Permanent Magnet Strength
There are two primary types of magnets: electromagnets and permanent magnets. Electromagnets are essentially magnets that have an on and off switch. They have magnet power in the presence of an electrical current and lose their power when this current stops.
As you may have inferred by their name, permanent magnets can create and perpetually maintain their own magnetic field. However, there are a few things that can affect magnet strength. So, how permanent is their magnetism?
Can Permanent Magnet Strength Be Lost?
There are various types of permanent magnet materials and applications that can affect strength. In general, a permanent magnet would only lose a small percentage of strength over several years (i.e. approximately 1% in 10 years) in ideal conditions. This percentage is so small that it doesn’t significantly alter its power. Yet, there are some conditions that can cause a permanent magnet to lose magnetism.
Temperature can have a vast effect on neodymium magnets. When exposed to cold temperatures, a neodymium magnet can slightly increase in strength. On the other hand, when exposed to extreme heat, it will gradually lose its power. And once it reaches the Curie point, the magnet will be demagnetized even after being restored to room temperature.
Water or Moisture
Water does not affect a magnet’s strength, but depending on what the magnet is made from, it can corrode. There are types that are used underwater for retrieving lost magnetic items and other necessary functions. Those lifting magnets are equipped with a special coating to protect from water corrosion.
It is possible to weaken the force of a magnet by applying a strong, repelling magnetic field to it for a prolonged period of time. However, the percentage of weakness would be minimal and would only noticeably affect magnets made of alnico or ceramic. Most of today’s strong magnets are either made of neodymium or samarium-cobalt.
In summary, with the proper care and storage a permanent magnet can hypothetically retain its strength forever. However if it is exposed to certain conditions it can also lose its “permanent” magnetism. Ultimately, figuring out whether or not a permanent magnet will lose its magnetism over time depends on its specific application. For more information and questions on permanent magnet strength, feel free to contact us.