Laboratory Tests on a Potential Probe with Zinc Reference Electrode for Monitoring of Cathodic Protection

Abstract Cathodic protection (CP) conditions of a metallic structure are verified by checking that the protection potential matches the protection criteria. Nowadays commercial probes are available to perform correct potential reading, eliminating the ohmic drop contribution. In this paper, a new probe with zinc reference electrode (Zn-RE) is proposed. Indeed, zinc is a promising material due to the low overpotential in active condition and the high exchange current density. Laboratory tests were carried out to select the composition of a suitable backfill of the probe and to verify the stability of Zn-RE during continuous monitoring of CP. As regard backfill composition, mixtures of gypsum-clay-cellulose and additives were tested with water absorption, electrolytic conduction and mass loss tests. Two mixtures were adopted to prepare potential probes with incorporated Zn-RE. CP tests were performed in soil-simulating environment for 40 days. Tests indicated that Zn-RE shows a good stability during continuous monitoring of CP.