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ppm weight, NACE, material selection

ppm weight, NACE, material selection

ppm weight, NACE, material selection

(OP)
Hey,
I have been given the salt content in formation water (as NaCl). The value is 290000 ppm (weight)
I have also been given the H2S content as 7000 ppm (volume I quess).

NACE MR0175 says to divide the 7000ppm by 10000 to get the mol%. Does this work for NaCl as well?

I'm trying to select a material that would hold up in these conditions..

Thank you

RE: ppm weight, NACE, material selection

I suspect all of your content/concentrations are ppm by weight.

10,000 ppm is 1% by weight, so 290000 ppm weight is 29% (this is a slurry, then, or did you hit an extra 0 in your typing?), 7000 ppm is 0.7%.

RE: ppm weight, NACE, material selection

(OP)
Actually, 290 000 is correct. I thought the levels were a bit too high, but that's the data from the customer..

So, NACE is actually saying that wt% H2S = mol% H2S ?

RE: ppm weight, NACE, material selection

No - it doesn't work for NaCl when using ISO 15156 because it defines acceptable materials in terms of chloride ppm only.  You will need to convert ppm NaCl to ppm Cl-.  Also, you will be working in partial pressure terms of H2S so why bother converting the H2S units before deriving a partial pressure?

Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
 

RE: ppm weight, NACE, material selection

(OP)
The reason I convert is simply because the equation for partial pressure in nace asks for input in the form of mol% H2S.

I'm not sure how to convert ppm NaCl to Cl- though, should have payed more attention in chemistry class I quess.

Thanks

RE: ppm weight, NACE, material selection

(OP)
Thanks!

RE: ppm weight, NACE, material selection

one thing you've to paid attention is that the H2S content is in the gas phase and not the total. Sometimes they give  you a value for gas+liquid, but you must use the conc in the gas phase.

S.

Corrosion Prevention & Corrosion Control
 

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