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Molybdenum Electrode Chemical Reactions in Molten Glass

Molybdenum electrode used in glass furnace will react with some trace elements in molten glass to occur chemical reactions.

(1) The reaction of molybdenum and oxygen, molybdenum has poor high-temperature oxidation performance, at high temperatures the following reaction will occur: Mo + O₂ = MoO₂,2MoO₂ + O₂ = 2MoO₃. Molybdenum in 380 ℃ oxidizing atmosphere begins to oxidize, accelerated oxidation at 600 ℃, more than 700 ℃ rapidly oxidized to produce volatile oxide MoO₃. MoO₃ will not protect molybdenum, so the oxidation will always be in the end and molybdenum will slowly be eroded away. Molybdenum oxidation rate is relative to the temperature and oxygen partial pressure in the gas. The higher the temperature and oxygen partial pressure, the faster the rate of oxidation is. Molybdenum electrode high temperature oxidation stability is poor, so during the operation the electrode should cover with reliable oxidation resistance measures, in order to ensure long-term stable operation of the electrode.

(2) The reaction of molybdenum and molten glass, molybdenum contact with the molten glass will not cause chemical reaction and will not color the glass. Small amount of molybdenum oxide dissolved in molten glass will make soda lime glass slightly yellowing, but usually very slight, less affected.

(3) The reaction of molybdenum with a variety of chemical mediators. Molybdenum electrodes have high chemical stability in a variety of reductive medium. The experiment shows that molybdenum chemical is stable in many corrosive media.

(4) The reaction of molybdenum and lead, arsenic, antimony, SO2^-3, molybdenum electrode is mainly applied to the reduction molten glass. In the molten glass, the lead, arsenic, antimony and SO2^-3 will react with molybdenum electrode and has impact on the molybdenum electrodes. Their potentials are higher than molybdenum, even failure of current the presence of oxides of these metals will be reduced to metal. When PbO content is 1%, the molybdenum electrodes have obvious erosion. These reducing metals will make electrode surface to form molybdenum oxide. Under reducing conditions, SO2^-3 ions will erode electrode to form corrosion products MoS₂. Antimony-containing soda lime glass react with electrode to form the droplets of metal antimony and calcium molybdate crystals deposited on the electrode surface. Antimony and molybdenum after reaction will form Mo₃Sb₇ and it will take away from the molten glass.

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