Welder Red Seal · Question
When using the GTAW process on aluminum, what part of the AC waveform provides the 'cleaning action' that removes the tough, high-melting-point aluminum oxide layer?
The cleaning action, or cathodic etching, occurs during the electrode positive (EP) half of the AC cycle. In this phase, electrons flow from the workpiece to th
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Question: When using the GTAW process on aluminum, what part of the AC waveform provides the 'cleaning action' that removes the tough, high-melting-point aluminum oxide layer?
Answer options:
- The electrode negative (EN) portion of the cycle ✅ The electrode positive (EP) portion of the cycle
- The zero-amperage crossover point
- The peak amperage of the EN portion
Correct answer: The electrode positive (EP) portion of the cycle
Explanation: The cleaning action, or cathodic etching, occurs during the electrode positive (EP) half of the AC cycle. In this phase, electrons flow from the workpiece to the tungsten, and positive gas ions are accelerated to the plate, bombarding and breaking up the refractory oxide layer ahead of the weld pool.
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