No-rinse pre-paint coating composition and method

An acid, aqueous composition containing by weight dissolved in its water:

• chromic acid and chromium phosphate as derived from phosphoric acid resulting from the oxidation of hypophosphorous acid in reacting with the chromic acid which latter is present in a stoichiometrically equivalent amount from about one percent to about one hundred percent over that needed to oxidize hypophosphorous acid to phosphoric acid,
• from none to about 0.01% of a non-foaming to low foaming wetting agent inert to iron, steel, galvanized iron or steel, zinc, aluminum, copper and brass, to the acidity of the composition and to oxidation;
• from none to about seven percent of particulate silica of from about 4 to about 60 millimicrons particle size, and which composition is selected from:
• (i) a concentrate with its aforesaid dispersed total solids content being from about two percent to an amount below that at which the composition will gel under its storage conditions;
• and
• (ii) a metal treating bath having as its total dispersed solids content the amount thereof provided by from about two percent to about fifteen percent by volume of the aforesaid concentrate.