X-Ray Photoelectron Spectroscopy Study on the Chemical Composition of Copper Tarnish Products Formed at Low Humidities

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Abstract
This work studies the chemical composition of copper tarnish products formed at 40, 60, and 80% relative humidity (RH) in an uncontaminated environment, for 21 days experimentation at 30°C. The experimental method used was X-ray photoelectron spectroscopy (XPS) in conjunction with Ar+Ar+ -ion sputtering. The main compounds found were cuprite (Cu2O)(Cu2O) and copper hydroxide [Cu(OH)2].[Cu(OH)2]. Differences were observed between 40, 60, and 80% RH. Copper specimens exposed to 40% RH show the thickest tarnish layers, while the thinnest correspond to the 80% RH specimens. The tarnish layer of the copper specimen exposed to 80% RH is constituted mainly by copper hydroxide. For the 40 and 60% RH copper specimens the tarnish layer is a mixture of copper hydroxide and cuprite. © 2000 The Electrochemical Society. All rights reserved.