exposed metal surfaces reduces the current capacity required for cathodic 

 protection, current requirements will increase as deterioration of the 

 paint progresses. (Also, some generic types of paints (e.g., coal tar 

 epoxy) are better insulators than others (e.g., vinyl) and will require 

 less current capacity.) Second, copper metal or cuprous-oxide-based 

 antifouling paints can accelerate corrosion of steel and induce heavy- 

 metal deposition attack of aluminum surfaces. While an organotin-type 

 antifoulant would be , preferable to reduce the possibility of accelerated 

 attack, it may pose some ecological concern. 



ANTICORROSION COATINGS 



Anticorrosion paints generally are classified as multicomponent and 

 single package types. The former contain at least two components which 

 react chemically and irreversibly to form a thermosetting film. The 

 latter form films initially by solvent evaporation and subsequently cure to 

 achieve greater film integrity through chemical and/or physical changes, 

 e.g., oxidation and polymerization. The multicomponent coatings have been 

 found to be the most protective for steel and other corrodible metals. 



Two-Component Epoxy Paints 



Amino-group-reacted epoxies have been established as the best anti- 

 corrosion paints for marine use. These paints, in the wet state, will dis- 

 place residual loose dirt, oil, and water which are sometimes found on 

 metal surfaces under industrial conditions. -^^ The applied polyamide epoxy 

 paints adhere and perform much better than other paints which are less 

 tolerant of moisture or other surface contaminants. 



For cathodically protected surfaces, a highly alkali-resistant epoxy, 



such as coal-tar-reacted epoxy catalyzed with a low molecular weight amine, 



33 

 is more resistant to the alkaline conditions at the cathode. Therefore, 



amine-reacted coal tar epoxies are recommended in lieu of epoxies reacted 



with amide for high potential (1.1 V) cathodically protected surfaces. 



Single-Component Paints 



The single-component paints proven for marine construction are those 

 based on vinyl and chlorinated rubber. ^'^ Occasionally, proprietary single- 



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