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cE ve <5 Vea, Gh T, M. 27 


CORROSION AND PROTECTION 
OF 
STEEL PILING IN SEAWATER 


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by Doc CUly 
Moa Lana ' 


Laverne L. Watkins 


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TECHNICAL MEMORANDUM NO. 27 
MAY 1969 | 


U. S. ARMY, CORPS OF ENGINEERS 


COASTAL ENGINEERING 
RESEARCH CENTER 


This document has been approved for public release and sale; 
its distribution is unlimited. 


Reprint or, re-publication of any of this material shall 


give appropriate credit to the U. S. Army Coastal Engineering 
Research Center. 


Limited free distribution of this publication within the 
United States is made by the U. S. Army Coastal Engineering 


Research Center, 5201 Little Falls Road, N. W., Washington, 
Dy Ca loots 


The contents of this report are not to be used for ad- 
vertising, publication, or promotional purposes. Citation 
of trade names does not constitute an official endorsement 
or approval of the use of such commercial products. 


The findings in this report are not to be construed 
as an official Department of the Army position unless so 
designated by other authorized documents. 


BL/WHO! 


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T. M. 27 


CORROSION AND PROTECTION 
OF 
STEEL PILING IN SEAWATER 


by 


Laverne L. Watkins 


TECHNICAL MEMORANDUM NO. 27 
MAY 1969 


U. S. ARMY, CORPS OF ENGINEERS 


COASTAL ENGINEERING 
RESEARCH CENTER 


This document has been approved for public release and sale; 
its distribution is unlimited. 


ABSTRACT 


The purpose of this report is to assemble in one paper much of 
the current knowledge involving corrosion of steel piling in seawater 
and methods of corrosion prevention. The study is based on a survey 
of literature. Causes of corrosion and the effects of environmental 
conditions such as galvanic couplings, marine fouling, abrasion, oxygen 
concentration and other factors are presented. Corrosion rates of bare 
steel piles and test results on protective coatings for steel are in- 
cluded. Factors involved in the use of cathodic protection and concrete 
jackets to protect steel piles are explained. The corrosion rates of 
plain carbon and low-alloy steels are compared. 


References surveyed show that flame-sprayed zinc sealed with 
saran or vinyl is possibly the best coating system tested. Concrete 
jackets of proper design and construction are reported to be very ef- 
fective. Cathodic protection also provides good corrosion protection. 
Combinations of cathodic protection with coatings or concrete jackets 
may be advantageous. 


There is great need for more data from which to determine the most 
economical method of protecting steel piling in seawater. 


FOREWORD 


This report was prepared in response to a request from the Office, 
Chief of Engineers, U. S. Department of the Army, for more design data 
concerning the corrosion of steel piling in seawater. It is one phase 
of the project "Study of Corrosion of Steel Piling in Seawater" which is 
being carried out under the Corps of Engineers' Engineering Studies 311 
sub-project, "Corrosion Mitigations", funded through the Rock Island 
District. Findings in this report relate directly or indirectly to the 
corrosion of steel piling in seawater. 


The report was prepared by L. L. Watkins, a project engineer in 
the Design Branch, under the general supervision of G. M. Watts, Chief 
of the Engineering Development Division and R. A. Jachowski, Chief of 
the Design Branch. 


At the time of publication, the Director of the Coastal Engineering 
Research Center was Lieutenant Colonel Myron Dow Snoke; the Technical 
Director was Joseph M. Caldwell. 


NOTE: Comments on this publication are invited. Discussion will be 
published in the next issue of the CERC Bulletin 


This report is published under authority of Public Law 166, 79th 
Congress, approved July 31, 1945, as supplemented by Public Law 172, 88th 
Congress, approved November 7, 1963. 


Section I. 


Section II. 


“CONTENTS 


ILE OIDUCILIGON, 6 6g oo oD oo 0 od 


STEEL PILING 


iio (Geiaereadl 6 6 0 eer rat ek ametiamaeeye ete ts 

2. Ordinary Gar bon Sheed. oO) oo 0 0° 

3. High Strength and Corrosion Fesiec ante Steels 
SeCGiwdom IIo SRVAWMUR 6 6 56 6 o 040 0 6 0 0 6 : 

Lo @e@aerel ¢ 5 6 0 

2. Salinity and Ghilertiadiise: ee 

Bo,  WEMOSHPENBUEES 5 16 6 oo 6 6 0 0 6 0 66 

he MLeewmoibaale Omeulinsies 595) ola 0 6 6 ooo 

5  dhileewipil@gil ROSISWECe 6 oo 6 6 46 6 6 0 

Crevice te eeGLey ones GEA RAN cee sath: IR ing: 

Yo  wWowllaisver Orpexoalsins 5 66°60 6 6 ; 

CrmmrBacteria kes.0 muh rlisk Gn Bae Sannin uotiown Ho 


Section IV. 


al 
2 


Section V. 


OA OW FWP 


Section VI. CORROSION RATE OF UNPROTECTED STEEL PILING IN 


dbo 
Bo 
3. 


CORROSION OF STEEL PILING IN SEAWATER . 


Gemermale: jo aie x6 Oe Oo 6 AG ois ieaecot suena 
The Corrosion Process SG 5S 


FACTORS AFFECTING THE CORROSION OF STEEL 


Gomera 6 6 6 60 6 00000 8 OOO 
IEHHOSHIOGUSS 60 006 6 010 8 G6 00 
OPgBSia COiMeESinsMENeGi 6 6 6 6405600 6 0 0 
jel VAIS o co 0 0 6 6 0 000 6 6 6 6 oO 
Sioulalaalay a Guia. co: ig. oa: OF ono. eacon bl -o MemuG=no 
Water MViCHOCHREYiyan se meailey oleae RaW ceaiueh aiciiel yeh ley te 
Marine Organisms... Oy Oe ee OED 
Galvanic Effect of Unlike ‘hebess 0 0 O10 


General .. , tO) C08 th Oe pOL ONaeLONnO 
Ordinary Cannon Sioci, 000600 00 
Infor “AMILIMGn SESS 6 6 6 65 6 68 


Section VII. CORROSION PROTECTION FOR STEEL PILING 


dbo 
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Gemenr, aul eate rae man ceuieey nial ise Ne bayell olertsqdvege svi aig ules 
IPSS wae Cognwalines 6 6 6 6 6 bo 

Go Migwedlisie Gogwdmes ¢ 6 6 66 0 6 6 0 6 
b. Non-Metallic Coatings ..... 6 0 


c. Surface Preparation for Goateings 
Glo | Iipabaisseg} store (Seeeil walalaligvs 5 6 5 6 


PILING IN SEAWATER 


SEAWATER 


Ww FF EPWWwWP Pw 


bh 
PARANA oO 


CONTENTS (Continued) 


Section VII (Continued) 


3 


hy 


5 6GCmemeESe JCS 555605660 06000505006050 0006060 0 
CehulaorllLe iPmeeeCwLOM 61600006000 6006 0005.0 0 
Go  Gememads 56°50 56 006000000000 0000000 0 
19g expalgoyestigule ©it Cehelechkle IigewSewleml oo oo 6 0 0 0 0.0 0 
@o Wyre CH Ceholaochle larewSewdOM 56 6 4 56 0 56000 0 0 

Gl, Genhyemle BySeemM 6 56 6 6 6 66 6 010 0 oll 
e. Electrolytic (Impressed Current) System ....... 
wo | NGOS Ibasheeilenlem 5 6 5b o 0 6 6 6 0 0 0 bo oO 6 8 oO 


Siar) WALICIEG | (COMCIIOISHHOINIS,, 56 5 0 6 6 6 6 0 610 60 0.0 000-6 


IIS MUIR, GINA) 6 4G 6 616 6 5.0 0 00.00.0000 0600000 6 


Appendix A. TABLES I THROUGH XV 


Appendix B. GLOSSARY OF CORROSION TERMS 


ILLUSTRATIONS 


Figure 


alee 


10. 


Corrosion of iron in 3% sodium chloride solution showing the 
CHE RG Che Weiolsreegabhas E¥alcl CyomehneMl 4 o 56 5060 60 000000 


ldneaeeYenG! Cas jolst Chal Croussetoysjaleya Oss willl pweeil 6 56 o 6 6 0 00 0 (0 


Variation of corrosion of iron as a function of the salinity, 
Deal (oti oulnner th nahin eerie ie lencuKoMlucha KUM H uch Msp Onde Oates iby ne 


Effect of velocity on corrosion of steel by seawater at 
Ehewnlofsolalnealies quieres) 6 6 6 6 0006000060 50606 0 6 


Corrosion rates of unprotected steel piling in seawater... 


Corrosion rates of unprotected steel piling at Boston 
Ghaye, WulenMele 5 GG 5 O06 0 0 0 0 6 6 6 0 6 OOo 60 HOD 


Corrosion rates of unprotected steel piling at Norfolk 
Eincl COCO SOLO 56 0 6 60 56 46 0 00 6H OO 


IRaliwigaligvs FoRCOPLILE 5 6 0 6 oO Oo 6 6 0 0 0°06 0 oo oO 8 


Seawater corrosion comparison for A-328 steel and mariner steel 


Effect of seawater velocity on corrosion rate of zine at 
Ehilostepqny WSMoKerenGwERS 5b 6 Oo 0 OO 0 6 0 oO O-0 0.0 0 6 0 6 0 06 


10 


12 


14 


15 


16 
18 


19 


22 


Figure 


lla. 
11b. 
ILS g 
126 


13a. 
LSI96 
Th. 


ise 


16, 


ILLUSTRATIONS (Continued) 


Comparative protection provided by the various 
corrosion dock panels. (Sheet 1 of 3).... 


Comparative protection provided by the various 
corrosion dock panels. (Sheet 2 of 3)... 


Comparative protection provided by the various 
corrosion dock panels. (Sheet 3 of 3).... 


Comparative protection provided by the various 
EINES siPCia POEINSGILS 59 60:5 9 6 6 6056 6 9 


Conerete Jackets for Steel H Piles ...... 
Concrete Jackets for steel sheet piling .. 
Example of galvanic corrosion cell ..... . 


Efficiency vs. operating voltage for full wave 
POC wWIINES 5g 50 6 60 0 000 0006000 00 6 0 


Efficiency vs. operating voltage for full wave 
WESC G6 5 6 co 6 0 0 0 0 0 


systems to 


systems to 


systems to 


systems to 


silicon 


25 


26 


yy 


45 


7 bet 


as bins a ‘to 


Tele ad May ce ; Be 


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( 


CORROSION AND PROTECTION OF STEEL PILING IN SEAWATER 


Section I. INTRODUCTION 


Steel piling is widely used in building marine structures. Steel 
sheet piling is often used in seawater to retain earth and prevent its 
erosion by water at such structures as bulkheads, quay walls, seawalls, 
and cellular construction for breakwaters and jetties. Steel H and 
cylindrical piles find wide use in seawater as supports for docks and 
offshore drilling platforms. They are also used in such structures as 
dolphins to resist lateral loads. 


Although steel has many advantages as a material for marine con- 
struction, it has the disadvantage of corroding in seawater if not 
protected. 


A number of factors may affect the rate at which steel corrodes in 
seawater. Some of the more important ones are the water temperature, the 
amount of dissolved oxygen, salinity, water velocity, abrasive materials 
in suspension, and the amount and type of marine organisms present. 
Effective methods of protecting steel from corrosion are to isolate the 
steel from the corrosive environment by a protective barrier or protect 
it by causing an electric current to flow to the steel from another source 
such as from another metal which is anodic to steel or from sources such 
as batteries or rectifiers. The latter method is known as cathodic pro- 
tection. Barrier type protection consists of organic and inorganic 
coatings and concrete encasement. 


Concrete jackets of good quality concrete and workmanship have a 
reputation for being effective in protecting steel from corrosion. However, 
the initial cost of this method is relatively high. No test data has been 
located from which to determine the protective life of concrete jackets 
on steel piling installed in seawater. 


Tests conducted by the U. S. Naval Civil Engineering Laboratory in- 
dicate that some of the relatively new coatings are performing fairly well 
on pile specimens in seawater. Tests data on these coatings have been 
incorporated in this report. Indications are that the initial costs of 
most of these coatings are considerably higher than the short-lived as- 
phaltic and coal-tar coatings commonly applied to steel piling in the past. 
Once the life spans of a number of the more durable coatings have been 
established, an analysis of the cost per year of protection will be very 
beneficial to designers and maintenance personnel. 


Better techniques and materials are being continually developed for 
cathodic protection and if properly designed and installed, it can be 
very effective for protecting steel piling below the water level. Steel 
above the water line must be protected by one of the other methods since 
submersion in seawater is required to complete the electrical circuit for 
cathodic protection. 


Section II. STEEL PILING 


1. General 


Steel sheet, H bearing, and cylindrical piles are made in a 
variety of sizes, and are used in marine structures such as piers, bulk- 
heads, jetties, groins, dolphins, and offshore drilling platforms. Piles 
for these structures are rolled from several types of steel such as ordi- 
nary carbon steel, high strength steel, and steel with both high strength 
and improved corrosion resistance. 


2. Ordinary Carbon Steels 


Carbon steels with American Society for Testing Materials (ASTM) 
(1959) designations A-328, A-252-55, A-36 and A-7 are among those used to 
produce steel piling. The minimum yield points of these steels range from 
30,000 to 38,500 pounds per square inch. These carbon steels give good 
service in unpolluted fresh water, but may deteriorate rapidly when ex- 
posed to splashing seawater or abrasive bottom materials in motion in 
seawater. 


3. High Strength and Corrosion Resistant Steels 


Several high-strength steels are now rolled into piling. Steels 
with ASTM designations A-440, A-441, and A-242 are in this category. In 
addition to these high-strength steels, another group of steels have been 
developed which contain columbium or vanadium. These steels have yield 
points ranging from approximately 45,000 to 55,000 pounds per square inch 
(Lindahl, 1964). Although these steels have higher strength, reports do 
not indicate any improvement in corrosion resistance. A high-strength 
low-alloy steel, which is often referred to as corrosion resistant steel, 
contains higher percentages of copper, nickel, silica and phosphorus than 
A-328 steel and is reported to be superior to,the A-328 steel in resisting 
corrosion in the splash zone. It was concluded from tests at Harbor 
Island, North Carolina, that the corrosion resistance of this steel in 
the splash zone is three times that of A-328 steel where mild wave action 
exists and tWice that of A-328 steel where considerable wave action 
exists (U. S. Steel, 1964). 


Section III. SEAWATER 
1. General 
Seawater contains most of the known chemical elements, but it 
is basically a solution of salts dissolved in water. This salt water is 
the home of many types of plant and animal life. This section describes 


some of the more important characteristics of seawater which influence 
the corrosion of steel piling installed therein. 


Cp Salinity and Chlorinity 


The salt content of seawater is usually expressed as 
salinity or chlorinity. Chlorinity is defined in Sverdrup, Johnson, 


2 


and Fleming (1942) as the number giving the chlorinity in grams per kilo- 
gram of seawater sample and is equal to the number giving the mass in 
grams of "atomic weight silver" just necessary to precipitate the holo- 
gens in 0.3285233 kilograms of the seawater sample. The chlorinity of 
seawater ranges from about 18 to 20 parts per thousand, averaging about 
19 parts per thousand. The term salinity is intended to denote the total 
amount of dissolved salt in seawater. For convenience, salinity is 
usually calculated from the chlorinity of seawater using the formula: 


Salinity = 0.03 + 1.805 X chilorinity 


The salinity of seawater ranges from approximately 33 to 37 parts per 
thousand and the average in the open sea is of the order of 35 parts per 
thousand (Shreir, 1963). 


3. Temperature 


Seawater surface temperatures, in general, range from -2° to 
35°C -(approximately 28° to 95° F). Its freezing point is -2° C. 
Fluctuations in the temperature of seawater at a given location decreases 
with depth (Baxter, et al, 1960). 


4, Electrolytic Qualities 


Electrolytes are substances containing tiny charged particles 
called ions. Electrolytes conduct electric current by the flow of ions. 
Seawater contains ions as a result of the dissolved salts. The analysis 
of a sample of water from the North Pacific Ocean (Fink, 1960) revealed 
the presence of various cations (positively charged ions) and anions 
(negatively charged ions) as shown below: 


Ions _in North Pacific Seawater Samples 


Cations Percent Anions Percent 
Na" 1.056 cl 1.898 
Me** 0.127 SO], 0.265 
ca** 0.040 HCO; 0.014 
K 0.038 Br7 0.0065 
sr’? 0.001 F 0.0001 

Sum: 1.262 Sum: 2.1836 
H, BO, (undissociated) 0.003 


Grand Total 3.449 percent 


The ions contained in seawater are a necessity in carrying out the electro- 
chemical process of corrosion. Further details on the part played by ions 
in the corrosion of steel piling are given in Section IV. 


5. Electrical Resistance 


The approximate electrical resistance range of seawater is 15 
to 4O ohm-cem compared to 300 to 20,000 ohm-cm for fresh water. Ohm-cm 
refers to the resistance of matter 1 square centimeter in cross-section 
and 1 centimeter long (U. S. Army Corps of Engineers, 1962). This dif- 
ference in electrical resistance between fresh water and seawater is one 
of the more significant factors which causes corrosion in seawater to 
proceed faster than in fresh water. 


6. pH Value 


Aqyeous solutions will always contain positively charged hydro- 
gen ions (H ) and negatively charged hydroxyl ions (OH ) as a result of 
the dissociation of water. It is the relative amounts of these ions that 
determine whether a solution is alkaline, neutral or acid. If hydrogen 
ions (H ) are in excess, the solution acts as an acid; if hydroxyl ions 
(OH ) are in excess, the solution acts as an alkali. The pH value of a 
solution is the means of denoting its degree of alkalinity, acidity or 
whether it is neutral. The pH value is calculated from the hydrogen ion 
concentration. The total amount of hydrogen and hydroxyl ions contained 
in a solution is nearly constant, therefore, it is known that, if-the 
‘hydrogen ion concentration is increasing, the hydroxyl ion concentration 
is decreasing. The hydrogen aad Loe ion constant for pure water 
has been determined to be 1071% or 107 T hydrogen gram ions per liter and 
107! hydroxyl gram ions per liter. The pH value of an electrolyte is 
determined by use of the formula: 


pH = Log _ 


Using this formula, neutral solutions have a pH value of 7.0. Acidity 
increases from neutral as the pH value decreases from 7.0. Acidity 
approaches a maximum in a solution as pH approaches 0. The alkalinity 
of a solution increases from neutral as the pH value increases from 7.0 
to a maximum of approximately 14.0. Seawater pH values normally range 
from 8.1 to 8.3 but may approach 7.0 in stagnant basins where hydrogen 
sulfide is present (Redfield, in Uhlig, 1948). 


7. Fouling Organisms 


Seawater is inhabited by many species of marine plants and 
animals. Some of these organisms are likely to become attached to 
marine structures and are known as fouling organisms. 


Fouling organisms which are considered to have possibilities of 
affecting metals in seawater have been divided by Clapp (Uhlig, 1948) 
into three groups: Sessile organisms, semimotile fouling organisms and 
motile organisms. 


Shell-building sessile organisms include annelids, barnacles, 
encrusting Bryozoa, mollusks and corals. WNon-shell-building sessile 


organisms include marine algae, fillimentous Bryozoa, coelenterate, tuni- 
cates and calcareous and Siliceous sponges. Semi-motile fouling organisms 
are those which possess the power to move if not restricted by outer 
forces, such as the growth of other organisms surrounding it. This group 
includes sea anemones, worms, certain crustacea and mollusks. Motile 
organisms such as worms, certain mollusks such as sea slugs and snails, 
may affect the corrosion of metal directly or indirectly due to the slimy 
film secreted by them (Clapp, in Uhlig, 1948). Ways in which fouling or- 
ganisms affect the corrosion of steel piling are given in paragraph 7, 
"Marine Organisms" of Section V. 


