Molybdate/sulfuric acid anodising of 2024-aluminium alloy: influence of inhibitor concentration on film growth and on corrosion resistance

In order to replace hexavalent chromium in anodising processes, molybdate species have been used as corrosion inhibitors. This article describes effects of molybdate additions to sulfuric acid on the anodising of Al 2024 alloy. Different electrochemical techniques were employed to study electrolytes, anodic film growth and corrosion resistance. These analyses have shown modifications as a function of molybdate concentration. At low concentrations, anodic layer formation was hindered and corrosion performance of these oxide films was slightly improved. On the contrary, at high concentrations, anodic layer growth was promoted and corrosion resistance was significantly improved.