Surface modification processes on European Union bronze reference materials for analytical studies of cultural artefacts

Abstract

This article presents research results obtained in the 4th framework (1994-1998) of the Standards, Measurements and Testing (SM& T) Program of the European Union, DG XII: the IMMACO project (Improvement of Means of Measurements on Archaeological Copper Alloys for characterization and Conservation). One of the aims of this project was to study copper alloy compositions of European objects dating from the Bronze Age to Roman times. This work has revealed that five types of alloys seem to be particularly representative of what was produced in these countries during this period. These alloy compositions will be certified as reference materials by the European Union. In the second part, artificial patinas have been made on the different bronze alloys using electrochemical polarizations as surface modification techniques. The characterization of the corrosion surfaces and interfaces formed during the treatment with "light microscopy" (LM) and scanning electron microscopy (SEM/EDX, X-Ray maping) have shown that the artificial patinas seem to be very close to those from excavations. As a consequence, the patined samples can be used as a substitute for genuine artifacts in the future to improve conservations techniques.