マイクロアーク酸化処理をしたアルミニウム合金のガス放出特性

概要

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Micro-arc oxidation (MAO) is an anodizing technique applied to valve metals. With MAO, a crystalline aluminum oxide layer can be grown on aluminum alloys. This paper examines MAO as a surface treatment for metals for vacuum use. A 17.6 μm-thick MAO layer was grown on an A5052 aluminum alloy surface employing 50 Hz AC and a maximum of 450 V. This oxide layer contained α-alumina and γ-alumina crystalline aluminum oxide, and actually consisted of two distinct layers: first, a dense layer about 500 nm thick directly on the substrate, and, second, a 17 μm-thick layer on the dense layer which included numerous voids, each about 10 μm in size. Neither layer had the fine pores - 20-30 nm-structures - exhibited by alumite film. The outgassing rate of a MAO-treated A5052 sample after 10 hours of evacuation was 1.0×10-5 Pa•m3•s-1•m-2, i.e., 1/30 that of alumite with sulfuric acid. The most dominant gas species was water. The MAO samples corrosion resistance to hydrochloric acid was the same as that of an alumite sample.
日本真空協会の論文
2007-03-20