| 摘要 |
PROBLEM TO BE SOLVED: To obtain a coated steel sheet excellent in weldability, workability and corrosion resistance, on the surface of a galvannealed steel sheet having a specified compsn. composed of Mg, Al and Zn and having an Ni plating substrate, by coating and baking a coating material contg. a specified amt. of Zn powder to a specified coating thickness. SOLUTION: A plating original sheet of an Al killed steel or the like is applied with an Ni prepating layer of about <=2.0 g/m<2> according to necessary, and, the surface of the substrate thereof is applied with galvannealing composed of, by weight, 0.05 to 3.0% Mg, 0.1 to 1.0% Al, and the balance Zn and excellent in bare corrosion resistance. The surface of this galvannealing layer is applied with chromate treatment to form a chromate coating layer in which the total chromium coating weight is regulated to about 10 to 50 mg/m<2> , the layer surface is coated with a coating material contg. Zn powder of >=80 wt.% to coating material non-volatile components, which is baked at about 100 to 280 deg.C to form coating of 1 to 30μm coating thickness. Moreover, in the case the coating thickness is 1 to 20μm and the average grain size of the Zn powder is more than the coating thickness, the content of the Zn powder may be regulated to 60 to <80%.
|
