties Works fair 

Drying Slow. Tacky after 3 days. 

1 Coat Oct. 29 T 56 B 29.82 W cloudy 

2 Coat Nov. 5 T 54 B 29.92 W clear 

3 Coat Nov. 10 T 60 B 30.02 W clear 

Note. — T stands for temperature (F) 
B " " barometer 

W " " weather 

Testing Effect of Various Prime Coats. — Some of the special 
tests made, included a series of plates prime-coated with different 
inhibitive pigments, and these tests were designed to determine 
which pigments offer the best results for such work. These 
plates were all second-coated with the same paint. It is the 
opinion of the authors that any good excluding paint may be 
used whether it is inhibitive in action or not, provided the 
contact coat is inhibitive. If, however, both coats can be 
designed so as to have the maximum possible value from both 
these points of view, the best results would, of course, accrue. 
The only way such data can be obtained is by careful observation 
of the results of exposure tests. 

Combination Formulas Tested. — By selecting a series of pig- 
ments which in the water tests showed inhibitive tendencies, and 
properly combining these pigments into a paint, it was thought 
possible that a more or less inhibitive paint would be produced. 
If this proved to be the case, it would follow that the selection 
and introduction into a paint of the stimulative pigments would 
inevitably produce a paint unfit for use on iron or steel. Formulae 
of both types were therefore used in these tests, and below the 
percentage composition of two of these is shown. 

Inhibitive White. 

Pigment Formula Paint Formula 

35 per cent Zinc Oxide 20.90 per cent. 

45 per cent Special White 26.87 per cent. 

5 per cent CaC0 3 2.98 per cent. 

15 per cent Silex 8.95 per cent. 

Japan 1.56 per cent. 

Raw Oil 38.74 per cent. 

Stimulative Black. 

Pigment Formula Paint Formula 

40 per cent Lampblack 8.18 per cent. 

40 per cent Natural Graphite . . 8.18 per cent. 

20 per cent Barytes 4.09 per cent. 

Japan 8.33 per cent. 

Raw Oil 71.22 per cent. 

Drawing Conclusions from Results of Field Tests. — At the 
present writing, the Atlantic City test plates have been in place 
fourteen months, and the authors do not consider that suffi- 
cient time has elapsed to justify definite conclusions or sweeping 
deductions. In a number of cases, however, the panels have actu- 
ally failed, and the corrosion effects are apparent to all observers. 
The authors fully recognize and desire to record here that in 
spite of the fact that they were the principal responsible persons 
in charge of the design and erection of these tests, nevertheless, 
in view of the fact that no official report of results obtained has 
yet been made to the American Society for Testing Materials, 
it would not be proper to enter upon a discussion of the relative 
durability of the different types of formulae, even if definite results 
had begun to show. 

It is, however, fair to record the results of scientific examina- 
tions of the paint surfaces, which have been made from time to 
time, leaving the conclusions which will naturally follow from 
these observations to be drawn later. The object of the authors 
in presenting a detailed description of the design and construc- 
tion of these fences has been solely to act as a guide for other 
experimenters who may desire at some future time either to 
duplicate or develop this form of field testing. It is by no means 
easy to carry out work of this kind which involves a very large 
amount of thought and labor. The experience gained by one 
set of experimenters will, of course, prove valuable to others 
who are pursuing the same line of research. 


The Inspection of Painted Surfaces. — In making an inspection 
of painted surfaces to determine the durability of various coatings, 
the chalking, checking, color, maintenance, elasticity of film, 
and other properties should be noted. 

By the term chalking is meant that condition of the film 
which allows removal of the pigment when rubbed with the hands 
or with cloth pads. Destruction of the oil, through the saponi- 
fication caused by alkaline pigments, is often the primary cause 
of chalking. 

By checking is meant that condition of the painted surface 
that shows checks, cracks, alligatoring (an appearance resembling 
alligator skin), etc. Checking may be seen very clearly by using 
a small but powerful magnifying glass. Surface, matt, coarse 
and deep are qualifying terms used to define the character of the 
checking which takes place. Paints which are not elastic and 
which become brittle are subject to checking, as well as some 
paints which chalk readily. 

Elasticity of film is noted by raising a portion of the film with 
the knife blade and peeling it off. Only very elastic paint will 
stand this test. Brittle coatings crumble up at once when this 
attempt is made. This test cannot, of course, be applied to the 
Atlantic City panels, but is in general use by car painters. 

Hardness of coating can be gauged to a certain extent by the 
appearance of the paint film and its resistance to abrasion. A 
small hard object is sometimes used to strike against the painted 
surface to determine its hardness. The hiding power and color 
maintenance of paints are also important features to consider 
in making an inspection. 

Continuity of coating and absence of disintegration, as well 
as other conditions of the paint film, is best determined by examina- 
tion with a microscope. This can be done by using the photo- 
microscope designed by one of the authors. This apparatus has 
proved of great value in field inspection work. Permanent 
records of the wearing of a paint from time to time can be 
obtained by using this instrument, and the progressive decay 
shown, determined with accuracy. 

The photomicroscope consists of a modified form of a Gordon 
photomicrographic tube such as is used for plate exposures in 
laboratory work. This tube contains a projection lens properly 
focused, and also an exposure shutter fixed on a lift pin. On the 


rear end of the tube is fitted a disk of metal, into which is placed 
a block of wood having a central annular opening the size of the 
tube. On the back of the wood is firmly set and screwed into 
position a film-pack holder, such as is used for the ordinary photo- 
graphic camera. The arm and body of a microscope, containing a 
draw tube fitted with objective and eye-piece, is mounted in a hori- 
zontal position on a solid iron base, bored and threaded to receive 
a screw from the top of a heavy tripod. The objective of the micro- 
scope is placed close to the painted surface, and by raising or lower- 

Fig. 42. — Photomicroscope for examining and photographing painted 
surfaces. (Gardner.) 

ing the tripod the microscope may be focused on any spot, by 
the regulation of the coarse adjustment. Minute abrasions or 
cracking of any nature can easily be detected. When all is ready, 
the tube camera is placed directly over the eye-piece of the micro- 
scope, and exposure is made by lifting the shutter cap for twenty 
or thirty seconds, according to the light conditions. No artificial 
illumination is necessary. The apparatus is shown in Fig. 42. 


In using the photomicroscope on the Atlantic City panels, 
one of the first effects shown was the appearance of minute crys- 
tals of sodium chloride deposited on the films from the saline 
atmosphere due to the close proximity of the ocean. 

A very interesting point brought out by these examinations 
is the fact that some of the paint films appeared to have the 
power of holding the salt crystals to a much greater degree than 
others, some, indeed, being almost free from salt. A sufficient 
amount of work has not yet been done along this line to enable 
definite conclusions to be drawn, but some of the results obtained 
are shown in order to stimulate further inquiry. In Figs. 43 a, 
b, and c are shown photomicrographs of three different paint coat- 
ings, to illustrate this point. 

The tendency of certain paint coatings to produce a slight 
wrinkling of the surface when softened by moisture is well known. 
This action, which is probably preliminary to a breaking down 
of the paint film, is shown in Fig. 44. 

As has been pointed out in a previous paragraph, certain 
pigments rapidly destroy the oil films and produce the phenomenon 
known as chalking. The appearance of chalked paint films is 
very characteristic under the photomicroscope. The effect is 
very well shown by Figs. 45 and 46. 

The cracking of paint films is a most important point in rela- 
tion to the general subject of the protection of iron and steel by 
paint coatings. It requires no evidence to prove that the open- 
ing up of cracks on the surface will allow water, and the other 
corroding influences, to make a ready entrance to the surface of 
the metal, and act as centers of corrosion. 

The photomicrographic method of studying paint films will 
undoubtedly lead to more definite information on this point 
than has been heretofore available. A study of the illustrations, 
as shown in Figs. 47, 48, and 49, indicates that cracks in different 
paint coatings are of a different nature and appearance. 

It is well known that although zinc oxide has many properties 
which make it an extremely valuable pigmentary substance, its 
tendency to crack constitutes its greatest fault. The cracking 
of a zinc oxide film is beautifully illustrated in Fig. 47. Another 
peculiar form of cracking is shown in Fig. 49 on a gypsum coating. 

Other types of cracking which are being closely followed by 
corrosion along the line of the cracks are shown in Figs. 50, 51, 52. 


The recent work of Walker, calling attention to the probability 
that cracks in paint films are responsible for a stimulated corro- 
sion effect owing to the depolarizing action of the open paint 
film, due to the absorption of nascent hydrogen, is particularly 
interesting when considered in relation to the effects shown in 
these illustrations. 

On Figs. 53 and 54 are shown two typical examples of check- 
ing. This action, just as in the case of cracking, must be con- 
sidered a preliminary step in the breaking down of a paint coat, 
leading to corrosion. Fig. 55 illustrates the effect produced by 
uneven brush work, leading to a special characteristic form of 
checking which is frequently observed as a preliminary step in 
the breaking down of paint coatings. 

Figs. 56, 57, 58 exhibit in a very interesting manner the 
breaking through of corrosion nuclei to the surface of the paint 
film. It must be apparent that although a paint film may be 
opaque, corrosion goes on underneath for a long time before 
the trouble becomes evident on the surface. A time comes, 
however, when little blisters make their appearance on the film. 
This appearance is a preliminary step to the breaking out of the 
tubercles of rust which are so familiar to all observers. 

The rusting of iron has frequently been compared to a malady 
or disease, and certainly these photomicrographs appear to show 
a striking analogy with the effects produced by disease in living 

The authors have stated in a previous paragraph that it is 
perfectly fair for every observer to call attention to specific cases 
of success or failure exhibited by the Atlantic City test panels, 
provided no sweeping conclusions are reached or deductions 
drawn. While bearing this in mind, it serves our purpose to 
present herewith some illustrations representing interesting con- 
trasts which the tests have already served to show. The authors 
do not hesitate to appear as defenders of the electrolytic theory 
of corrosion, and therefore of the value in general of inhibitive 
pigments. Fig. 59 illustrates the condition of a plate painted 
with zinc chromate, a distinctly inhibitive pigment. 

Fig. 60 shows the present condition of two plates painted 
respectively with pigments, one of which is a distinct stimulator 
of corrosion and the other of which saponifies and destroys the 
protective film. An inspection of this illustration shows that 


the plate painted with the gypsum is dark in color. This dark- 
ness is due entirely to the corrosion which is plainly seen to be 
taking place underneath the more or less transparent film. That 
this same action is going on under many of the opaque films can 
hardly be doubted, although it is not at the present time apparent 
to the eye. 

Fig. 59. — Perfect condition of plates painted with zinc chromate. 

It is well known that calcium carbonate as a pigmentary 
substance is used in two different forms — the natural, ground 
chalk (or whiting), and the precipitated calcium carbonate. In 
view of the fact that calcium carbonate is a useful ingredient in 
small percentage in many paint formulse, it is interesting to 


record the condition of the two plates which have served as a 
test of the relative value of these two forms. An inspection of 
Fig. 61, taken in conjunction with Fig. 62, in the same plate, 
appears to indicate that the whiting or natural form of calcium 
carbonate should be selected, if it must be used, for all protective 
paints for iron. 

Fig. 60. — On left, scaling and corrosion on plate 
painted with precipitated calcium carbonate. On 
right, corrosion showing through gypsum paint film. 

Other Field Tests and their Value. — J. Cruickshank Smith, 1 
in commenting on paints for the preservation of steel, makes an 
appeal for more field tests such as those already described, in 
the following words: "Although opinions vary as to what is the- 
oretically the best pigment, or, more correctly, combination of 
pigments, for the manufacture of protective coatings, the general 
consensus of technical opinion seems to be gradually coming to 
be that, with certain more or less obvious reservations, the com- 

1 A Plea for International Investigation concerning Protective Coatings 
for Iron and Steel. Paper submitted to 5th Congress, Internat. Assn. for 
Testing Materials, Copenhagen, 1909. 


position of the paint is less important than its physical state, 
and that one pigment or blend of pigments is more efficient than 
another as the basis for a protective paint mainly according to 
the degree in which it tends to produce certain definite physical 
and mechanical effects in the ultimate protective film. The 
problem that remains is the selection of that blend of pigments, 

Fig. 61. — Whiting (calcium carbonate) on steel. 

suspended in a suitably adjusted vehicle (the paint as a whole 
possessing the necessary physical properties), which will, under 
known conditions as to exposure and climatic conditions, yield 
a satisfactory protective film. Only exposure tests can solve 
this problem. 

"It is now generally accepted that such factors as fine state 
of division and uniformity in size of the pigmentary particles, 
viscosity of the paint, elasticity and strength of the paint film, 


and impermeability of the paint film to moisture and gases, are 
of paramount importance in determining whether or not a par- 
ticular paint will satisfactorily effect the purpose of a protective 
coating. In this connection, I would direct attention to the 
admirable scientific work recently accomplished, and still being 
conducted by the Scientific Section of the Paint Manufacturers' 

Fig. 62. — Precipitated calcium carbonate on steel. 

Association of the United States, and also by the various commit- 
tees of the American Society for Testing Materials. The official 
publications of these two bodies teem with technical matter, 
which no one who claims to be up-to-date in his knowledge of 
this subject can afford to be ignorant of." 

Another practical service test of paint is being carried on by 
Committee "E" of the American Society for Testing Materials 
on a Pennsylvania Railroad bridge at Havre de Grace, Mary- 


land. 1 In this test a number of protective paints, selected from 
those largely advertised in the American market, were used. 
The following outline of the tests will be of interest to the 
engineer and bridge builder, who have the protection of similar 
structures under their supervision. 

Tests on Preservative Coatings Carried on under the Super- 
vision of Committe "E" American Society for Testing Materials. 

"1st. — Actual Service Tests under Normal Conditions to 
be Applied to Full-Size Structures and Normal Panel Tests. 

"Under this head the Committee started a long-time service 
test in June, 1906, on part of the new double-track deck bridge 
of the Pennsylvania Railroad over the Susquehanna River, at 
Havre de Grace, Maryland. The bridge is about 4000 feet long, 
consisting of 16 spans. The trusses are 30 feet deep, and the 
panels 29 feet long. The paint was supplied by 19 manufacturers, 
and applied to 2 continuous spans of the bridge directly over the 
water, containing 19 panels. Each panel represented one paint 

"In addition to the test of the paint on the bridge proper, panel 
tests were also made on very carefully prepared steel plates, 2 
feet by 3 feet, the paint being applied by a most skilful workman, 
under the most perfect conditions possible. These panels were 
made in triplicate at 3 spreading rates, 600, 900, and 1200 square 
feet per gallon of paint. The panels are exposed on the lower 
chord of the bridge. 

"Conditions of surface, application, weather, etc., were care- 
fully noted and recorded. Complete analyses of the paints used 
in the test were made. The paints used in this tests were, in 
most cases, the representative proprietary coatings prepared for 
use on iron and steel structures. 

"The pigments included red lead, graphite, carbon, oxide of 
iron, white lead, zinc oxide, sulphate of lead, together with clay, 
silica, silicate and barytes. The oil was in the majority of cases 
a pure linseed oil, though in one case rosin or a resinate drier 
was detected. 

"The volatile matter was found to be turpentine or naphtha, 
or a mixture of the two. 

1 Resume* of Work done by the American Society for Testing Materials 
on Preservative Coatings for Iron and Steel, presented at the Annual Meet- 
ing of the International Society, September, 1909. 


"In the set was one heavy asphaltic varnish thinned with 

"The result of the inspection made in June, 1908, is as follows: 

"As was anticipated, no marked differences are noted in the 
majority of cases. As was clearly indicated at the inspection a 
year ago, the only example of an asphaltum varnish thinned 
with a petroleum solvent has failed to a marked degree after 
eighteen months' exposure. A carbon paint containing rosin in 
the oil has developed minute fissure cracks all over the surface. 
While it is by no means conclusive that this failure is due to the 
rosin, still it is worthy of note, and will be the subject of further 

"An example of difference of expansion of red lead under- 
coat and a carbon final-coat is shown in panel 14. The carbon 
coat has cracked badly on the bridge proper in cobweb-like 
cracks, showing the red of the under-coat. On another panel 
the same final-coat, however, applied both as an under-coat and 
as a final-coat, has not failed in this manner. 

"It is also interesting to note that one of the pure red lead 
pigments in straight raw linseed oil shows unmistakable evidence 
of alligatoring. 

"High gloss and tenacious film are shown by Panel 1. In 
this case the pigment consists of oxide of iron, red lead, and a 
carbon black, mixed with a varnish containing some gum and 
thinned with turpentine. 

"The other panels, as stated in the report of the sub-com- 
mittee, show in most cases a marked loss of gloss with minor 
differences in hardness, tenacity, toughness, and elasticity of 
film. These differences are, however, too slight to warrant an 
opinion at this time. 

"There is evidence of rusting to a slight degree on all sec- 
tions of the bridge, due to mechanical injury. These spots have 
been accurately noted and will be carefully Avatched at subse- 
quent inspections. In general, however, the paints are affording 
good protection, and it will require longer exposure to differen- 
tiate in the majority of cases. 

"An inspection made March 26, 1909, confirms the report of 
last June, with no marked changes of note to report. As stated 
in June, one of the red leads showed unmistakable evidence of 
alligatoring. At the inspection just made, the other sample of 


red lead shows the same condition though to a less marked degree. 
In both cases the alligatoring is most marked at the spreading 
rate of 600 square feet to the gallon, but the cracking is apparently 
superficial. Good protection is afforded, however, by both 

"In general, most of the paints are affording good protection. 

"It is- impossible to give details of the tests in this paper, 
but reference is made to reports of Committee ' E ' in Proceedings 
of the American Society for 1906, 1907, and 1908." 

Considering the fact that nearly all these paint coatings are 
reported to be in fairly good condition after about four years' 
exposure, it would appear that the conditions of service at this 
place are by no means severe. All the panels and sections are 
located far down on the bridge structure where they cannot come 
into direct contact with sulphurous gases from the locomotives. 
It is more than probable that in some other location more definite 
results of the tests would have been obtained in the time elapsed. 

Tests of Paint Coatings Designed to Resist Sea Air. — The 
attack of sea-water and a saline atmosphere upon paint coatings 
is very severe. The soluble salts which are constituents of sea 
water have the power of penetrating the hardest paint coatings 
known, and acting to a certain extent the part of paint removers. 
In the opinion of the authors, it is extremely important that the 
paint designed to protect metal exposed to sea-water and sea- 
air should contain inhibitive pigments. If such paints contain 
pigments which are stimulative in nature, it is logical to assume 
that in the presence of such easily ionized salts as the sea-water 
contains, energetic galvanic action might proceed, with subse- 
quent rapid pitting and corrosion. Moreover, the necessity of 
an extremely good excluding vehicle for paints, designed for the 
protection of marine structures, has been demonstrated by many 

Along the various resorts on the New Jersey coast, thousands 
of examples of the rapid decay of paint coatings applied to struc- 
tural metal may be seen. On some of the old steel piers which 
extend out to the ocean, ordinary coatings which have been 
renewed almost yearly are in many cases destroyed after a few 
months' exposure. The girders under the board walks, and the 
railings above them, offer striking examples of the fugitive nature 
of the ordinary paint coating when exposed to the action of salt 


spray and salt air. Steel must be used in some places where 
the use of concrete is not applicable, or where the present state 
of development of the art of erecting concrete structural material 
has not reached the necessary perfection. A combination of 
steel and concrete would probably prove the solution of many 
of the engineering problems at present met with, but the demand 
for an efficient paint to withstand salt exposure is as great as 
ever, and the tests which are under way may provide a solution 
of the difficulty. The management of Young's Old Pier, at 
Atlantic City, working in conjunction with the Carnegie Steel 
Company, have recently erected a series of columns or piles on the 
beach, under the supervision of one of the authors, in order to 
determine the resistance to corrosion, and permanence of a com- 
bination of one of the carefully designed types of modern steel 
and cement construction. The test consists of a series of five 
piers about 18 in. in diameter. The piers are made of steel sheet 
piling locked together, filled with concrete, and sunk to two thirds 
their depth in the sand, so that at low tide one third of the height 
of the piling is subjected to the action of the salt air, while at 
high tide the piling is completely covered. Details of construc- 
tion are shown in Fig. 63. Previous to assembling and erecting 
this piling, the steel parts were all carefully painted with different 
paint formulae to determine which was best suited for the purpose. 
The rise and fall of the tide, with the constant swirl of the sand 
in its grasp, causes an enormous and unusual abrasion effect on 
the paint coating, while the alternate exposure to the disintegrat- 
ing effect of the salt water and the oxidizing effect of the air offers 
one of the most severe tests to which a paint could be put. 

On the ocean end of Young's Old Pier, at Atlantic City, the 
United States Geological Survey, in cooperation with the authors, 
has placed a number of test panels. Among these test panels 
many grades of iron and steel, made by different processes and 
containing different percentages of impurities, are represented. 
Some of the plates are galvanized, some are tinned, and some are 
left in their original condition as received from the mill, with the 
ordinary coating of mill-scale. Inhibitive paint formulas have 
been placed upon a few of the plates, to determine whether a paint 
coating would be as serviceable as the tinned or galvanized plates 
unpainted. The writers do not feel that they have the delegated 
authority to analyze the results which are being obtained in this 






12 -35 Ib.U.S. Piling 


nt Grout 



High Water 


Experimental Steel Piling Piers. 
Jp Young's Old Pier 

/ | Atlantic City, N.J. 

Pig. 63. — Details of Construction of Test Piling at Atlantic City, N. J. 


series of tests, or to draw conclusions from them. They have been 
briefly described here to make the record of contemporary tests 

complete. The general appearance of these interesting tests is 
shown in Figs. 64 and 65. 

Many other tests have been made at Atlantic City, upon 
the girders under the board walk, the steel piling under some of 


the piers, and upon a series of plates exposed near the piers, and 
within a few years an abundance of useful information will be 

obtained on. the subject of protective coatings adapted for use 
in the neighborhood of salt water. 



The Importance of the Special Design of Paint Formulm. — One 
single variety of paint can no more fulfil all the purposes for 
which protective paints are used than can one kind of paint 
serve all the demands for the proper decoration and preser- 
vation of wood. The controversy in regard to mixed pigments 
as against straight white lead house paints is analogous to that 
which contrasts the mixed pigment with the straight red lead 
prime coatings for structural metal. In a like manner the gum 
varnishes used on the interior woodwork of houses correspond 
in a sense to the lacquers so largely used on brass and other metals 
for which protection is demanded. It may be said that there is 
a paint for every purpose, in the same sense that there is a special- 
ist in every field of scientific research and in every profession. 

Throughout this book and in the tests that have been outlined, 
we have been mainly considering those pigments which, mixed 
in definite proportions, will afford the best protection in a general 
way for bridges, structural framework for buildings, and all 
work on a large scale. We have now to consider the painting 
of special forms of metal which, because of certain peculiar 
conditions which have to be met, present a special problem. 

Galvanized Iron and Modern Methods Used in its Decoration 
and Preservation. — The painting of galvanized metal has always 
been considered by the master painter one of the difficult problems 
that must be met. Very large quantities of galvanized iron are 
used for siding and roofing purposes, especially in buildings and 
factories designed to be fire-proof. Railings, cornice work, 
gutters, drain pipes, fences and other accessories to the construc- 
tion of buildings and the maintenance of property, are galvanized 
and put into service without paint protection. Efficient protec- 
tion is not as a rule provided by the galvanizing processes, if the 
object is to preserve the metal for long periods of time, and paint- 



ing must be resorted to in order to erect another barrier against 
the attacking forces which produce rapid corrosion and decay. 
The peculiar greasy nature of a zinc-coated metal prevents the 
proper adhesion of ordinary paints, so that peeling and blistering 
result. In order to secure the proper adhesion of paint to gal- 
vanized iron, several different methods of treatment of the metal 
have been suggested. Acetic acid in the form of common vinegar, 
acid salts, ammonia, sal soda, mixtures of copper salts with 
muriatic acid and sal ammoniac, are in more or less general use 
among painters, the object, of course, being to produce a slightly 
roughened surface to which the paint will adhere. 

That these preliminary treatments are wrong in principle and 
quite unnecessary in practice, when proper paints are selected, 
is the firm conviction of the authors. The metals should, as a 
matter of fact, be given a priming coat of a sharp-toothed silicious 
pigment, ground in varnish. This should be well brushed onto 
the metal, so that the sharp angles of the pigment will form a 
union with the zinc surface. In short, the varnish serves the 
purpose of closely cementing the pigment to the zinc. In addi- 
tion to the sharp pigment, a certain proportion of a soft pigment, 
such as sublimed or corroded lead, is believed by some experts 
to be beneficial. Subsequent coats of paint of any desired for- 
mula may be applied provided the first or priming coat is properly 
designed. Varnish vehicles have been tried in connection with 
soft pigments, such as carbon black and lampblack, with some 
success, as far as proper adhesion is concerned, but in the opinion 
of the authors silicious pigments properly mixed with some form 
of lead pigment are much better and safer to use. 

Painting of Tinned Surfaces. — In the course of exposure 
tests near the seashore, which have been under the observation 
of the authors, in which the test pieces were tinned with five to 
forty pound coatings, the great importance of affording efficient 
paint protection of tinned surfaces immediately after erection 
was clearly shown. Some of the test plates actually showed 
evidences of rust at the end of two days' exposure, and at the end 
of a month nearly all were corroding rapidly. Tinned surfaces 
do not present as great painting difficulties as galvanized surfaces, 
and any good inhibitive composition may be selected for their 
protection. It is interesting to note that the use of graphite has 
been condemned by the Master Sheet Metal Workers' Associa- 


tion as positively dangerous for application to tin roofs. 1 As evi- 
dence accumulates, it becomes more and more apparent that this 
pigment is a natural stimulator, and when used as a contact 
coat has been a contributing cause to the failure of many tin 
roofs. The authors have designed an inhibitive formula based 
on knowledge gained from research and practical experiments 
which has given satisfaction in this class of work. This formula 
is composed of 98 per cent, pure iron oxide with 2 per cent, zinc 
chromate, ground in properly aged linseed oil, with or without a 
certain percentage of varnish. The use of inert natural iron 
oxides or ground hematites for this purpose is recommended. 
It should be stated, however, that before painting, the tin should 
be wiped so that the palm oil used in the process of manufacturing 
tin plate will be removed from the surface. The use of turpentine 
or benzine is recommended for this purpose. 

Bituminous Coatings and their Application for the Protection 
of Iron. — From the standpoint of the electrolytic theory of cor- 
rosion, it has repeatedly been stated in the foregoing pages that 
a natural insulator or non-conductor of electricity should be well 
adapted for the protection of iron. In view of the truth of this 
general principle it would seem that bitumonius compounds 
were peculiarly well adapted for the purpose. Unfortunately, 
many materials which are well adapted for the protection of iron 
from one point of view are too prone to fail from another. As a 
matter of fact, most bitumens will not stand free exposure to 
atmospheric conditions, water, and sunlight. It is a significant 
fact that in the cases in which bitumens have been successfully 
used it has been under conditions in which the material was not, 
so to speak, normally exposed to sunlight and the atmosphere. 
Asphalts (and by this term is meant the natural bitumens found 
in nature) do not withstand the action of water without under- 
going change. On the other hand, artificial bituminous sub- 
stances such as coal tar, both crude and refined, although they 
are sufficiently waterproof, undergo certain changes under the 
action of sunlight and the atmosphere, which materially change 
their nature. 2 It is for just these reasons that bituminous coat- 
ings instead of coming into general use as protective agents have 

1 Proc. Second Annual Convention, Nat. Assn. Master Sheet Metalworkers 
Indianapolis, August, 1906. 
-■ See illustration, p. 214. 


found only a limited and special field of application. A careful 
study of the subject serves to show that the useful application 
of bituminous paints and dips is confined to the cases in which 
the action of sunlight is excluded. Thus we find the use of bitu- 
men confined principally to the painting of pipe lines, smoke 
stacks, tunnel work, and piping generally. In short, to all cases 
in which either sunlight is excluded as a factor or where the tem- 
perature of the structure to be protected is so high that no other 
form of protective coating will serve. It is not the intention of 
the authors, however, to contend that properly refined coal tar, 
asphalts, and bituminous mixtures of various composition have 
not been used with more or less success. 

The value of such compounds has been increased by admix- 
ture with fossil gums, among which kauri gum may be mentioned. 
By mixing lime with hot coal tar a valuable mixture has also been 
produced for pipe dipping and other purposes, and in the authors' 
opinion such a mixture as this is well adapted for many purposes. 
The possible development of the use of steel for railroad ties will 
demand efficient protection, for which, owing to economical 
reasons, the bitumens must be made available. This phase of 
the subject will be discussed in a later paragraph. 

Baked japan coatings have come into general use in recent 
years. These coatings are compounded largely of high-grade 
asphaltic gums such as gilsonite and elaterite, sometimes mixed 
with a certain percentage of kauri or other fossil gums. The 
material to be coated is generally heated and then dipped in the 
hot mixture. In some cases the material is baked in ovens until 
the coatings become hard. 

The well-known Angus Smith method of baking pipes coated 
with linseed oil, and afterwards immersing in tanks of heated 
coal-tar pitch, or coal-tar pitch admixed with linseed oil, was the 
original process which has been followed by many others, notably 
the Sabin process. Asphaltum or gilsonite mixed with linseed 
oil or mineral oil has also come into some use for this purpose 
and with considerable success. For information in regard to the 
technology of these processes, the original authorities should be 
consulted. 1 

Regarding the Use of Coal Tar. — With regard to the use of 

1 See Sabin — Technology of Paint and Varnish. First Edition, 1906. 
John Wiley & Sons, New York. 


coal tar. Wood, 1 a well-known authority, says: "A coal-gas tar 
paint that has given very good results in the coating of gas-holder 
tanks and other situations where the metal is exposed to ammonia 
and sulphurous acids in solution, and to alternate melting and 
drying under a great range of temperature, is made as follows: 
Coal-gas tar is well boiled to evaporate the water and light hydro- 
carbon elements, and then 20 to 25 per cent, of caustic quicklime 
is sifted and well stirred in to neutralize the acid elements in the 
tar. This is to be kept hot for a few hours and then an equal 
quantity of good Portland or hydraulic cement is sifted and 
stirred in thoroughly. The mixture is applied hot to the clean 
dry iron, and can be repeated soon as cool or dry if the exposure 
conditions are to be very severe. In the latter case, a little more 
cement should be added, so that the caustic lime and cement 
mixture will contain 50 per cent, of each. The pigments thicken 
the coal tar and prevent it from running under sun temperatures 
and give a bond to the brush coating of neat Portland cement 
that should be applied to the coal-tar coat as soon as either the 
first or second coat of the mixture is dry. This coating can be 
repeatedly applied with advantage. It is impervious to gases 
and water and has no tendency to run at temperatures under 
130° to 140° F." 

The views of Spennrath 2 are also worthy of citation in regard 
to the use of bitumens as protective agents: "Tar paints were 
at one time largely used for the prevention of rust, but their 
employment has of late fallen into disrepute, the alleged protect- 
ive action having been shown to be of very doubtful efficacy. 
It is true that a coating of tar is altogether insusceptible to the 
chemical influence of the atmosphere and also to acids and alka- 
lies; but. at the same time, the tar itself contains substances 
capable of causing iron to rust. Crude tar, for instance, always 
contains moisture, and, in addition to this, acetic acid is present 
in wood tar, the water and acid quickly causing the iron to rust. 
Hence it is that sometimes very extensive rusting can be de- 
tected, often to a considerable degree, under the tarry coating. 
Water-free or acid-free tar would not exert such action; but the 
purification of the tar from these admixtures is troublesome, 

1 M. P. Wood. Rustless Coatings; Corrosion and Electrolysis of Iron and 
Steel. First Edition, 1905. John Wiley & Sons, New York. 

2 Iron Corrosion. L. E. Andes. Scott, Greenwood & Son, London, 1900. 


and increases the cost of this preparation, so that the advantages, 
as compared with oil paint, disappear. Finally, tar paints become 
softened by the sun's rays to such an extent that the mass runs 
and leaves the iron bare. Thus no security against rusting can 
ever be obtained by the use of tar paints." 

An immense amount of work has been done in recent years 
on the chemistry of the bitumens, and more reliable information 
is now available in regard to their refinement and treatment than 
ever before. As a matter of fact, engineers have been inclined 
to speak of tar and asphalt as though these materials were stand- 
ard substances in the same sense, for instance, as sugar and com- 
mon salt are known as standard substances. We now know, 
however, that this is very far from being the case. The character 
and quality of these substances, as a matter of fact, varies within 
wide limits and is dependent not only upon their source but upon 
the methods of preparation and refinement. As an instance 
of this, it is only necessary to refer to the widely differing quantity 
of free carbon or soot carried by different samples of refined coal 
tar. It is not only possible, but highly probable, that a coal tar 
containing, say, less than 20 per cent, of free carbon would be 
better adapted for a protective coating than one carrying from 
40 to 50 per cent, of this constituent. The following paragraph 
is included for the information of readers who may be especially 
interested in this phase of the subject. 

Tar Paints. 1 — Coal tar, if properly refined, makes an excellent 
paint or varnish, especially for metal surfaces which are subjected 
to the action of corroding gases. Crude coal tars vary greatly 
in composition, but always contain ammoniacal water which 
makes them unsuitable for use as paints. The presence of water 
greatly reduces the adhesive qualities of the tar, and ammonium 
salts tend to saponify some of the oily constituents, thus making 
them more or less soluble in water. A coating of crude tar is 
likely to blister and peel off in places shortly after application. 
Tars which have been boiled to remove the ammoniacal water 
are somewhat better than crude products, but are never as satis- 
factory as properly refined tar paints. 

Besides ammoniacal water, coal tars contain at least two other 
objectionable constituents from the standpoint of paint manu- 

1 In the preparation of this paragraph the authors are indebted for assist- 
ance to Prevost Hubbard, who has made a specialty of the study of bitumens. 


facture. These are naphthalene and free carbon. Both are the 
products of high temperatures to which the coal gases are sub- 
jected during the process of tar formation, and as they are usually 
present to a less extent on low temperature than in the high tem- 
perature tars, the former are to be preferred in the preparation 
of paints. Naphthalene is a crystallizable solid which is held in 
solution by the tar oils. It volatilizes slowly at moderate tem- 
peratures, although it is found mainly in the higher boiling frac- 
tions. If present in large amount, it makes a pasty paint which 
after drying commences to crack and disintegrate as the naph- 
thalene volatilizes. Excessive quantities of free carbon produce 
a lumpy, uneven paint, which is deficient in waterproofing 
properties. Free carbon also gives the bitumens a false consist- 
ency. If present in moderate amounts, it is perhaps not an alto- 
gether undesirable constituent, as it adds to the body of the tar 
and serves to some extent as a filler. Twenty per cent, free carbon 
would seem to be the maximum allowable limit. 

When refining a tar for the production of paint, it may merely 
be distilled until sufficient volatiles have been driven off to give 
it the desired consistency, or distillation may be carried to the 
formation of a moderately hard pitch which is afterwards cut back 
with certain of the distillates. The latter type is usually to be 
preferred. In the European countries, it is customary to employ 
an upright form of still with convex bottom for tar refining, but 
in the United States large horizontal cylindrical stills are com- 
monly used. The process of distillation may be briefly described 
as follows: The still is first charged with crude tar, all openings 
except that leading to the condenser closed, and firing commenced. 
As the tar becomes heated it begins to froth and foam and if not 
carefully fired will boil over into the condenser. This is due to 
the presence of water which is converted to steam while the tar 
is still viscous. Boiling over may also be caused by an excessive 
amount of free carbon which causes the vesicles of gas and vapor 
to adhere to the carbon particles and thus swell the volume of 
tar. The removal of water in the final stages gives rise to a 
peculiar noise made by the steam, which is sometimes called the 
rattles. After this noise ceases, distillation usually proceeds 
without further trouble, and the distillate is caught in fractions 
according to the needs of the distiller. Thus, the following 
fractions may be collected: 


(1) First runnings to 110° C. 

(2) Light oils, 110°-170° C. 

(3) Carbolic or middle oils, 170°-240° C. 

(4) Heavy, dead, or creosote oils, 240°-270° C. 

(5) Anthracene oils above 270° C. 

In the United States the distillate is usually divided into only 
two fractions, the light oils having a gravity of less than 1.00 and 
the creosote oils having a gravity greater than 1.00. The second 
fraction is collected until the residual pitch is of the desired 
consistency. If this pitch is sufficiently fluid it may be employed 
cold as a paint. It is preferable, however, to carry the distillation 
further and afterwards cut back the harder pitch with dead oils 
from which the naphthalene has been removed. Pitches which 
contain only the higher boiling oils as solvents for the heavier 
bitumens take a long time to dry, and for this reason it is some- 
times preferable to use a harder pitch which requires to be heated 
before application, but afterwards drys rapidly. A still more 
satisfactory paint is one produced by cutting a moderately hard 
pitch with about three-fifths its volume of light oils. Such paints 
may be applied cold and dry in a comparatively short time. 
Rapid drying paints and varnishes may be prepared by substitut- 
ing the more volatile tar naphtha for the light oils. They may 
be applied in very thin coats if desired by using a large amount 
of naphtha. Water-gas tar pitch makes an excellent base for 
these varnishes, as it contains but very small amounts of free 
carbon and naphthalene and produces a glossy black coating of 
uniform texture. 

To sum up the discussion of the use of bituminous paints and 
compounds as protective coats for iron, the authors wish to 
reiterate their opinion that in special cases, and if properly selected, 
there are no better materials available. For use, however, under 
general exposure conditions where sunlight and free atmosphere 
are elements in the problem, bitumens cannot be successfully 
used. The well-known effect which has been mentioned in pre- 
vious paragraphs as "alligatoring" is almost always produced 
on bituminous coatings exposed to the action of sunlight. This 
effect, which has been photographed from one of the panels on 
the Altantic City tests, is shown in Fig. 66. 

An accurate explanation of the phenomenon spoken of as 
alligatoring is not easy to give, but it probably depends on a 


superficial hardening of the outer or skin surface of the coating, 
underneath which the body of the material still remains to some 
extent plastic and elastic. The regular and diurnal expansion 
and contraction of the iron, which have sometimes been referred 

Fig. 66. — Alligatoring of coal tar over red lead. 

to as the breathing of steel, must gradually produce this tendency 
to cracking or checking of the superficial layer of the bituminous 
coating. The effects produced are exactly similar to the crazing 
of vitreous glazes which has produced so much discussion in the 
ceramic industry. Exactly the same effects are produced in some 


cases of linseed oil films in which an excess of unctuous or soft 
pigment has been used. It follows that if this checking effect 
spoken of as alligatoring continues for any length of time, the under- 
lying surface will become exposed to the corrosion influences. 

Paper Paints and Paper Preservatives. — A process proposed 
by Cross and Bevan has been described by Andes/ by which cellu- 
lose paper is dissolved in caustic soda lye, producing a highly pro- 
tective paint. Paraffined paper has also been used successfully as 
a protecting material. For further information in regard to these 
rather unusual methods the reader is referred to the literature 
as given in Appendix B. 

Painting Metals Subject to Marine Growths. — The dockage 
of steel ships which have been in the salt water for six months 
or more generally discloses a condition of surface below the water 
line that has caused naval constructors much concern. The 
thick crust of barnacles and marine growths must be scraped off 
if the ship is to make speed with the least coal consumption, but 
the tenacity that is shown in the adherence of the marine growth 
makes it impossible to avoid abrasion of paint coatings, in the 
cleaning process. That such growths are stimulators of corrosion 
there seems to be no doubt, and the only remedy seems to be in 
the application to the steel hull of the boat of a good, hard under- 
coat, with a top coat of paint containing materials which will act 
as poisons to the various growths, and prevent their action. Cer- 
tain semi-drying compositions, containing pine tar or crude oil, 
and having a percentage of some powerful poison, such as strych- 
nine, have been used as a vehicle for high-grade oxide of iron and 
lead pigments, and seem to have shown excellent results. 

Soaps of copper, arsenic, and other poisonous compounds, 
made by precipitating a saponified oil with salts of the above 
metals, are often dissolved in the vehicle of marine paints and are 
undoubtedly of value, especially the soaps of copper. Corrosive 
sublimate and oxide of mercury (mercury vermilion) are probably 
the most efficacious poisons to use for this purpose. 

The first, or under coating, for the ship plates should contain 
in the vehicle a good hard drying varnish to act as an excluder 
of water, and the outer coats should be those containing the 
poisonous pigments. A certain percentage of oil of a semi-dry- 
ing nature is sometimes advisable. 

1 Der Eisenrost, p. 252. 


Paints resistant to the action of sea water and saline atmos- 
pheres have already been discussed in a previous chapter. 

Painting Steel Cars. — The equipment of modern railroads 
has brought about great changes during the last few years in the 
construction of both freight and passenger cars. The old type* 
of wooden cars are rapidly being replaced by those of all steel 
construction, which are found to be safer and more efficient from 
every point of view. 

Before painting steel cars, the surface should be, and usually 
is, cleaned with the sand blast. The sand blast has been found 
more efficient than paint removers for removing old paint from 
steel surfaces. Old paint, under the abrasive action of the sand 
from the blast, readily wears down, and the continuous action 
of the sand upon the steel furnishes a good surface for the appli- 
cation of new paint. In order to give proper smoothness, the 
surface may be coated with a primer which generally consists 
of a silicious pigment, such as mineral black, with the possible 
addition of some willow charcoal ground in oil and varnish to a 
thick paste. After this has thoroughly dried, a coat of filler is 
usually applied, and then a coat of surfacer, these materials being 
preferably of inhibitive pigments and of different colors so that 
the inspector may know by the color the number of coats that have 
been applied. Two color coats are generally applied upon the 
surfacer and then several coats of the finishing varnish may be 
used. The authors do not wish to convey the impression that the 
above general outline of car painting is recognized as standard, 
but it is their desire rather to indicate that in the various primers 
and fillers that are used for car painting, the replacement of stimu- 
lative pigments with inhibitive pigments should be made, and 
when this condition prevails, not only on the first and second 
coats but throughout on all coats, the best results will probably 
be obtained. 

The ordinary type of sheet-steel coal carrier sometimes receives 
sand blast treatment and then spraying with paint, the small 
amount of time allotted the painter in his work requiring the use 
of excessive drier in order to get the cars second-coated, ready 
for lettering and stenciling, and out of the way to make room for 
others. Such methods should be revised. The authors have 
yet to see a car painted in the above manner that is not badly . 
corroded in all too brief a period, and it is doubtful whether 


many steel coal cars even survive their maiden trips without 
showing rust tuberculation. 

The use of pneumatic paint atomizing machines by large 
railroads has reduced materially the labor cost per car, and has 
probably resulted in a more uniform distribution of the paint, 
especially on rough and irregular surfaces. The use of excessive 
quantities of thinners should, however, be avoided when paint 
machines are used. 

The authors are aware of the numerous practical difficulties 
that the car painter and railroad engineer has to contend with. 
The modern steel coal-carrying freight car provided with lower 
dumps furnishes a specific instance of just such a difficulty. Our 
winter climatic conditions frequently cause the coal to freeze 
in the cars, so that in order to free the dump hoppers the railroad 
operatives find it necessary to beat upon the side of the cars with 
the nearest available weapon. It is evident that no paint coat- 
ing that has ever been designed will stand such heroic treatment. 
The only practical solution of this difficulty which presents itself 
is some system of inspection and maintenance which will provide 
for repainting at frequent intervals in the yards without waiting 
until complete failure demands the return of the car to the shops. 
The old wise saw that a " stitch in time saves nine" finds a pecu- 
liarly appropriate application not only to the conservation of 
steel shaped into cars and other containers, but also to the subject 
of the conservation of iron in general. As a matter of fact, such 
a system of maintenance as is outlined above has to some extent 
been tried, and it is not altogether an unusual sight in freight 
yards to see corrosion spots on cars being touched up with red 
lead. As far as this work has been carried on it constitutes in 
the opinion of the authors one step in the right direction. There 
is no reason, however, why an inhibitive paint compound should 
not be designed and compounded to a definite color scheme, so 
that retouching under this plan of maintenance could be carried 
on by expert painters in the freight yards. Surely the cost of 
maintenance as carried out by such a scheme would not in the 
end be greater than the steadily fixed charges laid upon all owners 
and operators of structural steel by the never ceasing attack of 
corrosive influences. 

Paints for Locomotives and Tenders. — In painting locomotives 
and tenders, large quantities of mineral black (a special grade of 


bituminous slate), ground in varnish, is generally used for the 
primer. After rubbing down, this coat is often followed with one 
containing white lead, carbon black, and silica. This coating 
is followed, after rubbing, with a body coating of ivory black in 
japan, and finally with several coats of special locomotive finish- 
ing varnish. The use of mineral black is not bad practice, as 
it has no special stimulative properties. In the opinion of the 
authors, however, 2 to 5 per cent, of special inhibitive pigment 
should be used in admixture with the pigment. 

Protection of Iron in Tunnel Work. — The protection of iron 
in tunnel work presents a problem of unusual difficulty. Con- 
stant seepage causes drippings of an extremely corrosive nature 
to come in contact with all exposed surfaces. Very often this 
exuded moisture found in tunnels is rich in chloride and other 
corrosive electrolytes. These salts act to a certain extent the 
part of paint removers. The atmosphere in tunnels is often rich 
in carbonic acid, sulphur dioxide, and invariably high in moisture 
content. These conditions call for the very best excluding and 
inhibitive paints that it is possible to design. It has already 
been stated that properly refined coal tar, treated with lime, 
is well adapted under certain conditions for use in the dark, and 
therefore should be useful in protecting the various forms of iron 
and steel used in tunnels. If oil paints are to be used, they 
should have a varnish vehicle of the highest type, made with 
gums of low saponification value, such as copal. A varnish paint 
of this nature has been found to give extremely good results on 
the cars running in the tunnels of the Pennsylvania Railroad 
under the Hudson River in New York City. 

Painting Train Sheds. — The train shed with its gigantic 
network of structural metal is constantly filled with the sulphur- 
laden gas belching from the numberless engines that operate 
therein. This gas condenses with the rising steam upon the 
painted metal surface, and often causes most disastrous results. 
In the large terminals a force of men are kept constantly at work 
repainting the maze of steel. The- engineer is ever on the look- 
out for some material that will last for a greater length of time. 
Excluding the fumes and gases by the use of a varnish paint 
seems to offer the best solution of the above problem. The 
varnish for such a paint must be, however, of the highest grade, 
and one that will withstand exposure without cracking or checking. 


The use of high-grade copal gums for this purpose is to be recom- 

Black japan made by fusing and properly treating eight pounds 
of kauri or copal gum in two gallons of oil, and mixed with about 
twenty gallons of boiled linseed oil containing 1 per cent, of 
litharge, forms a base into which may be added five gallons of 
high-grade asphaltum. When this composition is applied, it 
dries to a high glossy surface and forms an excellent excluder. 
Other paints, made of inhibitive pigments and possessing exclud- 
ing vehicles, have also proven most satisfactory for the above 
class of work. 

