| 摘要 |
PURPOSE:To produce a zinc-base composite plating steel sheet excellent in corrosion resistance and coating properties by subjecting a steel sheet to electrolytic treatment in an acidic aq. soln. of specified composition contg. specified metallic ions such as Zn<2+> and Fe<2+>, oxidative ions and phosphate ions. CONSTITUTION:A steel sheet or a plated steel sheet is subjected to electrolytic treatment while keeping it as a cathode in an acidic aq. soln. or dispersion liquid contg. 0.1-1.0mol./l Zn<2+>, 0.01-1.0mol./l metallic ion such as Fe<2+>, Co<2+>, Ni<2+>, Cr<3+>, Cr<6+>, Mo<6+>, Cu<2+>, Sn<2+> and Mn<4+>, 0.01-0.3mol./l oxidative ion and 0.001-0.1mol./l phosphate ion (as P2O5) as an essential component and furthermore if necessary, contg. a compd. of Si, Ti, Zr and Al etc. Thereby an eutectoid composite-plating film layer dispersed with metallic oxide and phosphate compd. in a plated zinc alloy film of Zn and iron group metal, Cr, Mo, Cu, Sn and Mn, etc., is formed. Thereby the zinc-base composite plating steel sheet excellent in corrosion resistance and coating properties is obtained at low cost.
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