Oxygen Interactions at the Surface of a Liquid Binary Alloy: Indium-Tin as a Test Case

When certain pure liquid metals interact with an oxidising atmosphere they form volatile oxides that can contribute to maintaining interface cleanness, so that the effective oxygen pressure necessary for oxidation is much greater than the thermodynamic saturation pressure. The application of the theoretical analysis of pure metals to liquid binary alloys and their oxides has indicated that the interactions between oxygen and a liquid alloy depend on the existence of a volatile oxide that prevents the surface oxidation even if the volatile oxide is formed by the metal with the lower percentage in the alloy composition. In this chapter we present the results of dynamic surface tension measurements on binary liquid alloys, made to determine oxygen interactions with a binary alloy through the validation of the theoretical oxidation/de-oxidation curve. In-Sn was chosen as test system. The experimental data on the effective oxygen pressure of In-Sn binary alloys of different compositions were compared with the data for the two pure metals and the theoretical predictions, revealing that the lower oxidizability of indium was shown to control indium-tin alloys with a tin content up to about 80 at% , due to the presence of the most volatile oxide In2O.