How to clean & remove rust from Japanese knives [simple tricks]

Author: Joost Nusselder, author of The Essential Japanese meal planner cookbook Updated November 2, 2022

Are you looking for the best way to clean and remove rust from your traditional Japanese knives?

If you’ve spent your money on premium Japanese steel knives, the last thing you want to see is rust – not only does it make the blade unaesthetic but getting rust on your food is very dangerous.

Some rust removal methods are more efficient than others. But, with my tips, you can keep your stainless steel knives or high carbon steel knives looking like new.

There are many methods out there for caring for your knives, but one method is both easy and effective: a simple vinegar rinse. After soaking, you can use a soft cloth and a bit of elbow grease to scrub off any rust.

In this article, I’m also sharing other ways to clean your knives and remove rust.

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How to remove rust from Japanese knife

There are several cleaning methods to disinfect, clean, and remove the rust from your precious Japanese knife. Thankfully, rusty knives aren’t so hard to clean and fix!

Of course, most people are familiar with the vinegar method but there are others too that you can try out.

White vinegar

The best quick and effective method to remove knife rust is to use vinegar.

First, rinse your knife off with warm water. If there is any food residue on the blade, use mild dish soap to remove it.

Next, soak your knife in a cup of vinegar for about 15 minutes. The acidity in the vinegar will help to break down the rust.

Depending on how much rust there is on your kitchen knife, you might have to soak it an additional 5 minutes. You’ll notice that reddish-orange flaky stuff is coming off.

After the knife has soaked, use a soft damp cloth to scrub the blade. You may need to put some elbow grease into it, but the rust should start to come off.

If it’s not coming off easily, you can soak it for a bit longer.

Once the rust is gone, rinse the knife well with warm water and dry it off. It’s going to look like you have a new knife!

That’s it! Just a few simple steps and your Japanese knife will be rust-free and looking good as new.

Apple cider vinegar

You’re likely wondering: can you use apple cider vinegar to remove rust from the kitchen knife?

The answer is yes! Apple cider vinegar (ACV) is made from fermented apples and has a higher acidity level than white vinegar.

So, if you’re looking for a more potent rust removal solution, ACV is your best bet.

To remove rust from your Japanese knife using ACV, follow the same steps listed above for regular white vinegar.

This vinegar can even target deeper rust spots and extremely rusty blades.

Using vinegar is also a great way to clean your flat top grill by the way!

Baking soda paste

I’m sure you’ve heard how useful baking soda is in the kitchen. It’s also excellent for removing rust.

The baking soda method for removing rust is easy and cheap.

To correctly remove rust from a Japanese chef knife, you should let it sit in a solution of baking soda paste for 5 – 10 minutes, after which you should wipe down the rusted areas with a cloth or sponge and use steel wool if needed for particularly rusted areas.

To make baking soda thick paste, you’ll need:

• 1/4 cup baking soda
• 3 tablespoons water

Instructions:

In a small bowl, mix together the baking soda and water until it forms a paste.

Baking soda removes rust from Japanese knives by acting as a mild abrasive. The paste is made by mixing three parts baking soda with one part water.

It can get rid of rust and this baking soda water is safe to use because it removes rust naturally without the use of harsh chemicals.

After the knife has soaked, use a soft cloth or sponge to wipe down the rusted areas. You may need to put some elbow grease into it, but the rust should start to come off.

If it’s not coming off easily, you can soak it for a bit longer. Once the rust is gone, rinse the knife well with warm water and dry it off.

You can even use an old toothbrush or other soft-bristled brush to scrub away the rust. You can scrub carbon steel blades as well as stainless steel.

Rust eraser

A rust eraser is a type of abrasive made from rubber or foam that is impregnated with a mild abrasive. Rust erasers are used to remove rust from metal surfaces by abrasion.

A good Asian rust eraser is the Rust Eraser Sabitoru (Medium and Fine 2-piece Set).

To use a rust eraser, simply rub the eraser over the surface of the knife in a circular motion until the rust is removed.

Using a rust eraser in conjunction with a sharpening stone is an excellent way to remove minor amounts of rust.

They are little sharpening stones with different grit grades that can be used in an “elbow grease”-style approach to scraping off the rust.

To get into hard-to-reach rust, a fine grit between 1000 and 3000 will be good, and these are great for getting into the spine or edge of the blade.

Use the white vinegar solution to soak or coat the knife again for this approach. Then use the rust eraser to scrub the blade clean.

