'Silver-copper alloys corrosion mechanisms...'

PAPER, PREPRINTS, ICOM-CC 18^th TRIENNIAL CONFERENCE

• Tissot, I^a,b. O.C. Monteiro^c, M.A. Barreiros^d, and M.F. Guerra^e. 2017. Silver-copper alloys corrosion mechanisms – new perspectives for the conservation assessment of cultural heritage objects. In ICOM-CC 18^th Triennial Conference Preprints, Copenhagen, 4-8 September 2017, ed. J. Bridgland, art. 1611. Paris: International Council of Museums.
  Silver-copper alloys corrosion mechanisms – new perspectives for the conservation assessment...
  
  ^{a Archeofactu  b NOVA University Lisbon  c University of Lisbon
  d National Laboratory of Energy and Geology (LNEG)  e ArchAm, UMR 8096 CNRS, Nanterre, France}

^{Abstract
The conservation of silver alloys has been largely based on studies of pure silver atmospheric corrosion mechanisms, resulting in the identification of Ag2S as the main corrosion product and discarding the importance of the other alloy constituents. This work studies the early stages of the atmospheric corrosion of sterling silver, considering the role of copper and its subsequent influence on conservation assessment. After corrosion in a sulfide solution, copper and sterling silver samples were analysed by UV-visible spectrophotometry, scanning electron microscopy with energy-dispersive x-ray spectrometry and x-ray diffraction. Naturally corroded samples were also studied for comparison. The relation between colour and the thickening of the corrosion layer with the formation, over time, of different compounds could be shown. The heterogeneous and porous film developed during the first stages is then replaced by a layer-by-layer structure composed of different corrosion products. Despite the low copper content in the alloy, Cu2O plays the major role in this process.}