Email: sabrina.grassini@polito.it

Keywords: Metallic artefacts, in situ measurements, corrosion

The scientific approach to the conservation of metallic works of art is nowadays based on the concept of preventive conservation, which is based on the principle that deterioration is not inevitable and ‘aging’ is only the result of known and controllable causes most of them correlated to the interaction between the materials and the surrounding environment. According to the Conservation Committee of the International Council of Museums (ICOM-CC) preventive conservation is defined as “all measures and actions aimed at avoiding and minimizing future damages”. Thus, the methodology of preventive conservation is indirect: controlling its causes reduces artefact deterioration.

In this contest, non-invasive diagnostic techniques and in situ measurements are very important tools for conservators to obtain valuable information on the artefact conservation state and on the environmental conditions to which the objects are exposed to, allowing long-lasting monitoring campaigns to be scheduled.

In the last years, the research group CoMeTA (Corrosion Measurements Tool for Artefacts) of Politecnico di Torino performed several measuring campaigns on bronze artworks and weathering steel structures exposed indoor and outdoor, in Italy and abroad, by a multi-analytical approach.

Electrochemical impedance spectroscopy (EIS) [1] has been employed to study the corrosion processes that are affecting metallic artworks, to assess the stability of the corrosion products layers and the protective effectiveness of conservation treatments and coatings; moreover, X-rays fluorescence (XRF) and Raman Spectroscopy have been employed for chemical and microstructural charaterisations. Finally, a 3D photogrammetry survey was carried out to create a complete documentation of the artworks. At the same time, the microclimatic conditions to which the artefacts are exposed to were monitored by means of smart sensors specifically designed for cultural heritage applications [2]. Indeed, the combination of all these techniques allowed identifying which corrosion products are present on the metallic surface, and to characterise their chemical and microstructural features, together with their electrochemical stability and to correlate them to the exposure conditions. Furthermore, it is possible to document all the analysis performed on the artworks and to integrate this information on a virtual 3D model, that can be stored and shared with curators and conservators.

The obtained results of the in situ monitoring campaigns will be presented and discussed, highlighting the advantages of the proposed approach and of the developed measuring devices, and discussing the challenges still open in the development of tailored safeguard methodologies for metallic artefacts.

References

1. Grassini S. et al, ‘A simple Arduino-based EIS system for in situ corrosion monitoring of metallic works of art’, Measurement (2018), 114, 508–514

2. Lombardo L. et al, ‘Wireless Sensor Network for Distributed Environmental Monitoring’, IEEE Transactions on Instrumentation and Measurement (2018), 67, 1214–1222.