March 1948
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY LITERATURE CITED
Assoc.
Official Agr. Chem., OfficialMethods of Analysis, 2.26,
27 (1945).
Burnett, R. S., and Fontaine, T. D.,
[email protected].,36, 284 (1944).
Circle, S. J., “Studies on Soybeafl Protein,” Dissertation, Universitv of Chicago (1941). Dalmatov, “V. A,, 6 u d u i Lab. Izucheniuu Bellca Belkovogo Obmena Organizme, 7 , 7 6 (1935). , Fontaine, T. D., and Burnett, R. S., IND.ENG.CHEM.,36, 164 (1944). Fontaine, T. D., Irving, G. W., Jr., and Markley, K. S., Ibid., 38, 658 (1946). Fontaine, T. D., Samuels, C., and Irving, G. W., Jr., Ibid., 36, 625 (1944). Hammarsten. 0..2. nhwsiol. Chem.. 102.85 11918). Osborne, T. B., and Campbell, G. F.,‘ J . Am. Chem. Soc., 18, 581 (1896).
(10) (11) (12) (13) (14) (15) (16) (17)
461
Ibid., 20,348 (1898). Ibid., 20,410 (1898). Osborne, T. B., and Harris, I. F., J . Biol. Chem., 3 213 (1907). Painter, E. P., and Nesbitt, L. L., IND.ENG.CHEM.,38, 95 (1946). Perov, S. S., and Lisitzuin, M., Trudui Belkovo Lab.. S b o m i k , 1932. Smith, A. K., and Circle, S. J., IND.ENG.CHEM.,30, 1414 (1938). Smith, A. K., Johnsen, V. L., and Beckel, A. C., Ibid., 38, 353 (1946). Staker, E. N., and Gortner, R. A., J . P h w . Chem., 35, 1565 (1931).
RECEIVED December 2, 1946. Scientific Paper 690 from the College of Agriculture, Agricultural Experiment Stations, State College of Washington .Pullman. Wash.
ANTIFOULING PAINTS
.
Preparation of Thin, Light Weight Paints for Application to High Speed Surfaced ALLEN L. ALEXANDER, PETER KING, AND J. E. COWLING Nuval Research Laboratory, Wushington, D . C . T h e problem of effectively preventing the attachment of fouling organisms to surfaces immersed in the sea is of long standing, and methods for combating this attachment have been the subject of intense study for many years; however, the development of thin, hard, flexible films applicable to high speed surfaces, such as the hulls of flying boats, is relatively new. The orthodox shipbottom finishes are automatically eliminated for use on flying boat hulls because of their weight, brittleness, lack of smoothness, and corrosive tendencies toward aluminum alloys. The present investigation describes in some detail the experimental work that has led to the formulation of efficient antifouling films no more than 2 mils in thickness, which effectively prevent the attachment of marine organisms to submerged surfaces for periods up to 8 months. Data are presented as to methods of evaluating such finishes along with comparative fouling data from several locations. From the experimental work described it is demonstrated that certain resinous constituents commonly considered as possessing poor wetting or grinding properties are more efficient in carrying toxic pigment for antifouling purposes than are the better grinding media so often desired in paint formulations.
