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Etching Aluminium

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Neil Wyatt05/02/2018 22:39:41
19032 forum posts
734 photos
80 articles

Has anyone tried doing this?

Lots of varying comment about etching aluminium out there.

The obvious choice of caustic soda is no good as it will destroy the etch resist.

Some sources say use ferric, others say its useless.

One source suggests using ferric exhausted by use on copper - seems a bit dubious?


Michael Gilligan05/02/2018 22:45:37
20182 forum posts
1053 photos

Haven't tried it myself but these guys seem to have the know-how: **LINK**


Mark Rand05/02/2018 23:01:35
1272 forum posts
28 photos

Chloride ions do quite a good job on aluminium oxide and aluminium is amphoteric. So, both ferric chloride and hydrochloric acid will work if the resist is stable in acid conditions. Don't bother with nitric or sulfuric acid. they'll tend to reinforce the oxide film.

Edited By Mark Rand on 05/02/2018 23:04:33

Ian P05/02/2018 23:01:50
2590 forum posts
114 photos

I suppose it depends on the reason you want to etch it. I assumed it was to create a keyed surface for accepting paint but as you mention resist it doesn't compute.

Ian P

Paul Lousick06/02/2018 00:37:45
2043 forum posts
722 photos

Etching is a process by which you apply an acid to metal, causing uncovered parts to be "eaten away" by the acid to etch a specific design in your metal. You apply that design using a "resist," a substance that covers the areas on metal that you do not want to be etched. The uncovered areas of the metal will etch, leaving behind a raised impression of your design.


I.M. OUTAHERE06/02/2018 02:04:01
1468 forum posts
3 photos

I havent tried any process personally except for basic circuit boards with ferric but you may be able to use electrolytic etching to do what you want , there is a basic explanation on the instructabled website . They use a vinyl mask but it has me thinking something similar could be 3D printed and glued on to the face to be etched to make a mask .


Brian H06/02/2018 07:51:01
2312 forum posts
112 photos

Wikipedia gives;

For aluminium


Les Jones 106/02/2018 08:25:21
2255 forum posts
156 photos

Hi Brian,
Sodium hydroxide is just the chemical name for caustic soda.


Neil Wyatt06/02/2018 09:04:19
19032 forum posts
734 photos
80 articles

I want to use photo-resist, which is developed using NaOH and exposing it to the solution for too long destroys it.

Kellers reagent has nitric, hydrochloric and hydrofluoric acids in it - no thanks! It's used for revealing grain structure anyway.

I'll do a trial with ferric as I have plenty in stock.

John Haine06/02/2018 09:34:17
4673 forum posts
273 photos
Washing soda, dissolves milk bottle tops and makes hydrogen.
Ian S C06/02/2018 09:56:41
7468 forum posts
230 photos

Washing Soda, or even baking soda would be a good place to start.

Ian S C

Neil Wyatt06/02/2018 14:01:19
19032 forum posts
734 photos
80 articles

Washing soda or baking will attack the resist too - they are weakly alkaline.


Roderick Jenkins06/02/2018 14:46:09
2183 forum posts
608 photos

One of my text books suggests Cupric Chloride as a metallurgical etch for ally. A quick Google suggests that people do use it for larger scale etching on ally so this might be a useful lead.



Dick H06/02/2018 15:53:37
109 forum posts
1 photos

This might be a bit of an aside but an old way of cleaning silver is to put a bit of aluminium foil in a brine (common salt) solution and then put a tarnished bit of silver in. It works, you can smell the hydrogen sulphide from the tarnish being removed. Afterwards the aluminium foil is pin holed, possibly selectively etched by the process. Perhaps an electrolytic process might be worth trying though the pH might change during the etch.


Mike Poole06/02/2018 16:56:48
3335 forum posts
73 photos

It seems the problem is not what will etch aluminium but what the resist will resist. I found to my cost that brick cleaner eats aluminium which I did know but forgot to remove an aluminium nameplate when derusting.


Neil Wyatt06/02/2018 17:06:35
19032 forum posts
734 photos
80 articles
Posted by Roderick Jenkins on 06/02/2018 14:46:09:

One of my text books suggests Cupric Chloride as a metallurgical etch for ally. A quick Google suggests that people do use it for larger scale etching on ally so this might be a useful lead.



That fits in with using ferric that's been exhausted etching circuit boards.

Johannes Grabsch06/02/2018 17:37:19
22 forum posts
2 photos

Look here Folks:

He says Lemon juice might work as well.



Alan Vos06/02/2018 18:19:46
162 forum posts
7 photos

I was once asked to write on aluminium light bulb caps using chromic acid and a stick. At the time I thought that was etching, but it seems it produces a 'corrosion resistant' oxide layer. It might work as a resist.

Ian S C07/02/2018 10:30:26
7468 forum posts
230 photos

Alan, you are right about the chromic acid, that's what we used in the aircraft industry to neutralize corrosion on aircraft skins{Alclad), then they got a coat of zinc chromate primer2012-09-15_0cfi painting (1)sam sands painting cfi (640x427).jpg

Ian S C

David George 107/02/2018 14:57:40
1836 forum posts
503 photos

Hi Neil What are you trying to etch into the aluminium? the last time I had something done I had it laser etched and it didn't cost a fortune.


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