A Study Of Corrosion Inhibitors For Bidi-rectional Electromigration Rehabilitation

Chloride-induced corrosion of carbon steel reinforcement is the most important cause of premature failure on reinforced concrete structures. Bidirectional electromigration rehabilitation for chloride-contaminated reinforced concrete structures, combined with the advantages of electrochemical chloride removal (ECR) and migrating corrosion inhibitors (MCI), is very promising means to prevent this rapid deterioration. Compared with traditional repair methods, bidirectional electromigration rehabilitation are less costly, more effectively, more friendly to the environment. The aim of this paper is to find out one or two corrosion inhibitors for bidirectional electromigration rehabilitation. Six amine-based inhibitors, triethylentetramine, dimethylamine, N, N-dimethylethanolamine, ethanolamine,1,6-hexanediamine, guanidine, were studied both in chloride-contaminated simulated concrete pore solutions and chloride-contaminated reinforced concrete specimens. In order to investigate the effectiveness of six amine-based inhibitors in preventing carbon steel chloride-induced corrosion, corrosion behaviors of steel in different solutions were studied by means of electrochemical potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS). At the same time, the permeability of six amine-based inhibitors, the effectiveness of chloride removal and the change of carbon steel were tested by the organic elemental analyzer, the rapid chloride test (RCT), electrochemical impedance spectroscopy (EIS), weak polarization method and scanning electron microscopy (SEM) in the chloride-contaminated reinforced concrete specimens.The study in simulated concrete pore solutions showed that the effectiveness of amine-based inhibitors was related with the pH value of the solution, inhibitors concentrations and chloride ion concentrations. The results indicated that, the drop of pH value and the increase of chloride ion concentration would result in the decline of corrosion resistance of reinforcing steel in the solution with same inhibitors concentration. At the same inhibitors concentration and chloride ion concentration, different amine-based inhibitors have different inhibiting effect in preventing carbon steel chloride-induced corrosion.The study on the chloride-contaminated reinforced concrete specimens showed that, under the same condition, six amine-based inhibitors had different permeability in concrete. And with different amine-based inhibitors, the effectiveness of chloride removal showed delicate difference. Compared with electrochemical chloride removal, the effectiveness of bidirectional electromigration rehabilitation was weaker. But the content of amine-based inhibitors in concrete pore solutions was twice-seven times than the rest of chloride. It is advantageous for amine-based inhibitors.In addition, electrochemical impedance spectroscopy (EIS) and weak polarization test indicated that, after bidirectional electromigration rehabilitation, the resistance of the concrete cover and the corrosion potential of steel were increased. This means corrosion resistance of steel was improved. But the corrosion current and the corrosion rate of steel were increased. Scanning electron microscopy (SEM) showed that, during the bidirectional electromigration rehabilitation, it is probably that alkaline corrosion occurred on rebar surface. Some time after the operation, with oxygen permeating, the steel may return into passivating state. And it is necessary to do more experiments on the lone-term efficiency of the inhibitors in real structures.