| 摘要 |
PURPOSE:To produce the titled steel sheet having excellent resistance to scratching, etc., by hot dip galvanizing the surface of the steel sheet, immediately treating the surface with an alkaline soln. at specified pH contg. Fe ions and a minor amt. of Ni ions and then chromating the surface. CONSTITUTION:The surface of a steel sheet is hot dip galvanized with Zn or a Zn-Al alloy and then immediately treated with an alkaline soln. at 9-14 pH contg. Fe ions and a minor amt. of Ni ions to deposit an eutectoid of Fe and Ni on the surface of the steel sheet. The Fe concn, is regulated to 0.05-5g/l, the Ni concn. is controlled to 0.01-1.0g/l, the treating temp. is adjusted in the range from room temp. to 70 deg.C, the treating time is regulated to <=15sec, the amt. of Fe deposited is controlled to 0.3-15mg/m<2> and the amt. of Ni deposited is adjusted to 5-100mg/m<2>. Then chromating is applied to form a chromate film so that the amt. of Cr deposited is adjusted to 5-100mg/m<2>. Consequently, a galvanized and chromated steel sheet having excellent resistance to oil staining, blackening and corrosion, can be obtained. |
