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- Niklasson, Annika, 1977
(författare)
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Atmospheric Corrosion of Historic Lead Organ Pipes
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The atmospheric corrosion of lead is investigated, with the aim to improve the understanding of the environmental degradation of historical organ pipes. Fieldwork is combined with laboratory investigations. The field studies included characterization of the organ environment and exposures of lead coupons. The environment inside the organ wind system of instruments suffering corrosion was mapped and compared with instruments unaffected by corrosion, in five countries in Europe. In the heavily corroded organs, relatively high concentrations of acetic and formic acid vapours were present, and large amounts of carboxylates accumulated on the lead coupons. The organic acids are emitted from woodwork in the organs.The effect of acetic and formic acid vapours in the ppb range of the atmospheric corrosion of pure lead was investigated under well controlled conditions in the laboratory. The combined effect of acetic and formic acid vapours was also examined. The influences of temperature, relative humidity, inorganic air pollutants (NO2 and SO2) and particulates (NaCl) were studied as well. Corrosion rate was measured gravimetrically and the corrosion products were analysed by XRD, ESEM, FIB, ion chromatography and quantitative carbonate analysis. The mechanism of corrosion attack is addressed.Traces of acetic acid vapour strongly accelerate lead corrosion. Mass gain is linear with time and depends linearly on the acetic acid concentration. Corrosion showed a relatively weak dependence on relative humidity in the range 50 - 95%. Lead corrosion was inversely related to temperature; mass gain was 50% higher at 4.0 ºC than at 22.0 ºC. The corrosion rate increased with decreasing temperature in the range 22.0 - 4.0 ºC. It is proposed that lead suffers electrochemical corrosion in the presence of traces of acetic acid vapour. The corrosion products were unevenly distributed. Lead acetate oxide hydrate (Pb(CH3COO)2∙2PbO∙H2O), plumbonacrite (Pb10O(OH)6(CO3)6), litharge (a-PbO) and massicot (b-PbO) were identified by X-ray diffraction.Formic acid vapour is also corrosive towards lead, although somewhat less so than acetic acid. In this instance the corrosion products, consisting of plumbonacrite and lead formate hydroxide (Pb(HCOO)(OH)), are evenly distributed. The combination of acetic and formic acid has a slightly synergistic effect on lead corrosion, which resulted in a more localized attack than for the acetic and formic acid exposures.The results show that acetic and formic acid vapours emitted from woodwork in the organs are decisive in the corrosion of historical organs. Methods for mitigating organ corrosion are discussed. The work in this thesis is a basis for formulating conservation strategies for historical organs.
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| 2. |
- Niklasson, Annika, 1977, et al.
(författare)
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Atmospheric corrosion of lead - The influence of formic acid and acetic acid vapors
- 2007
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Ingår i: Journal of the Electrochemical Society. - 1945-7111 .- 0013-4651. ; , s. 618-625
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Tidskriftsartikel (refereegranskat)abstract
- The present laboratory study investigates the influence of low concentrations of formic acid vapor and the combination of acetic and formic acid vapors on the atmospheric corrosion of lead. The samples were exposed to synthetic air with careful control of relative humidity (95%), temperature (22.00 degrees C), flow conditions and the concentration of formic acid (160 ppb), acetic acid (170 ppb) and CO2 (350 ppm). Exposure time was one, two and four weeks. Corrosion products were analyzed by gravimetry, ion chromatography, quantitative carbonate analysis, X-ray diffraction and environmental scanning electron microscopy. Cross sections of the corroded surface were prepared by focused ion beam milling. Formic acid vapor is very corrosive toward lead, although somewhat less so than acetic acid. The corrosion products, consisting of plumbonacrite (Pb10O(OH)(6)(CO3)(6)) and lead formate hydroxide [Pb(HCOO)(OH)], are evenly distributed. The combination of acetic and formic acid has a synergistic effect on lead corrosion. The corrosion products found were plumbonacrite and massicot (beta-PbO) together with an unidentified phase. Corrosion attack in the mixed pollutant exposure is more localized compared to the acetic and formic acid exposures, clearly indicating the electrochemical nature of corrosion.
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