Nace Sp0170 Pdf 2021 ((better)) Jun 2026

Refinery equipment, particularly in desulfurizing, hydrocracking, and hydrotreating units, often uses austenitic stainless steels because of their high-temperature strength and corrosion resistance. However, these materials are highly susceptible to . PTA SCC occurs when: NACE SP0170-2018

When utilizing an alkaline wash, use chloride-free or low-chloride water. High-chloride water can inadvertently trigger Chloride Stress Corrosion Cracking (Cl-SCC).

Note: Ensure you are obtaining the latest active revision, which may be labeled 2018 or updated with technical amendments labeled through 2021. Key Takeaways

: This standard is crucial for industries that have extensive metallic infrastructures, such as oil and gas, chemical processing, and power generation. Professionals involved in corrosion management, inspection, and maintenance within these sectors would find it particularly useful.

PTA is not typically present during normal refinery operations. Instead, it forms during shutdowns or turnarounds when the following sequence occurs: nace sp0170 pdf 2021

While NACE International merged with the Society for Protective Coatings (SSPC) in 2021 to form the , the most recent active version of this specific standard was released in 2018 . Key Purpose and Scope

NACE SP0170-2018 remains the active standard for protecting austenitic stainless steels from polythionic acid stress corrosion cracking (PTA SCC) during refinery shutdowns as of 2021, focusing on nitrogen purging and alkaline washing to mitigate risks. The standard, now managed by AMPP, outlines critical procedures for preventing corrosion in sensitized austenitic alloys common in hydrotreating and cracking units. Access the standard through the ANSI Webstore .

: These acids are relentless. They seek out "sensitized" areas—grain boundaries in the metal weakened by heat—and cause rapid, catastrophic cracking. A pipe that looked perfect yesterday can literally shatter today.

Polythionic acid stress corrosion cracking (PTA SCC) is a significant threat to the integrity of refinery equipment, particularly during shutdown, startup, and turnaround operations. , now managed by AMPP (Association for Materials Protection and Performance) , is the standard practice for mitigating this risk. typical cycles are 5–8 years.

NACE SP0170 is critical for preventing sudden failures during maintenance.

The system must remain pressurized under nitrogen for the entire shutdown. This strategy is perfect for units that do not require internal inspections or catalyst changes. 2. Alkaline Chemical Washing (Neutralization)

Displacing oxygen by maintaining a continuous, dry nitrogen blanket inside the equipment. The standard outlines specific pressure and purity levels required to maintain this barrier.

Essential for all 300-series stainless steel in high-sulfur refinery environments. as of 2025

: Maintaining low relative humidity to prevent the condensation necessary for acid formation.

: Maintaining the relative humidity below a critical threshold (typically 40%) to ensure liquid water cannot form. Pro-Tip for Operators

However, as of 2025, remains the active, current standard. A 2024 revision has not been released; typical cycles are 5–8 years.