Application of Electrochemical Impedance Spectroscopy in the Evaluation of Corrosion and Cathodic Protection in Reinforced Concrete

The electrochemical behavior of steel reinforcement in conditions of corrosion and cathodic protection (CP) was studied, using electrochemical impedance spectroscopy (EIS) and compared to reference (non-corroding) conditions. Polarization resistance (PR) method and potentio-dynamic polarization (PDP) were employed as well, in addition to AC 2 pin electrical resistance monitoring, thus deriving a comparison of the involved parameters. It was found out that EIS is readily applicable for evaluating electrochemical behavior of the steel surface not only for corroding or passive state, but also in conditions of CP, although the interpretation of derived parameters is not straightforward and is related to the properties of the product layers, formed on the steel surface in the different conditions. The evaluation of the electrochemical behavior of the steel surface, should take into account the crystallinity, morphology and composition of the surface layers, which were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX).