Abstract: A nickel and/or cobalt deposition process which can be run at a nearly neutral pH and which rapidly deposits nickel and/or cobalt in quantities large enough to improve the paint adhesion and post coating corrosion resistance, and which has a good solution stability, is achieved by treating zinc coated sheet steel with an aqueous solution that has a pH between 5 and 10 inclusive and comprises (A) a total of at least 0.01 g/L of metal ions selected from the group consisting of Ni.sup.2+ and Co.sup.2+ ions and (B) a sufficient amount to fully complex the metal ions recited in part (A) of complexing agents selected from the group consisting of ammonia and organic compounds having at least one amino group in the neutral region.

Abstract: A deeply and uniformly black coating with excellent adhesion and corrosion resistance can be formed on a wide variety of substrates by coating them with an aqueous composition containing an amount of chromium trioxide to give a stoichiometric equivalent of from about 30 to about 150 g/L of Cr.sup.6+ ; from about 20 to about 100 g/L of Cr.sup.3+ ; a component to provide a stoichiometrically equivalent amount of from about 0.5 to about 50 g/L of total Fe, Co, and Ni ions; from about 5 to about 200 g/L of dispersed or dissolved organic film forming polymer; and the balance water, with a weight ratio of Cr.sup..alpha.6 to Cr+3 between about 5 and about 1; and heating the coated substrate to a temperature between 100.degree. and 350.degree. C. for 5 seconds to 10 minutes.