EN 10025-5 Standard Guide

Hot-Rolled Products of Structural Steels with Improved Atmospheric Corrosion Resistance

1. SCOPE AND APPLICATION

EN 10025-5 specifies the technical delivery conditions for hot-rolled products of structural steels with improved atmospheric corrosion resistance (weathering steels). These steels develop a protective oxide layer when exposed to alternating wet and dry atmospheric conditions, eliminating the need for protective coatings in many applications.

Product Forms

Flat Products: Plates (thickness ≥3mm), sheet, strip, and wide flats

Long Products: I/H sections, channels, angles, T sections, bars, and rods

Thickness Range

Maximum thickness: 150mm for all product forms.

Typical Applications

Weathering steels are designed for structures exposed to atmospheric conditions:

• Bridges and footbridges

• Outdoor sculptures and architectural steelwork

• Railway wagons and freight cars

• Transmission towers and electrical infrastructure

• Storage tanks and silos

• Building facades and cladding systems

Key Characteristics

The improved atmospheric corrosion resistance is achieved through an auto-protective oxide layer that forms naturally on the steel surface. This layer contains alloying elements (P, Cu, Cr, Ni, Mo) that develop under alternating wet/dry weather cycles, providing long-term corrosion protection without the need for painting or coating in appropriate environments.

2. CLASSIFICATION AND DESIGNATION

Steel Grades and Quality Classes

Part 5 covers four strength classes (S235, S355, S420, S460) with five quality classes based on impact properties:

J0: 27J average impact energy at 0°C

J2: 27J average impact energy at -20°C

K2: 40J average impact energy at -20°C

J4: 27J average impact energy at -40°C

J5: 27J average impact energy at -50°C

Special Note: S355 is subdivided into W (standard) and WP (enhanced phosphorus content of 0.06-0.15%). The WP class provides superior weathering performance for severe atmospheric exposures but is available only in flat products ≤12mm and requires special welding precautions.

The following table shows all 19 grade/quality combinations (22 including WP variants) with their respective steel numbers:

Steel Grade	Steel Number	Strength Class	Quality	Weathering Type	Impact Properties
S235J0W	1.8958	S235	J0	W	27J at 0°C
S235J2W	1.8961	S235	J2	W	27J at -20°C
S355J0WP	1.8945	S355	J0	WP	27J at 0°C (P: 0.06-0.15%)
S355J2WP	1.8946	S355	J2	WP	27J at -20°C (P: 0.06-0.15%)
S355J0W	1.8959	S355	J0	W	27J at 0°C
S355J2W	1.8965	S355	J2	W	27J at -20°C
S355K2W	1.8966	S355	K2	W	40J at -20°C
S355J4W	1.8787	S355	J4	W	27J at -40°C
S355J5W	1.8991	S355	J5	W	27J at -50°C
S420J0W	1.8943	S420	J0	W	27J at 0°C
S420J2W	1.8949	S420	J2	W	27J at -20°C
S420K2W	1.8997	S420	K2	W	40J at -20°C
S420J4W	1.8954	S420	J4	W	27J at -40°C
S420J5W	1.8992	S420	J5	W	27J at -50°C
S460J0W	1.8966	S460	J0	W	27J at 0°C
S460J2W	1.8980	S460	J2	W	27J at -20°C
S460K2W	1.8990	S460	K2	W	40J at -20°C
S460J4W	1.8981	S460	J4	W	27J at -40°C
S460J5W	1.8993	S460	J5	W	27J at -50°C

Designation System

Steel designation format: S + Yield Strength + Quality + W (+ P if applicable) + Delivery Condition

Example: EN 10025-5 – S355J2W+N

S: Structural steel

355: Minimum yield strength (MPa) for thickness ≤16mm

J2: Quality class (27J at -20°C)

W: Weathering (improved atmospheric corrosion resistance)

WP: Enhanced phosphorus content (S355 only, flat products ≤12mm)

+N: Normalized/normalized rolled delivery condition

Quality Classification

All grades in Part 5 are classified as alloy special steels according to EN 10020.

3. MANUFACTURING PROCESS

Steel Making

Any steel making process except open hearth (Siemens-Martin) is permitted.

Deoxidation Practice

FN (rimming not permitted): S235 J0W/J2W and S355 J0WP/J2WP

FF (fully killed): All other grades – minimum 0.020% total aluminum or equivalent, with Al:N ratio of 2:1

Delivery Conditions

The manufacturer may select any of the following delivery conditions at their discretion, unless otherwise specified by the purchaser (Option 19):

+AR (As-rolled): Conventional hot rolling without normalized rolling or thermomechanical rolling.

