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Materials 2014, 7(5), 3353-3370; doi:10.3390/ma7053353
Article

Corrosion of Bronzes by Extended Wetting with Single versus Mixed Acidic Pollutants

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Received: 27 January 2014; in revised form: 25 March 2014 / Accepted: 21 April 2014 / Published: 28 April 2014
(This article belongs to the Special Issue Corrosion of Materials)
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Abstract: The corrosion of bronzes was examined in the context of single-acid versus mixed-acid (as in urban acid rain) solutions. Two bi-component bronzes (copper with either 3% Sn or 7% Sn) that closely represent those of historic artifacts were immersed for five weeks in conditions designed to replicate those experienced by statues and ornaments in cities where rainfall and humidity constantly produce an electrolyte layer on the surfaces of bronzes. Ions, acids, and particles of pollutants can dissolve in this layer, resulting in a variety of harsh corrosion processes. The kinetics of corrosion and the properties of the resulting patinas were monitored weekly by electrochemical impedance spectroscopy and open-circuit potential measurements. The sizes and appearances of the corrosion products were monitored and used to estimate the progress of the corrosion, whose crystalline structures were visualized using scanning electron microscopy with energy dispersive spectroscopy, identified by X-ray diffraction, and characterized by spectrocolorimetry. The electrochemical measurements demonstrated that greater damage (in terms of color change and corrosion product formation) did not correspond to deficiencies in protection. The mixed-acid solution did not corrode the bronzes, as would be expected from the additive effects of the single acids. The postulated mechanisms of metal dissolution appear to be specific to a particular bronze alloy, with the tin component playing an important role.
Keywords: bronze corrosion; tin influence; acid rain; electrochemical impedance spectroscopy; spectrocolorimetry bronze corrosion; tin influence; acid rain; electrochemical impedance spectroscopy; spectrocolorimetry
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Gianni, L.; Gigante, G.E.; Cavallini, M.; Adriaens, A. Corrosion of Bronzes by Extended Wetting with Single versus Mixed Acidic Pollutants. Materials 2014, 7, 3353-3370.

AMA Style

Gianni L, Gigante GE, Cavallini M, Adriaens A. Corrosion of Bronzes by Extended Wetting with Single versus Mixed Acidic Pollutants. Materials. 2014; 7(5):3353-3370.

Chicago/Turabian Style

Gianni, Liliana; Gigante, Giovanni E.; Cavallini, Mauro; Adriaens, Annemie. 2014. "Corrosion of Bronzes by Extended Wetting with Single versus Mixed Acidic Pollutants." Materials 7, no. 5: 3353-3370.


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