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topic 11260

Ammonium Bifluoride


A discussion started in 2001 but continuing through 2018

2001

Q. What is ammonia bifluoride? What is its context in cleaning steel-substrate?

Jack Lim
- Penang, Malaysia


2001

A. Ammonium bifluoride is a white crystal salt that when put in water forms HF. It is used to brighten aluminum and other metals. This chemical does an excellent job in brightening.

NL [last name deleted for privacy by Editor]
- Atlanta, Georgia


Ammonium Bifluoride

A. Hi Jack. Fluoride ions are the only thing that I am aware of that can dissolve silicon. Stainless steel castings, aluminum alloys, and some other metals may contain silicon which often must be dissolved or removed from the surface as part of the finishing process. For example, you can't anodize aluminum if it has excess silicon at the surface. But, as far as I can think of, it wouldn't be used in cleaning steel.

If properly managed, ammonium bifluoride can be somewhat less biohazardous than hydrofluoric acid (see letter 9462, "Hydrofluoric acid vs. ammonium bifluoride").

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey



2006

Q. Can we use Ammonium bifluoride for crystal shining process? We use HF currently.

Asim Emir
ab-ka - Turkey


Hi Asim. This site focuses on metal finishing, and I don't know a lot about glass or crystal finishing . . . but hopefully a reader who can help you will wander onto this page.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey



2001

Q. I have a concern. We are currently using Patclin 975 to brighten the aluminum in our plating line. I have to switch it to Ammonium bifluoride, but I am not sure the make up. Should we add Nitric acid or make it up with just water. I have a 6.2 gallon tank, so I don't know the appropriate amount of Ammonium bifluoride needed to makeup the solution. Any Ideas? Ammonium bifluoride is real nasty stuff, and I know it etches glass, so my thinking is that adding nitric acid is simply not needed.

Tim Shea
- South Deerfield, Massachusetts


2001

A. Please don't mix proprietaries like Patclin with non-proprietaries like nitric acid or ammonium bifluoride. Either take Patclin's advice, or switch to one of their competitors and take their advise, or start from raw chemistry. There is danger in adding things like ammonium bifluoride or nitric acid to a proprietary, because you don't know what's in the proprietary!

Nitric acid is one of the few oxidizing acids and its oxidation power is required for some applications. For example, copper does not dissolve in simple acids, but excesses of it must be removed from the surface of copper-bearing aluminum alloys before they can be anodized.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


2001

A. I'm not familiar with the Patclin product, but we've used scratch-built etchants here for years, including those with ammonium bifluoride.

We use nitric acid solutions ranging around 50% with anywhere from 1% to 10% ammonium bifluoride as a de-oxidizer/etchant. I would not use it as a brightener, it leaves more of a matte finish, but that resultant finish is dependent upon the aluminum alloy.

If you're looking for a bright dip, there are far better and safer solutions than bifluorides.

Bob Denney
avionics Tampa, Florida



(2005)

RFQ: Dear Sir ,

Please advise if you can provide us with ammonium bifluoride that we are seeking to import 2 FCL ,please quote us your best quotation , CIF Alexandria Port , Egypt.

Regards,

Ahmed Sadek
IMPORT EXPORT - Cairo, Egypt
^- Sorry, this RFQ is outdated
     View Current RFQs




2000

Q. I am looking for a pickle bath make up to strip some cast parts. I heard of a nitric ammonium bifluoride solution. What ratios? Are there other more suitable baths?

C Culp
- Tualatin, Oregon, USA


2000

A. The usual solutions for the removal of scale and rust from iron and steel products are hydrochloric or sulphuric acids. These are used in concentration ranges from a few ounces per gallon to very concentrated, depending on the type of work being processed. Cold rolled can be processed in weak hydrochloric acid, whereas heavily scaled construction plate is best pickled in sulphuric. Also the use of an inhibitor are common and are optionally used to prevent over-etching and to avoid pitting.

Best regards,

Rob Wells
- Pickering, Ontario


March 1, 2013

A. Hello, C. We are probably misunderstanding you. What material are the castings made of (aluminum, stainless steel, bronze, cast iron)? And what coating do you want to strip off of them (paint, powder coating, a metal plating of some sort)?

