Atomistic investigations on the passivity of chromia-forming alloys

Chromia-forming alloys are protected from corrosion by passive films formed on surface. The protective property of passive film relies on the internal barrier layer basically composed of chromium oxide, with the presence of some elements from the alloy substrate or the environment that may reinforce or reduce the passivity.

Modeling the oxide film growth help predict the durability of materials. It was well reported that the growth was limited by the defect diffusion in the barrier layer. Chromia defect chemistry has been well elaborated for high temperature environments [1], but still needs to be studied under electrochemical conditions [2]. Understanding the effects of dopants on the corrosion resistance and the relevant mechanisms is beneficial for alloy design. The role of molybdenum in the passive films has been well determined [3,4]. However, the atomistic investigation of some other important alloyed elements, such as nitrogen, are still underway.

The PhD student will work in the MATEIS laboratory in Lyon starting in 2025 to study the protective properties of chromia oxide scales formed in electrochemical environments and the effects of nitrogen on the passivity.

Theoretical simulations using Density functional theory (DFT) will be carried out to simulate the oxide surfaces under polarization in aqueous environments and to compute the properties related to oxide defects, including charge carrier densities. The computed results will be compared to those of experimental measurements and analyses, such as Electrochemical Impedance Spectroscopy (EIS) and X-ray Photoelectron Spectroscopy (XPS), in order to obtain insights on the alteration of the passivity due to the presence of the doping element.

References

[1] X. Huang, P.C.M. Fossati, L. Martinelli, S. Bosonnet, L. Latu-Romain, Y. Wouters, A DFT study of defects in paramagnetic Cr₂O₃, Phys. Chem. Chem. Phys. 24 (2022) 10488–10498.

[2] A. Kopač Lautar, A. Hagopian, J.-S. Filhol, Modeling interfacial electrochemistry: concepts and tools, Phys. Chem. Chem. Phys. 22 (2020) 10569–10580.

[3] X. Huang, D. Costa, B. Diawara, V. Maurice, P. Marcus, Atomistic insights on enhanced passivity: DFT study of substitutional Mo on Cr₂O₃ and Fe₂O₃ surfaces, Corros. Sci. 224 (2023) 111543.

[4] X. Huang, D. Costa, B. Diawara, V. Maurice, P. Marcus, Protection of Stainless Steels by Mo against Cl Attack: A DFT Study, J. Phys. Chem. C 129 (2025) 3913–3919.

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Highly motivated students with BAC+5 or master’s degree in materials science or equivalent