GALVANIZED STEEL SHEET EXCELLENT IN HEATING DISCOLORATION RESISTANCE, FUMING PROPERTY AT THE TIME OF HEATING, CORROSION RESISTANCE AFTER HEATING AND FLAWING RESISTANCE

摘要

PROBLEM TO BE SOLVED: To produce a galvanized steel sheet excellent in all of heating discoloration resistance, fuming properties at the time of heating, corrosion resistance after heating, flawing resistance and adhesion. ;SOLUTION: The surface of a galvanized steel sheet is provided with a chromate film as a 1st layer, in which the coating weight of a film formed by applying a treating soln., in which the weight ratio of trivalent chromium ions/all chromium ions (trivalent chromium ions + hexavalent chromium ions) is controlled to the ratio of 2/10 to 6/10, and as to phosphoric ions, the weight ratio of phosphoric ions/all chromium ions is controlled to the range of 1.0 to 4.0, and by executing drying is ≤100 mg/m2 expressed in terms of metallic Cr and a resin film as a 2nd layer of 0.1 to 3 g/m2 expressed in terms of SiO2 consisting essentially of straight silicone resin on the upper layer of the chromate film.;COPYRIGHT: (C)2000,JPO