Interfacial layer on archaeological mild steel corroded in carbonated anoxic environments studied with coupled micro and nano probes

The interfacial layer formed on archaeological artefacts corroded during 450 years in carbonated anoxic water was studied using FEG-SEM, Raman, STEM, STXM. This layers forms between the metallic substrate and an outer carbonate layer. Interfacial layer shows various thicknesses from about 100 nm to several mu m. It is made of a mix of iron oxides (maghemite or magnetite). A formation mechanism is proposed and based on slight pH increase at the interface. D2O labelling experiments show that the penetration of water in the pore network seems to be significantly hindered at the interface by the presence of the oxide layers. (C) 2014 Elsevier Ltd. All rights reserved.