Abstract

The effect of benzotriazole on the growth of anodic films on aluminium and an A1-3.5 wt% Cu alloy has been examined by transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). Films grown to relatively high voltages reveal flaws and oxygen-filled voids as a result of the surface morphology and copper enrichment and oxidation at the alloy/film interface. Benzotriazole, apart from increasing the efficiency of anodic film growth on the artificially aged alloy, also reduces the population density of the local features. The impedance response of films formed at relatively low voltages has been used to probe the early influence of benzotriazole on the macroscopic surface as well as flaws of the oxide-covered substrate.