Progress on Antifouling Coatings

A 21 day salt test of 2 inches by 4 inches mild steel sample coated with ten of these alloys by dipping gave the following results: In all cases corrosion started at the edges, and wherever blisters occurred in the coating: thereafter working underneath the protective coating. The pure selenium coated plate was between 30 and 40 percent corroded in spots appearing on both sides of the plate. The corrosion had not, as on some of the other plates, eaten into the plate. Of the remaining samples, several showed bad flaking and corrosion on one side with hardly any on the other. Wherever the coating remained, it was tough and in good condition. The selenium groups of metals appear to have value as antifouling agents. The anticorrosive properties of the selenium groups must be greatly improved before the antifouling properties can be properly evaluated. It is recommended that work with the selenium group be continued along the following lines: (a) Improve anticorrosive properties by developing an anti- corrosive coating to be applied to be steel before the antifouling coating is applied. Test anticorrosive properties by salt spray test. (b) When anticorrosive properties have been sufficiently developed, prepare standard antifouling test panels for further test at Norfolk.