12/08/2024
What is Corten steel?
Also known as Cor-Ten, it is a brand of weathering steel, in which the surface rust layer protects the steel beneath from further degradation, this gives Corten an increased life in comparison to mild steel.
The weathering process for Corten steel typically takes around 6-9 months, depending on weather conditions, while for mild steel it generally takes slightly longer. Once fully weathered, the two materials look very similar and can be hard to distinguish without closer inspection.
Mild steel is mainly composed of iron and a small amount of carbon. Corten steel, while also made up of iron and carbon, is an alloy steel. The additional alloying elements include chromium, nickel, copper and phosphorous, providing Corten steel with its unique self-protecting properties and giving it an edge in terms of longevity
While Corten was initially designed for use in more industrial settings it became popular with architects and artists and from here it found its way into gardens.
Is there a difference in colour finish between Mild Steel and Corten Steel?
There are very few differences between the aesthetic of Mild Steel and Corten Steel. All Carbon steel rusts. The differential in the aesthetic is the chemical composition of the Steel. So, Corten Steel will tend to start life more with yellowy and orange hues due to it containing elements of copper.
The Mild Steel will develop the patina in a more orange, red, and brown finish. Both steels will eventually look very similar when they reach their full patina. The only difference is that due to the protective patina layer, Corten Steel will retain its full patina finish whereas Mild Steel will likely continue to develop its patina and therefore colouration over a longer period.
Will the Patina from Corten Steel stain?
Corten Steel and Mild Steel will produce what we call “Run Off”. Run Off is the water that runs off the product in the early stage of the patina development that carries with it some of the colour of the patina. This may stain surfaces that the products are placed on.
This is common in all-natural steel products. There are certain mitigating actions you can take to manage this. Place the product on or surrounded by loose stone or chippings that can be turned over or replaced with a top layer to remove the runoff. Place the product on a slab of another protective layer that can be replaced or removed once the patina is fully developed.
