Study of iron sulphides in long-term iron corrosion processes: Characterisations of archaeological artefacts

Abstract : Iron sulphides are observed on long term anoxic corrosion profiles of iron artefacts. The archaeological nails studied came from two terrestrial sites (Glinet and Raadhuspladsen) and a subaquatic one (Arles-Rhône 3). Greigite (Fe 3 S 4) and/or mackinawite (FeS 1−x) are observed at the outer border of the corrosion product layer. The presence of mackinawite is discussed relatively to the establishment of stable anoxic burial conditions. The nails from the subaquatic site present pyrite globules in the transformed medium. The formation of pyrite (FeS 2) is attributed to the proximity of wood. The iron sulphides formation may also be explained by the presence of sulphate-reducing bacteria in the burial environment.