CHARACTERISATION OF NON-METALLIC INCLUSIONS IN Pb-Ca-Sn ALLOYS

Non-metallic inclusions in two Pb-Ca-Sn lead alloys used in the manufacture of lead-acid batteries were investigated and categorised. Samples of recycled lead alloys were analysed using scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDS). This technique enabled the analysis of the chemical composition of the alloys and the identification of non-metallic inclusions. Differential scanning calorimetry (DSC) confirmed the presence of non-metallic inclusions in two different recycled alloys. Non-metallic inclusions in lead alloys are detrimental, negatively impacting both the casting process and the mechanical and electrochemical properties of the alloys. Results indicate that oxide inclusions are predominant in Pb-Ca-Sn alloys. Non-metallic inclusions with stoichiometric compositions of PbO2, Pb2O3, Al2O3, and CaO were identified. Most of these inclusions were found near the surface of a sample, i.e., in the area most exposed to the atmosphere. The introduction of a protective atmosphere during the melting process could significantly reduce the occurrence of non-metallic inclusions.