A gas that does not normally combine chemically with materials. See PROTECTIVE ATMOSPHERE.
Inert gases such as argon or helium may be used as shielding gases in welding operations because they will not react with the materials being welded and they prevent atmospheric contamination of the puddle and the electrode.
Nitrogen is sometimes considered to be an inert gas; however, under certain conditions it will react to produce nitrides, which are undesirable. See ARGON,
HELIUM, GAS METAL ARC WELDING, and GAS TUNGSTEN ARC WELDING.