PT-402 Acid Etching Primer, when properly reduced with PT-1045 Reducer, meets and exceeds MIL-C-8514C. PT-402 is a polyvinyl butyral zinc chromate formulation that may be used to prime all plain or plated metallic surfaces.  Priming surfaces with PT-402 Acid Etching Primer prior to priming with epoxy primer MIL-PRF-23377 or by itself will ensure maximum adhesion and protection of all bake or air-dry finish coats (including lacquer finish coats).  The finely ground emulsions of zinc chromate pigments, resins and phosphoric acid hardeners are virtually non-settling.  Once applied, the Acid Etching Primer requires no sanding and has a pot life of 8 hours.  Extreme humidity can affect the bonding of the coating.