Accurate Control of Oxide Ions Content for Corrosion Studies: Application to SS316L and Its Alloying Elements in Molten LiCl-KCl
- 1 Laboratoire de Génie Chimique, Université de Toulouse, Toulouse, France
- 2 Laboratoire de Génie Chimique, Université de Toulouse, Toulouse, France
- 3 Laboratoire de Génie Chimique, Université de Toulouse, Toulouse, France
- 4 Orano, Châtillon, France
- 5 Orano, Châtillon, France
- 6 Laboratoire de Génie Chimique, Université de Toulouse, Toulouse, France
Abstract
The aim of this work was to study the influence of oxide ions concentration on the stability of 316L stainless steel and its alloying compounds (chromium, iron, nickel and molybdenum) in molten LiCl-KCl-Li 2 O at 550˚C. An in-situ oxide ions titration method using square wave voltammetry was developed to quantify oxide ions, to accurately control the experimental conditions. The influence of oxide ions concentration was then studied by linear sweep voltammetry and long-term immersions followed by SEM-EDS analysis on pure elements and SS316L. Results showed that chromium was stabilized in presence of O 2 − , iron was dissolved independently of [O 2− ], nickel was resistant to corrosion and molybdenum, which was stable in oxide-free media, was found reactive towards O 2− . On SS316L, a passivation layer was observed and an enriched chromium-oxygen layer was observed by SEM-EDS. Almost all the iron was dissolved and a small depletion of molybdenum was visible while nickel remained resistant to corrosion. Linear sweep voltammetry studies were consistent with SEM-EDS analysis and each alloying compound exhibited a similar behaviour in the SS316L as its pure form.
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