Whether you’ve found a knife in one of your old toolboxes or accidentally left your favorite knife outside in the rain, chances are you have encountered a nasty case of rust.
Many old timers considered rust the sign of a knife’s quality, but a rusted knife is also dangerous, useless, and downright ugly.
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We originally wrote this post way back in December 2011, but we thought it’d be a good idea to do update it with some better information, videos, and recommendations.
What is Rust?
If you only want to some methods for removing rust, skip these next two sections, but it will be helpful to learn more about why your blade is rusting.
First, let’s tackle the nature of rust.
Rust is the common name for a compound called iron oxide — that reddish-orange flaky stuff you see peppered on some metal. This forms when iron and oxygen react to moisture. It doesn’t even have to be water exactly, it could just be the presence of water in the air.
Here’s a more scientific explanation from How Stuff Works:
Iron (or steel) rusting is an example of corrosion — an electrochemical process involving an anode (a piece of metal that readily gives up electrons), an electrolyte (a liquid that helps electrons move) and a cathode (a piece of metal that readily accepts electrons). When a piece of metal corrodes, the electrolyte helps provide oxygen to the anode. As oxygen combines with the metal, electrons are liberated. When they flow through the electrolyte to the cathode, the metal of the anode disappears, swept away by the electrical flow or converted into metal cations in a form such as rust.
Why Do Knives Rust?
Here are the ingredients for rust: iron, water, and air.
For those who don’t know, iron is the secret ingredient of the steel found in your knife blades. So when you combine your knife with air and water, you get rust.
“But, wait, my blade is stainless steel,” you might be thinking. Unfortunately, stainless steel is only stain-resistant, not stain-proof. (The old saying goes “Stainless… not stainfree.”) I tackled the myth of stainless steel a while back, but the gist is that stainless steel has at least 10.5 percent chromium. People in the 1800s found iron-chromium alloys to be more resistant to corrosion because they create a protective layer.
Unfortunately, that means the blade will still rust (unless it’s ceramic) under certain conditions as long as it’s considered steel.
OK, so there may be one true stainless — as in stainfree — steel called H1. It is commonly found in the Spyderco Salt Series. It barely has any carbon and massive amounts of chromium. There were one or two claims that the steel rusted after years of use at sea, but those were never fully verified.
How to Remove Rust from Your Knife
Each of these methods can be used in conjunction with one another or repeated for particularly rusty blades. After removing the rust, I do recommend resharpening the blade after any method to ensure a sharp and safe blade.
Method #1 – Baking Soda to Remove the Rust
“Close-up Of Baking Soda On Spoon” by Aqua Mechanical is licensed under CC BY 2.0
Materials: Baking soda, water, toothbrush, steel wool (or sponge), cloth
1) Clean Your Knife
The first thing you want to do is thoroughly clean the blade of your knife because dirt can interfere with the removal of rust. Try to avoid water because that’s what mostly made your knife rust.
Instead, use some sort of cleaning solution and wipe it down with a cloth.
2) Create Baking Soda Paste
Next, create a little bit of baking soda paste. You can pour a fair amount of baking soda into a bowl and add some water (or lemon juice). Stir it up until it becomes a paste.
3) Scrub with toothbrush
Apply the thick paste to a toothbrush and liberally speed it across the blade. You can scrub only with the toothbrush if the rust isn’t too severe or set in.
4) Use steel wool or an abrasive sponge
For extremely rusty blades, you’ll need a little more abrasion to help remove the rust. Steel wool is commonly recommended though it can mess up your blade if you scrub too hard. Another alternative is a slightly abrasive sponge.
Be careful not to scrub too hard because you can scratch the blade or ruin the finish.
5) Wipe the blade clean
Finally, clean off the blade with a piece of cloth to remove the excessive baking powder. If you want to be really good to your blade, you can apply some mineral oil afterward to make sure it’s lubricated and protected from rust in the future.
Our old pals at Taylor Brands (we miss you) made a video using this essential method, which you should watch if you’re the visual type.
Method #2 – Vinegar Bath for Removing Rust
“Vinegar” by Chris Martin is licensed under CC BY 2.0
Materials: Pan or cup, white vinegar, sponge, cloth
1) Pour vinegar into a cup or pan
Be sure to use white vinegar, which contains a substance called acetic acid that will attack the rust. Other types of vinegar may leave stains.
