Electrochemical analysis of the degradation of lead alloy organ-pipes due to acetic acid

Abstract Lead is commonly used for making small size organ-pipes instead of using tin alloys. In fact, when the organ-pipes are small enough to avoid collapsing due to room temperature creep, lead can be used instead of other alloys with superior mechanical properties, because it is relatively cheap, it is easy to form into different shapes, the tonality of the obtained sounds are acceptable and the corrosion resistance is quite good. However, organic substances such as organic acids released from the wood made support of the organ-pipes and organic contaminations of the air pumped through the pipes may lead to a rapid degradation of lead. In this study, the effect of organic acids, such as acetic acid, on the degradation of lead-made organ-pipes was investigated. Lead made specimens obtained from real organ-pipes were exposed to organic-acid rich environments and the induced degradation was monitored by means of electrochemical techniques. In literature, it was evidenced that the degradation promoted by the organic acids leads to the formation of lead oxides and carbonates characterized by a very high volume, which promotes a quick degradation of the lead specimens. The effect of different concentrations of acetic acid on the degradation rate of the organ pipes was investigated by means of electrochemical impedance spectroscopy (EIS). The effect of the acid concentration on the corrosion process occurring on lead surface was evaluated by means of cathodic and anodic polarization measurements in both aerated and degassed conditions. The morphology of the degradation products was investigated by means of SEM during exposure time in the aggressive environment.