Characterization of Ag and Au nanolayers on Cu alloys by TLC, SEM-EDS, and ICP-OES

This paper reports a study on four historical samples from 19th century originating from Croatia, Europe, made of silver plated and gilded copper alloys. The investigation was carried out by chromatographic, spectroscopic, and microscopic techniques. Corrosion was identified in all samples by scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), although the samples were in well-preserved states. EDS has given the following average composition of elements Ag (82.99, 4.74, 6.34, and 15.54wt% in samples 1-4, respectively), Au (17.01wt% in sample 1), and Cu (0, 95.26, 93.66, and 84.46wt% in samples 1-4, respectively) for the outer layers of the samples. The exact sample elemental composition was determined by inductively coupled plasma optical emission spectroscopy (ICP-OES): 0.12, 0.22, 0.68, and 1.20wt% Ag in samples 1-4, respectively and 0.02wt% Au in sample 2, all on Cu alloys with impurities of Fe, Mn, Ni, Pb, Sb, Si, Sn, and Zn (in quantities 0.05-1.48wt%). Preliminary detection of metals was performed by thin-layer chromatography. Results of determined chemical composition were consistent with similar investigations, since silver-plated and gilded Cu alloys were the materials used in the production of similar samples through the history.