Why Do Magnets Lose Strength?

1. Is it Possible for a Magnet to Lose Strength?

Yes, all magnets can lose strength. Some lose strength through mechanical disadvantages which depends entirely on how they are used, but there are other things that can cause permanent magnetic loss to both neodymium and other various types of magnets. In this article we will go into detail about each way a magnet can lose its strength broken down into permanent loss and temporary loss and based on how the magnet is being used.

2. Magnet Temporary Strength Loss

Magnets have many interesting physical properties and some of them make it appear as if the magnet has gotten weaker, but in fact, the magnet has not changed at all. By understanding the cause of the temporary change in strength and taking proper countermeasures, you can get the most out of your magnets in any situation.

6 Factors that can cause temporary loss in magnetic strength

1. high leverage
2. low friction
3. gap
4. high temperature
5. magnetic shielding
6. what magnet is attracting to

I. Leverage tries to pry a magnet off of a surface

In physics, the farther out you hold a weight, the heavier it gets. This same rule applies when hanging objects with magnets in a horizontal fashion. The farther the object is sticking out from thr wall or surface the magnet is attached to, the more it will try to pull the magnet off of the surface.

How to reduce leverage issues

1. Minimalize how far object sticks out - The closer the object is to the surface the magnet is attached to, the lower the leverage. Our Leverage & Friction explains how to lower leverage.

2. Use multiple magnets - Using a magnet in each corner or in multiple places reduces leverage by helping prevent outward pull in those areas.

3. Add a mechanical stop - A mechanical stop helps mostly with friction issues, but resting vertically on a stop will also help slightly with lowering leverage. Our Magnetic Panels article demonstrates a working mechanical stop.

II. Friction prevents a magnet from sliding

Magnets pull towards themselves, but not from the sides. For this reason, magnets are more susceptible to sliding down vertical surfaces when hanging an object. Painted surfaces or any surfaces that have a low coefficient of friction with the magnet's coating will cause the magnet to slide more easily.

How to increase friction and prevent sliding

1. Use high-friction rubber magnets - Rubber coated magnets have a very high coefficient of friction and help prevent the magnet from sliding on many surfaces.

2. Avoid low-friction surfaces - Surfaces that have low friction such as glossy surfaces will cause the magnets to slip more easily. Learn more in our Friction & Magnets article.

3. Add a mechanical stop - A mechanical stop prevents the magnet from sliding down and the magnet prevents the object from falling off the wall. Check out our Magnetic Panels article to learn how to effectively use mechanical stop.

III. Gaps lower magnet pulling power

The farther away the magnet is away from another magnet or steel surface, the lower the pull force will be. The magnet has not gotten any weaker, it's just that non-ferrous material does not conduct magnetic fields as much and thus the pull force is lost. If the magnet gets closer, it will immediately gain power equal to the distance from the steel/magnet. Most of our magnets have pull force graphs listed on the product page, or you can estimate pull force in our magnet strength calculator.

How to reduce gaps to make magnets stronger

1. Make sure surfaces are clean - All debris on surfaces creates a gap that will lower pull force. Ensure surfaces are clean to reduce possible issues.

2. Avoid coated surfaces - If possible, try to not use any surfaces that have a coating. Even a thin coating like paint on a fridge lowers magnetic pull force.

3. Avoid excessive gaps - If the magnet cannot make direct contact with a surface, make sure that it is as close as possible to gain max pull strength. For example, make sure that a magnet is as close to the surface of the wood as possible in a magnetic knife block.

IV. Temperature causes temporary magnet strength loss

Heating a neodymium magnet up causes a temporary loss in pull force. The loss depends on the magnet heat grade, the shape of the magnet and whether or not it is in an assembly. You can learn more in our Temperature & Neodymium Magnets article.

How to protect a magnet against high temperatures

1. Increase magnet heat resistance - Get a high temp magnet or increase the magnet heat grade to increase max operating temp.

2. Add magnet to an assembly - If the magnet is part of an assembly, the assembly can sometimes absorb some of the heat and allow the magnet to perform better in demanding high heat environments.

3. Consider changing magnet shape - If the above fails, consider changing to a magnet shape that is less susceptible to heat.

V. Magnetic shielding can reroute magnetic flux

Magnetic shielding such as steel and Mumetal effectively reroute or conduct the magnetic flux and redirect it back to the opposite side of the magnet. In some applications, A magnet may be attached to thin steel, but still be needed to attract something on the other side. Our steel thickness calculator allows you to estimate how thick of steel you need for a magnet and help to see if any magnetic flux will not be absorbed.

How to prevent magnetic shielding

1. Avoid ferrous material between magnet and target - Ferrous metal or magnetic fields too close to the magnet will affect the magnet's pulling power. If your magnet is not getting the estimated pull force, this could be the cause. Make sure if there is ferrous metal nearby, that it is not between the magnet and what it is attracting to or any other place that may lower the magnet's pulling strength.

