How Surface Analysis Can Contribute to an Understanding of the Preventive Conservation of Brass Instruments

Federica Cocco;Marzia Fantauzzi;Bernhard Elsener;Antonella Rossi

Last

2023-01-01

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Abstract

Historical brass instruments can suffer corrosion during and after playing due to the high degree of humidity inside – but the surface chemistry inside the tuning slides remains essentially unknown. Based on a series of previously published works of the present authors, this paper describes in a comprehensive way how ex-situ xps surface analytical measurements can shed light on this topic. On freshly polished brass samples exposed to model solutions such as artificial saliva, a thick, polycrystalline surface film composed of copper-thiocyanate and zinc phosphate is formed, whereas in a phosphate buffer solution only a thin film composed of copper and zinc oxy-hydroxide and zinc phosphate is present. ‘As received’ brass samples from old instruments showed quite a thick surface film of copper and zinc oxy-hydroxide that protects the alloy beneath from corrosion. In combination with the in-situ electrochemical results, a first, tentative iden- tification of the surface film inside the tuning slides can be offered.