A welder is setting up a GTAW process to weld 6 mm thick 6061-T6 aluminum using alternating current (AC). They are using a conventional transformer-based power source. Which of the following tungsten electrode types and preparation would be most appropriate for this application?

Question: A welder is setting up a GTAW process to weld 6 mm thick 6061-T6 aluminum using alternating current (AC). They are using a conventional transformer-based power source. Which of the following tungsten electrode types and preparation would be most appropriate for this application?

Answer options: ✅ Pure tungsten, balled tip

• 2% Thoriated tungsten, pointed tip
• 2% Lanthanated tungsten, blunted tip
• Zirconiated tungsten, sharp pointed tip

Correct answer: Pure tungsten, balled tip

Explanation: For AC GTAW on aluminum using a conventional transformer-based power source, pure tungsten (EWP) with a balled tip is traditionally used to maintain arc stability and prevent tungsten inclusions. Thoriated, Lanthanated, and Zirconiated tungstens are generally preferred for DC applications or AC with inverter power sources, and pointed tips are not typically maintained for AC aluminum welding.