2) Soak the rusty knife
If you don’t want to soak the whole blade (or knife), you can also soak a paper towel in the vinegar and wrap it around the blade. Only leave the knife it for about five minutes. Any longer and you risk damaging your blade.
3) Wipe down the blade
After it’s done soaking, you’ll want to wipe down the blade. At this point, you may still want to do the baking soda or WD-40 method if there is still a little rust. I’d again recommend mineral oil for extra protection and cleaning.
Here’s a cool video showing the power of vinegar on a dive knife
Method #3 – WD-40 As Rust Remover
Materials: WD-40, fine sandpaper, cloth
I recommend this method for a larger knife like a machete or a knife you won’t be using for food preparation since WD-40 can be harmful if ingested. But it’s a quick and effective method of rust removal. Don’t use it for lubricant.
1) Spray WD-40 on the blade
This step needs little explanation. Spray the affected parts of the blade with a spritz of WD-40.
2) Gently sand the blade
You’ll want to use very fine sandpaper (think 400) to gently get the rust off the blade. Make sure not to touch the edge or you’re liable to mess it up.
3) Wipe it down
That should be enough to do it. If the rust is heavier, you may want to do one of the two previous methods. Again, avoid if you’re doing any food prep with the knife.
Natural Knife Rust Removal Methods
When you don’t have the materials around the house to get rust off your knife, there are a few natural methods you can use.
Potato Method
Certain foods also act as a good sources for rust removal. The potato is actually remarkably effective food for removing rust because of its oxalic acid.
Simply stick your knife into the potato for a few hours. After you remove it, wipe the blade with oil and the rust should be gone.
Onion to Remove Rust from a Knife
Onions are another food that helps get rid of rust naturally. If you saw back and forth into an onion, the rust will begin to come off by itself.
The sulphenic acids in onions are they key ingredients in getting your blade cleaned.
Dirt Method
Another more natural way many people suggest is to plunge your rust-covered knife into rich soil about two dozen times and then wipe it clean.
Everyone has their own method, so let us know in the comments what you do.
Grab a New Knife!
If your knife is beyond the amount of work you’re willing to put into it, it’s OK to move on.
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December 23, 2011 at 11:29 pm
baking soda also works! 😀
December 23, 2011 at 11:39 pm
Tabasco sauce works wonders as well.
August 26, 2015 at 6:59 pm
If it’s really bad, I spray with WD40 and let sit as mentioned. Then scrub with hot water and an SOS pad. Scotch-Brite pad next and finish off with Autosol polish.
July 15, 2017 at 1:06 pm
Will it work like that
September 21, 2017 at 10:20 pm
How Lon should we soak for in rag?
May 1, 2016 at 2:22 pm
Can you use dish soap to wipe is down?
June 29, 2016 at 9:31 am
I used the potato idea. Much to my surprise, it really worked. Even after 20 minutes I noticed a major difference. Thx guys for the science experiment. I was totally amazed.
July 1, 2016 at 3:34 pm
Glad it worked for you. It’s crazy to think how something so simple and mundane can work wonders on a rusty blade.
March 14, 2018 at 5:09 am
It worked for me too, amazing!!!
March 31, 2018 at 1:28 pm
Did you use oil because if you did what type because I want to try the potato method
September 18, 2016 at 4:55 pm
I tried the potato idea, although it did get rid of some of the rust, it left a stain of some kind on my knife that I can’t seem to get rid off..
September 18, 2016 at 7:54 pm
If it’s a carbon steel, you probably just forced a patina. This is actually a way to prevent rust in the future, but if you don’t like it you can polish it out.
October 24, 2016 at 3:19 am
Is that patina black my blade turned that color after I used vinegar smells like old metal don’t wanna cut food anymore cause of it
December 23, 2016 at 10:31 pm
Would any of these tricks work on a X-acto knife
July 22, 2017 at 9:18 am
Yes, most of these will work on an x-acto knife. Although I usually get away just using some 00 steel wool then sharpen it it after.
February 18, 2017 at 2:27 pm
I found one of my dads old knives in a shed and I am letting it sit in a gun oil soaked sock. Hope this works
September 13, 2017 at 10:44 pm
Hmmm… just need to find a potato big enough for my Cold Steel XL Espada lol.
