23Corrosion, Cathodic Protection
23.1 Process of Corrosion and Cathodic Protection
Cathodic protection [1,2] is an electrochemical practice for preventing corrosion of metallic structures exposed to a natural electrolyte, either submerged or buried. NACE is the worldwide corrosion authority and place to study. The process involves application of DC electrical current to the metal surface from an external source. Cathodic protection essentially means reduction or total elimination of natural corrosion on metal surface by forcing the metal to become cathodic.
Electrochemical corrosion takes place when two different metals come in contact with a conductive liquid (electrolyte). The current flows from the anodic metal through the liquid or moist soil to the cathodic metal. Anodic metal gets to be corroded, while the cathodic metal steel structure is protected from corrosion. Whenever electrical current leaves an anode to enter the electrolyte, small particles of iron are dissolved into solution, causing pitting at the anode. When current enters the cathode, molecular hydrogen gas is formed on the surface to preserve ...
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