Oxidation kinetics and behaviour of Pb – Zn alloy anodes

Abstract

Lead and its alloys are widely used in hydroelectric metallurgy, in the production of chemical power sources, electroplating, as well as in electrochemical methods of corrosion protection. To increase the resistance and reduce the anodic potential of lead-based electrodes, various methods are used which allow to solve new problems in industrial electrolysis. Currently, the main task is the creation of new anode alloys, which will allow for the optimal selection of the anode for each specific case. In this regard, lead and its alloys in the foreseeable future will remain the main material in the electrolysis production. Taking into account the operation of lead alloys at high temperatures and corrosive environments, the kinetics of oxidation of alloys of the Pb – Zn system containing up to 0.5 wt% zinc was investigated by thermogravimetry. It has been found that the addive of zinc to lead increases its resistance to oxidation in the solid state. It is shown that the oxidation of alloys occurs according to a hyperbolic mechanism and has the order of 10–4 kg·m–2·s–1. The anodic behavior of the alloys in the NaCl electrolyte medium was studied by the potentiostatic method at a potential sweep rate of 2 mV/s. It was found that zinc as an alloying component does not significantly improve the corrosion resistance of lead. In this case, with an increase in the additive of zinc to lead, the main electrochemical potentials (corrosion, pitting formation, and repassivation) of the alloys will mix in the field of positive values. With an increase of the concentration of chloride ion in the NaCl electrolyte, the corrosion rate of alloys increases, while the values of electrochemical potentials decrease.