- Processes are self-stimulating and self-propagating.- The rapid dissolution of metal within the pit tends to produce an excess of positive charge in this area, resulting in the migration of chloride ions to maintain electoneutrality.- High [MCI] → High(H'] -→ Stimulate the dissolution of more metals.- No oxygen reduction occurs within a pit (the solubility of oxygen is virtually zero in concentrated solutions). The cathodic oxygen reduction on the surfaces adjacent to pits tends to suppress corrosion; pits cathodically protect the rest of the metal surface.