Sulphur hexafluoride (SF6) is widely used by the magnesium industry as a protective atmosphere. It has been demonstrated that SF6 prevents molten magnesium from further oxidation by reacting with magnesium to make the surface film on the magnesium melt denser. However, due to its high greenhouse effect (GWP=23900), the alternatives of SF6 must be sought. In this paper, 1,1-difluoroethane (commercially named HFC-152a), whose GWP value is only 140 and far lower than that of SF6, was tested to check its capacity of ignition-proof and further-oxidation-proof. Similar to SF6, the melt’s surface film formed in the protective atmosphere containing HFC-152a has a shiny metallic appearance. The surface film’s microstructure has been characterized with X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD’s results showed that the film contains only MgO and MgF2 phases while SEM showed their morphologies are uniform.