Whether you collect swords or use them to practice martial arts, you should take steps to protect your swords from rust.
What is Rust?
While most people are familiar with the basic appearance of rust, few know its actual composition and properties.
Scientifically speaking, rust is an iron oxide (chemical Fe2O3) that's created through the oxidation of iron. When iron is exposed to water, oxygen or sunlight, certain chemical reactions occur in a process called oxidation, which results in rusting. Minor formations of rust can be cleaned and remove. If left unaddressed, however, it can literally eat through the metal, causing permanent damage to the blade.
I know what you're thinking: my sword is made of steel, not iron, so how does it rust? Even steel swords are susceptible to rusting due to the presence of iron. Steel is an alloy that contains iron; thus, it too may rust. The traces of iron buried deep within the steel will react to moisture, light and oxygen just the same.
Keep it Dry
The single most important tip to protect your sword from rusting is to keep it dry. Moisture provides rust the perfect environment in which to thrive. So by keeping sword dry, you'll naturally protect it from rusting.
Clean After Handling
Try to get into the habit of cleaning your sword after handling it. Using a line-free cloth, carefully wipe down the blade to remove any dust, dirt, debris and fingerprints.
For a deeper and more thorough cleaning, you may want to use a special sword cleaning product.
Apply Wax or Oil
In addition to cleaning your sword, you should also apply either wax or oil to the blade, further protecting it from rusting. If you asked ten different collectors which wax or oil to use, you would probably get ten different answers. With that said, some of the most popular choices include 100% mineral oil or gun oil. Regardless of which product you choose, test it beforehand by applying a small amount to a discreet area of the blade and waiting to see how it reacts.
Store in a Climate-Controlled Area
You can also protect your sword from rusting by storing it in a climate-controlled facility. More specifically, store your sword in an environment with 40-50% relative humidity. Humidity is a measurement of the amount of water vapor in the air. When the relative humidity rises beyond 60%, it indicates excessive moisture vapor that could otherwise contribute to rust and corrosion.
Photo credit: Seyi Ogunyemi
In case your sword starts to develop rust spots, we recommend high quality Japanese metal polish such as Pikal to remove rust from sword.