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This experimental field study interrupted the protection current offered by Impressed Current Cathodic Protection (ICCP) to ten in-service reinforced concrete structures. The study aimed to identify the long term effects of ICCP after it was recognised that some of the systems are now reaching the end of their design life and require a significant level of maintenance. It was found that after five or more years of ICCP, the steel remained passive for at least 24 months after interrupting the protection current despite chloride contamination that would represent a corrosion risk.

The corrosion of steel reinforcement in concrete structures induced by chloride ion contamination is a major problem. Deterioration starts with the loss of protection provided by the concrete cover as the result of chloride ingress. This is followed by corrosion initiation and then propagation. Recent advances in models of chloride penetration into concrete, based on mathematical models of the physical transport processes and an analysis of empirical data, have been made. Inhibitive and aggressive properties of solid phases present at the steel which affect corrosion initiation have been identified. Improved methods have been developed to monitor corrosion rates as well as chloride ingress into the concrete cover. An improved understanding of the deterioration processes has led to new developments in repair techniques.Prog. Struct. Engng. Mater. 2000; 2: 448d458