o 



o 



o 



-EPOXY 



PHENOLIC 



o 



o 



o 



o 



o 



■EPOXY 



Figure 94. Cross-linked epoxy phenolic. 



The disadvantages of epoxy phenolics, as compared to epoxies are: 



(a) Increased brittleness of coating; 



(b) lack of toughness and thus more subject to damage upon 

 impact (cracking, shattering, delamination) ; 



(c) requirement for heat in curing (not true with all epoxy 

 phenolics) ; 



(d) lack of availability in high build formulations; and 



(e) slightly more difficult to repair and topcoat due to 

 adhesion problems {see paragraph (8)}. 



(10) Phenolics . Phenolic coatings include baking phenolics of the 

 alcohol soluble type and phenolics of the oil soluble type in combination 

 with drying oils. The baking phenolics have excellent resistance to 

 corrosive chemicals, acids and caustics. They require baking for curing 

 (cross linking). The baking phenolics form tightly cross-linked coating 

 films with exceptionally high corrosion resistance, which is higher than the 

 epoxy-phenolics. Because of their tight cross linking they are brittle and 

 subject to damage and delamination if subject to impact. These materials 

 are used as linings for tanks, barges, and piping. 



The phenolic coatings designed for atmospheric service are made from 

 phenolic resin combinations and drying oils. These, at one time, were 

 considered the best air-drying coatings for water resistance and weak 

 chemical resistance; they were used extensively as marine maintenance 

 coatings. They are still considered superior, to most alkyd coatings in 



330 



