| 摘要 |
PROBLEM TO BE SOLVED: To use a treating bath which does not contain ions harmful for the environment and to impart excellent corrosion resistant performance even to an Al alloy in which an Al phase and an Si phase are coexistent on the surface such as an Si-contg. Al alloy represented by a 4000 series Al alloy. SOLUTION: This is a corrosion resistant film formed on an Al alloy having an eutectic Si phase, the film is composed of two phases of a film A consisting essentially of manganese oxide and contg. Mn by the atomic fractional rate satisfying the following inequality I, 0.3<=Mn/(Mn+O)<=0.5, a film Bx consisting essentially of Li-Al multiple oxide contg. Li by the atomic fractional rate satisfying the following inequality II, 0.2<=Li/(Li/Li+Al+O)<=0.3 or a film By consisting essentially of silisic acid-contg. aluminum hydroxide contg. Si by the atomic fractional rate satisfying the following inequality IV 0.01<=Si/(Si+Al+O)<=0.1, the film A is formed on the eutectic Si phase, and the film Bx or By is formed on the eutectic Al phase in the Al alloy.
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