Alteration and corrosion phenomena in Roman submerged glass fragments

In the present paper the surface analytical techniques of XPS (X-ray photoelectron spectroscopy) and SIMS (secondary ions mass spectrometry) have allowed an understanding of the alteration and corrosion phenomena occurring in Roman glass fragments. The samples come from the seawater archaeological site of the Roman ship Iulia Felix, which sank near Grado (Gorizia, Italy) in the second century A.D. Through XPS the surface concentration of the main chemical elements and their depth profiles have been obtained. Attention has been focused on the oxidation states of the elements, oxygen/silicon ratio, peculiar presence of carbonate salts and concentration trends of some elements in the outer atomic layers. Depth trends of aluminium, calcium, magnesium and carbon were studied also through SIMS depth profiles. The whole set of XPS and SIMS data allows the segregation of particular chemical species and the evolution of the original glass to a multilayer system.