Reducing greenhouse gas emissions from magnesium die casting

Abstract

The U.S. magnesium industry uses sulfur hexafluoride (SF 6) as a cover gas to prevent the rapid and hazardous oxidation of molten magnesium. While this gas is considered to be safe and effective in this application, it is one of the most potent and persistent greenhouse gases (GHG) found in the atmosphere. The U.S. Environmental Protection Agency (EPA) launched a collaborative initiative called the SF 6 Emission Reduction Partnership for the Magnesium Industry in 1999 to identify and implement practical technologies for improving the industry's environmental profile. EPA's Partners, joined by the International Magnesium Association (IMA), have voluntarily committed to eliminate the use of SF 6 by 2010. The Partnership and IMA's commitment sent a clear signal to industry suppliers and has precipitated the exploration of alternate cover gases that are just as effective as SF 6 but greatly reduce the process's climate impact. The focus of this study is to assess byproducts, degradation levels, and GHG emission factors for three different fluorinated cover gases (SF 6, AM-cover™, and Novec™ 612) in cold chamber die casting applications. The results of this study are used to describe two approaches that modify current Intergovernmental Panel on Climate Change (IPCC) Good Practice Guidance for estimating cover gas emissions from the magnesium industry.