| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent the lowering of surface hardness by adding sulfuric acid into an electrolyte for the anodic oxidation of aluminum and further adding oxalic acid or citric acid to suppress the dissolving power of a coating film due to the treating liquid. SOLUTION: The anodically oxidized coating film is formed with the electrolyte on the surface of an article composed of an aluminum alloy. Oxalic acid or citric acid is incorporated in the electrolyte together with sulfuric acid. The electrolyte is stored in a stationary bath and the aluminum article is dipped into the electrolyte and subjected to the anodic oxidation. Or the anodic oxidation is performed by circulating the electrolyte to flow on the treating surface of the aluminum article. By using the electrolyte, the electric conductivity is increased, the treating time to obtain the alumite coating film having a prescribed thickness is shortened and simultaneously the lowering of hardness of the film due to the dissolving action of the formed alumite coating film is prevented because the proportion of sulfuric acid to be used is decreased.</p> |