T
HE problem of effectively preventing the attachment of fouling organisms to surfaces immersed in the sea has long been of paramount interest to the navies of the world. Theories explaining the antifouling action of toxic paints (8) are numerous. The patent and technical literature is full of specific compositions for which .antifouling properties are claimed, and in the vast majority of cases these compositions consist primarily of the heavy metals (usually copper and mercury) or some derivative thereof dispersed in a heavy matrix, often of a relatively soft or plastic nature. Such compositions have gained widespread me, and their effectiveness has been attributed to the dissolution of the toxic material in sea water a t an established minimum rate ( 3 ) . By the application of thick films (current United States
Navy practice requires up to 60 mils) of antifouling paint t o ships’ bottoms, stores of toxic are provided capable of maintaining a high rate of solution over considerable periods. The solution rate may be controlled either by varying the permeability of the matrix or by regulating its solution rate ( 2 ) . Paints of this nature whose effective life may be predicted reasonably (8) are currently used by the United States Navy for the protection of the hulls of surface ships. By 1935 the flying boats (PB types) developed for the Yavy had reached such dimensional proportions that instances were reported where operations a t advanced bases lacking beaching facilities had been retarded, because of the formation of marine growth on aircraft hulls that had been permitted to rest in the water for periods up to 2 weeks. Efforts to adapt the conventional types of antifouling paint t o this application were abandoned early, BS it became quite evident that the added weight of thick plastic films could not be tolerated. Furthermore, the soft and uneven surfaces resulting from plastic paints and the danger of accelerated corrosion of the aluminum alloys in direct contact with compounds of the heavy metals were prohibitive. A coating applicable to the hull of a flying boat must be hard, flexible, smooth, and resistant to abrasion in order to withstand conditions obtaining during take-off and landing operations. As a result of the researoh reported here, new information has been developed concerning the behavior of some commonly used toxic materials dispersed in several media and applied in thin films (2.0 mils) when immersed in the sea. A composition meeting the requirements suggested here is currently in use and is described adequately by appropriate specification ( 4 ) . PANEL EXPOSURES
Laboratory tests for the determination of antifouling efficacy are somewhat inadequate (7), and resort must be made to the exposure of carefully prepared panels to actual fouling environment by immersion in the sea. For the initial phase of this invefltigation all panels were prepared in triplicate t o allow a study and comparison of the results from three separated areas of varying fouling intensity-namely Tahiti Beach, Fla., Guanta1 The first paper of this series appeared in INDU~TRIAL AND ENQINEERINQ namo Bay, Cuba, and San Juan, Puerto Rico. After completion CHEMISTRY, page 1028, August 1947. +
462
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 40, No. 3
matrix a t relatively loa weight percentages, but their efficiency in preventing the attachment of fouling presented a selective trend on which Panel Guantanamo Bay Tahiti Beach San Juan additional experiments were based. Relative NO. l a 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 performance of the materials is evident from Table 87 10 10 10 10 Q : Q 10 Q Q Q 8 10 10 10 10 1 88 9 Q 8 5 3 11. Although none of these formulations indicate 1010 9 7 0 3 6 2 1 1 0 44 9 8 8 6 5 10 9 Q 5 4 4 6 0 0 0 0 complete protection for 6 months, comparative 54 9 9 8 8 7 6 Q 1 0 1 0 1 0 9 8 9 8 2 1 0 5 2 2 1 1 0 0 7 7 6 4 3 0 1 0 0 0 0 values are ‘indicated in which C U D ~ O U Soxide and 5 Months. mercurous chloride predominate at the pigment ratios indicated. Since the efficiency of cuprous oxide as an active fouling preventative is well recognized (5, 6 , 8 ) , the of several hundred exposures it was apparent that good agreecomparative behavior of mercurous chloride as shown by the ment could be obtained in the evaluation of the coatings a t each data (Table 11)made it appear promising for adaptation to thin site, although, as might be expected, wide differences in the rate lacquer-type coatings. The use of copper and its salts was of attachment at each location were obvious. The data of restricted by requirements for light shades in the camouflage of Table I indicate the comparative rate of simultaneous attachoperational aircraft. Physiological hazards characteristic of most ment a t the three stations. All of the panels of this series were organomercurials proposed as antifouling agents (IO) are not so finished with antifouling paints exhibiting varying degrees of serious for mercurous chloride. In order to explore fully the more protection from fxcellent (panel 87) to none (panel 5 ) . B system efficient matrix for carrying this toxic, a series of exposures was of assigning numerical ratings describing the extent of fouling prepared in which mercurous chloride was dispersed