| 摘要 |
PURPOSE:To manufacture efficiently a cold-rolled steel sheet excellent in the phosphate treatability by electro-treating a surface of a continuously annealed cold-rolled steel sheet in an aq. acidic soln. contg. Zn or the like and forming properly a Zn series composite deposit of the proper Zn contact thereon. CONSTITUTION:The cathodic electro-treatment is performed on a surface of a continuously annealed cold-rolled steel sheet in an aq. acidic soln. contg. Zn, one and more kinds of Mn, Co, Ni and the inevitable impurities. By this treatment, a Zn series composite deposit having 50-90wt% Zn content is formed in 10-500mg/m<2> adhered quantity on the surface of the above-mentioned cold- rolled steel sheet. Thereby the continuously annealed cold-rolled steel sheet excellent in the phosphate treatability is obtained.
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