Influence of chloride induced corrosion on the effectiveness of impressed current cathodic protection in reinforced concrete

Chloride-induced corrosion is one of the primary deterioration mechanisms in reinforced concrete infrastructure, for which impressed current cathodic protection (ICCP) is widely applied as a mitigation strategy. Despite its extensive use, ICCP design is typically based on empirical current density values, while in practice both the required current and its spatial distribution are difficult to predict due to the combined influence of corrosion activity, concrete resistivity, and environmental conditions. This study investigates the effectiveness of ICCP under chloride-contaminated and realistic exposure conditions, with a particular focus on the interaction between electrochemical current demand and transport-controlled current distribution. Reinforced concrete slabs with varying chloride contents and cement types were exposed to outdoor Belgian and controlled climate chamber conditions. Corrosion behaviour was characterised using linear polarisation resistance and Tafel analysis, while ICCP performance was evaluated through controlled current application, current distribution measurements, and 24 h depolarisation testing. CP effectiveness is governed by the interaction between corrosion activity and concrete current distribution. Increasing chloride contamination increased corrosion current density, resulting in higher current demand to achieve the 100-mV depolarisation criterion. Higher corrosion activity led to a pronounced current localisation near the anode. High-resistivity concrete limits current penetration, restricting spatial effectiveness. The ratio between applied and corrosion current density provides a useful indicator to interpret polarisation behaviour but does not capture the non-uniform current distribution. Environmental conditions influenced both corrosion kinetics and ionic transport, causing temporal variations in ICCP response. The study provides a realistic insight in ICCP performance under practical exposure conditions.