ND-FE-B MAGNET INCLUDING A COMPOSITE COATING DISPOSED THEREON AND A METHOD OF DEPOSITING A COMPOSITE COATING ON THE ND-FE-B MAGNET

Abstract

An NdFeB magnet includes a magnet body and a composite coating of metal disposed on the body. The compositing coating has a plurality of plating layers disposed on the magnet body to cover and protect the magnet body and improve corrosion resistance of the magnet body. The plating layers include a first, a second, a third, and a fourth plating layers to cover the magnet body. The first plating layer contains Zn. The second plating layer contains a Zinc-Nickel alloy. The third plating layer contains Copper. The fourth plating layer contains Nickel. A method of depositing on a composite layer on an NdFeB magnet body.

Claims

1. An NdFeB magnet comprising: a magnet body; and a composite coating including a plurality of plating layers with each one of said plating layers being made from metal and disposed on said magnet body to cover and protect said magnet body and improve corrosion resistance of said magnet body.

2. The NdFeB magnet as set forth in claim 1 wherein said composite coating has a total thickness of between 0.4 m and 40 m.

3. The NdFeB magnet as set forth in claim 1 wherein said plating layers include a first plating layer containing Zinc disposed on said magnet body to cover said magnet body.

4. The NdFeB magnet as set forth in claim 3 wherein said first plating layer has a first thickness of between 0.1 m and 10 m.

5. The NdFeB magnet as set forth in claim 3 wherein said plating layers include a second plating layer containing a Zinc-Nickel alloy disposed on said first plating layer to cover said first plating layer.

6. The NdFeB magnet as set forth in claim 5 wherein said second plating layer has a second thickness of between 0.1 m and 10 m.

7. The NdFeB magnet as set forth in claim 5 wherein said second plating layer of has a Nickel content of between 5% to 25%.

8. The NdFeB magnet as set forth in claim 5 wherein said plating layers include a third plating layer containing Copper disposed on said second plating layer to cover said second plating layer.

9. The NdFeB magnet as set forth in claim 8 wherein said third plating layer has a third thickness of between 0.1 m and 10 m.

10. The NdFE-B magnet as set forth in claim 8 wherein said plating layers include a fourth plating layer containing Nickel disposed on said third plating layer to cover said third plating layer.

11. The NdFeB magnet a set forth in claim 10 wherein said fourth plating layer has a fourth thickness of between 0.1 m and 10 m.

12. A method of depositing a composite layer on an NdFeB magnet body, said method including the steps of: providing the NdFeB magnet body including grease and dust and rust and an oxide layer disposed on the NdFeB magnet body; cleaning the NdFeB magnet body to remove the grease, the dust, the rust, and the oxide layer from the NdFeB magnet body and produce a cleaned NdFeB magnet; activating the cleaned NdFeB magnet to produce an activated NdFeB magnet; depositing a composite layer on the activated NdFeB magnet; and said step of depositing the composite layer including a step of depositing a first plating layer containing Zinc having a first thickness of between 0.1 m and 10 m on the activated NdFeB after said step of cleaning to produce an NdFeB magnet including the first plating layer; said step of depositing the composite layer including a step of depositing a second plating layer containing Zinc-Nickel alloy having a second thickness of between 0.1 m and 10 m and having a Nickel content of between 5% to 25% on the NdFeB magnet including the first plating layer to produce an NdFeB magnet including the second plating layer; said step of depositing the composite layer including a step of depositing a third plating layer containing Copper having a third thickness of between 0.1 m and 10 m on the NdFeB magnet including the second plating layer to produce an NdFeB magnet including the third plating layer; said step of depositing the composite layer including a step of depositing a fourth plating layer containing Nickel having a fourth thickness of between 0.1 m and 10 m on the NdFeB magnet including the third plating layer to produce an NdFeB magnet including the composite layer.

13. The method as set forth in claim 11 wherein said step of depositing the first plating layer of Zinc is defined as electroplating the first plating layer containing Zinc onto the activated NdFeB magnet by rack or barrel plating using a first plating solution having a pH of between 3.0 and 6.0 and containing ZnCl being present between 20 g/L and 120 g/L, KCl being present between 120 g/L and 320 g/L, H.sub.3BO.sub.3 being present between 10 g/L and 100 g/L, and HT-MB zinc acid additive and zinc acid brightener being present between 0.1 g/L and 50 g/L.

