Neodymium-iron-boron cyanide-free cadmium-iron alloy plating process suitable for aerospace field

Abstract

The invention discloses a NdFeB cyanide-free cadmium-iron alloy plating process suitable for the aerospace field. The NdFeB cyanide-free cadmium-iron alloy plating process comprises the step that a sulfate zinc coating, a cyanide-free copper-zinc alloy coating, a cyanide-free cadmium-iron alloy coating and a passivation layer are sequentially prepared on a NdFeB substrate from inside to outside. According to the cyanide-free cadmium-iron alloy plating process, 25-35 g / L of cadmium chloride, 4-6 g / L of ferrous chloride tetrahydrate, 100-140 g / L of potassium chloride, 100-140 g / L of a coordination agent, 1.5-2.5 mL / L of a leveling agent, 1.5-2.5 mL / L of a brightening agent, 25-30 mL / L of an auxiliary agent and 25-35 g / L of a stabilizer are adopted, the pH value of a plating solution is 6-8, the temperature of a plating tank is 20-35 DEG C, the cathode current density is 0.5-1.5 A / dm < 2 >, and the cathode movement is 2-4 m / min. The surface of the prepared neodymium-iron-boron-plated cadmium-iron alloy colored passivated sample piece is free of white rust after being subjected to an acetate mist test for 360 h according to the GB / T 10125-2021 standard, and a plating layer has excellent corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a cyanide-free cadmium-iron alloy plating process of NdFeB applicable to the field of aerospace. Background Art

[0002] my country has rich reserves of rare earth metal ores and has accumulated and developed mining and processing technologies. my country has become the global production and market center of NdFeB permanent magnet materials. However, the poor corrosion resistance of NdFeB materials still restricts the development of NdFeB and related industries in my country. NdFeB permanent magnet materials are prepared by powder metallurgy and have defects such as sintering pores. NdFeB alloy has a multi-phase structure, including the main phase Nd2Fe14B, Nd-rich phase (Nd4Fe) and B-rich phase (Nd1+εFe4B4), and the volume fractions of each phase are approximately 84%, 14% and 2%, respectively. The main phase Nd2Fe14B is a magnetic phase. Because the Nd-rich phase and the B-rich phase are very active and easily oxidized, and the electrochemical potentials of the phases are very different, electrochemical corrosion is very likely to occur. [1] .

[0003] The porous surface of the sintered NdFeB matrix and the high chemical activity of the material itself bring some difficulties to its electroplating. The use of acidic plating solution, alkaline plating solution, or plating solution containing chloride to directly electroplate the surface of the NdFeB workpiece to prepare the bottom coating has residual corrosion problems when the plating solution is immersed in the pores on its surface, resulting in pitting corrosion of the coating and even partial shedding of the coating.

[0004] The existing electroplating process usually prepares protective layers such as zinc plating, nickel plating, copper + nickel + chromium combination plating, nickel + copper + nickel combination plating, nickel + tin combination plating, nickel + silver combination plating, nickel + gold combination plating, electroplated nickel + chemical nickel combination plating on the surface of NdFeB. At present, the most typical and effective methods are zinc plating and nickel plating, among which nickel plating is the most widely used. [2] GB / T 34491-2017 "Surface Coating of Sintered NdFeB" standard stipulates that the time for the nickel + copper + nickel combination coating to begin rusting in the neutral salt spray test according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test" is 48 hours for barrel plating and 16 hours for rack plating. Obviously, the corrosion resistance of this coating structure is far from meeting the growing technical needs of my country's aerospace field.

[0005] The citrate nickel plating solution is neutral and has a weak corrosive effect on the NdFeB substrate. The NdFeB nickel plating process reported in the literature generally uses the citrate nickel plating process to prepare the bottom coating, and then plating bright nickel to prepare the surface coating. [3] There are two defects in using this process to prepare protective decorative coatings on NdFeB workpieces: First, direct nickel plating on the surface of NdFeB workpieces has a high magnetic shielding effect. [4], which will significantly reduce the magnetic field strength of the NdFeB workpiece; secondly, nickel is directly plated on the surface of the NdFeB workpiece. The nickel plating layer is a cathodic plating layer and has no electrochemical protection effect on the NdFeB matrix. When there are pores in the plating layer or the plating layer is damaged, galvanic corrosion will occur and destroy the NdFeB matrix.

