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Titanium heaters in chromic acid solution
We use titanium sheathed heaters in 122-15% chromic acid containing free iron radicals. Temperature maintained is 70 Deg C.
We experience rapid corrosion of the wetted titanium tubes. Life experienced is 4-5 months when continuously immersed.
Kindly suggest ways to improve life.
regards
HEATER MANUFACTURER - MUMBAI, INDIA
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According to the chemical resistance charts and prior experience the only electric heater shells that stand up to chromic acid/sulfate plating solutions are those with an outer shell of Quartz or Teflon (PTFE).
Gene Packman- Great Neck, NY
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Hi Manoj
Wouldn't PVDF be a better material? Superb in acids. OK for max l40 C
... but doesn't like high pH.
| Freeman Newton - White Rock, British Columbia, Canada | Ed. note: Please keep Freeman in your thoughts & prayers. Message from Freeman, Dec. 2010 |
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As we all know, chromic acid is disgusting stuff that creeps everywhere and attacks just about everything. Gene and Freeman are right in suggesting a polymeric or ceramic coating to protect the heaters - pH will not be an issue because chromic acid has such a low pH that is almost falls off the scale!
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Trevor Crichton R&D practical scientist The Pheasantries - Chesham, U.K. |
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Use lead bonded heater for chrome solution.
Salim- Saudi Arabia
First of two simultaneous responses -- +++++
From the life of your Ti heaters, I will guess that you are using full rated heat in your heaters. For longer life, use derated heaters and for even longer life, use double derated heaters.
James Watts- Navarre, Florida
Second of two simultaneous responses -- +++++
Trev.
I didn't infer a 'coated' pvdf heat exchanger ... but a solid PVDF unit.
Disadvantages? Heat transfer is slower than metals. Advantages....ENORMOUS ....I sold one to a chrome customer who, as far as I know, is still using it.
Ptfe costs an arm and a leg. Mind you, Salim's suggestion of lead sounds very good ... and probably less expensive than pvdf.
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| Freeman Newton - White Rock, British Columbia, Canada |