Effects of heat-stable salts on the corrosion behaviours of 20 steel in the MDEA/H2S/CO2 environment

The effects of HSS (heat-stable salts) on the corrosion behaviours of 20 steel were explored using self-designed HTHP autoclave. The charateristics of corrosion scales were investigated by SEM, EDS and XRD. Corrosion scales of 20 steel formed in the liquid phase environment were mainly composed of FeS2, Fe3O4, and Fe. HSSs affected the corrosion rate through changing the morphology of corrosion scales of 20 steel. Inorganic salts enhanced the attractive force between ions and the hydrolysis of CH3COO− in organic salts promoted the ionisation of HS−, which accelerated the deposition of FeS on the surface of 20 steel to form a dense corrosion scales, thereby significantly reducing the corrosion rate of 20 steel. Inorganic–organic salts reduced the bonding opportunity between Fe2+ and S2− and allowed the formation of porous corrosion scales on the surface of 20 steel, thus increasing the corrosion rate of 20 steel.