Aqueous solutions assisted corrosion

A full description of photo-assisted semiconductor corrosion is not available. We have undertaken an analysis of this phenomena, relying on aqueous solution electrochemical equilibria considerations (16). 

It is necessary to exceed the critical anodic potential (23) bd for the electrochemical breakdown of passivation by pitting and consists of these factors (i) presence of halides at the interface (ii) induction time for the initiation of the breakdown process, leading to localized conditions that may increase the localized corrosion current density (iii) development of favorable conditions inside the pits for propagation when the local sites become immobile and localized at certain sites. Electrochemical breakdown of some metal oxides is possible in the case of copper, lead, and tin cathodically to metal while ferric oxide is reduced to the ferrous ion in aqueous solutions. Zinc and aluminum oxides are not cathodically reducible and in these cases hydrogen is reduced. The vigorous evolution of hydrogen assisted by electron conducting zinc oxide can accelerate the breakdown of passivity. 

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