ABSTRACT
Wash primers are a special group of corrosioninhibitive coatings designed for use on clean metal surfaces. They are also known as “washcoat primers,” “metal conditioners,” and “etch primers.”
The most widely utilized primers consist of a two-part system that is prepared at the point of use by simple mixing of specified proportions. The base grind portion contains a corrosion-inhibiting pigment, basic zinc chromate (also known as zinc tetroxy chromate), and a small amount of talc extender ground in an alcohol solution of polyvinyl butyral resin. The reducer portion consists of phosphoric acid, alcohol, and water. When these are mixed, a slow chemical reaction ensues, resulting in partial reduction of the chromate pigment. The life of the mixed primer is usually 8 to 12 h. Singlepackage primers are now in use.
