Corrosion mitigation was evaluated at 80 degrees C in a naturally aerated 30 wt % monoethanolamine (MEA) solution with a CO2 loading of 0.43 mol(CO2)/mol(alkalinity) for a FeCO3-coated A106 carbon steel sample fabricated from solutions of NaHCO3 and piperazine with CO2 loading. The results showed that spontaneous passivation of A106 carbon steel was promoted by this FeCO3 coating, which resulted in a Fe3O4 layer formation. FeCO3 was metastable in this aerated MEA solution and eventually would transform into Fe3O4. Overall, the FeCO3 coating reduced the corrosion rate by a factor of 70. In this case, a semi in situ process to form and/or recover a dense FeCO3 layer to mitigate corrosion in a postcombustion CO2 capture system is proposed. Because of its more environmentally friendly nature, easier process control, and faster FeCO3 coating synthesis, NaHCO3 is recommended as a FeCO3 fabrication solution with respect to a piperazine solution with CO2 loading.