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The AC corrosion behavior of X70 steel under the combined action of cathodic protection and AC interference was studied by the laboratory simulation experiments in two kinds of typical soil simulated environments with different contents of calcium ion (Ca2+), magnesium ion (Mg2+), and sodium ion (Na+). The mechanisms of AC corrosion in different environments were investigated by process parameter monitoring, electrochemical measurement, corrosion morphology, and product analyses. The results showed that the corrosion rate of X70 steel in the simulated environment with higher Na+ content was 2 times higher than that in the simulated environment with higher Ca2+ and Mg2+ content under the same CP potential and AC current density. The reason was analyzed and it was found that the performance of product film, AC current distribution through the double layer interface of steel/electrolyte, and the enrichment of some ions near the interface attributed to AC corrosion rate in different environments. [ABSTRACT FROM AUTHOR]