Which statement is true about noble/ inert shielding gases such as argon and helium?

• A. They will not mix with any other gas
• B. They react readily with most metals
• C. They will not combine chemically with any other material
• D. They must be cooled to be effective

Answer: (C)

The key idea is that noble shielding gases are chemically inert, so they don’t participate in reactions with the weld metal. Argon and helium form a protective blanket around the molten weld pool, physically displacing air and keeping oxygen, nitrogen, and hydrogen from contaminating the weld. Because of their complete outer electron shells, they don’t chemically bond with metals under typical GTAW conditions. That’s why the statement that they will not combine chemically with any other material is the best choice.

Note, they can mix with other gases or with ambient air if the shielding is disrupted, and gas blends (like argon with small amounts of other gases) are common to tailor weld characteristics. They don’t need to be cooled to be effective; they function as a shielding flow at room temperature. They also do not react readily with metals, which is precisely what makes them suitable for shielding.