EN 10025-5 Weathering Steel: A Comprehensive Comparison of S235J0W, S355J0W, S355J2W

Product Details

1. Core Definition & Standard Positioning

EN 10025-5 defines weathering steel as "low-alloy structural steel that resists atmospheric corrosion by forming a dense oxide layer (patina)." The naming convention and core positioning of the three grades are as follows:

Designation Breakdown:

Prefix (S): Structural steel;
Strength Class (235/355): Nominal yield strength (unit: MPa);
Impact Class (J0/J2): J = Impact test qualified, 0 = Impact at -0℃, 2 = Impact at -20℃;
Suffix (W): Weathering resistance.

Core Positioning:

S235J0W: Low-carbon, low-strength weathering steel for ambient-temperature, low-load non-critical structures;
S355J0W: Medium-carbon, medium-strength weathering steel for ambient-temperature, medium-to-high load structural components;
S355J2W: Medium-carbon, medium-strength weathering steel for low-temperature (-20℃), medium-to-high load critical structures.

Equivalence: All three grades align with the international weathering steel system, with S355J2W equivalent to Corten A (ASTM A242) and S355J0W equivalent to the ambient-temperature-adapted version of Corten B (ASTM A588).

2. Core Differences: Chemical Composition & Mechanical Properties

The fundamental distinctions between the three grades lie in strength class and low-temperature impact adaptability, with chemical composition supporting these performance variations—all data strictly adheres to EN 10025-5:2004.

2.1 Chemical Composition (Mass Fraction, %)

Element	S235J0W	S355J0W	S355J2W	Core Function
Carbon (C)	≤0.17	≤0.20	≤0.20	Controls strength and weldability; low content ensures toughness
Manganese (Mn)	≤1.40	≤1.60	≤1.60	Enhances strength and workability; higher content in S355 series matches strength class
Silicon (Si)	≤0.55	≤0.55	≤0.55	Promotes patina formation and improves oxidation stability
Phosphorus (P)	≤0.040	≤0.035	≤0.035	Strictly controlled to avoid low-temperature brittleness
Sulfur (S)	≤0.040	≤0.035	≤0.035	Minimized to prevent accelerated corrosion and welding defects
Copper (Cu)	0.20–0.50	0.20–0.50	0.20–0.50	Core weathering element; facilitates dense patina formation
Chromium (Cr)	0.30–1.20	0.30–1.20	0.30–1.20	Improves patina adhesion and corrosion resistance
Nickel (Ni)	0.05–0.50	0.05–0.50	0.05–0.50	Enhances low-temperature toughness to meet J2 impact requirements
Vanadium (V)	≤0.12	≤0.12	≤0.12	Grain refiner; balances strength and toughness

2.2 Mechanical Properties (Plate Thickness 6–16mm, Transverse Testing)

Performance Indicator	S235J0W	S355J0W	S355J2W	Key Application Implications
Yield Strength (Rp0.2)	≥235 MPa	≥355 MPa	≥355 MPa	S355 series offers 51% higher strength than S235, with significantly improved load-bearing capacity
Tensile Strength (Rm)	360–510 MPa	470–630 MPa	470–630 MPa	S355 series has higher tensile strength, suitable for heavy-load and thin-plate designs
Elongation (A50mm)	≥24%	≥21%	≥21%	S235J0W has superior ductility, facilitating bending and forming processes
Impact Toughness (CVN)	≥27 J (-0℃)	≥27 J (-0℃)	≥27 J (-20℃)	S355J2W withstands low-temperature impact, ideal for cold regions
Hardness (HB)	100–150	130–180	130–180	S355 series has higher hardness and better structural wear resistance

2.3 Corrosion Resistance Comparison

Sharing the core Cu-Cr-Ni weathering alloy system, the three grades exhibit nearly identical atmospheric corrosion resistance:

4–8 times higher than ordinary carbon steel (e.g., S235JR);
Forms a stable patina within 6–12 months of outdoor exposure, with a ≥95% integrity rate after 500 hours of salt spray testing;
Suitable for inland, industrial, and mild coastal environments; additional anti-corrosion treatment (e.g., coating) is recommended for severe coastal areas.

