Role of residual 2-amino-2-methyl-1-propanol and piperazine in the corrosion of X80 steel within an impure supercritical CO2 environment as relevant to CCUS

Abstract

The corrosion of steels in the supercritical CO2 environment with impurities in a carbon capture, utilization and storage system has attracted great interests in recent years. In this work, corrosion inhibition mechanisms of the residual 2-amino-2-methyl-1-propanol and piperazine from the CO2 capture process on X80 steel within an impure supercritical CO2 environment were investigated by weight-loss method and surface analysis techniques. The results showed that a small amount of 2-amino-2-methyl-1-propanol had marginal effect on the corrosion of steel. Corrosion rate was decreased as the 2-amino-2-methyl-1-propanol concentration increased further. When 100 ppm 2-amino-2-methyl-1-propanol + 50 ppm piperazine was added, a lowest corrosion rate was observed, reaching 0.41mm/a. Meanwhile, pitting corrosion was observed under all conditions. The combination of 2-amino-2-methyl-1-propanol and piperazine cannot inhibit pitting corrosion efficiently, while flow accelerated the propagation of pits in the presence of 2-amino-2-methyl-1-propanol. FeSO4 was confirmed as the corrosion product for all conditions. RNH3+, PZH+, Fe2O3 and Fe3O4 were detected in the corrosion products depending on the test conditions. The results indicated that the inhibition mechanism of piperazine and 2-amino-2-methyl-1-propanol was attributed to both the neutralization and adsorption effects on the steel surface. A non-uniform adsorption inhibition mechanism is proposed based on these test results.