NACE SP0170 (Standard Practice) provides critical guidelines for the protection of austenitic stainless steels and other austenitic alloys from Polythionic Acid (PTA) Stress Corrosion Cracking (SCC) during refinery equipment shutdowns. ANSI Webstore Core Purpose and Mechanism
While primarily aimed at 300-series stainless steel (e.g., 304, 316), the standard also covers other austenitic alloys prone to sensitization.
Austenitic stainless steels are highly valued in the refining, petrochemical, and chemical processing industries for their exceptional corrosion resistance and high-temperature strength. However, these alloys face a severe and rapid degradation mechanism during maintenance shutdowns: Polythionic Acid Stress Corrosion Cracking (PTA-SCC). To combat this specific threat, the Association for Materials Protection and Performance (AMPP)—formerly NACE International—published the standard practice , titled "Protection of Austenitic Stainless Steels and Other Austenitic Alloys from Polythionic Acid Stress Corrosion Cracking During Shutdown of Refinery Equipment."
Your PDF of SP0170 is the requirement; your shutdown report with pH logs, drying times, and photos is the proof of compliance.
The water used to blend the soda ash solution must be strictly monitored for chloride content (typically kept below 50 ppm, or ideally lower) to avoid introducing a secondary risk of chloride-induced stress corrosion cracking. nace sp0170 pdf
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: The standard includes recommendations for testing and commissioning CP systems to verify their performance.
It specifically targets , the shiny, high-grade metals we assume are invincible.
Corrosion is a major concern in various industries, including oil and gas, chemical processing, and construction. It can lead to significant financial losses, safety risks, and environmental damage. To mitigate these risks, industries rely on standards and guidelines for corrosion prevention and control. One such standard is NACE SP0170, a widely adopted guideline for corrosion prevention in the oil and gas industry. In this article, we will discuss the significance of NACE SP0170 PDF and its role in corrosion prevention and control. However, these alloys face a severe and rapid
During a shutdown, air (oxygen) and moisture (water) enter the system, reacting with sulfides to form polythionic acid ( H2SxO6cap H sub 2 cap S sub x cap O sub 6
NACE SP0170 PDF: Protecting Refinery Equipment from Polythionic Acid Stress Corrosion Cracking
Searching for the is common among three groups of professionals:
Guidance on choosing resistant materials and specific fabrication practices. She felt her stomach drop
). This depletes the immediate adjacent areas of chromium, dropping the local chromium content below the 12% threshold required to maintain a passive oxide layer. The grain boundaries become highly localized zones of low corrosion resistance. 2. Environmental Trigger (Polythionic Acid Formation)
Maya was a corrosion engineer newly moved to coastal operations and still learning to read standards the way older hands did — not only as rules but as stories about what had failed before. She read SP0170 the way one reads a map after a shipwreck: cataloguing measurement techniques, specifying coupon placements, describing stray current mitigation, listing allowable potential ranges. Each clause was precise, written for auditors and inspectors. It told her where to put probes and how to interpret millivolt shifts. It did not tell her where the leaks began.
In the world of oil and gas, refining, and chemical processing, material failure is not just an economic issue—it is a safety and environmental catastrophe waiting to happen. One of the most insidious threats to high-performance alloys is and Chloride Stress Corrosion Cracking (CSCC) . To combat this, engineers and integrity managers turn to a critical standard: NACE SP0170 .