Spotting the Difference in S355K2G1W and S355K2G2W

What’s the same between them?

Minimum yield strength: 355 MPa (up to 16mm)

Tensile range: 470–630 MPa

Impact toughness: 27J at -20°C (K2 rating)

Weathering elements: Copper (0.25–0.55%), Chromium (0.40–0.80%), Nickel (≤0.65%)

Weldability and formability: Nearly identical practices apply

What’s different?

The key difference is phosphorus (P) control.

S355K2G1W: Phosphorus ≤0.035% (standard low-phosphorus steel)

S355K2G2W: Phosphorus up to 0.12% (deliberately elevated for corrosion enhancement)

That’s it. The mechanical properties don’t change. The impact toughness requirement doesn’t change. But that extra phosphorus in G2W helps the steel form its protective patina a bit faster in mildly aggressive environments.

So which one should you choose?

Pick S355K2G1W when:

The structure faces normal atmospheric conditions (rural, urban)

You want maximum weldability and consistent low-temperature toughness

Your specifications call for standard phosphorus limits

Pick S355K2G2W when:

The structure sits in industrial or moderately corrosive environments

Faster patina formation is desirable

Your project follows EN 10025-5 with the “improved corrosion resistance” enhancement

A practical example. A rural footbridge in a clean environment? G1W works fine. A railway bridge near a chemical plant or an urban tunnel with exhaust exposure? G2W gives you that extra corrosion margin.

One caution. Don’t assume G2W is always “better.” Higher phosphorus, while helpful for corrosion, can slightly reduce toughness in very thick sections or complex welds if not managed carefully. For most standard applications, both grades perform excellently—the choice often comes down to regional preference or customer specification.