Electrochemical Investigation of Chloride-Induced Corrosion of Steel Reinforcement in Reinforced Concrete under Accelerated Laboratory Conditions

Abstract

Chloride-induced corrosion of reinforcing steel is one of the principal causes of premature deterioration and reduced service life of reinforced concrete structures exposed to aggressive environments. This study experimentally investigated the electrochemical behaviour of steel reinforcement embedded in concrete subjected to accelerated chloride exposure under laboratory conditions. Reinforced concrete specimens (100 × 100 × 100 mm) containing centrally embedded 12 mm diameter steel bars were prepared using a water–cement ratio of 0.45 and exposed to 0%, 1%, 3.5%, and 5% NaCl solutions for 28 days. Corrosion behaviour was evaluated using open circuit potential (OCP), half-cell potential (HCP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS), while compressive strength and surface morphology were also assessed. The compressive strength of the control specimens increased from 39.8 ± 0.9 MPa at 7 days to 46.7 ± 1.1 MPa at 28 days, whereas specimens exposed to 5% NaCl exhibited a lower 28-day strength of 40.9 ± 1.2 MPa. OCP values decreased from −125 ± 6 mV initially to −478 ± 19 mV after 28 days in the 5% NaCl specimens, while HCP values reached −501 ± 21 mV, indicating a greater than 90% probability of active corrosion. Corrosion current density increased from 0.36 to 4.18 µA/cm², whereas charge transfer resistance decreased from 82.7 to 12.9 kΩ, confirming significant electrochemical deterioration. Visual examination revealed progressive rust formation, pitting corrosion, longitudinal cracking, and steel mass loss increasing from 0.3% in the control specimens to 9.7% under 5% NaCl exposure. Correlation analysis showed a strong inverse relationship between corrosion current density and compressive strength (r = −0.971). The results demonstrate that increasing chloride concentration substantially accelerates reinforcement corrosion and that integrated electrochemical techniques provide reliable tools for assessing corrosion progression and predicting the durability of reinforced concrete structures.