Aluminum is welded with which current in GTAW

• A. DCEN
• B. AC
• C. DCSP
• D. Pulsed

Answer: (B)

Aluminum welds rely on removing the oxide layer as the weld progresses, and alternating current is the way to achieve that in GTAW. The arc, when polarity reverses, continually cleans the surface: the positive half-cycle helps disrupt and wash away the oxide, while the negative half-cycle concentrates heat into the base metal to promote proper fusion and wetting. This cycle keeps the oxide from getting baked into the weld and helps maintain a stable arc on aluminum, which would be hard to achieve with a fixed polarity. Pulsed current can be used in tandem with this approach to control heat input, but the essential requirement for welding aluminum in GTAW is alternating current.