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International audience; Corrosion experiments were performed on a ferrito-pearlitic (P285-NH) and a ferritic steel (Armco) in a synthetic solution representing the Callovo-Oxfordian porewater during a month at 120°C. Corrosion product layers (CPLs) were characterized from micro to nanoscale in terms of morphology (electron microscopies), composition (energy dispersive X-ray spectroscopy), and structure (µ-Raman, selected area electron diffraction). Both systems present a Ca-siderite bilayer which interface locates the metal original surface, and nano to micrometric magnetite islets on the internal carbonated layer and at the M/CPL interface. The impact of cementite is highlighted in terms of morphology of the CPL and corrosion mechanism.

International audience; Corrosion experiments were performed on two metallic substrates, a ferritic–pearlitic steel (P285NH) and a ferritic one (Armco), in silicate environment during 30 days at 120°C. Corrosion products were characterized in terms of morphology (scanning electron microscope and transmission electron microscopy), composition (energydispersive X-ray spectroscopy) and structure (µ-Raman, selected area electron diffraction, X-ray absorption near edge structure). Results show a nanometric inner layer made of compact and adherent nanocrystallized magnetite with, locally a thickness up to several micrometers due to the metal microstructure. An outer layer of Fe-rich phyllosilicate, smectite and serpentine, more porous than the inner one and poorly adherent is observed around both the samples.

International audience; This innovative study presents a local diagnosis approach based on nanoSIMS technique to determine the biotic/abiotic origin of iron sulphides of (sub)micron size heterogeneously located in the corrosion product layers of iron. For iron coupons corroded in controlled conditions, negative δ34Ssulphides-sulphates were obtained in biotic conditions contrary to δ34Ssulphides-sulphates obtained in abiotic ones. These results underline that nanoSIMS is a reliable local technique to detect the formation origin of (sub)micron iron sulphides. This successful methodology was then applied to a complex system representative of an iron corroded in the conditions similar to those of radioactive wastes storage in geological medium.

The study of anoxic corrosion process of ferrous metals is a matter of concern for industrial sector (pipelines, container for nuclear waste storage….) but also for cultural heritage objects conservation. Indeed, the formation and the presence of sulfide compounds in the corrosion products of buried objects, either in terrestrial or marine environments, can drastically change the corrosion mechanisms and, so, the conservation strategies for these objects. Particularly, in natural environment, the presence of microorganisms such as Sulfate-Reducing Bacteria (SRB) may influence the corrosion rate of ferrous objects by favoring the precipitation of iron sulfide phases and modifying then the initial corrosion process [1]. The determination of the iron sulfides nature and their distribution in the corrosion product layer is a crucial issue to address in order to anticipate the degradation of ferrous object during extraction, storage or conservation operations. In the present work, archeological ferrous samples, representative of long term corrosion systems, with or without bacteria exposition, have been considered. A multi-technique approach was developed to achieve an overall physico-chemical characterization and to cover the dimensions requirement of the corrosion systems. First, FE-SEM imaging coupled with EDS and µ-Raman spectroscopy were performed on the archeological ferrous samples enabling the localization and identification of the natural corrosion products. Mix of phases of greigite (Fe 3 S 4) and mackinawite (FeS) in a corrosion layer mainly constituted of iron carbonates were observed at a sub-micrometric scale, in consistency with the literature [2], showing the precipitation of greigite, mackinawite and/or pyrite (FeS 2) in the presence of bacteria or in sulfur environment. Then, Nano-Auger spectroscopy, owing to its local chemical characterization capability, was investigated to obtain a chemical diagnostic at a nanometric scale. Scanning Auger Microscopy (SAM) was performed to evaluate the ability of this technique to spatially discriminate different phases (iron sulfides, oxides and carbonates) at a local scale and extreme surface sensitivity (5nm escape depth). Then, thanks to µ-Raman mappings, specific areas presenting only one component were selected and identified for the acquisition of reference Auger spectra, and especially high energy resolution spectra of Fe-MVV and S-LVV regions. Finally, the spatial distribution of the different phases obtained with SAM could be compared with nano-SIMS experiments informing about the sulfur isotopic composition variations and the bio-origin of the sulfur phases.

