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Pre-Treatment of Aluminum 6063-T5/T6

We are trying to set up a pre-treatment system before powder coating for products manufactured with 6063-T5/T6 aluminum extrusion. Are there any products that will allow you to clean/etch in one process using a dip tank? We would like to achieve 2000-3000 salt spray hours and have a product that could be dumped to waste without any environmental problems. Thanks, Paul

Paul Koontz
- Sevierville, Tennessee USA
2002

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Hi Paul,

I suppose anything is possible, but a one-step process for Al prior to painting is really unlikely, IMO. If your paint is able to carry the load, then you may be able to clean in one step and then paint. If you want to reach this type of salt spray exposure interval, you will likely have to apply a conversion coating.

George Gorecki
- Naperville, Illinois
2002

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Practically every metal finishing chemical process vendor has in his line a product which combines Phosphoric Acid and a surfactant. Many aluminum extrusion finishers use this type of product as a dip then rinse off then paint. It offers no protection but in your case it will give an etched "tooth" to help bond the powder coat and the powder coat alone should give you the salt spray protection you desire.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2002

I have found that the best method to clean and prep aluminum is a solution containing surfactants and hydrofluoric acid in combo with sulfuric acid. The surfactants clean, the acids etch and the fluoride removes any underlying aluminum oxide which interferes with paint adhesion.

Tom Hager
- Grand Rapids, Michigan, USA
2002