Hyrdrofluoric nitric acid pickling

claya · Oct 9, 2020

We have a part that requires Hydrofuoric/Nitric acid pickle after finish machining.
1. Are any of you doing this (HF/N) now?
2. What is the procedure for disposing of the HF mixtures? What are the costs?
3. If you send it out for Pickling, what are the costs?
4. What are the safety procedures for handling/Storing HF mixtures?
5. If you store HF, what are the EPA, Fire reporting requirements?

We currently have Sulfuric, and Nitric, and use it very rarely, but familiar with the issues. HF is a different animal, or so I am reading. No need to tell me how bad/scary/dangerous HF is. Like to hear form those of you that are actually working with it.

clay

cameraman · Oct 10, 2020

claya said:
We have a part that requires Hydrofuoric/Nitric acid pickle after finish machining.
1. Are any of you doing this (HF/N) now?
2. What is the procedure for disposing of the HF mixtures? What are the costs?
3. If you send it out for Pickling, what are the costs?
4. What are the safety procedures for handling/Storing HF mixtures?
5. If you store HF, what are the EPA, Fire reporting requirements?

We currently have Sulfuric, and Nitric, and use it very rarely, but familiar with the issues. HF is a different animal, or so I am reading. No need to tell me how bad/scary/dangerous HF is. Like to hear form those of you that are actually working with it.

clay

I can't immediately answer all your questions...

But my question would be what concentrations of aqueous Hydrofluoric acid ?

And at what volumes / intended size of parts ?

What safety equipment / procedures do you already have in place ? (Thinking mainly fume hoods here ).

There are a lot of folks hacking together their own semiconductor manufactories in their respective garages using Hydrofluoric acid (for etching) that necessarily also hack together various fume hoods. And I believe there are ways to react active Hydrofluoric acid to make it less dangerous and easier to dispose of.

-

Here's Jerome/ Huygens optics hacking together a mini clean room ~ with a Hydrofluoric acid "Management" strategy ... (small quantities).

He has posted here before on PM regarding optical grinding. [His handle is JeromeV ~ I don't know how much he hangs out here / checks in ? ].

He's formally a Chemist also.

I've worked with many other pretty nasty chemicals on a larger scale for example huge heated tanks of 13.5 pH (opposite approach) powerful alkali for very different alloys.

The main danger / issues I see / perceive is scale and volume.

@claya what mix , blend , and concentration and specifically what alloys ?

Not a complete answer by any means but thought I'd help maybe to get the ball rolling on this topic a little bit as I'm interested too.

Not sure how "Cnc" it is but I guess the CNC section maybe has the right kind of "eye-balls" you want for the problem or what you are exploring ?

Rick Finsta · Oct 10, 2020

I'm a biochemist and spent a long time doing toxics/acid chemistry, and specifically using HF, professionally.

To be blunt, you don't want to handle HF. Even putting aside the EXTREME handling concerns (seriously, only two chemicals really got my heart rate up; HF, and aqueous Phenol, okay maybe a third and that is elemental Bromine), pretty much no matter what you're going to be creating RCRA Part C ("Hazardous") waste. I know most of the federal laws/regs here but can't begin to think of what a nightmare CA must be above and beyond that. You may have state agencies that require you to report against your generator quantity status, and for that matter you may need a generator ID, etc. Biggest concern will be corrosivity but depending on the material (likely a stainless) you'll have issues with watching concentrations of chrome as well for the toxicity characteristic. I'd have to look but you may also be generating a listed waste based on the constituents and process.

Bottom line is if you are asking what the regs are here, you're not prepared for them. Consultants make big money in this area, and honestly most of them don't know what they are doing, either. With "cradle to the grave" liability, you are left holding the bag even if the "environmental engineering firm" told you how to do what you did.

I would say find a subcontractor. This process is done all the time on food grade equipment (including tanker trucks) and it was always cheap to get done when I was in the environmental/waste industry at a company with a tanker fleet.

Hope that helps.

claya · Oct 10, 2020

Details:
We need to pickle ONE prototype part. It is 1" x 2" long. The material is NOT stainless.. Acid mix: 20%HF/20%Nitric/60%Diwater. A pint of HF49% is sufficient for what we need. We contacted a disposal service, waiting for a quote. They have to pick up the waste, we cannot deliver it too them.

