Chemical and electrochemical characterization of artificial sulphate patina on bronze

Abstract

Copper patinas are generally regarded as aesthetically pleasing and are supposed to protect copper against further corrosion. The preparation of artificial sulphate patina on bronzes has been realized by immersing the bronze into CuSO₄ solution. The effect of immersion time on the formation of the patina has been investigated. The sulphate patina obtained with immersion time of 500 h in CuSO₄ solution consists of flat area and crystals. The flat area in the patina is mainly made of cuprite, whereas the crystals are mainly composed of brochantite. The electrochemical measurement of sulphate patina in simulated acid rain with pH 3.1 shows that the protective effectiveness of patina decreases with time and the dissolution of patina is the key factor leading to the degradation of patina. The investigation of the formation mechanism of sulphate patina shows that the cuprite layer forms on the surface of bronze in the initial patination. Then, crystal brochantite grows on the surface of cuprite by the oxidation of cuprite and the incorporation of CuSO₄ solution.

Keywords

artificial sulphate patina / bronze / electrochemical characterization

References

[1] Graedel T E, Nassau K, Franey J P Copper Patinas Formed in the Atmosphere-I. Introduction [J]. Corros. Sci., 1987, 27(7): 639-657.

[2] Marušic K, Otmacic-Curkovic H, Horvat-Kurbegovic, . Comparative Studies of Chemical and Electrochemical Preparation of Artificial Bronze Patinas and Their Protection by Corrosion Inhibitor [J]. Electrochimi. Acta, 2009, 54(27): 7 106-7 113.

[3] Goidanich S, Toniolo L, Jafarzadeh S, . Effects of Wax-based Antigraffiti on Copper Patina Composition and Dissolution during Four Years of Outdoor Urban Exposure [J]. J. Cult. Herit., 2010, 11(3): 288-296.

[4] Muresan L, Varvara S, Stupnišek-Lisac E, . Protection of Bronze Covered with Patina by Innoxious Organic Substances [J]. Electrochimi. Acta, 2007, 52(27SPEC.ISS.): 7 770-7 779.

[5] de Oliveira F J R, Lago D C B, Senna L F, . Study of Patina Formation on Bronze Specimens [J]. Mater. Chem. Phys., 2009, 115(2–3): 761-770.

[6] Watanabe M, Higashi Y, Tomita M, . Microstructural Analysis of Artificially Formed Patinas on Copper [J]. Electrochem. Solid-State Lett., 2002, 5(8): B28-B31.

[7] Schlesinger R, Klewe-Nebenius H, Bruns M Characterization of Artificially Produced Copper and Bronze Patina by XPS [J]. Surf. Interface Anal., 2000, 30(1): 135-139.

[8] Balta I Z, Pederzoli S, Iacob E, . Dynamic Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy on Artistic Bronze and Copper Artificial Patinas [J]. Appl. Surf. Sci., 2009, 255(12): 6 378-6 385.

[9] Noli F, Misaelides P, Pavlidou E, . Investigation of Copper Patinas Using Ion Beam Analysis and Scanning Electron Microscopy [J]. Surf. Interface Anal., 2005, 37(3): 288-293.

[10] Kalliabakos G, Kossionides S, Misailides P, . Determination of Sulphur and Copper Depth Distribution in Patina Layers Using Nuclear Reaction Techniques[J]. Nucl. Instrum. Meth. B, 2000, 170(3): 467-473.

[11] Graedel T E Copper Patinas Formed in the Atmosphere-II. A Qualitative Assessment of Mechanisms [J]. Corros. Sci., 1987, 27(7): 721-740.

[12] Hou S, Li Y, Xie M, . Investigation of Patinas Formed on Chinese Bronzes Using Modern Multianalytical Techniques [J]. Surf. Interface Anal., 2007, 39(9): 775-782.

[13] George S Infrared and Raman Characteristic Group Frequencies Tables and Charts Third Edition[M], 2001 Chichester John Wiley & Sons LTD.

[14] Angelini E, d’Agostino R, Fracassi F, . Surface Analysis of PECVD Organosilicon Films for Corrosion Protection of Steel Substrates [J]. Surf. Interface Anal., 2002, 34: 155-159.

[15] He W, Odnevall W I, Leygraf C A Comparison between Corrosion Rates and Runoff Rates from New and Aged Copper and Zinc as Roofing Materials [J]. Water, Air, Soil Pollut., 2001 67-82.

[16] Bertling S, Odnevall W I, Berggren D, . Long Term Corrosion Induced Copper Runoff from Natural and Artificial Patina and Its Environmental Fate [J]. Environ. Toxicol. Chem., 2006, 25(3): 891-898.

[17] Fitzgerald K P, Nairn J, Atrens A The Chemistry of Copper Patination [J]. Corros. Sci., 1998, 40(12): 2 029-2 050.