Lower limit of H2S partial pressure in NACE MR0175/ISO 15156 for CRA material

[IxoraOhm]

Hello,
Good day to all,

I would like to know, what is the Lower limit of H2S partial pressure in NACE MR0175/ISO 15156 for CRA material?

It is stated that for carbon and low alloy steel, SSC is not expected unless the H2S partial pressure exceeds 0.3 kPa (sour service)

However, for CRA material eg; austenitic stainless steel, the reference as per Table A.2 (Environmental and materials limits for austenitic stainless steels used for any
equipment or components) states a max kPa threshold, but there is no lower limit, to approve the use of a non-sour grade certified SS316/SS316L material in an environment with even small traces (mol%) of H2S.
Non- sour grade certified SS316/SS316L material operating within the environment limit is also governed by manufacturing conditions as stated in footnote (a) and (b) in Table A.2.

Does this mean, any SS316 /SS316L material will require to be NACE certified unless proven to have a fluid composition of 0 mol% H2S?

Thank you.

 

[SJones]

Yes.

Steve Jones
Corrosion Management Consultant

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

All answers are personal opinions only and are in no way connected with any employer.

 

[SJones]

Although,please bear in mind that there is no such thing as "NACE certified."

Steve Jones
Corrosion Management Consultant

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

All answers are personal opinions only and are in no way connected with any employer.

 

[IxoraOhm]

Hi SJones,

Thank you for the explanation.

 

[SJones]

Apologies for providing a cursory answer. Always difficult to achieve much detail from a smartphone. If you are looking for some more depth behind my answer, it can be found in the Inquiries & Interpretations document.

Steve Jones
Corrosion Management Consultant

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

All answers are personal opinions only and are in no way connected with any employer.

 

[SJones]

https://isotc.iso.org/livelink/live...c=ll&objId=3340364&objAction=browse&sort=name

MP Inquiry #2009-11, Part 2, page 25

Steve Jones
Corrosion Management Consultant

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

All answers are personal opinions only and are in no way connected with any employer.

 

[IxoraOhm]

Hi Sjones,

Thank you for the link. I will look into it in detail.

I was under the idea that the FCC structure of austenitic stainless steel could perhaps give it a better resistance to cracking in terms of hydrogen diffusion when compared to BCC structure. As such a lower limit of H2S partial pressure should also be applicable for CRA, if there is a tolerance limit of 0.3kPa for carbon steel and low alloy steel.

I am however not clear on the statement "Due to the wide range of environmental cracking resistance of CRAs ..." as stated in MP INQUIRY #2009-11, Part 2.

Does this refer to other environment factors beyond temperature, H2S partial pressure and chloride effects?

Please advice. Thank you.

 

[SJones]

There is no "tolerance limit of 0.3 kPa" for carbon steel either - see MP Inquiry #2009-18. Also, HIC can occur with a partial pressure below 0.3 kPa, and HIC is addressed by ISO 15156-2.

No, the reply #2009-11 Part 2 does not refer to environment factors. It refers to a material characteristic: environmental cracking resistance.

Steve Jones
Corrosion Management Consultant

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

All answers are personal opinions only and are in no way connected with any employer.

 

[IxoraOhm]

Hi SJones,

Noted. Thank you for the explanation and information sharing.

 

[CH. Lee]

or would one specify that as NACE-complied SS316L?

which means the steel to fulfill at least this - Solution annealed, no cold work to enhance properties, hardness up to 22
HRC; as long as there is present of H2S, no matter how low

thx

 

[Chumpes]

if you are in wet H2S service (possibility of free water and H2S) then your stainless steel 316L should comply to one or another NACE standard (MR0103 or MR0175), i.e. limited hardness, delivery heat treatment, cold work, chemical addition, ... which is not a big deal for SS 316L that can be easily compliant.