Which welding process and current type are commonly used for aluminum welding, and why?

• A. GTAW (TIG) with AC is commonly used because AC helps break up oxide on aluminum; DC can be used for some alloys with proper filler
• B. SMAW with DC is best for aluminum
• C. GMAW with DC is the only method used for aluminum
• D. FCAW with AC is preferred for aluminum

Answer: (A)

Aluminum welds are highly affected by a thin, rapidly forming oxide layer that blocks proper bonding. Using TIG welding with alternating current is ideal because the AC arc naturally helps break up and sweep away that oxide while maintaining a stable, clean weld pool. The positive half-cycle aids oxide disruption and surface cleaning, while the negative half-cycle helps containment and root penetration, all under a protective argon shield. This combination gives excellent control of heat input, which is crucial for aluminum’s high thermal conductivity and tendency to burn through or warp if overheated. Direct current can be used for some alloys with the right filler, but it doesn’t remove oxide as effectively and can lead to porosity or poor wetting. That’s why AC TIG is the commonly used method for aluminum welding, with other processes being less reliable for producing clean, high-quality aluminum welds.