Effect of CO32- on the Electrochemical Behaviour of 14Cr12Ni3Mo2VN Stainless Steel in a Sodium Chloride Solution
International Journal of Electrochemical Science
The corrosion behaviour of 14Cr12Ni3Mo2VN martensitic stainless steel in a chloride solution with 20 mmol·L -1 Na2CO3 was investigated using X-ray photoelectron spectroscopy, open circuit potential analysis, electrochemical impedance spectroscopy, potentiodynamic polarization analysis, Mott-Schottkyanalysis,scanning electron microscopy and energy dispersive spectroscopy.It was found that the passivation films that form on14Cr12Ni3Mo2VN stainless steel in different test solutions were mainly
... ons were mainly composed of oxides and hydroxides of Fe, Cr and Mo. The formation and content of Cr2O3 in the passivation film were promoted and increased by the addition of CO3 2in solution, but the hydroxylation of Fe in the passivation film also occurred. The addition of CO3 2reduced the selfcorrosion potential of 14Cr12Ni3Mo2VN and the donor density Nd of the passivation film, inhibited the number and activation of metastable pits on the electrode surface, improved the pitting potential and impedance of the passivation film, and increased the corrosion resistance of the material. Fe, Cr,V and Mo in the corrosion pit were selectively dissolved, demonstrating that Fe migrated to the solution in the form of ions, while Cr,V and Mo deposited in the pit in the form of oxides or hydroxides. CO3 2had no significant effect on the selective dissolution and migration of alloying elements in the matrix but it could significantly reduce the repassivation potential and increase the difficulty of repassivation in the activated pits.