How to accelerate the corrosion of corten steel?

Corten steel is widely used in decoration for its original appearance and natural durability. But for practical reasons, it may be delivered non-rusted. To avoid waiting several months, we explain how to accelerate its corrosion using a very simple method.

A little recap about corten steel

In a previous article, I told you about the special characteristics of naturally rusted corten steel. It is a very aesthetic steel, much used in exterior design. You can find various kinds of corten steel objects that already have a patina in DIY or gardening stores to decorate your outdoors space. But before it takes on its final appearance, corten steel’s original state has no patina and the rust on it can take several months to appear and stabilise.

John Steel delivers your custom-cut corten steel as panels with no patina (non-rusted). This is so precision laser cutting can be used without damaging the material. So you need to be patient and wait for the steel to mature (a bit like a fine wine;)).

But this gives creative people like you lots of opportunities to really play with the material. You can make unique half-rusted/ half-painted pieces, but you can also weld the metal before the patina forms.

Cut out my custom corten steel panel

How can I speed up corten steel rusting?

Depending on the climate conditions and the size of the panel, corten steel may take several months to stabilise. Ideally, it must be subjected to alternating wet and dry periods, so that the patina forms consistently until the metal achieves a nice orange colour across its entire surface. But if the weather is a bit capricious, it may seem like this takes a long time.

My little trick to speed up the process is to spray saltwater regularly across the panel and let it dry. Repeat this every day and you’re sure to see rust form quite quickly.

In order to show you how it all works, we asked our special operative to repeat this process in mid-May.

• The cat was left in the garden and exposed to bad weather
• The frog was soaked regularly in a saltwater solution, then dried naturally under the veranda
• Photos were taken on D1, D3 and D11

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There is a clear acceleration of the process with saltwater, which gives you much faster corrosion across the whole surface, in only 10 days.

Rust on the cat which was left in the open for 10 days

Rust on the frog which has been regularly dipped in saltwater (10 days)

After 10 days, the patina on the frog is not yet perfect and the process can be repeated until the desired result is achieved. You can also allow any subsequent corrosion to occur naturally, in the open air until the rust has stabilised.

Cut out my custom corten steel sheet

Now you know everything about corten steel. If you have tested any other methods, I will be happy to hear your feedback.

Don’t forget to send us photos of your corten steel projects to makers@john-steel.com so that Brigitte can share them with the Steelsters community!

See you soon,

-John-