Localized corrosion is the accelerated attack of a passive metal in a corrosive environment at discrete sites where the otherwise protective passive film has broken down. Common forms of localized corrosion include pitting on a boldly exposed surface, corrosion in a creviced region shielded from the bulk environment, intergranular corrosion of an alloy with a susceptible grain boundary region, and exfoliation corrosion, which is a form of intergranular corrosion involving the prying apart of elongated grains by a voluminous grain boundary corrosion product.