Galvanic corrosion of carbon steel under concentration cell formation in MgCl2 solution as an inorganic pollutant and the effect of flow velocity

Abstract

Abstract The wastewater of petroleum refineries consists of various corrosive pollutants that are harmful not only for human and living organisms but also for the equipment and materials exposed to it. The galvanic corrosion of carbon steel in MgCl2 solution as a pollutant in petroleum refinery wastewater was studied under concentration cell formation. The influence of different operating parameters on the galvanic corrosion established by concentration cell was studied, and the concept of concentration cell corrosion was examined and discussed versus experimental results. The effects of some operating conditions on the galvanic behavior, such as the concentration of MgCl2 (0–2500 ppm) and solution flow velocity (150–1000 rpm), on corrosion rate, corrosion potentials, and corrosion current were investigated. New findings regarding the effect of corrosive substance concentration and the hydrodynamics on the corrosion rate of each electrode and the galvanic current were reported. It was found that the corrosion rate of carbon steel in both cell poles increases with increasing MgCl2 concentration in both free and galvanic corrosion. Increasing MgCl2 concentration also led to an increase in the galvanic currents and the corrosion rate of the two electrodes. The flow velocity in either cell terminal considerably influences the potentials, corrosion rates of both electrodes, and the galvanic current passing in the cell. A high flow velocity in the compartment with the more negative potential caused polarity reversal on some occasions.