CN115142101B - Surface protection process for neodymium iron boron permanent magnet - Google Patents

Surface protection process for neodymium iron boron permanent magnet Download PDF

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Publication number
CN115142101B
CN115142101B CN202211076045.8A CN202211076045A CN115142101B CN 115142101 B CN115142101 B CN 115142101B CN 202211076045 A CN202211076045 A CN 202211076045A CN 115142101 B CN115142101 B CN 115142101B
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copper
plating
permanent magnet
iron boron
neodymium iron
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CN115142101A (en
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张友亮
王祺岩
王春光
张蒙
李滨
张守华
邓志伟
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Antai Agco Technology Co ltd
Advanced Technology and Materials Co Ltd
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Antai Agco Technology Co ltd
Advanced Technology and Materials Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/38—Electroplating: Baths therefor from solutions of copper
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/085—Iron or steel solutions containing HNO3
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/086—Iron or steel solutions containing HF
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • C23G1/088—Iron or steel solutions containing organic acids
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/34—Pretreatment of metallic surfaces to be electroplated
    • C25D5/36—Pretreatment of metallic surfaces to be electroplated of iron or steel
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C25D7/001—Magnets

Abstract

The invention belongs to the technical field of surface protection of permanent magnets, and particularly relates to a surface protection process of a neodymium iron boron permanent magnet. The surface protection process of the neodymium iron boron permanent magnet comprises the following working procedures: chamfering, deoiling, acid washing, deashing, activating, alkali copper preplating, potassium pyrophosphate copper plating and nickel plating; the pre-plating copper solution adopted by the alkali copper pre-plating comprises the following components: 3.5-4.5 g/L of copper ions, 80-90g/L of complexing agent, and pure water as a solvent, and adding sodium hydroxide to adjust the pH value of the solution to 10-11; the potassium pyrophosphate copper plating solution adopted by the potassium pyrophosphate copper plating comprises the following components: 20-25g/L of copper pyrophosphate, 280-300g/L of potassium pyrophosphate and pure water as a solvent. The surface protection process for the neodymium iron boron permanent magnet reduces the influence of the plating solution on the neodymium iron boron base body, improves the bonding strength of the plating layer and the neodymium iron boron base body, and has no obvious reduction in residual magnetism and coercive force on the surface of the electroplated neodymium iron boron permanent magnet.

Description

Surface protection process for neodymium iron boron permanent magnet
Technical Field
The invention belongs to the technical field of surface protection of permanent magnets, and particularly relates to a surface protection process of a neodymium iron boron permanent magnet.
Background
The neodymium iron boron permanent magnet material has wide application, but because the neodymium iron boron permanent magnet material is a multi-phase alloy and the potential difference between phases is large, high-temperature oxidation, damp and hot hydrogen absorption and electrochemical corrosion are easy to occur, thereby influencing the service performance of the neodymium iron boron permanent magnet material. At present, the corrosion resistance of the neodymium iron boron permanent magnet material is improved by adding alloy elements or increasing a surface protective layer. The corrosion resistance of the alloy can be fundamentally improved by adding the alloy, but the corrosion resistance cannot be greatly improved, the magnetic energy property of the alloy can be influenced, the process is complex, and the cost is high; the corrosion resistance of the magnet can be greatly improved on the premise of ensuring that the magnetic energy characteristic is not influenced by adding the surface protective layer.
The surface protection method of the neodymium iron boron permanent magnet material mainly comprises the following steps: passivation, phosphating, electroplating, electroless plating, physical vapor deposition, thermal spraying, and the like. The electroplating chemical plating is the most widely applied protection technology at present, and the electroplated layer mainly comprises: ni-plated layer, zn-plated layer, ni-Cu-Ni-plated layer, and other Ni alloy layers and composite plating layers.
But with the extension of the application range of the neodymium iron boron, the defects of the electroplating process are more and more prominent. Because the combination of the electroplated layer and the matrix belongs to mechanical combination, the combination force is not high, the stress of the electroplated layer generates fluctuation change under the action of a variable temperature field, and the electroplated layer is easy to peel off. How to reduce the influence of the plating solution on the neodymium iron boron substrate and improve the quality of the electroplated layer and the film-substrate bonding strength is the direction of innovation and development of the current electroplating technology.
