Porosity is gas trapped as the weld metal solidifies. With aluminum TIG, start by checking contamination and gas coverage. A clean-looking coupon can still carry oil or moisture, and a flowing regulator does not prove that the weld pool is fully shielded.
Start with the plate and filler
Use clean, dry material and filler. Remove grease with a suitable cleaner following its instructions, and let the work dry. Clean the joint area with a dedicated stainless steel brush after degreasing. Avoid handling the prepared edges and filler with bare or dirty hands.
Check shielding at the torch
Confirm the shielding gas specified by your procedure and inspect the hose, torch and connections for leaks or damage. Shield the work from drafts. Review cup condition, torch angle and arc length, and use the flow recommended for the setup. Increasing flow blindly can create turbulence that draws air in.
Use a coupon to isolate the cause
Clean a fresh coupon of the same alloy and thickness and start with clean filler. Run a short test using the same setup, then change one thing at a time. Record the setup and result so you can distinguish a material preparation problem from a shielding problem. For work governed by a welding procedure or inspection standard, use its acceptance criteria and repair requirements.
Further reading
See TWI’s guide to avoiding porosity in aluminum welding. For hands-on practice, see Progressive Welding Solutions.
