Understanding NACE Standard MR0175-2003

The Two Highly Alloyed Austenitic Stainless Steel Families

This page addresses an inquiry regarding NACE Standard MR0175-2003, which has two highly alloyed austenitic stainless steel families. Paragraph 4.4 covers the family with Ni% + 2 Mo% >30 (and Mo>=2%), while Paragraph 4.5 covers the family with PREN >40. Both families have differing ranges for temperature, partial H₂S partial pressure, and maximum chloride content.

Clarification on Environmental Limits

The inquiry seeks clarification on which environmental limits to use for materials applicable to both categories, such as UNS S31254. The answer provided explains that if UNS S31254 has a PREN >40, then the less restrictive environmental limits in Paragraph 4.5 apply.

Reference and Further Reading

This question pertains to NACE MR0175/ISO 15156-3 A.3.2, Table A.8 and Table A.9, and the reference cited is ISO 15156 Maintenance Panel Inquiry #2003-19 Q1a. For more information on NACE Standard MR0175-2003, please refer to the official documentation.