International audience; Characterisation and determination of the bio-origin of iron sulphides in anoxiccorrosion systems thanks to isotopic analyses by nanoSIMS. This study is devoted to the determinationof the bacterial or inorganic origin of iron sulphides formed during anoxic corrosion processesby sulfur isotopic composition analyses. Broadly, these analyses are realized by IRMS on dissolved sulphidesand sulphates. Yet in this study, surface local isotopic analyses are realized by nanoSIMS in orderto preserve the information about the corrosion products’ localization. Two kinds of samples are studied:a sample (CBCC) corroded during 13 months in controlled laboratory conditions; and one archeologicalsample corroded during about 2000 years in not very well known conditions. When the corrosion system isperfectly well known, as for the CBCC sample, the local isotopic analyses by nanoSIMS actually enable toconclude on the (bio-)origin of the iron sulphides observed. However, when the isotopic composition of thesulphate’s source is unknown, as for the archeological sample, the origin of iron sulphides cannot alwaysbe determined.; Cette étude est consacrée à la détermination de l'origine biotique ou abiotique de sulfures de fer formés au cours de processus de corrosion anoxiques par l'analyse de la composition isotopique du soufre. Usuellement ces analyses sont réalisées par IRMS (Isotopic Ratio Mass Spectrometry) sur des sulfures et des sulfates préalablement dissous. Dans cette étude, en revanche, une nouvelle approche est utilisée, basée sur des analyses isotopiques locales de surface réalisées en nanoSIMS afin de conserver l'information sur la localisation des produits de corrosion. Deux types d'échantillons ont été étudiés : un échantillon (CBCC) corrodé pendant 13 mois en conditions contrôlées, et un échantillon archéologique corrodé pendant environ 2000 ans dans des conditions mal connues. Lorsque le système de corrosion est parfaitement connu, tel que le cas de l'échantillon CBCC, l'analyse isotopique locale par nanoSIMS permet effectivement de conclure sur la (bio-)origine des liserés de sulfures de fer formés. En revanche, lorsque la composition isotopique de la source de sulfates est inconnue, comme dans le cas de l'échantillon archéologique, il n'est pas toujours possible de conclure sur l'origine des sulfures de fer observés.

Cette étude porte sur l’étude (macroscopique et microscopique) de la transformation de la galène, minerai argentifère pour les périodes anciennes, et son évolution jusqu’au plomb, à partir d’un référentiel produit expérimentalement dans un four à moufle fonctionnant au charbon de bois. En effet, si la réaction chimique qui conduit du sulfure au plomb d’œuvre est identifiée depuis longtemps, sa reproduction dans un réacteur type bas-fourneau demeure insatisfaisante et les tentatives de compréhension des procédés de transformation de la galène restent largement infructueuses. Cette absence de maitrise du procédé bloque les possibles réflexions sur les bilans matières et sur le poids des exploitations minières dans les économies anciennes notamment pour ce qui touche à la circulation du plomb. Ainsi, deux grands moments dans cette chaîne de production doivent être mieux appréhendés : la phase de grillage de la galène et la réduction en plomb. Pour répondre à ces objectifs, la microspectroscopie Raman apporte une vision complémentaire de l’approche macroscopique sur la transformation de la galène argentifère, en particulier pour identifier les différentes espèces chimiques du plomb (oxydes, sulfates, oxysulfates) formées au cours de ces opérations. Lors de l’approche expérimentale choisie, la modification de ce minéral se produit selon les étapes suivantes : (1) apparition du soufre élémentaire et des sulfates dès les cinq premières minutes de grillage ; (2) diminution des sulfates au profit de l’apparition d’oxydes de plomb (PbO2, Pb3O4, puis signature de la transformation de Pb3O4 en PbO), à partir des résultats obtenus sur l’échantillon traité pendant dix minutes ; (3) poursuite de la diminution des sulfates avec apparition des carbonates de plomb, comme le laisse entrevoir la caractérisation de l’échantillon après trente-cinq minutes de transformation. This paper focuses on the study (macroscopic and microscopic) of the transformation of classic silver ore (galena: PbS) and its evolution from a repository produced experimentally in a muffle furnace operating at charcoal. While the chemical reaction that leads from the sulfide lead bullion is identified for a long time, its reproduction in a reactor bottom furnace remains unsatisfactory and attempts to understand the transformation processes of the galena remain largely unsuccessful. This lack of mastery of the process blocks possible reflections on material balances and weight mining in ancient economies including matters related to the circulation of lead. Thus two great moments in this production line must be better understood: the roasting phase of galena and the reduction into lead. To reach these objectives, µRaman spectroscopy provides a complementary view of the macroscopy approach to processing the silver galena especially to identify the various chemical species of lead (oxides, sulfates, oxysulfates, carbonates) formed during the transformation of galena. The transformation of the mineral occurs in the following steps: appearance of elemental sulfur and sulfates in the first minutes; reduction of sulfates in favor of the emergence of lead oxides; further reduction of sulfates with the appearance of cerusite.

