Galvanic Interactions of 15CDV6/MDN138 & 15CDV6/MDN250 Alloys in Natural Seawater

Abstract

The galvanic corrosion behavior of the metal combinations 15CDV6/MDN138 and 15CDV6/MDN250, with 1:1 area ratio, has been studied in natural seawater using the open well facility of CECRI’s Offshore Platform at Tuticorin for a year. The open circuit potentials of MDN138, MDN250, and 15CDV6 of the individual metal, the galvanic potential and galvanic current of the couples 15CDV6/MDN138 and 15CDV6/MDN250, were periodically monitored throughout the study period. The calcareous deposits on MDN138 and MDN250 in galvanic contact with 15CDV6 were analyzed using XRD. The electrochemical behavior of MDN138, MDN250, and 15CDV6 in seawater was studied using an electrochemical work station. The surface characteristics of MDN138 and MDN250 in galvanic contact with 15CDV6 have been examined with a scanning electron microscope. The results of the study reveal that the galvanic protection offered by 15CDV6 to MDN250 and MDN138 in natural seawater amounts to 93% and 98%, respectively, implying that the galvanic protection offered by 15CDV6 is continuous and effective, which has been further evinced from the adherent nature of the calcareous deposit film comprising compounds such as CaCO₃ (calcite, aragonite, and vaterite), MgCO₃ (magnesite), Mg(OH)₂ (brucite), and MgO (brucite).

Keywords

MDN138 / MDN250 / 15CDV6 / Galvanic corrosion / Natural seawater