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.
Steel is divided into two general categories: stainless and carbon.
Carbon steel 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 carbon steel but, with severe misuse, it can still rust.
Only titanium and ceramic knives are 100% rust proof since they do not contain iron.
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.
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.
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.
You can also soak the knife in white vinegar (apple cider vinegar might leave a stain) for 30 minutes. Afterward, use a scrubbing pad to remove the rust.
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 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 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.
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.
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.
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 sulphonic acids in onions are they key ingredients in getting your blade cleaned.
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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