Characterization of a buried archaeological bronze from the Celtic tomb n°1002 of La Fosse Cotheret (Roissy-en-France) (original) (raw)
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R. Mazzeo, S. Prati, M. Quaranta, G. Sciutto, 2012
The present review intends to give an overview on the type of information that is possible to gather from the application of different non-invasive and micro-destructive analytical techniques. Typically, methods that require the withdrawal of a sample, such as metallography, SEM-EDS, AAS, FTIR and Py-GC-MS are employed. Through their use, it is possible to identify the material constitution, to evaluate the degradation behaviour and the state of conservation of excavated bronze artefacts. It is also underlined how a non-invasive approach might be used whenever no sampling is allowed, though some limitation should be considered. Furthermore, analytical techniques play an important role in the characterisation and evaluation of the effectiveness of protective coatings and corrosion inhibitors before and after restoration procedures. An interesting aspect is the implication of science for the recognition of forgeries, when analytical studies provide evidences able to prove or deny objects' authenticity.
Integrated analytical methodologies for the study of corrosion processes in archaeological bronzes
… Acta Part B: Atomic …, 2011
The investigations on structure and micro-chemical composition of archaeological metal alloys are needed in archaeometry. The aim of this study is devoted both to acquire information about their provenance and production technology, and to improve our understanding about the corrosion processes. In this paper we present the study of the corrosion phenomena of bronze samples, laboratory-made according to binary, ternary and quaternary alloys typical of Roman archaeometallurgical production through an integrated methodology based on the use of non or micro invasive physical techniques. Among the analysed samples, two were artificially aged through burial in the archaeological site of Tharros, along the west coast of Sardinia (Italy). The corrosion products, typical of the bronzes in archaeological sites near the sea, have been characterized by non invasive and micro-destructive measurements. In particular, the corrosion patinas were examined through optical microscopy, scanning electron microscopy and microanalysis, X-ray fluorescence and laser ablation spectroscopy. The use of integrated technologies allowed us to determine both the elemental composition and surface morphology of the patina, highlighting the correlation between patina nature and chemical composition of the burial context. Moreover, data obtained by the laser-induced breakdown spectroscopy along the depth profile on the samples, have yielded information about the stratigraphic layers of corrosion products and their growth. Finally, the depth profiles allowed us to verify both the chemical elements constituting the patina, the metal ions constituting the alloy and the occurrence of migration phenomena from bulk to the surface.
X Study on the Specific Effects of Corrosion Processes on Ancient Bronze Artefacts
The paper presents the cases of the corrosion processes which take place on starting from the usage period when the primary patina is being formed and when the secondary patina starts, than continuing with the archaeological site where the contamination patina is obtained under the influence of the pedological processes. The paper is a review from the specialised literature and from the contributions of the authors. There has been used the direct analysis with optical instruments, electron microscopy and EDX.
More than 1800 bronze objects dating to c.600 bc were excavated from the site of the Sacred Animal Necropolis at Saqqara, Egypt between 1969 and 1971. While the important pieces had been accessioned by the Department of Ancient Egypt and Sudan and had been routinely cleaned using alkaline and/or acidic reagents in the 1970s, the residual group considered here, which includes numerous figurines and parts of sculpture, situlae and jewellery, had remained unregistered and uncleaned and so retained a burial corrosion crust. Both the metal substrates and the surface corrosion were studied to obtain information about objects that were under consideration for accession and to contribute to the wider study of this important site.
Characterization of Egyptian bronze archaeological artifacts
This paper presents the results of in situ non-destructive X-ray fluorescence determination of the chemical analysis of a collection of ten bronze statues that are on display at the Egyptian museum of Cairo. The statues are from the late period of the ancient Egyptian history. In addition, destructive technique X-ray diffraction analysis was applied on 11 damaged archaeological objects to determine the corrosion products and the alloy compositions. Specimens of the latter objects were subjected tometallographic examinations to determine the microstructure of the alloy. Surprisingly, the results indicated that all ten statues and 10 of the 11 damaged objects were made of lead – bronze alloy; the percentage of the lead varied from 3.43 to 18.04, the tin varied from 2.53 to 10.67. The chemical composition of the patina on eight damaged objects is essentially composed of (Cu2O) cuprite for all objects in addition to other compounds such as (SnO2) cassiterite in two objects, (PbCO3) cerussite in three other objects and (Cu2(OH)3Cl) atacamite or (Cu(OH)3Cl) paratacamite in two other objects. The formation of chlorides and carbonate resulted from the interaction between surrounding environment and the alloy. The results of the metallographic examinations indicated a nonhomogenous structure and the increase of the lead content increases the globular lead particles. In spite of this condition, the galvanic corrosion tendency when the alloy is exposed to moist air or soil is not possible as lead compounds are electrically insulating. Another advantage for using leaded bronze in making statues is being heavy and thus leads to stability.
