Effect of Alternating Current and Cathodic Protection on Corrosion of X80 Steel in Alkaline Soil

X80 steel was buried in alkaline soil for 0.5, 1, and 2 years under conditions of natural burial, alternating current interference, and cathodic protection. The morphology and influence mechanism of X80 steel corrosion under nine different test conditions were studied through field data collection, macroscopic morphology observation, weight loss analysis, electrochemical methods, and corrosion product analysis. The results show that the rate of corrosion of X80 steel decreased with increase in the burial time under different test conditions. The corrosion rate of X80 steel under 15 V_CSE and 30 V_CSE alternating current interference increased at least 4.66 and 4.73 times, respectively, compared with that under natural environment. At the same time, the corrosion morphology exhibited more numerous and deeper pits. Under the cathodic protection of Mg or Zn, the corrosion rate of X80 steel decreased noticeably, whether under natural environment or under alternating current interference. The cathodic protection efficiency of Mg and Zn was higher than 76.04% under different test conditions and periods. The corrosion products of X80 steel were mainly found to be α-FeOOH and γ-FeOOH, and the overall structure of the rust layer was relatively stable. Moreover, the resistance of the rust layer on the sample surface under cathodic protection was small, which indicates that cathodic protection can effectively alleviate alternating current corrosion.