硫酸電解浴による陽極酸化皮膜の諸性質におよぼす蓚酸添加の影響について

抄録

The effect of oxalic acid on the properties of anodic oxidation films produced by sulphuric acid process and the effect of some impurities in both on the films were studied.
The findings are summed up as follows:
(1) The properties of films are influenced by the concentration rate of sulphuric acid much more than by that of oxalic acid. The addition of oxalic acid does not make any sence, when the concentration rate of surphuric acid is 15% (volume), because under such situation, the addition of oxalic acid does not work much for the improvement in electrolytic efficiency and properties of anodic films. When 1-3% oxalic acid is added to sulphuric acid of low concentration of 4-6%, the electrolytic efficiency increases about 10% and erosion resistance of the films is considerably improved. The corrosion resistance is also improved in such case.
The films thus produced is clear and colourless and has no fault like pittings.
(2) Even if moe than 3% of oxalic acid is added the properties of film, for example, increase in thickness, does not improved much. But oxalic acid has a great preventable effect for formation of two layers distribution which takes place by increase in temperature.
(3) The film produced in the bath of low concentration of sulphuric acid and oxalic acid is very compact. It has, therefore, high erosion resistance but has low dye absorption property. In order to obtain good absorption property, longer time of oxidation is necessary than in the case of simple sulphuric acid bath.
(4) Effect of Al ion on the properties of film is almost same as in the case of simple sulphuric acid bath. Effect of anions such as NO₃ ino and Cl ino is much bigger than those of cation such as Fe and Cu ion.