8. Bacteria 


Seawater contains numerous types of bacteria. Anaerobic bac- 
teria which thrive in oxygen-free environments where sulfate is present 
are of concern to corrosion engineers where stagnant water exists. 
Sulfate reducing bacteria can cause corrosion of material without the 
presence of oxygen. 


A factor of significance in corrosion protection is that many ma- 
terials are suited to the metabolism of some types of marine bacteria 
(Muroaka, 1963). For this reason, many of the protective coatings for 
steel may be damaged or destroyed by marine bacteria. Muroaka gives 
four ways in which bacteria takes part in the fouling of marine struc- 
tures as follows: 


a. Being a source of food for barnacles. 
b. Affording footholds for other animals. 


e. Aiding sessile organisms in depositing 
their calcareous cements. 


d. Discoloring glazed or bright surfaces (fouling 
proceeds faster on dull dark surfaces). 


Section IV. CORROSION OF STEEL PILING IN SEAWATER 
1. General 


The corrosion of steel piling in seawater is caused by electro- 
chemical action. This corrosion process primarily involves the steel, 
an electrolyte, in this case seawater, and oxygen. As a result of the 
corrosion process, iron, the principal constituent of steel, is restored 
to the state in which it is mined as ore (iron oxide). Iron oxides that 
form on the surface of steel as a result of the corrosion process may 
greatly retard further reaction. Black iron oxide (Fe30)) offers good 
protection from further corrosion whereas the iron oxides (Fe203 and 
Hee Op ex Ho°) do not appreciably protect the underlying metals (Baxter 
and Steiner, 1960). 


2. The Corrosion Process 


Steel in contact with an electrolyte inherently has areas of 
differing electrical potential. The difference in potential causes 
electric currents to flow in the steel and through the electrolyte. 

The current flow in the electrolyte is in the form of ion transfers. 
Positive Fett ions are released into the solution (electrolyte) from 
the anodic surfaces of the steel. The positive ions in the electrolyte 
are attracted to the cathode since there is a reduction process present 
which produces OH ions. These ions combine to form Fe (0H)o(ferrous 
hydroxide). The OH ions are formed by the dissociation of water (H29) 
producing hydrogen atoms (H+) and the OH (Hydroxide ion). When an Fett 
ion is released into an electrolyte, it gives up two electrons (2e7)). 
These electrons are given up at the anode and flow through the metal to 
a cathodic area. Two hydrogen atoms (2H+) from dissociated water may 
combine with two electrons (2e ) at the cathode to form hydrogen mole- 
cules (Hj) which will either cling to the cathodic surfaces, bubble off 
as gas or combine with oxygen to form water. In addition to the re- 
action described above in the steel corrosion process, there can be 
other reactions such as the conversion of ferrous iron to ferric iron. 


Section V. FACTORS AFFECTING THE CORROSION OF 
STEEL PILING IN SEAWATER 


1. General 


A number of factors may influence the rate at which the corrosion 
process of steel piling proceeds in seawater. Some are: 


a. Water temperature 

b. Concentration of oxygen in electrolyte (seawater ) 
c. pH value of the seawater 

d. Marine fouling on piling 

e. Salinity of the seawater 

f. Velocity of the water relative to the structure 
g. Galvanic effect of unlike metals 


Details concerning the effects of these factors are given in the para- 
graphs to follow. 


2. Temperature 


Temperature affects the corrosion of steel in seawater in several 
ways. One is that chemical reactions of the corrosion process are ac- 
celerated in warmer water. Another is that the marine fouling organisms 
which may affect the corrosion rate are more numerous in warmer waters. 
Temperature also affects the capacity of the water to dissolve oxygen. 


Data compiled by LaQue (Uhlig, 1948) indicates that the tendency 
for the chemical process of corrosion to proceed faster in warmer water 
is often counteracted by the metal surface having a heavier protective 


covering of marine fouling. This is considered to be the reason some 
investigators have found that, contrary to expectations, corrosion in 
warmer waters has proceeded at practically the same rate as in cooler 
waters. 


3. Oxygen Concentration 


Oxygen can affect the corrosion of steel in seawater in several 
ways. It may cause variations in the electrical potential of metal areas 
in a solution when its concentration varies along the metal surface; it 
acts as a cathode depolarizer; it reacts with the ferrous atoms to form 
oxides of the metal. Areas of low oxygen concentrations on a metal sur- 
face are anodic to those of higher oxygen concentration (U. S. Army Corps 
of Engineers, 1962). 


Temperature and oxygen are interrelated in seawater corrosion. 
Figure 1 shows variations in the corrosion rate of steel in air-saturated 
and partially de-aerated sodium chloride solutions at various tempera- 
tures. Seawater near the surface is nearly saturated with oxygen in 
areas where considerable wave action and spray exists (Fink, 1960). 


4, pH Value 


There is little change in the corrosion rates of steel surfaces 
between pH values of 4 and 9.5 at a given temperature. The surface is 
in contact with a layer of hydrous ferrous oxide and corrosion can only 
progress as fast as oxygen can diffuse the protective layer (U. S. Army 
Corps of Engineers, 1962). As alkalinity increases from 9.5, the iron 
tends to become passive as the permeability of the surface layer by 
oxygen is decreased. As the pH value drops below 4, the protective 
corrosion product layer is dissolved and the acid reacts directly with 
the metal. An example of the effect of pH value on corrosion rate is 
shown in Figure 2. These curves were obtained by exposing mild steel 
specimens to water having an oxygen concentration of 5 milliliters per 
liter. Hydrochloric acid and sodium hydroxide were added as required 
to produce the desired acidity and alkalinity for the investigation. 


D>. Salinity 


Although the total salinity of seawater may vary in different 
locations, the proportions of various salts relative to each other re- 
main virtually the same (Fink, 1960). Of the various ions in seawater 
resulting from the dissolved salts, the chloride ion is the most sig- 
nificant. This is attributed to its being present in larger quantities 
and to its ability to penetrate corrosion product films to continue its 
activity in the corrosion process. Figure 3 shows the effect of sodium 
chloride concentration on the corrosion rate of iron and the solubility 
of oxygen as a function of salinity. Note that the concentration of 
sodium chloride does not affect the oxygen solubility until a concentra- 
tion of 5 to 10 grams per jiter is reached. 


Dissolved lron, mg/16_ hr. test 


Temperature , F 


Figure 1. Corrosion of iron in 3% sodium chloride solution showing the 
effect of temperature and aeration. From Fink, 1960 


8 


0.004 


Ho Evolution 
Begins 


0.003 


0.002 


0.001 


Average Specific Penetration — Inches/ Year/ MIO, / Liter 


pH 


Figure 2. Effect of pH on corrosion of mild steel 
(From U.S. Army, Corps of Engrs, 1962) 


Oxygen, mg per | 


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6. Water Velocity 


The highest water velocities. at pile structures which may signi- 
ficantly affect their corrosion are probably those caused by wave action. 
These velocities depend upon wave conditions possible at the site and 
should seldom exceed 25 feet per second. The effect of water velocity on 
corrosion rates in seawater is quite different from the effect in fresh 
water. It is more difficult to attain passivity of metals in seawater. 


Tests in neutral waters have shown that the corrosion rate in- 
creases with an increase in water velocity up to a certain point. Further 
velocity increase may then cause the corrosion rate to decrease (Copson, 
1952). The increase in corrosion rate with increased velocity is attrib- 
uted to the force of the water eroding the existing protective oxide 
films thereby exposing new metal to the corrosive environment. The de- 
crease in the corrosion rate when the water velocity exceeds a certain 
high has been shown to be due to the increased oxygen supply permitting 
a film of ferric hydroxide to form (Copson, 1952). This film apparently 
adheres to the metal at relatively high velocities. Other tests (Copson, 
1952) are reported to have shown that it is quite difficult to reach a 
state of corrosion passivity in seawater. Figure No. 4 shows the effects 
of water velocity on the corrosion of steel in seawater. The difficulty 
in producing corrosion passivity in seawater can probably be attributed 
to the chloride ions. Water with zero velocity (stagnant) can usually be 
expected to have a lower corrosion rate but a higher rate of localized 
pitting (Copson, 1952). 


7. Marine Organisms 


Marine organisms may affect the corrosion rate of steel piling 
in several ways, such as: 
a. Penetrating soft protective coatings and exposing base 
metal to seawater. 


b. Forming protective films on metal surfaces. 
ec. Burrowing into protective concrete encasements. 


d. Organisms smothered by larger ones may form acids 
which attack the metal surface. 


e. By producing metabolic byproducts, including hydrogen 
sulfide, acids, carbon dioxide and ammonia which may take part in the 
corrosion of metal (Snyder and Hull, 1965). 


f. The formations of fouling organism may cause localized 
stagnant water conditions which in turn create differential oxygen cells. 


8. Galvanic Effect of Unlike Metals 


Caution should be taken in connecting unlike metals or creating 
unlike conditions in the same metal or alloy for structures in seawater 


Corrosion Rate IPY 


Figure }., 


Meters Per Second 


Velocity Feet Per Second 


Effect of velocity on corrosion of steel 
by seawater at atmospheric temperature 
(From LaQue in Uhlig, 1948) 


since galvanic corrosion will result. When two unlike metals are con- 
nected in an electrolyte, such as seawater, an electric current flows 
in the metals and through the electrolyte. The least noble metal or 
alloy (the one highest in the galvanic series) will corrode. The metal 
which corrodes is also the one from which the current flows into the 
electrolyte. 


The order of some metals and alloys in the galvanic series as de- 
rived from tests in seawater are shown in Table XV, Appendix A; the 
information in this table is from a report by LaQue and Cox (1940). 
Revisions were made to show the current aluminum designation. The order 
of the metals in the various groups may change depending on incidental 
eonditions of exposure. Galvanic action due to combining metals shown 
within a group in Table XV should be relatively low (LaQue and Cox, 
1940). In the event it is desirable to use materials from different 
groups in combination, the galvanic effect will ordinarily be less if 
materials are selected from groups closest together in the table. 


Another practice which should ordinarily be foliowed when coupled 
unlike metals will be in contact with seawater is to keep the area of 
the anodic metal or alloy large in comparison to the cathodic material. 
This practice spreads the corrosion due to the galvanic electric current 
over a larger area. 


Section VI. CORROSION RATE OF UNPROTECTED STEEL 
PILING IN SEAWATER 


1. General 


The corrosion rate of unprotected steel piling in marine struc- 
tures can vary considerably depending on environmental conditions. Some 
of the more influential environmental factors were discussed in the 
preceding paragraphs. 


Due to the vertical extent of steel piling in marine structures, 
there are variations in environmental exposure, and therefore, differ- 
ences in rates of corrosion at various levels. Corrosion rates for steel 
piling should, therefore, be stated for particular exposure zones in 
order to be of value. 


2. Ordinary Carbon Steel 


There appears to be general agreement among corrosion special- 
ists that bare steel structures of ordinary steel continuously submerged 
in relatively uncontaminated seawater will corrode at a rate of approxi- 
mately 5 mils per year. As previously stated, corrosion rates can vary 
considerably between the various corrosion zones, and at the same zone of 
structures at different locations, depending on conditions at the site. 
Figures 5 through 7 show rates of loss of metal thickness at various 
elevations along unprotected piles installed at the locations indicated. 


Elevation 


Miami, Fla. Miami, Fla. Miami, Fla. Stamford, Conn. 


MLWO MLWO 


VTA / AY, \/ NY) 


20 


0) 10 20 O 10 20 


Corrosion Rate (Mils/ Year) 


Figure 5. Corrosion rates of unprotected steel piling in seawater. 
(After U. S. Army, Corps of Engrs, 1952) 


14 


LEGEND 


o———oo Average Rate (mpy) 
@—-———-® Maximum Rate (mpy) 
Oo Sample 2 feet above MHW 
Boston , Mass. Alameda , Calif. 


Distance (feet) 
Referred to MLW 


eae 


One half deo | -—- f= 4 —-——-—-—— 
Z 


a = 
= . 

s|\5 Mud line — 

o co) 
S\\c3 

2) = * C 

c|o 

ele 

w 
=| @ 
all 

‘}ac 

-3 2 
0 5 10 10} 5 10 


Corrosion Rate (Mils/ Year) 


Figure 6. Corrosion rates of unprotectea steel piling at Boston 
and Alameda. (After Brouillette and Hanna, 1960) 


15 


NOTE: The bars indicate the corrosion rate range 
for three samples tested at the given level. 
Lines drawn through the midpoint of these 


— i 1959 Measurement bars show the corrosion rate profile 
-—-(1 1965 Measurement determined from the samples. 
6 Coco Solo, Canal Zone 
a ee 
5 
4 
ag ° 
a= 
=|2 
ow] 2 
2} 2 
O}e 
a\L 
Sle 
MLW 
-| 
es ie a= 
<2. 
Half depth 


+] 


mud 
ao 
|e 
|S 
o|v 
wm; > | 
Lv = 
o\| {= 
o) 2 
c|;vo 
oO} aw 
-_—| 
YW) uu 
(ay||\c2 
@ 
o = 


Corrosion Rate (Mils/ Year ) 


Figure 7. Corrosion rates of unprotected steel piling at Norfolk and 
Coco Solo. (After Brouillette and Hanna, 1960) 


Profiles showing the pitting rates of the piles concerned in Figure 7 
are given in Figure 8. 


Tests indicate that when piling is installed where there is con- 
siderable movement of abrasive bottom materials, the portion of the 
piling subjected to the abrasion will deteriorate at the fastest rate 
(Ross, 1948, Alumbaugh, 1962). 


Observation of steel sheet pile groins installed at Palm Beach, 
Florida, indicated that the localized corrosion rate in the sand abrasion 
zone could be as high as 373 mils per year (Ross, 1948). Due to the 
severity of corrosion in this zone and the distinctive difference in the 
environment, it is felt that it should be treated as a separate zone 
when it exists. 


The most severe corrosion zone on steel piling after the abrasion 
zone is the splash zone when a structure is located where splashing water 
exists a large percentage of the time. Localized corrosion rates as high 
as 63 mils per year have been reported for this zone (Rayner, 1952). 


3. Low Alloy Steels 


Various metals have beer! added to steel with the objective of 
producing steel which is more corrosion resistant in a marine environment. 
Steel bars containing percentages of copper were tested by immersing in 
seawater and found to be somewhat more resistant to corrosion than ordi-~ 
nary steel (U. K. Department of Scientific and Industrial Research, 1928). 
However, in alternately wet and dry conditions, steel with higher copper 
content lost more weight than that with lower percentages of copper. The 
improved corrosion resistance of copper-bearing steel is attributed to 
the copper causing a more durable corrosion film to form which retards 
further corrosion. Ross (1948) reports that steel sheet pile groins 
containing copper showed no superiority over ordinary steel in tests at 
Palm Beach, Florida. Mariner steel piling, containing more copper, silica 
and phosphorus than A-328 steel, is expected to give 2 to 3 times the 
corrosion resistance of A-328 steel in the splash zone, depending on the 
degree of exposure to wave action (U. S. Steel, 1964). Figure 9 shows 
comparative corrosion rates for these two steels. 


Section VII. CORROSION PROTECTION FOR STEEL PILING 
1. General 


Methods now used to combat the corrosion of steel structures in 
seawater include the encasement of steel in concrete, the application of 
various protective coatings, cathodic protection, and various combinations 
of these methods. The paragraphs to follow will describe these methods 
of protection and present information of value when considering their 
WES o 


LEGEND 


o——————o_ 1959 Measurement 
o-———---o |965 Measurement 


Norfolk , Virginia Coco Solo, Canal Zone 


Distance (feet) 
Referred to MLW 
S 


MLW 


Distance (feet) 


Referred to Mudline 


SuOMNISEZO O Ge “we Bo 
Maximum Pitting Rate (Mils Per Year) 


Figure 8. Pitting profile. (From Brouillette and Hanna, 1966) 


NOTE: Mariner steel composition contains higher percentages 
of copper, nickel, silica, phosphorus than A-328. 


Distance from Top of Steel Specimen 


5 Years Exposure 9 Years Exposure 


Corrosion Rate (mils/yr. ) 


Figure 9. Seawater corrosion comparison for A-328 steel and mariner steel. 
(After U. S. Steel Corp., 1964) 


2. Protective Coatings for Steel Piling 


Protective coatings on steel piling are intended to act as a 
barrier to separate the steel surface from its corrosive environment. 
The development of suitable coatings for long-term protection of steel 
in seawater has been quite slow. Coating systems which appear to be 
worthwhile for protecting steel piling are, in general, rather new, and 
long-range test data are not available for many of them. However, test 
results located are presented. 


There are numerous types of coatings now in existence, many of which 
are used in combination with other types as well as alone. References 
to combination coating systems in this report will be made in terms of 
the basic type of topcoat material. 


Most of the test results on coatings contained in this report were 
obtained from tests carried out by the U. S. Naval Civil Engineering 
Laboratory. They have apparently done most of the testing of coatings 
suitable for steel piling. 


Some of the coating data presented resulted from testing coatings on 
mooring buoys and panels. Although the performance of coatings on mooring 
buoys may be similar to their performance on steel piling, this is not 
necessarily so. It is felt, however, that the performance of coatings on 
buoys relative to each other will be applicable for steel piling. Test 
results for coatings on steel panels are presented since very few tests 
have been made on steel piles. Any coating which fails on a steel panel 
should not be expected to protect a steel pile. In addition, coatings 
which perform well on panels should at least be considered good prospects 
for steel pile protection. Metallic coatings especially may be adversely 
affected by electrical currents caused by the pile passing through dif- 
fering environments that may not exist in tests of panels. 


Types of coatings in use today may be divided into a number of cate- 
gories, two of which are metallic and nonmetallic. Some useful test 
information has been discovered on coatings and is presented under these 
two classifications. Since surface preparation is an important factor 
when coating steel for marine exposure, information thereon has been 
included under this heading. 


The nonmetallic coatings may be further divided into organic and 
inorganic types. 


a. Metallic Coatings. Several investigations have been made to 
determine the corrosion protection ability of metallic coatings on steel 
piling. The metals involved were flame-sprayed zine and flame-sprayed 
aluminum. These metallic coatings have also been used in combination 
with other coatings. 


(1) Flame-Sprayed Zinc. The U. S. Naval Engineering Labora- 
tory has tested flame-sprayed zinc on steel piling (Alumbaugh, 1962). 


20 


The results of these tests are included in Tables II a and II b of 
Appendix A. These results show the flame-sprayed zinc coating to 
compare favorably with other high ranking coatings in the test except 

in the splash zone. Later tests of longer duration showed a number of 
other coatings to be quite superior to bare flame-sprayed zinc for pro- 
tecting steel in seawater. The poor performance of zinc in the splash 
zone is probably due to the tendency of splashing water to erode the 
protective corrosion film formed on its surface. Figure 10 shows that 
the corrosion of zine in seawater increases with water velocity at least 
within the velocity range of the test (Tuthill and Schellmoller, 1965). 


Other tests involving steel panels coated with flame-sprayed zinc 
which were exposed by total immersion in seawater at mean tide level, 
and in the atmosphere, have been carried out at various locations by 
the American Welding Society (1962). It was concluded from these tests 
that flame-sprayed zinc coatings 3 mils in thickness exposed alternately 
to seawater and atmosphere will give less than 6 years of corrosion 
protection to steel, also that a 6-mil flame-sprayed zine coating may 
give little more than 6 years of protection to steel exposed in the same 
manner. A later, 12-year report by the American Welding Society (1967) 
which gives results of a continuation of tests of totally immersed panels 
shows that flame-sprayed zinc coatings of 3 and 6 mils thickness have 
failed completely. Flame-sprayed zinc with thicknesses of 9, 12, 15 and 
18 mils was still protecting the steel, however, the zinc was almost 
entirely coverted to corrosion products. Exposure at mean tide level 
produced similar results. The results of testing flame-sprayed zinc 
panels sealed with vinyl and chlorinated rubber are given in this section 
under "Vinyls" and "Chlorinated Rubber". 


