A voltammetric and chronopotentiometric study of anodized aluminium in metal salt solutions

Voltammetric and chronopotentiometric experiments were carried out on anodi zed Al in solutions containing CuSO4, ZnSO4, CoSO4 and NiSO4. It it-as dete rmined that, independently of the electrochemical properties of the metal i ons, the first process, when increasing the cathodic potential, is H ion re duction, It has been deduced that H reduction takes place in large part fro m the H -containing layer formed at the solution, oxide interface. The meta l ion reduction proceeds at more negative potential, it-hen the H reduction is blocked The H reduction is blocked supposedly by the hydroxide layer fo rmed at the Al oxide surface through the bonding of the metal ions with fre e OH ions released due to the H, reduction. It has been concluded that the possibility for metal to be reduced from this hydroxide layer is quite real .