Paint Protection for Water Tanks. — Water tanks and other 
large steel containers present a double problem, as protection 
must be provided on both the inner and outer surface. The 
painting of the inside of steel water tanks has been in practice 
on American railroads for some time past. F. C. Peterson 1 of 
the Southern Pacific Railroad has recorded satisfactory results 
with the use of a formula composed of 25 lbs. dry red lead, 5 lbs. 
litharge, 5 lbs. Venetian red, 1 gallon boiled linseed oil, and 1 
gallon of turpentine. Three coats are usually given with this 
mixture. The use of natural hematite (iron oxide) in place of 
the Venetian red would be better practice. Venetian red gener- 
ally contains fifty per cent, or more of gypsum, which is partially 
soluble in water and is often the cause of the rapid failure of 
paint films. The results obtained with gypsum on the Atlantic 
City test panels would certainly not recommend its use in an 
inhibitive formula. 

Painting Steel Railroad Ties. — The rapid diminution of our 
forests, and the increasing cost of wood, may ultimately require 
the substitution of steel for railway ties. Steel ties are at present 
being experimented with on several railroads, and, while they 
have not as yet proved wholly satisfactory, some progress has been 
made, and we may feel certain that their final adoption in some 
form is sure to come. Steel ties must be protected or corrosion 
will soon weaken and destroy them, reducing their durability 
below that of the wooden tie. If, however, they are properly 
protected, there is no reason why they should not last for many 

1 Painting Insides of Steel Water Tanks. Paper read before the Mainte- 
nance of Way Master Painters' Association, Niagara Falls meeting Septem- 
ber, 1909. 


years. The authors believe that dipping in hot properly refined 
coal tar free from acid is the best treatment that has been suggested 
for the purpose. A mixture of 80 parts of coal tar, 5 parts of dry 
lime, and 15 parts of Portland cement is recommended as a good 
formula for a tie dip. The lime which in itself is an inhibitor 
neutralizes any free acid in the coal tar, while the cement appears 
to lead to a harder surface, which gives more resistance to the 
abrasive action of roadbed dust. In addition to this, it might 
be advisable to apply a preliminary dip coating designed to be 
inhibitive. The first cost of these treatments will be high, but 
if steel is to be used for the purpose, some such protection must 
be supplied. 

The operation of refrigerator cars would constitute a special 
menace to steel ties, unless mechanical devices are contrived to 
catch and discharge the brines. The Master Car Builders' Asso- 
ciation has appointed a committee to study this problem. In a 
paper on this subject, A. B. Phelps 1 of the Lake Shore Railroad 
says: "To those of you who have the care of bridges, interlocking 
plants or other iron or steel apparatus or other structures, I need 
not enlarge on the destructiveness of salt brine; to those of you 
who are not on trunk lines, and consequently have few, if any, 
refrigerator or stock cars passing over your road, I will simply say 
that salt is one of the most destructive agencies to steel and iron 
of which I know, and when brought in contact with steel bridges, 
if neglected, soon forms large, thick scales of corroded metal, 
greatly weakening the structure, and requiring the use of heavy 
hammers or chisel-pointed steel tools to remove them. Ordinary 
steel brushes will have no effect whatever on them. 

"This salt brine, of which I speak, is formed by the melting 
ice and salt used in cooling the contents of the car, and is allowed 
to drip directly from the bottom of the car, almost exactly on, 
or only a few inches from the rail, alighting on both the top and 
bottom flanges of the bridge, where it proceeds to get in its work 
of destruction. To prevent, not to cure, this evil is my theme. 
The present general construction of these cars is to provide an 
outlet underneath the icebox of about a 2-in. iron pipe, pro- 
truding into a metal cup, or box, holding about a quart, which 

1 The Destruction of Railroad Property by Refrigerator Car Drippings, 
Sixth Annual Convention Maintenance of Way Master Painters' Association 


when filled, forms a trap, so that warm air will not enter the ice- 
box from beneath. This cup is allowed to fill and spill, -and slop, 
and drip its contents the entire length of the road, and do its 
hellish work — that is strong language, but no stronger than the 
solution of which we are speaking. These conditions should never 
exist, and should not be allowed for one single day. Provision 
should be made, in building these cars, to retain the brine and 
carry it to and empty it at the terminals, or at the icing stations." 

Inhibitive Pigments for Railroad Equipment in General. — Red 
lead, basic lead chromate, zinc chromate, and bright neutral 
oxide of iron are inhibitive pigments which may be used in pro- 
ducing reds for semaphore, signal and switch targets on railroads. 
Genuine oxide of chromium is a most permanent green pigment, 
when this color is desired, for the above use. When this pigment 
is reinforced with a silicious pigment, its wearing value is increased 
without materially detracting from its color depth. Zinc-chrome 
green made from zinc chromate and inhibitive Prussian blue, is 
also a very permanent inhibitive color that should meet favor 
for signal work. 

All these pigments have been experimented with and carefully 
observed by both the authors under a wide range of service con- 
ditions, and are known to have given satisfactory results! 

The Preservation of Steel Mine Timbers. — The question of 
the substitution of wood by steel for timbering mines, is an im- 
portant one from several points of view. An enormous amount 
of valuable timber which might possibly be employed to better 
purpose above ground is used in mining operations. On the 
other hand the fear of rapid and dangerous corrosion of steel 
induced by the acid character of most mine waters has led many 
engineers to feel that the substitution of steel for wood might 
lead to extensive failure in the course of time. Woodworth has 
made an extensive research on this subject. 1 in the progress of 
which he has reached the following conclusions: 

"The application of economic principles to the use of steel 
demands that the life, on which its economical use is predicated, 
be lengthened to as long an extent as possible, and the preven- 
tion of waste and loss in the steel itself by preservative treatment. 

*R. B. Woodworth, M. Am. Soc. C. E., Engineer Carnegie Steel Co. 
Paper read before the West Virginia Coal Mining Institute, Huntington, 
W. Va., December 7, 1909. 


No iron has ever been or ever could be manufactured that would 
not rust in moist air unless it is protected by some sort of covering, 
for the reason that pure iron itself has a tremendous affinity for 
oxygen and the slightest contact between iron and oxygen in a 
more or less unstable condition causes immediately that combina- 
tion of iron and oxygen which is known by the name of oxidation 
or rust. This tendency to corrode is characteristic of the metal 
itself and is independent of the presence of the impurities it may 
contain. 1 Iron does not rust when entirely submerged in pure water 
or water not containing free air; neither does it rust in a perfectly 
dry atmosphere, the beginning of oxidation being due to the pres- 
ence of sufficient quantities of free oxygen, due to impurities con- 
tained in the air, in the presence of sufficient moisture to act as 
water of disassociation, this condition permitting the escape of 
hydrogen and the consequent oxidation of the steel or iron. 
The great variation which occurs in the rusting of iron and steel 
is probably due to unequal distribution of the impurities neces- 
sary in their manufacture. Iron does not occur in a pure state 
and in the process of the manufacture of wrought iron and 
steel, small traces of impurities occur more or less unequally dis- 
tributed throughout the mass. It has been claimed that the small 
proportion of manganese which steel contains adds greatly to its 
oxidizing tendencies. This, however, is not borne out by actual 
experience and the removal of manganese does not carry with it 
freedom from oxidation. 2 The difficulty lies not in any one cause 
or element contained in the steel but in their unequal distribution 
throughout the steel which permits differences of potential at 
different points. The prevention of this oxidation, however, is 
a very simple matter. Such steel as has already been installed 
in the mines of the United States has given entire satisfaction 
without any serious corrosion and without any protective treat- 
ment other than the use of preservative paint. In wet mines 
in England steel girders are frequently tarred before being put 
in, but the actual loss from corrosion is so small as to be a minor 
quantity even when the steel is not painted. In dry locations 
there is not much danger of any serious corrosion. In the speaker's 
judgment, however, true economy will require the painting of 
all steel for underground operations with one shop coat of good 

x The authors are not prepared to accept this unqualified statement as 
has been shown in preceding discussions. 

2 This statement may also require qualification. 


paint and with at least one field coat. If these are well worked 
in, the steel should need no further attention for years. What 
these coats should be has been the subject of considerable investi- 
gation, attention being had as well to atmospheric conditions as 
to the possibility of contact with acid waters, and while laboratory 
experiments have not been finally completed, the broad lines of 
preservative treatment may now be indicated. Steel should not 
be painted with carbon paints in whose manufacture sulphuric 
acid has been used and the use of coal tar products is, therefore,, 
to be avoided. The natural carbons, such as graphite, and hydro- 
carbons, such as asphalt and gilsonite, may be recommended 
for second coat work if properly ground and mixed with a good 
vehicle. For the first coat pigments should be used of a more or 
less inhibitive character, though it has been demonstrated that 
some of the best paints are not entirely inhibitive. The oxides 
of iron, such as Venetian reds, are usually manufactured by 
chemical processes and their use is to be avoided, though a good 
natural oxide of iron paint may be used under dry atmospheric 

" The correct theory which underlies the prevention of corro- 
sion in iron or steel is based on the use of a practically inhibitive 
pigment to prevent the inception of corrosion in the steel and the 
use of a second coat to protect the first from atmospheric and 
temperature conditions and to fill up thoroughly any vacancies 
or voids which may occur therein. To meet these conditions 
the pigment should be practically inert and its particles extremely 
small. While red lead is not absolutely inhibitive, it has been 
demonstrated in all kinds of exposures to be a first-class pigment 
for use in the preservative treatment of steel in almost any situa- 
tion and its particles are extremely minute. It is a very heavy 
pigment and settles quickly, necessitating the mixing of a new 
lot if it has stood over any length of time. The settling may 
be retarded by the use of barytes or asbestine, and the use of the 
latter is to be recommended by reason of its permitting a firm 
hold on the pores of the steel. The oil should be pure, as the 
matter of vehicle is of large importance, and the raw oil is better 
than the boiled. A mixture of red lead, oil and asbestine, in the 
proportions of at least 15 pounds of red lead and 2 pounds of 
asbestine to a gallon of oil, with sufficient japan drier to work 
well, may be recommended as probably the best under present 


conditions, and the use on this of a first-class graphite paint will 
serve thoroughly to protect the shop coat and to fill up any 
vacancies or voids therein, the particles of well-ground graphite 
being also extremely small. In the painting of steel the surface 
should be most carefully cleaned from all scale, rust, dirt, etc., 
and the paint should be applied in dry weather. No painting 
should be done in wet or freezing weather. When, for any reason, 
it is necessary to repaint, the repainting should be done on clean 
surfaces absolutely free from all rust, paint skins, dirt, etc. It is 
not sufficient to apply a new coat of paint over an old paint sur- 
face under which traces of corrosion appear; the new paint will 
cover the old surface and may adhere firmly thereto, but the 
corrosion goes on underneath just the same. This small atten- 
tion to detail characterizes all thorough work and is necessary 
for the entire preservation of steel or iron in any location. It is 
doubly necessary by reason of the fact that underground steel may 
not be examined and repainted with the readiness possible in above 
ground construction. At the same time it may be added that 
underground conditions are not nearly so secure on the steel as 
above ground conditions, and certainly the paint itself is not 
exposed to those alternating conditions of high and low tem- 
peratures, dryness and wetness, strong light and darkness, with 
which above ground construction has to do and which are especially 
accelerative to the deterioration of protective coating. The only 
serious condition underground is due to the presence of acid-laden 
waters, and the speaker's chemical analyses and laboratory 
investigations indicate that the objections due to this cause have 
been largely overstated. Experience and theory all indicate that 
only the simplest means are necessary for the absolute guarantee 
of an extremely long life for steel used in underground conditions." 
Painting of Steel Mine Timbers. — In a special communica- 
tion to the authors Mr. Woodworth gives an account of extended 
laboratory researches on the subject of painting steel mine tim- 
bers: "Mine water usually carries with it more or less free acid 
and its corrosive action is one of the reasons advanced why steel 
should not be used in substitution for the standard wooden con- 
struction, and this in spite of the fact that an experience of fifteen 
years in the use of square timber sets has proven that material 
can be very well protected from this corrosive action by the use 
of methods recommended in ordinary outdoor structural work. 


Conditions in mines vary greatly; in the long, dry passageways 
there is little danger of deleterious action; in damper situa- 
tions there may be running water carried in the side ditches, 
which may come in contact with the feet of the timber sets; and at 
shafts the timber may be exposed to the constant action of running 
water which may be more or less acid in accordance with the 
character of the overlying strata which may or may not contain 
beds of coal. To find the best methods of protective treatment 
to meet the worst conditions, laboratory tests were instituted. 

Samples of mine water were obtained from a number of anthra- 
cite and bituminous coal mines which were carefully analyzed in 
the laboratory of the Carnegie Steel Company at Homestead Steel 
Works for total solids and total free acid in parts per million, as 
shown on tables attached. From a comparison with a fuller 
analysis made by the Lehigh Valley Coal Company it was decided 
that practically the worst condition to be met would be that of 
an acid water containing 2320 parts of free sulphuric acid (H 2 S0 4 ) 
in a million and 128 parts of ferric sulphate Fe 2 (S0 4 )3. To expedite 
the action of the acid water on the samples to be tested it was 
decided to intensify ten times and to subject samples to a solu- 
tion containing 23,200 parts of sulphuric acid and 1280 parts of 
ferric sulphate to the million. In this connection it may be stated 
that investigations indicate the intensifying action of ferric sul- 
phate in solution as compared with a solution containing sulphuric 
acid only.. A mixture was prepared with 180 cubic centimeters 
of commercial sulphuric acid of 1.84 specific gravity and 79 drams 
of commercial ferric sulphate dissolved in one meter of water, 
giving 2.616 per cent, free sulphuric acid and .432 per cent, ferric 
sulphate, or 2.135 per cent. S0 3 and .432 per cent. FeS0 4 . 

One-half in. round steel rods 3J in. long were used for test 
purposes, with wide mouthed bottles 4£ in. high and 1? in. in 
diameter with necks If in. in diameter. The rods were painted 
with the pigments to be tested, inserted in holes bored in the 
corks and immersed in the above-mentioned solution, the bottles 
being properly labeled with the number of the pigment tested and 
the rods being marked by a file with the same number. Exami- 
nations were made at intervals of two or three days apart in 
the inception, of the test and at longer intervals on such pig- 
ments as remained. The rods which showed a deterioration of 
pigments under solution action or corrosion underneath the films 


were removed when such deleterious action became pronounced. 
Solutions were renewed when the reddish discoloration produced 
by solution action became pronounced provided the pigment 
showed no apparent signs of disintegration. The bottles were 
freely agitated at all such examinations and repeatedly between 
examinations as well. In some instances the solution continued 
clear and the pigment intact until the completion of the tests, 
which extended from December 23, 1908, to June 4, 1909, at 
which time the relative values of the pigments had been demon- 

The pigments tested were in part commercially prepared ready 
mixed paints, in part paints prepared from the raw materials in 
the laboratory, and in part special formulas furnished ready mixed 
by the Paint Manufacturers 7 Association of the United States. 
The vehicle used in the preparation of pigments in the laboratory 
was selected raw linseed oil purchased from the Pittsburg Plate 
Glass Company. The material painted was carefully cleaned 
from all mill rust, scale, etc., and the pigments applied carefully 
by brush. The first coat was allowed to harden thoroughly, 
some seven or eight days, or longer if necessary, before the appli- 
cation of the second coat, and the second coat was firm and hard 
in all cases before immersion in solution. 

In one or two cases the pigments failed utterly in two or three 
days from the inception of tests. In others the action of the acid 
water produced almost immediately a marked discoloration with- 
out further change or deleterious action for long periods and with- 
out any precipitation of solid matter. One hundred and thirteen 
different combinations were tested and after expiration of the 
tests thirty-one remained. The purely carbon paints, presum- 
ably manufactured from coal tar products, gave no good results; 
natural oxide of iron showed up fairly well. The best pigments, 
both for adhesion and for minimum deterioration of film and 
minimum corrosion underneath the film, were red lead and the 

On the basis of the results obtained in the execution of these 
tests it is recommended that steel mine timbers be painted at the 
shops with one coat of red lead and oil, mixed in the proportion 
of at least 15 pounds of red lead and 2 pounds of asbestine to 
a gallon of pure raw linseed oil, with sufficient japan drier to work 
well under the brush, and that a field coat be applied of first-class 


graphite paint. Material to be thoroughly clean from rust and 
mill scale before painting. The theory which underlies this rec- 
ommendation is based on the use of a practically inert pigment, 
thoroughly tried in all sorts of conditions, of firm adherence to 
metallic surfaces and of extremely small particles; and also on 
the use of a first-class excluder of likewise fine particles and firm 
adhesion thoroughly to protect the shop coat and to fill up any 
vacancies or voids therein.'' 

The tabulated results of Woodworth's laboratory experiments, 
which were courteously turned over to the authors for use at their 
discretion, were not included here owing to the fact that a large 
number of the paints experimented with are proprietary com- 
pounds. Woodworth's own summing up of his experiments has, 
however, shown that he came to the conclusion that a good grade 
of graphite on top of a good grade of red lead primer was best 
adapted to the purpose, and provided the most efficient protec- 
tion among all the compounds and methods of painting tried. 
With this conclusion the authors find themselves in complete 
accord, under the conditions which maintain in the experiments. 
The attack* of free acid here was very strong, and, as Woodworth 
points out, ten times stronger than is found in the average mine 
conditions. It is quite evident that under such conditions as 
these the primary object must be to select a pigment which will 
be highly resistant to acid attack. It is clear that of all pigments 
in common use no one is more resistant to the attack of mineral 
acids than carbon in its graphitic form. The conclusion of 
Woodworth, therefore, that a good reinforced inhibitive prime 
coating, topped with a good acid resisting excluder, is the best 
combination that could be used under the circumstances is in 
accordance with the opinion of the authors. The question, 
however, as to whether red lead is the best inhibitive primer which 
could be selected for the purpose has not yet been convincingly 

The Painting of Field Fence Wire. — Galvanized zinc coatings 
are almost exclusively depended upon for the protection of field 
fence wire. This subject has been discussed in detail in a pre- 
vious chapter. There can be no doubt of the fact that it is 
possible to prolong the life of wire for many years if the trouble 
is taken to place upon the zinc surface a top coating of properly 
selected paint. 


The painting of fence wire presents certain difficulties that 
are not met with in any other class of work. The round surface 
of the wire causes paint of the ordinary consistency to run from the 
upper part, where a thin film is left, to the under part of the wire, 
where it collects in quantity, forming thick, non-drying clots 
which absorb moisture. The authors have found that the best 
consistency for paint to be used on wire fences should be that 
possessed by a highly viscous cream; in fact, a thin paste is often 
advisable, if properly brushed out. A good soft hair, flat varnish 
brush about i-m. wide has been found the best conveyor for 
the paint. After the paint has been applied to the top and side of 
a wire fence for a considerable distance, the painter should go 
back and run the brush along the bottom of the wire so that the 
paint that has collected there will be uniformly distributed. 
Turpentine or other volatile diluents should not be used, and if 
reduction is found necessary, it should be with linseed oil, either 
raw or boiled. 

A quart of paint will cover something over 300 ft. of ordinary 
eleven-strand fabricated wire field fence. For the painting of the 
fencing surrounding a large farm, only a few gallons, therefore, 
would be required. It is not necessary to employ expert painters 
to apply paint to wire, and when ordinary care is exercised the 
farmer or his men can easily paint fencing at their leisure. The 
increase in the durability of the fence which painting provides 
should induce the farmer and other consumers to undertake the 
work even though it involves a certain amount of time and trouble. 

A recent inspection of the Steel Wire Test Fences at Pitts- 
burg by the authors indicated very clearly that the wire panel 
which was painted with an inhibitive formula was outlasting all 
other panels on which ordinary paint coatings had been used. 
The use of finely ground hematite with a small percentage of 
zinc chromate, ground in pure linseed oil with or without the addi- 
tion of varnish, should prove efficient for use on fence wire. 
Silicious primers, mixed with zinc or red lead, are also being used 
for a first coat on galvanized wire. Paints containing stimulative 
pigments, in the opinion of the authors, should not be employed 
on wire fencing, as they are almost certain to cause rusting and 
may even hasten the decay of the underlying zinc. Fig. 67 
shows the effect produced on ungalvanized wire in less than one 
year when a stimulative pigment has been used. 


Care should be taken to paint when the wire is perfectly dry. 
Moisture will lead to subsequent failure, causing non-adherence, 
blistering, and destruction of the film. Painting in very cold 
weather should also be avoided, as puckering and contraction of 
the paint skin will result. 

In nurseries, vineyards, and certain other places, a spray of 
copper sulphate is sometimes used as a destroyer of the animal- 
cule that live upon the growing plants. When this copper 

Fig. 67. — Section of wire painted with stimulative pigment. Enlarged. 
Failure resulted in less than twelve months. 

sulphate strikes the zinc-coated wire upon which the plants are 
supported, the zinc at once goes into solution and the copper is 
precipitated in a loose spongy mass upon the wire. Moisture 
at once attacks the imperfectly protected iron and serious corrosion 

If the wire supports for plants are coated with a good pro- 
tective paint, the above difficulties are to a large extent overcome, 
and chemical insecticides can be used without producing serious 

The authors have discussed with the manufacturers the pos- 
sibility of shop coating galvanized wire fencing with inhibitive 
compounds, but the perfectly reasonable objection has been raised 
that wire so treated would not withstand the abrasion due to 
transportation, handling, and mounting on the fence. For this 
reason it would seem that the painting of fencing should be 
done in place and after they are mounted on the posts. 

Prime Coati?igs for Structural Metal — It is always difficult 
for the engineer to decide what paint formula should be used 
for the prime coating on structural framework for modern build- 
ings. Probably red lead is in most general use for this work, 
where it has been found to give, generally speaking, a hard and 


satisfactory base upon which to place the finishing coat. Andes 1 
has stated in this connection : " We know that red lead forms a paint 
that strongly adheres to and hardens on iron, which it preserves 
from rusting; and we also know that the same paint is very 
durable when covered over by subsequent coatings' of good paint. 
On the other hand, red lead paint, by itself, must, by reason of its 
small proportion of oil, soon perish under atmospheric influences, 
and is therefore unsuitable for use as a finishing paint. Now 
there is another point of great importance in connection with 
painting on iron, namely, the teaching of experience that although 
a paint rich in oil or varnish may be applied over a paint contain- 
ing a high proportion of pigment to varnish, yet the converse 
practice must not be pursued; and this is the reason why the idea 
of painting with red lead was originally hit upon. This experi- 
ence primarily applied only to wood, but it seems also to have 
held good for iron. The words ( it seems ' are used advisedly, 
since no reliable experience to the contrary appears to have been 
gained, or at any rate published. 

"In most cases, though not always, iron structures receive 
a first coat of iron or red lead oil paint in the works when com- 
pleted, i.e. j when the individual girders, stays, etc., have been 
riveted and wrought into the most suitable condition for delivery. 
Nobody, however, troubles about whether the girders have been 
riveted out of doors — where they are exposed to the air and, more 
especially, to the deposition of moisture brought about by fluc- 
tuations of temperature — or under cover; and still less is any 
thought bestowed on the painting of the rivet holes, the stems of 
the rivets or the under side of the rivet heads. In many works 
the paint is laid on by day laborers who simply daub it on, often 
without suitable brushes, and the work is regarded as properly 
done if the metal is outwardly covered over with paint. Now the 
author readily admits that painting the rivet holes, and the 
rivets themselves, is a very tedious and often expensive task, and 
that very often there is insufficient space available for the rivets 
to dry after painting. Nevertheless, he holds that when it is a 
question of properly painting ironwork so as to fulfil the require- 
ment that all parts of the metal shall be thoroughly covered, and 
that the connections, in particular, shall be so carefully painted 
as to prevent the incursion of water, then all these considerations 

1 L. E. Andes. Iron Corrosion. Scott, Greenwood & Son, London, 1900 


of reducing the cost of production to a minimum must be put 
into the background." 

Zinc chromate, high-grade oxide of iron, and other pigments 
have proven equally as efficient as prime coaters, as red lead. 
For further information on this subject, see Chapter VIII on the 
results which are being obtained on the Steel Test Panels at 
Atlantic City, which should be watched with interest by engineers. 

As has been pointed out in a previous paragraph, red lead is 
not a standard substance and its inhibitive value may be easily 
affected by the process of manufacture by which it is prepared. 
As is described in a separate paragraph in a succeeding chapter, 
red lead is manufactured by two separate and widely different 
processes. It is not at all probable that the two products would 
show the same inhibitive value, as this value would depend upon 
the amount and character of the included impurities. 

The Use of Oil as a Shop or Prime Coating. — The subject of 
shop coatings for machinery and structural iron has received a 
great deal of attention. It has long been known that linseed oil 
is an active stimulator of corrosion when applied to iron, when 
its surface becomes abraded in the least degree. This opinion 
is borne out by recent work done by Walker. Walker's work on 
this subject has been referred to in a previous paragraph, but in 
view of its direct bearing on the subject under discussion, it will 
be well to recapitulate it here. Walker finds linseed oil to be, 
under certain conditions, an accelerator of corrosion. When a 
steel or iron surface painted with linseed oil becomes abraded at 
a particular spot, corrosion proceeds more rapidly in the presence 
of the coating of oil than without the coating. This is ascribed 
to the fact that the hydrogen, which is always evolved when iron 
rusts, is constantly removed by the linseed oil, which (being an 
unsaturated hydrocarbon) has the power of absorbing hydrogen 
and therefore acts as a depolarizer much in the same way that 
mill-scale acts by destroying the so-called " electrolytic double 
layer." 1 When, however, linseed oil contains pigments there is 
a marked decrease in the power of the oil to remove the hydrogen 
and act as a depolarizer. 

Perry 2 in commenting on the subject of shop coatings for 

1 See Chapters II and III. 

2 Bulletin No. 15, Scientific Section, Paint Manufacturers' Association 
of U. S. 


metal, states: "The addition of high-grade fossil resins, carefully 
compounded with a carefully treated oil, adds greatly to the 
power of a paint to resist penetration by gases and moisture, 
producing a better excluding paint and at the same time 
adding to the appearance. The glossy surface which a paint 
made along these lines possesses, renders the paint a better 
repellent or resister of moisture. The quality and percentage 
of gum used influences to a great extent the wearing properties of 
this kind of paint. 

"During the transportation of machinery and structural steel 
from the factory to the field and the workshop, there is met a 
state of condition that causes rapid corrosion. Moisture and 
gases attack the metal and assert their destructive action. In 
the past these results have been partially overcome by swabbing 
the metal with crude oil, in some cases, and, again, by giving the 
metal a dip in hot linseed or other drying oils or by applying tar 
and cheap paints as shop coats. The crude oil leaves upon the 
surface of the metal, even after wiping, a quantity of non-drying 
mineral oil which interferes with the drying of the paint coat 
which is afterward applied at the time of the assembling of 
the metal. It also prevents the paint coat from properly adher- 
ing to the steel surface, and this coat of crude non-drying oil, 
which still exists between the metal and the paint coat, is a 
source of never-ending trouble, causing peeling and shriveling. 
This crude oil treatment, therefore, should be avoided when- 
ever it is intended that the steel is to be subsequently painted 
with oil paints. 

"Where linseed oil instead of crude oil is used, a film of the 
oil is left upon the metal and rapidly oxidizes to a coat of linoxyn. 
This coat will protect the metal for a certain period of time, but 
is extremely porous and ultimately admits moisture. If, within 
this coating of linseed oil, there had been contained a proportion 
of pigment, or if the linseed oil had been developed by gums into 
a varnish or lacquer, then the excluding properties of the linseed 
oil would have been increased, and, if the formula were inhibitive 
in nature, the steel would be better protected from corrosion, and 
the application of future coats of paint, after assembling the steel, 
would have been practical and facilitated/' 

Mulder 1 states his views on the subject of shop coatings as 

1 Iron Corrosion. L. E. Andes. Scott, Greenwood & Son, London, 1900. 


follows: "Since boiled linseed oil dries, on wood, to form a not 
very hard layer of varnish, it cannot be anything else but preju- 
dicial to the adhesion of the subsequent paint, on iron, when the 
paint is separated from the metal solely by a layer of such linseed 
varnish, especially since the latter is, according to instructions, 
applied to the warm iron, a method which, in turn, cannot pro- 
mote adhesion. 

"This meaning will become clear if we imagine what would 
take place if the iron were coated with copal varnish. It is true 
that the residual varnish left by the drying of the linseed oil is 
tougher, and in so far better, than copal varnish; still it is a var- 
nish all the same. Now it is essential that the iron should be 
coated with a very adhesive paint, which will afterwards dry 
hard and fast, and that all intermediate layers should be avoided 
and dispensed with; consequently the use of linseed oil as a first 
coating for iron is to be discouraged." 

The authors desire to call attention to one point in connection 
with shop coatings, which has very generally been overlooked. 
The point referred to is the possible adhesion or absorption of 
water on the surface of steel. When kept in a humid atmosphere, 
at ordinary temperatures, the surface of steel is never quite dry, 
however much it may appear to be so. The consequence is that 
these layers of moisture are enclosed between the surface of steel 
and the protective coating. That this is a contributing cause 
to future trouble, if not failure, can hardly be denied. Mr. J. E. 
Stead, F. R. S., 1 a member of the council of the Iron and Steel 
Institute of Great Britain, has stated: "That when ships' plates 
were made at steel works, identification marks were frequently 
made with paints while the plates were hot; and it was remarkable 
that ten or twelve years afterwards, when the ships' bottoms 
were cleaned they found the steel uncorroded where the marks 
had been made. That pointed directly to the best method of 
protecting steel and iron. They ought to heat the metal so as to 
remove every trace of moisture from the surfaces, and then apply 
the paint to the hot metal. There was always a little moisture, 
which adhered to the surface of cold steel plates, after they had 
once been moistened, even when they appeared dry, and probably 
that was responsible in some measure for starting the corrosion 
under the paint applied to cold surfaces." 

1 Journ. Iron and Steel Institute, I, 1909, p. 98. 


Commenting on this important subject, Wood 1 states: "There 
are hundreds of records of the painting of important railway 
structures, where the first coat of boiled oil method was used, 
and, in the great majority of instances, the utter and rapid failure 
of the coating and the extra corrosion of the structure could be 
directly assigned to this so-called method of protection. The 
weather-resisting power of an oil coating is almost nil as compared 
with paint." 

"A foundation coat of oil is a direct cause of the blistering 
and peeling of the coatings spread over it. It is seldom dried 
enough before the other paints are spread over it to ensure a close 
adherence to the metal it covers. When the subsequent coats of 
paint are spread, the solvents and oils in them soften to some 
extent the underlying coat of oil, and a moderate heat from the 
sun causes the whole coating to blister or peel. Too much oil 
in a paint coating, particularly if the surplus oil is in or near the 
foundation coat, whether on a wooden or metallic surface, will 
generally cause peeling, regardless of the pigment used in the 

That linseed oil when used without pigments is not a desirable 
material for the prime coating of metal seems to be the universal 
opinion of authorities on the subject of the protection of iron. 
Further comment on the subject may be of interest. Brown 2 
says: "The most insidious enemy of the iron bridge is rust, and 
the primary object of painting it is to protect it from those ele- 
ments which cause destruction by rust. Rust is caused by the 
combination of the metal with oxygen to form the hydrate oxide 
of iron. This oxygen may be obtained from the air, from water, 
or from some other substance which acts as a carrier of oxygen 
or an oxidizing agent — always, however, in the presence of 
moisture. Now, one of the primary things to be considered in 
choosing a paint for ironwork is that it shall not contain in its pig- 
ment or vehicle any substance which is chemically active in such 
way as to convey oxygen to the iron. For if such a chemically 
active agent be introduced into the paint, sooner or later it will 

1 M. P. Wood. Rustless Coatings. First edition, John Wiley & Sons, 
New York, 1905. 

2 Edward Hurst Brown. Conditions that Must Be Met in the Ideal Paint 
for Railway Bridges. Proc. Third Annual Convention Maintenance of Way 
Master Painters' Assn. of U. S. & Canada, New York, Nov. 13 and 14, 1906. 


promote rather than prevent rust. Of course, so long as the oil, 
in an oil plant, remains intact, it envelops the particles of pigment 
and keeps them away from the iron, but in time the oil, which 
has hardened by absorbing oxygen from the air, begins to dis- 
integrate by the action of water coming from rain, hail, snow, or 
fog. Moreover, even the freshly applied oil is not absolutely 
impenetrable to moisture, as has been shown by numerous experi- 
ments, and, however completely the particles of the chemically 
active pigment may be covered by an oil film, they will neces- 
sarily come in contact with moisture — will decompose the water 
and absorb its oxygen, and convey it, together with the hydrogen, 
to the surface of the iron to cause rust. 1 For this reason the ideal 
paint for a steel or iron bridge should not contain a chemically 
active pigment, nor any strongly oxidizing agent in the way of 

We have also seen that linseed oil is permeable to moisture and 
to the gases and steam from locomotives. This was first clearly 
demonstrated, we believe, by Dudley, and to this fact may be 
ascribed the corrosion of the metal under an apparently intact 
coating of paint. It is true that in the mixture of oil with pigment 
in a very finely divided form, the tendency is for the pigment 
particles to more or less fill up the interstices in the oil film and 
render it less porous. How completely this is done depends more 
or less upon the shape of the minute particles of pigment, and, 
as Robert Job demonstrated in a paper read before the Franklin 
Institute of Philadelphia, it depends even more largely upon the 
fineness of grinding of the pigment particles. The finer the pigment 
is ground, the more perfect will be its protective power. This 
was shown very clearly by examination of the paint film under 
the microscope as well as by actual service test. 

Paint Coatings Used at Panama. — At Panama, up to the 
beginning of the American engineering regime, the isthmus re- 
sembled a vast junk shop, where millions of dollars 7 worth of 
metal could be seen in various stages of oxidation and decay. 

Little evidence was left to show that paint had been applied 
to most of the structural and fabricated metal used by the French 

1 This article was written without reference to the electrolytic explana- 
tion of corrosion, and is included here to show that independently of the theory 
engineers were beginning to recognize that pigments enveloped in oil were 
capable of stimulating corrosion. 


engineers. Some of the old locomotives, however, used by the 
French were pulled out of the mire and found to be in fairly good 
condition. Sections of the paint still adhering were removed by 
Speller 1 and, upon his return to the United States, analyzed and 
found to consist largely of zinc, lead and small percentages of oxide 
of iron used probably as a coloring material. The analysis of 
some of these paints appears below, and would almost seem to 
indicate that the French possessed years ago, some knowledge of 
the inhibitive properties of pigments. 



Oxide of 



of Iron 

Oil and 



White Paint 

White Paint (Exca- 
vating Machine) . . 

White Paint (La 

Red Paint (French 
Locomotive) . . . . 









Carb. of 














Recent progress in the art of compounding protective coat- 
ings makes it possible to design paints superior to the above, and 
it is probable that in the future the problem of protecting the 
iron work at the canal zone will not be found as difficult as it 
has been in the past. 

It should be remembered, however, in this connection that 
the metal used by the early French engineers and contractors 
was superior in quality to much of the metal that is in common 
use to-day. The authors must reiterate their opinion that the 
problem of protecting iron and steel depends largely upon the 
rust-resisting quality of the metal to be protected. 

Painting Various Municipal A ccessories, etc. Iron poles for trol- 
ley wires are sometimes imbedded in the earth after receiving a coat 
of tar. The upper part is then painted. The addition of lime to 
the tar used in painting the lower part of the poles is to be advised; 
in fact the addition of 20 per cent, of dry lime to the earth used in 
tamping around the pole will furnish some protection to the metal. 

1 Published by permission of F. A. Speller, National Tube Co. 


The paint for the upper part of the poles should be inhibitive. 
Carbon paints, which have been so largely used for this purpose, 
in the authors' opinion are generally stimulative in their action 
and should not be used unless on top of a good inhibitive primer. 

Lamp posts and letter boxes, which in the past have been 
painted with aluminum paint (a mixture of aluminum and zinc 
alloy powder suspended in bronzing liquid or collodion lacquer) 
have rusted rapidly. The vehicles of such paints are generally 
poor excluders and allow the moisture to get through to the 
metallic powder spread over the iron surface of the box or post. 
The metallic powders, being good conductors of electricity, inevi- 
tably lead to stimulated corrosion, for reasons which have been 
fully discussed in previous chapters. 

Proper protection of lamp posts, boxes, and other articles of this 
sort, can best be secured by using a good inhibitive paint formula 
ground in oil with or without a percentage of varnish. A good 
bronze green, made from zinc oxide, white lead, zinc chromate, and 
willow charcoal, makes a most excellent coating for such work, both 
from a decorative and inhibitive standpoint. The use of red lead, 
provided it is inhibitive in its nature, for fire signal boxes is to be 
recommended. Another composition equally as good from an inhib- 
itive standpoint may be made from bright red oxide of iron and 
basic chromate of lead, the latter possessing excellent inhibitive 

Painting Refrigeration Machinery. — The painting of conden- 
sers and pipes for carrying brine has presented a problem that has 
puzzled the makers of the best paints upon the market. Instances 
of the complete failure of several different types of paint tested 
on this class of work have come to the attention of the authors 
who have recommended the application of a special formula for 
this purpose. The formula which has given the best results is 
made of asbestine, willow charcoal, red lead and zinc chromate 
ground in oil containing forty per cent, of a high-grade kauri gum 
varnish. The wonderful results obtained with this inhibitive 
paint, which has withstood the formation upon its surface of nearly 
two inches of salty ice for over a year, only adds to the weight 
of the plea that has been put forward in successive chapters in 
this book, namely, that both the pigment and the vehicle should 
be given consideration from the standpoint of inhibition, exclud- 
ing value and moisture-resisting properties. 


Ornamental Iron Work Protection. — For the protection of 
iron grill work, porch railings, etc., etc., the Bower-BarfT and Wells 
processes have to some extent been successfully used, but the 
great majority of material of this kind must depend upon paint 
coatings for its protection. Red lead is very generally used for 
prime coating, and if inhibitive in nature serves the purpose well. 
In many cases the iron decoration of buildings has been painted 
a flat black, using lampblack in oil thinned with a large quantity 
of turpentine for flatting. The rapid evaporation of the turpen- 
tine leaves a porous surface. The unsightly rusted condition of 
much of this sort of work is a matter of common observation. 
If flat black is required for the finish, it should be put on over a good 
inhibitive primer. 



The Testing and Design of Paints. — Spreading value should, 
of course, receive careful attention in the selection of a protective 
paint, but this should not be allowed to be the first consideration. 
A paint that has a high spreading value would seem from one 
point of view to be the most economical, but if it fails to provide 
protection it will prove much more expensive in the end. No 
one knows this better than the painter, who is called upon to labor 
over rusted surfaces before repainting. Within reasonable limits, 
the paint that gives the best protection is the cheapest paint to 
use, no matter what its first cost may be. In order to determine 
in advance the efficiency of a paint, designed to protect iron from 
corrosion, recourse must be had to some form of preliminary 
test. In the following paragraphs the authors have endeavored 
to present a description of a number of such tests that have been 
proposed and used by various authorities, together with some 
directions which have a general bearing on protective paint testing. 

General Directions in Regard to Testing. — When a series of 
commercial paints are to be tested in the field for their relative 
merits, it is well to use both the definite and indefinite spreading 
rates, making two sets of tests. For instance, if there is sub- 
mitted for test six samples of paint, designed for the protection 
of iron, two steel plates should be used for each paint. The 
plates should be either sand-blasted or pickled in acid, and prop- 
erly prepared for the test, as previously outlined. 1 One plate 
should be painted with the quantity of paint demanded by the 
surface. The operator should, of course, properly brush the 
paint out and not leave too much upon the surface, otherwise 
wrinkling will ensue. The other plate should be painted with 
just the number of grams of paint that is required to produce a 
spreading rate of say 900 square feet, if this rate is adopted. 
Great care should be taken to have the same operator apply 

1 See p. 180. 


each paint tested, so that no great variable will be introduced in 
the preparation of the plates. The value of such tests is added to 
by including plates covered with the ordinary black mill-scale, as 
most structural steel is painted in this condition. Positive infor- 
mation may be obtained regarding the value of a paint when 
the tests are made upon both cleaned and uncleaned plates, as 
above outlined, and with definite and indefinite spreading rates. 

If the purchase of large amounts of paint is under considera- 
tion, samples should be submitted to the chemist for examination. 
If no specifications have been laid down for the composition of 
the paint, the chemist, if he so desires, may omit the analysis of 
the paint and may then proceed with the accelerated laboratory 
tests that are best suited to each paint, according to the pur- 
poses for which it is to be used. The results of the acceleration 
tests may be taken as fairly good evidence of how the paint will 
work in practice, but a series of practical exposure tests should 
also be started so that definite knowledge can be obtained in 
regard to their protective value. 

Throughout such tests the greatest care should be taken that 
the number of grams of paint applied to each panel is recorded, 
and when reporting on the value the number of grams of paint 
should be calculated to the spreading rate per gallon, so that the 
final report will include this factor. 

When testing pigments, if the proportions of pigment to 
vehicle, according to specific gravity, as used in the Atlantic City 
tests, are not satisfactory to the mind of the engineer making tests 
of this nature, the following method may appear more practical. 

The pigments should be ground in well-settled raw oil, the 
amount of oil being regulated according to the amount necessary 
to form a medium paste with the pigment. This paste should 
readily break up for thinning, by the addition of more oil, so 
that the final product will be in the proper condition for brushing, 
without leaving streaked marks upon the plate. For instance, 
91 lbs. of white lead requires 9 lbs. of oil to make a grinding paste. 
The subsequent addition of 31 lbs. of oil and 2 lbs. liquid drier pre- 
pares the composition for the brush. Eighty-four lbs. of zinc grinds 
with 16 lbs. of oil to a medium paste, which may be thinned with 
60 lbs. of oil and 4 lbs. drier to brushing consistency. In the case 
of lampblack, 25 lbs. of the pigment require 75 lbs. of oil to grind 
to a paste. The addition of 100 lbs. of oil is necessary to form 


a paint thin enough to apply to steel. After the oil has been 
added for the necessary flowing consistency a small amount of 
drier, generally about 12 to 15 lbs., should be added, in propor- 
tion to the nature of the pigment, which invariably affects the 
drying. For instance, in a paint high in lead and zinc, small 
quantities of drier are sufficient, whereas a paint containing 
lampblack or carbon black requires a large amount of drier. 

In nearly all exposure tests which have been recorded the 
pigments have constituted the variable, while the vehicle has 
been kept as constant as possible. There can be no doubt of the 
fact that more information is needed in regard to different com- 
binations between varied vehicles and the principal pigments. 

Laboratory Acceleration Tests. — Laboratory tests to deter- 
mine the protective power of pigments are of great value pro- 
vided they can be depended on to furnish advance information 
in regard to the probable action of a given paint compound. A 
great deal of work has been done along this line. In 1896, Smith 
carried out a series of tests to determine the value of various 
pigments, by boiling them in water contained in small iron cups, 
and observing the rate of corrosion. Other tests have been 
used, of a similar nature. 

Small iron cups painted on the inside have been filled with 
water, either pure or containing impurities, so as to approximate 
the action of the water or gases that the coatings would be 
exposed to in service. The liquid is allowed to evaporate, some- 
times with the aid of heat, the cups are then again filled and the 
operation continued in this way for some time. Observations 
are made from day to day, to see whether rusting is taking place, 
and a careful record of the first and successive breakdowns is made. 

A valuable apparatus for testing the value of paints which 
are to be submitted to alternate exposure to liquids and atmos- 
pheric gases was designed by Norton. It may be constructed 
from a box about 6 feet long, 2 feet wide, and 2 feet deep. In 
the middle of each end, on the top of the box, 2-in. steel collars 
may be placed to accommodate a 2-in. wood rod. Upon this 
rod may be placed a series of iron plates or disks, less than 24 
inches in diameter, painted with various paints, and punched in 
the middle so that they will slide along the rod. These plates 
are kept about 2 inches apart, when making the test. The box 
is then half filled with the liquid, which may be salt water, alka- 


line, or acid water. By mechanically turning the rod, the plates 
are kept slowly moving through the liquid in which they are half 
submerged. The test may be kept up for several weeks. The 
alternate exposure is severe, and some paints last in this test but 
a short while. 

Another method, which is satisfactory for large samples, is the 
acceleration test box, devised by one of the authors, for testing 
painted surfaces in an artificial atmosphere, containing various 
percentages of carbonic acid gas, ammonia, etc., duplicating 
atmospheric conditions in those localities in which the paint is to 
be used. This box may be also used for testing various steels, 
for their resistance to corrosion. The box is about four feet long, 
2 feet wide, and 2 feet deep, and is fitted with glass sides and 
top. The top of the box contains a row of girders, from which 
the samples are suspended from small hooks. The side of the 
box is fitted with a tubular opening, through which carbon dioxide 
may be passed. Water is kept in a tray at the bottom of the 
box, and thus the atmosphere of the box is kept constantly humid. 
The temperature of the box may be adjusted to suit the require- 
ments of the test. Ozone may be developed with a Ruhmkorff 
coil and sparker. In fact, any desired atmosphere can be intro- 
duced into the box. Samples of painted surfaces exposed to 
this test have failed in a remarkably short time. 

Another acceleration test has been proposed by Loesner, and 
is described in Andes' work on Iron Corrosion, as follows: "When 
the plates of sheet iron are coated with paint, rust forms — as 
is well known — on the surface of the metal after a short time. 
Owing, however, to the slowness of the reaction, immersion in 
water does not afford a suitable means for determining the dura- 
bility of paint, whereas, on the other hand, steam places a very 
convenient method at our disposal for this purpose. With this 
object, plates of sheet iron are cleaned perfectly bright on one 
side, by means of emery paper, the clean surfaces — which must 
not on any account be touched with the fingers — being then 
coated over with a thin uniform layer of the paint to be tested, and 
left to dry at the ordinary temperature for four days. The plates 
are next set, painted side downwards, over a boiling water-bath, 
so that the surface of the paint is just 2 inches (5 cm.) above 
the constant level of the water. At the end of fifteen hours, the* 
plates are dried for a short time at 100° C. (not higher), and the 


layers of paint impregnated with aniline oil applied with a soft 
brush. Being thus softened they can be removed, and the metal 
is then dried by means of alcohol. For the paint to be classed 
as good, the metal must have remained perfectly intact, a condi- 
tion readily recognized by the appearance of the scratches formed 
on the surface by the emery paper used in the initial cleaning. 
Many paints will stand this steam test after the painted iron has 
been heated to 100° to 105° C. for about five hours." 

