What type of current does AC welding use?

AC welding utilizes a periodically changing direction flow of electricity, which is characteristic of alternating current (AC). Unlike direct current (DC) that flows in a single direction, AC reverses direction periodically, allowing for various advantages in welding applications. The alternating nature of the current helps in stabilizing the arc, making it easier to control during the welding process.

This alternating current can produce a smoother weld and helps to clean the weld area by removing oxidation from the surface being welded. Additionally, because of the changing polarities, AC is often suitable for welding materials that are more challenging to weld with DC, such as aluminum and magnesium, as it can help alter the weld pool characteristics and heat input.

In contrast to the other options, a continuous flow of electricity suggests a DC system, which does not apply to AC welding. Also, the idea of a one-directional flow or a direct flow only through resistive materials does not accurately describe AC, as it specifically involves current that alternates its direction and can flow through a variety of materials given proper conditions.