Understanding the synergistic effect of CO2, H2S and fluid flow towards carbon steel corrosion

The synergistic effect of CO2, H2S and fluid flow towards carbon steel pipelines was studied by systematically evaluating the corrosion response of AISI 1020 carbon steel in aqueous solutions containing CO2 and CO2/H2S at various contents under the static and dynamic conditions at 60 degrees C. The results have revealed that the dissolved H2S can impede the formation of FeCO3 crystals by the preferential adsorption process of FeHSads+ to form the porous iron sulfide scale, through which the corrosive species, especially in dissolved CO2, can easily reach the steel/scale interface and accelerate the dissolution of steel matrix. On the other hand, the limited adsorption process of FeHSads+, enhanced mass transport of corrosive species/Fe2+ along with easy spalling of iron sulfide scale with poor adhesion are expected under the action of fluid flow, ultimately aggravating the localized and general corrosion of carbon steel.