Summary of Current State-of-the-Art Coatings 



Although it is technically feasible to provide antifouling protection 

 by using coatings on the OTEC cold water pipe, only a 2- to 3-yr service 

 life can be expected from the presently available commercial organotin- 

 and copper-based coatings. This service life is insufficient for the 

 planned use of the cold water pipe. 



Antifouling Techniques Under Development 



Antifouling techniques under development which would be applicable 

 for the FRP cold water pipe are: (1) long-lived antifouling coatings, 

 (2) inherently antifouling FRP, and (3) antifouling liners. 



Coatings . The use of existing antifouling coatings for the cold water pipe 

 has been discounted due to short service life. However, Navy and industry 

 are developing coatings with a longer antifouling service life. 



Developmental coatings, expected to be commerically available in the 

 early 1980' s, are based on organotin polymers (resins) in which the anti- 

 foulant is chemically attached. Ideally, release of the antifoulant 

 to the marine environment is controlled. Expected service life is 

 5 yr. Cost of coatings based on these resins is expected to be compar- 

 able to heavily loaded copper-based vinyl coatings. However, additional 

 expense may be incurred in applying and removing organotin coatings due to 

 their toxicity. The Research Organization of Ship's Compositions Manufac- 

 turers Ltd. (ROSCM) recommends that, during the application of organotin 

 paints, a respirator be used with the filter in addition to the protective 

 equipment recoimnended for use when applying copper-based paints. The 

 United States Navy has established guidelines for the safe application of 

 organotin paints. Presently, organotin polymers are also being investigated 

 by the Navy so that guidelines may be established for their safe handling. 



Experimental antifouling coatings are not limited to organotin-polymer- 

 based formulations. Extensive work has been performed in developing anti- 

 foulants based on organic compounds, other organometallic compounds, and 

 organometallic polymers. Formulations based on other organic toxics 

 include such compounds as diiodomethyl sulfone, 1 ,2 , 3-trichloro-4 , 

 6-dinitrobenzene, pentacyclic amides and 2-(N,N-dimethylthiocargamyolthio)- 



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