Intergranular Failure of Roman Silver Artefacts

Abstract

Silver objects obtained from archaeological excavations often exhibit an extended embrittlement. The causes of this embrittlement were studied on silver artefacts buried for more than one thousand years in the soil using light and electron microscopy techniques and EDX microanalysis. Our investigation revealed presence of chlorine, sulphur and oxygen along the grain boundaries suggesting that most likely, the catastrophic failure of the grave objects made of Ag–Cu alloys is caused by an intercrystalline corrosion attack. The role of possible grain boundary segregation and/or precipitation of copper as a path of easy corrosion is discussed.