For example, patent CN104630852A provides a rare earth permanent magnet with a multi-layer composite plating layer and its composite plating method, wherein the protective layer comprises a first nickel plating layer, a second copper plating layer, a third nickel plating layer and a fourth layer, and the fourth layer plating solution comprises: 40-60 g/L stannous pyrophosphate, 30-45 g/L nickel chloride, 250-320 g/L potassium pyrophosphate and 20g/L glycine. The composite electroplated coating not only can play the anti-corrosion effect of the conventional nickel electroplating, but also has certain protection to eyes of inspectors, and has black and bright color and certain decorative effect. However, nickel is a ferromagnetic metal element, and a coating is directly formed on the surface of the rare earth permanent magnet, so that a magnetic circuit of an internal magnetic element is shielded, the magnetism is weakened, the magnetism is reduced by about 3 to 5 percent, the performance of the material is greatly influenced, and the nickel plating solution in contact with a substrate is acidic, so that the substrate is corroded to different degrees in the electroplating process, and the magnetic performance of a product and the binding force of the coating are further influenced.
Patent CN110904480A provides a surface treatment method for improving corrosion resistance of a neodymium iron boron rare earth permanent magnet material, which comprises the steps of removing oil, pickling and activating the neodymium iron boron permanent magnet material, then carrying out sulfate electrogalvanizing to form a bottom zinc layer, then carrying out alkaline electrogalvanizing on a zinc-nickel alloy to form a zinc-nickel alloy coating, and finally carrying out passivation. The alloy coating disclosed by the invention belongs to an anodic coating and can play an excellent electrochemical protection role, but the zinc plating solution in contact with the substrate is also acidic, so that the substrate can still be corroded to different degrees in the electroplating process, and the magnetic property and the coating binding force of a product are further influenced.
In order to solve the influence of plating solution on a neodymium iron boron substrate, patent CN112725751A discloses a preparation method of a surface protective coating of an ultrathin neodymium iron boron permanent magnet, which is characterized in that a neodymium iron boron magnet subjected to surface cleaning treatment is subjected to direct-current magnetron sputtering coating to obtain a neodymium iron boron magnet with a copper gradient coating deposited on the surface, then surface pretreatment is carried out, and then a nickel-based coating is plated to obtain the neodymium iron boron magnet with a Cu-Ni combined coating deposited on the surface. The method solves the problem that the electroplating solution erodes matrix tissues in the surface treatment process of the permanent magnet to cause the reduction of magnetic performance, but the electroplating process is more complex and has higher operation difficulty, and the mass production is difficult to realize in the actual industry.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the surface protection process for the neodymium iron boron permanent magnet reduces the influence of a plating solution on a neodymium iron boron base body, improves the bonding strength of a plating layer and the neodymium iron boron base body, has no obvious reduction in residual magnetism and coercive force on the surface of the electroplated neodymium iron boron permanent magnet, is simple in process, and is suitable for large-scale production.
The surface protection process of the neodymium iron boron permanent magnet comprises the following working procedures: chamfering, deoiling, pickling, deashing, activating, pre-plating with alkali copper, plating copper with potassium pyrophosphate, and plating nickel;
in the alkali copper preplating process, the adopted preplating copper solution comprises the following components: 3.5-4.5 g/L of copper ions, 80-90g/L of complexing agent, and pure water as a solvent, and adding sodium hydroxide to adjust the pH value of the solution to 10-11; the temperature of the copper preplating solution is 15 to 25 ℃; the thickness of an underlying copper layer formed by the alkali copper preplating is 0.4 to 0.6 mu m;
in the potassium pyrophosphate copper plating process, the adopted potassium pyrophosphate copper plating solution comprises the following components: 20-25g/L of copper pyrophosphate, 280-300g/L of potassium pyrophosphate and pure water as a solvent; the temperature of the potassium pyrophosphate copper plating solution is 45 to 50 ℃; the thickness of an intermediate copper layer formed by potassium pyrophosphate copper plating is 5 to 6 mu m.
Preferably, in the pre-plating copper solution, the copper ion source is one of copper sulfate, basic copper carbonate and copper acetate.
Preferably, in the copper pre-plating solution, the complexing agent is one of sodium potassium citrate and sodium potassium tartrate.
In the chamfering process, the loading capacity is 10 kg/cylinder of D5 silicon carbide circular abrasive and 2 kg/cylinder of product; the speed is started for 50 revolutions for 2 hours, 70 revolutions for 2 hours, 80 revolutions for 1 hour, 90 revolutions for 2 hours, 110 revolutions for 2 hours and 120 revolutions for 1 hour.
