If you’re in the market for a stainless steel fridge, you’re probably wondering if your old magnets will stick to it. Or perhaps you came here just to learn more about the magnetic properties of stainless steel. So, do magnets stick to stainless steel?
Magnets stick to ferritic and martensitic stainless steel but not austenitic stainless steel. Although stainless steel is primarily made of iron, which is a magnetic metal, austenitic stainless steel has a crystalline structure that makes it almost completely non-magnetic.
The rest of this article will explain why magnets don’t stick to some types of stainless steel, what stainless steel is magnetic, and whether your magnets will stick to a stainless steel fridge and cookware.
Magnets don’t stick to stainless steels with a face-centered cubic crystalline structure because they’re non-magnetic. Ferritic stainless steel is magnetic because the molecules have a body-centered cubic structure. When nickel is added, it stabilizes the steel, making it non-magnetic.
Although ferritic stainless steels are very slightly magnetic, it’s not enough to make a magnet stick.
Since magnetism is caused by the motion of electrons, only a few materials have enough free electrons to be truly magnetic.
Iron, the base metal of any stainless steel alloy, is highly magnetic in its elemental form. However, adding austenite (usually nickel, nitrogen, or manganese) stabilizes the iron’s structure, making it non-magnetic.
Unlike the magnetic body-centered ferrite crystals, austenite stainless steel has a face-centered cubic crystal shape.
The inherently magnetic iron molecules in the cube’s corners face the nickel atom in the middle. This is what makes them lose most of their magnetism.
For all intents and purposes, magnets can’t attract austenitic stainless steel. Since austenitic stainless steel alloys are by far the most common, you might think that all stainless steel is non-magnetic.
According to the AISI grade, austenitic stainless steel is usually 200 or 300-series. If you see a label saying something like 301 or 303 etched into the item, it’s non-magnetic.
This little trick is helpful when shopping for non-magnetic stainless steel bolts and screws, but not much else. If you want to find out whether something made of stainless steel is magnetic, it’s best to test it with a small magnet.
Magnets can stick to ferritic, martensitic, and duplex stainless steel. Magnets stick relatively well to ferritic stainless steel because it has a body-centered cubic structure. According to the AISI grading standards, these magnetic stainless steel styles typically fall within the 400-series.
Ferritic stainless steel is called ferritic because it has a lot of ferrites (iron compounds). Since iron is highly magnetic, ferritic stainless steel retains that property because the crystal structure isn’t all that different.
Martensitic stainless steel is similar to ferritic stainless steel. It’s primarily composed of iron, chromium, and carbon.
The presence of ferrites alone isn’t what makes ferritic steel magnetic. The lack of austenite means that the body-centered atomic crystals can rotate to face a nearby magnetic field.
If there’s less than 2% nickel, it’ll be magnetic. Nickel completely demagnetizes iron atoms. The more nickel the alloy has, the less magnetic it’ll be.
As long as the iron atoms are free to rotate however they wish, the stainless steel is magnetic.
If you’re looking for magnetic stainless steel nuts and bolts, look for 400-series steel. You can rest assured knowing that these bolts will be attracted by your magnetic screwdrivers and other tools.
Duplex stainless steel is an equal mix of austenite and ferrite. As you’ve probably guessed, it’s only mildly magnetic compared to ferritic and martensitic stainless steel.
The stainless steel thickness matters, too. A thick stainless steel sheet is more magnetic than a thin one. Watch this YouTube video by K&J Magnetics demonstrating the phenomenon:
Magnets stick to all types of carbon steel. Carbon steel is highly magnetic because it contains a large percentage of iron. Additionally, carbon steel doesn’t have any nickel or other material that can interfere with the iron’s inherent ferromagnetism.
The primary difference between carbon and stainless steel is that carbon steel contains little to no chromium. This means that carbon steel is mostly iron and carbon with a few other trace elements.
Although chromium isn’t strongly magnetic, it doesn’t interfere with the iron’s magnetism like nickel does.
So, since magnets stick to iron, they stick to carbon steel too.
Carbon steel is very similar to ferritic stainless steel in terms of structure – the molecules have a body-centered cubic crystal structure.
It’s worth noting that carbon steel containing nickel exists too, but it’s not super common.
Magnets stick to stainless steel cookware that’s made of ferritic stainless steel. Most stainless steel cookware is made of ferritic stainless steel, but some cookware is made of non-magnetic austenitic steel. Austenitic steel contains nickel, a toxic metal, so avoid non-magnetic cookware.
You’ve probably heard of a trick where you can use a magnet to check if a pan or pot is really made of stainless steel. However, this isn’t a very good method.
Cookware can be made of non-magnetic stainless steel, such as austenitic stainless steel.
However, you should still avoid non-magnetic pots and pans whenever possible, but not for the reasons you might’ve expected.
Austenitic stainless steel contains nickel, which can leach into your food. Nickel concentrations are highest with brand-new pots and over longer cooking times.
Large nickel concentrations can cause serious poisoning that leads to kidney failure and heart problems.
Cookware made of ferritic stainless steel is much safer because it doesn’t contain nickel.
You can use a magnet to see if it sticks to the pan. If it does, it’s made of safe ferritic stainless steel. If it doesn’t, avoid using it or replace it altogether.
Magnets don’t stick to most stainless steel fridges. Most stainless steel fridges are made of 304 stainless steel, a non-magnetic austenitic stainless steel. However, a refrigerator made of ferritic stainless steel will be magnetic, so you can stick any strong magnet to it.
Chances are, your fridge is made of 304 stainless steel. Most fridges use this austenitic stainless steel type because it’s very common, shiny, and durable. And thanks to the economy of scale, it tends to be cheaper than other options.
If a retail store employee tells you the fridge is made of 18/10 or 18/8 stainless steel, that’s basically it. 18/10 means there’s 18% chromium and 10% nickel in the alloy.
Although nickel is toxic, it doesn’t really matter if your fridge contains nickel.
Unfortunately, nickel makes the iron in stainless steel non-magnetic. You’ll have to repurpose your old fridge magnets for something else. They won’t stick to the fridge no matter how strong the magnet is or how hard you try.
Magnets only stick to stainless steel if there’s no nickel in it. This type of stainless steel is commonly referred to as ferritic stainless steel, and it’s also referred to as 400-series stainless steel.
However, magnets can’t stick to austenitic stainless steel. And since austenitic is more common than ferritic, most stainless steel in our everyday lives is non-magnetic.
So, the only way to tell for sure is to use a magnet on the stainless steel surface that you want to test. This trick is also useful to check if a pan or pot contains nickel.
If the magnet doesn’t stick, avoid using that piece of cookware.
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