The evolution of the corrosion process of medieval objects through IR-spectroscopy

The investigation of the chemical composition and microstructure of archaeological metal artifacts is essential for understanding degradation processes, with a particular attention to the corrosion, often triggered by prolonged periods of burial. This study focuses on the characterisation of the metal structure of a set of agricultural tools remains dating from the 13th to 14th centuries, unearthed in the site of Cencelle, a medieval settlement near the Tolfa Mountains (central Italy), founded in the 9th century and abandoned since the 17th century AD (Annoscia, 2016). The main objective is to understand the underlying causes of degradation, assess conservation status, and unravel the composition of patinas and corrosion products formed during and after burial period (Grevey et al., 2020). To achieve these objectives, a comprehensive multi-analytical approach has been adopted, encompassing techniques such as Optical Microscopy, Electron Microscopy coupled with Energy Dispersive X-ray analysis, and Infrared spectroscopy. Significantly, infrared spectroscopy plays a crucial role in identifying both organic and inorganic materials within the samples, as well as to identify the nature of the patinas and the corrosion products growth on the samples surfaces also after their preparation. By analysing data acquired through Infrared spectroscopy, it becomes possible to identify compounds present in corrosion products and determine their implications on the conservation status of metal artifacts. This methodological framework offers detailed insights into the nature and composition of materials within the samples, enhancing understanding of degradation mechanisms, and guiding the formulation of conservation and restoration strategies. In conclusion, integrating Infrared spectroscopy with complementary analytical methodologies provides a robust approach for the systematic examination of archaeological metal artifacts and their associated degradation processes. The outcomes of this investigation provide substantive contributions towards the preservation and valorisation of medieval cultural heritage. Annoscia G. M. (2016) - Per una storia agraria di Leopoli-Cencelle: gli attrezzi agricoli (XIII-XV secolo). Scienze dell’Antichità 22.1, 177-187. Grevey A. L. et al. (2020) - Microstructure and long-term corrosion of archaeological iron alloy artefacts. Herit. Sci., 8(57), https://doi.org/10.1186/s40494-020-00398-9.