One paper (Horvick, 1964) suggests that for protecting steel con- 
tinually immersed in low velocity seawater, under normal conditions, 
one mil of zine coating should be specified for each year of protection 
required. 


Steel panels with a flame-sprayed zinc coating were tested by alter- 
nate immersion and extraction at quarter-hourly periods in a solution of 
20 grams of sodium chloride per liter of water for 2,390 hours (Orlowski, 
1965). The thickness of these zinc coatings were in the order of 1.5, 3 
and 5 mils. Some were sealed by cold phosphatization. A report on these 
tests states that: 


1. There was no appearance of rust. 


2. There may be a slight advantage resulting from sealing 
the zine coatings by cold phosphatization. 


3. The adhesion of vinyl paint to phosphatized paint is 
satisfactory. 


Recent test results (Alumbaugh and Brouillette, 1966) report flame- 
sprayed aluminum tobe far superior to flame-sprayed zine in protecting steel 


2| 


Corrosion Rate Mils / Year 


Velocity , Ft./Sec. 


Figure 10. Effect of seawater velocity on corrosion rate of zine at 
ambient temperature. (From Tuthill and Schellmoller, 1965) 


22 


piling from corrosion by seawater. The best flame-sprayed zinc coating 
of the test (5.5 mils thick) failed after 4 1/2 years, whereas one of the 
flame-sprayed aluminum coatings (4.5 mils thick) was still providing ex- 
cellent protection after 11 1/2 years exposure in seawater. However, 
when sealed with other types of topcoats, the flame-sprayed zinc was 

far superior to the flame-sprayed aluminum. For a comparison of flame- 
sprayed zinc coatings with others, see Figures 11 a-c. Figure llc shows 
that flame-sprayed zinc in combination with either saran, vinyl, epoxy, 
or furan have provided good protection to steel piling specimens for 

10 1/2 years. Further testing will be required to determine the maximum 
duration that these coating systems are effective. Alumbaugh and 
Brouillette (1966) further report that when a phenolic mastic coating 
was applied to a flame-sprayed zinc coating blisters occurred before the 
test specimen was exposed to seawater. 


(2) Flame-Sprayed Aluminum. Flame-sprayed aluminum coat- 
ings 6, 9, 12, 15 and 18 mils thick on steel panels were evaluated after 
6 and 12 years of exposure immersed in seawater at Freeport, Texas, and 
Wrightsville Beach, North Carolina. The results are given in reports by 
the American Welding Society (1962 and 1967). After 6 years there were 
small amounts of base metal corrosion on panels from both test sites 
(American Welding Society, 1962). Evaluation of the flame-sprayed alumi- 
num coatings after 12 years of exposure revealed that all unsealed coat- 
ings had blistered, but that there were no pits in the steel under the 
blisters (American Welding Society, 1967). 


Some steel panels coated with flame-sprayed aluminum and sealed 
with a wash primer and vinyl coat have been tested immersed in seawater 
for up to 12 years. The results of these tests are included under "Vinyl 
Coatings". Other steel panels with the flame-sprayed aluminum coating 
were exposed at meantide level for 12 years. The report of the 12-year 
inspection states that although mean tide level exposure is considered 
to be more severe in corroding bar steel than total immersion, it ap- 
peared to be no more severe for steel with flame-sprayed aluminum or 
zine. 


The results of a six-month test of flame-sprayed aluminum (Alumbaugh, 
1964) are included in Table III. 


Alumbaugh and Brouillette (1966) report that a 4.5-mil flame-sprayed 
aluminum coating is still effectively protecting steel in seawater after 
11 1/2 years of exposure. This process used powdered zinc. The fact that 
a thicker (5 mil) flame-sprayed aluminum coating using aluminum wire had 
practically failed after 11 1/2 years may or may not be of significance 
as to which is the better application method. 


b. Non-Metallic Coating. This group comprises many coatings, 
including both organic and inorganic. The earlier non-metallic coatings 
for steel piling were generally coal tar or asphalt; neither of which 
has been very successful in seawater. One of the major problems is pene- 
tration of these coatings by fouling organisms. Coal-tar epoxy coatings 


23 


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25 


See Table XIV, Appendix A, for coating detatls. 


See page 27 for footnotes. 


NOTES: 


Comparative protection provided by the various systems to corrosion dock 


panels. 


(From Alumbaugh and Brouillette, 1966) 


(Sheet 2 of 3) 


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26 


Footnotes for Figures lla, lib and lic 


Vinyl system is still protecting the steel very well, but the primer 
and topcoat have lost adhesion and can be peeled from panel. Removed 
from test. 


Epoxy-phenolic. 


TFE (Tetrafluoroethylene), System 110, is System 109 with the TFE 
emulsion finish. 


Panel was lost. 


Saran is not actually a vinyl, but is included in this group since its 
properties are similar to those of a vinyl. 


The letters designate different surfaces over which the coatings were 
applied. S = bare sandblasted steel; P = pretreatment primer, Formula 
117; Z = flame-sprayed zinc; A = flame-sprayed aluminum. 


Coatings in this group applied over bare steel and Formula 117 are 
also included under their particular generic types and are shown here 
for purposes of comparison. 


Notes: 1. The letters a (atmospheric), b (tidal) and c (immersed) above 


the bar graph indicate the zone in which the coating failed. 
2. Increased concentration of horizontal lines in the bar graphs 


indicates increased deterioration of coating. Solid black 
areas indicate complete failure. 


27 


have been applied to many pile structures since 1955 and are proving 

to be more durable than ordinary coal tars. Many other non-metallic 
coatings such as vinyls, rubbers, phenolics, sarans, mica-filled as-— 
phalt emulsions, epoxies, urethanes, polyester-glass flake, and furan 
are being tested for service on steel piling by the U. S. Naval Civil 
Engineering Laboratory, the National Bureau of Standards and the Coastal 
Engineering Research Center. Information on non-metallic coatings from 
tests in progress or completed are presented in paragraphs to follow. 


(1) Bituminus. A coal-tar coating cold-applied to steel 
piling for a test in seawater was in poor condition after 2 1/2 years 
in the zones that included the tide and sand abrasion. However, it was 
still effectively protecting the steel in the atmospheric and imbedded 
zone. The evaluation ratings given this coating at various test inter- 
vals up to 2 1/2 years are shown in Tables II a and II b. 


Panels coated with a system consisting of a coal-tar primer, a 
coal-tar enamel and a natural resin anti-fouling topcoat were reported 
to be in "remarkably good" condition after 6 years immersion in tropical 
seawater. See Table IV. These coatings were applied very thick (70-100 
mils). The same coating systems were considered inadequate for 6 years 
of exposure in seawater at mean tide level (Alexander, Forgeson, and 
Southwell, 1958). 


Asphalt and coal-tar coatings on steel were tested in seawater at 
a harbor and a surf site at Port Hueneme, California. After exposures 
ranging up to 6 years, these coatings were found to be quite good for 
marine atmospheric exposure but did not show long-term durability in 
the tidal and submerged zones. One of the primary causes of failure was 
damage to the coatings by fouling organisms. Substantiating this theory 
is the fact that anti-fouling coal-tar coatings gave longer protection 
than other types in these tests (Alumbaugh and Brouillette, 1966). See 
Figures lla and 12. 


(2) Vinyl. Vinyl coatings are one of the more successful 
coatings for protecting steel in seawater. Of 83 coating systems tested 
on steel panels exposed to seawater in the tide zone for 6 years, 3 vinyl 
systems including a topcoat of anti-fouling paint were among the five 
best coating systems (Alexander, Forgeson, and Southwell, 1958). These 
coatings are included in Table V which lists the 5 coatings considered 
satisfactory for the mean tide zone after 3 years exposure. The vinyl 
coatings, however, were not considered to adequately protect the metal 
panels after 6 years immersion in seawater (see Table IV). 


Vinyl coatings were included in coatings tested on piling driven in 
the surf zone at Port Hueneme, California (Alumbaugh, 1962). The ratings 
of the vinyl coatings (vinyl mastic and aluminum vinyl) after 2 1/2 years 
of exposure are shown in Tables II a and II b. These coatings were also 
tested on steel sheet piling and H piling driven at Cabras Island (off 
Guam) in the Marianas. The coating evaluation results of this test are 
given in Table VII. 


28 


Coating Types 


Resin Blends 


Phenolics 
Zinc-Rich 


Years of Exposure 


Sen Nes 


Notes: See Table XIV in Appendix A for coating system details. 
Increased concentration of horizontal lines tn the bar 
graph indicate tnereased detertoration of coating. 


Solid black areas indicate complete fatlure. 
1/ Same as 3/ above except 109f and 1107 


2/ S = coating failure on shore face of panel. 
O = coating fatlure on ocean face of panel. 


38/ Epoxy-phenolte. 
4/ Panel was lost. 


Figure 12. Comparative protection provided by the various systems 
to angle iron panels. 


29 


Steel panels coated with flame-sprayed aluminum, a wash primer 
and vinyl topcoat were immersed in seawater at Freeport, Texas, and at 
Wrightsville Beach, North Carolina. Inspection of the panels at the end 
of 12 years revealed that protection of the steel was excellent with the 
exception of panels having aluminum 3 mils thick. The other aluminum 
thicknesses tested were 6, 9, 12, 15 and 18 mils. Panels with the same 
coating system were also placed at mean tide level for alternate immersion 
and atmospheric exposure. These panels appeared to be in the same general 
condition as the totally immersed panels (American Welding Society, 1967). 


Of approximately 21 vinyl coating systems tested in Port Hueneme 
Harbor, a vinyl mastic had the longest exposure. After 9 1/2 years it 
was still providing a fair degree of protection to the steel (Alumbaugh 
and Brouillette, 1966). Two other vinyl systems with 6 1/2 and 8 years 
of exposure were performing very well. The performance of vinyl coatings 
and other types are given in Figures lla-c and 12. Other findings from 
these tests were that aluminum pigmented vinyls showed no conclusive 
superiority and that failure of vinyl systems could usually be attributed 
to poor adhesion. 


A coating system consisting of proprietary primer, vinyl, vinyl- 
alkyd and vinyl antifouling coats was rated in "good-fair" conditions 
after exposure for nearly 5 years on mooring buoys (Drisko, 1968). 
Three other vinyl coating systems (10, 11 and 12, Table VIII) performed 
poorly and were removed from the test due to failure after approximately 
21/2, 11/2 and 4 1/2 years, respectively. 


(3) Rubber. Short-term tests by the U. S. Naval Civil 
Engineering Laboratory showed neoprene synthetic rubber coatings to be 
relatively good for protecting steel piling from corrosion by seawater 
in each of the corrosion zones. Tables II a and II b show the ratings 
given to neoprene coatings after 2 1/2 years of testing on steel piling 
in the surf zone. 


Steel panels coated with neoprene rubber were exposed in the atmos- 
phere, at mean tide, and continuously submerged in seawater for 6 years 
along with 83 other coating systems. Alexander, Forgeson and Southwell, 
1958 report that a neoprene rubber coating ranked second only to vinyl 
coatings with antifouling topcoats in the mean tide exposure. Mean tide 
was stated to be the most severe of the test zones. Table V gives the 
five top-ranking coatings in this zone. The synthetic rubber coating 
ranked highest in protecting the steel in the seawater immersion test. 
It should be noted that the coating was exceptionally thick. 


Chlorinated rubber was used as a seal over flame-sprayed zinc applied 
to steel panels and exposed to seawater continuously immersed and at mean 
tide level (American Welding Society, 1962). After 6 years of exposure, 
an inspection of the panels revealed that the chlorinated rubber-seal coat 
appeared to be completely gone from the specimens totally immersed and 
from those at mean tide level, and that some of the sealed panels showed 
more corrosion than the unsealed ones. 


30 


A chlorinated rubber coating over a red-lead primer was applied 
to steel piling and the test specimens exposed in the surf of the outer 
harbor at Port Hueneme, California. At the end of six months, the 
coating rated relatively low as shown in Table III. 


A recent report (Alumbaugh and Brouillette, 1966) on tests including 
16 synthetic rubber coating systems shows that 9 systems were considered 
to have failed or to be on the brink of failure by the end of four years 
exposure in seawater. Figure 11b shows that System No. 11 which consisted 
of a 77-mil thickness of flame-sprayed rubber powder gave steel the 
longest protection of the synthetic rubber coatings. This system did 
not fail until after approximately 11 years of exposure in seawater. A 
17.5-mil coating system, consisting of a synthetic rubber primer and a 
neoprene finish coat plus accelerator, gave the second best performance 
of this generic group by protecting the steel for approximately 8 years. 


(4) Phenolics. A phenolic mastic coating was tested on steel 
piling for 2 1/2 years (Alumbaugh, 1962) and according to test results 
as shown in Tables Ila and IIb performed quite well with the exception of 
Zone “B' which was in the lower part of the tide zone. Due to the depth 
of the water, Zone B was also in the sand-abrasion zone. 


Phenolic mastic coatings were tested on mooring buoys for 5 years. 
The ratings of the coating at the end of 2 years was good-fair (Drisko, 
1965). See Table VIII. The coating rating was also good-fair after 5 
years (Drisko, 1968). 


A phenolic resin mastic coating applied to sheet and H piling driven 
in the surf along the coast of the Marianas was reported to have per- 
formed adequately in protecting the piling for 4 years (Bureau of Yards 
and Docks, 1963). See Table VII. 


In other tests at Port Hueneme, California, phenolic coatings 
performed better as a group than any other generic type (Alumbaugh and 
Brouillette, 1966). One phenolic mastic coating (System No. 72), given 
in Figure 1lb, gave complete protection to steel for approximately 9 
years. It was reported to be performing very well after 9 1/2 years 
of exposure. The same coating was also reported to have given the best 
performance on steel specimens subjected to the abrasive action of sand 
in the surf at Port Hueneme (Alumbaugh and Brouillette, 1966). 


(5) Saran. After 2 1/2 years of testing on steel piling, 
@ saran coating system rated quite good except in the sand-abrasion zone 
(Alumbaugh, 1962). Since saran was lower in cost than the other coating 
systems tested for 2 1/2 years, it was recommended as the most economical 
of the group to protect steel piling where sand abrasion does not exist. 
See Tables Ila and IIb. 


Saran was tested on mooring buoys by the U. S. Naval Civil Engineer- 
ing Laboratory (Drisko,1965). Ratings at the end of approximately 2 years 


3| 


are given in Table VIII. A later report on this test (Drisko, 1968) rated 
the saran to be in good-fair condition after 5 years of exposure. One 
source (Drisko and Brouillette, 1965) reports that saran has given excel- 
lent protection to steel panels exposed in shallow seawater for 4 years. 


A 6.5-mil coating built up with alternate coats of orange and white 
Formula 113/40 saran applied over sand-blasted steel was reported to 
be giving good protection after 10 1/2 years of exposure in seawater 
(Alumbaugh and Brouillette, 1966). Saran applied over flame-sprayed 
zine in the same tests was reported to be providing complete protection 
to the steel from rusting after 10 1/2 years. See Figures 1lb and lic. 


(6) Asphalt Emulsion, Mica-Filled. Tests of a mica-filled 
asphalt emulsion showed it to be inadequate in two corrosion zones after 
21/2 years of testing in seawater. This coating performed poorly in 
the upper tidal zone and afforded practically no protection in the abra- 
sion zone at the end of 2 1/2 years according to the evaluation ratings 
(Alumbaugh, 1962). 


(7) Coal-Tar Epoxy. Coal-tar epoxies are a blend of coal tar 
and epoxy resins. Although coal-tar epoxies have been rather extensively 
used as a coating on marine structures in the past few years, very little 
actual test data has been found concerning it. Table VIII gives the rating 
"sood-fair" for coal-tar epoxy over an epoxy primer tested on a mooring 
buoy for over 2 years (Drisko, 1965). A later report (Alumbaugh, 1964) 
on this test also rates the coating "good-fair" after 5 years of service. 


Two coats of catalyzed coal-tar epoxy primer and 1 coat of aluminum- 
filled catalyzed coal-tar epoxy topcoat giving a total thickness of 15 
mils were applied to steel and tested in shallow seawater. This coating 
is reported to have given excellent protection to the steel for 3 years 
(Drisko and Brouillette, 1965). 


Recent test data (Alumbaugh and Brouillette, 1966) shows coal-tar 
epoxies to hold considerable promise for protecting steel in seawater. 
A 12-mil coating did not fail until between 7 and 9 years of exposure. 
Thicker coatings (up to 24.5 mils) being tested are expected to be rated 
among the better coatings for protecting steel piling. See Figure lla. 
Figure 12 shows that coal-tar epoxy coatings were also among the better 
coatings in withstanding sand abrasion in the surf zone. 


(8) Epoxy. An epoxy coating has recently been developed which 
can be applied and cured on surfaces, under water, or dry. Based on short- 
term tests (Drisko and Brouillette, 1965),this coating is quite versatile. 
The coating is prepared for use by mixing two components and can be applied 
to surfaces under water or to dry surfaces by workmen using rubber gloves. 
Thicknesses exceeding 1/8 inch have been recommended for the coating. 


Tests of six months' duration were made to determine the adhesive 
strength of epoxy coatings to bare steel and to other types of coatings. 
The findings and conclusions given in a report (Drisko, et al, 1964) 
resulting from this test are as follows: 


32 


(a) The four underwater-curing epoxies tested adhered 
well to sandblasted steel and to a variety of protective coatings. 


(b) In general, the bonds formed by these epoxies lost 
no strength after the specimens were submerged for 6 months in flowing 
seawater. 


(c) The bonded specimens with protecting coatings 
failed under applied stress in four different ways and under forces 
differing widely in magnitude. 


(d) The four underwater-curing epoxies were similar in 
formulation; the major differences were in types and amounts of added 
fillers. 


(e) In these tests, none of the four proprietary epoxies 
performed significantly better than the others. 


(f) The underwater-curing epoxies tested can be used 
successfully to make underwater repairs to abrasion damage to recently 
applied protective coatings and to protect bare steel. 


Table X gives the force required to break the bond between the four 
underwater-curing epoxies and other protective coatings. The results of 
these tests indicate that the underwater-curing epoxy coatings may be 
of considerable value for patching other types of coatings. The cost, 
however, may prohibit its use as a primary coating on most types of 
marine structures. 


Polyamide- and amine-cured epoxy resin systems tested on steel in 
seawater performed quite well with the exception of systems 40, 41 and 68 
shown in Figure lla. System 88 in this test was giving- good protection 
to the steel after 9 years of exposure in seawater (Alumbaugh and 
Brouillette, 1966). An epoxy coating system tested on mooring buoys was 
rated to be in "good" condition after 2 years of seule (Drisko, 1965). 
See Table VIII.The coating was ‘also vated good after 5 years of service 
(Drisko, 196). 


(9) Urethane. Very little test data was found for urethane 
coatings. However, one report (Drisko,. 1965) rated a urethane coating 
"sood-fair" after nearly 2 1/2 years exposure on a mooring buoy in sea- 
water at San Diego, California. See Table VIII.The same coating rated 
fair-poor after nearly 5 1/2 years of exposure (Drisko, 1968). Tests 
by the U.S. Naval Civil Engineering Laboratory (Alumbaugh and Brouillette, 
1966), indicated that, based on their condition after 5 to 6 years of 
exposure, urethane coatings should rate quite high for protecting steel 
piling. The urethane system affording the best protection except in the 
abrasion zone was applied over a vinyl primer. 


SS) 


(10) Glass Flake Polyester. No test data was found concern- 
ing the protective ability of this coating for steel piling. However, it 
was reported to be the best of a number of coatings tested for the pro- 
tection of ship bottoms (Devoluy, 1965). Better resistance to abrasion 
and undercutting were claimed for this coating relative to others tested. 
Based on the above findings, it is felt that this coating may have some 
merit in protecting steel piling, especially in the sand abrasion zone. 


