| 摘要 |
PURPOSE:To prevent the deterioration of a processing soln. and to improve the workability, corrosion resistance, and blackening degree of treated steel by treating steel plated with a Zn-Ni alloy having a specified composition in specified thickness in a soln. contg. a nitric ion under specified conditions by alternating electrolysis. CONSTITUTION:The steel plated with a Zn-Ni alloy contg. 5-20% Ni at the rate of 10-40g/m<2> is treated in the processing soln. contg. a nitric ion. The steel is alternately kept at an anode and a cathode, and the ratio of the time of anodic treatment to the time of cathodic treatment is controlled to 0.1-1. The alternating cycle is controlled to 1-50Hz, the total treating time is adjusted to 1-30sec, the current density in the anodic electrolysis of the alloy-plated steel is regulated to 5-100A/dm<2>, the current density ratio of anode to cathode is adjusted to 1/0.1-1, and electrolysis is applied. The steel is then treated with a CrO3 chromating soln. to deposit a chromate film at the rate of 5-100mg/m<2>, expressed in terms of Cr, and/or a water-dispersible or water-soluble resin or a silica sol can be coated at the rate of 0.3-3g/m<2>, based on dry weight.
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