Investigation of iron long-term corrosion mechanisms in anoxic media using deuterium tracing

In the context of the nuclear waste storage and the preservation of metallic artefacts, the long-term corrosion of iron is studied. In an anoxic medium, the cathodic process involves the reduction of water into gaseous hydrogen and hydrogen-containing species that can precipitate with iron(II). Consequently, to understand the corrosion mechanisms, isotopic deuterium tracing (D2O) has been performed on archaeological artefacts to locate the precipitation zones in the corrosion layer. The presence of deuterium in the metallic matrix of the sample indicates that gaseous hydrogen has been formed and is a clue of the water reduction reaction. Moreover, the precipitation zones in the corrosion layer have been identified on its internal part. This is caused by the iron source location on this part of the corrosion layer. Deuterium concentration quantification made it possible to evaluate an instantaneous corrosion rate below 2 μm/year.