| Search our quarter-million Q&As |
Home of the finishing HOTLINE since 1989
-----Aluminum Welding Porosity -- Caused by Etching?
Q. We are performing TIG welding of 6061 T4 aluminum alloys sheet and plate (machined details). We every 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
Process Engineer - Centurion, Gauteng, South Africa
October 13, 2025
This is a meeting place for camaraderie & sharing, not a free consultancy. So some readers don't engage with anonymous posters.
A. Hello Darnelle
To ensure my understanding isn't flawed here. The porosity you are dealing with is present after welding and before any other process following the welding?
The etch should not be the cause, as it simply leaves you with a bare aluminium surface after etching and desmutting.
However, if you don't let the workpiece dry fully, or it is contaminated after the thorough chemical cleaning that you perform, that can give you problems.
If you are struggling with making sure the parts are dry, pre-heat them in an oven or use a torch to ensure that any moisture on the surface is removed.
As an anodizer we often see welds that have pores where Etch can get AFTER welding, and then shows as a fine white powder when we finish the anodizing. Even from subsea clients as well as aerospace. So porosity in aluminium welds does appear to be an issue that even high end customers face. So if you find a perfect solution, all the more power to you!
I'll be crossing my fingers for you.
Technician - Horsens, Denmark
October 21, 2025
Sorry! Finishing.com is temporarily Read-Only.
Ted Mooney is retiring but I have several offers to take it over.
We're working hard to make sure we find it the best new home.