Plating layer structure of neodymium iron boron trivalent chromium plating

Abstract

The utility model discloses a plating structure of neodymium iron boron trivalent chromium plating, which comprises a neodymium iron boron base body, and a citrate pre-nickel-plating layer, a nickel-copper alloy plating layer, a bright nickel-plating layer, a trivalent chromium plating layer and a nano polymer protective film which are sequentially prepared on the neodymium iron boron base body from inside to outside. According to the neodymium iron boron trivalent chromium plating coating structure disclosed by the utility model, the binding force of the coating is tested by a thermal shock method according to GB / T 5270-2005 < GB / T 5270-2005 < GB / T > 5270-2005 < GB / T > 5270-2005 > < GB / T > 5270-2005 > < GB / T > 5270-2005 > < GB / T > 5270-2005 > < The neutral salt spray test is carried out for 120 hours according to GB / T 10125-2021 Artificial Atmosphere Corrosion Test Salt Spray Test, no corrosive substance is generated on the surface of a plated part, and a plated layer has good corrosion resistance.

Description

Technical Field

[0001] The utility model belongs to the technical field of metal surface treatment, and particularly relates to a coating structure of trivalent chromium electroplating on neodymium iron boron. Background Art

[0002] The surface of the neodymium iron boron substrate has many pores, and the material itself has high chemical activity. During the electroplating process of neodymium iron boron workpieces, there are residual corrosion problems with the acidic or alkaline electroplating solutions immersed in the pores on the surface of neodymium iron boron. [1] , which affects the protective performance of the coating. In the past, the process of electroplating copper + nickel + chromium was usually used to prepare a protective layer on the surface of neodymium iron boron. However, cyanide electroplating copper and hexavalent chromium electroplating have high pollution problems, which limit the use of this process. The industry has conducted a lot of research on cyanide-free copper electroplating processes that can replace cyanide electroplating copper, but there is still a certain gap in performance between the developed divalent copper cyanide-free copper electroplating process and the cyanide electroplating copper process. [2] . Therefore, the current process usually prepares a pre-nickel plating layer by citrate nickel plating on the neodymium iron boron substrate, and then electroplates bright nickel and other coatings.

[0003] The electrode potential of the bright nickel plating layer is significantly more positive than that of the neodymium iron boron substrate. The nickel plating layer prepared by directly electroplating nickel on the neodymium iron boron substrate is a cathodic coating. When the coating is damaged or has pores, the corrosive medium destroys the neodymium iron boron substrate through galvanic corrosion. Therefore, the corrosion resistance of this coating structure is poor.

[0004] References: [1], Li Hongying, Hao Zhuangzhi, Liu Yuhui, etc., Research progress on corrosion mechanism and surface protection technology of sintered NdFeB permanent magnet materials [J], Mining and Metallurgical Engineering, 2016, 36(6): 118-124. [2], Qin Zuzu, Li Jiansan, Xu Jinlai, Research progress on cyanide-free copper electroplating processes at home and abroad [J], Electroplating & Finishing, 2015, 34(3): 149-152. Summary of the Utility Model

[0005] In order to solve the technical defect that directly electroplating nickel on the surface of neodymium iron boron does not have an electrochemical protection effect, the utility model provides a coating structure of trivalent chromium electroplating on neodymium iron boron. In order to achieve the above purpose, the utility model adopts the following technical scheme:

[0006] A coating structure of trivalent chromium electroplating on neodymium iron boron, comprising a neodymium iron boron substrate, and a citrate pre-nickel plating layer, a nickel-copper alloy plating layer, a bright nickel plating layer, a trivalent chromium electroplating layer, and a nano-polymer protective film sequentially prepared on the neodymium iron boron substrate from inside to outside;

[0007] The thickness of the nickel-copper alloy plating layer is 6-13 μm.

[0008] Preferably, the thickness of the citrate pre-nickel plating layer is 3-7 μm.

[0009] Preferably, the thickness of the bright nickel plating layer is 3 - 6 μm.

[0010] Preferably, the thickness of the trivalent chromium plating layer is 0.3 - 0.6 μm.

