DTNSRDC has been working on the development of gel coats based on organotin 

 epoxy and polyester formulations. Their manufacture is technically 

 feasible. 



Antif puling Liners or Sleeves . Protective plastic linings for metal pipe 



.^ ,.,,,.,.,, 111,113,114 , . . 



often are used m the chemical industry. Linings can vary m 



114 

 thickness, application method, and composition. They may consist of 



resin, such as an epoxy, or of a polyvinyl chloride pressure-sensitive 



self-adhesive tape; polyethylene sleeving, or glass-reinforced laminated 



114 

 tape. Linings can also incorporate a bactericide if such protection is 



needed in the specific pipe application. Adaptation of this concept may 

 provide a simple replenishment method of antifouling protection for the 

 OTEC cold water pipe. Liners or sleeves fabricated from a thermoset 

 organotin polymer (polyester or epoxy) of a glass-reinforced thermoset 

 organotin polymer could be positioned at intervals in each pipe section 

 and replaced at given overhaul periods. The applicability of this con- 

 cept would need further development in order to estimate cost and availa- 

 bility, although the resins basic to this development are still demonstrat- 

 ing antifouling effectiveness after 2 yr of exposure in both temperate and 

 tropical waters. 



Summary 



Methods for protecting FRP cold water pipe and warm water intake 

 screens have been examined. Commercially available antifouling coatings 

 cannot be used because of their relatively short service life. Develop- 

 mental coatings which may be available in the early 1980 's will be able to 

 provide longer-term antifouling protection (5 yr) . This may be extended by 

 periodic mechanical cleaning and touch-up with antifouling coatings which 

 can be applied underwater. Inherently antifouling glass- (fiber-) 

 reinforced plastics might provide long-term (10- to 15-yr) antifouling pro- 

 tection for both the cold water and warm water intake screens. Successful 

 completion of a Navy research program would lead to the limited availability 

 of these materials in the early 1980 's and, therefore, availability for use 

 in a developmental OTEC power plant. Cost could be reduced by utilizing a 



47 



