The corrosion behavior of X70 steel in simulated soil environment under asymmetric dynamic direct current (DC) interference was studied by immersion tests. The experimental results showed that the negatively asymmetric dynamic DC interference would induce localized corrosion. Under the same dynamic period of 160 ±80 s, when the negative half‐wave current density remained stable at −10 mA/cm² and the positive half‐wave one decreased from 7 to 1 mA/cm², the equivalent diameters of the localized corrosion zones became smaller and the steel samples demonstrated typical pitting corrosion morphologies. To further explore the effect of asymmetric dynamic DC interference on the localized corrosion behavior of carbon steel, a variety of experimental measurements were carried out including real‐time DC potential monitoring, in‐situ near‐surface pH measurements, cyclic voltammetry, and Mott–Schottky tests. It was found that the localized corrosion behavior was probably related to the breakdown of passive film formed on the metal surface exposed to negatively asymmetric DC current generated high pH conditions.

中文翻译：

---

X70钢在非对称动态DC干扰下腐蚀行为的实验研究。

通过浸没试验研究了X70钢在模拟土壤环境中在非对称动态直流电（DC）干扰下的腐蚀行为。实验结果表明，负不对称动态直流干扰会引起局部腐蚀。在160±80 s的相同动态周期下，当负半波电流密度保持稳定在-10 mA / cm ²时，正半波电流密度从7 mA降至1 mA / cm ²，局部腐蚀区的当量直径变小，钢样品表现出典型的点蚀形态。为了进一步探讨不对称动态直流干扰对碳钢局部腐蚀行为的影响，进行了各种实验测量，包括实时直流电势监测，原位近表面pH测量，循环伏安法和Mott-肖特基测试。发现局部腐蚀行为可能与暴露于负非对称直流电流产生的高pH条件的金属表面上形成的钝化膜的破坏有关。