アルミニウムへの電着における素材の純度の影響について

Abstract

As base metals 3 kinds of aluminium plates of different composition (99.9% Al, commercial aluminium, and 52S) are used in the experiments.Specimens are made by plating the anodized and plate mentioned above. The examination of the adhesive property of these specimens shows that the low grade aluminium has the best adhesive property.The cause of the difference in the adhesive properties is investigated, and the following results are obtained:i) The electron-microscopic observation of the oxide film shows that the inherent pores are slightly larger for the higher purity aluminium than the lower one. When the phosphoric acid bath is used, no relation exists between the adhesive property and pore size. The cell structure of the oxide film is more uniform and continuous in the high purity aluminium, while the low grade aluminium has many defects in the oxide film.ii) The anodized surface of low grade aluminium macro or micro-scopically rough.iii) The nucleation during initial plating is selective as a rule, and the higher the purity of aluminium is, the higher is the selectivity.iv) In the case of nickel bath, the lower the grade is, the higher is the electric potential, and the easier is the plating operation. This agrees with the well known fact that the nobler the metal is, the easier is the plating operation. The potential rises due to the anodizing, and the highest possible potential becomes almost as high as that obtained by using iron plates.