GTAW of chrome-moly uses which polarity?

• A. DC-
• B. DC+
• C. AC
• D. Alternating polarity

Answer: (A)

In GTAW, polarity determines where most of the heat of the arc goes: toward the workpiece or toward the electrode. Using direct current with the electrode negative concentrates heat into the workpiece, which for chrome-moly (a steel alloy) gives deeper penetration and a more stable, controllable weld. The tungsten electrode stays cooler and wears less under this setup, which is ideal for steel welding.

If the polarity were switched to the electrode positive, more heat would be drawn into the electrode, increasing tungsten erosion and reducing the heat available to the joint—not desirable for chrome-moly welding. Alternating polarity (AC) is mainly used for nonferrous metals like aluminum to clean oxide layers and maintain arc stability there; it’s not the typical choice for chrome-moly steel.