Inert gas can be found which is inexpensive and common. For example, carbon dioxide is sometimes used in gas mixtures for GMAW because it is not reactive to the weld pool created by arc welding. But it is reactive to the arc. The more carbon dioxide that is added to the inert gas, such as argon, will increase your penetration. The amount of carbon dioxide is often determined by what kind of transfer you will be using in GMAW. The most common is spray arc transfer, and the most commonly used gas mixture for spray arc transfer is 90% argon and 10%
Inert gas inert gases due to their high natural abundance (78.2% N, 1% Ar in air) and low relative cost. Unlike noble gases, an inert gas is not necessarily elemental and is often a compound gas. Like the noble gases the tendency for non-reactivity is due to the valence, the outermost electron shell, being complete in all the inert gases. This is a tendency, not a rule, as noble gases and other "inert" gases can react to form compounds. The inert gases are obtained by fractional distillation of air, with the exception of helium which is separated from a few natural gas