Complex behaviour of aluminium dissolution in alkaline aqueous 2-propanol solution

The corrosion behaviour of pure aluminium in oxygenated 1 M potassium hydroxide using aqueous 2-propanol over a wide range of concentrations (0 to 56 vol.%) is examined by potentiodynamic Tafel polarization measurements at 25°C. Analysis of the corrosion potential (Ecorr), corrosion current (icorr), polarization resistance (Rp), and cathodic (icath) and anodic (ianod) exchange currents reveals that 2-propanol at low concentration acts as a corrosion accelerator for aluminium. At high concentrations, however, corrosion is abated markedly, and at a concentration of 56 vol.% the corrosion rate almost vanishes. The results are explained in terms of weakening of the barrier-type, inner oxide film on aluminium at a low 2-propanol concentration and a blocking effect at a high concentration through interaction via the oxygen centre of the 2-propanol molecule.