For aluminum welding with GTAW, which current type is recommended?

• A. AC
• B. DCEP
• C. AC Balance? (not a valid option)
• D. DCEN

Answer: (A)

Aluminum oxide on the surface must be cleaned away during welding, and the way GTAW achieves that on aluminum is by using alternating current. The arc continuously reverses polarity, which provides a cleaning action during the negative half-cycle and exposes fresh metal for bonding during the positive half-cycle. This cleaning is essential for a stable arc and good fusion with aluminum.

Direct current setups (whether electrode negative or electrode positive) don’t provide that same, effective surface-cleaning action, so they’re not the usual choice for aluminum GTAW. The term AC balance isn’t a separate current type—it’s a setting that adjusts how much time the arc spends negative (cleaning) versus positive (heat). You still weld with alternating current, just tuned for cleaning versus penetration. So the recommended type is alternating current.