: Keeping oxygen out by maintaining a positive pressure of dry nitrogen within the equipment.
In a refinery environment, equipment made from austenitic stainless steels (like 300-series alloys) often develops sulfide scales on internal surfaces during operation. When the unit is shut down and opened, these sulfides react with moisture and oxygen in the air to form . These acids can cause rapid, catastrophic cracking in sensitized metals—sometimes within hours of exposure. Key Mitigation Strategies in SP0170
NACE standards are copyrighted and generally require purchase. You can obtain the most recent version (reaffirmed in 2018) as a downloadable PDF through the following authorized platforms:
The standard outlines several mandatory and recommended procedures to prevent PTA formation or neutralize it before damage occurs: