Failure Causes of Impressed Current Cathodic Protection in a Large Station

After the cathodic protection system of a large station had been in orperation for a period of time, the qualified rate of cathodic protection potential decreased greatly. The causes of the failure of the cathodic protection were analyzed from output parameters of potentiostat, soil resistivity, surface morphology of prepackaged high silicon cast iron anode and grounding resistance of anode. The results show that the soil where the anode was buried was relatively dry, so the soil resistivity was high. The dense oxide on the anode surface and the gravels in soil increased the contact resistance between anode and soil. The above-mentioned reasons led to the increase of loop resistance of the whole system. The loop resistance of the anode could be reduced by watering and using non-pre-packaged anodes.