S4 · Sensitization and Chloride SCC
Stress Corrosion Cracking (316L/304 Environments and Limits List)
List the environments, grades, and limiting conditions related to stress corrosion cracking: 4 typical components/processes, including recommended grades, specifications, failure causes, and standards.
Four Parts and Material List
| Part / Component | Recommended Grade | Specification / Thickness | Surface | Excessive delta-ferrite in welds | Standards |
|---|---|---|---|---|---|
| Intergranular Corrosion (Weld HAZ/Sensitization) | 304/304L/316L | Sensitization range 450–850°C; 316L 650–725°C ×30 min | Cr₂₃C₆ precipitation along grain boundaries → chromium depletion Cr<12% → | Low-carbon/stabilized (304L/316L/321/347); solution heat treatment; GB/T 4334 Method E; ASTM A262 Method B | GB/T 4334—2020; ASTM A262 |
| Chloride Stress Corrosion Cracking (SCC) | 304L/316L | 316L SCC in dilute chlorides at 95–120°C; accelerated in 40% MgCl₂ at 110°C; CO₂ 0.1 MPa, 65°C, Cl⁻ 120,000 mg/L, Iscc max 26.8% | Reduce stress, shot peening, duplex steel, high-nickel alloys | Control Cl⁻ and temperature; avoid tight dead corners | GB/T 4334; ASTM G36/G123; NACE MR0175 |
| Alkali Stress Corrosion Cracking (alkali embrittlement) | 304/316L | High-concentration NaOH + high temperature + tensile stress | Chloride selective corrosion near grain boundaries + stress | Post-weld stress relief; limit alkali concentration/temperature; select duplex steel or high-nickel | High delta-ferrite in welds |
| GB/T 4334; NACE related | 316LSelect Material | Material Selection | Welding Follow-Up | Delta ferrite > 3% significantly reduces corrosion resistance | ASTM A249/S7; ASME BPE |
Ferritic Mode, Preserve Austenite; Selectively Dissolve Excess Austenite in Corrosive EnvironmentsControl Heat Input/Composition; Maximize S7/ASTM A249 Ratio to 1.25; Use ≤10% Austenite for Crack Resistance but<4% for Corrosion ServiceTable: Standard Configuration
Specify Service Conditions Instead of Grades
- The most common grades in this sector are 316L (4), 304 (2), and 304L (2) — the numbers in parentheses indicate how many parts they apply to; this is a starting point for quoting and material ordering.
- Thickness range: 95–850 mm. Thin plates are typically formed parts (considering springback and deep-drawing cracking), while thick plates are typically welded structures (considering heat input and sensitization).
What are the common questions?
Which stainless steel is most used for the temperature–time–concentration limits of sensitization and chloride-ion stress corrosion cracking?
How many times are these 4 parts counted in total?
Which is the most common part type?
Which part type has the highest failure rate?
For which part type should I choose a thicker gauge?
The thickness range in the list is 95–850 mm. For thin plates, consider bending and surface quality; for thick plates, consider welding and structural strength. Values may vary by equipment manufacturer for the same location. Recheck against your drawing or operating conditions.
Related Materials and Adjacent Industries
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