| 摘要 |
PURPOSE:To produce surface treated steel products having a high degree of blackening and excellent corrosion resistance and discoloration resistance by subjecting an Ni plated material to an anodic electrolytic treatment in an acidic bath contg. specific ratios of the hydroxide, sulfate or phosphate of Na, etc., and nitrate ions. CONSTITUTION:The material subjected to Ni plating or Zn-Ni alloy plating contg. 5-20% Ni as an anode is subjected to the anodic electrolytic treatment with Ni or an alloy essentially consisting of Ni as a cathode in the acidic bath contg. 75-200g/l>=1 kinds of the hydroxide, sulfate or phosphate of Na, K, Ni and ammonium and 2-15g/l nitrate ions. The conditions for the above- mentioned treatment are specified to 30-200A/dm<2> current density and 50-500c/dm<2> coulometric density. The surface treated steel products of the high degree of blackening which has the stably which degree of blackening and has the excellent workability, weldability and corrosion resistance are thus obtd. Said steel products are preferably stuck with a chromate film at 5-100mg/m<2> in terms of Cr of resin or silicic acid sol at 0.3-3g/m<2> dry weight.
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