Threshold Chloride Concentration of Stainless Steels in Simulated Concrete Pore Solution

To evaluate whether stainless steel can replace carbon steel as rebar in reinforced concrete structures exposed to aggressive environment, the threshold chloride concentration of carbon steel, austenitic and duplex stainless steels were experimentally studied in this paper. The solutions with pH ranging from 9.5 to 13.6 were used herein to simulate the pore liquids in both alkaline and carbonated concretes. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were carried out in the solutions with chloride concentration ranging from 0 to 5.0M and at a temperature around 25°C. The activation of pitting corrosion was determined when corrosion current increased and polarization resistance decreased significantly. The test results show that the pH value has a great effect on the evolution of the film resistance, and stainless steels have much higher corrosion resistance than carbon steel subjected to chloride environments.