On-Site Identification of Corrosion Products and Evaluation of the Conservation Status of Copper Alloy Artworks Using a Portable Raman Spectrometer

Copper alloys form various corrosion products such as sulfides and chlorides. Chlorides can cause severe structural damage in 'bronze disease', making the early identification of corrosion products and conservation treatment important tasks. In this study, standard spectra were established for nine minerals of corrosion products using a portable Raman spectrometer, and their identification was verified by comparing them with benchtop micro-Raman spectra. The main characteristic bands were detected for most corrosion products, and the in situ applicability of the portable Raman spectrometer was demonstrated. However, for some samples, the signal-to-noise ratio was low, while the main characteristic peaks were still identifiable. In particular, dicopper chloride trihydroxides (such as atacamite and clinoatacamite) were clearly distinguished as corrosion products whose early identification is crucial. After the on-site analysis of copper alloy artworks exposed to outdoor environments for over 30 years, corrosion products such as malachite, brochantite, and moolooite were detected, indicating that portable Raman spectrometers are an effective tool for diagnosing conservation conditions. This study demonstrates that portable Raman spectrometers can be effectively used to identify corrosion products and assess the conservation state of copper alloy artworks and are expected to make significant contributions to future conservation and restoration efforts.