Study of Corrosion Potential Measurements as a Means to Monitor the Storage and Stabalization Processes of archaeological Copper Artefacts

Archaeological copper artefacts recovered from wet saline environments are often stored in tap water and stabilized in sodium sesquicarbonate solutions. Modification of the natural patina and development of active corrosion can occur during these processes. This implies that monitoring of storage/stabilisation processes is necessary. The focus of the study consists of examining how corrosion potential (Ecorr) measurements can contribute in providing information on the effectiveness of storage and stabilisation treatments. This paper reports on the Ecorr versus time plots of artificially prepared copper coupons (covered or not with corrosion layers) immersed in tap water and a sodium sesquicarbonate solution. Synchrotron radiation XRD was performed in parallel to understand the reactions that take place during the immersion processes

Electrochemical characterization of organic coatings for protection of historic steel artefacts

Figuras en el archivo zipElectrochemical techniques are mainly known in the field of cultural heritage conservation as a tool for the elimination of corrosion layers or the removal of chlorides. However, these techniques are also a valuable tool for assessing the anti-corrosive efficiency of protective coatings. The aim of this study was to evaluate the performance of different coatings for their use in metallic heritage conservation using polarization resistance (Rp) and electrochemical impedance spectroscopy (EIS). Carbon steel samples were prepared to simulate the surface composition and morphology of historic steel artefacts, and coated by a conservator-restorer following the common practices in conservation treatments. Three commercial organic coatings have been studied: a microcrystalline wax (RenaissanceTM) and a methyl acrylate/ethyl methacrylate copolymer resin (ParaloidTM B-72) dissolved in acetone –both them commonly used in conservation and restoration treatments– and a ethylene copolymer wax emulsion in water (PoligenTM ES- 91009), that has not been used so far for this purposes. Four commercial corrosion inhibitor additives were added to the ParaloidTM B-72 resin and PoligenTM ES-91009 wax. The additives were commercial preparations with the following known active components: a blend of triazoles (M435), an ammonium salt of tricarboxylic acid (M370), a calcium sulphonate (M109), and a bis-oxazoline (Alkaterge-TTM). Rp and EIS results showed that the best protection of the steel specimens was afforded by PoligenTM ES-91009 when applied in thick layers. None of the additives have shown a clear improvement of the protection properties of the coatings, and one of them impaired the barrier effect of the coating.Acknowledgements The authors express their gratitude to the Sixth Framework Programme of the European Commission for financial support of PROMET Project (Contract 509126). D.M. Bastidas expresses his gratitude to the CSIC of Spain for his contract under the I3P Programme, co-financed by the European Social Fund.Peer reviewe