Home/Technical Glossary/Cover Gas Cover Gas Cover gas – or shielding gas – is used to prevent rapid oxidation of the weld zone due to atmospheric oxygen. Argon, helium or nitrogen inert gas is directed at low pressure and flow volume into the weld zone during the welding process to shield the weld zone from atmospheric oxygen. The mechanical properties and weld strength are usually unaffected by cover gas. Welds made in the presence of cover gas are generally shiny and more cosmetically appealing. The cover gas can also be used to cool the part minimizing the heat affected zone, and overall thermal loading.