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What are the NACE MR0175 environmental limits for UNS S31254?

Question: NACE Standard MR0175-2003 has two different highly alloyed austenitic SS families, one (Paragraph 4.4) with Ni% + 2 Mo% >30 (and Mo>=2%) and one (Paragraph 4.5) with PREN >40. Both have two different ranges for temperature, partial H2S partial pressure, and maximum chloride content. Which environmental limits have to be used for materials applicable for both categories like UNS S31254?

 

Answer:

If UNS S31254 has a PREN >40, then the less restrictive environmental limits in Paragraph 4.5 apply.

This question is in relation to NACE MR0175/ISO 15156-3  A.3.2, Table A.8 and Table A.9

Reference: ISO 15156 Maintenance Panel Inquiry #2003-19 Q1a

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