TN-1 426

Technical Note N-1426

UNDERWATER-APPLIED COATINGS FOR STEEL STRUCTURES

By

Richard W. Drisko

March 1976

af

Sponsored By

NAVAL FACILITIES ENGINEERING COMMAND

Approved for public release; distribution unlimited.

CIVIL ENGINEERING LABORATORY
Naval Construction Battalion Center
Port Hueneme, California 93043

—.

ST

Unclassified
Pineal scerte sete Nt SE
SECURITY CLASSIFICATION OF THIS PAGE (When Date Entered)

REPORT DOCUMENTATION PAGE
1. REPORT NUMBER 2. GOVT ACCESSION NO,| 3. RECIPIENT'S CATALOG NUMBER

4. TITLE Ri Subtitle 5. TYPE OF REPORT & PERIOD COVERED

UNDE WATER-APPLIED COATINGS FOR STEEL ;
STRUCTURES Final; Jul 1973 - Jun 1975
PERFORMING ORG, REPORT NUMBER

6.

8. CONTRACT OR GRANT NUMBER(s)

7. AUTHOR(s)

Richard W. Drisko

10. PROGRAM ELEMENT, PROJECT, TASK
AREA & WORK UNIT NUMBERS

62761N
YF54.593.006.01.002
REPORT DATE

March 1976

13. NUMBER OF PAGES

17

14. MONITORING AGENCY NAME & ADDRESS(if different from Controlling Office) 15. SECURITY CLASS, (of this report)

9. PERFORMING ORGANIZATION NAME AND ADDRESS

CIVIL ENGINEERING LABORATORY
Naval Construction Battalion Center
Port Hueneme, California 93043
11, CONTROLLING OFFICE NAME AND ADDRESS 12.
Naval Facilities Engineering Command
Alexandria, Virginia 22332

Unclassified

1Sa. DECLASSIFICATION’ DOWNGRADING
SCHEDULE

16. DISTRIBUTION STATEMENT (of this Report)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from Report)
18. SUPPLEMENTARY NOTES

19. KEY WORDS (Continue on reverse side if necessary and identify by block number)

Underwater-applied coatings; steel structures; waterfront structures; corrosion; epoxy
coatings; sandblasting; waterblasting.

20. ABSTRACT (Continue on reverse side If necessary and identify by block number)

Several underwater-applied epoxy coatings were developed for protecting steel struc-
tures in seawater. The more promising formulations were laboratory and field tested at
different times using a brush, a roller, and a curved plastic applicator developed by the Navy
Coastal Systems Laboratory. The coating that was the easiest to apply underwater is now
marketed by a commercial supplier. Sandblasting was found to be the best method of pre-

paring steel surfaces for painting underwater, and waterblasting was the next best of the five
methods tested.

FORM ris
DD , jan 73 1473. EDITION OF 1 Nov 65 1s OBSOLETE Unclassified
SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered)

LOU

0 0301 0040208 7?

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SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered)

Library Card

Civil Engineering Laboratory

UNDERWATER-APPLIED COATINGS FOR STEEL STRUCTURES
(Final), by Richard W. Drisko

TN-1426 17 pp illus March 1976 Unclassified

1. Underwater-applied coatings 2. Steelstructures I. YF54.593.006.01.002

Several underwater-applied epoxy coatings were developed for protecting steel structures
in seawater. The more promising formulations were laboratory and field tested at different times
| using a brush, a roller, and a curved plastic applicator developed by the Navy Coastal Systems
| Laboratory. The coating that was the easiest to apply underwater is now marketed by a commer-
cial supplier. Sandblasting was found to be the best method of preparing steel surfaces for paint-
ing underwater, and waterblasting was the next best of the five methods tested.

Unclassified

SECURITY CLASSIFICATION OF THIS PAGE/When Data Entered)

CONTENTS

Page
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FIELD TESTING OF UNDERWATER-APPLIED PAINTS ON QUEEN MARY .... . 8
USE OF CEL UNDERWATER-APPLIED PAINT BY PORT OF LONG BEACH ... . 9
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LIST OF ILLUSTRATIONS

Figure 1. Corroded steel panels in specimen holder. Biles Sena 6
Figure 2. Waterblasting of steel panels above water

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Figure 3. Waterblasting of steel panels underwater

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Figure 4. Test panels cleaned by Treatment 1. .......... 8
Figure 5. Two test panels; left panel before wirebrushing

underwater and right panel after sandblasting. .... 11
Figure 6. Hydraulically powered wirebrush equipment used

for cleaning steel panels underwater. ......... Ii
Figure 7. Curved plastic applicator which was designed

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Figure 8. Coated test panel after curing underwater

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Figure 9. Equipment for supplying paint directly to

test specimen using compressed air from a

cylinder. (The pictured roller was not

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Table

Table

Table

Table

Table

Table

Basic Formulations of Underwater-Applied Paints.

