SURFACE TREATMENT FILM FOR GALVANIZED STEEL SHEET AND SURFACE TREATED STEEL SHEET

摘要

PROBLEM TO BE SOLVED: To provide a novel non-chromate treated steel sheet with which the occurrence of white rust occurring in zinc may be suppressed even if the steel sheet is treated with a treating bath not containing harmful ions. SOLUTION: The occurrence of the white rust of the surface treatment film for the galvanized steel sheet is suppressed by using the oxide and/or hydroxide of Ce and the oxide/hydroxide of Si as the essential components of the film. More specifically, the ratio of the oxide and/or hydroxide of Ce to the total oxide occupying in the film is in a range from 0.1 to 0.60 and the ratio of the oxide and/or hydroxide of Si to the total oxide occupying in the film from 0.2 to 0.8 and the ratio of SiO2 occupying in the oxide and/or hydroxide of Si is preferably 0.15 to 0.90.