How long do SmCo magnets last?
The lifespan of SmCo magnets depends on the grade, magnetic circuit and conditions in service. Heat, an opposing field, corrosion or a chipped edge can shorten that service life. A claim in years needs evidence for the actual part and assembly.
For a buyer, the useful question is how much magnetic change the product can tolerate before it stops working. A sensor, coupling and holding assembly can reach that point in different ways. Start with the required result at the working position, then select and qualify the custom samarium cobalt magnet against it.
What a service-life claim should include
Eclipse Magnetics explains that magnet longevity depends on application and environment. Its guidance on well-protected magnets does not establish a guaranteed life for a custom component. A purchaser still needs the proposed grade, duty cycle and acceptance limits.
Separate a temporary hot reading from a lasting change. Arnold’s technical paper on magnetization losses distinguishes these mechanisms:
| Observed change | Meaning for an evaluation |
|---|---|
| Reversible temperature change | The magnetic output returns when the magnet returns to its reference temperature. |
| Irreversible magnetic loss | Cooling alone does not restore the original output. Remagnetization may recover it if the material remains intact. |
| Permanent material damage | Corrosion or structural damage requires a different assessment; remagnetization does not repair the material. |
A room-temperature check after exposure and a measurement during hot operation answer different questions. Define which one the assembly must pass. Record the initial state before comparing later samples.
Seven checks for the lifespan of SmCo magnets
1. Define the magnetic result that must remain acceptable
Write down what the product needs: a field component at a sensor, flux in a defined fixture, torque from a coupling, or force under an agreed contact condition. Include the allowed change after exposure. A surface-field reading taken at an unspecified point may not be reproducible.
For a repeatable baseline, record the instrument, probe axis, measurement position, gap datum, part temperature and magnet orientation. Retain a fixture sketch with the approved sample. If the acceptance test uses the installed sensor, also record its settings and the mechanical position. The sensor magnet working-gap guide explains that setup in more detail.
Compare readings from the same method. If a later result changes, repeat the measurement after checking the fixture and temperature before attributing the difference to aging.
2. Record the complete temperature history
SmCo magnets in the 1:5 and 2:17 families have grade-specific operating limits. Request the proposed grade’s demagnetization curves at the intended temperatures. The working point and opposing field affect whether a temperature excursion causes lasting loss. Curie temperature is not an allowable continuous operating temperature.
Give the supplier the normal temperature, peak temperature, time at each peak, number of cycles and cooling conditions. Include manufacturing exposures such as adhesive cure or an assembly bake. A short peak in the factory and a continuous hot duty in the finished product need separate consideration. See the SmCo temperature selection guide for the grade and magnetic-circuit checks.
3. Check opposing fields and changes to the magnetic circuit
Account for magnetic conditions as well as temperature. Identify nearby coils, other magnets and operating states that create an opposing field. Assess that field with the proposed magnet’s curve at temperature.
Provide an assembly cross-section showing nearby steel and the working gap. Include any state in which the magnet operates outside its usual circuit, such as assembly or servicing. The data sheet for SmCo magnets cannot describe every installation. Ask the design reviewer which assembly states were included in the magnetic assessment and retain that assumption with the drawing.
4. Describe the atmosphere and any protective system
SmCo magnets need an environmental review even when corrosion resistance drives the selection. Arnold’s high-temperature SmCo paper discusses oxidation and protective measures for demanding hot environments. A coating, encapsulation or housing must suit the actual temperature and exposure.
State whether the part meets humid air, condensation, salt, cleaning fluid, process chemicals or vacuum. Describe exposure duration and the surfaces left uncovered. Include adhesives and mating parts in the review, because an intact magnet does not establish that the complete assembly remains usable.
If salt-spray testing is specified, agree the specimen, exposure and acceptance criteria. ASTM B117 cautions against predicting natural-environment performance from salt-spray results alone. A stated number of chamber hours is not a direct conversion into years of service.
5. Prevent damage during handling and mounting
SmCo magnets are hard and brittle. Adams’ material guidance notes the risk of chipping and cracking. Review thin sections, holes, edge condition and contact points before approving the drawing. Avoid treating a sintered magnet as a flexible structural part.
Show how the magnet is retained and which surfaces carry assembly loads. Ask whether fit, adhesive cure and thermal expansion could load an edge or move the working gap. For vibration or shock requirements, define the mounting and test conditions with the assembly designer.
6. Agree whether conditioning is required
Some applications require SmCo magnets to be conditioned before acceptance. Arnold’s stabilization guidance describes thermal and magnetic conditioning for the expected source of loss. The procedure depends on material selection and magnetic conditions.
For a custom order, ask whether the quote includes conditioning, how it will be performed and when the final magnetic acceptance test takes place. Record whether conditioning uses an open circuit or a defined assembly condition. Approve the resulting output range after that process. Do not assume that a supplier’s ordinary grade designation includes a particular treatment.
Conditioning addresses a specified change in magnetic state. It does not qualify an adhesive, prevent chipping or establish resistance to every atmosphere. Keep those requirements in the order specification if they affect service life.
7. Make the qualification test reproducible
Use a written qualification sequence. Record the sample identifiers, drawing and grade revisions, initial measurements, exposure conditions, measurements during exposure where required, and checks after return to the reference condition. State the allowed change and the treatment of damaged samples before running the test.
Consider a position-sensor assembly as an example. A field change measured after thermal cycling could come from a change in the magnet or from movement of its mounting. Measure at the specified datum, inspect the gap and compare the sensor response in the same assembly position. Keep these observations together so a material issue can be distinguished from an assembly issue.
An accelerated test supports a service-life claim only when its conditions and interpretation are justified for that application. Ask which failure mechanism the test represents and what evidence supports any extrapolation. Retain raw readings and photographs of the setup with the report; a pass label alone cannot explain a later disagreement.
Turn prototype results into purchasing requirements
Once prototype SmCo magnets pass, carry the acceptance method into the purchase specification. Keep the approved drawing revision, proposed grade, magnetization direction, coating or encapsulation, conditioning procedure and measurement fixture together. Agree how later lots will be sampled and which report accompanies delivery.
A useful lifespan RFQ includes:
- The required field, flux, force or torque and its measurement conditions.
- Finished dimensions, tolerances, magnetization and the assembly cross-section.
- Normal and peak temperatures, dwell times, cycles and manufacturing exposures.
- Opposing fields, atmosphere, chemicals, retention method and mechanical loads.
- Allowed change after exposure, proposed qualification method and quantity.
If the material family is still open, compare the proposed grades in the SmCo 1:5 and 2:17 guide. For a broader material decision, the SmCo versus NdFeB comparison explains which requirements to carry into both quotations.
Questions about the lifespan of SmCo magnets
Can a supplier guarantee a fixed number of years?
A fixed-life claim needs a defined part, environment, duty cycle, acceptance limit and supporting evidence. Ask for those conditions with the claim. A generic material-family description does not establish the life of the finished assembly.
Does a lower hot reading mean the magnet has worn out?
Check the output again at the specified reference temperature and position. Reversible temperature change, lasting magnetic loss and a shifted mounting require different follow-up. Keep the hot and cooled readings separate in the record.
Will SmCo always last longer than NdFeB?
Compare the grades in the actual application. SmCo and custom NdFeB magnets need their own temperature, magnetic-circuit and environmental review. Material choice alone cannot rank the service life of two finished assemblies.
Request a part-specific lifespan review
Send the drawing and service conditions through the SmCo magnet lifespan inquiry. Include the result the assembly must retain and the evidence required for approval. Magnetstek can review the specification and quotation scope; any life or performance commitment must be confirmed for the proposed part and conditions.
