Oxidation behavior of molten magnesium in atmospheres containing SO2

The microchemistry and morphology of the oxide layer formed on molten magnesium in atmospheres containing SO2 were examined. Based on the results and the thermodynamic and kinetic calculations of oxide-growth process, a schematic oxidation mechanism is presented. The results showed that the oxide scales with network structure were generally composed of MgO, MgS, and MgSO4 with different layers, depending on the SO2 content, the time and the temperature. The formation of MgSO4 was important for the formation of the protective oxide scales. The growth of the oxide scales followed the parabolic law at 973 K and was controlled by diffusion.

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► We found the film formed on molten magnesium had a two or three layers structure.
► The formation mechanism of film was investigated and a growth model was proposed.
► We found the formation of MgSO4 was critical and promoted the growth of the film.