Electrical properties of iron corrosion layers formed in anoxic environments at the nanometer scale

Florence F. Mercier-Bion (1, 2) , Jiaying Li (1, 2) , Hélène Lotz (1, 2) , Ludovic Tortech (3, 4) , Delphine D. Neff (1, 2) , Philippe Dillmann (1, 2)

1 LAPA - UMR 3685 - Laboratoire Archéomatériaux et Prévision de l'Altération
2 IRAMAT - LMC - IRAMAT - Laboratoire Métallurgies et Cultures
3 LICSEN - Laboratoire Innovation en Chimie des Surfaces et NanoSciences
4 E-POM - Edifices PolyMétalliques

The electrical properties of the corrosion layers on archaeological iron artefacts were determined by Conductive Atomic Force Microscopy. Different corrosion products were studied: Fe$^{II}$ carbonates, magnetite entrapped in the carbonate, and iron sulfides. The results indicate that the ferrous carbonate matrix is insulating, and that magnetite and iron sulfides have a conductive character, although these phases are not systematically connected to the metal. This suggests that electrons produced by the anodic dissolution of metal would be conducted to the external part of the corrosion product layer through a three-dimensional network of connected magnetite strips passing through the ferrous carbonate matrix.

Keywords: FESEM; Archaeological artefact; µRaman; Iron corrosion; C-AFM; Electrical properties

Domains: Material chemistry

Florence F. Mercier-Bion, Jiaying Li, Hélène Lotz, Ludovic Tortech, Delphine D. Neff, et al.. Electrical properties of iron corrosion layers formed in anoxic environments at the nanometer scale. Corrosion Science, 2018, 137, pp.98-110. ⟨10.1016/j.corsci.2018.03.028⟩. ⟨cea-01743218⟩