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Why neodymium magnets should be coated with three layers (nickel-copper-nickel)?

Neodymium magnets coated with a layer of nickel in the era of 1995,one layer coated neodymium magnets withdrawed from the historical stage from the year of 2000, that is to say, after year of 2000 nickel plating products are almost all nickel-copper-nickel(shorted as NiCuNi). With three layers plating, first of all, corrosion capacity is enough. Then two layers or direct copper nickel plating were not valaible?At that time,directly make copper plating on neodymium magnets was a big problem.it was difficult to ensure the bonding force,because NdFeB matrix will replace copper in copper plating solution,copper coating does not have enough adhesion,NdFeB after nickel plating has good adhesion.There's no need to worry about the adhesion of nickel and copper.

Directly make copper plating on the iron and boron in the copper plating solution,the copper plating layer does not have sufficient bonding force due to the generation of the copper in the copper plating solution.Therefore, a layer of nickel is required to ensure the binding force of the neodymium-iron-boron matrix.The advantage of copper plating is that the coating has less defects,has no shielding effect on magnetism, and is good in uniform plating property,small change in shape of workpiece by coating.

Now has broken through the technical difficulties of direct make copper plating on neodymium magnets.Direct copper plating and nickel plating is a trend,this coating design is more conducive to the thermal demagnetization of NdFeB components to achieve customer needs,generally can achieve 1.5-4.0% of the harsh heat demagnetization index.

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