S4 · Sensitization & Chloride SCC
Stress Corrosion Cracking (Media and 316L/304 Limit Table)
List the media, grades, and limiting conditions associated with Stress Corrosion Cracking: 4 typical components/processes, including recommended grades, specifications, failure causes, and standards.
Four Sections and Material List
| Section / Component | Recommended Grade | Specification / Thickness | Surface | Benefits of Delta Ferrite in Welds | Standard |
|---|---|---|---|---|---|
| Intergranular Corrosion (Weld HAZ/Sensitization) | 304/304L/316L | Sensitization range 450–850°C; 316L 650–725°C × 30 min | Cr₂₃C₆ precipitates along grain boundaries → chromium depletion (Cr)<12% → | Low carbon/stabilized (304L/316L/321/347); solution treatment; GB/T 4334 E method; ASTM A262 B method | GB/T 4334—2020; ASTM A262 |
| Chloride Stress Corrosion Cracking (SCC) | 304L/316L | SCC of 316L in dilute chloride at 95–120°C; 40% MgCl₂, accelerated 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 concentrated dead zones | GB/T 4334; ASTM G36/G123; NACE MR0175 |
| Alkali Stress Corrosion Cracking (Caustic Embrittlement) | 304/316L | High NaOH Concentration + High Temperature + Tensile Stress | Selective chloride corrosion near grain boundaries + stress | Post-weld stress relief; limit alkali concentration/temperature; choose duplex or high-nickel steel | High delta ferrite in welds |
| GB/T 4334; NACE-related | 316LSelect Material | Material Selection | Welding Traceability | 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 Configurations
Define Service Conditions Rather Than Specifying Grade
- The most common grades in this industry are 316L (4), 304 (2), and 304L (2) — the numbers in parentheses indicate how many parts each applies to, serving as a starting point for quoting and material ordering.
- Thickness range: 95–850 mm. Thin plates are often formed pieces (considering bend-back and deep-drawing cracking), while thick plates are typically welded structures (considering heat input and sensitization).
What questions are commonly asked?
Which stainless steel is most widely used for temperature-time-concentration limits of sensitization and chloride-ion stress corrosion cracking?
How many times are these 4 parts counted in total?
What 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 finish; for thick plates, consider welding and structural strength. Values may vary between equipment manufacturers for the same location. Recheck against your drawings or operating conditions.
Related Materials & Adjacent Industries
304Materials & Specifications304LMaterials & Specifications316LMaterials & SpecificationsStainless Fasteners: A2-70/A4-70/A4-80/D Series and Latest StandardsStainless FastenersCarbon Steel Flanges for Seawater Desalination: Pressure-Temperature-Corrosion Limits of 2205/2507Duplex & Desalination FlangesHygienic Diaphragm/Sanitary Valves: ASME BPE, Ra, and Temperature LimitsSanitary Valves