SURFACE TREATMENT METHOD FOR MAGNESIUM ALLOY AND CHEMICAL SET FOR SURFACE TREATMENT

摘要

PROBLEM TO BE SOLVED: To deposit a chemical conversion coating film by a chromium-free surface treatment method in place of the conventional chromate treatment to provide a chemical set used in the case of performing the surface treatment method. SOLUTION: The surface treatment method includes an activation treatment stage wherein a magnesium alloy is dipped into an aqueous solution of a carboxylic acid, a coating deposition treatment stage wherein the magnesium alloy subjected to the activation treatment is dipped into a chromium-free alkali or neutral aqueous solution, and a coating control treatment stage wherein the magnesium alloy deposited with a coating film is dipped into an aqueous solution containing an inorganic chloride and the fermentation matter of protein. The corrosion resistance of the magnesium alloy subjected to the surface treatment method is so excellent as to be equal to that of the magnesium alloy subjected to chromate treatment.