In heat resistance, resistance heating discoloration Characteristic and the surface of the spelter plated steel sheet

摘要

PROBLEM TO BE SOLVED: To produce a galvanized steel sheet free from harmful hexavalent chromium at all, further free from the exhaust of hexavalent chromium at all even in the production process and excellent in heat resistance, heating discoloration resistance and corrosion resistance not only in red rust resistance but also in white rust resistance.;SOLUTION: On this galvanized steel sheet excellent in heat resistance, heating discoloration resistance and corrosion resistance, a film layer of 0.1 to 2 g/m2 obtained by applying and drying an aqueous solution obtained by mixing colloidal silica of 10 to 100 pts.mass as solid content and a phosphonic compound of 1 to 50 pts.mass into magnesium biphosphate of 100 pts.mass as solid content is formed. It is also suitable that the film is further mixed with an aqueous resin of ≤20 pts.mass as solid content. The temperature in the applying and drying is preferably controlled to ≥150°C. Moreover, as the phosphonic compound, 1-hydroxyethylidene-1,1'-diphosphonic acid is suitably used.;COPYRIGHT: (C)2001,JPO