Do Magnets Rust?


Many magnets corrode when exposed to water. Water has a significant effect on magnets, since it lose much of their pull when rust corrodes them. Corrosion is terrible news because it increases maintenance costs and necessitates using more expensive magnets that must last much longer. So is it possible to prevent magnets from rusting? And how can you improve the efficiency of your magnets?

What is the Right Size Magnet for Magnet Fishing
What is the Right Size Magnet for Magnet Fishing

What Causes Magnet Rust?

Magnets attract metal because they are ferrous (related to or containing iron). Unfortunately, iron also rusts in the presence of oxygen and water. The magnet's attraction weakens with rust, eventually becoming inefficient. Rust can transform a magnet into a decade-long paperweight in a single year. As the density of the iron changes, so does the corrosion rate.

While cobalt, nickel, dysprosium, and other elements are used to produce ferromagnetic magnets, none of these metals are entirely resistant to corrosion.

Neodymium magnets are the strongest permanent magnets that can be used in wet environments; however, they are also the most susceptible to corrosion. As a result, manufacturers of neodymium magnets often add additional corrosion resistance by adding trace amounts of rare earth elements like dysprosium.

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What Causes Corrosion In Neodymium Magnets?

Since iron has the most pronounced ferromagnetic properties, it is typically used in the strongest magnets. Consequently, this means that iron can be found in every permanent magnet, including a neodymium magnet.

However, in the worst-case scenario, magnets with high iron content, such as neodymium, are highly susceptible to corrosion and demagnetization due to iron's high reactivity with water. You'll see light surface corrosion in these and low resistance to corrosion.

Neodymium magnets are the strongest permanent magnets on the market, but they are easily corrupted in wet conditions due to their high iron content, which usually lies between 64 and 68 percent. Almost always, neodymium magnets are coated before being used because they are so susceptible to corrosion.

What Is Used To Coat Neodymium Magnets?

Since corrosion can occur from even atmospheric moisture, neodymium magnets have a short lifespan. Nickel and copper are the standard coating elements used in neodymium magnets. Nonetheless, a wide variety of coating elements are available. Several of the most common coatings and characteristics set them apart.

Gold Coating (Ni-Cu-Ni-Au)

  • It is characterized by an ultrathin nickel coating atop the regular coating.
  • The gold-coating without nickel amounts to about 0.05 micrometers in thickness.
  • The entire coating thickness is around 12 micrometers.
  • Gold plating wears off quickly with repeated use and is only used for decorative purposes.

Nickel (Ni-Cu-Ni)

  • It's the most popular coating in use today.
  • Nickel's value-to-performance ratio is entirely satisfactory.
  • The coating thickness approximation is about 12 micrometers.

Copper (Ni-Cu)

  • This coating is a little less durable than nickel against rubbing and impact.
  • In addition, slightly lower corrosion resistance than a nickel.
  • The thickness is roughly 10 micrometers.
  • Like the gold plating on the magnets, the copper finish wears off over time. This means they serve as decorative.
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Epoxy resin (Ni-Cu-Ni-Epoxy)

  • It quickly breaks as it disintegrates upon impact.
  • The coating is almost entirely corrosion-proof.
  • The thickness is roughly 10 micrometers.
  • Any cracks in the coating will eventually let moisture in, ruining the magnet.
Epoxy coated neodymium magnet

Chrome (Ni-Cu-Ni-Cr)

  • They are more commonly used for sphere magnets because of their higher resistance to rubbing and pressure.
  • The thickness is roughly 15 micrometers.

What About Magnets Made Of Samarium Cobalt?

Even without any additional coating, samarium cobalt magnets exhibit a much higher level of corrosion resistance. However, most SmCo magnets are still coated, typically for aesthetic or functional reasons. As a result of their increased resistance, SmCo magnets are frequently used in magnet fishing, which involves continuous exposure to extremely harsh environments such as water.

Reduced Magnetic Performance But Enhanced Corrosion Resistance?

Alnico and Ferrite magnets naturally resist corrosion. However, they can't compare to the magnetic performance of neodymium and samarium cobalt magnets.

When exposed to water, the surface of some grades of alnico magnets will gradually corrode because they contain traces of iron. On the other hand, alnico is corrosion-proof when combined with other lubricants such as:

  • Oil
  • Solvents
  • Alcohol

Ceramic magnets, also known as ferrite magnets, are made from iron oxide and are impervious to corrosion. As a result of their unparalleled corrosion resistance, ceramic magnets are rarely coated. However, surface treatments are typically needed because ceramic magnets tend to be dirty on the outside.

Rare earth magnets will need to be replaced frequently if used in wet environments. The best option is simply switching out the small magnet for a larger one made of a different material that is more corrosion-resistant or resistant to corrosion altogether.

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Simple Homemade Solutions To Prevent Rust On Your Magnet

If you want to partake in magnet fishing or fix a magnet in a water-prone location, you'll need to ensure your magnets are watertight (rustproof). Coated magnets designed for use in water are available for purchase, but some DIY methods can help make your magnet watertight.

Using The Waterproof Epoxy Putty

The most user-friendly epoxy putty is water weld epoxy putty, which can be used in various plumbing and repair applications (such as fixing drains, tubs, fuel tanks, and so on). After the epoxy putty has dried, you can sand it down to a more refined finish to create a custom shape for your magnet. A bonus is that epoxy putty is versatile and can be used for other do-it-yourself repairs.

Two-part Epoxy

Two-part epoxy is generally used because it is waterproof. It will cure nicely if you slobber it on and wait a while. Epoxy has many benefits, one of which is that it can be sanded and polished without cracking or chipping over time.

All-Purpose Rubber Coating

Rubber coating can be painted on, sprayed, or dipped directly into the product and dried in the air to provide waterproofing.

Conclusion

Though magnets are easily corroded, there are many ways to keep them in good working order. Invest in shielding for your magnets if they will be used in conditions where corrosion is possible (e.g., where there is a lot of moisture in the air).

Magnet Fishing Adventure

Anthony is passionate about magnet fishing. He likes to go out magnet fishing with his friends. On this site he shares his knowledge, experience, and details about magnet fishing gear and research with you.

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