Corrosion mechanism of pure aluminium in aqueous alkaline solution

The corrosion of pure aluminium in alkaline solution has been explored usin g an open circuit potential transient, potentiodynamic polarization experim ent and a.c. impedance spectroscopy. The steady-state value of the open cir cuit potential (E-ocp(ss)) of pure aluminium in alkaline solution was obser ved to decrease with increasing rotation rate of the specimen, which is asc ribed to the enhanced anodic reaction. The extent of anodic polarization fo r the aluminium dissolution reaction on pure aluminium at E-ocp(ss) was fou nd to be greater than that of cathodic polarization for the water reduction reaction. This indicates that the rate of corrosion of pure aluminium is m ainly determined by the anodic reaction in alkaline solution. Based upon th e experimental results, a corrosion mechanism for pure aluminium has been p roposed in the presence of the native surface oxide film in alkaline soluti on, involving consecutive oxide film formation and dissolution, and simulta neous water reduction.