EIS analysis on the corrosion resistance of X80 steel under AC interference in simulated soil solution

In this work, the corrosion mechanism of X80 steel under AC interference was studied with electrochemical measurements. The surface potential was monitored at various AC current densities. EIS (electrochemical impedance spectroscopy) measurements were conducted at various AC voltage amplitudes and for various time durations. Variations in the modulus values of the real part and imaginary part were studied. In addition, to simplify the problem, EIS was measured under the effect of various DC potentials. The surface potential was of the same frequency as the AC interference, and the amplitude of the electrode surface potential was linear with the applied current density. As the AC current density increased, the charge transfer resistance decreased due to the acceleration of both the anodic and cathodic processes. When the AC current density reached a certain value, hydrogen and oxygen evolution occurred because the effective Faraday potential exceeded the corresponding critical reaction potential. With an increasing AC time, the charge transfer resistance increased, which was due to the formation of a protective corrosion product film. With the application of low-amplitude AC voltages, there was only a small change in the capacitance of the electric double layer. Nevertheless, with the application of AC voltages at higher amplitudes, the modulus values of the real and imaginary parts of EIS were all less rapid, and the ratio of the imaginary part and real part decreased.