| Formula | NdFeB |
|---|---|
| Relative strength | Strongest available |
| Max operating temperature | 80 °C standard, up to ~200 °C in high-temperature grades |
| Relative cost | Moderate |
| Corrosion resistance | Poor — almost always plated |
Grades are a strength number, not a quality number
N35 through to about N52. The number is roughly the maximum energy product in MGOe, so N52 stores more energy in the same volume than N42. A higher number is not a better magnet for every job — it is a stronger one, and strength usually costs temperature resistance.
The letter after the number is the temperature rating
No letter is the standard grade, then M, H, SH, UH and EH climb the temperature range. An N42SH tolerates considerably more heat than an N42, at a little less strength. If the assembly gets warm, the letter matters more than the number.
Maximum operating temperature is not the Curie temperature
These get confused constantly. The Curie point is where the material stops being magnetic altogether. The maximum operating temperature is far lower and is the point where it starts losing strength it will not get back. Design to the operating figure, not the Curie figure.
It will corrode if you let it
Bare neodymium rusts. Standard plating is nickel-copper-nickel, which is fine indoors and marginal outdoors. For wet or salty environments ask about epoxy or a fully encapsulated assembly rather than relying on plating.
It is brittle, not tough
Neodymium chips and cracks. Two large ones snapping together will shatter each other and take a fingertip with them. Design so they are never allowed to slam.
Ask us whether this suits the job
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