Optimisation of the setup of LPR and EIS measurements for the onsite, non-invasive study of metallic artefacts

Electrochemical techniques have been successfully applied in the past as non-destructive techniques to the cultural heritage field. In particular, linear polarisation resistance (LPR) and electrochemical impedance spectroscopy (EIS) have been employed for the onsite monitoring of corrosion on metallic works of art, providing valuable results. Such techniques have been successfully adapted from the industrial field for this particular kind of application, but a systematic evaluation of the influence of all experimental settings on the obtained results is still lacking: several factors and parameters can affect the results, and it is important to properly consider their influence for a reliable interpretation of data. Therefore, in this work, the influence of a series of experimental parameters was evaluated in order to obtain a reliable and time-effective setup by performing a series of tests on a bronze artefact. Several variables were considered, with particular attention to those affecting the reproducibility and reliability of the measurements, as well as the duration of each single acquisition. It was demonstrated, in fact, that an optimised experimental setup from the point of view of the duration could improve also reproducibility and reliability of the measurements. The optimised protocol was then adopted in the framework of a diagnostic campaign of the Monumento ai Caduti (War Memorial) of Lecco (IT)