Abstract
The dissolution behaviors of anodic oxide films during anodizing of Al at a constant current density in oxalic acid, orthophosphoric acid, and chromic acid solutions were investigated by measuring the change in anode potential with the anodizing time.
The structural features of anodic oxide films formed in oxalic acid solution were studied by eletron microscopy.
The results obtained were as follows.
1) Activation energies for the dissolution of the barrier layer were found to be 0.54eV for oxalic acid, 0.72eV for phosphoric acid, and 0.88eV for chromic acid.
2) In anodizing of Al in oxalic acid solution, both of the pore diameter and the cell size increased and the number of pores decreased with the increase in current density.
3) During the process in oxalic acid solution, in which anode potential of Al decreased with the anodizing time, the formation of pores in the oxide layers was found to be at the intersecting points of the ridges and also on the ridges themselves as seen in sulfuric acid solution.
