CORROSION THEORYDOE-HDBK-1015/1-93CorrosionCH-02Rev. 0Page 10Corrosion Theory Summary (Continued)The reduction step of the oxidation-reduction process is where a positively-charged ion gains electron(s). The reduction step for most metals,in an aqueous environment, is the reduction of hydronium ions. An example ofthe reduction step is:H O + e H + H O3 2+ -Passivity is the buildup of a stable, tenacious layer of metal oxide on the surfaceof the metal that acts as a barrier separating the metal surface from theenvironment. Passivity decreases or stops the corrosion process because of theformation of the layer.Polarization is the decrease in cell potential caused by the operation of theelectrochemical cell. Polarization can be in two forms; concentration oractivation. Concentration polarization is associated with the concentration ofions in solution which shields the metal, thereby causing a decrease in theelectrical potential of the cell. Activation polarization is the formation of a layercontaining absorbed hydrogen atoms that block the metal's surface from thecorrosion process.
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
