Influence of Unsupported Concrete Media in Corrosion Assessment for Steel Reinforcing Concrete by Electrochemical Impedance Spectroscopy

This work aims at studying the response of unsupported concrete media by Electrochemical Impedance Spectroscopy (EIS) and its influence in the results obtained for steel corrosion in reinforced concrete samples. Measurements carried out in full immersed samples correspond to a typical electrolyte media, presenting essentially a resistive behavior. Thus, rebar corrosion, which appears commonly at intermediate frequency region, can be assessed and easily interpreted.For samples in partial dry conditions the spectra show several time-constants distributed across the entire frequency range. In the high frequency region, the time constant is ascribed to dielectric properties of the system. At low frequencies the time constant corresponds to the ionic depletion, while the time constant at intermediate frequencies result from charge separation inside the material bulk, typically of unsupported media. Interpretation of the results obtained by EIS for concrete reinforced steel in partial dry conditions cannot be fully interpreted without considering the dielectric behavior of the system.