Synergistic Effect of Rapid Anodization and Hydration on the Distribution of the Etched Tunnels for Aluminum Foil

The concave structures and the hydrated layer prepared by the anodized treatment and hydration process were investigated for improving the uniform distribution of the etched tunnels during the DC electrochemical etching of aluminum foil. It is indicated that when the anodized time is 20 s and the following hydration time is 90 s, the proportion of merged tunnels and the unetched regions to the etched aluminum foil substantially decreased, thus resulting in the significant increase in the specific surface area. The potentiodynamic polarization and EIS results indicated that the prolonged hydration process can gradually reduce the corrosion resistance of aluminum foil, which ascribe to the transformation of the anodic alumina film into the hydrated layer. Based on the synergistic effect of the hydrated layer and the concave structures, the distribution of etched tunnels on the as-received aluminum foil can be improved observably.