cathodic protection

Definition

Method of protection for iron and steel against electrochemical corrosion. Two types of cathodic protection are: (1) Active, in which a low voltage (usually 40 to 50 volt) direct current is imposed between the exposed parts of a structure and the ground. (2) Passive, in which an anode (positive electrode) made of a more reactive metal (such as a magnesium alloy) is sacrificed to protect a structure acting as a cathode (negative electrode). Also called sacrificial protection. Cathodic protection is the most widely applied anti-corrosion control technique in electrolytically conducting environments such as seawater and soils containing water. Invented in 1824 by the UK scientist Sir Humphrey Davy (1778-1829) to protect the copper-cladded wooden ships from seawater corrosion. See also anodic protection.