If this is a one time deal, which is HIGHLY likely, we will neutralize (if even possible with HF) the mix and dispose it, or use the disposal company if the cost is reasonable. If we have to sign up and pay a bunch of hazmat fees for a binder full of regs ( and an on-site inspection) for a one time use, then it is not worth it. According to the disposal company, they pull a one-time EPA permit.

Acids don't scare us, we deal with the others safely. Am more concerned with the waste stream/disposal process specific for HF. Pretty sure we can pick up a gallon of HF from the local supplier we get the other acids from (or buy a pint online) with no regulatory gatekeepers.

It's the disposal and handling process I need insight on. Like to hear from shops that are either sending out for HF pickling, or managing small quantity batches in-house. This is not industrial scale. More like hobby or jewelry/goldsmith scale glass etching quantities. I know there are people using HF for glass etch and goldsmiths doing this on scale volumes we are talking about.

I just don't want to trigger a full scale fire marshall/hazmat on-site review once I buy a gallon. Or get slammed with a $500 disposal fee for a 1/2 gallon of liquid. The garage wafer etching setup is curious.

This part has to be pickled by someone after we are done with it. Just trying to research the practicality/cost of us adding HF to our cabinet to other acids we use every couple years on single prototype parts like this.

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triumph406 · Oct 10, 2020

claya said:
3. If you send it out for Pickling, what are the costs?

Ever thought of picking up the phone and making a couple of calls?

claya said:
4. What are the safety procedures for handling/Storing HF mixtures?

I know somebody who was using HF for etching aluminum model airplane cylinders prior to chroming. He got some on a finger when he wasn’t being carefull enough. He said it was about a year before the very considerable pain went away. He said he was very carefull (evidently not that one time), and it wasn’t the first time he’d used HF

claya said:
5. If you store HF, what are the EPA, Fire reporting requirements?

How hard is it for you find out?

claya said:
We currently have Sulfuric, and Nitric, and use it very rarely, but familiar with the issues. HF is a different animal, or so I am reading. No need to tell me how bad/scary/dangerous HF is. Like to hear form those of you that are actually working with it.
clay

You’ve read it’s bad/scary/dangerous and you still want to use it for one part?

Presumably your not the poor sucker who has to handle the HF. “if he’s carefull it should be OK”

If it were you I’m sure it would be a different story.”we need to send that out, way to dangerous to use here”

think about it. your in california, you want to HF pickle a single part 1" x 2" and your contemplating doing it in house. how could that possibly make any sense??

claya · Oct 10, 2020

triumph406 said:
Ever thought of picking up the phone and making a couple of calls?

I know somebody who was using HF for etching aluminum model airplane cylinders prior to chroming. He got some on a finger when he wasn’t being carefull. He said it was about a year before the very considerable pain went away. He said he was very carefull, and it wasn’t the first time he’d used HF

How hard is it for you find out?

You’ve read it’s bad/scary/dangerous and you still want to use it for one part?

Presumably your not the poor sucker who has to handle the HF. “if he’s carefull it should be OK”

If it were you I’m sure it would be a different story.”we need to send that out, way to dangerous to use here”

think about it. your in california, you want to HF pickle a single part 1" x 2" and your contemplating doing it in house. how could that possibly make any sense??

Ya. Have calls in all over. Did that first, still waiting for callbacks. PM is my fallback when I can't get local answers, or soon enough. Plus there are a lot of experts here on alternate solutions.

We don't have a lot of resources here, so the ones we do have are always difficult to reach even without all this lockdown nonsense.

Not scared, just cautious, looking for actual users with experience. Companies and hobbiests work with HF safely all over. But it is so much easier to scare the living daylights out of people than educate...

Fully aware of the HF safety/handling. I can read an sds. Just collecting info, trying to save our customer the effort of bringing it in-house there, and adding another profitable process we can 100% control here. If it's smarter to send out we will do that, or pass it on to the customer. We call it good business, and supporting our customers.

Yes. I will be the one handling the part and HF. Thank you for the assumption and diss... That was tremendously helpfull.

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DanielG · Oct 10, 2020

Rick Finsta said:
To be blunt, you don't want to handle HF. Even putting aside the EXTREME handling concerns (seriously, only two chemicals really got my heart rate up; HF, and aqueous Phenol, okay maybe a third and that is elemental Bromine).

