Abstract
The pulse wave was synthesized by chopping of the d. c. constant voltage source using a microcomputer and a power transistor. Anodic oxidation of aluminum was performed by these synthesized pulse wave. The current waveform of anodic oxidation was classified into three types according to the shape and the number of inflections: the type B by which a barrier layer was formed, the type P by which a porous film was formed and the type D by which the anode was dissolved. The current waveform, observed when anodic oxidation of aluminum was performed in a electrolyte of 0.05M borax added to 0.5M boric acid or of 9.08M phosphoric acid, was influenced by the temperature of the electrolyte and the anodizing time. It was evident that the barrier layer of the phosphoric acid film was chemically dissolved when the OFF time of the pulse wave was changed from 25ms to 50 ms. No capacity current at the start of anodic oxidation in 1M sulfuric acid was observed even when the current waveform for each pulse every 25ms was stored in a wave memory. The Al3+ ions in 1M sulfuric acid were found to cause a major disturbance in the leading edge of the capacity current. The similar phenomenon also appeared when stirring of the electrolyte was stopped.
