Detecting structure and composition of passive film on Mo-containing stainless steel formed in alkaline environment by aberration-corrected TEM.

In this paper, the structural and compositional evolution of the passive films formed on the Mo-containing stainless steels induced by chloride ions in 0.1 mol L−1 NaOH solution has been studied by means of aberration-corrected transmission electron microscopy and X-ray photoelectron spectroscopy. Mo is enriched at the outer layer of the passive film, which is attributed to the induction of Cl-. Moreover, MoO 4 2- is formed due to the alkaline solution, which impedes the film formation process and inhibits the thickening of the film. Consequently, the positive effect of Mo in the passive film on the corrosion resistance is strongly suppressed. [Display omitted] • The evolution of passive film induced by Cl- in NaOH solution is observed. • The passive film is homogeneous in element distribution in alkaline solutions. • The direct experimental evidence for the formation of NiFe 2 O 4 spinel is observed. • Mo incorporated in passive films is induced by Cl- is directly visualized. • The positive effect of Mo is suppressed due to the formation of MoO 4 2-. [ABSTRACT FROM AUTHOR]