Preliminary study and characterization of some of the metals statues belonging to the corpus of artifacts found in San Casciano dei Bagni (Siena).

Archaeological excavations conducted since 2019 in San Casciano dei Bagni (Siena), an area under study since 2017, have uncovered a monumental sacred complex from Etruscan and Roman ages closely linked to the presence of thermal water (between 39 and 42°C). The building is erected on pre-existing Etruscan structures and has different architectural phases from the early Tiberian age until the building was abandoned and closed in the 5th century AD. As of 2021/22, excavations within the bath have uncovered a corpus of artifacts, including several bronze statues, associated with the unique context of the Bagno Grande. In this Etruscan and Roman thermal-mineral sanctuary, archaeologists have found evidence of centuries of history that can further enrich historical, sacred-cultural, and manufacturing knowledge of this long period, thanks in part to the contribution of archaeometallurgy. This not only allows for an understanding that can enhance the field of materials science, but also ensures optimal approach for conservative studies, needed interventions, museum display and accessibility of the artifacts. This study concerns the metallurgical and electrochemical characterization of some bronze statues found in the Bagno Grande pool. Understanding the technology and composition of the materials used, as well as studying and evaluating the alteration layers created over time and their response to corrosion, is an important initial phase of investigation. Preliminary non-destructive analyses were conducted by XRF (X-Ray Fluorescence) spectroscopy for preliminary characterization of the alloys, which were then compared with SEM-EDS (Scanning Electron Microscopy-Energy Dispersion Spectroscopy) analyses. After micro-sampling, optical microscope observations were made to better understand the structure of the various alloys under investigation. For the study of the alteration layers and their corrosion response, electrochemical tests were carried out using techniques such as LSV (linear sweep voltage) and EIS (electrical impedance spectroscopy). These techniques were used to study the kinetics and rate of electrochemical reactions at the interface. In addition, electrochemical parameters such as corrosion potential and current density provide crucial information on the current state of the artifacts. The integration of this information with data obtained from the previously mentioned analytical techniques allows a comprehensive preliminary view of the metallurgical characteristics and degree of preservation of the statues of San Casciano dei Bagni. This multidisciplinary and interdisciplinary approach is essential to evaluating the state of conservation of the artworks and to planning restoration interventions aimed at preserving this cultural heritage for future generations.