Corrosion mitigation via a pH stabilization method in monoethanolamine-based solutions for post-combustion CO2 capture

A pH stabilization method was investigated to mitigate corrosion in aqueous 5 M monoethanolamine for post-combustion CO2 capture. The room temperature pH of a naturally aerated CO2-loaded solution (i.e., 9.7) was adjusted with NaHCO3 powders to 9.3 and 9.1, and its effect on corrosion of A106 carbon steel was studied. Lower pH initially accelerated corrosion but promoted protective FeCO3 layer formation and subsequently A106 passivation (i.e., Fe3O4 formation). Dissolved oxygen also played a pivotal role by functioning as an additional oxidizer, retarding FeCO3 formation via preferentially oxidizing Fe2+ to form rust, and promoting passivation of A106 under the FeCO3 layer.