Corten B vs Corten A
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
Corten B
Structural & HSLA Steel
Corten B is the structural weathering grade, normally supplied to ASTM A588 chemistry: lower phosphorus than Corten A, with vanadium for strength in thicker welded construction. It is the bridge and heavy-structure member of the weathering family.
Standards: DIN S355J2W type (EN 10025-5, near) · AISI A588 (chemistry basis) · GB Q355NH (near)
Corten A
Structural & HSLA Steel
Corten A is the original weathering steel composition (Cu-Cr-Ni-P alloyed), forming a dense, self-protecting rust layer that removes the need for painting. The high phosphorus content suits plate and sheet; it is the architectural and container industry’s standard weathering grade.
Standards: DIN S355J0WP type (EN 10025-5) · AISI A242 type (near) · JIS SPA-H (near) · GB 09CuPCrNi-A (near)
Chemical composition compared (%)
| Element | Corten B | Corten A |
|---|---|---|
| C | ≤0.19 | ≤0.12 |
| Si | 0.30–0.65 | 0.25–0.75 |
| Mn | 0.80–1.25 | 0.20–0.50 |
| P | ≤0.040 | 0.07–0.15 |
| S | ≤0.050 | ≤0.035 |
| Cr | 0.40–0.65 | 0.30–1.25 |
| Ni | ≤0.40 | ≤0.65 |
| Cu | 0.25–0.40 | 0.25–0.55 |
| V | 0.02–0.10 | — |
Properties compared
| Property | Corten B | Corten A |
|---|---|---|
| Yield strength | ≥345 MPa | ≥355 MPa |
| Tensile strength | ≥485 MPa | 470–630 MPa |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: Corten B · Corten A. Substitution decisions for certified parts stay with the design authority.