In GTAW, which statement about cleaning action is true?

• A. The AC balance control affects cleaning action
• B. The AC balance has no effect on cleaning action
• C. The DCEN polarity controls cleaning action
• D. The waveform determines cleaning action

Answer: (A)

In GTAW, cleaning action happens during the portion of the AC cycle when the arc polarity causes the surface oxide on the workpiece to be oxidized and lifted off by the arc. This cleaning occurs during the electrode-positive half-cycle, when the workpiece side becomes the positive, and the oxide layer is more effectively cleaned away by the arc.

The AC balance control adjusts how much of the cycle is spent in that electrode-positive (workpiece-cleaning) condition. A higher balance means more cleaning action because the arc spends more time in the positive state; a lower balance reduces cleaning action. That’s why the statement about AC balance affecting cleaning action is the best answer.

The other ideas aren’t as precise: relying on DCEN won’t provide the same, cyclical cleaning effect you get with AC; saying the cleaning action is determined solely by the waveform is vague, since it’s specifically the proportion of positive (cleaning) time that drives cleaning effectiveness.