抄録
On the electro-polished surface of aluminum, the thin oxide film covers. This film will hinder the growth of oxide film in sulfuric acid. It can be removed by immersing in the hot caustic soda solution or mixed solution of phosphoric acid and chromic acid. But, by these methods, the electro-polished surface is ocassionally clouded.
The ununiformity of the thickness of oxide film causes the difference of reflecting power. In this report, it was recognized by electron microscopic observation that the warm bath process of sulfamic acid is very effective to remove the oxide film.
