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Abstract

Chloride induced corrosion of steel in concrete is a major threat to the construction industry leading to the premature failure of concrete structures. Electrochemical injection of corrosion inhibitor (EICI) into concrete is a promising technique for existing concrete structures, which can serve as a rehabilitative measure to retard or reduce rebar corrosion. An attempt has been made to evaluate the effectiveness of a hybrid inhibitor formulation injected into chloride contaminated concrete. The optimised current density of 0.5 A/m2 was found to be a minimum requirement with maximum efficiency. During EICI, the amount of free chloride removed from cover concrete was also tested. The mechanism of inhibitive action was established through FTIR, SEM, EDAX and MIP studies.

4. Conclusions

Electro injection of organic corrosion inhibitors into the concrete revealed the following conclusions.  Rebar potential measurements after EICI treatment indicated passive condition of the rebar even though the chloride content strongly reduced the passive film on steel surface.  Potentiodynamic polarization technique proved that the EICI treatment is able to shift the rebar potential (þ300 mV) towards passive region with the result the corrosion rate of rebar also reduced considerably.  Electrochemical impedance studies indicated that systems after EICI showed a 5 fold increase in Rct values when compared to system before EICI.  Analysis of free chloride contents proved that the removal of chloride at the steel-concrete interfacial region is an added advantage during EICI treatment.  FTIR studies indicated that the functional group of the inhibitors namely -NH2, C–H and C≡C move towards the cathode of embedded rebar and adsorbed on the metal surface and thereby provide inhibition.  SEM analysis indicated that the hybrid inhibitor formulation act as pore blocking agent.  MIP studies proved that nearly 50% reduction in porosity was observed for concrete samples after EICI.