Improper Way to Store Used Hydrogen Peroxide and Muriatic Acid

[bloxstompboxes]

Apparently, storing used etchant in a 20oz old plastic coke bottle with a closed cap is not a good way to store etchant. I am not sure why but I now have a freshly sprayed green laundry room, ceiling, counter top, washer, dryer, water heater, and all. Nothing looks damaged or corroded except for the stains. The bottle blew out the bottom and I guess shot up at the ceiling and down to the floor. It literally is everywhere. Did the peroxide cause the bottle to swell until it burst? Laying next to it was a smoke detector with the battery still in it and it was just found now making a weird noise and then went off when I picked it up. It's in the trash now for obvious reasons. The only reason the bottle was in there is because of a large plastic wash sink that I use for etching. When I am done, the used etchant goes in the bottle. It's too cold to be doing this outside now. I once had a full 2 liter in there and this didn't happen.

I am very embarrassed to admit to this but what is the proper way to store used etchant until it is thrown away? I've heard of people accidentally leaving a bottle uncapped and things several feet away being corroded but not an explosion.

[digi2t]

DANG!! Think I'll stick with vero.

Hopefully, no physical harm to anyone?

[bloxstompboxes]

Nope. Luckily no one was at home. I just came home to it and was like, WTF?!!! I still can't understand it. The bottles do pfft like a soda bottle, but I never thought they would explode. To clarify, my bottle was capped. I can only guess it the peroxide caused a pressure build up that blew the bottom out. But why this never happened before, I don't know.

[Harry]

Man, that's nuts! I had mine in a glass pickle jar with no issues.... Maybe, a $1 bottle of hydrogen peroxide emptied and thoroughly cleaned would be better? Not sure what others use though.

[CodeMonk]

Apparently, storing used etchant in a 20oz old plastic coke bottle with a closed cap is not a good way to store etchant. I am not sure why but I now have a freshly sprayed green laundry room, ceiling, counter top, washer, dryer, water heater, and all. Nothing looks damaged or corroded except for the stains. The bottle blew out the bottom and I guess shot up at the ceiling and down to the floor. It literally is everywhere. Did the peroxide cause the bottle to swell until it burst? Laying next to it was a smoke detector with the battery still in it and it was just found now making a weird noise and then went off when I picked it up. It's in the trash now for obvious reasons. The only reason the bottle was in there is because of a large plastic wash sink that I use for etching. When I am done, the used etchant goes in the bottle. It's too cold to be doing this outside now. I once had a full 2 liter in there and this didn't happen.

I am very embarrassed to admit to this but what is the proper way to store used etchant until it is thrown away? I've heard of people accidentally leaving a bottle uncapped and things several feet away being corroded but not an explosion.

I was doing some etching one night with Hydrogen Peroxide and Muriatic Acid.
I went out to my workshop the next morning and found this.
The previous night it was shiny.
The OPEN etching tank was about 10 feet away.


I store my used etchant in a large clear plastic bottle and keep it outside.
I'm not sure, but I seem to remember hearing or reading that sunlight has a neutralizing effect on that etchant type.
I could be wrong though.
But I've never had any problems with containers exploding.

Maybe contact you local waste disposal facility for proper methods of disposal.
Hell, maybe even call a local university and have a chat with a chemistry professor.

Related thread : http://www.diystompboxes.com/smfforum/index.php?topic=71869.0

[Jdansti]

The solution seems to have evolved a gas which caused the pressure in the bottle to build until the bottle failed.  I've heard of peroxides causing explosions when mixed with organic materials such as solvents, but not with inorganic substances such as HCl or copper. Is there any chance some alcohol, acetone, sugar from the soda bottle, or other organic material (even solid organics like cotton or paper) were mixed with the solution?  I guess there's a remote possibility that the type of plastic that soda bottles are made from might not be compatible with peroxide.

[R.G.]

FeCl is many ugly things, but it does not evolve gasses and explode bottles.

[stallik]

FeCl is many ugly things, but it does not evolve gasses and explode bottles.

Unless you put some metal in there? Just wondering if a contaminant could change this... What was the screw cap made of?

[KazooMan]

I am pretty certain it was just a buildup of oxygen gas from the peroxide.  Strong solutions of hydrogen peroxide (30 % and greater) are used in chemistry labs.  They generally come in a polyethylene or polypropylene bottle with a cap that is designed to release the pressure.  The simplest of these is a cap with a hole in the center and a plastic liner with a slit in it that lines up with the hole.  They will leak if tipped over.

Some types of plastic bottles can handle more pressure than others.  A Coke bottle may seem like it it is designed to hold a lot due to the carbonation in the soda, but it really can't handle much.  It is also not designed to hold a strong acid. 

