Annika Niklasson

Influence of Acetic Acid Vapor on the Atmospheric Corrosion of Lead

The present study investigates the influence of low concentrations of acetic acid vapor 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), acetic acid concentration (170-1100 ppb), CO2 concentration (350 ppm), and flow conditions. The exposure times were between 1 and 4 weeks. Mass gain results are reported. The corrosion products were analyzed by ion chromatography, quantitative carbonate analysis, and X-ray diffraction. The surface morphology of the exposed samples was investigated with environmental scanning electron microscope. The results show that low concentrations of acetic acid vapor are very corrosive toward lead. The mass gain is linear with time and depends linearly on the acetic acid concentration. It is suggested that the corrosion of lead in the presence of traces of acetic acid vapor is electrochemical in nature. The corrosion products found were plumbonacrite, Pb10O(OH)(6)(CO3)(6), lead acetate oxide hydrate (Pb(CH3COO)(2)center dot 2PbO center dot H2O), and lead oxide, PbO. (c) 2005 The Electrochemical Society.

Atmospheric Corrosion of Lead The Influence of Formic Acid and Acetic Acid Vapors

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.

Acetic Acid Vapor Corrosion of Lead–Tin Alloys Containing 3.4 and 15% Tin

Lead-tin alloy pipes in historic organs frequently suffer from damaging atmospheric corrosion. Organic acids emitted from the wood of organ cases had been established previously as the cause of deterioration in pure lead pipes. In the present study, lead-tin alloy samples containing 3.4 and 15 atom % tin were subjected to laboratory exposure experiments under atmospheres of 1100 ppb acetic acid, 350 ppm CO2, and 60 or 95% relative humidity (RH). Wet and dry corrosion mass gains were monitored, and corrosion product compositions and morphologies were characterized by grazing incidence angle X-ray diffraction and scanning electron microscopy. Cross sections were cut through corrosion sites using a focused ion beam milling method, and elemental information was obtained using wavelength dispersive and energy dispersive X-ray analyses. The corrosion products and morphologies observed in the alloys are the same as those reported for pure lead, but the corrosion susceptibilities of the alloys show a much stronger dependence on RH. The presence of 3.4 or 15 atom % Sn provides corrosion protection at moderate humidity, but this protective effect breaks down at high humidity. These findings highlight the importance of humidity control as well as pipe material selection in the conservation of historic and newly constructed organs.

Focused ion beam and electron microscopy analysis of corrosion of lead-tin alloys: Applications to conservation of organ pipes

Across Europe, lead-tin alloy organ pipes are suffering from atmospheric corrosion. This deterioration can eventually lead to cracks and holes, preventing the pipes from producing sound. Organ pipes are found in compositions ranging from >99% Pb to >99% Sn. For very lead-rich (>99% Pb) pipes, organic acids emitted from the wood of organ cases have previously been identified as significant corrosive agents. In order to study the role of alloy composition in the susceptibility of pipes to organic acid attack, lead-tin alloys containing 1.2-15 at.% Sn were exposed to acetic acid vapors in laboratory exposure studies. Corrosion rates were monitored gravimetrically, and corrosion product phases were identified using grazing incidence angle X-ray diffraction. In a new method, focused-ion beam (FIB) cross sections were cut through corrosion sites, and SEM and WDX were used to obtain detailed information about the morphology and chemical composition of the corrosion layers. The combination of FIB and SEM has made it possible to obtain depth information about these micron-scale layers, providing insight into the influence of acetic acid on alloys in the 1.2-15 at.% Sn range.