A Guide to Cleaning Rusted Kitchen Knives

Rust is a nuisance anywhere in the household, but there’s something particularly annoying about finding it on kitchenware, say, a set of knives. While rusting is a natural process likely to occur when using metal knives, it’s preventable. But what do you do if rust has already formed?

There are numerous products for cleaning rusted kitchen knives, including natural cleaners such as vinegar, baking soda, and lemon juice. If these don’t get the job done, you can use store-bought rust-removal chemicals to clean more stubborn rust stains on your knife blades.

This article will serve as your guide to removing rust from your kitchen knives and preventing it from forming in the first place. You’ll also learn the differences in how the two most popular knife blade materials rust and which between the two is best suited for you.

Why Are My Kitchen Knives Rusting?

Your kitchen knives are rusting because the iron in the blade steel comes into contact with water and oxygen. Iron and oxygen are attracted to each other like magnets. When the two elements combine in a chemical reaction called oxidation, ferric oxide—often called rust—forms.

Given that oxygen is abundant in the atmosphere and knives are constantly wet from washing, the knife blades are prone to rust without proper care. Rust causes metal to decay, and if not dealt with quickly, the affected metal will get weaker and eventually fall apart.

Kitchen Knife Handling Habits That Can Cause Rusting

With the elements that lead to rusting ever-present in the kitchen, how come not everyone’s kitchenware gets rusty? Could how you’re handling your knives and other utensils be predisposing them to rust?

Here are some bad habits that might be causing your knives to rust:

  • Cleaning your knives in the dishwasher: the heat in the dishwasher causes the metal part of your knife to expand. As a result, this weakens the blade’s integrity and creates microscopic gaps in the metal that water may seep into, causing rust to develop. 
  • Leaving your knives on wet surfaces: most of us are guilty of doing this. When you leave your metal kitchenware in the sink or on a wet countertop, you expose them to both water and air.
  • Storing your knives while they are still wet: putting away your kitchen knives when they aren’t adequately dry creates the perfect conditions for rust to form. 

What Can Make Rusting Worse?

Common substances found in your household and kitchen can make rusting worse. These include salt, acids (e.g., acetic acid and citric acid), and chemicals such as bleach. Temperature changes can also worsen rusting.

Types of Steel and How They Rust

There are two general categories of steel: stainless and carbon. 

Carbon steel predominantly comprises iron with a small percentage of carbon and other metals. Stainless steel also primarily contains iron, at least 10.5% chromium, carbon, and a few other metals.

The chromium in stainless steel surrounds the iron and protects it from oxidation. However, chromium reduces the blade’s durability, which leads to an increased frequency of sharpening.

Can Stainless Steel Kitchen Knives Rust?

Stainless steel kitchen knives can rust. Although stainless steel is more resistant to rust than carbon steel due to the chromium alloyed into the metal, it’s still not rust-proof. 

If the passive chromium oxide layer that acts as a protective barrier against oxidation is compromised, you may notice specks of rust on the knife blade. The thin layer works by preventing the iron in the alloy from reacting with water and oxygen in the atmosphere and forming iron oxide.

In addition to the formation of rust, small holes or pits can also develop deep in the metal structure. This is a localized and more damaging form of corrosion known as pitting corrosion. It occurs when the chromium oxide layer on the steel is physically or chemically damaged, exposing the steel underneath to corrosive environments.

Choosing Between Carbon Steel & Stainless Steel Knives

Your choice of blade material will depend on the kind of cook you are. Serious cooks typically prefer carbon steel knives because they have sharper edges that make slicing, dicing, and chopping more effortless.

If you live in a coastal or high-humidity area, stainless steel knives are best as carbon steel rusts quickly in these climates.

Let’s explore the pros and cons of carbon steel and stainless steel knives.

