Effect of Ga on the Oxide Film Structure and Oxidation Resistance of Sn-Bi-Zn Alloys as Heat Transfer Fluids.

The effect of gallium on the oxide film structure and overall oxidation resistance of low melting point Sn-Bi-Zn alloys was investigated under air atmosphere using thermogravimetric analyses. The liquid alloys studied had a Ga content of 1-7 wt.%. The results showed that the growth rates of the surface scale formed on the Sn-Bi-Zn-Ga alloys conformed to the parabolic law. The oxidation resistance of Sn-Bi-Zn alloys was improved by Ga addition and the activation energies increased from 12.05 kJ∙mol to 22.20 kJ∙mol. The structure and elemental distribution of the oxide film surface and cross-section were found to become more complicated and denser with Ga addition. Further, the results of X-ray photoelectron spectroscopy and X-ray diffraction show that Ga elements accumulate on the surface of the liquid metal to form oxides, which significantly slowed the oxidation of the surface of the liquid alloy.