You carefully purchase magnets for your facility to ensure you’re selecting enough strength and the right size without going over budget. You’re doing your best to be diligent, but are you also considering how much the coating will interfere with your magnetic force?  It’s an important factor to consider. Although a millimeter or two of distance between a magnet and another object might not seem like a much, every bit of distance reduces a magnet’s overall effectiveness. In some applications, even a tiny distance is enough to render an otherwise sound magnet totally useless.

The Trouble With Coatings

Before we discuss how coatings can interfere with your work, let’s review why coatings are so important. Coatings are essential on most magnets because of their susceptibility to corrosion (like neodymium magnets) and because they’re so brittle (like neodymium, ferrite, and samarium-cobalt magnets). The coatings grant the magnets extra durability. But the extra durability comes at a price. As we’ve said, any distance between the actual magnet and the object in front of it will decrease the magnet’s strength. This is especially true in applications when rubber or plastic are better suited than a metal coating. While a nickel (or other metal) coating will actually help transfer the magnetic field, rubber and plastic won’t. Instead, they’ll maintain constant separation between the magnetic field and the object being acted upon.

Determining How Much Force is Lost

To calculate how much strength is lost, you can use the inverse square law, which states that a magnet’s force changes in inverse proportion to the square of the distance from the source. In plain English: A magnet’s force drops rapidly even over small distances. We conducted an internal study by measuring a magnet’s force at 1mm away, and then again at 2mm away. We found that this tiny increase in distance dropped the magnet’s strength by a factor of four. Here’s another way of thinking about it: When you touch the surface of a magnet, you’re exposed to 100% of its force. But from just two inches away, the magnet’s strength declines to 10%. Obviously, where strength is essential, proximity is crucial.

What to Watch in a Coating

When maintaining strength is a factor, it’s best to use a metal-based coating, like nickel. As we said, this will transfer the magnetic strength and help hold on to surrounding objects. However, bigger magnets require multiple coatings for physical protection, sometimes with a nickel layer inside, then a copper layer, then another nickel layer on the outside. Because there are so many layers creating distance from the magnet, the overall strength decreases. If you need a waterproof, non-slip, or colorful coating, you’ll be better off with plastic or rubber. The problem, of course, is the constant distance between the magnet and the surrounding objects. If you need to use a plastic or rubber coating, you may want to use a bigger magnet than you normally would in order to make up for the lost strength.

How Apex Can Help

When you need to find the perfect magnet coating for your business, contact Apex Magnets. We provide magnet coatings in nickel, plastic, rubber, and epoxy. And if you require a custom design to fit your needs, we can do that as well.