When GTAW welding 5052 aluminum sheet using an inverter-based AC power source, the welder notices excessive tungsten erosion and an unstable arc, despite using a 2% Ceriated tungsten electrode with a properly blunted tip. The tungsten currently has a purple band. What adjustment would most likely resolve these issues?

Question: When GTAW welding 5052 aluminum sheet using an inverter-based AC power source, the welder notices excessive tungsten erosion and an unstable arc, despite using a 2% Ceriated tungsten electrode with a properly blunted tip. The tungsten currently has a purple band. What adjustment would most likely resolve these issues?

Answer options: ✅ Increase the AC balance to a higher percentage of electrode negative.

• Switch to a pure tungsten electrode and ball the tip.
• Decrease the AC frequency setting on the power source.
• Reduce the shielding gas flow rate to conserve gas.

Correct answer: Increase the AC balance to a higher percentage of electrode negative.

Explanation: Excessive tungsten erosion and unstable arc with an inverter AC power source on aluminum, especially with a ceriated tungsten, often indicates insufficient cleaning action. Increasing the AC balance (more electrode negative time) will shift the waveform to provide more cleaning action on the base metal, which is crucial for aluminum, and can stabilize the arc and reduce tungsten erosion. Pure tungsten with a balled tip is for transformer machines, decreasing AC frequency can worsen arc stability, and reducing gas flow rate can lead to contamination.