1. How Corten Steel Works in a Facade
Corten steel is a weather-resistant, high-strength steel that overcomes the corrosion problem of ordinary steel by a controlled alloying approach. In the beginning, the exposed surface rusts like common steel, but before long the alloying elements, mainly copper, chromium, nickel and phosphorus, cause a dense protective film, the patina, to form on the surface. This layer restrains further rust development and gives the material its rust-red colour. The patina replaces paint: the facade is maintenance-free in suitable atmospheres, and the surface becomes more stable with time. The mechanism requires alternating wet and dry cycles, so facade detailing must keep the panels drained and free-drying.
2. Grades Commonly Used for Curtain Walls
Curtain wall panels are produced from several weathering steel grades, depending on the governing standard of the project. Common designations include Corten A (ASTM A242 type), S355J0WP and the older Fe510 C1K1 and E 36WA3 designations (European system), WR50A (British system), and SPA-H, B480NQ, Q345GNH and 09CuPCrNi-A in the Asian systems. These grades are broadly similar in corrosion performance but differ in composition limits and mechanical property tables, so the grade named in the contract must be supplied with its own mill certificate. Panel stock is hot-rolled steel in thicknesses typically from 1 mm to 300 mm, widths of 300–4050 mm and lengths of 300–15000 mm, with custom dimensions available.
3. Representative Properties of Corten A Panel
For a Corten A type panel in the 6–12 mm thickness range, representative minimum values are a yield strength of 345 MPa, a tensile strength of 485 MPa and a minimum elongation of 20%. Actual heats show variations in the single-element analyses, and the values on the mill certificate, not typical heats, govern the acceptance of the order. Where the curtain wall carries its own weight only, thinner panels are common; where the steel is part of the structural bracing, the strength values are used in the design calculation.
4. Design Details for a Durable Curtain Wall
Four details decide the service life of a weathering steel curtain wall. First, drainage: panels must shed water and dry out; horizontal surfaces and crevices that trap water delay the patina and accelerate corrosion. Second, run-off: during the first one to three years, rust-coloured water stains glass, light-coloured stone and paving, so drips, offsets and, where needed, temporary runoff barriers must be designed. Third, fixing: fasteners and brackets should be stainless or galvanized steel, and the fixings must allow for thermal expansion of the panels, which is greater than for coated steel because the surface is dark and absorbs heat. Fourth, environment: bare corten is not suitable within reach of marine salt spray or in permanently damp conditions; in those locations the steel must be coated or a different material selected.
5. Inspection and Maintenance
A corten curtain wall needs periodic inspection rather than painting. Loose rust particles during the stabilisation period can be brushed off, and debris, leaves and bird droppings should be removed because they hold moisture against the steel. Joints, seals and fasteners should be checked, especially in the first years when the patina is still forming. Where the facade is combined with glass or stone, the staining risk is highest in the first one to three years and should be monitored; the run-off diminishes as the patina stabilises.
Frequently Asked Questions
Which corten grades are used for curtain walls? Corten A (ASTM A242 type), S355J0WP, SPA-H, Q345GNH and 09CuPCrNi-A are common choices, depending on the project standard; the supplied grade must match the contract and carry a mill certificate.
What is the strength of Corten A panel? In the 6–12 mm thickness range, representative minimum values are 345 MPa yield, 485 MPa tensile and 20% elongation.
Does a corten curtain wall need painting? No. The patina is the protective layer. In coastal, industrial or permanently damp environments the patina cannot stabilise and a coating system or another material is required.
How do I prevent rust staining on glass and stone? Design drips and offsets so that run-off does not flow from the steel onto adjacent surfaces, and consider temporary runoff barriers during the first one to three years of patina formation.
What thickness of corten is used for curtain wall panels? Panels are typically 1–6 mm for infill cladding and up to 12 mm or more where the steel contributes to the structure; thickness is selected from the wind load and deflection limits.
Can corten curtain walls be used in coastal cities? Bare corten is not recommended within reach of marine salt spray. In coastal locations, coated weathering steel, stainless steel or aluminium systems are the usual alternatives.
