Patent ID: 6280535
Filing Date: 2001-08-28
Classification: C23C

Abstract:
A process for manufacturing a chromate-coated galvanized steel sheet with a lead-containing coated film having excellent anti-black patina and anti-white rust properties, characterized in that a galvanized steel sheet with a lead-containing coated film obtained by plating a steel sheet in a galvanizing bath containing 0.05 to 0.3% by weight of Pb and 0.1 to 0.3% by weight of Al is coated with a chromate coating solution consisting essentially of hexavalent chromium ions, trivalent chromium ions, nitrate ions and water in such proportions that the trivalent chromium ions have a molar ratio of 1/9 to 1/1 to the hexavalent chromium ions, while the nitrate ions have a molar ratio of 0.1 to 1.6 to the total of the chromium ions, and that the sheet is dried at a sheet temperature of 40-250.degree. C. without being washed with water, whereby a chromate film having a coating weight of 5 to 50 mg/m.sup.2 in terms of metallic chromium is formed thereon, and that at least a portion of lead enriching the surface of the coated film is removed in the step of coating the sheet with the chromate coating solution.