ISSN 0862-5468 (Print), ISSN 1804-5847 (online) 

Ceramics-Silikáty 46, (4) 133 - 139 (2002)


THE MECHANISM OF DISSOLUTION OF MOLYBDENUM IN GLASS MELT AND THE EFFECT OF ALTERNATING CURRENT
 
Matěj Jiří 1, Krupková Eva 1, Hulínský Václav 2
 
1 Laboratory of Inorganic Materials Joint workplace of the Institute of Inorganic Chemistry of the Academy of Sciences of the Czech Republic and the Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague, Czech Republic
2 Department of Glass and Ceramics, Institute of Chemical Technology, Prague Technická 5, 166 28 Prague, Czech Republic

Keywords: Molybdenum, Mechanism of dissolution, Glass melt, Alternating current
 

The molybdenum corrosion and lead precipitation rates together with the overall electrode current were investigated in terms of the potential of the molybdenum electrode in three glass melts. Two of them contained 24 wt.% lead oxide, one of them containing also a small addition of arsenic oxide, and the third glass melt was free from lead oxide. The comparison of the rate of precipitating lead, of the corrosion rate and of the total electrode current in the melt free from arsenic oxide showed that molybdenum is for the most part transferred into the glass melt in the form of Mo(VI) even at potentials substantially more negative than the rest corrosion potential. The stationary polarization curves obtained for all the three glass melts exhibited courses typical of passivation. In the case of melts containing lead oxide the passivation already set in at the rest corrosion potential, or in the presence of arsenic oxide even at a more negative potential. Alternating current can affect the corrosion and lead precipitation rate in various glass melts in both directions. The accelerating effect always occurs in parallel with reduction of the mean electrode potential and vice versa. The effect of the electrode potential, of the alternating current and of the content of alkalies on the corrosion rate in the glass melts, can be explained by affecting the presence or layer thickness of molybdenum dioxide on the electrode.


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