Electrochemical impedance measurements in the conservation of metals

Abstract

This chapter presents an overview on the electrochemical impedance measurements in the conservation of metals. Electrochemical Impedance Spectroscopy (EIS) has proved a useful technique in corrosion science, in the field of protective coatings characterization. The EIS technique and applications to the field of cultural heritage field are still under development. A specially designed measurement methodology is described for field application on outdoor bronzes. A measurement made on a (bronze + microcrystalline wax) system allows the characterization quantitatively of the evolution of the corrosion resistance during ageing. Several EIS applications for the characterization of coatings to be applied on bronze art works could be suggested, which can effectively support research on more effective corrosion protection treatments. Metals and alloys have a tendency to interact with their environment forming oxides and other compounds that are more stable. In some cases the new compounds form a uniform, adherent and stable layer on the metal surface, preventing the metal from interacting further. In other situations the product formed is either porous or flakes away easily, leading to a continuous loss of metal. Studies of these types of interaction lie in the field of corrosion science. The corrosion behavior of metals and alloys is due to a complex interaction of several factors related to both the metallurgical properties of the metal (composition, structure, etc.) and environmental factors (humidity, pollution, biological aspects, etc.).