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Etching 316L Stainless Steel

May 20, 2008


My name is Wilson, I make pipeline inspection cameras. I am located in the UK.

Here's my question... I want to get expoxy to stick to 316L stainless. I don't care what it looks like after its etched, I just want it to stick. Should I use FeCL3 or an acid mix? I used a dichromate/H2SO4 etch and it appears to have had no (visible) effect.

I have all the usual acids except HF for which I do not have the facilities to handle safely.

BTW I've seen a lot of interest by people hoping to accurately etch stainless.

If you etch anything using a resist there will be undercutting of the material being etched. This may not matter if you're only etching 80um deep but if you're trying to etch .5mm deep, 10um wide gulleys in copper or stainless, you *will not* get what you want. The etchant will broaden the cut under the resist so instead of getting this:

| |
| |
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You'll get this:

/ \
/ \
/ \
/ \

If you want to cut deep thin tracks, use a CNC controlled EDM machine.


Wilson Logan
prototyper - Paisley, Renfrewshire, Scotland

May 22, 2008


A method I have used before for etching stainless before bonding is a 30% sulfuric acid etch at 60C ± 2C for 10 minutes followed by a desmut with sulfuric/dichromate at 60C ± 5C for 5 minutes. If there is a tenacious smut layer the parts may require a second dip in the desmut or wiping off with a wet cloth.

Just one possibility for you.

Brian Terry
Aerospace - Yeovil, Somerset, UK

May 27, 2008

If you only want to etch the 316L stainless steel I would use FeCl3 - it is a proven technology and not difficult to do, albeit very messy. An alternative pretreatment may be to shotblast the steel prior to etching it - this will give you an even rougher surface that will allow the epoxy to adhere better. I would also recommend you speak with the manufacturers of Araldite - Huntsman Advanced Materials. There is a massive range of epoxy resins around and there may be one specifically for stainless steels.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK

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