Since aqueous corrosion is electrochemical in nature, it is logical that electrochemical techniques can be used in its control. The electrochemical corrosion cell is made up of four essential components: the anode or electrode at which oxidizing processes take place and usually corrosion; the cathode -the electrode surface at which reducing reactions take place and corrosion does not usually occur; the electrolyte—an aqueous solution of ionizable substances; and an electronic conducting path between the anodic and cathodic areas. Whether the metal will corrode or not in specific environments has to do with the thermodynamic stability of the metal and the kinetics of the various processes that take place at the anodic and cathodic sites. Pourbaix has produced diagrams which show domains of immunity, corrosion. and passivity in a plot of solution potential vs pH. Since the equations used in the production of this diagram are thermodynamic equations, interpretation of the diagram shows only the possible, the probable, and the impossible.
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