Abstract
The excavations in the necropolis of the Francavilla Marittima archaeological area, in Calabria, have brought to light the rich burial artifacts and materials, dated between the end of the ninth and sixth centuries BCE. SEM/EDS analysis was conducted on some sections taken from a bronze artifact classifiable as an armilla or fibula fragment. Our aim was to elucidate the nature of the corrosion processes acting on the specimen. SEM investigation detected the segregation of tin towards the outer layer and a depletion of the copper content in the same region. Furthermore, the elemental distribution maps of the sections analyzed evidenced the presence of chloride ions in the border area between the corrosion patina and the metal alloy. Such anion migration of chloride ions into the interior of the alloy leads to a particular variant of the type of corrosion of structure that in the literature has been identified as structure I.
A cavity electrode designed for electrochemical measurements of powders was used to perform cyclic voltammetry experiments devoted to explore the activity of the patina covering the surface of the bronze fragment. The surface layer consists mainly of tin and tin oxides; the layer immediately beneath it contains copper oxides. An increase of reactivity was shown in an acidic environment. The activity of the patina is greatly reduced at pH 5 and appears to be zero at neutral pH.
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Acknowledgments
The authors thank the University of Calabria for financial support. The authors are grateful to Dr. Rossella Pace and the Association for the International School of Archeology “Lagaria” NPO for having given the permission to access the artifact and the literature data.
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Imbardelli, D., Gallucci, M.C. & Chidichimo, G. SEM and electrochemical characterization of bronze artifacts from the Francavilla archaeological site. Archaeol Anthropol Sci 9, 567–578 (2017). https://doi.org/10.1007/s12520-016-0396-y
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DOI: https://doi.org/10.1007/s12520-016-0396-y