抄録
Physical properties and compositions of hard coatings formed by AC process were investigated in comparison with those by DC process. Electrolysis was carried out at current density 3 A/dm2 and at bath temperature 10-20°C, using a sulfuric acid solution containing chromic acid ion (potassium dichromate, chrome (VI) oxides and oxide powders (aluminum oxide, glass beads). Addition of both potassium dichromate and glass beads provided the best properties in hardness for the AC process films by their combined effects, while the hardness and abrasion properties were improved by the addition of chromic acid ion and oxide powders. These characteristic features are thought to result from an increase in aluminum content in the film by the addition of chromic acid, and also from the levelling of the film surface caused by the addition of oxide powders. But AC process films generally showed lower hardness than DC process films. It is considered, on the basis of AAS, EPMA and SIMS analyses, that this lower hardness is attributable to a smaller amount of aluminum oxide contained in AC process films.
