An increase of 22 per cent in lead usage is expected in the European Union by 2050. During lead
refining, the Harris process is a critical step in which a salt melt is used to remove arsenic, tin and
antimony. During this process, the caustic salt melt absorbs these impurities, requiring regular
evacuation before saturation. Current metallurgical practices for: 1) determining the end point of the
lead alloy involve time-consuming sampling and offline analysis, and 2) determining the end point of
the caustic salt melt are based on subjective visual observations by the operator. In the context of
Industry 4.0 concept, automating these processes becomes desirable, as smart sensors
systematically collect real-time data in an unbiased manner. This research focuses on monitoring
the Harris refining process using objective methodologies. Two different methodologies are
investigated. The first methodology focuses on electrical conductivity changes of the caustic salt
melt as function of Sb content. For this study, synthetic and industrial samples are used. A lab-scale
electrical conductivity set-up was built to accommodate the aggressiveness of the salt melt. Initial
findings suggest a promising relationship between electrical conductivity and Sb content in the
caustic salt melt. Although the results are preliminary, the study provides valuable insights by
enabling real-time measurements. The second methodology focuses on measuring the
electromotive force (EMF) in lead doped with Sb at pilot-scale. Multiple probes are reevaluated for
their effectiveness in Sb measurement. Ultimately, a partially stabilised MgO probe with Ni as a
reference, without cardboard and copper protection caps, yields promising results. A correlation
between EMF and Sb content is observed. However, repeatability issues arise due to possible wire
interference at low temperatures. The results underscore the potential of advanced measurement
techniques in optimising lead alloy production within the context of Industry 4.0.