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Remove surface oxide of Al-alloy

2004

Hi,

I want to study the texture of an aluminum alloy after fatigue test. I did the heat treatment before the texture measurement. The kikuchi pattern is not clear because of the surface oxidation. Is there any chemical method to remove the surface oxide within several microns. I hope to keep most of the surface feature. The method I have used is anodizing. But it removes too much of the surface material.

Best regards,

Jinxia Li
student - Lexington, Kentucky

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Your techniques are not altogether clear -- Alloy? Heat treatment to produce equi-axed grains or for a T6 temper? Is "anodizing" an electrolytic dissolution?

In any event, unless studying the effect of surface oxide upon fatigue, the surface oxide must be removed prior to testing. Finish machining should be performed after heat treatment. ASTM E466 describes polishing fatigue specimens down to a 0.2 micron (8 microinch) finish. If surface observations are to be made, specimens may be electropolished per ASTM E3 or ASTM E1558. Probably mandatory for miniature specimens to be examined by electron diffraction.

For chemically removing aluminum oxide, I favor the method of ASTM B137. Alternatives are concentrated nitric acid (50-100 vol.%) or a commercial aluminum deoxidizer solution (check for a local anodizing company).

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.
2004