S4 · Sensitization & Chloride SCC

Stress Corrosion Cracking (316L/304 Media and Boundary List)

List the media, grades, and boundary conditions related to Stress Corrosion Cracking: 4 typical components/processes, including recommended grades, specifications, failure reasons, and standards.

Describe the condition, get material selection advice View Products

Steel coils, sheets, and fastener flanges in stock — Metal products: Coils, sheets, fasteners, and flanges (Illustration; Material selection based on media, temperature, and drawings)

Four parts and material list

Part / Component	Recommended designation	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 grains → 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	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%	Intergranular/crystalline cracks caused by synergy between Cl⁻, tensile stress, and temperature.	Reduce stress, Choose duplex steel, Choose high nickel alloys, Control Cl⁻, Control temperature, Avoid 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 crystal 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	Track Weld	Delta-Ferrite > 3% Significantly Reduce Corrosion Resistance	ASTM A249/S7；ASME BPE

Ferrous Modes Retain Ferrite, Excess Ferrite Corrodes SelectivelyControl Heat Input/Composition, Max S7/ASTM A249 Ratio 1.25, Ferrite 4-10% for Crack Resistance but Lower for Corrosion ServiceTable: Standard Configurations

Specify Usage Conditions, Over Specifying Grades

What's the most common grade in this industry? —— 316L (4), 304 (2), 304L (2)
Thickness range: 95–850 mm

Common issues

Stress corrosion cracking due to sensitization: Which stainless steel is used most for temperature-time-concentration boundaries?

Based on the total number of parts, the most common are 316L (4), 304 (2), and 304L (2). Specific to a part still depends on the medium and temperature.

Which part is the most problematic?

Typically "Intergranular corrosion (welding HAZ/sensitization)": Low carbon/stabilized (304L/316L/321/347); Solution treatment; GB/T 4334 E method; ASTM A262 B method; Recommended grade 304/304L/316L, sensitization range 450–850°C; 316L 650–725°C × 30min. This condition recommends specifying medium concentration, temperature, and cleaning methods in the design phase.

How thick should I select for thickness?

Thickness range in the list is 95–850 mm.

Forming and surface for thin plates, welding and structural strength for thick plates; values from different equipment manufacturers may vary by your drawing or operating conditions, review them.