14. The method as set forth in claim 11 wherein said step of depositing the second plating layer is defined electroplating the second plating layer containing Zinc-Nickel alloy onto the polished NdFeB magnet by rack or barrel plating using a second plating solution containing Zn.sup.2+ ions being present between 2 g/L and 20 g/L, Ni.sup.2+ ions being present between 1 g/L and 10 g/L, a metal complexing agent being present between 50 g/L and 200 g/L, and NaOH being present between 20 g/L and 200 g/L.

15. The method as set forth in claim 11 wherein said step of depositing the third plating layer is defined as electroplating the third plating layer containing Copper onto the washed NdFeB magnet by rack or barrel plating using a third plating solution having a pH of between 7 and 10 and containing Copper Pyrophosphate being present between 20 g/L and 120 g/L, Potassium Pyrophosphate being present between 100 g/L and 300 g/L, and a Copper Pyrophosphate agent and a Copper Pyrophosphate brightener being present between 0.1 g/L and 50 g/L.

16. The method as set forth in claim 11 wherein said step of depositing the fourth plating layer is defined as electroplating the fourth plating layer containing Nickel onto the NdFeB magnet including the third plating layer by rack or barrel plating using a fourth plating solution having a pH of between 3 and 5 and containing NiSO.sub.4 being present between 150 g/L and 350 g/L, NiCl.sub.2 being present between 10 g/L and 100 g/L, H.sub.3BO.sub.3 being present between 10 g/L and 100 g/L, and an Ni-88 Brightener and an A-5 softener being present between 0.1 g/L and 50 g/L.

17. The method as set forth in claim 11 wherein said step of depositing the first plating layer further including steps of: polishing the NdFeB magnet including the first plating layer to produce a polished Nd-Fe-b magnet; said step of polishing being further defined as polishing the NdFe-b magnet using a polishing solution containing nitric acid being present between 0.1 vol. % and 3 vol. % to produce then polished NdFeB Magnet; and said step of polishing further including a step of rinsing the polished NdFeB magnet.

18. The method as set forth in claim 11 wherein said step of depositing the second plating layer further includes a step of washing the NdFeB magnet including the second plating layer using water to produce a washed NdFeB magnet.

19. The method as set forth in claim 11 wherein said step of activating the cleaned NdFeB magnet is define as corroding the cleaned NdFeB magnet with an acidic solution present between 0.1 wt. % and 2 wt. %.

20. The method as set forth in claim 11 wherein said step of depositing the third plating layer further includes steps of: activating the NdFeB magnet including the third plating layer; said step of activating the NdFeB magnet including a step of corroding the NdFeB magnet including the third plating layer using a solution containing hydrochloric acid having a concentration of between 1 vol. % an d 5 vol. %; and said step of activating the NdFeB magnet further including a step of washing the NdFeB magnet the third plating layer using water after said step of corroding;

21. The method as set forth in claim 11 further including a step of shaping the NdFeB magnet body prior to said step of cleaning the NdFeB magnet body; and said step of shaping the NdFeB magnet being further defined as grinding and chamfering the NdFeB magnet in a centrifugal or vibratory polishing machine for 1 to 10 hours.

Description

DESCRIPTION OF THE ENABLING EMBODIMENT

[0008] It is one aspect of the present invention to provide an NdFeB magnet. The NdFeB magnet includes a magnet body and a composite coating. The composite coating includes a plurality of plating layers with each one of the plating layers being made from metal and disposed on the magnet body to cover and protect the magnet body and improve corrosion resistance of the magnet body. The composite coating includes a first, second, third, and fourth plating layers.

[0009] The first plating layer of the composite coating contains Zinc disposed on the magnet body. It should be appreciated that, in another embodiment of the present invention, the first plating layer can consist only of Zinc. The first plating layer has a first thickness of between 0.1 m and 10 m to cover said magnet body. The second plating layer of the composite coating contains Zinc-Nickel alloy disposed on the first plating layer. In other words, the second plating layer is disposed directly over the first plating layer. In one embodiment of the present invention, the second plating layer contains Zinc-Nickel alloy wherein the Zinc-Nickle Alloy has a Nickel content of between 5% to 25%. It should be appreciated that, in another embodiment of the present invention, the second plating layer can consist only of Zinc-Nickel alloy. The second thickness of between 0.1 m and 10 m to cover the first plating layer. The third plating layer of the composite coating, disposed on the second plating layer, contains Copper and has a third thickness of between 0.1 m and 10 m to cover the second plating layer. It should be appreciated that, in another embodiment of the present invention, the third plating layer can consist only of Copper. The fourth plating layer of the composite coating, disposed on the third plating layer, contains Nickel and has a fourth thickness of between 0.1 m and 10 m to cover the third plating layer. It should be appreciated that, in another embodiment of the present invention, the fourth plating layer can consist only of Nickel.

