Effect of AC Interference on the Corrosion Behavior of Pipeline Steel under Disbonded Coatings

The effects of AC interference on the corrosion behavior of X80 steel under disbonded coatings were investigated using electrochemical tests and corrosion morphology observation. The results showed that when there was no AC interference, with the prolongation of test time, only the self-corrosion potentials (E_corr) of the samples at the damaged point and 4 cm away from the damaged point fluctuated slightly, and E_corr of the samples far away from the damaged point had no change, and were basically in a stable state. After AC interference was applied, E_corr of the samples shifted negatively with the increase of the AC interference voltage. The closer to the damaged point, the greater the influence of AC interference on the E_corr of the samples. The corrosion current density (J_corr) of the sample at each point first decreased and then increased, and the J_corr of the sample at the damaged point changed greatly. AC interference increased the corrosion tendency and corrosion rate of the samples under the disbonded coating, and the corrosion rate of the sample at the damaged point was affected greatly, and the corrosion morphology was localized corrosion.