| 摘要 |
PURPOSE: To develop a rustproof steel sheet for the automobile excellent in joined part corrosion resistance, coating suitability, weldability, etc., by forming specified amts. of the phosphate crystal film and phosphate film on both sides of galvanized steel sheet. CONSTITUTION: The surface of a thin steel sheet such as mild-steel sheet and high-strength steel sheet is plated with Zn, Zn-Ni alloy, etc., then a phosphate crystal film is formed on one side of the substantially unoxidized steel sheet before winding and oiling at 0.05-0.5g/m<2> , and a phosphate film is formed on the other side at 0.5-3.0g/m<2> . A rustproof steel sheet for the automobile excellent in chemical convertibility, coating suitability, joined part corrosion resistance and weldability is obtained.
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