Regarding a previous Ask the Expert Q & A: What is a suitable coating or a MOC that can stand HF at 100 degrees C? Additional details about HF: Concentration: 60% Composition: 15% Operating temperature as I said before is around 100 deg C. Current MOC of the vessel is SS316 ti. Thickness reduced by 1 mm due to the corrosive action of HF and I am still continuing a search albeit futile for a suitable MOC or a coating material. Referring to the suggestion of Hastelloy C-276, on the same lines, I have come to know that Hastelloy C 2000 has comparatively better properties. But the main problem would be cost optimization, since the cost of the material, fabrication, installation costs, etc. would be too high. On coating materials, I have read on the DuPont website on the seemingly excellent mechanical and chemical properties of ETFE or commonly known by its trade name Tefzel, though I am not sure about its successful contribution in this scenario.
Topic: How can I find an appropriate material of construction at a cost I can afford?26 October 2010
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Brian Dalder Forum Moderator 179 Posts
Re: How can I find an appropriate material of construction at a cost I can afford?26 October 2010 at 1:29pmWelcome to my world! The best, and in some cases only, solutions often come with a high price tag. Many plastic linings have been used successfully for concentrated HF but in your case the high temperature is an issue. The upper temperature limit is often determined not by diffusion of HF nor the chemical and thermal stability of the polymer, but by the complex stress patterns that develop during lining and in service as a result of the large difference in thermal expansion between the plastic lining and the shell. For glass-backed or polyester backed resins used in lining carbon steel vessels, the suggested temperature limit is 60 degrees C for FEP, PFA, ECTFE, and PVDF. For HF concentrations higher than 48%, the temperature limit is even lower. Bonded and baked linings have been used with some success but due to the aforementioned thermal expansion issues such linings are not recommended above 80 degrees C. You might want to try contacting an HF manufacturer for some MOC suggestions. Good luck finding an appropriate material of construction at a cost you can afford.