Why has your wood-burning stove rusted? Find out what causes rust on a woodburner

A wood-burning stove is a big investment, so the last thing you want to see is rust appearing on it.

Unfortunately, rust and corrosion can sometimes happen. In this article we’re going to explore some of the causes of rust on a woodburner. Hopefully you’ll be able to find out why your wood-burning stove has rusted and minimise the risk of it corroding further in the future.

There are two things that are the main causes of rust on a woodburner. If you gave a couple of minutes’ thought as to what you associate as being the causes on any other piece of metal you could probably name them. That’s right, moisture and inactivity.

Extended exposure to water and oxygen are the causes of rust in ferrous metals. When your cast iron stove is exposed to moisture and is not being used regularly, it is susceptible to the process of oxidation. The oxygen combines with the metal in a chemical reaction to produce a new compound: ferric oxide, which is rust.

So, if you want to keep your woodburner rust-free, you need to keep it dry and in regular use. Let’s explore some of the circumstances in which the ideal conditions for rust might happen in your stove.

Summer rainfall

When it rains, it is inevitable that some water will come down your flue. This is a regular occurrence throughout winter. But once you light your stove, the rainwater evaporates back up the flue before it has had chance to cause any damage.

Issues are more likely to arise in summer, when you’re not using your stove regularly. A summer downpour might result in rainwater sitting inside your stove system for weeks or even months.

There are a couple of things you can do to mitigate the risk of rainwater causing your stove to rust. Firstly, you could fit a chimney cowl that limits the amount of rain that’s able to get inside your flue in the first place.

Secondly, we would recommend lighting your stove occasionally even when the temperature isn’t really cool enough to warrant it. An occasional fire through the summer months will evaporate any moisture that has found its way into your appliance and keep it dry.

Condensation

Other than rainwater, the other form of moisture which your woodburner will most often encounter is condensation. As a considerable piece of metal, you woodburner – when it’s not lit – is probably one of the coldest things in your home.

If your property is susceptible to damp air, has poor ventilation or if you’re doing something that’s likely to add a lot of moisture to the air, such as drying clothes on radiators, you might see water on the outside of your wood-burning stove. This is the result of the moisture in the air cooling, condensing and settling as water when it comes into contact with the cold surface of your stove.

The main ways to avoid condensation causing rust on your stove are the same measures you would follow to reduce moisture in the air. This includes:

  • Opening windows regularly.
  • Using extractor fans.
  • Using a dehumidifier.
  • Not drying clothes on radiators.

In some properties, high levels of moisture in the air are unavoidable. If you do spot condensation on your woodburner, use a dry cloth to take the water away as quickly as possible. This will minimise the chances of it causing risk.

Stale air

Leaving your stove out of use for an extended period of time can cause it to corrode. When there’s no air movement through your stove system, the air that’s inside just sits and can start to cause corrosion inside your stove. If there’s a high moisture level in that air, the problem is even worse.

You can help to overcome this problem by leaving the stove door ajar when it’s out of use for a while. This will encourage a flow of air and ventilation that will keep your air inside your stove nice and fresh. And as discussed above, lighting your stove occasionally – even when you don’t really need to light it – will keep rust and corrosion at bay.

Other objects

Another common cause of rust is people placing other objects on their stove. When your woodburner is out of use, you might be tempted to decorate it. Flower-filled vases, metal plant pots and other decorations are among the things we’ve seen adorning unlit woodburners. But any item that is limited the air supply to the surface of your stove (particularly if it also contains moisture) is only going to increase the likelihood of corrosion.

No matter how good your stove embellishment looks, we would suggest avoiding it in order to protect your appliance from corrosion.

Removing rust from a woodburner

If you do find some rust on your wood-burning stove, it’s not the end of the world. Hopefully the information above will help you to avoid similar problems in future. In the meantime, you might be wondering what is the best way of dealing with rust on a woodburner. Here is a similar process to follow to get your stove looking as good as new again.

How to remove rust from a wood-burning stove

  • Wait for your stove to cool. You should never remove rust from a hot stove.
  • Using small, gentle, circular motions, remove all the rust from the stove with wire wool.
  • Wipe the stove down with a damp cloth to ensure that all the rust particles are removed from the stove surface.
  • Once the stove is dry, restore your stove’s finish using specialist stove paint. Stove paint is made to withstand very high temperatures, so it’s important you don’t use any other type of paint.
  • You will probably need to give a second coat of stove paint. Make sure the first coat is completely dry before starting the second coat.
  • Only light your stove again in accordance with the instructions on the stove paint.

Remember: the rust is formed by oxygen combining with the metal itself, so it is impossible to remove the rust without also taking away the original finish. Accept that you’re going to be stripping away the paint, then focus on restoring it to the best of your ability.

Keep in mind that most stoves have a matt / flat black enamel finish. Others will have a glossy / metallic finish. Make sure you pick the appropriate stove paint for your appliance.

If your stove is an unusual colour, you might have to track down the manufacturer’s paint in order to achieve an exact match.

If you’re currently treating rust on a woodburner you can buy stove paint here and wire wool from any DIY or hardware store, and many supermarkets.

Preventing rust on a wood-burning stove

Once your stove is restored to its former glory, following the advice above to prevent or minimise the risk of a recurrence of rust on your woodburner.

That includes:

  • Lighting your woodburner regularly throughout the year.
  • Fitting a cowl to reduce the amount of rainwater getting into your flue or chimney.
  • Dry clothes outdoors whenever possible and don’t leave damp clothes on a radiator.
  • Open windows regularly and/or ensure your home is well ventilated.
  • Use a dehumidifier if there are high moisture levels in the air in your property.
  • Leave the stove door ajar when the appliance is not in regular use.
  • Do not place other objects (especially damp or metal objects) on your stove.

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