Kitchen knives can rust if they are made of steel. Don’t worry, the rust is not dangerous and you can still safely use the knife. The only issue with rusted knives is that it is unsightly and can add impurities to your food preparation. Also, if rust is not treated, it can end up making a knife unusable.
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, reacting with iron found in a metal.
There are various DIYs that you can use to remove rust from your kitchen knife, ranging from the use of baking soda to the potato use.
Read on to know how you can easily deal with rusty knives.
Types of Steel and How They Rust
Steel is divided into two general categories: stainless and carbon.
The carbon one is made up of mostly iron with a small percentage of carbon and a few other metals. Stainless steel is made up of iron, chromium (about 15%), carbon, and a few other metals. The chromium surrounds the iron and protects it from being oxidized by oxygen. However, chromium reduces the durability of the blade–it’ll need to be sharpened more often than carbon steel.
Stainless steel is more resistant to rust than carbon steel but it does not mean that it is rust-proof. It can withstand moisture more than the carbon but, with severe misuse, it can still rust.
Only titanium and ceramic knives are 100% rust proof since they are ironless.
Why Do Knives Rust?
Here are the ingredients for rust: iron (metal), 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.
Kitchen knives rust when you leave them with moisture for a while. For example, storing an improperly dried knife.
How to Prevent Rusting on Knives
- Do not wash your knives in the dishwasher. The extreme heat will cause the metal to expand and contract, causing stress points that can become the seeds to rust.
- Wash your knives with dish soap after each use and dry them off. The oxygen in water can easily bond to the iron and this is the most common source of rust.
- Avoid salt water. If you are going to work in a salt water environment, use a titanium or ceramic knife.
- Do not soak your knives or leave them overnight in water. The water hastens the rusting process and reduces your knives' lifespan.
How to Get Rust off a Knife
There are a few methods you can use to remove rust from knives. They will remove the sight of rust but the rust will never be cured. Basically, you need to use something that is acidic to free the oxidized iron from the rest of the metal.
1. Using Lemon Juice
You might have known lemon as a great product to use when you have cold or applying on a freshly cut fruit like avocado to avoid oxidation and darkening. Besides that, lemon is a great alternative you can use to remove rust on your kitchen knives.
The natural citric acid in the lemon juice is responsible for getting rid of the rust.
Take a lemon, slice it in half, and run one side on the rusted metal. If the rust is small, you can remove it with a scrubbing pad. If it is large, you might need to leave the lemon on the spot for 30 minutes before it will start falling off.
If the rusting was heavy, you can carefully use a piece of steel wool to clean and get rid of it.
2. White Vinegar for Rust Removal
Vinegar is one of those must have kitchen items. It is known as a natural cleansing agent with its antiseptic properties. White vinegar also contains about 5 to 6% of acetic acid, which is a weak acid.
The acetic acid properties on vinegar will get rid of the rust in a simple and straightforward way.
You'll only need to soak and leave the knife in white vinegar for 30 minutes. Afterward, use a scrubbing pad or steel wool to remove the rust, especially if rust has accumulated for a while.
If dealing with newly rusted knife, after soaking on vinegar, just use a piece of soft cloth or towel to wipe. You should not use apple cider vinegar as it's likely to leave rust stains on your knives.
3. Baking Soda
In the baking soda method, you'll need to create a little bit of baking soda paste. You can pour a fair amount of baking soda into a bowl and add some water. Stir it up until it becomes a paste.
Apply the thick baking soda 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.
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.
Finally, clean off the blade with a piece of cloth to remove the excessive baking soda. If you want to be really good to your blade, you can apply some oil afterward to make sure it’s lubricated and protected from rust in the future.
4. Removing Rust with Citric Acid
Another way you can remove rust from your kitchen knife is using citric acid. This is a common product that you can purchase from health food stores or supermarkets. It is quite effective in removing rust.
The process of removing rust is simple: Add about three tablespoons of citric acid on a bowl of hot water, submerge your knife and leave it overnight. The next day, you'll just need to scrub off the freshly dissolved rust.
The major disadvantage of using citric acid, is that it removes rust together with other coatings or paint on the knife. But if your knife was just stainless steel with rust, then it's a great method of successfully removing rust on kitchen knives.
5. Metal Glo to Remove Rust
Metal Glo is a popular chemical solution that you can use stubborn rust on your carbon or stainless steel kitchen knives.
It is a carefully formulated solution that is safe for cookware, silverware, knives, or even jewelry.
When using metal glo or any other chemical solution on kitchen knives, rub it along the grain pattern to avoid chances of scratching the metal.
Apply the thick paste of metal glo evenly on the metallic part of the knife.
Natural Rust Removal Methods on Kitchen Knives
When you don’t have the materials around the house to get the rust off your knife, there are a few natural methods you can use.
1. Potato Method
Certain foods also act as a good sources for rust removal and the use of potatoes is one of the natural methods for removing rust.
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, to allow oxalic acid enough time to remove rust from your knives.
After you remove from the potato, wipe the blade with oil and the rust should be gone. To prevent rusting in the future, you should consider applying oil on your knives, especially when storing over long periods.
Something to note, is that the potato method can be a great way to remove rust when it's not much. With rust that has been left for a while, you should consider more effective ways than just the potato. Maybe combine with dish soap.
2. Onion Method
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 sulfonic acids in onions are the key ingredients in getting your blade clean and removing rust spots
Things to Know When Removing Rust on Knives
1. Prevention is always the Best Method
If you can prevent your knives from getting rusty in the first place, that's the best approach. You'll only need to maintain, apply some preventive measures and you are good to go.
For example, it helps to apply some mineral oil from time to time. Mineral oil will keep rust at bay, even when storing your knife for long periods.
2. Protect your Knife Blades
Before choosing cleaning products on your rusty knife, make sure you understand the implications this may have on the blade of your knife. If you succeed to remove rust but you scratch the blades and render them unusable, you'll have lost it.
Look for methods that will clean your knife and also protect the knife blade. Vinegar is a great option, not to mention it also has antiseptic properties, making it amazing for your kitchen.
3. Some Rusty Spots may be Irreversible
While there are various methods you can use to get rid of rust, you should also understand that some rust spots are permanent. If you'd left your pocket knife for months and it has high rust levels, it may be hard to get rid of the rust spots successfully and purchasing a new one may be the best alternative.
4. The Type and Make of Blade Matters
Before choosing a rust removal method, make sure you understand the type of material used and how it interacts with various products. For example, using dish soap and potato method, coupled with scrubbing with steel wool can provide tremendous results on one knife and not another.
As such, don't do anything because you saw it with a friend, research and make sure it can remove the rust on your knife. But some products such as vinegar and soda baking powder are safe and gentle on blades, most times.
5. A Rusty Knife can be a Health Hazard
A knife rust introduces harmful elements in your food elements, as it exposes the metal to and leaves it to get into food during preparation. As such, you should be prompt to remove rust on your kitchen knives and use the most appropriate method, for example baking soda.
The earlier you deal with rust on your knives, the easier you can remove it and you've greater chances of continuing to use your knives.
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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