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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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What tank or lining materials are okay for HF, nitric, and other acids?
Q. I've been recommended a pickling mixture of 4% hydrofluoric acid, 12% nitric acid to remove oxide scale at 60 °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?
Thanks
Tony
Tony Fulford- Reading, UK
2000
A. I'd suggest talking to a manufacturer of flexible PVC linings (either glued in place or drop-in style) about this application--it sounds fine to me.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. Hi Tony,
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.
Cheers!
Freeman Newton [dec.]
R.I.P. old friend (It is our sad duty to
advise that Freeman passed away 4/21/12)
A. 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 60 °C 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
A. 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- Pomona,California
A. Tony,
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
Multiple threads merged: please forgive chronology errors and repetition 🙂
Coating for Electropolish Containment Tank
Q. I am looking for a material that can be applied to our spill containment tank around our electropolish tanks. Our containment tank developed some cracks when it was moved. I need a coating that will stand up to the electropolish solution and something that will seal cracks in the tank to allow it to be washed out.
Brad Wilson- Simi Valley, California , USA
2003
A. I don't think I'd trust anything but a drop-in flexible liner considering the cracks and the poor adhesion to an old surface that I'd expect. What is the containment tank made of? Polypro? FRP?
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
|
A. Too many unsaid variables. Concentration of each component of your EP solution. If there are proprietary components, you better ask the manufacturer of what you can use and more specifically, what you should not use. Next, what is the ambient temp under the tank. Drip spills or splashes? Initial gut reaction is pull the tanks out, use a chopper fiberglass unit with the appropriate formulation, smooth out, apply a very tight weave veil coat and at least two coats of gel coat on top of that. Put the tanks back in. James Watts- Navarre, Florida A. Brad, You didn't spec out what that thar tank is made of ... and lacking info, how in the heck do you expect anyone to try to help you? Freeman Newton [deceased] (It is our sad duty to advise that Freeman passed away April 21, 2012. R.I.P. old friend). |
Multiple threads merged: please forgive chronology errors and repetition 🙂
Liner material for nitric acid tanks
Q. We have to use an existing Mild steel tank to supply nitric acid (60% concentration). I would like to know the type of liner material to be provided in the tank. Size of the tanks is 3 m X 3 m X 4 m. Also please note that the lining is to be preferably done at a construction site.
Thanks,
Engineering & Consultancy - Bangalore, Karnataka, India
2004
A. Nitric acid tanks would ideally be made of 316L stainless steel, but a PVC drop-in liner will work if you don't overheat it when adding acid.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
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