[0010] It is another aspect of the present invention to provide a method of depositing a composite layer on an NdFeB magnet body. The method includes a first step of providing the NdFeB magnet body including grease, dust, rust, and an oxide layer disposed on the NdFeB magnet body. The next step of the method is shaping the NdFeB magnet body. It should be appreciated that the step of shaping can be performed by grinding and chamfering the NdFeB magnet in a centrifugal or vibratory polishing machine for 1 to 10 hours.

[0011] After shaping the NdFeB magnet body, the NdFeB magnet body is cleaned to produce a cleaned NdFeB magnet. The step of cleaning can include steps of removing the grease, removing the rust and the oxide layer, and removing the dust from the NdFeB magnet body. The step removing the grease can be performed by hot-dipping the NdFeB magnet body in a universal degreasing powder solution to remove the grease from the NdFeB magnet body. Following the step of hot-dipping and the step of removing the grease, the NdFeB magnet body can be rinsed using water. The step of removing the rust and the oxide layer from the NdFeB magnet body can be performed by washing the NdFeB magnet using an acid solution containing nitric acid of between 1 wt. % to 10 wt. %. After removing the rust and the oxide layer, the dust is removed from the NdFeB magnet body by subjecting the NdFeB magnet to an ultrasonic cleaning process.

[0012] After cleaning the NdFeB magnet body, the surface of the cleaned NdFeB magnet is activated to produce an activated NdFeB magnet. The step of activating the cleaned NdFeB magnet can be performed by corroding the NdFeB magnet with an acidic solution. The acidic solution has a concentration of between 0.1 wt. % and 2 wt. %. After activating the surface of the NdFeB magnet, the activated NdFeB magnet is cleaned by washing the NdFeB magnet using tap water and pure water. After producing the activated NdFeB magnet, the next step of the method includes depositing a composite layer on the NdFeB magnet. The step of depositing the composite layer includes step of depositing a first, second, third, and fourth plating layer on the activated NdFeB magnet.

[0013] The step of depositing the first plating layer includes a step of depositing a first plating layer containing Zinc having a first thickness of between 0.1 m and 10 m on the activated NdFeB magnet to produce an NdFeB magnet including the first plating layer. It should be appreciated that, in another embodiment of the present invention, the first plating layer can consist only of Zinc. The step of depositing the first plating layer containing Zinc can be performed by electroplating the first plating layer containing Zinc onto the activated NdFeB magnet. The step of electroplating the first plating layer can be conducted by rack or barrel plating using a first plating solution having a pH of between 3.0 and 6.0. The first plating solution contains ZnCl present between 20 g/L and 120 g/L, KCl present between 120 g/L and 320 g/L, H.sub.3BO.sub.3 present between 10 g/L and 100 g/L, and HT-MB zinc acid additive and zinc acid brightener present between 0.1 g/L and 50 g/L. It should be appreciated that the step of depositing the first plating layer can further include a step of polishing the NdFeB magnet including the first plating layer by using a polishing solution containing nitric acid being present between 0.1 vol. % and 3 vol. % to produce a polished NdFe-b magnet. After polishing, the polished NdFeB magnet is rinsed using water or pure water.

[0014] The step of depositing the second plating layer is further defined as depositing a second plating layer containing Zinc-Nickel alloy having a second thickness of between 0.1 m and 10 m on the NdFeB magnet including the first plating layer to produce an NdFeB magnet including the second plating layer. In other words, the second plating layer is disposed over the first plating layer to cover the first plating layer. The Zinc-Nickel ally also has a Nickel content of between 5% to 25%. It should be appreciated that, in another embodiment of the present invention, the second plating layer can consist only of Zinc-Nickel alloy. The step of depositing the second plating layer can be conducted by electroplating the second plating layer of Zinc-Nickel alloy onto the NdFeB magnet including the first plated layer by rack or barrel plating using a second plating solution. The second plating solution contains Zn.sup.2+ ions present between 2 g/L and 20 g/L, Ni.sup.2+ ions present between 1 g/L and 10 g/L, a metal complexing agent present between 50 g/L and 200 g/L, and NaOH present between 20 g/L and 200 g/L. The step of depositing the second plating layer further includes a step of washing the NdFeB magnet including the second plating layer using water to produce a washed NdFeB magnet.