Special Variations of Basic Formulations

LIST OF TABLES

by Changing Part B.

Bonding Strengths of Formulations Used at

Different Temperatures .

Bonding Strength of Formulation 101-19 in

Different Waters .

Bonding Strengths of Formulation 101-2 on
Steel Surfaces Cleaned by Different Methods

Summary of Underwater Coating Experiments

at Panama City .

vi

Page

INTRODUCTION

The Navy has miles of steel waterfront structures situated in very
corrosive environments. The protective coatings on these structures are
subject to accelerated deterioration both by the environment and by
impact and abrasion. While deteriorated coatings in dry areas are
relatively easily repaired, those located between tides or underwater
have in the past been very difficult, if not impossible, to repair.

In 1962, the Shell Chemical Company offered coating and adhesive
manufacturers a two-component epoxy formulation designed to cure on
either dry, damp, or underwater surfaces. Shortly thereafter several
coating manufacturers began marketing products (generally called splash-
zone compounds) that were prepared directly from, or were variations of,
this formulation. These products were so viscous that they had to be
applied by the palm of the hand at 1/8 to 1/4 inch thicknesses rather
than by a brush or roller at the usual paint thicknesses. The Navy
investigated [1-9] the use of these products and prepared a specification~
for them. Because they were difficult and costly to apply, the Civil
Engineering Laboratory (CEL) conducted the present investigation into
lower viscosity coatings that could be applied underwater by brush or
roller.

MATERIALS INVESTIGATED

Most of the commercially available coatings that can be applied by
brush underwater have been laboratory-tested by CEL. The vast majority
of these have been solvent-free epoxies, but some polyester formulations
have been tested. The polyester materials have generally been easier to
apply, but they cure much more slowly and tend to be soft and more
easily damaged. Because the epoxy coatings have been more durable, this
CEL investigation was limited to them. Of the Navy-devised epoxy formu-
lations, those utilizing amine-adducts as curing agents showed the most
promise. Two of the more promising basic formulations, 101 and 102,
were prepared by a coating supplier in batch quantities. The composition
of these formulations is shown in Table 1. Table 2 shows several varia-
tions that were made in the curing agent to improve such properties as
wetting of substrate (101-19 and 102-19) and rate of curing (101-5 and
102-5).

@ MIL-P-28379 (YD), Plastic Compound, Epoxy-Polyamide, Marine Splash-
Zone Application.

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Table 2. Special Variations of Basic Formulations by
Changing Part Be

e d Tin
MP = e
2 20 Biocide

(by weight)

Formulation Part BP LO

Number (by weight) (by weight) (by weight)

Weights shown in table were used with 100 parts of Part A of
either 101 or 102.

Part B of 101 and 102 are identical.
Ancamine LO of Anchor Chemical Company.
2, 4, 6-Tri (dimethylaminomethyl) phenol.

Reaction product of tributyltin oxide and fatty acids of
linseed oil.

LABORATORY TESTING

A laboratory procedure was developed for determining the bonding
strength of underwater-applied coatings to steel. A small, 1/8-inch-
thick steel panel is sandblasted to white metal.” It is then placed in a
tank of seawater and brush-coated with an underwater-applied coating.
After curing underwater for 1 week, the coated panel is dried and lightly
sanded. One or more steel probes are then bonded to the sanded coating
using a high-strength, quick-setting adhesive. After the adhesive has
cured overnight, the probe is pulled from the panel using a table model
Instron testing machine.

The bonding strengths of the six formulations in Table 2, which
were applied and cured at the various temperatures indicated, are listed
in Table 3. It can be seen from this table that:

(1) The 101-19 formulations were the easiest to apply.

(2) Of the three sets of curing conditions, application and curing
at 70°F generally resulted in the greatest bonding strength, and
application and curing at 40°F generally resulted in the weakest.

b Steel Structures Painting Council Surface Preparation No. 5.

