Do nickel plated magnets have a single layer?

Answer: Yes, NdFeB double-layer nickel (nickel copper nickel) is actually an improvement on the early single-layer nickel, but it was gradually replaced by nickel copper nickel in the late 1990s. Now, most magnet manufacturers are electroplating nickel copper nickel.
In the early days, nickel plating on NdFeB was usually single layer. The porosity of nickel coating is high, and it is a typical cathodic coating at this time, so unless the coating is very thick (up to 20 ~ 25um), it can not protect the NdFeB substrate, but accelerate its corrosion. However, barrel nickel plating is not easy to thicken, and too thick nickel layer (because nickel is ferromagnetic metal) will seriously affect the magnetic properties of NdFeB magnets. So single layer nickel plating on NdFeB is not an ideal choice. At present, only a few products with low anti-corrosion requirements are still coated with single layer nickel, and the majority of other NdFeB nickel plating are using multi-layer coating combination.
PS: double layer nickel has better corrosion resistance than single layer nickel, so it is recommended to use nickel copper nickel, which is more beautiful in appearance and cheaper in price.