Magnesium

Liquid magnesium does not automatically form a passivating oxide layer on the surface of the melt. A mixture of gases must be used to prevent the molten magnesium from vaporizing and catching fire. Typically a small amount of SF₆ or SO₂ in a carrier gas is used to promote the formation of an oxide layer to prevent magnesium from vaporizing and catching fire.

The carrier gas can be argon, nitrogen or very dry air depending on the application, and may also include small amounts of CO₂. The selection of the proper protective atmosphere for molten magnesium involves several variables, and safety concerns which should be addressed when choosing a protective atmosphere.

Argon is used for metering of liquid metal for magnesium cold chamber die casting. The argon is used to displace the magnesium to the shot sleeve and for protection at the shot sleeve.

Argon is used to reduce hydrogen and remove small non metallic inclusions. Argon is bubbled through the molten magnesium to carry hydrogen and non metallic inclusions to the surface.