Alternating current (AC) is preferred for welding which metals?

Alternating current (AC) is preferred for welding aluminum and magnesium due to the unique properties of these metals. When welding with AC, the positive and negative cycles allow for better cleaning action on the oxide layer that forms on aluminum and magnesium surfaces. This oxide layer has a high melting point and can hinder the welding process if not properly addressed.

The alternating nature of AC effectively breaks down this oxide layer during the positive half-cycle, while the negative half-cycle provides the heat needed to create a strong weld. This improves arc stability and overall weld quality. In contrast, using direct current (DC) might require additional cleaning or preparation to remove the oxide layer, making AC a more efficient choice for these specific metals.

While other metals like steel, titanium, and stainless steel can be welded with AC, it is not the preferred method for those materials as they do not have the same cleaning requirements as aluminum and magnesium.