A novel method for testing the pigment portion of paints, to 
determine whether the pigment is inhibitive or stimulative, was 
developed by one of the authors during his researches. The 
pigments to be tested are rubbed up with sufficient water to 
make thick water-color paints, and are then flowed or brushed 
upon the clean blades of steel table knives. After the coatings 
are dry the knives are laid on a wet blotter and covered with a 
sheet of wet blotting paper. At the end of forty-eight hours the 
surfaces are cleaned off with running water and a stiff brush. 
This acceleration test has been found to give results which agree 
with the oil film tests. 

The appearance of the knife blades after being used in this 
test is shown in Fig. 68a and 6. 1 

Perry developed the foregoing test so that it could be made 
applicable to the examination of paints ground in oil. He 
recommends that a portion of the paint when it is received 
for examination be placed in a test tube and shaken several 
times with benzine, in order to extract the vehicle, the extractions 
being disregarded and the separated pigment used for the test. 
Small centrifugal machines for the accommodation of the test 
tubes may be used for the extraction. The pigment is removed 
from the test tube and placed upon a sheet of druggists' filter 
paper. It is then moistened and with the finger rubbed to a 
soft paste. A razor blade, or other small piece of steel highly 
polished, is then covered with the paste together with the paper, 
and laid upon a porcelain dish within a cigar box. Several differ- 
ent pigments may be tested in the same way and included in the 
same box. The box is kept constantly humid by lining the sides 
and top with druggists* filter paper kept constantly moist with 

1 One of the authors has recently devised a new form of acceleration 
test which promises to give valuable results but which has not been suf- 
ficiently developed to publish. 


fee v 

Fig. 68a and b. — Showing the appearance of knife blades used in 
Cushman's test. 


water. At the end of a few hours the box may be opened and 
the steel plates removed from their wrappings of paper and pig- 
ment. After washing and scrubbing with a tooth brush, in order 
to remove any pigment which persists upon the metal, the amount 
of corrosion which has taken place may be easily ascertained. 
Another acceleration test which gives valuable information has 
recently been devised by one of the authors, but as the work 
was done in a government laboratory and has not yet been pub- 
lished, it cannot properly be included here. 

It is natural that there should be considerable difference of 
opinion among both paint manufacturers and consumers in 
regard to the value of acceleration tests. It is noteworthy that 
the same discussion has been going on for years in regard to 
Portland cement, and yet all cement is bought and sold subject 
to acceleration tests. It is the authors' firm conviction that 
the same conditions will eventually be developed in the purchase 
of protective paints. Extravagant claims made by manufac- 
turers will not always satisfy the consumer, and "best by test" 
will inevitably replace "best by claim." There are perhaps a 
thousand "best" protective paints in the market, and among 
them the consumer is at present at a loss to decide. In no section 
of technical industry are standard tests more necessary than in 
the one under discussion here. 

Design of Protective and Inhibitive Paint Coatings. — In the 
manufacture of paints, the various pigments are usually ground 
in oil to a paste, and stored away in that form in mixing tanks. 
This practice is followed by the larger manufacturers who have 
the proper facilities. When an order is received for any special 
combination, the proper weights of each paste, according to the 
percentage composition of the paint desired, are mixed together 
and thinned with the necessary amount of oil and drier. For 
instance, if a white paint was desired for iron and steel, and, in the 
judgment of the engineer ordering the paint, the following compo- 
sition was considered best to use in the locality where the work 
was to be done: 

Pigment Composition 

Basic Carbonate — White Lead 67 per cent. 

Zinc Oxide 20 per cent. 

Asbestine 3 per cent. 

Calcium Carbonate 10 per cent. 


with this working formula the paint-maker could proceed with the 
manufacture of the product. If about five gallons of this paint was 
desired, the following amount of paste would be used, these amounts 
being proportioned to the percentage composition of the mixture: 

Basic Carbonate — White Lead in Oil 

Zinc Oxide in Oil 

Asbestine in Oil 

Calcium Carbonate in Oil 

Raw Linseed Oil (2§ gals.) 

Drier (& gal.) 

Turpentine ( T \ gal.) 

Weight per gallon, 16 lbs., 5 oz. 

Analysis of this paint would show the following composition: 















88.95 lbs. 

Per Cent, 
in Pigment 

Per Cent, 
in Vehicle 

Per Cent, in 

Total Pigment 

and Vehicle 

Basic Carbonate — White Lead 

Zinc Oxide 

Asbestine - 

Calcium Carbonate 

Raw Oil 





















This paint could be tinted to any color desired. For instance, 
100 lbs. of the white base could be tinted with 5 lbs. zinc chromate, 
in order to get inhibitive yellow paint, or with 3 lbs. of a good 
inhibitive black pigment, in order to secure a good gray tint. 

For special formulas, however, the pigments specified in the 
formula are generally weighed out in their proper proportion 
and mixed and ground in linseed oil. If the formula called for 
200 gallons of green paint, and the pigment specified was as follows: 

Special White 52 per cent- 
Silica 22 per cent. 

Zinc Yellow , 7 per cent. 

Medium Chrome Yellow 8 per cent. 

Prussian Blue (Inhibitive) 6 per cent. 

Whiting 5 per cent. 


this could be made by weighing out the following amounts of 
pigments in oil, mixing and grinding: 

750.0 lbs. 

Special White 

312.5 " 


112.5 " 

Zinc Chromate 

125.0 " 

Neutral Lead Chromate 

87.5 £f 

Prussian Blue (Inhibitive) 

62.5 " 


600.0 " 

Raw Oil 

2050.0 lbs. 

This paint could be thinned for application with: 

2050 lbs. of above paste 
100 £< Drier 
850 " Raw Linseed Oil 

3000 lbs. 

This paint would weigh about 12J lbs. per gallon. 

Inhibitive Paint Formulas. — The authors have frequently 
been asked to design protective and inhibitive paints for special 

While it would appear unwise for the authors to attempt 
standardization of paint formulae, or to define the percentage 
composition of paints intended for iron and steel, it is believed 
that to give the formulas of a few paints which have proven of 
value in field tests would be a matter of interest to the manufac- 
turers of protective coatings, as furnishing a basis upon which 
to make further tests. In various parts of this book there has 
been given a general outline of the composition of paints of espe- 
cial value for special purposes. The following formulas would 
be of value for general use on iron work : 


Metallic Brown (neutral) 60 per cent. 

Zinc Lead 20 per cent. 

Zinc Oxide 20 per cent. 

Chocolate Color 

Metallic Brown (neutral) 90 per cent. 

Willow Charcoal 5 p er cent. 

Zinc Chromate 5 per cent. 



Bright Red Oxide (free from acid or sulphur) 95 per cent. 

Zinc Chromate 5 per cent. 


Bright Red Oxide 65 per cent. 

China Clay 15 per cent. 

Red Lead 15 per cent. 

Zinc Chromate 5 per cent. 


Willow Charcoal and Bone Black 68 per cent. 

Zinc Chromate 2 per cent. 

Inert 30 per cent. 


Sublimed Blue Lead 60 per cent. 

Willow Charcoal 20 per cent. 

Inert 20 per cent. 


Zinc Oxide 45 per cent. 

Sublimed White Lead 25 per cent. 

Inert 15 per cent. 

Zinc Chromate 5 per cent. 

Inhibitive Prussian Blue 5 per cent. 

Medium Chrome Yellow 5 per cent. 


Inhibitive Prussian Blue 4 per cent. 

Zinc Chromate 3 per cent. 

Chrome Yellow 8 per cent. 

Asbestine 15 per cent. 

Zinc Lead or Zinc Oxide and Corroded 1 

White Lead 70 per cent. 


Zinc Oxide 60 per cent. 

Corroded or Sublimed White Lead 30 per cent. 

Asbestine 10 per cent. 


Zinc Lead 20 per cent. 

Zinc Oxide 20 per cent. 

Corroded or Sublimed White Lead 50 per cent. 

Kaolin or Silica 10 per cent. 

- If corroded lead is used, it must be in small proportion on 
account of its action on the green. 


Wire Fence Paint. — On the wire fences at Pittsburg several 
paints of the inhibitive and stimulative pigment types were 
tested. Excellent results were obtained with the use of a paint 
of approximately the following composition: 

Natural Bright Iron Oxide 65 per cent. 

Silica 20 per cent. 

Willow Charcoal 5 per cent. 

Red Lead 5 per cent. 

Zinc Chromate 5 per cent. 

100 per cent. 

This paint, ground in oil alone, would afford good protection 
to wire, but when ground in a vehicle of the following nature, 
it would prove of even more value: 

Boiled Linseed Oil 23 per cent. 

Raw Linseed Oil 45 per cent. 

Kauri Varnish 20 per cent. 

Turpentine and Drier 12 per cent. 

100 per cent. 

Another paint showing good results on the Pittsburg wire 
fences was of the following composition : 

Zinc Chromate 90 per cent. 

Inhibitive Prussian Blue 10 per cent. 

100 per cent. 

This paint, however, is quite expensive on account of the 
large percentage of zinc chromate. 

The carbon black and graphite paints applied to the wire 
fences showed very bad results, corrosion becoming apparent 
within six months after their use. 

Condenser Paint. — The use of a formula of the following com- 
position will be found of value in painting condensers and pipes 
subjected to low temperatures: 


Willow Charcoal or Drop Black 40 per cent. 

Red Lead 25 per cent. 

Asbestine and China Clay 30 per cent. 

Zinc Chromate _5 per cent. 

100 per cent. 



Boiled Linseed Oil 20 per cent. 

Treated China Wood Oil 20 per cent. 

Raw Linseed Oil 50 per cent. 

Turpentine and Drier 10 per cent. 

100 per cent. 
Or the Boiled Linseed Oil and China Wood Oil may be 
replaced with Copal Varnish. 

Paint for Iron Piping. — A paint that would prove efficient 
for use at the seashore for protecting piping exposed to the weather, 
could be made of the following composition : 

White Lead 55 per cent. 

Zinc Oxide 20 per cent. 

Silica 10 per cent. 

Willow Charcoal 10 per cent. 

Zinc Chromate 5 per cent. 

100 per cent. 

Formula Labeling. — The purchasing agent of the large cor- 
poration is often at a loss, when buying paint, to know whether 
he is securing that grade for which he has contracted. The 
labeling of house paints in various States by certain manufac- 
turers was brought about by legislation as well as by a desire for 
honesty. The analysis printed upon the label is generally con- 
sidered as an evidence of the manufacturer's desire to make a 
good paint, otherwise the analysis would not appear. Formula 
labeling on paints for iron and steel may come in the near future, 
and . such an innovation will probably be welcomed by the 
engineer, architect, purchasing agent, and consumer. 



The Requisites of Protective Coatings. — Although this book 
deals largely with paints for the protection of steel and iron, the 
wide interest of late that has been exhibited by the engineer, 
regarding the composition and value of various paints, demands 
that a brief description of the physical properties of pigments 
and the prime requisites of paints should also be included. 

A proper understanding of certain basic laws regarding 
materials for the fabrication of protective coatings is absolutely 
essential to the factory superintendent or chemist who is called 
upon to specify paints, and should also be of interest to the painter, 
architect, and engineer who constantly use and depend upon 
these products. 

Meaning and Cause of Hiding Power. — Structural material 
of various kinds differ in the demands made upon the paint used 
for their protection and decoration. That the film should 
have proper covering and hiding power, or opacity, is essential. 
Opacity in a paint is dependent upon the difference in the refract- 
ive indices of the pigment and the vehicle with which the pigment 
is mixed. The farther apart the indices of refraction of the com- 
posite pigment and the vehicle, the greater the opacity. Greater 
protection from the powerful rays of the sun is afforded the struc- 
tural material upon which opaque paints are applied. Proper 
hiding of the surface is necessary from a protective as well as a 
decorative standpoint. 

Whiteness. — White pigments should not darken when made 
into paint. White lead, zinc oxide, and barytes are all examples 
of white pigments, which when ground in oil produce white paints. 
The barytes in such a formula becomes transparent in its oil 
coating, but has no darkening influence on the composition. 

Lithopone, when ground in oil and painted out, gives a whiter 
surface than any other pigment. For outside work, however, it 
is not well suited on account of its liability to turn dark. Zinc 



oxide is generally taken as a standard of whiteness, and is used 
for comparison with various other pigments when determining 
their degree of whiteness. 

Stable and Chemically Active Pigments. — Pigments are some- 
times classified according to their behavior in oil, as " chemically 
active" or "inert." The term "inert pigments" generally applies, 
however, to that group of pigments which when ground in oil 
show relatively slight opacity but extreme stability toward the 
oil. There are some white pigments which are of great value 
for their hiding power and other properties, but which, because 
of their basic or alkaline nature, show chemical activity towards 
the oil in which they are ground, causing saponification, and final 
disintegration of the paint film. Such pigments are chemically 
active, and are often the cause of chalking, checking, and dis- 

Spreading Value. — The number of square feet over which a 
paint is spread is an important consideration. Some pigments 
in oil have a relatively low, while others have excessive spreading 
quality. Too high-spreading quality causes the formation of 
thin films which do not properly resist the action of the elements. 
A number of authorities believe that a combination of pigments, 
in proper percentages, of both types, gives a paint of improved 
spreading quality, and makes it easier to produce a film of the 
proper thickness. 

Effect of Gases on Paints. — Some pigments are not affected 
by sulphurous gases, while others darken under such exposure, 
and are materially changed in color. Zinc oxide and basic sul- 
phate-white lead are good examples of base white pigments upon 
which sulphur gas has practically no effect, while basic carbonate- 
white lead is an example of a pigment easily affected, the black 
sulphide of lead being the product formed. 

Paint Coat Strengthened and Preventives to Settling. — Mag- 
nesium and aluminum silicates (asbestine and talcose) have 
been suggested and much used for reinforcing paint coats. These 
pigments, the former in needle-shaped particles, and the latter 
in flake form, are believed by many authorities to possess 
value in overcoming the defects of certain prime white pigments 
when used in too large a percentage. It is claimed that they not 
only increase the abrasion resistance of the film, but render it 
much stronger. They are also largely used by the paint manu- 


facturer to-day as anti-settlers, as they have the property of hold- 
ing up heavy pigments and preventing the settling and hardening 
of paints in which they are used. The holding up or non-settling 
property of paints is vitally necessary. Anti-settlers should be 
used with moderation, however, as excessive use may be con- 
sidered an adulteration. 

Excluding Properties and Elasticity. — A paint coating for iron 
should possess the property of being an excluder of moisture. It 
should be impervious to rains and storms. It should also possess 
enough elasticity to conform with the expansion or contraction of 
the materials upon which it is used. This elasticity is largely 
dependent upon the proper regulation of the percentages of pig- 
ments contained in the paint. Linseed-oil films are very elastic, 
but through progressive oxidation they soon become deficient 
in this property, whereas linseed-oil films, containing various 
pigments in the proper proportion, maintain their elasticity and 
increase in tensile strength. 

That the pigments which go into the formation of a paint should 
be of different sizes, is the conclusion of Perry 1 in his elaborate 
researches upon the physical properties of paint films. Following 
is a brief resume of the work of this authority : — The law of mini- 
mum voids which applies to concrete also applies to a paint 
coating. The pigments which are made by sublimed processes 
are extremely fine, and serve the same purpose as sand in con- 
crete, while pigments coarser in nature are comparable to the 
broken stone or rock. The use of asbestine has been likened to 
the use of reinforcing rods and wire mesh in concrete, and adds 
strength to the paint coating. — If Perry's conclusions are 
accepted, it is evident that a paint, made by combining in certain 
percentages pigments of each type, is far superior to a paint 
made of one single pigment. 

Working Properties of Paints. — The so-called tooth of pig- 
ments is a term applied by the master painter to paint which 
works well under the brush, and gives proper penetration without 
too much slipping greasiness or excessive flow. The use of pig- 
ments, such as silica and silicates and barytes, gives this so-called 

In concluding this general and brief discussion of the proper- 
ties of pigments in their relations to paint films, the authors have 
1 The Physical Properties of Paint Films. 


endeavored to present all statements made, from an unbiased point 
of view. There are a number of paint authorities who believe that 
a paint compounded of a single good pigmentary substance, and 
an efficient vehicle provides as adequate protection as it is pos- 
sible to obtain. While not agreeing with these authorities, the 
writers believe that their views should be given the fullest con- 
sideration. In the course of time thorough testing will remove 
these varying opinions from the realm of theory to that of fact. 

Description of Pigments in General Use for Painting Iron. — 
The following descriptions of the properties of the various pig- 
ments is given with a view of presenting information in a concise 
form, which it is believed will be useful to many persons on whom 
the responsibility for protective paint design falls. 

Basic Carbonate-white Lead. — Basic carbonate-white lead is 
made by several processes: 

The Old Dutch Process; 

The Carter (or Quick) Process; 

The Precipitation Process; 

The Electrolytic Process; 

The Mild Process, etc. 

In the Old Dutch Process, pure lead buckles are placed in 
clay pots with dilute acetic acid, the pots being subsequently 
stacked up and covered with boards and tan bark. The fermen- 
tation of the tan bark raises the temperature and causes the 
formation of carbon dioxide, which acts on the acetate of lead 
formed within the clay pots, producing a basic carbonate of 
lead. After two months or more the action is completed and the 
white lead is broken up, ground in water, floated to separate the 
"blue" or uncorroded lead, then dried in copper pans. It is 
sold dry or ground in oil. 

In the Carter Process, the lead is made in two weeks by act- 
ing upon finely atomized lead particles with dilute acetic acid and 
carbon dioxide gas (the latter generated from burning coke) 
within large revolving cylinders. 

The Mild Process uses no acid, depending upon the oxidation 
effect of air blown upon finely divided particles of lead, agitated 
in water. The hydrate of lead thus formed is subsequently 
carbonated. This material does not require the washing neces- 
sary for lead made by other methods of manufacture, as it 
contains no free acetic acid. 


By the above processes, a white product having the composi- 
tion 2PbC0 2 • PbOH 2 , is formed, generally containing about 85 
per cent. PbO, and 15 per cent, carbon dioxide and water. It 
is soluble in dilute mineral acids or acetic acid. The acetic acid 
solution is generally used for the assay of white lead, and may be 
precipitated as lead chromate with standard volumetric bichro- 
mate solutions. Lead salts may be precipitated with hydrogen 
sulphide, to form the black sulphide of lead, and this reaction is 
also used in analytical work. All forms of basic carbonate-white 
lead are easily reduced to metallic lead, by the use of the blow- 
pipe, in the presence of a reducing substance such as charcoal. 

Basic carbonate-white lead has a specific gravity of 6.8, and 
grinds in 9 per cent, of oil to a stiff paste. It may then be thinned 
to a working consistency with 38 per cent, of oil. As generally 
reduced by the master painter, 100 lbs. are mixed with 4 to 6 
gallons of oil, with the addition of one quart of turpentine and a 
pint of drier, the amount of oil or turpentine varying with the 
nature of the surface to be painted and the conditions prevailing. 
Basic carbonate-white lead is an extremely opaque pigment and 
possesses excellent body. It is somewhat deficient in spreading 
rate and is, therefore, generally mixed with zinc oxide or other 
pigments of high spreading values, when used for general paint- 
ing purposes. It is easily affected and darkened by sulphurous 
gases, and should not be used with other pigments containing 
sulphur in any form. 

It is claimed that on account of its alkaline nature it acts 
upon the saponifiable oil in which it is ground, forming lead soaps, 
which are the active cause of the chalking of white lead — the 
greatest evil attending its use. Solubility in carbonic acid of 
the atmosphere and decay in the presence of sodium chloride may 
be active causes of the rapid chalking of this pigment at the 
seashore. Checking in some climates appears to proceed rapidly 
on white lead, in a deep hexagonal form, leaving a series of rough 
crests and cracks. This checking is secondary to the chalking 
which takes place. 

It generally has inhibitive tendencies, and is a valuable con- 
stituent of certain paints intended for the protection of iron and 

Landolt 1 says: "White lead, used alone and in a pure state, 
1 Iron-Corrosion and Anti-Corrosive Paints. L. E. Andes. 


is not a good paint for iron-work. Apart from the fact that the 
pure white of the pigment will speedily become impaired and 
dirty, the paint also sets hard in a short time, the elasticity dis- 
appears, and cracks are formed. For this reason white lead is 
mixed with other substances, in the first place to impart color 
to the paint, and furthermore for the purpose of increasing its 
power of absorbing oil, this latter, or linseed varnish, being the 
principal agent determining the durability of the coating. 

"The more oil required by a pigment in order to produce a 
distributable paint, the better will it be adapted for use on iron, 
especially in the open air, provided it satisfies the other condi- 
tions, of covering power, neutrality, and capacity of resistance 
to acids." 

Zinc Oxide. — Zinc oxide is a very valuable prime white base 
pigment, the larger quantity being produced by the roasting and 
sublimation of Zincite and Franklinite, the latter being found in 
large quantities at Franklin Furnace, New Jersey. The New 
Jersey zinc oxide runs about 99 per cent, pure, while that pro- 
duced in Wisconsin contains upward of 5 per cent, of lead sulphate. 

Another variety used, and which is usually about 99.5 per 
cent, pure, is produced by the sublimation and oxidation of 
spelter, this variety being the standard for whiteness, and known 
as French Process Zinc Oxide. 

This pigment has a specific gravity of 5.2, and grinds in about 
16 per cent, of oil to a stiff paste, 100 lbs. of which may be thinned 
for application with 64 lbs. of oil. It is a very opaque pigment, 
and possesses excellent spreading properties, being used in admix- 
ture with basic carbonate-white lead for outside paints. Being a 
very white fine pigment by nature, it acts well with the lead 
pigments, and helps to overcome the chalking tendency which 
the latter may possess. Because of its stable nature, and extreme 
whiteness, it is an excellent base for delicate colors, bringing 
out their purity of tone. Zinc oxide has good drying properties 
of itself, but the use of litharge aids its drying and is the safest 
kind of drier to use with this pigment. Progressive oxidation 
gives zinc oxide a hard surface, and consequently does not resist 
the changes in temperature as well as when in combination with 
a softer pigment. Zinc oxide is invaluable as a pigment base for 
enamels, being possessed of great body and whiteness, and giving 
a high, permanent gloss when ground in varnish. The checking 


of zinc oxide is very regular and characteristic, being of a distinct 
triangular form. Nearly all zinc oxides are fairly good inhibitive 


Zinc oxide is soluble in most mineral acids to a clear solution. 
Solutions of zinc oxide in acetic acid may be titrated with standard 
ferrocyanide of potash solutions, this being a quick volumetric 
method used in its determination. Solutions of zinc may be 
precipitated with sodium carbonate, and the white zinc carbonate 
thus formed ignited to the oxide and weighed as such. 

Basic Sulphate-White Lead (Sublimed White Lead) . — Basic 
sulphate-white lead (sublimed white lead) is made from galena, 
an ore containing a very high percentage of sulphide of lead. 
This ore is mixed with fuel, placed in furnaces, and volatilized. 
The fume is brought into contact with air, and becomes oxidized 
to a basic sulphate of lead. The fumes are then drawn through 
flues and air-cooled pipes to bags or receivers. 

Basic sulphate-white lead is an amorphous pigment, of great 
fineness, and almost of the same characteristic whiteness that is 
exhibited by basic carbonate-white, lead. It has a specific gravity 
of 6.2, and grinds in about 10 per cent, of oil to a stiff paste that 
may be thinned for application, to brushing consistency, by the 
addition of 38 per cent, of oil to 100 lbs. paste. 

This pigment possesses extreme chemical stability, and is 
not subject to the blackening caused by sulphurous gases, as is 
the case with some pigments. Delicate colors, such as greens, 
blues, and yellows, may be mixed with this pigment without any 
action on the color. This stability renders it invaluable for 
many tinted paints. 

The tendency of certain lead pigments to liver or become 
thick in cold weather is often due to the presence of sulphites, 
but a pure basic sulphate-white lead, free from sulphites, does 
not exhibit any great amount of stiffness under the brush during 
cold weather. 

Commercial basic sulphate-white lead usually runs very uni- 
form in its composition, analysis showing it to contain approxi- 
mately 70 per cent, of lead sulphate, 20 per cent, of lead oxide, 
and 5 per cent, of zinc oxide. The lead sulphate is chemically 
combined with the lead oxide, forming a stable and definite 
chemical compound. An examination of the pigment under the 
microcsope shows absence of crystals, thus proving that the lead 


oxide present is chemically combined and not in its regular crys- 
talline form. Lead oxide is insoluble in ammonium acetate, but 
when chemically combined with lead sulphate it readily goes 
into solution when treated with ammonium acetate. This solu- 
bility of basic sulphate of lead is utilized by the analytical chemist 
in the detection, separation, and estimation of sublimed white 
lead in mixed paints. 

Sublimed Blue Lead. — Sublimed blue lead is made by burn- 
ing coarsely broken lumps of galena, admixed with bituminous 
coal, in a special form of furnace. The fumes which are vola- 
tilized from this mixture are very complex in their chemical make- 
up, and in color are white, blue, and black. After being drawn 
through the cooling pipes by the suction of huge fans, whereby 
the fumes are cooled, the pigment is deposited in bags. This 
pigment is bluish black in color, and has been highly recommended 
for use on iron and steel. Its composition runs approximately 
as follows: 

Lead Sulphate 50 per cent. 

Lead Oxide 35 per cent- 
Lead Sulphide 5 per cent. 

Lead Sulphite 5 per cent. 

Zinc Oxide 2 per cent. 

Carbon 3 per cent. 

The color of the pigment is largely due to the carbon and the 
lead sulphide. Its specific gravity is 6.4, and it grinds in 10 
per cent, of oil, to a stiff paste, 100 lbs. of which may be thinned 
with about 26 lbs. of oil to working consistency. Some manu- 
facturers use it in mixture with iron oxide and other pigments for 
the production of paints for metal surfaces. Wood and others 
have found it of value for this purpose. It has a tendency to 
chalk, but this may be overcome by admixture with other pig- 
ments such as zinc oxide and iron oxide. Lane has found it of 
especial value admixed with lampblack. 

The selection of this, as well as all other pigments, should, 
in the authors' opinion, be decided by tests, and as far as possible 
by the observation of its protective action under service condi- 

Lithopone. — Lithopone is probably the whitest pigment 
known, and is extremely desirable for the manufacture of high- 
grade enamels, the amount consumed for this purpose being very 


large. It is manufactured by the double decomposition of zinc 
sulphate and barium sulphide, two soluble salts which interact 
to produce two pigments chemically combined, namely, zinc sul- 
phide and barium sulphate. The resulting product is filter- 
pressed, and furnaced, after which it is rendered more opaque by 
disintegrating the heated pigment in cold water. It is after- 
ward thoroughly washed, and again filter-pressed, then dried and 
ground. The production of this pigment is carried out in the 
factory under certain definite and critical temperatures. Proper 
control of the solutions for their purity and strength is constantly 
maintained, and the greatest care throughout the process is neces- 
sary in order to produce a high-grade product. 

Although lithopone is a very stable pigment, it has very 
peculiar photogenetic qualities, and when exposed to the action 
of the actinic rays of the sun, in the presence of moisture, darken- 
ing of the pigment results. The pigment sometimes resumes its 
normal color, however, in a very short time after the darkening. 
In the absence of moisture, this darkening cannot take place. 
It is most excellently suited as a pigment for inside use, but for 
outside use it requires a very large percentage of some more stable 
pigment, such as zinc or calcium carbonate, in order to prevent 
this rapid darkening and to prolong its life. . 

Lithopone has a specific gravity of 4.25, and grinds in about 
13 per cent, of oil to a -paste that may be subsequently thinned 
with 60 lbs. of oil to 100 lbs. paste in order to form a paint of 
the proper flowing consistency. When spread, it shows high cov- 
ering value and brushes exceedingly well. This pigment is some- 
times a fairly good inhibitive pigment, but must be admixed with 
other pigments when designed for use on iron or steel, because of 
its rapid disintegration when exposed outside. Lead driers should 
not be used with lithopone. 

Zinc Lead White. — This pigment is made by the reduction 
of sulphur-bearing ores of lead and zinc, in especially constructed 
furnaces. Volatilization of the lead and zinc, and subsequent 
oxidation, takes place, with the formation of a pigment fume 
consisting of about equal parts of zinc oxide and lead sulphate. 
The fume is cooled by passage through long metal pipes, and 
collected in bags. Subsequent treatment for whitening and 
desulphurization is then made, and the pigment as placed upon 
the market is extremely fine in its particle size. 


This pigment has a specific gravity of 4.4, and grinds in about 
12 per cent, of oil. It is a most excellent pigment for use in 
tinted paints, but is seldom used alone for white paints, because 
of a very slight yellowish tint. It has proved of considerable 
value when mixed with varying percentages of white lead and 
zinc oxide, and some inert pigments. In its chemical stability 
it resembles basic sulphate-white lead, and is very well suited 
for the manufacture of paints containing delicate colors, such as 
blues and greens. It is generally somewhat inhibitive, and in 
this case may be used with safety on iron and steel. 

Leaded Zinc. — In manufacturing this pigment, various grades 
of lead and zinc ores are mixed, roasted, and furnaced. The 
fume therefrom is cooled through pipes, and collected in bags; 
the process in some ways resembling those used in the manu- 
facture of zinc lead white and sublimed white lead. This pig- 
ment has a specific gravity of 5.8 and the analysis shows the 
presence of about 25 per cent, of lead sulphate and 75 per cent. 
of zinc oxide, with traces of zinc sulphate and sulphur dioxide. 
The product is a very stable pigment, resembling zinc oxide and 
zinc lead white. This pigment oftimes contains a small percent- 
age of zinc sulphate which may affect the life of the paint in which 
it is used. Zinc sulphate also has the effect of causing paints to 
liver to some extent. Because of the presence of a soluble salt 
such as zinc sulphate it must be used with care when intended as 
the basis of a paint for iron and steel. 

Barium Sulphate (Barytes). — Barium sulphate, or barytes, is 
one of the most important pigments used in the manufacture of 
paints. It occurs as a mineral in large quantities and very widely 
distributed. In its preparation for the market, the mineral is- 
ground, washed in acid to free it from iron and to whiten its 
color. It is then washed several times and dried. Flotation of 
the pigment produces a very fine grade. The pigment is used 
in large quantity as a base upon which to precipitate colors, and 
also together with other white pigments in the manufacture of 
ready-mixed paints. It renders the paint coating more resist- 
ant to abrasion, and gives to the paint certain very important 
brushing qualities. It is a very stable pigment, not being ma- 
terially affected by either acid or alkali and can be used with the 
most delicate colors. In oil, it is transparent and must be mixed 
with opaque pigments when used in mixed paints. It is a very 


heavy pigment, having a specific gravity of 4.4, and grinding in 
about 10 per cent, of oil. It is generally used with lighter pig- 
ments, such as asbestine, in order to prevent its settling. 

Blanc Fixe is an artificial form of barium sulphate, made by 
mixing solutions of soluble barium salts with sodium sulphate 
or other soluble sulphates, causing precipitation of barium sul- 
phate. This material has a somewhat lower gravity (4.2) than 
the natural barytes and does not have the same tendency to 
settle out when used in paints. This pigment is also used as a 
base for colors and also in ready-mixed paints, giving good brush- 
ing qualities to the paint. It has more opacity in oil than barytes 
and for some purposes is better suited than the natural form of 
barium sulphate. Both barytes and blanc fixe are liable to con- 
tain traces of acids or acid salts, and they must be carefully 
tested, before using in paints to be applied to iron or steel. 

Gypsum (Calcium Sulphate). — Gypsum, or calcium sulphate, 
is found in nature very widely distributed. In its natural form it 
contains about 20 per cent, water of combination. It has come 
into wide use in the manufacture of various colors, and is often 
found in ready-mixed paints. It is a very stable pigment, and, 
although it lacks any hiding power in oil, when ground in water 
it is very opaque, and is largely used as a base for distemper 
colors. It is slightly soluble in water, however, and when pres- 
ent in a paint coating it is liable to leach out. It should never 
be used upon iron or steel, because of the corrosion which it is 
certain to cause, due to the ease with which it is ionized in the 
presence of water. It has a specific gravity of 2.3 and grinds 
in about 22 per cent, of oil. This pigment is present to a great 
extent in Venetian red. 

Magnesium Silicate (Asbestine and Talcose). — This pigment 
comes in two forms: as asbestine and as talcose. The former is 
very fibrous in nature and is a very stable pigment to use in the 
manufacture of paint on account of its inert nature and tendency 
to hold up heavier pigments, and prevent settling. It also has 
the property of strengthening a paint coat in which it is used. 
The talcose variety is very tabular in form, and is also somewhat 
largely used in the manufacture of mixed paints. Both varieties 
are transparent in oil, and they are very inert toward iron or steel. 
They have a gravity of about 2.7 and grind in about 32 per cent, 
of oil. 


Whiting (Calcium Carbonate) . ■ — Whiting, or calcium car- 
bonate, occurs very widely distributed in nature, as chalk. After 
proper purification' and grinding it forms a pigment with a specific 
gravity of about 2.8, which grinds in about 20 per cent, of oil. 
It is used largely in distemper work and also to a considerable 
extent in the manufacture of oil paints, being considered very 
valuable in small percentages in neutralizing any free acid con- 
tained in the linseed oil. It spreads very well and does not settle 
to any marked extent. The artificial, precipitated form of cal- 
cium carbonate is much lighter in gravity (2.5), and requires 
about 25 per cent, of oil for grinding. This form possesses more 
hiding power and, although it has a tendency to chalk, it is very 
valuable for certain purposes. The precipitated form should not 
be used in inhibitive paints, owing to the fact that it generally 
contains occluded impurities which tend to stimulate corrosion. 

Aluminum Silicate (China Clay). — Aluminum silicate, or 
China clay, is a widely distributed pigment found in granitic 
formations. This pigment plays an important part in the 
manufacture of paints. It is a fine, amorphous, white powder, 
extremely permanent, and when ground in oil shows very little 
hiding property. It has a specific gravity of 2.6 and grinds in 
28 per cent, of oil. It is a very stable compound, not being 
affected by ordinary acids. 

Silica. — This is a most valuable white pigment, used in 
immense quantities for wood fillers, and in moderate percentages 
in mixed paints, both for iron and for wood. It is usually of 
great purity, often running over 97 per cent. SiCh, and when 
ground in oil becomes perfectly transparent. In combination 
with white lead and zinc oxide it produces a most excellent wear- 
ing paint, both for seashore and inland use. It has marked tooth 
and spreading properties. It is a good extender for iron and steel 
paints, and gives the coating a harder surface. 

Litharge. — Litharge (PbO), or lead monoxide, in color is a 
yellowish red pigment, made by submitting metallic lead for several 
hours to oxidation under intense heat, in reverberatory furnaces. 
It has a specific gravity of 10 and grinds in about 9 per cent, of 
oil. It comes into large usage as a drier in the manufacture 
of boiled oil or japans. It is generally very inhibitive and gives 
a good, hard drying, elastic film. 

Red Lead. — Red lead is a very heavy, brilliant red pigment, 


made by submitting litharge to further oxidation in reverberatory 
furnaces. It has a specific gravity of 8.7. It varies in color 
and strength of tone, according to the degree of oxidation and 
physical structure. It is considered as one of the most valuable 
pigments known for the protection of steel and iron, and has been 
used for this purpose for many years. 

Red lead is also produced by heating litharge with sodium 
nitrate, in large iron pots, the interaction taking place forming 
red lead and sodium nitrite, the latter being a very valuable salt 
in the manufacture of para reds. Red lead, when used pure, is 
almost always mixed at the time of application, the average for- 
mula being 30 lbs. of red lead to the gallon of oil. No drier is 
required, because of the rapid drying nature of the red lead itself. 
Because of the stiffness of red lead in oil and the difficulty in 
spreading a properly proportioned mixture, thinning with turpen- 
tine and volatile thinners is sometimes resorted to by workmen, 
causing a loss in the protecting value of the mixture. This pig- 
ment is more or less affected by sulphurous gases, under the action 
of which it turns brown. Admixture with certain inert pigments 
is to be recommended, in some cases. The inhibitive nature of 
red lead will vary according to the method used in its manufac- 
ture and the quantity and kind of impurities which it carries. It 
should always be tested, if possible, before its selection as a pro- 
tective agent. 

Orange Mineral. — Orange mineral is produced by the oxida- 
tion in reverberatory furnaces of white lead which is slightly off 
color. It is of the same chemical composition as red lead, but 
it possesses a different tone. Because of the tendency of oxides 
of lead in linseed oil to absorb oxygen, and cause stiffening and 
hardening of the mixture, these pigments are seldom used alone 
in prepared paint. Admixture with other pigments prevents this 
hardening for a long period. This is another pigment the inhibi- 
tive power of which is found to vary, owing to indefinite impuri- 
ties introduced in its manufacture. 

Artificial Iron Oxides. — There are a great number of iron 
oxide pigments used for the protection of iron and steel, and they 
vary in their specific gravity as well as composition. There can 
be obtained iron oxides of over 99 per cent, purity, and these 
are generally made by the burning of copperas (ferrous sulphate), 
but the resulting materials are apt to contain traces of sulphuric 


acid which have not been thoroughly burned out. Oxides made 
by the above process should be carefully tested previous to use 
on iron or steel. 

Venetian Reds. — The so-called Venetian reds are made by 
the calcination of mixtures of copperas and lime, the interaction 
taking place forming ferric oxide and calcium sulphate. The 
percentage of iron in these Venetian reds varies from 15 to 45 
per cent. Because of the soluble nature of the calcium sulphate 
in this pigment, when not dead burnt, and the ease with which it 
is ionized in the presence of water, it is considered as a dangerous 
material to use upon iron or steel. Some Venetian reds are made 
by mixing iron oxides with gypsum and calcium carbonate. These 
are considered safer pigments to use, being free from acid, espe- 
cially when the latter pigment is present. 

Metallic Brown. — There are many other oxide of iron ores 
which are used in the making of paints, and one very important 
ore is called Prince mineral, or Prince metallic brown. This ore is 
mined largely in Pennsylvania, and is found as a natural hydrated 
iron oxide and also as a carbonate (siderite). It is roasted for 
several hours at a cherry red heat, the hydrated oxide or carbonate 
being changed to the sesquioxide. It is then ground and made 
ready for shipment. This pigment contains a considerable quan- 
tity of silica and alumina. It has been used both on wood and 
steel with considerable success for many years, and is considered 
as one of the standard pigments for protective paints. 

Indian Red. — Natural hematite ores and Persian Gulf ores 
are pigments of great value, and when of the proper shade are 
termed Indian red. The term Indian red is also applied some- 
times to Artificial Iron Oxides made by calcining copperas. These 
pigments generally run over 95 per cent, oxide of iron, with varying 
percentages of silica. The shade and tone of Indian red, although 
varying in many samples, is distinctively more pleasing than many 
of the brown oxides. The natural iron oxides, made from hematite 
ores, some of which are termed bVight red oxide and Indian red, have 
a gravity of 3.5 to 5.2 and grind in about 20 to 25 per cent, of oil, 
while the Venetian red and Prince's metallic brown have a gravity 
of 3.1 and grind in approximately 25 per cent of oil. The natural 
iron oxides make valuable body pigments for inhibitive paints. 

Ochre, Sienna, and Umber. — There are several other iron 
oxide pigments, such as ochre, sienna, and umber, the ochre being 


a hydrated ferric oxide admixed with clay. The umber is similar 
in composition to the sienna (consisting of iron and aluminum 
silicate with varying percentages of manganic oxide which gives 
it the brown color), but containing a much higher percentage of 
manganic oxide. These pigments vary in gravity from 3 to 3.5 
and they grind in from 35 to 50 per cent, of oil, according to their 
chemical composition. These pigments are seldom used alone 
in paints for iron and steel. 

Graphitic Pigments. — There are two forms of graphite: the 
natural, and the artificial. The natural has a gravity of about 
2.6, and the artificial of about 2.2. Both varieties grind in approxi- 
mately the same amount of oil, namely 45 per cent. The natural 
product is an allotropic form of carbon found in many localities, 
and contains varying percentages of carbon admixed with silica, 
and sometimes oxide of iron. The artificial or Acheson graphite 
contains about 90 per cent, carbon. Burning of this latter variety 
gives an ash consisting of carbide of silicon, with a very small 
percentage of silica, iron, and alumina. 

Both pigments have been used to a great extent for painting 
steel and iron, but inasmuch as they have a very excessive spread- 
ing rate, a very thin film is produced, which sometimes suffers 
early decay. Graphite paints are therefore generally mixed with 
heavier pigments, such as red lead, or sublimed blue lead, pro- 
ducing superior paints. Graphites are not considered good 
inhibitors by the authors on account of the ease with which they 
conduct electric currents and thus excite corrosion. The pig- 
ment itself is very inert, and has practically no action upon the 
oil in which it is ground, except to retard drying. It is a very 
unctuous or greasy pigment and unless reinforced with pigments 
that have more tooth, it slides under the brush and the particles 
tend to segregate. 

Bone Black. — Bone black is a pigment made from ground 
bones burned in highly heated iron retorts for several hours. This 
pigment sometimes contains traces of organic matter and oil 
which retard its drying. In composition, it runs about 85 per 
cent, calcium phosphate and 15 per cent, of carbon. Its gravity 
is 2.68, and it grinds in 50 per cent, of oil to a -stiff paste. The 
authors consider it generally an excellent inhibitor, and it has 
been used in certain inhibitive paints where dark colors are de- 
manded, to replace carbon black and lampblack. 


Lampblack. — Lampblack is a very pure form of carbon, 
often being over 99 per cent. pure. This pigment is made from 
the combustion of oils, and is very uniform in its composition. 
It is extremely permanent and has wonderful tinting strength. 
It has a gravity of 1.82 and grinds in 75 per cent, of oil. It is 
an extremely slow drying pigment. It possesses great tinctorial 
values and is used in large quantities for the tinting of paints. 
In the authors' opinion, it is not safe to use as a contact coat on 
iron surfaces, as, like the graphites, it is a good conductor of 
electricity and therefore acts the part of a stimulator. As a 
top coating it possesses distinct merit, because of its resistivity 
to water and its action in preventing early decay of the oil with 
which it is used. 

Carbon Black. — Carbon black is made from the combustion 
of natural gas, and contains approximately 99 per cent, pure 
carbon. It has a specific gravity of 1.85 and grinds in 84 per 
cent, of oil. It has been largely used in admixture with white 
lead for paints to be used upon steel and iron, but recent investi- 
gations have proven that it is a stimulative compound and is 
dangerous to use as a prime coating material. It may be used 
with perfect safety as an excluder, when an inhibitive pigment 
is used for the under coating. 

Vine Black and Willow Charcoal. — These pigments are made 
from the charring of certain grades of wood, and may contain 
slight traces of alkali which probably account for the excellent 
inhibitive values which they seem to show. They have a specific 
gravity of about 1.4 and grind in about 33 per cent, of oil. 

Mineral Black Pigments. — Mineral black is a pigment made 
by grinding an especially black form of slate. Although this 
pigment does not possess very much tinting value, it has proven 
of considerable merit as an inert pigment for addition to certain 
paints. The so-called Keystone filler is made from a bituminous 
schist ore and forms a dark-colored pigment containing over 50 
per cent, of silica, the balance being alumina and carbon, with 
small quantities of calcium carbonate and iron compounds. This 
pigment is used extensively as a filler for steel and iron surfaces, 
especially for machinery. 

Orange Chrome Yellow. — Orange chrome yellow is a pigment 
used largely for tinting purposes and is made from the nitrate 
or acetate of lead, chromate of soda, and alkali. It is really a 


mixture of the neutral chromate of lead and the basic chromate 
of lead. It is liable to contain small quantities of chromate of 
soda, basic nitrate or basic acetate of lead, and sulphate of soda. 
It has a specific gravity of 6.9 and grinds in 20 per cent, of oil. 
It has good inhibitive values when the impurities are not acid in 

Medium Chrome Yellow. — Medium chrome yellow is a pure 
neutral chromate of lead made from either the nitrate or acetate 
of lead, and chromate of soda. It has a gravity of 5.8 and grinds 
in 30 per cent, of oil. It is used in large quantity as a tinting 
material, its strength depending largely upon the method of 
manufacture. Like all precipitated pigments, the yellow is 
likely to carry down small quantities of impurity from the mother 
liquor. While theoretically an inhibitor, this pigment has not 
given a very good account of itself on test. 

American Vermilion. — American Vermilion is made by boil- 
ing white lead and chromate of soda, and adding small quantities 
of sulphuric acid in order to brighten the shade. A basic chromate 
of lead is thus formed. This pigment sometimes contains free 
chromates which account for its excellent inhibitive value. It 
contains 98 per cent, of lead compounds, and has a specific gravity 
of 6.8. It grinds in 16 per cent, of oil. It could probably be 
improved as an inhibitor, if the acid treatment for brightening 
was omitted. 

Lemon Chrome Yellow. — Lemon chrome yellow is manu- 
factured from the acetate or nitrate of lead, bichromate of soda, 
and sulphuric acid, or a salt of this acid, and is really a mixture 
of sulphate of lead and chromate of lead. It sometimes contains 
traces of acetate of soda, It may also contain up to 60 per cent, 
of lead sulphate. It has a gravity of 6.2 and grinds in 20 per 
cent, of oil. It is not a good inhibitive, for the reasons given in 
the description of medium chrome yellow. 

Barium Chromate. — Barium chromate is a pale yellow pig- 
ment in color, made from barium chloride and chromate of 
soda. It sometimes contains traces of barium chloride. Like 
many other precipitated, very slightly soluble chromates, its 
inhibitive value is not high. 

Zinc Chromate. — Zinc chromate is a beautiful yellow pigment 
manufactured from zinc oxide, sulphuric acid, and bichromate 
of potash, or zinc salts and bichromate of potash. It has a fairly 


high solubility and always contains some impurities. It gen- 
erally contains free chromates and uncombined zinc oxide. This 
pigment has a specific gravity of 3.5 and grinds in 25 per cent, 
of oil. Like the rest of the chromate pigments, it is a very slow 
drying material, often requiring over a week to set up, unless 
considerable drier is added. In spite of the impurities which it 
carries, it has shown itself to be the most inhibitive pigment 
known and has demonstrated its value in even small percentage 
in paints for iron and steel. It dries to a hard adherent film that 
tends to protect metal from corrosion. The authors recommend 
at least a 2 per cent, addition of zinc chromate to all inhibitive 
contact coats for iron and steel surfaces. 

Zinc-and-B avium Chromate. — Zinc-and-barium chromate is 
made by precipitation of a solution of zinc and barium chlorides, 
with chromate of soda. It is a pigment less soluble than zinc 
chromate, and has proven very efficient as an inhibitive compound. 

Chrome Green (Blue Tone) . — Chrome green (blue tone) is 
made from nitrate of lead, bichromate of soda, and oil of vitriol, 
precipitated on white lead and Chinese blue. The resultant 
product contains chromate of lead, sulphate of lead, Chinese 
blue, and white lead. It sometimes contains traces of nitrate 
of lead and nitrate of soda. It has a gravity of 4.4 and grinds in 
25 per cent, of oil. On account of the contained impurities and 
the comparatively low solubility of this chrome pigment, it does 
not appear high in the inhibitive class. 