Table 3. Bonding Strengths of Formulations Used at Different Temperatures

Application
and Curing Bonding Strength Ease of
Temperature (kg/sq cm) Application
(i)

Mixing
Temperature
(OF)

Formulation
Number

27; 49; 194 good-fair
31; 16; 23; 8¢ fair
18; 14; 200 fair

53; 31; 19; 487 fair
53; 19; 18; 22¢ fair
3; 12; 16,95 fair

3223 29 o good

14; 15; 25; 8; 11; 124 good
13; 11; 5; 10; 7; 78 good®

25; 36; 22; 400 fair
20; 14; Ze 23 fair
6;5;4; 44 fair

25; 31; 63; 264 fair
14; 11; 16; 134 fair
8; 4; 13; 84 fair

27; 32; 37; 19; 14; 23 good
9; 4; 9; 6; 3; 124 fair
103 s Ts Gs Nils 72 fair

@ Some adhesive failure; some coating failure.
b Adhesive bond failed; no bonding failure of coating to steel.
© Applied well, but did not level well.

d Coating failure only.

Although most of the underwater-applied coating work was conducted
with seawater, deionized water and freshwater were also used in one brief
test to determine if the paints could be used in these waters at 70°F.
Formulation 101-19 was brush-applied to pairs of sandblasted steel
panels in tanks of deionized water, tap water, and seawater. In all
cases the coating was easily applied. After curing overnight, one panel
from each pair was wiped with a cloth saturated with a 50/50 mixture of
methylethyl ketone and toluene in order to remove any surface film such
as might be formed from amine migration to the surface. These panels
were then returned to their respective tanks, and all six panels were
topcoated with 101-19. The unwiped panels in the deionized and tap
water tanks were noticeably more difficult to coat than the others.

After curing underwater for 1 week, the bonding strengths of the paints
on each panel were determined as previously described; the results of
these tests are shown in Table 4. Although the unwiped panels in the
deionized and tap water tanks were more difficult to topcoat, the topcoat
bonded as well as or better than the wiped panels.

FIELD SURFACE-PREPARATION TESTS

A small field test was conducted at Port Hueneme on steel panels to
determine the effect on bonding strength of different methods of prepar-
ing their surfaces for underwater painting. Six sandblasted© steel
panels (2-3/4 inch by 6 inch) were corroded to a similar degree by
exposure for 8 days in a 5% salt spray cabinet. They were then secured
in place on a wooden specimen holder (Figure 1) and treated with different
methods of surface preparation as follows:

Treatment 1 — Waterblasted above water at 10,000 psi and 10 gpm
(Figure 2)

Treatment 2 — Waterblasted underwater at 10,000 psi and 10 gpm
(Figure 3)

Treatment 3 — Waterblasted underwater at 8,500 psi and 10 gpm
with 16-30 mesh copper slag abrasive injected

Treatment 4 — Manual wirebrushing underwater

Treatment 5 — Sandblasting above water (accepted optimum surface
preparation procedure)

Treatment 6 — Uncleaned control

After cleaning, the panels given treatments 1, 2, and 4 had a
similar crudely cleaned appearance (Figure 4), while those given Treat-
ments 3 and 5 had a white metal appearance.

@ rece : :
Steel Structures Painting Council Surface Preparation No. 5.

Table 4. Bonding Strength of Formulation 101-19
in Different Waters

Wiped With Bonding Strength
Solvent (kg/sq cm)

Deionized
Deionized

Tap

Tap
Salt
Salt

2 No intercoat failure.

Some intercoat failure.

Figure 1. Corroded steel panels in specimen holder.

Figure 2.

Waterblasting of steel panels above water (Treatment 1).

~

Figure 3.

Waterblasting of steel panels underwater (Treatment 2).

Figure 4. Test panels cleaned by Treatment 1.

Each cleaned panel was brush-coated underwater with CEL Formulation
101-2 and cured underwater for 1 week before the bonding strengths of
the coating were determined as previously described. All the panels were
coated relatively easily. The results shown in Table 5 indicate that
sandblasting (Treatment 5) gave the best bonding strength and waterblast-
ing underwater (Treatment 2) the next best. Waterblasting above water
(Treatment 1), waterblasting underwater with added abrasive (Treatment
3), and wirebrushing (Treatment 4) resulted in a much reduced bonding
strength, but it was still well above that of the uncleaned control
panel (Treatment 6).

