Material of construction for nitric-HF?
I've been recommended a pickling mixture of 4% hydrofluoric acid, 12% nitric acid to remove oxide scale at 60 deg C.
What materials can I use ?
I guess glass is out due to the HF. Also not all plastics are compatible with nitric acid.
Is stainless steel OK ?
- Reading, UK
I'd suggest talking to a manufacturer of flexible PVC linings (either cemented in place or drop-in style) about this application--it sounds fine to me.
Ted Mooney, P.E.
Pine Beach, New Jersey
I have some doubts that stainless will survive your 'mix' although nitric protects stainless as you know. Why don't you check with the corrosion charts of any local s.s. supplier?
PVC by itself is no good due to temperature deflection (but only perhaps as a lining) but I don't like the idea of the plasticized PVC, which linings are made of, in conjunction with nitrics, especially fairly hot ones as the plasticizer will get leached out.
You should be OK a glass reinforced PVC, a so-called dual laminate. Then there's CPVC, PVDF and the weldable fluorocarbons, which cost a mint. All will take that mix.
White Rock, British Columbia, Canada
(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).
We used a very heavy (about 1/4") vinyl liner in a heated nitric HF tank and it lasted about 10 years. It would not last as long at 60C which is near the upper limit of most vinyl liners. You are probably looking at a CPVC tank with a fiberglass coating for strength. They tend to be dear when it comes to price.James Watts
- Navarre, Florida
Tony, Your best bet is to use a polypro outer tank with a 1/4" PVC liner. The liner will need to be replaced at least once per year. For heating.. Use Hot water through a teflon coil. Keep the pressure though the coil below 20 pounds per square inch. George Fischer ( GF) manufacturers the best line of teflon coils. For teflon heaters less than 12000 watts call Lufran. Sincerely,Skip Schaefer
Unless you enjoy replacing your tank on an annual basis, I suggest using a PFA teflon tank. If you are using 4% HF, 12% nitric acid, a PFA tank will give you the best longevity for your money.Jono Choi
- Arcadia, California, USA
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