[0011] A pre - nickel plating layer is prepared on the surface of neodymium - iron - boron by using a neutral citrate nickel plating process, and there is basically no residual corrosion problem of the plating solution remaining in the pores on the surface of neodymium - iron - boron. Bright nickel is plated on the nickel - copper alloy plating layer. The electrode potential of the bright nickel plating layer is significantly more negative than that of the nickel - copper alloy plating layer, and the bright nickel plating layer has an electrochemical protection effect on the nickel - copper alloy plating layer. This coating structure can effectively prevent corrosive media from eroding the neodymium - iron - boron substrate. Trivalent chromium plating is carried out on the bright nickel plating layer. When the coating is corroded, the corrosive media first corrodes the bright nickel plating layer in the transverse direction, but the chromium plating layer has high corrosion resistance and has a good protective effect on the nickel plating layer.

[0012] Compared with the prior art, the present utility model has the following beneficial effects:

[0013] 1. The coating structure of trivalent chromium plating on neodymium - iron - boron disclosed by the present utility model prepares a bright nickel plating layer and a trivalent chromium plating layer on the nickel - copper alloy plating layer, overcoming the defect that the current process of directly carrying out citrate pre - nickel plating and bright nickel plating on the neodymium - iron - boron substrate does not have an electrochemical protection effect.

[0014] 2. The coating structure of trivalent chromium plating on neodymium - iron - boron disclosed by the present utility model has a salt spray resistance performance far higher than the requirements of the standard of GB / T34491–2017 "Surface Coatings on Sintered Neodymium - Iron - Boron". BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings described herein are used to provide a further understanding of the present utility model, form a part of this application, and do not constitute an improper limitation to the present utility model. In the drawings:

[0016] Figure 1 is a schematic diagram of the coating structure of Embodiment 1 and Embodiment 2 of the present utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The present utility model will be described in detail below in conjunction with the drawings and specific embodiments. Here, the illustrative embodiments and descriptions of the present utility model are used to explain the present utility model, but do not limit the present utility model.

[0018] A coating structure of trivalent chromium plating on neodymium - iron - boron includes a neodymium - iron - boron substrate, and a citrate pre - nickel plating layer, a nickel - copper alloy plating layer, a bright nickel plating layer, a trivalent chromium plating layer, and a nano - polymer protective film sequentially prepared on the neodymium - iron - boron substrate from the inside to the outside.

[0019] The matrix of the Nd-Fe-B workpiece is ground, degreased, and activated according to the current pretreatment process.

[0020] After the pretreatment of the Nd-Fe-B workpiece, a citrate pre-nickel plating layer is prepared by the current citrate nickel plating process.

[0021] Preferably, the thickness of the citrate pre-nickel plating layer is 3 - 7 μm.

[0022] Preferably, the citrate nickel plating process is as follows:

[0023] Nickel sulfate hexahydrate 180 - 250 g / L, sodium chloride 10 - 12 g / L, boric acid 30 - 35 g / L, magnesium sulfate 30 - 40 g / L, pH value of the plating solution 7.0 - 7.2, plating bath temperature 50°C - 60°C, cathode current density 1 - 1.5 A / dm 2 , cathode moving speed 4 - 6 m / min.

[0024] After the citrate pre-nickel plating of the Nd-Fe-B workpiece, a nickel-copper alloy plating layer is prepared by the current nickel-copper alloy plating process.

[0025] Preferably, the thickness of the nickel-copper alloy plating layer is 6 - 13 μm.

[0026] Preferably, the nickel-copper alloy plating layer is prepared by the Nistar 6070 bright nickel-copper alloy plating process of Superbond Chemical Industry:

[0027] Nickel sulfate hexahydrate 180 - 220 g / L, copper sulfate pentahydrate 8 - 12 g / L, trisodium citrate 50 - 60 g / L, sodium dihydrogen ethylenediamine tetraacetate 20 - 30 g / L, boric acid 28 - 35 g / L, sodium chloride 5 - 8 g / L, NISTAR 6070 brightener 0.3 - 0.7 mL / L, NISTAR 6071 auxiliary agent 6 - 10 mL / L, NI-35 wetting agent 0.3 - 1.0 mL / L, pH value of the plating solution 4.3 - 4.8, plating bath temperature 50°C - 55°C, cathode current density 2.6 - 3.2 A / dm 2 , cathode moving speed 3 - 5 m / min.

