What is the effect of using AC current in GTAW?

Using AC current in Gas Tungsten Arc Welding (GTAW) is particularly advantageous for welding non-ferrous metals, specifically aluminum and magnesium. This is due to the unique characteristics of AC current, which alternates polarity. The positive cycle of AC current cleans the oxide layer typically found on aluminum surfaces, facilitating better arc stability and weld quality. The negative cycle helps to penetrate the base metal more effectively.

This cleansing action is crucial because aluminum has a strong oxidation tendency, and the oxide layer can interfere with fusion, leading to defects in the weld. Thus, using AC current allows welders to achieve a cleaner, stronger weld when working with these metals, making it the preferred choice for aluminum and magnesium applications.

While it is true that AC current can enhance arc stability and that other current types can lead to varying amounts of spatter, these factors are secondary to its specific application in welding materials like aluminum and magnesium. Therefore, the emphasis on AC current's effectiveness in welding these metals makes this choice the most appropriate.