Which tungsten types are preferred for AC welding?

• A. Green and Brown
• B. Red and Yellow
• C. Blue and White
• D. Green and Red

Answer: (A)

For AC TIG welding, you want a tungsten electrode that can sustain a stable arc with alternating current and, ideally, without radioactive materials. Green tungsten is pure tungsten, which provides clean, stable arc characteristics suitable for AC. Brown tungsten is lanthanated, a versatile option that performs well on both AC and DC and tends to last longer. Together, these two types give reliable arc stability and life for AC welding, including aluminum where arc-start and oxide cleaning are important.

Thoriated tungsten (red) is tailored for DC welding and involves thorium, a radioactive material, making it less ideal for AC. Zirconated (blue) and cerated (orange) tungstens can be used for AC, but the combination of pure (green) and lanthanated (brown) is commonly preferred for the balance of performance and safety.