Muriatic acid etching

[Cinder]

So I'm trying to etch my enclousure with muriatic acid. I'm having an issue where the acid seems to eat through my toner in some places, resulting in small spots on large blank surfaces after cleaning and spraying the enclosure. Anyone have any tips for fixing this? I tried painting over the areas with nail polish to "reinforce" the mask, but it seems like a measure that I shouldn't need to take. My printer is set to max density as far as I can tell, and the transfer looks perfect when I look at it before etching.

Further I have some issues with determining how deep of an etch is "enough", I use 30% muriatic acid straight out of the bottle for the process. I first tried putting the enclosure face down into a container with the acid - this reacts incredibly aggressively and really demolishes a lot of the toner mask as mentioned above. The second way I tried was to put the enclosure face up and using a paintbrush to apply the acid, waiting for about a minute to let the fizzing calm down, then rinsing in water and applying again. I did this for about 5-7 times just now, but I see that a lot of the small lines in my design lose definition, which I really couldn't tell until I brought the enclosure in and painted/sanded it.

Any muriatic acid specialists here who could give me some advice on application methods and waiting times for etching?

[Kevin Mitchell]

Recently I've looked into enclosure etching and after searching the forums I could not find any teks about doing so with muriatic acid. I've only used the muriatic/peroxide solution to etch my pcbs. Can you refer me any references/guides that you are following using such solution to etch your enclosures?

There's probably many reasons why people use other etching solutions for enclosures. I'm sure this is one of them.

Sorry I'm not much of help here 

[Cinder]

Here's a couple:

http://www.effectsbay.com/2009/12/d-i-y-at-home-acid-etching/
http://www.effectsbay.com/2009/12/d-i-y-at-home-acid-etching/

I think muriatic acid should be fine, I have a friend who is a blacksmith and uses it to make damascus steel etchings.
I'm basically just trying to figure out the best practices to make it work, and I'm not too far off I think.

[chicago_mike]

I use muriatic acid in a 1 part to 2 parts mix with hydrogen peroxide.

This works with both pcbs and enclosure etching.  I usually etch the pcbs first then reuse the mix to etch an enclosure since its diluted and used, it's not as harsh on the aluminum.

Oh, and I recently got that yellow toner transfer paper you can get off e-bay. That stuff works almost perfect for pcbs and enclosure etches.  If you over run the iron on the paper though, you can get the clear plastic to stay on the actual pcbs or enclosure so after you do the transfer, look to see if theres any clear plastic coating on the surface that you don't want.

[Cinder]

I've only used the acid straight from the bottle, where does one get the hydrogen peroxide?
As far as I can tell the acid should do the trick just by itself when brushed on, I just think I did too many applications on my last try.

How deep do you usually etch? I think I might have gone a bit too deep last time around, finishing with spray paint and 800/1200 grit really shouldn't remove a lot of material.
Maybe I should just try to dilute my acid with a bit of water... hydrogen peroxide seems a bit of a hassle to get in any decent sized bottle in Sweden.

[bloxstompboxes]

I can't imagine it would be that hard to get hydrogen peroxide. I buy it by the quart, I think, for about a dollar at the local wal-mart. Surely a nearby pharmacy would have it too.

[PRR]

> I think muriatic acid should be fine, I have a friend who is a blacksmith and uses it to make damascus steel

Steel is much tougher than copper or toner.

If I was hammering, I'd use a far smaller hammer on copper than steel. Likewise I would expect to cut-down an acid from the strength the steel-worker uses.

[chicago_mike]

You can get hydrogen peroxide at your local walmart , CVS, Walgreens...it's used to clean wounds, but in reality you shouldn't use it for that.   Years and years after they tell you to use it they finally tell you NOT too...

Anyhow, I etch, well, I like to etch, kinda deep, but I don't bother measuring, I just eyeball it.  Be careful with brushing. I just pout it on carefully with a glass measuring cup or dip it in the pcbs etching container I have.  If I have to use a sharpie, I make a few passes and wait a while for it to dry.

[davent]

First aid section will have 3% peroxide, hair colouring/dying section may have 20 or 30%.

[chicago_mike]

True...that way you can bleach your bum at the same time...

[PRR]

> used to clean wounds, but in reality you shouldn't use it for that

Peroxide is still invaluable for cleansing certain deep wounds.

