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Etching aluminum to see gain flow

What is the best Etchant for Aluminum so that you can see the gain flow?

Graham Best
- Wrexham
2002

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Graham,

It depends on how "tight" the grain structure of the alloy is.. I've seen wide fluctuations (sp) from alloy to alloy.. lot to lot.. and even in the same lot. Sometimes just a 5% NAOH etch, followed up by a 30%-50% HNO3 desmut will do the trick. Another option, which has given me good results is a 3%-5% (by weight) HCl solution. A big difference you will see, will depend on how the alloy was formed. I see a big difference between extruded, and plate material. You will also see a difference if you look at the "outside" of a piece of plate, compared to the inside (this, of course is more visible with thicker pieces). Another option would be elctropolishing..as this etches, and brightens the material, there-by making the grain structure easier to see.

Marc Green
anodizer - Boise, Idaho
2002

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I am going to have to agree with Marc on this one, a 5% NaOH Etch followed by a 30-50% Nitric desmutt has had the best results in our facility. I recommend Oakite [Chemetall] products, like the Oakite Etch 160 and the Oakite Deoxidizer LNC, both meet BAC, Mil and ASTM requirements.

Good Luck,

Tony Schmaltz
- Kent, Washington
2002