CHROMATE TREATED ZINC BASE PLATED STEEL SHEET HAVING EXCELLENT BLACK DENATURATION RESISTANCE, CORROSION RESISTANCE, COATING MATERIAL ADHESION PROPERTY AND LUBRICITY AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To impart excellent white rust resistance, black denaturation resistance and coating material adhesion property by treating steel sheet surfaces by using an aq. resin-contg. chromate treating liquid contg. inorg. components of specific compsns. and resin emulsion components and specifying a pH value and Cr coating weight. SOLUTION: The inorg. components are of 1/10-3/10 in the weight ratio of tervalant Cr ions to the total of hexavalent and tervalent Cr ions and are of 1.0-3.0, 0.05-0.5, 0.05-0.5 respectively in the ratios of the respective ions of nitric acid, phosphoric acid and Co to the total Cr ions. The resin emulsion components are the resin emulsion of 10/100-20/100 in the weight ratio of the solid contents of an aq. resin emulsion surfactant of an acrylic copolymer subjected to emulsification polymn. in the presence of a nonionic reaction type surfactant having a C=C bond in a hydrophobic group and having a polyethylene oxide group as a hydrophilic group and an acrylic copolymer. The pH value of the chromate treating liquid is =3 and the Cr coating weight 5-50 mg/m3 .