Which statement describes oxide behavior during AC GTAW?

Which statement describes oxide behavior during AC GTAW?

• A. Oxide surfaces are disrupted on the positive portion of the cycle while the electrode is cooled on the negative half
• B. Oxide surfaces are disrupted on the negative portion while the electrode is heated on the positive half
• C. Oxide layers are unaffected by AC
• D. AC eliminates oxide layers entirely

Answer: (A)

The main idea is that AC GTAW provides a cleaning action of the workpiece oxide during the positive half of the cycle, while the electrode is kept cooler during the negative half. When the electrode becomes positive relative to the workpiece, the arc energy concentrates at the workpiece surface, breaking up and disrupting the oxide layer so fresh metal is exposed for bonding. On the negative half, the electrode is effectively cooled, which helps control tungsten heating and maintains stable welding conditions for the next cleaning cycle. This is why oxide surfaces are disrupted on the positive portion of the cycle, with the electrode cooled on the negative half. The other statements don’t match this alternating-action behavior: AC does not simply leave oxides untouched, nor does it completely eliminate oxide layers.

The main idea is that AC GTAW provides a cleaning action of the workpiece oxide during the positive half of the cycle, while the electrode is kept cooler during the negative half. When the electrode becomes positive relative to the workpiece, the arc energy concentrates at the workpiece surface, breaking up and disrupting the oxide layer so fresh metal is exposed for bonding. On the negative half, the electrode is effectively cooled, which helps control tungsten heating and maintains stable welding conditions for the next cleaning cycle. This is why oxide surfaces are disrupted on the positive portion of the cycle, with the electrode cooled on the negative half. The other statements don’t match this alternating-action behavior: AC does not simply leave oxides untouched, nor does it completely eliminate oxide layers.