Abstract
<p>In this paper, a study of the corrosion products formed on archaeological bronze artefacts excavated in Tharros (Sardinia, Italy) is presented. The investigation was carried out by means of the combination of different analytical techniques, including optical microscopy, micro-Raman spectroscopy (µ-RS), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy and X-ray diffraction. The artefacts under study are three bronze coins from the Phoenician–Punic period that are deeply corroded due to the chloride-rich soil of the Tharros excavation site. µ-Raman spectroscopy was chosen to investigate the corroded surfaces of the artefacts because it is a non-destructive technique, it has high spatial resolution, and it makes it possible to discriminate between polymorphs and correlate colour and chemical composition. Through µ-RS, it was possible to identify different mineralogical phases and different polymorphs, such as cuprite (Cu<sub>2</sub>O), copper trihydroxychloride [Cu<sub>2</sub>Cl(OH)<sub>3</sub>] polymorphs, hydroxy lead chloride laurionite [PbCl(OH)] and calcium carbonate polymorph aragonite. The experimental findings highlight that micro-Raman spectroscopy can be used to provide further knowledge regarding the environmental factors that may cause the degradation of archaeological bronzes in soil.</p>
Highlights
In the past few decades, a series of cutting-edge analytical techniques have found an ever-growing application in the cultural heritage conservation field, offering interesting insights into the provenance, history and fabrication methods of cultural heritage artefacts
Raman spectroscopy has become a fundamental tool in conservation science, as it does not require sampling of the artefact under study and the analysis can be performed in museum galleries, storage facilities and conservation laboratories thanks to the use of portable instrumentation [1], [2]
This paper deals with the application of micro-Raman spectroscopy (μ-RS) for the analysis of the corrosion products of some metallic artefacts. μ-RS furnishes an identification of the corrosion products by determining the vibration modes and the bond vibrations in the structure [4]
Summary
In the past few decades, a series of cutting-edge analytical techniques have found an ever-growing application in the cultural heritage conservation field, offering interesting insights into the provenance, history and fabrication methods of cultural heritage artefacts. Among these techniques, Raman spectroscopy has become a fundamental tool in conservation science, as it does not require sampling of the artefact under study and the analysis can be performed in museum galleries, storage facilities and conservation laboratories thanks to the use of portable instrumentation [1], [2]. Μ-RS has the advantage of being a fast and non-destructive technique, and, in backscattering geometry, it is especially suitable for analysing surfaces
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