(11) Furan. Four protective coating systems involving furan 
have been tested on bare steel for periods up to 10 1/2 years: Formula 
117 pretreatment primer plus vinyl red lead, iron oxide primer, flame- 
sprayed zinc, and flame-sprayed aluminum. Of these systems, furan over 
flame-sprayed zinc has given good protection for 10 1/2 years (Alumbaugh 
and Brouillette, 1966). Furan's performance when applied over the other 
coating materials and applied on bare steel has been fair in comparison 
to other coatings tested. See Figures lla, lle and 12. 


ec. Surface Preparation for Coatings. The proper preparation 


of the metal surface is of primary importance when applying a protective 
coating of steel piling. Metal surface preparation methods include blast 
cleaning, pickling, solvent cleaning, hand tool cleaning, power tool 
cleaning and flame cleaning. 


Blast cleaning is commonly used in the surface preparation of steel 
piling when significant quantities are involved. Although varying degrees 
of surface blast cleaning are used, a surface blasted to white metal can 
be expected to give best results. Blast cleaning to this extent, however, 
is usually not economical for many structures. Commercial blast cleaning 
which requires the removal of all oil, grease, mill scale, rust, and other 
surface contaminants is considered adequate for many of the protective 
coating systems. 


Pickling is another method of metal surface preparation which pro- 
motes relatively long paint life for most coatings, when the proper 
procedures are used (Steel Structure Painting Council, Volume 2, 196). 
However, facilities for pickling large structural items are rather 
limited. 


Solvent cleaning, hand tool cleaning, power tool cleaning, and 
flame cleaning may also be used to prepare steel pile surfaces for 
coating. These methods are considered to be more limited in use and 
effectiveness than blast cleaning or pickling. 


Specifications and details concerning the various metal surface 
preparation methods and their uses are contained in a report by the 
Steel Structures Painting Council, Volumes 1 and 2, (1964). 


d. Primers for Steel Piling. Specially formulated coatings 
known as primers are often applied to bare metal surfaces before other 


coatings are applied. Prerequisites for maximum performance of primers 
as given in Jarboe (1964) are as follows: 


34 


1. Possess high specific adhesion, permitting satisfactory 
performance over clean sandblasted metal. 


2. Have high chemical resistance. 


3. Exhibit satisfactory wetting properties when applied to 
the metal to fill and penetrate rather than bridging 
crevices, pits, and pores found in most applications. 


h. Contain high solids for coverage and provide adequate 
protection to sharp corners and edges. 


5. Have minimum of drag in brush application and possess 
good spray properties. 


6. Perform satisfactorily over old oxidized painted surfaces, 
rusty metallic surfaces, and even slightly damp surfaces. 


7. Show compatibility with various generic types of topcoats. 
8. Contain adequate amounts of inhibitive pigments. 
9. Dry to a tack-free stage in a reasonably short time. 


10. Possess satisfactory weatherability in the event finish 
coats are not to be applied for three to six months. 


Although all of these characteristics may be difficult to obtain in a 
primer suitable for marine structures, they are, nevertheless, desirable. 


Post curing inorganic primers such as zinc-lead silicate for steel 
are stated to have a long and proven record in corrosion prevention and 
to have performed outstandingly in the chemical and marine industries, 
either top-coated or bare (Gelfer, 1964). Other qualities stated for 
post-cured inorganic primers are: 1. excellent acceptability of topcoats; 
2. ability to be cured quickly and effectively under varying conditions 
of temperature and humidity. The principal disadvantages of post-cured 
inorganic primers are the added cost and processing required in applying 
the curing agent and removing the residue from it before further coating 
can proceed. 


A post-cured zinc-lead silicate primer performed satisfactorily for 
18 months when used as a control for testing self-curing inorganic primers. 
Panels coated and scored showed little or no corrosion in the scored area 
and were otherwise unaffected (Gelfer, 1964). 


In other tests by the U. S. Naval Civil Engineering Laboratory (Drisko 
and Brouillette, 1965), a post-cured inorganic zinc silicate primer has 
provided excellent protection to steel in shallow seawater for two years 
regardless of the deterioration of the topcoat during this period. In 
these tests, the vinyl phenolic primer coat did not adequately adhere to 
the zine silicate primer. 


35 


3. Concrete Jackets 


A method sometimes used to protect steel in marine structures 
from corrosion is to encase or jacket the steel in concrete. Two methods 
of jacketing steel H piles with concrete as given by Ayers and Stokes 
(1961) are shown in Figure 13a. Figure13b shows methods of protecting 
steel sheet piling in straight walls and cellular construction with con- 
erete jackets. To effectively protect steel from corrosion, the concrete 
must be of good quality, properly placed and cured, and of adequate 
thickness. Ayers and Stokes (1961) show a minimum thickness of | inches 
fer Conerete jackets! over siteeill. 


When concrete is permeated by seawater due to use of a poor quality 
concrete or inadequate concrete thickness, corrosion of the steel occurs. 
Since the corrosion product volume is greater than the original steel 
volume, pressure is exerted on the surrounding concrete. If this pressure 
is greater than the opposing tensile strength of the concrete, the con- 
erete will crack and eventually spall, exposing the steel. According to 
information in Griffin (1965), corroding metal can exert pressures up to 
about 4,700 pounds per square inch on the concrete. 


Salt-free concrete has a pH value of about 13 (highly basic). Under 
this condition a tough corrosion film builds up on the surface of steel 
embedded in the concrete and the steel becomes passive in respect to 
further corrosion. When chloride ions enter concrete, the pH value is 
lowered and the passive film of corrosion products is destroyed, allowing 
further corrosion (Griffin, 1965). 


A good quality concrete for jacketing steel in marine structures 
should have high strength, be relatively impermeable and have good bonding 
characteristics. Information by Finley in Wood (1963) recommends 7 1/2 
bags of cement per cubic yard of concrete and 5 gallons of water per bag 
of cement for corrosion protection in splashing water or alkaline soil. 
Low water-cement ratios are desirable. 


In areas where freezing and thawing exists, entrained air is recom- 
mended to prevent concrete deterioration. Mather (1957) reports that 
tests by the Portland Cement Association showed that proper use of air 
entrainment improved the performance of concrete with respect to freezing 
and thawing and to exposure to solutions of sulfate salt. Tests by the 
Corps of Engineers at Treat Island, Maine, also showed that the proper 
entrainment of air in concrete was the most important factor in improving 
the durability of concrete to severe weathering. Tyler (1962) reports 
that air entrainment in concrete aids by slowing the rate of seawater 
penetration. Lyse (1961) reports that the percent of air voids in con- 
crete should be 10 to 12 percent for best resistance to freezing and 
thawing where exposed to seawater. 


Another factor which may be important when considering concrete pro- 


tection for steel piles is the rigidity of the structure. It seems quite 
possible that concrete jackets on seacoast pier piling, for example, 


36 


Welded 
fabric 
SI 4 in. min 


SECTION 


FULL JACKET 


PARTIAL JACKET 
Concrete jackets for steel H piles. 
Ayers and Stokes, 1961) 


Figure 13a. 
(After 


SECTION 


ELEVATION 


Steel sheet piling-straight wall construction 


Cap line 
Sass a that ae 


Cap line 


24"x2'slotted bars on 
alternate sheet piles 


SECTION A-A 


SECTION B-B 
Steel sheet piling-cellular construction 
Concrete jackets for steel sheet piling. 
and Stokes, 1961) 


Figure 13b. 
(After Ayers 


37 


might be cracked due to flexing of the structure by the force of the 
waves. 


Procedures suggested to minimize the deterioration of reinforced 
concrete should, in general, be applicable to concrete-jacketed steel 
piles. Some pertinent precautionary measures suggested in Mather (1957) 
from Warren (1956) for preventing deterioration of reinforced concrete 
in coastal structures are: 


1. Careful selection of the cement. The most durable from the 
standpoint of chemical composition were said to be those 
with low tricalcium aluminate content, and the special 
aluminous cements. 


2. Care with the aggregate, which must be tough and nonreactive 
to cement; and careful grading of aggregates. 


3. High quality maximum density concrete. Rich mixtures - 1:1:3 
or 1:1:2 were suggested. 


4, Restriction of all working stresses to reasonable values. 


5. Cover to be not less than 2 inches, preferably 3 inches; 
and square edges on beams and piles to be avoided. 


6. Thorough curing in air before exposing to the tides or to 
splash, to obtain a hard outer skin. 


7. Removal of mill scale from steel before installation. 


8. Water/cement ratio to be as low as possible, with correction 
for the moisture content of the agregates. 


9. Special care in placing the concrete to avoid segregation, 
particularly in underwater work. 


10. Use of vibrators to obtain maximum consolidation. 


The Corps of Engineers has conducted tests on over 2,500 concrete 
specimens at exposure stations located at Treat Island (Eastport), Maine, 
and St. Augustine, Florida. The tests were initiated in 1935. The con- 
crete specimens were covered by seawater with the rising tides and ex- 
posed to atmosphere at low tides. Conclusions from these tests as given 
by Cook (1953) are as follows: 


1. The entrainment of properly regulated quantities of air is 
the most important factor in the improvement of the durability 
of concrete under severe weathering conditions that has been 
developed by these investigations. At Treat Island, well-made 
concrete of good quality materials will not ordinarily with- 
stand the exposure for more than one winter unless the concrete 
contains the proper amount of entrained air. 


38 


2. The use of various non-air-entraining admixtures did not 
appear to be of material benefit in increasing the dura- 
bility of plain concrete but were not harmful in that they 
did not appear to decrease the durability of air-entrained 
concrete. 


3. The use of air entrainment does not protect concrete which 
contains unsound aggregate. 


4, The blending of natural cement with plain portland cement 
greatly improves the durability of concrete if by so doing 
the proper amount of entrained air is produced in the 
concrete. 


5. No definite trends in the effect of curing conditions on 
durability have been revealed. 


6. Aluminous cement produced highly durable concrete. 


7. The use of absorptive form-lining improves the durability 
of concrete surfaces. 


8. The quality of horizontal construction joints appears to 
be governed primarily by the quality of the concrete at 
the top of the lower lift. 


9. The use of cement with a tricalcium aluminate content in 
excess of 12 percent has resulted in concrete that is non- 
durable in warm seawater. The use of Type II cement with 
a tricalcium aluminate content less than 8 percent appears 
warranted for such exposure. 


Although the above conclusions were not based on tests of concrete jackets 
on steel piles, they should be considered when designing concrete jackets. 


The literature surveyed did not indicate a life expectancy for steel 
piling with concrete jackets in the critical corrosion areas. Ayers and 
Stokes (1961) reported that concrete jacketing of steel piling has proven 
very effective when it extends from the top of the piling, above high 
tide to well below mean low water. They also concluded that concrete 
jackets in the tide range and cathodic protection below low tide was the 
most complete system for protecting steel piling. One publication reported 
that a reinforced concrete sheet pile wall at Neptune Beach, Florida, was 
still in good condition except for storm damage after 16 years of service, 
also that service records indicate that good concrete can endure for 50 
years or more without excessive maintenance (Mather, 1957). 


39 


4h. Cathodic Protection 


a. General. Cathodic protection is another method of mitigating 
the corrosion of steel piling in seawater. This method is suitable for 
protecting the immersed zone of the piling. Protective coatings for steel 
are often used in combination with cathodic protection in order to reduce 
the area requiring protection. 


b. Principle of Cathodic Protection. Corrosion of steel is 


an electrochemical process which takes place in a corrosion cell. Cor- 
rosion cells exist when a metal, or metals, which are electrically con- 
nected, have areas differing in electrical potential and are in contact 
with an electrolyte such as seawater. Electrodes of corrosion cells are 
either cathodic or anodic. The electric current leaves the metal surface 
at the anode and travels through the electrolyte to the cathode by ion 
transfer while electrons flow through the metal from the anode to the 
cathode. Corrosion of the metal occurs at the anode where the electric 
current leaves the metal. Cathodic areas of metal are usually unaffected 
by the entry of electric current, however, in some cases a protective 
film results on the metal surface such as calcareous deposits which may 
develop when seawater is ‘the electrolyte. 


Cathodic protection of a metal is based on forcing a reversal in the 
direction of electric current flow from that which normally occurs when 
the metal is corroding. The current must have sufficient magnitude and 
polarity to force the metal to be protected to become the cathodic elec- 
trode. Cathodic areas do not corrode when an adequate electric current 
flows to them. The current density required for the cathodic protection 
of steel varies with the type of steel being protected, its condition, 
and its environment. Field tests at the structure site and experience 
should be utilized in estimating current density requirements. The cur- 
rent density required for the corrosion protection of bare steel installed 
underground or in fresh water usually ranges from 1 to 6 milliamperes per 
square foot of surface area whereas from 3 to 10 milliamperes per square 
foot of surface area is usually required for installation in seawater. 
The range of current densities for coated steel sheet piling are usually 
within the range of 0.5 to 6.0 milliamperes per square foot for the sea- 
water side and 0.95 to 1.0 milliampere per square foot for the land side. 
(U. S. Army Corps of Engineers, 1962). 


c. Types of Cathodic Protection. Two types of cathodic protec- 


tion systems are used - the galvanic system and the electrolytic system. 
The basic difference in these two systems is that, in the galvanic system, 
the source of the required electric current is the difference in electri- 
cal potential between two connected unlike metals in an electrolyte. The 
anodic metal corrodes as current flows to the cathode. The principle is 
illustrated in Figure 14, In the electrolytic system, direct current 
electricity of sufficient magnitude is supplied by an outside source. 

The source is usually a rectifier, which converts alternating current 
electricity to direct current which flows from one or more anodes through 
the electrolyte to the metal being protected. 


40 


Electrical OT EN se 


Electron Flow 


Electrically charged particles 
(Ions) break away from Anode 
material and move through 
Electrolyte to Cathode. 


Cathode material 
does not corrode. 


Anode material corrodes. 


Container 
Ions from Anode are 


neutralized by Electrons 
from Cathode. 


Figure 14. Example of Galvanic Corrosion Cell. 


4| 


Characteristics of galvanic and rectifier cathodic protection systems 
compared by Husock (1962) follows: 


Galvanic Ine wabrealSwe 
1. Requires no external power External power required 
2. Fixed driving voltage Voltage can be varied 
3. Limited current Can be designed for almost 


any current requirement 


4, Usually used in lower Can be used in almost any 
resistivity electrolytes resistivity environment 

5. In underground applications Interference with neighboring 
interference with neighbor- structures must be considered 
ing structures is usually 
negligible 


d. Galvanic System. In this system a galvanic corrosion cell 
is formed by installing an electrode which will be anodic to the metal 
to be protected (cathode) when the two are connectea in an electrolyte. 
See Figure 14. The anodes are sacrificed to protect the cathodic metal. 
The anodes may be replaced periodically, if required. 


(1) Galvanic Anodes for Steel. The principal materials 

which have been used for galvanic protection of marine structures 
ot steel are magnesium and zinc. Although aluminum is anodic to steel, 
a surface film forms on the aluminum which hinders its generation of 
protective current when coupled to steel as sacrificial anodes. Aluminum 
alloy anodes have been developed and used in seawater applications (Husock, 
1962). In laboratory tests, alloys of aluminum mercury and zinc have 
attained efficiences of 95 percent with potentials in the order of 1.05 
volts. The electrical output per pound of metal consumed was 1,290 ampere 
hours (Reding and Newport, 1966). A comparison of zinc and magnesium 
anode characteristics from Husock (1962) is given below. 


Characteristic Zinc Magnesium’ 
Efficiency (approximate percent ) 90 50 
Theoretical consumption (lbs/ampere yr) 23.5 8% 
Approximate actual consumption (lbs/ampere yr) 26.0 oO 
Solution potential* gal Lo D5 


*Referred to a copper sulphate electrode. 


42 


Table XII gives the consumption rates in seawater, cost per pound 
and cost per ampere-year for magnesium, zinc and aluminum along with 
other anode materials suitable for impressed current systems. 


The use of magnesium has been favored when higher driving forces 
are required. Hosford (1963) states that magnesium anodes in seawater 
tend to disintegrate rather rapidly unless restricted, therefore, zinc 
anodes are generally better in seawater environments. 


e. Electrolytic (Impressed Current ) System. This system is 


often employed in cathodic protection systems where it is desirable to 

use relatively high currents and voltages, where numerous galvanic anodes 
would ordinarily be acquired, where flexibility of voltage and/or current 
is desired, and where automatic control is desired. The source of cur- 
rent for impressed current systems is usually a rectifier if alternating 
current is available. Batteries or other direct current electrical sources 
can be used if necessary. 


(1) Rectifiers. Rectifiers are used in impressed current 
systems to transform alternating current into direct current of the 
proper voltage. Rectifiers are also provided with a means of controlling 
the amperage. A rectifier consists basically of a circuit breaker, step- 
down transformer, stack, meters and a weatherproof enclosure. Selenium 
and silicon are the two materials generally used in constructing rectifier 
stacks. The selenium rectifier has been used extensively in cathodic 
protection systems in the past. Selenium rectifiers age with time. The 
aging consists of an increasing resistance in the direction of current 
flow and a decreasing resistance in the opposite direction. Selenium 
rectifiers are generally estimated to last 10 years when operated below 
maximum rating (National Association of Corrosion Engineers, 1965). 
Silicon rectifiers, however, offer the important advantages of apparently 
not being affected by age, increased efficiency, and compactness relative 
to selenium rectifiers. Figures 15 and 16 show efficiency curves for 
selenium and silicon rectifiers. On an operation basis, the National 
Association of Corrosion Engineers (1965) lists preferable types of 
rectifiers as follows: 


Conditions Type Rectifier 
Above 30 volts d-c, single phase Silicon 
Above 44 volts d-c, three phase Silicon 
Below 30 volts d-c Selenium 


(2) Impressed-Current-System Anodes. Although there are 


numerous materials that can be used as anodes in impressed current systems, 
disadvantages encountered eliminate many for practical applications. The 
types of anodes generally used in impressed current systems protecting 
structures in seawater are graphite, high-silicon cast iron and various 


43 


~~ 
oO 
Cc 
@® 
= 
i 
1-28 Volt DC 6 
Rating 2 
cb) 
> 
Cc 
29-56 VoltDC S 
Rating = 
(‘S 
cob) 
2 
97-84 Volt DC @ 
Rating 
0 10 20 30 40 50 60 70 
Actual DC Operating Voltage 
100 
~ 
(Ss) 
Cc 
2 
1-44 Volt DC = 
Rating fan 
Cc 
iS 
45-88 Volt DC » 
Rating o 
> 
Cc 
(o} 
oO 
ie 
fo) 
oO 
a 
: Uf | te ee es len 
220 10 20 30 40 50 60 70 
Actual DC Operating Voltage 
Figure 15. Efficiency vs. operating voltage for full wave selenium 


rectifiers. (After U. S. Army Corps of Engrs, 1962) 


44 


Percent Conversion Efficiency 


70 


U 10 


hana DC cisterns vehene. 


Figure 16. Efficiency vs. operating voltage for full wave silicon 
rectifiers. (After U. S. Army Corps of Engrs, 1962) 


45 


platinized metals. Graphite anodes are usually superior to high-silicon 
cast iron for seawater installations whereas high-silicon cast iron 
anodes are usually superior for fresh water installations (Husock, 1962). 
According to one report (Toncre and Rice, 1966), high-silicon iron anodes 
were selected over graphite anodes for brackish water installation after 
running tests on the two types. Composition changes are continually 
being made on basic anode materials to improve their performance. There- 
fore, information on the relative merits of each type should be checked 
just prior to selection. 


