In GTAW, what is the purpose of shielding gas flowing from the gun nozzle?

• A. Increases arc stability
• B. Cools the base metal
• C. Protects the molten weld metal from atmospheric contamination
• D. Lubricates the weld

Answer: (C)

Shielding gas creates an inert envelope around the weld zone, preventing air—especially oxygen, nitrogen, and moisture—from contacting the molten metal and the tungsten electrode. If air reaches the weld, oxidation and porosity can form, weakening the joint and leading to defects. The gas flow keeps the weld environment clean, allowing proper fusion and a sound bead. It isn’t used to cool or lubricate the weld (those are not the roles of the shielding gas), though the gas can affect arc stability and bead shape by maintaining a stable, consistent atmosphere.