16039
Accession Number
29894
Title Of Article Chaper
Chemical and structural properties of ancient metallic artefacts: multitechnique approach to study of early bronzes
Title Of Journal Book
British Corrosion Journal
Volume
35
Issue
1
Pages
43-47
Collation
5 p. : ills.
Reference Bibliography
Includes bibliographic references
Language Of Text
English
Literature Type
Serial
Literature Level
Analytic
Abstract
The results are presented of a characterisation study of the microstructure and microchemistry of archaeological bronze (Cu-Sn) artefacts from the eighth to the sixth century BC. Metallographic examination, with optical and electron optical microscopy, has been performed on polished sections of early Iron Age studs and bracelets fround in incineration tombs of the Necropolis of Chiavari in Italy. A heterogeneous microstructure of the bronze was observed, exhibiting a wide range of grain sizes, and a predominant -phase solid solution containing / and / eutectoid phases decorated with a high density of inclusions. The composition of grain boundary surfaces was determined, using scanning Auger microscopy (SAM), on specimens fractured in vacuo. The extent of tin segregation at the grain boundaries was 3-5 times greater than that in the grain interiors. Copper rich sulphides occasionally containing the oligoelements (iron and lead) were identified as the predominant type of inclusions formed at the grain interfaces nd within the grains. Analysis of the corrosion patina at the surface of the bronze artefacts was conducted by combining X-ray diffraction, scanning electron microscopy with energy dispersive X-ray analysis, and SAM. The patina was found to exhibit a multilayered structure and a complex chemical composition forming various crystallographic phases including malachite, cuprite, and copper-tin oxide. Corrosion of the underlying bronze matrix proceeded along the grain boundaries, where the sacrificial corrosion of tin reacting with diffused oxygen and chlorine was identified. The results of this study have been used to clarify the metallurgy and manufacturing processes of the examined finds, and to evaluate the state of their degradation.
Keywords
chemical; structure; property; metal; artifact; bronze
pub_id
16039