[0006] According to the traditional process, hydrochloric acid, sulfuric acid, and nitric acid pickling methods are usually used to remove oxides on the surface of NdFeB workpieces. [5] Production practice has proved that the use of hydrochloric acid or sulfuric acid pickling method has the problem of hydrogenation of metal neodymium. After the hydrogen produced in the pickling reaction penetrates into the NdFeB matrix, the hydrogen atoms will slowly react with the metal neodymium to form neodymium hydride, causing the metal neodymium to be converted into a powdery substance. Using nitric acid pickling method to remove the oxide on the surface of NdFeB can avoid the problem of hydrogenation of metal neodymium, but nitric acid has a passivating effect on the metal surface, affecting the bonding strength between the matrix and the coating.

[0007] References: [1]. Yan Fenying, Zhao Chunying, Zhang Lin, Research progress of surface protection technology of NdFeB permanent magnet materials [J], Electroplating and Finishing, 2012, 34(8): 22-25. [2]. Li Hongying, Hao Zhuangzhi, Liu Yuhui, et al., Research progress of corrosion mechanism and surface protection technology of sintered NdFeB permanent magnet materials [J], Mining and Metallurgical Engineering, 2016, 36(6): 118-124. [3]. Guangzhou Chaobang Chemical Co., Ltd., A coating structure of NdFeB nickel plating and rare earth electrolytic protection: 202222706008.2 [P], 2023-03-17. [4]. Meng Chao, Wang Qun, Shi Meiwu, Preparation and properties of iron-nickel alloy magnetic shielding film [J], Safety and Electromagnetic Compatibility, 2015, 27(4): 58-61. [5]. Zhao Qing, Du Nan, Xiao Jun, et al., Research on nickel plating process on surface of NdFeB workpieces [J]. Materials Protection, 2003, 36(6): 32-33. Summary of the invention

[0008] In order to solve the problems of magnetic shielding and lack of electrochemical protection in direct nickel plating of NdFeB workpieces, the present invention provides a cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field. In order to achieve the above purpose, the present invention adopts the following technical solutions: A cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field comprises the following steps: (1) Grinding, chamfering, degreasing, and activation of NdFeB workpieces; (2) After the NdFeB workpiece is pre-treated, the sulfate zinc coating is prepared using the current sulfate zinc coating process; (3) After the NdFeB workpiece is zinc plated with sulfate, a cyanide-free copper-zinc alloy coating is prepared by using a polymerized thiocyanate copper-zinc alloy plating process; (4) After the NdFeB workpiece is plated with copper-zinc alloy without cyanide, a cyanide-free cadmium-iron alloy plating process is used to prepare a cyanide-free cadmium-iron alloy coating; (5) After the NdFeB workpiece is plated with cadmium iron alloy, post-treatment is performed to prepare a passivation layer; The cyanide-free cadmium iron alloy plating process includes the following components and process parameters: Cadmium chloride 25-35g / L, ferrous chloride tetrahydrate 4-6g / L, potassium chloride 100-140g / L, complexing agent 100-140g / L, leveling agent 1.5-2.5mL / L, brightener 1.5-2.5mL / L, auxiliary agent 25-30mL / L, stabilizer 25-35g / L, plating solution pH 6-8, plating tank temperature 20-35℃, cathode current density 0.5-1.5A / dm 2 , cathode moves 2-4 m / min; The leveling agent includes 5-10 g / L of trimercapto-s-triazine, 30-60 g / L of organic amine epoxy derivative, and 5-10 g / L of sodium hydroxide; The stabilizer comprises sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:(2-3); The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid. The above components are mixed evenly to obtain the complexing agent; the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:(1-2):(4-6); The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate; wherein component A is 30-80 g / L, component B is 30-80 g / L, component C is 60-100 g / L, and isopropyl alcohol is 280-320 g / L; The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate composed of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; wherein the polyacrylamide with a molecular weight less than 8000 is 50-80 g / L, the condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin is 20-50 g / L, the sodium salt of 2-ethylhexyl sulfate is 30-80 g / L, and the D component is 30-60 g / L.

