Corten steel is an alloy of steel with various other metals that makes it resistant to long-term corrosion. Though its exposure to the atmosphere results in rusting and weathering, however, unlike normal mild steel, Corten still starts to form a stable patina as time goes by, by greatly reducing the formation of rust later on; in other words, it retards the oxidation process.
Corten steel was developed as a weathering steel that stabilizes after a few years to avoid the need for painting, while mild steel continues to rust if not painted, and eventually disintegrates over time. Since Corten steel gradually slows the rusting process and stabilizes after a few years, it is the material of choice for making shipping containers, railway coaches, and rail lines.
Corten steel has now found a new application as a façade material. Besides its stabilizing property, which has caught the fancy of facade designers, it’s the brilliant colour phases that Corten steel goes through as it comes into contact with wet and humid conditions over a period of time. The colour changes from grey to brilliant yellow orange and red before turning to darker shades of red and brown.
Project using Corten steel
The 3-unit row house in Thane near Mumbai was being redesigned. The client initially wanted HPL or ACP of similar shades for the building’s facade, but we proposed Corten steel. The façade is created as a rectangular arch, which starts at the first floor of the row house and reaches up to the full height of the building. The detailing of the arch was very important as all the three row houses had to look identical, which meant that the size of panels and level of joints were crucial.
Since it was not a straight-faced facade but a 3-dimensional arch and angular, there were more challenges than initially envisaged. The most critical decision was the introduction of a groove around each panel, which posed huge problems as the grooves had to match the entire surface from the left side of the arch to the ceiling, and then down to the right side of the arch. This challenge was not initially visualized but we did not alter the initial design, and executed the façade successfully.
Corten Steel is a 100% recyclable and a 100% fire proof material with zero maintenance and can be well adapted for constructing a sustainable façade
Ar. Harish Gupta
The entire work was done during the second phase of the pandemic and the cyclonic rains of 2021, which posed huge safety challenges due to which the work progressed more on dry days and was almost at a standstill on rainy days. However, the silver lining of working with Corten steel in the monsoons is the colour transformation the metal goes through with every cycle of rain and sunshine – from bright yellow to orange to red - colours that remind one of the spring time bloom of the Gulmohor tree.
Corten steel needs to be properly specified for thickness and support structure as it is a weathering façade. Care needs to be taken that the façade’s detailing and execution is such that it will last for 25 to 30 years before requiring any maintenance.
Since Corten steel does not require cleaning or painting during the life of the façade, there is cost saving, plus the metal has a salvage value at the end of the façade’s life.
