Evaluation of the performances of a biological treatment on tin-enriched bronze

• Published in: Environmental science and pollution research international 2017, Vol.24 (3), p.2150-2159
• Main Authors: Albini, Monica, Chiavari, Cristina, Bernardi, Elena, Martini, Carla, Mathys, Lidia, Joseph, Edith
• Format: Article
• Language: English
• Subjects: Acid rain; Aging; Aging (artificial); Aging (metallurgy); Aging (natural); Alloying elements; Alloys; Aquatic Pollution; Art and Cultural Heritage; Atmospheric Protection/Air Quality Control/Air Pollution; Atomic absorption analysis; Atomic absorption spectroscopy; Beauveria bassiana; Biological treatment; Copper; Copper base alloys; Copper converters; Corrosion; Corrosion products; Cultural heritage; Cultural resources; Earth and Environmental Science; Ecotoxicology; Enrichment; Environment; Environmental Chemistry; Environmental Health; Environmental science; Exposure; Fourier transforms; Fungi; Heavy metals; Metals; Microscopy, Electron, Scanning; Natural environment; Oxalates; Preservation; Rain; Rain water; Runoff; Scanning electron microscopy; Spectral analysis; Spectrometry; Spectrometry, X-Ray Emission; Spectrophotometry, Atomic; Spectroscopy; Spectrum Analysis, Raman; Storm runoff; Tin; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-016-7361-2

Recently, research gives emphasis to eco-friendly and sustainable approaches for the preservation of cultural heritage that could offer advantages in terms of compatibility, durability and safety. Hence, a biological treatment, based on a specific fungal strain of Beauveria bassiana , is exploited for the stabilization of soluble and/or active bronze corrosion products, converting them into copper oxalates. The chemical stability of the latter represents a real improvement for the long-term preservation of bronze, especially in case of exposure to acid rain. However, the corrosion behaviour of bronze differs from that of pure copper due to the presence of additional alloying elements. In natural environments, the selective dissolution of copper leads to a relative tin-enrichment within the corrosion layers, mostly in unsheltered areas exposed to rainwater runoff. To understand the influence of tin-enrichment on the formation of oxalates, pure tin and artificially tin-enriched bronze coupons were treated with this novel biological system and, in the case of bronze coupons, exposed to accelerated ageing. Tin enrichment and accelerated ageing were performed through runoff tests. Before and after treatment and ageing, the sample surface was characterized through Fourier transform infrared (FTIR) and Raman spectroscopies, scanning electron microscopy coupled to energy dispersive spectroscopy (SEM-EDS). Metals released in the ageing solutions were analysed through atomic absorption spectrometry (AAS). The analytical results allowed to better understand the response of unsheltered areas from outdoor bronze monuments to the biological treatment proposed.