I have already tried basic etchants like HF, NaOH solutions, Keller's regaent and orthophosphoric acid solution. None of the above etchants gave positive response
Dear Dhal,
Have you tried the NaOH solution at hot temperature?
I normally use NaOH solution at ~60°C and it works properly.
Yours Sincerely
Thanks Leandro
I tried orthophosphoric acid at elevated temperature, however i have not done the same for other etchant. I ll definitely try this suggestion.
Abhijeet,
Try using Barkers reagent (20V, 0.5mA) for few seconds (less than a minute) and observe using polarized light.
In a second approach, you might be able to heat the specimen before you etch it.
What is the etching time when you use NaOH?
Hope this is helpful.
@Sudeep While etching using NaOH i started from 5s immersion and then progressed upto 30 s immersion with a 5s increase for every experiment.
You may etch your specimen of the high-magnesium aluminium EN AW 5083 alloy (AlMg4,5Mn0,7) with: Methanol (25 cm3) + HCl conc. (25 cm3) + HNO3 conc. (25 cm3) + HF conc. (1 drop), from 10s to 1min:
http://www.metallographic.com/Etchants/Aluminum%20etchants.htm
For aluminium alloys the best way to reveal the microstructure is to use electrochemical etchanting. You will get color images with visible grains. It is especially good for material after SPD (severe plastic deformation) and special heat treatments. The downside is that you need special equipment fortunetly it is relatively cheap. For aluminium I would recomend to You the following parameters: 0,4% HBF4 acid 2-3 x 25 sec 15 V. I'm attaching some of my own micrographs (aluminium 5754).
The above electrochemical method seems as a good tool for scholars in engineering (metallography) studying, also, mechanical stress in Al, Al-alloys, etc.
Anodizing is a method of increasing the corrosion resistance[1,2] of a metal part by forming a layer of oxide on its surface. So, Piotr Maj proposed an electrochemical process that is not, just, a simple, common, "etching", but it is a very complex[1,2] electrochemical "texturing/coloring", or a contrast (enhancing decorative) dyeing[3] method by anodizing[1-3] Al, Al-alloys, etc.
1. Anodizing https://en.wikipedia.org/wiki/Anodizing , and https://en.wikipedia.org/wiki/Photosensitive_Anodized_Aluminum
2. What Is Anodizing? https://www.thebalance.com/what-is-anodizing-2340009 https://www.thebalance.com/metal-alloys-2340254
3. A list of technical publications https://www.anodizing.org/page/pub_publications
I agree with You proffesor that the method is not that trivial. But on the other hand, from the technical point of view, the needed equipment is relatively cheap and quite common. The anodizing process can be even done with a proper etchant, 3R12 battery and some skill this technique.
Carlos Araújo Queiroz have you ever tried this solution for etching Al5083?
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