Corten A588 Weathering Steel
High-strength, low-alloy structural steel with enhanced atmospheric corrosion resistance. Widely used in bridges, transmission towers, building facades, and heavy equipment where a stable patina eliminates the need for painting.
Material Overview & Common Uses
A588 weathering steel (commonly referred to by the trademark COR-TEN) is a high-strength low-alloy (HSLA) steel that develops a tightly adherent oxide layer (patina) when exposed to the atmosphere. The alloying elements – copper, chromium, nickel, and phosphorus – promote the formation of a stable rust-like finish that protects the base metal from further corrosion. Unlike standard carbon steels, A588 does not require painting for exterior exposure and exhibits 20–30% higher yield strength than A36. Typical applications include railway cars, bridge girders, transmission poles, architectural cladding, and industrial ventilation equipment. It is also used in non‑marine outdoor structures where maintenance access is difficult.
Core Technical Properties & Sizing
| Property (Metric) | Value (Imperial) | Specification Range |
|---|---|---|
| Yield Strength (min) | 50 ksi (345 MPa) | 345–400 MPa for thickness ≤ 100 mm |
| Tensile Strength | 70 ksi (485 MPa) | 485–620 MPa |
| Elongation in 2” (50 mm) | 18% min | 18–21% |
| Density | 0.284 lb/in³ (7.85 g/cm³) | Standard steel density |
| Modulus of Elasticity | 29,000 ksi (200 GPa) | 200 GPa |
| Thermal Expansion (20–100°C) | 6.5 × 10⁻⁶ /°F (11.7 × 10⁻⁶ /°C) | Same as low‑alloy steel |
| Poisson’s Ratio | 0.29 ± 0.01 | 0.29 |
Common Size Availability (Hot‑Rolled Plate)
- Thickness: 3/16″ (4.76 mm) through 4″ (101.6 mm)
- Width: 48″ (1220 mm) through 120″ (3050 mm)
- Length: 120″ (3050 mm) through 480″ (12200 mm)
- Standard surface: as-rolled with mill scale (patina develops after exposure)
Never Run Out of Critical Supplies
Automate your shop floor inventory. SupplyGrid tracks consumables, manages Kanban bin replenishment, and automatically generates POs when you hit your minimum thresholds.
Try SupplyGrid Free →Machinability, Tooling & Feeds
A588 is in the medium‑machinability range for low‑alloy steels. Its machinability rating is approximately 45–55% of AISI 1212 free‑machining steel. The material exhibits moderate chip‑breaking characteristics; use of chip‑breaker inserts and high‑pressure coolant is recommended. Carbide tooling (C-2 or C-5 grade) offers the best combination of tool life and surface finish. High‑speed steel can be used for lower‑volume operations but will require reduced speeds.
Recommended Turning Parameters (Carbide Inserts, Uncoated)
| Operation | Cutting Speed (SFM) | Feed (IPR) | Depth of Cut (DOC) |
|---|---|---|---|
| Rough Turning | 150–200 | 0.015–0.025 | 0.080″–0.200″ |
| Finish Turning | 200–250 | 0.008–0.012 | 0.020″–0.060″ |
| Face Milling | 180–220 | 0.010–0.018 in/tooth | 0.060″–0.150″ |
| Drilling (HSS twist drill) | 60–80 | 0.006–0.012 (1/4″ drill) | Peck as needed |
Coolant: water‑soluble emulsion 5–8% concentration, flood applied. For dry machining, reduce speeds by 15–20%.
Common Defects & Quality Control
| Defect | Description | QC Method / Rejection Criterion |
|---|---|---|
| Lamellar Tearing | Step‑wise cracking in thickness direction due to inclusion bands or through‑thickness tensile stress | Ultrasonic inspection per ASTM A578; reject if indication exceeds 50% of nominal thickness |
| Surface Scale / Red Rust | Thick mill scale or premature corrosion before patina formation | Visual + magnetic thickness gauge; scale thickness > 0.010″ should be removed by abrasive blasting |
| Weld Zone Cracking | Hydrogen‑induced or heat‑affected zone (HAZ) cracking from improper preheat | MT (magnetic particle) per ASTM E709; any linear indication > 1/16″ is rejectable. Verify preheat 100–150°C |
| Segregation / Banded Microstructure | Lighter‑etched bands in micro‑etch showing non‑uniform MnS or alloy segregation | Metallographic exam at 100×; reject if banding score > 3 per ASTM E1268 |
| Incorrect Chemical Composition | Cu, Cr, Ni below specified minimum | Optical emission spectrometry (OES) on each heat; reject any element below 95% of required min |
Acceptance standards per AWS D1.1 for weldments and AISC for structural applications.
Storage, Handling & Racking Guidelines
A588 weathering steel should be stored in a dry, well‑ventilated area to prevent premature rusting before patina development. If outdoor storage is unavoidable, ensure the material is elevated off the ground (minimum 6″) and sloped for drainage. The patina layer will form naturally over 2–5 cycles of wet/dry exposure, but the initial surface must be free of oil, grease, or paint that would inhibit uniform oxidation. Do not stack on bare ground. When racking, use non‑metallic spacers to avoid galvanic coupling with dissimilar metals.
Recommended Storage Conditions
| Parameter | Specification |
|---|---|
| Indoor Temperature | 10–30 °C (50–86 °F) |
| Relative Humidity | ≤ 50% preferred; ≤ 70% acceptable with ventilation |
| Outdoor Exposure | Elevate on dunnage, cover with breathable tarp to allow ventilation |
| Maximum Unprotected Exposure | 3 months; after that, apply a temporary clear acrylic barrier if final appearance is critical |
| SupplyGrid Reorder Point | Set at 35% of average monthly usage – auto‑PO generated when bin quantity drops below 30% |