Preferably, the chamfering process may be performed using a four-barrel centrifugal chamfering machine.
In the oil removing process, the neodymium iron boron permanent magnet material is subjected to ultrasonic cleaning for 50 to 70s in an oil removing agent aqueous solution with the temperature of 50 to 60 ℃ and the concentration of the oil removing agent of 20 to 25mL/L, and then ultrasonic water cleaning is carried out. The ultrasonic cleaning and water washing function is to remove oil stains and dust stains attached in the chamfering process. The degreasing agent can be any type of degreasing agent, such as CY-1 degreasing agent (Shenzhen Jinbaojie environmental protection engineering Co., ltd.).
In the acid washing process, the neodymium iron boron permanent magnet material is soaked in mixed acid liquor at room temperature for 90-100s, then soaked in water for 20-30s, and ultrasonically washed for 50-60s.
Preferably, the mixed acid solution comprises: 15-20mL/L of nitric acid, 20-25g/L of acid washing additive and water as solvent. The pickling additive is preferably sodium gluconate, and can coarsen the matrix and improve the binding force of the product.
In the ash removal process, the neodymium iron boron permanent magnet material is soaked in an ammonium bifluoride aqueous solution with the ammonium bifluoride concentration of 15-20g/L at room temperature for 25-30s, and then is washed with water through ultrasound for 50-60s. When the neodymium iron boron permanent magnet material is soaked in an ammonium bifluoride aqueous solution, the neodymium iron boron permanent magnet material can be continuously shaken to enhance the ash removal effect; wherein, the ammonium bifluoride is used as a dust remover, which can ensure the smooth surface of the product.
In the activation process, the neodymium iron boron permanent magnet material is soaked in a citric acid aqueous solution with the citric acid concentration of 20-25g/L for 15-20s at room temperature. When soaking in citric acid aqueous solution, can constantly shake neodymium iron boron permanent-magnet material to reinforcing activation effect.
In the nickel plating process, the adopted surface nickel plating solution comprises the following components: 45-50g/L boric acid, 40-45g/L nickel chloride, 300-320g/L nickel sulfate, 2-3mL/L SB-71 additive, 2-3mL/L SB-72 additive, 1-2mL/L NS-AP additive and pure water as solvent; the temperature of the surface nickel plating solution is 45 to 50 ℃; the thickness of the surface nickel layer formed by nickel plating is 3 to 4 mu m.
Wherein the SB-71 additive, the SB-72 additive and the NS-AP additive are all produced by Nippon world metals Co.
The conventional neodymium-iron-boron permanent magnet material generally adopts a nickel-copper-nickel plating layer, and if the copper-nickel plating layer is directly plated, the bonding force between the plating layer and the neodymium-iron-boron substrate is difficult to ensure, because the neodymium-iron-boron substrate can replace copper in a copper plating solution, the copper plating layer does not have enough bonding force, and the bonding force between the plating layer and the neodymium-iron-boron substrate is ensured by internally pre-plating the nickel layer. However, nickel is a metal element with ferromagnetism, and after a plating layer is formed, a shielding effect is generated on a magnetic circuit of an internal magnetic element, the magnetism is weakened, the magnetism is reduced by about 3 to 5%, and the performance of the material is influenced to a great extent.
The surface of the neodymium iron boron permanent magnet material is firstly subjected to alkaline copper pre-plating to form a priming copper layer, then potassium pyrophosphate copper plating is carried out to form an intermediate copper layer, and finally a surface nickel layer is plated to form a copper-nickel plating layer. When the alkali copper is preplated, the method adopts the preplating copper solution with low copper ion concentration and high complexing agent concentration, greatly reduces the occurrence of displacement reaction in the electroplating process, quickly plates a layer of copper, and then replenishes the thickness of a copper layer by potassium pyrophosphate copper plating, further makes up the defects of the preplating copper (such as high porosity and the like), and breaks through the technical difficulty of direct copper plating of neodymium iron boron. Like copper and zinc, the copper and the zinc are diamagnetic metal elements, have no shielding effect on magnetism, have good uniform plating property and low corner effect, and the plating layer has small change on the shape of a workpiece; the design of the plating layer of directly plating copper and then plating nickel is more beneficial to meeting the requirement of the thermal demagnetization index of the neodymium iron boron element, and the binding force can also meet the requirement.
