INVESTIGATION OF THE COMPOSITION AND STRUCTURE OF THE PATINA ON ARCHAEOLOGICAL COPPER COINS FROM CAPE ST. ATHANAS, BYALA, VARNA REGION

Abstract

This study presents analyses of the chemical and phase composition of the patina in historical technological objects discovered during archaeological excavations on Cape St. Atanas, Byala, Varna region. The objects studied are early Byzantine copper coins, whose surfaces have undergone prolonged corrosion changes as a result of centuries-long stay in a soil environment located in close proximity to the Black Sea. X-ray fluorescence spectral analysis, energy dispersive X-ray spectroscopy (EDS/EDX) and X-ray structural phase analysis were used to characterize the patina. The applied methods determined the elemental and phase composition of the surface layer and identified the main corrosion products. It was found that the patina is mainly composed of copper oxides, with iron oxides and lead-containing phases also recorded, formed as a result of prolonged oxidation and diffusion processes. The obtained results contribute to the clarification of the mechanisms of patina formation, the state of preservation of the archaeological artifact and the influence of the coastal environment on corrosion processes, providing valuable information for its archaeometric interpretation, conservation and restoration.