Hydrofloric Acid 2

[jmcgrath]

Dear All,

I am testing out new materials for a project that I am working on and I have just been asked it they will stand up to attack by Hydrofloric Acid. From what I can tell there is very little that can stand up to this acid, but I need to know more about it first.

Where does it naturally occur?
Is it likely to be found with petroleum products?
General background on it.

If anyone can help I would be very grateful.

Regards,

John

 

[sciguyjim]

HF is a nasty acid, but there are others much worse. The only place I can think of where it might be produced naturally is in volcanoes. It's best known for its ability to etch glass. It can also cause very painful, sometimes deadly, acid burns if the concentrated acid gets on your skin, and it doesn't stop chewing through your skin until it reaches the calcium in your bones. It is never used with petroleum products but it can be formed in an engine if an additive or solvent containing fluorine is burnt in the cylinders. The vapors will corrode your oxygen sensor (as will the acids HCl, HBr, HI, etc.)

 

[tomwalz]

Start with the MSDS. This is a great site.

http://hazard.com/msds/

I can't think of anywhere it occurs naturally. (Doesn't mean it doesn’t)

If you are going to play with Fluorine compounds you need to be careful of more than just HF. HF is the famous, bad one but there are lots of other fluorine compounds that are nasty to very nasty.

Try Google. Esp.

http://gnp.enviroweb.org/hf1.htm

tom

 

[jmcgrath]

Guys,

Thanks for the tips.

John

 

[rembrandt]

1. Hydroflouric Acid is used in the Alkylation Process in the Oil Refining Industry, usually for producing Unleaded
Fuels.
2. Aluminium, Carbon Steel and Monel all resist attack by HF
and the plants generally are made of these materials.
3. Do Not use Stainless Steels or Silicone Gaskets, they have no resistance.
4. 'HF' Acid is unstable, and is classed as a 'Fuming' Acid,
it readily and rapidly causes vapour clouds at ambient temperatures and atmospheric pressures
5. It is theoretically possible for Trace Residues to find their way offsite in the fuels, but unlikely to accumulate in vehicle fuel systems in any meaningful quantity, however
they could accumulate in storage tanks over a period of time if the conditions were right.

 

[sciguyjim]

I worked for an oil refining company for 8 years and never heard about HF being used in any refining process. Then again, in my research group, there wasn't a need to know all the refining steps one could possibly use. 18 years later, I'm still learning new things about that business.

 

[jmcgrath]

Thanks for all the info guys. I was origionally asking if HF could be naturally occurring in an oil well and it seems that the answer is no. The reason is that I have been testing a new product for corrosion resistance against CO2, H2S and other chemicals that can occur downhole at 200C and 15K psi. I was then asked if it would also stand up to HF acid and I was stumped.

I don’t want to test with any new acids until I know if there is a chance it could appear naturally in a well bore.

If anyone has any other thoughts on the subject then I would be happy to hear them.

Regards,

John McGrath

 

[butelja]

I believe that HF is used in refineries in the HF alkylation process where unbranched hydrocarbons are alkylated to form branched hydrocarbons which have a higher octane value. Another method of doing the same thing is Sulfuric Acid alkylation, but it generates large amounts of spent acid contaminated with hydrocarbons. The HF process generates less waste, but has to deal with the much nastier HF as opposed to oleum/sulfuric acid.

 

[Hush]

It may not be naturally occuring but I have heard of it being used in acid fracs to break down silicates. This might be why the question has been posed.

 

[jmcgrath]

Hush (and everyone else)

I have found out from another source in the Coiled Tubing industry that HF is used as an acidiser to clean out perforations and such like and that it is not naturally occurring in a well bore.

Thanks for everyone’s input.

Regards,

John McGrath

 

[AlanD]

Thinking intuitively

HF is far too reactive to remain present if it did form naturally. The fluoride ions will virtually react with anything to form a stable compound.

 

[Tombei]

HF, in its various diluted concentration, is one of the most used acid in Wafer Fabrication.

As mentioned, it is a nasty acid as it is odorless and looks like water. It attacks calcium and that is why when this acid is accidently spilt on a person, he has to be treated immediately before it penetrates into the skin and attack the bone.

 

[ghopkins]

As far as materials of construction go, there are several flourpolymers that hold up well - up to 70% concentration and 150C.

These are Kynar-PVDF, Halar-ECTFE, Tefzel-ETFE, Teflon-FEP, Hyflon-MFA, Teflon-PFA and of course PTFE.

See the websites for Dupont, Ausimont, and Atofina for more information on these flouropolymers.

http://www.ausimont.com/docs/matl_plastics.html

http://www.atofinachemicals.com/kynarglobal/index.cfm

http://www.teflon.com/

For structural integrity, use corrosion resistant fiberglass with a flouropolymer lining.

 

[keeled]

generally HF can be handled by fluoropolymers depending on your concentration and temperatures, some good sites to visit are:

http://www.symalit.ch

a manufacturer of fluoropolymer sheet

http://www.ausimont.com

manufacturer of fluoropolymer resins

http://www.dupont.com/teflon/chemical/tefz.html

remember HF permeates fluoropolymers so it is important to know the pressure and temperature so it can be proberly designed for and constructed for this phenomenon.

good luck!

 

[tomwalz]

Something to keep in mind is just what sort of process you have and what intermediate compounds might be generated unintentionally.

I ran across this analyzing a brazing process. In the brazing process, apparently you just melted the braze alloy onto the carbide using a flux that traps oxygen. However the braze alloy was silver, copper, nickel, zinc and cadmium. The flux was organic salts of potassium and fluorine. The tungsten carbide had a cobalt binder as well as various trace materials. The heating was done with an oxy-acetylene torch (figure 5,000 F) in a saw shop atmosphere so figure standard atmosphere plus oil, grease, metal fines, etc. A process this sloppy with this much energy and this many chemicals meant that there was the possibility for all sorts of accidental compounds and reactions.

Just because you do not have pure HF does not mean that you do not have HF or HF like compounds created incidentally. Also as powerful as HF is it can be potentiated by the addition of other chemicals.

If you do a spectrographic analysis or similar and find Fluorine (other halogens, etc.) you might want to consider what can happen to it during the processing.

tom