Understanding the corrosion of CO2-loaded 2-amino-2-methyl-1-propanol solutions assisted by thermodynamic modeling

• Corrosivity of AMP is investigated with SEM, XRD, FIB and thermodynamic modeling.
• Liquid phase speciation was determined by employing an electrolyte-NRTL model.
• HCO3− concentration plays an important role in the formation of protective FeCO3.
• FeCO3 is metastable in amine solution with dissolved O2 and passivation occurs.
• Lower corrosion occurs in AMP than in MEA due to faster FeCO3 & Fe3O4 formation.

Corrosion of A106 carbon steel in a naturally aerated 30 wt.% 2-amino-2-methyl-1-propanol-based solution (AMP, a sterically hindered primary amine) with 0.43 molCO2/molAMP was evaluated at 80 °C. Substantial decrease in corrosion rate, i.e., over two orders of magnitude, was observed over the initial 70 h, which is the result of formation of a protective FeCO3 layer followed by passivation of the A106 surface. Mechanisms for formation of these protective layers are discussed with comparison to corrosion in a 30 wt.% monoethanolamine solution as well as with the help of thermodynamic modeling of the AMP-H2O-CO2 system. Experimental solubility data from literature were employed to extract a thermodynamic model for aqueous solutions of AMP with concentrations ranging from 17.8 to 36.6 wt.% at various CO2 loadings. Liquid phase speciation was determined by employing an electrolyte-NRTL model. The AMP carbamate stability constant, molecule-ion pair, and molecule–molecule interaction parameters in the studied concentrations were obtained. The determined CO2 equilibrium properties are in agreement with previously reported experimental data.