The Effect of Drying Time on the Performance of Antifouling Compositions

Abstract

In order to study the effect of drying time on the performance of antifouling compositions, two proprietary ship's bottom paint systems, commercially obtainable in this country, were tested on a raft after being allowed to dry for periods of 3, 12 and 24 hours and 10, 30, 45,60,75,snf 90 days respectively. Both systems used, one being of an oil-base type and the other of a vinyl resin type, consist of wash primer, anticorrosive and antifouling compositions. Shot-blasted mild steel panels (300^<mm>×300^<mm>×4.5^<mm> in size) were primed with one coat of wash primer, and after about 4 hour drying, it was followed by 3 or 4 coats of anticorrosives at intervals of approximately 24 hours between coats and finally by one or two coats of anitifouling compositions except for 100^<mm> wide patches (to be used for non-toxic controls) at the same intervals on both sides. Most of these panels, however, being seriously damaged by a typhoon in the course of the test, this work could not be carried out with a successful finish. The hope of the authors is that this paper will be considered as an interim report about the subject to date and form a point of departure for further investigations. It is suggested that antifouling compostitions in general may possibly be subject to atmospheric exposure for a fairly longer time, the extent of which depends on their types, formulations and others, without any detrimental effect on the performance than as recommended by their manufacturers. In this connection, it is not certain whether such failures of antifouling paint films as chalking, checking and cracking resulted from a long time weathering can be responsible for increasing their leaching rates, namely resistance to fouling (with subsequent shorter life and premature decay of coatings as well). This is, in the authors' opinion, one of the most important problems demanding urgent researches. In this paper the effect of film thickness of antifouling composititions on the performance is considered and some of the precausions to be taken when carring out these kinds of experiments are also given. In addition, conventional testing procedures and methods are briefly discussed from technical standpoint.