Corrosion of 316 ss and Duplex 2205 SS

What would be the expected time to failure of 316 SS piping or Duplex 2205 SS (2 inch) with gypsum slurry flowing through it that contains
12,000 ppm of chloride? The slurry flows at 5 ft/s. How does 316 SS compare in cost to Duplex 2205 SS?
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You do not give the temperature. You do not say if the failure is by erosion, chloride SCC, pitting, weld / weld line attack, or general corrosion. You also do not give the wall thickness or schedule of the piping, or allowable degree of thinning. You do not give the full chemical or physical properties of the slurry.
In practice this sort of thing generally comes down to local experience.
The duplex will be better against SCC, for other mechanisms I would not want to say if there would be a large difference.
Cost will depend on the availability of the sizes and fittings you want. Duplex is often not as available as 316.

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I appreciate the response. Yes, I should have included the other relevant info. I am currently designing the system, and was curious of the failure times of the two materials. The max operating temperature is 130 degree F. We are not sure yet how it would fail, but I imagine it would be SCC or pitting. Any corrosion is a concern. The pipe would be 2 inch schedule 40 with a wall thickness of 0.154 inches. I am unsure of the allowable degree of thinning, but I imagine any thinning over 0.05 inches is undesirable. Are you aware of how much thinning is too much for this thickness of pipe? Gypsum itself is CaSO42H2O which is 172.17 gm. Again, the chloride level is 12,000 ppm. I am operating under the assumption that Duplex would last longer than 316 SS. My question is really what kind of time frame we are looking at. From experience, which we don't have with this situation, will 316 SS last a year or two, or are we looking at a longer time frame? Any help in better understanding the longevity of these materials would be appreciated.
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On Apr 16, 5:43 am, snipped-for-privacy@cinergy.com wrote:

Michael:
My advice would be to first contact the Nickel Institute (www.nickelinstitute.org) in Toronto. They can advise you. Their list of papers contains the following one they can mail you which appears relevant. If it is not, they have three hundred others.
14055 - CORROSION RESISTANCE OF DUPLEX AND 4-6% MO-CONTAINING STAINLESS STEELS IN FGD SCRUBBER ABSORBER SLUGGY ENVIRONMENTS (2000)
By B. S. Phull, W. L. Mathay, R. W. Ross, reprinted from Corrosion 2000 Field tests using spectrum racks were performed in six operating flue gas desulphurization (FGD) scrubber absorbers to determine the corrosion resistance of a 22CR-5Ni duplex alloy, a 4% Mo-containing (Type 317LMN) stainless steel, and a 6%-Mo-containing stainless steel. Type 316 stainless steel and alloy C-276 specimens served as highly- susceptible and highly-resistant controls, respectively. The chloride levels in the six absorber slurry environments ranged from ~9,000 to 70,000 ppm. The pH was typically ~5.5 with the slurry temperature in the 120-154F (~49-68C) range. Duplicate specimens were tested with "loose" and "tight" crevices for two exposure periods.
If you are in a hurry then you also can download it (for a fee) from www.nace.org as conference paper 00578
Pittsburgh Pete
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Thanks for the recommendation. Both sites appear to be helpful in further understanding these materials and our situation.
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I appreciate the response. Yes, I should have included the other relevant info. I am currently designing the system, and was curious of the failure times of the two materials. The max operating temperature is 130 degree F. We are not sure yet how it would fail, but I imagine it would be SCC or pitting. Any corrosion is a concern. The pipe would be 2 inch schedule 40 with a wall thickness of 0.154 inches. I am unsure of the allowable degree of thinning, but I imagine any thinning over 0.05 inches is undesirable. Are you aware of how much thinning is too much for this thickness of pipe? Gypsum itself is CaSO42H2O which is 172.17 gm. Again, the chloride level is 12,000 ppm. I am operating under the assumption that Duplex would last longer than 316 SS. My question is really what kind of time frame we are looking at. From experience, which we don't have with this situation, will 316 SS last a year or two, or are we looking at a longer time frame? Any help in better understanding the longevity of these materials would be appreciated.
You probably need someting better than 316, SCC is a possibility. Timing is unpredictable, but can be quite short, particularly if you get temperature excursions. Papers of the type suggested will give some guide to the possible options for super austenitic /super duplex materials. If prices of totally corrosion resistant alloys are too high, you might want to consider using thicker pipe to give a greater corrosion allowance. I dont want to comment too much as I dont know if the slurry will cause erosion or flow related corrosion on the bends.
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