Metal corrosion in polychrome baroque lead sculptures: a case study

Author(s)

de Faria, Dalva L. A. ^[1] ; Puglieri, Thiago S. ^[1] ; Souza, Luiz Antonio C. ^[2]

Affiliation

^[1] Univ Sao Paulo, Inst Quim, BR-05508000 Sao Paulo - Brazil

^[2] Univ Fed Minas Gerais, Lab Ciencia Conservacao Lacicor, Escola Belas Artes, BR-31270901 Belo Horizonte, MG - Brazil

• Document type: Journal article
• Source: Journal of the Brazilian Chemical Society; v. 24, n. 8, p. 1345+, AUG 2013.
• Web of Science Citations: 2

Abstract

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. (AU)

• FAPESP's process: 11/13760-8 - Impact of microenvironment chemical composition on heritage objects: mechanisms and monitoring
• Grantee: Thiago Sevilhano Puglieri
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 06/58748-7 - Reactivity, dynamics and spectroscopy of complex systems
• Grantee: Marcia Laudelina Arruda Temperini
• Support Opportunities: Research Projects - Thematic Grants