ASTM A847 Corten Steel Pipes – Weathering Steel Structural Pipe & Tube
ASC LLP, Mumbai, supplies ASTM A847 Corten steel pipes and tubes. These are cold-formed welded and seamless weathering-steel structural tubing in round, square and rectangular sections, for architecture, bridges, poles and outdoor structures. Material comes with EN 10204 3.1 certificates. See our full Corten steel range.
What is ASTM A847?
ASTM A847 / A847M is the specification for cold-formed welded and seamless high-strength, low-alloy (HSLA) structural tubing with improved atmospheric corrosion resistance. In other words, it is the structural pipe and hollow-section spec for weathering (“Corten”) steel. The steel contains copper and usually chromium, nickel, silicon and phosphorus. In alternating wet and dry outdoor exposure, these elements form a dense, adherent rust layer (patina) that slows further corrosion. That allows the tube to be used unpainted.
A847 is for structural use. It is not a pressure-piping specification, and the standard notes it is not intended where low-temperature notch toughness is important.
ASTM A847 – Quick Facts
- Product: cold-formed welded or seamless structural tubing – round, square, rectangular and special shapes
- Strength: 345 MPa (50 ksi) yield, 485 MPa (70 ksi) tensile, minimum
- Corrosion index: 6.0 minimum, calculated to ASTM G101
- Size limits: welded up to 1626 mm (64″) periphery and 15.9 mm wall; seamless up to 813 mm (32″) periphery and 12.7 mm wall
- Finish: bare (to weather naturally); pre-weathered or painted on request
- Certificate: EN 10204 3.1 including corrosion index
How Corten (Weathering) Steel Protects Itself
- Patina: in the first 1 – 3 years of wet–dry cycles, a fine, tight oxide layer forms. Its colour changes from orange to a dark brown.
- Low maintenance: once stable, the patina slows corrosion to a fraction of the rate of plain carbon steel, so painting is not needed in suitable environments.
- Strength: 50 ksi yield allows lighter sections than A500 Grade B tube.
- Where it does not work well: the patina does not stabilise if the steel stays wet, is buried or immersed, or is exposed to sea spray, de-icing salt or heavy industrial pollution. In those conditions it must be protected or another material used.
Design & Fabrication Tips for A847 Tube
- Drainage: avoid pockets where water or debris collects; seal or drain closed sections.
- Run-off staining: early rust run-off can stain concrete and paving – plan drips and drainage.
- Welding: for exposed welds, use weathering-grade consumables (Ni-Cu type) so the welds weather to the same colour.
- Bolting: use weathering-steel bolts (for example ASTM F3125 Type 3).
- Matching plate: ASTM A588, A242 and Corten plates for base plates and gussets.
ASTM A847 Round Pipe Size & Weight Chart
| OD (in) | OD (mm) | Wall (mm) | Weight (kg/m) | Welded | Seamless |
| 2⅜” | 60.3 | 3.91 | 5.44 | Yes | Yes |
| 3½” | 88.9 | 5.49 | 11.29 | Yes | Yes |
| 4½” | 114.3 | 6.02 | 16.07 | Yes | Yes |
| 6⅝” | 168.3 | 7.11 | 28.26 | Yes | Yes |
| 8⅝” | 219.1 | 8.18 | 42.55 | Yes | Yes |
| 10¾” | 273.1 | 9.27 | 60.31 | Yes | No – over 813 mm periphery |
| 12¾” | 323.9 | 9.53 | 73.88 | Yes | No – over 813 mm periphery |
| 16″ | 406.4 | 9.53 | 93.27 | Yes | No – over 813 mm periphery |
Typical round sizes – other OD × wall combinations within the A847 limits on request. Square and rectangular A847 tube is also available (for example 50 × 50 to 300 × 300 mm and 100 × 50 to 400 × 200 mm, 3 – 12.5 mm wall). Weights are plain-end values for steel at 7.85 g/cm³.
ASTM A847 Mechanical Properties
| Property | ASTM A847 (round and shaped) |
| Tensile strength, min. | 485 MPa (70 ksi) |
| Yield strength, min. | 345 MPa (50 ksi) |
| Elongation in 50 mm, min. | 19% (walls 3.0 mm and over) |
| Flattening test | Round tube only, per lot |
ASTM A847 Specifications & Tolerances
| Item | Requirement |
| Specification | ASTM A847 / A847M |
| Type | Cold-formed welded or seamless structural tubing |
| Shapes | Round, square, rectangular, special |
| OD tolerance (round) | ±0.5% up to 48.3 mm OD; ±0.75% for 50 mm and over |
| Outside dimension (square / rectangular) | ±0.5 mm up to 63.5 mm; ±0.6 mm to 88.9 mm; ±0.7 mm to 139.7 mm; ±1% over 139.7 mm |
| Wall tolerance | ±10% of specified wall (weld seam excluded from the plus limit) |
| Straightness | 3.2 mm per 1.5 m of length (⅛” per 5 ft) |
| Squareness / corner radius | 90° ±2°; outside corner radius max. 3 × wall |
| Length | Random or specified mill lengths; cut lengths on request |
| Certificate | EN 10204 3.1 with chemistry, corrosion index and tensile results |
ASTM A847 Chemical Composition
| Element | Heat analysis (%) | Product analysis (%) |
| Carbon (C) | 0.20 max. | 0.24 max. |
| Manganese (Mn) | 1.35 max. | 1.40 max. |
| Phosphorus (P) | 0.15 max. | – |
| Sulphur (S) | 0.05 max. | 0.06 max. |
| Copper (Cu) | 0.20 min.* | 0.18 min.* |
| Atmospheric corrosion index (ASTM G101) | 6.0 min. | – |
*The copper minimum does not apply when both chromium and silicon are 0.50% or more. Within these limits, mills add Cr, Ni, Si and P to reach the corrosion index – typical A847 steels are similar in chemistry to A588 or A606 Type 4.
