What is S355K2G2W Weathering Steel

S355K2G2W is a weathering steel grade under the European standard EN 10025-5. It belongs to a family of steels designed to resist atmospheric corrosion without needing paint or protective coatings. Instead of fighting rust, it uses rust to its advantage.

The name tells the story.

S = Structural steel

355 = Minimum yield strength of 355 MPa for thicknesses up to 16mm

K2 = Guaranteed impact toughness of 27J at -20°C (Charpy V-notch test), with strict individual low limits

G2 = Weathering steel variant with higher phosphorus content (up to 0.12%) for faster, more reliable patina formation

W = Weathering steel (improved atmospheric corrosion resistance)

What makes it special?

Unlike ordinary carbon steel that needs paint to survive outdoors, S355K2G2W contains specific alloying elements—copper (0.25–0.55%), chromium (0.40–0.80%), and nickel (≤0.65%). These elements, combined with higher phosphorus, create a dense, stable, and adherent patina when the steel is exposed to repeated wet-dry cycles. This patina seals the surface and slows further corrosion to under 0.01mm per year.

Where is it used?

S355K2G2W appears in:

Bridges and highway structures

Railway cars and wagons

Transmission towers

Building facades and architectural features

Shipping containers and heavy structural parts

Outdoor sculptures and landscape installations