A MECHANISTIC APPROACH TO THE ELECTROFORMATION OF ANODIC LAYERS ON COPPER AND THEIR ELECTROREDUCTION IN AQUEOUS-SOLUTIONS CONTAINING NAHCO3 AND NA2CO3

The electrochemical behaviour of Cu in solutions containing Na2CO3 + NaHCO3 (8.8 < pH < 11.1) has been studied using potentiodynamic and potentiostatic techniques complemented by Scanning Electron Microscopy. The initial stages of the anodic layer formation involve the electroformation of a thin inner Cu2O layer followed by the growth of a CuO/Cu(OH)2-CuCO3 complex outer layer. Soluble Cu(II) species were detected in the entire anodization potential range. Kinetic models devised for phase change electrochemical processes have been applied to explain the characteristics of anodic and cathodic current transients.