August 21, 2024

Why Do Magnets Lose Their Strength? Demagnetization and Proper Magnet Handling

For many food processing plants and companies, magnetic separation is an important part of the quality assurance and safety of the final product. But without proper measures for validation and maintenance, demagnetization presents itself as a possible challenge.
This article explores the causes, remedies, and factors that impact magnet strength over time—allowing you to stay on top of your equipment and overall quality.

Exploring How Magnets Lose Their Strength

Magnetic separators gradually lose strength over time – it is inevitable. However, there are certain factors which can make magnets lose their strength more quickly.
This phenomenon, known as magnetic degradation or demagnetization, can be attributed to a variety of physical and environmental factors. Understanding these elements is essential to maximizing the lifespan and effectiveness of your carefully chosen magnetic separators.

Physical and Environmental Factors Leading to Loss of Magnetism

Magnets are not impervious to the world around them; their magnetic forces can be influenced or even diminished by several factors:

• Temperature Fluctuations: Excessive heat can agitate a magnet’s atomic particles, leading to alignment disruption and a decrease in magnetic force. When a magnet is heated, its kinetic energy increases, causing the molecules to move faster and become more sporadic. Some magnets are built to withstand high temperature products, however, big temperature changes such as submerging a heated magnet into cold water for cleaning, can lead to thermal shock which will likely have negative effects on magnet strength as well.
• Mechanical Stress or Physical Impact: Physical impacts, such as dropping or banging, and repetitive stress or vibration can cause a magnet to crack or dent, and can reduce the magnetic field.
• Electrical Currents: Exposure to strong electrical currents can demagnetize a magnet, especially if the magnet is not designed to withstand such environments.
• Corrosive Elements and Oxygen Absorption: The presence of moisture, oxygen absorption, or corrosive chemicals can lead to rust and decay in ferromagnetic materials, subsequently degrading their magnetic strength. Abrasive products can also wear down a magnet’s surface and cause demagnetization.
• Age: Over time, magnets naturally lose their magnetism, although this process is gradual and usually occurs over a span of decades.

The Result of Demagnetization on a Magnet’s Properties

As magnets undergo demagnetization, their properties alter significantly:

• The once robust magnetic field weakens, which can lead to a reduced ability to attract or hold onto ferromagnetic materials.
• Their coercivity, or resistance to becoming demagnetized, may decrease, making them more susceptible to external magnetic influences.
• In some cases, a magnet can experience a complete loss of magnetization, rendering it entirely ineffective for its intended purpose.

Understanding the causes of how magnets lose their strength is a crucial step in preventing premature magnet failure and ensuring their optimal performance throughout their intended lifecycle. Understanding this can help in asking the right questions of your magnet supplier to ensure steps are being taken at the time of manufacture to reduce the risk of demagnetization.

Influence of Temperature on Magnets

When considering magnets’ resilience and performance, temperature plays a pivotal role that cannot be overlooked. Just like many other materials, magnets are sensitive to fluctuations in their thermal environment. Understanding this sensitiveness is crucial for ensuring optimal performance in applications where magnets are subjected to a range of temperatures.

Temperature Extremes and Their Impact on Magnetic Strength

Both ends of the temperature spectrum can profoundly affect a magnet’s magnetic properties. At elevated temperatures, magnets may begin to lose their magnetization. This loss occurs because thermal energy agitates the magnetic domains, causing misalignment and a reduction in the magnet’s strength. On the flip side, cold temperatures can enhance magnetic properties to a certain point, but extremely low temperatures may lead to brittleness and physical damage, thus indirectly affecting magnetic strength.

Understanding Magnetic Saturation and Demagnetization

Permanent magnets are integral to numerous industrial and consumer applications, providing the motive power in electric motors or the sensing capabilities in various electronics. However, to maintain their performance, it’s crucial to understand the concepts of magnetic saturation and demagnetization.

What Is Magnetic Saturation?

Magnetic saturation occurs when a magnet’s domains are fully aligned and can no longer increase their magnetic ability in response to an external magnetic field. At this point, the magnet has reached its maximum magnetization level and cannot be made stronger. Trying to add more magnetic force simply generates heat, as the material absorbs the extra energy without a corresponding increase in magnetic strength.