Compared with the prior art, the invention has the following beneficial effects:
(1) When the alkaline copper is preplated, the used copper plating solution is alkaline liquid, the corrosion to a material substrate in the plating process of the plating layer is extremely low, and meanwhile, the plating layer is plated compactly under the environment of ensuring the concentration of low copper ions and the concentration of a strong complexing agent, so that the displacement reaction between the copper solution and the substrate is avoided, and the magnetic performance of a product and the binding force between the substrate and the plating layer are further ensured; after the alkali copper is preplated, the thickness of the copper layer is supplemented by potassium pyrophosphate copper plating, the defects of the preplated copper (such as high porosity) are further made up, and the technical difficulty of direct copper plating of the neodymium iron boron is broken through;
(2) According to the invention, sodium gluconate is used as an acid pickling additive, so that the substrate can be coarsened, ammonium bifluoride is used as a deashing agent, the surface of the product is smooth, and the bonding strength between the substrate and the plating layer is further ensured;
(3) The surface protection process for the neodymium iron boron permanent magnet reduces the influence of the plating solution on the neodymium iron boron base body, improves the bonding strength of the plating layer and the neodymium iron boron base body, has no obvious reduction of the surface magnetic performance (remanence and coercive force) of the electroplated neodymium iron boron permanent magnet, is simple in process, and is suitable for large-scale production.
Detailed Description
The present invention is further illustrated by the following examples, but the scope of the present invention is not limited thereto, and modifications of the technical solutions of the present invention by those skilled in the art should be within the scope of the present invention.
The starting materials used in the examples are, unless otherwise specified, commercially available conventional starting materials; the processes used in the examples, unless otherwise specified, are conventional in the art.
Some of the raw material sources used in the examples are as follows:
permanent magnet (model 52H): aike science and technology, inc.;
CY-1 degreasing agent: shenzhen Jinbaojie environmental engineering Limited;
SB-71 additive, SB-72 additive, NS-AP additive: nippon world Metal Co.
Example 1
The surface electroplating is carried out on the neodymium iron boron permanent magnet material by adopting the copper-nickel electroplating process, and the steps are as follows:
(1) Chamfering: the permanent magnet has a mark of 52H, the specification of 11 multiplied by 1.8 multiplied by 0.76mm, and the grinding chamfer angle R is less than or equal to 0.1. Grinding and chamfering are carried out on the neodymium iron boron permanent magnet material, equipment used for chamfering is a four-cylinder centrifugal chamfering machine, the loading capacity is 10 kg/cylinder of D5 silicon carbide round type grinding materials, and the product is 2 kg/cylinder; the speed is started for 50 revolutions for 2 hours, 70 revolutions for 2 hours, 80 revolutions for 1 hour, 90 revolutions for 2 hours, 110 revolutions for 2 hours and 120 revolutions for 1 hour.
(2) Oil removal: and ultrasonically cleaning the chamfered Nd-Fe-B permanent magnet material for 50 seconds in a CY-1 degreasing agent aqueous solution with the temperature of 50 ℃ and the CY-1 degreasing agent concentration of 20mL/L, continuously shaking for degreasing, then sequentially carrying out ultrasonic water washing, and removing dust attached in the chamfering process.
(3) Acid washing: the neodymium iron boron permanent magnet material is cleaned in mixed acid liquor (the composition is 15mL/L nitric acid, 20g/L sodium gluconate and water as solvent) at room temperature for 90s, then soaked in water for 20s and ultrasonically washed for 50s.
(4) Ash removal: and (3) putting the acid-washed neodymium iron boron permanent magnet material into an ammonium bifluoride aqueous solution with the ammonium bifluoride concentration of 15g/L at room temperature, continuously shaking and soaking for 25s, and then washing with ultrasonic water for 50s.
(5) Activation: and putting the neodymium iron boron permanent magnet material into a citric acid aqueous solution with the citric acid concentration of 20g/L at room temperature, shaking continuously, and soaking for 15s.
(6) Pre-plating of alkali copper: the adopted pre-plating copper solution comprises the following components: 4.0g/L of copper ions, 85mL/L of sodium potassium citrate and pure water as a solvent, and adding sodium hydroxide to adjust the pH value of the solution to 10, wherein the copper ions are copper sulfate; the temperature of the solution for pre-plating copper is 15 ℃; the plating current density is 0.1A/dm, the roller speed is 16r/min, and the plating is finished until the plating thickness reaches 0.6 μm, so as to form the priming copper layer.
