What is the purpose of postflow in a GTAW shielding gas system?

• A. To extend arc length
• B. To preheat the workpiece
• C. To wash away spatter
• D. To continue shielding after the arc stops

Answer: (D)

Postflow is the continuation of shielding gas after the welding arc stops. The weld pool and heat-affected zone stay hot and reactive as they cool, so keeping an inert blanket in place prevents air from oxidizing the metal, which can cause discoloration, porosity, and other quality issues. It also helps purge any residual air or moisture from the weld area, reducing defects during cooling. This protection is about maintaining shielding during the critical cooling phase, not about extending the arc, preheating, or washing away spatter.