水酸化バリウムを基液としたアルカリ性浴中におけるアルミニウムの陽極酸化 Anodization of aluminum in barium hydroxide alkaline baths
Hydroxide solution of alkaline-earth metal is easy to form carbonate by absorbing carbon dioxide in air. This absorption was able to be prevented simply by setting carbon fluoride membrane on the liquid surface. In the present investigation, anodization of aluminum was done by this method in barium hydroxide bath. The properties of the anodized film were compared with those produced in other alkaline baths such as sodium carbonate and sodium hydrate baths and in sulfuric acid baths. Furthermore, sodium aluminate acid and sodium tetraborate were added to barium hydroxide bath in order to improve hardness and abrasion resistance of the soft film produced in alkali, and the effects were examined. As a result, the films obtained in barium hydroxide baths were superior to those with the same thickness (8 μm) obtained in sodium hydrate and sodium carbonate baths in the hardness and the resistance to alkali corrosion. Among all the films tested, the film obtained in sodium-tetraborate-added barium hydroxide bath was found to have the highest hardness and greatest alkali resistance. These properties were attributable to the formation of fine cell structure from SEM observation of the film surface, and were thought to be related to the composition ratio of Al and O and the film density. From the results of an EPMA analysis and surface roughness measurement, the addition of sodium tetraborate was found to suppress the dissolution of the formed film, and also to reduce the unevenness of the film surface.
軽金属 47(9), 500-505, 1997-09-30
The Japan Institute of Light Metals