[0015] The step of depositing the third plating layer is further defined as depositing the third plating layer containing Copper having a third thickness of between 0.1 m and 10 m on the NdFeB magnet including the second plating layer to produce an NdFeB magnet including the third plating layer. In other words, the third plating layer is disposed over the second plating layer to cover the second plating layer. It should be appreciated that, in another embodiment of the present invention, the third plating layer can consist only of Copper. The step of depositing the third plating layer can be conducted by electroplating the third plating layer containing Copper onto the washed NdFeB magnet by rack or barrel plating using a third plating solution. The third plating solution has a pH of between 7 and 10 and contains Copper Pyrophosphate present between 20 g/L and 120 g/L, Potassium Pyrophosphate present between 100 g/L and 300 g/L, and a Copper Pyrophosphate agent and a Copper Pyrophosphate brightener present between 0.1 g/L and 50 g/L. The step of depositing the third plating layer further includes a step of activating the NdFeB magnet including the third plating layer. The step of activating the NdFeB magnet can be conducted by corroding the NdFeB magnet including the third plating layer using a solution containing hydrochloric acid having a concentration of between 1 vol. % and 5 vol. %. After activating, the NdFeB magnet including the third plating layer is washed using water.

[0016] The step of depositing the fourth plating layer is further defined as depositing the fourth plating layer containing Nickel having a fourth thickness of between 0.1 m and 10 m on the NdFeB magnet including the third plating layer to produce an NdFeB magnet including the composite layer. In other words, the fourth plating layer is disposed over the third plating layer to cover the third plating layer. It should be appreciated that, in another embodiment of the present invention, the fourth plating layer can consist only of Nickel. The step of depositing the fourth plating layer can be conducted by electroplating the fourth plating layer containing Nickel onto the NdFeB magnet including the third plating layer by rack or barrel plating using a fourth plating solution. The fourth plating solution has a pH of between 3 and 5 and contains NiSO.sub.4 present between 150 g/L and 350 g/L, NiCl.sub.2 present between 10 g/L and 100 g/L, H.sub.3BO.sub.3 present between 10 g/L and 100 g/L, and an Ni-88 Brightener and an A-5 softener being present between 0.1 g/L and 50 g/L. The first, second, third, and fourth plating layers, together, defines the composite coating on the NdFeB magnet.

[0017] When electroplating the first, second, third, and fourth plating layers on to the NdFeB magnet, it should be appreciated that the NdFeB magnet, i.e. the activated NdFeB magnet and the NdFeB magnet including the first, second, or third plating layers, is a cathode immersed in the first, second, third, or fourth plating solutions. The metals plating on the NdFeB magnet is the anode.

[0018] After depositing the composite coating, the method includes a step of drying the NdFeB magnet. To dry the NdFeB magnet including the composite coating, the NdFeB magnet is first washed using tap water and pure water. After washing, the NdFeB magnet including the composite layer is desiccated.

[0019] It should be appreciated that, the steps of shaping the NdFeB magnet, cleaning the NdFeB magnet and the activating of the cleaned NdFeB magnet steps allows a strong first plating layer containing Zinc to form on the surface of the NdFeB magnet whereby the first plating layer containing Zinc is resistant to the thermal demagnetization. After forming the first plating layer on the NdFeB magnet, transition layers, e.g. the second plating layer containing Zinc-Nickel alloy and the third plating layer containing Copper, are disposed over the first plating layer. This ensures that the adhesion between the plating layers is strong and improve the corrosion resistance of the composite coating. Finally, the fourth plating layer containing Nickel is disposed over the third plating layer to improve the adhesive and the stability of the plating layers. In addition, the fourth plating layer containing Nickel also provides wear and corrosion resistance to the NdFeB magnet.

[0020] Implementing examples below provide a better illustration of the present invention. The implementing examples are used for illustrative purposes only and do not limit the scope of the present invention.

