Influence of Cr on reduction behavior of rust formed on low alloy steels in flowing 3. 5% NaCl solution

The reduction behavior of rust layer formed on carbon steel and on Cr- containing steels was investigated in flowing 3. 5mass% NaCl solution via potentiodynamic polarization curve, EPMA, XRD, and XPS. The results show that the weight loss of Cr- containing steels is lower than that of carbon steel. Fe3+ in the rust layer participated in the cathodic reaction with the corrosion process. Cr concentrated in the inner rust layer formed on the experimental steels, and exited in the form of Cr3+. This concentration behavior of Cr increases the corrosion potential of experimental steels and decreases the amount of Fe3O4 in the inner rust layer. Inhibition of reduction of rust results in a decrease of corrosion of metal. Moreover, inhibition of rust reduction suppresses the reduction reaction of oxygen, owing to the decrease of conductivity of rust layer. Therefore, the corrosion resistance of experimental steels can be improved by suppressing the cathodic reaction in flowing 3. 5 mass% NaCl solution.