Effect of Chloride Concentration on the Electrochemical Corrosion of Iron Embedded in Cement-Based Concrete: An Integrated Study Using Electrochemical Techniques

Abstract

This study investigated the electrochemical corrosion behaviour of iron embedded in concrete under control, low-chloride, and high-chloride conditions using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, linear polarization resistance (LPR), and open-circuit potential (OCP) measurements. The results indicated a progressive reduction in impedance with increasing chloride exposure. The approximate low-frequency impedance difference decreased from 67.99 kΩ·cm² in the control to 31.55 kΩ·cm² under low-chloride conditions and 12.57 kΩ·cm² under high-chloride conditions, representing reductions of 53.6% and 81.5%, respectively. The illustrative potentiodynamic parameters showed an increase in corrosion current density from 0.18 µA/cm² in the control to 0.82 µA/cm² and 2.15 µA/cm² under low- and high-chloride conditions, respectively. Similarly, the estimated polarization resistance decreased from 144.4 kΩ·cm² to 31.7 kΩ·cm² and 12.1 kΩ·cm², corresponding to reductions of 78.1% and 91.6%, respectively. OCP measurements revealed potential shifts of −8.59 mV, −38.59 mV, and −28.59 mV over 60 minutes for the control, low-chloride, and high-chloride conditions, respectively, with the high-chloride condition maintaining the most negative potential. Collectively, these trends suggest that increasing chloride exposure reduces the electrochemical resistance of iron in concrete and may promote destabilization of its protective passive film. However, some numerical parameters are illustrative and have not been independently verified against the original experimental measurements. Equivalent-circuit fitting, validated Tafel analysis, and appropriate Stern–Geary calculations are therefore required before definitive corrosion-rate estimates can be established.