The 2018 revision updated the previous version to reflect better understanding of materials sensitization and improved application techniques for alkaline cleaners. The focus remains on providing minimum requirements to ensure integrity, though many plants follow more stringent internal procedures based on this standard.
Ensure surfaces remain coated with the soda ash residue during air exposure. Continuous chemical protection.
Formerly known as , the full title of this standard is: “Protection of Austenitic Stainless Steels and Other Austenitic Alloys from Polythionic Acid Stress Corrosion Cracking During Shutdown of Refinery Equipment.”
This method is a specialized form of purging that uses dry air to prevent the formation of liquid water. While seemingly contradictory to nitrogen purging, which uses an inert gas, dry air purging focuses on the second critical condition for SCC: the presence of a liquid water phase. This method relies on maintaining the relative humidity within the equipment below a certain threshold so that free water cannot condense on the metal surfaces. This denies the electrolyte necessary for the electrochemical corrosion reaction to proceed . nace sp0170 pdf
Would you like to know more about cathodic protection systems or corrosion prevention in general?
If utilizing an alkaline wash, pre-mix the soda ash solution using demineralized or low-chloride water. Ensure corrosion inhibitors are added if specified.
: Keeping oxygen out by maintaining a positive pressure of dry nitrogen within the equipment. The 2018 revision updated the previous version to
Understanding the document's evolution is important when sourcing a PDF, as using an outdated version can have severe consequences.
The standard outlines several mandatory and recommended procedures to prevent PTA formation or neutralize it before damage occurs:
You can buy the latest NACE SP0170-2018 PDF directly from the AMPP Store or ANSI Webstore . Continuous chemical protection
In the demanding environment of oil and gas refining, ensuring the integrity of equipment during shutdowns is critical. One of the most insidious threats to austenitic stainless steels and other austenitic alloys is , a phenomenon that occurs primarily during shutdown, start-up, or standby periods.
The technical standard , officially titled "Protection of Austenitic Stainless Steels and Other Austenitic Alloys from Polythionic Acid Stress Corrosion Cracking During a Shutdown of Refinery Equipment," is a foundational document for asset integrity in the petroleum refining industry. Maintained by the Association for Materials Protection and Performance (AMPP) , this standard maps out exact operational workflows to shield critical components from devastating, rapid structural failures during planned downtimes.
It was originally issued in 1970 (as RP0170) and has undergone several revisions to include modern refinery practices. NACE SP0170-2018
Engineers realized they couldn't just use "stronger" steel. In sour environments, harder steel actually cracks faster. They needed a playbook for protection.
Surfaces are sprayed or flushed with an alkaline solution, such as soda ash ( Na2CO3cap N a sub 2 cap C cap O sub 3 ), ammonium hydroxide ( NH4OHcap N cap H sub 4 cap O cap H