[0009] In some embodiments, the polythiocyanate copper-zinc alloy plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 18-24 g / L, polymeric zinc thiocyanate 9-13 g / L, polymeric sodium thiocyanate 130-170 g / L, copper-zinc alloy electroplating brightener 8-12 mL / L, plating solution pH 10-12, plating tank temperature 35-55 ° C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, a copper-zinc alloy plate with a copper mass fraction of 68% is used as an anode, and the anode moves 3 to 5 m / min; the copper-zinc alloy electroplating brightener comprises the following components by weight: 60 to 100 parts of N,N'-di-n-propylethylenediamine, 10 to 20 parts of water-based polyurethane resin, 80 to 120 parts of polyacrylamide with a molecular weight less than 8000, and 770 to 870 parts of deionized water.

[0010] In some of the embodiments, the thickness of the cyanide-free cadmium iron coating is 8 to 24 μm.

[0011] In some of the embodiments, the thickness of the cyanide-free copper-zinc alloy coating is 6-10 μm.

[0012] In some embodiments, the activation is carried out using a lactic acid activation process: Lactic acid 40-80 mL / L, operating temperature 20-35°C, activation time 20-40 s.

[0013] In some of the embodiments, the sulfate zinc plating layer is prepared by the current sulfate zinc plating process: 350-450 g / L zinc sulfate heptahydrate, 25-35 g / L boric acid, 14-18 mL / L ZL-94 brightener, 5.0-5.8 pH value of the plating solution, 15-45 ° C plating tank temperature, 1-4 A / dm 2 , the cathode moves 3 to 5 m / min.

[0014] In some of the embodiments, the thickness of the sulfate zinc plating layer is 10-20 μm.

[0015] In some of the embodiments, the passivation layer includes a hexavalent chromium color passivation layer, a hexavalent chromium military green passivation layer, a hexavalent chromium black passivation layer, and a trivalent chromium blue-white passivation layer.

[0016] In some of the embodiments, the hexavalent chromium color passivation layer is prepared by HC-5 low-chrome color passivation process: the volume concentration of HC-5 high-protection low-chrome color passivator is 2% to 4%, the passivation temperature is 20 to 35° C., the pH value of the passivation solution is 1.3 to 2.0, the passivation time is 5 to 15 seconds, and weak air stirring or workpiece swinging; In some of the embodiments, the hexavalent chromium military green passivation layer is prepared by OVG-31 military green passivation process: OVG-31 military green passivation agent 80-120 mL / L, passivation solution pH 1.0-1.6, passivation temperature 20-30° C., passivation time 30-90 s, air stirring or swinging the plated piece; In some of the embodiments, the hexavalent chromium black passivation layer is prepared by BZ-71 cadmium plating black passivation process: BZ-71A cadmium plating black passivation agent 80-100mL / L, BZ-71B cadmium plating black passivation agent 80-100mL / L, passivation solution pH 1.1-1.5, passivation temperature 20-35°C, passivation time 15-40s, air stirring or swinging the plated piece.

[0017] In some of the embodiments, the trivalent chromium blue-white passivation layer is prepared by TRIROS TCP-185 trivalent chromium blue-white passivation process: TRIROS TCP-185 trivalent chromium blue-white passivation agent 40-80 mL / L, passivation solution pH 1.8-2.5, passivation temperature 20-30°C, passivation time 20-40s, air stirring or swinging the plated piece.

