such as those containing mercury, trialkyllead, arsenic, and other chemi- 

 cals, have been made and used.°2 However, today's environmental protection 

 restrictions discourage common usage; they could not be justified for use 

 on an OTEC plant. 



Antifouling Sheet Material 



The first practical antifouling sheet material was manufactured by 

 the B. F. Goodrich Company and called "No-Foul." The material is an 80-mil- 

 thick black neoprene rubber impregnated with tributyltin oxide (TBTO) . ' 

 Due to the large amount of antifoulant in the No-Foul sheet, its service 



Q C 



life is much longer than 4 mils of typical antifouling paint. 



Impregnants 



Antifoulants have been used to impregnate the outer surfaces of con- 

 crete and wooden pilings. There is no practical way to restore the anti- 

 foulant when it is exhausted. This limiting toxic content also occurs in 

 paints or sheet-type coatings. Ecological concerns would depend upon the 

 nature of the impregnant used. 



Toxic Metal Sheathing 



Copper metal and its alloys have been used for fouling prevention in 

 spite of their limited effectiveness. Some drawbacks for its use are: 

 (1) the sheets are difficult to form and attach on highly curved surfaces 

 and (2) galvanic corrosion problems occur when the sheets are not isolated 

 from other metals. Recent work employing plasma spray techniques to apply 

 copper metal and alloy powders to nonmetallic substrates has eliminated 

 forming and attachment problems; however, continued effort is required to 

 assess the long-term performance of this new technique. Environmental 

 considerations would be minimal with this approach. 



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