For the first time, corrosion products of a 450 year old archaeological iron nail were investigated at the nanometer level using STXM. NEXAFS acquisitions at the Fe L-edge were performed on a thin film taken of the metal–corrosion products including the interface. Comparison with Fe L-edge reference spectra gathered on maghemite (Fe₂O₃), magnetite (Fe₃O₄), siderite (FeCO₃), chukanovite (Fe₂(OH)₂CO₃) and metallic iron (Fe) showed the presence of an interfacial layer of about 100 nm at the metal–corrosion product interface consisting of maghemite and magnetite. Further from this interface, corrosion products are mainly constituted of Fe-carbonates, as well as smaller quantities of iron oxides, probably maghemite. These results support the hypothesis of the presence of a nanolayer controlling the corrosion processes at the metal–corrosion product interface, proposed during former studies at the macroscopic and microscopic levels. They also bring important new insights for the prediction of very long term corrosion of steels, especially into the fields of cultural heritage conservation and storage of nuclear wastes.

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.

Improvement of an LA-ICP-MS methodology tailored to quantify trace elements in small slag inclusions and application to armour for provenance study.