Ceramics-Silikáty 50 (1) 32-38 (2006)

Cathodic behavior of molybdenum electrode in various glass melts

V. Čierna, J. Matěj, M. Maryška, V. Hulínský, A. Langrová

The cathodic behavior of molybdenum electrode has been investigated in model glass melt of the basic composition of 16Na₂O, 10CaO, 74SiO₂ (wt.%) with additions of SO₃ or Sb₂O₃ or without additions at 1400°C. There exists a range of catho-dic potentials reduced by some hundreds millivolts against the rest state where the reduction of electroactive species acting as depolarizers of molybdenum corrosion may be suppressed. The potentials of the maximum suppression of lead or antimony precipitation correspond to potentials at which the anodic molybdenum oxidation finishes. The layers of molybdenum silicides have been not found on the electrode at those potentials. In glass melt containing sulfur trioxide, the sulfur depletion of glass in electrode vicinity takes place. At more reduced potentials, the subsequent formation of silicon and formation of the silicides Mo₃Si, Mo₅Si₃ and MoSi₂ occurs. The formation of silicon and silicides is impeded by presence of the electroactive glass components mentioned above. The overall cathodic current increases at the same time. That is probably due to the prefe-rential reduction of the electroactive species by reduced alkali metal.

Keywords: Molybdenum electrode, Cathodic behavior, Glass melt