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This paper describes the use of several microbeam analysis techniques for the chemical characterization of corrosion compounds on ancient bronze objects. They include optical microscopy, SEM-EDX, TOF-SIMS, SR-FTIR, SR-XRD, and XANES. The objective is to investigate which combination of analysis methods is most suitable for this type of application, taking into account aspects such as limited sampling and the ability of obtaining spatial information. Results show that SR-XRD in combination with optical microscopy and SEM-EDX is able to provide a complete description of the layered structure both on elemental and molecular level.

Literature results of chemical bronze analyses originating from Near Eastern excavation sites have been assembled to obtain a general overview of the Mesopotamian bronze technology during the 3rd millennium BC. Results show that at the end of the 4th and at the beginning of the 3rd millennium BC arsenic alloys with an arsenic concentration up to 5% were generally into use, while tin bronzes were introduced during the middle of the 3rd millennium. This introduction appears almost synchronously over the entire region of Mesopotamia, although there is an indication that the tin bronze introduction was slightly later in southern Mesopotamia.

This paper focuses on the corrosion behaviour of tin objects stored in museums. A set of authentic objects was investigated using optical microscopy (OM) and scanning electron microscopy with energy dispersive X-ray detection (SEM-EDX). The goal existed in acquiring information on the appearance of the corroded surfaces and the chemical composition of the alloys. The analyses made it possible to obtain an overview of typical corrosion forms seen on ancient tin objects. In order to study the influence of the alloying elements and corrosive agents on the corrosion behaviour, a simulation study was set up in which five ancient alike tin alloys were produced and artificially corroded by using different corrosive agents. The corroded surfaces were analysed using OM, SEM-EDX and Fourier transform infrared spectroscopy (FTIR) and the results were compared with those obtained from the authentic samples. © 2004 Elsevier SAS. All rights reserved.Keywords: Ancient tin alloys; Corrosion; OM; SEM-EDX; FTIR Research aimsThe objective of this paper is to contribute to a better understanding of the degradation of tin objects present in museum collections. Specific emphasis has been laid on the study of factors which may influence the corrosion, such as the alloying elements and the corrosive agents. IntroductionSeveral publications mention tin to be corrosion resistant. Results have indeed shown that under natural conditions water and atmospheric oxygen have no harmful effects on metallic tin, although tarnishing of tin is sometimes observed in indoor atmospheric conditions [1][2][3]. Nevertheless, tin may also suffer from corrosion by mineral acids and organic acids in the presence of air [2]. This general idea has in the past led to believe that tin objects stored under normal museum conditions are little affected by atmospheric corrosion. As a result tin pest was often considered as the major deterioration cause of tin objects stored in museums. Tin pest is a physical phenomenon, i.e. an allotropic transformation of metallic white tin (b-tin) to grey (a-tin) which occurs at low temperatures, namely below 13.2°C. Metallic white tin is very ductile, while grey tin is brittle. Both have different crystallinity and density-white tin (7.29 g cm -3 ) and grey tin (5.77 g cm -3)-which result in the transformation of the objects into powder when tin pest occurs [4]. Once an object is harmed by tin pest it will be completely destroyed after a period of time. No treatment is possible in this case. The corrosion of tin on the other hand is (electro)chemical by nature and can be treated in many cases. The most typical and most stable corrosion product of tin is tin(IV)oxide, SnO 2 [4].The general belief that tin is not affected by corrosion, and on the other hand the general assumption that tin pest is the main degradation form of tin objects, has led to the fact that today many of the tin objects which are present in museums are in a certain state of decay. Detailed examination of several museum objects has, however, shown that...