S4 · Sensitization and Chloride SCC
Stress Corrosion Cracking (Environments and Limits for 316L/304)
A list of environments, grades, and limiting conditions related to stress corrosion cracking: 4 typical components/processes, including recommended grades, specifications, failure causes, and standards.
Four Sections and Material List
| Part / Component | Recommended Grade | Specification / Thickness | Surface | Excess Delta Ferrite in Weld Seams | Standards |
|---|---|---|---|---|---|
| Intergranular Corrosion (Weld HAZ / Sensitization) | 304/304L/316L | Sensitization range 450–850°C; 316L 650–725°C ×30min | Cr₂₃C₆ precipitation at grain boundaries → chromium depletion (Cr)<12% → | Low-carbon/stabilized (304L/316L/321/347); solution heat treatment; GB/T 4334 E method; ASTM A262 B method | GB/T 4334—2020; ASTM A262 |
| Chloride-Induced 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% | Stress relief, shot peening, duplex steel, high-nickel alloys | Control Cl⁻ and temperature; avoid concentrated stagnant zones | GB/T 4334; ASTM G36/G123; NACE MR0175 |
| Alkaline Stress Corrosion Cracking (Caustic Embrittlement) | 304/316L | High-concentration NaOH + high temperature + tensile stress | Selective chloride corrosion near grain boundaries + stress | Post-weld stress relief; limit alkali concentration/temperature; select duplex steel or high-nickel alloy | High delta ferrite content in weld seams |
| GB/T 4334; related to NACE | 316LSelect Material | Material Selection | Weld Tracking | 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 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 industry are 316L (4), 304 (2), and 304L (2) — the numbers in parentheses indicate how many parts they apply to, as a starting point for quoting and material ordering.
- Thickness range: 95–850 mm. Thin plates are often formed parts (accounting for springback and cracking during deep drawing), while thick plates are typically welded structures (accounting for heat input and sensitization).
What Are the Common Questions?
Which stainless steel is most commonly 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 part type is the most common?
Which part type has the highest failure rate?
For which part type should a greater thickness be selected?
The thickness range in the list is 95–850 mm. For thin plates, consider bending and surface treatment; for thick plates, consider welding and structural strength. Values may vary by equipment manufacturer for the same location. Verify against your drawing or operating conditions.
Related Materials and Adjacent Industries
304Material and Specifications304LMaterial and Specifications316LMaterial and SpecificationsStainless Steel Fasteners: A2-70/A4-70/A4-80/D Series and Latest StandardsStainless Steel FastenersCarbon Steel Flanges for Seawater Desalination: Pressure-Temperature-Corrosion Limits for 2205/2507Duplex Flanges and DesalinationHygienic Diaphragm Valves/Clean Valves: ASME BPE, Ra, and Temperature LimitsSanitary Valves