Basic Structure of Passive Layers of Cu-Sn Alloys Applied to Patinas of Archaeological Bronzes

The passive bronze corrosion structures have been characterized on numerous single-phase archaeological bronzes from Late to Early Bronze Age period (1500-900 BC), from metallographical examinations of cross-sections of artifacts. This paper focuses on the microstructure and the elementary composition of the passive patinas by SEM and EDX analysis (ultrathin window). A basic structure of the protective patinas is first described, then, deviations to the standard model are given. This model of passive structure and its deviations well agree with observations of archaeological bronzes.