| 摘要 |
PROBLEM TO BE SOLVED: To provide a conversion treated steel sheet having exceedingly improved corrosion resistance by allowing fluorides to coexist in a chemical conversion coating formed on the surface of an Al-Si alloy plated layer as well as oxides or metallic hydroxides. SOLUTION: An Al-Si alloy plated steel sheet in which, preferably, the content of Si as the total in the plated layer is controlled to 5 to 13 mass%, and the content of Si in the surface layer is controlled to 10 to 80 mass% is used as a base material. A chemical conversion coating in which the oxides or hydroxides and fluorides of valve metals such as Ti, Zr, Hf, V, Nb, Ta, Mo and W; wherein, the oxides exhibit high insulation resistance coexist is formed on the surface of the base material. In the oxides or hydroxides and fluorides contained in the chemical conversion coating, the ratio of the numbers of atoms atom, i.e., F/O is preferably controlled to 1/100 or higher. The chemical conversion coating may contain soluble or hardly soluble metallic phosphates or combined phosphates.
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