Chrome Green (Yellow Tone). — Chrome green (yellow tone) 
is made from nitrate of lead, Chinese blue, and bichromate of 
soda. It is liable to contain small traces of lead salts. It has 
a gravity of 4 and grinds in 22 per cent, of oil. 

Chrome Green (Oxide). — Pure oxide of chromium is pro- 
duced in the wet process by precipitation of reduced chromium 
salts with alkalies, or, by Guignet's process, by fusion of bichro- 
mate of potash with borax, subsequently washing the green 
powder that is formed, to remove the potassium borate or other 
soluble salts. It is a very valuable, permanent green, possess- 
ing unequalled permanence. It is therefore used for signal and 
semaphore work on railroads. It possesses good body and cover- 
ing capacity, and it is inhibitive rather than stimulative. It is, 
however, rather high in cost. 

Prussian Blue. — Prussian blue is a ferri-ferrocyanide of iron 


made from prussiate of potash and copperas, by interaction 
of their solutions, the precipitate formed being subsequently 
oxidized. This pigment has a gravity of 1.9 and grinds in about 
55 per cent, of oil. Like all precipitated pigments, the Prussian 
blues should be tested for inhibitive value, before their selection. 
Prussian blue has a marked action in preserving the oil with which 
it is used, from early decay. It presents a very glossy surface 
even after long exposure. 

Ultramarine Blue. — Ultramarine blue is a very bright blue 
pigment made from silica, china clay, soda ash, and sulphur, 
chemically combined by burning in pots and furnaces. The 
resulting product is ground and bolted. It has a specific gravity 
of 2.4 and grinds in 30 per cent, of oil. It is not considered a 
good inhibitive on account of its sulphur content. 

Naples yellow, cadmium yellow, verdigris, cobalt, and Bruns- 
wick greens and blues, Vandyke brown, and the various alizarin 
lakes and coal tar colors are seldom used in paints for iron and 
steel. No description therefore is given of these pigments. 



Linseed Oil. — Linseed oil is the Only vegetable oil possessing 
the necessary drying power and other properties that is produced 
to-day in sufficiently large commercial quantities to meet the 
demands of the paint and varnish manufacturer. Attempts have 
been made to introduce other vegetable oils such as China wood 
oil, soya bean oil, etc., but their use has been limited by their 
scarcity or on account of peculiar characteristics which render 
them unsuited for general purposes. 

Linseed oil is produced by crushing and grinding flax seed in 
specially constructed mills, either of the plate or screw type, 
the oil being forced out, leaving a residuum of oil cake or flax 
meal which is used for cattle food The use of heat in conjunction 
with the crushing of the oil secures a better yield, and causes the 
oil to assume a golden yellow color; the color of cold pressed oil 
is considerably lighter. 

Another process utilizes 'the solvent power of naphtha upon 
linseed oil. After the crushed seed has been well extracted, the 
naphtha is distilled from the mixture, leaving the linseed oil. 
The naphtha is recovered by condensation and used over again 
for the same purpose. 

The flax plant is grown in Russia, India, North America, and 
Argentine, the latter country producing the largest quantity and 
representing an average output of over 100,000,000 gallons per 
year, while the amount of seed produced in the United States 
gives a yearly production of over 60,000,000 gallons of oil. Minne- 
sota, North and South Dakota, are the states in which most of 
the seed produced in this country is grown. 

The best method of bleaching linseed oil is by proper ageing 
and exposure to sunlight. "Unfortunately this method cannot 
always be resorted to. Several methods are in use, such as blow- 
ing with steam or air, the acid treatment, the use of artificial 
oxidizing agents, etc. Linseed oil that is treated with sulphuric 



acid must be carefully tested before using in paint intended for 
iron and steel. Blown linseed oil must also be guarded against, 
as it is rather viscous and is very apt to cause curdling of paint. 
Mechanical processes of producing pure oil, such as rapid cooling 
after the oil has been subjected to heat, throws out a large per- 
centage of foots and other objectionable materials, Oil pro- 
duced in this manner is generally of good quality. 

Linseed oil is a triglyceride of oleic, linoleic, isolinoleic, and 
other organic acids. It is a saponifiable oil, and when treated 
with alkali the acid part of the oil forms salts or soaps, liberating 
free glycerine. 

When spread upon glass in a thin film, raw linseed oil dries 
in about four days. This drying takes place by progress ve oxi- 
dation, the oil increasing in weight by the addition of oxygen, 
without any appreciable decomposition or elimination of its own 
constituents. The initial oxidation is slow, but the formation of 
peroxides causes the oxidation to proceed very rapidly. The use 
of certain non-drying pigments with linseed oil, such as carbon 
black or lampblack, retards this drying for several days, while the 
use of other pigments, such as zinc oxide, red lead, litharge, and 
white lead, increases the drying action of the oil. It is therefore 
apparent that in the manufacture of paint, the amount of drier 
to use must depend on the composition of the paint. 

Chemical Characteristics of Linseed Oil, — Linseed oil pos- 
sesses certain characteristics which are utilized by the chemist 
to determine its purity. Among the most important of these 
characteristics are the saponification value, the iodine number, 
the acid value, and the specific gravity. If the oil is suspected 
of adulteration with mineral oils, treatment with caustic alkali 
will at once yield evidence whether such is the case. Linseed 
oil is almost totally saponifiable, and in the presence of alkali 
forms a soap, while mineral oils are unsaponifiable and are 
unacted upon by the alkali. The saponification value of lin- 
seed oil is approximately 192, other saponifiable oils varying to 
greater or lesser extent in this value. 

Linseed oil always contains traces of free vegetable acid- 
uncombined with glycerine, the amount generally averaging not 
over one per cent. The presence of a high percentage of free 
acid in an oil would indicate the addition of rosin or rosin oil, as 
the latter oils both possess a very high percentage of free uncom- 


bined acids. Excessive free acid in linseed oil is often the cause 
of the gelatinization or thickening of paints containing lead and 
zinc, this action being due to the formation of soaps with the pig- 
ments of basic nature, in the paint. 

All vegetable oils differ in the amount of iodine which they 
are capable of absorbing; this iodine absorption property being 
in direct relation to the ability of the oil to absorb oxygen. The 
iodine absorption test is very valuable in the determination of 
the purity of an oil. 

The specific gravity of an oil is also a good criterion of its 
purity, and often will readily indicate whether the oil has been 
adulterated with lighter or heavier mineral oils. The presence 
of petroleum products may be noted by their odor, and this latter 
test is also used when linseed oil is suspected of containing fish 
oils, the characteristic fishy odor being developed when the oil 
is slightly heated. 

The Maumene test, or rise in temperature, when oil is treated 
with sulphuric acid, has been of value in detecting the presence 
of petroleum spirits. The flash test is also in vogue for this 
purpose. The refractive index and oxygen absorption test are 
also used in the determination of the purity of linseed oil. 

When a sample of raw linseed oil is spread upon glass, and the 
drying observed, the condition of the film is sometimes indicative 
of the presence of mineral or fish oils, cloudiness of film or exces- 
sive tackiness indicating their presence or the presence of some 
semi-drying oil such as cottonseed oil. 

The following characteristics of linseed oil gives the average 
results of several analyses of the pure oil: 

Specific Gravity at 15.5° C 932 to .935 

Acid Number 5 to 7 

Saponification Value 187 to 192 

Unsaponifiable Matter 8 to 1.5% 

*Iodine Number ISO to 190 

*(May sometimes be as low as 160.) 

During the drying of linseed oil, certain changes in its molecular 
structure, due to the absorption of oxygen, takes place, and the film 
may become more or less porous, allowing the admission of moist- 
ure which would cause the corrosion of underlying iron. Toch 1 

: M. Toch. The Chemistry and Technology of Mixed Paints, p. 88. 
D. Van Nostrand Co., New York, 1907. 


has stated that moisture goes through a linseed oil film by form- 
ing a semi-solid solution with the oil, as microscopic examination 
of films fails to reveal the existence of pores. While Toch's state- 
ment is undoubtedly true, it does not argue that a form of porosity 
does not exist. Semi-solid solution demands intra-molecular 
spaces that can be occupied by water molecules. Whether we 
call these spaces pores or something else, they must exist, even 
though the microscope is incapable of resolving them. 

The use of linseed oil as a shop coating is not good practice 
and has probably been the cause of much damage. Repainting 
over such a coating, with good results, is almost an impossibility. 
When a linseed oil film on iron is abraded at any point on the 
surface, corrosion will proceed rapidly. As Walker 1 has shown, 
the hydrogen which is evolved during the initial start of corro- 
sion would, under ordinary conditions, form an electrolytic double 
layer, to some extent preventing further corrosion. The linseed 
oil, being an unsaturated hydrocarbon, acts the part of a depolari- 
zer and therefore the action is accelerated. Inhibitive pigments 
in the oil, however, retard this action and overcome the stimu- 
lating effect of the oil film. 

The presence of mucilaginous and albuminous matter and 
certain solid fats causes the "foots" or cloudy sedimentation 
in linseed oil. A high percentage of foots should be avoided, 
because of the high acid number and destructive effect on the 
dried film of linseed oil. 

Boiled Oil. — Boiled linseed oil is made by adding lead or 
manganese salts or oxides to raw linseed oil, heated to 350° F. 
Solution takes place, with the production of an oil which has 
very rapid drying power. When spread in a thin film on glass, 
eight hours is sufficient to set the oil up very firmly without tacki- 
ness. This oil is extremely valuable in the manufacture of paints 
for iron and steel. 

Other methods of making boiled oil produce inferior products; 
the so-called "bung hole" oil, in which a liquid drier, or thick 
mixtures of boiled oil containing salts and oxides, is added to cold 
raw oil in the barrel, is quite common. This method is to be 
deplored, as it produces an inferior grade of oil. 

Chinese Wood Oil. — Chinese wood oil is obtained from the 

1 Wm. H. Walker. The Function of Oxygen in the Corrosion of Metals. 
Trans. Amer. Electrochem. Soc, Vol. XIV, 1908. 


nuts and seeds of the Chinese tung tree, and imported in large 
quantities for use in the manufacture of special varnishes and 
paints. The raw oil is unsatisfactory for use, drying white and 
unelastic, but when heated at certain temperatures, less than 
250° F., and treated with salts or oxides, then thinned with oil 
and benzine, an excellent product is obtained. The treated oil 
dries rapidly, with a high gloss and heavy body, producing a hard, 
elastic film which seems to be relatively moisture proof. On 
account of these properties, it is largely used in the manufacture 
of floor paints and enamels,- but has not as yet received any 
special application in the manufacture of paints for iron or steel. 
Films, however, made with this oil seem to possess excellent 
excluding and moisture resisting properties. 

Toch l says: "By the use of China wood oil, paints are made 
which dry in damp atmospheres. The advantage which the 
Chinese and Japanese have had over the Europeans on this 
subject has been recognized for a long time. It is now known to 
have been due to their knowledge of the proper manipulation 
of China wood oil. For the making of marine paints and water- 
proof paints China wood oil is indispensable." It is probable 
that this material will be more extensively used in the future for 
making up protective paints for iron. 

Soya Bean Oil. — This oil is produced from the soya bean 
which grows in Manchuria, 2 the product being used largely in the 
manufacture of soaps. It possesses such close resemblance to 
linseed oil that it is difficult for the analyst to determine its pres- 
ence. Experiments are being made to utilize it in place of lin- 
seed oil, but only a few hundred gallons have been received in 
this country up to the present time. Soya has a slightly darker 
color than linseed oil. The following chemical characteristics 
will show how closely it resembles the latter: 

Specific Gravity 924 

Saponification Value 192 

Iodine Value 122-130 

It dries rather slowly, with the production of an elastic film. 

1 M. Toch. Chemistry and Technology of Mixed Paints. D. Van 
Nostrand Co., New York, 1907. 

2 Attention is called to the fact that the Soya bean grows well in many 
parts of the United States although it has not been used as a source of paint oil. 


Special treatment may render this oil of great value in the manu- 
facture of protective paints. 

The Use of Driers. — The necessity of having the oil dry 
gradually, but still with enough speed to prevent undue tacki- 
ness with the resulting dust-catching properties, demands the 
use of a drier that will cause oxidation to proceed uniformly and 
with the proper rate of speed. The too rapid oxidation of lin- 
seed oil, with the formation of linoxyn, is the cause of the non- 
elasticity and brittleness of some paints that have been recently 
used. This effect is more noticeable in paints containing japan 
driers than in those containing oil driers, the latter being the 
safest of the two varieties to use. Japan driers are manufactured 
by fusing resins with salts and oxides of zinc, lead, manganese, 
and other metals, reducing the mass at the proper time with 
turpentine or light mineral oils. The drying action of japan 
driers is very rapid. The oil driers are made by heating linseed 
oil with salts or oxides of metals, at a high temperature, subse- 
quently thinning down with more oil and volatile diluent, prefer- 
ably turpentine. 

Oxides of lead and manganese are the most widely used chemi- 
cals for the making of driers. Manganese starts the drying action 
and causes rapid surface drying. The lead drier causes the 
oxidation to proceed throughout the film and should generally be 
in the larger proportion Red lead and litharge are also used, 
but red lead causes a brittleness of paint films, while litharge gives 
a paint film very elastic properties. 

Turpentine. — This remarkable and highly prized paint 
diluent is distilled from the sap of the pine tree. The largest 
quantity is being produced in the pine forests of Georgia and 
South Carolina. In its pure form it is a water white liquid, 
easily recognizable by its distinctive odor. When added to paint, 
it prevents thickening of the paint and causes the paint to work 
very freely under the brush, increasing its spreading properties. 
It is largely used for flatting purposes, and it evaporates slowly 
but completely, causing more rapid oxidation of the oil in which 
it is used. It evaporates on paper without a stain, and this test, 
accompanied by tests for its specific gravity, polymerization 
value, and flash point, makes its adulteration easily detected. 

Sulphuric acid, when mixed with turpentine, results in the 
formation of a brownish colored, thick liquid, the turpentine 


being polymerized with the acid to other compounds. The 
presence of mineral oils which are unacted upon by sulphuric 
acid, is readily shown by this test, and they separate and float 
upon the top of the polymerized liquid. 

A pure turpentine will show the following characteristics, 
within very close limits : 

Specific Gravity 86 to .87 

Boiling Point 156° C. 

95% will distil between 150 and 165. 

Polymerization test — less than 5% should be unacted 
upon by sulphuric acid. 

Spot test — should completely dry on filter paper with- 
out stain, and without affecting the water-absorptive 
properties of the paper. 

Flash point — should not be under 40° C. 

Wood turpentine is made by distilling pine debris and logs. 
This process produces a liquid having an odor very much more 
penetrating than pure gum spirits, and its effect upon workmen 
is sometimes serious. Proper refining may remove pyroligneous 
and formic acids, pyridine bases, and creosote, which it contains 
in small quantities, producing a product that is almost identical 
in painting values with the pure gum spirits. It has been found, 
however, that the most highly refined wood spirits contains a 
slight difference in the relative percentage of pinene, and turpene, 
to that contained in pure gum spirits. 

Paraffine Spirits. — These are produced to-day by the refin- 
ing of petroleum and asphaltum products. In the refining of 
petroleum, several light oils, such as benzine and naphtha, are 
produced and are largely used by the painter as cheap diluents. 
They evaporate very rapidly, but their excessive use should be 
condemned. The very low flash point of these products make 
them somewhat dangerous. Several higher boiling point oils are 
produced in the distillation of petroleum and asphaltum com- 
pounds. In their flash point and boiling point they resemble 
pure turpentine, and they answer to the spot test satisfactorily. 
They possess the same flowing and flatting properties as pure 
turpentine, and are being used in considerable quantities as a 
substitute for this material. 

Benzol. — This product is obtained by the distillation of coal 
tar, and is a chemical compound corresponding to the symbol C 6 H 6 . 


It is a water-white liquid of excellent penetrative and solvent prop- 
erties. It has been found valuable as a diluent for coal tar and 
asphaltum paints, and is largely used in the manufacture of paint 
and varnish removers. 

Lacquers and their Application. — By the term "lacquer" is 
meant the pale varnishes so largely used in the protection of 
brass, copper, and silver ornamental work. Lacquers have been 
used to some extent in the protection of steel and iron, and a 
short outline of their manufacture will not be out of place. 

There are three distinct varieties of lacquers, known as gum 
lacquer, cotton lacquer, and the combination lacquer. Gum 
lacquers are produced by dissolving broken gums, such as kauri, 
sandarac, and shellac, in cold grain alcohol, fusel oil, acetone, and 
other solvents. They may be colored with various coal tar 
dyes. They are applied with a brush, and rapidly dry to a very 
transparent film with a high gloss. Materials so lacquered are 
often baked to insure a harder film. 

The most widely used lacquer is cotton lacquer. This lacquer 
is made by dissolving soluble nitrated cotton in amyl acetate. 
The cotton is manufactured by immersing perfectly clean absorb- 
ent cotton in a mixture of nitric and sulphuric acid. The cotton 
used may be either the long, staple variety, or the short-fibered, 
pulp variety; the former producing the best and most elastic 
lacquer. During immersion in the acid, the cotton becomes 
nitrated, taking up two molecules of nitric acid. The strength 
of the acid, and temperature at which nitration takes place, are 
extremely important, as several varieties may be produced, all 
of which have different solvent values. The cotton after nitra- 
tion is removed from the acid and thoroughly washed and neu- 
tralized. It is then dried and treated with solvent. Amyl 
acetate, acetone, wood, and grain alcohol are used as solvents, 
but only the first-named solvent produces a transparent film. 
Articles to be coated with cotton lacquer must be dipped, as 
brushing causes streaking. 

Combination lacquer is made by combining a gum lacquer 
and a cotton lacquer, the solvents of which have been properly 
adjusted to prevent settling out or curdling of either constituent. 
Combination lacquers are very serviceable and of extreme value 
for protecting metal ornaments. 

One of the authors has used a chromated lacquer which has 


given good results in protecting iron articles on a small scale. 
Gum shellac is dissolved in grain alcohol and the insoluble wax 
filtered out. Chromic acid is then introduced into the lacquer 
by adding tiny pinches at a time until saturation has taken place. 
If the chromic acid is added carelessly or in large increments, 
violent oxidation will take place, and the lacquer may take fire. 
For this reason it is well to have the vessel containing the solu- 
tion surrounded by ice water while the lacquer is being chromated. 

Perry has developed a chrome resinate which gives promise 
of proving itself a valuable constituent of inhibitive vehicles. 
This compound is soluble either in benzol or linseed oil, and when 
used in very small percentage may be of value as an additional 
fortifier against corrosion. 

Varnishes. — Varnishes will not be discussed here, as they 
are used almost entirely for interior decorative purposes. It has 
been demonstrated, however, that a percentage of high-grade 
varnish in a paint renders that paint a better excluder of mois- 
ture. If the varnish be of a nature that will stand exposure, its 
use is desirable, in some instances. 


Presenting a Discussion before the American Institute 
of Mining Engineers on the Corrosion of Water 
Jackets of Copper Blast Furnaces. 

The Corrosion of Water Jackets of Copper Blast Furnaces. 1 — 
During the two years in which the new reduction-works of the 
Copper Queen Consolidated Mining Company have been in oper- 
ation at Douglas, Arizona, there has developed a remarkable 
condition in regard to the corrosive action of the water used to 
cool the jackets of the blast furnaces. 

Were it not for the many contradictory features, it might 
pass as one of the unavoidable troubles due to the composition 
of the water. This water, obtained from wells 600 ft. deep, is 
also used in the steam boilers, and its composition, as shown by 
the following analysis, does not indicate the presence of any 
ingredient which would explain the corrosion: 

Grains per U. S. 

Silica 0.861 

Iron oxide and alumina 0.223 

Calcium carbonate 0.261 

Calcium sulphate 

Magnesium carbonate 

Sodium and potassium sulphates 14.850 

Sodium and potassium chlorides 9.732 

Sodium and potassium carbonate 6.482 


The jackets are made of inner plates 0.5 in. thick, and an 
outer plate f in. thick, with f in. stiffeners between the inner and 
outer plates. In from ten to twelve months the inner plates have 
been reduced by corrosion to a thickness of from i to T V in., while 
the outer plate in the same time is reduced by less than T V in., 
and " the stiffeners show very little corrosion. The plates are 

1 Transactions of the American Institute of Mining Engineers. By George 
B. Lee, Douglas, Arizona. (Toronto Meeting, July, 1907.) 



pitted and eaten away in some places more than in others. There 
is practically no scale found on the jackets, but when cleaned 
considerable iron oxide is found in the bottoms. 

With an action so marked, serious trouble would be expected 
in the boilers, but, on the contrary, a recent inspection by a 
boiler insurance company gave an almost perfect report on the 
large boiler plant, which consists of eight 500-h.p. Sterling boilers. 
There was no pitting in the tubes. The inspector's attention 
was particularly called to the pitting of the jackets. The cast- 
iron impellers of rotary pumps that pump to the cooling tower 
from the hot-well are pitted in spots quite as deeply as the jackets. 
A sheet-iron pipe 0.25 in. thick, that has carried all the hot water 
for the jackets of eight furnaces, has never leaked. Some wrought- 
iron pipes, handling water at a temperature of from 65° to 80° F., 
have been almost destroyed by pitting, while others in the same 
line have not shown a leak. 

These notes are offered in the hope that some member of the 
Institute may have met this problem before, and can throw light 
on this interesting subject. 


William Kent, Syracuse, N. Y. (communication to the Secre- 
tary *) : The analysis of the water shows it to be somewhat 
unusual; it is rather high in sodium and potassium sulphates and 
chlorides, 24.58 grains per gal., and very low in calcium car- 
bonate, 0.261 grain per gal. There are three theories which may 
account for the corrosion: 

1. Air Bubbles Lodging on the Iron. — It is well known that 
even pure water, such as the water of condensation from steam- 
heating systems, is an active agent in causing the pitting of the 
nipples used for connecting cast-iron radiators and the iron or 
steel return water-pipes, and the presence of air in the water is 
supposed to be the real cause of corrosion. 

2. Electrolytic Action. — The water containing sulphates and 
chlorides may act as an electrolyte, and different portions of the 
steel plate, having slight variations in chemical composition, may 
act as two different metals or electrodes. 2 

1 Received July 17, 1907. 

2 See Dr. Cushman's paper on Corrosion, read at the 1907 meeting of the 
American Society for Testing Materials. 


3. Chemical Action. — At certain temperatures potassium 
sulphate may attack iron, forming iron and potassium sulphate. 

Possibly all three of these actions may take place at the same 

The remedy indicated is the addition of a little milk of lime 
to the water. This will neutralize any acid reaction of the potas- 
sium sulphate, and form a precipitate of calcium sulphate, which 
will make a protective coating on the iron and prevent all three 
of the actions above described. 

James Douglas, New York, N. Y. (communication to the 
Secretary l ) : The following extracts from correspondence with 
Mr. Lee give some additional particulars concerning the corrosion 
of the jackets: 

Douglas, Ariz., June 12, 1906. 

We have just taken out from one of our new furnaces a jacket, 
which has been in use five months. I find the same trouble as 
before, the inner sheet is very badly pitted. The outer sheet and 
the angles that space the inner and outer sheets do not appear to 
be attacked. 

In connection with this, I wish to call attention to the fact 
^fchat our boilers, which have been in use now for two years, have 
just been inspected by the insurance company and have received 
an almost perfect clearance. Apparently the corrosion is due 
to some peculiar condition that exists with the fire on one side and 
water on the other; and also that there is a difference between 
this condition and that obtaining in the boilers. The steel plate 
on the outside, which is much thinner to start with, and which is 
air-cooled on one side, with hot water on the other, far outlasts 
the thicker inner sheet, and the T-irons, or angles, which are 
immersed in the water between the two sheets, seem to be very 
little attacked. 

In connection with this peculiar action, I would call attention 
to the impellers in the rotary pumps which circulate the water 
for the condensers in the power plant. These are made of cast- 
iron; and we find that at certain points they are very badly pitted, 
being eaten away to a depth of a quarter of an inch for a space 
of one or two inches in area; and right next to this there will be 
spaces that are apparently not attacked at all. We have had 

1 Received September 28, 1907. 


whole lengths of pipe, leading from the supply tanks to the power- 
house, which were perforated, and lengths next to them apparently 
very little attacked. The surface of the jacket seems to be more 
uniformly attacked, but even on this there are smooth spots that 
have apparently resisted this action. 

You will see from the above that materials as different as 
flange steel and cast iron are both attacked by the water; that 
steel exposed to very hot water, such as exists in the boilers, is 
apparently not attacked; that pipes handling water not over 
75° F. are attacked; that pumps handling water both cold and 
moderately heated are attacked; and that steel surfaces heated 
on one side and with water on the opposite side of, say, 140 to 
150° F., are badly attacked, while plates cooled on one side by the 
air and exposed to the same water are very little attacked. 

I suggested that samples of the inner shell and a stay-bolt 
be sent for inspection by the members of the Institute, and that 
the temperature of the water in contact with the inner and the 
outer shell be taken. To this request the following reply, dated 
December 11, 1906, was made: 

Complying with your request, I am sending to-day, by express,* 
a stay-bolt and piece of metal from a water jacket. The tem- 
peratures which you suggested taking of the jacket water near 
the inner sheet and near the outer sheet have been taken repeatedly, 
and I enclose a statement showing the range of temperature. 
You will note that, as the temperature increases, the variation 
also increases. We have just now a report from the inspector 
of the Hartford Boiler Insurance Company, in which we are given 
an absolutely clear bill on the entire battery of boilers, six of 
which have been in use 3-5- years.' 

I believe I told you on your last trip here that we are now 
making experiments by feeding oil into the water as it goes to 
the jackets, with the hope of coating the inside of the jacket with 
a film of oil, and possibly preventing the corrosive action of the 



Temperature of Water in Jackets Near the Inner or Fire Side and 
Outer or Air Side. 

Outside Degrees F, 

Inside Degrees F. 

Outside Degrees F. 

Inside Degrees F. 










In answer to a request as to the effect of this oil, Mr. Lee 
wrote August 28, 1907, as follows: 

I am in receipt of your wire of the 22d in regard to corrosion 
of water jackets. Apparently the use of oil has been of some 
benefit in reducing this corrosion, as the amount of jackets 
renewed seems to be little more than it was, though the number 
of jackets in use is considerably larger. I recently had occasion 
to examine a jacket which had been taken out, and found a very 
peculiar condition; namely, there was a place about 6 by 8 in. 
right in the middle of the place which seemed to be quite smooth 
and not pitted at all, while all around, it was very badly corroded. 
This jacket had been in use about a year and a half. 

I have received a very interesting letter from Mr. Beardsley, 
who was formerly with the Mt. Lyell Company in Tasmania, 
giving me a number of experiences that he had had of corrosion 
of jackets, and, as far as he was able, the causes. In one instance 
well-water was substituted for the former supply. The well- 
water seemed to be highly charged with gas, and they experience 
great difficulty from the jackets burning. This he attributed 
to the formation of gas-bubbles on the fire-sheet. By mixing 
the city water and this water the trouble was very much reduced 
and a return to the city water stopped it entirely. This, of 
course, is quite a different experience of ours, which is not one 
of burning, but one of interior corrosion. 

The following letter, dated London, September 17, 1907, is 
from George M. Douglas, a member of our staff, who was an 
engineer for some time on the White Star and other steamship 
lines: On reading the correspondence you have received from 
Mr. Lee at Douglas regarding the corrosion of the inner plates of 


the furnace-jackets, I suggest that this might be caused by some 
electrolytic action. This same corrosion takes place in the Scotch 
type of marine boiler, particularly when the water contains a 
little salt. This boiler is somewhat analogous in form with the 
jacket, having a hot inner plate, a water space, and relatively 
cool external shell. 

This corrosion is prevented by hanging zinc plates on the stay- 
rods between the spaces affected. It is also a practice to put 
zinc plates near the water inlet, so that any free acid in the enter- 
ing water may combine with the zinc and be neutralized. 

Perhaps a similar application of zinc to the jacket shells at 
Douglas might prove beneficial. I suggest applying it in the 
following manner: The zinc plates should be about f in. thick, 
and about 8 in. wide, and 16 in. long. Some authorities object 
to the application of zinc direct to the iron, though it is customary 
to do so in British engineering practice. 

A suitable means would be to have brackets made of copper 
strips, | in. by 1.5 in., placed about a foot above the bottom of the 
jacket on the inner shell, into which brackets the plate could be 
inserted from the top. 1 I also suggest that a plate be put where 
the water jacket enters. Two plates of the size mentioned on 
each side and one on each end of jacket (should there be any corro- 
sion there) is enough. I do not know what the size of the furnaces 
is. But the relative proportion of zinc surface to iron surface 
should be about one to ten. A good contact should be insured 
between the zinc and the copper and iron, or, if copper is not used, 
between the zinc and iron. 

It is not enough merely to place the plates in the water space; 
they should be well fastened to the jacket. 

Under the same date, Mr. Douglas, in response to an inquiry 
from me, made, in substance, the following statement, which, 
although not directly pertinent to the present discussion, may 
be valuable as a contribution to the general question of the cor- 
rosion of steel and iron: 

With regard to the corrosion of stern-posts and plates in the 
vicinity of propellers on ships, I should say that this action seems 
to be well understood as due to the fact that the propeller-blades 

1 This suggestion is not a good one, as the zinc would be destroyed in 
protecting the copper instead of the iron. A. S. C. 


etc., on one hand, and the stern-posts and plates, on the other 
hand, are of different material, so that a galvanic action is set up, 
the salt water acting as an electrolyte. If all these parts were of 
exactly the same material, no corrosion would take place ; but this 
is not the case in practice. The stern tube is usually of bronze, 
and the propeller of bronze and steel, with blades of manganese 
bronze. An interesting case is on record, of a vessel on which 
iron propeller blades were replaced by blades of bronze. Imme- 
diately upon this change, the corrosion of the stern post and sur- 
rounding plates became so great they had to be renewed after 
only one voyage to the Cape. They were afterwards protected 
by zinc sheathing; and it is now the custom to protect such parts 
by sheathing of zinc or some metal of similar electro-chemical 

Though these facts are interesting, I fear they will not help 
you much in dealing with your jackets, since the conditions of 
your problem are by no means the same as those of the marine 
practice above stated, in which both the origin and the remedy 
of the trouble seem to be clearly established. 

With regard to the general question of the corrosion of steel or 
iron plates, however, I may call your attention to one point 
which may be worthy of consideration — namely, the electro- 
chemical relations between metals and their oxides. According 
to a leading author, 1 "every metal is electro-positive to its own 
oxide." When steel or wrought-iron, with oxide scale upon it, 
is placed in an oxidizing liquid, the conditions of active corrosion 
are complete; and even without a specially oxidizing medium, 
it is asserted that a galvanic action may be set up in the presence 
of air and moisture between the metal and its scale. It is there- 
fore regarded as very important that no "black oxide" should be 
left on the plate; for, though in itself it tends to protect the sur- 
face (the black or magnetic oxide of iron resisting ordinary oxidiz- 
ing agents), yet if, in finishing, handling, or subsequently using 
the plates, portions of it should be knocked off, the remaining 
portions contribute to the corrosion of the exposed metal. 

In 1879, Sir Nathan Burnaby declared, as the result of his 

1 Metallic Structures: Corrosion and Fouling, and their Prevention, by 
John Newman, p. 36. London: Spon & Chamberlain (1896). See also 
Rustless Coatings, Corrosion and Electrolysis of Iron and Steel, by M. P. 
Wood. London: Chapman & Hall (1904). 


observation, that when mill-scale was left upon plates and angles 
used in ships, its effect upon neighboring surfaces of bare metal 
was as strong and continuous as that of copper. 

Jn 1882, Mr. Farquharson conducted for the British Admiralty, 
at different naval stations, exhaustive experiments as to the 
action of mill-scale on ships' metal exposed to the conditions of 
marine use, and found: (1) that no "pitting" occurred in mild 
steel freed from all scale; (2) that the loss of weight by corrosion 
was practically the same for clean mild steel and clean iron; and 
(3) that the action of mill-scale in inducing corrosion is consider- 
able and continuous — equal in these respects to that of an equal 
amount of copper. 

The Admiralty practice is to pickle all ships' metal, for the 
removal of mill-scale. The scale may also be removed by sand- 
blast, or by means of a gasoline-torch, followed with a scraper 
and a wire brush. Pickling, however (in dilute sulphuric or hydro- 
chloric acid), is probably more thoroughly effective. 

The rivets should be of the same material as the plates. Iron 
rivets in steel plates might cause trouble. 

Hiram W. Hixon, Victoria Mines, Ontario, Can. (communica- 
tion to the Secretary *) : I have had difficulties here similar to 
those encountered at Douglas, and I found the cause to be the 
carbonic acid given off when the water was warmed. All the 
water in the streams in this country contains organic matter com- 
ing from peat-bogs and muskegs. It is brown in color, and when 
it strikes the fire-sheets of the jackets the carbonic acid is given 
off and travels up along these fire-sheets because of the bosh in 
the furnace. The lower side of the tuyeres was much pitted, and 
they leaked badly until I had copper tubes put in in place of 
iron ones. 

The inner or fire-sheets were destroyed most rapidly opposite 
the cold-water inlet, whare the greatest amount of carbonic 
acid was given off. Our boilers are not affected and are perfectly 
clear of scale. I think the acid is liberated in the feed-water 
heater, in which there are copper tubes, and after it is in a gaseous 
condition it does not attack iron, or at least the water is necessary 
to make it destructive. The pipes leading from the feed-water 
heater to the boilers are destroyed, but the boilers are not. 

1 Received through Dr. Douglas, Sept. 28, 1907. 


The Canadian Copper Company had a purifying plant for 
the feed-water, and the pipe leading "from the purifier to the dif- 
ferent boilers went over the boilers, and each lead to the boiler 
came out of the bottom of the main pipe. Tests made of the 
water to the different boilers showed that the water to the boilers 
nearest the purifier was much less acid than the water to the boiler 
at the end of the feed-pipe. The superintendent spoke to me 
about it, and I suggested that the acidity of the water was due 
to carbonic acid dissolved in the water, and that being a gas it 
had a tendency to enrich the water in the top of the feed-pipe, 
and, consequently, the water drawn off for the first boiler from 
the bottom of the main contained less acid than the water which 
went to the last boiler. 

I think the trouble at Douglas is due to the water supply 
coming from the deep wells containing carbonic acid, and this 
acid is probably due to the source of the water being something 
in the nature of a mineral spring, such as Saratoga, Manatau, or 
Apollinaris. Ordinary chemical tests would fail to detect any 
mineral acid, and the gas being small in quantity would escape 

The remedy for the trouble is to use copper fire-sheets, or to 
run the water through cooling towers and use it after the carbonic 
acid has escaped. 

C. D. Van Arsdale, New York, N. Y. (communication to the 
Secretary *) : There are several explanations which present 
themselves regarding the corrosion of the water jackets of the 
Douglas furnaces. The most obvious of these — namely, that 
the composition of the water is itself directly responsible — may 
be dismissed as improbable. Analysis of the water shows that 
it may be called a good boiler-water for this region, since it con- 
tains very small amounts of incrusting solids and the non-incrust- 
ing solids are not excessive; and this opinion is verified by its 
causing practically no boiler troubles. Since no corrosion takes 
place in the boilers, it is evident that the dissolved constituents 
of the water do not alone afford sufficient explanation. 

Granting that the water is itself non-corrosive, there is nothing 
in the working of the ordinary water jacket to account for the 
difficulty, otherwise such corrosion would be more or less gener- 

1 Received October 31, 1907. 


ally observed in other plants. It would, therefore, seem that the 
only explanation left is electrolytic action; but it is not evident 
what is the cause for electrolysis. 

It is well known that lack of uniformity in the composition 
of iron will cause corrosion on account of action due to minute 
local galvanic couples. If this is the cause, then a suitable remedy 
would be to hang zinc sheets inside the jackets, as has already 
been suggested. Another cause of electrolytic corrosion may 
be stray currents from some source. In the same way much 
trouble has been experienced from corrosion of gas- and water- 
mains in cities, due to stray electric currents passing along them. 
A very small current has been found sufficient to cause a great 
amount of trouble, but if this should be found to be what is caus- 
ing the electrolytic action in the jackets, it should be quite simple 
to put a stop to it. 

The different temperatures observed in different parts of the 
jackets might also be sufficient to cause some corrosion, since 
electrical currents can be produced in an electrolyte by electrodes 
of the same metal, portions of which are at different temperatures. 
This could be obviated by a circulation of water in the jackets 
sufficiently rapid to do away with any differences of temperature. 

The fact that the jackets are much more corroded on the fire 
side seems to indicate that the electrolytic action is due not to 
lack of uniformity of the iron, but to one or both of the other 
causes mentioned. 

The Corrosion of Water Jackets of Copper Blast Furnaces. 1 — 
C. D. Demond, Anaconda, Mont, (communication to the Secre- 
tary): In order to throw some light on this interesting subject, 
a series of experiments were made with strips of mild steel, con- 
taining about 0.14 per cent, of C and 0.22 per cent, of Mn. These 
strips were thoroughly cleaned and brightened before use, salts 
were added to distilled water until it corresponded as nearly as 
possible to the analysis given by Mr. Lee, and in this water at 
different temperatures were placed four strips of steel; while four 
other strips, at corresponding temperatures, were placed in the water 
used at the Washoe Reduction Works. The latter plant has had 
no trouble from corrosion of furnace jackets, pipelines or boilers. 

1 (Transactions of the American Institute of Mining Engineers, xxxix, 
806-817.) A discussion of the paper of Geo. B. Lee, Trans., xxxviii, 877 to 
884 (1908). 



The analysis of the water used at the Washoe works is: 

Grains per 0. S. 


CaC0 3 2.92 

CaS0 4 0.76 

MgCU 0.64 

MgC0 3 0.58 

A1 2 3 0.12 

Fe 2 3 0.12 

SiOa 0.58 

NaCl 0.35 

Organic matter, etc. . 1.16 


This water is neutral to litmus; while the artificial Copper 
Queen water is very slightly alkaline, which Mr. Lee informs us 
is also true of the water at Douglas. 

Both waters were well aerated by pouring from beaker to 
beaker, and by blowing in air from the experimenter's lungs. 
The results of these tests, given in Table I, show that there is 
no significant difference between the effects of the two waters. 

Table I. — Oxidation of Ikon Per Square Inch of Surface* When 
Immersed in Certain Waters. 

Artificial Copper Queen Water 

Average Temperatures 

First 50 Hours 

Second 50 Hours 


70° F. 

















Washoe Water 

70° F. 









6.618 . 







* These results were obtained by carefully rubbing all the rust from 
the iron, dissolving it, and determining its quantity by titration. 

At two temperatures the strips of steel in the Copper Queen 


water showed less rust than those in the Washoe water, while at 
the other two temperatures they showed more. Another experi- 
ment indicated that distilled water would have given about the 
same results. Hence, the corrosion of the Copper Queen jackets 
must be due to some other cause than the quality of water. I 
am informed, however, that the water is raised from artesian 
wells by means of compressed air, and, after being used in the 
furnace jackets, is passed over a cooling tower, and later goes 
to the jackets again. Hence it probably contains an excessive 
amount of dissolved oxygen. It will be noticed that rusting 
increased with the temperature, up to 150° F., as is true of 
chemical actions in general; but at 185° there was decidedly 
less rust than at 150°, presumably due to the water at the higher 
temperature being unable to hold enough oxygen in solution to 
keep up the rate of oxidation. 

The small differences of temperature (9° to 14° F.) do not 
seem sufficient to account for the inner plates rusting more than 
six times as fast as the outer; but is it not probable that the 
temperature of the very surface of the inner plates is considerably 
higher than is shown by inserting a thermometer in the water, 
and that an unusual amount of dissolved oxygen at this tempera- 
ture is the cause of the trouble? The jackets would probably 
suffer much less if the water were discharged as near the boiling 
point as practicable, and returned directly to the supply tanks; 
the return pipe should dip well beneath the surface of the water 
in this tank, since a plunging stream would entrain a fresh quan- 
tity of air. This would lessen the amount of dissolved oxygen, 
and rust cannot form without oxygen. Referring to the first two 
paragraphs of Mr. Hixon's discussion, 1 it is the gases in solution 
that are active, not those given off; and the probable reason for 
his jackets corroding most rapidly opposite the cold-water inlet 
is that the water at that point still holds the gases in solution. 
The absence of rust in the Copper Queen boilers, and in those 
at the Victoria mines, is perhaps due to the elimination of absorbed 
gases immediately on entering the boilers and before the water 
can touch the metal. It is certain that the temperature of the 
water increases very rapidly upon entering the boilers. 

We have experimented with several other remedies. The 
well-known use of zinc is completely effective when the zinc is 

1 Trans., xxxviii., 882 (1908). 


properly distributed; but this metal corrodes so rapidly that it 
has to be frequently renewed. Copper, on the other hand, 
increases the rusting of the steel, these results being due to the 
electro-chemical relations of the metals. 

Knowing that solutions of alkalies and alkaline salts suffi- 
ciently strong will prevent rusting, we tried the effect of lime, at 
approximately the temperature of the water in the Copper Queen 
jackets. An increase in the quantities of lime added up to 0.1 
per cent, gave increased benefit, amounting to practically com- 
plete prevention with the Washoe water, and reducing the rust 
in the artificial Copper Queen water about 60 per cent. The 
difference was evidently due to the reaction of the lime with the 
sulphates and carbonates in the latter water. Larger amounts 
of lime would probably complete the cure, but the precipitate 
might have to be settled out. 

Dr. A. S. Cushman 1 found, in certain experiments, that 
potash bichromate completely prevented rust when dissolved in 
water at the rate of 1 lb. or more in 1500 gallons. Our tests 
indicates that, even in using the water over and over in the jackets, 
the bichromate would be slowly exhausted, requiring fresh addi- 
tions at intervals. We have not yet determined what the cost 
of treatment would be ; but the protective effect is very striking. 

The elimination of dissolved oxygen from the water is sug- 
gested as the practical remedy in this particular case; but we may 
take occasion here for some further remarks on the general sub- 
ject of rusting. 

The fact that some wrought-iron pipes at Douglas are prac- 
tically unaffected, while others in the same line, as well as the 
furnace jackets, are badly corroded, strongly suggests that there 
is some trouble with the metal itself, and that it is not a question 
of wrought iron versus steel. Indeed, the most recent and 
reliable industrial and scientific investigations show that the long- 
standing controversy as to the relative rust-resisting qualities 
of wrought iron and steel is largely a beating of the air. The 
real question seems to be one of care in the processes of produc- 
tion. Cushman 2 very ingeniously demonstrates that an appar- 

1 Bulletin No. 30, Office of Public Roads, U. S. Department of Agriculture, 
and Proceedings of the American Society for Testing Materials, Vol. VII, 
p. 211 (1907). 

2 hoc. cit. 


ently homogeneous piece of iron or steel carries a multiplicity of 
positive and negative poles of an electrolytic system; and the 
electrolysis between them increases the speed of rusting at the 
positive pole, while preventing rust at the negative. He sug- 
gests that this polarity is due to uneven distribution of certain 
chemical constituents of the metal. In answer to the fact that 
frequent investigations have failed to show this uneven distribu- 
tion, he says 1 that "such extremely small differences in the 
chemical composition as might easily escape detection in ordi- 
nary chemical analysis are still sufficiently large to account for 
slight differences of electrical potential.' 7 He might have added 
that there may be considerable difference in composition which 
chemical methods cannot detect, because it is impossible to 
sample the segregations separately. Frank N. Speller, 2 on the 
other hand, thinks that variations of density may sometimes 
account for the polarity. However, there is no doubt as to the 
existence of the polarity; and its effect was well shown in one of 
our test strips, 4 in. long, after an exposure of 50 hours in water. 
A large part of the surface shows perfectly bright, but other parts 
are badly rusted. Mr. Lee says "the plates are pitted and eaten 
away in some places more than in others"; also, that in one case 
"there was a place about 6 by 8 in. right in the middle of the plate 
which seemed to be quite smooth and not pitted at all, while 
all around it was very badly corroded. " The greater the differ- 
ence of potential the greater will be the action at particular 
spots, which will increase the pitting and quickly produce holes 
in one piece of metal, while another piece, of the same size and 
thickness, long remains serviceable, even if yielding the same 
amount of rust in a given time, because the action is uniformly 
distributed. This action of iron is similar to that of zinc. The 
latter, when pure, dissolves very slowly in acid, but w r hen impure 
it dissolves readily, because of the electrolysis between the spots 
of pure zinc and the spots of impurities. 

The fuller details of this explanation accord with the present- 
day theory of physical chemistry. Cushman's results confirm 
earlier work by Whitney, and are independently verified by 

1 Farmers' Bulletin No. 239, U. S. Department of Agriculture, p. 20. 

2 Applied Science, Proceedings of the Toronto Engineering Society, Jan- 
uary, 1908, p. 125. 


There may be many hundred independent local circuits on a 
few square feet of surface. Cushman * says that, in almost all 
modern steel woven-wire fences some wires will be found to far 
outlast others. It is just this point of unevenness of lasting 
quality in wires from successive heats in the same mill, which 
have practically the same chemical composition, that is hard to 
explain by any theory but that of galvanic or electrolytic action. 

These ideas suggest the use of better steel for furnace jackets, 
though the fact that the rapid corrosion has occurred with jackets 
purchased from at least ten different manufacturers 2 makes it 
appear that better metal is hard to obtain. Moreover, in view 
of the satisfactory service of the outer plates, it may seem, at 
first thought, that the contention for better steel is not well made. 
But the key to this difficulty probably lies in the different his- 
tories of the inner and outer plates in the steel mill. 

