For many years, there were two competing proposals (Weisser 1975). The actual mechanism of dezincification is still not completely agreed upon. General terms for this process are "dealloying," "selective corrosion" or "selective leaching." More specific terms applying to the loss of specific metals are "decuprification" for loss of copper, "destannification" for loss of tin and "dezincification" for loss of zinc. In many alloys, corrosion may result in the loss of the more reactive component of the alloy, with the less reactive component left behind.
Brasses are alloys of mainly copper and zinc, with small percentages of other elements such as tin, lead or arsenic. Sterling silver, an alloy of silver and copper, contains two metallic elements steel contains one metallic element (iron) and one non-metallic element (carbon). The dezincification process Dealloying and dezincificationĪn alloy is a mixture of two or more elements, where at least one of the elements is a metal.
The Note also describes a demonstration of mild dezincification.
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This Note explains what dezincification is and where it can be encountered in conservation as well as how to prevent and treat it. Mild dezincification may simply cause a cosmetic change, namely, the colour of the surface turning from yellow to pink, but severe dezincification can lead to the weakening of brass and even its perforation. When brass corrodes, it can undergo dezincification, a process in which zinc is lost and copper is left behind. List of abbreviations CAC Canadian Association for Conservation of Cultural Property M molarity MRS Materials Research Society SCE standard calomel electrode SHE standard hydrogen electrode V volt wt% weight percentage Introduction