Nace Sp0170 Pdf 2021 !link! Instant

AMPP - The Association for Materials Protection and Performance Key Mitigation Strategies

NACE SP0170, also known as "Control of Stray Current Corrosion," provides guidelines and best practices for the control of stray-current corrosion that can affect pipelines, metallic structures, and other infrastructure. Stray current corrosion is an electrochemical process that can lead to significant damage and leaks in pipelines and similar structures.

), which can accidentally be triggered if the wash water contains trace chlorides.

When sulfide-containing equipment made of austenitic stainless steel is shut down and exposed to air (oxygen) and moisture (water), a chemical reaction occurs: oxygen and water react with sulfide corrosion products (iron sulfides) to form polythionic acid (H₂SₓO₆). This acid, combined with tensile stresses in the steel (often residual stresses from welding or fabrication), causes intergranular cracking. If not mitigated, this cracking can propagate rapidly, leading to leaks or catastrophic failures when the unit is repressurized. nace sp0170 pdf 2021

The Chemistry of Polythionic Acid Stress Corrosion Cracking (PTA SCC)

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A positive pressure must be maintained continuously throughout the shutdown to prevent ambient air from leaking inward. AMPP - The Association for Materials Protection and

The primary purpose of the document is to prevent rapid, catastrophic intergranular cracking of refinery equipment during downtime, turnaround, and maintenance phases. It outlines precise procedural options—such as nitrogen purging, alkaline washing, and dehumidification—to isolate susceptible stainless steels from the environmental triggers of PTA SCC. Understanding the Threat: Polythionic Acid SCC

Stay safe, stay compliant, and always refer to the most current standard.

, or soda ash) solution mixed with clean, low-chloride water. Sodium nitrate ( NaNO3cap N a cap N cap O sub 3 The Chemistry of Polythionic Acid Stress Corrosion Cracking

"The 2021 version is only for new equipment." Truth: The PDF clearly states that existing equipment can remain in service if it was qualified under a previous revision. However, any repair, modification, or re-rating after the 2021 publication date must comply with the new rules.

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The danger begins the moment the unit is turned off for maintenance. This is where steps in.