in a number was used as proposed by Young ( 7 ) in which a perfect panel of vehicles; from these it was evident that certain nonoxidizing rates ten, and one completely fouled is rated zero. Although types of matrices function more efficiently as binders for toxic exact numerical ratings do not follow for each location studied, pigments than do drying oil varnishes containing alkyd of phenolic comparative intensities ale in close agreement, with San Juan resins. Resins of this type that were considered t o be of value showing the highest rate of attachment, and Guantanamo Bay consisted of acrylic polymers, Vinylite, and chlorinated rubber, and Tahiti Beach following, respectively. Because of the inthe latter appearing to be among the better film forming materials. convenience of shipping panels beyond the continental limits SPECIFIC FORBIULATION STUDIES during war time, later exposures were confined t o Tahiti Beach, During the past several years the fouling intensity a t Miami A series of experiments was prepared to determine the effect of Beach has been demonstrated to compare favorably with that varying the ratio of toxic and pigment to binder. Composition a t Tahiti Beach (S), and several experiments were exposed there. data along with pertinent fouling data are presented in Table The data of Tables 1711-X were collected from panels immersed 111. As might be expected, the higher concentrations of mera t Miami Beach. curous chloride are more useful in preventing the attachment of 811 formulations were applied to panels of 24ST aluminum fouling organisms. A value of approximately 8% toxic by alloy prepared by riveting together two panels size 4 X 12 volume in the dried film appears necessary to maintain adequate inches and allowing a 1-inch lap at the center to simulate current performance for periods up t o 6 months, when applied in thin hull construction in flying boats. The rivets of 17ST alloy were films of less than 2 mils. The per cent of nontoxic pigment, kept under refrigeration after heat treatment until used. Before however, is critical in maintaining a high rate of efficiency (9). riveting, the smaller (4 X 12 inch) panels were given a light coat For example, panels 295, 285, and 139 displayed a fair degree of of zinc chromate primer ( I ) , after which a strip of zinc chromate protection throughout the entire exposure period a t a toxic tape 1 inch in width was laid along one edge to be included in the volume of 570 a t relatively high pigment volumes. On the other seam. After assembly the entire panel was given a second coat of hand, panel 171 containing a higher per cent of toxic a t a much primer a few hours before the succeeding top coats of antifouling lower pigment volume failed rapidly. Similarly, panel 286 a t paint were applied. The selection of this type of panel appeared low toxic and high pigment volume performs much more effecjustified inasmuch as initial corrosion often appeared on rivet tively than do panels 162 and 170 at higher toxic levels. heads and beneath the seam when inadequately protected by The mercurous chloride in the formulation of panel 295 was inferior coatings. withheld frnm the batch, as it was put in the mill and was stirred Many mercury compounds, including a number of organic in after grinding, in an experiment t o determine the effect of derivatives, are susceptible to easy reduction with the liberation grinding as it might govern the rate of fouling attachment. of free mercury. I n all formulations described here calomel Although it is unsafe to base conclusions on a single experiment, appeared quite stable, but caution was exercised to ensure adethe fouling data on panel 295 as compared with those on panel quate priming before application of top coats. Scribed panels 284 indicate that perhaps the effect of the toxic is slow in manifinished with formulations containing calomel and phenoxyfesting itself, but once it begins to function it is as efficient as propylene oxide compared most favorably with similarly prepared when ground into the formulation. Panel 168, which served as a samples finished with specification (An-E-3) enamel with respect to corrosion tendencies.
TABLEI. RELA4TIVEFOULING INTENSITIES AT GUANTANAMO BAY, TAHITI BEACH,AND S.4N JUAN (h/IONTHLY)
I
TABLE 11. RELATIVEEFFICACY OF SEVERAL TOXICP
SELECTIOh OF TOXICS AND VEHICLES
9 considerable number of pure toxic materials have been studied by laboratory methods ( 7 ) for their possible inclusion in antifouling paints, but some doubt exists as to their precise role when incorporated into an organic matrix and immersed in the sea. Final evaluation must await results of actual exposure. A number of preliminary experiments indicated that an efficient matrix for dispersing toxic compounds consisted of 6041, chlorinated rubber (125 centipoises) and 40% alkyd resin of iiiedium oil length. Selected toxic compounds were dispersed in this
Panel No. Q
Toxic In Other Dry Pigment Film, % ’ ZnO 40 36 ZnO ZnO 40
% ’ Toxic & pigment (Wt.) in
Monthly Fouling Ratings 1 2 3 4 5 6 10 10 Q Q 10 7 10 Q 4 2 2 2 10 Q 9 8 5 4
Toxic Dry Film 66 cut0 63 Zn(CN)z 10 12 66 2Hg0 1cut0 52 ZinccyanTi02 36 64 10 Q amide 10 10 TjOn 36 64 53 HgCle Ti02 36 64 10 10 54 HgiClt a Vehicle = 607, chlorinated rubber, 407, alkyd resin.