IMPLEMENTING EXAMPLE 1

[0021] In Implementing Example 1, barrel plating is used for plating the NdFeB magnet. The NdFeB magnet body including grease, dust, rust, and an oxide layer is shaped by grinding and chamfering the NdFeB magnet in a centrifugal polishing machine to a size having a radius between 0.2 mm and 0.3 mm for 3 hours. After shaping the NdFeB magnet body, the NdFeB magnet body is cleaned to produce a cleaned NdFeB magnet. First, the grease is removed from the NdFeB magnet body by hot-dipping the NdFeB magnet body in a universal degreasing powder solution having a volumetric concentration of 40 g/L to remove the grease from the NdFeB magnet body. Following the step of hot-dipping and the step of removing the grease, the NdFeB magnet body is rinsed using water for 1-2 minutes. Then, the rust and the oxide layer are removed from the NdFeB magnet body by washing the NdFeB magnet using an acid solution containing nitric acid of 3 wt. % for 60 seconds. After removing the rust and the oxide layer, the dust is removed from the NdFeB magnet body by subjecting the NdFeB magnet to an ultrasonic cleaning process for 3 minutes.

[0022] After cleaning the NdFeB magnet body, the surface of the cleaned NdFeB magnet is activated by corroding the NdFeB magnet with an acidic solution to produce an activated NdFeB magnet. The acidic solution contains nitric acid present in 1 wt. % for 15 seconds. After activating the surface of the NdFeB magnet, the activated NdFeB magnet is cleaned by washing the NdFeB magnet using tap water for 60 seconds and, then, using pure water for 60 seconds. After producing the activated NdFeB magnet, the activated NdFeB magnet is disposed in a hexagonal shaped barrel for depositing a composite layer on the activated NdFeB magnet to produce an NdFeB magnet including the composite layer. The step of depositing the composite layer includes step of depositing a first, second, third, and fourth plating layers on the activated NdFeB magnet.

[0023] The first plating layer contains Zinc and is disposed on the activated NdFeB magnet by electroplating the first plating layer of Zinc onto the activated NdFeB magnet to produce an NdFeB magnet including the first plating layer. The first plating solution has a pH between 3.0 and 6.0 and also contains ZnCl present between 20 g/L and 120 g/L, KCl present between 120 g/L and 320 g/L, H.sub.3BO.sub.3 present between 10 g/L and 100 g/L, and HT-MB zinc acid additive and zinc acid brightener present between 0.1 g/L and 50 g/L. It should be appreciated that, based on the sizes of the NdFeB magnet body, different sizes of the barrel can be used for controlling the thickness of the plating layers. During the electroplating process, the thickness of the first plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the first plating layer is polished by using a polishing solution containing nitric acid present at 1 vol. % to produce a polished NdFe-b magnet. After polishing, the polished NdFeB magnet is rinsed using water and pure water for 60 seconds.

[0024] Then, the NdFeB magnet including the first plating layer is placed in a tank containing Zinc-Nickel alloy for electroplating the second plating layer on the NdFeB magnet including the first plating layer to produce an NdFeB magnet including the second plating layer. The second plating layer contains Zinc-Nickel alloy. The Zinc-Nickel ally also has a Nickel content of between 5% to 25%. A second plating solution is used when electroplating the second plating layer. The second plating solution contains Zn.sup.2+ ions present between 2 g/L and 20 g/L, Ni.sup.2+ ions present between 1 g/L and 10 g/L, a metal complexing agent present between 50 g/L and 200 g/L, and NaOH present between 20 g/L and 200 g/L. During the electroplating process, the thickness of the second plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the second plating layer is washed using water to produce a washed NdFeB magnet.

[0025] Next, the third plating layer is electroplated on the NdFeB magnet including the second plating layer to produce an NdFeB magnet including the third plating layer. The third plating layer contains Copper. A third plating solution is used when electroplating the third plating layer. The third plating solution has a pH of between 7 and 10 and contains Copper Pyrophosphate present between 20 g/L and 120 g/L, Potassium Pyrophosphate present between 100 g/L and 300 g/L, and a Copper Pyrophosphate agent and a Copper Pyrophosphate brightener present between 0.1 g/L and 50 g/L. To avoid displacement during the plating, the NdFeB magnets having the second plating layer can charged before placing it in the third plating solution. During the electroplating process, the thickness of the third plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the surface of the NdFeB magnet including the third plating layer is activated by corroding the NdFeB magnet including the third plating layer using a solution containing hydrochloric acid having a concentration of 3 vol. % for 35 seconds. After activating, the NdFeB magnet including the third plating layer is washed using water.

