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

Materials

Liliana Gianni²  Giovanni E. Gigante¹  Mauro Cavallini³ 

[1] Dipartimento di Scienze di Base e Applicate all’Ingegneria, Università di Roma La Sapienza, Via A. Scarpa 14/16, 00161 Rome, Italy; E-Mails:;Department of Analytical Chemistry, Ghent University, Krijgslaan 281-S12, 9000 Ghent, Belgium;Dipartimento di Ingegneria Chimica Materiali Ambiente (DICMA), Università di Roma La Sapienza, Via Eudossiana 18, 00184 Rome, Italy; E-Mail:

关键词: bronze corrosion;    tin influence;    acid rain;    electrochemical impedance spectroscopy;    spectrocolorimetry;   

DOI  :  10.3390/ma7053353

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland