Eddy Foy

Characterisation of corrosion layers formed on ferrous archaeological artefacts buried in anoxic media

Abstract In the context of the in situ conservation and preservation of archaeological artefacts, the long term corrosion mechanisms of iron in anoxic soils are studied. To this purpose, a first step is the characterisation of the corrosion layers formed on archaeological artefacts provided from the archaeological site of Glinet (the sixteenth, Normandy, France). On all the corrosion systems formed on artefacts, the main phases constitutive of the corrosion layer are siderite (FeCO3), an iron carbonate containing hydroxide groups [probably chukanovite Fe2(OH)2CO3] and magnetite (Fe3O4). Furthermore, the arrangement of these phases reveals three corrosion distribution types with corresponding corrosion pattern diagrams.

Interfacial layers at a nanometre scale on iron corroded in carbonated anoxic environments

Two tests of iron corrosion in compacted clay and clay slurry were performed for several years. The corrosion systems, and especially the interfacial layer between the metal and the corrosion products, were investigated post mortem by SEM-FEG, μRaman, MET and STXM. An Fe(III) oxide layer systematically developed at a nanometer scale between the metal and an outer layer of carbonates. Its presence could explain the slowing down of the corrosion rate usually observed for these systems. Depending of the compactness of the environment the nature of the interfacial layer is not the same.

Influence of iron corrosion on nuclear glass alteration processes: nanoscale investigations of the iron-bearing phases

ABSTRACT A carbon steel container including nuclear glass has been altered for 2 years in Andra’s Underground Research Laboratory to simulate the behaviour of waste package. Post-mortem analyses at different scales (macro–micro–nano) have been performed to identify neoformed phases on iron corrosion products (ICP) and in the glass alteration layer (GAL). It has been shown at nanometric scale that important quantities of iron and silicon were found in the GAL and in the ICP respectively. Using a comparative approach with phyllosilicate references, STXM, at Si-K edge, suggests presence of trioctahedral species in the GAL and in ICP. Relevant fits of the STXM spectra are obtained with a Fe-rich chlorite for the nanostructured GAL, which could be formed according to chloritisation mechanism. This paper is part of a supplement on the 6th International Workshop on Long-Term Prediction of Corrosion Damage in Nuclear Waste Systems.