Q: I need a material that is resistant to a small concentration of hydrofluoric acid at room temperature? Can you offer any suggestions?

A: Two materials come to mind. First in terms of metal alloys Monel 400 bolts are resistant to most concentrations of hydrofluoric acid. If you prefer a polymer, then I would suggest PTFE. PTFE fasteners are known for their inertness to most acids, even hydrofluoric acid. PTFE is ideal for low temperature, high purity applications.

Q: I’m using aqueous Hydrofluoric acid in a silicon etching process but amy Nickel 200 bolts aren’t holding up. Is there a better material I can use?

A: Nickel 200 fasteners are excellent for use in anhydrous hydrofluoric acid, but in the aqueous form of HF acid they offer limited resistance. The good news is that there is a solution. Monel 400 is one of the few materials that can offer protection from hydrofluoric acid corrosion.  Monel bolts have excellent resistance to HF in all concentrations up to the boiling point.