Case Histories of Ancient Silver Embrittlement

Abstract

This article discusses six cases of ancient silver embrittlement. The diagnostic techniques and results are surveyed, followed by the most likely explanations of embrittlement. There are two basic types of embrittlement: corrosion-induced, and microstructurally induced, which can act synergistically. Corrosion-induced embrittlement takes several forms, including what appears to be intergranular and transgranular stress corrosion cracking. The main intrinsic factor facilitating corrosion-induced embrittlement is retained cold-work in the silver. Microstructural embrittlement is characterized by intergranular fracture, most probably due to low-temperature segregation of lead to the grain boundaries. Knowledge of the details of embrittlement can be essential for optimizing the restoration and conservation of damaged artifacts.

Electrochemical Characterization of Coinage Techniques the 17th Century: The maravedís Case

“…Copper‐silver alloys are present as either non‐equilibrium solid solutions or two‐phase microstructures . In silver‐copper solid solutions there is possibility of internal oxidation with copper corroding preferentially to form copper compounds . Silver oxidation species (chloride, sulfide, or oxide, mainly) can also be formed; the nature of the corrosion product is therefore highly dependent upon the corrosion environment .…”

Significance of Discontinuous Precipitation of Copper in Ancient Silver

“…Also, only a sample from the Kantharos inner cup was available to the NLR, and although fractography was possible, the sample was too fragile to be prepared for metallographic examination. Tables 2 and 3 survey the results, which have been described previously [1,[23][24][25][26][27][28][29][30], but not all together and not with the emphasis on discontinuous precipitation of copper. The results relevant to this theme will be considered in the following sections, but in the meantime it should be noted that the Vase and Cauldron case studies have demonstrated the primary importance of retained cold-work in causing and facilitating corrosion-induced embrittlement [23,24,26].…”

Integrated three-dimensional models for noninvasive monitoring and valorization of the Morgantina silver treasure (Sicily)

“…Consequently its behavior with the environment can change as a function of the chemical composition or technological processing. [14][15][16][17] The black tarnish of the silver, such as in the Scylla medallion (Fig. 20), can be caused by the presence of sulfide in the air, especially in unfavorable environmental conditions in which the relative humidity is over 40%.…”