8
5
3
2
9 10
7
2 8
0
Q
6
.
INDUSTRIAL AND ENG INEERING CHEMISTRY
March 1948
TABLE 111. FOULING EFFICIENCY us. TOXIC CONTENT Panel
No. 241 284 163 171 295d 285 139 162 170 286 164 287 168
Compositiona, Vol. HgCl CuRb RClc 11.1 23.3 27.2 1 0 . 3 2 7 . 0 33.0 8 . 1 21.8 26.7 5.6 . . . 68.0 5 . 0 30.0 36.6 5 . 0 30.0 36.6 5 . 0 27.0 33.0 3.5 9.5 43.4 3.5 9 . 5 43.4 2 . 8 27.4 33.4 1.8 ,9 . 9 4 6 . 2 0.5 28.1 34.0 Control
Yu
pigment 24.2 29.0 23.2 15.8 28.5 28.5 31 .O 10.1 10.1 29.0 10.5 29.7
pigment +Toxic 35.3 39.3 31.3 21.4 33.5 33.5 36.0 13.6 13.6 31.8 12.3 30.2
Monthly Fouling Ratings 1 2 3 4 6 6 10 10 10 10 10 10 8 10 10 10 10 10 9 9 10 10 10 10 0 6 1 0 0 10 8 10 8 8 9 9 7 10 10 8 8 9 7 10 10 10 9 7 0 3 1 8 5 2 1 1 8 4 2 7 4 9 9 10 2 0 0 7 4 10 1 6 1 8 7 9
%
TABLE IV. FORMULA WITH NORMAL RESINATELOADING Chlorinated rubber Dibutyl phthalate Copper resinate Mercurous chloride Titanium dioxide Zinc oxide Carbon black Phenoxy propylene oxide Xylol
.'
5.8 377.0
1000 .o
control in this series, was finished with three coats of nontoxic aluminized acrylic lacquer applied over two coats of zinc chromate primer. This system was formerly used for finishing aircraft hull bottoms. I n early formulations containing mercurous chloride, considerable trouble was encountered as a result of settling of the heavy toxic. I n a number of instances fused copper resinate had been studied as a possible fouling preventative. It was noticed that these formulations exhibited outstanding stability characteristics with reference to pigment settling. In succeeding experiments copper resinate was examined with a view t o preventing severe settling. It has proved exceptionally efficient when included a t 50% of the total weight of mercurous chloride. The evidence so far is somewhat inconclusive as to the value of the poorly soluble copper resinate as an aid in the prevention of fouling attachment. Although copper resinate was examined originally with a view toward exploiting any antifouling characteristics which it might possess, its value as a suspension agent was so outstanding in stabilizing heavy pigment dispersion that it was continued as a major ingredient of most experimental formulations. Because of a relatively high pigment volume ratio maintained throughout these experiments, acceptable flexibility characteristics in the dried film were difficult to obtain. The properties contributed by copper resinate affecting flexibility were studied in considerable detail by varying the amount of copper resinate present in typical formulations. Although the use of a high viscosity chlorinated rubber produces films of increasing flexibility, other properties such as sprayability are affected adversely. Therefore, in arriving a t an optimum combination, it was necessary to include chlorinated rubber representing a wide variety of viscosities. As a result of these experiments it may be concluded that copper resinate does not affect the flexibility of the dried film adversely, but, on the other hand, there is slight evidence to indicate that increased amounts tend t o render the film less brittle. Table IV gives the formula in which the copper resinate was varied, with a norMal loading of the resinate appearing in the formula. Phenoxy propylene oxide has been demonstrated (6) as a stabilizer for chlorinated rubber and was found to contribute to the general anticorrosive properties of these films.
