General Aspects of the Pitting Corrosion

Htxtmchemical attack of metals and their alloys can bc broadby divided into two a?lpes; genzal and ! d i z e d cmsion. b utse of general ccrrro:;oe, the m d c dissolution takes place over the mtire nlefd surface leading very often to the generation of r more or less prohctive layer that may redwe the corrosion rate considerably. This type of curnosion is predictable an can be mwt. readily controlled. The localized curnosion, however, mum when the protective film that covers the mctal ur alloy breaks down at s local pit in the surface md rapid corrosion attack a pmclxates into h e metal. HE. 1 shows the schmatic eross-section of a localked attack where. after the 1-1 nlpture of the passive lilm, the reactions take place that lead to Xocdid conosim [I].