+N (Normalized/Normalized rolled): Final deformation in a specific temperature range achieving properties equivalent to normalizing. Products in this condition CAN be hot formed or normalized after delivery.

+M (Thermomechanical rolled): Final deformation achieving properties not achievable by heat treatment alone, including processes with increased cooling rate.

IMPORTANT: Mechanical properties are independent of the delivery condition. Products in any delivery condition (+AR, +N, or +M) must meet the same minimum requirements. Option 19 allows specifying a required delivery condition if needed for subsequent processing.

4. CHEMICAL COMPOSITION

The following tables show the heat analysis limits (% by mass) for weathering steels. Key weathering elements (Cr, Cu, P) are highlighted.

S235W Chemical Composition

Entry-level weathering steel for general structural applications:

Grade	C max	Si max	Mn	P max	S max	Cr	Cu	CEV max
S235 J0W/J2W	0.13	0.40	0.20-0.60	0.035	0.035	0.40-0.80	0.25-0.55	0.44

S355WP Chemical Composition

Enhanced phosphorus content for superior weathering performance:

IMPORTANT: S355WP is available only in flat products ≤12mm. The enhanced phosphorus content (0.06-0.15%) provides superior weathering but requires special welding precautions due to increased cold cracking susceptibility.

Grade	C max	Si max	Mn max	P	S max	Cr	Cu	CEV max
S355 J0WP/J2WP	0.12	0.75	1.00	0.06-0.15	0.035	0.30-1.25	0.25-0.55	0.52

S355W, S420W, and S460W Chemical Composition

Higher strength weathering steels with controlled chemical composition:

Grade	C max	Si max	Mn	P max	S max	Cr	Cu	CEV max
S355W (all qualities)	0.16	0.50	0.50-1.50	0.030-0.035	0.025-0.035	0.40-0.80	0.25-0.55	0.52
S420W (all qualities)	0.20	0.65	0.50-1.35	0.030-0.035	0.030-0.035	0.40-0.80	0.25-0.55	0.52
S460W (all qualities)	0.20	0.65	≤1.40	0.030-0.035	0.030-0.035	0.40-0.80	0.25-0.55	0.52

Carbon Equivalent Value (CEV)

CEV is used to assess weldability and is calculated as:

CEV = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15

Maximum CEV values are thickness-dependent. For nominal thickness ≤150mm, the CEV limits are 0.44 for S235W and 0.52 for all other grades.

Key Alloying Elements for Weathering

Chromium (Cr): 0.40-0.80% – Forms stable oxide layer

Copper (Cu): 0.25-0.55% – Enhances corrosion resistance

Phosphorus (P): Max 0.035% (W class) or 0.06-0.15% (WP class) – Improves patina formation

Nickel (Ni): Max 0.65% – Stabilizes oxide layer

Molybdenum (Mo): Max 0.30% – Enhances corrosion resistance

Product Analysis

Product analysis may be requested (Option 2) with permissible deviations from the heat analysis values specified in the standard.

5. MECHANICAL PROPERTIES

Tensile Properties

The following table shows tensile properties for thickness ≤16mm. Properties decrease with increasing thickness (six thickness ranges up to 150mm are specified in the standard):

Grade	Thickness (mm)	ReH min (MPa)	Rm (MPa)	A min (%)
S235W	≤16	235	360-510	24
S355WP	≤16	355	510-680	22
S355W	≤16	355	470-630	22
S420W	≤16	420	520-680	19
S460W	≤16	460	540-720	17

Note: ReH = Yield strength (upper yield strength), Rm = Tensile strength, A = Elongation after fracture (% min on gauge length Lo = 5.65√So)

Impact Properties

Impact testing is performed using Charpy V-notch test pieces with 2mm striker, tested longitudinally:

Quality Class	Test Temperature	Minimum Impact Energy	Test Type
J0	0°C	27J average	Charpy V-notch
J2	-20°C	27J average	Charpy V-notch
K2	-20°C	40J average	Charpy V-notch
J4	-40°C	27J average	Charpy V-notch
J5	-50°C	27J average	Charpy V-notch

Acceptance Criteria: Average of three test pieces ≥ minimum value. One individual value may be < minimum but ≥ 70% of minimum.

Subsized Specimens: Minimum values are reduced in direct proportion to the cross-sectional area when full-size specimens cannot be obtained.

Test Piece Exemptions

• Flat products/sections: No impact test for thickness <6mm

• Bars/rods: No impact test for diameter <16mm (round) or thickness <12mm (rectangular)

• S355 WP class: Impact properties verified only if specified (Option 3)

Through-Thickness Properties

Option 4 allows specification of through-thickness properties (Z15, Z25, Z35) per EN 10164 for applications requiring tensile strength perpendicular to the rolling plane.