Cherry (1965) reports that graphite and silicon iron anodes suffer 
breakage when subjected to heavy seas. If these anodes are placed on 
the bottom, as is sometimes done to lessen their exposure to wave action, 
their efficiency may be impaired due to increased anode to electrolyte 
resistance caused by gas surrounding an anode which has been embedded 
in mud. 


Platinized titanium anodes are apparently becoming popular in other 
countries. Platinized titanium anodes have been tested (Tonere and Rice, 
1966) and are expected to cut initial costs and operating costs of 
cathodic protection systems. The long life of platinized titanium anodes 
and the relative ease with which they can be installed are the factors 
that are expected to reduce the costs of cathodic protection. Platinized 
titanium anodes are generally used in the form of long thin rods. Copper 
cores are used in platinized titanium anodes over 2 feet long to improve 
their conductivity (Lowe, 1966). 


Tonere and Rice (1966) report that the copper cored platinized 
titanium anodes presently in use by one company are 1/8 inch in diameter 
and have platinum coatings 0.0001 to 0.0002 inch thick. The average 
current density was reported to be of the order of 120 amperes per square 
foot. These anodes, most of which were installed vertically, have been 
in operation for up to 33 months with no apparent loss in their current 
capacity. Laboratory tests were performed to discover why corrosion of 
the titanium allowed two anodes to fall to the bottom. Observations 
reported from these testis are that: 


1. If the copper core is exposed to the electrolyte, there 
is no loss in anode efficiency when the copper core is 
consumed if the anode has no mechanical load below the 
exposed copper core. 


2. If under the same conditions, a mechanical load is placed 
below the point of copper core exposure, the anode will 
dissolve anodically near the break and quickly fail. 


Another report, Cherry (1965), states that after 5 years of service 
there are indications that platinized titanium anodes should last in ex- 
cess of 10 years. The most successful suspension system for these anodes 
reportedly utilized steel pipe with an unplastisized polyvinyl chloride 


46 


assembly at the bottom to hold the anode. The steel pipe was hinged at 
the top to permit easy inspection of the anodes. The anodes were placed 
about 2.5 feet from the side of the piles and about 6 feet below low 
water. 


Direct current ripples, resulting from difficulty in producing 
constant voltage direct current from rectified alternating current 
electricity, are reported to be detrimental to the life of platinized 
titanium anodes (Lowe, 1966). However, the report states that on smaller 
systems it is usually more economical to use lower current densities and 
thicker platinum films instead of the expensive three-phase installations 
or voltage smoothing systems. 


f. Anode Installation. Manufacturers produce a variety of sizes 
and shapes of galvanic anodes. Some are equipped with special facilities 
for mounting. 


One of the primary design problems in cathodic protection systems 
is the provision of an arrangement of anodes which will adequately and 
efficiently protect the structure concerned and yet withstand destructive 
forces from wave action, ice, boats and floating debris. Cathodic systems 
designed to protect structures such as sheet pile bulkheads may be de- 
Signed with anodes resting on the bottom. However, the useful life of 
anodes resting on the bottom may be reduced due to pitting caused by non- 
uniform environment. Also, unstable bottom conditions may cause excessive 
coverage of the anodes by sediments and reduce their effectiveness. These 
factors should be investigated if this type of installation is being 
considered. Systems designed to protect numerous vertical members, such 
as piling supporting a pier, may use anodes suspended between piling at 
a depth sufficient to lessen the possibility of damage by floating objects. 
Some of the more recent installations have anodes supported on pipes which 
are hinged at the top or mounted on cables that can be wound up on winches. 
These methods provide for easy removal of anodes for inspection and aid 
in prevention of storm damage. 


47 


Section VIII. CONCLUSIONS 


The corrosion rate of steel piling in seawater varies considerably 
depending on water conditions and the zone of exposure on a given pile. 
According to information from various reports, the loss of steel thick- 
ness in seawater may vary from no loss to as much as 373 mils per year. 
The higher rate occurred where sand abrasion was present in steel sheet 
pile groins. The corrosion rate of bare steel submerged in normal sea- 
water is generally considered to be 5 mils per year. 


Since corrosion rates of steel piling may vary widely in seawater, 
the estimation of corrosion rates should be guided by test data from 
structures having as nearly as possible the same exposure conditions as 
the proposed structure. This survey indicates that more pile corrosion 
test data are needed for estimating corrosion rates, especially in colder 
waters. 


Considerable progress is being made in the development of coatings 
capable of protecting steel piling in seawater. Partially completed 
tests indicate that such coatings as saran, phenolic mastic, coal-tar 
epoxy, epoxy, flame-sprayed aluminum coatings, and flame-sprayed zinc 
coatings topcoated with saran, vinyl, epoxy or furan, may effectively 
protect steel piling in seawater for 15 or more years provided severe 
conditions such as sand abrasion are not involved. Where sand abrasion 
exists, incomplete tests indicate that phenolic mastic and coal-tar epoxy 
coating systems, and possibly others, may approach 10 years of effective 
protection for steel in seawater. Coating systems consisting of flame- 
sprayed zine topcoated with saran or vinyl appear to be two of the most 
effective coatings for steel tested to date. 


Surface preparation of steel is very important when coatings are to 
be applied for seawater exposure. Blasting the surface with abrasive 
material and pickling are the generally accepted methods of surface 
preparation. Commercial blasting is considered adequate for many coat-— 
ings. When better blasted surfaces are required, near white or white 
blasting of the steel is specified. 


Cathodic protection systems, properly designed, and maintained are 
very effective in preventing the corrosion of steel immersed in seawater. 
Cathodic protection is often used in combination with protective coatings, 
the coatings protect the unsubmerged portion of the steel and reduce the 
area of submerged steel requiring cathodic protection. 


Properly designed concrete jackets are reported to be very effective 
in protecting steel from corrosion by seawater, however, there is appar- 
ently very little data available for accurate evaluation. 


There appears to be a great need for data to develop the initial 
cost, and cost per year of protection, for various corrosion protection 
methods. Such information is needed to determine the most economical 
protection system for a given structure. 


48 


LITERATURE CITED 


Alexander, A. L., Forgeson, B. W. and Southwell, C. R. (1958), "Perform- 
ance of Organic Coatings in Tropical Environments", paper presented 
at Northeast Region Meeting of National Association of Corrosion 
Engineers, Boston, Mass., 6-8 October 1958. 


Alumbaugh, R. L. (1964), "Field Test Data on Coatings for Steel Piling 
in Sea Water", Materials Protection, pp. 34-45. 


Alumbaugh, R. L. (1962), "Protective Coatings for Steel Piling: Results 
of 30-Month Tests", U. S. Naval Civil Engineering Laboratory, 
Technical Report R-194, 


Alumbaugh, R. L. and Brouillette, C. V. (1966), "Protective Coatings 
for Steel Piling: Results of Harbor Exposure on Ten-Foot Simulated 
Piling", U. S. Naval Civil Engineering Laboratory, Technical Report 
R-490, 


American Society for Testing and Materials, (1959), 1958 Book of ASTM 
Standards, Part 8, Philadelphia, Pennsylvania. 


American Welding Society, Committee on Metallizing (1962), "Corrosion 
Tests of Metallized Coated Steel, 6-Year Report" AWS C2.8-62. 


American Welding Society, Committee on Metallizing (1967), "Corrosion 
Tests of Metallized Coated Steel, 12-Year Report", AWS C2.11-67. 


Ayers, J. R. and Stokes, R. C. (1961), "Corrosion of Steel Piles in Salt 
Water", Journal of Waterways and Harbors Division, WW3, Proceedings 
of Amertean Soctety of Civil Engineers. 


Baxter, J. F. and Steiner, L. E. (1960), Modern Chemistry, Prentice-Hall, 
Englewood, N. J. 


Bethlehem Steel Corporation, "Steel H Piles", Handbook 2196, p. 32. 


Brouillette, C. V. and Hanna, A. E. (1960), "Corrosion Survey of Steel 
Sheet Piling", U. S. Naval Civil Engineering Laboratory Technical 
Report 097. 


Brouillette, C. V. and Hanna, A. E. (1966), "Second Corrosion Survey of 
Steel Sheet Piling’, U. S. Naval Civil Engineering Laboratory 
Technical Report R-467. 


Cherry, P. B. (1965), "Cathodic Protection of Jetties", Corrosion Pre- 
vention and Control, pp. 26-28. July 1965. 


Cook, H. K. (1953), "Exposure Research on Concrete in Sea Water", Proc. 


of Third Conference on Coastal Engineering (October 1952), Council 
on Wave Research, pp. 217-230 


49 


LITERATURE CITED (Continued) 


Copson, H. R. (1952), "Effects of Velocity on Corrosion by Water", 
Industrial and Engineering Chemtstry, Vol. 44, p. 1745. 


Devoluy, R. P. (1965), "Protective Coatings for Ship Bottoms", Materials 
Protectton. April 1965. 


Drisko, R. W. (1965), "Protection of Mooring Buoys, Part VI. Result of 
Fifth Rating Inspection", U. S. Naval Civil Engineering Laboratory 
Technical Report R 385. 


Drisko, R. W. (1968), "Protection of Mooring Buoys, Part XI. Results of 
Tenth (Final) Rating Inspection", U. S. Naval Civil Engineering 
Laboratory Technical Report R 585. 


Drisko, R. W., and Brouillette, C. V. (1965), "Protective Coatings in 
Shallow and Deep Ocean Environments", paper presented at Western 
Region Conference, National Association of Corrosion Engineers, 
8-12 November 1965, Honolulu, Hawaii. 


Drisko, R. W., Cobb, J. W. and Alumbaugh, R. L. (1964), "Underwater- 
curing Epoxy Coatings", U. S. Naval Civil Engineering Laboratory 
Technical Report R 300, May 1964. 


Fink, F. W. (1960), "Corrosion of Metals in Sea Water", U. S. Department 
of The Interior, Office of Saline Water, Research and Development 
Progress Report No. 6. 


Gelfer, D. H. (1964), "Permanent Primers for Steel: Comparison of Self- 
curing and Post-curing Inorganic Zine Coatings", Matertals Pro- 
tection, March 1964, pp. 54-61. 


Griffin, D. F. (1965), "Corrosion of Mild Steel in Concrete", U. S. Naval 
Civil Engineering Laboratory, Port Hueneme, California, TR 306 Sup. 
August 1965. 

Hosford, H. W. (1963), "Cathodic Protection of Marine Structures", The 
Harco Corporation, Paper No. HC-3, 25-638. 


Horvick, E. W. (1964), "Specifications and Specifying", American Zine 
Institute, Inc., Technical Seminar, May 27, 1964. 


Husock, B. (1962), "Fundamentals of Cathodic Protection", American 
Institute of Electrical Engineers, conference paper, St. Louis, 
Missouri, Harco Corp. Paper No. DP-3. 


Jarboe, E. D. (1964), "Organic and Inorganic Primers", Materials Protec- 
tion, March 1964, pp. 14-21. 


LaQue, F. L. and Cox, G. L. (1940), "Some Observations in the Potentials 


of Metals and Alloys in Sea Water", Proceedings, Amertcan Soctety 
for Testing and Materials, Volume 40. 


50 


LITERATURE CITED (Continued) 


Lindahl, H. A. (1964), "Developments in Steel for Marine Applications", 
unpublished paper presented at American Shore and Beach Preserva- 
tion Meeting, New York. 


Littauer, E. L. (1966), "Impressed Current Systems for Corrosion Protec- 
tion", Geo-Marine Technology, June 1966, pp. 17-23. 


Lowe, R. A. (1966), "Platinized Titanium as Anode Materials", Materials 
Protection, April 1966, pp. 23-24. 


Lyse, I. (1961), "Durability of Concrete in Sea Water", Journal, American 
Conerete Institute, June 1961. 


Mather, B. (1957), "Factors Affecting the Durability of Concrete in 
Coastal Structures", U. S. Army Corps of Engineers, Beach Erosion 
Board, Technical Memorandum No. 96, 1957. 


Muroaka, J. S. (1963), "The Effects of Fouling by Deep-Ocean Marine 
Organisms", Undersea Technology, May 1963, pp. 24-28. 


National Association of Corrosion Engineers (1965), "What Field Personnel 
Should Know about Rectifiers", Materials Protection, April 1965, 
pp. 75-82. 


Orlowski, P. (1965), "Protection by Metallization Against Corrosion and 
the Effects of Seawater Life’, Corroston Prevention and Control, 
February 1965, pp. 29-30. 


Rayner, A. C. (1952), "Durability of Steel Sheet Piling in Shore Struc- 
tures", U. S. Army Corps of Engineers, Beach Erosion Board Technical 
Memorandum No. 12, February 1952. 


Reding, J. T. and Newport, J. J. (1966), "The Influence of Alloying Ele- 
ments on Aluminum Anodes in Sea Water", Materials Protection, Vol. 
5, No. 12, pp. 15-18, December 1966. 

Ross, C. W. (1948), "Experimental Steel Pile Groins, Palm Beach, Florida", 
U. S. Army Corps of Engineers, Beach Erosion Board Technical Memo- 
randum No. 10. 


Shreir, L. L. (1963), Corrosion, John Wiley & Sons, New York, N.Y. 


Snyder, R. M. and Hull, S. (1965), "Parametric Variables Affecting 
Corrosion", Geo-Marine Technology, July 1965, pp. 17-24. 


Steel Structures Painting Council (1964), Steel Structures Painting Manual, 
Volume 1, 1964. 


Steel Structures Painting Council (1964), Steel Structures Painting Manual, 
Volume 2, 1964. 


5| 


LITERATURE CITED (Continued) 


Sverdrup, H. U., Johnson, M. W. and Fleming, R. H. (1942), The Oceans, 
Prentice-Hall, Inc., Englewood Cliffs, N. J. 


Tonere, A. C. and Rice, L. (1966), "Impressed Current Anodes in Brackish 
Water", Matertals Protectton, April 1966, pp. 61-63. 


Tuthill, A. H. and Schellmoller, C. M. (1965), "Guidelines for the Selec- 
tion of Marine Materials", International Nickel Company, June 1965. 


Tyler, I. L. (1964), "Concrete in Marine Environments", Symposium on 
Conerete Construction in Aqueous Environments (SP-8), American 
= Concrete Institute. 

Uhlig, H. H. (1948), The Corroston Handbook, John Wiley and Sons, New 

Worle, No Mo 


United Kingdom, Department of Scientific and Industrial Research (1928), 
"Deterioration of Structures of Timber, Metal, and Concrete Ex- 
posed to the Action of Sea-Water", H. M. Stationery Office for 
the Department, Westminster, 5S.W. 1, England. 


U. S. Army, Corps of Engineers, Office of the Chief of Engineers (1963), 
"Painting Hydraulic Structures and Appurtenant Works", CE-1409, 
October 1963. 


U. S. Army, Corps of Engineers (1962), "Corrosion Control", TM-5-811-4, 
formerly EM 1110-1-184, August 1962. 


U. S. Navy, Bureau of Yards and Docks (1963), "Long Range Systematic 
Study, Protective Coatings for Steel Piling, Four Year Evaluation 
W 
Report » April 1963. 


U. S. Steel Corporation (1964), "Mariner Steel Sheet and H-Piling" May 196}. 
Pp ry 


Warren, L. R. (1956), "Some Notes on the 1953 Congress of the Permanent 
International Association of Navigational Congresses", Transactions 
of South African Institution of Civil Engineers, Vol. 6, No. 10, 
October 1956, pp. 289-294. 


Wood, L. E. (1963), "Protection of Reinforcing Steel", U. S. Army, Corps 


of Engineers, Ohio River Division Laboratories, Technical Report 
No. 2-30. 


52 


Ila 


IIb 


sal 


APPENDIX A 


TABLES I THROUGH XV 


Coating Description and Application Data for Tables IIa, IIb 


System Performance Ratings on Steel Sheet Piling after 
12=, 18=, 24, and 30-Month Exposures .. . 


System Performance Ratings on Steel "H" Piling after 12-, 
Gs, Bho, exael BO=Merieia IbGIOSUEES 06 6 50 0 5 0 0 5 6 


Coating System Description and Performance Ratings, Phase 1 - 
6-Month Test 


Ratings for Coatings Immersed in Seawater 

Ratings for Coated Panels Tested at Mean Tide. . 
Dasewaljowalya Cay WASMENL Inches Swiss o 6 6 6 6 6 6 0 0 0 G6 o oO 
Fourth Year Coating System Ratings 

Overall Rating and Length of Service for Coated Buoys 
Coating Descriptions and Thicknesses 

Force Required to Break Apart Bonded Panels 

Coating System Details for Table X 

SkeyormakeaLCalenl AiaoclS Wee oo o o 

Test Specimen Rating System for Tables Ila, IIb, and VIII 
Description of Coatings in Figures lla-c and 12 


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TABLE Ila 


System Performance Ratings on Steel Sheet Piling 
After 12-, 18-, 24-, and 30-Month Exposures 


Ratings 
Exposure 
System Period System Splash Tidal Zone Embedded 
Number (Months) Type Zone Area “Au Rreay iB}! Zone 
12 9 Q+ 6 9 
1. 18 Aluminum 9 9+ D 9 
2h Vinyl 9 9 3 9 
30 9 9 al 9 
12 9 Q+ 9) 9 
6 18 9 9 8 9 
2k Nba 9 9 T 9 
30 9 9 { 8) 
12 9 10 7 O+ 
iT 18 Phenolic 9 Q+ iff 9 
2h Mastic 9 Q+ 5 9 
30 9 he 4 Q+ 
12 9 10 O+ O+ 
9 18 NV 9 9 9 9 
Dh eoprene 9 8 8 9 
30 9 8 8 9 
12 9 8 9 O+ 
13 18 Coal Tar 9 6 6 + 
2h 9 5 3 9 
30 9 4 1 9 
12 9 8 7 Q+ 
16 18 Asphalt 9 if 4 Ox 
an Emulsion 9 6 2 9+ 
30 9 D alt O+ 
12 9 10 9 10 
20 18 pecs 8 9 9 Q+ 
Dh prayed 7 9 8 O4 
30 Zine 6 9 8 O+ 
12 g 9 10 t 9 
23 18 ner 9 Q+ 5 9 
Dh (Formula 9 O+ i 9 
30 113.49) 9 O+ 3 9 
From Alumbaugh (1962) 


Notes: 1. See Table I for coating system details. 
2. see Table XIII for rating system note. 


TABLE ITb 


System Performance Ratings on Steel "H" Piling 
After 12-, 18-, 24-, and 30-Month Exposures 


Ratings 
Exposure _ 
System Period System Splash Tidal Zone Embedded 
Number (Months) Type Zone Area "A" Area "'B" Zone 
12 9 Q+ 8 9 
1 18 Aluminum 9 9 if ) 
2h Vinyl 9 9 if 9 
30 9 9 5) 9 
a2 9 9+ 9 Q+ 
6 18 Vinyl 9 9 8 9 
eh Mastic 9 9 8 9 
30 9 9 il; 9 
2 9 10 9 9+ 
7 18 Phenolic 9 10 9 9 
24 Mastic 9 10 8 9 
30 9 10 t 9 
12 9 ake) O+ O+ 
18 9 9 9 9 
2 Dh Neoprene FA 9 9 9 
30 9 8 9 9 
12 9 8 2) 9 
18 9 6 8 9 
ILS} yh Coal Tar 9 5 6 9 
30 9 4 4 9 
12 9 8 8 Q+ 
18 Asphalt 9 il 6 Q+ 
2h Emulsion 9 6 5 O+ 
30 9 5 4 Q+ 
ae ASHI 3 10 Q+ 10 
20 1 Sprayed 9 9 ae 
2k Zine i 2 9 9 
30 6 9 9) 9 
Ae 9 10 9 9 
18 ae 2 he 9 9 
2 anes) ‘ oe e 9 
30 9 O+ uf 9 


From Alumbaugh (1962) 
*Due to equipment problems during driving operation these piles were 
driven to such a depth that no splash zone existed. 
Notes: 1. See Table I for coating system details. 
2. See Table XIII for rating system note. 


