ALTERNATIVES TO SF6/SO2 FOR MAGNESIUM MELT PROTECTION - FINAL REPORT OF THE IMA-SINTEF COLLABORATION PROJECT

Over the past decade, increasing global awareness of the greenhouse effect has resulted in an international push towards reduction of known greenhouse gases. For the magnesium industry, this push has involved minimizing and reconsidering the use of SF6 – which is an extremely potent greenhouse gas – in the cover gas mixtures used to protect liquid magnesium from oxidation. In October 2000, the International Magnesium Association (IMA) commenced a collaborative research project with SINTEF Materials Technology in Trondheim, Norway, for the purpose of identifying and testing alternatives to SF6, a potent greenhouse gas, for magnesium melt protection. This report details the main findings of the IMA/SINTEF collaboration project. In short the research findings can be summarized as: • Three promising SF6 replacements, HFC 134-a, HFE 7100 and Novec™612, have been identified and tested in both laboratory and pilot scale for their relative technical and environmental performances. • All three tested compounds (HFC 134-a, HFE 7100 and Novec™612) provide technically better melt protection than SF6 under identical testing conditions. • All three replacement compounds provide a lower total greenhouse gas impact than SF6. • It is suggested that, for a site implementation of a new cover gas blend, a gas "optimization" based on technical and environmental performance but with an element of economic consideration – is necessary