Galvanic effects induced by siderite and cementite surface layers on carbon steel in aqueous CO2 environments

Siderite (FeCO3) and cementite (Fe3C) layers develop naturally on carbon steel surfaces in aqueous dioxide (CO2) environments. This study evaluates galvanic corrosion induced by such when coupled to bare steel. In CO2-saturated, 50 °C, pH 5 conditions, the Fe3C-filmed acted as net cathode, significantly enhancing rates. Galvanic currents FeCO3-filmed were much lower, with FeCO3 removed from surface Fe3C was revealed concomitantly It is proposed that presence of amongst layer responsible for interaction, rather than itself.