In aluminum welding, how do TIG and MIG shielding gas usage differ?

• A. TIG uses a pure inert gas such as argon (sometimes with helium); MIG aluminum welding uses argon or argon-helium blends depending on alloy and position.
• B. TIG uses oxygen-rich gas; MIG uses nitrogen.
• C. Both use the same shielding gas composition.
• D. TIG uses carbon dioxide; MIG uses argon.

Answer: (B)

Shielding gas protects the molten aluminum from rapid oxidation, and the two processes use inert gases but in slightly different ways. For TIG welding, you typically shield with a pure inert gas like argon, and sometimes a small amount of helium is added to adjust heat and arc stability for certain thicknesses or joint positions. MIG welding of aluminum also uses inert gas, usually 100% argon or an argon–helium blend, with the blend chosen to influence arc characteristics, heat input, and deposition based on the alloy and welding position. Gases containing oxygen or nitrogen are not used for aluminum shielding in these processes because they can cause oxide formation or arc instability. So the key difference is the TIG setup tends to rely on a pure inert gas (argon, possibly with helium), while MIG uses argon or argon–helium blends to optimize the weld.