on the formulation.* On the average, the majority of organotin paints 

 tested were effective for 12 to 18 months in temperate waters. Copper- 

 and organotin-based marine coatings based on a variety of organic film- 

 forming polymers are available. However, the coatings which give the best 

 overall performance are formulated with vinyl-base polymers, chlorinated 

 rubber, or epoxy resins. Organotin antifouling formulations show the 

 greatest promise as antifoulants effective against a broad spectrum of 

 marine organisms. -^^-'-'-'-^■^ These are generally based on tributyltin oxide, 

 tributyltin fluoride, or triphenyltin fluoride (TPhTF) . Copper and organo- 

 tin antifouling coatings are commercially available. 



The degradation of organotins in the seawater environment is not well 



defined. Studies by M&T Chemical Company indicate the mechanism is 



1 03 

 hydrolysis of the organotins in seawater. Presently, studies are being 



performed by Dr. M. Good and Dr. L. M. Frenzel of the University of New 

 Orleans to investigate the release mechanisms of organotin antifouling 

 materials. In addition. Dr. F. Brinckman of the National Bureau of 

 Standards has developed an analytical method which uses a combination of 

 atomic absorption spectroscopy and liquid chromatography for the determina- 

 tion of organotins in very low concentrations. There is evidence that the 



103 

 organotins may decompose in seawater to inorganic tin, but further 



studies are needed to verify this for tributyltin-containing compounds, 

 especially those employed as antifoulants. 



Most reinforced plastic structures are glass-reinforced. Other rein- 

 forcements for plastics include fibers of graphite, boron or metal, and 



104 

 natural and synthetic organics. Many data exist for marine application 



of glass-reinforced plastics, specifically polyesters and epoxies, in small 

 boat hulls, various ship appendages, sonar bow domes, and piping systems. 

 Surface preparation of an FRP pipe prior to coating would follow practice 

 that is standard for the given material and coating. For example, glass- 

 reinforced plastic structures normally are sandblasted or sanded, rinsed 

 with freshwater or solvent, and then dried thoroughly before painting. In 

 general, a primer system is applied prior to the antifouling coating. Both 

 are generally sprayed on. 



''Montemarano, J. A., DTNSRDC (Code 2865), personal communication. 



42 



