Effect of cathodic protection potential change caused by alternating current interference on corrosion behavior of X90 steel in 3% NaCl solution

Cathodic protection (CP) is a key method widely used in corrosion protection of buried pipelines. However, under the condition of AC interference, the cathodic potential on the pipeline will change significantly, which will lead to serious corrosion of the pipeline. In this paper, the corrosion behavior of X90 steel under the changing CP potential caused by AC interference was studied by corrosion rate, corrosion morphology and polarization curve. The results showed that the larger the applied AC current density was, the more seriously the CP potential changed. The general corrosion rate and pitting rate of X90 steel increased linearly with the increase of change degree of CP potential, and the severity of surface corrosion was much greater than under the AC current density, showing the DC corrosion characteristic. The negative deviation of the corrosion potential of X90 steel was positively proportional to the change degree of the CP potential of X90 steel, and the corrosion current density was consistent with the general corrosion rate. Moreover, the anode control degree was much higher than that under the AC current density, which was mainly caused by the increase of galvanic cells on the surface corrosion.