[0018] The copper-zinc alloy coating is prepared on the zinc coating by using the polymerized thiocyanate copper-zinc alloy coating process. Similar to the cyanide copper coating process, the prepared coatings can form good bonding strength. As time goes by, the zinc atoms in the zinc coating can diffuse into the copper-zinc alloy coating, and the copper atoms and zinc atoms in the copper-zinc alloy coating can also diffuse into the zinc alloy coating, so that there is no obvious interface between the two coatings, thereby further increasing the bonding strength between the two coatings.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The cyanide-free cadmium-iron alloy plating process of NdFeB applicable to the aerospace field of the present invention has excellent corrosion resistance, which overcomes the technical defect of poor corrosion resistance of the existing protective layer of NdFeB workpieces; 2. The cyanide-free cadmium-iron alloy plating process of NdFeB applicable to the aerospace field of the present invention adopts a sulfate zinc plating process to prepare a zinc plating layer on the surface of the NdFeB workpiece, which overcomes the high magnetic shielding problem of the nickel plating layer prepared on the surface of the NdFeB workpiece by using a citrate nickel plating process; 3. The cyanide-free cadmium-plated iron alloy process for NdFeB applicable to the aerospace field adopts a grinding method to remove the oxide scale on the surface of the NdFeB workpiece, and a lactic acid activation method to remove the oxide film on the surface of the NdFeB workpiece, thereby overcoming the problem of hydrogenation of metal neodymium caused by the hydrochloric acid or sulfuric acid pickling method, and also overcoming the problem of passivation of the surface of the NdFeB workpiece by the nitric acid pickling method; 4. The cyanide-free cadmium-iron alloy plating process of NdFeB applicable to the aerospace field of the present invention has a pH of 5 to 5.8 in the sulfate zinc plating solution, which is very weak in acidity and has no corrosive effect on the NdFeB matrix. Therefore, the bottom plating layer prepared by the sulfate zinc plating process can effectively seal the pores on the surface of the NdFeB workpiece, and there is no residual corrosion problem on the NdFeB workpiece matrix; 5. The cyanide-free cadmium-iron alloy plating process of NdFeB applicable to the aerospace field of the present invention adopts a polymerized thiocyanate copper-zinc alloy plating process to prepare a copper-zinc alloy plating layer on a zinc plating layer, and a good bonding force can be formed between the two plating layers; 6. The cyanide-free cadmium-iron alloy plating process of NdFeB applicable to the aerospace field of the present invention prepares a cyanide-free cadmium-iron alloy coating on the copper-zinc alloy coating. The cadmium-iron alloy coating is an anodic coating relative to the copper-zinc alloy coating, which can effectively prevent the corrosive medium from corroding toward the substrate, thus overcoming the defect that direct nickel plating on the surface of the NdFeB workpiece has no electrochemical protection effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of the present application, and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a schematic diagram of the coating structure of Example 1, Example 2, Example 3 and Example 4 of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0022] A cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field comprises pretreatment of NdFeB workpieces, and sequentially preparing a sulfate zinc plating layer, a cyanide-free copper-zinc alloy plating layer, a cyanide-free cadmium-iron alloy plating layer, and a passivation layer on a NdFeB substrate from the inside to the outside.

[0023] Grinding, chamfering, degreasing and activation of NdFeB workpieces.

[0024] Preferably, the activation adopts a lactic acid activation process: Lactic acid 40-80 mL / L, operating temperature 20-35°C, activation time 20-40 s.

[0025] After pretreatment of the NdFeB workpiece, the sulfate zinc coating is prepared by the current sulfate zinc coating process.

[0026] Preferably, the thickness of the sulfate zinc plating layer is 10 to 20 μm.

[0027] Preferably, the sulfate zinc plating layer is prepared by the ZL-94 sulfate zinc plating process of Tianjin Feige Group United Chemical Plant: Zinc sulfate heptahydrate 350-450g / L, boric acid 25-35g / L, ZL-94 brightener 14-18mL / L, plating solution pH 5.0-5.8, plating tank temperature 15-45℃, cathode current density 1-4A / dm 2 , the cathode moves 3 to 5 m / min.

[0028] The specific process is "galvanizing → water washing → film removal with 0.5% mass fraction sulfuric acid → water washing".

[0029] After the NdFeB workpiece is galvanized, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a cyanide-free copper-zinc alloy plating layer.

[0030] Preferably, the thickness of the cyanide-free copper-zinc alloy coating is 6 to 10 μm.

[0031] Polymeric cuprous thiocyanate 18-24 g / L, polymeric zinc thiocyanate 9-13 g / L, polymeric sodium thiocyanate 130-170 g / L, copper-zinc alloy electroplating brightener 8-12 mL / L, plating solution pH 10-12, plating tank temperature 35-55 ° C, cathode current density 0.5-1.5 A / dm 2 The cathode moves 3 to 5 m / min, and a copper-zinc alloy plate with a copper mass fraction of 68% is used as the anode, and the anode moves 3 to 5 m / min.

