Which current is preferred for welding stainless steel with TIG?

• A. AC
• B. DCEN
• C. DCEP
• D. DCOP

Answer: (B)

The polarity of the TIG current determines where most heat goes during the weld. For stainless steel, using direct current with the electrode negative (DCEN) sends most heat into the workpiece, giving deeper penetration, a stable arc, and better control of heat input. This helps produce a clean, well-formed weld bead and reduces tungsten wear in the non-consumable electrode.

Alternating current is mainly used for aluminum to provide oxide cleaning action, which isn’t necessary for stainless steel and can introduce variability. Direct current with the electrode positive (DCEP) would put more heat into the electrode and less into the workpiece, leading to shallower penetration and more rapid tungsten wear—not desirable for stainless steel welding.