Why is DCEP not commonly used with GTAW?

• A. Maximum heat is concentrated at the electrode, requiring a large electrode
• B. Maximum heat is concentrated at the work, requiring larger current at the workpiece
• C. It produces deeper penetration
• D. It prevents oxide cleaning action

Answer: (A)

The main idea being tested is how polarity affects where most of the arc heat goes and why that matters for a nonconsumable electrode like in GTAW. When using direct-current electrode positive, the electrode becomes the anode, so most of the arc heat is deposited at the electrode tip. In GTAW the electrode is a nonconsumable tungsten tip, and heating it this way causes it to overheat, wear quickly, or even degrade, which is undesirable for maintaining a stable arc and weld quality. To keep the tungsten cool and to maintain arc stability, you don’t want heat concentrated in the electrode, so DCEP is not commonly used with GTAW. Instead, DCEN (electrode negative) or AC keeps more heat in the workpiece or balances heat, preserving the tungsten and extending electrode life.