[0032] Preferably, the copper-zinc alloy electroplating brightener comprises the following components in weight fractions: 60-100 parts of N,N'-di-n-propylethylenediamine, 10-20 parts of waterborne polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight less than 8000, and 770-870 parts of deionized water.

[0033] Preferably, the copper-zinc alloy electroplating brightener is prepared as follows: 770 to 870 parts by weight of deionized water are added to a reaction tank, 60 to 100 parts of N,N'-di-n-propylethylenediamine, 10 to 20 parts of waterborne polyurethane resin, and 80 to 120 parts of polyacrylamide with a molecular weight less than 8000 are added under stirring, and the brightener is obtained by stirring evenly.

[0034] Preferably, the polyacrylamide with a molecular weight less than 8000 includes any one or two of polyacrylamide with a model number of GRO-70, polyacrylamide with a model number of IC-113, polyacrylamide with a model number of IC-125, and polyacrylamide with a model number of IC-213.

[0035] After the NdFeB workpiece is plated with copper-zinc alloy, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy plating layer.

[0036] Preferably, the thickness of the cyanide-free cadmium iron alloy coating is 8 to 24 μm.

[0037] Cadmium chloride 25-35g / L, ferrous chloride tetrahydrate 4-6g / L, potassium chloride 100-140g / L, complexing agent 100-140g / L, leveling agent 1.5-2.5mL / L, brightener 1.5-2.5mL / L, auxiliary agent 25-30mL / L, stabilizer 25-35g / L, plating solution pH 6-8, plating tank temperature 20-35℃, cathode current density 0.5-1.5A / dm 2 , the cathode moves 2 to 4 m / min.

[0038] Preferably, the leveling agent includes 5-10 g / L of trimercapto-s-triazine, 30-60 g / L of organic amine epoxy derivative, and 5-10 g / L of sodium hydroxide.

[0039] Preferably, the stabilizer comprises sodium gluconate and sodium hydrogen succinate, and the mass ratio of sodium gluconate to sodium hydrogen succinate is 1:(2-3).

[0040] Preferably, the complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the above components are mixed evenly to obtain the complexing agent; the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:(1-2):(4-6).

[0041] Preferably, the brightener comprises three components A, B and C, wherein component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate; wherein component A is 30-80 g / L, component B is 30-80 g / L, component C is 60-100 g / L, and isopropyl alcohol is 280-100 g / L.

[0042] Preferably, the auxiliary agent includes polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and component D, and component D is consistent with component C in the brightener; wherein the polyacrylamide with a molecular weight less than 8000 is 50-80 g / L, the condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin is 20-50 g / L, the sodium salt of 2-ethylhexyl sulfate is 30-80 g / L, and the component D is 30-60 g / L.

[0043] After the NdFeB workpiece is plated with cadmium-iron alloy, a passivation layer is prepared using the current cadmium plating post-treatment process. Preferably, the passivation layer includes a hexavalent chromium color passivation layer, a hexavalent chromium military green passivation layer, a hexavalent chromium black passivation layer, and a trivalent chromium blue-white passivation layer.

[0044] Preferably, the hexavalent chromium color passivation layer is prepared by HC-5 low-chrome color passivation process: the volume concentration of HC-5 high-protection low-chrome color passivator is 2% to 4%, the passivation temperature is 20 to 35°C, the pH value of the passivation solution is 1.3 to 2.0, the passivation time is 5 to 15s, and weak air stirring or workpiece swinging is performed.

[0045] Preferably, the hexavalent chromium military green passivation layer is prepared by OVG-31 military green passivation process: OVG-31 military green passivator 80-120 mL / L, passivation solution pH 1.0-1.6, passivation temperature 20-30°C, passivation time 30-90s, air stirring or swinging the plated piece.

[0046] Preferably, the hexavalent chromium black passivation layer is prepared by BZ-71 cadmium plating black passivation process: BZ-71A cadmium plating black passivation agent 80-100mL / L, BZ-71B cadmium plating black passivation agent 80-100mL / L, passivation solution pH value 1.1-1.5, passivation temperature 20-35°C, passivation time 15-40s, air stirring or swinging the plated piece.

[0047] Preferably, the trivalent chromium blue-white passivation layer is prepared by TRIROS TCP-185 trivalent chromium blue-white passivation process: TRIROS TCP-185 trivalent chromium blue-white passivation agent 40-80 mL / L, passivation solution pH 1.8-2.5, passivation temperature 20-30° C., passivation time 20-40 s, air stirring or swinging the plated piece.

[0048] After passivation, the NdFeB workpiece is dried using a conventional drying process.

[0049] Embodiment 1: like Figure 1 As shown, a cyanide-free cadmium-iron alloy plating process for NdFeB suitable for the aerospace field includes pre-treatment of a NdFeB substrate 1, and sequentially preparing a sulfate zinc plating layer 2, a cyanide-free copper-zinc alloy plating layer 3, a cyanide-free cadmium-iron alloy plating layer 4, and a hexavalent chromium color passivation layer 5 on the pre-treated NdFeB substrate 1 from the inside to the outside.

[0050] 1. Pre-treatment: The NdFeB workpiece substrate 1 is subjected to “grinding and chamfering → water washing → weak alkaline ultrasonic degreasing → water washing → lactic acid activation → water washing”.

[0051] The lactic acid activation process is: lactic acid 60mL / L, operating temperature 28°C, activation time 30s.

[0052] 2. Sulfate zinc plating: After pretreatment, the NdFeB workpiece is subjected to ZL-94 sulfate zinc plating process of Tianjin Fei Ge Group United Chemical Plant to prepare a sulfate zinc plating layer 2, and the thickness of the zinc plating layer is 15 μm.

[0053] Zinc sulfate heptahydrate 400g / L, boric acid 30g / L, ZL-94 brightener 16mL / L, plating solution pH 5.4, plating tank temperature 30℃, cathode current density 2A / dm 2 , cathode moves 4m / min.

[0054] The specific process is "galvanizing → water washing → film removal with 0.5% mass fraction sulfuric acid → water washing".

[0055] 3. Copper-zinc alloy: After the NdFeB workpiece is galvanized, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a cyanide-free copper-zinc alloy coating 3, and the thickness of the copper-zinc alloy coating is 8 μm.

[0056] 1) Preparation of copper-zinc alloy electroplating brightener: Calculated by weight, 820 parts of deionized water were added to a reaction tank, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of polyacrylamide with model GRO-70 were added under stirring, and stirred evenly to obtain the brightener.

[0057] 2) Plating: Polymeric cuprous thiocyanate 21g / L, polymeric zinc thiocyanate 11g / L, polymeric sodium thiocyanate 150g / L, copper-zinc alloy electroplating brightener 10mL / L, plating solution pH 10.5, plating tank temperature 45℃, cathode current density 1.0A / dm 2 The cathode moves at 4 m / min, and a copper-zinc alloy plate with a copper mass fraction of 68% is used as the anode, and the anode moves at 4 m / min.

[0058] 4. Cadmium-plated iron alloy: After the NdFeB workpiece is plated with copper-zinc alloy, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy plating layer 4, and the thickness of the cadmium-iron alloy plating layer is 12 μm.

[0059] 1) Preparation of leveling agent: The leveling agent includes 7.5 g / L of trimercapto-s-triazine, 45 g / L of an organic amine epoxy derivative with a product model of GDX sold by Sefik New Materials Co., Ltd., and 7.5 g / L of sodium hydroxide. According to the formula requirements, sodium hydroxide is dissolved in water, and trimercapto-s-triazine is added, stirred to dissolve, and then the organic amine epoxy derivative is added, and water is added to the required volume to obtain the leveling agent.

[0060] 2) Preparation of stabilizer: The stabilizer includes sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:2.5. Sodium glucoheptanoate and sodium hydrogen succinate are mixed together according to the formula ratio requirements, and stirred evenly to obtain the stabilizer.

[0061] 3) Preparation of complexing agent: The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:1.5:5. Nitrilotriacetic acid, sulfosalicylic acid, and malic acid are mixed together according to the formula ratio and stirred evenly to obtain the complexing agent.

