Ceramics-Silikáty 56 (3) 280-285 (2012)

REACTION PRODUCTS AND CORROSION OF MOLYBDENUM ELECTRODE IN GLASS MELT CONTAINING ANTIMONY OXIDES AND SODIUM SULFATE

J. Matěj, A. Langrová

The products on the interface of a molybdenum electrode and glass melt were investigated primarily at 1400°C in three model glass melts without ingredients, with 1 % Sb₂O₃ and with 1 % Sb₂O₃ and 0.5 % SO₃ (wt. %), both under and without load by alternating current. Corrosion of the molybdenum electrode in glass melt without AC load is higher by one order of magnitude if antimony oxides are present. The corrosion continues to increase if sulfate is present in addition to antimony oxides. Isolated antimony droplets largely occur on the electrode-glass melt interface, and numerous droplets are also dissipated in the surrounding glass if only antimony oxides are present in the glass melt. A comparatively continuous layer of antimony occurs on the interface if SO₃ is also present, antimony being always in contact with molybdenum sulfide. Almost no antimony droplets are dissipated in the glass melt. The total amount of precipitated antimony also increases. The presence of sulfide on the interface likely facilitates antimony precipitation. The reaction of molybdenum with antimony oxides is inhibited in sites covered by an antimony layer. The composition of sulfide layers formed at 1400°C approximates that of Mo₂S₃. At 1100°C, the sulfide composition approximates that of MoS₄. Corrosion multiplies in the glass melt without additions through the effect of AC current, most molybdenum being separated in the form of metallic particles. Corrosion also increases in the glass melt containing antimony oxides. This is due to increased corrosion in the neighborhood of the separated antimony droplets. This mechanism also results in the loosening of molybdenum particles. The amount of precipitated antimony also increases through the effect of the AC current. AC exerts no appreciable effect on either corrosion, the character of the electrode-glass interface, or antimony precipitation in the glass melt containing SO₃.

Keywords: Molybdenum electrode, Corrosion, Glass melt, Antimony oxides, Sulfate