The potential of steel embedded in concrete provides information relative to the thermodynamics of corrosion. However, potentials measured, using a reference electrode placed on the surface of the concrete, can contain misleading information relative to the condition of the steel. Errors can be included in the measurements due to ohmic drop and polarization of the cathodic sites resulting from corrosion (anodic) current flow. In addition, the difference in polarization characteristics of the anode and cathode, when cathodic protection is applied, can make selection of a meaningful cathodic protection criterion somewhat difficult. In this paper, measurements taken utilizing concrete specimens under laboratory conditions are presented. These measurements demonstrate the conditions which affect the selection of the appropriate cathodic protection criterion.
Keywords: Corrosion potential, cathodic protection criteria, concrete, chlorides.