How to Stop a Katana From Rusting

Whether you collect swords or use them to practise martial arts, you need to take steps to protect your swords from rust.

Knowing how to care for your katana is essential.

What is rust?

Most people know what rust looks like, but few know its actual composition and properties.

Scientifically speaking, rust is an iron oxide (Fe2O3) created by the oxidation of iron. When iron is exposed to water, oxygen or sunlight, certain chemical reactions take place in a process called oxidation, which results in rust. Small areas of rust can be cleaned off. Left untreated, however, rust can literally eat into the metal and permanently damage the blade.

My katana is made of steel, not iron, so how can it rust?

Even steel swords can rust because of the iron they contain. Steel is an alloy that contains iron, so it can rust too. The traces of iron within the steel react in the same way to moisture, light and oxygen.

Keep it dry

The most important tip for protecting your sword from rust is to keep it dry. Moisture gives rust the ideal environment in which to develop. By keeping your sword dry, you naturally protect it from rust.

Clean the sword after handling it

Try to get into the habit of cleaning your sword after handling it. Using a lint-free cloth, wipe the blade carefully to remove dust, dirt, debris and fingerprints.

For a deeper, more thorough clean, you can use a product made specially for cleaning swords.

Apply wax or oil

As well as cleaning your sword, you should also apply wax or oil to the blade to protect it further from rust. If you asked ten different collectors which wax or oil to use, you would probably get ten different answers.

That said, popular choices include 100% mineral oil or gun oil. Whichever product you choose, test it first by applying a small amount to an inconspicuous area of the blade and waiting to see how it reacts.

Store your sword in a climate-controlled place

You can also protect your sword from rust by storing it in a climate-controlled place. Specifically, store your sword in an environment with a relative humidity of 40 to 50%. Humidity is a measure of the amount of water vapour in the air. When relative humidity rises above 60%, it indicates an excessive amount of water vapour that could contribute to rust and corrosion.

If your sword starts to show rust spots, we recommend using a high-quality Japanese metal polishing product, such as Pikal, to remove the rust from your sword.