[0026] Then, the fourth plating layer is disposed on the NdFeB magnet including the third plating layer to produce an NdFeB magnet including the composite coating. The fourth plating layer contains Nickel. A fourth electroplating solution is used when electroplating the fourth plating layer. The fourth plating solution has a pH of between 3 and 5 and contains NiSO.sub.4 present between 150 g/L and 350 g/L, NiCl.sub.2 present between 10 g/L and 100 g/L, H.sub.3BO.sub.3 present between 10 g/L and 100 g/L, and an Ni-88 Brightener and an A-5 softener being present between 0.1 g/L and 50 g/L. During the electroplating process, the thickness of the second plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the composite coating is washed and dried using a blow dryer or a centrifugal dryer. The first, second, third, and fourth plating layers, together, defines the composite coating on the NdFeB magnet. The order of the plating layers are Zn, Zn+Ni Alloy, Copper, and Nickel.

[0027] The NdFeB magnet including the composite coating produced in accordance with Implementing Example 1 has a size of 9.14 mm6.39 mm0.85 mm and has a label of 48H. The NdFeB exhibits no change in size after 96 hours of salt spraying test. In addition, the thermal demagnetization of the NdFeB magnet including the composite coating is less than 2% at 120 C. The thrust bearing for the composite coating on the NdFeB magnet is greater than 300N. In comparison, the surface of an NdFeB magnet including a NiCuNi coating begins to rust after 72 hours of the salt spraying test. At 120 C. the thermal demagnetization of the NdFeB magnet including the NiCuNi coating is 8%. The thrust bearing for the NiCuNi coating on the NdFeB magnet is 220N.

IMPLEMENTING EXAMPLE 2

[0028] In Implementing Example 2, rack plating is used for plating the NdFeB magnet. The NdFeB magnet body including grease, dust, rust, and an oxide layer is shaped by grinding and chamfering the NdFeB magnet in a centrifugal polishing machine to a size having a radius between 0.4 mm and 0.5 mm for 10 hours. After shaping the NdFeB magnet body, the NdFeB magnet body is cleaned to produce a cleaned NdFeB magnet. First, the grease is removed from the NdFeB magnet body by hot-dipping the NdFeB magnet body in a universal degreasing powder solution having a volumetric concentration of 40 g/L to remove the grease from the NdFeB magnet body. Following the step of hot-dipping and the step of removing the grease, the NdFeB magnet body is rinsed using water for 1-2 minutes. Then, the rust and the oxide layer are removed from the NdFeB magnet body by washing the NdFeB magnet using an acid solution containing nitric acid between 1 wt. % and 10 wt. % for 90 seconds. After removing the rust and the oxide layer, the dust is removed from the NdFeB magnet body by subjecting the NdFeB magnet to an ultrasonic cleaning process for 5 minutes.

[0029] After cleaning the NdFeB magnet body, the surface of the cleaned NdFeB magnet is activated by corroding the NdFeB magnet with an acidic solution to produce an activated NdFeB magnet. The acidic solution contains nitric acid present between 0.1 wt. % and 1 wt. % for 30 seconds. After activating the surface of the NdFeB magnet, the activated NdFeB magnet is cleaned by washing the NdFeB magnet using tap water for 60 seconds and, then, using pure water for 60 seconds. After producing the activated NdFeB magnet, the activated NdFeB magnet is disposed on a rack for depositing a composite layer on the activated NdFeB magnet to produce an NdFeB magnet including the composite layer. The step of depositing the composite layer includes step of depositing a first, second, third, and fourth plating layers on the activated NdFeB magnet.

[0030] The first plating layer contains Zinc is disposed on the activated NdFeB magnet by electroplating the first plating layer of Zinc onto the activated NdFeB magnet to produce an NdFeB magnet including the first plating layer. The first plating solution has a pH between 3.0 and 6.0 and also contains ZnCl present between 20 g/L and 120 g/L, KCl present between 120 g/L and 320 g/L, H.sub.3BO.sub.3 present between 10 g/L and 100 g/L, and HT-MB zinc acid additive and zinc acid brightener present between 0.1 g/L and 50 g/L. During the electroplating process, the thickness of the first plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the first plating layer is polished by using a polishing solution containing nitric acid present between 1 vol. % and 3 vol. % to produce a polished NdFe-b magnet. After polishing, the polished NdFeB magnet is rinsed.