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A-8 


TABLE IV 


Ratings for Coatings Immersed in Seawater 


Coating Service Rating ** 
Number of Coets and Thickness 3 Years 6 Years 


Coating Description (mils) Unscribed Scribed Unscribed Scribed 
Phosphoric acid 
pretreatment 


1. Coal-Tar Primer 
2. Coal-Tar Enamel 
304. Natural Resin A-F+ 80-100 10 10 9 8 


Phosphoric acid 

pretreatment 

1. Coal-Tar Primer 

2. Coal-Tar Enamel 

3-4. Natural Resin A-F* 70-85 10 10 8 8 


Phosphoric acid 

pretreatment 

1. Synthetic Rubber 
(Neoprene) 

2-13. Synthetic Rubber 


(Neoprene) 4O-55 10 10 8 9 
Phosphoric acid 
pretreatment 
1-2. Alkyd Primer 
3. Hot Plastic A-F 41 10 10 0) all 


Phosphoric acid 

pretreatment 

1. Coal-Tar Primer 

2. Coal-Tar Enamel 

3. Hot Plastic A-F 85-115 10 10 if 5 


Wash Primer Pretreatment 
1-3. Vinyl Primer t 
4-5, Vinyl A-F t 8.5 10 10 i 5 


Wash Primer Pretreatment 
1-2, Vinyl Primer Tt 


2-8, Waal Ae a 18 10 10 3 6 
Phosphoric acid 
pretreatment 
1-2. Vinyl Primer 
3-10. Vinyl Enamel 18-27 10 9 9 5 
+ 
*Experimental NRL formula + Navy cold plastic A-F paint. 
** See Table VI for rating system details tT Similar competitive systems 


From Alexander, et al (1958) 


TABLE V 


Ratings for Coated Panels Tested at Mean Tide 


Coating Service Rating* 


Number of Coats and Thickness 3 Years 6 Years 
Coating Description (mils) Unscribed Scribed Unscribed Scribed 


Wash primer pretreatment 
1 Vinyl Primer 
2 Vinyl A-F od 7 8 2 2 


Wash primer pretreatment 
1-3 Vinyl Primer 
hO5 Vinyl A-F 8 10 10 5 5 


Wash primer pretreatment 
1-3 Vinyl Primer 


4-8 Vinyl A-F 18 10 10 6 6 
Phosphoric acid 
pretreatment 
1-3 Synthetic Rubber 2-250 8 9 5 5 
1 Synthetic Rubber 2-3) 10 10 7 5 
*See Table VI for rating system notes From Alexander, et al (1958) 
TABLE VI 
Description of Visual Rating System 
Numerical 
Value Condition of Coating and Panel 
10 Perfect (no deterioration of any kind) 
9 Slight deterioration of coating 
8 Intermediate (between 7 and 9) 
1 Deterioration evident with a few defects in coating; 


continued protection of underlying metal; coating 
considered satisfactory. 


6 Moderate deterioration, some coating defects, slight 
corrosion of underlying metal surface. Some surface 
preparation and repainting necessary for continued 
protection. Coating considered unsatisfactory. 


From Alexander, et al (1958) 


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A-|4 


TABLE XI 


Coating System Details for Table X 


Primer Additional Coats TOTAL 
No. of Thickness No. of Thickness Thickness 
Coating System e Coats (mils) e Coats (mils) (mils) 
1 Coal Tar MIL-C-18480 A 1 - Coal Tar 
(MIL-C-18480 A) 2 - he 
2 Vinyl Pretreatment Primer 1 1/2 Vinyl Alkyd 
(MIL-P-15328 B) Enamel 
Vinyl (MIL-P-15929A) 5 6 (MIL-P-15936 B) 2 4 10 1/2 
3 Saran Saran 1 - Same as primer 4 = 
Alternate coats 
of orange & white 6 1/2 
4 Inorganic Inorganic Vinyl Mastic 2 10 1/2 
Zine Silicate - Zine Silicate 1 2 
Vinyl Mastic Vinyl-phenolic 1 1 13 1/2 
5) Phenolic Mastic Catalyzed Mica- Catalyzed 
filled Phenolic al 10.1/2 Phenolic 1 8 1/2 19 
6 Epoxy Catalyzed epoxy 1 21/2 Catalyzed Epoxy 
Phenolic Topcoat 2 12 1/2 15 
ae Mica-filled Pretreatment Primer at 1/2 Mica-filled 
Asphalt Emulsion (MIL-P-15328 B) Asphalt Emulsion 3 16 20 1/2 
Phenolic (MIL-P-12742A 2 4 
8 Epoxy Catalyzed Epoxy al 21/2 Catalyzed Epoxy 3 7 1/2 10 
9 Urethane Catalyzed Urethane 1 11/2 Catalyzed Urethane 3 8 1/2 10 
10 Coal Tar Epoxy Coal Tar Epoxy 2 91/2 Aluminum-filled 
Catalyzed Coal Tar 1 5 1/2 15 
A Epoxy Two-package Epoxy 
with asbestos filler 1 187 1/2 - = - 187 1/2 
B Epoxy Two-package Epoxy 1 187 1/2 - - - 187 1/2 
C Epoxy Two-package Epoxy 1 187 1/2 - - - 187 1/2 
D Epoxy Two-package Epoxy al, 187 1/2 - - = 187 1/2 


plus Copper Oxice 


From Drisko, et al (1964) 


A-15 


TABLE XII 


Sacrificial Anode Data 


Consumption Rate Cost per Cost per 
Material Lb. per Amp-Year Pound Amp-Year 
Lead/Platinum 
Minimum 0.004 $0.0093 
Maximum 0.013 $2.32 0.0301 
Graphite 
(In coke breeze) 
Minimum @,alal. OROKm 
Maximum O.44 0.70 0.308 
Lead/Silver 
Minimum 0.10 O,2-7 
Maximum ORS 0 Creel 1.09 
High Silicon Cast Iron 
Minimum Q.4e 0.197 
Maximum Dp 0.47 algeplely 
Aluminum 80% Efficiency Goal 0.50 4.05 
Zine 90% Efficiency 26.0 0.20 5.20 
Magnesium 50% Efficiency Mod 0.50 515 


Platinum: Unqualtfied tneluston of platinum in this table ts not 
realistic since the consumption rate ts dependent upon the anode prepa- 
ration technique. Thus, bulk platinum has an extremely Low consumption 
rate, whereas platinum deposited onto an tnert substrate such as titanium 
or tantalum is consumed at a rate of about 6 mg/amp-year at high current 
densities. Platinum is priced today at between $3.22 and $5.80 per gram. 


From Littauer (1966) 


A-|6 


TABLE XIII 


Test Specimen Rating Systems for Tables Ila, IIb, and VIII 


Table No. Rating System 
IIa and IIb Ratings are based on ASTM Photographic Reference 


Standards (ASTM Designation: D610-43) for evaluating 
the degree of resistance to rusting obtained with 
coatings on steel surfaces. 


Walagie Excellent - Coating in essentially the same condition 
as when first placed in service. 


Good - Coating has very minor deterioration. 


Fair - A significant amount of coating deteri- 
oration and/or rusting, but still in 
serviceable condition. 


Poor - Coating deterioration and rusting serious 
enough to lead to an early removal from 
service. 


From Alumbaugh (1962); Drisko (1965) 


A-I7 


TABLE XIV 


Description of Coatings in Figures lla-c and 12 


No. of Thickness 
System and Color Coats (mils) 
SERIES 1 

Hot-applied coal-tar enamel - 34Yb (black) 

Cold-applied coal-tar primer alt 

Hot-applied coal-tar enamel iL 90.0 
Total 90.0 

Neoprene brushing compound (black) 

Neoprene primer Al 

Neoprene finish plus accelerator 6 9.0 
Total 9.0 

Aluminum-pigmented chlorinated rubber (aluminum) 

Chlorinated rubber red-lead primer ill 

Aluminum-pigmented chlorinated rubber finish 2 2.0 
Woeedl 2 

Chlorinated rubber (gray) 

MIL-C-15328 (Formula 117), pretreatment primer dL 

Chlorinated rubber intermediate 2 

Chlorinated rubber finish 2 DoD 
Wtonnel =545 

Thiokol-vinyl resin blend (black) 

Thiokol-vinyl resin finish 3 (oc 
Gone L 1/6) 

Vinyl (gray) 

Vinyl resin finish 4 4.0 
Total © 

Aluminum-pigmented vinyl (aluminum) 

Pretreatment primer 1 

Vinyl red-lead primer all 

Aluminum-pizgmented vinyl finish 1 4.0 
Total® 

Vinyl (gray) 

MIL-C-15328 (Formula 117), pretreatment primer al 

Anticorrosive intermediate 2 

Vinyl finish 2 Bod 
ayoGEL 265) 


From Alumbaugh and Brouillette (1966) 


A-\8 


aOR 


dLko 


Io 


ILS} 


1h. 


ALD)6 


16.6 


Lo 


TABLE XIV Continued 


System and Color 


Vinyl (gray) 

Single package pretreatment primer 
Stainless-steel-pigmented intermediate 
Clear vinyl finish 


Saran (orange) 
Saran (alternate white and orange coats) 


Flame-sprayed Thiokol (black) 
Flame-sprayed Thiokol powder 


Flame-sprayed zinc (gray) 
Flame-sprayed zinc powder 


Flame-sprayed aluminum (aluminum) 
Flame-sprayed aluminum powder 


Flame-sprayed zinc (gray) 
Flame-sprayed zinc wire 


Flame-sprayed aluminum (aluminum) 
Flame-sprayed aluminum wire 


SERIES 2 


Saran (white) 
Saran (Formula 113/49), alternate orange and 
white coats 


Saran (white) 

MIL-C-15328 (Formula 117), pretreatment primer 

Saran (Formula 113/49), alternate orange and 
white coats 


A-|\9 


No. of Thickness 
Coats (mils) 

dL 
2 

IL, 250 

Total 2.0 

5 6.0 

ieee GoO) 

il 66.0 

Total 66.0 

iL 300) 

GMoRBeLIL. S}oO) 

aL Ho5 

Motel eS 

ile Do) 

Moca Dye 

all 560) 

Totals eS O 

1 6.5 

Total 6.5 

lt 0.5 

8 od 

Total 8.0 


As} 


19. 


20. 


ZN 


Cor 


230 


eh, 


25. 


TABLE XIV Continued 


System and Color 


Saran (white) 

Flame-sprayed zinc wire 

Saran (Formula 113/49), alternate orange 
and white coats 


Saran (white) 

Flame-sprayed aluminum wire 

Saran (Formula 113/49), alternate orange 
and white coats 


Vinyl antifouling (black) 

MIL-P-15929 (Formula 119), vinyl red-lead primer 

MIL-P-16189 (Formula 129), vinyl antifouling 
finish 


Vinyl antifouling (black) 

MIL-C-15328 (Formula 117) 

MIL-P-15929 (Formula 119) 

MIL-P-16189 (Formula 129) 
finish 


> pretreatment primer 
» vinyl red-lead primer 
> vinyl antifouling 


Vinyl (orange) 
Flame-sprayed zinc wire 
MIL-P-15929 (Fornula 119), vinyl red-lead primer 


Vinyl (orange) 
Flame-sprayed aluminum wire 
MIL-P-15929 (Formula ALL) vinyl red-lead primer 


Vinyl-acrylic lacquer (clear) 
Vinyl-acrylic lacquer finish 


Vinyl-acrylic lacquer (clear) 
MIL-C-15328 (Formula 117), pretreatment primer 
Vinyl-acrylic lacquer finish 


No 
Coats 

1 
1 

Total 
aE 
1 

Total 
2 
3 

Total 
a 
2 
3 

Total 
AL 
D 

Total 
all 
D 

Total 
6 

Total 
all 
6 

Total 


9 Olt Thickness 
(mils) _ 


154 
V1 


26. 


Cale 


28. 


29. 


S10)e 


Sl 


32 


33. 


She 


TABLE XIV Continued 


System and Color 


Vinyl-acrylic lacquer (clear) 
Flame-sprayed zine wire 
Vinyl-acrylic lacquer finish 


Vinyl-acrylic lacquer (clear) 
Flame-sprayed aluminum wire 
Vinyl-acrylic lacquer finish 


Cold plastic antifouling (black) 
Formula 145, cold plastic antifouling finish 


Cold plastic antifouling (black) 
MIL-C-15328 (Formula 117), pretreatment primer 
Formula 145, cold plastic antifouling finish 


Cold plastic antifouling (black) 
Flame-sprayed zine wire 
Formula 145, cold plastic antifouling finish 


Cold plastic antifouling (black) 


Flame-sprayed aluminum wire 
Formula 145, cold plastic antifouling finish 


Vinyl (gray) 
Vinyl finish 


Vinyl (gray) 
MIL-C-15328 (Formula 117), pretreatment primer 
Vinyl finish 


Vinyl (gray) 
Flame-sprayed zine wire 
Vinyl finish 


No. of 


Coats 


a 


re 


Thickness 
(mils) 


Total 


Total 


Total 


Total 


Total 


Total 


Total 


Total 


Total 


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O|C oO 


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oul 


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Noa 


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WIj1 O 


FW 
1 O 


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VWI 


N01 
(eo) 


MUI 
(eo) 


WO 
WO Ul 


ar 


AU 
WO VI 


35. 


36. 


37. 


So. 


39. 


ho. 


Wi. 


ye, 


TABLE XIV Continued 


System and Color 


Vinyl (gray) 
Flame-sprayed aluminum wire 
Vinyl finish 


Phenolic mastic (gray) 
Catalyzed phenolic mastic primer 
Catalyzed phenolic mastic finish 


Phenolic mastic (gray) 

MIL-C-15328 (Formula 117), pretreatment primer 
Catalyzed phenolic mastic primer 

Catalyzed phenolic mastic finish 


Phenolic mastic (gray) 
Catalyzed mica-filled phenolic mastic primer 
Catalyzed phenolic mastic finish 


Phenolic mastic (gray) 
Flame-sprayed aluminum wire 
Catalyzed phenolic mastic primer 
Catalyzed phenolic mastic finish 


Epoxy (white) 
Catalyzed epoxy red-lead primer 
Catalyzed epoxy finish 


Epoxy (white) 

MIL-C-15328 (Formula 117), pretreatment primer 
Catalyzed epoxy red-lead primer 

Catalyzed epoxy finish 


Epoxy (white) 
Flame-sprayed zinc wire 
Catalyzed epoxy finish 


NOs) Cre Thickness 
Coats (mils) 

al ByA0) 
5 Bod) 
Wore 4 5) 

AL 5 
1 me) 
Total 9.0 

al 0.5 
il I 5 
1 4.0 
Total 9.0 

IL i. © 
al, So5 
Total 19.5 

dl 360 
alt 550 
all 550 
tence 13.0) 

2 305) 
2 3.2 
AoE 1 oO) 

alt O55 
2 h.0 
2 3.3 
Motoleuon© 

i, 3.0 
2 5.5) 
Total a5 


*This system was not compatible with the flame-sprayed zinc coating and 


reacted chemically when applied as a topcoat. 


mastic was not tested over the flame-sprayed zinc wire. 


Consequently, the phenolic 


43. 


yh, 


45. 


6. 


ur 


48. 


ho. 


50. 


TABLE XIV Continued 


System and Color 


Epoxy (white) 
Flame-sprayed aluminum wire 
Catalyzed epoxy finish 


Chlorinated rubber (red) 
Chlorinated rubber red-lead primer 
Chlorinated rubber finish 


Chlorinated rubber (red) 

MIL-C-15328 (Formula 117), pretreatment primer 
Chlorinated rubber red-lead primer 

Chlorinated rubber finish 


Chlorinated rubber (red) 
Flame-sprayed zinc wire 
Chlorinated rubber finish 


Chlorinated rubber (red) 
Flame-sprayed aluminum wire 
Chlorinated rubber finish 


Furan (gray) 
Vinyl red-lead, iron oxide primer 
Furan finish 


Furan (gray) 

MIL-C-15328 (Formula 117), pretreatment primer 
Vinyl red-lead, iron oxide primer 

Furan finish 


Furan (gray) 
Flame-sprayed zine wire 
Furan finish 


WOo Che 


Coats 


ine) 


WM EF 


Thickness 
(mils) 
255 
6.5 
Toads 910 
2s 
50) 
Totals: 5/0 
0.5 
2.0 
3.0 
Motil sey) 
2.0 
6.0 
Totals OHO 
305) 
prey 
Total 9.0 
dd 
Sod) 
Moai 5740) 
ORD 
oS 
3.5 
Moca Slo 
350) 
Lo 
Rotana 


pile 


Des 


D3. 


pie 


D2« 


56. 


a1 


58. 


TABLE XIV Continued 


System and Color 


Furan (gray) 
Flame-sprayed aluminum wire 
Furan finish 


Neoprene brushing composition (black) 
Synthetic rubber primer 
Neoprene finish plus accelerator 


Neoprene brushing composition (black) 


Synthetic rubber primer 
Neoprene finish plus accelerator 


Neoprene brushing composition (black) 
Flame-sprayed zinc wire 

Synthetic rubber primer 

Neoprene finish plus accelerator 


Neoprene brushing composition (black) 
Flame-sprayed aluminum wire 
Synthetic rubber primer 

Neoprene finish plus accelerator 


SERIES 3 


Zine inorganic silicate (gray) 
Zine inorganic silicate (post-cured) 


Zine inorganic silicate (gray) 
Zine inorganic silicate (post-cured) 
(Panel contained window)* 


Zine inorganic silicate (gray) 
Zine inorganic silicate (post-cured) 
(Panel contained window)* 


MIL-C-15328 (Formula 117), pretreatment primer 


No. of Thickness 
Coats (mils) 

1 BO) 

3 4.0 

uejeel 1/50) 

2 3.0 

3 5.0 

Total 8.0 

a Oo5 

2] 3.0 

3 5.0 

Total 8.5 

all 3.0 

Al, AL 6) 

3 6.0 

To Fade MORO 

1 3}.4(0) 

ll 1.0 

3 605 

UkereeL ILO), 5) 

2 550 

Totals. © 

aL 4.0 

Total 4.0 

2 5) 00) 
Notary 


*Before coating, a piece of l-inch by 6-inch masking tape was applied 
the middle of the tidal zone on one face of these sandblasted panels. 
the coatings were cured, the masking tape was removed leaving a "window" of 
uncoated sandblasted metal to be exposed to the tidal environment. 


to 
After 


TABLE XIV Continued 


No. of Thickness 
System and Color Coats (mils) 
59. Zine inorganic silicate (gray) 
Zine inorganic silicate (post-cured) IL Zod) 
Mortal er >) 
60. Zinc-dust-pigmented polystyrene (gray) 
Zinc-dust-pigmented polystyrene @ Sod. 
Total a5) 
61. Zinc-dust-pigmented polystyrene (gray) 
Zine-dust-pigmented polystyrene 2 4.0 
(Panel contained window)* Total .0 
62. Copper antifouling paint (brown) 
Iron oxide, zine chromate primer 1 50 
Mica-pigmented insulating coat 2 2.0 
Antifouling finish 2 2.0 
Totads i5r 
63. Copper antifouling paint (brow) 
MIL-C-15328 (Formula WA )) 5 pretreatment primer AL O25 
Iron oxide, zine chromate primer 2 od 
Mica-pigmented insulating coat 2 2.0 
Antifouling finish 2 200) 
Total -0 
64. Aluminum-pigmented vinyl (aluminum) 
Flame-sprayed aluminum wire att 305 
Aluminum-pigmented vinyl finish 3 300) 
Total 5 
65. Neoprene (black) 
Neoprene primer 2 2o5) 
Neoprene finish plus accelerator 3 (oD 
Total 10.0 
SERIES 4 
66. Aluminum-pigmented vinyl (aluminum) 
MIL-C-15328 (Formula 117), pretreatment primer iL 0.5 
MIL-P-15929 (Formula 119), vinyl red-lead primer 2 4.0 
Aluminum-pigmented vinyl finish 2 2.0 
Moitaly enon 


*Before coating, a piece of l-inch by 6-inch masking tape was applied to 
the middle of the tidal zone on one face of these sandblasted panels. After 
the coatings were cured, the masking tape was removed leaving a "window" of 
uncoated sandblasted metal to be exposed to the tidal environment. 


