How To Remove Rust From A Knife

By Bobby B.  |  July 13, 2020  | Blog

It can be a frustrating sight to see rust spots starting to appear on you kitchen knives.  You read the packaging and it said the knives where stainless steel or “corrosion resistant”.  You’re probably wondering what happened, how to remove rust from your knife, and how to prevent it from happening in the future. 

What likely happened was you put your knives in the dishwasher or left them soaking or wet somewhere.  There’s an old saying that really rings true here… it’s stain “less”, not stain “free” steel.  Rust needs three things to form, carbon, water, and oxygen.  All steel knife blades have some carbon in them.  Some have more than others because it’s the main ingredient for hard, sharp blades, but they all have some amount.   No one likes to hear this, but you should never put your kitchen knives in the dishwasher.  

Whether that’s what happened, or it was something else, the key now is trying to salvage the knife.  Luckily, there are several ways to attempt removing rust from a knife blade, and many of the things you’ll need are household items you probably already have laying around.

5 Ways To Get Rid of Rust on Knives

We personally believe strongly in maintaining your knives correctly from day 1 so this doesn’t happen, and therefore really don’t have much experience on this topic.  But, it’s a topic that’s important to many of our readers and something commonly asked about, so we’ve scoured the interwebs for the best options.

These are common methods you’ll find around web that people try and swear by.  They range from ludicrous to sensical, and everything in between.  These methods mainly pertain to standard stainless steel knives.   

Before we go any further though, we need to offer a word of caution.  Many sites out there are recommending that you use steel wood to remove rust or balled up tin foil to get ride of rust stains on your knives.  If you’re cleaning a rusty knife that you’d otherwise be throwing away, go at it.  If you’re removing rust (small amounts) from an otherwise good, expensive knife, please uses these as a last resort.  They can and will scratch and/or further damage your knife when too much pressure is applied!

The Vinegar Method

Teaching you how to remove rust from a knife with vinegar is a simple task.  The hardest thing to remember is to make sure you use white vinegar.  For one, that should ensure it has acetic acid, which is the ingredient that attacks the rust.  But another reason is that other, darker vinegar could actually add to staining the knife blades in some cases. 

You’ll want to fill up a tall cup with the vinegar so that it covers the portion of the blade with the rust spots.  Be sure not to fill it up to where it’s covering the handles if they’re made of something other than stainless steel.  Leave the knife or knives sit in there for roughly 5 minutes, then pull it out and scrub the rust away with a sponge.  Hopefully this takes care of the rust spots and you’re done!

The Baking Soda Method

It’s not difficult to figure out how to remove rust from a knife using baking soda.  Just take some of the baking soda and mix it with a little water until you’ve made a paste.  After you’ve wiped the knife blade clean, liberally apply the baking soda paste on the blade with a toothbrush.  You’ll want to make sure and scrub extra good where the rust spots are to try and loosen them up.

If it appears you were successful in getting rid of the rust, go ahead and wipe the blade with a clean cloth.  If not, leave the baking soda on the knife for a period of time and try to scrub with the toothbrush again before wiping it off.

The Lemon Juice Method

Using lemon juice to remove rust from a knife is similar to the vinegar method, with just a couple small differences.  Again, it’s an easy task anyone can attempt with things they probably already have at home.  First, fill a tall glass half full with lemon juice.  It doesn’t matter if it’s from a bottle or a freshly squeezed lemon.  Then, fill the remainder of the glass with warm water from the tap.  

Place your rusty knives in the lemon juice, blade down of course, and let them sit for up to 10 minutes.  This should give the corrosion spots plenty of time to loosen up.  Pull the knives out and wipe the blades with a scrub pad or sponge.  Be sure not to use a pad with metal in it or you’ll need to be concerned with scratching the blade.  If it’s just small amounts of surface rust, this should do the trick.

The Potato & Onion Methods

This one probably sounds pretty crazy.  I know it did to use when we first heard it, but it’s worth a shot if have a rusty knife in the kitchen. 

Potatoes:  Potatoes have oxalic acid in them, which is surprisingly effective to get rust off knives.  The idea with this one is to stab the knife blade into a potato and let it sit for a couple hours before taking it out and cleaning it off.