463
Paints were prepared by grinding in pebble mills for 48 hours. Two spray coats were applied to panels of anodized aluminum alloy (24ST) 20 mils in thickness, to which one spray coat of zinc chromate primer (AN-P-656b) had been applied. Where 125-centipoise chlorinated rubber was used as a binder, all formulations successfully passed the flexibility test of bending over a mandrel 3/16 inch in diameter. The thickness of the top coats varied between 1.5 and 2.0 mils. The volume of copper resinate in the dried film ranged between 0 and 12.5y0 in increments of 1%. Final evaluations were made after panels had aged for 6 weeks under controlled conditions of temperature and humidity. A second series was prepared in which the copper resinate varied between 0 and 22%, where the binder was prepared from chlorinated rubber having a viscosity of 25 centipoises. Other conditions were the same as given. The results from the examination of these formulations 'are presented in Table V. In this instance all films possessed relatively poor flexibility. None compared favorably with those prepared with 125-centipoise chlorinated rubber. It is significant perhaps that all films containing less than 16% copper resinate failed, whereas those containing greater amounts passed, with one exception in which thickness may have been a factor. A third series was studied in which chlorinated rubber having a viscosity of 66 centipoises was used with the results indicated in Table VI. I n a separate experiment 807, of the chlorinated rubber was replaced with a medium grinding alkyd varnish in which copper resinate was varied from 0 to 2570 by volume. All formulations failed to withstand bending over a 6/16-inchmandrel. Therefore, the conclusion is evident that copper resinate does not affect flexibility adversely in films of the type studied, but rather it may be expected to produce slight improvement when used a t the higher ratios. COMPARISON OF NATURAL AND SYNTHETIC CHLORINATED RUBBER
In order to meet conditions imposed by the scarcity of chlorinated rubber, studies were conducted in which up t o Soy0of the chlorinated rubber was replaced with a poorly wetting alkyd resin based on dehydrated castor oil. Experiments with resins normally considered as excellent grinding media produced paints poor in antifouling properties; this lent evidence t o the theory that a poorly wetting matrix is preferable in the formulation of efficient short-life antifouling paints. It was soon apparent, however, that although considerable protection was afforded b y such compositions, they do not compete with matrices based on 100% .chlorinated rubber. With the increasing availability of synthetic chlorinated rubber, a series of exposures were made to determine. the relative efficiency of the synthetic product com-
TABLE v. FLEXIBILITY O F 25-CENTIPOISE CHLORINATED RUBBERFILMS N 0. 1 2 3 4
Film Cu Resinate, T hie kness. VOl. 70 Mils 22.14 2,s 20.35 3.2 18.52 2.7 1 6 . 6 0 (and lower) 2.7
Flexibility over J/ls-In. Mandrel Passed Failed Passed All failed
TABLE VI. FLEXIBILITY O F 66-CENTIPOISE CHLORINATED RUBBERFILMS No. 1 2 3 4 5 6
Film Thickness, Mils 22.14 2.9 20.35 2.5 18.52 2.4 2.4 10.60 14.58 2.6 1 2 . 5 8 (and lower) 2.7
Cu Resinate, Vol. %
Flexibility over Mandrel of 114 in. b/la in. Passed Passed Passed Passed Passed Passed Passed Passed Failed Passed Failed Passed
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
464
TABLE VII. CHLORINATED SYNTHETIC RUBBERCOMPARED CHLORINATED RUBBERPAINTS
TO
~~
Film Thickness, Mils T~~ Primer coats 0.3 1.9 0.5 2.1 3.3 0.5
Panel No. 673 677 67 1
Film Compn. " 100% RC1 100% RC1 20%,RC1, 80% alkyd re8m 0.6 3.5 20% , R k l , 80% alkyd 675 resin 0.5 2.5 100% 20-cp. SRCl 676 100% 20-cp. SRCI 0.7 2.0 672 2.'% 0.8 20% 20-cp. SRCI, 80% 670 alkyd 2.6 20% 20-cp. SRCI, 80% 0.5 674 alkyd 0.3 1.6 100% 125-cp. SRCl 679 1.7 1 0 0 7 ~m - c p . SRCI 0.5 681 3.7 20% 125-cu. SRCl, 80% 0.4 680 aikyd 20% 125-cp. S R C l , 8 0 % 0 3 3 2 678 alkyd * RC1 = chlorinated rubber: SRCl = synthetic
Monthly 1 2 10 Q 10 10
.