Lemon juice

This is another one of the most popular natural rust removal methods that work on carbon steel knives too.

The acidic nature of lemon juice will help to break down the rust on your Japanese knives.

First, rinse your knife off with warm water. If there is any food residue on the blade, use mild dish soap to remove it. Next, soak your knife in a cup of lemon juice for about 15 minutes.

After the knife has soaked, use a soft cloth or sponge to scrub the blade. You may need to put some elbow grease into it, but the rust should start to come off. If it’s not coming off easily, you can soak it for a bit longer.

Once the rust is gone, rinse the knife well with warm water and dry it off.

Salt

You’re probably surprised to see salt on the list. It’s not just for seasoning your food – salt can actually be used to remove rust.

The abrasive nature of salt will help to scrub away the rust.

First, rinse your knife off with warm water. If there is any food residue on the blade, use mild dish soap to remove it. Next, make a paste out of salt and water. You can do this by mixing 1 cup of salt with 1/2 cup of water.

Once the paste is formed, rub it onto the rusted areas of your knife. Let it sit for 10 minutes before rinsing it off with warm water. Dry your knife off with a soft cloth and voila – your Japanese knife is rust-free!

There you have it! These are all simple methods for cleaning and removing rust from your Japanese knives. With just a little bit of time and effort, you can keep your knives looking and performing like new.

Steel wool

Another way to clean and remove rust from your Japanese kitchen knives is with steel wool. This method is a bit more abrasive, so it’s best to use it on small areas of rust or if the other methods haven’t worked.

Steel wool is made of very fine strands of steel that can be used to scrub away rust.

First, rinse your knife off with warm water. If there is any food residue on the blade, use mild dish soap to remove it.

Next, take your steel wool and rub it on the rusted areas of your knife. You may need to put some elbow grease into it, but the rust should start to come off.

If it’s not coming off easily, you can soak it for a bit longer.

Once the rust is gone, rinse the knife well with warm water and dry it off.

Potato method: best for very light rust

I know it sounds odd – using a potato to remove the rust from your knife’s blade?

But, if your blade only has light signs of rust, this method can be quite efficient. Although it’s not as powerful as using vinegar, you can use the potato to lightly scrub off stains and rust.

To use this method, first, rinse your knife off with warm water. If there is any food residue on the blade, use mild dish soap to remove it.

Next, take a potato and cut it in half. Be sure to wash your half potato with dish soap first so it’s not dirty at all.

Use one-half of the potato to rub the rust off your knife. You may need to put some elbow grease into it, but the rust should start to come off. If it’s not coming off easily, you can soak it for a bit longer.

Once the rust is gone, rinse the knife well with warm water and dry it off.

The reason why potato can remove rust is that it contains oxalic acid. These break down the rust particles.

Also, you can sprinkle a bit of baking powder on the edge of the potato and then start scrubbing – this method can turn out even more efficient.

Onions: a natural way to clean rust

Yes, onions are another vegetable you can use to remove rust and clean knives.

Generally, onions don’t have as many acids as potatoes and can be used to eliminate light rusts that the potato approach cannot.

First, slice the onion horizontally. Next, rub the sliced onion over the rust marks with the cutting knife. Then, to break up acids, apply pressure on onions and massage them into rusted areas.

For particularly rusty blades, you have to keep massaging the onion into the knife blade.

While carefully brushing onions onto the surface, place your knife on the floor. It is safer to have onions in your hand. A chopped onion may require the addition of finely crushed salt to make it abrasive.

Or, you can go over with a slightly abrasive sponge after the onion method.

Very fine sandpaper

You may have to resort to this method if your blade is severely rusted. This is a more abrasive way of rust removal but can be done if you’re careful.

First, rinse your knife off with warm water and dry it completely. Next, take very fine sandpaper – 400 grit or higher – and gently rub it on the rust spots.

You don’t want to use too much force or rub too hard, or you could damage the steel or carbon steel blade.

Once the rust is gone, rinse the knife well with warm water and dry it off.

Sharpen the knife

As efficient as sharpening stones can be, they are also the harshest and necessitate a higher level of skill and knife control to use.

If you’re looking to remove rust from a piece of metal, a sharpening stone is a good option because it removes layers of steel to form an edge.

Sharpen your rusty knife if it’s very rusty and seems like a lost cause – it might work better than you expect. This is a good way to save an expensive Japanese knife.

As the process is similar to simply sharpening your knife with a whetstone, it’s best for blades with rust forming around the edge.