In the field of nuclear waste management, prediction of the radionuclides migration through the geosphere has to take into account the effects of temperature. The chosen substrate, zirconium diphosphate, was previously described concerning its surface acidity properties for several temperatures (25 °C, 50 °C, 75 °C, 90 °C). Edges for uranyl sorption were obtained in NaClO4medium, and the europium(III) sorption edges were realized in KNO3medium to evaluate the influence of the complexing nitrate ions. Influence of the temperature, the nature of the cation and the nature of the substrate were pointed out by comparing the edges for the different systems. A structural investigation (TRLFS) was carried out to define experimentally, at the microscopic level, the sorption equilibria. Only UO22+and Eu3+were sorbed on both ZrP2O7surface sites (≡Zr–O and ≡P–O), the nitrate medium having no influence on the sorbed species. Furthermore, temperature did not change the sorption mechanisms. The surface complexation modelling of both investigated systems was realized using i) the constant capacitance model ii) the results of the substrate characterizations iii) uranyl sorbed complex determinations. The formation of bidentate surface complexes onto the ≡Zr–O site is not accompanied by a proton release, whereas the formation of bidentate surface complexes onto the ≡P–O site is followed by a release of 2 protons, for both cations and at all temperatures studied. The determined sorption constants increase with temperature, as was expected from the analysis of the sorption edge positions.

This paper reports a comparative study of three methods for determining the surface charge and acid–base behavior of a TiO2 rutile material. Electrophoretic mobility measurements were performed using two different batch protocols: (i) a “static” mode that consisted of immersing the rutile powder in aqueous solutions of given pH's and ionic strengths for 10 h, and (ii) a “dynamic” mode that consisted of using an automatic titrator to continuously adjust the solution pH with a contact time of 15 min. The same apparatus (a Nanosizer from Malvern) was used to measure the zeta potential of the particles in both methods. These batch experiments were next compared to the determination of the surface charge of rutile using nonlinear chromatography in column experiments. In that case, the rutile powder was compacted to enable the formation of a proper column bed. Therefore, Raman scattering and X-ray photoelectron spectra were used, as well as other physical information such as specific surface area and morphology of the particles, to verify that the rutile powder and compacted form were identical. The three approaches were then compared and discussed in relation to the acid–base behavior of the rutile material.

