The Electrochemical Study on the Corrosion of Refractory by Molten Glass (1)

Abstract

A systematic study on the E. M. F. between simple oxides and common glasses was carried out using a vacuum tube voltmeter for the cell Pt/solid oxide/glass melt/Pt set in a Pt ribbon resistance furnace.Sodium silicate, potassium silicate, commercial window glass, lead glass, and borosilicate glass were used. All these glasses, except the window glass, were melted from pure materials in Pt-crucible. Solid oxides used were kaolin, SiO2, Al2O3, ZrO2, CaO, MgO, BaO, ZnO etc. Two types of solid oxide electrode were used. One was a Pt wire covered with a thin layer of a solid oxide being essentially the same as that used by Plumat, and the other was a small sintered rod whose one end was wound with Pt wire. The latter showed as good results as the former, provided that good contact was assured between Pt wire and the oxide rod.Factors influencing the E. M. F. of above cells would certainly include (1) temperature distribution in the cell, (2) atmosphere, (3) oxgen pressure inside the molten glass. The effect of the factor (3) was investigated and was confirmed as being most influential.Cell: Pt/kaolin/window glass/Pt was studied. It was confirmed that the change of the structure of kaolin took place during the preheating of the electrode and the kind of the cation absorbed in kaolin affected the E. M. F. greatly, though this problem ought to be studied more closely.For the cells “Pt/simple oxide/glass melt/Pt” all mesaurements were carried out at 1000°C, because it has been reported that the temperature itself has little effect upon the E. M. F. of above mentioned cells in the temperature range from 900°C to 1300°C.The E. M. F. of these cells suggested that the radius (r:A) and the number of electric charge of the cation of the solid oxide electrode (z) have some relations to the EM. F. of the cell. For each glass the E. M. F. values were plotted against the parameter (r/z). The figure showed that the E. M. F. of oxide electrodes come upon a linear line. The plot for ZnO failed to fit on the line in many cases, which may probably be interpreted by the non rare gas type electronic structure of Zn++. According to the figures (8-12) the straight lines may be represented by the equation, V=A-B (r/z), whereV is E. M. F. (volt), A and B are the constants for each glass.As B in above equation has nearly equal value for all glasses, suggesting that the electric charge was carried by same kind of cation. It will be possible to replace B by c(zc/rc) and obtain the equation in the following form, V=A-c(zc/rc)/(z/r), where zc is the number of charge of the cation carrying the electric charge in molten glass, rc the radius of cation, and c a constant representing the type of glass.