Mechanisms of Enhancing the Corrosion Resistance of Rebar in Chloride-Contaminated Concrete

Abstract Research relating to the performance of reinforcement in concrete usually deals with factors affecting damage to the concrete matrix, protection and repair techniques, and ways to assess corrosion rates and determine the life time of a reinforced concrete structure. However, little is known about the electrochemistry of passivity breakdown on iron and its alloys in concrete, although much is known about this phenomenon on metals in contact with homogeneous aqueous environments. The Point Defect Model (PDM) for the growth and breakdown of passive films has been developed as a general model for passivity breakdown on metals in aqueous solutions and has been shown to accurately describe the processes that lead to growth of the passive film on metals and the mechanisms by which passivity breakdown occurs. The PDM is adapted and used here, for the first time, to describe the initiation of corrosion due to chloride ion on steel bars embedded in concrete. The theory describes the role of alloying elements and inhibitors in enhancing the resistance of alloys to passivity breakdown, and has allowed us to formulate the principles of designing corrosion resistant materials for use in concrete environments.