Advantages of Carbon Steel

  • Have razor-sharp edges
  • Remain sharp for a long time
  • More durable

Disadvantages of Carbon Steel

  • Need more maintenance
  • More prone to rusting

Advantages of Stainless Steel

  • Rust-resistant
  • More appealing to the eye and can be used decoratively

Disadvantages of Stainless Steel

  • Become dull faster
  • Less durable

How To Clean Knives Rust

The elements needed to initiate the chemical reaction that leads to rusting are all present in your kitchen. Fortunately, you can save rusted blades and restore them to their former glory using items also readily available in your kitchen or store bought products.

How To Clean Rust off Kitchen Knives Using Kitchen Ingredients

If you have any of the items below in your kitchen, you can remove rust from your kitchen knives:

  • White Vinegar
  • Baking soda
  • Lemon
  • Table salt
  • Dishwasher salt
  • Potato (Yes, that potato)
  • Citric acid
  • Onion

But wait a minute—didn’t I say in a previous section that acids and salts can worsen rusting? How then can they also help get rid of rust?

If you recall, I also mentioned that rust causes metal to decay. But since the surface of the metal corrodes first, you can use these substances to break down the rusted parts and then wipe them off to reveal the unaffected metal underneath. 

It’s a lot like exfoliation. You scrub off the old cells to reveal the fresher, more youthful skin underneath.

Here’s how to get rid of rust using the aforelisted kitchen ingredients.

Prepare a White Vinegar Soak

Cleaning rust off your kitchen knives using a vinegar soak is pretty straightforward. It requires little effort since chemistry does all the hard work for you.

To use this method to get rid of rust, follow these steps:

  1. Soak your rusty knives in undiluted vinegar overnight. 
  2. Give the blades a good scrub the following day using steel wool.
  3. If there are any stubborn rust spots, repeat the process.
  4. Once satisfied, rinse and dry your knives thoroughly before storing them in a cool, dry place. 

Make a Baking Soda Paste

For thin blades and light rust stains, you can use baking soda. So long as your knives don’t look like they were salvaged from the Titanic, this should do the trick.

Here’s how to go about it:

  1. Make a paste out of baking soda and water.
  2. Coat your blades with the paste and let it sit for an hour or so. 
  3. When the time is up, thoroughly scrub your knife blades using steel wool.
  4. Rinse the knives and completely dry them using a dish towel or paper towel.

Clean With Lemon and Salt

The abrasiveness of salt combined with the acidity of lemon juice makes for an effective rust buster. Some articles may recommend baking soda instead of salt, but this is counterproductive. Since baking soda is a weak base, it will neutralize the effect of the citric acid in the lemon juice.

To proceed with this technique, follow these steps:

  1. Sprinkle salt over the rusty areas and follow by squeezing lemon juice.
  2. Leave it for two hours. 
  3. After two hours, scrub the blades using the lemon rind. 
  4. If the rust stains are tough, you can use steel wool.
  5. When satisfied, rinse well, dry thoroughly, and store your knives in a cool, dry place.  

Use Dish Soap and a Salted Potato

Potatoes contain oxalic acid—an acid found in many household cleaning products. Oxalic acid dissolves rust, making potatoes a potentially powerful rust remover. 

This method of rust cleaning involves the following steps:

  1. Slice half a potato.
  2. Drip some dishwashing soap onto your potato slice.
  3. Sprinkle salt or baking soda over your potato slice to act as an abrasive. 
  4. Start scrubbing your blade with the potato, focusing on parts where the rust stains are stubborn. Do this patiently until the rust starts to dissolve. 
  5. Rinse thoroughly and dry well.

Clean Using Citric Acid

This rust-removal technique involves simply soaking the knives in a citric acid cleaning solution. You can purchase citric acid, also referred to as sour salt, in your local grocery store, hardware store, or kitchenware store.

Follow these easy steps to try this straightforward technique:

  1. Add three tablespoons of citric acid to a bowl of hot water.
  2. Immerse your rusty blades in the solution overnight. By the following day, the rust should have dissolved significantly. 
  3. Scrub the knife blades with steel wool.
  4. Rinse thoroughly and dry well.

Use an Onion

The sulfenic acids present in onions make them effective rust removers. However, it’s not a popular technique for cleaning rust owing to the pungent smell of onions and the painstaking process of running the blade through the onion until you see results.

