CN114255950A - Neodymium-iron-boron magnet with composite coating on surface and preparation process thereof - Google Patents
Neodymium-iron-boron magnet with composite coating on surface and preparation process thereof Download PDFInfo
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- CN114255950A CN114255950A CN202111497503.0A CN202111497503A CN114255950A CN 114255950 A CN114255950 A CN 114255950A CN 202111497503 A CN202111497503 A CN 202111497503A CN 114255950 A CN114255950 A CN 114255950A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
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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
- 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
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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
- C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
- C25D5/34—Pretreatment of metallic surfaces to be electroplated
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
Abstract
The invention relates to the technical field of neodymium iron boron magnet production, in particular to a neodymium iron boron magnet with a composite coating on the surface and a preparation process thereof; the invention comprises a neodymium iron boron substrate and a composite coating electroplated on the surface of the neodymium iron boron substrate, wherein the composite coating is sequentially provided with a zinc-nickel alloy plating layer, a copper plating layer, a nickel plating layer and a tin plating layer in structure, so that a complete, compact, uniform and bright composite coating is obtained; on the basis of ensuring the bonding strength of the plating layer and the neodymium iron boron substrate, the defects of thin plating layer and poor corrosion resistance and wear resistance caused by a single process are overcome, so that the prepared corrosion-resistant multi-plating neodymium iron boron has good corrosion resistance and wear resistance, the composite plating magnet has small influence and firm bonding force.
Description
Technical Field
The invention relates to the technical field of neodymium iron boron magnet production, in particular to a neodymium iron boron magnet with a composite coating on the surface and a preparation process thereof.
Background
The neodymium iron boron is composed of multiple phases, the potential difference of each phase is large, particularly, the low potential of the neodymium-rich phase is very active and is easy to corrode, so that the problems of rusting, pulverization or magnetism loss and the like are caused, and the application of the neodymium iron boron magnet is greatly restricted.
At present, a composite plating process is adopted to form a plating layer with excellent corrosion resistance and small influence on the thermal demagnetization of the magnet on the surface of the neodymium iron boron magnet; at present, the neodymium iron boron magnet generally adopts the types of plating layers of zinc plating, double nickel plating, nickel-copper-nickel plating, aluminum plating and epoxy plating, which have advantages but disadvantages, wherein the double nickel plating and the nickel-copper-nickel plating have large influence on the thermal demagnetization rate of the magnet (particularly mobile phone parts and products with small size specification), and the plating layers of the zinc plating, the aluminum plating and the epoxy plating layers are softer and have poor wear resistance; when the product needs to have good wear resistance and low thermal demagnetization rate, the existing coating is generally difficult to meet, the adhesion force of the coating is low, and the coating is easy to fall off.
Disclosure of Invention
In order to overcome the defects, the invention aims to provide the neodymium iron boron magnet with the composite coating on the surface, which comprises a neodymium iron boron base body and the composite coating electroplated on the surface of the neodymium iron boron base body, wherein the composite coating is sequentially composed of a zinc-nickel alloy plating layer, a copper plating layer, a nickel plating layer and a tin plating layer in structure, the corrosion resistance and the wear resistance are good, the influence of the composite coating magnet is small, and the binding force is firm; also provides a preparation process of the neodymium iron boron magnet with the composite coating on the surface.
The technical scheme for solving the technical problem is as follows:
a neodymium iron boron magnet with a composite coating on the surface comprises a neodymium iron boron base body and the composite coating electroplated on the surface of the neodymium iron boron base body; the structure of the composite coating is a zinc-nickel alloy plating layer, a copper plating layer, a nickel plating layer and a tin plating layer in sequence; the zinc-plated nickel alloy layer is directly electroplated on the surface of the neodymium iron boron substrate.
As an improvement of the invention, the composite coating further comprises an aluminum coating, and the aluminum coating is coated on the surface of the tin coating by adopting a cold spraying mode.
As a further improvement of the invention, the composite coating further comprises an aluminum oxide passivation layer, and the aluminum oxide passivation layer is formed on the surface of the aluminum coating in a dip plating mode.
As a further improvement of the invention, the thickness of the zinc-plated nickel alloy layer is 0.06-3 microns.
As a further improvement of the invention, the nickel content in the zinc-plated nickel alloy layer is 1% -8%.
