X-ray fluorescence for the study of the patinas on an outdoor bronze monument

The aim of this paper is the analysis of main elements of the patinas on an outdoor bronze monument, through the use of a portable Energy Dispersive X-Ray Fluorescence (EDXRF) equipment. In particular we investigated the concentration of copper, tin, lead, calcium, iron, sulphur and chlorine on the patinas of a bronze statue dedicated to Sigismondo Castromediano, which was created in 1905 and later placed in Lecce (Apulia, Southern Italy). Thanks to the versatility of the EDXRF portable apparatus we carried out a complete scan of the monument in a relatively short time. This has enabled us to obtain useful information on the patinas in a completely non-invasive way. EDXRF experimental data demonstrated that the two analysed parts of the monument are constituted by different bronzes, whereas the elements that characterize the depositions are equivalent in the two monitored parts. Moreover, multivariate statistical analysis was carried out in order to identify possible correlations and/or differences of elemental composition among the patinas of these two statues. Finally, a X-Ray Diffraction (XRD) analysis was carried out on a sample of deposit collected from an area of the statue not exposed to the washing away, in order to identify the phases of the deposit and to evaluate possible corrosion products. The main results of XRD analysis show that there are not corrosion products and the deposit is due to suspended particulate. The information obtained can be helpful for both archaeological and conservation studies for possible future monitoring and/or restoration work of the statue in object.