Localized Corrosion of Aluminum: Blister Formation as a Precursor of Pitting

Blisters have been observed in the oxide film of aluminum in aqueous chloride solutions. They can be initiated by short duration ((sic) 1 msec), low voltage pulses. Such blisters grow only if the steady-state potential of the specimen is above the pitting potential. The growth proceeds laterally along the oxide-metal interface. Upon breaking, as a result of gas pressure from within, pitting corrosion begins. Thus, in this instance, blisters are experimentally demonstrable precursors of pits.