We don't know what coating you are trying to remove, nor what substrate you are trying to not harm, so the general implication of Rob's reply would be that you don't use ammonium bifluoride except when it is required (because it is a severe biohazard). Good luck.

Regards,

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey



July 17, 2015

Q. We are presently making up a nitric acid/ammonium bifluoride
etch solution for aluminium. We are decorative anodising Jig Plate but are having problems with the finish, white spotting and stains. We believe as Ted has stated to have silicon in the aluminium.

The nitric acid in the solution is 50%. What addition of ammonium bifluoride should we add to the bath.

Nigel Bell
- Northern Ireland


simultaneous July 17, 2015

A. One pound per gallon.

robert probert
Robert H Probert
Robert H Probert Technical Services
supporting advertiser
Garner, North Carolina
Editor's note: Mr. Probert is the author of Aluminum How-To / Aluminio El Como
and co-author of The Sulfamate Nickel How-To Guide


July 21, 2015

Good day Nigel.

I am not familiar with aluminum Jig Plate material.
I have used this make-up prior to zincate/electroplate.
Nitric (for copper) - 50%. Sulfuric (for magnesium) - 25%. Water -25% Ammonium bifluoride (for silicon) - 8-16 oz/gal.
As you well know, there is a tremendous amount of heat generated during make-up. Extreme caution must be exercised, additions must be made EXTREMELY slowly, as I am sure you are aware.
I used a stainless tank lined with PVC, with sufficient space between to allow for a flowing cold water jacket.
During lab testing, I found conventional addition of acid to water generated extreme heat. I added the sulfuric to nitric, then water.
I am not by any means recommending this, but it worked for me.
This is a very nasty beast.
Hope this helps, and good luck.

Regards,

Eric Bogner
Lab Tech. - Whitby, On., Canada.


July 23, 2015

Q. Robert / Eric.

Thanks for your feedback on this. Our tank size is 400 litres. We have already added 25 Kg which equates to approximately 9 ounces per gallon. This seems to work well but if need be can move towards the 16 ounces. Our immersion time is 25 seconds.

Just a note. We are going into the nitric/ammonium post anodise for 25 seconds. We are aware that the anodic coating may strip so we are being very cautious. We did trials pre and post anodise, and post anodise is giving us a better finish. No white spotting or stains after dying and seal.

Regards
Nigel.

Nigel Bell [returning]
- Northern Ireland


July 23, 2015

A. Hi Nigel,
Interesting that you can apply nitric/ammonia bifluoride etch post anodize before seal. At 25s dip time, understandable it may remove some of the anodize coating but, as a point of interest, does it make the anodize whiter in appearance ? Thanks.

cheah

SK Cheah
- Penang Malaysia


July 27, 2015

info Hi SK,

We actually dye the parts red. The nitric / ammonium dip pre dye and seal brightens the anodising leaving the finish with a real sheen.

Regards
Nigel.

Nigel Bell
- Northern Ireland



March 6, 2018

Q. We are working on ammonium bi-fluoride market. I don't know much about the chemical but that it is used as finishing products and sometimes in cleaning process ... I just want to know how much of this chemical holds as the percentage of specialty chemicals (E.g., 10% of all specialty chemicals sales approximately).

Aakansha Tyagi
Straits Business Group - Pune, Maharashtra, India


March 2018
wikipedia
Specialty Chemicals

Comparatively Speaking: Commodity vs. Specialty Chemical

Hi Aakansha. Yes, it is used in finishing products, certain cleaning products, glass etching products, etc. Apparently, somewhere around a million pounds is produced annually.

I think you would have to be very clear on exactly what "specialty chemicals" means to you before anyone could try to answer that question because per Wikipedia and other sources, ammonium bi-fluoride sounds more to me like a commodity chemical or pseudo-commodity chemical than qualifying as a "specialty chemical" (although I don't know of a list of one vs. the other).

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


March 8, 2018

Q. Hi Mr.Ted Mooney,

So you mean to say about a million pounds of this inorganic chemical is being produced annually round the globe?

