Electrochemical and passivation behavior investigation of ferritic stainless steel in alkaline environment

• Immersion time plays important roles in evolution of passive film composition and resistance.
• Passive film presenting a thinner n-type layer in simulated concrete pore solution.
• The primary constituents of passive film is (Cr, Fe)-oxides without chloride ions.

The electrochemical behavior of 430 ferritic stainless steel in alkaline environment was evaluated by potentiodynamic curves, electrochemical impedance spectroscopy (EIS), Mott–Schottky, X-ray photoelectron spectroscopy (XPS) and Auger Electronic Spectrometer (AES). The results confirmed that n-type semiconducting behavior of the passive film is formed on the surface of 430 ferritic stainless steel after immersion in the alkaline solution. Based on the evaluations of the passive film by AES and XPS analysis, it can be concluded that the primary constituents of the passive film is (Cr, Fe)-oxides, like the Cr2O3, Cr(OH)3, FeOOH and Fe3O4. In addition, no chloride ions are detected in the passive film.