Effect of Oxygen and Heat Stable Salts on the Corrosion of Carbon Steel in MDEA-Based CO2 Capture Process

Abstract

The objective of the present study was to evaluate the corrosion properties of carbon steel in MDEA/H2O/CO2/O2/HSS (methyldiethanolamine/water/carbon dioxide/oxygen/heat stable salts) mixtures related to the CO2 capture process in fossil fuel-fired power plants. Short-term and long-term corrosion tests were performed in 50 wt% MDEA solutions at 50°C under atmospheric pressure with different combinations of CO2, O2, and HSS (bicine [C6H13NO4], formate [HCOO−], sulfate [SO42−]). Corrosion behavior of carbon steel was evaluated using electrochemical methods (linear polarization resistance [LPR], electrochemical impedance spectroscopy [EIS], and cyclic polarization), weight-loss measurements, and surface analytical techniques (scanning electron microscopy [SEM] and energy-dispersive spectroscopy [EDS]). The results of short-term corrosion tests indicated that the addition of CO2 in the MDEA systems significantly increased the corrosion rate and changed the corrosion behavior from a passive to an active state. However, the corrosion rates of carbon steel did not change significantly with the addition of O2 and HSS. The corrosion rates of carbon steel decreased with time under MDEA/CO2 systems, whereas it maintained the initial values throughout the tests in MDEA/CO2/O2 and MDEA/CO2/O2/HSS environments. The order of the corrosiveness was MDEA/CO2/O2/HSS > MDEA/CO2/O2 > MDEA/CO2. The corrosion morphology of carbon steel in MDEA/CO2 systems with O2 and HSS showed uniform attack with preferential dissolution of ferrite.