Electrochemical inhibitor injection for control of reinforcement corrosion in carbonated concrete

This paper describes preliminary investigations into the effectiveness of an electrochemical method of injecting organic base corrosion inhibitors into carbonated concrete containing embedded steel bars on which corrosion had been pre-initiated. The corrosion inhibitors studied were pure compounds of ethanolamine (pK(a) similar to 9.5) and guanidine (pK(a) similar to 13.6). They were injected from aqueous solutions placed in contact with the surfaces of the water-saturated concrete specimens by applying constant current electrolysis between anodes located within the inhibitor solutions and embedded steel bars acting as cathodes. The concentration profiles of the inhibitors penetrating the concrete cover were examined and the influence of the various treatments on the corrosion rates of the embedded steel bars was estimated by linear polarisation resistance measurements, carried out repeatedly during exposure of the treated specimens to cyclic wetting and drying over several months. The stability of the concentration profiles of the inhibitors was evaluated and measurements of corrosion weight losses of the steel bars were also undertaken on completion of the exposure regimes. It was found that the specimens treated with the inhibitors showed significantly reduced corrosion when compared with untreated control specimens that were subjected to similar exposure.