New permanent reference electrode for protection of underground pipelines and storage tanks

Abstract

Copper/copper sulphate electrodes are commonly used as reference electrodes in the cathodic protection of underground pipelines and storage tanks. They require periodic replacement of the internal electrolyte, owing to the seasonal wet/dry cycles of the soil. Also, they experience various problems including: (i) agglomeration of CuSO₄ crystals at the electrode tip resulting in possible loss of the electrochemical connection between the cell and the soil solution; and (ii) leakage of the CuSO₄ electrolyte into the surrounding soil, possibly resulting in the deposition of copper on the steel surface and consequent galvanic corrosion of the protected structure. In the present study, a new reference electrode has been developed in an attempt to: (i) provide quick recovery from dry-out when the soil re-wets; (ii) avoid salt agglomeration; and (iii) prevent accelerated corrosion of the structure as a result of the leakage of electrolyte from the electrode. In the present study, progress towards these goals is reported. It is concluded that metal/metal oxide electrodes with an internal electrolyte of hygroscopic salts would be viable for such applications.