A good knife can last for decades if properly maintained.
But there’s one problem that’s more common than any other, rust.
Let’s take a look at why knives go rusty in the dishwasher, what you can do to prevent it and I’ll give a recommendation of knives that won’t go rusty in a dishwasher.
Rust is the common term for Iron Oxide. Iron Oxide requires three elements, iron, oxygen and water. Knives contain iron, so when knives are left in a very humid environment like a dishwasher Iron Oxide has the opportunity to form and create rust on the blade. To prevent rust you should minimize the moisture surrounding the knife.
Looking for a dishwasher-safe knife?
By far the best choice is the Global Chef’s knife. Check it out on Amazon here.
Or look at my fully review of the Global at the bottom of the article.
The cause of rust
The elements required to form iron oxide, the chemical term for rust, are iron, oxygen and water.
Rust will have the opportunity to accumulate on any item that contains iron since both oxygen and water are all around us in abundance.
Knives, really any kitchen utensils, are at particular risk as kitchens are often places where there’s lots of water and humidity.
Why do knives rust in the dishwasher
Knife blades contain iron and of course, oxygen is always going to be present unless you vacuum wrap your knives!
The reason for knives rusting in the dishwasher is the abundance of moisture.
Not only are the knives washed in water, but they will also be sitting in a very humid environment once the dishwasher has finished unless the dishwasher is emptied immediately.
Quality stainless steel knives are resistant to rusting and a quick wash in the dishwasher is unlikely to result in a rusty, crumbing knife blade.
But persistent use of the dishwasher and leaving your knives in there for a long time will cause damage eventually.
Different stainless steel knives come with different levels of rust-resistant, generally, a cheaper set of knives are more likely to rust than an expensive one.
That’s because high quality stainless steel tends to have more Chromium, the element that makes stainless steel rust resistant.
But now, lets figure out how we can stop our kitchen knives rusting in the dishwasher.
How to prevent knives rusting in the dishwasher
If you want to continue using a dishwasher to clean your knives, but you want to minimize the risk of them rusting then I would advise following these guidelines.
Minimize the the amount of time knives are in a humid environment.
Avoid placing your knives flat otherwise water will site on the flat surface of the.
Try to set your washing cycle to the shortest setting possible.
Once the dishwasher cycle has finished then either:
- Empty the dishwasher immediately, making sure the knives are wiped down and dry before storing them
- If you don’t have time to empty the dishwasher right away then open the dishwasher door and slide out the drawers. The heat will allow the moisture inside to evaporate pretty quickly so the knives should be dry in a few minutes.
Top tips for preventing knives from rusting
If you take care of your knives they can easily last for decades, so here are my top tips for avoiding rust gathering on your knives.
- Never leave knives wet. This is rule number 1 and it applies strongly to stainless steel and carbon knives. Dry-wipe your knives after every use and never leave them in a humid environment.
- Wipe food off your knives after every use. Never leave your knives with food on it as this can contain moisture and the acidity of many foods (especially fruit) can also cause damage if not removed.
- Don’t store knives with other wet items. Don’t dry your knives just to place them next to a stack of slightly wet pots and pans, they should be stored in a nice dry drawer.
- Never leave your knives in a closed dishwasher. If you have carbon knives never put it in the dishwasher at all. But if they are all stainless steel then you can get away with using a dishwasher. Just make sure that you at least open the door and bring the drawers out once the wash has finished to let them air dry.
The difference between carbon and stainless steel knives
Carbon knives should never be washed in the dishwasher, they will rust very easily and should always be washed and dried by hand after every use.
Let’s take a look at why.
Stainless steel knives are rust-resistant. This is because the metal alloy used to form the blade has been mixed with chromium, commonly known as chrome.
Chromium reacts with oxygen to create chromium oxide, this reaction occurs more quickly than iron oxide can form and as a result, the blade forms a protective layer of chromium oxide.
This layer prevents oxygen from reaching the iron, thus preventing the occurrence of iron oxide, so the knife becomes rust-resistant.
The chromium won’t always will though. If the iron oxide does manage to for first then the knife can still form rust spots.
Therefore different grades of stainless steel knives contain different amounts of chromium.
Cheaper blades will contain closer to 10% chromium, whilst the most resistant blades will be nearer to 15%.
Carbon blades many contain very little or no chromium at all, therefore the iron is completely exposed and will react with oxygen and water very quickly, causing rust to form.
For this reason, carbon knives should never be washed in the dishwasher or left unnecessarily wet for any amount of time. They require much more care than stainless steel knives and should be wiped down and dried by hand after every use.
In case you were wondering, carbon steels are still preferable by some people as you can create a shaper edge along the blade.
Knives that don’t rust in the dishwasher
When you’re looking for a knife that will be dishwasher safe you should focus on two things:
- The Chromium level in the steel (it should be 15% or more)
- The hardness of the steel (it should be HRC 58 or less)
Chromium is the element that makes stainless steel resistant to rust, so the more the better.
Knives using hard steel can more easily chip along the blade edge, that’s a problem in a dishwasher as there is plenty of sharp sudden movement both during the cycle and whilst bringing the trays in and out.
There is one brand that fits these two requirements better than any other, the Japanese knifemaker Global.
Global 8 Inch Chef’s Knife
View on Amazon (opens new tab)
When it comes to ultimate rust resistance, you can’t do better than a Global knife.
Global use their own, specially formulated steel, Cromova 18.
The 18 stands for 18% Chromium. Chromium is the element that makes stainless steel knives resistant to rust and corrosion.
15% Chromium is considered as very rust-resistant steel. At an incredible 18% there are few knives in the world that can match the rust resistance of Global.
The added benefit of this steel is that it’s relatively soft. That means the steel is more flexible and less brittle than other knives.
This is a large benefit if you’re using a dishwasher because this knife is far less likely to chip along the edge when it bumps into other items during the washing cycle.
There are very few chef’s knives that I would say are perfectly dishwasher safe, but this Global knife certainly is and I’d highly recommend it.
