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 degrees C. Analysis of the corrosion potential (E(corr)), corrosion current (i(corr)), polarization resistance (R(p)), and cathodic (i(cath)) and anodic (i(anod)) 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.