(7) And (3) potassium pyrophosphate copper plating: the adopted potassium pyrophosphate copper plating solution comprises the following components: copper pyrophosphate 20g/L, potassium pyrophosphate 280g/L and pure water as solvent; the temperature of the potassium pyrophosphate copper plating solution is 45 ℃; the electroplating current density is 0.12A/dm, the drum rotating speed is 18r/min, and the electroplating is finished until the plating thickness reaches 5.0 μm, so that an intermediate copper layer is formed.
(8) Nickel plating: the adopted surface nickel plating solution comprises the following components: 50g/L of boric acid, 45g/L of nickel chloride, 320g/L of nickel sulfate, 2mL/L of SB-71 additive, 3mL/L of SB-72 additive, 2mL/L of NS-AP additive and pure water as a solvent; the temperature of the surface nickel plating solution is 50 ℃; electroplating at a current density of 0.15A/dm and a drum rotation speed of 20r/min until the thickness of the nickel layer reaches 4.0 μm to form a surface nickel layer.
Example 2
The surface electroplating of the neodymium iron boron permanent magnet material is carried out by adopting the copper-nickel electroplating process of the invention, and the steps are as follows:
(1) Chamfering: the permanent magnet has a mark of 52H, the specification of 11 multiplied by 1.8 multiplied by 0.76mm, and the grinding chamfer angle R is less than or equal to 0.1. Grinding and chamfering are carried out on the neodymium iron boron permanent magnet material, equipment used for chamfering is a four-cylinder centrifugal chamfering machine, the loading capacity is 10 kg/cylinder of D5 silicon carbide round type grinding materials, and the product is 2 kg/cylinder; the speed is started for 50 revolutions for 2 hours, 70 revolutions for 2 hours, 80 revolutions for 1 hour, 90 revolutions for 2 hours, 110 revolutions for 2 hours and 120 revolutions for 1 hour.
(2) Oil removal: and ultrasonically cleaning the chamfered neodymium iron boron permanent magnet material for 70s in a CY-1 degreasing agent aqueous solution with the temperature of 60 ℃ and the CY-1 degreasing agent concentration of 25mL/L, continuously shaking for degreasing, then sequentially carrying out ultrasonic water washing, and removing dust attached in the chamfering process.
(3) Acid washing: the neodymium iron boron permanent magnet material is cleaned in mixed acid liquor (the composition is 20mL/L nitric acid, 25g/L sodium gluconate and water as solvent) at room temperature for 100s, then soaked in water for 30s and ultrasonically washed for 60s.
(4) Ash removal: and (3) putting the acid-washed neodymium iron boron permanent magnet material into an ammonium bifluoride aqueous solution with the ammonium bifluoride concentration of 20g/L at room temperature, continuously shaking and soaking for 30s, and then washing with ultrasonic water for 60s.
(5) Activation: and putting the neodymium iron boron permanent magnet material into a citric acid aqueous solution with the citric acid concentration of 25g/L at room temperature, and continuously shaking and soaking for 20s.
(6) Pre-plating of alkali copper: the adopted pre-plating copper solution comprises the following components: 4.5g/L of copper ions, 90mL/L of sodium potassium tartrate and pure water serving as a solvent are added, sodium hydroxide is added to adjust the pH value of the solution to 11, wherein the copper ions are basic copper carbonate; the temperature of the solution for pre-plating copper is 20 ℃; the plating current density is 0.1A/dm, the roller speed is 16r/min, and the plating is finished until the plating thickness reaches 0.5 μm, so as to form the priming copper layer.
(7) And (3) potassium pyrophosphate copper plating: the adopted potassium pyrophosphate copper plating solution comprises the following components: 25g/L of copper pyrophosphate, 300g/L of potassium pyrophosphate and pure water as a solvent; the temperature of the potassium pyrophosphate copper plating solution is 50 ℃; the electroplating current density is 0.12A/dm, the drum rotating speed is 18r/min, and the electroplating is finished until the plating thickness reaches 5.5 mu m, so that an intermediate copper layer is formed.
(8) Nickel plating: the adopted surface nickel plating solution comprises the following components: 45g/L boric acid, 40g/L nickel chloride, 300g/L nickel sulfate, 3mL/L SB-71 additive, 2mL/L SB-72 additive, 1mL/L NS-AP additive and pure water as solvent; the temperature of the surface nickel plating solution is 45 ℃; electroplating at a current density of 0.15A/dm and a drum rotation speed of 20r/min until the coating thickness reaches 3.5 μm to form a surface nickel layer.