[0028] After the nickel-copper alloy plating of the Nd-Fe-B workpiece, a bright nickel plating layer is prepared by the current bright nickel plating process.

[0029] Preferably, the thickness of the bright nickel plating layer is 3 - 6 μm.

[0030] After the bright nickel plating of the Nd-Fe-B workpiece, a trivalent chromium plating layer is prepared by the current trivalent chromium plating process.

[0031] Preferably, the thickness of the trivalent chromium plating layer is 0.3 - 0.6 μm.

[0032] Preferably, the trivalent chromium electroplated layer is prepared by using the Trich-6561 chloride trivalent chromium electroplating process of Superbond Chemical Industry Co., Ltd.:

[0033] Trich-6561 starting salt 400 - 450 g / L, Trich-6563 complexing agent 65 - 85 mL / L, Trich-6564 stabilizer 1 - 2 mL / L, Trich-6565 wetting agent 1 - 3 mL / L, wherein the mass concentration of trivalent chromium is 23 - 25 g / L, the mass concentration of boric acid is 55 - 60 g / L, the pH value of the plating solution is 2.5 - 3.0, the plating bath temperature is 25°C - 36°C, and the cathode current density is 8 - 16 A / dm 2 , with moderate air agitation.

[0034] After the neodymium iron boron workpiece is electroplated with trivalent chromium, a nano-polymer protective film is prepared by an electrolytic protection process.

[0035] Preferably, the nano-polymer protective film is prepared by using the PROTEZVY 1126 electrolytic protection process of Superbond Chemical Industry Co., Ltd.:

[0036] PROTEZVY 1126 MUP starting agent 30 - 40 mL / L, PROTEZVY 1126 ADDITIVE C additive 70 - 90 mL / L, sodium hydroxide 0.15 - 0.25 g / L, the pH value of the bath is 3.4 - 4.0, the operating temperature is 55°C - 65°C, and the cathode current density is 0.05 - 0.1 A / dm 2 , and the electrolysis time is 3 - 10 min.

[0037] After the electrolytic protection of the neodymium iron boron workpiece, it is washed with water and dried. Example 1

[0038] As Figure 1 shown, a coating structure of trivalent chromium electroplating on neodymium iron boron includes a neodymium iron boron substrate 1, and a citrate pre-plated nickel layer 2, a nickel-copper alloy coating 3, a bright nickel plating layer 4, a trivalent chromium electroplated layer 5, and a nano-polymer protective film 6 prepared in sequence from the inside to the outside on the neodymium iron boron substrate 1.

[0039] 1. Pretreatment:

[0040] The neodymium iron boron substrate 1 is subjected to "grinding chamfering → water washing → chemical degreasing → water washing → ultrasonic degreasing → water washing → lactic acid activation → water washing" by using the current pretreatment process.

[0041] 2. Pre-plated nickel:

[0042] After the pretreatment of the neodymium iron boron workpiece, a citrate pre-plated nickel layer 2 is prepared by using the current citrate nickel plating process, and the coating thickness is 5 μm.

[0043] Nickel sulfate hexahydrate 230 g / L, sodium chloride 12 g / L, boric acid 33 g / L, magnesium sulfate 33 g / L, the pH of the plating solution is 7.2, the plating bath temperature is 55 °C, and the cathode current density is 1.2 A / dm 2 , and the cathode moves at 5 m / min.

[0044] 3. Nickel-copper alloy plating:

[0045] After pre-plating nickel on the neodymium-iron-boron workpiece, a nickel-copper alloy coating 3 is prepared by using the Nistar 6070 bright nickel-copper alloy plating process of Superbond Chemical Industry, and the coating thickness is 10 μm.

[0046] Nickel sulfate hexahydrate 190 g / L, copper sulfate pentahydrate 9 g / L, trisodium citrate 55 g / L, disodium hydroxylethylidene diphosphonate 23 g / L, boric acid 30 g / L, sodium chloride 6 g / L, NISTAR 6070 brightener 0.5 mL / L, NISTAR 6071 auxiliary agent 8 mL / L, NI-35 wetting agent 0.6 mL / L, the pH of the plating solution is 4.6, the plating bath temperature is 53 °C, and the cathode current density is 2.8 A / dm 2 , and the cathode moves at 4 m / min.

