The initial behaviour of freshly etched copper in moderately acid, aerated chloride solutions |
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Authors: | G. Bech-Nielsen M. Jaskula I. ChorkendorffJ. Larsen |
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Affiliation: | a Department of Chemistry, Building 207, The Technical University of Denmark, Kemitorvet, DK-2800 Lyngby, Denmark b ICAT, Department of Physics, Building 312, The Technical University of Denmark, DK-2800 Lyngby, Denmark |
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Abstract: | When freshly etched samples of various types of copper were exposed in moderately acid, aerated chloride solutions, two phenomena were observed. First the corrosion potential and the pH of the solution decreased over a shorter time, then the potential increased over a long period (600-1500 min), following an s-shaped pattern. Increase in pH during the second stage was avoided using a pH-stat. The corrosion rate increased little or not at all over the entire period. A tentative interpretation of the short-term behaviour is presented with some reservation. The long-term development of the potential suggests phase formation or transformation following the Avrami pattern. By suitable derivations it was possible to fit the development of potentials to the Avrami equation. Subsequent examinations by Auger spectroscopy proved the presence of thin layers of Cu2O on the copper surfaces, increasing in thickness with exposure time. The dissolution kinetics can be described in terms of two parallel electrochemical reactions and a simultaneous non-electrochemical dissolution reaction. |
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Keywords: | Freshly etched copper Avrami equation Potentials of metal-oxide couples Corrosion measurements by titration (CMT) Thin Cu2O layers |
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