If you want to try this method regardless, do this:

  1. Saw back and forth through your onion until the rust begins coming off. 
  2. Use steel wool to get rid of the stubborn rust stains.
  3. And lastly, like with every other technique, rinse your knives thoroughly and dry them well.

How To Clean Rust off Kitchen Knives Using Store Bought Chemical Products

If there’re still rust stains left on your kitchen knives after using one or more of the above natural rust removers, you can purchase rust removal products in your local hardware store to eliminate these tough stains. 

Bear in mind that some of these chemicals can be toxic if not properly handled or used. So make sure to read the instructions and follow them strictly to avoid any unfortunate incidents.

Here are some chemical rust removers you can use if the homemade rust removers fail:

  • Metal Glo 
  • Whink Rust Stain Remover
  • Bar Keeper’s Friend

Metal Glo Polishing Paste

My number one recommendation for chemical rust removers is Metal Glo Polishing Paste. The product is certified safe for cutlery and cookware and is suitable for cleaning and polishing any metal surface—including carbon steel, gold, copper, and brass. 

To use Metal Glo, follow these steps:

  1. Place a small amount of the product on a soft cotton cloth or buffing wheel.
  2. Using medium pressure, rub the paste on the affected surface in circular motions.
  3. Buff to a light luster.
  4. Do not allow the paste to dry on the surface.

Whink Rust Stain Remover

Whink Rust Stain Remover is a low-concentration hydrofluoric acid solution. It quickly and easily removes heavy rust, but you can also use it to clean rust stains off various household surfaces, such as soft furnishings, carpets, and bathroom fixtures.

However, since Whink Rust Stain Remover is an acid-based rust removal product, you should not use it on anything too delicate. 

Here’s how to use the rust remover:

  1. Read all instructions before using the product.
  2. Always use heavy-duty rubber gloves to protect your hands.
  3. Do not mix with other household cleaners.
  4. Dilute the solution with water when using it on your kitchen knives. 
  5. Apply the solution to rusty blades until the stains come off. No scrubbing is needed.
  6. Rinse thoroughly and dry well.

Bar Keepers Friend Powdered Cleanser

Bar Keepers Friend Powdered Cleanser is an all-purpose household cleaner that’s suitable for use on almost any metal surface. It’s made with oxalic acid, the same compound found in potatoes, but in concentrated form. Consequently, it’s effortless to use, requiring minimal effort to achieve the desired results.

Follow the steps below to use the rust-removal agent correctly:

  1. Sprinkle some of the powder directly over the rust spots on the knife blade.
  2. Take a damp cloth and rub the rust areas. 
  3. For hard to remove rust, create a paste by adding water.
  4. Apply the paste to the rust spots, leave it for 20 to 30 minutes, and then wipe away.

Depending on how tough the rust is to remove, repeat this as many times as necessary to remove the rust from your knives and get them looking good as new. 

How To Clean Rust off Kitchen Knives Using Store Bought Non-Chemical Products

Another great way to get rid of rust on your kitchen knives is to use rust erasers. A rust eraser is a tool made from a special compound designed to remove rust from knives and other stainless steel and carbon steel surfaces. They resemble the school erasers you likely used back in your school days and are ideal for routine maintenance of your kitchen knives. 

I recommend Rust Eraser – Single from Amazon.com. It removes rust and other surface blemishes on metal and gives your knife blades a brushed satin finish. To use the rust eraser:

  1. Place the knife on a flat surface.
  2. Grab the knife firmly. 
  3. Start rubbing the eraser over the area of concern.
  4. Always rub in the direction of the grain on your steel blade and towards the edge.
  5. Rinse with warm water.
  6. Dry the knife completely.

Some rust erasers might require you to soak them first for a few minutes before using them.

Now let’s discuss the pros and cons of rust erasers.

