Advanced Plasma Treatment for Cleaning and Protecting Precious Metal Artefacts

Low pressure plasmas can be successfully carried out to develop a non-destructive and reversible procedure for cleaning and protecting precious metal artefacts. In this study, cold plasma treatments were applied on Ag-based alloys with microchemical and microstructural features similar to ancient artefacts, buried for six months in the archaeological site of Tharros (Sardinia, Italy). Dry etching in H2 plasma allows to completely remove the patina without affecting the bulk properties, while SiOx thin films, deposited in a glow discharge fed with TEOS, Ar and O2, exhibit good corrosion protection.