Actually as I need to find the market for the chemical and I am not sure about it, so I was considering it under specialty chemicals.

Also the chemical does not have any analytical use such as in research and other fields?

Also as being a toxic substance, is it preferable? And after China which is the largest producer of the chemical?

Aakansha Tyagi
- Pune, Maharashtra, India


March 2018

A. Hi Aakansha. When questions are posted I try to spend a few minutes of googling so I can learn from them, but I'm a plating equipment engineer not a chemical market researcher. I quickly found a reference which said a half million pounds was manufactured some years ago with projections of about a million by now; don't rely on my second-hand numbers though, find the sources of the data yourself.

Ammonium bifluoride is sold in reagent grade; I'm not sure about analytical grade or possible analytical uses.

Sorry, I don't understand what you mean by "being a toxic substance, is it preferable?". Certainly if a less toxic but affordable alternative is available for some particular purpose, that alternative would be used. In some ways it's less dangerous than hydrofluoric acid and is used as an alternative to HF in some applications. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


March 9, 2018

A. Hi Aakansha, Ted,

Ammonium bifluoride is sold in analytical grade for some uses, we use it to remove iron in chromate analysis (you make an error in excess by oxidizing iron if you don't add it).

As Ted said, it is widely used as an alternative to hydrofluoric acid, and I don't know whether there is or not some safer alternative.

I think that if you are working manufacturing this product, the best you can do to know better the market is going to your actual clients and see for yourself what do they make with your product.

Best of luck!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina



September 26, 2018

Q. Hi,
I did a goggle search and found your website. It's very interesting and so helpful.
Can you please let me know if the Ammonium bi-chloride ^bifluoride is good to remove aluminum silicates? It appeared as a white residues on my aluminum parts.
How much ABF should be used and how long to dip it? Or, do you have any suggestion for other chemicals?

Thank you.

M Pham
- Houston, Texas USA


September 2018

A. Hi M. Commercial cleaners available to consumers are dangerous and contain 2-5% ABF. But whether that is the right strength for your application and how long you would need to dip those parts with unknown amounts of silica stain is hard to say ... but in order of magnitude probably several seconds to a minute or so; certainly not hours.

Chloride and fluoride are very different things and you need to be very careful of typos that could mislead you or others. You didn't introduce yourself and your situation, so we're not confident that you can safely use such fluorides (for example, is this an industrial application in a plant which has a safety program including haz-mat training? do you have Calcium Gluconate Gel [linked by editor to product info at Amazon] on hand?). People are reluctant to suggest using fluorides unless you're quite sure what your white residues are. Where did they come from, what's the process? Would avoiding them through the use of DI water be more practical?

Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"


September 28, 2018

Q. Hi Ted,
We are working in an industrial plant that participates in a Safety program. Our workers in the plant miscalculated and over-used a heavy-duty cleaner, so the aluminum parts got white residues after the cleaning process. I sent the sample to a lab and it was identified as aluminum silicates.
I goggled and found your group discussed about the HF and ABF. (Sorry, my question is for ABF, Ammonium bi-fluoride, not chloride. It's a typo). Very interesting and very helpful.
In 2001 you posted "fluoride ions are the only thing that I am aware of that can dissolve silicon". I heard about the HF, but would like to use the AMF because it's less hazardous than HF (according to the discussions in your group). Would you please give me some advice about the ABF? I just need to use it to remove the Al silicates from our 10 pieces of cast aluminum parts. Should I need a corrosion protection after the cleaning with ABF?
Thank you for your help.

M Pham [returning]
- Houston, Texas


September 2018

A. Hi again. Several seconds to a minute of so in 5% ABF is the best guess I can make from this distance. No guarantees that this will fix your problem though, because over-etched aluminum may have other alloying ingredients left on its surface besides silicon. It's hard to say what corrosion protection you need, but aluminum is frequently chromate conversion coated. You might consider sending the parts to an aluminum processing shop who can etch, desmut, and conversion coat them for you. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"

----
Closely Related Threads:
Letter 9462, "Hydrofluoric acid vs. ammonium bifluoride -- are they interchangeable? Is one safer?"
Letter 34536, "How to Do Ammonium Bifluoride Analysis"




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