How long do magnets last?

Many factors can influence the time it takes to lose its magnetic properties. However, magnets maintain their magnetization for hundreds of years, for example, a permanent magnet, more specifically a samarium magnet, takes 700 years to lose half of its magnetic strength. If we go to neodymium and ferrite magnets, they have almost permanent magnetism.

The factors that affect the lifetime of a magnet are:

  • The lifetime: the lifetime of a magnet is not eternal, with the passage of time the magnets inevitably lose their magnetization, a bad care can cause an acceleration of demagnetization.

  • Temperature change: depending on the type of permanent magnet, we can use a magnet at one temperature or another, since a neodymium magnet and an alnico magnet are not the same.
    The neodymium magnet has a working temperature of 80ºC to 200ºC, while the alnico magnet can withstand temperatures from -250ºC to 425ºC.

    When choosing the permanent magnet we want to use, we will have to take into account the application we want to use it for. It is not the same to be used for holding it inside furnaces or in magnetic separators.

  • Contact with other magnetic elements: when storing a magnet we must take into account that there is some kind of magnetic insulator, such as a plastic separator. As we already know, plastic is one of the most known and used magnetic insulators nowadays; in this way, we will avoid that the presence of ferromagnetic elements that around do not damage the magnetization of the magnet.

    In the same way, we have to take into account that there is no other type of permanent magnet nearby since the permanent magnet with greater magnetic strength takes away strength from the smaller one. Also keeping magnets with opposite charges nearby can affect and accelerate the loss of charge of the magnet.

  • Damage and physical shock: a magnet that has fallen to the ground or has been hit several times will have its magnetic power damaged. Depending on the magnet some have a higher resistance to corrosion than others, a clear example is the neodymium magnet that despite being the most powerful magnet has a lower tolerance to corrosion, so it is usually used with a nickel-plated coating, which serves as protection against scratches and external chemical agents.

    To extend the life of the magnets we have to take into account these factors and treat the magnets correctly with the appropriate care.

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