Metallic heritage artefacts represent cultural traces of our past, and for this reason, their preservation and transmission to future generations is important. To protect copper-based artworks exposed outdoors, several conservation strategies are followed, including the use of organic corrosion inhibitors. Inhibitors are usually borrowed from the industrial field. However, the surface state of the metal with the presence of complex corrosion layers, and the protocol of inhibitors' application differ considerably from the industrial ones.The present study specifically addresses corrosion inhibitors for conservation of copper-based exposed artifacts by an innovative physico-chemical approach. The approach takes into account the complexity of the corrosion layer under investigation: a naturally corroded copper plate, representative for outdoor long-term corrosion have been chosen. For the study, three organic molecules, characterized by different chemical functions have been selected as test inhibitors: benzotriazole (BTAH), an azole compound, employed in conservation, which efficiency is debated and its use discouraged due to toxicity; decanoic acid (HC10) a long-chain fatty acid that has been proposed as treatment for heritage objects; benzotriazole-5-carboxylic acid (5CBT), a compound with mixed azole-carboxylic functions.The reactivity of the inhibitors with synthetic mineral phases representative of corrosion products as well as ancient corroded samples (100 years) before and after 6-months outdoor exposure have been investigated by combining observations at the nanoscale (TEM, FIB-tomography) to those obtained at the microscale (Raman, SEM-EDS) and global/bulk observations (colour, surface tension, XRD). Additional experiments in marked environment allowed to investigate changes in permeability (D₂O immersion) and the evolution of passive behavior (KBr immersion).Two reaction mechanisms have been observed and a relationship with the efficiency and durability of the inhibition is proposed. The molecules BTAH and 5CBT interaction with copper atoms occurs via the azole function and both molecules react according to an adsorption-precipitation mechanism forming an adsorbed amorphous complex (nanometric film) on the substrate mineral phase (cuprite and brochantite). The two treatments on the ancient corrosion layers differ for their depth of penetration, with Cu-BTAH complex formation being detected until the cuprite inner layer, while 5CBT complexation is observed only in the outer part of the brochantite. This has an impact on the water permeability and passivity, with the BTAH treatments showing the best results, and suggests a complex formation with the outer cuprite layer in this last treatment. The carboxylic function in HC10 leads to the precipitation of copper decanoate by a dissolution-precipitation mechanism. Crystals of decanoate are formed on the outer surface of brochantite: this confers near super-hydrophobicity to the sample after treatment. However, the lack of bond between the precipitate and the surface determines the loss of the surface-deposited hydrophobic layer after 6 months of outdoor exposure.In addition to these phenomenological results, a new methodology based on the KBr experiment for testing inhibitors for copper corroded artefacts is also proposed., Le patrimoine métallique est un témoin culturel de notre passé et, pour cette raison, sa préservation et sa transmission aux générations futures sont importantes. Plusieurs stratégies sont utilisées pour la protection du patrimoine cuivreux exposée en extérieur, dont l’utilisation des inhibiteurs de corrosion organiques. Les inhibiteurs utilisés pour le patrimoine sont généralement empruntés au domaine de l’industrie. Cependant, l’état de surface du métal, couvert par des couches de produits de corrosion complexes, et le protocole d’application des inhibiteurs diffèrent considérablement de l’application industrielle.La présente étude porte spécifiquement sur les inhibiteurs de corrosion pour la conservation des artefacts exposés à base de cuivre par une approche physico-chimique innovante. L'approche prend en compte la complexité de la couche de corrosion étudiée : une plaque de cuivre naturellement corrodée, représentative de la corrosion extérieure à long terme a été choisie. Pour l'étude, trois molécules organiques, caractérisées par des fonctions chimiques différentes ont été sélectionnées comme inhibiteurs de test : le benzotriazole (BTAH), un composé azolé, employé en conservation, dont l'efficacité est débattue et l’utilisation déconseillée en raison de sa toxicité ; l'acide décanoïque (HC10) un acide gras à longue chaîne qui a été proposé comme traitement pour les objets patrimoniaux ; l'acide benzotriazole-5-carboxylique (5CBT), un composé à fonctions mixtes azole-carboxyliques. La réactivité des inhibiteurs avec des phases minérales synthétiques représentatives des produits de corrosion ainsi que des échantillons corrodés anciens (100 ans) avant et après 6 mois d'exposition extérieure ont été étudiées en combinant des observations à l'échelle nanométrique (MET, FIB-tomographie) à celles obtenues à l'échelle microscopique (Raman, MEB-EDS) et des observations globales/globales (couleur, tension de surface, XRD). Des expériences complémentaires en milieux marqués ont permis d'étudier les évolutions de perméabilité (immersion en D₂O) et de comportement passif (immersion KBr). Deux mécanismes réactionnels ont été observés et une relation avec l'efficacité et la durabilité de l'inhibition est proposée. Les molécules caractérisées par la fonction azole (BTAH et 5CBT) réagissent selon un mécanisme d'adsorption-précipitation formant un complexe amorphe adsorbé (film nanométrique) sur la phase minérale substrat (cuprite et brochantite). Les deux traitements sur les couches anciennes de corrosion diffèrent par leur profondeur de pénétration, la formation du complexe BTAH étant détectée jusqu'à la couche interne de cuprite, tandis que la complexation 5CBT n'est observée que dans la partie externe de la brochantite. Ceci a un impact sur la perméabilité de l'eau et la passivité pour les traitements au BTAH qui montrent les meilleurs résultats, et suggère une formation de complexe Cu-BTA sur la partie externe de la couche de cuprite dans ce dernier traitement. La fonction carboxylique dans HC10 conduit à la précipitation du décanoate de cuivre par un mécanisme de dissolution-précipitation. Des cristaux de décanoate se forment sur la surface externe de brochantite : cela confère une quasi-superhydrophobie à l'échantillon après traitement. Cependant, le manque de liaison chimique forte entre le précipité et la surface induit la perte de la couche hydrophobe déposée en surface après 6 mois d'exposition à l'extérieur.En plus de ces résultats phénoménologiques, une nouvelle méthodologie basée sur l'expérience KBr pour tester les inhibiteurs des artefacts corrodés par le cuivre est également proposée.

