Mechanism of Electrolytic Coloring of Anodic Oxide Film on Aluminum by Anodic Stripping Method

In order to find out the mechanism of elelctrolytic coloring of anodic oxide film of aluminum, the electrolytically colored films in several electrolytes such as nickel, cobalt, copper, tin, selenium and aluminum-magnesium solution were used for the anodic stripping. In the nickel solution and the cobalt solution, nickel and cobalt in the film pores were dissolved at the peak potential of the anodic polarization curves, and the films were completely decolorized. This suggests that nickel and cobalt in the colored films would be deposited in the film pores under the metallic state. In the copper solution and the tin solution, the films were not completely decolorized. This implies that copper and tin would not only be deposited under the metallic state but deposited under the state of oxide and hydroxide. In the selenium solution, the film was not decolorized at all. This suggests that selenium would be deposited under the state of oxide. The aluminum-magnesium solution yielded a white film, which was slighty decolorized. This implies that aluminum was not dissolved because of being deposited in the film pores under the state of oxide and hydroxide, while magnesium was dissolved because of uncomplete oxidization and hydration. The result is that the anodic stripping method provided three kinds of deposit states in the film pores; only metal, only metal oxide (hydrate), and a mixture of them.