Examination of archaeological bronze parts using micro-computed tomography and metallography

Abstract

Archeological finds, such as old coins among which some show signs of corrosion, are, in general, unique pieces even though several copies exist of individual types. Subferrati, Roman coins with an iron core and a bronze coating, for instance, could be examined by conventional computed tomography (CT). The CT image allows an easy distinction of corrosion products, metallic iron, and the bronze so that appropriate sections could be selected from the images for metallography. The micro-CT technology even allows examining smaller archaeological objects to get an overview. The resolution of the micro-CT is a function of the object size and lies between 5 and 10 μm. The following metallographic examinations are intended to characterize the microstructure. Apart from these examinations, SEM analyses may also be performed on the sections. Different bronze pieces from cremation and inhumation burials were examined. Micro-CT provides a well recognizable contrast between corrosion products and the metallic bronze. If several similar objects exist, micro-CT examinations allow a decision to be made on which parts are suitable for metallographic analyses and which are not.