For years the manufacturers have fully appreciated the prac- 
tical benefit of an increased amount of work put upon steel, at 
the proper temperature, in improving the physical properties. 
The National Tube Company has found that the resistance to 
rusting is greatly increased by similar treatment, and this com- 
pany has developed a special method of applying it. 3 Now the 
rolling of the outer plates of the water jackets to a thickness of 
f in. necessarily requires more work than rolling the inner plates 
to 0.5 in. and we may therefore expect the former to be more 
resistant to rusting. The angle-iron stiffeners, which Mr. Lee 
says do not rust seriously, probably received a good deal of work. 
The fact that stay-bolts rusted badly at the ends next to the inner 
plates, while being little affected at the other ends, is explained 
by the electrolytic theory as follows: It is well known that rust, 
once formed, increases the rate of corrosion. Mr. Speller 4 re- 
ports finding a potential as great as 50 millivolts between one 
clean iron and another rod exactly similar which had a very 
slight coat of rust, both being immersed in water. When both 
rods were clean, the potential was much less. The rust on the 
inner plates of the water jackets will set up a current between 

1 Farmers' Bulletin No. 239, TJ. S. Department of Agriculture, p. 21. 

2 Private letter from Mr. Lee. 

3 Private letter from Frank N. Speller of the National Tube Co. 

4 Applied Science, Proceedings of the Toronto Engineering Society, Jan- 
uary, 1908, p. 125. 


itself and a stay-bolt, which will corrode the latter. This current, 
in seeking the path of least resistance, will pass from the stay- 
bolt through the water and back to the rust of the inner plate 
without going as far as the outer plate. This effect will be de- 
cidedly less in the case of angle-iron stiffeners, because the latter 
do not have the intimate contact with the inner plate that the 
stay-bolts have, and therefore the electric current meets more 

Speller found the voltage between steel and mill-scale to be 
greater than between the metal and ordinary rust. It may be 
that, for some peculiar reason, this scale is always worse on the 
0.5-in. than on the f-in. plate, though this is hardly probable. 
However, it is advisable to see that all scale and rust are thor- 
oughly removed before the jackets are put together. I believe 
that the main point is the working of the metal in the mill. The 
steel manufacturers are making important investigations with 
valuable practical results, but if they do not yet supply 0.5-in. 
steel of suitable quality, it may be well to try jackets made wholly 
of f-in. stock. 

Arthur S. Dwight, New York, N. Y. (communication to the 
Secretary l ) : Several times in the course of my smelter work 
have I experienced trouble from corrosion of blast-furnace water 
jackets, particularly of the wrought-iron or steel jackets com- 
monly used in copper smelting, and in a manner very similar to 
that described by Mr. Lee, but, in my case, always traceable in 
the end to acid water. 

The troubles at Douglas seem to be somewhat more aggra- 
vated than one usually encounters, and the causes more obscure. 
I understand that, like most of the smelters in the Southwest, 
the Copper Queen works has two distinct systems of water pipes, 
one for the regular high-pressure service, distributing fresh water 
to all parts of the plant, and for fire protection; while the other, 
at low pressure, circulates the jacket water between the blast- 
furnaces and a system of cooling towers. The water in the jacket 
circulatory system has numerous opportunities to pick up soluble 
sulphates, principally in the vicinity of the blast furnaces (where 
it is almost impossible to prevent copper flue-dust from sifting 
into the launders and open places in the circuit) , or by flue-dust 
being blown into the waters of the ponds and cooling tower. 
1 Received September 7, 1908. 


Although the tests for acidity in the jacket water which Mr. 
Lee has made from time to time have failed to show the presence 
of acid, and although we may perhaps properly suspect some 
other cause to be the principal one, I am strongly inclined to 
think, nevertheless, that the troubles are aggravated by the 
presence of acid in the water, particularly as it seems to be 
admitted that the corrosion is somewhat more evident in the 
circulatory system than it is in the service system. 

The fact, however, that some pitting and corrosion also occur 
in the fresh-water line points to the presence of some peculiar 
property in the water itself. The irregularity with which some 
sections of pipe and some jacket sheets are corroded, while others 
in the vicinity, or even adjacent parts of the same piece of metal, 
are entirely free from attack, would point to faulty material, or 
perhaps careless heat treatment in the manufacture of the steel. 
But, granting all this, we are still far from a satisfactory answer 
to the riddle. The Copper Queen smelter is built of the best 
materials currently obtainable, purchased from various makers, 
and, as it stands, represents better than average modern smelter 
construction. The analysis of the water gives no clue; in fact, 
it must be said to be unusually harmless looking. The theory 
of electrolysis does not seem to meet the conditions. By the 
process of eliminating those theories which fail to satisfy, we 
are finally confronted with the question: can the fact that this 
water is raised from the deep wells by compressed air have any 
bearing on the problem? Is it not possible, that, by the intimate 
commingling of the water and air at high pressure, such thorough 
aeration might occur as would make the water an extraordinarily 
active oxidizing agent? This could easily be determined by 
experiment. Personally, I should consider this a surprising fact 
if it proved to be the correct explanation, but the logic of the 
situation seems to point to some such cause out of the ordinary. 

In this connection, it may be pertinent to give some of my 
own experiences with troubles of this kind, and the remedy that 
was developed. 

The most serious case of corrosion of pipes and water jackets 
I have ever had occurred while I was in charge of the operations 
of the Greene Consolidated Copper Company, at Cananea, 
Sonora, Mexico, especially during the latter part of 1905. Cananea 
is not more than sixty miles distant from Douglas, and there is 


some similarity in the conditions of water supply to the furnaces 
and in the character of the ground-water, etc. 

Our troubles were made the subject of a long series of studies 
by R. L. Lloyd, who was then superintendent of the smelting 
department, and to him is due the credit for finding a practical 
and satisfactory remedy. It seems to me proper, therefore, that 
he should be allowed to tell it in his own way, and I insert the 
following extract describing the episode in detail from a letter 
written by him at my request, and which I have his permission 
to include in this discussion: Complying with your request to give 
you the details of the manner in which we worked out the troubles 
at Cananea in connection with the serious corrosion of the water 
jackets and pipes in the circulatory system of the blast furnaces, 
I take pleasure in giving you the facts as I can recall them, though 
I am at a disadvantage in not having my notes on the subject 
accessible. I agree with you in thinking that the troubles which 
Mr. Lee describes as being so serious at the Douglas plant are 
almost identical with those which we experienced, and I think it 
very probable that the same remedy may correct his difficulties 

At Cananea, the main part of the trouble occurred in the long 
pipe-lines which extended from the water-cooling tower to the 
jackets. There was also trouble in the jackets, particularly at 
the joints around the tuyeres. It was noticed that wherever 
iron and brass were in contact, as, for instance, at the brass 
valves, the corrosive action was greatly intensified, presumably 
on account of local electrolysis. The trouble at one time assumed 
such proportions that it became very difficult indeed to keep 
the pipe-lines and jackets in sufficiently good repair for steady 
operation, and many expedients were tried in the attempts to 
discover a remedy. Slaked lime was used to neutralize the acid 
in the water, but the results were only partly successful, and were 
attended with the serious disadvantages arising from the accumu- 
lation of the lime in the tanks, and the formation of lime scales 
on the smaller pipe-lines. We then tried crude sodium carbonate, 
such as we had been using to prevent scale in the boilers, which 
gave better results than the lime, but was still far from satisfac- 
tory. Large slabs of zinc were also connected up in various 
places, especially in the steel overflow-tank, in the attempt to 
counteract electrolysis. 


After much study and experiment we finally determined the 
primary cause of the acid in the water to be the absorption of 
fumes of S0 2 by the sprayed water in the cooling tower, which 
was situated on the leeward side of the smelter with respect to 
the prevailing winds, and on top of a hill, nearly on a level with 
the top of the furnace building. The S0 2 gas in the smelter 
fumes blowing through the cooling-tower was dissolved by the 
falling water and slowl} r became oxidized, and eventually formed 
a dilute solution of sulphuric acid. The amount of corrosive 
sulphates was further augmented by the fact that more or less 
flue-dust got into the water system by sifting into the launders 
around the furnaces and under the feed floor, as is likely to happen 
at any smelter plant, as usually constructed. The position of 
the cooling tower was unfortunate, but on account of limitations 
of space it could not have been avoided, even if the trouble due 
to the smelter fumes had been anticipated. 

While working hardest to correct the difficulty, which threat- 
ened to be most serious, I read an article published in pamphlet 
form by an author whose name I have among my notes, but 
unfortunately not now accessible, which mentioned the effect 
of arsenic salts in deterring the solubility of iron and steel in 
acid solutions. I was at once very much interested to know if 
this could possibly have any bearing on this problem, and I 
proceeded to "doctor" the water system with commercial arsenic 
oxide. The good effect of this addition was felt very quickly, 
and the corrosion was practically ended. From that time on, 
1 kg. of arsenic oxide was added to the water system each week, 
and a portion of the water in the circulatory system was allowed 
to run to waste, being replaced by fresh water, when analyses 
showed that the amount of sulphates was getting high. 

In this manner we were able to avoid the corrosion of the 
jackets. It was noticed that even when the water became appre- 
ciably acid there was little or no trouble from corrosion of the 
pipe system and jackets, though we always endeavored to keep 
the acid neutralized with commercial sodium carbonate. 

It is to be regretted that Mr. Lloyd's citation of the article 
from which he obtained the suggestion for trying arsenic oxide 
cannot be made more concise at this time, but if it proves to be 
a matter of special interest it can doubtless be supplied later; 


meantime, perhaps the paper may be known to some members 
of the Institute, who can complete the facts. 

In this connection, it would be interesting to ascertain whether 
there is as much trouble experienced from corrosion of pipes and 
water jackets in smelting works treating large quantities of 
arsenical copper ores, as there is in plants like Douglas and 
Cananea, which treat ores exceptionally free from arsenic. It 
is not impossible that the arsenic fumes might automatically 
furnish the needed antidote for the acid in the water. Person- 
ally, I have no comparison which I can present from my own 

The following incident, which recently came to my attention, 
presents what seems to be an interesting confirmation of the 
deterrent action of arsenic in the corrosion of iron. A car-load 
of commercial sulphuric acid was purchased by a western steel 
works for pickling wire. The acid refused to work properly, 
though chemical tests showed it to be of proper strength. The 
steel company complained to the acid-makers, who sent an expert 
to investigate. He looked over the situation, promptly sent the 
lot back to the factory, and substituted a new lot of acid for it. 
Though inclined to be reticent about the cause of the trouble, 
the expert finally admitted to the chemist of the steel works 
that this particular car-load of acid had been made from pyrites 
containing considerable arsenic, and that there was an appreciable 
amount of arsenic in the acid, stating, furthermore, that had his 
company known the purpose for which the acid was to be used, 
they never would have sent the kind they did. 

Corrosion of jig screens and other iron work in wet-concen- 
tration mills might also be averted by applying the arsenic remedy, 
though I have never heard of its being tried. 

J. A. Thomson, Pullman, Wash, (communication to the Sec- 
retary l ) : In reference to this pitting and corrosion in the 
water jackets of blast furnaces, to my mind there is no mystery 
or fancied " electrolytic" action in the question. It is simply 
an effect of the air carried by water, fed to the jackets to keep 
them cool and the action is as follows: As soon as the cold water 
comes in contact with the warm part of the jacket, it is heated 
and compelled to give up its air, which, being in contact with the 
plate, settles thereon. The circulation being sluggish, it is only 
1 Received April 27, 1908. 


when the bubbles have grown sufficiently large that they rise, 
and this rise is hindered to some extent by the bosh. During the 
period of rest, the air, containing both oxygen and carbonic acid, 
will attack the iron, and when small irregularities have been 
thus formed, subsequent bubbles find still better lodgment and 
speedily effect the formation of pit-holes. 

If the water is fed to the jacket near the bottom, and if it is 
saturated with air, it can be shown that every square inch of 
heated surface of the jacket generates about 4.5 cu. in. of air 
per hour, equal to about one bubble i in. in diameter per second. 

The great difference of temperature between the water and 
the fire side of the jacket plate, with the consequent straining 
of the grain of the plate, quickly loosens all rust as it is formed, 
so that metallic iron is always exposed to the air given up by 
the water. 

The smooth parts mentioned as having escaped this pitting 
may be accounted for in a number of ways. At the start, such 
a spot may have had some adhering slag or other substance 
which reduced the heat at that point, so that the first irregulari- 
ties produced would be formed away from that spot, and the 
bubbles would be more continuously produced where they found 
good lodgment. Or, again, the spot may be a patch (of the kind 
found in all plates) which has been clean-rolled in the making. 
There are also various other causes. This sort of thing is a fre- 
quent occurrence in the pitting by similar causes on the furnaces 
of marine boilers. 

The same reasoning, but reversed, will apply to the outside 
sheets. There is no extra heat on the outer side of the sheet, 
hence bubbles do not form there, but only on the hot sheet next 
the furnace. 

As to the impellers of the rotary pumps, this case is similar 
to the action on a ship's propeller, in which the air is not driven 
out by the heat, but is abstracted by the partial vacuum formed, 
and in which, in spite of the high velocity of the water, there 
seems to be sufficient time for the mischief to be done. Even 
bronze blades are sometimes pitted in the same way. 

My recommendation would be in the line of putting the water 
under pressure before admitting it to the jackets; that is, let the 
inlet to the jacket have a non-return valve like a large feed- 
check, with a stem carrying a weight, so that the pump feeding 


the jacket would have to force the water against, say, 20 or 30 
pounds per square inch. From under this check a small (say, 
f in.) pipe should lead back to the well. The water being 
under pressure before entering the jacket, a large part of the 
entrained air will escape through this pipe. I do not mean the 
jacket to be under pressure, but only the pipe to the inlet. I 
have no doubt this arrangement would give much relief. I have 
used it many times as a remedy for pitting in marine boilers. 

Of course, I presume there are no unknown acids in the water, 
and that is just ordinary potable water, as seems to be proved 
by the fact that the boilers are said not to have been attacked 
in any way. 

With regard to the statement of George M. Douglas, his 
experience in the White Star boats must have been decidedly 
limited, or he would not talk of a little salt water causing corro- 
sion. It is a common practice to fill new boilers with sea-water 
at first, for the purpose of preserving them; and when I went to 
sea we had no evaporation to make fresh water, and if we ran 
short, we made up with sea-water. I have run a ship from Han- 
kow, China, to London, forty-three days' hard driving, without 
opening a cock that was not open at the start, and not a pint 
of fresh water to make up waste, only the sea to draw from, and 
at the end of the voyage the boilers were in excellent condition. 

If a satisfactory way cannot be devised to introduce the water 
under pressure, I think that the use of nickel steel would solve 
the whole problem. 


References to Books and Magazine Articles 

The following abbreviations have been used: Diag., diagrams; Dr., drawings; ed., 
edition; 111., illustrations; n. d., no date; n. s., new series; no., number; p., page; pi., plate; 
pt., part; v., volume; w., words. 


England — Patent office. 

Abridgment of specifications, new series. 1855-1904. 111. 

Class 20, Buildings and structures. 1906 p. 

Class 41, Electrolysis. 430 p. 

Class 123, Incrustation and corrosion, prevention and removing in steam generators, 
water heating pipes and the like. 2781 p. 

Class 95, Paints and compositions, antifouling. 496 p. 

Class 113, Ships. 1661 p. 

Abridgments of all British patents, arranged by subjects. Much information on pre- 
servative coatings. Classifications for the periods 1617-1855 and 1904-1908 are in prepa- 

Uberziehen des eisens mit anderen metallen. 3 p. 1908. (In Stahl und 
eisen, Gesamt-inhaltsverzeichnis der jahrgange 1 bis 26, 1881-1906. 1908. 
p. 242.) 

Indexes carefully the contents of "Stahl und eiaen," giving rust prevention methods 
under eleven different heads. Includes patents. 


Adie, R. 

On the corrosion of metals. 10 p. 1845. (In Minutes of proceedings 
of the Institution of Civil Engineers, v. 4, p. 323.) 

Shows that saturated salt solutions are a great protection from corrosion. 

Akerman, R. 

Ueber das rosten des eisens. 4,200 w. 1882. (In Stahl und eisen, 
v. 2, p. 417.) 

Considers theory of rusting, especially of protective metal coatings, and of the influ- 
ence of manganese in the rusting of steel. 

Alford, H. Carroll. 

Corrosion of iron and its prevention. 2,200 w. 1901. (In Proceed- 
ings of the St. Louis Railway Club, v. 5, April 12, p. 9.) 

Theory of rust formation and preventive measures. 

1 Reprinted by permission from The Monthly Bulletin for July, 1909, issued by the Car- 
negie Library, Pittsburgh, Pa; with additions and corrections to February, 1910. 



American Society for Testing Materials. 1,800 w. 1906. (In Iron age, 

v. 77, p. 2057.) 

Abstracts of papers at ninth annual meeting of the society; corrosion of tube steel, 
corrosion of wire fencing, electrolysis in structural steel, etc. 

Andes, Louis Edgar. 

Der eisenrost; seine bildung, gefahren und verhutung unter besonderer 
beriicksichtigung der verwendung des eisens als bau- und constructions 
material. 292 p. 111. 1898. 

Treats very fully of rust formation and gives many methods of prevention, chiefly by 
preservative paints. 

Andrews, Thomas. 

Effect of stress on the corrosion of metals. 6,000 w. 111. 1894. (In 
Minutes of proceedings of the Institution of Civil Engineers, v. 118, p. 356.) 

Bauer, 0. 

Uber den einfluss der reihenfolge von zusatzen zum flusseisen auf die 
widerstandsfahigkeit gegen verdiinnte schwefelsaure. 1,000 w. Diag. dr. 
1905. (In Mitteilungen aus dem Koniglichen Material prufungsamt, v. 23, 
p. 292.) 

Considers the influence of aluminium and tungsten on the corrosion of steel in dilute 
sulphuric acid. 

Bradford, W. A. 

Corrosion vs. so-called corrosion. 2,500 w. 4 ill. 1909. (In Metal 

Worker, v. 72, October 2, p. 45.) 

Effect of water and other destructive agents on various kinds of pipe. 

Breuil, Pierre. 

Corrosion tests on copper steels. 400 w. Dr. 1907. (In Journal of 
the Iron and Steel Institute, v. 74, p. 41.) 

Experiments using sulphuric acid as corrosive liquid "make copper steels "rank in value 
with nickel steels in every respect of corrosion." 

Breuil, Pierre. 

Corrosion tests on the [copper] steels as rolled. 1,200 w. 1907. (In 
Journal of the Iron and Steel Institute, v. 74, p. 60.) 

Tests show corrosion to take place much more slowly with rolled steel. 

Brown, A. Crum. 

On the chemical processes involved in the rusting of iron. 1,200 w. 
1888. (In Journal of Iron and Steel Institute, v. 33, p. 129.) 

Discussion, 800 w. 

Rusting caused by action of carbon dioxide and oxygen. 

Bruhl, Paul. 

On the preservation of instruments and machinery in Bengal. 10,000 w. 
1903. (In Engineer, London, v. 96, p. 101, 125, 147.) 

Effect of warm, moist climate, particularly on delicate instruments. 

Buchanan, J. F. 

Corrosion of metals. 2,200 w. 1904. (In Foundry, v. 24, p. 160.) 
Briefly considers relative corrosion of the more useful metals and alloys. 

Burgess, Charles F. 

Corrosion of iron from the electrochemical standpoint. 32 p. Diag. 


Burgess, Charles F. — continued. 

dr. ill. 1908. (In Transactions of the American Electrochemical Society, 
v. 13, p. 17.) 

Discussion, 6 p. 

The same without discussion. (In Electrical review, New York, v. 53, 
p. 371, 436.) 

Considers the influence of strain and of inequalities of temperature on corrosion. 

Burgess, Charles F. & Engle, S. G. 

Observations on the corrosion of iron by acids. 3,000 w. 1906. (In 
Transactions of the American Electrochemical Society, v. 9, p. 199.) 

Effect of normal solutions of sulphuric and hydrochloric acids on electrolytic iron. 

Calvert, F. Crace. 

Experiments on the oxidation of iron. 1,000 w. 1871. (In Chemical 
news, v. 23, p. 98.) 

Paper before the Manchester Literary and Philosophical Society. 

Indicates that "carbonic acid ia the agent which determines the oxidation of iron." 

Corrosion and protection of metal surfaces. 9,500 w. 1897. (In Work- 
shop receipts, v. 5, p. 283.) 

Takes up copper, iron and steel, lead, silver and zinc. 

Corrosion of iron. 4,700 w. 1907. (In Electrochemical and metallurgi- 
cal industry, v. 5, p. 363.) 

Gives in condensed form papers by Walker and Cushman. 

See also editorial, p. 343. 

Corrosion of iron: rusting. 3,500 w. 1907. (In Engineering news, v. 58, 
p. 328.) 

See also editorial, p. 339. 

The same. (In Iron and coal trades review, v. 75, p. 1566.) 
Consideration of paper by Cushman, with reference also to Walker's experiments. 

Cranfield, W. 

Iron; its oxidation, corrosion, protection. 7,000 w. 1909. (In Jour- 
nal of gas lighting, v. 106, p. 443.) 

Paper before the Yorkshire Junior Gas Association. 

Discusses theory, corrosive agents and the preservative values of various coatings. 

Crowe, Edward. 

Corrosion of iron and steel. 2,600 w. Dr. 1909. (In Proceedings of 
the Cleveland Institution of Engineers, session of 1908-09, p. 148.) 

The same, condensed. 1,200 w. (In Iron and coal trades review, v. 78, 
p. 341.) 


Does not enter into the theory of corrosion, but describes special instances and suggests 
causes and methods of prevention. 

Curious case of corrosion. 200 w. 111. 1894. (In Engineering, v. 57, p. 

Illustration of an iron bar in which laminations appear; certain layers badly corroded 
and intermediate ones bright. 


Curry, B. E. 

Electrolytic corrosion of the bronzes. 6,800 w. Diag. 1906. (In 
Journal of physical chemistry, v. 10, p. 474.) 

Determination of effect of corrosion in common salt solutions. 

Curry, B. E. 

Electrolytic corrosion of the bronzes. 25 p. Dr. 1906. (In Trans- 
actions of the American Electrochemical Society, v. 9, p. 173.) 

"It is the purpose of this research to study the corroding effects of some of the more 
common reagents on the copper-tin series of alloys." 

Cushman, Allerton S. 

Corrosion of fence wire. 31 p. 1905. (In United States — Depart- 
ment of agriculture. Farmers' bulletin no. 239.) 

The same, condensed. 3,000 w. (In Iron age, v. 77, p. 207.) 
Investigation undertaken for the mutual advantage of consumer and manufacturer. 
Claims that the uneven distribution of manganese causes part of the trouble, owing to elec- 
trolytic action. 

Cushman, Allerton S. 

Corrosion of iron. 18 p. Dr. Ill, 1907. (In Proceedings of the 
American Society for Testing Materials, v. 7, p. 211.) 

Cushman, Allerton S, 

Corrosion of iron. 35 p. Dr. 111. 1907. (In United States — Office 

of public roads. Bulletin no. 30.) 

The same. (In Chemical news, v. 99, p. 8, 14.) 

The same, condensed. 4,400 w. (In Iron age, v. 80, p. 370.) 

See also editorial, p. 995. 

The same, condensed. 5,500 w. (In Scientific American supplement, 
v. 64, p. 151.) 

Abundant references to original sources. 

Describes and illustrates experiments of the author tending to establish the electrolytic 
theory of corrosion. Author's own belief is that "the whole subject . . is an electrochemi- 
cal one, which can be readily explained under the modern theory of solutions." 

Cushman, Allerton S. 

Corrosion of steel. 4,000 w. 1908. (In Journal of the Franklin In- 
stitute, v. 165, p. 111.) 

Cushman, Allerton S. 

Electrolysis and corrosion. 3,800 w. 1908. (In Proceedings of the 

American Society for Testing Materials, v. 8, p. 238.) 
The same. (In Engineering record, v. 58, p. 349.) 
Discussion of electrolytic corrosion and its physico-chemical explanation. 

Cushman, Allerton S. 

Electrolytic theory of the corrosion of iron. 2,200 w. 1907. (In Trans- 
actions of the American Electrochemical Society, v. 12, p. 403.) 

Discussion, 600 w. 

The same. (In Electrical engineer, London, v. 47, p. 701.) 

Cushman, Allerton S. 

Preservation of iron and steel. 32 p. 6 ill. 1909. (In Journal of the 
Iron and Steel Institute, v. 79, p. 33.) 


Cushman, Allerton S. — continued. 

The same. 11,000 w. 111. 1909. (In Iron and coal trades review, 
v. 78, p. 735.) 

The same. (In Engineering, v. 87, p. 710, 742.) 

The same, slightly condensed. (In Engineer, London, v. 107, p. 537, 

The same, slightly condensed. (In Ironmonger, v. 127, p. 14.) 

Discussion and correspondence 4,500 w, p. 93. 

Consideration of the nature and degree of protection to metala by metallic coatings, 
paints and cement, with applications of the electrochemical theory. 

Cushman, Allerton S. 

Preservation of iron and steel. 40 p. Dr. 111. 1909. (In United 
States — Office of public roads. Bulletin no. 35.) 

Reviews theories of corrosion and methods of protection commonly in use; and shows 
principles that should guide in the selection of the paint pigment to be used as coating. 

Davis, B. 0. E. 

Corrosion of iron. 900 w. 1907. (In Chemical engineer, v. 5, p. 174.) 
Experiments indicate that water and oxygen are the only essentials for corrosion. 

Davis, W. A. 

Rusting of iron. 4,400 w. Dr. 1907. (In Science progress in the 
twentieth century, v. 1, p. 408.) 

Traces development of theories, concluding that rusting is caused by the action of water 
containing traces of acid on iron in the presence of oxygen. 

Dunstan, Wyndharn Rowland, and others. 

Rusting of iron. 26 p. Dr. 1905. (In Journal of the Chemical So- 
ciety, v. 87, pt. 2, p. 1548.) 

Claims proof that for the rusting of iron the presence of oxygen and water only is neces- 
sary, and that "in the ordinary atmospheric rusting of pure iron electrolytic action does not 

English, F. M. 

Lecture on toncan metal. 2,500 w. 1909. (In Metal worker, v. 71, 
June 12, p. 67.) 

The same. (In Industrial world, v. 43, p. 730.) 

Description of a metal with the working properties of soft steel which offers unusual 
resistance to corrosion. Theory of corrosion is taken up. 

Fraser, Alexander G. 

Relative rates of corrosion of acid and basic steel. 16 p. Folding pi. 
1907. (In Journal of the West of Scotland Iron and Steel Institute, v. 14, 
p. 82.) 

Discussion, p. 112. 20 p. 

The same, condensed. 1,600 w. (In Iron age, v. 79, p. 1196.) 

Tests in air, river water, salt water and sulphuric acid. 

Friend, J. Newton. 

Corrosion of iron. 1,500 w. 1909. (In Engineering, v. 88, p. 531.) 

Paper before Iron and Steel Institute. 

Claims that pure water is not sufficiently active to cause the corrosion of pure iron in 
the presence of oxygen alone. 


Friend, J. Newton. 

Rusting of iron. 28 p. Dr. 1908. (In Journal of the Iron and Steel 
Institute, v. 77, p. 5.) 

Experimental results indicate that "the rusting of iron is primarily the result of acid 
attack" rather than of electrochemical nature, and that the hygroscopic nature of rust under- 
lies its corrosive action. 

Garrett, John Henry. 

Action of water on lead; being an inquiry into the cause and mode of 
the action and its prevention. 116 p. 1891. 

Gee, W. W. Haldane. 

Electrolytic corrosion. 6,500 w. Diag. dr. 1908. (In Electrician, 
London, v. 61, p. 66, 98.) 

The same, condensed. 4,500 w. (In Electrical engineering, London, 
v. 3, p. 559.) 

The same, condensed. 1,300 w. (In Electrical review, London, v. 62, 
p. 692.) 

Paper before the Manchester local section of the Institute of Electrical Engineers. 

Notes on conditions under which corrosion takes place. 

Gesellschaft fur Hochdruck-Rohrleitungen. 

Wasserbeschaffenheit und korrosionen. 4,000 w. 111. 1909. (In its 
Rohrleitungen, p. 127.) 

Considers action of water on iron, especially of boiler-waters, and methods of protection. 

Gore, G. 

Influence of ordinary chemical corrosion [on voltaic action]. 5 p., n. d. 
(In his Art of electrolytic separation of metals, p. 65.) 

Considers influence of kind of substance on chemical corrosion, influence of temperature 
on corrosion and includes table showing corrosion series of the metals at 60° F. and 160° F. 

Gore, G. 

On some relations of chemical corrosion to voltaic current. 10 p. 1884. 
(In Proceedings of the Royal Society of London, v. 36, p. 331.) 

"Chief object of this research was to ascertain the amounts of voltaic current produced 
by the chemical corrosion of known weights of various metals in different liquids." 

Gore, G. 

Some relations of heat to voltaic and thermo-electric action of metals 
in electrolytes. 2,800 w. 1883. (In Proceedings of the Royal Society of 
London, v. 36, p. 50.) 

Abstract. Many experiments tended to show that "the most chemically-positive metals 
were usually the most quickly corroded, and the corrosion . . was usually the fastest with 
the most acid solutions . Corrosion was not the cause of pure thermo-electric action of 
metals in liquids." 

Gore, G. 

Some relations of heat to voltaic and thermo-electric action of metals 
in electrolytes. 40 p. 111. 1883. (In Proceedings of the Royal Society of 
London, v. 37, p. 251.) 

Examines "the relations of the thermo-electric to the chemico-electric behaviour of metals 
in electrolytes, and to ordinary chemical corrosion, and the source of voltaic currents." 


Recherches sur l'oxydabilite' relative des fontes, des aciers et des fers 


Gruner — continued. 

doux. 1,000 w. 1883. (In Comptes rendus des stances de I'Acad&nie des 
sciences, v. 96, p. 195.) 

Hambuechen, Carl. 

Experimental study of the corrosion of iron under different conditions. 
40 p. Diag. ill. 1900. (In Bulletin of the University of Wisconsin; en- 
gineering series, v. 2, no. 8.) 

"Bibliography," p. 274. 

Concludes that character and rapidity of corrosion upon physical and chemical prop- 
erties of the object and that "the application of stress to metals causes an increase in chemi- 
cal activity." 

Hamlet, William M. 

On the protection of iron and other metal work. 750 w. 1903. (In 
Chemical news, v. 88, p. 219.) 

Paper before the Royal Society of New South Wales. 

Brief review of theories and recent work. 

Heyn, E. & Bauer, O. 

Uber den angriff des eisens durch wasser und wasserige losungen. 104 p. 
Folding pi. 190S. (In Mitteilungen aus dem Koniglichen Material pru- 
fungsamt, v. 26, p. 1.) 

The same, condensed. 4,800 w. (In Stahl und eisen, v. 28, p. 1564.) 

The same, abstract translation. 400 w. (In Journal of the Iron and 
Steel Institute, v. 78, p. 663.) 

Experiments to determine the cause of corrosion, the necessary active agents, the influ- 
ence of contact of iron with other metals, comparative corrosion of irons of different compo- 
sitions and the comparative attack of various liquids on iron. 

Howe, Henry M. 

Corrosion of iron. 11 p. 1895. (In his Metallurgy of steel, ed. 4, 
v. 1, p. 94.) 

Considers influence of surrounding conditions and of chemical composition, and the 
relative values of protective coatings. 

Howe, Henry M. 

Relative corrosion of wrought iron and steel. 5,600 w. 1895. (In 
Mineral industry, v. 4, p. 429.) 

The same, condensed. 1,600 w. (In Journal of the Iron and Steel In- 
stitute, v. 50, p. 427.) 

Gives results both from laboratory experiments and from actual industrial use. 

Howe, Henry M. 

Relative corrosion of wrought iron and steel. 1,800 w. Dr. 1906. 

(In Proceedings of the American Society for Testing Materials, v. 6, p. 155.) 
Discussion, 7,000 w. 

The same, condensed. 1,300 w. (In American machinist, v. 29, p. 49.) 
The same, condensed. (In Engineering magazine, v. 31, p. 750.) 
The same, condensed. (In Industrial world, v. 40, p. 228.) 
The same, condensed. (In Iron age, v. 77, 2047.) 
Rapid corrosion of steel in many instances may be due to the inferior quality of the steel. 


Howe, Henry M. 

Relative corrosion of wrought iron, soft steel, and nickel steel. 1,500 w. 
Dr. 1900. (In Engineering and mining journal, v. 70, p. 188.) 

Irvine, Robert. 

On the corrosion of iron. 500 w. Dr. 1891. (In Journal of the So- 
ciety of Chemical Industry, v. 10, p. 237.) 

Attributes corrosion largely to galvanic action between dissimilar varieties of iron. 

Knudson, Adolphus A. 

Electrolytic corrosion of the bottom of oil tanks and of other structures. 
4,300 w. Dr. 111. 1908. (In Transactions of the American Electrochemi- 
cal Society, v. 14, p. 189.) 

Discussion, 900 w. 

The same. (In Canadian engineer, v. 19, p. 154.) 

Corrosion of oil-tanks thought to be caused by galvanic action set up by the distribu- 
tion of acid or alkaline electrolytes over the iron surface. 

Koller, Theodore. 

Praktische erfahrungen uber rostschutzmittel und deren bedeutung 
fur die technik. 4,500 w. 1901. (In Glasers annalen fur gewerbe und 
bauwesen, v. 48, p. 161.) 

Considers atmospheric action on metals and composition of many protective coverings. 

Kosmann, B. 

Ueber die corrosion von fluss- und schweisseisen und liber den zerfall 
von legirungen. 2,100 w. 1893. (In Stahl und eisen, v. 13, pt. 1, p. 149.) 

The same, condensed. (In Journal of the Iron and Steel Institute, v. 43, 
p. 399.) 

Difference in resistance to corrosion of ingot and weld iron is held to be due entirely to 
difference in their chemical composition. 

Lee, George B. 

Corrosion of water-jackets of copper blast-furnaces. 500 w. 1907. (In 
Transactions of the American Institute of Mining Engineers, v. 38, p. 877.) 

Brief discussion. Complete discussion will appear in succeeding volume. 

Lincoln, Azariah Thomas. 

Electrolytic corrosion of brasses. 38 p. Diag. ill. 1907. (In Trans- 
actions of the American Electrochemical Society, v. 11, p. 43.) 

Experimental data and conclusions from corrosion products of brasses exposed to solu- 
tions of the more common sodium and ammonium salts. 

Lincoln, Azariah Thomas, & Bartells, G. C. jr. 

Additional experiments on the electrolytic corrosion of brasses. 7 p. 
Diag. 1908. (In Transactions of the American Electrochemical Society, 
v. 13, p. 331.) 

Tests of corrosion in "synthetic sea water." 

Lincoln, Azariah Thomas, and others. 

Electroytic corrosion of brasses. 36 p. Diag. 1907. (In Journal of 
physical chemistry, v. 11, p. 501.) 

ExDcriments on the corrosion of copper-zinc brasses in normal solutions of sodium and 
ammonium salts. 


Lindsay, Charles C. 

On the corrosion and preservation of iron and steel. 32 p. Dr. 1881. 
(In Transactions of the Institution of Engineers and Shipbuilders in Scot- 
land, v. 24, p. 77.) 

The same, condensed. 2,000 w. (In Scientific American supplement, 
v. 12, p. 4570.) 

Consideration of the cause and action of corrosion and methods for its prevention by 
coatings of paint, metal or magnetic oxid. 

McAlpine, William J. 

Corrosion of iron. 1,200 w. 1868. (In Transactions of the American 
Society of Civil Engineers, v. 1, p. 23.) 

Cites instances of preservation of water-pipes, iron submerged in salt water, etc. 

McBride, James. 

Corrosion of steam drums. 8,000 w. 111. 1891, 1894. (In Transac- 
tions of the American Society of Mechanical Engineers, v. 12, p. 518; v. 15, 
p. 1087.) 

Includes lengthy discussion. 

Mallet, Robert. 

First report upon experiments, instituted at the request of the British 
Association, upon the action of sea and river water, whether clear or foul, 
and at various temperatures, upon cast and wrought iron. 59 p. 1839. 
(In Report of the eighth meeting of the British Association for the Advance- 
ment of Science, p. 253.) 

Summary of knowledge of the subject to that time (1839), indicating directions in which 
further investigation was necessary. 

Mallet, Robert. 

Second report upon the action of air and water, whether fresh or salt, 
clear or foul, and at various temperatures, upon cast iron, wrought iron, and 
steel. 88 p. 1840. (In Report of the tenth meeting of the British Asso- 
ciation for the Advancement of Science, p. 221.) 

Experiments on the relative rates of corrosion of different irons in fresh and salt water 
and the protection of iron and steel by coatings of paint or metal. 

Mallet, Robert. 

Third report upon the action of air and water, whether fresh or salt, clear 
or foul, and at various temperatures, upon cast iron, wrought iron, and steel. 
53 p. 1843. (In Report of the thirteenth meeting of the British Associa- 
tion for the Advancement of Science, p. 1.) 

Mason, F. H. 

Rusting of iron. 1,200 w. 1908. (In Mining and scientific press, v. 97, 
p. 329.) 

"Comments on conclusions of Tilden and describes original experiments in which potas- 
sium bichromate was found to retard corrosion. 

Mason, William P. 

Action of water upon metals; tanks, pipes, conduits, boilers, etc. 19 p. 
Dr. 1902. (In his Water supply, p. 394.) 

Data compiled from various sources, giving references. 


Milton, James Tayler. 

Corrosion and decay of metals. 5,000 w. Dr. 1908. (In Mechanical 
engineer, v. 22, p. 530, 580.) 

Lecture before the Institute of Marine Engineers. 

Explanation of theory of corrosion, with examples. Considers corrosion as due to the 
action of a liquid or agent in such a way that the current leaves the metal to enter the cor- 
rosive agent. 

Milton, James Tayler, & Larke, W. J. 

The decay of metals. 20,800 w. 111. 1903. (In Minutes of proceed- 
ings of the Institution of Civil Engineers, v. 154, p. 138.) 

"In this paper the ordinary oxidation of iron and steel will not be dealt with; but a 
deterioration which sometimes occurs in cast iron and other metals, from causes which are 
to some extent obscure, will be considered." 

Considers principally brass, bronzes, Muntz's metal, etc. Well illustrated with photo- 
micrographs, etc. 

Discussion and correspondence. 

Moody, Gerald Tattersall. 

Rusting of iron. 3,300 w. Dr. 1906. (In Journal of the Chemical 
Society, v. 89, pt. 1, p. 720.) 

Challenges Dunstan's conclusions and asserts that carbonic acid must be present, in 
however minute quantity, before rusting begins. 

Mugdan, M. 

Uber das rosten des eisens und seine passivitat. 7,000 w. 1903. (In 
Zeitschrift fur elektrochemie, v. 9, p. 442.) 

The same, abstract. 250 w. (In Journal of the Iron and Steel Insti- 
tute, v. 64, p. 720.) 

Finds that rust forms more readily in solutions of nitrate, chlorid, sulphate, and per- 
chl orate. 

Murray, M. Thornton. 

Rust. 5,000 w. 1908. (In Iron and coal trades review, v. 77, p. 2104.) 
Paper before the Staffordshire Iron and Steel Institute. 
Considers theories and recent developments. 

Murray, M. Thornton. 

Rust; its formation and prevention. 1,500 w. 1908. (In Mechani- 
cal engineer, v. 21, p. 679.) 

The same, with comment. (In Iron and coal trades review, v. 76, p. 2087.) 

Brief review of theories. 

Newman, John. 

Metallic structures; corrosion and fouling and their prevention; a prac- 
tical aid-book to the safety of works in iron and steel, and of ships, and to 
the selection of paints for them. 374 p. 1896. 

Record of author's experience, supplemented by information compiled from many sources. 
Omits electrolysis but considers nearly all other causes of corrosion. 

Parker, William. 

On the relative corrosion of iron and steel. 11,200 w. Dr. 1881. (In 
Journal of the Iron and Steel Institute, v, 18, p. 39.) 

Effects of exposure in air, in sea-water, in marine boilers, etc. 


Pennock, J. D. & Morton, D. A. 

Commercial aqua ammonia; its effect upon iron, its impurities, and 
methods for determining them. 3,500 w. 1902. (In Journal of the Ameri- 
can Chemical Society, v. 24, p. 377.) 

Concludes that concentrated ammonia solutions not only do not rust clean iron but 
prevent its rusting in the presence of corrosive agents. 

Report of committee U on the corrosion of iron and steel. 700 w. 1907. 
(In Proceedings of the American Society for Testing Materials, v. 7, p. 209.) 
Offers suggestions as to the conditions for experiments on the connection between the 
rapidity of solution in acid and natural corrosion. 

Report of committee U on the corrosion of iron and steel. 2,000 w. Diag. 
1908. (In Proceedings of the American Society for Testing Materials, v. 8, 
p. 231.) 

Contains specifications for tests of steel wire and remarks on the value of acid and im- 
mersion tests in determining resistance to corrosion. 

Rhead, E. L. 

Some probable causes of corrosion of copper and brass. 3,000 w. 1909. 
(In Mechanical engineer, v. 24, p. 525.) 

Paper before the Institute of Metals. 

Gives instances of actual corrosion of brass and copper in use, with only suggestions 
as to causes. 

Rhodin, John G. A. 

Corrosion of copper and copper alloys. 9,000 w. Diag. dr. 1907. (In 
Engineer, London, v. 104, p. 53, 75, 108.) 

See also editorial, p. 63. 

Considers alloys as balanced or unbalanced, of which the former have the better mechani- 
cal properties. Regards the unbalanced alloys as having a voltaic combination formed. 

Rhousopoulous, O. A. 

Uber die reinigung und konservierung der antiquitaten. 1,900 w. 1905. 
(In Chemiker zeitung, v. 29, pt. 2, p. 1198.) 

Discusses the corrosion and cleaning of Greek antiquities. 

Richards, Theodore William, & Behr, G. E. jr. 

Electromotive force of iron under varying conditions, and the effect of 
occluded hydrogen. 43 p. Diag. dr. 1906. 

Takes issue (p. 20) with conclusion that corrosion is necessarily increased by stress. 

Rudeloff, M. 

Bericht iiber vergleichende untersuchungen von schweisseisen und flus- 
seisen auf widerstand gegen rosten. 125 p. 111. 1902. (In Mittheilun- 
gen aus den Koniglichen Technischen Versuchsanstalten, v. 20, p. 83.) 

The same, condensed. 4,000 w. (In Stahl und eisen, v. 23, p. 384.) 

The same, abstract. 1,500 w. (In Journal of the Iron and Steel Insti- 
tute, v. 63, p. 713.)- 

Extensive experiments on the relative resistance to corrosion of wrought-iron and steel, 
considering the effect of different conditions and coatings and giving the relative corrosive 
action of various agencies. 

Rudeloff, M. 

Untersuchungen iiber die widerstandsfahigkeit von seildrahten gegen 


Rudeloff, M. — continued. 

rosten. 4,000 w. 111. 1900. (In Mitteilungen aus den Koniglichen Tech- 

nischen Versuchsanstalten, v. 18, p. 107.) 

Results of many tests on the mechanical properties of rusted wire. Numerous tables 
and diagrams. 

Rust and paint researches. 1,200 w. 1909. (In Engineering record, v. 59, 
p. 674.) 

Editorial outline of value of experiments and theories of Cushman and Walker. 

Rusting of iron. 3,500 w. 1908. (In Engineering, v. 85, p. 329.) 
Editorial review of theoretical and experimental work. 

Rusting of iron. 1906-07. (In Nature, v. 74, p. 540, 564, 586, 610; v. 75, 
p. 31, 390, 438, 461.) 

Letters by Friend, Moody, Richardson, Meehan, Dunstan, and Stromeyer concerning 
the theory of rusting and the action of carbon dioxide. 

Rusting of iron and the Rochester, N. Y., steel conduit. 3,500 w. 1909. 
(In Engineering, v. 88, p. 272, 304.) 

Review of work and conclusions of many recent investigators of the cause of corrosion. 

Sang, Alfred. 

Corrosion of iron and steel. 49 p. 1909. (In Proceedings of the En- 
gineers' Society of Western Pennsylvania, v. 24, p. 493.) 

Discussion, 21 p. 

Comprehensive treatment of the subject, tracing the development of the theory of cor- 
rosion and methods for its prevention. References given in full. 

Schleicher, A. & Schultz, G. 

Untersuchungen uber das rosten von eisen. 2,400 w. Diag. 1908. 
(In Stahl und eisen, v. 28, p. 50.) 

Experiments on the differences of potential of metal plates separated from one another 
in water. 

Sebelien, John. 

.Uber die korrosion und die reinigung metallischer antiquitaten. 1,200 w. 
1906. (In Chemiker zeitung, v. 30, pt. 1, p. 56.) 

Refers to work of Axel Krefting in cleaning rusted antiquities by the reducing action 
of nascent hydrogen. 

Sexton, A. Humboldt. 

Corrosion and protection of iron and steel. 11 p. 1900. (In his Chem- 
istry of the materials of engineering, p. 132.) 

Sexton, A. Humboldt. 

Corrosion and protection of metals. 147 p. 1906? 

Treats of corrosion of iron, steel, lead, zinc, copper, etc., and protection both by paints 
and metallic coatings. 

"Useful and generally accurate summary of present knowledge." 

Review. 1,000 w. (In Engineering news, v. 56, p. 184.) 

Speller, Frank N. 

Corrosion of iron and steel. 900 w. 1907. (In Proceedings of the 
Engineers' Society of Western Pennsylvania, v. 22, p. 472.) 

The same. (In Iron age, v. 79, p. 478.) 

Discussion, 1,800 w. 

Gives results of tests showing steel to be superior to wrought-iron. 


Speller, Frank N. 

Puddled iron versus soft steel. 2,200 w. 111. 1905. (In Iron age. 
v. 75, p. 1666, 1881.) 

Claims equal resistance of iron and steel to corrosion, in reply to statements of Roe. 

Spencer, Thomas G. 

Deterioration of lead sheaths of aerial and underground telephone cables, 
4,000 w. HI. 1909. (In Telephony, v. 17, p. 216. 

Abstract. Considers causes of deterioration under six heads: (1) Mechanical injury; 
(2) Chemical decomposition; (3) Electrolysis; (4) Vibration; (5) Lightning; (6) Impuri- 
ties in the lead. Author is chemist to Stromberg Carlson Telephone Mfg. Co., which has 
printed this paper for free distribution to its customers. 

Spurrier, Harry. 

Oil corrosion in cylinders. 1,200 w. 1906. (In Power, v. 26, p. 403.) 
Effect on cast-iron, brass and bronze, of butyric acid, etc. 

Stoughton, Bradley. 

Corrosion of iron and steel. 15 p. 111. 1908. (In his Metallurgy of 
iron and steel, p. 422.) 

"References on corrosion," p. 436. 

Thurston, Robert H. 

Properties of iron and steel. 2,500 w. 1901. (In his Materials of en- 
gineering, ed. 8, revised, pt. 2, p. 328.) 

The same. 1,200 w. 1885. (In his Text-book of the materials of con- 
struction, p. 210.) 

Discusses corrosion, durability and preservation of iron and steel. 

Thwaite, Benjamin Howard. 

Coefficients of corrosion of iron and steel. 400 w. 1880. (In Journal 
of the Iron and Steel Institute, v. 17, p. 667.) 

Abstract of paper showing effects of corrosion under various conditions. Shows danger 
of contact of different metals. 

Tilden, William Augustus. 

Rusting of iron. 3,500 w. Dr. 1908. (In Journal of the Chemical 
Society, v. 93, p. 1356.) 

Shows that carbonic acid is not necessary to corrosion, but that it hastens the action 
and that rusting is due initially to electrolytic action, resulting in the production of ferrous 
hydroxide or carbonate. 