It works by killing "all" life. The germs more than your flesh (you are bigger). Yes, on small self-treatable wounds it does maybe more harm than good (kills-off the wound edges so they won't heal well). If a doctor advises it (as when a friend had a cyst carved out of his back), it's still the right stuff.

[greaser_au]

If a doctor advises it (as when a friend had a cyst carved out of his back), it's still the right stuff.

This is exactly what I was told to do with an excision in my back.

david

[greaser_au]

Copper suphate and rock salt would appear to be a much safer proposition www.printstudio.org.au/sa/stijnman_zinc.pdf‎

david

[Cinder]

In Sweden you can't buy hydrogen peroxide that easily, it's NOT readily available at any hardware store as some have stated here.
They passed some law years ago to restrict purchases of the chemical due to it's use in bombmaking.

Maybe I will still pass by a paintshop and see if they wouldn't carry it..
Otherwise I'm thinking I will just dilute the acid with water to ease off the reaction a little bit.

[Brisance]

Steel is much tougher than copper or toner.

not chemically, HCl, pure won't react with copper, but reacts with steel, for copper you need an oxidisong factor, be it H2O2 or the NO3 ion of nitric acid.

[chicago_mike]

Ah! thanks for the clarification on the peroxide!

MG chemicals sells Ammonium persulfate and sodium persulfate for etching as well.

But yeah find out what chemicals you CAN get in your country. I can legally buy all the muriatic acid I want in Illinois, but I have to sign for it at the store. Meth heads and all apparently.

[davent]

In Sweden you can't buy hydrogen peroxide that easily, it's NOT readily available at any hardware store as some have stated here.
They passed some law years ago to restrict purchases of the chemical due to it's use in bombmaking.

Maybe I will still pass by a paintshop and see if they wouldn't carry it..
Otherwise I'm thinking I will just dilute the acid with water to ease off the reaction a little bit.

Read on a forum where someone had seen in a cooler in an Apoteket(?) store.

Never seen it hardware stores here but in Pharmacies or hair/beauty supply stores. Used for first aid and hair bleaching. Can find it too in well stocked grocery stores.

[WhiskeyMadeMeDoIt]

I have used muriatic acid many times for etches.  Straight acid will be a problem because the reaction is very exothermic.  It will be very hot and melt your toner.  You do not need hydrogen peroxide either.  Dilute the acid 2 parts water to 1 part acid. If you can use a fish tank bubbler to get some oxygen going. That is what the hydrogen peroxide does.   Before using it on the aluminum etch a PCB or drop in some copper and make it turn into cupric cholride.  It will be green
Use that as your etchant. It works well and will be more predictable.  Take your time and periodically brush the scum layer off as it etches. Use a foam brush.  It an take 5 to 25 minutes for a good etch.  It will vary depending on your etchant temp and ambient air
Do it outside it will create hydrogen gas and the acid fumes are corrosive

[chicago_mike]

If you do it on a hot sunny day, and swish the etchant around it goes faster.   The etchant gets warm! And yeah it turns a cool emerald green.

I have some of those dollar store plastic food containers to use as etchant containers.

[Cinder]

Thanks for all the replies guys, I did do a LOT of testing the past few days.
The best results I got this far is by brushing on the acid on top of the enclosure, but this isn't perfect either. I didn't try to dilute it yet which I will do in the future, but for now I'm just trying to get to finish my first pedal.

After failing many, many times I decided to try the caustic soda approach just to see the difference and maybe succeeding, and indeed it looks like a much less aggressive reaction than with the muriatic acid - another reason to dilute it with water next time. Another really nice thing about the caustic is I don't have to leave my apartment complex to spread the nasty fumes from the muriatic. The con is definitely the time it takes, caustic is much slower - anyone tried caustic and putting the enclosure face down into it to speed things up - it doesn't seem to be as much of an exothermic reaction as the muriatic?

I definitely think the muriatic will work if I just find the right method, which is what I've been experimenting the past two days, but I've had so many pitfalls with toner transfers coming off, smudging, acid eating through the toner, toner coming off due to heat etc etc. A lot of things that can go wrong is what I've found out basically, but then again my first design is really demanding to get a good result - gotta aim high, right?

I'll try to keep you guys posted as I go, still having a lot of fun experimenting, but I really hope that tomorrow I will be able to put a pedal together.. fingers crossed!