What Is S355J2W Corten Steel Sheet?
S355J2W is a weathering structural steel defined in EN 10025-5. The designation means a minimum yield strength of 355 MPa (S355), impact energy of at least 27 J at −20 °C (J2), and weathering performance (W). When the sheet is exposed to the atmosphere, a protective rust layer forms on the surface and inhibits deep penetration of corrosion, which saves many years of painting and expensive maintenance.
In older catalogues the same material appears as S355J2G2W, the designation used in the withdrawn standard EN 10155. The current standard EN 10025-5 renames it S355J2W, so both names describe the same type of steel.
From EN 10155 to EN 10025-5: Why Designations Changed
EN 10155, the original European standard for weathering structural steels, was superseded by EN 10025-5:2004, which reorganised the grade designations. The old suffix G1W/G2W was replaced by the letter W with the impact class, so S355J2G2W became S355J2W. Material number 1.8965 remains valid for the grade.
When ordering or comparing certificates, always state the governing standard edition; a certificate issued to EN 10155 and one issued to EN 10025-5 should be reconciled through the material number and the mill test certificate.
Equivalent Grades Across National Standards
The table below lists the commonly quoted equivalents for S355J2W sheet.
| Standard system | Grade |
|---|---|
| EN (current) | S355J2W (1.8965) |
| EN (former designation) | S355J2G2W |
| USA | A709-50W |
| DIN practice | WTSt52-3 |
| JIS | SMA50CP |
Equivalences are approximate: each standard defines its own composition limits and testing requirements. The acceptance basis should always be the governing standard of the order together with the mill test certificate.
S355J2W Compared With Carbon Steel and Stainless Steel
Compared with ordinary carbon steel, S355J2W sheet has clearly better atmospheric corrosion resistance because the protective rust layer limits further oxidation. The steel is therefore used for vehicles, bridges, towers, containers and other steel structures exposed to the weather.
Compared with stainless steel, weathering steel contains only trace alloying additions such as phosphorus, copper, chromium, nickel, molybdenum, niobium, vanadium and titanium. The total alloy content is only a few percent, well below the alloy levels of stainless steel, which keeps the material price relatively low while still offering a useful level of corrosion resistance in atmospheric service.
Maintenance and Installation Notes for Corten Sheet
Weathering steel is very low maintenance, but a periodic maintenance schedule is still recommended. Regular checks and cleaning help the patina develop evenly. Remove shrink wrap and other packaging as soon as the delivery is received, because trapped moisture under packaging can cause an uneven, blotchy patina.
Design details matter: avoid water traps, provide drainage, and keep dissimilar metal contact in mind where stainless steel fasteners or members meet corten sheet. Runoff from the steel can stain adjacent concrete, stone or paving, so drainage paths should be planned accordingly.
Frequently Asked Questions
What is S355J2G2W?
S355J2G2W is the former EN 10155 designation of S355J2W. After EN 10155 was withdrawn, EN 10025-5 renamed the grade S355J2W; the material number 1.8965 is unchanged.
Which US grade is equivalent to S355J2W?
The commonly quoted US equivalent is ASTM A709-50W. Equivalence tables are a guide only; the mill certificate and the governing standard of the order define acceptance.
Does corten steel sheet need maintenance?
It is very low maintenance, but periodic checks and cleaning are recommended, and packaging should be removed promptly after delivery so that the patina develops evenly.
Can stainless steel be welded to corten steel?
Yes, it is done in practice, for example in rail coach floor assemblies where austenitic stainless steel plate is welded to corten steel by metal active gas (MAG) welding. The joint design, filler selection and galvanic corrosion behaviour should be considered for the service environment.
Why is rust not magnetic?
Iron is magnetic, but the chemical reaction that forms rust changes the material. Rust products include weakly magnetic or non-magnetic oxides, so a thick rust layer reduces the magnetic response compared with clean iron or steel.
Is weathering steel a cheaper alternative to corten steel?
COR-TEN is a brand name for weathering steel. Standard grades such as S355J2W are specified by designation under EN 10025-5 rather than by trademark, and buying to a standard designation is the normal way to procure the material at standard prices.
