Noninvasive Solution for Electrochemical Impedance Spectroscopy on Metallic Works of Art

Abstract

Metallic works of art of cultural relevance are continuously subjected to corrosion as the environment becomes increasingly polluted. A fast and simple method to in-situ assess the conservation conditions is therefore required. This paper describes the development and performance of dry and gel-based electrodes which can be used to asses the surface conservation state without the need to move the artifacts and which do not cause any damage to them. The electrodes can be used with a portable electrochemical impedance spectroscopy system, without employing electrochemical cells. The proposed solution does not provide all the information one can obtain using an electrochemical cell, but however it can discriminate between protective coatings. It can be used to assess the protective capability of corrosion products layers and natural patinas and it can therefore enable a non-invasive routine surface assessment to be conducted that could be extremely useful for people working in the field of conservation of Cultural Heritage.

In Situ Electrochemical Impedance Spectroscopy Measurements and their Interpretation for the Diagnostic of Metallic Cultural Heritage: A Review

“…On the other hand, the thickness of the gel is not homogenous as the RE occupies part of the thickness in the central area. This introduces distortions in the measurement because of inhomogeneous distribution of current as a function of the coating resistivity ,. The fact is that, as can be seen in Figure of reference, results from ECG and dry electrodes (see section 2.2.2) are quite different from traditional cells, and the use of these electrodes has been discarded in subsequent studies by the same authors.…”

A novel gel polymer electrolyte cell for in-situ application of corrosion electrochemical techniques

“…Two different interactions can occur in the gel-waterelectrolyte systems, leading to opposite changes in the diffusion of the ions: on one hand, adsorption of ions on the gel and obstruction of their diffusion paths by the macromolecules decrease the diffusion coefficient in the medium; on the other hand, gel-water interactions increase the diffusivity of ions in the gelified electrolyte [30].This change in the diffusion of ions within the electrolyte would be responsible for the minor change in the electric conductivity of the electrolyte, R e . However, as opposed to commercial electrocardiography electrodes, our G-PE keeps the good conductivity of traditional liquid electrolytes [10][11][12].…”

“…al used commercial electrocardiogram electrodes to study patinas and protective coatings on monuments [10,11]. While this system is non-destructive and well suited for in-situ measurements, the low conductivity of the gel electrodes may be a limitation for the measurement of low impedance systems and causesinhomogeneities in the current distribution [12]. Additionally, EIS results obtained with this electrodes show significant differences with those obtained with conventional cells at low frequencies.…”

Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures

“…Alternative geometries to the standard fluid cell have been previously explored for the purpose of making measurements in situ, yet none adequately address the need to be able to take measurements without having electrical contact to the underlying substrate. For example, in three studies the substrate must be exposed by removing some of the protective coating [17], and in two other studies, damaged coatings must be pre-soaked with electrolyte to enable the measurement, causing potential damage to the substrate [18]. In the latter two studies, without pre-treatment, the electrode setups were only able to provide information about the surface of the protective coating because their soft-polymer electrodes did not contain fluid electrolyte to penetrate micropores that would have enabled diffusion information to be obtained.…”