TABLE
Fouling Rating8 3 4 5 6 7 Q 9 Q 7 6 10 Q 9 8 7 3 0 0 0 0
9
6
9
7
7
3
0
0
0
10 9 8
9 9 7
Q
9 7
8
7
Q
9 Q
6
3
2
0
0
0
0
10 10
Q
8
7 9
7
6 8
6
2
0
0
1 1 0 0
9
Q 5
9 3
0
Q 0
0
0
8
6
4
0
0
0
0
6
chlorinated rubbei.
L7III. FOCLISG RESISTANCE
Binder Comvn., Vol. 74 in
a
6.5 6.5 5.0 4.0 1.0 0 6 . 0 5.0 7.5 6.5 5.5 3.5 0 0
20 125-cp. RC1, 80 5/10 50 125-cp. RCI, 50 5/15 80 125-cp. RC1.20 '/4 Failed 20 20-cp. RC1,SO Failed 50 20-cp. RCI, 50 80 20-cp. RCI, 20 Lt. gi'ay .'/4 . Control enamel Smallest diameter t h a t film will pass.
pared with natural rubber. The fo~.mulationsshown in Table VI1 were prepared at, equal toxic-pigment-binder ratios and exposed at Miami Beach for a period of 7 months LTith the results indicated. Each preparation \?as exposed in duplicate, and, with the exception of the data on panel 672 during the final 2 months, excellent agreement, is demonstrated between duplicate experiments. The data indicate the relatively inferior performance of alkyd vehicles even when mqdified with chlorinated rubber. It is apparent further that the viscosity of the chlorinated rubber, either natural or synt,hetic, has no part,icular influence on the final results. Earlier experiments had indicated slight preference for the higher viscosities. These data have been substantiated further by experiments using chlorinated synthetic rubber from another source of supply.
Vol. 40, No. 3
The investigation was continued along a line intended to produce films displaying desirable physical properties while retaining satisfactory antifouling characteristics; formulations were prepared using both natural and synthetic chlorinated rubber in which one of the more flexible butyl methacrylate polymers was used in the role of plasticizer. Ability to withstand fouling attack along with compositional data is presented in Table VIII. All films were pigmented at 10% with mercurous chloride and 2670 hiding pigment. An opportunity is afforded to notice the flexibility properties contributed by chlorinated rubbers of varying viscosity. The data of Table VI11 show the value of chlorinated rubber as a matrix again, inasmuch as dilution with butyl methacrylate permits slight acceleration in the rate at which fouling accumulates. Hovxver, increased flexibility is obtained, which is rssential for a successful application to aircraft. The foregoing experiment was repeated using three synthetic chlorinated rubbers from two sources with the results shown in Table IX. The data in Tables VI11 and I X indicatr that the flexibility of the films under consideration is still somewhat short of that most desirable. Even better protection was obtained against fouling attack by increasing further the pigment volume, with the result that flexibilitv was so p3or a i t o cause elimination from further consideration. B reduction of pigment improved substantiallv the flexibility of these films, but iLntifouling properties n-ere reduced to such an extent that little or no worthwhile protection had been retained. DP SCUS STON
In recognition of the inadequacies of heavy plastic antifouling paints as used on ship hulls, considerable information was developed to aid in the design of coatings intended for application to the thin and easily corrodible hulls of flying boats. Cuprous oxide long has been recognized as one of the most efficient tovics used in orthodox antifouling paints. Experience in this laboratory demonstrated that mercurous chloride in similar and even reduced concentrations prohibits the attachment of fouling equally efficiently, when incorporated into appropriate matricrs, and thus a greater latitude is permitted in color design than is possible with copper compounds. It was shown that concentrations of mercurous chloride above 8q0 by volume in a dry film in which the total pigment volume exceeds 30cT,, affords excellent protection from fouling attack for periods up to 6 months bv films not exceeding 2 mils in thickness. Although copper resinate does not contribute directly as a toxic, it produces excellent dispersion, and packaged paints are free from caking and settling over extended periods. Chlorinated rubber serves as an outstanding matrix for thin antifouling films but must be modified considerably to produce acceptable flexibility characteristics. Two synthetic chlorinated rubbers were examined extensively and perform as well as, or better than, the natural product in producing successful antifouling coatings. ACK WOW LEDGMEYT
TABLE IX. FOULING RESISTANCE .
