Long-term corrosion behaviour of low carbon steel in anoxic soils approached by archaeological artefacts (original) (raw)
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Materials and Corrosion-werkstoffe Und Korrosion, 2009
In the context of the prediction of materials behaviour used in the nuclear waste storage, the understanding of iron corrosion mechanisms in anoxic environment is of great importance. Information can be obtained using complementary analytical tools. Interactions between burial soil and archaeological artefacts are studied by performing on site soil measurements. Moreover, archaeological artefacts are studied on transverse sections using a combination of microbeam techniques. The specific interest of this project lies in the study of ferrous thick corrosion layers formed in anoxic environments.
Journal of Raman Spectroscopy, 35, 739-745, 2004
The description and identification of corrosion products formed on archaeological iron artefacts need various approaches at different observation scales. For this study, samples from five sites were prepared using two techniques. The first consists in cutting cross-sections perpendicular to corrosion layers. This allows local observations and analysis of the corrosion layer stratigraphy at different levels. The second consists in performing manual grinding or abrading of the corrosion layers starting from the current surface of the excavated artefact to the metal core. It allows the description of the successive layers and is well adapted for the analysis on a larger scale. In addition to these two observation scales, the identification of the iron oxides formed needs the coupling of several complementary techniques. Elementary compositions were determined by scanning electron microscopy–energy-dispersive x-ray (SEM–EDX) analysis and electron probe microanalysis (EPMA). Structural identification was performed by x-ray micro-diffraction under synchrotron radiation (µXRD) and micro-Raman spectroscopy. These analyses were performed on the same samples with both x-ray diffraction and Raman spectroscopy in order to ensure a reliable characterization. In some cases there are some ambiguities or overlapping between signatures of different phases by µXRD (such as maghaemite–magnetite) or Raman spectroscopy (such as goethite–magnetite) which can be overcome by the association of the two methods. The final aim is to set up an analytical methodology that will be optimal for the study of ancient iron corrosion products. It is the first step in the study of long-term mechanisms of iron in soil.
Corrosion of iron archaeological artefacts in soil: characterisation of the corrosion system
Corrosion Science, 2005
This paper presents a study made on 40 iron archaeological artefacts buried in soil during several centuries. Samples were taken with the adhering soil and cross-sections were made. The used characterisation techniques are optical and electronic microscopies, EDS coupled to SEM, EPMA, micro-XRD under synchrotron radiation, micro-Raman spectrometry. A specific vocabulary is proposed to describe the corrosion layout. The most identified corrosion layout is made of several ten micrometers zones of magnetite and/or maghemite embedded in a goethite matrix. A corrosion mechanism is proposed in order to explain this profile. When the soil water contains more chlorine or carbonates, some specific corrosion product appear as akaganeite, oxychlorides and siderite.
Study of archaeological artefacts to refine the model of iron long-term indoor atmospheric corrosion
Journal of Nuclear Materials, 2008
The study of long-term indoor atmospheric corrosion is involved in the field of the interim storage of nuclear wastes. Indeed study of archaeological artefacts is one of the only mean to gather information on very long periods. Concerning ancient items, due to the complexity of the system, it is necessary to couple many analytical techniques from the macro to the microscopic scale. This enables to propose a description of the Amiens cathedral chain rust layers, made of a matrix of goethite, with lepidocrocite and akaganeite locally present and marbling of a poor crystallized phase associated to ferrihydrite. Electrochemical measurements permit to study the reduction capacity of the rust layer and to draw reduction mechanisms of the so-called active phases, by in situ experiments coupled with X-ray diffraction and X-ray absorption spectroscopy.
Applied Geochemistry
This article is part of an ongoing study on the long-term corrosion behaviour of ferrous archaeological artefacts. The aim of this study is to correlate the corrosion products formed on ancient artefacts in an anoxic medium to the environmental data using thermodynamic modelling. For this purpose, measurement campaigns have been conducted on the archaeological site of Glinet (16th century, High Normandy (Seine-Maritime), France) where the evolution of the pore water chemistry has been recorded for a period of one year. Three evolution steps have been distinguished after the oxidizing perturbation which was induced by the piezometers installation. The first step was related to an oxidizing environment in which pore water was in equilibrium with a Fe(III) precipitated phase: ferrihydrite (FeOOH·0.4 H2O). The second step was considered as an intermediate step and Fe speciation had evolved; equilibrium was achieved between ferrihydrite and a Fe(II) carbonate phase: siderite (Fe(II)CO3)....
Corrosion Stability of Corrosion Products on an Archaeological Iron Artefact
2012
A spearhead of archaeological and cultural significance has been found and analysed in Serbia. In the corrosion products of the artefact, the dominant phases were goethite (αFeO(OH)) and magnetite (Fe3O4) whose presence explains a good preservation of the base metal, iron, over the centuries and the artefact stability after excavation. Besides goethite and magnetite, the corrosion products were identified to contain, to a lesser extent, less stable lepidocrocite (γ-FeO(OH)) and the phases that come from the rocks and soil from the surrounding environment (plagioclase). The phases containing chloride ions were not detected in the corrosion products (akaganéite, β-Fe8O8(OH)8Cl1.35), which indirectly indicates that the content of chloride ions was not significant in the underground exploitation conditions. The lack of chloride ions also contributed to the corrosion stability of the artefact during the period after excavation.