FIELD TESTING OF UNDERWATER-APPLIED PAINTS ON QUEEN MARY

With the cooperation of CDR John W. McAdams and Mr. Marvin M. Wolff
of the Queen Mary Department of the City of Long Beach, a field test of
four CEL formulations was conducted on the Queen Mary on 21 January
1975. These four formulations were 101-2, 102-2, 101-5, and 102-5.

The area selected for the test was located partly above and partly below
water on the steel propeller box on the port side. It was given only a

Table 5. Bonding Strengths of Formulation 101-2 on Steel
Surfaces Cleaned by Different Methods

Treatment Breaking Strength
Number@ (kg/sq cm)

Method of Failure

coating
mostly adhesive
coating

coating

both coating and adhesive

coating

a ee
See text for description of treatments.

cursory cleaning by scraping and wirebrushing to remove loose paint,
chalk, and other surface contamination. The four orange paints were
applied in 1-foot squares that were easily distinguished from the adjacent
red paint. The portions above water were still wet from the rinsing

when painted. Application was faster above water and generally smoother.
Formulations 101-2 and 102-2 were much easier to apply than 101-5 and
102-5. They all displayed a tendency to sag from a vertical surface

when applied above water.

USE OF CEL UNDERWATER-APPLIED PAINT BY PORT OF LONG BEACH

Pier C at the Port of Long Beach had numerous weak areas (about
200) where holes or thin places had occurred in the steel sheet piling.
A contract was negotiated with Pacific Marine Enterprises of Seal Beach,
California, to cut out these areas and repair them by welding in steel
plates. The contract specified coating the oval-shaped plates (about 3
to 6 sq ft in area) with CEL epoxy paint and touching up by brush the
weld areas. The procedure used was to roll two coats of formulation
101-19 onto the steel plates to give about 20 mils dry film thickness,
weld these plates in place, clean the welds, and apply two coats of
paint to them underwater.

FIELD TESTING AT PANAMA CITY

During the week of 10-14 March 1975, a cooperative field test was
conducted with the Naval Coastal Systems Laboratory, Panama City, Florida.
The test site was located in St. Andrews Bay, an inlet of the Gulf of
Mexico. The experiment was conducted on a platform located about
20 feet underwater and about 20 feet from an NCSL pier facility. The
temperature of the water was about 65 F (18.3°C). The experiment was
conducted to (1) compare ease of application of two underwater-applied
formulations with each other under laboratory-controlled conditions, (2)
compare ease of application of underwater-applied paints to sandblasted
and wirebrushed steel specimens and to vertically and horizontally
placed steel specimens, and (3) field test the NCSL-developed coating
applicator.

Experimental specimens 2 feet by 2 feet by 1/4 inch were prepared
from rusty, mild steel plates either by sandblasting in an NCSL shop
prior to immersion or by wirebrushing underwater (Figure 5). The sand-
blasted finishes were no better than a Steel Structures Painting Council
Surface No. 6 (Commercial Blast Cleaned Surface Finish); wirebrushing
underwater was accomplished by a diver using a hydraulically powered
wirebrush (Figure 6).

The underwater surface preparation and the material applications
were accomplished by different two-man teams; in all cases, the team
consisted of an NCSL-civilian diver and a military diver. A curved,
plastic applicator (Figure 7), designed and fabricated by NCSL, was used
to coat the steel specimens. A portion of coating was poured onto the
steel and then spread with the applicator.

Experiments on individual specimens (see Figure 8, for example) are
described in detail below and then summarized in Table 6 for easy
comparison:

Spectmen 1. A rusted panel was secured in a horizontal position
and wirebrushed underwater. The 101-2 formulation was somewhat difficult
to apply underwater with the curved plastic applicator. A metal pressure-
feed system (Figure 9) was used with Specimens 1 and 2 to place portions
of the coating on the steel before being spread with the applicator.
The equipment was quite messy to clean up, so with subsequent specimens
the coating was poured directly from the can onto the steel.

Spectmen 2. A sandblasted, horizontally held steel panel was
coated with some difficulty with the 101-2 formulation. It was a
little easier to coat than the Specimen 1 panel.

Spectmen 3. A rusted panel was secured in a vertical position and
wirebrushed underwater. It was extremely difficult to coat it with the
101-2, and, consequently, only about half of it was coated.

Specimen 4. A sandblasted, vertically held steel panel was coated
with extreme difficulty with the 101-2 formulation. It was almost as
difficult to apply as with Specimen 3. Consequently, only about three-
quarters of it was coated.

