pH Effect of Natural Gas Hydrate on X80 Steel Solid—Liquid Phase Scouring Corrosion

[Image: see text] In order to solve the problem of pipeline erosion–corrosion under acidic conditions with different CO(2) contents of natural gas hydrate (NGH), the influence of different pH values on the erosion corrosion of X80 steel under dynamic conditions was studied. The erosion and corrosion behavior of X80 pipeline steel in multiphase flow (0.5% sand + 3% NaCl aqueous solution) at different pH was studied by rotating a cylindrical electrode apparatus combined with the electrochemical method in this paper. By analyzing the electrochemical impedance spectroscopy of the Tafel curve, the results showed that under dynamic solid–liquid two-phase conditions, with the decrease of the pH value, the self-corrosion potential of X80 steel samples was positively shifted, and the corrosion current density showed a trend of gradually increase. When the pH value is 2.0–3.0, the ac impedance spectrum of X80 steel samples shows a reactance arc in the high-frequency region and an inductive reactance arc in the low-frequency region. With the increase of the pH value, the radius of the capacitance and resistance arc of the impedance spectrogram increases gradually, and the time of the Bode spectrogram is “half peak” in the low-frequency region. As the time constant increases, the impedance decreases and the phase angle decreases; the overall polarization resistance R(p) on the surface increased gradually and the corrosion rate decreased significantly. Therefore, the pH value of the content of NGH with different CO(2) contents has obvious influence on the solid–liquid two-phase erosion corrosion of X80 steel. With the increase of the pH value, the corrosion resistance of X80 steel increases, the corrosion rate decreases, and the corrosion strength decreases.