S4 · Sensitization and Chloride SCC
Stress Corrosion Cracking (316L/304 Media and Boundary Reference)
Reference of media, grades, and boundary conditions for stress corrosion cracking: 4 common components/processes, including recommended grades, specifications, failure causes, and standards.
Four Sections and Material Reference
| Section / Component | Recommended Grade | Specification / Thickness | Surface | High Delta Ferrite in Welds | Standards |
|---|---|---|---|---|---|
| Intergranular Corrosion (Weld HAZ/Sensitization) | 304/304L/316L | Sensitization range 450–850°C; 316L 650–725°C ×30min | Cr₂₃C₆ precipitates at grain boundaries → chromium depletion Cr<12% → | Low carbon/stabilized (304L/316L/321/347); solution treatment; GB/T 4334 Method E; ASTM A262 Practice B | GB/T 4334—2020; ASTM A262 |
| Chloride Stress Corrosion Cracking (SCC) | 304L/316L | 316L SCC in dilute chlorides at 95–120°C; 40% MgCl₂, 110°C accelerated; CO₂ 0.1MPa, 65°C, Cl⁻ 120,000mg/L, Iscc max 26.8% | Reduce stress, shot peening, duplex steel, higher-nickel alloys | Control Cl⁻ and temperature; avoid concentrated dead corners | GB/T 4334; ASTM G36/G123; NACE MR0175 |
| Alkaline Stress Corrosion Cracking (Alkaline 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 higher-nickel steel | High Delta Ferrite in Welds |
| GB/T 4334; NACE related | 316LSelect Material | Material Selection | Track Welding | Delta ferrite > 3% significantly reduces corrosion resistance | ASTM A249/S7; ASME BPE |
Ferrite mode, retain austenite; selectively dissolve excess austenite in corrosive mediaControl heat input/composition; maximize S7/ASTM A249 ratio 1.25; use ≤10% austenite for crack resistance but<4% for Corrosion ServiceTable: Standard Order
Specify operating conditions instead of grades
- The most common grades in this industry are 316L (4), 304 (2), and 304L (2) — the numbers in parentheses indicate how many sections they apply to, which is the starting point for coating and material ordering.
- Thickness range: 95–850 mm. Thin plates are often formed parts (considering springback and cracking in deep drawing), 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 sections counted in total?
Which type of section is the most common?
Which type of section has the highest failure rate?
For which type of section should I select greater thickness?
The thickness range in the list is 95–850 mm. For thin plates, consider bending and surface finish; for thick plates, consider welding and structural strength. Values for the same location may vary by equipment manufacturer. Re-verify with your drawings or operating conditions.
Related Materials and Adjacent Industries
304Materials and Specifications304LMaterials and Specifications316LMaterials and SpecificationsStainless Fasteners: A2-70/A4-70/A4-80/D Series and Latest StandardsStainless FastenersCarbon Steel Flanges for Seawater Desalination: 2205/2507 Pressure–Temperature–Corrosion LimitsDuplex Flanges and DesalinationSanitary Diaphragm Valves/Sanitary Valves: ASME BPE, Ra, and Temperature LimitsSanitary Valves