). These acids, in conjunction with the sensitized (sensitization occurs due to Chromium Carbide precipitation) microstructure of the stainless steel, lead to rapid intergranular cracking, often causing failure upon restart. Key Requirements of NACE SP0170-2021
The 2021 revision provides sharper thresholds for defining sour environments. While ISO 15156 uses partial pressure of H₂S (>0.05 psi or 0.3 kPa), SP0170-2021 adds specific footnotes for low-temperature and high-pressure scenarios where traditional rules may fail.
(Standard Practice) is the premier global guideline for the protection of austenitic stainless steels and other austenitic alloys from polythionic acid (PTA) stress corrosion cracking (SCC) during a shutdown of refinery equipment . Managed and published by the Association for Materials Protection and Performance (AMPP) —formerly NACE International—this document outlines critical operating parameters and preventive procedures for petroleum refinery materials, inspection, operations, and maintenance personnel. nace sp0170 pdf 2021
For new equipment designs, NACE SP0170 recommends evaluating chemically stabilized grades like 321 or 347 stainless steel, which resist sensitization during high-temperature operations.
What do you have available (to check chloride thresholds)? Share public link While ISO 15156 uses partial pressure of H₂S (>0
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Essential for all 300-series stainless steel in high-sulfur refinery environments. For new equipment designs, NACE SP0170 recommends evaluating
The most direct way to stop the acid from forming is to prevent oxygen from ever touching the internal metal surfaces.
While the 2012 version was heavily used, updates such as NACE SP0170-2018/2021 ensure the methods reflect modern refinery practices.
The official source for all NACE standards.