As a further improvement of the invention, the thickness of the tin coating is 0.1-0.3 micron.
A preparation process of a neodymium iron boron magnet with a composite coating on the surface comprises the following steps:
step S1, preprocessing the neodymium iron boron substrate;
step S2, electroplating a zinc-nickel alloy plating layer on the surface of the neodymium iron boron substrate;
step S3, electroplating copper on the surface of the zinc-plated nickel alloy layer to form a copper-plated layer;
step S4, electroplating nickel on the surface of the copper plating layer to form a nickel plating layer;
step S5, electroplating tin on the surface of the nickel plating layer to form a tin plating layer.
As a modification of the present invention, the method further includes step S6; and step S6, cold spraying aluminum powder on the surface of the tin-plated layer to form an aluminum coating.
As a further improvement of the present invention, the method further includes step S7; and S7, putting the neodymium iron boron substrate into nitric acid passivation solution, and forming an aluminum oxide passivation layer on the surface of the aluminum coating.
As a further improvement of the present invention, the method further includes step S8; and step S8, cleaning the surface of the neodymium iron boron substrate by using pure water, and baking.
The invention comprises a neodymium iron boron substrate and a composite coating electroplated on the surface of the neodymium iron boron substrate, wherein the composite coating is sequentially provided with a zinc-nickel alloy plating layer, a copper plating layer, a nickel plating layer and a tin plating layer in structure, the corrosion resistance and the wear resistance are good, the influence of a composite coating magnet is small, and the binding force is firm.
Drawings
For ease of illustration, the present invention is described in detail by the following preferred embodiments and the accompanying drawings.
FIG. 1 is a block diagram of a process for preparing the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, the neodymium iron boron magnet with a composite plating layer on the surface of the invention comprises a neodymium iron boron substrate and the composite plating layer electroplated on the surface of the neodymium iron boron substrate; the structure of the composite plating layer is a zinc-nickel alloy plating layer, a copper plating layer, a nickel plating layer and a tin plating layer in sequence; the zinc-plated nickel alloy layer is directly plated on the surface of the neodymium iron boron substrate.
The invention comprises a neodymium iron boron substrate and a composite coating electroplated on the surface of the neodymium iron boron substrate, wherein the composite coating is sequentially provided with a zinc-nickel alloy plating layer, a copper plating layer, a nickel plating layer and a tin plating layer in structure, the corrosion resistance and the wear resistance are good, the influence of a composite coating magnet is small, and the binding force is firm.
According to the invention, zinc plating is not needed, the composite coating has almost no influence on the thermal demagnetization rate of the magnet, the binding force between the composite coating and the neodymium iron boron substrate is very good, the ejecting force requirement of a client is met, the corrosion resistance of the composite coating is greatly improved, and the zinc-nickel alloy plating layer is used as a priming layer and is not easy to fall off.
Furthermore, the composite coating also comprises an aluminum coating, and the aluminum coating is coated on the surface of the tin coating by adopting a cold spraying mode.
And further, the composite coating also comprises an aluminum oxide passivation layer, and the aluminum oxide passivation layer is formed on the surface of the aluminum coating in a dip plating mode.
The invention also provides a preparation process of the neodymium iron boron magnet with the composite coating on the surface, which comprises the following steps:
step S1, preprocessing the neodymium iron boron substrate;
step S2, electroplating a zinc-nickel alloy plating layer on the surface of the neodymium iron boron substrate;
step S3, electroplating copper on the surface of the zinc-plated nickel alloy layer to form a copper-plated layer;
step S4, electroplating nickel on the surface of the copper plating layer to form a nickel plating layer;
step S5, electroplating tin on the surface of the nickel plating layer to form a tin plating layer.
Further, step S6 is also included; and step S6, cold spraying aluminum powder on the surface of the tin-plated layer to form an aluminum coating.
Still further, step S7 is also included; and S7, putting the neodymium iron boron substrate into nitric acid passivation solution, and forming an aluminum oxide passivation layer on the surface of the aluminum coating.
Still further, step S8 is included; and step S8, cleaning the surface of the neodymium iron boron substrate by using pure water, and baking.
