California Air Resources Board

SACRAMENTO - Two California magnesium casting foundries have eliminated their use of a very potent greenhouse gas with 24,000 times the global warming potential of carbon dioxide (CO₂). Consolidated Precision Products Corp of Pomona and Azusa, and Magnesium Alloy Products Company of Compton, which employ about 400 Californians, worked closely with the Air Resources Board (ARB) to eliminate the use of sulfur hexafluoride (SF₆) in their casting processes as required by a state regulation.

“This is an excellent example of collaboration between government and industry to identify and use robust alternatives that meet manufacturing specifications while eliminating the use of a highly potent greenhouse gas,” stated Richard Corey, ARB’s Executive Officer.

The companies faced difficulties complying with the regulatory deadline because of the stringent requirements associated with altering the casting process used in the production of flight critical components for aircraft. Because of this extensive procedure, the companies requested a two-year exemption from compliance and this was granted after a full ARB review with assistance from the California Metals Coalition (CMC), which represents the metalworking industry in California.

Decades ago, the companies replaced sulfur dioxide (SO₂) with SF₆ as a cover gas to prevent corrosion during the magnesium casting process.  Molten magnesium will oxidize (burn) on contact with ambient air.  Working closely with the CMC and the companies, ARB commissioned a study with Cal Poly Pomona in 2009, led by Dr. Victor Okhuysen, to evaluate acceptable alternatives to SF₆ in the foundry casting process. The CMC helped facilitate the testing and worked as an intermediary between the foundries and the principal investigator. During this time, Consolidated Precision Products Corp and Magnesium Alloy Products Company made a considerable investment in effort, time and money in changing to an alternative cover with significantly lower greenhouse gas emissions.

Going forward, both California magnesium foundries will now use flux, which is a granular cover material, to protect the molten magnesium during melting and ladle transfer. A trace amount of HFC-134a, a common and widely available refrigerant with a much lower global warming potential, will be used to purge the empty cavity of the mold.

The result is the removal of the equivalent of 35,000 metric tons of carbon dioxide and retention of 400 well-paying, specialized jobs. Consolidated Precision Products Corp and Magnesium Alloy Products Company represent a small, but important niche in California’s metalworking industry. All parties’ willingness to collaborate in finding a greener production process provides an alternative to SF₆ with proven use in commercial production for other magnesium casters around the country.