Long-term corrosion resistance of metallic reinforcements in concrete-a study of corrosion mechanisms based on archaeological artefacts

This paper presents an analytical study on ferrous reinforcements embedded in binders found in ancient buildings aged from the Gallo-Roman period to the beginning of the 20th c. AD. The study of this kind of archaeological analogues is necessary to improve knowledge on the long-term corrosion behaviour of low carbon steels that could be used in concrete to build the substructure of nuclear wastes storage or reversible disposal facilities. The corrosion system can be described as a multi-layer pattern made of metal, a dense corrosion product layer, a transformed medium and a binder. The morphological, and physico-chemical properties like composition, structure and porosities of each part were studied with different analytical methods like optical and electronical microscopies, Energy Dispersive Spectrometry coupled with Scanning Electron Microscopy, Electron Probe MicroAnalysis, Mercury porosimetry, micro-Raman spectroscopy and micro-Diffraction under Synchrotron Radiation. Moreover, average corrosion rates were evaluated. These rates are relatively low compared to the same parameters measured on low alloyed contemporary steels and are comparable with corrosion rates noted for passivated systems.