Specifically, the steps of the present invention are as follows:
step S1, preprocessing the neodymium iron boron substrate;
step S2, electroplating a zinc-nickel alloy plating layer on the surface of the neodymium iron boron substrate;
step S3, electroplating copper on the surface of the zinc-plated nickel alloy layer to form a copper-plated layer;
step S4, electroplating nickel on the surface of the copper plating layer to form a nickel plating layer;
step S5, electroplating tin on the surface of the nickel-plated layer to form a tin-plated layer;
step S6, cold spraying aluminum powder on the surface of the tin-plated layer to form an aluminum coating;
step S7, placing the neodymium iron boron substrate into nitric acid passivation solution, and forming an aluminum oxide passivation layer on the surface of the aluminum coating;
and step S8, cleaning the surface of the neodymium iron boron substrate by using pure water, and baking.
In step S1, the specific steps of preprocessing the ndfeb substrate are as follows:
1. grinding and chamfering the neodymium iron boron substrate for 1-15 h by adopting a centrifugal or vibrating machine;
2. soaking the alloy oil powder removing solution in hot water at the temperature of 50-60 ℃ to remove the oil stain on the surface of the neodymium-iron-boron matrix, wherein the specific technological parameters are as follows: soaking in 30-60 g/l of oil removal powder for oil removal for 5-30 h;
3. fully cleaning the surface of the neodymium-iron-boron matrix by using water;
4. washing the rust and oxidation loose layer of the neodymium iron boron substrate for 20-120 s by nitric acid with the content of 30-80 mL/L;
5. ultrasonic equipment is adopted to ultra-clean loose surface ash on the surface of the neodymium-iron-boron matrix after acid cleaning;
6. activating the surface of the neodymium-iron-boron matrix by using nitric acid with the concentration of 2-15 mL/L;
7. and then ultrasonic equipment is adopted to ultra-clean loose surface ash on the surface of the neodymium-iron-boron matrix after acid cleaning.
In step S2, performing zinc-nickel alloy electroplating on the surface of the neodymium iron boron substrate by using an electroplating zinc-nickel alloy solution in a barrel plating or rack plating mode to form a zinc-nickel alloy plating layer, wherein the thickness of the zinc-nickel alloy plating layer is 0.06-3 micrometers, and the nickel content in the plating layer is 1% -8%; the specific process parameters are as follows: the zinc-nickel alloy electroplating solution contains 180 g/l to 350g/l potassium chloride, 10 g/l to 50g/l zinc chloride, 10 g/l to 50g/l nickel chloride, 20 g/l to 40g/l boric acid, 5ml/l to 45ml/l jar opener, 0.3ml/l to 5ml/l main polishing agent, 1ml/l to 5ml/l stabilizer and 50ml/l to 200ml/l buffer; PH of the zinc-nickel alloy electroplating solution: 4.5-6.5; operating at a temperature of 10-40 ℃; the cathode current density is 0.1A/dm-5A/dm, and the zinc-nickel alloy electroplating time is 10 min-90 min; activating the surface of the neodymium iron boron substrate by using hydrochloric acid, and then cleaning by using ultrasonic; specifically, hydrochloric acid with the pH value of 1.5-3.0 is used for activation, and the activation time is 10-60 s; then ultrasonic cleaning is carried out.
In step S3, electroplating copper on the zinc-nickel alloy plating layer by using an electroplating copper solution in a barrel plating or rack plating manner to form a copper plating layer; specifically, a copper layer of 0.1-0.3 microns is electroplated on the surface of the substrate by using an electroplating copper solution in a barrel plating or rack plating mode; the specific process parameters are as follows: the copper electroplating solution comprises 200ml/l to 800ml/l of cyanide-free alkali copper cylinder opening agent A, 100ml/l to 200ml/l of cyanide-free alkali copper cylinder opening agent B, 50ml/l to 150ml/l of cyanide-free alkali copper complexing agent, 0.5ml/l to 5ml/l of cyanide-free alkali copper auxiliary agent and 0.1ml/l to 1ml/l of cyanide-free alkali copper brightener; the PH value of the electro-coppering liquid is 9.0-11.5; the temperature is 20-50 ℃; cathode current density 0.1A/dm-5A/dm has been completed; the copper electroplating time is 30-200 min; and activating the surface of the plating layer by using hydrochloric acid or sulfuric acid with the content of 1 ml/L-30 ml/L, and cleaning by using ultrasonic.
