PROCESS OF PRODUCING ALUMINUM SUBSTRATE FOR MAGNETIC RECORDING MEDIA

摘要

An aluminum substrate suitable for making high-density magnetic recording media is produced by anodising a surface of the aluminum material in an aqueous chromic acid solution at an electrolytic voltage higher than 60 volts. The anodic film thus formed has no black spot defects as also exhibits no cracks when the substrate is heated at a high temperature for forming a magnetic recording layer. The effect is further improved by adding a small amount of oxalic acid to the electrolyte.