Etching with Muriatic Acid and Hydrogen Peroxide

[miter53]

I got 30 percent H2O2 at a beauty supply store. I don't think its any more hazardous than the acid. You need to be super careful with both. It was about $2 for 4 oz. and I mix 2 parts HCl to 1 part H2O2. Etches take 5-10 minutes rather than 30-60 minutes.

[m-Kresol]

as long as you take the necessary precautions you're good. As stated before, HCl is dangerous, since it's corrosive and also releases HCl gas especially in the beginning when the bottle is fresh, so do not inhale those fumes.
H₂O₂ will gives you skin irritations (white splotches) and will bleach your clothes. Contents of over 25% are considered explosive (H₂O₂ is a metastable compound and will decompose to H₂O and O₂), so be specially careful with those.

[davent]

With a fresh mix of 3% peroxide and HCl i don't think i've ever been longer then 5minutes for an etch. From taking a pcb transparency from the printer to having the etched board in hand ready for drilling ~30 minutes, add a few minutes before if you need to size a piece of raw pcb.

[alanp]

They use H2O2 to bleach the tripes at work (soda ash is put in as well).

During the chemical training course we are warned that if it gets on your skin, it will burn and burn and not stop until it either runs out, or reaches either bone or the other side, I forget which.

Combined with the problem of DISPOSING of the damn stuff in a safe, ecologically sound manner, I'd rather just give Keefe money to do my etching.

[m-Kresol]

They use H2O2 to bleach the tripes at work (soda ash is put in as well).

During the chemical training course we are warned that if it gets on your skin, it will burn and burn and not stop until it either runs out, or reaches either bone or the other side, I forget which.

Combined with the problem of DISPOSING of the damn stuff in a safe, ecologically sound manner, I'd rather just give Keefe money to do my etching.

Oh man, they really wanted to scare you. H2O2 is explosive in high concentrations (as mentioned above it decomposes forming oxygen gas, and every "burning" reaction goes faster if there is more oxygen than the usual 20% in air). Also it will have serious affects when it gets in your eyes, swallowed or any of that sort. With skin though, you will just get a white, irritating burning stain, which will peel off the skin after some time (kind of like sunburn, but white). It will, however, surely not eat through you (especially not your bone).
We had one assistant who went up to a student, who was complaining that his reaction did not work. the assistants response? he put a few drops of the h2o2 on his fingers and said: "not getting white. not good anymore" (read with a russian accent) Not so corrosive after all...

The conclusion is that you always have to know what you're doing and take the right precautions. I did not yet do anything with high voltages, since I still lack experience. Same applies to chemicals I guess. If you do not know how they will react with each other or what hazards they have, look it up or let a professional do it for you.

[irmcdermott]

So m-Kresol, you seem to be the resident chemical expert, so if someone uses a Muriatic Acid & H2O2 mix to etch boards, what is the best way to neutralize is before you properly dispose of it? I've always read that Washing Soda (which I think may be sodium carbonate?) is effective. Would you know if that is true? One of the reasons I stopped etching was because I never new the proper way to do it. Our county does a yearly (yes, only once a year) hazardous waste collection day. Wish it was more than that.

[miter53]

The good part of using the HCl/H2O2 etchant is that, as I understand it, you don't need to dispose of it for a long time. See the following:
http://www.instructables.com/id/Stop-using-Ferric-Chloride-etchant!--A-better-etc/

[Haberdasher]

i have been etching with muriatic and h2o2 for a few years now, and my lung feels GREAT!

but seriously, i etch in tupperware and i set it up right next to the garage door, which is open when i etch.  so i'm practically outside when i do it.  i snap the tupper lid on it when i'm done.  no problems that i know of yet, but you have to be careful when you take the lid off the acid jug.  don't breathe next to the undiluted stuff or it'll get ya for sure.  very fum-ey!.

[davent]

The drugstore peroxide i buy is sold for cleaning wounds so not very hazardous. Bottle directions: Use full strength as required for open sores, cuts, wounds, abrasions and insect bites. Keep in a cool dark place.

No hazardous waste pick up here, ever, but there are a few (municipal) drop off centers open at least six days week.

Never had any success with the regeneration of the mix. i use the smallest plastic container big enough for the board to lie flat in and mix up just enough to wash over the board. Consider it a one shot mix maybe a tablespoon at a time.