Example 3
The surface electroplating of the neodymium iron boron permanent magnet material is carried out by adopting the copper-nickel electroplating process of the invention, and the steps are as follows:
(1) Chamfering: the permanent magnet has the brand number of 52H, the specification of 11 multiplied by 1.8 multiplied by 0.76mm, and the grinding chamfer angle R is less than or equal to 0.1. Grinding and chamfering are carried out on the neodymium iron boron permanent magnet material, equipment used for chamfering is a four-cylinder centrifugal chamfering machine, the loading capacity is 10 kg/cylinder of D5 silicon carbide round type grinding materials, and the product is 2 kg/cylinder; the speed is started for 50 revolutions for 2 hours, 70 revolutions for 2 hours, 80 revolutions for 1 hour, 90 revolutions for 2 hours, 110 revolutions for 2 hours and 120 revolutions for 1 hour.
(2) Oil removal: and (3) ultrasonically cleaning the chamfered Nd-Fe-B permanent magnet material for 60s in CY-1 degreasing agent aqueous solution with the temperature of 55 ℃ and the CY-1 degreasing agent concentration of 22mL/L, continuously shaking for degreasing, then turning to ultrasonic water washing, and removing dust attached in the chamfering process.
(3) Acid washing: the neodymium iron boron permanent magnet material is cleaned in mixed acid liquor (the composition is 18mL/L nitric acid, 22g/L sodium gluconate and water as solvent) at room temperature for 95s, then soaked in water for 25s and ultrasonically washed for 55s.
(4) Ash removal: and (3) putting the acid-washed neodymium iron boron permanent magnet material into ammonium bifluoride aqueous solution with the ammonium bifluoride concentration of 18g/L at room temperature, continuously shaking and soaking for 25s, and then washing with ultrasonic water for 55s.
(5) And (3) activation: and putting the neodymium iron boron permanent magnet material into a citric acid aqueous solution with the citric acid concentration of 22g/L at room temperature, and continuously shaking and soaking for 18s.
(6) Pre-plating of alkali copper: the adopted pre-plating copper solution comprises the following components: copper ions of 3.5g/L, potassium sodium tartrate of 80mL/L and pure water as a solvent are added, and sodium hydroxide is added to adjust the pH value of the solution to 10.5, wherein the copper ions are copper acetate; the temperature of the copper pre-plating solution is 25 ℃; the electroplating current density is 0.1A/dm, the roller speed is 16r/min, and the electroplating is finished until the plating thickness reaches 0.4 μm, so that the priming copper layer is formed.
(7) And (3) potassium pyrophosphate copper plating: the adopted potassium pyrophosphate copper plating solution comprises the following components: 22g/L of copper pyrophosphate, 290g/L of potassium pyrophosphate and pure water as a solvent; the temperature of the potassium pyrophosphate copper plating solution is 45 ℃; electroplating at a current density of 0.12A/dm and a drum speed of 18r/min until the thickness of the plated layer reaches 6.0 μm to form an intermediate copper layer.
(8) Nickel plating: the adopted surface nickel plating solution comprises the following components: 48g/L boric acid, 42g/L nickel chloride, 310g/L nickel sulfate, 2.5mL/L SB-71 additive, 2.5mL/L SB-72 additive, 1.5mL/L NS-AP additive and pure water as solvent; the temperature of the surface nickel plating solution is 48 ℃; electroplating at a current density of 0.15A/dm and a drum rotation speed of 20r/min until the thickness of the nickel layer reaches 3.0 μm to form a surface nickel layer.
Comparative example 1
The comparative example adopts a conventional nickel-copper-nickel electroplating process to carry out surface electroplating on the neodymium iron boron permanent magnet material, and comprises the following steps:
(1) Chamfering: the permanent magnet has a mark of 52H, the specification of 11 multiplied by 1.8 multiplied by 0.76mm, and the grinding chamfer angle R is less than or equal to 0.1. Grinding and chamfering are carried out on the neodymium iron boron permanent magnet material, equipment used for chamfering is a four-cylinder centrifugal chamfering machine, the loading capacity is 10 kg/cylinder of D5 silicon carbide round type grinding materials, and the product is 2 kg/cylinder; the speed is started for 50 revolutions for 2 hours, 70 revolutions for 2 hours, 80 revolutions for 1 hour, 90 revolutions for 2 hours, 110 revolutions for 2 hours and 120 revolutions for 1 hour.