Traube, Moritz. 

Ueber die langsame verbrennung des kupfers bei gegenwart verdiinnter 
schwefelsaure oder einer losung von kohlensaurem ammon. 800 w. 1885. 
(In Berichte der Deutschen Chemischen Gesellschaft, v. 18, pt. 2, p. 1887.) 

Hydrogen peroxide is formed in the slow oxidation of copper in presence of dilute sul- 
phuric acid or ammoninum carbonate. 

Traube, Moritz. 

Ueber die mitwirkung des wassers bei der langsamen verbrennung des 
zinks, bleis, eisens und palladiumwasserstoffs. 3,400 w. 1885. (In Berichte 
der Deutschen Chemischen Gesellschaft, v. 18, pt. 2, p. 1877.) 

Author's theory is that in slow oxidation of metals water is decomposed with formation 
of hydrogen peroxide and that nascent oxygen cannot be formed simultaneously. 


Turner, Thomas. 

Corrosion of iron and steel. 20 p. 1908. (In his Metallurgy of iron, 
ed. 3, p. 413.) 

Review of old and new theories and methods of prevention, with abundant references 
to other works. 

Walker, William H. 

Corrosion of iron and steel, and modern methods of preventing it. 3,000 
w. 1909. (In Engineering record, v. 59, p. 222.) 

Abstract of paper before Boston Society of Arts. 

Considers theory of prevention, and satisfactory conditions attainable. 

Walker, William H. 

Detection of pin-holes in tin plate. 1,200 w. 111. 1909. (In Journal 
of industrial and engineering chemistry, v. 1, p. 295.) 

Plate is covered with a gelatine coating containing potassium ferricyanide. Where 
pin-holes exist, the iron is attacked and blue spots appear in the gelatine coating. 

Walker, William H. 

Electrolytic theory of the corrosion of iron and its applications. 12 p. 
4 111. 1909. (In Journal of the Iron and Steel Institute, v. 79, p. 69. 

The same. 4,000 w. 111. 1909. (In Iron and coal trades review, v. 78, 
p. 749.) 

The same. (In Engineering, v. 87, p. 708.) 

The same. (In Mechanical engineer, v. 23, p. 677.) 

The same, condensed. 1,100 w. (In Ironmonger, v. 127, p. 13.) 

Discussion and correspondence, 4,500 w., p. 93. 

Walker, William H. 

Functions of oxygen in the corrosion of metals. 5,000 w. 1908. (In 
Transactions of the American Electrochemical Society, v. 14, p. 175.) 

The same, condensed. 1,700 w. (In Electrochemical and metallurgical 
industry, v. 7, p. 150.) 

Considers the corrosion of zinc-plated iron wire and of tubes and shells of steam-boilers. 

Walker, William H. 

Protection of iron and steel from corrosion. 6,000 w. 111. 1909. (In 
Engineering magazine, v. 37, p. 198.) 

Treats of the ionic nature of corrosion and the method of observing its progress and 
location by means of indicators. 

Walker, William H. & Dill, Colby. 

Effect of stress upon the electromotive force of soft iron. 4,600 w. Diag. 
dr. 1907. (In Transactions of the American Electrochemical Society, v. 11, 
p. 153.) 

The same condensed. 1,800 w. (In Electrochemical and metallurgical 
industry, v. 5, p. 270.) 

See also editorial, p. 254. 

Experimental results tend to show that differences of potential are not necessarily the 
result of stress. 

Walker, William H. & Dill, Colby. 

Influence of stress upon the corrosion of iron. 3,100 w. Diag. 1907. 
(In Proceedings of the American Society for Testing Materials, v. 7, p. 229.) 

Discussion, 500 w. 


Walker, William H. and others. 

Corrosion of iron and steel. 5,600 w. 1907. (In Journal of the Ameri- 
can Chemical Society, v. 29, p. 1251; v. 30, p. 473.) 

The same. (In Chemical news, v. 97, p. 31, 40.) 

Indicates that iron dissolves in water in the absence of both carbon dioxide and oxy- 
gen, and that on the surface of iron exposed to corrosion there is a marked difference in po- 
tential on different areas. 

Wemlinger, J. R. 

Development and use of steel sheet piling, with some data on the preser- 
vation of steel buried in the ground. 3,300 w. 1909. (In Engineering- 
contracting, v. 31, p. 406.) 

Whitney, W. R. 

Corrosion of iron. 5,000 w. Dr. 1903. (In Journal of the American 
Chemical Society, v. 25, pt. 1, p. 394.) 

Emphasizes fact that the effect of carbonic acid on corrosion is cyclic and that under 
favoring conditions "even a, trace of carbonic acid may dissolve an unlimited quantity of 

Williams, F. H. 

Influence of copper in retarding corrosion of soft steel and wrought iron. 
400 w. 1900. (In Proceedings of the Engineers' Society of Western Penn- 
sylvania, v. 16, p. 231.) 

Indicates that presence of copper retards corrosion. 

Zinnpest, 1,800 w. 111. 1909. (In Dinglers polytechnisches journal, v. 324, 
p. 90.) 

Investigations of Cohen on alteration forms of tin and corrosive. effects. 


This section includes only destructive action of stray currents from street-railways. 
For other articles on electrolytic corrosion see under Corrosion, General and theoretical, and 
Protection, Cement, and concrete. 

Abbott, Arthur Vaughan. 

Electrolysis from railway currents 4,200 w. 111. 1899. (In Cas- 
sier's Magazine [electric railway number], v. 16, p. 371.) 

Popular, well illustrated article. 

Adams, Alton D. 

Prevention of electrolysis. 3,000 w. 1900. (In Municipal engineer- 
ing, v. 18, p. 1.) 

Cause, injurious effects, and urgent need of preventive measures. 

American Gas Institute. 

Committee on electrolysis; conclusions of committee and reprints of 
papers. 35 p. Dr. 1908. 

For previous report see American Gas Light Association. 

Includes conclusions from previous report and reprints of papers by Ganz. 

American Gas Institute. 
Report of committee on electrolysis. 165 p. 1906. (In Proceedings of 
the American Gas Institute, v. 1, p. 761.) 

Same as report of the American Gas Light Association. 


American Gas Light Association. 

Report of committee on electrolysis. 173 p. Dr. 1906. 

"This report is limited to the consideration of direct-current electricity, and is, there- 
fore, contingent upon future developments in the use of alternating-current electricity for 
traction purposes." Introductory note. 

"Committee advances no new theories and can suggest no new remedies. It avoids 
controversial treatment and deals solely with the indisputable facts that have been de- 
veloped by experience. To this end the Committee's endeavor has been to establish authori- 
tatively the universal state of the art of electric traction with reference to electrolysis." 

Report consists of five sections: (1) Theory of electrolytic corrosion; (2) Electrolysis 
in America; (3) Electrolysis in Great Britain; (4) Electrolysis in Germany; (5) Summary 
and conclusions. 

Barbillion, A. 

Forme du potentiel dans les rails servant au retour de courant. 800 w. 
1899. (In L'Eclairage electrique, v. 21, p. 94.) 
Theoretical, using calculus. 

Bates, Putnam A. 

Guarding against electrolysis of underground pipes. 3,300 w. 1906. 
(In Engineering record, v. 54, p. 122.) 

The same. (In Railroad gazette, v. 41, p. 185.) 

The same, condensed. 2,400 w. (In Electrical review, New York, v. 47, 
p. 737.) 

Tests by author show that wrought-iron or lead service pipes are more susceptible than 
cast-iron mains. Deals fully with cause and effect of stray currents and briefly with methods 
of protection. Considers complete metallic circuit to be only satisfactory solution, but men- 
tions several less efficient remedies. 

Beadle, Alec A. 

Electrolytic corrosion in underground pipes. 1,200 w. 1905. (In 
Electrical review, New York, v. 46, p. 19.) 

Effect of stray currents and methods of prevention. 

Bericht des Erdstromkommission [des Deutschen Vereins von Gas-und 
Wasserf achmannern] . 3, 600 w. 1 906 . (In Journal f tir gasbeleuchtung 
und wasserversorgung, v. 49, p. 620.) 

The same, translated. 1,500 w. (In Electrician, v. 57, p. 533.) 

Tables and data showing conditions in many German cities. 

Blake, Lucien I. 

Electrolysis at Kansas City, Kan. 3,600 w. 111. 1899. (In Engineer- 
ing record, v. 40, p. 239.) 

Lengthy report. 

Blake, Lucien I. 

Electrolysis of cast-iron water-mains. 1,300 w. 1899. (In Electrical 
world and engineer, v. 34, p. 934.) 

Bonding of city water and gas mains to prevent electrolysis. 1,200 w. 1908. 
(In Industrial world, v. 82, p. 104.) 

Contains statement of chief of Electric bureau of Philadelphia, describing excellent 
results obtained from bonding of mains in that city. 


Brigden, W. W. 

Electrolysis of water and gas pipes. 4,200 w. 1901. (In Municipal 
engineering, v. 20, p. 287.) 

Plea for double trolley as the only reliable remedy. 

British view of electrolysis. 1,600 w. 1900. (In Engineering record, v. 42, 
p. 41.) 

Gives protective regulations passed by Parliament and by Board of Trade. 

Brophy, William. 

Electrolysis. 3,500 w. 1896. (In Electrical review, New York, v. 28, 
p. 276.) 

Causes of metal corrosion and methods of prevention. 

Brophy, William, & Gray, A. R. 

Insulating couplings for protecting pipe systems from electrolysis. 1,600 
w. 1904. (In American gas light journal, v. 80, p. 91.) 

Two letters favoring their use. 

Brown, Harold P. 

Electrolysis of cast-iron water pipes at Dayton, Ohio. 3,400 w. 1898. 
(In Municipal engineering, v. 16, p. 84.) 

The same, condensed. 2,500 w. (In Street railway journal, v. 14, p. 

General results of more than 2,500 electrical measurements, with practical suggestions 
for remedy and prevention. 

Brown, Harold P. 

Latest method of electrolysis prevention. 2,200 w. 111. 1897. (In 
Electrical engineer, New York, v. 24, p. 350.) 

Brief comparison of European and American systems, and description of system de- 
signed by author. Insulated return conductor is used and in this case made from old rails 
at one-sixth the cost of copper. 

Brown, Harold P. 

Method of permanently protecting underground pipes from electrolytic 
corrosion. 2,800 w. Dr. 1895. (In Street railway review, v. 5, p. 157.) 

Successful method of pipe protection must solve following problems: to keep pipes at 
least one volt negative to rails; to diminish flow of current on pipes; to secure permanent 
non-oxidizable contact of low resistance between pipes and necessary feeder wires. 

Brownell, E. E. 

Electrolysis from facts and figures. 3,500 w. 111. 1900. (In Journal 
of the New England Water Works Association, v. 14, p. 363.) 

Considers trouble entirely due to defective construction of electric railways. Suggests 

Burgess, C. F. 

Boiler corrosion as an electrochemical action. 23 p. Diag. 111. 1909. 
(In Journal of the Western Society of Engineers, v. 14, p. 375.) 

With discussion. 

Research in the chemical engineering laboratories of the University of Wisconsin to 
investigate some of the peculiar conditions of corrosion encountered in operation of locomo- 
tive boilers. 

Claude, M. G. 

Ueber den verlauf der ruckstrome von strassenbahnen und uber ihre 


Claude, M. G. — continued. 

elektrolytischen wirkungen. 2,000 w. Dr. 1902. (In Elektrotechnische 
zeitschrift, v. 23, p. 68.) 

Corrosion of iron. 9,600 w. 1908. (In Transactions of the American 
Electrochemical Society, v. 14, p. 151.) 

General discussion, opened by A. F. Ganz, on the corrosion of underground structure. 
He suggests five questions that must be solved. 

Court decision as to responsibility for damage by electrolysis to gas mains. 
1,300 w. 1901. (In Engineering news, v. 45, p. 12.) 
Holds street-railways responsible for negligence. 

Davis, F. A. W. 

Electrical current. 3,000 w. 111. 1901. (In Journal of the New Eng- 
land Water Works Association, v. 15, p. 225.) 

Illustrated discussion of damages to underground pipe. Claims that patent pipe coatings 
are no protection against electrolysis. 

Davis, F. A. W. 

Electrolysis. 24 p. 111. 1899. 

Appendix, 15 p. 

Paper before the Central States Water Works Association. 

Consideration of extent of damage due to electrolysis, with data from many cities. 

Davis, F. A. W. 

Electrolysis in American cities. 3,400 w. 111. 1899. (In Municipal 
engineering, v. 17, p. 349.) 

Twenty illustrations showing ravages of electrolysis. 

Dawson, Philip. 

Return circuit; electrolytic action. 3,000 w. 111. 1897. (In his Elec- 
tric railways and tramways, p. 36.) 

Considers damages due to and methods of checking electrolysis. 

Deterioration of structural steel by corrosion and electrolysis. 2,800 w. 111. 
1906. (In Architects' and builders' Magazine, v. 8, p. 33.) 

From a paper by James B. Cook before the Memphis Engineering Society. 

Emphasizes especially the dangers of corrosion in buildings of the steel skeleton type. 

Elder, J. 

Untersuchungen des einflusses der vagabundirenden strome elektrischer 
strassenbahnen auf erdmagnetische messungen. 5,300 w. 111. 1900. (In 
Elektrotechnische zeitschrift, v. 21, p. 193.) 

Electric traction troubles. 1,400 w. 1900. (In Nature, v. 63, p. 83.) 
Account of stray current disturbances in England. 

Electrolysis. 2,400 w. Dr. 1905. (In International library of technology, 
Electric railways, §39, p. 18.) 

The same, condensed. 1901. (In same, Electrical engineering, v. 4, §23, 
p. 25.) 

Electrolysis. 5,S00 w. Dr. 111. 1906. (In Journal of the New England 
Water Works Association, v. 20, p. 34.) 

Topical discussion, in which experiences in Cambridge, New Bedford, etc., are given. 


Electrolysis from electric railway return currents. 500 w. 1895. (In 
Electrical world and engineer, v. 27, p. 136.) 

Refers to article in "Pittsburg leader" giving conditions in Pittsburg. Discusses methods 
of prevention. 

Electrolysis in Providence, R. I. 3,000 w. 111. 1900. (In Engineering 
record, v. 42, p. 105.) 

Abstract and comments on report by A. A. Knudaon and others. 

Electrolysis of gas and water mains. 500 w. 1903. (In New international 
encyclopaedia, v. 6, p. 623.) 

Electrolysis of underground pipes in Brooklyn. 1,300 w. 1894. (In Street 
railway journal, v. 10, p. 169.) 

Electrolysis of water mains in Dayton, Ohio. 1,000 w. 1898. (In Engi- 
neering record, v. 38, p. 442.) 

Summary of examinations and reports by Harold P. Brown, E. E. Brownell and others. 

Electrolysis of water mains in Newark, N. J. 2,200 w. 1908. (In En- 
gineering record, v. 58, p. 548.) 

Investigation by an expert of cause and amount of corrosion, with recommendations. 

Elektrolytische zerstorungen durch vagabundierende strome. 1,750 w. 1901 . 
(In Journal fiir gasbeleuchtung und wasserversorgung, v. 44, p. 801, 802.) 
Extracts from "Gas world," giving many methods of dealing with stray currents. 

Ellicott, E. B. 

Protection of water pipe from electrolysis. 7,500 w. 111. 1901. (In 
Journal of the Western Society of Engineers, v. 6, p. 529.) 


Farnham, Isaiah H. 

Destructive effect of electrical currents on subterranean metal pipes. 
9,800 w. 111. 1894. (In Transactions of the American Institute of Elec- 
trical Engineers, v. 11, p. 191.) 


Fernie, F. 

Notes on the corrosion of lead-covered cables. 2,700 w. Diag. 1907. 
(In Electrical engineering, London, v. 1, p. 1037.) 

Considers theory of corrosion by electrolysis, with experimental data and special cases. 

Fleming, J. A. 

Die elektrolytische korrosion von wasser- und gasleitungen durch die 
ruckleitungsstrome der elektrischen bahnen. 3,700 w. Dr. 1898. (In 
Zeitschrift fiir elektrochemie, v. 5, p. 241.) 

Fleming, J. A. 

On the electrolytic corrosion of water and gas pipes by the return cur- 
rents of electric tramways. 6,000 w. Dr. 1898. (In Electrician, v. 41 
p. 689.) 

The same. (In Electrical engineer, London, v. 28, n. s. v. 22, p. 290.) 
Deals with causes and conditions of injurious electrolysis but does not consider remedies. 


Folwell, A. Prescott. 

Pipes and conduits; prevention of deterioration. 1,000 w. 1900. (In 
his Water-supply engineering, p. 527.) 

Considers briefly the injurious effects of stray currents. 

French opinion of electrolysis of pipes. 1,600 w. 1901. (In Engineering 
record, v. 43, p. 515.) 

Claims that no injurious effects will occur where difference of potential between pipes 
and rails is less than one to one and one-half volts. 

Gaines, Richard H. 

Corrosion of the steel water supply conduit at Rochester, N. Y. 10,000 
w. Dr. 111. 1908. (In Engineering news, v. 59, p. 578.) 

See also editorial, p. 593, and letter by A. H. Sabin, p. 673. 

Gaines, Richard H. 

Electrochemical corrosion of the Rochester steel conduit. 41 p. 1908. 
(In Transactions of the American Electrochemical Society, v. 13, p. 55.) 

Discussion, 6 p. 

"Caused by electrolysis, the current for which resulted from chemical processes between 
water solutions in the soil and the metal." 

Gaisberg, S. freiherr v. 

Riickleitungsnetz der elektrischen strassenbahnen in Hamburg. 3,200 
w. 111. 1903. (In Elektrotechnische zeitschrift, v. 24, p. 492.) 

Describes preventive measures. 

Ganz, Albert F. 

Electrolysis. 5,000 w. Dr. 1907. (In Proceedings of the American 
Gas Institute, v. 2, p. 653.) 

Particular attention is paid to current measurements and to the location of the path of 
stray currents. 

Ganz, Albert F. 

Theory of electrolytic corrosion. 1,400 w. 1908. (In Sibley journal of 
engineering, v. 23, p. 10.) 

From a pamphlet by the American Gas Institute, committee on electrolysis. 
Simple presentation of theory of electrolysis and the part played by stray current. 

Gray, John. 

Electrolytic action of return currents in electrical tramways. 2,000 w. 
1896. (In Electrical review, London, v. 38, p. 3.) 

[Haber, F.] 

Dr. Haber's report on electrolysis at Karlsruhe. 4,000 w. Dr. 1906. (In 
Journal of gas lighting, v. 95, p. 578.) 

Haber, F. 

Die vagabundierenden strassenbahnstrome und die durch sie bedingte 
gefahrdung des rohrnetzes in der stadt Karlsruhe i. B. 7,900 w. 111. 1906. 
(In Journal fur gasbeleuchtung und wasserversorgung, v. 49, p. 637.) 

Description of electrical and electrochemical phenomena of stray currents; methods of 
detection and measurement; conditions existing in Karlsruhe. 


Haber, F. & Goldschmidt, F. 

Der anodische angriff des eisens durch vagabundierende strome im erd- 
reich und die passivitat des eisens. 25 p. Dr. 1906. (In Zeitschrift fiir 
elektrochemie, v. 12, p. 49.) 

The same, condensed. 2,100 w. (In Elektrotechnische zeitschrift, v. 28, 
p. 794.) 

The same, condensed. 1,600 w. (In Electrician, v. 57, p. 931.) 

Extensive experimental investigation of corrosion of iron electrodes by electric currents. 

Haber, F. & Goldschmidt, F. 

Effect of earth return current on iron pipes. 1,600 w. Dr. 1906. (In 
Electrical review, London, v. 59, p. 446.) 

See also editorial, p. 442. 

Haskell, John C. 

Electrolysis. 3,000 w. 1896. (In Journal of the New England Water 
Works Association, v. 10, p. 278.) 

Conditions in Lynn, Mass. 


Hayden, J. L. R. 

Alternating-current electrolysis. 8,000 w. 1907. (In Transactions of 
the American Institute of Electrical Engineers, v. 26, pt. 1, p. 231.) 

Discussion, p. 264. 16,000 w. Diag. dr. 

Tests "to determine . . to what extent alternating currents passing between any 
metallic conductor and the ground would produce electrolytic corrosion." 

Herdt, Louis A. 

Electrolysis of Winnipeg water mains. 3,000 w. 111. 1909. (In Cana- 
dian engineer, v. 18, p. 197.) 

Detailed report of extent of damage caused by stray currents, and recommendations for 
remedying the trouble. 

Herrick, Albert B. 

Electrolysis. 900 w. 111. 1901. (In his Electric railway handbook, 
p. 310.) 

Outlines briefly the theory of current distribution and electrolysis. 

Herrick, Albert B. 

Electrolysis. 2,000 w. 1901. (In Street railway review, v. 11, p. 37.) 

History, chemistry and prevention. 

Herrick, Albert B. 

Electrolysis as caused by the railway return current. 7,300 w. Dr. 
1904.. (In Street railway journal, v. 23, p. 516.) 

Presents methods of testing and most successful remedies. 

Herrick, Albert B. 

Electrolysis from the ground return current of street railways. 4,000 w. 
111. 1900. (In Street railway journal, v. 16, p. 472.) 

Causes, detection and remedies. 

Herrick, Albert B. 

Ground current of electric railways, 3,000 w. Dr. 1898. (In Engi- 
neering magazine, v. 15, p. 451.) 

Discussion of the causes and effects of electrolysis. Considers best preventive measures 
to be judicious bonding and intelligent use of feeders. 


Herrick, Albert B. 

Methods of determining the resistance of the railway feeder circuits and 
the ground return losses. 1,300 w. Dr. 1898. (In Street railway journal, 
v. 14, p. 186.) 

Herrick, Albert B. 

Some fallacies regarding electrolysis. 4,400 w. Dr. 1898. (In Street 
railway journal, v. 14, p. 775.) 

Considers physical and electrical conditions necessary to the existence of electrolysis, 
tests, remedies and the attitude of electric railway companies. 

See also editorial, p. 789. 

Hewitt, Charles. 

Return circuits of electric railways, 3,000 w. 1896. (In journal of 
the Franklin Institute, v. 142, p. 51.) 

The same, condensed. (In Electrical world and engineer, v. 28, p. 49.) 

Explains destructive electrolysis and preventive devices. 

Hoopes, Maurice. 

Notes on pipe electrolysis. 1,400 w. Dr. 1895. (In Electrical world 
and engineer, v. 25, p. 603.) 

Makes use of a graphical method, which in the author's opinion presents the various 
phases in a clearer way than any other. 

Humphreys, W. H. 

Electrolysis in water-pipes. 6,500 w. 1902. (In Electrical engineer, 
London, v. 36, n. s. v. 30, p. 189.) 

Favors double wire system, and in its absence advocates connecting negative terminal 
of dynamo to pipe lines. 

Humphreys, W. H. 

History of the electrolysis question. 7,500 w. 1902. (In Journal of 
gas lighting, v. 80, p. 336.) 

Jackson, Dugald, C. 

Corrosion caused by railway return currents. 750 w. 1896. (In Elec- 
trical world and engineer, v. 28, p. 684.) 

Experiments to determine injurious effects on iron and lead. Claims that corrosion 
occurs wherever a current leaves a pipe or cable covering, however small the difference of 
potential may be. 

Jackson, Dugald C. 

Corrosion of iron pipes by the action of electric railway currents. 7,000 
w. 1894. (In Journal of the Association of Engineering Societies, v. 13, 

p. 509.) 


The same, condensed. (In Street railway journal, v. 10, p. 566.) 

Jenkins, E. H. 

Electrolysis. 1,000 w. 1900. (In Street railway review, v. 10, p. 260.) 
Chiefly preventive measures. 

Kallmann, Martin. 

Administrative und sicherheitstechnische regulative fur elektrische stark- 
stromvertheilungsanlagen in den strassen des stadtgebietes Berlin. 10,800 w. 
Dr. 1895. (In Elektrotechnische zeitschrift, v. 16, p. 211.) 


Kallmann, Martin. 

Isolationskontrollsystem zur direkten anzeige von stromentweichungen. 
7,200 w. Dr. 1898. (In Elektrotechnische zeitschrift, v. 19, p. 683.) 

Kallmann, Martin. 

System zur kontrolle der vagabondirenden strome elektrischer bahnen. 
10,000 w. 1899. (In Elektrotechnische zeitschrift, v. 20, p. 163.) 
Deals largely with methods of measurement. 

Kapp, Gisbert. 

Verminderung der vagabundirenden erdstrome bei elektrischen bahnen. 
1,800 w. 1896. (In Elektrotechnische zeitschrift, v. 17, p. 43.) 

Plea for increased number of feeders. 

Kintner, S. M. 

Alternating-current electrolysis? 1,000 w. 111. 1905. (In Electric 
journal, v. 2, p. 668.) 

Records experiments of the electrolysis of wrought-iron and lead pipe buried for one 
year. No appreciable action took place on the iron plates and very slight action on the lead. 

Knudson, Adolphus, A. 

Cause and effect of electrolytic action upon underground piping systems. 
11,200 w. 111. 1901. (In journal of the New England Water Works Asso- 
ciation, v. 15, p. 244.) 

The same condensed. (In Engineering record, v. 43, p. 322.) 

Advocates double trolley system as the only remedy. 

Knudson, Adolphus A. 

Corrosion of metals by electrolysis. 6,000 w. 111. 1903. (In Trans- 
actions of the American Electrochemical Society, v. 3, p. 195.) 

The same. 5,000 w. (In Electricity, v. 24, p. 217, 230.) 

With reference to stray currents and injurious effects. Deals largely with testing, giv- 
ing history of surveys in vicinity of New York City. 

Knudson, Adolphus A. 

Corrosion of metals underground by electrolysis. 4,000 w. 111. 1909. 
(In Journal of the Franklin Institute, v. 168, p. 132. 

Comprehensive, general treatment of causes and effects. 

Knudson, Adolphus A. 

Effect of joint resistance on railway electrolysis. 1,400 w. Dr. 1900. 

(In American electrician, v. 12, p. 119.) 

Shows that electrolysis is not always prevented by the independent return and advo- 
cates double overhead or underground construction as the only perfect method. 

Knudson, Adolphus A. 

Electrolysis in Jersey City. 1,700 w. 111. 1899. (In Engineering 
record, v. 39, p. 233.) 

Report, giving many tests and recommending more frequent tap connections from return 
wire to rails. 

Knudson, Adolphus A. 

Electrolytic corrosion of water-pipes at Bayonne, N. J. 3,000 w. 111. 
1904. (In Engineering news, v. 52, p. 437.) 

Rapid corrosion of steel and lead pipes. 


Knudson, Adolphus A. 

Lead-covered cables a cause of electrolysis upon gas and water pipes. 
2,200 w. 9 Dr. 1 111. 1909. (In Journal of the New England Water- 
Works Association, v. 23, p. 164.) 

Knudson, Adolphus A. 

Remedies for electrolysis. 2,400 w. 111. 1906. (In Cassier's maga- 
zine, v. 30, p. 337.) 

Double trolley is a complete cure, but most of the attempts have been merely palliative. 
The following are considered: (1) More perfect bonds at the joints and improving the track 
return by auxiliary copper feeders; (2) making pipes part of return circuit by bonding to 
rails or direct to power-house negatives; (3) insulating pipes from the ground; (4) insulat- 
ing joints in mains. 

Krohn, Sigvald. 

Ueber messungen der elektrischen strome in den stadtischen rohrleitun- 
gen. 2,000 w. Dr. 1901. (In Elektrotechnische zeitschrift, v. 22, p. 269.) 

Langmuir, Irving. 

Relations between polarization and the corrosion of iron pipes by stray 
currents. 5,200 w. Diag. dr. 1907. (In Stevens Institute indicator, v. 24 f 
p. 348.) 

Experiments with unprotected pipes and with pipes buried in lime and in cement. 

Lars en, Absalon. 

Ueber den elektrolytischen angriff elektrischer strome auf eisenrohren 
in erde und die dabei auftretende polarisation. 1,200 w. 1902. (In Elek- 
trotechnische zeitschrift, v. 23, p. 841. 

Larsen, Absalon. 

Ueber periodische stromwendung als mittel zur verringerung elektro- 
lytischer zerstroungen durch vagabundirende strome. 1,900 w. 111. 1902. 
(In Elektrotechnische zeitschrift, v. 23, p. 868.) 

Gives illustration of gas-pipes which were subjected to tests showing that periodically 
reversing the current tends to diminish the destructive effects of stray currents. 

Leybold, W. 

Destruction of gas-pipes by means of electricity. 3,500 w. 1901. (In 
Electrical engineer, London, v. 24, n. s. 28, p. 372.) 

Liability of reinforced concrete to electrolytic damage. 1,600 w. 1907. 
(In Engineering news, v. 57, p. 328.) 

Editorial consideration of Knudson's experiments, indicating lines for further investi- 

Low, George P. 

Rail bonding and its bearing on electrolytic corrosion. 4,500 w. 111. 
1894. (In Transactions of the American Institute of Electrical Engineers, 

v. 11, p. 857.) 

Considers the elimination of electrolytic corrosion to be dependent on judicious bonding- 

McGowan, H. E. 

Electrolysis; the effect of stray trolley currents. 1,800 w. 111. 1901. 
(In Stevens Institute indicator, v. 18, p. 163.) 


McGowan, H. E. — continued. 

Relief found in coating all w rough t-iron pipe with a paint composed chiefly of coal-tar 
and rubber; also in connecting the pipes to the rails where the former are positive. 

McLeary, Samuel H. 

An interesting case of electrolysis. 800 w. 111. 1906. (In Electrical 
age, v. 37, p. 273.) 

Electric railway in Porto Rico on which stray currents caused very rapid corrosion, es- 
pecially at point of contact between rails and spikes. 

Maury, Dabney H. 

Electrolysis of underground metal structures.' 22 p. 111. 1900. 

Bound with Report of the special committee on electrolysis, American Water Works 

The same, condensed. 5,800 w. (In Engineering news, v. 44, p. 38.) 

The same, condensed. 2,900 w. (In Street railway review, v. 10, p. 433. 

The same, condensed. 1,700 w. (In Engineering record, v. 41, p. 467.) 

Maury, Dabney H. 

Surveys for electrolysis and their results. 6,000 w. 1903. (In Engi- 
neering news, v. 50, p. 74.) 

Purpose of surveys, instruments, methods and results. 

Method of checking electrolysis of gas and water pipes. 700 w. Dr. 1895. 
(In Street railway journal, v. 11, p. 603.) 

Method of Harold P. Brown. Pipes are connected with negative pole of dynamo, con- 
nections with pipe and rail bonds being made of "plastic alloy," said to be a perfect contact 

Michalke, Carl. 

Stray currents from electric railways. 101 p. 111. 1906. 

Bibliography, by translator, p. 91-101. 

"All the calculations in the text are elementary in character, the rigorous mathematical 
treatments being given in the footnotes." Preface. 

Michalke, Carl. 

Die vagabundierenden strome elektrischer bahnen. 85 p. 1906? 

Summarizes present (1906) knowledge of destructive electrolysis and presents in an avail- 
able form much hitherto scattered information from technical periodicals. 

Morse, C. H. 

Electrolysis of water-pipes. 3,500 w. 1893. (In Journal of the New 
England Water Works Association, v. 7, p. 139.) 
Effects and suggested remedies. 

Newbaker, C. A. 

Cure of electrolysis by independent returns. 4,000 w. Dr. 1900. (In 
American electrician, v. 12, p. 72.) 

Prevention of electrolysis; electroless pipe covering on underground piping. 
450 w. 111. 190' 7 . (In American inventor, v. 16, September, p. 3.) 

Problem of electrolysis. 1,600 w. 1899. (In Engineering record, v. 39, 
p. 465.) 

Editorial discussion of the responsibility for damages. 



Zur frage der vagabundirenden strome. 2,700 w. Dr. 1896. (In 
Elektrotechnische zeitschrift, v. 17, p. 34.) 

Theoretical, using calculus. 
Report of the commission of the German gas and water companies for the 
investigation of earth currents. 1,500 w. 1906. (In Electrician, v. 57, 

p. 533.) 

Outline of report on conditions in nine German cities, 1904-06. 

Rhodes, George I. 

Some theoretical notes on the reduction of earth currents from electric 
railway systems by means of negative feeders. 2,500 w. Diag. 1907. 
(In Transactions of the American Institute of Electrical Engineers, v. 26, 

pt. 1, p. 231.) 

Discussion, p. 264. 16,000 w. Diag. dr. 

Rowland, Arthur J. 

Electrolysis by electric railway return currents. 5,000 w. 1895. (In 
Electrical world and engineer, v. 25, p. 127.) 

"Where we have the highest differences of potential [between pipes and rails] the smallest 
current may be flowing and least electrolytic action taking place." 

Rowland, Arthur J. 

Electrolysis from electric railway service. 3,800 w. Dr. 1897. (In 
American electrician, v. 9, p. 156.) 

Proper road construction to avoid harmful effects. 

Sever, George F. 

Electrolysis of underground conductors. 25 p. 1904. (In Transac- 
tions of the International Electrical Congress, St. Louis, v. 3, p. 666.) 

Statistical report. Presents five tables giving following data: (1) Street railway prac- 
tice in U. S. regarding use of return feeders; (2) Recommendations to municipalities by 
city and other engineers; (3) Electrical features of various municipal ordinances; (4) Sum- 
mary of opinions of municipal officers; (5) Summary of expert opinion concerning electrolysis. 


Sheldon, Samuel. 

Conditions of electrolytic corrosion in Brooklyn. 1,600 w. 1900. (In 
Transactions of the American Institute of Electrical Engineers, v. 17, p. 335.) 

Discussion, 1,300 w. 

The same, without discussion. (In Electrical world and engineer, v. 35, 
p. 868.) 

The same, without discussion. (In Street railway journal, v. 16, p. 514.) 

Siebel, F. P. 

Electrolysis of iron pipe. The pitting of iron, particularly pipe, its 
causes and possible preventives. 3,000 w. 4 ill. 1909. (In Ice and re- 
frigeration, v. 37, p. 116.) 

Chemical and bacteriological examination of water and of pipe exposed therein. Favors 
wrought-iron pipe, and recommends city ordinances for prevention of stray currents. 

Spang, H. W. 

Electrolysis; general electrical and lightning protection. 2,500 w. Dr. 
ill. 1906. (In American gas light journal, v. 84, p. 801.) 


Spang, H. W. 

Unscientific electric engineering; destruction of underground pipes, etc. 
2,500 w. 1904. (In American gas light journal, v. 80, p. 85.) 

Stearns, F. P. 

Electrolysis on the metropolitan water works. 1,600 w. 1905. (In 
Engineering record, v. 52, p. 120.) 
Abstract of chief engineer's report. 

Stone, Charles A. & Forbes, H. C. 

Electrolysis of water pipes. 10,000 w. Dr. 1894. (In Journal of the 
New England Water Works Association, v. 9, p. 25.) 

Conditions necessary to destructive action and how trouble may be recognized. Con- 
siders all known means of prevention, classifying them as complete remedies, partial remedies, 
and useless schemes. 


Storrs, H. A. 

Electrolysis. 4,500 w. Dr. 1895. (In Journal of the New England 
Water Works Association, v. 10, p. 33.) 

Considers remedies where electric roads are already^ in operation; preventive measures 
where electric roads are to be installed; legal aspects. 

Strecker, K. 

Ueber die ausbreitung starker elektrischer strome in der erdoberflache. 
7,000 w. Dr. 1896. (In Elektrotechnische zeitschrift, v. 17, p. 106.) 

For purposes of wireless telegraphy. 

Swinburne, James. 

Electrolysis of gas mains. 3,000 w. Dr. 1902. (In Electrician, Lon- 
don, v. 49, p. 642, 681.) 

Causes, effects, and precautions to minimize injurious effects. 

Teichmuller, J. 

Ueber methoden zur verringerung der gefahren vagabundirender strome 
bei elektrischen bahnen, insbesondere die Kapp'sche methode der schienen- 
entlastung. 2,000 w. Dr. 1900. (In Elektrotechnische zeitschrift, v. 21, 
p. 436.) 

Method making rails the neutral wire of three-wire system. 

Ueber die elektrolytische zerstorung der rohrleitungen durch vagabundirende 
strome. 9,500 w. Dr. 1900. (In Journal fur gasbeleuchtung und wasser- 
versorgung, v. 43, p. 265, 285, 310.) 

Ulbricht, R. 

Diskussion uber die frage der storungen wissenschaftlicher institute 
durch elektrische bahnen. 40,000 w. 111. 1895. (In Elektrotechnische 
zeitschrift, v. 16, p. 417, 443.) 

Paper and lengthy discussion, giving theory of stray currents and conditions causing 
disturbance of physical laboratories. Many diagrams. 

Ulbricht, R. 

Gefahrdung von metallrohrleitungen durch elektrische bahnen. 2,000 w. 
111. 1902. (In Elektrotechnische zeitschrift, v. 23, p. 720.) 


Ulbricht, R. 

Zur frage der gefahrdung von metallrohrleitungen durch elektrische 
bahnen, 3,000 w. Dr. 1902. (In Elektrotechnische zeitschrift, v. 23, 

p. 212.) 

Mathematical treatment of the damage done by stray currents. 

Vail, J. H. 

Importance of complete metallic circuit electric railways. 5,600 w. 111. 
1894. (In Proceedings of the National Electric Light Association, v. 17, 
p. 102.) 

Advocates proper track bonding, etc. 

The same, without discussion. 3,100 w. (In Street railway journal, v. 10, 
p. 199.) 

Vorschlag der erdstrorn-kommission des Verbandes Deutscher Elektrotech- 
niker fiir leitsatze betreffend den schutz metallischer rohrleitungen gegen 
erdstrome, elektrischer bahnen, 1,500 w. 1903. (In Elektrotechnische 
zeitschrift, v. 24, p. 376.) 


Ueber die einwirkung der bodenbeschafTenheit auf gusseiserne rohren. 
2,600 w. 1893. (In Journal fur gasbeleuchtung und wasserversorgung, 
v. 36, p. 552.) 

West, Jul. H. 

Bericht der kommission fiir die untersuchung der erdruckstrome elek- 
trischer bahnen. 1,900 w. 1900. (Im Elektrotechnische zeitschrift, v. 21, 
p. 706.) 

Of 90 German cities having electric roads only two or three report corrosion which can 
be ascribed to earth return currents. 

Wynkoop, Hubert S. 

Destructive effects of vagrant electricity. 2,000 w. 111. 1900. (In 
Popular science monthly, v. 56, p. 357.) 

Non-technical article showing destructive effects and suggesting remedies. 

Ziehl, Emil. 

Verminderung der erdstrome bei mit wechselstrom betriebenen ueber- 
landbahnen mit schienenrtickleitung. 2,800 w. Dr. 1902. (In Elektro- 
technische zeitschrift, v. 23, p. 145.) 

Andrews, Thomas. 

Corrosion of metals during long exposure in sea-water. 7,500 w. 111. 
1885. (In Minutes of proceedings of the Institution of Civil Engineers, 
v. 82, p. 281.) 

Andrews, Thomas. 

On galvanic action between wrought-iron, cast metals and various steels 
during long exposure in sea-water. 5,000 w. 111. 1884. (In Minutes of 
proceedings of the Institution of Civil Engineers, v. 77, p. 323.) 


Anti-fouling compounds. 2,500 w. 1904. (In Scientific American supple- 
ment, v. 58, p. 23956.) 

Translated from "Farber-zeitung." Deals with preparations for submarine use. 

Bell, Benjamin. 

On zinc sheathing for ships. 3,400 w. 1869. (In Transactions of the 
Institution of Naval Architects, v. 10, p. 174.) 

Cohen, Ernst. 

On the corrosion of condenser tubes and sea-water conductors. 12 p. PI. 

1902. (In Transactions of the Institution of Naval Architects, v. 44, p. 


Describes action of sea-water on brass, copper, and tin-plated condenser tubes. 

Coles, Cowper P. 

On the preservation of iron ships' bottoms and the means of keeping 
them clean. 3,400 w. 1866. (In Transactions of the Institution of Naval 
Architects, v. 7, p. 155.) 

Proposes coating the ships' bottoms with cement to prevent corrosion. 

Davy, Humphrey. 

On the corrosion of copper sheeting by sea-water and on methods of 
preventing this effect; and on their application to ships of war and other 
ships. 2,300 w. 1824. (In Philosophical transactions of the Royal So- 
ciety of London, v. 114, p. 151.) 

Considers corrosion of copper an electrochemical action and prevents it by zinc plates 
in electrical connection with the copper. 

Decay of metallic sheathing under water. 900 w. 1907. (In Engineer, 
London, v. 103, p. 559.) 

Abstract of report of the public analyst, New South Wales, concerning the causes of 
failure of modern Muntz metal. 

See also letter from G. A. Muntz, p. 598. 

Diegel, H. 

Einiges iiber die korrosion der metalle im seewasser. 95 p. Folding pi. 

1903. (In Verhandlungen des Vereins zur Beforderung des Gewerbfleisses, 
v. 82, p. 91.) 

The same, condensed. 4,500 w. (In Zeitschrift des Vereines Deutscher 
Ingenieure, v. 47, p. 1122.) 

The same, abstract. 400 w. (In Journal of the Iron and Steel Institute, 
v. 65, p. 677.) 

Extensive experiments lead author to claim that impure metals do not corrode in salt 
water faster than pure metals. Foreign elements introduced were phosphorus and nickel. 

Diegel, H. 

Das verhalten einiger metalle in seewasser. 12,000 w. 111. 1904. (In 
Stahl und eisen, v. 24, pt. 1, p. 567, 629.) 
Considers alloys of copper, nickel, and iron. 

Farquharson, J. 

Corrosive effects of steel on iron in salt water. 4,800 w. 1882. (In 
Transactions of the Institution of Naval Architects, v. 23, p. 143.) 
Experiments indicating that contact of iron and steel should be avoided. 


Ferguson, W. B. 

Two instances of unusual repairs to vessels. 3,300 w. PI. 1907. (In 
Transactions of the Society of Naval Architects and Marine Engineers, v. 15, 
p. 179.) 

With discussion. 

Discussion deals with the serious corrosion of iron and steel bolts used for fastening sheath- 
ing, and the advantages of brass composition bolts. Compares merits of copper, zinc, and 
galvanized-iron sheathing. 

Grantham, John. 

On copper sheathing for iron ships, considered at the present stage of 
our experience. 3,000 w. 1869. (In Transactions of the Institution of 
Naval Architects, v. 10, p. 174.) 

Hay, W. J. 

On the protection of iron ships from oxidation and fouling. 7,000 w. 
1863. (In Transactions of the Institution of Naval Architects, v. 4, p. 149.) 
Describes satisfactory use of author's copper oxide paint. 

Isherwood, B. F. 

Experiments made by Mr. Uthemann to discover a process for prevent- 
ing the corrosion of copper and brass by sea-water under the conditions 
found in the surface-condensers of marine steam-engines. 7,600 w. Dr. 
1907. (In Journal of the American Society of Naval Engineers, v. 19, p. 

Johnstone, George. 

Notes on the serious deterioration of steel vessels from the effects of 
corrosion. 7 p. 1901. (In Transactions of the Institution of Engineers 
and Shipbuilders in Scotland, v. 45, p. 71.) 

Discussion, 28 p. 

Especially on corrosion of internal parts of vessels and on vessels in the tropics. 

King, Frank B. 

Notes on the corrosion of a cast steel propeller blade. 1,000 w. 1894. 
(In Transactions of the American Society of Mechanical Engineers, v. 15, 
p. 961.) 

Lewes, Vivian B. 

On the corrosion and protection of iron and steel ships. 7 p. 1887. 
(In Transactions of the Institution of Naval Architects, v. 28, p. 247.) 

Discussion, 13 p. 

Considers the best preservative composition a gum dissolved in a volatile solvent, mixed 
with finely divided zinc. 


Note sur l'alteration des m<Haux par l'eau de mer. 2,200 w. 111. 1897. 
(In Annales des ponts et chaussees, memoires, ser. 7, v. 14, 3e trimestre, 
p. 338.) 

The same, condensed. 900 w. (In Engineering news, v. 39, p. 85.) 
Describes condition of metals after exposure to the action of sea-water for several hun- 
dred years. 


Pallet, Robert. 

On the corrosion and fouling of iron ships. 60 p. 1872. (In Trans- 
itions of the Institution of Naval Architects, v. 13, p. 90.) 

Discussion, 10 p. 

"Catalogue of British patent inventions," p. 135, 17 p. 

tting of propeller blades. 900 w. 1908. (In Engineer, London, v. 105, 
Editorial discussion. 

itting of propeller blades. 1,300 w. 1909. (In Engineer, London, v. 107, 

Editorial discussion, recommending the use of a harder alloy. 

Mt, J. W. 

Corrosion of steel rails by sea water in tropical countries. 400 w. Dr. 
101. (In Engineering news, v. 46, p. 394.) 

hoades, Henry E. 

Corrosion of propeller shaft, U. S. S. Rhode Island. 1,200 w. Fold- 
g pi. 1907. (In Journal of the American Society of Naval Engineers,. 
19, p. 379.) 

The same, slightly condensed. 1,000 w. (In Mechanical engineer, v. 20, 

ibin, Alvah Horton. 

Experiments on the protection of steel and aluminum exposed to sea 
ater. 8,000 w. 1896. (In Transactions of the American Society of Civil 
agineers, v. 36, p. 483.) 

Condition of plates with various preservative coatings after six months' immersion in 

Discussion and correspondence. 

ibin, Alvah Horton. 

Experiments on the protection of steel and aluminum exposed to water. 
000 w. 1899. (In Transactions of the American Society of Civil Engineers, 
43, p. 444.) 

Continuation of above experiments. 


The same, condensed. (In Engineering news, v. 40, p. 54.) 

lerman, Edward C. 

Experiments on the corrosion of steel in contact with bronze in sea- 
iter. 700 w. Diag. dr. 1909. (In Engineering news, v. 61, p. 292.) 

See also editorial, p. 292. 

The same. (In Mechanical engineer, v. 23, p. 472.) 
Results show little loss of steel when protected by zinc strips. 

einmetz, Joseph A. 

Note on corrosion of aluminum. 500 w. 111. 1903. (In Transactions 
the American Electrochemical Society, v. 3, p. 217.) 

Corrosion in free-board plates of nickel-aluminium from a dismantled yacht. 

"The writer's view is that . . . [the corrosionl was intensified by the use of steel rivets 
contact with aluminum plates, uniting them to bronze plates, the whole immersed in salt 
.ter and subject to conditions of severe atmospheric changes and exceeding humidity." 


Thomson, William. 

Notes on the oxidation and corrosion of iron and steel. 2,400 w. 1894. 
(In Journal of the Society of Chemical Industry, v. 13, p. 118.) 