A847 vs Other Weathering & Structural Grades
| Spec | Product | Weathering? | Yield / tensile min. (MPa) |
| ASTM A847 | Structural pipe & tube | Yes | 345 / 485 |
| ASTM A588 | Plate, shapes, bar | Yes | 345 / 485 |
| ASTM A242 | Plate, shapes, bar | Yes | 345 / 480 (≤ 19 mm) |
| ASTM A606 Type 4 | Sheet & strip | Yes | 340 / 480 (hot rolled) |
| ASTM A709 Gr 50W | Bridge plate & shapes | Yes | 345 / 485 |
| ASTM A871 Gr 60 / 65 | Plate for tubular structures & poles | Yes | 415 / 520 – 450 / 550 |
| ASTM A572 Gr 50 / 65 | Plate & shapes | No – not weathering | 345 / 450 – 450 / 550 |
| ASTM A500 Gr B | Structural tube | No | 290 / 400 (round) |
A572 Grade 65 is often called “Corten” by mistake – it is a high-strength steel without the copper / chromium additions that give weathering resistance.
Applications of ASTM A847 Corten Pipes
| Sector | Typical A847 applications |
| Architecture | Facade frames, columns, canopies, screens and pergolas |
| Bridges & infrastructure | Pedestrian bridges, railings, sign gantries and sound-barrier posts |
| Poles & towers | Lighting and transmission poles, masts |
| Landscape & art | Planters, bollards, sculptures and outdoor furniture frames |
Not recommended for marine splash zones, immersion, buried service or areas with frequent de-icing salt, unless protected by coating.
Why Buy A847 Corten Pipe from ASC LLP?
- Genuine weathering steel: A847 tube with 3.1 certificates showing chemistry and corrosion index – not ordinary carbon steel sold as “Corten”.
- Round and hollow sections: pipe, square and rectangular tube, cut lengths.
- Complete Corten package: Corten tubes, Corten welded pipes, Corten seamless pipes and Corten plates.
- Export packing that keeps the steel dry during transit, so patina forms evenly on site.
Send section, size, wall, length and quantity to sales@amardeepsteel.com, call 022-67439130 or contact us.
Frequently Asked Questions – ASTM A847 Corten Steel Pipes
What is ASTM A847?
ASTM A847 is the specification for cold-formed welded and seamless high-strength, low-alloy structural tubing with improved atmospheric corrosion resistance. It covers weathering (Corten) steel pipe and round, square and rectangular tube.
What are the mechanical properties of ASTM A847?
ASTM A847 tubing has a minimum yield strength of 345 MPa (50 ksi), a minimum tensile strength of 485 MPa (70 ksi) and minimum elongation of 19% in 50 mm for walls of 3.0 mm and over.
Is ASTM A847 the same as Corten steel?
Cor-Ten is a trade name for weathering steel. ASTM A847 is the ASTM specification for weathering steel structural tubing, so A847 pipe and tube is often called Corten pipe. The equivalent plate specifications are ASTM A588 and A242.
What is the corrosion index requirement for A847?
A847 steel must have an atmospheric corrosion index of at least 6.0, calculated from its chemistry using ASTM G101.
Is ASTM A572 Grade 65 a Corten steel?
No. ASTM A572 Grade 65 is a high-strength low-alloy structural steel without weathering properties. Weathering grades include ASTM A588, A242, A606 Type 4, A709 Grade 50W, A871 and, for tube, A847.
Can A847 Corten pipe be used near the sea?
Weathering steel is not recommended in marine splash zones, areas with salt spray or de-icing salts, or where it stays permanently wet, because the protective patina does not stabilise. In these conditions it should be coated or another material used.
Global Reach
ASC LLP supplies Corten weathering steel pipes, tubes and plates to architects, fabricators and infrastructure projects in the USA, Europe, the Middle East and Asia, with secure packing and full documentation. Buyers worldwide rely on our ASTM A847 Corten steel pipes for certified material and traceability.
Countries We Export To
UNITED STATES, EUROPE, UK, UAE, SAUDI ARABIA, OMAN, KUWAIT, JORDAN, QATAR, INDONESIA, MALAYSIA, BRAZIL, SPAIN, ITALY, FRANCE, GERMANY, BAHRAIN, SRI LANKA, AZERBAIJAN, AUSTRALIA, AUSTRIA, PHILIPPINES, TURKEY, RUSSIA, IRAN, IRAQ, CANADA, KOREA, JAPAN, YEMEN, FINLAND, ZIMBABWE, HUNGARY, PORTUGAL, VIETNAM, MOROCCO, THAILAND, SOUTH AFRICA, MEXICO, SINGAPORE, GREECE, KUWAIT, POLAND, NEW ZEALAND, SWEDEN, SWITZERLAND, BELGIUM, BHUTAN, BANGLADESH, TAIWAN, ROMANIA, CAMBODIA, KAZAKHSTAN, AFGHANISTAN.
