Microstructure and chemical composition of a Sardinian bronze axe of the Iron Age from Motya (Sicily, Italy)

Highlights: • A Sardinian axe of Iron Age from Motya is studied. • The microstructure is investigated by SEM-analysis. • The microanalysis is performed by EMPA analysis. • The axe is made of Cu-Sn matrix with large Pb-globules. • Lead compounds are the main corrosion products. -- Abstract: A bronze axe of the Iron Age found in Motya (Sicily, Italy), in prehistoric strata dating from the 10^th century BC (before the foundation of the Phoenician colony), has been characterised using Scanning Electron Microscopy (SEM-EDX), X-ray diffraction (XRD) and Electron Microprobe Analysis (EMPA). The axe was studied using micro-and invasive analyses, aiming to explore microstructure, corrosive process and to acquire quantitative chemical analysis. The results revealed that the axe is composed by a leaded-Cu-Sn alloy. The external layer is affected by a moderate porosity, decuprification and destannification processes, and Pb enrichment. The X-ray maps pictured the distribution of Cu, Pb, Sn, As, Cl, S and O and showed the features of the matrix, containing globules of Pb with different size. The corrosion products were examined using X-ray diffraction (XRD), that revealed the occurrence of cuprite (Cu₂O), cassiterite (SnO₂), laurionite (PbClOH), cerussite (PbCO₃), litharge (PbO), anglesite (PbSO₄) and plumbonacrite (Pb₅O(OH)₂(CO₃)₃). The matrix is composed by Cu 86.9–95.4 wt% and Sn 2.8–6.9 wt% with arsenic impurities (0.6–1.3 wt%).