The electrochemical techniques for the diagnosis and restoration treatments of technical and industrial heritage: three examples of metallic artefacts

From technical and industrial heritage, curators are in charge of numerous and important collections of metallic items which are representative of the industrial and technical development of our societies. The diagnosis of the conservation state and the choice of the restoration treatment are important questions that have to be solved by curators to avoid expensive restoration works. This paper proposes to show how simple electrochemical techniques can be used as an efficient tool to contribute to the diagnosis of the conservation state of metallic artefacts and to monitor the restoration treatment through three examples. In the case of the very-corroded aluminium alloys of aircraft belonging to the Air and Space Museum (Le Bourget, France), stationary electrochemical measurements are able to characterise the allowable electrochemical effect of thick corrosion layer on the corrosion rate of metal but are not sufficient to give a complete diagnosis. In contrary, for the bronze part of the miner's lamp collection of the Mining History Centre of Lewarde, France and the nickel-plated steel of an ancient typewriter of the Musée des Arts et Metiers, Paris, France, an inhibition treatment based on sodium carboxylate within the framework of temporary conservation treatment was applied with success, on the basis of the electrochemical results obtained in the present study.