Figure 2: The Bronze Artifact

Figure 2 shows one of the bronze artifact that has been submitted to several chemical–physical characterizations : a bronze plate, found in the Tepe sofalin at 79cm depth. The bronze artifact has been found in a better conservation state with respect to the artifacts buried near the surface, that often affects the mechanical properties of the bronze archaeological artifacts. Intergranular corrosion phenomena are related to intrinsic metallurgical features, whose formation is induced during the manufacturing of the artifacts carried out in ancient times by repeated cycles of cold or hot mechanical work and thermal treatments.
Figure 3 shows a bronze bowl found in the Tepe sofalin, after recovery from the excavation. The bronze bowl reveals,
already at a visual examination, its noteworthy brittleness. The corrosion attacks are evident on a wide area of the artifact; because of the long-lasting contact with the soil, a complex environment whose different parameters as geological and hydrological factors and chemical composition can play an important role in the corrosion processes.
A first phase in the formation of the secondary patina is the transformation of cuprite into malachite and atacamite, (Fig. 2,3). The secondary patina often presents crystal formations on its surface (Fig 4), as structural arrangements. The secondary patina, by developing in contact with some microstructures from the site, embeds them into the surface of the object (by processes of mineralization), forming the tertiary, or the contamination patina (Sandu et al,2012; Constantinides,2002). The tertiary patina is shaped without metallic core.