الفهرس 
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Abstract
Corrosion of metals is defined as the spontaneous destruction of metals in the
course of their chemical, electrochemical or biochemical interaction with the
environment. Corrosion cause waste of natural resources (1) since an appreciable
fraction of all metals produced from the remaining deposits of commercially
unstable ore is dispersed and lost in the form of corrosion products.
I. Principles •IOf Corrosion
Metals undergo chemical reaction with non-metallic elements in their
environment (2), producing chemical compounds that are either oxides or salts,
commonly known as corrosion products. These compounds may accelerate, impede,
or have no influence on the course of corrosion. The character of these compounds
particulary their solubilities in the surrounding medium, their position with
reference to the metal surface, and their physical properties will have considerable
influence on the course of the reactions. If these substances are highly insoluble and
deposited as an impervious film in ultimate contract with the metllic surface,
Surface, the corrosion reaction may be retarded or stopped, if soluble or not
precipitated on the surface, the rate of corrosion will be unaffected, and if only part
of the surface is covered with corrosion products the action may be accelerated in
the uncovered areas producing pitting.
11. Types Of Corrosion
i. Localized Corrosion
Pitting and cervice corrosions are electrcchemical in nature and result in loss
of metal at localized anodic areas. The pitting anodic area occurs as the result of
localized breakdown of a film at the surface or by mechanical or chemical action.
Pitting corrosion may occur in any metal but the most common and spectacular.