Influence of H2S and CO2 Partial Pressures and Temperature on the Corrosion of Superduplex S32750 Stainless Steel

This study analyzes the effects of varying H2S and CO2 concentrations and temperature on the pH of geothermal fluids flowing through superduplex S32750 stainless-steel pipelines, classified as corrosion-resistant alloys (CRAs). Corrosive decay is evaluated by comparing OLI Studio software simulations with experimental data from the literature. The results indicate that an increase in the partial pressure of either gas lowers pH levels, with temperature exerting a more pronounced exponential effect on corrosion than gas partial pressure. When both gases are present, the dominant gas dictates the corrosion behavior. In cases where CO2 and H2S are in equal proportions, FeS2 forms as the primary corrosive product due to the higher potential corrosivity of H2S. The H2S/CO2 ratio influences the formation of passive films containing chromium oxides or hydroxides (Cr2O3, Cr(OH)3), iron oxides (Fe2O3, Fe3O4), or iron sulfides (FeS).