The impact of the interruption of impressed current cathodic protection on the steel/concrete interface

The corrosion of steel reinforcement in concrete structures is a global problem causing billions of dollars to be spent in repairs and maintenance to keep structures in a safe and functional state. Amongst the several techniques used to tackle this problem, Impressed Current Cathodic Protection (ICCP) has proven to be an effective method of stopping ongoing corrosion and preventing it from occurring in the future. Recent studies have shown that once passivity of steel is achieved, the applied current can be interrupted but yet be able to offer residual protection. A project is underway to study the duration of this residual effect and how it varies with the total amount of charge passed through the system. This paper reports on preliminary trial experiments which monitor a number of parameters, including, steel potential, current, pH, relative humidity and temperature at the steel/concrete interface before, during and after the application of cathodic protection.