As all countries producing power by nuclear industry, France plansto bury radioactive waste in a deep geological site. The concept includes embedding the radionuclides in a glassy matrix and confining them in a steelcontainer. This container should last over 1000 years in a water satured anoxic environment, containing carbonate and clay species. Previous studies onlaboratory experiments (, Comme tous les pays produisant de l’électricité par la filière nucléaire, la France envisage d’enfouir les déchets radioactifs en site géologique profond. Le concept comprend l’enrobage des radionucléides dans une matrice vitreuse et son confinement dans un conteneur en acier. Ce conteneur doit résister plus de 1000 ans dans un environnement anoxique saturé en eau, contenant des espèces carbonatées et argileuses. De précédentes études sur menées sur des expériences de laboratoire (

The first goal of this project was to develop a methodology based on the study of the sulfur isotopic composition enabling the determination of iron sulfides origin, biotic or abiotic, within the corrosion products layers (CPL). Then, the aim was to apply this methodology to real corrosion systems in order to determine the mechanisms of iron sulfides formation. Sulfur isotopic analyses methodologies, adapted to micrometric iron sulfides layers observed in real corrosion systems, were developed in nanoSIMS and ToF-SIMS. The study of iron sulfides formed in anoxic carbonated medium with or without sulphate-reducing bacteria validated the use of these methods for the determination of iron sulfides origin. The application of these methods coupled with the precise characterization of irons sulfides formed in the real corrosion systems show two kind of corrosion pattern. In pattern 1, the iron sulfides are localized in the external part of the CPL. They result from the Fe2+ migration from the metal surface to areas rich in biotic S2-. In this pattern, corrosion rates are lower than 20 μm/year for laboratory systems, and lower than 5 μm/year for archaeological objects. In pattern 2, the large presence of conductive phases in the CPL results in the delocalization of electrons, and so a disequilibrium of the charges at the metal’s surface. That leads to the migration of biotic S2- in the CPL till the metal where they precipitate in iron sulphides. This pattern shows high corrosion rates (~100 μm/an) that might be resulting from the accumulation of biocorrosion and chloride corrosion mechanisms., Ce travail de thèse avait pour objectif de développer une méthode basée sur l’étude de la composition isotopique du soufre (δ 34S) permettant de déterminer l’origine, biotique/abiotique, des sulfures de fer au sein des couches de produits de corrosion (CPC). Puis, il s’agissait d’appliquer la méthodologie développée à des systèmes réels afin de déterminer les mécanismes de formation de ces sulfures de fer. Des méthodes d’analyse isotopique du soufre adaptées aux liserés de sulfures de fer micrométriques observés dans les systèmes réels ont été développées en nanoSIMS et ToF-SIMS. L’étude de sulfures de fer formés en milieu carbonaté anoxique en présence, ou non, de bactéries sulfato-réductrice a permis de valider l’emploi de ces méthodes pour la détermination de l’origine des sulfures de fer. L’application de ces méthodes isotopiques couplées à la caractérisation des sulfures de fer dans les systèmes réels a mis en évidence 2 faciès. Le faciès 1 pour lequel les sulfures de fer sont situés en externe de la CPC. Ils résultent de la migration des ions Fe2+ produits au niveau du métal jusqu’aux zones riches en ions S2- d’origine biotique. Les vitesses de corrosion y sont inférieures à 20 μm/an pour les systèmes de laboratoire et à 5 µm/an pour les objets archéologiques. Et le faciès 2 pour lequel la forte présence de phases conductrices dans la CPC entraîne une délocalisation des électrons, conduisant à la migration des ions S2- d’origine biotique vers le métal où ils précipitent sous forme de sulfures de fer. Ce faciès présente de fortes avancées de corrosion locales (200 µm) qui seraient dues à l’accumulation de phénomènes de corrosion par les chlorures et de biocorrosion.