Pitting corrosion on aluminium in absence of chloride

Fitting corrosion has been the cause of numerous failures in industrial pipes and tubes, especially in environments containing chlorides. The problem is most acute when there is a source of copper ions, since these can plate out on, for example, aluminium and give rise to an effect similar to galvanic corrosion. Strong evidence is presented to suggest that, when copper ions are available, pits can initiate in aluminium even in the complete absence of chloride. However, the presence of chloride is still required if acidification is to occur in the occluded solution within the pit, a necessary precursor for sustainable rapid pit propagation.