Abstract
It was found that the color tone of anodized films on Al-Mn or Al-Mn-Mg alloys were sensitively changed in accordance with the conditions of heat treatments of mother alloys before anodizing. The relationship of the heat treatments before and after working to the color tone of anodized film was investigated, and the following results were obtained.
1) When Al-Mn-alloys were precipitation heat treated at about 400°C before or after working, and then anodized, the color tone of the films was black.
2) The color tone of anodized films was sensitively changed according to the temperature of heat treatment. It was uniformly grayed when the alloys were treated at about 550°C.
3) The color tone of the films was deep black, when they were sealed in boiling distilled water.
4) The color tone of the films was changed to brown by the addition of Si. It was slightly changed to brown by the addition of Fe, but showed no change by Mg. Color streaks were often evident on anodized films of Al-Mn alloys (especially, on rolled plates). However, the streaks can be prevented by the addition of Mg to the alloys.
