COMPARISON OF THE COMPOSITION AND STRUCTURE OF THE POROUS ALUMINA FILMS FORMED BY AC AND DC ANODIZING

The composition and structure of porous alumina films formed in H 2SO 4 solution by AC and DC anodizing have been investigated separately.The two kinds of porous films are all composed of (Al 2O 3) 4·H 2O,Al(OH) 3 and Al 2(SO 4) 3,but sulphur and sulphide are also found in AC anodizing films.The pore shape of DC anodizing films are more regular than that of AC anodizing films.The surface morphology of AC anodizing films is much coarsened.