Roman sophisticated surface modification methods to manufacture silver counterfeited coins

By means of the combined use of X-ray photoelectron spectroscopy (XPS), optical microscopy (OM) andscanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) the sur-face and subsurface chemical and metallurgical features of silver counterfeited Roman Republican coinsare investigated to decipher some aspects of the manufacturing methods and to evaluate the technolog-ical ability of the Roman metallurgists to produce thin silver coatings. The results demonstrate that over2000 ago important advances in the technology of thin layer deposition on metal substrates were attainedby Romans. The ancient metallurgists produced counterfeited coins by combining sophisticated micro-plating methods and tailored surface chemical modification based on the mercury-silvering process. Theresults reveal that Romans were able systematically to chemically and metallurgically manipulate alloysat a micro scale to produce adherent precious metal layers with a uniform thickness up to few microm-eters. The results converge to reveal that the production of forgeries was aimed firstly to save expensivemetals as much as possible allowing profitable large-scale production at a lower cost. The driving forcescould have been a lack of precious metals, an unexpected need to circulate coins for trade and/or a com-binations of social, political and economic factors that requested a change in money supply. Finally, someinformation on corrosion products have been achieved useful to select materials and methods for theconservation of these important witnesses of technology and economy.