Stress Relief Warning

Maximum stress relief temperature is 580°C for >1 hour (560°C for +N flat products) to avoid property deterioration. If higher temperatures or longer times are intended, minimum values should be agreed upon at time of order.

Test Direction

Transverse test pieces for flat products ≥600mm wide. Longitudinal test pieces for all other products.

6. TECHNOLOGICAL PROPERTIES

Weldability

Weathering steels are suitable for welding per EN 1011-2. Welding behavior depends on material properties, dimensions, shape, and service conditions.

Important Welding Considerations:

Pre-welding: Remove oxide layer 10-20mm from joint edges

Filler metal: If using filler without improved atmospheric corrosion resistance, ensure weld itself is weather resistant

S355 WP class: Special precautions required due to high phosphorus content (0.06-0.15%)

Cold cracking risk: Increases with thickness and strength level (hydrogen, brittle HAZ, tensile stress)

Formability

Hot Forming: ONLY permitted for +N (normalized/normalized rolled) condition – NOT for +M or +AR

Cold Forming: Reduces ductility (refer to CEN/TR 10347 for guidance)

Flangeability (Option 11)

When specified, plate, sheet, strip, wide flats, and flats (width <150mm) with nominal thickness ≤20mm are suitable for flanging without cracking with the following minimum bend radii:

Grade	Thickness Range (mm)	Min Bend Radius (Transverse)	Min Bend Radius (Longitudinal)
S235W	>1.5 to 20	2.5 × t	2.5 × t
S355WP	>1.5 to 12	4 × t	4 × t
S355W	>1.5 to 20	4 × t	5 × t

Note: t = nominal thickness of the product. S355WP available only ≤12mm.

7. SURFACE PROPERTIES

Strip: Surface should not impair application with adequate processing

Plates and wide flats: EN 10163-1 and EN 10163-2, Class A subclass 1 default (Option 15 for other)

Sections: EN 10163-1 and EN 10163-3, Class C subclass 1 default (Option 16 for other)

Bars and rods: EN ISO 9443, Class A default (Option 17 for other)

8. INTERNAL SOUNDNESS (OPTIONAL)

Ultrasonic testing may be agreed upon for the following products:

Option 6: Flat products ≥6mm (except hot rolled strip and plate cut from strip) per EN 10160

Option 7: H beams with parallel flanges and IPE beams per EN 10306

Option 8: Bars per EN 10308

9. DIMENSIONS, TOLERANCES, AND MASS

Dimensions and tolerances for each product type are specified in the relevant European Standards:

• Hot rolled plates: EN 10029 (Class A default, Option 18 for other)

• Plates cut from strip: EN 10051 (Option 34 for EN 10029)

• Strip: EN 10051

• I/H sections: EN 10034, EN 10365

• Channels: EN 10279, EN 10365

• Angles: EN 10056-1, EN 10056-2

• T sections: EN 10055

• Flat bars and wide flats: EN 10058

• Square bars: EN 10059

• Round bars: EN 10060

• Hexagon bars: EN 10061

• Bulb flats: EN 10067

• Taper flange I sections: EN 10024

• Rod: EN 10017

Nominal Mass: Calculated using 7850 kg/m³ volumetric mass

10. TESTING AND INSPECTION

Type of Inspection

Specific or non-specific inspection per EN 10204. CE marking is typically required (Option 33 to exclude for non-CPR products) and must fulfill both EN 10025-5 and EN 10025-1.

Mandatory Tests for Specific Inspection

Heat analysis: Once per cast

Tensile test: Per test unit

Impact test: Per test unit for S235 J0/J2W and all S355W, S420W, S460W qualities (except size restrictions). For S355 WP class only if specified (Option 3).

Test Unit Definition

60 tonnes or part thereof from same cast, form, grade, quality, delivery condition, and thickness range. Exception: 80 tonnes for heavy sections >200kg/m or all sections if cast exceeds 200 tonnes.

