Key takeaways
- The coating drawing should define formulation or plating, base layers, preparation, thickness and edge coverage.
- Salt-spray hours are test exposure, not months of outdoor life. ASTM B117 provides no universal conversion.
- An epoxy system may provide electrical insulation only if its formulation, thickness and integrity meet the insulation requirement. Zinc is conductive.
- Adhesion and temperature limits require qualification of the actual protective system.
Overview
Overview
Epoxy and zinc are different protective approaches for NdFeB. The best system for a part depends on exposure, coating coverage, dimensions and assembly. Unidentified salt-spray tables cannot establish a universal ranking or a fixed thermal cutoff.
Side-by-side
Side-by-Side Comparison
Reference properties and design questions. A count of comparison points does not establish a material or supplier recommendation.
| Criterion | Epoxy Coating | Zinc Coating |
|---|---|---|
| System | Specified epoxy formulation, process and base layers | Specified zinc plating and surface treatment |
| Thickness | Agreed polymer and total thickness | Agreed plating and total thickness |
| Corrosion testing | State method, preparation and failure criterion | State method, preparation and failure criterion |
| Humidity and thermal cycling | Qualify under the actual exposure | Qualify under the actual exposure |
| Electrical isolation | Verify insulation resistance and coating integrity | Conductive; separate insulation may be needed |
| Adhesive bond | Qualify preparation, adhesive, cure and load | Qualify preparation, adhesive, cure and load |
| Cost | Current quotation for the full stack | Current quotation for the full stack |
| Magnetic working gap | Include the finished coating thickness | Include the finished coating thickness |
Confirm source conditions and the actual part requirements before using reference values as acceptance limits.
Use cases
Conditions for considering each option
When Epoxy Coating wins
- The selected epoxy system passes the required environmental and assembly tests.
- Verified electrical insulation is required by the design.
When Zinc Coating wins
- The selected zinc system passes the required exposure and retention tests.
- Its finished thickness and quotation suit the part.
How to choose
Decision Framework
Decision framework
Specify protection on all exposed surfaces, including edges. Do not leave bare NdFeB edges to save coating cost unless an approved assembly design protects them. Qualify the coating stack, thickness, adhesive and temperature together; neither a generic salt-spray value nor a resin name can decide the selection.
Specs
Related NdFeB Grades
N42SH
150°C classN42SH reference: 40–43 MGOe at 20°C, with a nominal 150°C temperature class.
Reference; drawing review required
N42H
120°C classN42H reference: 40–43 MGOe at 20°C, with a nominal 120°C temperature class.
Reference; drawing review required
N48H
120°C classN48H reference: 45–48 MGOe at 20°C, with a nominal 120°C temperature class.
Reference; drawing review required
N45SH
150°C classN45SH reference: 43–46 MGOe at 20°C, with a nominal 150°C temperature class.
Reference; drawing review required
Industries
Related Applications
EV Motors
NdFeB magnet design inputs for permanent-magnet traction motors, auxiliary drives and e-axles.
Robotics
NdFeB design inputs for robot joint motors, compact actuators and servo drives.
Industrial Automation
NdFeB magnets for stepper motors, servo drives, linear actuators, magnetic couplings, and factory automation equipment across European and North American manufacturing.
Questions
Frequently Asked Questions
Is epoxy coating the same as powder coating?
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Epoxy describes resin chemistry. Electrophoretic coating and powder application are different processes with different formulations and thickness control. State the required process and qualified coating system.
Can zinc-coated magnets be used outdoors?
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Only after evaluation of the complete protective system and exposure. A result such as 24 or 48 hours of salt spray cannot predict failure within months. Test the intended coating and enclosure rather than assigning a service life from a generic table.
Does coating affect magnetic performance?
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Coating changes finished dimensions and the working gap. Conductive layers may affect current paths. Quantify the effect in the actual circuit; no universal percentage loss is established here.
Which coating is better for medical devices?
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Evaluate the finished device and intended biological contact. Barrier properties do not establish biocompatibility, sterilization survival or MR safety. The device qualification plan determines the coating evidence required.
Need help deciding?
Share your drawing, operating conditions and acceptance requirements for review. Human response within 1 business day.