[0031] Then, the second plating layer is electroplated on the NdFeB to produce an NdFeB magnet including the second plating layer. The second plating layer contains Zinc-Nickel alloy. The Zinc-Nickel ally also has a Nickel content of between 5% to 25%. A second plating solution is used when electroplating the second plating layer. The second plating solution contains Zn.sup.2+ ions present between 2 g/L and 20 g/L, Ni.sup.2+ ions present between 1 g/L and 10 g/L, a metal complexing agent present between 50 g/L and 200 g/L, and NaOH present between 20 g/L and 200 g/L. During the electroplating process, the thickness of the second plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the second plating layer is washed using water to produce a washed NdFeB magnet.

[0032] Next, the third plating layer is electroplated on the NdFeB magnet including the second plating layer to produce an NdFeB magnet including the third plating layer. The third plating layer contains Copper. A third plating solution is used when electroplating the third plating layer. The third plating solution has a pH of between 7 and 10 and contains Copper Pyrophosphate present between 20 g/L and 120 g/L, Potassium Pyrophosphate present between 100 g/L and 300 g/L, and a Copper Pyrophosphate agent and a Copper Pyrophosphate brightener present between 0.1 g/L and 50 g/L. During the electroplating process, the thickness of the third plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the surface of the NdFeB magnet including the third plating layer is activated by corroding the NdFeB magnet including the third plating layer using a solution containing hydrochloric acid having a concentration between 1 vol. % and 5 vol. % for 60 seconds. After activating, the NdFeB magnet including the third plating layer is washed using water.

[0033] Then, the fourth plating layer is disposed on the NdFeB magnet including the third plating layer to produce an NdFeB magnet including the composite coating. The fourth plating layer contains Nickel. A fourth electroplating solution is used when electroplating the fourth plating layer. The fourth plating solution has a pH of between 3 and 5 and contains NiSO.sub.4 present between 150 g/L and 350 g/L, NiCl.sub.2 present between 10 g/L and 100 g/L, H.sub.3BO.sub.3 present between 10 g/L and 100 g/L, and an Ni-88 Brightener and an A-5 softener being present between 0.1 g/L and 50 g/L. During the electroplating process, the thickness of the second plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the composite coating is washed and dried using a blow dryer or a centrifugal dryer. The first, second, third, and fourth plating layers, together, defines the composite coating on the NdFeB magnet. The order of the plating layers are Zn, Zn+Ni Alloy, Copper, and Nickel.

IMPLEMENTING EXAMPLE 3

[0034] In Implementing Example 3, barrel plating is used for plating the NdFeB magnet. The NdFeB magnet body including grease, dust, rust, and an oxide layer is shaped by grinding and chamfering the NdFeB magnet in a centrifugal polishing machine to a size having a radius between 0.2 mm and 0.3 mm for 1 hour. After shaping the NdFeB magnet body, the NdFeB magnet body is cleaned to produce a cleaned NdFeB magnet. First, the grease is removed from the NdFeB magnet body by hot-dipping the NdFeB magnet body in a universal degreasing powder solution having a volumetric concentration of 40 g/L to remove the grease from the NdFeB magnet body. Following the step of hot-dipping and the step of removing the grease, the NdFeB magnet body is rinsed using water for 1-2 minutes. Then, the rust and the oxide layer are removed from the NdFeB magnet body by washing the NdFeB magnet using an acid solution containing nitric acid of 3 wt. % for 30 seconds. After removing the rust and the oxide layer, the dust is removed from the NdFeB magnet body by subjecting the NdFeB magnet to an ultrasonic cleaning process for 1 minute.

[0035] After cleaning the NdFeB magnet body, the surface of the cleaned NdFeB magnet is activated by corroding the NdFeB magnet with an acidic solution to produce an activated NdFeB magnet. The acidic solution contains nitric acid present between 0.1 wt. % and 1 wt. % for 5 seconds. After activating the surface of the NdFeB magnet, the activated NdFeB magnet is cleaned by washing the NdFeB magnet using tap water for 60 seconds and, then, using pure water for 60 seconds. After producing the activated NdFeB magnet, the activated NdFeB magnet is disposed in a hexagonal shaped barrel for depositing a composite layer on the activated NdFeB magnet to produce an NdFeB magnet including the composite layer. The step of depositing the composite layer includes step of depositing a first, second, third, and fourth plating layers on the activated NdFeB magnet.

