'Atmospheric corrosion of patinated silverwork'

PAPER, CORROSiON AND MATERIALS PROTECTION, 35

• Isabel Tissot^a,b, O.C. Monteiro^c, Maria Alexandra Barreiros^d, Maria Guerra^e. Atmospheric Corrosion of Patinated Silverwork: a Conservation Challenge. Corrosão e Protecção de Materiais (Corrosion and Materials Protection), LNEG - National Laboratory of Energy and Geology, 2016, 35, pp.15-19. 10.19228/j.cpm.2016.35.05. hal-02426539.
  Atmospheric corrosion of patinated silverwork: a conservation challenge
  
  ^{a Laboratory LIBPhys, NOVA University Lisbon b Archeofactu c Centre for Chemistry and Biochemistry, Faculty of Sciences, University of Lisboa
  d National Laboratory of Energy and Geology, LEN/UER e ArchAm - UMR 8096 CNRS, MAE, Nanterre, France}

^{Abstract
Patination has been frequently used by jewellers to modify the colour of silver alloys. By application of a solution of sulphur compounds, blackish or bluish surfaces can be obtained, but the intentionally produced silver-sulphur compounds are chemically similar to the atmospheric corrosion products that develop on silver alloys. The conservation of patinated silver objects, such as Art Nouveau jewellery, raises thus analytical challenges. In order to define accurate conservation treatments, the patina and corroded surfaces characterisation is mandatory. In this study, sterling silver samples were patinated and subjected to corrosion by immersion in a sulphide containing solution. The identification of the chemical compounds present on the patinated sterling silver before and after corrosion was carried out by UV-visible spectrophotometry, X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectrometry. Data obtained suggest a two-stage corrosion process: a decrease of the silver compounds patina thickness caused by its dissolution, followed by the formation of corrosion products with different compositions and morphologies containing silver and copper sulphur compounds.}