Advantages of Rust Erasers

  • Ideal for rubbing away corrosion or scuff
  • Give your kitchen knives a new, shiny and clean look
  • Don’t damage engravings or logos
  • Very affordable
  • Easy to store

Disadvantages of Rust Erasers

  • Don’t remove watermarks—you will need special solutions for that
  • Could remove paint
  • They’re small and hence uncomfortable to use on larger surfaces

How To Prevent Your Knives From Rusting

Once you get the rust off your kitchen knives using the aforementioned rust-removal techniques, it now becomes a matter of keeping the rust off. So how exactly do you keep your kitchenware rust-free? Glad you asked.

Here are 3 Ps to remember about rust prevention:

  • Proper cleaning
  • Proper storage
  • Protective coating

Dry Your Knives Before Storing Them

How many times have you tossed a knife into the drawer or slid it into the knife holder without thoroughly drying it? Too many to count? I’ve been guilty of this too. We somehow convince ourselves that the blades will eventually dry, so what’s the big deal?

Sure, they will dry. But the time the moisture sits on the blade’s surface is enough for the chemical reaction that causes rust to begin.

Try to remember water is the main culprit of rusting. So after cleaning and rinsing your knives and other metal utensils, always ensure to dry them before storing them. Otherwise, your kitchenware will be at risk of developing rust spots.

Overall, proper cleaning of your knives should consist of three steps, not two: wash, rinse, and dry. 

Store Your Knives in a Cool Dry Place

If you dry your knives thoroughly before putting them away, then place them somewhere damp, oxidation will still occur, and rust will start forming on the blades. So make sure your storage cabinets and knife blocks are as dry as you can get them.

When you notice more than one or two utensils start to get rust spots, despite storing them well-dried, inspect your storage spaces. They may be damp and will likely result in more of your kitchen utensils becoming rusty.

While you’re at it, check the state of utensils you hardly use and have stored away. Are they rusted or still in pristine condition? If the former, more will likely follow suit if the storage area remains corrosive-friendly.

Apply a Protective Coating on Your Knives

Applying mineral oil to your knives and other metalware in the kitchen can help prevent rust. But doesn’t oil pack moisture onto the knife blades, you ask? 

Oil creates a protective layer on the blade’s surface, which reduces direct contact with water and air. 

Act Quickly When You Notice Rust Start To Form

Don’t wait until the rust spreads to get rid of it. As soon as you notice rust spots or stains on your knife, try one of the homemade rust removers suggested in this guide to clean the rust off. 

Delaying action may cause rusting to penetrate deeper into the metal, which will reduce the chances of natural rust-removal techniques becoming successful.

When Should I Get Rid of My Rusty Kitchen Knife?

You should get rid of your rusty kitchen knife when rust damage is extensive and does not seem to improve after trying various rust-removal techniques. Rusted kitchenware can contaminate your food, causing health problems. So ensure to remove all the rust before using the utensil in question.

What Type of Knives Do Not Rust?

Ceramic and titanium kitchen knives do not rust. Unlike the popular carbon steel or stainless steel knives, ceramic and titanium blades do not contain iron, which is one of the three chemical elements required for rust to form. No iron, no rust.

Debunking Myths About Rust

There are myths surrounding rust that I want to address as I wrap up. These myths have permeated our thinking, leading to incorrect assumptions about rust and what causes it to form. 

First up on the chopping block: stainless steel doesn’t rust. 

False. Stainless steel isn’t impervious to rust. When exposed to corrosive environments for extended periods, the protective layer of chromium oxide may get damaged, making rusting possible.

Next up on the chopping block: rust can cause tetanus. 

Tetanus is caused by a bacteria called Clostridium tetani. Getting cut by your rusty kitchen knife isn’t going to cause tetanus. However, any damage to the skin, whether caused by a rusty object or not, allows the tetanus-causing bacteria to enter your body.

Conclusion

Nobody likes unsightly rust stains on anything in the house, least of all on kitchen items that come in contact with food. If your kitchen knives are rusty, you can help restore them such that they look new again using items in your kitchen or store-bought products.

After successfully removing the rust from the blades, ensure to always dry them well after cleaning and store them in a cool, dry place henceforth to prevent rust.

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