This measurement study was conducted to evaluate the greenhouse gas (GHG) emissions
and occupational exposure associated with five cover gas technologies used in a cold chambered die casting operation. Sulfur hexafluoride (SF6) is widely used for the protection of molten magnesium, but with the goal of eliminating the use of SF6 in this application by 2010, the magnesium industry and U.S. Environmental Protection Agency (EPA) have been evaluating the use of alternative gases. This study expands upon previous research by evaluating additional alternative cover gases and including an occupational exposure component. This study examined the use of AM-CoverTM using HFC-134a (supplied by Advanced Magnesium Technologies), MTG-ShieldTM using NovecTM 612 (supplied by Matheson Tri-Gas, Taiyo Nippon Sanso, and 3MTM), sulfur dioxide (SO2) (gas blender supplied by Polycontrols Inc.), and frozen
carbon dioxide (CO2) and SF6 (both provided by Lunt Manufacturing) on a single cold
chambered magnesium die casting machine located at a Lunt Manufacturing facility in
Hampshire, Illinois. Each cover gas mixture was evaluated under identical process and machine operating parameters. With the exception of frozen CO2, each cover gas was injected into and extracted from the crucible headspace under similar parameters to characterize emissions and byproducts as the cover gases interact with the melt surface and undergo thermo-degradation. The results reported were from measurements taken inside the crucible headspace and from worker exposure/ambient air sampling points.

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SOURCE: Bartos, S. C. “Characterization of Emissions and Occupational Exposure Associated with Five Melt Protection Technologies for Magnesium Die Casting”. U. S. Environmental Protection Agency. Contract GS-10F-0124J. October 2007.