Which polarity is used for GTAW on ferrous metal?

Which polarity is used for GTAW on ferrous metal?

• A. Direct current electrode negative
• B. Direct current electrode positive
• C. Alternating current
• D. Direct current with no polarity control

Answer: (A)

GTAW heat distribution depends on polarity: with the electrode negative, most of the arc heat is concentrated in the workpiece rather than the tungsten. This is ideal for ferrous metals like carbon steel or stainless steel because it provides deeper penetration and better fusion control, while also reducing tungsten erosion since the electrode is carrying the current in a negative direction. Using the electrode positive would shift more heat into the tungsten, leading to faster electrode wear and shallower penetration into the metal, which is undesirable for steels. Alternating current is useful for metals that need oxide cleaning (like aluminum) and for maintaining a stable arc in some situations, but for ferrous metals GTAW is typically done with direct current electrode negative to achieve the best penetration and control.

GTAW heat distribution depends on polarity: with the electrode negative, most of the arc heat is concentrated in the workpiece rather than the tungsten. This is ideal for ferrous metals like carbon steel or stainless steel because it provides deeper penetration and better fusion control, while also reducing tungsten erosion since the electrode is carrying the current in a negative direction. Using the electrode positive would shift more heat into the tungsten, leading to faster electrode wear and shallower penetration into the metal, which is undesirable for steels. Alternating current is useful for metals that need oxide cleaning (like aluminum) and for maintaining a stable arc in some situations, but for ferrous metals GTAW is typically done with direct current electrode negative to achieve the best penetration and control.