The Demagnetization Process and Its Effects

Demagnetization, on the other hand, is a process whereby magnets lose their strength (magnetism). Several factors can cause this, such as exposure to heat, strong physical shocks, or corrosive environments. When demagnetization occurs, it results in a declined performance of the magnet. The magnet no longer has the same pulling force or field strength, which might render it ineffective for its intended function.

• Heat: A common cause of demagnetization, which can cause the magnetic domains to lose their alignment.
• Physical shocks: Sharp impacts or stress can disturb the alignment of magnetic domains.
• Stray magnetic fields: External magnetic fields can realign the magnet’s domains in different directions, effectively reducing its strength.

Recognizing these phenomena and their implications helps develop strategies to preserve magnetic strength and extend the lifespan of magnetic tools and components.

The Importance of Regular Magnet Validations and Inspections

Magnets play a crucial role in various applications, from electric motors to holding tools in place, to removing metal from food processing lines. Regular validations and inspections of food processing magnets are crucial to for maintaining adequate foreign metal fragment controls. With the knowledge of the status of your magnetic separators, you can monitor your magnets’ strength effectively.

Understanding How Physical Damage Impacts Magnet Strength

Physical damage to magnets is a critical factor that can make magnets lose their strength. Users and manufacturers must be aware of the types of damage that can occur and how to mitigate these issues to preserve magnet functionality.

Common Types of Physical Damage to Magnets

Magnets can suffer from a variety of physical impairments, each with the potential to weaken the magnetic field. Here are the most commonly observed:

• Chipping and cracking: Brittle magnets like hard ferrites and some rare earth magnets can chip or crack if dropped or struck. This can cause a slight reduction in the magnetic material volume, thus reducing the overall magnetic strength.
• Physical alterations: Cutting or drilling into a magnet can change its magnetic domain alignment, which can reduce its strength. The exact impact depends on the extent and location of the alteration.
• Surface wear: Repeated abrasive contact can gradually wear down the surface of a magnet, particularly in industrial settings, leading to a decrease in magnetic performance. Abrasive products such as cereal or rice can slowly erode the surface of the magnet and reduce it’s strength.

Preventing and Repairing Physical Damage to Magnets

To maintain the strength and longevity of your magnets, consider the following prevention and repair strategies:

• Handling precautions: Use care when handling magnets to avoid accidental drops or collisions. Soft padding or specialized handling equipment can reduce the risk of physical damage.
• Do not modify magnets: Any physical modification of a magnet should be done by the manufacturer and experienced professionals using appropriate tools and techniques to minimize danger, damage and preserve magnetic integrity.
• Protective coatings: Manufacturers can supply magnets with additional abrasion-resistant technology to help shield the magnet from physical abrasion.
• Consider what measures are taken in the manufacturing process of the magnet you plan to purchase, to prevent and reduce the risk of magnetic strength loss over time.

In cases where physical damage has already occurred, expert assessment is advised to evaluate the possibility of the need for replacement. Significant damage usually warrants a fresh component. Ensuring proper care in handling and storage is the best line of defense against physical detriments to magnet strength.

Corrosion and Oxidation: The Silent Enemies of Magnet Strength

Corrosion and oxidation occur when metallic elements within magnets react with moisture, oxygen, and other environmental chemicals. These reactions can lead to the formation of an oxide layer on the magnet’s surface, which disrupts the uniformity of the magnetic material and hence, impairs the alignment of magnetic domains. This degradation results in a weakened magnetic field, rendering the magnet less effective or, in some cases, useless.

Thankfully, there are strategies to mitigate the risks of corrosion and oxidation. Implementing the following protective measures can prolong the lifespan and maintain the potency of your magnetic separators:

• Control Environmental Exposure: Reducing humidity levels and preventing the contact of the magnet with chemicals that can accelerate corrosion is key to preservation.
• Maintain Physical Integrity: It is critical to ensure that the magnet’s surface is not compromised by scratches or dents, as these can make the underlying material more susceptible to oxidizing agents.

Ensure Your Magnets Reach Their Full Potential With Magnattack Global

Our risk assessments and validations can help you maximize your foreign metal fragment controls. Learn about the status of your magnetic separators and whether they are adequate for their duty. Magnattack’s expert team helps your manufacturing process optimize the magnet placement in order to maximize effectiveness, as well as monitor performance. Contact us today to get started.