Rust can make your knife unsightly. But that’s not just it. If left to stay long, it could corrode your knife’s blade, rendering it unusable. Even worse, you could get tetanus if you unintentionally cut yourself with the rusted knife. So, you must get rid of the rust.
So then, how do you get rid of rust on a knife? Many methods exist for removing rust from a knife, including natural and non-natural. For natural methods, you can use vinegar, baking soda, lemon juice, salted potatoes, or a grinder. Non-natural methods include using WD-40, oxalic acid, citric acid, or phosphoric acid.
But what causes rust, and how do these removal methods work? This article will discuss everything you need to know about how to get rid of rust on a knife.
What Causes Rust On a Knife?
Even the best chef knife will rust when you expose it to water and oxygen for a long time. This happens when you don’t dry or clean your knife correctly after use.
You see, most blades are either stainless steel or carbon steel. And as it turns out, steel is a form of iron alloy. Now, rust or hydrated ferric oxide, usually forms when iron particles come into contact with moisture and oxygen.
How To Get Rid of Rust On a Knife Using Natural Methods
By using household products, there are many natural ways to remove rust from your knife. Let’s find out how each method works.
1. Using Lemon Juice or Lemon
Lemon contains large amounts of citric acid. Meanwhile, its juice boasts a pH between 2 and 3, rendering it highly acidic.
To remove rust on your knife:
- Cover the rust spots with salt
- Cut a 1/2 slice of a lemon and squeeze its juice over the salt layer
- Leave the mixture on the knife for at least two hours
- Scrub your knife using the lemon rind until there are no more rust stains
- Lastly, rinse your blade thoroughly to remove the lemon residue and dry it
2. White Vinegar Solution
White vinegar contains acetic acid that is powerful enough to dissolve rust. This is how you use it:
Soak your rusted Japanese kitchen knives in a bowl filled with vinegar overnight. This method works best for blades with significant corrosion. So, for minor rust, you can soak the knives for up to 30 minutes.
After soaking, scrub any remaining rust stains using a scouring pad or steel wool. Then, wash your knife with soapy water and dry it well.
3. Baking Soda and Water Paste
Baking soda, also known as sodium bicarbonate, is a mild abrasive. As such, it works best to eliminate mild rust on knives. Here is how to prepare the paste:
- Mix one tablespoon of baking soda with two cups of water to form a thick paste
- Cover all the rust spots on your knife with the paste
- After an hour, scrub your knife with a soft sponge to remove the remaining stains
- Next, rinse your blade thoroughly with warm water and dry it
4. Salted Potato and Dish Soap
All potatoes are rich in oxalic acid. When this acid reacts with rust, it forms an iron oxalate compound that you can quickly rinse off with water.
To put this method into action:
- Cut a potato in half.
- Coat one half (the cut side) with dish soap.
- Sprinkle some salt on top.
- Rub all the rust stains on your knife with the potato. Then, rinse the blade and dry it.
5. Grinder and Vinegar
This method works best when you have an extremely rusty butcher’s knife or cleaver.
- Soak your knife in vinegar overnight.
- Then, grind your rusty knife using a grinder to eliminate any bumpy holes created by rust.
- Next, use sandpaper with 80 to 400 grit to sand your blade, giving it a smooth finish.
How To Remove Rust On a Knife Using Chemical Removers
Besides homemade products, you could also use chemical removers to get rid of rust on the kitchen knife. These include
WD-40 is a multi-use product that you can get from a hardware or supermarket near you. It contains lubricating properties that may help break down the bonds between rust and a knife’s metal surface.
- Start by spraying the WD-40 on the rusty spots of your knife.
- Let the liquid sit for about 10 minutes before scraping the rust with a wire brush.
- Use sandpaper to remove any remaining rust stains.
- Wash the knife with water and soap and dry it.
2. Citric Acid
Citric acid is an organic compound used as a preserving and flavoring agent. But because of its weak acidic nature, it can remove rust stains on kitchen knives, including Japanese kitchen knives and others.
This is how it works:
- Put about 400 ml of warm water in a plastic container.
- Add 15 grams of citric acid powder to the water.
- Put your rusty knife inside the citric acid solution until there is no more bubbling.
- Scrub the blade with a scouring pad, rinse it, and dry it.
3. Phosphoric Acid
Phosphoric acid is commonly used as a chemical-cleaning agent for metal. Instead of dissolving rust like most products, phosphoric acid bonds with ferric oxide to create water and iron III oxide.
To use this chemical rust remover:
- Wear safety goggles and protective gloves
- Then use a paintbrush to apply the phosphoric acid jelly to your knife’s rusty blade
- Let the jelly sit for around 5 minutes, and scrub the rust with steel wool
- Clean your knife thoroughly with water, ensuring the jelly does not come into contact with your skin
- Next, scrub the knife with baking soda and a brush. Then, rinse the blade and dry it.
6. Oxalic Acid
Oxalic acid usually converts rust into iron oxalate, a water-soluble salt that dissolves in water and quickly rinses away. Here is how it works:
- Buy oxalic acid from a hardware store and mix it with water in a 1:10 ratio.
- Dip your rusty knife inside the solution for at least 20 minutes.
- Scrub the rust with a brush and rinse the blade with water before drying it.
Will Coca-Cola Remove Rust On a Knife?
Yes. This is because Coca-Cola has phosphoric acid, which changes rust to a water-soluble compound that is easy to remove.
- Simply put coke in a small bowl.
- Wet a sheet of aluminum foil with the cola and scrub the rust on your knife’s blade.
- Lastly, rinse the knife and let it dry.
Alternatively, you can soak the knife inside the bowl of coca cola for at least 24 hours. This works best when the rust is severe.
How To Keep Rust Off My Knives
“Prevention is better than cure”- so says the proverb. Take the following measures to prevent rust on your kitchen knives.
- Always wash and dry your knives thoroughly after every use
- Never leave your knife sitting in the sink or dishwasher
- Wax the blade regularly with blade wax containing beeswax
- Always store your knives in a low-humidity and dry area
- Apply a thin layer of vegetable, olive, or canola oil on the blade periodically
Below, we will respond to commonly asked questions regarding how to get rid of rust on a knife.
Q: Can you remove rust from a knife using bleach?
No. Bleach cannot dissolve rust stains. Instead, this chemical compound may create more rust. This is because bleach contains sodium hypochlorite, an oxidizing agent, and rust usually forms through oxidation.
Q: Can Toothpaste Remove Rust on a Knife?
No. Toothpaste cannot remove rust itself on a knife. However, it can eliminate rust stains when used along with baking soda.
Q: Can soapy water alone remove rust on knives?
No. You only use soap and water to remove any oil residue, dirt, or grease on the knife’s surface. This allows the rust remover product to penetrate through the rust stains for easy removal.
Water and moisture are the primary reasons your knife may rust. Luckily, there are many methods how to get rid of rust on a knife. You could use vinegar, baking soda solution, lemon juice, a potato, or a grinder.
Also, chemical products are available, including oxalic acid, WD-40, citric acid, and phosphoric acid. By the way, the best thing is to prevent rusting your knives.