Experiments on the value of protective coatings and on the action of caustic soda, etc., 
on iron and steel, with special reference to structures exposed to the spray of salt water. 


La corrosion du cuivre par l'eau de mer; moyens de la prevenir. 2,000 
w. 1905. (In Le Genie civil, v. 47, p. 344.) 


Corrosion of copper in sea water. 2,800 w. 111. 1905. (In Engineer, 
London, v. 99, p. 442.) 

The same. (In Journal of the American Society of Naval Engineers, 
v. 17, p. 467.) 

Experiment has failed to produce any alloy which will replace copper for condenser tubes, 
etc. The paper describes successful attempts to overcome the chemical action of sea-water 
by electrolytic action between the copper of tubes and the iron of spirals enclosing them. 


Schutz des kupfers und seiner legierungen gegen die zerstorung durch 
seewasser. 2,000 w. 1905. (In Zeitschrift des Vereines Deutscher Inge- 
nieure, v. 49, pt. 1, p. 733.) 

An attempt to determine the best alloys for marine condenser tubes. 

Younger, A. Scott. 

Corrosion and failure of propeller shafts. 5,500 w. Folding pi. 1900. 
(In Transactions of the Institution of Naval Architects, v. 42, p. 263.) 


Plans suggested as a remedy: 

1. Increased diameter of shaft. 

2. (a) Re-introduction of outer bearing. 
(&) Minimum weight for propeller. 
(c) Increased water ballast. 

3. Abolish brass liners and run shaft on white metal with oil or tallow surrounding it. 


[Brass corrosion by sugar vapor.] 400 w. 1888. (In American Society of 
Mechanical Engineers, v. 9, p. 429.) 
Remedy suggested is a coating of paraffin. 

Dagron, James G. 

Protection from corrosion of iron-work used as covering for railroad 
tunnels. 700 w. Dr. 1892. (In Transactions of the American Society of 
Civil Engineers, v. 27, p. 324.) 


Method for protection consisted of "hermetically sealing the iron-work from the access 
of steam and locomotive gases by a flat arch of hollow fire-brick tiles." 

Dudley, William L. 

Effect of coal gas on the corrosion of wrought iron pipe buried in the 
earth. 1,100 w. 1908. (In Journal of the American Chemical Society, 
v. 30, p. 247.) 

Experiments in earth saturated with coal gas, indicating that amount of corrosion is 
determined by the chlorine content in the earth. 


Friend, J. Newton. 

Action of air and steam on pure iron. 2,000 w. 1909. (In Engineering, 

v, 88, p. 526.) 

Paper before Iron and Steel Institute. 

Concludes that pure iron heated in steam becomes tarnished, and that the action takes 
place in two stages: first, the dissociation of the steam, second, the union of the dissociated 
oxygen with the iron and the liberation of free hydrogen. 

Kent, William. 

Rapid corrosion of iron in railway bridges. 2,000 w. 1875. (In Jour- 
nal of the Franklin Institute, v. 99, p. 437.) 

Considers sulphurous acid one of the most active corrosive agents. 

Protecting low overhead structures from gases and blasts of locomotives. 
1,600 w. 1904. (In Engineering news, v. 52, p. 371.) 
Report of a committee, presenting opinions from many sources. 

Thorner, Will. 

Ueber ursache und verhinderung der starken oxydation des eisernen 
eisenbahn-oberbaues im tunnel. 15 p. Dr. 1889. (In Stahl und eisen, 
v. 9, p. 821.) 

Recommends covering the rails with a, tar coating and covering the ground and sides 
with limestone or milk of lime. 


Aynsley, C. Murray. 

On the preservation of boilers. 9,000 w. 1880. (In Van Nostrand's 
engineering magazine, v. 23, p. 395.) 

Discussion of protective coatings for boilers, action of feed-waters and their treatment. 

Baucke, H. 

Beitrag zur metallographie des flusseisens. 1,600 w. III. 1899. (In 
Baumaterialienkunde, v. 4, p. 349.) 

The same, in French, (In Baumaterialienkunde, v. 4, p. 349.) 

The same. (In Stahl und eisen, v. 20, pt. 1, p. 260.) 

The same, condensed translation. 600 w. (In Journal of the Iron and 
Steel Institute, v. 57, p. 427.) 

Microscopic examination of badly corroded boiler tubes. 

Boiler corrosion [and] Boiler incrustation [and] Boiler compositions. 7 p. 
1909. (In Spons' Workshop receipts for manufacturers and scientific ama- 
teurs, revised ed., v. 1, p. 145.) 

Boiler incrustations. 9,500 w. 1896. (In Workshop receipts, v. 2, p. 42.) 

Cary, Albert A. 

Cure for corrosion and scale from boiler waters. 7,200 w. 111. 1897. 
(In Engineering magazine, v. 12, p. 959.) 

First of a series of articles. Treats of pitting, grooving and general corrosion, theories in 
explanation, means of prevention. 

Christie, William Wallace. 

Corrosion. 35 p. 111. 1906. (In his Boiler-waters, p. 68.) 

Treats rather fully the corrosion of boilers, the action of different feed-waters and the 

dangers of pitting. 


Churchill, W. W. 

Preservation of surface condenser tubes in plants using salt or contami- 
nated water circulation. 3,000 w. 1906. (In Science, v. 47, p. 405.) 

The same, (In Power, v. 26, p. 598.) 

Paper before the American Association for the Advancement of Science. 

Considers the prevention of electrolytic corrosion. Author presents Oliver J. Lodge's 
views on electrolytic conduction and Faraday's laws of electrolysis as a basis for his views. 

Corrosion and incrustation; a source of boiler explosions. 2,400 w. 111. 
1908. (In Boiler maker, v. 8, p. 279.) 

Corrosion of condenser tubes. 1,000 w. 111. 1909. (In Mechanical en- 
gineer, v. 24, p. 504.) 

Illustrates the appearance and location of the corrosion, and finds it due to stray cur- 
rents passing through the condenser. 

Cribb, Cecil H. & Arnaud, F. W. F. 

On the action of slightly alkaline waters on iron. 5,600 w. 111. 1905. 
(In Analyst, v. 30, p. 225.) 

The same, condensed. (In Engineering, v. 81, p. 32.) 

Experiments indicate increased corrosion in alkaline solution, though less rapid in boilers 
than under ordinary conditions. 

Ford, John D. 

Corrosion of boiler tubes. 5,200 w. 111. 1904. (In Journal of the 
American Society of Naval Engineers, v. 16, p. 529.) 

The same, condensed. 1,000 w. (In Iron and steel magazine, v. 10, 
p. 349.) 

Extensive experiments made for the United States navy department at the laboratory 
of the National Tube Co., McKeesport, to determine relative corrodibility of lap-welded 
Bessemer steel, lap-welded iron, seamless cold-drawn steel and seamless hot-drawn steel boiler 

Fremont, Ch. & Osmond, F. 

Les sillons de corrosion dans les toles de chaudieres a vapeur. 4,200 w. 
111. 1905. (In Revue de mStallurgie, v. 2, p. 775.) 

Investigation of cause of lines of corrosion in boiler plates. 

Gibbons, W. H. 

Physical reasons for rapid corrosion of steel boiler-tubes. 800 w. 111. 
1895. (In American engineer and railroad journal, v. 69, p. 157.) 

Considers difference in corrodibility of tubes made from the "top" and the "bottom" 
of an ingot, with its application to the relative corrosion of steel and charcoal iron. 

Greth, J. C. William. 

Chemical aspect of impurities in steam boilers. 3,600 w. 1909. (In 
Industrial world, v. 43, p. 1572.) 

Considers the effect of the different impurities in boiler waters and their corrosive influ- 

Greth, J. C. William. 

Impurities causing scale and corrosion. 4,200 w. 1909. (In Boiler 
maker, v. 9, p. 115.) 

Paper before the American Institute of Chemical Engineers. 

Discusses action on boilers of salts and acids, the formation of scale and methods of soften- 
ing the water. 


Grossmaniij J. 

Corrosive action of magnesian and other waters on steam boilers. 2,000 
w. Dr. 1909. (In Engineer, London, v. 107, p. 262.) 

Experiments tend to show that magnesian waters containing in solution also calcium 
carbonate are not exceptionally corrosive, and that after softening such waters may be more 
corrosive than in their natural state. 

Hopkins, Albert A. ed. 

Incrustation of boilers. 600 w. 1901. (In the Scientific American 
cyclopedia of receipts, ed. 2, p. 266.) 

Gives receipts for various preventives and remedies. 

Huntly, G. Nevill. 

Sulphur as a cause of corrosion in steel. 1,600 w. 1909. (In Journal 
of the Society of Chemical Industry, v. 28, p. 339.) 

Considers action resulting from the solution of the sulphur present as sulphide in the 
boiler metal. 

Kirtley, William. 

On the corrosion of locomotive boilers and the means of prevention. 
8,800 w. 111. 1866. (In Proceedings of the Institution of Mechanical 
Engineers, v. 17, p. 56.) 

Considers corrosion due both to chemical action of water and mechanical action of strain. 
The trouble may be obviated by removing one of these causes, i.e., by proper boiler design, 
eliminating springing at joints, etc. 

La Coux, H. de. 

Eaux corrosives et incrusto-corrosives dans les generateurs de vapeur. 
14,500 w. 1899. (In Le Genie civil, v. 36, p. 117, 139, 149.) 
Substances causing corrosion and means of prevention. 


Sur les causes d'alteration int^rieure des chaudieres a vapeur. 600 w. 
1880. (In Comptes rendus des stances de l'Academie des sciences, v. 91, 
p. 217.) 

Chief cause is oxidation due to oxygen set free during decomposition of water. 

M'Namara, R. E. 

Incrustation and corrosion; causes and prevention in steam boilers and 
pressure vessels of the varied industries. 2,600 w. Dr. ill. 1909. (In 
Boiler maker, v. 9, p. 63.) 

Considers the corrosive ingredients common in boiler waters. 

M'Namara, R. E. 

Incrustation and corrosion; causes and prevention in steam boilers and 
pressure vessels of the varied industries. 3,300 w. 111. 1909. (In Boiler 
maker, v. 9, p. 85.) 

Considers especially the attack of corrosive liquids in the packing-house and paper- 
making industries. 

Norris, W. J. 

Corrosion in steam boilers. 5,000 w. 1882. (In Transactions of the 
Institution of Naval Architects, v. 23, p. 151.) 

Disagrees with theories of galvanic action; production of hydrochloric acid in boiler 
by decomposition of water; action of fatty acids produced by decomposition of lubricants, 
etc. Ascribes all boiler corrosion to simple oxidation by presence in water of free oxygen 
derived from the air. 


Palmer, J. Edward. 

Corrosion of steel boiler tubes on vessels fitted with turbine engines. 
1,000 w. 1907. (In Journal of the American Society of Naval Engineers, 
v. 19, p. 54.) 

The same. (In Engineering news, v. 57, p. 426.) 

Corrosion caused by copper deposits in the tubes, carried over by the steam from the 
bronze turbine blades. 

Paul, James Hugh. 

Corrosion in steam boilers. 20 p. 111. 1891. (In Transactions of the 
Society of Engineers, v. 31, p. 147.) 

Chemical properties of iron; manufacture of boiler plates; corrosive natural waters; 
artesian well waters; corrosion in marine boilers; action of zinc. 


Phillips, David. 

On the comparative endurance of iron and mild steel when exposed to 
corrosive influences. 25 p. Dr. 1881 . (In Minutes of proceedings of 
the Institution of Civil Engineers, v. 65, p. 73.) 

Discussion, 40 p. 

Considers admiralty tests and tests by the author indicating greater resistance to cor- 
rosion of iron. 

Rinne, H. 

Kesselmaterial und kesselkorrosionen. 5,000 w. Dr. 1904. (In Stahl 
und eisen, v. 24, pt. 1, p. 82.) 

Considers the corrosion of boiler tubes of different qualities of iron and the influence 
of other conditions. 

Rowan, F. J. 

On boiler incrustation and corrosion. 2,000 w. 1876. (In Report of 
the 46th meeting of the British Association for the Advancement of Science, 
p. 229.) 

Reviews knowledge and experiments to date (1876) on the action and prevention of 

Scaife (William B.) & Sons Co. 

Corrosion. 900 w. Ill, 1907. (In their Water purification for all 
purposes, p. 47.) 

Considers corrosive action of different boiler feed-waters. 

Sexton, A. Homboldt. 

Study of the corrosion of condenser tubes. 4,500 w. 111. 1905. In 
Engineering magazine, v. 30, p. 211.) 

The same. (In Journal of the American Society of Naval Engineers, 
v. 17, p. 1150.) 

Causes and prevention. Considers only brass tubes. 

Sickles, E. C. 

Corrosion of condenser tubes. 3,000 w. Diag. dr. ill. 1908. (In 
Power, v. 28, p. 349.) 

Influence on the choice of condenser equipment for electric power plants. 


Summerfield, R. D. 

Prevention of scale and corrosion in boilers. 2,400 w. 1900. (In 
Electrical engineer, London, v. 32, p. 91.) 

Need of water analysis, treatment of acid waters, etc. 

Wakeman, W. H. 

Grooving, pitting, and corrosion in steam boilers. 1,800 w. 1906. (In 
Industrial world, v. 40, p. 869.) 

Treats briefly of water softening, boiler compounds, galvanic action and action of acid 
in feed-water. 

Worthington, Walter F. 

Corrosion of boiler tubes in the United States navy. 5,000 w. PI. 
1900. (In Journal of the American Society of Naval Engineers, v. 12, p. 589.) 

Causes of corrosion are discussed, especially from the action of the different impurities 
in feed-water. 

Yarrow, A. F. 

Some experiments having reference to the durability of water-tube boilers. 
2,600 w. (In Transactions of the Institution of Naval Architects, v. 41, 
p. 333.) 

' Discussion. 

From experimental results assumes that both from acid corrosion and from the action 
of steam nickel steel boiler-tubes will be far more durable than those of mild steel. 


Brackett, Dexter. 

Water pipes on metropolitan water works. 2,000 w. 1899. (In Jour- 
nal of the New England Water Works Association, v. 13, p. 325.) 

Deals briefly with protection of steel pipe from corrosion. Favors ordinary tar coating, 
carefully applied, for outside, and paraffin or vulcanite for inside of pipes. 

Committee report on relative corrosion of wrought iron and steel pipes. 
1,600 w. Dr. ill. 1909. (In Plumbers' trade journal, v. 14, p. 214.) 

The same, slightly condensed. 1,300 w. (In Heating and ventilating 
magazine, v. 6, p. 12.) 

Report to American Society of Heating and Ventilating Engineers. 

Tests indicate steel pipe of good quality to be as durable as wrought-iron pipe. 

[Corrosion of iron water pipe.] 900 w. 1897. (In Journal of the New Eng- 
land Water Works Association, v. 11, p. 222.) 

Discussion, showing that pipe in which water is standing is less liable to corrosion than 
that through which water is flowing and thus affording a fresh supply of oxygen. 

Corrosion of pipe in coal mines. 450 w. 111. 1906. (In Iron age, v. 78, 
p. 80.) 

Results showing superiority of " Spellerized " steel pipes in the sulphur water of coal 

[Corrosion of water pipe.] 3,000 w. 1884. (In Transactions of the New 
England Water Works Association, 1884, p. 41.) 

Deals briefly with various kinds of service pipes, preferring lead, cement-lined, and gal- 
vanized in the order named. 


Filling of service pipes by sediment or tuberculation. 1,200 w. 1893. (In 
Journal of the New England Water Works Association, v. 8, p. 105.) 

Topical discussion on pipe corrosion, etc., considering enamel pipe inferior to either gal- 
vanized or cement lime. 

Freund, Martin. 

Uber eine eigenartige zerstorung von wasserleitungsrohren. 2,800 w. 
1904. (In zeitschrift fur angewandte chemie, v. 17, pt. 1, p. 45.) 

Investigation of a destructively corroded cast-iron water-pipe, giving analyses of original 
metal and of the corroded portions. 

Greth, J. C. William. 

Scaling and corroding substances and their elimination from water for 
boilers. 5,000 w. 1909. (In Industrial world, v. 43, p. 578.) 

Howe, Freeland, jr. 

Action of water on pipes. 5,000 w. 1908. (In Journal of the New 
England Water Works Association, v. 22, p. 43.) 

Consideration of the nature of water and of iron pipe and of the electrolytic action that 
takes place. 

Howe, Henry M. & Stoughton, Bradley. 

Relative corrosion of steel and wrought iron tubing. 20 p. 111. 1908. 
(In Proceedings of the American Society for Testing Materials, v. 8, p. 247.) 

Discussion, 15 p. 

The same. (In Industrial world, v. 83, p. 1244.) 

Believes that modern steel tubing is equal to wrought-iron tubing and that the preju- 
dice against it is due to practical experience with other tubing. 

Hutton, F. R. 

Note on the action of a sample of mineral wool used as a non-conductor 
around steam-pipes. 2,800 w. 1882. (In Transactions of the American 
Society of Mechanical Engineers, v. 3, p. 228.) 

States that in presence of moisture mineral wool causes very rapid corrosion of iron pipes. 

Jamieson, Matthew Buchan. 

Internal corrosion of cast-iron pipes. 14 p. Dr. 1881. (In Minutes 
of proceedings of the Institution of Civil Engineers, v. 65, p. 323.) 

Consideration of composition of rust, methods of cleaning pipes and the harmful effects 
of corrosion. 

Murdoch, Gilbert. 

Life of cast-iron water pipe at St. John, N. B. 5,000 w. 1894. (In 
Engineering news, v. 31, p. 15.) 

Abstract of report giving cause of pipe failure. 

Rust in galvanized iron water service pipe. 6,000 w. 1909. (In Metal 
worker, v. 71, March 27, p. 48; April 3, p. 52; April 10, p. 45; April 17, p. 
48; April 24, p. 39.) 

Continued discussion, by letter, in reply to questions by editor concerning the presence 
and prevention of corrosion in water-pipe. 

Siebel, E. P. 

Pitting of iron, particularly pipe; its causes and possible preventives. 
3,000 w. 111. 1909. (In National engineer, v. 13, p. 192.) 
Paper before the Chicago section of the Society of Brewing Technology. 


Siebel, E. P. — continued. 

Regards pitting as due to electrochemical decomposition in the presence of water and 
dependent upon the homogeneity of the material. Wrought-iron pipe considered more dura- 
ble than steel pipe. 

Spataro, D. 

Corrosion of cast-iron pipes. 800 w. 1893. (In Journal of the Iron and 
Steel Institute, v. 44, p. 522.) 

Abstract translation from "L'Industria." 

Considers the action of air and water jointly on cast-iron pipes and of the ground in which 
they are placed. 

Speller, Frank N. 

Wrought pipe-threading and relative durability of steel and iron. 3,000 
w. Dr. ill. 1905. (In Journal of the Canadian Mining Institute, v. 8, 
p. 46.) 

The same. (In Iron age, v. 75, p. 741.) 

Review and illustrations of the United States navy department tests on pitting. Ex- 
periments by National Tube Co., showing that, in resistance to corrosion, common iron and 
Bessemer steel are both slightly superior to charcoal iron. 

Stewart, A. W. 

Corrosion in metal pipes on board ship. 6,200 w. 1903. (In Trans- 
actions of the Institution of Naval Architects, v. 45, p. 183.) 
The same, abstract. (In Engineer, London, v. 95, p. 374.) 


Considers the action of impurities on the pipes, especially of chlorine and organic im- 

Thomson, T. N. 

Relative corrosion of wrought-iron and soft steel pipes. 2,800 w. Dr. 
ill. 1908. (In Heating and ventilating magazine, v. 5, p. 15.) 

The same, slightly condensed. 2,500 w. (In Iron age, v. 81, p. 434.) 

See also letter by G. Schuhmann, p. 520. 

Paper before the American Society of Heating and Ventilating Engineers. 

Conclusion from experiments is that "plain steel pipe is more durable than plain wrought- 
iron pipe when used to convey hot water and subject only to internal corrosion." 

Wrought-iron pipe versus steel pipe. 1,300 w. Dr. 1908. (In Heating 
and ventilating magazine, v. 5, p 8.) 

Contains extracts from a pamphlet published by the Beading Iron Co., claiming that 
wrought iron is the more durable. 


Marriott, William. 

Strengthening and maintaining of early iron bridges. 10 p. 1905. (In 
Minutes of proceedings of the Institution of Civil Engineers, v. 162, p. 213.) 

Discussion, 47 p. 

Maintains that no iron bridge rusts as rapidly as new steel bridges, probably due to want 
of homogeneity or to segregation in the steel. 

Preservation of structural steel in tall buildings. 600 w. 1903. (In En- 
gineering record, v. 47, p. 129.) 

Pabst building, New York City. Steel cage building; framework encased in- brick and 
terra-cotta well preserved. 


Removal of a steel frame building. 800 w. 1903. (In Engineering news, 
v. 49, p. 113.) 

Good condition of steel in Pabst Hotel, New York City, five years after erection. 

Snow, J. P. 

Corrosion of structural steel as affected by its chemical composition. 
500 w. 1906. (In Proceedings of the American Society for Testing Materials, 
v. 6, p. 148.) 

Suggests investigation of part played by manganese and phosphorus. 

Taylor, H. N. 

Earnest boost for tin roofs. 2,000 w. 1908. (In Waterproofing and 
fireproonng, v. 2, November, 1908, p. 7.) 

Claims tin has greater weather-resisting qualities than copper, sheet-lead or zinc. 

Taylor, H. N. 

Tin is a lasting roofing material; instances in which roofs covered a cen- 
tury ago are still protecting buildings from the weather. 1,600 w. 111. 1908. 
(In Waterproofing and fireproofmg, v. 2, December, 1908, p. 7.) 

Taylor, H. N. 

Tin roofs on chemically fireproofed sheathing boards. 1,500 w. 1909. 
(In Metal worker, v. 71, p. 44.) 

Corrosion of tin from under side, believed to have been caused by moisture coming in 
contact with the chemicals used in fireproofing the wood. 

Thomson, John M. 

Chemistry of certain metals and their compounds used in building, and 
the changes produced in them by air, moisture and noxious gases. 13,000 w. 
1896. (In Journal of the Society of Arts, v. 44, p. 861, 873, 885.) 


Asbestos protected metal. 600 w. 1908. (In Railway age, v. 45, p. 449.) 
Sheet-steel is protected by layers of asbestos felt embedded in an asphaltic material. 

Birkmire, William H. 

- Finishing iron and steel. 1,000 w. 1897. (In his Architectural iron 
and steel, p. 156.) 

Short chapter on bronzing, enameling, electroplating, galvanizing, painting, and lac- 

Harper, Robert B. 

Comparative values of various coatings and coverings for the preven- 
tion of soil and electrolytic corrosion of iron pipe. 25,000 w. Diag. 111. 
1909. (In American gas light Journal, v. 91, p. 429, 475, 528, 575, 625, 667.) 

Paper before the Illinois Gas Association. 

Comprehensive consideration of protection afforded by coatings of different types. 

Hiscox, Gardner D. ed. 

Plating. 17,000 w. 1907. (In his Henley's twentieth-century book of 
recipes, formulas, and procesess, p. 565.) 

Description of all methods for the various metals, with many receipts. 

See also Electroplating, p. 286. 


Hiscox, Gardner D. ed. 

Rust preventives. 2,400 w. 1907. (In his Henley's twentieth-century 
book of recipes, formulas, and processes, p. 623.) 

Gives many receipts for preparations and coatings. 

Hopkins, Albert A. ed. 

Rust. 4,500 w. 1901. (In his Scientific American cyclopedia of re- 
ceipts, ed. 2, p. 491.) 

Gives methods and formulas of rust preventives for various articles of iron. 

Polleyn, Friedrich. 

Putzmateri alien fur eisen zum entfernen von rost. 28 p. 1909. (In 
his Putzbaumwolle und andere putzmaterialien, p. 218.) 

Treumann, Julian. 

Die mittel zur verhlitung des rostes. 6,000 w. 1898. (In Stahl und 
eisen, v. 18, pt. 2, p. 882, 940.) 

Deals'principally'with methods of rust prevention in structural iron and steel work. 

Wood, Matthew P. 

Rustless coatings, corrosion, and electrolysis of iron and steel. 432 p. 
111. 1904. 

Gives much valuable information on metal preservation. Deals fully with paints and 
pigments, galvanizing and other metallic coating processes. Contains bibliographic foot- 


Action of cinder concrete on steel. 300 w. 1897. (In Engineering news, 
v. 37, p. 186.) 


Experiences sur le ciment arme. 4,500 w. Dr. 1902. (In Annates 
des ponts et chaussees, memoires, ser. 8, v. 3, ler trimestre, p. 181.) 

The same, condensed. 200 w. (In Transactions of the American Society 
of Civil Engineers, v. 51, p. 124.) 

The same, condensed. 100 w. (In Taylor & Thompson's Treatise on 
concrete, plain and reinforced, p. 430.) 

Argues against the belief that cement does not attack iron. Chemical union takes place 
between metal and cement, forming silicate of iron, soluble in water, and unless special care 
is taken in waterproo6ng the concrete this salt is dissolved and corrosion takes place. 

Buel, Albert W. 

Protection of metal work in concrete. 1,400 w. 1898. (In Engineer- 
ing record, v. 38, p. 278, 409.) 

Letter, claiming that perfect protection may be secured without use of paint. 

Buel, Albert W. & Hill, C. S. 

Preservation of iron in concrete. 1,000 w. 1906. (In their reinforced 
concrete, ed. 2, p. 370.) 

The same. (In American Steel & Wire Company's Handbook and cat- 
alogue of concrete reinforcement. 1908. p. 26.) 

Cement paste for protecting steel. 250 w. 1908. (In Mining and scien- 
tific press, v. 97, p. 744.) 

Successful coating used by the Pennsylvania railroad, said to be cheap and durable. 


Concrete as a preservative of steel from rust. 1,000 w. 1905. (In En- 
gineering news, v. 53, p. 316.) 

Editorial emphasizing necessity for proper precautions in applying the concrete. 

See also letter, p. 316. 

Corrosion of iron in concrete. 3,500 w. 1898. (In Engineering record, 
v. 27, p. 253, 272.) 

Corrosion of reinforcing metal. 900 w. 1906. (In Iron age, v. 78, p. 1667.) 
Summary of report of committee of the Structural Association of San Francisco, recom- 
mending the exclusion of cinder concrete as a fireproofing or floor material. 

Corrosion of reinforcing metal in cinder- concrete floors. 2,200 w. 1906. 
(In Engineering news, v. 56, p. 458.) 

Contains report in full of a committee to the Structural Association of San Francisco, 
recommending that the building laws be so amended as to exclude cinder concrete from use 
in floor slabs. 

See also editorial, p. 461. 

Durability of steel in concrete. 900 w. 1902. (In Engineering record, 
v. 46, p. 280.) 

Comment on experiments of Breuille. 

Electrolytic corrosion, and iron and steel in concrete. 1,400 w. 1907. (In 
Engineering, v. 84, p. 430.) 

Editorial discussion of recent (1907) experiments. 

Experiment to indicate whether iron rusts when imbedded in concrete. 150 w. 
1904. (In Report of the Boston Transit Commission, v. 10, appendix F, 
p. 80.) 

Two-year tests gave excellent results. 

Experiment to indicate whether steel imperfectly cleaned is preserved from 
further rusting by imbedding the same in concrete. 200 w. 1904. (In 
Report of the Boston Transit Commission, v. 10, appendix F 2, p. 81.) 
No apparent increase of rust in two years. 

Fox, William H. 

Corrosion of steel in reinforced cinder concrete. 1,600 w. Dr. 1907. 
(In Engineering news, v. 57, p. 569.) 

Records experiments in which reinforced cinder concrete was exposed to steam and to 
water for about 40 days. Results showed unmistakable signs of corrosion. 

Himmelwright, A. L. A. 

Corrosion of steel in cinder concrete. 1,200 w. 1907. (In Iron age, 
v. 79, p. 141.) 

Believes that cinder concrete should not be condemned and that the corrosion observed 
in San Francisco took place during construction. 

Hinrichsen, F. Willy. 

Zur kenntnis des einflusses von koksasche auf den rostangriff von eisen. 
1,400 w. 1907. (In Mitteilungen aus dem Koniglichen Materialprufungsamt, 
v. 25, p. 321.) 

Found that the sulphur in coke ashes has very little action on iron enclosed in cement 
and ashes. 


Immunity from rusting of reinforcing steel in concrete. 900 w. 111. 1908. 
(In Engineering news, v. 59, p. 524.) 

Results of tests at the Prussian Royal Testing Institution, showing that ordinary ten- 
sion cracks do not allow corroding influences of the atmosphere to affect the steel. 

Keep water away from steel. 2,700 w. 1908. (In Waterproofing and fire- 
proofing, v. 2, October, 1908, p. 15.) 

Claims that by capillary action "steel will draw moisture through two feet of cement." 
Non-scientific article. 

Knudson, Adolphus A. 

Electrolytic corrosion of iron and steel in concrete. 3,200 w. Diag. dr. 
ill. 1907. (In Transactions of the American Institute of Electrical En- 
gineers, v. 26, pt. 1, p. 231.) 

Discussion, p. 264. 16,000 w. Diag. dr. 

The same, without discussion. (In Electrician, London, v. 59, p. 213.) 
"In no sense can concrete be considered an insulator, and . it is from all appear- 
ances just as good an electrolyte as any of the soils found in the earth." 

Langsdorf, A. S. 

Electrolysis of reinforced concrete. 1,200 w. Diag. dr. ill. 1909. (In 
Journal of' the Association of Engineering Societies, v. 42, p. 69.) 
The same. (In Engineering-contracting, v. 31, p. 327.) 
In general an amplification of earlier experiments of Knudson, confirming his results. 


Experiences sur l'alteration des ciments arm6s par l'eau de mer. 3,000 
w. 1899. (In Annales des ponts et chauss6es, memoires, ser. 7, v. 18, 4e tri- 
mestre, p. 229.) 

Results of experiments indicate that cement is not impermeable to salt water and that 
in time the action of the water will be destructive. 

Lindeck, St. 

Ueber die elektrische leitungsfahigkeit von cement und beton. 3,500 w. 
Dr. 1896. (In Elektrotechnische zeitschrift, v. 17, p. 180.) 

Gives in tabular form results of many tests proving that for insulating purposes asphalt 
concrete is superior to cement concrete. 

Matthews, Ernest R. 

Corrosion of steel reinforcement in concrete. 500 w. 1909. (In Iron 
and coal trades review, v. 78, p. 544.) 

The same. (In Mechanical engineer, v. 23, p. 441.) 

Abstract of paper before the Society of Engineers. 

Conclusions are that concrete, properly mixed, gives almost perfect protection to steel, 
with no need for a cement coating. 

More evidence as to possible corrosion of steel imbedded in cinder concrete. 
1,400 w. 1906. (In Engineering news, v. 56, p. 549.) 

Letter from A. L. A. Himmelwright arguing in favor of the use of cinder concrete in floor 
construction. Writer's belief is that the corrosion observed in San Francisco buildings took 
place during construction. 

See also letter, p. 661. 

Newberry, Spencer B. 

Chemistry of the protection of steel against rust and fire by concrete. 
1,700 w. 1902. (In Scientific American supplement, v. 54, p. 22335.) 

The same. 1,000 w. (In Engineering news, v. 47, p. 335.) 


Nicholas, U. James. 

Tests on the effect of electric current on concrete. 3,200 w. 111. 1908. 
(In Engineering news, v. 60, p. 710.) 

Shows that electrolytic corrosion of reinforcing steel takes place at that anode, and that 
under certain conditions concrete and cement are in no sense insulators. 

Norton, Charles L. 

Corrosion of steel frames of building. 1,500 w. 1902. (In Iron age, 
v. 70, November 6, p. 7.) 

Report of the Insurance Engineering Experiment Station of the Associated Factory- 
Mutual Fire Insurance Companies, Boston. 

Norton, Charles L. 

Corrosion of the steel frames of buildings. 1,800 w. 111. 1902. (In 
Technology quarterly, v. 15, p. 343.) 

Tests showing that concrete to be effective in preventing rust must be dense, without 
voids or cracks, mixed and applied quite fresh to clean metal. 

Norton, Charles L. 

Protection of steel from corrosion. 1,600 w. 1904. (In Engineering 
news, v. 51, p. 29.) 

Laboratory experiments, tending to show that concrete properly applied is an almost 
perfect preservative. 

Norton, Charles L. 

Tests to determine the protection afforded to steel by Portland cement 
concrete. 1,700 w. 111. 1902. (In Engineering news, v. 48, p. 333.) 

Indicate that neat Portland cement is a good preventive of corrosion and that corro- 
sion in cinder concrete is due to rust in the cinders and not to the sulphur. 

Preservation of iron in concrete. 700 w. 1903. (In Engineering record, 
v. 47, p. 554.) 

Observations on condition of iron embedded in concrete since 1890. 

Preservation of materials of construction; an informal discussion. 33 p. 
111. 1903. (In Transactions of the American Society of Civil Engineers, 
v. 50, p. 293.) 

Chie0y methods of preventing corrosion of iron and steel when embedded in concrete. 

Preservation of steel in ferro-concrete. 1,100 w. 1909. (In Engineering 
review, London, v. 20, p. 352.) 

Brief discussion of recent views and work, with special consideration of conclusions of 
E. E,. Matthews, in a paper before the Society of Engineers. 


Ueber die oxydation des eisens und den eisenbeton. 400 w. 1908. (In 
Tonindustrie-zeitung, v. 32, pt. 2, p. 2049.) 

Iron can be absolutely protected by a concrete coating, owing to the fact that iron is 
not oxidized by alkaline solutions. 


Ueber die ursachen des verschwindens des rostes in eisenbeton. 900 w. 
1909. (In Tonindustrie-zeitung, v. 33, p. 283.) 

Sabin, Louis Carlton. 

Preservation of iron and steel by mortar and concrete. 1,100 w. 1905= 
(In his Cement and concrete, p. 336.) 


Sabin, Louis Carlton — continued 

Claims that if properly mixed and applied, both stone and cinder concrete not only pre- 
vent corrosion, but arrest the formation of rust when already started. 

Schaub, J. W. 

Some phenomena of the adhesion of steel and concrete. 1,400 w. 1904. 
(In Engineering news, v. 51, p. 561.) 

Points out that a chemical union takes place between the iron and the cement and that 
this union is dissolved in water. 

Steel protecting paste. 300 w. 1909. (In Compressed air, v. 14, p. 5252.) 
Consists of a mixture of Portland cement, red lead, linseed oil, and a dryer. Used as 
protection against gaseous fumes. 

Taylor, Frederick W. & Thompson, S. E. 

Fire and rust protection. 1,400 w. 1905. (In their Treatise on con- 
crete, plain and reinforced, p. 427.) 

Considers briefly the evidence favorable to protection of both clean and rusty steel by 
concrete; chemical union of steel and cement, cement paint, etc. 

Tests on rusting of steel rods embedded in concrete. 600 w. 1908. (In 
Engineering news, v. 59, p. 525.) 

Tests made by J. M. Braxton, United States engineer. 

Thwaite, Benjamin Howard. 

Preservation of iron and steel. 1,900 w. 1906. (In Iron and steel 
magazine, v. 11, p. 411.) 

From "Concrete and constructional engineering." 

Calls attention to excellent results obtained by use of cement and concrete coverings. 

Toch, Maximilian. 

Electrolytic corrosion of structural steel. 1,300 w. 111. 1906. (In 
Proceedings of the American Society for Testing Materials, v. 6, p. 150.) 

Tests of steel embedded in various mixtures of concrete show that the concrete is no 
protection unless the steel is otherwise insulated. 

Toch, Maximilian. 

Electrolytic corrosion of structural steel. 1,800 w. 1906. (In Trans- 
actions of the American Electrochemical Society, v. 9, p. 77.) 

The same, without discussion. 1,000 w. (In Chemical engineer, v. 4. 
p. 125.) 

The same, condensed. 1,500 w. (In Electrochemical and Metallurgical 
industry, v. 4, p. 215.) 

Denies that concrete is a complete protector against corrosion, and cites experiments 
showing that in structural steel embedded in concrete rapid corrosion takes place at the anode 
while the cathode is protected. 

Toch, Maximilian. 

Permanent protection of iron and steel. 2,300 w. 111. 1903. (In 
Journal of the American Chemical Society, v. 25, p. 761.) 

Considers that metal work, coated with cement paint, then with hydrocarbon insulat- 
ing paint, will be perfectly protected when embedded in masonry. 

Turner Construction Co. 

Concrete as preservative of steel. 700 w. 1904. (In Engineering 
record, v. 50, p. 146.) 


Turner Construction Co. 

Experiments on concrete as a preservative of steel exposed to sea-water. 
400 w. Dr. 1904. (In Engineering news, v. 52, p. 153.) 
Shows concrete to be an excellent protection against corrosion. 

Verhalten von eisen im beton. 400 w. 1903. (In Stahl und eisen, v. 23, 
pt. 1, p. 650.) 

Abstract from " Zentralblatt der bauverwaltung." 

Only clean iron, free from rust, should be used in concrete, and the rods should not be 
too near the surface. 

Wagoner, Luther, & Skinner, T. H. 

Corrosion of reinforcing metal in cinder concrete floors. 2,000 w. 1906. 
(In Engineering news, v. 56, p. 458.) 

The same. 1,000 w. (In Engineering record, v. 54, p. 552.) 

Examination of San Francisco buildings after the fire, showing corrosion so great as to 
render floors unsafe in from six to ten years after construction. Considers presence of coal 
or coke in cinder especially detrimental and in general condemns the use of cinder concrete. 

Whiskeman, James P. 

Official report of preservation of structural steel in a tall New York build- 
ing. 1,800 w. 111. 1903. (In Engineering record, v. 47, p. 394.) 

Report to the superintendent of buildings on the Pabst building. Shows that paint 
is unsatisfactory for underground protection and calls attention to the efficiency of cinder 


Brannt, William T. & Wahl, W. H. ed. 

Enamels and enameling. 2,500 w. 1886. (In their Techno-chemical 
receipt-book, p. 115.) 

Mainly receipts, with very brief directions. 

Cooley, Arnold J. 

Enamel. 1,800 w. 1891. (In his Cyclopedia of practical receipts, ed. 
6, p. 631.) 

Receipts mainly. 

Enameling. 20,000 w. Dr. 1901. (In Engineer, London, v. 92, p. 194, 
238, 204,1323, 347.) 

Ddbaildd (general treatment of the whole subject of enameling. 

Griinrwald,! Julius. 

Thboiie i und praxis der blech- und guessemail-industrie; handbuch der 
modernern emailliertechnik, nebst auszug aus der geschichte der kunstemaille 
und emaihinalerei. 144 p. 1908. 

On thtei raw materials and technical processes, with special reference to industrial enamel- 

Hiscox, Gardner D. ed. 

Enameling. 20 p. 1907. (In his Henley's twentieth-century book of 
recipes, formulas, and processes, p. 290.) 

Reviews steps of process and apparatus, and gives many receipts for enamels. 

See also Glazes, p. 377. 


Hiscox, Gardner D. ed. 

Lacquers. 3,200 w. 1907. (In his Henley's twentieth-century book of 
recipes, formulas, and processes, p. 437.) 

Receipts for lacquers for metals and alloys. 

Hopkins, Albert A. ed. 

Enamels. 4,800 w. 1901. (In his Scientific American cyclopedia of 
receipts, ed. 2, p. 197.) 

Hopkins, Albert A. ed. 

Lacquering. 5,400 w. 1901. (In his Scientific American cyclopedia 
of receipts, p. 296.) 

Receipts for lacquers for the various metals, etc. 

Lacquers and paints for metals. 5,000 w. 1903. (In Engineer, London, 

v. 96, p. 264, 288.) 

Discusses ornamental rather than purely protective coverings, giving proper methods 
of application. 

Randau, Paul. 

Enamels and enameling; an introduction to the preparation and appli- 
cation of all kinds of enamels for technical and artistic purposes; tr. from the 
German by Charles Salter. 188 p. 111. 1900. 

Rietkotter, Karl. 

Die herstellung geschweisster emaillerten behalter. 1,500 w. 8 dr. 
1909. (In Stahl und eisen, v. 29, pt. 2, p. 1273.) 

Schlemmer, J. 

Zur entwicklung der emaillierung auf gusseisen und ahnlicher verfahren. 
2,000 w. 1906. (In Stahl und eisen, v. 26, pt. 1, p. 350.) 

Discusses various methods of forming protective coatings on east iron, whether by ordi- 
nary enameling or otherwise. 

Standage, H. C. 

Practical polish and varnish maker. 260 p. 1892. 

Contains many receipts and formulas for varnishes, lacquers and japans for metals. 

Underhill, Dillon. 

Enameled cast-iron sanitary ware. 7,000 w. 111. 1909. :(I-n Foundry, 
v. 34, p. 1, 66, 125.) 

Series of articles on the manufacture of porcelain enameled ware, in which :the jnefchods 
of moulding, pattern-making, designing, annealing, and enameling are fully discussed. 

Vollkommer, Joseph. 

Enameling as an industry. 2,600 w. 1899. (In Iron age, v. "63," March 
23, p. 10.) 

Treats especially the preparation of the metal for enameling and the application of the 

Wood, Matthew P. 

Rustless coatings for iron and steel; tinning and enameling metals, 
lacquering, and other preservative methods. 75 p. 111. 1894. (In Trans- 
actions of the American Society of Mechanical Engineers, v. 15, p. 998.) 



Burgess, Charles F. 

Investigation of the properties of zinc coatings. 7,000 w. Diag. dr. 
1905. (In Electrochemical and metallurgical industry, v. 3, p. 17.) 

Electrolytic zinc coatings better than metal in the molten condition. 

Cold galvanizing; the process and apparatus employed by the U. S. Electro 
Galvanizing Company. 2,000 w. Dr. 1906. (In Iron age, v. 77, p. 1980.) 

Collins, A. Frederick. 

Cold galvanizing for iron and steel. 1,000 w. 1907. (In Scientific 
American, v. 110, p. 94.) 

Considers its advantages over the hot process. 

Cowper-Coles, Sherard. 

Electro-positive coating for the protection of iron and steel from corro- 
sion. 3,500 w. 111. 1906. (In Electrical engineer, London, v. 44, p. 296.) 

Paper before the British Association for the Advancement of Science. 
Fully illustrated description of electro-zincing plant and process. 

Cowper-Coles, Sherard. 

Galvanising of iron and steel surfaces. 4,600 w. Dr. ill. 1905. (In 
Iron and coal trades review, v. 71, p. 1607.) 

Paper before the Society of Engineers. 

Cowper-Coles, Sherard. 

Metallic preservation of iron and steel surfaces. 8,300 w. III. 1905. 
(In Transactions of the Society of Engineers, v. 45, p. 183.) 

Galvanizing, particularly the sherardizing process of the author. 
Discussion. Three folding plates. 

Cowper-Coles, Sherard. 

Protective metallic coatings for iron and steel. 15,000 w. 111. 1898. 
(In Transactions of the Society of Engineers, v. 38, p. 139.) 

The same, ivithout discussion. 13,000 w. (In Industries and iron, v. 25, 
p. 284, 304, 324.) 

Effect of various corroding agents on metals; cleaning by pickling and sand blast; pro- 
tective zinc coatings. 

Discussion. Two folding plates. 

Cowper-Coles, Sherard. 

Recent improvements in electro-galvanising. 1,300 w. Dr. ill. 1898. 
(In Cassier's magazine, v. 13, p. 306.) 

Emphasizes the economy of the process and the durability of the zinc coating obtained. 

Cowper-Coles electro-zincing process. 600 w. 111. 1895. (In Electrical 
review, London, v. 36, p. 119.) 

Does not describe process but gives good illustrations of plants in operation. 

Davies, Herbert E. 

Action of water on zinc and galvanized iron. 5,000 w. 1899. (In 
Journal of the Society of Chemical Industry, v. IS, p. 102.) 

Shows that all kinds of water attack zinc and that a moderate degree of hardness favors 
the action. 

Electrogalvanising. 500 w. 111. 1906. (In Electrician, v. 57, p. 533.) 

Treatment of boiler and condenser tubes. 


Electrolytic tinning. 1,000 w. 1909. (In Electrical magazine, v. 11, p. 

' Tin is deposited from solution at a temperature of between 50 and 60 degrees. 

Flanders, W. T. 

Galvanizing. 2,800 w. . 1896. (In Iron age, v. 57, p. 518.) 

Directions for operations in bot galvanizing. 

Flanders, W. T. 

Galvanizing and tinning. 93 p. 111. 1900. 
Contains forty pages on the practice of hot galvanizing. 

Galvanisation electrique du fer. 2,500 w. Dr. 1897. (In Le Genie civil, 

v. 31, p. 38.) 

Considers methods of electro-galvanizing, especially those of Wagner and of Cowper- 

Harbord, F. W. 

Protecting steel from corrosion. 4,200 w. 111. 1904. (In his Metal- 
lurgy of steel, p. 529.) 

Brief description of galvanizing and tinning processes. 

Lees, T. G. 

Internal corrosion of wire ropes. 1,800 w. 1897. (In Colliery guar- 
dian, v. 74, p. 792.) 

Abstract of paper before the Chesterfield and Midland Counties Institution of En- 

Describes favorable results obtained by the use of galvanized wire ropes. 

Moldenke, R. 

Galvanizing. 1,600 w. 1906. (In Foundry, v. 27, p. 245.) 

Brief consideration of operation of the hot galvanizing process. 

Mowry, Edward S. 

Electro-galvanizing. 600 w. 1906. (In Iron age, v. 77, p. 352.) 

Letter claiming marked inferiority of electro-galvanizing to hot galvanizing. 

Porter galvanizing process. 1,500 w. Dr. 1904. (In Iron age, v. 74, 
August 18, p. 2.) 

Description of machine for removing excess metal on galvanized articles. 

Recent developments in galvanizing; " sherardizing," the dry galvanizing 
process of Cowper-Coles. 1,200 w. 111. 1909. (In Scientific American 
supplement, v. 67, p. 149.) 

Recent improvements in galvanising. 2,000 w. 111. 1895. (In Engineer, 
London, v. 79, p. 494; v. 80, p. 343.) 

Brief notice of early galvanizing and well illustrated description of Cowper-Coles process. 

Reese, George C. 

On an improvement in the art of galvanizing. 1,400 w. 111. 1897. 
(In Journal of the Franklin Institute, v. 144, p. 312.) 

Improvement consists in removing the excess of zinc coating in a centrifugal separator 
instead of by the wiping method. 

Sang, Alfred. 

Art of galvanizing. 9,000 w. 1907. (In Foundry, v. 30, p. 417, 486.) 
The same. (In Iron age, v. 79, p. 1552, 1646.) 


Sang, Alfred — continued 

The same. (In Iron and coal trades review, v. 75, p. 1564.) 

The same. (In Scientific American supplement, v. 64, p. 21, 42.) 

