Oxidation of molten AZ91D Mg alloy in hexafluoropropylene/air atmospheres

The oxidation behavior of molten AZ91D Mg alloy in the mixture of 0.05-5% hexafluoropropylene and air at 670-800 degrees C was investigated by TG, XRD, SEM, EDS and XPS. Results show that the oxidation of the melt in 0.05 % hexafluoropropylene/air atmosphere at 700 degrees C obeyed a linear rate rule, while under other conditions it followed a parabolic rate law. The apparent activation energy was 82.78 kJ mol(-1) for the reaction of the melt in 0.1 % hexafluoropropylene/air atmosphere at 670-800 degrees C. The film formed on the melt surface mainly consisted of MgF2, MgO, C and small amounts of AlF3.