Which polarity is used when TIG welding steel?

• A. DCEN (Direct Current Electrode Negative)
• B. DCEP (Direct Current Electrode Positive)
• C. AC (Alternating Current)
• D. DCG (Direct Current Ground)

Answer: (A)

Polarity controls where most of the heat goes in TIG welding. For steel, using DC with the electrode negative (DCEN) is preferred because the current flows from the tungsten into the workpiece, directing most heat into the metal. This gives deeper penetration and a stable arc, while also reducing heat at the tungsten tip so the electrode wears less and the weld remains clean.

If the electrode were positive (DCEP), more heat would be placed into the electrode, causing faster tungsten erosion and often shallower penetration in steel. Alternating current (AC) is mainly used for aluminum and magnesium to help break oxide layers; steel doesn’t require that cleaning action, and AC makes heat distribution less predictable for steel welds. The remaining option isn’t a standard GTAW polarity and isn’t used for controlling heat in this context.