Passivation-induced physicochemical alterations of the native surface oxide film on 316L austenitic stainless steel

Time of Flight Secondary Ion Mass Spectroscopy, X-Ray Photoelectron Spectroscopy, in situ Photo-Current Spectroscopy and electrochemical analysis were combined to characterize the physicochemical alterations induced by electrochemical passivation of the surface oxide film providing corrosion resistance to 316L stainless steel. The as-prepared surface is covered by a 3c2 nm thick, mixed (Cr(III)-Fe(III)) and bi-layered hydroxylated oxide. The inner layer is highly enriched in Cr(III) and the outer layer less so. Molybdenum is concentrated, mostly as Mo(VI), in the outer layer. Nickel is only present at trace level. These inner and outer layers have bandgap values of 3.0 and 2.6 122.7 eV, respectively, and the oxide film would behave as an insulator. Electrochemical passivation in sulfuric acid solution causes the preferential dissolution of Fe(III) resulting in the thickness decrease of the outer layer and its increased enrichment in Cr(III) and Mo(IV-VI). The further Cr(III) enrichment of the inner layer causes loss of photoactivity and improved corrosion protection with the anodic shift of the corrosion potential and the increase of the polarization resistance by a factor of 3c4. Aging in the passive state promotes the Cr enrichment in the inner barrier layer of the passive film

Trivalent Chromium Conversion Coatings on 2xxx aluminium alloy intermetallic particles by 3D ToF-SIMS imaging

International audienc

Rôle des impuretés métalliques dans la corrosion du magnésium

International audienc

ToF-SIMS depth profile of the surface film on pure magnesium formed by immersion in pure water and the identification of magnesium hydride

Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) was used to examine the film formed on pure magnesium by immersion for 2 min in ultra pure water. The ToF-SIMS data indicates that there is magnesium hydride within the surface film. The presence of MgH(2) is a result of the Mg corrosion mechanism. (C) 2009 Elsevier Ltd. All rights reserved

Influence of alumina thickness on formation of TCP layer on aluminium

International audienc

Effect of AA2024 aluminium alloy pretreatments on copper redeposition and formation of TCP layer studied by XPS and ToF-SIMS

International audienc

Surface modifications of Al-Cu-Li alloy in mild and aggressive electrolytes

International audienc

Influence of BSA adsorption on the oxide layers developed on 70Cu-30Ni alloy in static artificial seawater

Copper alloys usually used in cooling circuits of industrial plants can be affected by biocorrosion induced by biofilm formation. The global objective is to study the influence of biomolecules adsorption, which is the first step in biofilm formation, on the electrochemical behaviour of 70Cu-30Ni (wt. %) alloy and the chemical composition of oxide layers. In this work, the chosen biomolecule was the bovine serum albumin (BSA, model protein) and electrochemical measurements performed after 1 h of immersion in static artificial seawater were combined to surface analyses. In the presence of BSA, the charge transfer resistance deduced from EIS data at Ecorr is higher, corresponding to lower corrosion current. Without BSA, two oxidized layers are shown by XPS and ToF-SIMS: an outer layer mainly composed of copper oxide (Cu2O redeposited layer) and an inner layer mainly composed of oxidized nickel, with a global thickness of  ~30 nm. The presence of BSA leads to a mixed oxide layer (CuO, Cu2O, Ni(OH)2) with a lower thickness (~10 nm). Thus, the protein induces a decrease of the dissolution rate at Ecorr and hence a decrease of the amount of redeposited Cu2O and of the oxide layer thickness