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INDUSTRIAL AND ENGINEERING CHEMISTRY
ratio with toxic concentration, an expected but conclusive finding. On the other hand, a general sensitivity to light has been confirmed. Panels were exposed in bright sunlight, and duplicates in the shade only a few feet away showed heavier fouling. The difference is not marked and certainly cannot influence choice of paint color. The consistency or hardness of the antifouling paint, independent of its permeability and exfoliating characteristics, may influence the type and extent of fouling. Figure 3 shows a stripped-off paint film which was initially soft and gummy and remained so during immersion. The photograph presents both sides of this stripped film; the embedding tendency of the barnacles, with consequent injury to the underlying surface by contact-corrosion effects, is conclusively demonstrated. I n general, we believe that the harder the exposed paint film can be, all other factors being equal, the better protection it will afford against fouling. ACKNOWLEDGMENT
It is a pleasure to record the cooperation and assistance of Peter Gray, associate professor of biology a t the University
Vol. 35, No. 4
of Pittsburgh, under whose direction the laboratory evaluations of primary toxicity were carried out. LITERATURE C I T E D
Baerenfaenger, C., meeting of Verein Deutscher Ingenieure. Kiel, 1937. Clapp, W. F., Am. h s s o c . Advancement Sci., Symposium on Corrosion, Gibson Island, Md., 1941. Oshima, S., J. SOC.Chem. Ind. Japan, 37,589 (1934); 38, 69, 170 (1935). Pratt, H.S.,“Manual of the Common Invertebrate Animals”, rev. ed.. Philadelphia, P. Blakiston’s Son & Co., 1935. U. S. Navy Dept., Bur. of Ships, “Docking Report Manual”, p. 6 (1942)
Wray, R. I., and Van Horst, A. R., IND.ENG.CHEM.,28, 1268 (1936). Young, G. H.,and Gray, Peter, U. S Patent 2,287,218 (June 23, 1942). ZoBell, C. E., Natl. Paint, Varnish Lacguer Assoc., Sci. Sect.. Circ. 588 (1939). ZoBell, C. E., Oficial Digest Federatzon Paint & Varnish Production Clubs, 17, 379-285. CONTRIBUTION from t h e Multiple Fellowship of Stoner-Mudge, Ino., at Mellon Institute.
Heavy Metal Compounds as Toxic Agents G. H. YOUNG AND W. IC. SCHNEIDER
HE previous paper described a procedure for the preliminary evaluation of toxic compounds designed for use in antifouling paints. It was demonstrated that the ions of a variety of heavy metals might be expected to have lethal action on Cypris larva and other embryonic fouling organisms. Accordingly, an extensive series of test panels was prepared for marine exposure a t Daytona Beach, Fla., involving controlled concentrations of representative heavy metal compounds in a suitable oleoresinous short-oil vehicle. Several commercial antifouling paints were included in the series for comparison purposes.
T
PREPARATION OF PANELS
The wood panels were 7 X 12 X l1j8inch seasoned poplar, primed with three brush coats of a 40-gallon phenolic spar varnish. The steel panels were prepared in duplicate, freshly sandblasted, and primed with two brush coats of two selected anticorrosive primers. A 25-gallon, 60 per cent tung oil-40 per cent linseed oil, phenolic varnish pigmented with zinc tetroxy chromate was one primer; an 8gallon, 50 per cent tung oil-50 per cent linseed oil, coumarone varnish pigmented with red lead was the other. The latter varnish was also selected to carry the toxic components because the permeability measurements had demonstrated its optimum moisture transniission characteristics. The experimental antifouling compositions evaluated are described in Table I ; a series of paints comprising two or more toxic agents was prepared from these primary formulations, and the combinations are listed in Table 11. Additional panels were painted with four commercial antifouling paints and with two paints made up according t o a Navy formula (1). I n one case red cuprous oxide was used; in the other, yellow.
EXPOSURE OF M E T A L COMPOUNDS
The panels were placed on test in December, 1941, and examined a t monthly intervals. At the end of one month the following paints still rated 9 or better; a t this stage the controls (containing no toxic) rated 7-8: AF-1,2, 7, 9, 11, 13, 14, 16, 17; proprietary paints 1, 2, and 3; Navy formula 16 with red and with yellow cuprous oxides. At the end of 2-month immersion, the following paints rated 8 or better, the controls rating 5-6: AF-2, 9, 11, 13, 16; proprietary paints 1and 3; both Navy formula 16 paints. At the end of 4.5 months the following paints rated 8 or better, the controls rating 2-3: AF-2 and 11; proprietary paints 1 and 3. The relative appearance of these paints is shown in Figure 1. .1
PAINTS CONTAINING SINGLE TOXICS TABLE I. EXPERIMENTAL [Vehicle, 50-50 tung-linseed, 8-gallon coumarone varnish (65 % ’ solids) ; pigment-vehicle ratio 2/11 Pigment Composition Toxic component % Inert % Code No. AF-1 AF-2 AF-3 AB-4 AF-5 AF-0
Yellow mercuric oxide Copper powder Copper arsenite Red cuprous oxide Zinc oxide Sublimed blue lead
60 60 GO 60 60 60
Barytes Barytes Barytes Barytes Barytes Barytes
40 40 40 40 40 40
At 6.5-month exposure only AF-2 and proprietary paints 1 and 3 were still actively antifouling, rating 8 or better. Figure 2 illustrates these paints, together with certain of the others, now failing. After 9 months the two good proprietaries and AF-2 still rated 8 or better; all the remaining panels were rated at 3 or worse and hence were removed.
