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be a satisfactory matrix in this re- spect. It would appear that the toxics must be available in such a manner as to slowly leach out of the film, create a minute zone of con- taminated water adjacent to the film, and thus discourage the attachment of fouling growths. The material cost of the coal-tar rosin antifouling paint is approxi- mately $2.00 per gallon. The de- termination on the part of the bur- eau of construction and repair that - a mixture of cuprous oxide and mer- curic oxide is more effective than either material alone, lead recently to a change in the manufacturing formula for antifouling paint, for- mula 15A whieh is now as follows for 100 gallons: ; Ingredient Quantity PI COWO PAIS: oi) es cocresetscectassecccccsones 70 Gum shellac, Ibs... 82 OCCA SUM, MOB Loess cas ccc cone vpccneeviant 95. PING Olly BSAISS eco. oo ccv ck tose bactavecees 12% Zine oxide (dry), IbS..........0.. 165 Indian’ red’ (dry); TDS. 2.5...82c.08. 165 Mercuric oxide, Ibs. ..............00. 40 Cuprous oxide. IDS .6 seks cans 120 Weight per gallon, Ibs. ............ 10% Spreading rate per gal., sq. ft. 330 At the present time there are two main classes of antifouling paints in use. These are: (a) Varnish paint using a gum of some kind as a binder and depending on the evapo- ration of a solvent for drying and described above; (b) Hot plastic paint of a waxy consistency contain- ing no volatile thinner, applied in a melted. condition and hardening on cooling. As a result of considerable experiment, development and testing, the chemical warfare service of the war department found that paints of the hot plastic type will prevent foul- ing and corrosion for longer periods although they are more expensive to manufacture and apply than varnish paints. Plastic Anti-Fouling Paint | Development of the hot plastic type of antifouling paint was undertaken by the chemical warfare service in 1922. A successful commercial prod- uct was analyzed and a paint known as B-2 was developed. This paint was of the following composition: Weight Material % LS Woe ho be Peer ote PARP CEM eRe RPE RE AY OTE RE EEEE 30 TES tale EY] ik aes eae a ee ae eae cores 11 Lead rosinate precipitaed ........ 9.1 PTOBG> DALPAVUAILE! s ccchcaeovcteessekscacssese 18 IMICTENTIC! TOSINALC. csicssicct ssc caccccease 12 SEATED Risa bse NO ae SI eo le Be Re 2.7 PP AVIS (BV OO So iicccs2s scpon coed hese cusaeee vases 7S PPURDEMUINC 4.26 5 oa hics ck hoskaisdccscs 3.5 The process of manufacture of this hot plastic paint was as follows: The rosin and lead soaps were melted and the mercury soap added. This in turn was melted and thor- oughly mixed and the arsenic and Paris green added and stirred in. The solution was thinned with turpentine when partially cool. (Later on, in the manufacture of this paint, pine oil 22 was substituted for the turpentine on account. of the higher boiling point of the pine oil which would cut evapora- tion losses during the heating). This paint was then subjected to fouling test, the paint being applied to steel plates, submerged in salt water and inspected at regular intervals. After being submerged for six months, the plates were inspected and showed practically no fouling. In an effort to establish the com- parative value of various toxic in- gredients in this paint, another series of paints was made in which the toxics were used singly and in combinations with inert materials substituted for the omitted constituents. As a result of tests of this paint, it was found that arsenic trioxide had no toxic value; that Paris green was effective as a toxic, that mercuric rosinate had some value as a toxic although not as much as Paris green. Following the tests of these paints applied to plates and submerged for ‘periods, the paint was actually ap- plied on naval vessels. Accordingly, a quantity of this B-2 antifouling paint and an anticorrosive paint was prepared and applied to the U. S. S. Kine. The vessel was undocked in May and docked in April for examina- tion. It was discovered that although this paint had shown up well on plate tests, it did not stand up in actual service. Although not excessive, there was considerable fouling and the paint was missing in a few spots on the flat of the bottom of the vessel. More Experiments Undertaken As a result of: these findings, fur- ther experiments were undertaken. Based on the formula of the B-2 paint, a number of paints were made and tested. One of these, referred to as B-3, was selected for service tests on the bottoms of vessels. The composi- tion of this paint is given in the fol- lowing table: Material Parts ROSIN OWA oie toes 41.7 Basic copper acetate ..........00. 9.75 Raw: linseed: Ole ee ea 10.5 Stearic acid (double pressed) 10.5 1 By Wa) os Wy gh ests mamma eee eer a One ee ies 8 Arsenic trioxide, amorphous.... 8 Acetic acid (50 per cent) ........ 2 Mercuric acetate (60 per cent WSO ee ere wi In making this paint, the rosin is melted in a small amount of water after which the copper acetate is added until copper rosinate is formed. The other materials tabulated are then added in the proportion given in the table. The material is then heated un- til green and of uniform consistency after which it is thinned with five parts of pine oil. As a result of a study of all data obtained on the hot plastic type of paint, the chemical warfare service drew the following tentative conclu- sions: (1) That the principal toxics are mercury and copper with lead and MARINE REvirw—August, 1932 arsenic as secondary toxics, probably ~ acting as boosters to the other two; (2) That the physical condition of the film is the principal factor influencing the efficiency of the paint so long as the toxics are present in sufficient quantity; (3) That an equilibrium is reached between the mercury and lead on the one hand, and the fatty acids (including rosin) on the other. This equilibrium is largely independ- ent of the combinations in which the constituents are added, although the time required will vary between large limits depending on the original com- binations and the amount of cooking given in making up the paint; (4) That, given the proper amount of cop- per, arsenic, and acetate radical, these constituents combine to form copper acetoarsenite, since this compound “may be recovered as such from the finished paint; (5) That the equilib- rium point, as well as the amount of copperarsenite formed, will be deter- mined by the relative amounts of the constituents present, excesses remain- ing as free rosin, free acid, As’ O°, etc.; (6) That the paint may be made much more cheaply by combining the raw materials in the kettle than by mak- ing the various ingredients separately. Quality and Cost Considered It is worthwhile to point out that in the case of vessels which are dry- docked periodically for purposes other than cleaning and repainting, a more inexpensive paint might well be sub- stituted for the more expensive types. However, it remains for the operator to determine for himself just which method of procedure will reduce the upkeep cost of his vessel to the great- est extent. All items of upkeep expense which are directly attributable to fouling should be itemized. To the sum of these various items should be added the cost of drydocking, cleaning and repainting. Also the expense result- ing from reduced speed of vessels, greater fuel consumption, wear and tear on machinery, and the reduced earnings due to necessary layup for this purpose out of each year. Com- pared with the sum of. these items, the cost of the expensive but also more efficient antifouling paint with its longer period of effectiveness, should be considered. By some such method as this, the operator should determine which will be the least costly in the long run— the more efficient paint with its longer protective life or the less expensive covering which necessitates semian- nual scraping and repainting of bot- toms. Hardie-Tynes Mfg. Co., Birmingham, has been awarded contract for pump shell and liners for the dredge BLACcK- WATER for the United States engineer at Montgomery, Ala., here at $3429 and crankshaft section for the engi- neer at Savannah at $4595.