Interfacial tension between aluminum and cryolite alumina melts

The interfacial tension (IFT) between aluminum and cryolite melts containing different salt additions (AIF(3), NaF, Na2SO4, NaVO3) has been measured by the capillary depression method under the condition of electrolysis. The interfacial tension was found to be strongly dependent on the n(NaF)/n(AlF3) ratio (cryolite ratio, CR). The addition of Na2SO4, decreases the IFT of the alumina/electrolyte interface. We also found a different influence of conditions of electrolysis on IFT in the systems with and without Na-2,SO4- In the systems without Na2SO4 the IFT decreases with increasing current density, and vice versa in the systems with Na2SO4. Addition of NaVO3 has no effect on the IFT between aluminum and the cryolite-alumina electrolytes.