Scientific Achievements: Pipe Material Analysis

Samples have been taken from selected pipes in the field study organs. The material used for the production of the corroded pipes has been characterized in terms of microstructure and chemical composition of the alloy. Phase composition and morphology of corrosion products on the surface of samples have also been identified. It is worth pointing out that most organ pipes are manufactured with a wide range of lead-tin alloys, from nearly pure lead to nearly pure tin with many other intermediate possibilities. A pipe organ may consist of hundreds to thousands of pipes, arranged in different stops (i.e. sets of pipes with similar tone quality) and each stop contains a number of pipes that correspond to the notes on the keyboards and on the pedal keys. Producing such a high number of pipes requires an effective manufacturing process as well as the use of a material with good casting properties and good workability. Lead-based and tin-based alloys are both suitable for this purpose (Guruswamy 2000; ASM Handbook 1999, 2). The process used nowadays for manufacturing organ pipes still closely resembles the process described in the eighteenth-century book on organ building by Dom Bedos de Celles (Dom Bedos de Celles 1977). The first step (Figure 3.1a) of the construction of a pipe is the production of the metal sheet by casting molten metal on a flat bench covered with sand or cloth. The metal sheet is then hammered (Figure 3.1b) or rolled or scraped to desired thickness. The shape of the different parts of the pipe (foot, body and languid) are traced and cut from the sheet (Figure 3.1b). In the final step, the sheet is bent and soldered (Figure 3.1b). Recycling scrap metal is a common organ building practice that leads to the production of sheets with slightly different compositions. Different sheets can be used for manufacturing different pipes in the same stop or different parts of the same pipe, therefore pipes constructed with different materials can be exposed to the same environment because they belong to the same organ: this situation is the ideal case for studying the influence of material parameters on corrosion behavior.