Trivalent chromium passivate solution and process for yellow passivate film

Abstract

An aqueous acidic solution and process for treating receptive metal surfaces, particularly zinc and zinc alloy surfaces, to impart a light-yellow iridescent passivate film thereon imparting improved corrosion resistance thereto. The aqueous solution contains effective amounts of chromium ions substantially all of which are in the trivalent state, hydrogen ions to provide a pH of about 1.2 to about 2.5, an oxidizing agent and cerium ions present in an amount effective to activate the bath and promote the formation of a light-yellow passivate film on the metal substrate. The treating solution may optionally further contain halide ions, a wetting agent and additional metal ions selected from the group consisting of iron, cobalt, nickel, molybdenum, manganese, lanthanum, lanthanide mixtures of rare earth oxides as well as mixtures thereof.

Dependencies are inferred from the claim text.