When MIG welding aluminum, what polarity and current type are typically used, and why?

When MIG welding aluminum, what polarity and current type are typically used, and why?

• A. DC polarity is commonly used with argon shielding; balances oxide removal and deposition.
• B. AC polarity is commonly used with argon shielding.
• C. DC negative polarity with helium shielding.
• D. DC positive polarity with CO2 shielding.

Answer: (B)

Aluminum wears a stubborn oxide layer that must be disrupted by the arc to weld cleanly. Running the MIG weld with alternating current and argon shielding provides both cleaning action and good deposition. The positive half-cycle helps remove and break up the oxide on the surface, while the negative half-cycle focuses heat into the weld for proper fusion and filler metal deposition. Argon is the preferred shielding gas because it is inert and gives a stable arc with aluminum, minimizing additional oxidation and porosity. Using a DC setup or other gases like CO2 or helium would either fail to clean the oxide effectively or alter heat and oxidation in ways that lead to poorer welds. So, AC polarity with argon shielding is the typical choice for MIG welding aluminum.

Aluminum wears a stubborn oxide layer that must be disrupted by the arc to weld cleanly. Running the MIG weld with alternating current and argon shielding provides both cleaning action and good deposition. The positive half-cycle helps remove and break up the oxide on the surface, while the negative half-cycle focuses heat into the weld for proper fusion and filler metal deposition. Argon is the preferred shielding gas because it is inert and gives a stable arc with aluminum, minimizing additional oxidation and porosity. Using a DC setup or other gases like CO2 or helium would either fail to clean the oxide effectively or alter heat and oxidation in ways that lead to poorer welds. So, AC polarity with argon shielding is the typical choice for MIG welding aluminum.