ppm weight, NACE, material selection

[FC2008]

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

 

[SMF1964]

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%.

 

[FC2008]

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 ?

 

[SJones]

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

 

[FC2008]

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

 

[SJones]

Here's a clue: Na = 23 Cl = 35 !

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[FC2008]

Thanks!

 

[strider6]

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