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Etude des mécanismes de formation et de croissance des films passifs formés sur les alliages Fe-Ni et Fe-Cr

Abstract : This report is devoted to the study of formation, growth and ageing (t > 100 h) mechanisms of electrochemical films formed on Fe-Ni (25, 50 & 75 at.% Ni) and Fe-Cr (5-30 at.% Cr) alloys in borate solution (pH 9.2) or in dry oxidizing atmosphere (native or ESO films). Cathodic reduction experiments and depth analysis performed by electron spectroscopy (AES, XPS) with ion sputtering allowed to determine in a semi-quantitative way the depth composition and the thickness changes which occur during the film ageing in order to display the film growth mechanisms. Results can be summarized by the following points :
(1) A fast film formation stage takes place by preferential oxidation of iron (Fe-Ni) or chromium (Fe-Cr) ; (2) A slow film growth results from the competition between the ionic mobility under electric field according to the Cabrera-Mott model and the barrier effect induced by internal layers enriched either by chromium oxide (Fe-Cr) or iron oxide (Fe-Ni) which decreases iron (Fe-Cr) or oxygen (Fe-Ni) diffusivity inside the film; (3) This barrier efficiency enlarges at increasing iron contents in Fe-Ni alloys and becomes optimum beyond 15 at.% Cr in "stainless" Fe-Cr alloys which disclose more resistant aged films.
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https://tel.archives-ouvertes.fr/tel-00135102
Contributor : Muriel Bouttemy <>
Submitted on : Tuesday, March 6, 2007 - 4:09:46 PM
Last modification on : Thursday, October 22, 2020 - 2:24:02 PM
Long-term archiving on: : Tuesday, April 6, 2010 - 9:41:56 PM

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  • HAL Id : tel-00135102, version 1

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Muriel Bouttemy. Etude des mécanismes de formation et de croissance des films passifs formés sur les alliages Fe-Ni et Fe-Cr. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 2006. Français. ⟨tel-00135102⟩

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