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Basic Information

photo collage of the products manufactured with magnesium and the Magnesium Partnership logo


In 1999, EPA and the U.S. magnesium industry, with the support of the International Magnesium Association (IMA), launched a voluntary partnership to better understand and reduce emissions of sulfur hexafluoride (SF6), a very potent greenhouse gas. EPA’s partnership with the magnesium industry promotes technically feasible and economically attractive actions aimed at minimizing SF6 emissions and reducing the threat of global climate change.

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SF6 has been widely used by the magnesium industry for more than 25 years. Magnesium producers, casters, and recycling companies commonly use a cover gas of dilute SF6 in dry air and/or carbon dioxide (CO2) to protect the molten metal from oxidation and potentially violent burning. Without protection, molten magnesium will oxidize in the presence of air and form magnesium oxide (MgO) deposits that greatly reduce the quality and strength of the final product. In contrast, an effective cover gas, such as SF6, modifies and stabilizes the MgO surface film to form a protective layer that prevents further oxidation (see Molten Magnesium images).

photo of Molten Magnesium with Cover Gas
Molten Magnesium with
Cover Gas
photo of Molten Magnesium without Cover Gas
Molten Magnesium without
Cover Gas

Courtesy 3M™ Company

Although studies are underway to characterize the reaction byproducts of SF6 and molten magnesium, it appears most of the SF6 introduced to the molten metal surface is emitted to the atmosphere and that only a small portion reacts or decomposes. With a global warming potential (GWP) 23,900 times as strong as CO2 and a 3,200-year atmospheric lifetime, reducing SF6 emissions will have significant environmental benefit for many future generations. In 2002, the U.S. magnesium industry’s SF6 emissions were equal to 2.4 million metric tons of CO2, a 42% improvement since launching the partnership in 1999.

EPA conducted its first measurement study of magnesium die casting emissions in September 2002.

Measured SF6 Emissions From Magnesium Die Casting Operations (PDF) (5 pp, 118K, About PDF) by S. Bartos, J. Marks, R. Kantamaneni, and C. Laush. This paper was presented at The Minerals, Metals, and Materials Society’s (TMS) 132nd Annual Conference, held in San Diego, California, in March of 2003. The paper describes a study conducted at Product Technologies, one of EPA’s magnesium die casting partners, to measure SF6 degradation and by-products in typical hot-chambered die casting equipment.

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Mitigation Options

In just a few short years, EPA and its magnesium industry climate protection partners have made tremendous progress, reducing emissions intensity by more than 40% from 1999 to 2002. The industry is succeeding in cost effective pollution prevention stories by optimizing equipment designs and operation and improving SF6 gas management practices. These activities and technological innovations have directly contributed to the partnership’s success and provided both economic and environmental benefits. More detailed information on the costs of reducing SF6 emissions from magnesium operations is available at EPA’s High GWP Home Page.

In February 2003, EPA’s partners and the International Magnesium Association added their support to the President’s Climate VISION Climate VISION Exiting EPA, initiative by establishing a goal to eliminate SF6 emissions by year-end 2010. To meet this technically aggressive commitment, the industry will need to further evaluate and implement alternative cover gases such as HFC-134a, 3M’s fluorinated ketone, Novec™ 612, and possibly sulfur dioxide (SO2). Table 1 shows the atmospheric lifetimes and GWPs of these chemicals compared to SF6.

Table 1: Global Warming Potential (100 year)*

Compound Atmospheric Lifetime (years) Global Warming Potential (100 Year)
CO2* 200-300* 1*
3M™ Novec™ 612(C3F7C(O)C2F5) 0.014** ~1**
HFC-134a 14.6* 1,300*
SF6 3,200* 23,900*

* IPCC 1995
** 3M™

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EPA & Partner Responsibilities

Under the agreement, EPA will:
Partners agree to:

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Partner Opportunities

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