Which statement about EWTH (Thoriated Tungsten) is true?

• A. Not suitable for DCEN
• B. ThO2 0.6% improves current carrying capacity
• C. Not suitable for steel alloys
• D. Works with AC welding aluminum

Answer: (B)

Thoriated tungsten electrodes use thorium oxide to boost electron emission at the tip, which makes arc starting easier and allows higher current to be carried in DC TIG. This increased current-carrying capacity is the practical reason these electrodes are favored for DC welding of steels and similar alloys. The statement that ThO2 content improves current-carrying capacity aligns with this behavior, which is why it’s considered true.

The other ideas don’t fit as well: thoriated tungstens are indeed suitable for DC welding, especially on steel; they’re not typically used for AC welding of aluminum—aluminum is usually welded with tungsten doped with zirconium or lanthanum for better arc stability on AC.