Non-invasive surface analysis of ancient bronze arrowheads with scanning electron microscopy and X-ray powder diffractometry

In this research, surfaces of eight ancient metal arrowheads were investigated regarding chemical composition, homogeneity, and products of corrosion. To perform that, two nondestructive techniques were applied: Scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray powder diffractometry (XRPD). Importantly, both methods did not require sampling, cutting, nor significant cleaning of the historical artifacts, which made the measurements not only nondestructive but noninvasive too. SEM-EDS measurements provided information on the morphology and elemental composition of the surfaces of the studied objects as well as the distribution of chemical elements on the surfaces and supported crystalline phase analysis. It was revealed that the arrowheads were cast of tin bronze, but some of them contained high amounts of lead and admixtures of antimony and arsenic while copper and tin oxides and lead carbonates were found as the major corrosion products. In some cases, distribution of elements in the surface exhibited serious nonhomogeneity, probably resulting from limited solubility of the casting metals and degradation processes. Based on the obtained results, authenticity and declared provenience of the arrowheads were assessed in reference to the characteristics of similar objects described in literature.