Characterization of corrosion behaviors of steel in concrete by time and frequency domain electrochemical methods

Corrosion behaviors of the steel embedded in ordinary Portland concrete (OPC) and high performance concrete (HPC) specimens, before and after the exposure to NaCl solution for 360d, were investigated by using three kinds of time or frequency domain electrochemical methods, that is, linear polarisation resistance (LPR), electrochemical impedance spectroscopy (EIS) and galvanostatic pulse method (GPM) in this study. Three electrochemical parameters: concrete resistivity, polarization resistance and double layer capacitance which are related with steel corrosion were extensively compared. The results indicated that the corrosion behaviors of steel in OPC and HPC specimens before and after the exposure were different due to the varying corrosion rate-limiting determinants (pH value of concrete pore solution, resistivity and permeability of concrete cover). These three electrochemical methods are all capabling of representing steel corrosion state with good correlation.