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

Highlights: • 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.