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304 ss heat exchanger


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#1 Guest_Vern Ellis_*

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Posted 11 April 2012 - 12:20 AM

I have a customer with a ss 304 heat exchanger which they did not chemically treat until about 2 years ago. One side is process, the outside of the tubes is recirculation cooling water. The tubes have 1/8" of deposit, analysis not back yet but it probably is some type of silica. This deposit is slowly dissolving but they want to hurry it up. If it is silica, can it be removed with something like hydrofluoric acid? If so should a corrosion inhibitor be used? Thanks for the forum Dick. Vern Ellis, CWT, WaterTech Specialties, Inc.

#2 Guest_dick@richardhouriganinc.com_*

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Posted 11 April 2012 - 11:30 AM

Vern, I cannot imagine a worse scenario. Hydrofluoric acid is the best possible choice for Silica and probably the worst possible choice for 304 Stainless Steel. If that is your only option you definitely would need an excellent corrosion inhibitor. The best acid to use in cleaning 304 Stainless Steel is Nitric Acid, but that will not attack the silica. Immediately, I don't have an answer, but I have a number of books here that I can review.

My thoughts are this:
  • Perhaps, when we get the complete analysis back, you will find that it is NOT pure silica. There may be some minor components of the deposit that you can attack. Most deposits are a matrix of mixed minerals, bioslime, etc.
  • Next, I will look for a corrosion inhibitor for the 304 Stainless if it turns out that hydrofluoric acid must be used.
  • Another water treater may have already encountered this problem and be willing to post their solution here.
  • You need to warn your customer that the heat exchanger could possibly be damaged by any attempted cleaning.


#3 Guest_Vern Ellis_*

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Posted 12 April 2012 - 01:25 AM

Vern, I cannot imagine a worse scenario. Hydrofluoric acid is the best possible choice for Silica and probably the worst possible choice for 304 Stainless Steel. If that is your only option you definitely would need an excellent corrosion inhibitor. The best acid to use in cleaning 304 Stainless Steel is Nitric Acid, but that will not attack the silica. Immediately, I don't have an answer, but I have a number of books here that I can review.

My thoughts are this:

  • Perhaps, when we get the complete analysis back, you will find that it is NOT pure silica. There may be some minor components of the deposit that you can attack. Most deposits are a matrix of mixed minerals, bioslime, etc.
  • Next, I will look for a corrosion inhibitor for the 304 Stainless if it turns out that hydrofluoric acid must be used.
  • Another water treater may have already encountered this problem and be willing to post their solution here.
  • You need to warn your customer that the heat exchanger could possibly be damaged by any attempted cleaning.


Thanks Dick. When I get the analysis back I will post it here. Vern Ellis

#4 Guest_dick@richardhouriganinc.com_*

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Posted 12 April 2012 - 11:55 AM

Okay, Vern. Perhaps you will get lucky, and there will be something better to work with.



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