Silver surface enrichment in ancient coins studied by micro-PIXE

In order to gain insight into the silver enrichment process and the effects on the data obtained with these techniques, a set of silver roman denarii were cross sectioned and analyzed at the Centro Nacional de Aceleradores micro-PIXE facility. Elemental maps show silver surface enriched layers up to 250 μm thick. Besides, silver-enriched surface layers are not found for alloys with 96-98 wt.% Ag.