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Aluminum Welding Porosity -- Caused by Etching?

Q. We are performing TIG welding of 6061 T4 aluminum alloys sheet and plate (machined details). We ever so often have serious issues with our weld quality, especially porosity in the weld metal.
The source of the porosity is often directed at the alkaline etching that we perform prior to the welding to ensure we have a clean weld area prior to welding. We have good controls to manage the etching process and the line is an automated line that ensures consistent processing.

Can the alkaline etching process contribute to weld porosity? I believe our alkaline etching process is well controlled and cannot be the source of the porosity in the welding process.

Our alkaline etching process employed is as follows:
Mechanical prep of area to be welded
Emulsion clean (BONDERITE C-AK 6849 AERO) with RO rinse
Alkaline clean (BONDERITE C-AK 4215NC-LT AERO) with two rinses (drag out and RO rinse)
Alkaline etch (BONDERITE C-AK ALUM ETCH 2 AERO) RO rinse
Acid de-smut (Ardrox 295 GD) with two rinses (drag out and RO rinse)
Drying @ 60°C
RO feed water for rinses is <20 µS/cm, rinse baths are constantly over flowed to allow for clean rinses.
Chemical analysis of the baths is done weekly, etch rate determination is done daily using 6061 coupon.
Alkaline etch bath is made up fresh every month and the de-smut bath is made up fresh every 3 months

Darnelle
Process Engineer - Centurion, Gauteng, South Africa
October 13, 2025

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