| 摘要 |
PROBLEM TO BE SOLVED: To produce a blackened plated steel sheet excellent in corrosion resistance, showing a color tone of uniform black to grayish black and usable with noncoating by blackening a plating film in a hot dip Zn-Al alloy plated film by short time treatment. SOLUTION: In the case a hot dip Zn-Al alloy plated steel sheet contg. 2 to 80% Al is treated by an alkali aq. soln. of pH >=11, and Al-riched phases in the plating surface layer part are removed to a depth of 0.05 to 5μm to form fine raggedness on the surface, the plating surface is blackened. In the case a chromate film with 10 to 150mg/m<2> Cr coating weight and/or an organic resin film with 0.2 to 5μm thickness is formed on the above plating film, its corrosion resistance is furthermore improved.
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