VI. Steel too thin also lowers a magnet's strength

In our latest article Testing Magnet Strength, we talk about the importance of using a thick piece of steel when testing magnets. A magnet needs a large enough piece of steel to attract to in order to achieve its maximum pull force, so using a small piece of steel or having a magnet attach to a screw etc. for a wall hanging will likely yield less strength than the maximum listed on the product page.

How to ensure magnet has a large enough object to attract to

1. Use a large enough target - Make sure that the metal the magnet is attaching to is enough to get the full pull force. Our general rule of thumb is that a diameter or size of steel at least double the diameter or size of the magnet should be enough to achieve close to the maximum pull force. Our steel thickness calculator can also be used to see if the steel is thick enough for the magnet being used.

3. Magnet Permanent Strength Loss

Above we mentioned ways magnets can temporarily lose their strength with things such as a gap, low friction and leverage etc. Now we will list out all of the major ways magnets can permanently lose their strength.

Top 4 ways magnets can permanently lose their strength

1. Temperature
2. External magnetic fields
3. Mechanical destruction
4. Oxidation and corrosion

I. Temperature can permanently lower magnet strength

High temperatures can permanently lower magnetic strength in one of two ways. The first way is if the temperature exceeds the magnets maximum operating temperature. This causes permanent loss in proportion to the amount the max operating temp was surpassed. The second type of permanent loss is when the magnet's curie temperature is surpassed. This will cause a full permanent loss of magnetic strength.

To learn more about how high temperatures affect strength loss you can check out our High Temperature Strength Loss article.

How to prevent permanent loss due to heat

See above heat loss prevent for more details.

II. External magnetic fields can demagnetize magnets

Neodymium magnets are very strong against coercion or being demagnetized, but if exposed to a strong enough external magnetic field, they are also susceptible to becoming demagnetized.

How to prevent demagnetization

Keep neodymium magnets away from any strong electrical currents and in certain environments like an MRI machine, ensure that the magnets are able to handle the strength of the magnetic field present.

III. Physical destruction of magnets causes strength loss

This goes without saying, but mechanical destruction of a neodymium magnet causes permanent magnetic strength loss. If there is less magnet left, there are fewer magnetic domains aligned and therefore the overall pull force will be lower as well.

How to protect your magnets from mechanical shock and wear

One of the simplest ways to protect your magnet is by getting a magnet with a plastic coating or rubber coating or in a steel cup assembly like our pot mounting magnets. The coatings and assemblies absorb a large part of the impact and prevent shattering of the magnets.

IV. Corrosion of magnets causes permanent strength loss

Oxidation and corrosion of neodymium magnets will cause the magnet to permanently lose pull force. Oxidation and other types of corrosion cause physical destruction of areas of the magnet exposed and therefore causes loss. While most of our magnets come with a standard nickel-copper-nickel plating, the magnet will still rust if exposed to moisture or other corrosive chemicals.

How to prevent oxidation and corrosion of neodymium magnets

You can prevent corrosion by using a plastic coating or rubber coating, keeping the magnet away from wet and moist environments and not using the magnet near any substances that will corrode the outer coating layers. You can learn more about magnet coatings in our Magnet Coatings article and about how magnets rust and corrode in our Can Magnets Rust? article.

4. How to Make Your Magnets Stronger

Checklist to improve magnet strength

1. Are the surfaces clean? - Clean all surfaces (wipe oil/paint/dust) and remove any spacer/gap material.

2. Is magnet flush with surface? - Make sure magnet/s are both flush with each other or surface attached to.

3. Is there a gap? - Use stronger magnet/s or try to get the magnet as close as possible to what it is attaching to.

4. Is the steel thick enough? - Check our steel thickness calculator and use a larger or thicker target for the magnet if necessary.

5. Is there low friction? - If the magnet is sliding, use rubber-coated magnets, add a mechanical stop, or roughen the contact patch.

6. Is the magnet pulled of? - If the magnet is getting pulled off the surface, bring the load closer to the surface, use multiple magnets (one at each corner etc.) or add a mechanical stop.

7. Is the magnet too hot? - Check the magnet grade and make sure it's not hotter than its max operating temp. If so, change to stronger heat grade of high temp magnets, add to an assembly or reconsider magnet shape.

8. Is the magnet rusting or corroding? - Consider changing to a plastic coated magnet or a rubber coated magnet for additional corrosion protection.

9. Has the magnet been damaged? - Check for chips and cracks. Chips and cracks can lower pull force so replace magnet if needed.

Need help picking the right magnet for your application or product? Contact us with your details and we'll help you find the best magnet for the job.