In step S4, electroplating nickel on the neodymium iron boron substrate by using an electroplating nickel solution in a barrel plating or rack plating manner to form a nickel-plated layer; specifically, a nickel electroplating solution is used for electroplating a 0.1-0.3 micron nickel layer on the surface of the neodymium iron boron substrate in a barrel plating or rack plating mode; the specific process parameters are as follows: the nickel electroplating solution comprises 200g/l to 350g/l of nickel sulfate, 30g/l to 80g/l of nickel chloride, 45g/l to 60g/l of boric acid, 0.1ml/l to 1ml/l of nickel plating additive and 0.5ml/l to 6ml/l of wetting agent; the PH value of the nickel electroplating solution is 4.0-5.0; the temperature is 40-60 ℃; cathode current density 0.5A/dm-10A/dm has been completed; the nickel electroplating time is 30-100 min; and finally, activating the surface of the coating by using sulfuric acid with the content of 1-30 ml/L, and cleaning by using ultrasonic.
In step S5, tin is electroplated on the surface of the nickel-plated layer to form a tin-plated layer, wherein the thickness of the tin-plated layer is 0.1 to 0.3 micrometers, so as to increase corrosion resistance, and to prepare for subsequent aluminum-plating and increase adhesion.
In step S6, aluminum powder is cold-sprayed on the surface of the tin-plated layer to form an aluminum coating layer, thereby increasing the corrosion resistance.
In step S7, the neodymium iron boron substrate is placed in the nitric acid passivation solution, and an aluminum oxide passivation layer is formed on the surface of the aluminum coating to increase the oxidation resistance and corrosion resistance of the aluminum coating.
In step S8, the surface of the neodymium iron boron substrate is cleaned by pure water and baked at the temperature of 55-60 ℃; specifically, after nickel plating, the nickel plate was washed with pure water and then baked at a temperature of 60 ± 5 ℃.
In the invention, the electroplating mode is that the neodymium iron boron substrate is immersed in a solution of metal salt to be used as a cathode, the metal to be plated is used as an anode, and after a direct current power supply is switched on, a metal plating layer is deposited on the substrate of the cathode.
In the invention, the composite coating is arranged, so that the adhesive force is increased, the coating is not easy to fall off, the porosity is reduced, compact coatings are obtained, the magnetic loss rate is reduced, and the oxidation resistance and the corrosion resistance of the coating are improved.
The present invention provides several embodiments, as follows:
example 1:
taking a barrel plating mode as an example, firstly, grinding and chamfering the neodymium-iron-boron matrix to R0.2mm-0.6 mm, and grinding and chamfering for 1 h-15 h; after chamfering, soaking alloy degreasing powder solution in hot water to remove oil stains on the surface of the neodymium-iron-boron matrix, then fully cleaning the surface of the matrix with water, and pickling for 20-120 s by using nitric acid with the nitric acid content of 30-80mL/L to clean a rust stain and oxidation loose layer on the surface of the neodymium-iron-boron matrix; ultrasonic equipment is adopted to ultra-clean loose surface ash on the surface of the neodymium-iron-boron matrix after acid cleaning; washing the surface of the neodymium-iron-boron matrix with nitric acid with the nitric acid content of 30-80mL/L for 20-120 s by acid washing to clean the rust and oxidation loose layer; then the treated product is put into an electroplating roller, and zinc-nickel alloy is electroplated on the surface of the neodymium iron boron matrix by using an electroplating zinc-nickel alloy solution in a barrel plating mode, wherein the specific process parameters comprise: 180(g/l) to 350(g/l) potassium chloride, 10(g/l) to 50(g/l) zinc chloride, 10(g/l) to 50(g/l) nickel chloride, 20(g/l) to 40(g/l) boric acid, 5ml/l to 45ml/l vat opener, 0.3ml/l to 5ml/l main light agent, 1ml/l to 5ml/l stabilizer and 50ml/l to 200ml/l buffer agent; the PH value of the zinc-nickel alloy solution is 4.5-6.5; the temperature condition is 10-40 ℃; cathode current density 0.1A/dm-5A/dm has been completed; and electroplating the zinc-nickel alloy for 10-90 min.
