Effect of carbonation on the electrochemical behavior of corrosion resistance low alloy steel rebars in cement extract solution

Abstract

In this paper, cyclic voltammetry technique, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Mott-Schottky measurement combined with surface morphology observation were applied to investigate the electrochemical behavior of carbon steel (CS) and three Cr modified low alloy steels in the carbonated cement extract solution. Results show that pH plays an important role in the formation of passive films on steel rebars. In non carbonated cement extract solution, corrosion behaviors of CS and Cr modified steel vary slightly, and Cr addition brings down the amount of defects in passive film. In carbonated cement extract solution, pitting potential shifts negatively as pH value decreases. Polarization resistance declines and the density of the current carrier in the passive film increases. With Cr content increasing, corrosion current density declines; pitting potential, polarization resistance and passivation range are magnified. Besides, the effect of Cr is more significant in lower pH. The good-to-poor sequence of corrosion resistance is: 5Cr>3Cr>1.5Cr>CS, and 5Cr steel possesses the best corrosion resistance.