To paraphrase the first aid instructions given at my wife's former lab:
slather yourself in calcium paste and call 911, they'll take to the one hospital in town that can handle this type of chemical burn, where they'll inject more calcium into you, hopefully before your bones dissolve.

Still not quite a terrifying as dimethyl mercury.

snowman · Oct 10, 2020

DanielG said:
To paraphrase the first aid instructions given at my wife's former lab:
slather yourself in calcium paste and call 911, they'll take to the one hospital in town that can handle this type of chemical burn, where they'll inject more calcium into you, hopefully before your bones dissolve.

Still not quite a terrifying as dimethyl mercury.

Nah, with HF, you die of a heart attack long before your bones dissolve.

I'd rather play with HF than concentrated H2SO4 on most days. Either one requires the same safety, only the PPE for HF is easier to wear. That and splashes from HF can become deadly real quick.

You absolutely need a hood, or dedicated space to do it.

No clue on the requirements on a state level. On a federal level, you can just order up a bottle without triggering any audits.

The ions dissolved from the alloy will determine how the waste is handled. Small time, you will be a conditionally exempt waste generator. If however the waste has specific metals dissolved, it becomes RCRA waste and there is no conditionally exempt anymore.

HF is an acid that is really expensive to use in large corporations, just because of the red tape.

claya · Oct 10, 2020

We have a flow hood, with active carbon and hepa filtration. We are more engineering lab, than most machine shops.. But will probably just do the pickling outdoors. Advice?

We will produce maybe a quart of waste mix. Where does that classify us? We are simply removing potential hydrocarbon oils off the surface off a refractory metal. It is a VERY expensive & time sensitive part on a VERY VERY expensive program.

If we can do this here, then that opens some doors for us. Our customer is not interested in doing pickling in-house. And there are other customers that will benefit also.

The hazmat company is working up a quote. I expect that to be eye-watering for Kali. They have to send a truck out. To pick up a 1 quart plastic bottle of 20%HF/20%Nitric. They said HF cannot be neutralized without creating another hazmat. Comments on that?

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snowman · Oct 10, 2020

You do not have an appropriate setup to do the pickling....and given the danger, I would NOT proceed. Doing something like this outside is moving a reaction you aren't familiar with to an uncontrolled environment.

Neutralization at that concentration acid will be extremely exothermic and must be done very slowly. Anything less than slowly and you will end up with steam. Steam explosions and HF is a recipe for death.

john.k · Oct 10, 2020

Anyone who does stainless fabrication will have a tank of nitric/HF for removing rust stains .....I have bottles of the gel for topical application stored under the house......HF is also used in the well known allumin brighteners /cleaners .....yes ,protective clothing is needed ,for sure ...........I recall Crazy Col ,the junk merchant bought a large quantity of HF from the air force ,to get the valuable plastic lined drums......I asked him about the acid....they had run it out on the ground in his junkyard,so it went in to the drain behind.Neutralized by the alkaline soil,or by the concrete drain.

john.k · Oct 10, 2020

When I was at the refinery tons of HF was used in the alkylation towers.....the tanker driver used to regularly let a hoseful run out on the ground,about once a week......I got a tiny spot in an eye ,when the wind was swirling up the dust,had double vision in one eye for months...(Hospital doc said it wasnt possible to have double vision in one eye....it is)

sfriedberg · Oct 10, 2020

claya said:
Or get slammed with a $500 disposal fee for a 1/2 gallon of liquid.

If you can get the paperwork done for 10 times that much, you will be doing great. And $50,000 in fees and administrative costs (including your in-house costs) in CA before you successfully wash your hands of the whole business would not astonish me.

Send it out, especially if it's just one part.

claya · Oct 10, 2020

sfriedberg said:
If you can get the paperwork done for 10 times that much, you will be doing great. And $50,000 in fees and administrative costs (including your in-house costs) in CA before you successfully wash your hands of the whole business would not astonish me.

Send it out, especially if it's just one part.

Is why I am asking. Hazmat waste service is quoting pickup. If it is even $5k, then of course, not worth it. Really appreciate the advice.

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snowman · Oct 10, 2020

claya said:
Is why I am asking. Hazmat waste service is quoting pickup. If it is even $5k, then of course, not worth it. Really appreciate the advice.

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I think realistically you are looking at a few grand.

Any waste is going to have to be analyzed and characterized to determine how to dispose of it.

You don’t have the facility to use hf safely...and I highly doubt you have the workman’s comp insurance either.

