Corrosivity of HFC125 as Shielding Gas for Magnesium Melt under High Temperature

Abstract

HFC125 is a potential substitutive to SF₆ in terms of its protective effectiveness, reduced GWP and cost. In the present study, corrosivity of HFC125 containing nitrogen atmosphere to the medium-carbon steel of C45E4 was examined by systematic experiments under the temperatures and HFC125 concentrations commonly used in Mg die-casting practice. For comparison, the corrosivity of SF₆ containing nitrogen atmosphere was examined in the identical conditions, followed by X-ray diffraction and X-ray fluorescence characterization of the corrosion products. The results show that the HFC125 containing nitrogen atmosphere was less corrosive to C45E4 than SF₆ containing one in long-playing corrosion under identical conditions. Oxidation was the major cause of the corrosion to C45E4 and HFC125 or SF₆ was of secondary contribution. HFC125 or its decomposition was deduced to corrode C45E4 to produce fluorides; SF₆ or its decomposition was deduced to react with C45E4 to produce sulfides.