Gig 


68- 


682. 


69. 


70. 


(ate 


(22 


(Abs 


(Se 


734. 


Th. 


TABLE XIV Continued 


System and Color 


Zine-dust-pigmented polystyrene (gray) 
Zine-dust-pigmented polystyrene 


Epoxy (white) 
Catalyzed epoxy red-lead primer 
Catalyzed epoxy finish 


Zine inorganic silicate (gray) 
Zine inorganic silicate (post-cured) 


Vinyl (gray) 

Vinyl-phenolic strontium chromate, iron 
oxide primer 

Vinyl finish 


Vinyl mastic (black) 

Vinyl-phenolic strontium chromate, iron 
oxide primer 

Vinyl mastic finish 


Phenolic mastic (gray) 
Catalyzed mica-filled phenolic mastic primer 
Catalyzed phenolic mastic finish 


Furan (black) 
Vinyl red-lead, iron oxide primer 
Furan finish 


Neoprene brushing compound (black) 
Synthetic rubber primer 
Neoprene finish plus accelerator 


No. of 
Coats 


fo 


Thickness 
(mils) 
2.0 
No Galween© 
S}50((2.5)) 
3.5(4.0) 
Total 6.5 
25>), 
Total 2.5 
150 
pry 
Totaly s6n5 
eS 
9.0 
Total 10e5 
TO>5 (6.0) 
5.0 (8.0) 
Total 15.5(14.0) 
To O((45)) 
5.5(6.0) 
Total 6.5(7.5) 
2.0 
29.0 
Total 31.0 


#Where there are differences between the number of coats or coating thick- 
nesses applied to the 4-inch by 10-foot panels and the angle iron panels, 
the values for the angle iron panels are given in parentheses in this 
appendix. 


A-26 


7). 


(So 


ie 


TTL. 


78. 


19. 


80. 


81- 


81. 


82. 


TABLE XIV Continued 


System and Color 


Chlorinated rubber (red) 
Chlorinated rubber red-lead primer 
Chlorinated rubber finish 


Cold-applied coal tar (black) 

MIL-C-15328 (Formula 117), pretreatment 
primer 

MIL-C-18480 coal-tar coating compound 

MIL-C-15203 bituminous emulsion finish 


Cold-applied coal tar (black) 
MIL-C-18480 coal-tar coating compound 
MIL-C-15203 bituminous emulsion finish 


Cold-applied coal tar (black) 

MIL-C-15328 (Formula 117), pretreatment 
primer 

MIL-C-18480 coal-tar coating compound 


Cold-applied coal tar (black) 
MIL-C-18480 coal-tar coating compound 


Mica-filled asphalt emulsion (black) 

MIL-C-15328 (Formula 117), pretreatment 
primer 

JAN-P-735* (Formula 84/47), alkyd zinc 
chromate primer 

Mica-filled asphalt emulsion finish 


Gilsonite asphalt (black) 
Gilsonite asphalt 


Cold plastic antifouling (black) 
MIL-C-15328 (Formula 117), pretreatment 
primer 


MIL-P-18996 (Formula 14), anticorrosive primer 2 


Formula 145, cold plastic antifouling 
finish 


*Current designation is TT-P-6h5. 


Thickness 
(mils) 


Total 30. 


Mowe, 255 (S2¢ 


Total 23.0 


opal eer 


SOD 
Total 32.5 


125.0 
Total 125.0 


0.5 
30D 


Al, 5 
itenceL 2565 


83. 


8h. 


85. 


86. 


87- 


Miho 


88. 


89. 


90. 


91. 


*Current designation is MIL-L-18389 (Formula 113/54). 


TABLE XIV Continued 


System and Color 


FlameOsprayed zinc (gray) 
MIL-M-3800 zine wire, flame-sprayed 


Flame-sprayed aluminum (aluminum) 
MIL-M-3800 aluminum wire, flame-sprayed 


Hot plastic antifouling (red-brown) 

MIL-C-15328 (Formula 117), pretreatment primer 
MIL-P-18996 (Formula 14), anticorrosive primer 
Formula 15 HP, hot plastic antifouling finish 


Saran (white) 
Saran (Formula 113/49)*, alternate orange 
and white coats 


SERIES 5 


Coal-tar epoxy (black) 
Catalyzed coal-tar epoxy 


Epoxy (gray) 
Catalyzed epoxy primer 
Catalyzed epoxy finish 


Oil-base (gray) 
Oil-base red-lead primer 
Oil-base cement-pigmented finish 


Oil-base (gray ) 
Oil-base lead suboxice, iron oxide primer 
Oil-base lead suboxide finish 


Aluminum-pigmented vinyl (aluminum) 
Pretreatment primer 

Vinyl red-lead primer 
Aluminum-pigmented vinyl finish 


A-28 


ine) 


MO 


Thickness 
(mils) 


12. O50) 


Total 


Total 


Total 


12 J0(15)/0) 


92. 


50 


os 


QDo0 


96- 


96L. 


ile 


OTL. 


98- 


982. 


TABLE XIV Continued 


System and Color 


Neoprene (black) 
Synthetic rubber primer 
Neoprene finish plus accelerator 


Chlorinated rubber-vinyl (gray) 

MIL-C-15328 (Formula 117), pretreatment 
primer 

MIL-P-15929 (Formula 119), vinyl red-lead 
primer 

Chlorinated rubber-vinyl finish 


Aluminum-pigmented chlorinated rubber 
(aluminum) 

Chlorinated rubber red-lead primer 

Aluminum-pigmented chloninated rubber 
finish 


Vinyl (gray ) 
Aluminum-pigmented vinyl-Thiokol primer 
Vinyl finish 


High-build vinyl (gray) 

Vinyl-phenolic, strontium chromate, iron 
oxide primer 

High-build vinyl finish 


Epoxy (gray) 

Catalyzed epoxy primer 
Catalyzed epoxy body coat 
Catalyzed epoxy finish 


Vinyl antifouling (red-brown) 

MIL-C-15328 (Formula 117), pretreatment 
primer 

MIL-P-15929 (Formula 119), vinyl red-lead 
primer 

MIL-P-15931 (Formula 121), vinyl anti- 
fouling finish 


NO W 


Thickness 
(mils) 


Total 


Total 


Total 


Total 


Total 


Total 


Total 


TABLE XIV Continued 


No. of Thickness 
System and Color Coats (mils) 
99- Chlorosulfonated polyethylene (gray) 
99L. Vinyl red-lead, iron oxide primer 2 LES) 
Catalyzed chlorosulfonated polyethylene 5 To 
finish pe ot 
Total a) 
100- Zinc-filled modified epoxy (gray) 
1004. Catalyzed zinc-filled modified epoxy 3 6.0(7.5) 
Total 6.0(7.5) 
101- Epoxy (gray) 
1014. Catalyzed epoxy primer 1 3.0 (2.0) 
Catalyzed epoxy finish 2 9.0 
Total 12.0(11.0) 
102- Aluminum-pigmented urethane (aluminum) 
102L- Catalyzed urethane red-lead primer 2(3) 1.5 
Catalyzed urethane intermediate il I55)((L..0)) 
Catalyzed aluminum-pigmented urethane 4 Bod (3.0) 
finish 
Noted 
103- Aluminum-pigmented coal-tar epoxy 
(aluminum) 
103L. Catalyzed coal-tar epoxy red-lead primer il Hos (5.5) 
Catalyzed coal-tar epoxy intermediate 2 Wh (15 555) 
Catalyzed aluminum-pigmented coal-tar il 2.5) (2-0) 
epoxy finish 
Total 24.5(23.0) 
104. Vinyl antifouling (red-brown) 
Pretreatment primer all OS 
Vinyl red-lead primer i 5 
Vinyl intermediate (black) iL D5 
Vinyl antifouling finish 2 5.0 
once S)5) 
105. Vinyl (gray) 
Pretreatment primer il O65 
Vinyl red-lead primer 2 Lo 5 
Vinyl intermediate (black) aL 2.0 
Vinyl finish 2 eS. 
Total ~6N5 


TABLE XLV Continued 


No. of Thickness 
System and Color Coats (mils) 
106. Aluminum-pigmented vinyl (aluminum) 
Pretreatment primer Al, O65 
Vinyl red-lead primer 2 dod 
Aluminum-pigmented vinyl finish 3 Ws) 
ewe, 6oS 
77a. Cold-applied coal tar (black) 
MIL-C-18480 coal-tar coating compound 19.5 
MIL-C-15203 bituminous emulsion finish 2 9.5 
Total 29.0 
107- Cold-applied coal-tar antifouling (black) 
1074. MIL-C-18480 coal-tar coating compound 5(5)* 211.0 (22.5) * 
MIL-C-15203 bituminous emulsion finish 1(0) SOMO) 
(top 1/3) - 
Coal-tar antifouling finish (bottom 2/3) iLL) oO (GoO) 


Total 26.0(top 1/3) 


28.0(bottom 2/3) 
108. Coal-tar epoxy (black) 
Catalyzed coal-tar epoxy 2 8.0 
Total 810 


109- Epoxy (cream) 


109L. Catalyzed epoxy primer al ILo@ 
Catalyzed epoxy intermediate AL Pod 
Catalyzed epoxy finish iL 335 5(Sio0) 

Totaly imeOon) 

110- Tetrafluoroethylene (blue-green) 

1104. Catalyzed epoxy primer iL 35 (Bo) 
Catalyzed epoxy intermediate il, 250. (355) 
Catalyzed epoxy finish 1 Ih, O. (Bs©) 
Tetrafluoroethylene emulsion finish 1(2) O55 (2.05) 

Total 8.0(10.0) 

111. Tetrafluoroethylene (blue-green) 

MIL-C-15328 (Formula II). pretreatment aL Ol 

primer 
Tetrafluoroethylene emulsion finish 4 Sod) 
Topas 0 


*System 1074 consisted of five coats of MIL-C-18480 over the entire panel to 
give 22.5 mils and one coat of the antifouling coating on the top half of the 
panel for a total film thickness of 29.5 mils. 


112- 


1122. 


113- 


ILS Vie 


114- 


LAV z 


115- 
ML 


116- 


iG 


117- 


dL (So 


118- 


ALAS VA 


119- 


1192. 


120- 


1202. 


TABLE XIV Continued 


System and Color 


Urethane (green) 
Vinyl red-lead, iron oxide primer 
Catalyzed urethane finish 


Urethane (green) 
Pretreatment primer 
Catalyzed urethane finish 


Coal-tar urethane (black) 
Catalyzed coal-tar urethane finish 


Vinyl (gray) 
Pretreatment primer 
Vinyl iron oxide primer 
Vinyl finish 


Epoxy (gray) 
Catalyzed epoxy zine chromate primer 
Catalyzed epoxy finish 


Coal-tar epoxy (black) 
Catalyzed coal-tar epoxy finish 


Coal-tar epoxy (black) 
Catalyzed coal-tar epoxy finish 


Zine inorganic silicate (gray) 
Zine inorganic silicate (self-cured) 


Modified phenolic (gray) 
Catalyzed modified-phenolic primer 
Catalyzed modified-phenolic finish 


A-32 


WH 


ins) [= 


(mils) 
Total 


Total 65) 


9.5(10.0 
more, © 55(10.0)) 


; 5) 
Total 11.0(10.0) 


Total oD) 


15 5((16,,0))) 
Total 16.5(16.0) 


17.5 
We wey Af >5 


Totals NO 


6.0 
650) (8.0) 
Total 12.0(14.0) 


ine) 


TABLE XIV Continued 


No. of Thickness 
System and Color Coats (mils) 
121- Polystyrene-pyrobitumen mastic (black) 
121Z. Phenolic red-lead primer all ito@ 
Polystyrene-pyrobitumen mastic finish 2 14.5(16.0) 


aoe, 1555 (GI50) 


122- Urethane (gray) 


1227. Catalyzed urethane zinc chromate primer ali ‘LOL. 5) 
Catalyzed urethane finish 7(6) 6.5(8.0) 
aseul 15555) 
123- Epoxy phenolic (gray) 
123Z. Catalyzed epoxy primer ; IL 350) (6.5) 
Catalyzed epoxy-phenolic finish 3 5 @ 


Total Th.oGh.5) 


124- Epoxy (white) 


12h4Z. Catalyzed epoxy zinc chromate primer 1 355 (CUh.0) 
Catalyzed epoxy finish all O55. (@.5) 
iene, WES O(GSs5)) 
125- Urethane (gray) 
125Z. Catalyzed urethane zinc chromate primer al LoS (2.0) 
Catalyzed urethane finish 3 ©>5((GL055)) 
Mowe ILIGO (ALS) 
126- Vinyl-alkyd (black) 
126Z. MIL-C-15328A (Formula 117), pretreatment iL 0.5 
primer 
MIL-P-15929A (Formula 119), vinyl red-lead 5 655 (5.5) 
primer 
MIL-E-15932A (Formula 122-1), vinyl-alkyd 2 550 (5) 
finish 


Total 12.0(10.5) 


127- Urethane (black) 


127Z. Catalyzed epoxy zinc chromate primer aL 2.5350) 
Catalyzed urethane finish 3 Ho SNM 75) 
Total 10.0 
SERIES 6 
128- Coal-tar epoxy (black) 
128Z. Zine inorganic silicate (self-cured) 1 2.5 
Catalyzed coal-tar epoxy finish dl, 9.0 
inorweL ab 5 


TABLE XIV Continued 


NOm Os Thickness 
System and Color Coats (mils) 
129- Vinyl-alkyd (gray) 
129Z. Zine inorganic silicate (self-cured) 1 3.0 
MIL-P-15328B (Formula 117), pretreatment ill 0.5 
primer 
MIL-P-15929B (Formula 119), vinyl red-lead 3 6.0 
primer 
MIL-E-15936B (Formula 122-27), vinyl-alkyd 2 4.5 
finish 
Total 14.0 
130- Epoxy (gray) 
130Z. Zinc inorganic silicate (post-cured) 4 350 
Catalyzed epoxy lead-silico-chromate primer 1 2oO 
Catalyzed epoxy intermediate a 4.0 
Catalyzed epoxy finish all 2.0 
Wo wewL Il ~O 
131- Vinyl-alkyd (gray) , 
131Z. Zine inorganic silicate (post-cured) dk 300 
MIL-P-15328B (Formula 117), pretreatment ile O45 
primer 
MIL-P-15929B (Formula 119), Vinyl red-lead 5 550 
primer 
MIL-E-15936B (Formula 122-27), vinyl-alkyd 2 5.5 
finish 
Total 14.0 
132- Epoxy (gray) 
132Z. Zine inorganic silicate (self-cured) al oO) 
Catalyzed epoxy mastic iron oxide and 2 5.0 
chromate primer 
Catalyzed epoxy finish Al 2o5 
Total 12.5 
133- Vinyl-alkyd (gray) 
133Z. Zine inorganic silicate (self-cured) ile h.0 
MIL-P-15328B (Formula WAI) 5 pretreatment 1 O55 
primer 
MIL-P-15929B (Formula AALS) )) 3 vinyl red-lead 3 55) 
primer 
MIL-E-15936B (Formula 122-27), vinly-alkyd 2 5.0 
finish 
Total r10 


134- 


1342. 


13 


135Z. 


136- 


1362. 


ISS 


1372. 


138- 


1382. 


Is} 


1392. 


TABLE XIV Continued 


System and Color 


Vinyl (gray) 

Zine inorganic silicate (post-cured) 

Vinyl mastic iron oxide and chromate primer 
Vinyl mastic intermediate 

Vinyl finish 


Vinyl-alkyd (gray) 

Zine inorganic silicate (post-cured) 

MIL-P-15328B (Formula 117), pretreatment 
primer 

MIL-P-15929B (Formula 119), vinyl red-lead 
primer 

MIL-E-15936B (Formula 122-27), vinyl-alkyd 
finish 


Epoxy (gray) 

Zine inorganic silicate (self-cured) 
Catalyzed epoxy lead-silico-chromate primer 
Catalyzed epoxy intermediate 

Catalyzed epoxy finish 


Vinyl-alkyd (gray) 

Zine inorganic silicate (self-cured) 

MIL-P-15929B (Formula 119), vinyl red-lead 
primer 

MIL-E-15936B (Formula 122-27), vinyl-alkyd 
finish 


Epoxy (gray) 

Zine inorganic silicate (self-cured) 
Acrylic zine chromate, zine oxide primer 
Catalyzed epoxy finish 


Vinyl-alkyd (gray) 

Zine inorganic silicate (self-cured) 

MIL-P-15328B (Formula 117), pretreatment 
primer 

MIL-P-15929B (Formula 119), vinyl red-lead 
primer 

MIL-E-15936B (Formula 122-27), vinyl-alkyd 
finish 


No. of 


Coats 


PREP 


ne 


PREH 


PPP 


Thickness 
(mils) 


Or on 
UI UO 


Or 
(je) 


Total 


bh 
M1 
(oe) 


WWh — 
SOOO) 


[pu 
=| 
[e) 


Total 


Total 14.0 


10.0 
Uweyoeyl al 


1h0- 


1402. 


1hyi- 
WEN 


142- 


1h27. 


143- 
1432. 


Tye 
THz. 


TABLE XIV Continued 


System and Color 


Aluminum-pigmented hydrocarbon resin 
(aluminum) 
Zine inorganic silicate (self-cured) 
Modified phenolic-epoxy red iron oxide 
tie coat 
Aluminum-pigmented hydrocarbon resin finish 


Vinyl-alkyd (gray) 

Zine inorganic silicate (self-cured) 

MIL-P-15328B (Formula 117), pretreatment 
primer 

MIL-P-15929B (Formula AALG))) vinyl red-lead 
primer 

MIL-E-15936B (Formula 122-27), vinyl-alkyd 
finish 


Aluminum-pigmented hydrocarbon resin 
(aluminum ) 
Zine inorganic silicate (post-cured) 
Modified phenolic-epoxy red iron oxide 
tie coat 
Aluminum-pigmented hydrocarbon resin finish 


Vinyl-alkyd (gray) 

Zine inorganic silicate (post-cured) 

MIL-P-15328B (Formula 117), pretreatment 
primer 

MIL-P-15929B (Formula 119), vinyl red-lead 
primer 

MIL-E-15936B (Formula 122-27), vinyl-alkyd 
finish 


Vinyl-alkyd (gray) 

MIL-P-15328B (Formula 117), pretreatment 
primer 

MIL-P-15929B (Formula 119), vinyl red-lead 
primer 

MIL-E-15936B (Formula 122-27), vinyl-alkyd 
finish 


Thickness 
(mils) 


3.0 
iLO) 


9 


90) 
Mee i330) 


Total 14.0 


Totals aslR©, 


Total 15.0 


Total 10.5 


From Alumbaugh and Brouillette (1966) 


A-36 


TABLE XV 


Galvanic Series in Seawater 


Magnesium (Continued from previous column) 


Magnesium alloys Muntz metal 


Manganese bronze 
Zine Naval brass 
Galvanized steel or galvanized 


WEROUE AS asters Nickel (active) 


Inconel (active) 


Aluminum 5052-H Yellow brass 
Aluminum 3004 Admiralty brass 
Aluminum 3003 Aluminum bronze 
Aluminum 1100 Red brass 
Aluminum 6053-T Copper 

Silicon bronze 
Cadmium pape 


70-30 copper nickel 
Comp. G-bronze 


Aluminum 2117-T Comp. M-bronze 

Aluminum 2017-T 

Aluminum 2024-T Nickel (passive) 
Inconel (passive) 

Mild steel 

Wrought iron Monel 

Cast iron 18-8 stainless steel 


type 304 (passive) 
18-8-3 stainless steel 


Ni-Resist type 316 (passive) 


13% chromium stainless steel 
type 410 (active) 


50-50 lead tin solder 


18-8 stainless steel 
type 304 (active) 
18-8-3 stainless steel 
type 316 (active) 


Lead 
URaLral 
After LaQue and Cox (1940) 


APPENDIX B 
GLOSSARY OF CORROSION TERMS 


Terms used in corrosion prevention and maintenance techniques are defined 
below. 