October 19, 2018 at 12:19 pm
Use several of them in a row
November 28, 2017 at 11:01 pm
I only have Balsamic Vinaigre would that not work like the white Vinaiger?
January 23, 2021 at 7:41 am
Colored vinegar might leave a stain. White (clear) vinegar will not.
December 2, 2017 at 4:01 pm
I didn’t know a knife could rust until I found a 35+ yr. old Schrade that I used to keep out in the garage completely rusted out. I sharpened it in that condition, and continue to use it in the garage (of a different home). I call it my “junk knife”. I don’t plan on cleaning it up.
I thought all knives were “stainless”. Not so. You’ve got to be careful: H-1 has a Chromium content of 14.0-16.0 %–it is blown away by a handful of other steels, which have 17%, another handful which have 18%, and yet another handful that have 20% Chromium content. AND, H-1 has an extremely low Carbon content, 0.15%, which means you have to sharpen it all the time.
One more thing-this place says over 11% is stainless. I have seen 12%. 13%. Max, 14%. I’ll go with the max, 14%, just to make sure.
Later, Kenny
January 10, 2018 at 4:24 pm
Method 2, #1–That’s ‘acetic’ acid, not “acidic” acid. All acids are acidic.
January 11, 2018 at 8:52 am
Thanks for the correction. It’s been fixed.
February 21, 2018 at 8:10 am
From my experience depends on the amount of rust and pitting. Evaporust probably the best chemical treatment I’ve tried for mild rust. For deep rust use abrasive sanding pads
March 31, 2018 at 1:25 pm
I haven’t tried any methods but I want to try the potato method. I want to know what type of oil I need to use
January 23, 2021 at 7:47 am
Oil to prevent more rust after the potato try depends on the type of use of the knife. If in the kitchen, only natural organic oils for cooking should be used. Clearer the better–won’t stain. If a utility knife in your tool crib, a light machine oil will do.
November 21, 2021 at 9:45 am
I think kitchen oils will gum up. I use mineral oil.
April 28, 2018 at 8:33 am
Im currently trying the baking soda method on an old old butchers knife my grandfather gave us, its looking better already! It was covered in thick rust and dirt and even just after an hour or so of work on it the rust is almost gone! Im looking into things to sharpen it with and polish it with so its back to its original reflective shine!
June 13, 2018 at 3:30 pm
Is the vinegar method good for a knife that has a black blade? Will it fade the color?
January 23, 2021 at 7:49 am
A “black blade” is not enough information to advise you. Different materials or surface treatment might make almost any blade look “black”.
November 9, 2018 at 7:31 pm
I try the baking soda paste with steel wool
It work amazing with severe rust on a cleaver
December 19, 2018 at 4:38 pm
Would these methods work for an antique Islamic Omani Saudi Dagger? It has a lot of rust on it and I would like to remove it but I don’t want to compromise the integrity of it? Also, one side has engraving on it.
January 18, 2019 at 10:45 am
Thanks. Glad it could help.
February 10, 2020 at 9:25 pm
Agree , So nice to have people use cheap household products that work in a little elbow grease. Very sincere
March 15, 2019 at 5:35 pm
Are any of these methods particularly better or worse for Shun knives?
March 16, 2019 at 9:32 am
These are mostly fine for Shun knives. If you are worried, you can use Flitz — which is what Shun officially recommends. Their FAQ page has more info.
March 31, 2019 at 11:19 am
I have a rusted scout knife with some enamel decoration on the blade. Can you reccomend a safe method to remove rust without affecting the enamel work?
May 21, 2019 at 9:12 am
I would like instruct knife owners on a very important aspect of knife care or rather a preventive method of not inviting rust and corrosion on the surface of the steel blades in the first place. I learned this many years ago from an old gunsmith who also made very high quality knifes for hunters and military men.
He showed me the effects of firearms and knives stored within their respective holsters and sheathes, especially those made of leather. The processing of leather requires the use of various chemicals, especially one known as TANNING ACID. If the item, gun or knife is left stored within the leather encasement, corrosion is sure to follow. So, when not using, never store your weapons within those scabbards of leather. I store all my knives with a coating of RIG grease, then wrapped in waxed paper. I have guns and knives treated with this method for over sixty years , no rust, no pitting, no imperfections of any kind. Give it a try.
