Fabrication of Highly Adherent Aluminum Surface by Anodizing

The relation between the nanostructure and adhesion of the porous oxide formed by anodizing of aluminum was investigated. Porous anodic oxide with large pore was found to have higher adhesion for the aluminum surface. However, much lower adhesion was found when excess chemical dissolution formed fibrous and irregularly shaped oxides on aluminum. Moreover, the adhesive force was low for oxide with shallow pore depth, even for large pore diameters. However, the aluminum surface adhesion was high when the anodic oxide pore depth was approximately 200 nm or more. By controlling the electrolyte temperature and the Joule heat generation appropriately using high current density anodizing, the aluminum surface adhesion was improved considerably by one-step constant current anodizing treatment. The surface-treated aluminum also showed good adhesion to paint.