Effect of two-step anodizing on suppression of burning of aluminum surface during high current anodizing

Abstract

The effect of two-step anodizing on the suppression of burning of aluminum surface during high current anodizing was investigated in oxalic acid-based electrolyte. When second anodizing at high current density was performed on aluminum coated with a first alumina layer with different thicknesses, the growth of the anodic film during the second anodizing was better with thinner first layer. On the other hand, when the same second anodizing was performed on aluminum coated with a first layer with different cell diameters, the larger cell diameter of the first layer was more effective in preventing burning. The relatively large concave arrays on aluminum formed by the first anodizing also inhibited burning during the second anodizing. In each method, it was found that prevention of burning could be achieved by dispersing pore generation sites and suppressing local current concentration during the second anodizing.