| Abstract: | Tarnishing of a single phase 14 carats Au-Ag-Cu alloy was studied using the Tuccillo-Nielsen test. Auger Electron Spectroscopy and coulometry were employed for the characterization of the composition and the thickness of the surface layers formed. X-ray diffraction was used for further characterization of thicker layers. The layer formation followed linear kinetics. The tarnished layer at short test durations of 0.5 to 5 hours consisted mainly of Ag2S, CuS and Cu2S or compounds near to this stoichiometry. The composition of the top surface of the tarnished layer is constant but its global composition changes with the duration of the tarnishing test. |