[0036] The first plating layer contains Zinc and is disposed on the activated NdFeB magnet by electroplating the first plating layer of Zinc onto the activated NdFeB magnet to produce an NdFeB magnet including the first plating layer. The first plating solution has a pH between 3.0 and 6.0 and also contains ZnCl present between 20 g/L and 120 g/L, KCl present between 120 g/L and 320 g/L, H.sub.3BO.sub.3 present between 10 g/L and 100 g/L, and HT-MB zinc acid additive and zinc acid brightener present between 0.1 g/L and 50 g/L. It should be appreciated that, based on the sizes of the NdFeB magnet body, different sizes of the barrel can be used for controlling the thickness of the plating layers. During the electroplating process, the thickness of the first plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the first plating layer is polished by using a polishing solution containing nitric acid present at 1 vol. % to produce a polished NdFe-b magnet. After polishing, the polished NdFeB magnet is rinsed using water and pure water for 60 seconds.

[0037] Then, the NdFeB magnet including the first plating layer is placed in a tank containing Zinc-Nickel alloy for electroplating the second plating layer on the NdFeB magnet including the first plating layer to produce an NdFeB magnet including the second plating layer. The second plating layer contains Zinc-Nickel alloy. The Zinc-Nickel ally also has a Nickel content of between 5% to 25%. A second plating solution is used when electroplating the second plating layer. The second plating solution contains Zn.sup.2+ ions present between 2 g/L and 20 g/L, Ni.sup.2+ ions present between 1 g/L and 10 g/L, a metal complexing agent present between 50 g/L and 200 g/L, and NaOH present between 20 g/L and 200 g/L. During the electroplating process, the thickness of the second plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the second plating layer is washed using water to produce a washed NdFeB magnet.

[0038] Next, the third plating layer is electroplated on the NdFeB magnet including the second plating layer to produce an NdFeB magnet including the third plating layer. The third plating layer contains Copper. A third plating solution is used when electroplating the third plating layer. The third plating solution has a pH of between 7 and 10 and contains Copper Pyrophosphate present between 20 g/L and 120 g/L, Potassium Pyrophosphate present between 100 g/L and 300 g/L, and a Copper Pyrophosphate agent and a Copper Pyrophosphate brightener present between 0.1 g/L and 50 g/L. To avoid displacement during the plating, the NdFeB magnets having the second plating layer can charged before placing it in the third plating solution. During the electroplating process, the thickness of the third plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the surface of the NdFeB magnet including the third plating layer is activated by corroding the NdFeB magnet including the third plating layer using a solution containing hydrochloric acid having a concentration between 1 vol. % and 5 vol. % for 10 seconds. After activating, the NdFeB magnet including the third plating layer is washed using water.

[0039] Then, the fourth plating layer is disposed on the NdFeB magnet including the third plating layer to produce an NdFeB magnet including the composite coating. The fourth plating layer contains Nickel. A fourth electroplating solution is used when electroplating the fourth plating layer. The fourth plating solution has a pH of between 3 and 5 and contains NiSO.sub.4 present between 150 g/L and 350 g/L, NiCl.sub.2 present between 10 g/L and 100 g/L, H.sub.3BO.sub.3 present between 10 g/L and 100 g/L, and an Ni-88 Brightener and an A-5 softener being present between 0.1 g/L and 50 g/L. During the electroplating process, the thickness of the second plating layer is controlled to be between 0.1 m and 10 m. After electroplating, the NdFeB magnet including the composite coating is washed and dried using a blow dryer or a centrifugal dryer. The first, second, third, and fourth plating layers, together, defines the composite coating on the NdFeB magnet. The order of the plating layers are Zn, Zn+Ni Alloy, Copper, and Nickel.

[0040] Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims. These antecedent recitations should be interpreted to cover any combination in which the inventive novelty exercises its utility. The use of the word said in the apparatus claims refers to an antecedent that is a positive recitation meant to be included in the coverage of the claims whereas the word the precedes a word not meant to be included in the coverage of the claims.