[0047] 4. Bright nickel plating:

[0048] After nickel-copper alloy plating on the neodymium-iron-boron workpiece, a bright nickel plating layer 4 is prepared by using the current bright nickel plating process, and the coating thickness is 4 μm.

[0049] 5. Trivalent chromium plating:

[0050] After bright nickel plating on the neodymium-iron-boron workpiece, a trivalent chromium plating layer 5 is prepared by using the Trich-6561 chloride trivalent chromium plating process of Superbond Chemical Industry, and the coating thickness is 0.5 μm.

[0051] Trich-6561 starting salt 440 g / L, Trich-6563 complexing agent 82 mL / L, Trich-6564 stabilizer 1.5 mL / L, Trich-6565 wetting agent 2 mL / L, where the mass concentration of trivalent chromium is 24.5 g / L, the mass concentration of boric acid is 59 g / L, the pH of the plating solution is 2.7, the plating bath temperature is 28 °C, and the cathode current density is 14 A / dm 2 , with moderate air agitation.

[0052] 6. Electrolytic protection:

[0053] After trivalent chromium plating on the neodymium-iron-boron workpiece, a nano-polymer protective film 6 is prepared by using the PROTEZVY 1126 electrolytic protection process of Superbond Chemical Industry.

[0054] PROTEZVY 1126 MUP cylinder opening agent 32 mL / L, PROTEZVY 1126 ADDITIVE C additive 75 mL / L, sodium hydroxide 0.18 g / L, bath solution pH is 3.6, operating temperature is 62 °C, cathode current density 0.07 A / dm 2 , electrolysis time is 8 min.

[0055] 7. Drying:

[0056] After the electrolytic protection of the neodymium iron boron workpiece, it is subjected to "water washing → pure water washing → drying". Example 2

[0057] As Figure 1 shown, a coating structure of trivalent chromium plating on neodymium iron boron includes a neodymium iron boron substrate 1, and a citrate pre-plated nickel layer 2, a nickel-copper alloy coating 3, a bright nickel coating 4, a trivalent chromium plating layer 5, and a nano-polymer protective film 6 sequentially prepared on the neodymium iron boron substrate 1 from inside to outside.

[0058] 1. Pretreatment:

[0059] The neodymium iron boron substrate 1 is subjected to "grinding and chamfering → water washing → chemical degreasing → water washing → ultrasonic degreasing → water washing → lactic acid activation → water washing" using the current pretreatment process.

[0060] 2. Pre-plated nickel:

[0061] After the pretreatment of the neodymium iron boron workpiece, the citrate pre-plated nickel layer 2 is prepared using the current citrate nickel plating process, and the coating thickness is 4 μm.

[0062] Nickel sulfate hexahydrate 210 g / L, sodium chloride 12 g / L, boric acid 30 g / L, magnesium sulfate 40 g / L, bath solution pH is 7.1, bath temperature is 50 °C, cathode current density 1.2 A / dm 2 , cathode movement 5 m / min.

[0063] 3. Plated nickel-copper alloy:

[0064] After the pre-plated nickel of the neodymium iron boron workpiece, the nickel-copper alloy coating 3 is prepared using the Nistar 6070 bright nickel-copper alloy plating process of Superbond Chemical Industry, and the coating thickness is 9 μm.

[0065] Nickel sulfate hexahydrate 210 g / L, copper sulfate pentahydrate 11 g / L, trisodium citrate 65 g / L, sodium dihydrogen ethylenediaminetetraacetate 27 g / L, boric acid 32 g / L, sodium chloride 7 g / L, NISTAR 6070 brightener 0.5 mL / L, NISTAR 6071 auxiliary agent 8 mL / L, NI-35 wetting agent 0.6 mL / L, bath solution pH is 4.5, bath temperature is 52 °C, cathode current density 3.0 A / dm 2, the cathode moves at 4 m / min.

