(Keynote) The Electrochemical Behavior of an Inhibitor Containing Ce³⁺ for a Low-Alloy Steel in a 3.5% NaCl Solution

The effects of Ce3+ ions on the electrochemical behavior of a low-alloy steel in a 3.5% NaCl solution were investigated by polarization curves in conjunction with EIS spectra. The results show that Ce3+ ions were beneficial to promoting the anodic passivation and improving the performance of the inhibitory film. The inhibitor containing Ce3+ was an anodic inhibitor with the inhibitory efficiency of 94.0%. The net-shaped film formed on the surface of low-alloy steel in a 3.5% NaCl solution with the inhibitor containing Ce3+ was observed. The EIS spectra of the low-alloy steel in a 3.5% NaCl solution with the inhibitors were composed of a capacitive loop at high frequency region and an inductive impedance loop at low frequency region and there were two time constants. The charge-transfer resistance (Rt) increased with immersed time. And that the charge-transfer resistance (Rt) of the inhibitor containing Ce3+ was higher than that of the inhibitor containing no Ce3+. Therefore, the inhibitor containing Ce3+ had a higher inhibitory efficiency than the inhibitor containing no Ce3+. Simultaneously, based on the EIS spectra, the equivalent circuit was developed. Finally, The EIS spectra were fitted by Simplex method with the equivalent circuit. It was found that all electrochemical parameters of the equivalent circuit increased with immersed time, indicating that the inhibition efficiency of the inhibitor increased with immersion time. As regards the equivalent circuit, if the equivalent resistance (R0) and the inductive impedance (L) would increase enough with the immersion time, EIS spectra would have a capacitive loop with one time constant. In this case, the inhibitory film on the electrode surface become more and more uniform and integrated.