Corrosion study of metals of cultural and historical interest in Sulphide, Sulphate and Chloride Solutions, and their preservation

摘要

Silver, iron and bronze artifacts were used by ancient cultures. Nowadays, the historic heritage can be appreciated at museums around the world. However, in some historical places, the exhibition of artifacts made of iron or bronze is sometimes exposed to environmental conditions and they suffer corrosion damage. Although the study of the corrosion behaviour of metals by using electrochemical techniques has been a very powerful tool for assessing oxidation as well as degradation of materials, the use of electrochemical methods in environments such as museums has not yet been addressed. In this paper, an electrochemical study of Sterling silver (0.925), standard bronze and brass is carried out by using a monitoring of corrosion potential, linear polarisation resistance, polarisation curves, electrochemical impedance spectroscopy, and electrochemical noise for monitoring corrosion in immersion, as a first stage in evaluation of these materials in controlled conditions. Electrolytes used are: (a) ammonium sulphide, since it promotes severe damage mainly in silver; (b) sodium sulphate, as some artefacts are exposed in industrial environments; and (c) sodium chloride, because plenty of cultural and historical metallic artefacts are exposed in-shore.