Water, the universal solvent, is an indispensable part of everyday life. However, there’s one aspect of industrial life that can dispense with good old H2O. We refer, of course, to our permanent magnets, which are susceptible to corrosion, a sworn enemy of magnetic strength. How does moisture affect different magnets, from those with traditional iron compositions to more unorthodox cobalt ones? We’ll immerse you in the topic—just be careful not to immerse your magnets in water.
Rust never sleeps, as Neil Young once sang. But it can put a once-effective magnet to rest for good. The effects of moisture on a magnet are apparent with traditional iron magnets. The subtleties of chemistry are very much on display here. Iron is naturally magnetic. This is true whether it’s in its elemental form or existing as a part of an alloy like steel. Iron oxide, the combination of iron and oxygen—we know it better as rust—is decidedly non-magnetic. All it takes is the addition of oxygen to take magnetism away, and moisture in the air reliably imparts that oxygen. The more of your magnet’s surface area rusts, the less power it will have. Eventually, an abundance of rust will send it to the scrap heap.
Neodymium is an interesting element. It’s one of the rare-earth elements of the lanthanide series and is a powerful permanent magnet. However, its relative rarity means that it doesn’t stand alone in the construction of industrial magnets. Neodymium works with iron and boron to form NdFeB magnets, some of the most powerful permanent magnets in industrial settings. However, their high iron content makes them incredibly susceptible to corrosion, perhaps more than their rare-earth name might indicate. Forget storing these in a humid place—even ambient moisture in the atmosphere can be enough to initiate corrosion on the surface of a neodymium magnet. Operators must use and store these magnets with close attention to environmental conditions.
What samarium-cobalt magnets lack in strength relative to neodymium magnets, they more than make up for in specialized applications where corrosion resistance matters most. In assessing how moisture affects different magnets, you’ll find that the samarium-cobalt construction is the one that moisture least affects. This makes these magnets ideal for use in marine environments and areas where high humidity would prematurely ruin iron or neodymium magnets. Not only are SmCo magnets practically impervious to degeneration from exposure to water, but they’re also resistant to heat. While iron magnets start to lose their charge around 80 degrees Celsius, a samarium-cobalt alloy retains its magnetism up to 300 degrees Celsius, giving it uncanny durability.