FILM FORMATION METHOD AND METALLIC MATERIAL

To provide a method for forming a film having high corrosion resistance on the surface of a metal by plasma electrolytic oxidation.SOLUTION: A first film is formed on the surface of a metal by subjecting the metal to an anodic oxidation treatment without causing plasma discharge in a state where the metal is immersed in a first electrolytic solution containing a first water-soluble compound. A second film having a composition different from that of the first film is formed between the metal surface and the first film in a state where the metal is immersed in a second electrolytic solution containing a second water-soluble compound having a composition different from that of the first electrolytic solution, by generating plasma discharge between the metal and the second electrolytic solution to subject the metal to a plasma electrolytic oxidization treatment.SELECTED DRAWING: Figure 2 【課題】金属の表面に対して、耐食性の高い皮膜を形成することができるプラズマ電解酸化による皮膜形成方法を提供することを目的とする。【解決手段】第１水溶性化合物を含有する第１電解液に金属を浸漬させた状態で、プラズマ放電を伴わない陽極酸化処理を施すことにより、金属の表面に第１皮膜を形成し、第２水溶性化合物を含有し、第１電解液とは組成の異なる第２電解液に金属を浸漬させた状態で、金属と第２電解液との間にプラズマ放電を発生させてプラズマ電解酸化処理を施すことにより、金属表面と第１皮膜の間に第１皮膜とは異なる組成を有する第２皮膜を形成する。【選択図】図２