Reducing Corrosion Rate for Electric Water Heater in Welding Joints by Using Sacrificial Anodes

Abstract

Corrosion represents one of the major challenges confronting companies under the Ministry of Industry and Minerals, including the General Company for Electrical Industries, which manufactures electric water heaters typically made of galvanized iron. During the production process, components of the heater are joined using arc welding, where the heat generated during welding causes the removal of the galvanization layer in the welded areas. This results in the development of electrochemical potential differences between galvanized and non-galvanized regions, leading to the formation of localized anodic and cathodic zones. Consequently, electrochemical reactions are initiated, involving the flow of electrons from the anodic to the cathodic regions in the presence of a conductive medium (water), thereby accelerating the corrosion process in the welded zones. In this research, a linear polarization system (Potentiostat MLab-200) was employed to measure the corrosion current density (Icorr) and corrosion potential (Ecorr), followed by the calculation of corrosion rates at various temperatures 30, 40, 50, 60, and 70°C under conditions simulating the actual operation of an electric water heater. The results indicated that the corrosion rate of galvanized iron prior to welding was approximately 2.0 mpy at 70 °C, whereas it increased to 3.0 mpy after welding at the same temperature. To mitigate this corrosion, a sacrificial zinc anode was introduced into the heater system, which reduced the corrosion rate to 1.9 mpy at 70°C. This implementation contributed to prolonging the service life of the heater and enhancing its operational efficiency.