Letter 33032

Are ammonium bifluoride and hydrofluoric acid interchangeable?  

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I'm working in a consulting company in Russia. And we faced with the project about chemical factory. Our client was producing hydrofluoric acid and now thinking about replace this production with production of ammonium bifluoride. In this case it is not a mater of safety, but they think that it is easier for transportation, storage and use because ABF is dry. What do you think about this?

And another question. I wonder is ABF and HF totaly interchangeable or they have some different characteristics.

Victoria Kiryakova
Alt - Saint-Petersburg, Leningradsky, Russia

They are not totally interchangeable. It is common to use ABF in an acid solution as a source of flouride ions. It will work very nicely on many, but not all applications.

James Watts
- Navarre, Florida

Even though they both produce a corrosive fluoride solution,ABF and HF are quite different.
HF is water-soluble in all proportions while ABF is soluble only up to ~28% at room temperature. ABF, in solution, yields ~ 1/3 as HF and ~2/3 as ammonium fluoride(AF) and; as such, provides a somewhat buffered solution. ( a 28% solution of ABF will produce ~ 9% HF and 18% AF) In fact, semiconductor-chip manufacturers use different ratios of HF and AF to produce various "Buffered Oxide Etches" that dissolve silica chips at various rates.
ABF has been used as aluminum brighteners for wheel (hub-cap) cleaners. . . some formulaters have inappropriatly advertised these as a "non-acid" wheel cleaner.
Bottom line here is that the ABF solution will still produce a extremely hazardous liquid.

Mike Berg
- Chesterfield, MO, USA

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