10

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Figure 5. Two test panels; left panel before wirebrushing underwater
and right panel after sandblasting.

Figure 6. Hydraulically powered wirebrush equipment used for cleaning
steel panels underwater.

11

Figure 7. Curved plastic applicator which was designed and fabricated
by NCSL.

Figure 8. Coated test panel after curing underwater overnight.

12

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Figure 9. Equipment for supplying paint directly to test specimen
using compressed air from a cylinder. (The pictured
roller was not used in the field test.)

Specimen 5. A rusted panel was secured in a horizontal position
and wirebrushed underwater. The 101-19 formulation was easily applied
to the steel panel. A little cratering of the paint (contraction to
expose bare metal) occurred, but the paint was readily spread back over
such areas.

Spectmen 6. A sandblasted, horizontally held steel panel was
easily coated with the 101-19 formulation. As with Specimen 5, there
was some cratering, but this was no problem.

Spectmen 7. This specimen was coated similar to Specimen 6, except
that the panel was held in a vertical position. Again the paint was
easily applied, and some small cratering was noted. On the following
day, this specimen was given a second coat of the 101-19 formulation,
which was also easily applied.

Specimens 8 and 9. These were wirebrushed and sandblasted specimens,
respectively, which were held in a vertical position. Both were easily
coated with the 101-19 formulation.

14

From the testing at Panama City it was found that:

1. The steel, pressurized equipment for supplying paint to the
surface of the substrate or applicator is extremely difficult and costly
to clean for reuse. A system with a collapsible, disposable plastic bag
for a reservoir would be much more practical.

2. Whenever paint application problems are encountered, a sand-
blasted surface is somewhat easier to coat than a wirebrushed surface,
and a horizontal surface is somewhat easier to coat than a vertical
surface.

3. CEL formulation 101-19 is an easily applied, versatile product
that can effectively coat underwater-sandblasted or -wirebrushed steel
surfaces in both horizontal and vertical positions. It can be applied
as a topcoat to itself.

4. The NCSL underwater paint applicator can be effectively used to
apply 101-19, but it may not presently be in its most effective form.

SUMMARY

From the laboratory and field testing, it was determined that
Formulation 101-19 was the most practical of those tested. It is avail-
able commercially for use by the Navy or private industry. The choice
of a brush, roller, or curved plastic applicator varies with the indi-
vidual diver and the job. The roller and plastic applicator are best
used on large, flat surfaces, while the brush can be used on any type of
surface. A relatively stiff, round brush appears to be especially
effective. Sandblasting was the most effective of the five surface
preparation systems tested; waterblasting was the next best.

15

REFERENCES

1. Naval Civil Engineering Laboratory. Technical Report R-300:
Underwater-curing epoxy coatings, by R. W. Drisko, J. W. Cobb, and R. L.
Alumbaugh. Port Hueneme, CA, May 1964. (AD439344)

2.——._ Technical Report R-390: Bonding of underwater-curing
epoxies, by R. W. Drisko. Port Hueneme, CA, Jun 1965. (AD464942)

3.——.._ Technical Note N-833: Laboratory studies of underwater-
curing epoxies, by R. W. Drisko and J. W. Cobb. Port Hueneme, CA, Aug
1966. (AD81887L)

4.——_. Technical Note N-925: Bonding to steel of underwater-curing
epoxies, by R. W. Drisko. Port Hueneme, CA, Sep 1967. (AD821145L)

5. Technical Report R-522: Application of underwater-curing
epoxies to steel sheet piling at USNSB, New London, by R. W. Drisko.
Port Hueneme, CA, Apr 1967. (AD812944L)

6.————.. Technical Report R-622: Investigations of underwater-curing
epoxies, by R. W. Drisko. Port Hueneme, CA, Apr 1969. (AD852997L)

7.——.. Technical Note N-1026: Effects of temperature and pressure
on splash-zone compounds, by R. W. Drisko, A. E. Hanna, and C. V.
Brouillette. Port Hueneme, CA, Mar 1969. (AD850612L)

8.———.. Technical Note N-1064: Splash-zone, underwater-curing,
epoxy coatings, by R. W. Drisko. Port Hueneme, CA, Oct 1969. (AD863030L)

9. R. W. Drisko. ‘‘Underwater marine applications of coatings and
adhesives,’®? Journal of Paint Technology, vol 47, no. 600, Jan 1975 pp
40-42.

16

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