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AbstractAbstract
[en] Archaeological objects of Gallo-Roman and Merovingian time, and from a battlefield of World War 1, were studied to better understand long term corrosion phenomena of iron in clay soils. This study is part of the French national program about nuclear waste deep repository, conducted by the ANDRA (French national Agency for Radioactive Waste Management). Iron archaeological analogues make a valuable contribution to the specifying of containers for long lived and high level wastes (HLWs), because they provide access to the considered time scale. The experimental issue is divided into two major parts: - a physico-chemical characterisation of corrosion products, by Raman spectroscopy; - an electrochemical study of the behaviour of the different corrosion layers. Although the metallic material is different between ancient artefacts (ferrite) and 1914-1918 remains (hypo-eutectoid steels), the same stable phases are identified in their corrosion products: mainly iron oxides and oxi-hydroxides. From a macroscopic point of view, these products are staggered into two layers: an internal one, and an external one, which contains soil markers. Under the microscope, a complex composite structure appears. Goethite a-FeOOH, which was identified on each object, is frequently in contact with the metal core. The average corrosion rate in the burial environment, deduced from the layers thickness, highlights a significant slowdown of corrosion after the first burial time, about one century. The electrochemical study showed the predominant role of transport phenomena in the pores of corrosion layers. The behaviour of the metal - internal layer system is well explained by a model of porous electrode (De Levie theory). Despite its porosity, the internal layer is protective, as it leads to a significant decrease of the corrosion rate (about ten time). (author)
[fr]
Des objets archeologiques d'epoque gallo-romaine, merovingienne et de la Premiere Guerre Mondiale, ont ete etudies afin de mieux comprendre les mecanismes de corrosion a long terme du fer dans les sols. Cette etude se rattache a la thematique 'analogues archeologiques' du programme de l'Agence nationale pour la gestion des dechets radioactifs (ANDRA) sur le stockage des dechets de haute activite a vie longue en couche geologique profonde. Les vestiges archeologiques base fer, permettent ainsi de contribuer a la prevision du comportement de conteneurs ou surconteneurs de dechets, qui seraient realises en fer ou en acier non ou faiblement allie. Une double approche a ete suivie: - la caracterisation physico-chimique des produits de corrosion, notamment par spectroscopie Raman; - l'etude du comportement des couches de corrosion identifiees au moyen de methodes electrochimiques. Si le materiau metallique est different entre objets anciens (ferrite) et vestiges de 1914-1918 (aciers hypoeutectoides), on retrouve les memes phases stables dans leurs produits de corrosion: oxydes et oxy-hydroxydes de fer essentiellement. D'un point de vue macroscopique, ces produits s'etagent en deux couches: interne et externe, cette derniere contenant des marqueurs du sol. Au microscope, une structure composite complexe apparait. La goethite a-FeOOH, toujours presente, est frequemment au contact direct du metal. La vitesse de corrosion moyenne pendant l'enfouissement, deduite des epaisseurs de couches, traduit un ralentissement important de la corrosion au dela de la premiere phase d'abandon, de l'ordre du siecle. L'etude electrochimique a montre le role preponderant des phenomenes de transport dans les pores des couches de corrosion. Le comportement du systeme metal - couche interne est correctement traduit par un modele d'electrode poreuse (theorie de De Levie). Malgre sa porosite, la couche interne s'avere protectrice, entrainant une diminution de la vitesse de corrosion d'un facteur 10. (auteur)Original Title
Corrosion a long terme du fer et des aciers non ou faiblement allies dans les sols a dominante argileuse. Caracterisation physico-chimique et etude electrochimique d'analogues archeologiques
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15 Nov 2002; 252 p; 84 refs.; Available from the INIS Liaison Officer for France, see the 'INIS contacts' section of the INIS website for current contact and E-mail addresses: http://www.iaea.org/inis/contacts/; These Docteur de l'Universite Technologique de Compiegne; Specialite: Sciences mecaniques pour l'ingenieur
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Report
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Thesis/Dissertation
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ARCHAEOLOGICAL SPECIMENS, CLAYS, CONTAINERS, CORROSION, CORROSION PRODUCTS, CORROSION PROTECTION, CORROSION RESISTANCE, ELECTROCHEMISTRY, FRENCH ORGANIZATIONS, GOETHITE, IRON, IRON HYDROXIDES, IRON OXIDES, LOW ALLOY STEELS, OXIDATION, RADIOACTIVE WASTE DISPOSAL, RADIOACTIVE WASTE STORAGE, RAMAN SPECTROSCOPY, SCALING
ALLOYS, CARBON ADDITIONS, CHALCOGENIDES, CHEMICAL REACTIONS, CHEMISTRY, ELEMENTS, HYDROGEN COMPOUNDS, HYDROXIDES, IRON ALLOYS, IRON BASE ALLOYS, IRON COMPOUNDS, LASER SPECTROSCOPY, MANAGEMENT, METALS, MINERALS, NATIONAL ORGANIZATIONS, OXIDE MINERALS, OXIDES, OXYGEN COMPOUNDS, RADIOACTIVE WASTE MANAGEMENT, SILICATE MINERALS, SPECTROSCOPY, STEELS, STORAGE, TRANSITION ELEMENT ALLOYS, TRANSITION ELEMENT COMPOUNDS, TRANSITION ELEMENTS, WASTE DISPOSAL, WASTE MANAGEMENT, WASTE STORAGE
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