Is UNS N08825 Resistant to Sulfur?

Introduction

This page addresses an inquiry about whether UNS N08825 is resistant to sulfur without limitations on pH, temperature, H₂S partial pressure, and chloride. The remarks column in Table A.13 states that some combinations of values for these parameters might not be acceptable, and the inquiry seeks clarification on how to interpret this.

Answer

Table A.14 indicates that Type 4c alloys, including UNS N08825, are currently resistant to sulfur under any combination of conditions up to and including 132°C (270°F). However, recent discussions in the Maintenance Panel have identified that the term “”sulfur resistant”” is not adequate in itself, and defining levels of resistance is underway through three test techniques and resultant three groups.

Environmental Limits

The user is cautioned that although no environmental limits have currently been defined below 132°C for UNS N08825, some combinations of parameters, including elemental sulfur form, may not be acceptable.

Reference

This question pertains to NACE MR0175/ISO 15156-3 A.4, Table A.12, and the reference cited is ISO 15156 Maintenance Panel Inquiry #2015-08.