Concerns Using Aluminum Flux Tank

If we use a flux tank with our wave soldering system that is constructed from aluminum, and we use water soluble flux, could the flux become contaminated by contact with the aluminum tank?

S. S.

Expert Panel Responses

If aluminum being used as a holding tank for flux is not a good idea. The tank will corrode from the acids and leach into the flux. This is especially true with the OA (organic acid) flux type you are using. Try to be 100% certain that the vessel is aluminum. Even some grades of stainless steel can pit on the surface with OA flux. This would give the visual effect as if the vessel is rusting. You can use warm water to clean this off and get your best confirmation or simply ask the supplier what the material is made of. If confirmation is made that the material is aluminum you will need to replace this. Consult with your supplier. One additional comment. The replacement material type will be dependent on the flux delivery system being used. If this is a pressurized vessel flux supply system, outlined as a vessel that uses compressed air or nitrogen to push the liquid flux out to the nozzle, the replacement vessel should be stainless steel with at least a 316 grade or better. Considering the flux is alcohol based, there are NFPA regulations that would dictate the use of an inert gas to pressurize a vessel when flammable materials are being used. I hope this information is helpful.

John Norton
Eastern Manager
Vitronics Soltec

John Norton started his soldering career in 1983 for Hollis Engineering. He has also worked with Electrovert as a technical training manager and Vitronics Soltec for the last ten years. He has held various technical development and sales positions.

It is possible for contamination to occur, very much so. Aluminum is an active metal. It will react under both acidic and basic conditions, which would create aluminum ions solubilized into the flux solution, especially aqueous solutions. Most likely it would only be trace amounts, but finite and measurable. Alcohol based fluxes will be much less of a problem, but nonetheless the possibilities are still there. Based on my years of ink and coatings chemistry, aluminum vessels are a "no-no". My advice is either a plastic or glass lined container, or good old fashioned stainless steel. I'd be very happy to discuss this further with any/all interested parties.

Jim Williams
Chairman
Polyonics, Inc.

Jim Willimas is a PhD Chemist in Polymers and Materials Science. He specialize in printing, cleaning, inks, and coatings used in electronics manufacturng operations. Williams has more than 30 years experience.

Aluminium is chemically attacked by acid solutions and, as such, the water soluble flux is not compatible with this material. I would recommend a stainless steel tank for this application.

Bryan Kerr
Principal Engineer - CMA Lab
BAE Systems

Bryan Kerr has 35 years experience in providing technical support to PEC assembly manufacturing. His experience ranges from analysis of materials and components to troubleshooting and optimizing, selecting reflow, cleaning, coating and other associated processes.

Using Aluminium flux tank is not the best idea especially if using a VOC Free flux as this will attack the tank. I would change to Stainless Steel for VOC Free. If using alcohol based Water Soluble then I would imagine this too could be an issue for Aluminium, not knowing the chemistries involved in your chosen flux I would prefer a welded Polyprop tank which is fairly cheap to construct to cope with ALL flux types.

Greg York
Technical Sales Manager
BLT Circuit Services Ltd

Greg York has over thirty two years of service in Electronics industry. York has installed over 600 Lead Free Lines in Europe with Solder and flux systems as well as Technical Support on SMT lines and trouble shooting.

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