Research On Corrosion Behavior Of Super13Cr Stainless Steel Under CO₂Environment

With autoclave, electrochemical test and SEM, EDS, XPS, the corrosion mechanism of super13Cr stainless steel under the high temperature and pressure CO2environment was investigated.The results showed that:corrosion rate of super13Cr stainless steel under CO2environment, exacerbated with temperature increasing in the gas phase, and in the gas phase increased firstly then stabilized after140℃. The corrosion rate exacerbated with CO2partial pressure increasing and reduced after2.5MPa; With the increase of concentration of Cl", the rate exacerbated constantly in the gas, but it was inhibited after50g/L in liquid phase. The pitting corrosion rate and depth of the steel exacerbated as the increase of temperature and Cl-concentration.The occurrence of corrosion could be resisted because the Cr element existed in the form of Cr2O3in the surface scale of super13Cr stainless steel.In electrochemical tests, it could be seen from the polarization curve that as the temperature and the concentration of Cl-rised, the corrosion potential and pitting potential of super13Cr stainless steel has been reduced, corrosion resistance was poor, and the stability of the corrosion product films reduced. In addition, it is more prone to corrosion under acidic environment than under basic environment, and the passivation film of the metal is more easy partially destroyed and occure pitting corrosion. It was seen from the impedance spectra that as the temperature increased, the coefficient of diffusion increased, the impedance of the electric double layer and corrosion product film were reduced, and resistance corrosion of the material dropped. Polarization resistance (R2+R3) of the steel decreased with Cl-increasing, and the film became loose, the resistance corrosion reduced. When the pH changed, the capacitor of the passive film was greater than electric double layer, the adsorption phenomena occurred, and the surfaces was most rough.The corrosion product film of super13Cr stainless steel could be more dense as pH increases, and the corrosion resistance of the steel enhanced.