Which gas or gas combinations can be used for GMAW on nonferrous metals such as aluminum and copper?

• A. Argon
• B. Air
• C. Nitrogen
• D. Argon, Helium, Argon-Helium

Answer: (D)

GMAW on nonferrous metals relies on an inert shielding gas to keep the molten metal from oxidizing and contamination from occurring. Argon is the standard shield for aluminum and copper because it provides a stable arc and clean beads. Helium can be used too, though it’s more costly, because it adds heat to the arc, which can improve penetration and travel speed on these metals. A mixture of argon and helium combines the stability of argon with the extra heat from helium, making it a versatile choice for nonferrous welding.

Air and nitrogen aren’t suitable shielding gases for aluminum or copper because they introduce reactive components that contaminate the weld and degrade quality. Nitrogen isn’t typically used for shielding these metals in GMAW for the same reason. Therefore, the gas options that can be used are argon alone, helium, or an argon-helium blend.