1. Inorganic Chemistry of Organ Pipes: Composition and Corrosion Catherine M. Oertel Department of Chemistry and Biochemistry Oberlin College Created by Catherine M. Oertel, Oberlin College (catherine.oertel@oberlin.edu) and posted on VIPEr (www.ionicviper.org) on September 30, 2010. Copyright Catherine M. Oertel 2010. This work is licensed under the Creative Commons Attribution Non- commercial Share Alike License. To view a copy of this license visit http://creativecommons.org/about/license/www.ionicviper.orghttp://creativecommons.org/about/license/

2. Photos courtesy of Ibo Ortgies, Göteborg Organ Art Center Organ at St. Jacobi Church in Lübeck, Germany, built in 1636-1637 and containing pipes from the 15 th century This is an example of an organ with pipes that have been severely damaged by corrosion, in many cases preventing them from sounding.

3. lead  -tin Organ pipes are typically made from lead-tin alloys, and examples can be found representing compositions across the phase diagram.

4. Corrosion: An Electrochemical Process metal native oxide (nanometer- scale) electrolyte O 2(g) OH ─ (aq) M n+ (aq) e─e─ anode cathode CO 2(g) HX (g) HX (aq) CO 2(aq) ⇌ HCO 3 − (aq) + H 3 O + (aq)

5. Exposure chambers have controlled temperature, humidity, and atmosphere. Lead-tin alloy samples were exposed to acetic acid vapor in the laboratory. Acetic acid emitted from the wood of organ cases is a primary cause of corrosion.

6. Alloy containing 15% Sn/85% Pb after 4-week exposure to 1100 ppb acetic acid 100  m 10  m

7. sec Alloy containing 15% Sn/85% Pb, exposed to 1100 ppb acetic acid

8. What can be done?  Filtration and venting systems can be used to reduce acid concentrations inside cases, and humidity control is also important.  Wood coatings such as alkaline earth hydroxide nanoparticles are being tested to reduce acid emissions.  Sensors are being designed and tested to monitor conditions in organ cases and alert conservators of high organic acid concentrations or conditions promoting condensation of moisture on pipes. A dosimeter for detecting high organic acid concentrations is tested in an organ in Olkusz, Poland. Image from: http://goart.gu.se/cgi-bin/senslev1/sensorgan.taf

9. Where can you learn more? News feature: Clarke, T. “Music and Chemistry: Organ Failure,” Nature 2004, 427, 8-9. Research articles: Oertel, C.M.; Baker, S.P.; Niklasson, A.; Johansson, L.-G.; Svensson, J.-E. “Focused-Ion Beam and Electron Microscopy Analysis of Corrosion of Lead-Tin Alloys: Applications to Conservation of Organ Pipes,” Mat. Res. Soc. Symp. Proc. 2008, 1047, Y05-01. Oertel, C.M.; Baker, S.P.; Niklasson, A.; Johansson, L.-G.; Svensson, J.-E. “Acetic Acid Vapor Corrosion of Lead-Tin Alloys Containing 3.4 and 15 at.% Tin,” J. Electrochem. Soc. 2009, 156, C414-C421. Giorgi, R.; Chelazzi, D.; Fratini, E.; Langer, S.; Niklasson, A.; Rademar, M.; Svensson, J.-E.; Baglioni, P. “Nanoparticles of Calcium Hydroxide for Wood Deacidification: Decreasing the Emissions of Organic Acid Vapors in Church Organ Environments,” J. Cult. Heritage 2009, 10, 206-213.