1. Corrosion Resistance
Weathering steel (Corten/A588/Q355NH etc.)Contains alloying elements such as Cu, Cr, Ni, P, which form a dense, protective patina layer on the surface.Corrosion rate is 2–8 times slower than normal steel; can be used unpainted outdoors long-term.
Normal carbon steel (Q235, SS400, A36)No protective alloy composition.Rusts quickly and continuously; rust layer is loose and porous, allowing moisture to penetrate deeper.
2. Surface Rust Behavior
Weathering steelRusts initially, then stabilizes into a tight, dark brown patina and stops deepening.Almost no further corrosion after the protective layer forms.
Normal steelRusts non‑stop, gradually becoming thicker, flaky, and eventually causing pitting and perforation.
3. Mechanical Properties
Weathering steelHigh‑strength low‑alloy steel; generally higher yield and tensile strength than mild steel.Better fatigue resistance and toughness in atmospheric environments.
Normal steelLower strength; softer and more ductile in basic grades.
4. Service Life
Weathering steelService life outdoors can reach several decades when properly designed.
Normal steelRusts through quickly outdoors, usually only a few years without painting.
5. Coating Requirement
Weathering steelCan be used unpainted in most atmospheric environments.
Normal steelMust be painted or galvanized; otherwise it corrodes rapidly.
6. Cost
Weathering steelMore expensive due to alloying and production process.
Normal steelLower cost, widely available as a general structural material.
7. Typical Applications
Weathering steelBridges, containers, building facades, outdoor sculptures, landscape structures, transmission towers.
Normal steelGeneral construction, internal components, temporary structures, parts not exposed to weather.