[0066] 4. Bright nickel plating:

[0067] After the neodymium iron boron workpiece is plated with nickel - copper alloy, a bright nickel plating layer 4 is prepared by the current bright nickel plating process, and the coating thickness is 5 μm.

[0068] 5. Trivalent chromium electroplating:

[0069] After the neodymium iron boron workpiece is plated with bright nickel, a trivalent chromium electroplating layer 5 is prepared by using the Trich - 6561 chloride trivalent chromium electroplating process of Superbond Chemical Industry, and the coating thickness is 0.5 μm.

[0070] Trich - 6561 starting salt 410 g / L, Trich - 6563 complexing agent 70 mL / L, Trich - 6564 stabilizer 1.5 mL / L, Trich - 6565 wetting agent 2 mL / L, where the mass concentration of trivalent chromium is 23.5 g / L, the mass concentration of boric acid is 56 g / L, the pH of the plating solution is 2.8, the plating bath temperature is 30 °C, and the cathode current density is 14 A / dm 2 , with moderate air agitation.

[0071] 6. Electrolytic protection:

[0072] After the neodymium iron boron workpiece is trivalent chromium electroplated, a nano - polymer protective film 6 is prepared by using the PROTEZVY 1126 electrolytic protection process of Superbond Chemical Industry.

[0073] PROTEZVY 1126 MUP starting agent 38 mL / L, PROTEZVY 1126 ADDITIVE C additive 85 mL / L, sodium hydroxide 0.2 g / L, the pH of the bath solution is 3.7, the operating temperature is 58 °C, and the cathode current density is 0.08 A / dm 2 , and the electrolysis time is 6 min.

[0074] 7. Drying:

[0075] After the electrolytic protection of the neodymium iron boron workpiece, it is "washed with water → pure water washed → dried".

[0076] Test example 1:

[0077] The neodymium iron boron trivalent chromium electroplated samples prepared in Example 1 and Example 2 were subjected to a neutral salt spray test for 120 h according to GB / T 10125–2021 "Artificial atmosphere corrosion test - Salt spray test", and there was no rust on the surface of the plated parts. The neutral salt spray non - rusting time of the coating structure prepared by the present utility model is 2.5 times the rusting time of 48 h in the neutral salt spray test of the nickel + copper + nickel coating on the surface of neodymium iron boron specified in GB / T 34491–2017 "Surface coatings on sintered neodymium iron boron".

[0078] Test Example 2:

[0079] For the neodymium iron boron trivalent chromium electroplated samples prepared in Example 1 and Example 2, the adhesion of the coating was tested by the thermal shock method in accordance with GB / T 5270–2005 "Review of Test Methods for Adhesion of Metallic Coatings on Metallic Substrates - Electrodeposited and Chemically Deposited Coatings". The plated parts were heated in a heating furnace to 250 °C and kept warm for 30 min, then taken out and suddenly cooled in water at room temperature. No blistering or peeling occurred on the coating, indicating that the coating structure prepared by the present utility model has good adhesion.

[0080] The technical solutions provided by the embodiments of the present utility model have been introduced in detail above. Specific examples are used herein to elaborate on the principles and implementation manners of the embodiments of the present utility model. The descriptions of the above embodiments are only applicable to help understand the principles of the embodiments of the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several modifications and improvements can still be made, and these all fall within the protection scope of the present utility model.

Claims

1. A coating structure of NdFeB trivalent chromium plating, characterized in that: The invention comprises a neodymium iron boron substrate, and a citrate pre-nickel plating layer, a nickel-copper alloy plating layer, a bright nickel plating layer, a trivalent chromium plating layer, and a nano polymer protective film which are sequentially prepared from the inside to the outside on the neodymium iron boron substrate; The thickness of the nickel-copper alloy plating layer is 6-13 μm.

2. The NdFeB trivalent chromium plating structure according to claim 1, characterized in that: The thickness of the citrate pre-nickel plating layer is 3-7 μm.

3. The NdFeB trivalent chromium plating structure according to claim 1, characterized in that: The thickness of the bright nickel plating layer is 3-6 μm.

4. The NdFeB trivalent chromium plating structure according to claim 1, characterized in that: The thickness of the trivalent chromium plating layer is 0.3-0.6 μm.

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