In order to solve the problem of pipeline erosion–corrosion under acidic conditions with different CO₂ 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 CO₂ 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.

中文翻译：

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天然气水合物的pH对X80钢固液冲刷腐蚀的影响

为了解决酸性条件下不同CO ₂的管道腐蚀问题研究了天然气水合物（NGH）的含量，动态条件下不同pH值对X80钢腐蚀腐蚀的影响。本文通过旋转圆柱电极装置结合电化学方法研究了X80管线钢在多相流（0.5％砂+ 3％NaCl水溶液）中在不同pH下的腐蚀和腐蚀行为。通过分析Tafel曲线的电化学阻抗谱，结果表明，在动态固液两相条件下，随着pH值的降低，X80钢样品的自腐蚀电位正向偏移，腐蚀电流密度呈逐渐增加的趋势。当pH值为2.0–3.0时，X80钢样品的交流阻抗谱在高频区域显示一个电抗电弧，在低频区域显示一个感应电抗电弧。随着pH值的增加，阻抗谱图的电容半径和电阻弧逐渐增大，并且Bode谱图的时间在低频区域为“半峰”。随着时间常数的增加，阻抗减小，相角减小。整体极化电阻表面的R _p逐渐增加，腐蚀速率明显降低。因此，不同CO ₂含量的NGH的pH值对X80钢的固液两相侵蚀腐蚀有明显的影响。随着pH值的增加，X80钢的耐蚀性增加，腐蚀速率降低，腐蚀强度降低。