China Neodymium And Ferrite Magnets Manufacturer & Supplier 
First of all, what is nickel plating?
Nickel plating refers to the way of plating a layer of nickel on a metal or non-metals by electrolytic or chemical methods, which is called nickel plating.Nickel plated nickel electroplating and chemical plating nickel. Bright nickel is obtained in the plating solution with brightener, and dark nickel is obtained in the electrolyte without brightener. Magnets are generally electroplated nickel and bright nickel.
As we all know, the corrosion resistance and oxidation resistance of NdFeb magnets are very weak if not plated, so it is generally necessary to extend the service life by plating. Nickel plating is one of the common surface treatment processes for magnetic materials. Basically, our nickel plating is nickel copper nickel three layer, and some customers ask whether their products can only be plated with a layer of nickel?
First of all, the answer is yes!
Rare earth neodymium magnets electroplating nickel-copper-nickel demonstration diagram;
In the early days, when the neodymium magnets need to plated nickel, it is generally only single layer of nickel. The nickel caoting is a cathode plating of the iron matrix. Due to its high porosity, it is necessary to use copper plating as the base or multiple layers of nickel plating. Therefore, the thickness of the coating is generally 20-25um, otherwise it can not only protect the NdFeb strong magnetic matrix, but also accelerate its corrosion and oxidation. And nickel plating can not be too thick, because nickel is a ferromagnetic metal, too more nickel layer may affect the magnetism of neodymium magnet.
Later, it was improved to double nickel (we also called three layer plated: nickel-copper-nickel), not only due to the process is more and more exquisite, but also because of the change of the times, the demand for products is more and more strict. In the 1990s, single-layer nickel was replaced by nickel-copper-nickel. Until today, many magnet manufacturers basically use nickel-copper-nickel plating. At present, only a small part of the products on the market with low anti-corrosion requirements still use single layer nickel plating, and the rest mostly use multi-layer plating combination
In conclusion: You can choose single layer nickel plating, but double layer nickel (Ni-Cu-Ni) is generally recommended, which has better corrosion and oxidation resistance, better appearance than single layer nickel and it won't cost much more than it.
For other coated magnets click: Special Coated Magnets
More posts about magnet nickel plating;
Neodymium Magnet Nickel vs Electroless Nickel Coating