Q355GNH weathering steel plate is composed of ordinary carbon steel with a small addition of copper, nickel, chromium, and other corrosion-resistant elements during the smelting process, which enhances the atmospheric corrosion resistance of the material.
Unlike stainless steel, Q355GNH is not completely rust-proof - it will oxidize when exposed to air. However, the corrosion layer that forms on the surface is a compact amorphous oxide film that adheres firmly to the base metal, preventing further reaction with the atmosphere.
Q355GNH weathering steel plates can be used painted, uncoated, or stabilized, depending on environmental conditions. The painting requirements are the same as for common carbon steels.
One of the most remarkable features of Q355GNH steel is that it can serve effectively without coating, which makes it especially cost-efficient.
In environments with low air pollution or moderate humidity, the plates can be used bare and directly exposed to the atmosphere. Over the years, a stable protective patina develops, the corrosion process slows down, and the surface turns into an elegant chocolate-brown appearance.
Since Q355GNH weathering steel does not suffer from paint aging or peeling, it requires no repainting or maintenance, which greatly reduces lifecycle costs and eliminates the negative impact that painting might cause during use.
Chemical Composition (%)
| Element | C (≤) | Si | Mn | P | S (≤) | Cr | Cu | Ni |
|---|---|---|---|---|---|---|---|---|
| Q355GNH | 0.12 | 0.25–0.75 | 1.0–1.6 | 0.04–0.12 | 0.04 | 0.40–0.80 | 0.20–0.50 | 0.20–0.50 |
Mechanical Properties
| Property | Thickness (mm) | Yield Strength (MPa) | Tensile Strength (MPa) | Elongation (%) |
|---|---|---|---|---|
| Q355GNH | ≤16 | ≥355 | 470–630 | ≥20 |
| Q355GNH | 16–40 | ≥345 | 470–630 | ≥19 |
| Q355GNH | 40–63 | ≥335 | 470–630 | ≥18 |
Advantages
Excellent atmospheric corrosion resistance
Can be used unpainted, reducing maintenance work
Stable oxide film prevents further corrosion
Natural weathered patina provides aesthetic value
Long service life and cost-effective performance
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