It’s one of those things where if it were me, I’d just do it, neutralize the waste, dispose of it ethically and charge a helluva a lot for it. But I’ve been working with the shit for years. It’s not something that you should be doing based off internet discussions.

Finishing.com will give you more precise info, as well probably be able to recommend a local shop that is equipped.

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triumph406 · Oct 10, 2020

Hydrofluoric Acid Safety Supplies – HFAcidSafety.com

claya · Oct 10, 2020

triumph406 said:
Hydrofluoric Acid Safety Supplies – HFAcidSafety.com

Thanks. Have been reading up on this.

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Rick Finsta · Oct 11, 2020

Someone reached out via PM to ask about using pickling paste on welds and this is what I sent back in response:

What HF does (Cliff's Notes version) is move quickly through tissue and right to the bone, where it interacts with calcium and can kill you very quickly with a small amount of surface contact (SDS are generally worthless but that "fatal in cotact with skin" thing is real). The less concentrated it is, the lower the danger, but the danger is still there (you just need more contact area or time). There are a few things I would have at a minimum (and this isn't necessarily the legal minimum, or the newest industry best practices since I left industry several years ago):

1) A plan. You're using paste, but what happens when some gets on the ground/bench? What about on your skin or clothes? Just think about it now before it happens as time is a major factor in the damage it will do. When using concentrated (over 12.5% IIRC) we actually dried every surface in the production bays and if ANY liquid was found errantly sitting anywhere when we were done handling the HF, it was treated as an HF spill. That's just an example. You don't want someone coming into the area not knowing that the risk is there and wiping up a glob with their hand, for instance.

2) PPE - Acid/Organic cartridge, full face respirator (we actually always required supplied breathing air with an acid/organic escape cartridge), and at the very least an apron and gauntlet gloves or sleeves that are rated for HF. If you are using a half mask and glasses, I would at least suggest moving up to a face shield. The paste form helps keep the HF from evaporating just sitting there, but for weld post processing if there is heat present then it will obviously volatilize quickly.

3) OH SHIT preparations. Keep Calcium Gluconate on hand, and contact your local emergency room and make sure they know how to treat HF burns. I would also personally want an eye wash station (one that mounts on a sink or one that hangs on the wall with its own water supply would be fine).

It sounds like you've worn PPE and understood that the danger was there. No way I would be caught using the stuff without that Calcium Gluconate gel on hand, though.

I hope that helps. I don't like to be alarmist, but to be blunt, handling materials like this require a level of care that is not present in most machine or fab shops I've seen.

HF requires handling care and procedures that are far above and beyond any other acid. For disposal, it should not be neutralized, it should be complexed with something (generally, a Calcium salt) so that if it is comingled later in the waste treatment process the danger does not return. A "Lab Pack" contractor is generally who you'd use to pick up waste like this, if you're still looking.

Let me reiterate this since the OP mentioned exactly what he'd be using: NO MACHINE SHOP SHOULD BE HANDLING 49% CONCENTRATED HYDROFLUORIC ACID. It is not a question of if, but when, someone will be severely injured or killed. Anyone who talks about this stuff in a cavalier manner has no business anywhere near it. There, you've heard a subject matter expert give his $0.02.

ss_user · Oct 11, 2020

HF absolutely loves nerve endings which is why toe pain and healing problems. We used reasonable amounts of perchloric acid along with nitric and sulfuric for mineral dissolution. A cinch compared to HF or 30% peroxide. Got a bit of 30% peroxide on my hand; the sink was two steps closer than the safety shower. Guess which one I picked. ;-) For real stupidity weigh out mg amounts of dry mycotoxins (carcinogenic) in an low humidity environment where static electricity is a problem. When handling chemicals there are lots of ways to damage yourself.

seiner · Oct 11, 2020

john.k said:
Anyone who does stainless fabrication will have a tank of nitric/HF for removing rust stains .....I have bottles of the gel for topical application stored under the house......HF is also used in the well known allumin brighteners /cleaners .....yes ,protective clothing is needed ,for sure ...........I recall Crazy Col ,the junk merchant bought a large quantity of HF from the air force ,to get the valuable plastic lined drums......I asked him about the acid....they had run it out on the ground in his junkyard,so it went in to the drain behind.Neutralized by the alkaline soil,or by the concrete drain.

Your Kidding right?????/

Hyrdrofluoric nitric acid pickling

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