| 摘要 |
PROBLEM TO BE SOLVED: To form a film with high corrosion resistance, or to form a film in a short time. SOLUTION: This method comprises electrolyzing a magnesium alloy which has been pre-treated like degreasing, in an alkaline electrolytic solution to which sodium hydroxide and phosphoric acid are added, with a polarity inversion power supply which outputs each of positive and negative power periodically. Thereby, it electrolytically forms magnesium oxide by action of phosphoric acid during positive polarity of alkaline electrolysis, smooths the treated surface with an action similar to electrolytic polishing during negative polarity, and grows the film with high corrosion resistance mainly consisting of the magnesium oxide, by further repeating inversion of the positive polarity and the negative polarity. The method further comprises pre- treating a magnesium alloy including magnesium of 92% or more, by degreasing or the like, and then electrolyzing it in the alkaline electrolytic solution to which sodium hydroxide and sodium sulphonate are added, with the polarity inversion power supply. Thereby, it electrolytically forms magnesium hydroxide during positive polarity of the alkaline electrolysis, and forms a thick film in a short time, which has been impossible with a conventional anodic oxidation.
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