Combined use of GDOES, SEM plus EDS, XRD and OM for the microchemical study of the corrosion products on archaeological bronzes

By means of the combined use of glow discharge optical emission spectrometry (GDOES), scanning electron microscopy + energy dispersive spectrometry (SEM + EDS), X-ray diffraction (XRD) and optical microscopy (OM), corrosion products, i.e., the patina, grown on archaeological leaded bronze artefacts used by Punics and Romans, have been studied. This innovative approach has been utilised in order to gain further insight into the microchemical structure of the corrosion products as well as for selecting the cleaning and restoration methods. For all of the archaeological artefacts, the results show that via the innovative use of GDOES, it is possible to obtain reliable and reproducible quantitative elemental composition depth profiles for the outermost corroded layers, which are briefly discussed in combination with the microchemical features obtained via SEM + EDS, XRD and optical microscopy. Finally, the results show that GDOES, with its ability to provide routine and rapid analysis of layers of thickness up to 120 mum, seems to be a powerful technique in studies of the corrosion products on archaeological bronzes, with the aim of restoring and conserving ancient high tin or low tin leaded bronzes.