Revealing the temperature effects on the corrosion behaviour of 2205 duplex stainless steel from passivation to activation in a CO2-containing geothermal environment

The temperatures and pressures influencing the formation mechanism of the passive film and corrosion products, as well as passivation performance of 2205 duplex stainless steel (DSS), were systematically studied via immersion tests, electrochemical measurements, and various advanced surface techniques. The results indicate that the passive film at 150 °C was an amorphous structure, while the corrosion products were comprised of nano-polycrystalline FeCr2O4, CrOOH, and NiFe2O4 at 300 °C. A Ni-rich layer was observed at the inner interface in both temperatures. A thermodynamic assessment was to validate the experimental results and reveal fundamental corrosion mechanisms of 2205 DSS exposed to the geothermal environments.