Gaseous Oxidation Rates of Liquid Lead and Solid Iron through Molten Oxide Layer and Effects of Applied Current Flows

Abstract

A certain quantity of liquid PbO, PbO-SiO₂, Na₂O-B₂O₃or Na₂O-GeO₂has been put on liquid lead or solid iron in a crucible suspended from a thermobalance and then oxidized under air or O₂-Ar mixtures at 900 to 1 000°C. The effect of supplied currents upon the rates has also been determined by the thermobalance.
The following results were obtained. When no current was supplied, the oxidation rate of liquid lead obeyed the parabolic law. The rate was increased with increase of temperature and the partial pressure of oxygen in gases and decreased with the increase of SiO₂content in PbO-SiO₂melts. When solid iron was oxidized through Na₂O-B₂O₃and Na₂O-GeO₂, no change in weight could be measured because of very small oxidation rate.
When liquid lead covered with PbO-SiO₂and solid iron covered with Na₂O-B₂O₃were oxidized with galvanostatic currents, the rates were accelerated by the currents and satisfied Faraday's relation at 900 to 1000°C and with the currents less than 400mA. At lower temperature, however, the rates deviated from Faraday's relation even with smaller currents.