Inert Gas

An inert gas is a gas which does not change under a given set of conditions.  Inert gases are often used in welding, sealing, or marking applications in an effort to avoid unwanted chemical reactions which may degrade a part. These unwanted reactions include oxidation and hydrolysis which are reactions with oxygen and the moisture in air.

Purified nitrogen and argon are most commonly used as inert gases due to their high natural abundance (78% N2, 1% Ar in air) and relatively low cost.