Inspection Documents (EN 10204)

Type 2.2: Test report (manufacturer)

Type 3.1: Inspection certificate (manufacturer’s inspector)

Type 3.2: Inspection certificate (manufacturer + independent body)

Test Methods

Chemical analysis: EN 10315, EN ISO 15350, or CR 10320

Tensile test: EN ISO 6892-1 (method A or B). Upper yield strength (ReH) determined, or 0.2% proof strength (Rp0.2) if no yield phenomenon

Impact test: EN ISO 148-1 (V-notch, 2mm striker)

11. MARKING, LABELING, AND PACKAGING

Required Marking: Grade/quality/delivery condition, identification number (cast/sample), manufacturer name/trademark

Methods: Painting, stamping, laser marking, barcoding, durable adhesive labels, attached tags

Location: Close to one end or on end cut face (manufacturer’s discretion)

Bundled products: Label on bundle or top product

Option 10: Special type of marking can be specified

12. AVAILABLE OPTIONS

BS EN 10025-5 provides 19 options that may be specified at the time of inquiry or order to customize the technical delivery conditions:

Option	Description	Category
1	Steel making process details	Manufacturing
2	Product analysis	Chemical
3	Impact properties verification (S355 WP)	Mechanical
4	Through-thickness properties (Z15/Z25/Z35)	Mechanical
6	Ultrasonic testing flat products (EN 10160)	Testing
7	Ultrasonic testing H/IPE beams (EN 10306)	Testing
8	Ultrasonic testing bars (EN 10308)	Testing
10	Special marking type	Marking
11	Flangeability without cracking (≤20mm)	Formability
13	Impact test each plate/coil	Testing
14	Impact and tensile test each plate/coil	Testing
15	Other surface class (plates/wide flats)	Surface
16	Other surface class (sections)	Surface
17	Other surface class (bars/rods)	Surface
18	Other thickness tolerance (plates)	Dimensional
19	Delivery condition (+AR, +N, or +M) required	Manufacturing
30	Transverse impact test pieces	Testing
33	No CE marking (non-CPR products)	Documentation
34	Plates from strip per EN 10029	Dimensional

13. QUICK REFERENCE SUMMARY

Most Popular Grades

S355J2W: Most widely used weathering steel (bridges, outdoor sculptures, railway wagons, architectural steelwork). Impact 27J at -20°C. Excellent balance of strength, toughness, atmospheric corrosion resistance.

S355J0WP: Enhanced phosphorus content for superior weathering (severe atmospheric exposure, coastal non-marine). Available only flat products ≤12mm. Special welding precautions required.

S460J2W: High strength weathering steel (long-span bridges, transmission towers, high-rise structures). Impact 27J at -20°C. Weight-critical applications.

S235J2W: Entry-level weathering steel (general structural work, non-critical outdoor). Impact 27J at -20°C. Most economical.

Key Advantages of Weathering Steels

Auto-protective oxide layer: Forms naturally under wet/dry cycles, eliminates painting

Long service life: Up to 8× corrosion resistance vs carbon steel in atmospheric conditions

Reduced maintenance: No painting/coating required in appropriate environments

Aesthetic appeal: Distinctive rust-brown patina becomes uniform over time

Environmental benefits: No VOC emissions from paints, reduced lifecycle impact

Cost-effective: Lower total cost of ownership despite higher initial material cost

CRITICAL DESIGN CONSIDERATIONS

SUITABLE environments: Rural, urban, industrial atmospheres with wet/dry cycles

NOT SUITABLE: Marine atmospheres, permanent water contact, high chloride/sulfate environments, enclosed spaces with condensation

Surface protection required: When significant chemical content in air, permanent moisture exposure, or marine atmosphere

Patina formation: Takes 1-3 years to fully develop, appears uneven during formation

Design for drainage: Avoid water retention areas, ensure proper ventilation, prevent crevice corrosion

Descale before painting: If painting applied, mill scale must be removed first

Consult manufacturer: For suitability evaluation in specific applications/environments

Runoff considerations: Oxide runoff during early stages can stain adjacent surfaces – plan accordingly

Fabrication Reminders

• Hot forming: ONLY for +N condition – NOT for +M or +AR

• Cold forming: Reduces ductility

• Welding preparation: Remove oxide layer 10-20mm from joint edges

• Stress relief limits: 580°C max for >1 hour (560°C for +N flat products)

• CE marking: Typically required unless Option 33 specified

• Part 5 is stand-alone: Complete technical delivery conditions (use with Part 1 only for CPR applications)

Grade Selection Matrix

Grade	Typical Applications	Key Advantages
S235W	General structures, low stress, economical choice	Most economical, good formability, adequate weathering
S355WP	Severe atmospheric exposure, coastal non-marine	Enhanced P content (0.06-0.15%), superior weathering
S355W	Bridges, outdoor structures, most versatile	Best balance of strength, toughness, weathering
S420W	Higher strength, weight reduction required	Reduced weight, improved strength/weight ratio
S460W	Long spans, weight-critical structures	Maximum strength, optimal for demanding applications