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topic 3124

How do I etch aluminum without producing smut?


I need to etch aluminum without producing smut. I think nitric acid would work, but I would like something less hazardous. Any recommendations will be greatly appreciated.

Jerry Wilcox
- Mineral Springs, Arkansas


At the risk of oversimplification, you have it a bit backwards. Normally you etch aluminum with a sodium hydroxide (caustic soda) solution. This exposes the alloying metals like copper, which become known as smut, and which are removed with a desmutter (which can be nitric acid).

If you use a pure grade of aluminum, I should think that you can etch it with caustic soda without bringing up much smut.

Ted Mooney, Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey
Striving to live "Aloha"


Dear Jerry, First of all you can't etch aluminum without a smut. Ted is right with nitric acid, depending on the alloy. Best bet is to contact a chemical supplier and have them work with you to assure a quality finish.

Paul Davis
- Atlanta, Georgia


Hi Jerry, It is possible to etch aluminum with minimum smut by using a combination of hydrofluoric acid and nitric acid. This will result in a mild etched surface that is usually suitable for powder coatings which will cover the etched surface anyway. I tend to agree with Paul in that the best people to help you will be the chemical suppliers who have developed the products minus the associated problems if you attempt to do it yourself. Best Regards Elango

Elango Govin
- Kuala Lumpur

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