AC Corrosion Electrode Process of X90 Steel Based on Equivalent Circuit Model

The change law of corrosion potential and real-time potential waveform of X90 steel under the action of alternating current was clarified by electrochemical test; an equivalent circuit model including anodic electrode process and cathodic electrode process was established and solved by Multisim. By analyzing the effects of anodic and cathodic charge transfer resistances (R_a, R_c) and electric double layer capacitance on AC corrosion potential and anodic and cathodic Faradaic currents (I_a, I_c) and non-Faradaic currents (I_dl), the effects of electrode process kinetic parameters on AC corrosion were analyzed. The results showed that with the increase of AC density, the degree of negative shift of corrosion potential of X90 steel first increased and then decreased, and reached the minimum value when the current density was 100 A/m². The real-time potential waveform had the same frequency and waveform as sinusoidal AC interference. As Ra increased, the Faradaic current through both the anodic and cathodic processes gradually decreases When the anodic process and the cathodic process had different charge transfer resistances, a rectification effect would occur when the alternating current passes through the corrosion electrode, causing a DC bias in the waveform of the real-time potential, causing the corrosion potential to shift. Compared with the charge transfer resistance, the electric double layer capacitance had a more obvious effect on the corrosion process of the electrode under the action of alternating current.