Paper before the American Foundrymen's Association. 

Considers theory of galvanizing and methods in use, with particular reference to sherardiz- 

Sang, Alfred. 

Electro-cementizing, a process for simultaneously annealing, cleaning, 
and zinc-coating wire. 2,500 w. 1 dr. 1909. (In Iron age, v. 84, pt. 2, 
p. 1484.) Trans. Am. Elec. Chem. Soc, XVI, p. 257. 

The same. (In Brass world and platers' guide, v. 5, p. 442.) 

Paper before American Electrochemical Society, October, 1909. 

Coating thoroughly alloyed to metal underneath. Oxides other than zinc may also be 

Sang, Alfred. 

Old and new methods of galvanizing. 10,000 w. 1907. (In Proceed- 
ings of the Engineers' Society of Western Pennsylvania, v. 23, p. 546.) 

Description of hot and cold methods of galvanizing and of sherardizing. Frequent 
references to original sources. 

Sang, Alfred. 

Theory and practice of sherardizing. 2,800 w. 111. 1907. (In Elec- 
trochemical and metallurgical industry, v. 5, p. 187.) 

Notes on the operation of the process and on its advantages. 

Sexton, A. Humboldt. 

Rusting and protection of iron and steel. 26 p. 111. 1902. (In his 
Outline of the metallurgy of iron and steel, p. 570.) 

Corrosion of various forms of iron, and prevention, chiefly by tinning and other metallic 

Sherardizing; a new process for protecting iron and steel from corrosion. 
2,200 w. 111. 1904. (In Iron age, v. 74, October 20, p. 12.) 

Furnace process, invented by Sherard-Cowper Coles, for coating iron and steel with 
metallic zinc. 

Sherardizing; a, new method of galvanizing. 800 w. 1908. (In Industrial 
world, v. 82, p. 250.) 

Szirmay, Ignaz. 

Erprobung der rostsicherheit von verzinkten eisen- und stahldrahten, 
sowie von stacheldraht aus verzinkten eisen- und stahldrahten. 1,300 w. 1905. 
(In Zeitschrift fiir elektrochemie, v. 11, p. 333.) 

Comparative tests of corrodibility of galvanized iron and steel wire and of iron and steel 
articles galvanized by the hot and the electrolytic processes. 

White, Henry I. 

Electrolytical galvanizing. 1,600 w. 1906. (In Iron age, v. 77, p. 

Describes process, claiming superiority in protection of iron with a thinner, more even 

Wood, Matthew P. 

Rustless coatings for iron and steel, galvanizing, electro-chemical treat- 


Wood| Matthew P. — continued 

ment, painting and other preservative methods. 80 p. 111. 1894. (In 
Transactions of the American Society of Mechanical Engineers, v. 16, p. 


On the formation of the black oxide of iron on iron surfaces for the pre- 
vention of corrosion. 7 p. 1877. 

Discussion, 8 p. 

Paper before the Liverpool Polytechnic Society. Iron is heated to a cherry-red, then 
kept in contact with dry steam for several hours. A protective coating of black oxide is 


Treatment of iron to prevent corrosion. 5,000 w. 1879. (In Journal 
of the Society of Arts, v. 27, p. 390.) 

Discussion, 4,000 w. 

Describes author's process of coating with black oxide, giving testimonials concerning 
the process by its users. 

The same without testimonials. (In Scientific American supplement, 
v. 7, p. 2762, 2778.) 


Zinc white as paint, and the treatment of iron for the prevention of cor- 
rosion. 3,200 w. 1877. (In Journal of the Society of Arts, v. 25, p. 254.) 

Discussion, 3,200 w. 

Barff process for the protection of iron. 650 w. Dr. 1879. (In Engi- 
neering, v. 28, p. 441.) 

The same. (In Scientific American supplement, v. 9, p. 3393.) 

Bower, George. 

On the preservation and ornamentation of iron and steel surfaces. 7 p. 
1881. (In Journal of the Iron and Steel Institute, v. 18, p. 166.) 

Discussion, 10 p. 

Bower, George. 

Preservation and ornamentation of iron and steel surfaces. 7,300 w. 
1883. (In Transactions of the Society of Engineers, v. 23, p. 59.) 

Metal protection by a film of magnetic oxide, produced directly by Barff process and 
indirectly by joint process of the author and his son. Describes separate processes and the 
combined or Bower-Barff. 

Carulla, F. J. R. 

Artificial magnetic oxide of iron. 1,500 w. 1909. (In Engineering, 
v. 88, p. 532.) 

Paper before the Iron and Steel Institute. 

Description of a magnetic oxide, early discovered by Gregory and recently introduced 
by Wuffing, valuable as a protection when applied in the form of a paint. 

Gesner rust-proof process. 600 w. 111. 1890. (In Iron age, v. 45, p. 544.) 
The same. (In Industries, v. 8, p. 451.) 

Furnace process, giving to iron and steel a dark blue rust-proof coating. 


Maynard, George W. 

Bower-Barff rustless iron process. 4,000 w. 111. 1883. (In Trans- 
actions of the American Society of Mechanical Engineers, v. 4, p. 351.) 

Describes furnace process for covering metals with a coating of magnetic oxide of iron. 

Percy, John. 

On the protection from atmospheric action which is imparted to metals 
by a coating of certain of their own oxides, respectively. 1,500 w. 1877. 
(In Journal of the Iron and Steel Institute, v. 11, p. 456.) 

The same. (In Engineering, v. 24, p. 304.) 

Iron and copper given as examples. 

Piatt, Charles. 

Oxide films on iron wire. 1,000 w. 1892. (In Engineering and mining 
journal, v. 54, p. 78.) 

Wire exposed to action of steam and acid vapor; heated; dipped in oil bath and again 

Sang, Alfred. 

Inoxidation processes for protection of iron and steel. 2,500 w. 1909. 
(In electrochemical and metallurgical industry, v. 7, p. 351.) 

Review of processes for protecting iron by a magnetic oxide coating, with full references 
to original sources. 

Thwaite, Benjamin Howard. 

On the preservation of iron by one of its own oxides. 13 p. Dr. 1883. 
(In Minutes of proceedings of the Institution of Civil Engineers, v. 74, p. 

The same. (In Scientific American supplement, v. 19, p. 7625.) 

Treats especially the Bower-Barff process. 

Weigelin, G. 

Inoxydation des eisens. 6,000 w. 1908. (In Stahl und eisen, v. 28, 
p. 957, 1022.) 

Considers the manner and conditions of the formation of a magnetic oxide coating aa 


Weigelin, G. 

Der inoxydationsofen. 1,800 w. 1904. (In Stahl und eisen, v. 24, 
pt. 2, p. 1443.) 

A type of regenerative gas-furnace used in the Bower-Barff process of coating iron with 
non-corrosive magnetic oxide. 

Weightman, William H. 

Oxidation of metals and the Bower-Barff process. 3,000 w. 111. 1885. 
(In Transactions of the American Society of Mechanical Engineers, v. 6, 
p. 628.) 

Considers the oxidation of iron and steel by nitre to be superior to the Bower-Barff 
process in economy, in simplicity of application and in results. 

Andes, Louis Edgar. 

Iron corrosion, anti-fouling and anti-corrosive paints. 275 p. 111. 


Anti-corrosive paints; their qualities and composition. 4,000 w. 1902. 
(In Engineering, v. 73, p. 837.) 

Points out lack of an entirely satisfactory vehicle for metal-protecting paint. Considers 
the nature and function of dryers. Classifies pigments as basic, acid and neutral, of which 
only the strongly basic are valuable in metal protection. 

Asphalt coatings for water pipe. 1,500 w. 1900. (In Engineering news, 

v. 43, p. 331.) 

Tests of various asphalt coatings, leading to the conclusion that "mineral rubber" asphalt 
is without exception the best pipe covering on the market. 

Baker, Ira O. 

Tests of bridge paint. 1,200 w. 1899. (In Railroad gazette, v. 31, 

p. 166.) 

Summary of experiments. 

Bishop, A. J. 

Principles underlying car and locomotive painting, describing the vari- 
ous processes and reasons for using materials as they are used. 5,000 w. 
1903. (In Proceedings of the Northwest Railway Club, v. 8, April, p. 5.) 

The same, condensed. 2,500 w. (In Railroad gazette, v. 35, p. 437.) 

Blanch, Joseph G. 

Effect of electricity on paint. 1,300 w. 1905. (In Proceedings of the 
American Society for Testing Materials, v. 5, p. 445.) 

Claims that a local electrochemical action takes place between metal surfaces and cer- 
tain kinds of paint, thereby accelerating internal corrosion. 

Blount, Bertram. 

Best means of preserving iron and steel work in railway construction. 
900 w. 1908. (In Bulletin of the International Railway Congress Asso- 
ciation, v. 22, p. 31.) 

Considers bituminous preparations the best preservatives. 

Broom, William. 

Information on the preservation of iron and steel structures. 11 p. 
Pamphlet considering the properties and value of various paints as metal preservatives. 

Butts, H. M. 

What advancement has been made in paints for the protection of metal 
parts and particularly steel cars? 3,000 w. 1904. (In Proceedings of the 
Central Railway Club, May, p. 27; September, p. 12.) 


Carulla, F. J. R. 

New blue-black iron paint as a protective coating. 1,000 w. 1907. 
(In Journal of the Iron and Steel Institute, v. 75, p. 204.) 
The same. (In Mechanical engineer, v. 20, p. 446.) 
Preservative paint is a by-product obtained from spent chloride pickling liquors. 

Cheesman, Frank P. 

Priming coats for metal surfaces; linseed oil vs. paint. 2,600 w. 1907. 
(In Proceedings of the American Society for Testing Materials, v. 7, p. 479.) 


Cheesman, Frank P. — continued. 

The same, condensed. 2,000 w. (In Engineering news, v. 58, p. 135.) 
Considers oil coatings much inferior to paint as preservatives. 

Cheesman, Frank P. 

Proper paints for metals. 500 w. 1904. (In American gas light jour- 
nal, v. SO, p. 91.) 

Letter disapproving of use of boiled oil and of painting machine. 

Coating cast iron with tin. 1,000 w. 1909. (In Railway and engineering 

review, v. 49, p. 176.) 

Abstract of article in the "Mechanical World." 

Iron is first given a thin coating of copper, then covered with a metallic paint consisting 
of a carrier and finely divided tin or tin-lead alloy. 

Coffignier, Ch. 

Peintures sous-marines et peintures ignifuges. 1,200 w. 1909. (In 
Revue de metallurgie, v. 6, p. 734.) 

Cushman, Allerton S. 

Inhibitive power of certain pigments on the corrosion of iron and steel. 

2,000 w. Dr. 1908. (In Proceedings of the American Society for Testing 

Materials, v. 8, p. 605.) 

The same^ (In Engineering record, v. 58, p. 328.) 

Tests were made on the action of air and water combined on about 50 pigments. 

Custer, E. A. & Smith, F. P. 

Paint as a protection for iron. 7,500 w. 1S96. (In Proceedings of the 
Engineers' Club of Philadelphia, v. 12, p. 291.) 

Gives as essentials of a proper protective coating: adhesion, non-corrosion, toughness, 
elasticity and resistance to water. 


De Wyrall, Cyril. 

Preservative coatings for iron and steel. 900 w. 1904. (In Proceed- 
ings of the American Society for testing Materials, v. 4, p. 445.) 

Considers the vehicle, rather than the pigment, the life of the coating. 

Dudley, Charles B. 

Tests of paint. 22,000 w. 1904. (In Engineering record, v. 50, p. 

Considers only paints for metal protection. Admits that the only reliable test is that 
of actual service, but believes from experiment that a paint to afford thorough protection 
must be water-resistant in a greater degree than those now available. 

Durability of paints. 2,600 w. 1906. (In Engineering, v. 81, p. 90.) 
Editorial discussion of experiments of Job and of service tests. 

Gardner, Henry A. 

Excluding and rust-inhibiting properties of paint pigments for the pro- 
tection of steel and iron. 12 p. 1909. (In Proceedings of the annual con- 
vention of the Master Car and Locomotive Painters' Association, v. 40, p. 

The same, condensed. 2,500 w. (In Engineering-contracting, v. 32, 
p. 302.) 

Gives Cushman's basic classification of pigments as "inhibitors," "indeterminates," 
and r ' stimulators." Gives results of extensive tests of pigments under various conditions. 


Gerber, E. 

Painting of iron structures exposed to the weather. 101 p. 1895. (In 
Transactions of the American Society of Civil Engineers, v. 33, p. 485.) 

With reference to best methods of rust prevention on Liland structures. Describes 
existing conditions, determined by inspection of more than fifty bridges; paints used; their 
relative durability, and conclusions arrived at. 

Discussion and correspondence. 

Gill, Augustus H. & Foster, S. A. 

Contributions to our knowledge of white lead and of its protecting prop- 
erties. 800 w. 1904. (In Technology quarterly, v. 17, p. 145.) 

Record of experiments. 

Gill, Augustus H. & Johnson, C. C. 

Comparison of various tests applied to paints used for the protection of 
iron. 1,200 w. 1903. (In Technology quarterly, v. 16, p. 32.) 

Goodall, Frank C. 

Steatite as a pigment for an ti- corrosive paint. 2,500 w. 1890. (In 
Transactions of the Institution of Naval Architects, v. 31, p. 134.) 

Discussion, 5,500 w. 

Harrison, Arthur B. 

Protective coatings for iron and steel.. 2,700 w. 1906. (In Engineer- 
ing record, v. 54, p. 9.) 

Classifies protective coatings as: (1) linseed oil paints; (2) v rnish and enamel paints; 
(3) carbon coatings that dry by evaporation. Favors a coating of a certain mineral wax 
resembling ozokerite, covered by a specially prepared linseed-oil paint. 

Hazelhurst, J. N. 

Painting. 25 p. 1901. (In his Towers and tanks for waterworks, 
p. 172.) 

Considers chemical and galvanic action upon metals, metal cleaning, and the applica- 
tion of various coatings. 

Heckel, George B. 

Methods for protecting iron and steel against corrosion. 5,600 w. Ill, 
1908. (In Journal of the Franklin Institute, v. 165, p. 449.) 

Appendix, 1,000 w. 

Reviews recent (1908) work and gives suggestions concerning preservative paints. 

Job, Robert. 

Protection of structural work from rust. 900 w. 1906. (In American 
manufacturer and iron world, v. 78, p. 38.) 

Claims that the best quality of linseed-oil used with a fine and properly prepared pig- 
ment will efficiently protect steel for six years or longer under any ordinary circumstances. 

Job, Robert. 

Results of an investigation of certain structural paints. 800 w. 1904. 
(In Proceedings of the American Society for Testing Materials, v. 4, p. 439.) 

Discussion, 1,000 w. 

Job, Robert. 

Results of an investigation of the durability of paints for the protection 
of structural work. 6,500 w. 111. 1904. (In Journal of the Franklin 
Institute, v. 158, p. 1.) 

Attributes permanence largely to fineness of pigment. 


Koons, Charles. 

Protection of iron and steel in car construction, also as applying to build- 
ing material. 2,000 w. 1902. (In Proceedings of the St. Louis Railway- 
Club, v. 7, July 11, p. 3.) 

Attributes successful protection largely to proper cleaning before painting. Various 
kinds of paint are discussed. 
Lawrence, (W. W.) & Co. 

Protective coatings for iron and steel. 15 p. 

Pamphlet considering the causes of failure in paints and the qualities necessary in a. 
successful coating, with special reference to the products of the Lawrence Co. 

Lilly, George W. 

Painting and sand-blast cleaning of steel bridges and viaducts. 6,500 w. 
Dr. 1902. (In Engineering news, v. 47, p. 322.) 

Lays stress on thorough cleaning. Calls attention to economy of sand blast and efficiency 
of pneumatic painting machine. Describes plastering of a, viaduct with a, composition of 
Portland cement, red lead, and linseed-oil. 

Lilly, George W. 

Sand blast cleaning of structural steel. 13,600 w. 111. 1903. (In 
Transactions of the American Society of Civil Engineers, v. 50, p. 254.) 

Experience in preparing some badly corroded structures for painting. 

Lowe, Houston. 

Factors that affect results in painting. 3,800 w. 1905. (In Proceed- 
ings of the Engineers' Society of Western Pennsylvania, v. 21, p. 197.) 

Discussion, 3,200 w. 

The same, without discussion. (In Iron trade review, v. 38, p. 44.) 

Considers painting of structural work. 

Lowe, Houston. 

Hints on painting structural steel and notes on prominent paint materials. 
Ed. 4. 45 p. 1905. 

McDonald, Hunter. 

Painting railroad bridges. 1,400 w. 1900. (In Railroad gazette, v. 32,, 

p. 265.) 

Briefly describes laboratory tests of twenty different kinds of paint. 

Mackenzie, William B. 

Painting metal bridges. 3,800 w. 1897. (In Canadian engineer, v. 5, 

p. 67.) 

Considers corrosion, oil and pigments. Gives "record of twenty-four painted platea 
exposed on a steel railroad bridge over an arm of the sea." 

Methods of testing the protective power of paints used on metallic structures- 
700 w. 1906. (In American machinist, v. 29, p. 794.) 

Concludes that durability of anti-rust preparations depends on quality of the linseed- 
oil used. 

One thousand more paint questions answered. 614 p. 1908. 

Compiled from the "Painters magazine." 

"Painting iron and metal work," p. 102-122. Discusses forty-four separate topics under 
these heads. 


Paint as a preservative of iron from rust. 3,300 w. 1905. (In Engineer, 
London, v. 95, p. 509.) 

Chemistry of various paints, giving preference to red lead or red oxide of iron paint. 

Paint Manufacturers' Association of the United States — Scientific Section. 
Bulletin no. 4, 6-10, 12, 15-16, 19-20. 

No. 4. Methods for the analysis of the vehicle constituents of paint. 15 p. 

No. 6. Annual report (1st) of the Scientific section. 93 p. 111. 1908. 

No. 7. Preliminary report on steel test fences. 15 p. 111. 1908. 

No. 8. Report of Committee "E" on preservative coatings for iron and steel. 19 p. 
6 pi. 1908. 

No. 9. Recent technical developments in paint manufacture. 53 p. 111. 1909. 

No. 10. Protective coatings for conservation of structural materials, by R. S. Perry. 
43 p. 1909. 

No. 12. The function of oxygen in the corrosion of metals, by W. H. Walker. 16 p. 

No. 15. Protective coatings for structural material, by R. S. Perry. 20 p. 1909. 

No. 16. Annual report (1st) on wearing of paints applied to Atlantic City test fence, 
1909. 314 p. 23 pi. 1909. 

No. 19. Laboratory study of panels of Atlantic City and Pittsburg test fences. 67 p. 
32 pi. 1909. 

No. 20. Concrete coatings, by H. A. Gardner. 19 p. 1909. 

With this is bound a preliminary bulletin, "Physical characteristics of a paint coating," 
by R. S. Perry. 25 p. 16 pi. 1907. 

Paints for iron. 1,200 w. 1899. (In Engineer, London, v. 88, p. 29.) 

Experiments showing that the most desirable paints are those containing red lead or 
orange lead. 

Paints suited for engineering structures. 4,000 w. 1904. (In Engineer, 
London, v. 97, p. 542; v. 98, p. 41.) 

Discusses chemical composition and physical properties of various paints. 

Parry, Ernest J. & Coste, J. H. 

Chemistry of pigments. 280 p. 111. 1902. 

Describes the uses and methods of application of pigments, the chemistry of the processes 
of manufacture of the different varieties, methods of analysis, nature of probable impurities, 
adulterations, etc., and gives analysis of genuine and sophisticated pigments. 

Perry, Robert S. 

Protective coatings for iron and steel, with discussion. 30 p. 1909. 
(In Paint Manufacturers' Association, Scientific section. Bulletin no 13.) 

Paper before American Chemical Society. 

Perry, Robert S. 

Protective coatings for structural metal. 19 p. 1909. (In Journal of 
the Western Society of Engineers, v. 14, p. 399.) 

With discussion. 

Outlines the results of recent investigations and describes a simple accelerated test for 
durability of protective coatings. 

Practicability of establishing standard specifications for preservative coat- 
ings for steel. 1,500 w. 1905. (In Proceedings of the American Society 
for Testing Materials, v. 5, p. 426.) 
Topical discussion. 

Preservation of iron from rust. 4,000 w. 1898. (In Engineer, London, 
v. 85, p. 27.) 

Questions the efficacy of linseed-oil and pigments and recommends a "varnish" in which 
the chief ingredient is pitch or asphalt. 


Preservative paints for iron chemically considered. 4,000 w. 1899. (In 
Engineering, v. 67, p. 238.) 

Explains the chemical nature and reaction of a single red lead and red oxide of iron paint. 
Argues strongly against glycerole as an ingredient on account of its hygroscopic nature. 

Prevention of rust in iron and steel structures. 1,100 w. 1896. (In Scien- 
tific American, v. 75, p. 454.) 

Editorial plea for greater care in painting, etc. 

Protection of iron by paint. 2,600 w. 1897. (In Engineer, London, v. 84, 
p. 389.) 

Claims that rusting beneath paint is due not to admission of air through cracks in the 
paint, but to the hygroscopic nature of the paint, which leads to swelling, porosity and lack 
of adhesion. 

Quest, W. O. 

Best method of painting and maintaining steel cars. 2,100 w. 1903. 
(In Railway age, v. 36, p. 332.) 

Suggestions for improved methods amd better materials. 

Report of committee E on preservative coatings for iron and steel.- 2,000 w. 

1903. (In Proceedings of the American Society for Testing Materials, v. 3, 
p. 47.) 

Tentative report suggesting lines for further investigation. 

Report of committee E on preservative coatings for iron and steel. 30 p. 

1904. (In Proceedings of the American Society for Testing Materials, v. 4, 
p. 137.) 

Discussion. 12 p. 

The same, condensed. 800 w. (In Iron and steel magazine, v. 8, p. 143.) 
Compilation of individual opinions of members of the committee concerning best methods 
of testing preservative coatings. 

Report of committee E on preservative coatings for iron and steel. 2,600 w. 

1905. (In Proceedings of the American Society for Testing Materials, v. 5, 
p. 79.) 

Discussion, 3,000 w. 

Report of sub-committees on standard methods of conducting field and service tests, 
permeability and permanency of paint films, and preparation of iron and steel surfaces for 

Report of committee E on preservative coatings for iron and steel. 6,200 w. 

1906. (In Proceedings of the American Society for Testing Materials, v. 6, 
p. 47.) 

Discussion, 2,300 w. 

Experiments begun with different paints on an exposed part of a new bridge of the Penn- 
sylvania Railroad. 

Report of committee E on preservative coatings for iron and steel. 1,500 w. 

1907. (In Proceedings of the American Society for Testing Materials, v. 7, 
p. 140.) 

Describes carrying out of tests started in 1906, method of inspection of condition of 
paints, etc. 

Report of committee E on preservative coatings for iron and steel. 6,500 w. 


Folding pi. 1908. (In Proceedings of the American Society for Testing 
Materials, v. 8, p. 165.) 

Contains as appendixes detailed reports of results of analyses of bridge paints by P. H. 
Walker and P. C. Mcllhiney. 

Sabin, Alvah Horton. 

Industrial and artistic technology of paint and varnish. 372 p. 111. 

Treats in non-technical language of paints and varnishes, their history, fabrication and 
uses. Particularly valuable for chapters on rust prevention, and water-pipe coatings. Con- 
tains but little chemistry. 

Review, 2,200 w. (In Engineering news, v. 52, p. 338.) 

Sabin, Alvah Horton. 

Paints and varnishes. 5,500 w. 1900. (In Journal of the Association 
of Engineering Societies, v. 24, p. 146.) 

Considers paints and methods for iron protection. 

Sabin, Alvah Horton. 

Paints for the protection of iron work. 2,800 w. 111. 1898. (In En- 
gineering news, v. 39, p. 69.) 

Shows importance of thorough claeaning of metal surfaces and of thorough drying of one 
coat of paint before applying another. 

Sabin, Alvah Horton. 

Protection of metal work. 1,600 w. 1899. (In Engineering record, 
v. 39, p. 120.) 

Insists on complete cleaning of metal and thorough drying of paint. 

Sabin, Alvah Horton. 

Technology of paint and varnish. 4,500 w. 1904. (In Cassier's maga- 
zine, v. 25, p. 330.) 

Sabin, Alvah Horton. 

Theory and practice of painting on metal. 65 p. 111. 1905. 

Sabin, Alvah Horton. 

Theory and practice of protective coatings for structural metal. 8,000 w. 
1900. (In Proceedings of the Engineers' Club of Philadelphia, v. 17, p. 87.) 

Experiments on metal plates painted with various preparations and immersed in fresh 
and salt water. 

Selby, O. E. 

Painting the Louisville and Jeffersonville bridge. 12,000 w. Dr. 1898. 
(In Transactions of the American Society of Civil Engineers, v. 39, p. 19.) 

Methods, cost, etc. 

Lengthy discussion and correspondence. 

Simon, Edmund. 

Ueber die entstehung des rostes unter der das eisen schtitzenden oelfar- 
bendecke. 2,400 w. 1897. (In Dinglers polytechnisches journal, v. 305, 
p. 285.) 

Claims that paint is hygroscopic and permeable to moisture and gases. Abundance of 
linseed-oil is desirable. 


Smith, Harry. 

Protective paints for iron. 4,800 w. 1899. (In Journal of the So- 
ciety of Chemical Industry, v. 18, p. 1093.) 

Tests of a large number of paints, indicating red lead and similar pigments as the best 
preservatives, followed by zinc white and white lead. 

Smith, J. Cruikshank. 

On the value of physical tests in the selection and testing of protective 
coatings for iron and steel. 11 p. 1909. (In Journal of the Iron and Steel 
Institute, v. 79, p. 81.) 

The same, condensed. 2,400 w. (In Iron and coal trades review, v. 78, 
p. 729.) 

The same, condensed. 2,400 w. (In Mechanical engineer, v. 23, p. 646.) 

The same, condensed. 1,100 w. (In Ironmonger, v. 127, p. 20.) 

Discussion and correspondence, 4,500 w., p. 93. 

Discusses tests that should be applied to the paint itself and tests of the uniformity, 
strength, elasticity, permeability, etc., of the paint film. 

Spennrath, I. 

Protective coverings for iron. 40 p. Dr. 1895? 
Gives results of many tests, chiefly on oil paints. 

Standage, H. C. 

Painting of iron and steel structures. 7,800 w. 1907. (In Painters 
magazine, v. 34, p. 28, 70.) 

Consideration of mechanical, physical, and chemical properties necessary in successful 
paints, and their application. 

Standage, H. C. 

Preservation of iron in building structures. 4,000 w. 1897. (In Builder, 
v. 73, p. 200. 

Detrimental effects of glycerol in paints. 

Stebbings, W. L. & Condron, T. L. 

Report upon the condition of the ironwork in the old "United States post- 
office and custom house building in the city of Chicago. 1,200 w. 1897. 
(In Journal of the Western Society of Engineers, v. 2, p. 420.) 

Committee report, calling attention to the durability of structural iron when proporly 
painted before erection. 

Stern, L. M. 

Rust prevention. 54 p. 111. 1907. 

The same, condensed. 5,000 w. (In Iron age, v. 80, p. 1466.) 

The same, condensed. 2,200 w. (In Metal worker, v. 68, December 28, 
p. 42.) 

Considers severe conditions of exposure to which metal may be subjected and the pre- 
servative paints most suitable. 

Taylor, H. N. 

About time to paint tin roofs; advice as to the proper pigments to use 
and methods of application to prevent corrosion and decay, with hints as to 
material to avoid. 900 w. 1909. (In Waterproofing and fireproofing, v. 3, 
March, 1909, p. 16.) 

Advocates painting tin on both sides and repainting in spring or fall every four or five 
years. Condemns graphite paints. Gives specifications. 


Tests of various paints on the 155th St. viaduct. New York city. 1,000 w. 
Dr. 1898. (In Engineering news, v. 40, p. 14.) 
Includes report by Henry B. Seaman. 

Tests of various paints on the 155th St. viaduct, New York City, 1,000 w. 
1902. (In Engineering news, v. 48, p. 164.) 

Paints exposed to sulphurous fumes. Carbon paints most durable. Asphalt and rubber 
compounds unsatisfactory. 

Thompson, Gustave W. 

Certain solubility tests on protective coatings. 1,500 w. 1908. (In 
Proceedings of the American Society for Testing Materials, v. 8, p. 601.) 

Experimental results indicate in general that the best protective coatings are those which 
contain the lowest percentage^ soluble substance. 

Toch, Maximilian. 

Insulating paints. 2,500 w. 1905. (In Transactions of the American 
Electrochemical Society, v. 8, p. 133.) 

Mainly an outline of necessary qualities and of suggestions for research. 

Toch, Maximilian. 

Protection of steel against corrosion. 3,500 w. 1908. (In Transac- 
tions of the American Electrochemical Society, v. 14, p. 207; v. 15, p. 391.) 

Discussion, 700 w. 

Shows the weakness of mediums "for inhibiting corrosion of iron or steel in transit" 
and emphasizes the necessity for insulating paint at contact-points of two pieces of steel. 

Todd, James. 

Protective coatings for structural material. 800 w. 1909. (In Rail- 
road age gazette, v. 46, p. 1018.) 

Letter on the use and preparation of linseed-oil as a protective coating. 

Tolmer, M. L. 

Preservation, maintenance and probable durability of rolling stock with 
metal underframes and metal upperframes. 3,400 w. Dr. 1896. (In 
American engineer, car builder, and railroad journal, v. 70, p. 171.) 

Results of careful investigation by Eastern Railroad of France. Recommends cleansing 
and painting of metal underframes every three years. Metal upperframes do not greatly 
lengthen the life of the car. Machine riveting has great advantages over hand riveting in rust 
prevention. Estimates useful life of cars- at fifty to sixty years, depending on type. Dia- 
grams show extent of corrosion. 

Toltz, Max. 

Paint tests. 5,000 w. 1896. (In Journal of the Association of Engi- 
neering Societies, v. 18, p. 351.) 

Classifies paints. Outlines a method of iron and steel painting arrived at after careful 


See also v. 19, p. 175. 

Value of white paints on engineering structures. 3,500 w. 1903. (In 
Engineer, London, v. 96, p. 227.) 

Explains lack of .durability of white paint. 

What is the best method of painting steel cars? 2,200 w. 1905. (In Pro- 
ceedings of the American Society for Testing Materials, v, 5. p. 436.) 

Considers both new cars and repainting. Lays stress on painting immediately after 


Whited, Willis. 

Bridges. 5,500 w. 1906. (In Proceedings of the Engineers' Society of 
Western Pennsylvania, v. 22, p. 141.) 

The same, condensed. (In Railway and engineering review, v. 46, p. 


Design and painting of bridges. 

Wilgus, W. J. 

Paint tests. 1,200 w. 1897. (In Journal of the Association of Engi- 
neering Societies, v. 19, p. 175.) 

Discussion of paper by Max Toltz. Outlines methods for iron painting considering 
both new work and repainting. 

Wood, Matthew P. 

Protection of ferric structures. 63 p. 1901. (In Transactions of the 
American Society of Mechanical Engineers, v. 22, p. 757.) 

Discusses both successful and unsuccessful examples. 

Wood, Matthew P. 

Rustless coatings for iron and steel. 40 p. 111. 1897. (In Transac- 
tions of the American Society of Mechanical Engineers, v. 18, p. 251.) 

Wood, Matthew P. 

Rustless coatings for iron and steel; paints: of what composed, how de- 
stroyed, classification as true pigments and inert substances, adulterants, 
etc. 43 p. 1895. (In Transactions of the American Society of Mechanical 
Engineers, v. 16, p. 663.) 

Wright, J. D. 

Best method of painting and maintaining steel cars. 1,700 w. 1903. 
(In Railway age, v. 36, p. 331.) 

Composition and application of paints. 

And€s, Louis Edgar. 

Anti-corrosive weatherproof paint containing paper. 200 w. 1900. (In 
his Iron corrosion, anti-fouling and anti-corrosive paints, p. 240.) 

The same. (In his Der eisenrost, p. 252.) 

Process of Cross & Bevan by which cellulose paper is dissolved in caustic soda lye, etc., 
producing a highly protective paint. 

Barker, Louis H. 

Protection of iron and steel structures; memoranda of eleven years' tests 
of various paints. 1,000 w. 111. 1905. (In Proceedings of the American 
Society for Testing Materials, v. 5, p. 431.) 

The same. (In Iron age, v. 76, p. 148.) 

The same, condensed. 600 w. (In Engineering and mining journal, v. 80, 
p. 252.) 

The same, condensed. (In Railway and engineering review, v. 45, p. 


Barker, Louis II. — continual. 

Tubulin- results of puint U'hU, with remarks on the value of paraffin paper an a protec- 
tive rovi-rinK- 

Prevention dc In rouille pur 1c papier poraffind. 600 w. 1905. (In Lc (Irnit* 
civil, v. 17, p. 304.) 

Protecting sleol stnidmvs. 1,500 w. 111. 1905. (In Railway age, v. 39, 

pt. 1, p. Ml.) 

Dosoribos Barker's successful uso of paraffin paper as a protecting material. 



Acid test to determine corrosion resistance 96 

Alkaline solutions, inhibitive effect of, on corrosion 100 

Alloys, preservation of metal by means of coatings of 155 

Aluminum paint on letter-boxes, results of 237 

silicate (China clay) 262 

Anions, formation of 19 

Annealed metals and strained metals, relative stability of 85 

Annealing, effect of, on corrosion of steel 99 

Arrhenius 18 

Asbestine (magnesium silicate) 261 

Assembling of iron and steel structures with varying carbon types, 

effect of, on corrosion 76 

Barium sulphate (barytes) 260 

Barnacles, paints to discourage growth of 215 

Barytes (barium sulphate) 260 

Basic carbonate (white lead) 255 

Benzol 276 

Bichromate, its effect on iron 112 

solutions as inhibitors Ill 

Bituminous coatings 208 

Blending of pigments 197 

Blue lead (sublimated) 258 

Boiled oil 273 

Boilers, lessening of corrosion in, due to removing air from feed-water . . 101 

corrosion of 101, 160 

Bone-black 265 

Bower-Barf process 158 

Brown on the best paint for metal structure 235 

Calcium sulphate (gypsum) 261 

Carbon, black 266 

influence of, on the corrosion of steel 75 

Carbonic-acid theory as explaining corrosion 35 

Cars, painting steel 216 

Cations, formation of 19 

China clay (aluminum silicate) 262 

Chinese wood oil 273 

its place in manufacturing of marine and waterproof paints 274 

Chromates, as pigments, results of 163 


366 INDEX 


Chrome green (blue tone) 268 

yellow tone 268 

oxide 268 

yellows, orange 266 

medium 267 

lemon 267 

Chromic acid, as inhibiting corrosion 44 

Coatings, prime, for machinery 231 

Colloids, absorbent tendencies of 34 

action of, under the effect of electrolysis - 33 

electro-chemical properties of 33 

Concrete, its effect on corrosion of embedded iron and steel 11 

Condensers, formulas of paint for use on, at low temperatures .... 249 

Corrosion, comparison between, of wrought iron and cast iron .... 66 

in boilers and piping due to use of peat-bog feed-water 286 

effect of depolarization due to certain paint films on 118 

effect of assembling of metals with varying carbon types on their . . 76 

effect of the heat treatment of iron and steel on their 83 

effect of the presence of potash bichromate on 291 

effect of the presence of stimulative agents on 114 

effect of vibration on, of iron and steel 109 

electrolytic theory of 6, 40 

factors which stimulate 123 

problem of 1 

protection of iron from, by zinc coatings 59 

relation, in fresh water and sewage 102 

stimulated by alkaline oilers 115 

tests on resistance to, at Young's Old Pier, Atlantic City 202 

theories to explain 35, 44 

of boilers 160 

of boilers, effect on, of removing air from feed water 101 

inhibited by alkaline solutions 100 

inhibited by hydroxyl ions 110 

of rails, effect of active service on 108 

of water jackets 279 

of woven wire fence 142 

Corrosion of iron and steel, comparative 65 

factors which inhibit 124 

effect of their chemical purity on 67 

effect of careless manufacturing on 66 

effect of presence of carbon on 75 

effect of annealing on 99 

effect of presence of manganese on 78 

effect of occluded hydrogen on 71 

effect of phosphorus, sulphur and silicon on 79 

hastened by stresses and strains 2, 83 

inhibited by pigments containing certain oxidizing agents 113 

INDEX 367 


stimulated by the presence of mill-scale 121 

stimulated by wounds in the surface 120 

by presence of platinum 62 

Coslet process, the 160 

Cribb on the peroxide theory of corrosion " 40 

Delta metal 81 

Design of paints 239, 245 

Dewees Wood's process 159 

Divers, on the peroxide theory of corrosion 40 

Double layer, electrolytic 45, 46 

Driers 275 

Elasticity in paint 253 

Electrolysis, action of colloids under the effect of 33 

shown by phenol-phthalein 32 

Electrolytic action in corrosion, as shown by the ferroxyl reagent. ... 51 

action, the corroding effect of 44, 81 

double layer : 45, 46 

process of making white lead 54 

theory of corrosion 6, 40 

Electro-chemical relationship between metals 30 

Excluding properties of paints 253 

Experiment to test solubility of iron in pure water 42 

to show flow of electric current in a corroding can covered with 

depolarizing lacquer 116 

with bichromate to induce passivity 113 

Fences, painting wire 227 

woven wire, corrosion of 142 

Ferrocyanide 15 

Ferroxyl 48 

indicator 49 

test, Walker's modification of 154 

Formulas for inhibitive paints 247 

for use in condenser plants 249 

for iron piping 230 

Forth bridge 1 

Galvanized metal, painting of 206 

Galvanizing, electric method of 146 

hot-dip method of 108 

hot-dip method of, suggested improvements in 144 

of iron, function of zinc in 63 

vapor, method of 146 

Gases, effect of, on paints 252 

Gesner's method 159 

368 INDEX 


Graphitic pigments 265 

Gypsum (calcium sulphate) 261 

Hat-dip galvanizing process, suggested improvements in 144 

Heat treatment, effect of its, on corrosion of steel 83 

Hemholz, on polarization 26 

Hiding power of pigments 251 

Howe, H. M., on the conditions that bring about rapid corrosion . . 11 

Hydrolysis 20 

Hydroxy 45 

Ions 27 

ions, the presence of in corrosion 44 

ions as inhibitors of corrosion 110 

Impurities, effect of, on solubility of metals 10 

Indian red 264 

Indicator, the ferroxyl 49 

the phenol-phthalein 31 

Inert and chemically active pigments 252 

Inhibit, factors which, corrosion of iron and steel 124 

Inhibition of corrosion 110 

Inhibitive paints, formulas for 247 

Inhibitive pigments for use on railroad equipment 221 

Inspection of iron work, need of frequent 2 

Ions 19 

the formation of 22 

Iron and steel, corrosion of, action of zinc upon 62 

corrosion of, as aided by the presence of platinum 62 

comparative corrosion of ' 65 

paints designed for, general description of 254 

Iron, chemical purity as resisting corrosion 67 

oxides, artificial, for painting iron and steel 263 

pitting of 48 

Japan, baked, coatings 209 

black 219 

Jones, on formation of ions 22 

on theory of electrification of colloidal particles 33 

Joune, on the effect of silicon on the solubility of iron 160 

Kee's, discovery of passivity 28 

Knudson on stimulation of corrosion due to alkaline oilers 115 

Krassa, on making iron passive _. . . . 159 

Labeling paint, the advisability of 250 

Lacquers and their application 277 

INDEX 369 


Lampblack 266 

Leaded zinc 260 

Linseed oil 270 

chemical characteristics of 27 

Maumene^s test of 272 

physical characteristics 273 

films, physical characteristics of 177 

Litharge 262 

Lithopone 258 

Locomotives and tenders, painting 217 

Machinery, prime or shop coatings for 231 

Magnesium silicate (asbestine and talcose) 261 

Manganese, effect of, on corrosion of steel 78 

Manufacture, the effect of careless, on corrosion of iron 67 

Marine growths, paints to act as posions on 215 

Matheson, Erving, on comparative corrosion of iron and steel 66 

Meritens' method 159 

Metal, painting while hot 233 

prime coatings for 231 

structures, Brown on the best kind of paint for 235 

Metallic brown 264 

Mild process of making white lead the 254 

Mill-scale, as stimulating corrosion of iron and steel 121 

its action on neighboring surfaces of iron and steel 286 

Mine timbers of steel, painting 221 

Mineral black .' 266 

Moody on the peroxide theory of corrosion 40 

Mulder on prime coatings for metal 233 

Municipal accessories, the painting of various 236 

Munroe, observation on effect of hardening on the preservation of 

steel 75 

Mollet, Abbe" 15 

Occluded hydrogen, effect of, on corrosion of iron and steel 71 

Ochre, sienna and umber 264 

Oil coating, results of 234 

Old Dutch process of making white lead 254 

Orange, mineral 263 

Ornamental iron work, protection of 238 

Osmotic pressure 15 

Paper paints 215 

Parafnne spirits 276 

effect of sea-water upon 201 

Paint films, tests on solubility of 178 

the depolarizating action of, and its effect on corrosion 118 

370 INDEX 


Paint formulas, inhibitive 247 

Painting tinned surfaces 207 

Paints and preservatives for paper - 215 

effect on corrosion of chromates in 163 

elasticity and excluding properties of 253 

for railroad equipment generally 221 

tar 211 

testing and designing of 239 

tests of, in water suspension 163 

to discourage marine growths 215 

vehicles for 270 

water-shedding properties of 171 

Pennock on the effect of presence of alkaline on corrosion 115 

Peroxide theory of corrosion 39 

Perry on prime or shop coatings for metals 232 

Phenol-phthalein, as an indicator 31, 48 

Phillips, David, on comparative corrosion of iron and steel 66 

Phosphorus, sulphur and silicon, effects of, in steel on its corrosion 79 

Photomicroscope 188 

Pitting of boilers, prevented by the removal of air from feed-water. . . . 101 

of iron 48 

Pigments, blending of 197 

chart of rust inhibiting 168 

properties of 251 

with inhibitive oxidizing agents 113 

Piping, formula of paint for iron 250 

painting of 259 

Platinum, presence of, as aiding the corrosion of iron and steel .... 62 

Polarization 26 

as resisting corrosion 45 

Preece, on copper sulphate test 130 

Preservation of metals 6 

by coatings of alloys 155 

two coatings 152 

Precipitation process for making white lead 254 

Prime coatings for structural metal 229 

Process in manufacture of basic carbonate (white lead) 254 

Properties of pigments 251 

Prussian blue 268 

Purity of iron as an aid in resisting corrosion 67 

Railroad equipment in general, protecting paints for 221 

Railroad ties of steel, painting 219 

Railroad train sheds, painting of 218 

Red lead 262 

Refrigerating machinery, paint 237 

plants, formula for paint for 249 

INDEX 371 


Resistance of metals to rust 2 

Rust formation of 51 

resistance of metals to 2 

Rusting as primarily due to attack of hydrogen ions 44 

Sabin process of coating pipes 209 

Sea-water, effect of, upon paint 201 

Savy, on carelessness of manufacture as condusive to corrosion of 

iron and steel 2, 66 

on corrosion of structural iron and steel 1 

on corrosion of steel 65 

on effect on corrosion of assembling metals with varying carbon 

types 76 

on effect on corrosion of occluded gases 68 

on immunity from rust of iron and steel in active service 108 

on influence of carbon on the corrosion of iron and steel 75 

Service, action, as protecting rails from corrosion 108 

Settling, preventives of 252 

Sherardizing process 146 

Sienna 264 

Silica 262 

Snow, J. P., on corrosion of railroad signal bridges built partly of 

wrought iron and partly of steel 77 

Smith, Angus, method of coating pipes 209 

Solution tension of iron as not the same at all points 16 

Solutions 14 

Soya bean oil 274 

Spreading value : 252 

Spennrath, on bitumens as protective coating 210 

Stacks, painting of 209 

Stead, J. E., on the advisability of heating metal before painting. . . 233 

Stimulative agents, effect of, on corrosion 114 

Stimulation of corrosion, factors which cause 123 

Strains in iron and steel, the effect of, on corrosion 83 

Strengthened and preventives of settling of paint coats 252 

Stress and strain, part played by, in corrosion 2 

Structural metal, prime coatings for 229 

Talcose (magnesium silicate) 261 

Tanks, water, paint protection for 219 

Tar, coal, the use of 209 

paints 211 

Tassin, on copper-clad steel 155 

Test, ferroxyl, Walker's modification of 154 

for pin holes in zinc coatings 139 

of paint coatings designed to resist sea air 201 

372 INDEX 


Testing galvanized coatings 130, 138 

of paint 239, 241 

Tests at Young's Old Pier 202 

by Carnegie Steel Company on paints for steel mine timbers . . . 225 

of galvanized wire at Pittsburg 1908 148 

for penetration of moisture on paint films 172 

of pigments in water suspension 164 

on preservative coatings 199 

of zinc coatings, Walker on 141 

Thompson's tests on solubility of paint films 178 

Tinned surfaces, painting of 207 

Toch, on linseed oil films 177 

on making iron passive 159 

Tooth of pigments 253 

Tunnels, protection of iron in 218 

Turnbull's blue compound 48 

Turpentine 275 

Ultra marine blue 269 

Umber „ 264 

Van't Hoff's observation on osmotic pressure and gas pressure 18 

Varnishes 278 

Vehicles for pigments 270. 

Venetian reds 264 

Vermilion American 267 

Vibration, effect of on corrosion 109 

Vine black and willow charcoal 266 

Walker on effect of segregation and of impurities on corroson of iron 67 

on oxygen's part in corrosion 101 

on polarization 26 

on testing galvanized coatings 137 

on testing zinc coverings 141 

suggests indicator for ferrous ions 48 

Walker's modification of ferroxyl test 154 

test for detecting pin holes and cracks in zinc coatings 139 

and Campbell's test for determining effect of imperfections .... 139 

Water jackets, corrosion of 279 

Wells process 158 

White lead, basic carbonate 255 

basic sulphate (sublimated) 257 

Whiting (calcium carbonate) 262 

Whitney on electrolytic theory of corrosion 40 

on peroxide theory of corrosion 40 

Willow charcoal 266 

Wire drawing and subsequent annealing influence of, on solubility on iron 91 

INDEX 373 


Wire, galvanized, tests at Pittsburg 1908 148 

of field fences, painting 227 

Wood, on condition of New York City's elevated railroads 1 

on power of certain pigments to protect iron and steel 113 

on use of coal tar 210 

Working the properties of paints 253 

Wounds in surface of iron and steel as stimulating corrosion 120 

Young's Old Pier, tests on resistance to corrosion in sea-water at . . 202 

Zinc, action of, on corrosion of iron 62 

Zinc and barium chromate 268 

chromate 267 

lead white 259 

oxide 256