S4 · Sensitization & Chloride SCC
Stress Corrosion (316L/304 Media and Limit Values List)
List of media, steel grades and limit conditions related to stress corrosion: 4 typical components/processes, including recommended steel grades, specifications, causes of failure and standards.
Four Parts and Material List
| Part / Component | Recommended Steel 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 ×30min | Cr₂₃C₆ precipitates along grain boundaries → chromium depletion Cr<12% → | Low carbon/stabilized (304L/316L/321/347); solution annealing; 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, high-nickel alloys | Control Cl⁻ and temperature; avoid concentrated dead zones | GB/T 4334; ASTM G36/G123; NACE MR0175 |
| Alkaline Stress Corrosion (Alkaline Embrittlement) | 304/316L | High-concentration NaOH + High temperature + Tensile stress | Chloride-selective corrosion near grain boundaries + stress | Post-weld heat treatment for 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 | Trace 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 Configuration
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 parts they apply to, as a starting point for quotation and material ordering.
- Thickness range: 95–850 mm. Thin sheet is often formed parts (considering bending and deep-drawing cracks), while thick plate is usually welded structures (considering heat input and sensitization).
What are the frequently asked questions?
Which stainless steel is most commonly used for the temperature-time-concentration limit of sensitization and stress corrosion caused by chloride ions?
How many times do these 4 parts count in total?
Which type of part is most common?
Which type of part has the highest failure rate?
For which type of part should I choose a thicker thickness?
The thickness range in the list is 95–850 mm. For thin plates, consider bending and surface finish; for thick plates, welding and structural strength. Values may vary between equipment manufacturers for the same position. Verify again with your drawing or operating conditions.
Related Materials and Adjacent Industries
304Materials and Specifications304LMaterials and Specifications316LMaterials and SpecificationsStainless Steel Fasteners: A2-70/A4-70/A4-80/D Series and Latest StandardsStainless Steel FastenersCarbon Steel Flanges for Seawater Desalination: 2205/2507 Pressure-Temperature-Corrosion LimitsDuplex Flanges and DesalinationHygienic Diaphragm Valves/Cleaning Valves: ASME BPE, Ra and Temperature LimitsSanitary Valves