TIG (Tungsten Inert Gas) is a welding method where an electric arc is maintained between a non-melting electrode and a workpiece in an atmosphere of inactive gas. I.e. the gas does not contribute to a chemical reaction in the process. The arc is melting the adjoining metal and the possible filler metal. The weld pool, like the electrode is protected from the oxygen and nitrogen in the air with the protective gas.

The electrode can be of pure or alloyed volfram(tungsten).

The welding gas is usually Argon(Ar) but also Helium(He) and mixes between Helium and Argon are used.