Forgery remain - Fe Alloy - Roman Times

Naima. Gutknecht (HE-Arc CR, Neuchâtel, Neuchâtel, Switzerland) & Valentina. Valbi (Laboratoire Métallurgie et Culture (LMC), Belfort, Franche-Comté, France)

Complementary information

Excavation "Les Terres de Diane". Rural site exploited form the neolithic age to the gallo-roman age. The site was dedicated to multiple activities (artsanal and agricultural) among which siderurgic activity is documented by the presence of forgery remains dating form the second half of the first century and the second century.

The schematic representation below gives an overview of the corrosion layers encountered on the object from a first visual macroscopic observation

Analyses performed:

Metallography (etched with Nital reagent 3%), SEM-EDS, Raman spectroscopy.

After etching, the microstructure shows the presence of iron equiaxe grains (Figure 7) characteristics of a ferritic structure. Ghost structures next to the weld show the presence of phosphorous and a possible migration of P from one metal sheet to another during the welding process (Figure 8). The SEM-EDS analysis confirmed the composition of the metal being almost pure iron (Fe > 99%) with low percentages of phosphorous (P<1%) varying over the sample. The central metal sheet presents elongated slag inclusions composed of glassy matrix with wustite dendrites. One weld is well executed (Figure 8) while the other one was not completed and the space within the two metal sheets is filled with slag inclusions and corrosion products (Figure 9).

The metal is covered with a thick layer of corrosion products (thickness 4-6 mm).