Demagnetization: What causes it and how to prevent it

Demagnetization can be defined as the reduction and/or loss (deprivation) of magnetic properties.

You may have heard of demagnetization. It is a concept we are very familiar with in the magnetic separation industry! If you work around or with magnets, it is important to know what demagnetization is, what causes it, and how to prevent it.

So, what is demagnetization?

Demagnetization can be defined as the reduction and/or loss (deprivation) of magnetic properties.

It is inevitable that a magnet will naturally slowly decline in strength over time. Some ‘settling-in’ strength loss is also normal in the beginning of a magnetic assembly’s life, where opposing poles are constantly in repulsion. Magnets, however, can and will remain magnetic for a very long time if properly cared for and if they are assembled correctly.

Our validation reports have included some magnets that are 20+ years old and still adequate for final product protection! This is due to how the magnets are assembled, how they are cared for, and specific measures that are taken in the manufacturing process to reduce the likelihood of rapid, early magnet strength loss.

What causes demagnetization?

Demagnetization can be caused by many different factors.

  • Poor handling, such as dropping or banging, or excessive vibration

Rough handling causes damage to a magnet, such as swelling, dints, and even exposed magnetic elements, which is very dangerous for product safety.

  • Poor quality manufacturing procedures, such as loose magnet assemblies, low-grade rare earth material, welding, or heating near magnet assemblies

This can pose a serious safety risk. Operators should never weld, cut, or grind magnets.

  • Thermal shock and operation temperatures

A typical example of how thermal shock can occur is during cleaning. For instance, taking a magnetic probe out of hot, liquid product and submerging it in cold water to clean, or the opposite way around.

Operating temperatures can also be a cause of demagnetization. It is important to ensure that the magnets installed in high-temperature product are designed and constructed with the correct grade of magnet material to withstand the heat.

  • Oxygen and moisture absorption, corrosion

This is usually caused by moisture or oxygen ingress, which can be due to poor design or damage to magnet canister. Rare earths are very susceptible to oxygen absorption. This cause is one of the most common causes of demagnetization. Special manufacturing procedures should be undertaken by magnet manufacturers to avoid this from happening. Your magnet supplier should be able to tell you what they have done during the manufacturing process to reduce the likelihood of magnet strength loss due to oxygen absorption.

  • Poor quality magnetic elements

Low-quality, lower-cost magnetic separators can rapidly lose their strength, despite being 10,000 gauss on supply! It’s important that your magnet manufacturer or supplier can tell you what procedures have been undertaken to reduce the likelihood of magnet strength reduction and what grade of magnets are being used. For food applications, low grade and low-cost magnets should be avoided.

  • Abrasive product

Abrasive products and tonnage rates can contribute to magnet wear, which can lead to rapid demagnetization once magnet elements are exposed. A magnet will wear more quickly in an abrasive product stream, such as corn, seed, cereal, or grain. Some magnet manufacturers have developed very durable magnet designs where magnet bar surfaces have increased durability and hardness, whilst ensuring product flows smoothly over the magnet bar.

  • Electronic fields from surrounding equipment

Alternating fields are used to demagnetize magnets. Motors, welding leads, welding arc, lighting, and other electric currents can cause partial demagnetization.

How to prevent demagnetization

Once a high-grade rare earth permanent magnet loses its strength, it cannot be ‘recharged’. Therefore, it is crucial to properly handle and take care of magnetic separators, as well as invest in quality equipment that will last the distance and protect your product and assets.

It’s always a good idea to consult a food-focused magnet supplier when choosing a magnetic separator for an application, as well as to ask questions regarding proper maintenance, handling, and cleaning.

Annual magnet validations are a great way of monitoring the strength and condition of your magnets. Contact us today to book a magnet validation.