(2) Oil removal: and ultrasonically cleaning the chamfered Nd-Fe-B permanent magnet material for 50s in CY-1 degreasing agent aqueous solution with the temperature of 50 ℃ and the CY-1 degreasing agent concentration of 20mL/L, continuously shaking for degreasing, then turning to ultrasonic water washing, and removing dust attached in the chamfering process.
(3) Acid washing: the neodymium iron boron permanent magnet material is cleaned in mixed acid liquor (the composition is 15mL/L nitric acid, 20g/L sodium gluconate and water as solvent) at room temperature for 90s, then soaked in water for 20s and ultrasonically washed for 50s.
(4) Ash removal: and (3) putting the acid-washed neodymium iron boron permanent magnet material into an ammonium bifluoride aqueous solution with the ammonium bifluoride concentration of 15g/L at room temperature, continuously shaking and soaking for 25s, and then washing with ultrasonic water for 50s.
(5) And (3) activation: and putting the neodymium iron boron permanent magnet material into a citric acid aqueous solution with the citric acid concentration of 20g/L at room temperature, shaking continuously, and soaking for 15s.
(6) Plating a bottom nickel layer: electroplating the activated neodymium iron boron permanent magnet material in a priming nickel plating solution, wherein the priming nickel plating solution comprises the following components: 50g/L of boric acid, 45g/L of nickel chloride, 320g/L of nickel sulfate, 2mL/L of SB-71 additive, 3mL/L of SB-72 additive, 2mL/L of NS-AP additive and pure water as a solvent; the temperature of the priming nickel plating solution is 50 ℃; the electroplating current density is 0.15A/dm, the drum rotating speed is 20r/min, and the electroplating is finished until the plating thickness reaches 3 mu m, so that the priming nickel layer is formed.
(7) Copper plating: electroplating the neodymium iron boron permanent magnet material plated with the bottom nickel layer in a copper plating solution, wherein the adopted copper plating solution comprises the following components: copper pyrophosphate 20g/L, potassium pyrophosphate 280g/L and solvent pure water; the temperature of the copper plating solution is 45 ℃; the electroplating current density is 0.12A/dm, the drum rotating speed is 18r/min, and the electroplating is finished until the plating thickness reaches 3.5 mu m, so that an intermediate copper layer is formed.
(8) Plating a surface nickel layer: electroplating the copper-plated neodymium iron boron permanent magnet material in a surface nickel plating solution, wherein the adopted surface nickel plating solution comprises the following components: 50g/L of boric acid, 45g/L of nickel chloride, 320g/L of nickel sulfate, 2mL/L of SB-71 additive, 3mL/L of SB-72 additive, 2mL/L of NS-AP additive and pure water as a solvent; the temperature of the surface nickel plating solution is 50 ℃; electroplating at a current density of 0.15A/dm and a drum rotation speed of 20r/min until the thickness of the nickel layer reaches 3.5 μm to form a surface nickel layer.
Comparative example 2
The comparative example adopts the conventional process to directly carry out surface copper-nickel electroplating on the neodymium iron boron permanent magnet material, and is different from the comparative example 1 only in that the working procedures of copper plating and surface nickel layer plating are directly carried out after the activation working procedure, and the working procedure of bottom nickel layer plating is not carried out.
Comparative example 3
In the comparative example, the surface treatment is carried out on the neodymium iron boron permanent magnet material by adopting the method disclosed in the embodiment 1 in the patent CN110904480A, and a zinc-nickel coating with the total coating thickness of 7 microns is formed (the thickness of the zinc coating is 4 microns, and the thickness of the zinc-nickel alloy coating is 3 microns).
The products prepared in each example and comparative example were tested and the test results are shown in table 1.
Table 1 results of performance tests of examples and comparative examples
Figure 928585DEST_PATH_IMAGE001
As can be seen from the data in table 1, the protective coatings prepared in embodiments 1 to 3 of the present invention have good bonding strength with the ndfeb substrate, the plating solution has little influence on the ndfeb substrate, and the surface magnetic properties (remanence and coercivity) of the electroplated ndfeb permanent magnet are not significantly reduced.
