Ferrous Carbonate Precipitation Kinetics and Its Impact CO2 Corrosion

Abstract

Abstract Recent evidence indicates that ferrous carbonate (FeCO3, siderite) plays a critical role in forming corrosion resistant scale. The temperature dependent precipitation kinetics of ferrous carbonate were studied using a powerful new "temperature ramped" approach. The activation energy calculated using a second order precipitation model (123 kJ/mol) qualitatively indicates that precipitation was controlled by surface reaction rate over the temperature interval studied. At low temperatures (<60 C), precipitation is expected to progress more slowly than corrosion reactions. At elevated temperatures (>175 C), transport limited ferrous carbonate deposition should be limited by the corrosion reaction. Corroding surfaces may be immediately passivated by FeCO3 precipitation at high temperature. At intermediate temperatures, ferrous carbonate may drive the corrosion reaction by removing iron from solution at approximately the same rate as it is provided by corrosion. The techniques developed in this research could easily be adapted for use with a number of other reduced metal systems.