kitchen knives

Rust is a natural process, but the answer for the question ‘Why do knives rust in the dishwasher’ is still a mystery to many people. 

All home cooks expect their cutlery to last for decades to come. That is why they normally get frustrated when noticing specks of rust on their blades.

This article will show you how rust can form on your knives, and ways to prevent it from happening.


Why Do Knives Rust In The Dishwasher?

According to retired chef BenK from “Rust is technically iron oxide, which is the result of the natural reaction of 3 elements: oxygen, metal, and water. That is why knives and all-metal utensils are susceptible to rust once they contact oxygen or water.”

Knives are made of iron, and oxygen always exists, except you wrap the cutlery tightly! Thus, the only reason causing rust around knives is the excess humidity or moisture in the dishwasher. 

It also means you can prevent rust from forming by minimizing the moisture of the knife’s surrounding environment.

However, it is hardly possible as cutlery is usually washed and sits in the dishwasher for hours. If you don’t take out your knives immediately once the wash is over, there’s a high chance of them showing those worrisome rust spots very soon.

High-quality stainless steel kitchen utensils, including knives, are rust-resistant, and it is unlikely for them to leave a crumbly, rusty blade just after a few washes. 

Nevertheless, the thing is different when it comes to persistent washing in a dishwasher. The longer you let these metal items sit in the dishwasher, the more likely they will suffer from rust.

There are various types of stainless steel blades with different resistance levels to rust. But generally, an expensive set is more impervious to wear and rust than a cheap one. 

The reason is that high-quality, costly knives usually contain more chromium, making them more rust-resistant.


How To Prevent Your Knife From Rusting In The Dishwasher?

Though rusting in a dishwasher is an irreversible process, there are a few things you could do to minimize the potential risks.

  • Minimize the time that your knives stay in a dishwasher
  • Do not place knives flat as water will sit on the surface of their blades for longer
  • Select the shortest washing cycle in the dishwasher
  • Once the dishwasher has done its job, you should immediately take out all your utensils and empty the machine and make sure that the cutlery is completely dry before you store them.
kitchen knives
Knife Steel The Coolest Equipment Stainless Steel

If you are too busy to empty the dishwasher, at least try to open its door and take out the drawer. The heat will speed up the evaporation of the inside moisture so that blades and other kitchen utensils can get dry after a few minutes.

If you plan to use your knives for a long time, here are our secret tips to avoid rust on your cutlery.

  • Never leave kitchen knives wet. It is the most important rule, which can apply to both carbon and stainless steel utensils. Remember to dry-wipe them after use and do not leave them to stay in any humid environment.
  • Wipe down the remaining food on the blades after use. Food has a chance of containing moisture, which potentially causes rust. That is not to mention that the acidity in some kinds of food, especially fruits, can eventually leave permanent damage to these items.
  • Do not keep knives in the same place as other wet utensils. It is no point in drying knives to place them with many different wet pans or pots. Instead, it would help if you store your knives in a separate dry drawer.
  • Never put knives in a closed dishwasher. It is extremely true with carbon blades. But stainless steel knives can still withstand dishwasher use as long as you open the dishwasher’s door and take the drawer out when finished to let them dry.

Which Type Of Knife Will Less Rust In The Dishwasher?

When looking for a kind of knife that will not rust in the dishwasher, you should bear in mind 2 factors: the chromium level and the steel hardness. 

Chromium is a rust-resistant element for stainless steel. So, the higher its level is, the better resistance your knives get. According to scientists, the minimum level of chromium in stainless steel blades for effective results is 15%.

In terms of steel hardness, a dishwasher creates many abrupt movements when cycling and while you put the tray out or in. 

Therefore, knives that use tougher steel will more easily chip along the edge of the blade. The ideal level of hardness should be no more than HRC 58. 

So, let’s make a short and simple summary. Carbon cutlery contains no, or almost no, chromium, so it will rust easily, especially when you put it in the dishwasher and soak it in water for a while.

For better rust-resistant levels, stainless steel blades with high chromium levels and low HRC are wiser investments.


How To Remove Rust From Knives? 

If you’re guilty of neglecting your knives and start seeing some rusty spots, there are some steps you can take to rescue your knives instead of throwing them away.

First, fill a glass with white vinegar or lemon juice and soak the rusted blades into it. 

It aims at attenuating the rust so that it is much easier to clean. Let the blades be soaked for approximately 5 minutes before taking them out and wiping with a cloth. 

Avoid using harsh scourers as they may scratch your knives and remove the chromium layer on the stainless steel material, making them more vulnerable to rust. Thus, our recommendation is to use a soft one instead, such as a sponge, etc. 

And last but not least, after eliminating all the stains, follow the prevention guidelines strictly to prevent rust from happening again.


The Bottom Line

Hopefully, this article helps you know clearly the simple answer to ‘Why do knives rust in the dishwasher’ now. Sadly, the rusting process is inevitable, but you can completely prevent it happening sooner with some simple tips we suggest above. 

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