What current is used for aluminum and magnesium welding?

• A. Direct Current
• B. Alternating Current
• C. Pulsed DC
• D. Direct Current Electrode Positive

Answer: (B)

Aluminum and magnesium form oxide films that are hard to weld through, so the current chosen must both carry the arc and periodically reverse polarity to clean that oxide away. Alternating current does exactly that: it keeps the arc stable while the polarity swaps, providing cleaning action on the workpiece during the positive half-cycle and good fusion during the negative half-cycle. This helps produce a clean, consistent weld with fewer porosity issues. Direct current alone keeps one polarity and won’t provide the necessary oxide cleaning, making it less suitable for these metals. Pulsed DC is still a form of DC and doesn’t reverse polarity, so it doesn’t deliver the same cleaning effect. Direct Current Electrode Positive concentrates heat and is not ideal for aluminum welding, where cleaning and arc balance are important.