An investigation into the cause of corrosion on indoor bronze sculpture

Abstract

Corrosion noted on a number of nineteenth and twentieth century indoor bronze sculptures in the collection of the National Gallery of Canada was the cause for a major condition survey of its Canadian, American, and European bronzes. The results led to a comprehensive study, which included material analysis. This article outlines the steps undertaken to determine the extent and type of corrosion, its possible cause(s), and potential remediation. The survey included 136 bronzes, of which 40 were selected for an in-depth study. Indoor air quality tests of the current building, housing the collection since 1988, were carried out. The dossiers and database records of the selected sculptures were reviewed to investigate their condition, treatment, and storage history. The metal, patina, and corrosion products were subjected to analysis. More areas of corrosion were generally associated with predominantly green patinas and chloride-containing compounds identified in either patina or corrosion samples. The most frequently identified compounds in the patina samples were atacamite, a copper(II) chloride hydroxide, and cuprite, a copper(I) oxide. The most frequently identified compounds in the corrosion samples were atacamite and rouaite, a copper(II) hydroxide nitrate. The analysis determined that the current environment is not contributing to the surface alterations of the sculptures; however, past storage conditions, chemical residues from artificial patination, and likely casting residues are the main causes of the current condition.

Protection of bronze artefacts through polymeric coatings based on nanocarriers filled with corrosion inhibitors

“…The coating formulations have been prepared in the form of liquid mixtures and have been applied on the bronze substrates (Cu 85%, Sn 5 %, Zn 5%, Pb 5 %) by either manual deposition or spray coating. The alloy composition was selected based on the most common metal composition of bronze works of art [4]. Contact angle measurements have been exploited to assess the wetting behavior of the coating formulations on the bronze disks.…”

A new bio-based organogel for the removal of wax coating from indoor bronze surfaces

“…Wax, lacquer, or varnish were applied to saturate the surface color and protect the patina and the metal surface from corrosion [4][5][6]. Among these different materials, natural wax -such as beeswax -is one of the mostly used coating for indoor bronzes, thanks to its properties such as low water vapor permeability and low gloss [7]. Waxes could also be applied as a maintenance treatment.…”

The bronze panel (paliotto) ofSan Moisèin Venice: materials and causes of deterioration

“…SO 2 , NO x , O 3 and organic compounds [1]). It is also worth noting that the current environment may not be the only factor in determining surface alterations of bronze artefacts: modifications in storage conditions, chemical residues from artificial patination and possible traces of materials related to casting procedures are also important causes of degradation [2]. Therefore, this paper presents the results of the diagnostic investigations that were carried out in view of the recent restoration intervention.…”

“…Image of the Paliotto (altar panel) before restoration, with indication of the three assembled sections (A-C), and the sampling points[1][2][3][4][5][6][7][8] …”