Cement-modified enamel coating for enhanced corrosion resistance of steel reinforcing bars

The corrosion performance of smooth steel rebar coated with pure enamel, mixed enamel, and double enamel, and embedded in mortar cylinders were quantified in 3.5 wt.% NaCl solution using open-circuit potential (OCP), linear polarization resistance (LPR), and electrochemical impedance spectroscope (EIS) tests over a period of 173 days. The mixed enamel was prepared by adding calcium silicate contained in cement into the pure enamel. The double enamel consisted of an inner pure enamel layer and an outer mixed enamel layer. Results indicated that after 27 days of immersion, corrosion initiated and was rapidly developed in uncoated and the mixed enamel coated specimens. Although the OCP indicated a high likelihood of corrosion initiation, the pure enamel and double enamel coated rebar had significantly lower corrosion current densities, and thus remained in passivity throughout the entire test period. This behavior was further verified by the forensic study and EIS results.