Celsius Celsius® weathering grade

Celsius® weathering grade

Combining the corrosion resistance of weathering steel, with a true hot finished structural hollow section, Celsius® is now available in weathering grade.

Weathering steels have small additions of copper and chromium that help improve the corrosion resistance of the steel to atmospheric sources for a long, maintenance-free life. Through natural wet-dry cycles, the steel forms a dense surface patina which prevents corrosion.

Combining the properties of weathering steel with the intrinsic benefits of a true hot finished hollow section, weathering grade Celsius provides a Unique opportunity for the construction of long-life, maintenance-free structures.

  • Weathering steel forms a dense patina which protects it from oxygen, slowing corrosion for a useful life of 50 to 120 years.
  • Weathering steel doesn’t need any further protection eliminating, in most cases, the need for galvanising, painting and ongoing maintenance.
  • The natural and evolving patina of weathering grade Celsius® blends in perfectly with the natural environment.
  • All Celsius® hollow sections are true hot finished, so free from internal stresses and with tight corner radii to maximise weldable-surface and enhance aesthetic appeal, whilst avoiding the risk of brittle fracture which occurs in some cold formed products.
  • The corner radius on squares and rectangles is 2T max. This exceeds the requirements of EN 10210:2006.
  • Weathering grade Celsius® has a low CEV of 0.44 max. This guarantees excellent weldability.
  • Suitable for galvanising (where necessary) and for low temperature applications (40J @ -20°C). 
  • Batch-tested and fully traceable, supplied with a full 3.1 test certificate.
  • All Celsius® sections are CE marked and fully compliant with the Construction Products Regulation.
  • Available in a wide range of circular, square and rectangular hollow sections with a wall thickness up to 16mm.
  • Full technical support in material selection and application available.

High strength hot finished hollow sections suitable for a wide range of construction and mechanical applications. Weathering grade Celsius® is suitable for all external applications to European and American design standards.

Mechanical properties

Yield strength;
ReHmin N/mm2;
Tensile strength;
Elongation % min
L0;= 5,65 √S0
Impact strength
10mm x 10mm
Carbon equivalent
(CEV) max
T ≤ 16mm 3mm < T ≤ 100mm T ºC J  
355 470-630 22 -20 40 0.44

CEV value exceeds the requirements of S355J2WH, prEN 10210 (2016).

Chemical composition % by mass

C max Si max Mn P max S max Nb max V ma Al total min Ti max Cr max Ni max Mo max Cu max N max
0.16 0.50 0.50
0.025 0.008 0.050 0.10 0.020 0.03 0.40
0.40 0.10 0.25
  • Chemical composition meets or exceeds the requirements of S355J2WH, prEN 10210 (2016).
  • Available in grades S355J2H and S355K2H.
  • Chemistry and mechanical properties comply with ASTM A847
  • The steel is aluminium-killed.


Dimensional tolerances are to EN10210: Part 2 – for full details, please consult our publication Celsius® 355NH Technical Guide.

Inspection and testing
Celsius® Weathering Grade hollow sections are subject to specific
inspection and testing and are supplied with an inspection certificate
type 3.1 to EN 10204.

Celsius® Weathering Grade hollow sections are manufactured and CE marked in accordance with EN10210-1&2:2006 grade S355J2H or S355K2H. Manufactured from steel with improved atmospheric corrosion resistance (chemistry complies with the requirements for EN10025:-5 S355K2W). 3.1 test certification to EN10204.

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