NACE SP0170 provides essential protocols for protecting austenitic stainless steels from polythionic acid stress corrosion cracking (PTA-SCC) during refinery shutdowns. The standard details mitigation strategies, including nitrogen purging, alkaline washing, and dehumidification to prevent catastrophic equipment failure caused by acid formation. The official, copyrighted PDF can be purchased through the AMPP store.
In some scenarios, maintaining a continuous purge of extremely dry air (with a dew point typically below -40°C/-40°F) is acceptable. Keeping the relative humidity near zero prevents the chemical reaction required to generate the acid. Material Selection as a Long-Term Solution
You need both standards. MR0175 tells you which material to buy. SP0170 tells you how to protect that material when you shut down the unit. nace sp0170 pdf
Two years ago, a rival engineer had specified a standard epoxy coating under the saddle. But SP0170, buried in a non-mandatory appendix most people ignored, had a footnote: “For elevated temperature service above 400°F, mechanical isolation is preferred over coatings alone.”
In conclusion, NACE SP0170 plays a critical role in the protection of reinforced concrete structures from corrosion. By following the guidelines outlined in the standard, engineers, contractors, and asset owners can ensure the effective application of cathodic protection systems, thereby enhancing the durability and safety of infrastructure. In some scenarios, maintaining a continuous purge of
The NACE SP0170 PDF is an indispensable tool for refinery engineers, inspectors, and fabricators. It provides a proven, safe method to prevent catastrophic weld corrosion in high-temperature sulfur service. However, resist the temptation of free, shady downloads. Purchase the official standard from AMPP to ensure you have the latest, legally compliant, and complete information.
NACE SP0170 is designed for times when sulfide-coated equipment is opened to the air. MR0175 tells you which material to buy
The application of NACE SP0170 is vital for several reasons:
When austenitic stainless steels (such as 304 or 316) are exposed to temperatures between 425°C and 815°C (800°F to 1500°F), chromium carbides precipitate along the grain boundaries. This depletes the adjacent zones of chromium, leaving the grain boundaries vulnerable to localized corrosion.
If you’d like, I can:
The alkaline wash neutralizes any polythionic acid as soon as it forms.