Abstract
The corrosion of refractories is considered as a process by which refractories come to equilibrium with the condition of environment where they are used. The state of corroded refractories was studied in order to explain the feature of the process.
Surface layers of the refractories used in the superstructure of the glass-melting furnaces for sheet glass were chemically analyzed. Their Na2O contents were approximately constant and their Na2O levels (chemical potential) were considered to be equal to those of the environment where the refractories were used. Na2O increase was essentially the only change in the composition of the surface layers of the refractories under service.
Therefore the surface layer of the refractories could be considered as one system, which was opened for alkali but closed for the other components and alkali content in the system was affected by the alkali level in the environment. The state of the corroded refractories could be estimated from the equilibrium state of the system with Na2O level equal to that of the environment.
The refractories corroded by molten glass at temperatures from 1300°C to 1500°C were investigated by electron beam microanalysis and analytical data were obtained about the interface. zones between the refractories and glass. Na2O level for each data was approximately constant and seemed to be close to that of the glass. Therefore in this case also Na2O content in the surface of the refractories was considered to be equilibrium with the Na2O level of the environment (glass). The content of CaO in the interface zones, however, increased also at higher temperatures and the influence of CaO could not be ignored. (CaO+Na2O)/Al2O3 mole ratios of the zones were nearly constant at any temperatures. Therefore at higher temperatures Ca2+ ions were considered to enter into the interface zone partially instead of Na+ ions.
