The formation of black patina on copper in humid air containing traces of SO{sub 2}
- Univ. of Goeteborg (Sweden). Dept. of Inorganic Chemistry
The formation of a black patina on copper in humid air containing traces of SO{sub 2} was investigated using on-line analysis of SO{sub 2} and corrosion product characterization (X-ray photoelectron spectroscopy, Fourier transform infrared absorption spectroscopy, X-ray diffraction, and quantitative analysis of sulfite). In humid air (>75% RH) with 4 to 69 ppb SO{sub 2}, a dull black cuprite patina (200 to 300 nm thick) formed after 20 h exposure. However, when concentrations of SO{sub 2} were higher, copper remained shiny, as did samples exposed at low humidity. Sulfate was the dominant sulfur species on shiny as well as on black samples. At high SO{sub 2} concentrations copper is suggested to be passivated by a layer of chemisorbed sulfite on the thin air-formed oxide film, while at low concentrations the film breaks down. Corrosion mechanisms are suggested for this active/passive transition on the copper surface. The formation of cuprite on the black samples resulted in a high corrosion rate, and an inverse correlation between SO{sub 2} concentration and corrosion was found. These results are in agreement with field studies on outdoor copper and bronze where the formation of a black cuprite patina and a high corrosion rate is observed in environments with low levels of SO{sub 2}.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 452213
- Journal Information:
- Journal of the Electrochemical Society, Journal Name: Journal of the Electrochemical Society Journal Issue: 1 Vol. 144; ISSN 0013-4651; ISSN JESOAN
- Country of Publication:
- United States
- Language:
- English
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