I don't know how much muriatic acid you are talking about here or the concentration or how much copper residue got spread around.  You should probably put on some good rubber gloves, eye protection, and give everything a thorough wash down with water.

[J0K3RX]

Possible solution - Put it in a container with a small hole or holes in the lid. Make the holes small enough to release pressure but not big enough to spill the contents if you move it or whatever... I use ferric chloride but mine is stored in a rectangular Tupperware container with a lid and a I wrote in black sharpie on the side NOT EYEWASH!     I wouldn't store it outside unless it's where no kids or animals can get to it.. Learned my lesson with Antifreeze, I guess it tastes like Kool-Aid   And whatever you do DO NOT MIX BLEACH or CHLORINE WITH AMMONIA!!!

[Jdansti]

^Good idea, except muriatic acid (HCl) gives off fumes and it will corrode metal near the bottle if it is vented. You'd have to store it away from people, pets, and appliances.

[bloxstompboxes]

Yeah, it was just 3% peroxide mixed 2 to 1 with the muriatic acid. I've been using the hp presentation paper recently, which leaves that white fuzz behind, so I wonder if that was the catalyst that set it off.

I know I should have stored it outside but really thought that the plastic was thick enough and strong enough to hold it. I usually only etch a couple of boards at a time and don't reuse the solution afterward. I know it's supposed to be resusable, but I have never had much luck with it. You could still see through the bottle so it wasn't a dark heavily used etchant.

Like I said it makes the same noise when opening, to a lesser degree, like when opening a coke bottle filled with coke. I have always had a respect for the substance and treated it with care but never suspected this. I thought last night about a small pinhole in the cap to release pressure to prevent the same thing from happening again. I've heard some people poor that stuff down the drain but I have a septic system that is already screwed up. I can't imaginge the mess that would create if I dumped it down the drain.

I feel like an idiot for storing it inside. The wife, needless to say, was a little pissed about it. I now have some painting and cabinet repair to do. Crap.

[J0K3RX]

I guess if you could figure out a way to bring it to a neutralized state when you are finished that would be good... Check with your local pool supply place, they "should" know how to store and dispose of these chemicals. When I used to have a pool at a house I sold a few years ago I used to store all of the pool and deck chemicals outside in a big Rubbermaid cabinet... They make smaller ones of course..  I would use muriatic acid for cleaning the deck area which was stone and then hose it off into the run-off grate... never really dawned on me where it actually went after that   luckily I'm lazy and only did that about once a year..  Anyway, I don't have a pool anymore (Thank God!!) so I don't have to worry bout that no more!



Edit: Better give your water heater a good inspection! If any of that stuff happens to make it's way through your copper pipe you may have mess that dwarfs what you have now!

[bloxstompboxes]

I suppose if it is dilluted with enough water HCL is ok, but this has hydrogen peroxide and, I believe, cupric chloride in it once it has been used. Like I said, I can't pour it down the drain but neither can I pour out in the yard or anything. There are no storm sewers on my street and that just brings images of National Lampoon's Christmas Vaction to mind. Besides, disposing of it wasn't the issue. I was simply storing it in a container until it was full and then I would dispose of it. Suppose I might try a small hole in the cap and leave it outside.

[R.G.]

FeCl is many ugly things, but it does not evolve gasses and explode bottles.

Unless you put some metal in there? Just wondering if a contaminant could change this... What was the screw cap made of?

Even then, the FeCl would probably eat it up fast enough that it would vent. 

As a side note, I ran onto an etching technique that I'd heard of, but never tried. I'm going to have to try it the next time I have to etch a board at home.

You do some quick calcs on how much FeCl it takes to eat up your square inches (or cm²) of copper, and pour that amount of FeCl into a shallow sponge, then wipe the FeCl  sponge over the PCB to be etched until the copper dissolves. Nitrile or other inert gloves are obviously required, as are safety glasses or a face shield, and other splash preventative equipment. But the story is that the wiping removes the iron/copper smut from the etched surface more quickly than rocking or bubbling, and that you get a PCB etched in a couple of minutes.

This would be GREAT if it works. It completely eliminates storing partially- or totally-used etchant, so you leave it in the same bottle you bought it in. You toss the sponge into a non-leaking bottle/bag/something for ecologically-politically-proper disposal, or use something to solidify it, like perhaps a concrete/cat litter/etc material to solidify it so it won't leach and can be disposed of with solid waste.

[bloxstompboxes]

On a lighter note, my etchings have been turning out beautifully. Print on hp presentation paper, run through cheap and modded laminator about 6 times. Let cool a couple of minutes, put in sink of cold mildly soapy water and peel the paper off real easily, throw in the above mentioned solution for 5-10 minutes, rock it back and forth, and presto. Can't imagine I'll go back to an iron unless my laminator craps out.