April, 1943
INDUSTRIAL AND ENGINEERING CHEMISTRY
It is significant that, with the unique exception of proprietary paint 3, only paints carrying a high concentration of metallic copper were really effective after the first several months’ exposure. (The toxic agent in proprietary paint 3 is organic in nature.) Cuprous oxide (either red or yellow) is intermediate in antifouling effect, and the remaining compounds were relatively ineffective under the test conditions.
A possible exception is mercuric oxide, which appears to have some specificity against algae and other water-line growths, but is definitely inferior even to cuprous oxide against calcareous shell-depositing organisms. EFFECTOFCOPPERCONTENT
A study of the pigment compositions of the experimental paints (AF-1 to 16) reveals that, because the pigmentbinder ratio was constant, the independent variable can be considered as (a) copper content and (b) copper oxide content, I n effect, the remaining “toxic” agents were inert extenders. Rearranging the formulas in the order of decreasing toxic content, the following table results: Code No.
-Percentage Copper
of PigmentCopper oxide
Inert
437
With one exception (AF-7), which failed prematurely, the tabulation almost exactly parallels the order in which the paints ceased to protect against fouling, AF-2 being best and AF-15 poorest. To verify this relation to active copper content a supplementary panel series was prepared in duplicate in which the vehicle was a 6-gallon tung oil-coumarone type varnish,
TABLE 11. EXPERIMENTAL PAINTS CONTAININQ S ~ V E R A L TOXICS Code No. AF-7 AF-S AF-9 AF-10 AF-11 AF-12 AF-13 AF-14 AF-15 AF-16 AF-17
Paint Compn. Compriaing Equal Parts o AF-1. AF-2 AF-1; AF-3 AF-2, AF-3 AF-1, AF-4 AF-2, AF-4 AF-3, AF-4 AF-1, AF-2, AF-3 AF-1, AF-2 AF-4 AF-1, AF-3: AF-4 AF-1, AF-2 AF-3 AF-4 AF-1. AF-2: AF-3: AF-4, AF-6, AF-6
containing only leafed copper powder a t loadings of 1, 3, 6, 9, and 12 pounds per gallon. These antifouling paints were applied to freshly sandblasted panels primed with two brush coats of quick-drying red lead (alkyd type vehicle). I n one set the copper paint was applied by spraying, in the other by brushing. Three to four months of exposure a t Daytona Beach were sufficient t o demonstrate that antifouling efficiency was almost directly a function of copper content, and that ti loading of a t least 6 pounds per gallon of copper is needed t o
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INDUSTRIAL AND ENGINEERING CHEMISTRY
produce a highly effective antifouling paint. This result confirms the previous findings and suggests that many copper paints described in the past may have carried insufficient toxic agent for maximum performance ( 2 ) .
Figure 2.
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appeared to have some beneficial action against marine algae; their effectiveness against shell-forming organisms, however, was far below that of copper and copper oxide. This effect is undoubtedly attributable to their low ioniza-
Wood Panels Exposed 6.5 Months
Panel 1 is control (rating 0); panel 3 is proprietary paint 2, which wan already fouling a t the 2-month inspection. Panels 5 and 7 are Navy formula 16 using red and yellow copper oxide i n that order.
Comparisons of the nature and extent of fouling on the spray-coated panels with those painted by brushing indicated no significant differences. The advantage, if any, favored spray application, as would be expected. OTHER COPPER COMPOUlVDS
I n a third exposure series the following additional copper compounds were evaluated in test formulations comprising the toxic ingredient in two different vehicles a t a constant pigment-vehicle ratio of 1 to 1: copper arsenite, oxychloride, oleate, linoleate, naphthenate, pentachlorophenate, tetrachlorophenate. Exposure a t Daytona Beach demonstrated than none of these compounds is effectively toxic, as employed in antifouling paints. The organic acid salts and the phenates
Panels 4 and 2 are proprietary paints 3 and 1, respectively. Panel 10 is paint AF-2; panel 8 is another formulation which failed early in the test.
tion tendency; only compounds capable of releasing copper ion seem to have utility as antifouling agents. ACKNOWLEDGMENT
We are grateful for the cooperative assistance of S. B. Tuwiner, of the Phelps Dodge Corporation, who supplied certain of the materials employed in this investigation. LITERATURE CITED
(1) Instructions for Painting and Cementing Vessels of the U. S. Navy, Appendix 6 , Formula 16 (April, 1939). ( 2 ) Tuwiner, S B., and Dodge, D. A,, IND.EXG.CHEM.,33, 1154
(1941).
CONTRIBUTION of t h e Multiple Fellowship of Stoner-Mudge. Inc., a t Mellon Institute.
