Multisecular corrosion behaviour of low carbon steel in anoxic soils: Characterisation of corrosion system on archaeological artefacts

Abstract

International audienceIn 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

Oxidation of chukanovite (Fe 2 (OH) 2 CO 3 ): Influence of the concentration ratios of reactants

“…This compound has a structure very similar to that of chukanovite [13]. These results are also in agreement with previous analysis of corrosion product layers of ferrous archaeological artefacts that showed chukanovite often associated with goethite ␣-FeOOH while no GR compound was found [2,3].…”

“…However, the mostly reported Fe(II) hydroxysalt is the Fe(II)-hydroxycarbonate chukanovite (Fe 2 (OH) 2 CO 3 ). It has been commonly found as a main component of the corrosion product layers formed on iron archaeological artefacts excavated form anoxic soils [2][3][4]. It was also observed on carbon steel buried in clay at 80-90 • C [5,6], i.e.…”

“…The Fe(II)-hydroxychloride ␤-Fe 2 (OH) 3 Cl was for instance observed as the main component of the layers covering iron bars found in shipwrecks dated from the Gallo-Roman period [1]. However, the mostly reported Fe(II) hydroxysalt is the Fe(II)-hydroxycarbonate chukanovite (Fe 2 (OH) 2 CO 3 ).…”

Stability of Clay Barriers Under Chemical Perturbations

“…The actual mineral paragenesis results from the competition between the mineral dissolution and precipitation kinetics, the local geochemical conditions (pH, Eh), and the transport of reaction products. In some archaeological artifacts, siderite (enriched in Ca 2þ ) and chukanovite are present at the contact with the iron surface and a thin discontinuous magnetite layer is displaced toward the interface with clay mineral (Neff et al, 2005;Saheb et al, 2009Saheb et al, , 2010. This feature can be interpreted as relics of an early oxic stage.…”

Détermination de la bio-origine des sulfures de fer présents dans les systèmes de corrosion anoxiques par analyse de la composition isotopique du soufre en nanoSIMS

“…La formation de sulfures de fer lors de processus de corrosion anoxique constitue une problématique majeure que ce soit pour la conservation d'objets archéologiques in situ sur leur site d'enfouissement [1][2][3] ou pour la prévision de la durée de vie d'ouvrages métalliques enfouis dans les sols tels que les oléoducs [4,5] ou encore les barrières en acier non ou faiblement allié, surconteneurs et chemisage, prévus dans le cadre du stockage des déchets nucléaires de haute activité en milieu géologique profond [6,7]. En effet, la formation de sulfures de fer est susceptible de modifier les processus de corrosion.…”