panel SO.
1
Binder Compn., Vol. 7 in Dry Film Butyl synthetic RCI acrylate 20 10-cp. SRCI, 80
2
3
10-cp. SRC1, 50 10-cp. SRCI, 20
Flexii,ility, In.0 Failed
1 9.5
50
Failed
9 . 5 9.5
80
6/10
Monthly Fouling Ratings 2 3 4 5 6 9.5 9 8.5 8.0 7.5
. 9.5 9
9
8.5
7.0
5.5
7
6.5
3j5
1.0
4
Q.5 9.5
9
8 . 5 8.0 8.5
5
9.5 9.5 9
8 . 5 6 . 5 7.5
66-cp. SRCI, 20 Failed 80 66-cp. SRC1, 50 Failed 50 80 l/a 6 66-cp. SRC1, 20 20 $/la 7 75-100-cp. SRCI, 8 0 b 50 5/10 8 75-100-cp. S R C I , 50 Q 75-100-cp. 80 a/ls SRCI, 20 10 Control 1.t. gray enamel a Smallest diameter t h a t film will pass. b Different source of supplv.
7
9.5
Q
9.5
9 . 5 9.5
6.5
4.0
0'
9.5
8.5
8.0
9.5 9.5
9
8.5
6.5
4.0
g.5
9
Q
8.0
5.5
2 5
0
0
0
0
0
0
The interest and support of James E. Sullivan and A. M. Malloy are gratefullv acknowledged. The cooperation of Charles M. Weiss, of the Woods Hole Oceanographic Institution, and A. C. Frue is appreciated for exposing and reading the panels for a number of the fouling tests at Miami Beach. LITERATURE CITED
Joint Army-Navy Specification for :Zinc Chromate Primer, AN-TT-P-656b (1944). Ketchurn, B. H., Ferry, J. D., and Burns, A. E., Jr., IND. RKG. CHEM.,38,931-6 (1946). Ketohum, B. H.. Ferry, J. D., Redfield, A. C., and Burns, A. E., Jr., Ibid., 37, 456-60 (1945). Navy Aeronautical Speaification, Paint, Antifouling for hircraft Hull Bottoms, 14-559-1 (1946). P a t t e r s o n , G. D., private communication (1941). Visscher, J. P., U. S. Bur. Fisheries, Bull. 43, 193-252 (1927). Young, G. H., et al., IND. ENG.C H E ~ I3. ,5 , 4 3 2 , 436 (1943). Ibid., 36, 341 (1944). Ibid., 36, 1130 (1944). Young, G. H., et nl., U.
S. Patents 2,390,408 and 2,398,069 (1946). RECEIVED May 2, 1947. Presented before the Division of Paint, Varnish, and Plastics Chemistry a t the 111th Meeting of the AMERIOAN-CHEMICAL SorIETY Atlantic City, N. .J.
