Table of Contents. 1. General. 2. Selection of Materials and Fabrication. Practices. 3. Dry Nitrogen Purging to Exclude Oxygen. 4. Intertek Inform
Austenitic stainless steels are the backbone of the refining, petrochemical, and chemical processing industries. These materials offer exceptional resistance to high-temperature oxidation and general corrosion. However, during refinery shutdowns and maintenance turnarounds, these premium alloys face a catastrophic degradation mechanism: Polythionic Acid Stress Corrosion Cracking (PTA-SCC).
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 .
Corrosion waits for no one. A refinery shutdown is a vulnerable time for austenitic stainless steel equipment. Without the guidance found in , you risk irreversible Stress Corrosion Cracking that could lead to costly repairs or, worse, safety hazards.
A corrosion inhibitor (typically a nitrate-based compound) is added to the solution to prevent chloride stress corrosion cracking, as soda ash solutions can sometimes concentrate chlorides. nace sp0170 pdf
NACE SP0170 (formerly designated before the society renamed its “Recommended Practices” to “Standards Practices”) is titled: “Protection of Austenitic Stainless Steels and Other Austenitic Alloys from Polythionic Acid Stress Corrosion Cracking (SCC) During Shutdowns and Start-ups.”
Air introduced into the system must be dehumidified to a very low dew point (typically below -18°C or 0°F).
In simple terms: When you have a carbon steel pipe or vessel handling hot, sulfur-containing hydrocarbons (typical in crude units or hydrotreaters), the weld area is chemically different from the base metal. It corrodes much faster. NACE SP0170 tells you how to stop that—usually by applying a corrosion-resistant alloy (CRA) weld overlay.
Purge system with dry hydrogen/nitrogen to remove volatile hydrocarbons. Safety and surface preparation. Table of Contents
: Special considerations for refinery reactors.
The solution must completely wet all internal surfaces via circulation or spraying before the equipment is exposed to air. The alkaline film must remain on the surface throughout the entire shutdown; if it washes away, it must be reapplied. 4. Use of Chemically Stabilized or Low-Carbon Alloys
Digital copies are sold via the ANSI Webstore and other distributors like Intertek Inform .
“I’m telling you,” Marina said, finally leaning back, “that nobody reads the boring standards until something’s on fire. But the people who wrote SP0170 in 2017—they were thinking about this exact Tuesday night. They already saved your line. I’m just reading the instructions.” “I’m telling you
Marina Vasquez was a corrosion engineer, which meant she spent most of her time thinking about things falling apart. Metal rusting, pipelines thinning, bolts fusing into useless lumps of iron oxide. Her job was to slow down entropy.
This standard was first published in 1970 as a recommended practice (RP), designated as . It has since been updated several times, evolving to its current form as a standard practice (SP) numbered SP0170. Today, the standard is owned and maintained by Task Group 173 of the Association for Materials Protection and Performance (AMPP) .
Ensure that any water used for rinsing or chemical blending contains less than 50 ppm chlorides to prevent secondary cracking modes.