Mg/Sr-CONTAINING HOT-DIP ALUMINIZED STEEL SHEET FREE FROM LIGHT BROWN INITIAL RUSTY STAIN, AND ITS MANUFACTURE

摘要

PROBLEM TO BE SOLVED: To produce an Mg- and Sr-containing hot-dip aluminized steel sheet free from the occurrence of light brown initial rusty stain without deteriorating its excellent corrosion resistance and superior surface characteristic. ;SOLUTION: The Mg/Sr-containing hot-dip aluminized steel sheet free from light brown initial rusty stain is obtained by applying chromate treatment to the plating-layer surface of a steel sheet on which an Mg- and Sr-containing hot-dip aluminizing layer is formed. The hot-dip aluminizing layer has a composition consisting of, by mass, 3-13% Si, 2-8% Mg, 0-10%; (including 0%) Zn, 0.1-1.0% Sr, and the balance Al with inevitable impurities. The coating weight of chromate at the chromate treatment is regulated to ≥5 mg/m2 expressed in terms of Cr coating weight. This plated steel sheet can be manufactured by a process where chromate treatment is performed to remove an Mg- and Sr-concentrated layer from the surface of the plating layer and simultaneously form a chromate layer.;COPYRIGHT: (C)2000,JPO