However, when the rust is concentrated around the blade’s spine or either side, it is much more difficult to remove using a sharpening stone.

The rust in these hard-to-reach places can be removed with a sponge or steel wool and the solution described above.

Why do Japanese knives rust?

Even if you buy expensive Japanese knives, you can still end up with a rust-covered knife if you don’t care for it properly.

It’s all about maintaining your Japanese knife properly and after all, prevention is always much better than damage control when it comes to rust.

To understand how to keep a knife from rusting, you must first understand why blades rust under certain circumstances.

Knives rust for a variety of reasons, but the most common is moisture.

Water (and even humidity) can cause rusting because it contains oxygen, which causes a chemical reaction that creates rust.

So, if you’re not careful to dry your knives after washing them, they could develop rust spots. Another common cause of rust is exposure to saltwater or salty air.

This is because salt is a corrosive element that can speed up the rusting process.

So, if you live near the ocean or use a lot of salty ingredients in your cooking, you’ll need to be extra careful to dry your knives after washing them and keep them stored in a dry place.

It’s tempting to think that if your knife is made of stainless steel, it won’t stain or rust but that’s simply not the case.

Unfortunately, your blade might be stain-less rather than stain-free, so, unless you have a ceramic knife, your blade will rust.

In case you don’t know, rust is a gritty substance with an orange flaky color and texture which forms on the metal. It occurs due to iron oxidation which is a common chemical reaction.

When the metal is exposed to moisture and oxygen, it causes a reaction that creates rust.

Because a steel knife is made of iron, it will rust if it is exposed to water and air for an extended period of time. This is not an instantaneous process though.

However, the rust starts to form if you keep water on a knife for long enough. Truth is, rust will eventually form, and yes, even stainless steel blades are susceptible to this.

Learn about the best ways to store your Japanese knives here (+ best knife stands reviewed)

How to prevent rust on your Japanese knives?

There are some key things you can do to prevent rust formation and ultimately a rusty knife:

• Wash and dry your knives immediately after use. It’s important to wash your knives as soon as you’re done using them so that any water or moisture has a chance to evaporate before it has a chance to cause rusting.
• Be sure to dry your knives thoroughly after washing them. This step is just as important as the first one!
• If you’re using your knives near salt water or in a humid environment, be sure to clean and dry them even more frequently.
• Store your knives in a dry place. If you’re not using your knives, be sure to store them in a dry place such as a drawer or cupboard.
• Do not store your knives in their sheaths for extended periods of time. If you’re not using your knives, it’s best to store them without their sheaths so that any moisture can evaporate and they won’t be susceptible to rusting.

How to prevent rust spots after cleaning: use a mineral oil afterward

After you’ve removed the rust from your knife, it’s important to protect it from further corrosion.

You can do this by using a mineral oil – also known as gun oil. This will help form a barrier between your knife and water or any other substance that could cause rust.

To use this method, simply apply a small amount of mineral oil to a clean, soft cloth and rub it into the blade.

Be sure to wipe off any excess oil so it doesn’t attract dirt or dust. You can do this by using a second clean, soft cloth.

It’s important to reapply this oil regularly – at least once a week – to keep your blade in the best shape. The oil provides a good protective layer for kitchen knives.

The Japanese bladesmiths like to use KUROBARA 100% Pure Tsubaki Japanese Knife Maintenance Camellia Oil because it prevents carbon steel from rusting. It also ensures your sharp blades stay that way for longer.

Just be sure to note that after you clean your knife blade, you need to re-sharpen it (preferably using a whetstone).

Takeaway

Whether we use them for cooking or for protection, knives are a vital tool in our day-to-day routine.

By taking care of your knives and ensuring that they are clean and rust-free, you can not only prolong their life but also ensure that they are always functioning at their best.

Rust removal is extremely important for stainless steel knives and carbon steel knives alike because a rusted knife is downright dangerous.

The simplest way to remove rust and stains on your Japanese blade is to use white vinegar or a simple baking soda paste. These two methods are cheap and efficient and don’t damage the knife.

Next, learn about Aogami vs shirogami (The difference between white and blue steel)

Check out our new cookbook

Bitemybun's family recipes with complete meal planner and recipe guide.

Try it out for free with Kindle Unlimited:

Read for free

Joost Nusselder, the founder of Bite My Bun is a content marketer, dad and loves trying out new food with Japanese food at the heart of his passion, and together with his team he's been creating in-depth blog articles since 2016 to help loyal readers with recipes and cooking tips.