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engineJune
New Contributor

Hydrofluoric acid + nitric acid + water storage

Hi there,

I have a question about storing a solution comprised of 1 part hydrofluoric acid (technical grade, 70 percent), 2 parts
nitric acid (40 degree Baume minimum), and 3 parts water. 

I've seen guidelines saying anything hydrofluoric is stored in needs to be a polyethylene or lead, but I'm not sure once it has been mixed with water and nitric acid. 

We have the raw ingredients, and want to create a small amount of this pickling recipe into a separate container as to not contaminate any of the sources. We can either keep it, or use it up in one use.

What material does that container need to be?

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scooke
Contributor III

Re: Hydrofluoric acid + nitric acid + water storage

Dear June,

SAFETY FIRST!!  Use ONLY Polyethylene or Teflon containers for any solution of HF.

Because of the high reactivity toward glass and moderate reactivity toward many metals, hydrofluoric acid is usually stored in plastic containers (although PTFE is slightly permeable to it). Hydrogen fluoride gas is an acute poison that may immediately and permanently damage lungs and the corneas of the eyes. Aqueous hydrofluoric acid is a contact-poison with the potential for deep, initially painless burns and ensuing tissue death.

Even 7% solutions can be deadly if spilled on exposed skin.

https://ehs.unc.edu/chemical/hfa/chemical-safety-information-hydrofluoric-acid/

It should only be contained in Polyethylene or Teflon containers, within an additional polyethylene tray of sufficient volume to contain any storage containment leakage.

Guidelines for the Safe Use of Hydrofluoric Acid

The following link is from a commercial supplier of the pickling mixture.

https://www.columbuschemical.com/MSDS/SDS/Nitric%20Acid-Hydrofluoric%20Blend%203867.pdf

As nasty as the stuff is if released, you really don't want to compromise on safety.  Treat even 'dilute' solutions as potentially as dangerous as any concentrated solutions.  Keep plenty of Calcium Gluconate on hand, and appropriate neutralizing agents around in case of any spills.

Best regards,

Steven

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