How do I prevent corten steel staining my patio?

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How do I prevent corten steel staining my patio?

Corten steel is a weather resistant steel which makes a wonderful and high class addition to your garden or outdoor space. However, you may have heard that the rust colouring can ‘run-off’ and stain surrounding surfaces. In this article, we’ll take a look at some of the claims and discuss things you can do to minimise the issue.

a small rectangle corten raised bed in an outdoor garden with wooden fence panels behind

Does corten steel produce a ‘run-off’?

It is true that weathered steel planters and other products will produce a rust-coloured run-off that can stain patios and surrounding areas. However, this is mainly an issue during the weathering process, which is when the corten steel achieves its beautiful, unique, and protective rust-like coating. This usually takes between six and nine months to complete (although this does depend on your local environment and weather conditions) and, after this, any run-off will be significantly less of a problem.

Does corten steel rust rub off on clothes?

During the early stages, the rust may rub off on clothes or other materials but, once fully weathered, you will have to rub pretty hard to get anything to rub off.

What can I do about the run-off?

Thankfully, there are many relatively simple steps you can take to reduce or eliminate the risk of corten steel from staining your lovely patio. Let’s take a look at some of them:

  1. Complete the weathering process before placing in position: You can place your corten product on top of grass, soil or even gravel which will not cause any issues and allow the product to weather for 6-9 months until the material has fully weathered before moving to its final position.

  1. Use a weathering treatment: There are some weathering treatments on the market that will speed up the naturally weather-dependent process of corten steel achieving its attractive orange-brown patina. Some of these have a better chance of success than others so be sure to do your research first. It may be a good idea to test the treatment on an area that is not seen (the inside of a planter for example) to see what effect it has on the corten steel.
  1. Use a protective layer: You may choose to place your corten product on a drip tray (make sure the water in the drip tray can drain without causing an issue) or on a protective layer that can easily be replaced once the weathering process is complete. This could be gravel or a replaceable slab or something else, but make sure that any run-off can’t run off this protective layer!
  1. Opt for easily replaceable materials: You may wish to position the corten steel product on grass, soil or other loose materials such as stone, slate, or wood chippings. These materials can easily be turned over or replaced to eliminate any run-off stains.
  1. Leave a gap: Another popular way to avoid run-off stains is leaving a small 10mm gap between the corten product and your patio will allow the run-off to escape into the gap and not stain anything important. You could also add some gravel between the paving and the product if you don’t want to see a gap.

 If none of the above steps are going to work for you then you could opt for an alternative material that does not produce any run-off. Please see our blog post on what are the alternatives to corten steel?

Sealing Corten Steel

 We often get asked about sealing corten steel and you may see this option discussed online. However, we do not generally recommend applying a sealant to corten steel because corten was originally developed to be left outside, untouched without a finish being applied. Furthermore, any sealant is unlikely to last for the lifetime of the material so repeated applications will be needed creating ongoing maintenance and costs.

While run-off does occur it doesn’t have to pose a problem if you follow some of the steps we’ve outlined, allowing you to enjoy the unique beauty of corten steel in your outdoor space without any concerns.