Corrosion phenomena and patina on archaeological low-tin wrought bronzes: New data

Abstract

The study reports a systematic examination and analysis of low-tin wrought bronzes from archaeological burial environments in the Mediterranean. The corrosion profiles occurring on samples taken from thirty-six predominantly Corinthian and Illyrian helmets from excavations in Greece, were analysed using polarised metallography, SEM-imaging, SEM-EDX and X-Ray Diffraction methods. Analysis confirms and expands understanding of existing corrosion models for copper dissolution producing smooth tin enriched patinas that preserve the original surface as a marker layer. SEM-EDX compositional analysis of corrosion profiles with complementary imaging is used to discuss the conditions in which certain corrosion profiles are formed. The study reveals how analysis of samples from many objects of a similar manufacture, buried for similar time periods, can be used to develop detailed understanding of corrosion processes and provide better understanding of the likely appearance of the objects in antiquity.