الفهرس 
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Abstract
Pitting is a form of an extremely localized attack that results in holes in the metal • These holes may be small or large in diameter, but in most cases they are relatively small. Pits are sometimes isolated or so close together that a rough surface appears. Generally a pit may be described as a cavity or hole with the surface diameter almost same as its depth. Pitting is one of the most destructive and insidious forms of corrosion. It causes equipment to fail because of perforation with only a small percent weight loss of the entire structure. It is often difficult to detect pits because of their small size and because the pits are often covered with corrosion products. Pits usually grow in the direction of gravity. Most pits develop and grow downward from horizontal surfaces; lesser number start on veritical surfaces.
Pitting may be considered as the intermediate stage between general overall corrosion and complete corrosion resistance. It is the extreme of heterogeneous corrosion of all types of corrosion.