The rollers with different specifications can be selected according to the number and the size of the neodymium iron boron base body, and the thickness of the zinc-nickel alloy plating layer is controlled to be 0.06 micron; and the nickel content in the plating layer is 3 percent; after zinc and nickel plating, hydrochloric acid with the pH value of 1.5-3.0 is adopted, and the activation time is 10-60 seconds; cleaning with ultrasonic wave; then transferring the substrate to electro-coppering, and electroplating a copper layer of 0.1 micron on the surface of the substrate by using electro-coppering liquid; the technological parameters are as follows: 200ml/l to 800ml/l of cyanide-free alkali copper cylinder opening agent A, 100ml/l to 200ml/l of cyanide-free alkali copper cylinder opening agent B, 50ml/l to 150ml/l of cyanide-free alkali copper complexing agent, 0.5ml/l to 5ml/l of cyanide-free alkali copper auxiliary agent and 0.1ml/l to 1ml/l of cyanide-free alkali copper brightening agent; the PH value of the electro-coppering liquid is 9.0-11.5; the temperature is 20-50 ℃; cathode current density 0.1-5A/dm; the copper electroplating time is 30-200 minutes; in order to avoid the replacement reaction in the copper plating process, the neodymium iron boron substrate can be charged into a groove; after copper electroplating, activating the surface of the plating layer by using hydrochloric acid or sulfuric acid with the content of 1 ml/L-30 ml/L, and cleaning the plating layer by using ultrasonic; electroplating nickel, namely electroplating a 0.1 micron nickel layer on the surface of the substrate by using an electroplating nickel solution; the specific process parameters are as follows: comprises 200g/l to 350g/l of nickel sulfate, 30g/l to 80g/l of nickel chloride, 45g/l to 60g/l of boric acid, 0.1ml/l to 1ml/l of nickel plating additive and 0.5ml/l to 6ml/l of wetting agent; the PH value of the nickel electroplating solution is 4.0-5.0; the temperature is 40-60 ℃; cathode current density 0.5A/dm-10A/dm has been completed; the nickel electroplating time is 30-100 min; the thickness of the electroplating coating is 0.1 micron; activating the surface of the plating layer by using sulfuric acid with the content of 1 ml/L-30 ml/L after nickel electroplating, and cleaning the plating layer by using ultrasonic; electroplating tin on the surface of the nickel-plated layer to form a tin-plated layer with the thickness of 0.1 micron, cleaning with water, baking at the temperature of 60 +/-5 ℃, and cold-spraying aluminum powder on the surface of the tin-plated layer to form an aluminum coating with the thickness of 0.1 micron; then putting the neodymium iron boron substrate into 4.0 g/l nitric acid passivation solution to form an aluminum oxide passivation layer on the surface of the aluminum coating; and finally, cleaning the surface of the neodymium iron boron substrate by using pure water, and drying.
The process method of example 1 is applied to carry out experiments on neodymium iron boron products with the electroplating specification of 9.14 × 6.39 × 0.83 and the mark of 48H, and the neutral salt spray test is carried out for 120 hours after the plating without change; the thermal demagnetization at 120 ℃ is less than 2.5 percent; the thrust value of the plating layer is more than 500N when the plating layer is subjected to a thrust test, and rust spots appear in 48 hours when the product is subjected to a neutral salt spray test after the same product is electroplated by adopting a nickel-copper-nickel process; the average value of thermal demagnetization at 120 ℃ is less than 5 percent; the average thrust value of the plating layer is 300N when the plating layer is subjected to a thrust test.