Adsorption. The taking up of one substance at the surface of another is 
termed adsorption. It is the tendency exhibited by all solids to condense 
upon their surfaces a layer of any gas or solute with which such solids 
are in contact. 


Aeration cell (oxygen cell). An aeration cell is an electrolytic cell, 

the e.m.f. of which is caused by a difference in air (oxygen) concentra- 
tion at one electrode as compared with that at another electrode of the 

same material. 


Aggressive carbon dioxide. Free carbon dioxide in excess of the amount 
necessary to prevent precipitation of calcium as calcium carbonate is 
termed aggressive carbon dioxide. 


Amphoteric corrosion. Amphoteric materials are those materials that are 
subject to attack from both acid and alkaline environments. Aluminum 

and lead, commonly used in construction, are subject to amphoteric cor- 
rosion in highly alkaline environments. Such corrosion is usually caused 
by a chemical reaction resulting from a concentration of alkaline products 
formed by the electrochemical process. The use of cathodic protection in 
highly alkaline environments, therefore, intensifies the formation of 
alkaline products. 


Anaerobic. Anaerobic means free of air or uncombined oxygen. 


Anion. A negatively charged ion of an electrolyte which migrates toward 
the anode under the influence of a potential gradient. 


Anode. The electrode of an electrolytic cell at which oxidation occurs. 
In corrosion processes, usually the electrode that has greater tendency 
to go into solution. Typical anodic processes are anions giving up 
electrons, metal atoms becoming ions in solution or forming an insoluble 
compound of the metal, and the oxidation of an element or group of ele- 
ments from a lower to a higher valence state. 


Anode corrosion efficiency. The ratio of the actual corrosion of an 
anode to the theoretical corrosion calculated from the quantity of 


electricity that has passed or discharged from the anode. 


Anodic polarization. That portion of the polarization of a cell that 
occurs at the anode. 


Anolyte. The electrolyte of an electrolytic cell that is adjacent to 
the anode. 


B-1 


Calomel electrode. A half-—cell consisting of mercury, a paste of mercury 
and calomel (mercurous chloride), and a standard solution of potassium 
chloride saturated with calomel. It is used as a standard electrode in 
potential difference measurements. 


Cathode. The electrode of an electrolytic cell at which reduction occurs. 
In corrosion processes, usually the area that is not attacked. Typical 
cathodic processes are cations taking up electrons and being discharged, 
oxygen being reduced, and the reduction of an element or group of elements 
from a higher to a lower valence state. 


Cathodic corrosion. Corrosion resulting from a cathodic condition of a 
structure, usually caused by the reaction of alkaline products of elec-— 
trolysis with an amphoteric metal. 


Cathodic polarization. That portion of the polarization of an electroly- 
tic cell which occurs at the cathode. 


Cathodic protection. Reduction or prevention of corrosion of a metal 
surface by making it cathodic to the electrolyte, for example, by use of 
sacrificial anodes.or impressed electrical currents. 


Catholyte. The electrolyte of an electrolytic cell adjacent to the 
cathode. 


Cation. A positively charged ion of an electrolyte which migrates toward 
the cathode under the influence of a potential gradient. 


Caustic embrittlement. Embrittlement of a metal resulting from contact 
with an alkaline solution. 


Cavitation erosion. Damage of a metal associated with the formation and 
collapse of cavities in the liquid at a solid-liquid interface. 


Chalking. The development of loose removable powder at, or just beneath, 
a coating surface. 


Checking. The development of slight breaks in a coating that do not 
penetrate to the underlying surface. Checking may be described as visible 
(as seen by the naked eye) or as microscopic (as seen under the magnifica- 
tion of ten diameters). 


Chemical conversion coating. A protective or decorative coating produced 
in situ by chemical reaction of a metal with a chosen environment. 


Coating resistance. The electrical resistance of a coating to the flow 
of current. Unit of measurement is ohms for one square foot of coating. 
Typical values range from less than 1,000 ohms to more than 1,000,000 
ohms for one square foot. 


B-2 


Coefficient of corrosion. A term used in applied cathodic protection. 
The reciprocal of anode corrosion efficiency. 


Concentration cell. An electrolytic cell, the e.m.f. of which is the 
result of a difference in concentration of the electrolyte or active 
metal at the anode:and the cathode. 


Concentration polarization. That portion of the polarization of an 
electrolytic cell produced by concentration changes resulting from pas- 
sage of electric current through the electrolyte. 


Contact corrosion (crevice corrosion). Corrosion of a metal at an area 
where contact is made with a material usually nonmetallic. 


Corrosion. Destruction of a metal by chemical or electro-chemical 
reaction with its environment. 


Corrosion fatigue. Reduction of fatigue durability by a corrosive 
environment. 


Corrosion fatigue limit. The maximum repeated stress endured by a metal 
without failure in a stated number of stress applications under defined 
conditions of corrosion and stressing. 


Corrosion mitigation. The reduction of metal loss or damage through 
use of protective methods and devices. 


Corrosion prevention. The halting or elimination of metal damage through 
use of corrosion-resisting materials, protective methods, and protective 
devices. 


Couple. A pair of dissimilar conductors in electrical contact. 
Couple action. (See galvanic corrosion. ) 


Cracking (of coating). Breaks in a coating which extend through to the 
underlying surface. Observation under a magnification of ten diameters 
is recommended where there is difficulty in distinguishing between 
cracking and checking. 


Crazing. Crazing is a network of checks and cracks appearing on a 
surface. 


Critical humidity. The relative humidity above which the atmospheric 
corrosion rate of a given metal increases sharply. 


Current density. The current per unit of cross-sectional area. In 
cathodic protection work, the current density is usually expressed in 
milliamperes per square foot. 


Deactivation. The process of prior removal of the active corrosion 
constituents, usually oxygen, from a corrosive liquid by controlled 
corrosion of expendable metal or by other chemical means. 


Decomposition potential (or voltage). The practical minimum potential 


difference necessary to decompose the electrolyte of a cell at a 
continuous rate. 


Depolarization. The reduction of counter e.m.f. by removing or 
diminishing the causes of polarization. 


Deposit attack. Corrosion occurring under or around a discontinuous 
deposit on a metallic surface. 


Dezincification. Corrosion of a zine alloy, usually brass, involving 
loss of zine and a residue or deposit that remains in situ of one or 
more less-active constituents, usually copper. 


Differential aeration cell. (See aeration cell.) 


Drainage. Conduction of current (positive electricity) from an under- 
ground metallic structure by means of a metallic conductor. 


a. Forced drainage. Drainage applied to underground metallic 
structures by means of an applied e.m.f. or sacrificial 
anode. 

b. Natural drainage. Drainage from an underground metallic 


structure to a more negative structure, such as the 
negative bus of a trolley substation. 


Driving force (driving potential). The electromotive force generated in 
a galvanic cell or the electromotive force applied to an electrolytic 


cell. 


Electroendosmosis. (See electroosmosis. ) 


Electrolysis. The production of chemical changes in an electrolyte 
resulting from the passage of electricity. 


Electrolyte. A chemical substance or mixture, usually liquid, containing 
ions that migrate in an electric field. 


Electromotive force series (e.m.f. series). A list of elements arranged 
according to their standard electrode potentials, the sign being positive 
for elements having potentials that are cathodic to hydrogen and negative 
for those elements having potentials that are anodic to hydrogen. (This 
convention of sign, historically and currently used in European litera- 
ture, has been adopted by the Electrochemical Society and by the National 
Bureau of Standards, and it is employed in this publication. The 
opposite convention of G. N. Lewis has been adopted by the American 
Chemical Society. ) 


Electronegative potential. A potential corresponding in sign to those 
of the active or anodic members of the e.m.f. series. Because of the 
existing confusion of sign in the literature, it is suggested that 
"anodic potential" be used whenever "electronegative potential" is 
implied. (See Electromotive force series.) 


Electroosmosis. The flow of a liquid in the soil solution or membrane 
because of difference in electrical potential on the two sides of the 
membrane. As a result, the soil dries out at or near the anode, causing 
an increase in soil resistivity. The principle has been used to migrate 
considerable volumes of water to dry out and stahilize soil during 
construction. 


Klectropositive potential. A potential corresponding in sign to poten- 
tials of the noble or cathodic members of the e.m.f. series. It is 
suggested that "cathodic potential" be used whenever "electropositive 
potential” is implied. (See e.m.f. series.) 


Embrittlement. Severe loss of ductility of a metal or alloy. 


Erosion. Destruction of a metal or other material by the abrasive action 
of liquid or gas, usually accelerated by the presence of solid particles 
of matter in suspensiom and sometimes accelerated by corrosion. 


Exfoliation. Scaling off a surface in flakes or layers is termed 
exfoliation. 


Film. A thin, not necessarily visible, layer of material. 


Fogged metal. A metal the luster of which has been sharply reduced by 
a film of corrosion products is termed fogged metal. 


Fretting corrosion. Corrosion at the interface between two contacting 
surfaces, accelerated by relative vibration between them of an amplitude 
that is high enough to produce slip. 


Galvanic cell. A cell consisting of two dissimilar conductors in contact 
with an electrolyte, or two similar conductors in contact with dissimilar 
electrolytes. More generally a galvanic cell converts energy liberated 
by a spontaneous chemical reaction directly into electrical energy. 


Galvanic corrosion. Corrosion associated with the electric current of a 
galvanic cell that consists of dissimilar electrodes. It is also known 
as couple action. 


Galvanic series. A list of metals and alloys arranged according to their 
relative potentials in a given environment. 


Graphitization (graphitic corrosion). Corrosion of gray cast iron in 


which the metallic iron constituent is converted into corrosion products, 
leaving the graphite intact. 


Half-cell. A conducting material (usually metallic) in contact with an 
electrolyte. It is used as a standard reference in potential tests. 
For further explanation, reference is made to paragraph 8-01 g- in this 
manual. 


Hydrogen embrittlement. Hydrogen embrittlement is caused by the entrance 
of hydrogen into the metal, for example, through pickling or cathodic 
polarization. 


Hydrogen overvoltage. Overvoltage associated with the liberation of 
hydrogen gas is termed hydrogen overvoltage. 


Impingement attack. Corrosion associated with turbulent flow of a liquid. 
For some metals the action is considerably accelerated by entrained 
bubbles in the liquid. 


Inactive. (See passivity. )} 
Inhibitor. As applied to corrosion, an inhibitor is a chemical substance 


or mixture that if added to an environment (usually in small concentration) 
effectively decreases corrosion. 


Intercrystalline corrosion. (See intergranular corrosion. ) 


Intergranular corrosion. Preferential corrosion at grain boundaries of 
a metal or alloy. It is also called intercrystalline corrosion. 


Internal oxidation. The precipitation of one or more oxides of alloying 
elements beneath the external surface of an alloy as a result of oxygen 

diffusing into the alloy from the external source. It is also known as 

subscale formation. 


Ton. An electrically charged atom or group of atoms. 
Local action. Corrosion caused by local cells on a metal surface. 


Local cell. A cell the e.m.f. of which is due to difference of potential 
between areas on a metallic surface in an electrolyte. 


Long-line current. Current flowing through the earth, from an anodic to 
a cathodic area that returns along an underground metallic structure. 
Usually occurs where the areas are separated by considerable distances 
and where the current results from concentration cell action. (See 
positive electricity.) 


Matte surface. A surface of low specular reflectivity. 
Metallizing. The process of spraying a surface with a metal. 
Metal replacement. The deposition of a metal from a solution of its ion 


on a more anodic metal accompanied by ane solution of the latter SCE o 
It is also called "immersion plating.' 


B-6 


Mill scale. The heavy oxide layer formed during hot fabrication or heat- 
treatment of metals. The term is applied chiefly to iron and steel. 


Molality. Molality is the concentration of a solution expressed as the 
number of gram molecules of the dissolved substance per 1,000 grams of 
solvent. 


Noble metal. A metal which in nature occurs commonly in the free state, 
or a metal or alloy whose corrosion products are formed with a low nega- 
tive or a positive free-energy change. 


Noble potential. A potential substantially cathodic to the standard 
hydrogen potential. 


Open-circuit potential. The measured potential of a cell during which 
no significant current flows in the external circuit. 


Overvoltage. The difference between the potential of an electrode at 
which a reaction is actively taking place and another electrode at 
equilibrium for the same reaction. 


Oxidation. Loss of electrons by a constituent of a chemical reaction. 


Parting. Parting refers to the selective corrosion of one or more 
components of a solid-solution alloy. 


Parting limit. The maximum concentration of a more noble component in 
the alloy, above which parting does not occur within a specific environ- 
ment. 


Passivator. An inhibitor which appreciably changes the potential of a 
metal to a more cathodic value. 


Passive-active cell. A cell the e.m.f. of which is due to a potential 
difference between a metal in an active state and the same metal in a 
passive state. 


Passivity. 


a. An active metal in the e.m.f. series, or an alloy composed 
of such metals, is considered passive if its electrochemical 
behavior becomes that of an appreciably less active or noble 
metal. 


|o 


A metal or an alloy is passive if it substantially resists 
corrosion in an environment where, thermodynamically, 
there is a large free-energy decrease associated with its 
passage from the metallic state to appropriate corrosion 
products. 


Patina. A green coating, consisting principally of basic sulfate and 
occasionally containing small amounts of carbonate or chloride, which 
forms on the surface of copper or copper alloys exposed to the atmos-— 
phere for a long time. 


pH. A measure of hydrogen ion activity defined by pH = log, 9 (1/aH+) where 
aH = hydrogen ion activity = the molal concentration of hydrogen ions 
multiplied by the mean ion activity coefficient. 


Pickle. A solution or process used to loosen or remove corrosion products, 
such as scale and tarnish, from a metal. 


Pitting erosion. (See cavitation erosion. ) 


Pitting factor. The depth of the deepest pit resulting from corrosion, 
divided by the average penetration as calculated from weight loss. 


Polarization. The production of a counter e.m.f. by the products formed 
or by the concentration changes resulting from passage of current through 
an electrolytic cell. 


PPM. Parts per million. 


Positive electricity. A body is said to possess positive electricity 
when it has a deficiency of electrons. 


Potential. When a point is said to be at a certain potential, the 
meaning is that there is a voltage difference of that amount between 
the point concerned and a given reference. See also standard electrode 
potential. 


Prime coat. A first coat of paint, originally applied to improve ad- 
herence of the succeeding coat, but now frequently containing a corrosion 
inhibitor. 


Reaction limit. The minimum concentration of an alloy component below 
which appreciable attack of an alloy takes place in a given environment, 
but above which the alloy is corrosion resistant. 


Redox. The term "redox" is an abbreviation of oxidation-reduction 
potential, used to determine whether soil is aerobic or anaerobic. The 
redox-potential is obtained between a platinum electrode and a calomel 
half-cell. 


Reduction. Gain of electrons by a constituent of a chemical reaction. 
Relative humidity. The ratio, expressed as a percentage, of the amount 


of water present in a given volume of air at a given temperature to the 
amount required to saturate the air at that temperature. 


B-8 


Remote electrode (remote earth). The potential of a structure-to-earth 
will change rapidly near the structure, and if remote earth is reached, 
there will be little or no variation in the voltage. Remote earth is any 
location away from the structure at which the potential gradient of the 
structure to earth is constant. 


Resistivity. The specific resistance of a material. It is defined as 
the resistance in ohms of a centimeter cube of material, measured across 
opposite faces. Since the resistance of a material varies directly with 
length and inversely with area, the resistance (R) can be written in an 
equation R = p(l/a). By rearrangement solving for p, p = R(1/a); where R 
is in ohms, 1 is in centimeters and a is in square centimeters. Thus the 


2 
: ey ie ee ae hm ; 
units of resistivity are a or ohm-cm. 
Rusting. Corrosion of iron resulting in the formation of products on 


the surface, consisting largely of hydrous ferric oxide. 


Scaling. The formation of partially adherent layers of corrosion products 
on a metal surface at high temperature. 


Season cracking. Cracking resulting from a combination of corrosion and 
internal stress. A term usually applied to stress-corrosion cracking of 
brass. 

Self-corrosion. (See local action.) 

Slushing compound. A nondrying oil, grease, or similar organic compound 
that, when coated over a metal, affords at least temporary protection 


against corrosion. 


Spalling. The chipping or fragmenting of a surface or surface coating 
caused, for example, by differential thermal expansion or contraction. 


Stray current corrosion. Corrosion caused by an electric current through 
paths other than the intended circuit or by an extraneous current in the 
earth. 


Stress corrosion. Corrosion of a metal accelerated by stress. 


Stress corrosion cracking. Cracking resulting from the combined effect 
of corrosion and stress. 


Subscale formation. (See internal oxidation. ) 


Tarnish. Discoloration of a metal surface as the result of formation of 
an adherent continuous film of corrosion products. 


Tuberculation. The formation of localized corrosion products scattered 
over the surface in the form of knoblike mounds. 


B-9 


Underfilm corrosion. Corrosion that occurs under lacquers and similar 
organic films in the form of randomly distributed hairlines (most 
common) or spots. 


Weld decay. Corrosion notably of austenitic chromium steels at specific 
zones away from a weld. 


B-10 


UNCLASSIFIED 


Security Classification 


DOCUMENT CONTROL DATA- R&D 


(Security classification of title, body of abstract and indexing annotation must be entered when the overall report is classified 
. ORIGINATING ACTIVITY (Corporate author) 2a. REPORT SECURITY CLASSIFICATION 


Coastal Engineering Research Center (CERC) UNCLASSIFIED 
Corps of Engineers, Department of the Army 
Washington, D.C. 


- REPORT TITLE 


CORROSION AND PROTECTION OF STEEL PILING IN SEAWATER 


. DESCRIPTIVE NOTES (Type of report and inclusive dates) 
- AUTHOR(S) (Firat name, middle initial, last name) 


Laverne L. Watkins 


6. REPORT DATE 7a. TOTAL NO. OF PAGES 7b. NO. OF REFS 
May 1969 99 55 


8a. CONTRACT OR GRANT NO. 98. CRIGINATOR’S REPORT NUMBER(S) 


b. PROJECT NO. Technical Memorandum No. 27 


9b. OTHER REPORT NO(S) (Any other numbere that may be aselgned 
thie report) 


10. DISTRIBUTION STATEMENT 


This document has been approved for public release and sale; its distribution 
is unlimited. 


11. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY 


13. ABSTRACT 


The report, based on a survey of literature, assembles much of the current knowledge 
concerning corrosion and protection of steel piling in seawater. Causes of corrosion 
and effects of environmental conditions are presented. Results of tests on protective 
coatings for steel are included. Corrosion rates of bare steel piles and the factors 
involved in the use of cathodic protection and concrete jackets are explained. 
References surveyed show that flame-sprayed zinc sealed with vinyl is possibly the 
best coating system tested. More data is needed from which to determine the most 
economical method of protecting steel piling in seawater. 


DD ,72%..1473 Sscocere ton anuv use. men? UNCLASSIFIED 


Security Classification 


UNCLASSIFIED 


Security Classification 


KEY WORDS 


steel piling 
corrosion 
protective coatings 
concrete jackets 
flame-spraying 
vinyl 


epoxy 


UNCLASSIFIED 


Security Classification 


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