Since the 1990s, two types of epoxy coatings have been commonly specified and used for iron valves in the waterworks industry: fusion-bonded epoxy and liquid epoxy. Both coatings are based on thermo-set epoxy systems with similar corrosion resistance and are described in the American Water Works Association’s Standard AWWA C550, “Protective Interior Coatings for Valves and Hydrants.”
Fusion-bonded epoxy is applied to preheated components in powder form in an electrostatic or fluidized bed process followed by thermal curing. Liquid epoxy is a two-component mixed material that is applied by spray, brush or other methods and chemically cures after application. The purpose of this article is to explain the typical requirements that apply to these coatings and compare some of their properties.