Threshold chloride level and characteristics of reinforcement corrosion initiation in simulated concrete pore solutions

Threshold chloride level (Cth) and corrosion behavior of reinforced steel bar (rebar) have been studied in three kinds of simulated concrete pore solutions (SPSs). The rebars with two different surface conditions were immersed in SPSs and open circuit potential (OCP) and linear polarization resistance (LPR) were monitored with stepwise chloride addition. Different electrochemical techniques for Cths and rebar corrosion initiation of all cases are discussed and compared with results from the literature. The results indicate that Cths acquired from both OCP and LPR techniques are relatively consistent. Cths, represented by the threshold expression [Cl−] or [Cl−]/[OH−], exhibit an increasing trend with increasing SPS pH. Corrosion resistance of both sandblasted and prerusted bars can be improved by raising the pH of the SPS solution; the extent of improvement is more pronounced for sandblasted bars. Once initiated, severe pit corrosion occurs on sandblasted bars with more abrupt OCP and corrosion current density variation exhibited.

► Threshold chloride levels determined by OCP and LPR are in good agreement.
► [OH−] inhibits rebar corrosion on the entire simulated pore solution pH range.
► Once initiated, more severe pit corrosion on sandblasted than pre-rusted bars.