13Mおよび1.5M硫酸溶液中のAlダイカスト合金ADC12のアノード酸化挙動

抄録

ADC 12 specimens were anodically oxidized in 13M and 1.5M sulfuric acid solutions at constant current densities (i_a), and the amounts of oxide film (W_oxide), Al³⁺ions dissolved in the solutions (W_d) and the volume of gas evolved from the anode (V_g) were examined as functions of the anodizing conditions. There was more W_d, less V_g, and more W_oxide in the 13M solution than in the 1.5M solution. This suggests that the Al³⁺ions dissolution current (i_d) is larger, O₂ gas evolution current (i_g) is smaller, and oxide formation current (i_ox=i_a-(i_d+i_g)) is larger in the 13M solution than in the 1.5M solution. Since the films formed in the 13M solution had larger values of i_ox and larger amounts of SO₄^2-ions than the films formed in the 1.5M solution, the film weight, coating ratio, Si content, and thickness were larger for the 13M-films than for the 1.5M-films. Because microvoids were present in both the barrier layer and the porous walls, the hardness of the 13M-films was lower than that of the 1.5M-films.