Which tungsten electrode symbol denotes a red stripe?

• A. EWTh-3
• B. EWTh-2
• C. EWTh-1
• D. EWTh-4

Answer: (B)

Tungsten electrodes are color-coded to identify their alloying content, especially thorium. A red stripe on the electrode indicates thorium-containing tungsten. In the SMWIA notation EWTh-2, the “Th” shows thorium, and the “2” specifies 2% thorium content. So this symbol corresponds to the thorium-containing tungsten with 2% thorium, which is why it denotes the red stripe. The other symbols imply different thorium contents (and would be associated with different stripe colors or none), so they don’t match the red-stripe designation.