Assessment of cathodic protection applied to above ground reinforced concrete

Abstract

Standard practice allows the use of developing expertise in the assessment of cathodic protection of steel in concrete. This work sets out a theoretical and empirical basis for such an assessment. Assessment may be based on the observation that, at protection current densities typically used in reinforced concrete, the degree of polarization provides an indication of steel corrosion risk. An example is, a steel polarization of 55 mV or more achieved by a protection current of 5 mA m−2 or less is indicative of passive steel reinforcement. Such risk assessment criteria are supported by both theory and practice. Polarization is generally a consequence, not a cause, of steel passivity in concrete. The removal of chloride from, or the generation of hydroxide at the steel surface dominate the restoration of steel passivity. Flexibility over the degree of polarization required in cathodic protection systems may be used to address adverse effects associated with the delivery of protection current.