Effect of Chemistry and External Electric Potential on Interfacial Tension between Steel and Slag

When two liquids immiscible in each other (one of them an ionic solution) get into contact, segregations at the interface occur and electric potential between both phases is generated. This is the case, for example, when liquid metal comes into contact with liquid slag. In this article, electrocapillary measurements in steel-slag melts are performed. The metal drop weight in the liquid slag method is used for investigation. Using this method, the interfacial tension and the potential can be measured simultaneously. Low alloyed steels with high and low S and O activities in contact with slags with different basicities are used for investigations and the effect of electrical potential on the interfacial tension γ is measured. The interfacial tension increases with increasing basicity and decreasing S and O activities independent of applied electrical potential. With lower oxygen and sulphur contents of steel, γ increases clearly, whereas, the zero charge electrical potential $\Delta {\phi }_{zc}$ does not change. The maximum value of γ, corresponding to $\Delta {\phi }_{zc}$, is shifted to more negative electric potential for acid slags compared to the basic slags. The slope of the γ decrease is higher at the negative electric potential differences compared to the positive differences.