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Etching aluminum to reveal microstructure
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How can I see the microstructure of aluminium alloy? What is the etching solution for it ?
Ben [last name deleted for privacy by Editor]- Malaysia
+In the metals lab, we use a freshly prepared mixture of 10 parts nitric acid, 1 part hydrofluoric acid, balance distilled water. Use a cotton swab or Q-tip to develop the grain structure on the surface of a highly polished specimen. Use a new swab each time to apply etchant for about 10 seconds only. Rinse and dry to examine. Repeat as necessary. You will develop improved technique with experience. Aluminum alloys will respond vastly different from relatively unalloyed aluminum, also.
W. Carl Erickson
- Rome, New York
+You etch aluminum in HF acid plus water. You can find in metals handbook (metallography).
Behnam Taki
anodizing - Teheran, Iran
Each alloy of aluminum needs a special solution etch, for example I can see precipitate particle of 2024 by keller solution. for keller composition ref metals hdbk.
HABIBOLAHY
- isfahan-iran
April 12, 2008Purer version of aluminium alloys require electropolishing prior to electroetching to reveal the grain structure by developing an anodic film. ASTM Metals Handbook on Metallography gives details on electropolishing & electroetching techniques.
Shankar Nayak
- Mumbai, India
April 4, 2011
Hello to all,
My name is Shannon, and I am currently undertaking a final year project to complete me bachelor of engineering (Mechanical). My project is looking at the lubrication ability of an ionic liquid (for the chemistry fold P1444 DPP)on 3 aluminium alloys and to understand how microstructure effects performance.
The question I pose is, does anyone know of an etchant or etchants and process that will work on 5052, 6061, 7075 grade aluminium alloy. The catch is, I have been told these etchants must be HF free.
I have scoured the internet, ASM handbook and other texts.
Your help is greatly appreciated.
Shannon
student and research assistant - Geelong, Victoria, Australia
April 5, 2011
There are some etchants for aluminum that don't use HF. Mix 1 g NaOH + 100 mL water, swab specimen for 5-15 seconds, then rinse with cold water. The other common etchant is Barker's reagent, which is an electrolytic method: 4-5 mL HBF4 (48%) + 200 mL water. Specimen is anode, use Al or Pb or stainless steel cathode, anodize for 40-80 seconds at 20 V dc. Microscopic examination requires crossed polarizers. The last method is a color etchant detailed in a past issue of Struers Structure magazine: A Universal Method for the Mechanical Preparation of Aluminium Alloy Specimens with High Edge Retention and their Subsequent Colour Etching.
www.struers.com/resources/elements/12/2431/38art1.pdf
Automotive component & module supplier - Michigan, USA