Abstract
It is well known that the thickness of anodic oxide films on Al formed at low current densities is limited by chemical dissolution of the films in the bath during anodization. On the other hand, when anodizing at high current densities, the occurrance of burning limits the film thickness, which decreases with increasing current density.
Based on the above facts, the maximum film thickness obtained under galvanostatic anodization was analyzed and calculated using both the chemical dissolving rate for oxide films and the burning occurrance curve. It is theoretically and experimentally demonstrated that the critical thickness of oxide film can be formed on Al only by using a high speed anodizing process, in which, after initial galvanostatic anodization at high current density, current density decreases with time along the burning occurrance curve.
