The Effects of an Applied Voltage on the Corrosion Characteristics of Dense MgO
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Abstract
In a recent investigation Mills and Riaz [1] showed that industrial oxide refractory corrosion by liquid oxides could be changed by the application of a small voltage across the liquid oxide-refractory interface. They explained their result in terms of penetration of the refractory pores with liquid oxide. Their analysis of the corrosion effect was to some degree limited by the use of an industrial refractory material in the study. Further, it was not clear whether their findings were limited to solely industrial refractories or had wider ranging application to more dense ceramic type solid oxide systems. In this study, a simpler and more easily characterized solid oxide (dense MgO) has been used to examine the effects of an applied voltage on the solid oxide in a liquid oxide melt. The dissolution rate of an MgO ceramic in a CaO-SiO2-Al2O3 and CaO-SiO2- Fe2O3-FeO-MgO liquid oxide composition at various applied voltages has been measured at 1540°C. It was found that the MgO corrosion in the CaO-SiO2-Al2O3 system was insensitive to an applied voltage over the voltage range –0.5 to 0.3 V. In the CaO-SiO2-Fe2O3-FeO-MgO liquid oxide system the MgO corrosion rate showed a maximum at –0.45 V. This effect has been explained by considering the consequences of an applied voltage on the rate of Marangoni flow at the liquid oxide-refractory-gas interface and in turn, the flow effect on the rate of the mass transfer controlled MgO dissolution reaction.
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