3. Product Forms & Dimensional Range

The three grades share similar supply forms and dimensions, with S235J0W offering a richer range of thin-gauge products due to its lower strength:

Specification	S235J0W	S355J0W	S355J2W
Thickness Range	1.5–120 mm	3.0–150 mm	3.0–150 mm
Width Range	1000–3200 mm	1000–3200 mm	1000–3200 mm
Length Range	2000–12000 mm	2000–12000 mm	2000–12000 mm
Supply Forms	Steel plates, coils, strips, profiles	Steel plates, coils, structural sections, heavy plates	Steel plates, coils, structural sections, heavy plates
Weld Compatibility	No preheating required (≤25mm); compatible with arc welding and gas metal arc welding	No preheating required (≤25mm); post-weld stress relief recommended for heavy-load structures	No preheating required (≤25mm); humidity control required for welding in low-temperature environments

4. Application Scenarios: Precise Alignment with Core Needs

Application division of the three grades is primarily based on load class and ambient temperature, avoiding overperformance or underperformance:

4.1 S235J0W: Ambient-Temperature, Low-Load Non-Critical Structures

Typical Applications: Lightweight building facades, decorative grilles, fencing, road signs, pedestrian bridge (non-load-bearing components), small atmospheric pressure storage tanks, agricultural machinery parts;
Core Advantages: Lowest cost, excellent ductility, suitable for simple forming, no need to bear high stress;
Limitations: Not suitable for heavy-load, low-temperature environments, or critical load-bearing structures.

4.2 S355J0W: Ambient-Temperature, Medium-to-High Load Structures

Typical Applications: Highway guardrails, port platforms, industrial plant frames, medium-span bridges (ambient-temperature regions), transmission tower supports, mining machinery bases;
Core Advantages: Balances strength and cost, adapts to most ambient-temperature outdoor heavy-load scenarios, and enables material cost reduction through thin-plate design;
Limitations: Not suitable for environments below -0℃ (prone to brittle fracture).

4.3 S355J2W: Low-Temperature, Medium-to-High Load Critical Structures

Typical Applications: Bridges in cold regions (above -20℃), high-rise building structural frames, wind turbine foundations, offshore platform secondary structures, industrial equipment supports in low-temperature regions;
Core Advantages: Combines high strength and low-temperature toughness, maintaining structural stability even in harsh cold environments—first choice for critical projects in cold regions;
Core Value: Avoids brittle failure risks in low-temperature environments, ensuring higher safety throughout the service life.

5. Production Process & Quality Control

The three grades share the same production process, with additional process controls for low-temperature toughness required for S355J2W:

Alloy Smelting: Precise proportioning of Cu, Cr, and Ni elements; S355J2W requires optimized nickel content and deoxidation processes to ensure low-temperature toughness;
Hot Rolling & Cooling: Thermo-Mechanical Control Process (TMCP) is adopted; the S355 series requires controlled finish rolling temperature (850–950℃) to refine grain structure;
Weathering Resistance Testing: Each batch undergoes atmospheric exposure testing or accelerated salt spray testing to verify patina formation capability;
Impact Testing: S235J0W and S355J0W undergo -0℃ impact testing, while S355J2W is mandatory for -20℃ impact testing—non-conforming batches are prohibited from leaving the factory;
Certifications: All grades must pass CE certification (EN 10204 3.1/3.2), with ISO 9001 and ISO 14001 system certifications available; third-party test reports can be provided for critical projects.

6. Selection Guide: Three Steps to Determine the Optimal Grade

Decision Step	Key Judgment Factor	Corresponding Grade Selection
Step 1: Clarify Ambient Temperature	Long-term operating temperature ≥0℃	S235J0W/S355J0W
	Long-term operating temperature ≤-20℃ (cold regions)	S355J2W
Step 2: Determine Load Class	Low load (non-load-bearing/lightweight load-bearing)	S235J0W
	Medium-to-high load (load-bearing structures/heavy-load components)	S355J0W/S355J2W
Step 3: Balance Cost & Safety	Cost-sensitive, non-critical structures	S235J0W/S355J0W
	Critical structures, safety prioritized (e.g., bridges, high-rises)	S355J2W

Typical Selection Cases:

Park landscape railings in inland regions → S235J0W (ambient temperature, low load, cost-sensitive);
Industrial plant frames in ambient-temperature regions → S355J0W (ambient temperature, medium-to-high load, cost-performance priority);
Highway bridges in Northern Europe → S355J2W (low temperature, high load, safety-critical).

7. Conclusion

S235J0W, S355J0W, and S355J2W under EN 10025-5 essentially form a product system with "consistent weathering resistance, graded strength, and low-temperature adaptability":

S235J0W is the "economical basic grade," suitable for ambient-temperature, low-load non-critical scenarios, winning with cost advantages;
S355J0W is the "ambient-temperature main grade," balancing strength and cost, covering most ambient-temperature outdoor heavy-load projects;
S355J2W is the "low-temperature safety grade," centered on -20℃ impact toughness, ensuring the safety of critical structures in cold regions.

The core of grade selection is "no overspecification, no underperformance": Avoid cost waste by replacing S235J0W with S355J2W, and prevent safety risks caused by using S235J0W or S355J0W for critical loads in low-temperature environments. All three grades achieve low maintenance and long service life (over 50 years) through self-protective patina, making them sustainable alternatives to traditional painted carbon steel in outdoor engineering.