May 21, 2019 at 9:20 am
I use a can of soda – pepsi – coke, and aluminum foil works great
February 10, 2020 at 9:32 pm
Sure bc coke Has a molecule similar to bleach what is it? It does happen oily residue
May 21, 2019 at 8:45 pm
I have used Navel Jelly to dissolve rust before, is it OK to use on a knife?
May 22, 2019 at 2:33 pm
If you don’t mind performing some fairly mindless manual labor, you can remove rust and scratches from a blade using steel wool. Get some coarse, medium, and several grades of fine steel wool; turn on the television, and sit in front of it with a towel across your lap. Start with the coarse wool, and progress to as fine as you like – you can get a mirror finish if that’s what you want. I’ve done this to remove scratches made while sharpening; it works very well.
October 10, 2019 at 8:25 pm
I have my dad Scharde USA. Pocket knife 3 blade he has been gone -23 years know the long pointed blade is the only one rusted I think it’s the one he used the most! Can I clean it with Vinegar then oil it or use the baking soda? It’s a keepsake, he always had it in his pocket if you ask to cut something he pulled it out and opened it for you!
February 6, 2020 at 10:08 am
Cheers mate, goodonya.
April 3, 2020 at 2:48 pm
You only need three things to quickly remove rust spots from your knives: white vinegar, a tall cup and a scrub sponge.
July 7, 2020 at 8:25 pm
Found a “no name” brand fixed blade knife earlier in last years fishing season by the river that was heavily rusted. I brought it home and tried the potato method, baking soda method, and vinegar method all with no success. I wound up using a nylon bristled brush on my drill tool on low speed to remove the rust (the other methods may have loosened the rust up, not sure) before I sharpened it. it is now very sharp, both figuratively & literately.
October 18, 2020 at 8:09 am
These are some excellent tips for removing rust. The methods of using vegetables or fruits to clean rust off of knife blades is very interesting. I haven’t heard of that before.
January 13, 2021 at 11:14 pm
Does anyone know what this black stuff on my knife that made these little holes in my blade might be
July 20, 2021 at 12:20 pm
I have not tried the potato trick, but I have used white vinegar and apple cider vinegar to remove rust on knives and tools. Sometimes the vinegar leaves a sort of whitish stain or finish, but I have soaked items for as long as a week. I’d suggest to people to try the least caustic or finish altering methods first.
Washing, oiling and wiping would be first. Then a dish scrubbing sponge or a scouring pad, SOS pad, along with, oil, vinegar or baking soda. One can also try toothpaste or Flitz and an old toothbrush.
Polishing by hand (sandpaper or sponges) will require a little effort and take a while unless you use power tools, but it’s cheap and once you have the blade looking nice it’s a very satisfying feeling.
Of course if you power tools like a Dremel or such it’ll be faster.
December 21, 2021 at 4:30 pm
Be cautious about leaving a knife in a pan of vinegar. I did that with a totally rusted up slip joint pocket knife, after 2 days it had eaten away not only rust but a good bit of the steel. Springs and blades both. But didn’t seem to affect the scales which I think are none.
May 30, 2022 at 8:38 am
Thank you for providing complete information. You mentioned that it’s best to resharpen the knife after removing the rust. Do you have any tips on how to do it at home?
August 19, 2022 at 1:41 am
Thank you for this informative article! I love how the methods can be easily done at home. I like how you included a video as well. Is there a type of knife that doesn’t rust?
February 23, 2023 at 11:11 pm
how about using a laser cleaning machine?
July 12, 2024 at 6:32 am
If you’re storing any kind of steel long term, cosmoline grease is amazing at preventing rust. All you need is a very thin layer. But for my EDC, I use Hoppe’s 9 Elite gun oil. Or CLP. Light coat and let ’em dry and the oil forms a very effective and fairly long lasting protective coating. As for rust removal, if the rust is deeper than just surface rust and you don’t want to put in the labor, a decent chelation agent like Evapo-Rust is highly effective if not super budget friendly. It takes almost zero work and I’ve never had it damage and kind of finish or handle/scale material at all. Got rid of the iron oxide only.