초록 ▼

A production method for a lead-containing hot-galvanized chromated steel sheet with excellent resistance to blackening and white rust formation comprises: (a) plating a steel sheet in a hot-galvanizing bath containing 0.05-0.3 wt. % lead and 0.1-0.3 wt. % aluminum; (b) coating this with a chromating

A production method for a lead-containing hot-galvanized chromated steel sheet with excellent resistance to blackening and white rust formation comprises: (a) plating a steel sheet in a hot-galvanizing bath containing 0.05-0.3 wt. % lead and 0.1-0.3 wt. % aluminum; (b) coating this with a chromating solution containing chromium (VI) ions, chromium (III) ions and nitrate ions in which the Cr(III)/Cr(VI) molar ratio is 1/9-1/1 and the nitrate ion to total chromium ion molar ratio is 0.1-1.6; and (c) without washing with water, drying the sheet at 40-250 deg. C., to form a 5-50 mg/m integral 2 (in terms of chromium) chromate film.

대표청구항 ▼

[ What is claimed is:] [1.]1. 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 plati

[ What is claimed is:] [1.]1. 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.