Which polarity is used for TIG welding aluminum?

• A. DCEP
• B. AC
• C. DCEN
• D. DCG

Answer: (B)

Aluminum TIG welding relies on AC to both clean the surface and weld effectively. Aluminum naturally forms a stubborn oxide layer that must be disrupted as you weld. The alternating current keeps this oxide under control: during the positive portion of the cycle, the arc helps break up and remove the oxide, exposing fresh metal; during the negative portion, the heat goes into the workpiece to promote proper fusion and a stable weld pool. A balance control lets you adjust how much time is spent on each half-cycle, trading off cleaning action against penetration.

Using a direct current polarity (whether electrode positive or negative) doesn’t provide that built‑in cleaning action, and a nonstandard DC setting isn’t used for aluminum TIG welding.