| 摘要 |
PURPOSE:To develop a weldable painted steel sheet which decreases generation of coated film powder during pressing of the steel sheet by forming a chemical conversion-treated film on the surface of the steel sheet and forming further a Zn-rich coated film contg. Zn powder and specifically composed Zn-Mg alloy powder thereon. CONSTITUTION:A chromate chemical conversion film 2 is formed on the surface of a cold-rolled steel sheet or plated steel sheet 1 subjected to plating of Zn or Al. A Zn-rich coating film 5 contg. 60-91wt% total of Zn powder 3 and Zn- Mg alloy powder 4 and the balance consisting of straight chain epoxy resin having 1-100,000mol.wt. is coated thereon. The ratio of the Zn powder/Zn-Mg alloy powder is made to 50/50-98/2 and a specified amt. of 1 or >=2 kinds among Al, Ni, Cu, Si, Ti, Sb, Cr, Be, Co, In, Sr, Mo and Zr are incorporated into the Zn-Mg powder. A rust preventive pigment is added to the Zn-rich coating film, as necessary.
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