Corrosion mechanism of steels in MDEA solution and material selection of the Desulfurizing equipment

Abstract

In the present study, the corrosion properties of three steel were evaluated in 45 wt.% Methyldiethanolamine (MDEA) solution, saturated to the hydrogen sulfide (H2S) and carbon dioxide (CO2) as in the oilfields. Corrosion tests were performed using dynamic high temperature (HT) autoclave for various temperature conditions. Corrosion behavior of steels was monitored using electrochemical methods (Tafel polarization and Electrochemical Impedance Spectroscopy). Indoor autoclave loss tests showed that at a lower temperature (40°C ~ 60°C, corrosion rate of 20#, 304L and 316L are low, but increased significantly as the temperature rises. Electrochemical studies suggested that in the MDEA desulfuration solution containing H2S / CO2, 20 #, 304L and 316L steels are mainly susceptible to H2S corrosion. With the increase in temperature, the corrosion potentials of the three steels shift negatively, the charge transfer resistance decreases, which accelerate the metal anode dissolution rate significantly.