Metal Corrosion in Polychrome Baroque Lead Sculptures: a Case Study

Polychrome lead sculptures from Oratory Museum in Ouro Preto (Minas Gerais, Brazil) kept inside a glass showcase were severely degraded. The formed corrosion products were analyzed by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ener...

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Bibliographic Details
Published in:	Journal of the Brazilian Chemical Society Vol. 24; no. 8; pp. 1345 - 1350
Main Authors:	Faria, Dalva L. A. de, Puglieri, Thiago S., Souza, Luiz Antonio C.
Format:	Journal Article
Language:	English
Published:	Sociedade Brasileira de Química 01-08-2013
Subjects:	CHEMISTRY, MULTIDISCIPLINARY formic acid Pb corrosion Raman formaldehyde preventive conservation
Online Access:	Get full text
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Summary:	Polychrome lead sculptures from Oratory Museum in Ouro Preto (Minas Gerais, Brazil) kept inside a glass showcase were severely degraded. The formed corrosion products were analyzed by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray fluorescence (EDX) and Raman microscopy and proved to be mostly Pb carbonates and formates. Although carbonate is a very common finding in Pb atmospheric corrosion, Pb formates can be formed by the action of formic acid or formaldehyde, being their origin a key point to be investigated. Environmental simulations with Pb coupons exposed to possible sources of these volatile organic compounds led to the conclusion that the degradation process was caused mainly by the curing process of the painted showcase baseplate. However, cleaning products, which can also contain formaldehyde as preservative, proved to be potentially harmful to Pb, accelerating its corrosion.
ISSN:	0103-5053 1678-4790
DOI:	10.5935/0103-5053.20130170