[alanp]

Oh man, they really wanted to scare you. H2O2 is explosive in high concentrations (as mentioned above it decomposes forming oxygen gas, and every "burning" reaction goes faster if there is more oxygen than the usual 20% in air). Also it will have serious affects when it gets in your eyes, swallowed or any of that sort. With skin though, you will just get a white, irritating burning stain, which will peel off the skin after some time (kind of like sunburn, but white). It will, however, surely not eat through you (especially not your bone).
We had one assistant who went up to a student, who was complaining that his reaction did not work. the assistants response? he put a few drops of the h2o2 on his fingers and said: "not getting white. not good anymore" (read with a russian accent) Not so corrosive after all...

The conclusion is that you always have to know what you're doing and take the right precautions. I did not yet do anything with high voltages, since I still lack experience. Same applies to chemicals I guess. If you do not know how they will react with each other or what hazards they have, look it up or let a professional do it for you.

The stuff at work comes in big drums, and is pretty concentrated (don't know the exact figure.)

[rullywowr]

I use h202 and muriatic acid in a well ventilated area with great results   I like to warm it on my toaster oven for better etching.   Just don't breathe in the fumes.

[m-Kresol]

So m-Kresol, you seem to be the resident chemical expert, so if someone uses a Muriatic Acid & H2O2 mix to etch boards, what is the best way to neutralize is before you properly dispose of it? I've always read that Washing Soda (which I think may be sodium carbonate?) is effective. Would you know if that is true? One of the reasons I stopped etching was because I never new the proper way to do it. Our county does a yearly (yes, only once a year) hazardous waste collection day. Wish it was more than that.

You can neutralize the acid with sodium carbonate. This will lead to quite strong gas formation (CO2) just to be warned. So just at it a spoon at a time, so not to spill the acid. When the degasing stopps, the solution is near neutral, just slightly basic. I would still not recommend pouring it down the drain. Not because it will harm your pipes or anything, but rather because copper and aluminum chlorides or whatever compounds you have after etching do not belong there and should be collected and disposed of in a more responsible fashion. Too bad they don't collect it more often at your place.
But as Keefe stated above, the etching solution should be good for quite a few etches. I use iron chloride, which can be kind of regenerated by adding a little bit of hydrochloric acid.
Hope I could help, cheers.

[irmcdermott]

Thanks!

[Gledison]

I've had this same problem.

My theory is that some of the newer "safer" muratic acid that they sell at the big box stores do not work as well.  Also some hydrogen peroxides contain phosphoric acid.  Not sure if that matters either.

But the mix that doesn't work well on copper clad can pretty much disintegrate an aluminum enclosure in a few minutes...

I'm definitely not a chemist but I think some of the inert ingredients in some of the products cause the solution to not work as well on copper.

Hey mate,
You can try sulfuric acid instead of hydrochloric acid! 3:1 hydrogen peroxide!
The best would be to use a 30% hydrogen peroxide solution BUT you have to be carefull! You need to create a steong oxidant solution and higher the concentration quicker the etch!
Im still on ferric chloride and quite happy with it. Just heat it up a bit on a hot water bath and the etching takes 15 min..
Cheers

Sorry to jump on the train so late (didn't see the thread in December), but I have to intervene here! DO NOT EVER, EVER, EVER mix sulfuric acid with hydrogen peroxide, especially in their concentrated forms! This stuff is for professionals only and we hardly ever use it! It forms peroxodisulfuric acid, which is also called Piranha solution. It is one of the most aggressive acids I know of and I only use it to clean porous glass filters, if nothing else does the job.
This stuff forms EXPLOSIVE compounds (I know of some rather unpleasant accidents), so please DO NOT use this stuff. If anything, it will also eat your protective coating (photoresist or toner transfer) and possibly your epoxy substrate.

As for hydrochloric acid (muriatic acid) with H2O2, I also have to advise you to work with safety goggles, gloves and in a well ventilated area! You will form chlorine gas, which is toxic (gives nice lung edema) and also a strung oxidizing agent. I only used ironchloride so far and that has done the trick for me. If you really want to use muriatic acid and H2O2, just dose enough of the peroxide so you see a reaction going on. For your own safety, I recommend not taking to much of it.

Mate, that's why I said 'carefull' . I assume people know that they are handling harsh chemicals. You are totally right with caring of peroxides. They should not be kept at home unless under cold temperatures and used by people that know what are doing.
That's why I'm still suggesting ferric chloride. Might not be the greatest one, but is safe regarding possible explosions.