| 摘要 |
PROBLEM TO BE SOLVED: To improve the thermal crack resistance and corrosion resistance of a film by applying an AC/DC superposing method in which direct current is applied with alternating current and executing the treatment under an electrolyzing conditions in which the AC components do not contain negative components, and the AC components are contained in the DC components at a specified ratio. SOLUTION: An AC/DC superposing method is applied, and as to the electrolyzing conditions, the AC components do not contain negative components and contain by >=5% of the DC components. By the AC/DC superposing method satisfying the conditions, a structure in which each cell and/or pore composing an anodically oxidized film is fused and branched or a structure in which voids are introduced into a space between the adjacent cells or into the cell walls is formed. In the former structure, stress caused on the film under the environment of a heat cycle, or the like, is dispersed to prevent the generation of cracks. Moreover, in the latter structure, voids enable the relaxation of the stress caused by a heat cycle, or the like, and even if cracks are generated, by the effect similar to pinning, their propagation is suppressed. As a result, the corrosion resistance and wear resistance as the whole of the film can be maintained.
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