Peroxide free of chromium (iii) - passivation layers solution of the bearings, and a method of passivating of substrates with this solution

摘要

An aqueous acidic peroxide-free solution for treating receptive metal surfaces to impart a chromium passivate film thereon contains trivalent chromium ions, hydrogen ions to provide a pH of 1.2 to 2.5, nitrate ions as the essential oxidizing agent to activate the hydrated trivalent chromium to form a chromate film on the substrate, and iron, cobalt, nickel, molybdenum, manganese, aluminium, lanthanum and/or cerium ions to activate the formation of the chromate passivate film. The use of peroxide as an oxidizing agent is avoided, as are its accompanying problems such as high consumption of oxidizing agent and rapid loss. The aqueous acidic solution can also contain sulphate ions, halide ions, organic carboxylic acid, a silicate compound, and a wetting agent.