component paints are found to vary in performance from batch to batch. 

 Consequently, they should be comparison-tested with recommended Government 

 specification coatings before they are considered for use. Some of these 

 Government specification coatings will be identified in the latter part 

 of this section. 



Zinc-Rich Primers 



In new construction, such as an OTEC power plant, preconstruction 



35-37 

 primers are generally used on all steel members before assembly. 



These primers are thin, but adequately protect steel plate. When the steel 



structure is completed, the primer, generally a zinc-dust coating, usually 



is overcoated with another zinc-rich primer coat followed by an epoxy 



anticorrosion paint. Therefore, the final paint system becomes a zinc 



primer overcoated with an epoxy coating to form a combination system. 



Often, when the zinc coating is damaged in construction, it is touched 



up with a fresh zinc coating. Typically, the best performing zinc-rich 



paints utilize the inorganic silicates. -^""^^ 



Anticorrosion Coatings Systems for Steel and Titanium 



Three Government specification paint systems are recommended for the 

 general protection of steel from corrosion attack in the seawater and OTEC 

 power plant environment. These are coal tar epoxy, polyamide epoxy, and 

 the zinc-rich primer in conjunction with an epoxy. These materials are 

 listed in Table 4 and are available from commercial sources.'^-'- There is 

 also a compositional specification which covers a Navy-formulated polyamide 

 epoxy paint system. ^2 while titanium does not require anticorrosion 

 coatings, epoxy paints may be used as undercoats for subsequent antifouling 

 paints. 



Anticorrosion Coatings for Aluminum 



Aluminum is more reactive than steel. It requires more chemical 

 treatment than steel for resisting corrosion. ' To obtain a durable 

 coating on aluminum, the primer must contain passivators such as chromates. 

 There are two paint systems recommended for aluminum: one a polyamide epoxy, 

 and the other a vinyl primer system. These are listed in Table 5. 



19 