A multitechnique study of archeological bronzes
Surface and Interface Analysis, 2008
We used XPS, X-AES, synchrotron radiation-induced total electron yield X-ray absorption spectroscopy (XAS), synchrotron radiation-induced photoelectron microscopy (PEM), and electron-probe microanalysis (EPMA) techniques to explore the elemental and microchemical properties of two tin-bronzes (denoted A and B) found at a necropolis located in Fossa (Abruzzo, Italy), and dating from the late ninth century B.C. EPMA shows that the bulk elemental composition of the two bronzes is very much alike as far as the leading metals are concerned, whereas the main differences are limited to the composition of trace elements (A is notably richer in Pb and much poorer in Co). PEM highlights lateral chemical inhomogeneities with a spatial resolution in the submicron range. X-AES Cu L 3 MM spectra show that the content of metallic copper is more abundant in the surface region of A than in B. XPS finds that the amount of carbon-bearing species is about 40% more abundant in the former sample. A significant enrichment of metallic copper at the surface of the same bronze is confirmed by XAS Cu L 2,3 edge experiments. We interpret the 'high' carbon content found at the surface of bronze A as arising from intentional rubbing with organic substances, e.g. oil. The fact that the same bronze features a higher 'metallization' of surface copper suggests that such a procedure proved successful in minimizing the oxidation induced by the surroundings. We discuss the diagnostic potential of our multitechnique approach as a means for studying the surface chemistry of ancient metalwork.
Bronzes from the Sacred Animal Necropolis at Saqqara, Egypt: a study of the metals and corrosion
The British Museum Technical Research Bulletin 3, 2009
More than 1800 bronze objects dating to c.600 bc were excavated from the site of the Sacred Animal Necropolis at Saqqara, Egypt between 1969 and 1971. While the important pieces had been accessioned by the Department of Ancient Egypt and Sudan and had been routinely cleaned using alkaline and/or acidic reagents in the 1970s, the residual group considered here, which includes numerous figurines and parts of sculpture, situlae and jewellery, had remained unregistered and uncleaned and so retained a burial corrosion crust. Both the metal substrates and the surface corrosion were studied to obtain information about objects that were under consideration for accession and to contribute to the wider study of this important site.
Uncommon corrosion phenomena of archaeological bronze alloys
Applied Physics A: Materials …, 2006
In the framework of the EFESTUS project (funded by the European Commission, contract No. ICA3-CT-2002-10030) the corrosion products of a large number of archaeological bronze artefacts are investigated by means of the combined use of scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and optical microscopy (OM) and tentative correlation of their nature with the chemical composition of the artefacts and the burial context is proposed. The results provide good insight into the corrosion layers and evidence in some bronze Roman coins and artefacts; the occurrence of uncommon corrosion phenomena that give rise to the formation of a yellowish-green complex chlorinephosphate of lead (pyromorphite, (PbCl)Pb 4 (PO 4) 3) and of a gold-like thick layer of an iron and copper sulphide (chalcopyrite, CuFeS 2). The micro-chemical and micro-structural results show that the coins were buried in a soil enriched in phosphorus for the accidental presence of a large amount of decomposing fragments of bones or in an anaerobic and humus rich soil where the chalcopyrite layer has been produced via the interaction between the iron of the soil, the copper of the coin and the sulphur produced by the decomposition of organic matter in an almost oxygen free environment. Finally, some unusual periodic corrosion phenomena occurring in high tin bronze mirrors found at Zama (Tunisia) are described.
Acta IMEKO
A categorization of corrosion morphologies of archaeological Sn bronzes was carried out on archaeological Iron Age objects. The objects come from a Celtic deposit located in central France (Tintignac, Corrèze) and are dated between 2nd and 3rd cent BC. Being samples of corroded metals taken from a single find spot, parameters connected to the features of the alloy and known to influence the corrosion morphologies were thoroughly considered. Global processes were highlighted, and corrosion mechanisms were characterized with a multi-analytical protocol (SEM-EDS, micro-Raman spectroscopy, image analyses) according to the detected morphology. Elaboration of the results was carried out with a multicomponent approach. Results show the presence of 5 different morphologies correlated to the alloys characteristics of the objects. Alloy composition, microstructure, degree of deformation and grain size were found to influence the corrosion products formed and the morphology of the attack. In p...