Investigation of a potentiostatic reduction treatment for leaded copper alloys
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The corrosion and conversion of highly leaded copper alloys is a problem for many collections. This was investigated using the Covesea coins as a case study. These coins were actively corroding, producing a white, powdery corrosion product. Some coins were completely disintegrated. Potentiostatic reduction was investigated as a possible technique for the conservation of the highly leaded copper alloys. A series of potentiodynamic experiments was formulated and carried out to determine the behaviour of lead-copper mixtures in different electrolytes. Potentiostatic reduction of leaded copper samples showed that the lead corrosion products were reduced successfully. The copper appear to be passivated by a layer of copper oxide. The treatment was considered ethical for the Covesea coins, as it succeeded in reducing the volume of lead corrosion, stopping further disintegration. However, this treatment would not be suitable for all leaded copper alloys.