Pit Morphology and Surface Film Formed on Aluminum by Triangular Anodic Pulse Current Etching in Hydrochloric Acid Solution

The effect of the current waveform on etch morphology and surface film of aluminum produced in 3.6% HCl solution at 323K was studied using scanning electron microscopy (SEM) and Auger spectroscopy (AES). Current forms used for etching were asymmetrical triangular anodic pulses having a maximum current density of 0.5A/cm2 at tm within an on time of 10-2s, and the off time between pulses was varied from 0 to 0.1s. The change of the etched surface depended on tm, and off time was found due to the amount of etch products composed of an anodic film of Al2O3 shown by AES analysis and a small quantity of aluminum hydroxide observed by SEM. The etched morphology was classified into three stages by current sweep rate. Above 200A/cm2s (tm 5×10-3s). The anodic film thickness increased with increasing tm and off time.