EXAMPLE 2
Taking a rack plating mode as an example, firstly, grinding and chamfering a product to R0.2mm-0.6 mm, and vibrating and chamfering for 1 h-15 h; soaking an alloy degreasing powder solution in hot water after chamfering to remove oil stains on the surface of the substrate without iron and boron, then fully cleaning the surface of the substrate with water, and pickling for 120s to clean a rusty and oxidized loose layer on the surface of the substrate by using nitric acid with the nitric acid content of 80 mL/L; ultrasonic equipment is adopted to ultra-clean loose surface ash on the surface of the pickled matrix; cleaning a rust and oxidation loose layer on the surface of the matrix for 20-120 s by adopting nitric acid with the nitric acid content of 30-80 mL/L; then the treated product is put into a hanger, and zinc-nickel alloy is electroplated on the surface of the product matrix by using an electroplating zinc-nickel alloy solution in a rack plating mode, wherein the preparation process parameters comprise: 180(g/l) to 350(g/l) potassium chloride, 10(g/l) to 50(g/l) zinc chloride, 10(g/l) to 50(g/l) nickel chloride, 20(g/l) to 40(g/l) boric acid, 5ml/l to 45ml/l vat opener, 0.3ml/l to 5ml/l main light agent, 1ml/l to 5ml/l stabilizer and 50ml/l to 200ml/l buffer; the PH value of the zinc-nickel alloy solution is 4.5-6.5; the temperature condition is 10-40 ℃; cathode current density 0.1A/dm-5A/dm has been completed; electroplating the zinc-nickel alloy for 10-90 min; hanging tools with different specifications can be selected according to the number and the size of the neodymium iron boron base body, and the thickness of the galvanized layer is controlled to be 0.1-15 micrometers; and the nickel content in the plating layer is 5% -15%; after zinc and nickel plating, hydrochloric acid is adopted, the pH value is 1.5-3.0, and the activation time is 10-60 s; cleaning the substrate by using ultrasonic, transferring into electro-galvanizing copper, and electroplating a copper layer of 0.1-15 microns on the surface of the substrate by using an electro-coppering liquid; the technological parameters are as follows: 200ml/l to 800ml/l of cyanide-free alkali copper cylinder opening agent A, 100ml/l to 200ml/l of cyanide-free alkali copper cylinder opening agent B, 50ml/l to 150ml/l of cyanide-free alkali copper complexing agent, 0.5ml/l to 5ml/l of cyanide-free alkali copper auxiliary agent and 0.1ml/l to 1ml/l of cyanide-free alkali copper brightening agent; the pH value is 9.0-11.5; the temperature is 20-50 ℃; cathode current density 0.1A/dm-5A/dm has been completed; the copper electroplating time is 30-200 min; in order to avoid the replacement reaction in the copper plating process, the product can be charged into a groove; after copper electroplating, activating the surface of the plating layer by using hydrochloric acid or sulfuric acid with the content of 1 ml/L-30 ml/L, and cleaning the plating layer by using ultrasonic; electroplating nickel, namely electroplating a nickel layer of 0.1-15 microns on the surface of the substrate by using an electroplating nickel solution; the technological parameters are as follows: 200g/l to 350g/l of nickel sulfate, 30g/l to 80g/l of nickel chloride, 45g/l to 60g/l of boric acid, 0.1ml/l to 1ml/l of nickel plating additive and 0.5ml/l to 6ml/l of wetting agent; the pH value is 4.0-5.0; the temperature is 40-60 ℃; cathode current density 0.5A/dm-10A/dm has been completed; the nickel electroplating time is 30-120 min; electroplating the coating layer for 0.1-10 microns; activating the surface of the plating layer by using sulfuric acid with the content of 1 ml/L-30 ml/L after nickel electroplating, and cleaning the plating layer by using ultrasonic;
electroplating tin on the surface of the nickel-plated layer to form a tin-plated layer with the thickness of 0.1 micron, cleaning with water, baking at 55 ℃, and cold spraying aluminum powder on the surface of the tin-plated layer to form an aluminum coating with the thickness of 0.1 micron; then putting the neodymium iron boron substrate into 4.0 g/l nitric acid passivation solution to form an aluminum oxide passivation layer on the surface of the aluminum coating; and finally, cleaning the surface of the neodymium iron boron substrate by using pure water, and drying.
The process method of example 2 is applied to carry out experiments on neodymium iron boron products with the electroplating specification of 9.14 × 6.39 × 0.83 and the mark of 48H, and the neutral salt spray test is carried out for 120 hours after the plating without change; the thermal demagnetization at 120 ℃ is less than 2.3 percent; the thrust value of the plating layer is larger than 550N in the thrust test, and after the same product is electroplated by adopting a nickel-copper-nickel process, rust spots appear in the product after the product is subjected to a neutral salt spray test for 48 hours; the average value of thermal demagnetization at 120 ℃ is less than 5 percent; the average thrust value of the plating layer is 300N when the plating layer is subjected to a thrust test.