Onions:  Similarly, onions have sulphonic acids that will assist with getting rid of rust from knives.  In the case of onions, you just want to start sawing back and forth with the knife blade through the onion, letting the friction between the knife and the onion do the work.  The claim is that this will help clean the rust.  Make sure not to use the onion after adding rust to it!

Remove Rust With Bar Keepers Friend

If you’ve never heard of it, you’re in for a treat.  There’s a popular cleaner out there called Bar Keepers Friend, and it’s amazingly effective on rust removal on stainless steel.  While you may or may not have this already around the house, it is a cheap, effective, easy solution for removing rust from knives.  So if all else fails, buy some Bar Keepers Friend and foll the instructions below.

Just add some of the cleaner on the rusty knife blade.  It comes as a powder and there’s no reason to be stingy with it.  Go ahead and use plenty.  Grab a wet sponge or rag and work the cleaner around into the blade for a few minutes.  You’ll probably even notice most of the rust coming off while scrubbing.  Once done, rinse off the knife and wipe it with a dry towel.  BOOOOOM!  The rust should be gone.  

Removing Rust From Carbon Steel Knives

As you probably already know, stainless steel knives and carbon steel knives are quite different in their corrosion resistant properties (Read More:  Best Steels For Kitchen Knives).  Not only is rust forming on carbon steel knife blades much more common, but the methods for cleaning rust off carbon steel knives is different too.

There are 2 good ways to do this…

The easiest/cheapest way to cleaning rust off a carbon steel knife is with Bar Keepers Friend.  The process for doing this is basically the same as we described above for stainless steel knives.  To further demonstrate and prove it works, this video shows the removal of rust taking place on a carbon steel blade.

There’s another way to remove rust and even the patina that carbon steel knives leave behind, and it’s a product called Rust Erasers.  They typically come in a set of one fine and one medium grain, and they make it easy to clean up your carbon steel blades.  Again, here’s a video showing them in action so you can see how they work and proof that they work.  

We get it, the rush is an eye-sore, but do keep in mind that the patina that forms on carbon steel blades can actually help protect the blades from rust forming.  You may or may not want to actually remove the patina.

How To Prevent Rust From Forming on Knives

The best way to make sure you never have to clean rust off knives again is to understand how to prevent your kitchen knives from rusting in the first place.  Here are a few steps you can take that will put you in the pest position for rust prevention on our knives.

When To Clean Your Knives:  It’s always best to clean your knives immediately after using them.  If you’re too busy to clean them correctly, at least take towel and wipe them dry until you can.

How To Clean Your Knives:  Hand-washing your kitchen knives with soap and warm water will always give the best results.  Of course, most importantly, dry them right away and store them in a dry area.

Avoid the Dishwasher:  Dishwashers leave untensils wet for extended periods of time and often have a steam cycle.  This is especially damaging if you tend to leave items in there overnight.  Just don’t do it.  Hand-washing knives isn’t that difficult and worth it to save your expensive knives from damage.  Steak knives tend to be the knives that get thrown in the dishwasher the most.  Though we don’t recommend it, the best steak knives for the dishwasher are those that are specifically listed as such by the manufacturer.

Never Soak Knives:  There are multiple reasons to never soak your knives.  One is the blades forming rust, the other is potentially damaging the handles, especially if they’re made of wood.

Knife Storage:  Store your knives in an area where they can stay dry.  Knife blocks can be detrimental to your blades if you put them away wet.  If you don’t have a set, or even if you do, strongly consider a magentic knife holder for easy storage.

Rusty Knife Recap

The good news is that rusty knives can often be cleaned and resurected.  Depending on how much corrosion we’re talking about, it may more may not be worth the effort.  Removal of small rust spots usually aren’t that difficult.  As you’ve read above, there are many methods to try.  They aren’t difficult or expensive either, so give them a whirl.

Larger rust removal jobs will depend on the value of the knife.  You’ll have to decide if it’s worth your time based on the original cost, or perhaps sentimental value of the knife to you or your family.  

Just Get a New Knife!

If you’ve tried several of the ways to clean rust off knives and it’s just not working, consider buying a new knife.  It’s okay to treat yourself to a new one, just promice yourself that you’ll take care of it better this time.