Comparative example 1 adopts conventional nickel-copper-nickel electroplating process to carry out surface electroplating on neodymium iron boron permanent magnet material, and it can be seen that magnetic property is obviously reduced due to shielding effect of nickel layer to basal body, and binding force is low, mainly because priming nickel plating solution is acidic, partial corrosion is generated to basal body, and nickel plating layer stress is large, and binding strength is influenced.
The comparative example 2 adopts the conventional process to directly plate a copper-nickel layer on the surface of the neodymium iron boron permanent magnet material, the surface of the product is easy to generate replacement reaction, a layer of loose replacement copper is formed, and the bonding force of the plating layer and the appearance of the product are greatly influenced.
Comparative example 3 the method disclosed in example 1 of patent CN110904480A is adopted to plate a zinc-zinc nickel layer on the surface of a neodymium iron boron permanent magnet material, wherein the zinc layer is the same as the copper layer, and has no shielding effect on the substrate, and the magnetic loss is equivalent, but the binding force value is lower, because the plating solution of sulfate electrogalvanizing is also acidic, partial corrosion is generated on the substrate, and the binding strength is affected; in addition, the zinc-nickel alloy plating solution has high maintenance difficulty and high maintenance cost.

Claims (6)

1. A surface protection process for a neodymium iron boron permanent magnet is characterized by comprising the following steps: the method comprises the following steps: chamfering, deoiling, pickling, deashing, activating, pre-plating with alkali copper, plating copper with potassium pyrophosphate, and plating nickel;
in the acid washing process, soaking the neodymium iron boron permanent magnet material in mixed acid liquor at room temperature for 90-100s, then soaking in water for 20-30s, and ultrasonically washing for 50-60s; the mixed acid solution comprises the following components: 15-20mL/L nitric acid, 20-25g/L sodium gluconate and water as a solvent;
in the alkali copper preplating process, the adopted preplating copper solution comprises the following components: 3.5-4.5 g/L of copper ions, 80-90g/L of complexing agent, and pure water as a solvent, and adding sodium hydroxide to adjust the pH value of the solution to 10-11; the temperature of the copper preplating solution is 15 to 25 ℃; the thickness of an underlying copper layer formed by the alkali copper preplating is 0.4 to 0.6 mu m;
in the potassium pyrophosphate copper plating process, the potassium pyrophosphate copper plating solution used consists of: 20-25g/L of copper pyrophosphate, 280-300g/L of potassium pyrophosphate and pure water as a solvent; the temperature of the potassium pyrophosphate copper plating solution is 45 to 50 ℃; the thickness of an intermediate copper layer formed by potassium pyrophosphate copper plating is 5 to 6 mu m;
in the nickel plating process, the adopted surface nickel plating solution comprises the following components: 45-50g/L boric acid, 40-45g/L nickel chloride, 300-320g/L nickel sulfate, 2-3mL/L SB-71 additive, 2-3mL/L SB-72 additive, 1-2mL/L NS-AP additive and pure water as solvent; the temperature of the surface nickel plating solution is 45 to 50 ℃; the thickness of the surface nickel layer formed by nickel plating is 3 to 4 mu m.
2. The surface protection process for the NdFeB permanent magnet according to claim 1, wherein: in the pre-plating copper solution, the copper ion source is one of copper sulfate, basic copper carbonate and copper acetate.
3. The surface protection process for the NdFeB permanent magnet according to claim 1, wherein: in the pre-copper plating solution, the complexing agent is one of sodium potassium citrate and sodium potassium tartrate.
4. The surface protection process for the NdFeB permanent magnet according to claim 1, wherein: in the oil removing process, the neodymium iron boron permanent magnet material is subjected to ultrasonic cleaning for 50 to 70s in an oil removing agent aqueous solution with the temperature of 50 to 60 ℃ and the concentration of the oil removing agent of 20 to 25mL/L, and then ultrasonic water cleaning is carried out.
5. The surface protection process for the NdFeB permanent magnet according to claim 1, wherein: in the ash removal process, the neodymium iron boron permanent magnet material is placed into an ammonium bifluoride water solution with the ammonium bifluoride concentration of 15-20g/L at room temperature, soaked for 25-30s, and then ultrasonically washed for 50-60s.
6. The surface protection process for the NdFeB permanent magnet according to claim 1, wherein: in the activation process, the neodymium iron boron permanent magnet material is soaked in a citric acid aqueous solution with the citric acid concentration of 20-25g/L for 15-20s at room temperature.
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