How can corten steel last when it rusts?

Where does corten steel come from?

The United States of America Steel Corporation developed corten steel in the 1930s to make coal cars for the railways and bridges, where maintenance of the underside was particularly difficult. With corten steel, you could avoid having to paint the steel, and at the same time have a strong and weldable type of steel that is weather resistant. Corten steel was subsequently used for several forms of protection (among other facade cladding) in the early 1960s. Today, corten steel is still used in architecture in many places - for example the Bryggen in Vejle, the Steam Kettle Building in Silkeborgs Papirfabrik and Farum Midtpunkt.

Why does corten steel last even if it rusts?

Corten steel rusts quickly on the surface, but it corrodes more slowly than mild steel. Corten steel holds up well - even if it looks rusty. Corten steel only rusts on the surface, and the rust on the surface helps to protect the steel.

Why does corten steel flake?

Corten steel's appearance develops over time, and it is normal for it to flake a little at the bottom, where there is the most water. It has no effect on the durability of the corten steel. Here it is also important to note that rust is 7 times thicker than the original steel. 2 mm corten steel thus becomes 14 mm rust. This means that 0.3mm of rust comes off in 2.1mm flakes, which can make it look worse than it is. The flakes won't go away (unless they break off) and they will protect the steel underneath. If you want to remove some of the flakes for aesthetic reasons, you can use a sponge or some sandpaper.

How does the color of the corten steel develop?

The color of corten steel changes over time. The color will change over time from orange, reddish brown, brown to almost black.



Does corten steel rub off on tiles and wood?

At the beginning of the rusting process, the rust may drip, and stains may appear. This can be avoided by placing a bit of tarpaulin under the edges of the planter box on which the rust can then drip. After a few months, the rusting process will not go nearly as fast, and smudging will no longer occur.

Why does corten steel rust differently?

It is normal for corten steel to rust at different rates. This may be because there is still an oil layer on the plates, which rust more slowly. It can help to wash off the plates, which are not very rusty, in salt water once. When the plates get rain, the process will really speed up, and the rusting process will start more.