Which tungsten electrode type is described as having the poorest heat resistance and electron emission characteristics?

Which tungsten electrode type is described as having the poorest heat resistance and electron emission characteristics?

• A. Lanthanum tungsten
• B. Zirconium tungsten
• C. Pure tungsten
• D. Thoriated tungsten

Answer: (C)

In GTAW, tungsten electrodes are doped with oxides to improve how easily they emit electrons and how well they stand up to the arc heat. Doped tungstens—such as lanthanum-tungsten, zirconium-tungsten, or thoriated tungsten—provide more stable arc starting, higher current-carrying capability, and better resistance to tip erosion under heat. Pure tungsten has no such dopants, so it emits electrons less readily and wears away more quickly when exposed to the arc, especially at higher currents. That combination means it has the poorest heat resistance and electron emission characteristics among the options.

In GTAW, tungsten electrodes are doped with oxides to improve how easily they emit electrons and how well they stand up to the arc heat. Doped tungstens—such as lanthanum-tungsten, zirconium-tungsten, or thoriated tungsten—provide more stable arc starting, higher current-carrying capability, and better resistance to tip erosion under heat. Pure tungsten has no such dopants, so it emits electrons less readily and wears away more quickly when exposed to the arc, especially at higher currents. That combination means it has the poorest heat resistance and electron emission characteristics among the options.