Probing the initial corrosion behavior of X65 steel in CCUS-EOR environments with impure supercritical CO2 fluids

•Corrosion differences of CO2-rich and H2O-rich phases with impurities are compared.•The corrosion of X65 steel is more serious in CO2-rich phase at the initial stage.•The film evolution and sedimentary state are diverse in CO2-rich and H2O-rich phases.•The impurities have more significant effect on the film evolution in CO2-rich phase.•The origins for corrosion differences of CO2-rich and H2O-rich phases are unmasked. The initial corrosion behavior of X65 steel in CO2-rich and H2O-rich environments with 0.08 bar O2, 0.08 bar SO2 and 0.08 bar H2S impurities were investigated. × 65 steel experiences more serious corrosion in CO2-rich phase than in H2O-rich phase at the initial stage, which is strongly associated with the enhanced cathodic processes by impure supercritical CO2 and impurity interactions according to OLI simulation. The evolution and sedimentary state of corrosion products are quite different in two environments despite the identical film compositions. The impurities present more significant effect on the film evolution in CO2-rich phase than that in H2O-rich phase.