HOT-DIP ALUMINUM-ZINC ALLOY COATED STEEL SHEET EXCELLENT IN WHITE RUST RESISTANCE

摘要

PROBLEM TO BE SOLVED: To provide a hot-dip Al-Zn alloy coated steel sheet excellent in corrosion resistance. SOLUTION: This invention is based on the information that the occurrence of corrosion in a hot-dip Al-Zn alloy coated steel sheet is caused by the preferential melting and corrosion of coarse Zn aggregated parts in a plating film in the initial stage of corrosion and that white rust resistance can effectively be improved by controlling the existence density of the coarse Zn aggregated parts. In this hot-dip Al-Zn alloy coated steel sheet in which Al is contained by 35 to 95 wt.% in a plating film and coating weight per side is regulated to (15 to 100) g/m2, the number of the Zn aggregated parts of >=2μm diameter existing in the plating film is regulated to <=10 pieces per length of 5 cm in an arbitrary section of the film.