In aluminum welding, what technique helps reduce porosity due to oxide layer?

• A. Mechanical oxide removal pre-weld, use AC with balanced waveform, and proper travel and shielding gas.
• B. Use DCEN and skip oxide removal.
• C. Use hardening filler metal only.
• D. Increase shielding gas flow beyond 100 CFM.

Answer: (A)

Aluminum oxide on the surface forms a film that can trap hydrogen and seep into the weld, causing porosity. The most effective way to prevent that is to remove the oxide before welding and to keep the arc actively cleaning the surface as you weld. Mechanically removing the oxide pre-weld—by grinding, brushing, or scarfing—gets rid of the film at the joint. Using alternating current with a balanced waveform provides a cleansing action: the arc polarity changes helps break up and sweep away oxide while exposing fresh metal. Coupled with proper travel speed to control heat input and with adequate shielding gas to protect the weld from air, these steps work together to minimize porosity. The other approaches don’t directly address the oxide layer—DCEN lacks the cleaning action, skipping oxide removal leaves the film in place, changing filler metal doesn’t remove oxide, and simply increasing gas flow isn’t a reliable solution and can cause issues.