Analysis of grain boundaries in an embrittled ancient silver necklace

Archaeological silver objects are often found to be embrittled to some extent. Using light and scanning electron microscopy techniques, X-ray diffraction and AES, the causes of this embrittlement were studied on a silver artefact buried for more than 1000 years in soil. This investigation revealed the presence of chlorine, sulphur and carbon at grain boundaries of the Ag-Cu based object suggesting that most likely, the substantial embrittlement is caused by an inter-crystalline corrosion attack. The role of copper enrichment at the grain boundaries as a possible path of preferential corrosion attack is discussed. Copyright (C) 2008 John Wiley & Sons, Ltd.