| 摘要 |
PURPOSE:To produce the title high-performance colored surface-treated steel sheet at a high rate in a short time, by electrolyzing a steel sheet in an aq. soln. contg. a cationic polymer, a zinc ion, a coloring metal ion, a chemical conversion coating forming agent, etc., with the steel sheet as the cathode. CONSTITUTION:A steel is electrolyzed in the aq. soln. contg. a water-soluble cationic polymer such as the polymer of a quaternary amine and the metal ions such as the zinc ion, Fe<2+>, and Cr<3+> whose oxides are colored and contg. the hexavalent chromium compd., phosphate, sol such as silica sol having <=about 100mum particles diameter, a water-soluble polymer such as polyacrylic acid, and the chemical conversion coating forming agent consisting of >=1 kind among chelate compds. with the steel sheet or a plated steel sheet as the cathode. The pH of the aq. soln. preferably adjusted to 1.5-3.0. Subsequently, a guard coat is coated, as required, in 0.5-3mu thickness. By this simple process, a colored surface-treated steel sheet having excellent appearance, workability, and corrosion resistance and also having strong resistance to cracking is obtained at low cost.
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