[Jdansti]

FeCl is many ugly things, but it does not evolve gasses and explode bottles.

Unless you put some metal in there? Just wondering if a contaminant could change this... What was the screw cap made of?

Even then, the FeCl would probably eat it up fast enough that it would vent.  

As a side note, I ran onto an etching technique that I'd heard of, but never tried. I'm going to have to try it the next time I have to etch a board at home.

You do some quick calcs on how much FeCl it takes to eat up your square inches (or cm²) of copper, and pour that amount of FeCl into a shallow sponge, then wipe the FeCl  sponge over the PCB to be etched until the copper dissolves. Nitrile or other inert gloves are obviously required, as are safety glasses or a face shield, and other splash preventative equipment. But the story is that the wiping removes the iron/copper smut from the etched surface more quickly than rocking or bubbling, and that you get a PCB etched in a couple of minutes.

This would be GREAT if it works. It completely eliminates storing partially- or totally-used etchant, so you leave it in the same bottle you bought it in. You toss the sponge into a non-leaking bottle/bag/something for ecologically-politically-proper disposal, or use something to solidify it, like perhaps a concrete/cat litter/etc material to solidify it so it won't leach and can be disposed of with solid waste.

I've done the sponge technique and it works just fine. I also use another technique. I take a thick Ziploc freezer bag and put about a tablespoon of FeCl in it with the board. I fill the sink with hot water and place the bag in it for 5 min. This gets the FeCl nice and warm. Then I rub the board through the bag, occasionally placing it back in the hit water to rewarm the FeCl. It doesn't take long for the copper to start dissolving. When done, I just flush the tablespoon of etchant down the drain. I wouldn't dispose of it this way if I were doing a lot of boards, but one tablespoon every few months is like pissing in the ocean.

Edit: this might not be a good idea for a septic system. There may not be enough dilution.

[Keppy]

Yeah, it was just 3% peroxide mixed 2 to 1 with the muriatic acid.

That's what I use. I've stored used etchant in a tupperware in a cupboard without issues. I squeeze air out of the container as much as possible (not much), but otherwise don't do anything special. It's possible that if pressure built up the lid would pop open, but probably just at a corner and just enough to release the pressure. I can't imagine problems like what you describe. I would probably advise a wide container with a snap-on lid, rather than a screw-on one. I wouldn't store it in a container that's not airtight because of the corrosive fumes, but something that vents under pressure is good.

I know it's supposed to be resusable, but I have never had much luck with it.

Me either.

You could still see through the bottle so it wasn't a dark heavily used etchant.

That's probably why. Re-use over a long time requires a lot of dissolved copper in the solution, and I never seem to reach that threshold before running out of oxygenation from the peroxide.

As far as disposal, I neutralize the acid with baking soda before disposing of it. This foams up a great deal, so use a large container if you try this. Like, bucket-size. Then you can mix it with a solidifying agent like R.G. mentioned. The kitty litter thing seems like a good idea too, since it's designed to deal with acid anyway so you could probably skip the baking soda.

[bloxstompboxes]

As far as disposal, I neutralize the acid with baking soda before disposing of it. This foams up a great deal, so use a large container if you try this. Like, bucket-size. Then you can mix it with a solidifying agent like R.G. mentioned. The kitty litter thing seems like a good idea too, since it's designed to deal with acid anyway so you could probably skip the baking soda.

The kitty litter idea sounds good. As for the container, I have a ziplock one outside still from the very first board I did and it still is holding strong the last I checked. Doesn't hold much though but maybe enough to store old echant until I decide to use the kitty litter idea. I had originally planned to keep using it but couldn't store it in the house due to possibility of spillage. If its outside like now, it's too cold to use. But for storage outdoors, that might work.

[R.G.]

I know it's supposed to be resusable, but I have never had much luck with it.

Me either.

You could still see through the bottle so it wasn't a dark heavily used etchant.

That's probably why. Re-use over a long time requires a lot of dissolved copper in the solution, and I never seem to reach that threshold before running out of oxygenation from the peroxide.

If you can find a source of more than 3% peroxide, you can just top it up. 3% peroxide rapidly becomes ... water. Adding new peroxide is fairly simple if you can get it at a higher concentration so it doesn't dilute the HCl as much.

An interesting (well, to me anway) etching technique I've never seen described is plating the copper off the board. If the board is masked with an electrical insulator, and maybe anything at all, you could run a plating tank from the PCB to a sheet of copper. The copper is removed from the board and plated onto the sheet. This has issues in that any islands that form are not electrically continous, and might stop etching. But it ought to be good enough to get the copper thin and then to toss the remaining very thin copper into a plating tank to remove the thinner remains.