Abstract: A chromate treatment of metal coated steel sheets comprising subjecting the sheets to a cathodic electrolytic treatment to form a chromate film thereon and subjecting the sheet to an anodic electrolytic treatment to form an anodic electrolytic film on the chromate film and to convert the chromate film. The treatment is applicable to various metal coated steel sheets, such as those coated with zinc, zinc alloy, aluminum, aluminum alloy, lead and lead alloy, and is effective to improve the corrosion resistance of the sheets, the quality of paint coating applied on the sheets and the adaptability of the sheets to a cation electro-deposition paint coating.

Abstract: A method of treating a zinc plated steel surface provides improved corrosion resistance and painting properties. The surface is rendered cathodic in the presence of an aqueous treatment liquor containing 5-70 g/l of hexavalent chromium, 0.01 to 5 g/l of trivalent chromium, 5-100 g/l of silica and/or silicate and 0.05-10 g/l of nitrate in which the ratio of Cr.sup.3+ /Cr.sup.6+ is within the range 1/50-1/3.

Abstract: A coating process for aluminum-zinc alloy plated sheet steel provides an article having a surface of improved formability and enhanced corrosion resistance; appearance and paintability. The coating is applied in aqueous form at a prescribed pH value and dried. The aqueous coating contains a water dispersible or water soluble resin and hexavalent chromium in desired proportions.

Abstract: Disclosed is a composition and method for its use to improve the corrosion resistance of conversion-coated metal surfaces. The composition contains a myo-inositol phosphate ester or soluble salt thereof and is applied as a rinse of the conversion coating.