Glow discharge optical emission spectrometry (GDOES) analysis of the patina on ancient bronzes

Glow discharge optical emission spectrometry (GDOES) has been used for obtaining elemental concentration depth profiles of the corrosion product layers , i.e. the patina, grown on Roman are Punic bronze ancient artefacts found during the archaeological excavation of Tharros (western Sardinia, Italy). For all these materials, the results show via GDOES it is possible to obtain reliable and reproducible quantitative data for the ancient metal artefacts taking into account that bronze artefacts are not homogeneous. Some examples of the GDOES analytical capability as elemental depth concentration profiles through thick bronze patinas are shown and briefly discussed in combination to the microchemical features obtained via electron microscopy (SEM+EDS) and X-ray diffraction (XRD). The results provide a good insight into the microchemical structure of the patinas evidencing selective corrosion and depletion phenomena and further, show clearly the interaction between the soil and air constituents with the corrosion products.