Any suggestions on how to etch aluminium. We're looking to permanently mark aluminium using a cut-out template if possible.

Any suggestions would be gratefully received.

You can either go the annodising route (search elsewhere on site for details), or you can use Caustic Soda.
Caustic will strip the oxidised layer off the surface and if masked can be used to create patterns to suit.
Beware though that Caustic Soda is a very dangerous chemical and will give severe burns!

Terry

I thought about caustic soda first off.... what precautions do I need to take?

Usual sort of things you would do for acids really!

Thick rubber gloves, goggles, rubber apron, that sort of thing!

What are you hoping to acheive with your etching?
Putting text onto panels to decorate?
If that is it then a sticky back plastic stencil can be made and the Caustic puddled onto it. You would have to ensure that it could not come into contact anywhere else though! Once it has done its job you just hose it off.

That is exactly what I thought of... better make up some templates then

Now where do i get caustic soda?

Red Devil drain cleaner in the US is the best source for small amounts. I do not know of a similar brand in your neck of the woods.

[Edited on 23/3/05 by Piledhigher]

Depending on size I would shot blast the surface ..Alu is very easy to do Ive just done my zetec rocker box cover..It can easily be maskd with sticky back plastic.....

quote:

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Originally posted by Hellfire
That is exactly what I thought of... better make up some templates then

Now where do i get caustic soda?

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I would favour the sand/shot blasting method if you have a compressor.

Mick

What a dilemma... shot blasting or soda?

We have no compressor or know anyone with a shot blaster. The etching is intricate'ish... and I've read a few website saying that the surface of the aluminium when etched with soda can be coloured using ink thereby permanently colouring it similar to anodising. So, on that basis it looks like we are going to attempt to soda etch it.

On a seperate note - I thought I had seen caustic soda before... from my home brewing days, cleaning the demi-jons Therefore most BIY shops should sell it too

IIRC it was the same stuff i used to buy to de-coke my two stroke exhaust systems too - a bike shop might be able to help...

Caustic Soda (Sodium Hydroxide/Lye) should be available in any home store or hardware store. It usually comes in plastic tubs with child-proof lids. As mentioned, it will cause severe burns if the (made up) liquid touches the skin or any organic material such as denim jeans etc. Beware of dried caustic solution; it reactivates when wetted again. Neutralise any spills with acetic acid (houshold white vinegar will do). It would also pay to keep some 50/50 vinegar/water close by when you're working with caustic in case of accidents. If you get any caustic on your hands or face, just flush with the 50/50 mix which will arrest the caustic action.
Sign makers nearly all do cut vinyl signs these days. You could get your design cut out by a sign writer and apply it to your aluminium, then add some flour to a little caustic solution and mix it into a paste. The paste will sit better on the job and will adhere better to any slopes. Adding a single drop of Fairey Liquid will also help break the surface tension and make the job easier.
Wash the aluminium in the vinegar solution and then rinse in clear water. Done.

Thanks for that very detailed description of the process using Caustic Soda Rorty.

After a few test samples it turned out that the image detail wasn't quite what I expected. The caustic soda burned away the adhesive and left "out of template" burns.

I eventually used a template and then painted with high temperature paint. Sealing it all with acrylic varnish to complete the job.

Thanks for the advice...


[Edited on 9-4-05 by Hellfire]