Which tungsten electrodes are good choices for DC welding?

• A. Pure tungsten only
• B. 1% thorium electrode and 2% thorium bearing electrodes or the zirconium bearing electrode
• C. Green and brown tungsten
• D. Zirconium free tungsten

Answer: (B)

When welding with direct current, you want a tungsten electrode that keeps a stable, easy-to-start arc and resists rapid wear at the electrode tip. Thorium-containing tungsten (such as 1% or 2%) and zirconium-bearing (zirconia) tungsten deliver excellent arc stability and reliable electron emission under DC, which makes them well-suited for DC welding. They resist contamination and burn-off better than pure tungsten, helping you maintain a clean weld and consistent arc characteristics when the electrode is the negative or positive pole.

Pure tungsten can be used in some DC situations, but it tends to burn off more quickly and is harder to start and maintain an arc at higher currents, so it isn’t the best general choice for DC welding. The other color-coded or zirconium-free tungsten types don’t provide the same combination of easy arc starting and long electrode life under DC, so they’re not as favorable for DC applications.

So, the best choices for DC welding are thorium-containing electrodes (1% or 2%) and zirconium-bearing electrodes.