Pitting corrosion nonuniform attack

In certain specific soil chemistries the metal corrosion may be nonuniform, concentrated in relatively small areas that form sharply defined local holes called pits (Figs. 11-12), that grow deep into the metal and can cause failure by perforation. The pits are usually small in diameter, isolated from each other, and occur in more anodic metal areas with respect to the rest of the surface. The pitting corrosion is a very dangerous form of localized metal attack and sometimes cannot be detected by simple visual examination. 

Pitting corrosion is a highly nonuniform type of corrosion wherein there is highly localized attack in a small area that results in the formation of pits on the surface of the corroding metal. Pitting corro-... 

Microorganisms tend to attach themselves to solid surfaces, colonize, proliferate, and form biofilms which may in turn produce an environment at the biofilm/metal interface radically different from the bulk environment in terms of pH, dissolved oxygen, organic and inorganic species. Since the biofilm tends to create nonuniform surface conditions, localized attack might start at some points on the surface leading to localized corrosion, usually in the form of pitting [22]. 

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