Experiments in a large-scale flow loop provide an example of a somewhat increased corrosion rate under multiphase flow conditions caused by a low concentration of H2S in a CO2 saturated environment. Under operating conditions that prevent scale formation, the addition of 3ppm H2S in the gas phase increased the corrosion rate of AISI C 1018 and API 5L X-65 carbon steels, while the addition of H2S concentrations of 15ppm and greater tended to retard corrosion. The same effect was not found in single-phase flow. A vapor-liquid equilibrium model for dilute aqueous solutions of H2S/CO2 was developed to provide a tool for estimating water chemistry of a closed system such as a flow loop or an autoclave.
Keywords: hydrogen sulfide, carbon dioxide, acid gas, vapor-liquid equilibrium model