Conservation is no longer a pipe dream
Lead and lead-tin alloys of metal pipes constitute the central sounding part of organs. A major threat to organs is indoor atmospheric corrosion of lead and lead-tin alloys. Moreover, inappropriate protective treatments can cause irreversible damage to unique and irreplaceable instruments. Within the EU-funded project PBCOATINGS (New strategies for corrosion inhibition coatings for lead and its characterization by in-situ spectroelectrochemical studies), researchers investigated the underlying chemical processes to develop effective conservation methods. The researchers found an effective treatment in the immersion of lead objects in melted tetradecanoic acid. The resulting coating is a thick, compact layer of lead ditetradecanoate. They studied these coatings and their corrosion resistance to optimise the deposition process. A series of electrochemical experiments showed their superior quality when compared to classical micro-crystalline wax polish treatments widely used by conservators. The lead coated samples were exposed to a humid and oak vapour rich atmosphere for up to 59 days. Linear sweep voltammograms and electrochemical impedance spectroscopy signals revealed that these coatings are stable over time. In time-lapse electrochemical impedance spectroscopy and X-ray diffraction experiments, only hints of corrosion products were detected. The extensive dataset produced during these experiments is being analysed after the end of the PBCOATINGS project. The researchers are investigating the growth of lead carboxylate layers with scanning electron microscopy and mass-gain experiments over different time periods. The low cost and simplicity of the new coating method make it an interesting candidate to test on real organ pipes. Future work will need to focus on determining the best immersion time to create coatings with enhanced anticorrosion efficiency to protect heritage organs.
Keywords
Pipe organ, lead-tin alloys, atmospheric corrosion, PBCOATINGS, electrochemical impedance spectroscopy, anticorrosion
