Investigating corrosion systems in archaeological artifacts from Motya (Sicily, Italy): A Micro-Raman Spectroscopy and Correlative Imaging approach

Raman spectroscopy is a non-destructive technique which can provide a unique fingerprint of the corrosion products embedded within the patina of archaeological artifacts, leveraging molecular vibrational modes analysis. Its sensitivity and capability for discriminating between corrosion products make it a valuable tool, particularly due to its ability to delve into structural characterization at the microscale and produce qualitative phase distribution maps. In this research, we employed micro-Raman spectroscopy in combination with correlative imaging techniques and imaging tomography to investigate corrosion phenomena in nails from the Phoenician-Punic site of Motya (Sicily, Italy). To accomplish this, we used Correlative Light and Electron Microscopy, Micro-Raman spectroscopy, and X-ray Microscopy. This approach involves the integration of complementary investigation techniques to perform multiscale and multimodal experiments, all focused on the same area of interest. The aim of this study is to investigate the stratification of corrosion layers and the mechanism of transformation of Fe products formed under specific conditions that occurred in lagoon-like environment. Recognizing the spatial distribution and interconnectivity of mineral phases and cracks within corrosion layers was crucial for comprehending the corrosion process's evolution. The results showed remarkable differences in the condition of the nails and provided 3D imaging of the internal structures, revealing cracks and the original shape of the nails.