According to the invention, a composite plating layer structure of a zinc-nickel alloy plating layer, a copper plating layer, a nickel plating layer, a tin plating layer, an aluminum coating and an aluminum oxide passivation layer is adopted, and the neodymium iron boron magnet is directly electroplated with the zinc-nickel plating layer after being subjected to grinding, chamfering, oil removal, acid washing, ultrasonic cleaning and activation, so that the zinc-nickel plating layer which is very firmly combined with a base body and has no influence on the thermal demagnetization of the magnet can be obtained; the zinc-plated nickel layer is taken as a base, and the transition layer is sequentially electroplated with copper, so that the binding force among the layers is ensured, and the corrosion resistance of the plating layer is greatly improved; the nickel coating is plated on the copper plating layer, so that the plating layer is stable and wear-resistant, the binding force of the plating layer is increased, the tin coating is formed on the nickel coating to increase the corrosion resistance of the plating layer, the aluminum coating is added on the tin coating to reduce the magnetic loss rate and increase the corrosion resistance, and then the aluminum oxide passivation layer is added on the aluminum coating to increase the oxidation resistance; the invention has a complete compact, uniform and bright composite plating layer; on the basis of ensuring the bonding strength of the coating and the neodymium iron boron substrate, the defects of thin coating and poor corrosion resistance and wear resistance caused by a single process are overcome, so that the prepared corrosion-resistant multi-coating neodymium iron boron has good corrosion resistance and wear resistance.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A neodymium iron boron magnet with a composite coating on the surface is characterized by comprising a neodymium iron boron base body and the composite coating electroplated on the surface of the neodymium iron boron base body; the structure of the composite coating is a zinc-nickel alloy plating layer, a copper plating layer, a nickel plating layer and a tin plating layer in sequence; the zinc-plated nickel alloy layer is directly electroplated on the surface of the neodymium iron boron substrate.
2. The ndfeb magnet with the composite coating on the surface according to claim 1, wherein the composite coating further comprises an aluminum coating, and the aluminum coating is coated on the surface of the tin coating by means of cold spraying.
3. The ndfeb magnet with the composite coating on the surface according to claim 2, wherein the composite coating further comprises an aluminum oxide passivation layer, and the aluminum oxide passivation layer is formed on the surface of the aluminum coating by adopting an immersion plating method.
4. The NdFeB magnet with the composite coating on the surface as claimed in claim 3, wherein the thickness of the zinc-nickel alloy coating layer is 0.06-3 microns.
5. The NdFeB magnet with the composite coating on the surface according to claim 4, wherein the nickel content in the zinc-nickel alloy plating layer is 1% -8%.
6. The NdFeB magnet with the composite coating on the surface according to claim 5, wherein the thickness of the tin coating is 0.1-0.3 microns.
7. A preparation process of a neodymium iron boron magnet with a composite coating on the surface is characterized by comprising the following steps:
step S1, preprocessing the neodymium iron boron substrate;
step S2, electroplating a zinc-nickel alloy plating layer on the surface of the neodymium iron boron substrate;
step S3, electroplating copper on the surface of the zinc-plated nickel alloy layer to form a copper-plated layer;
step S4, electroplating nickel on the surface of the copper plating layer to form a nickel plating layer;
step S5, electroplating tin on the surface of the nickel plating layer to form a tin plating layer.
8. The process for preparing a neodymium-iron-boron magnet with a composite coating on the surface according to claim 7, further comprising the step of S6;
and step S6, cold spraying aluminum powder on the surface of the tin-plated layer to form an aluminum coating.
9. The process for preparing a neodymium-iron-boron magnet with a composite coating on the surface according to claim 8, further comprising the step of S7;
and S7, putting the neodymium iron boron substrate into nitric acid passivation solution, and forming an aluminum oxide passivation layer on the surface of the aluminum coating.
10. The process for preparing a neodymium-iron-boron magnet with a composite coating on the surface according to claim 9, further comprising the step of S8;
and step S8, cleaning the surface of the neodymium iron boron substrate by using pure water, and baking.
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| CN115198260A (en) * | 2022-06-22 | 2022-10-18 | 中国科学院赣江创新研究院 | Method for improving corrosion resistance of neodymium iron boron magnet |
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| CN115198260A (en) * | 2022-06-22 | 2022-10-18 | 中国科学院赣江创新研究院 | Method for improving corrosion resistance of neodymium iron boron magnet |
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