[0062] 4) Prepare brightener: The brightener comprises three components, A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate. 30kg of isopropanol is added to 40kg of water and mixed evenly, 5.5kg of component A, 4kg of component B and 8kg of component C are added, stirred to dissolve, and water is added to 100L to obtain the brightener.

[0063] 5) Preparation of auxiliary agents: The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; 6.5 kg of polyacrylamide with a molecular weight less than 8000, 3.5 kg of a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, 5.5 kg of sodium salt of 2-ethylhexyl sulfate, and 4.5 kg of the D component are added to 70 kg of water, stirred to dissolve, and water is added to 100 L to obtain the auxiliary agent.

[0064] 6) Plating: Cadmium chloride 30g / L, ferrous chloride tetrahydrate 5g / L, potassium chloride 120g / L, complexing agent 120g / L, leveling agent 2.0mL / L, brightener 2.0mL / L, auxiliary agent 27mL / L, stabilizer 30g / L, plating solution pH 7, plating tank temperature 28℃, cathode current density 1.0A / dm 2 , cathode moves 3m / min.

[0065] 5. Hexavalent chromium color passivation: After the NdFeB workpiece is plated with cadmium iron alloy, the hexavalent chromium color passivation layer 5 is prepared using the HC-5 low chromium color passivation process of Chaobang Chemical.

[0066] The volume concentration of HC-5 high protection low chrome color passivator is 3%, the passivation temperature is 28℃, the pH of the passivation solution is 1.6, the passivation time is 8s, and the workpiece swings.

[0067] The specific process is "1.5% volume fraction nitric acid polishing → water washing → passivation → water washing → drain after leaving the tank → use high-pressure air to blow away the residual water on the surface of the plated part".

[0068] 6. Drying: After passivation, the NdFeB workpiece was dried at 60°C for 10 minutes.

[0069] Embodiment 2: like Figure 1 As shown, a cyanide-free cadmium-iron alloy plating process for NdFeB suitable for the aerospace field includes pretreatment of a NdFeB substrate 1, and sequentially preparing a sulfate zinc plating layer 2, a cyanide-free copper-zinc alloy plating layer 3, a cyanide-free cadmium-iron alloy plating layer 4, and a hexavalent chromium military green passivation layer 5 on the pretreated NdFeB substrate 1 from the inside to the outside.

[0070] The NdFeB workpiece substrate 1 is subjected to “grinding and chamfering → water washing → weak alkaline ultrasonic degreasing → water washing → lactic acid activation → water washing”.

[0071] The lactic acid activation process is: lactic acid 60mL / L, operating temperature 20°C, activation time 30s.

[0072] 2. Sulfate zinc plating: After pretreatment, the NdFeB workpiece is subjected to ZL-94 sulfate zinc plating process of Tianjin Fei Ge Group United Chemical Plant to prepare a sulfate zinc plating layer 2, and the thickness of the zinc plating layer is 15 μm.

[0073] Zinc sulfate heptahydrate 450g / L, boric acid 35g / L, ZL-94 brightener 16mL / L, plating solution pH 5.2, plating tank temperature 30℃, cathode current density 3A / dm 2 , cathode moves 4m / min.

[0074] The specific process is "galvanizing → water washing → film removal with 0.5% mass fraction sulfuric acid → water washing".

[0075] 3. Copper-zinc alloy: After the NdFeB workpiece is galvanized, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a cyanide-free copper-zinc alloy coating 3, and the thickness of the copper-zinc alloy coating is 8 μm.

[0076] 1) Preparation of copper-zinc alloy electroplating brightener: Calculated by weight, 820 parts of deionized water were added to a reaction tank, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of IC-113 polyacrylamide were added under stirring, and stirred evenly to obtain the brightener.

[0077] 2) Plating: Polymeric cuprous thiocyanate 24g / L, polymeric zinc thiocyanate 13g / L, polymeric sodium thiocyanate 170g / L, copper-zinc alloy electroplating brightener 10mL / L, plating solution pH 10, plating tank temperature 45℃, cathode current density 1.0A / dm 2 The cathode moves at 4 m / min, and a copper-zinc alloy plate with a copper mass fraction of 68% is used as the anode, and the anode moves at 4 m / min.

[0078] 4. Cadmium-plated iron alloy: After the NdFeB workpiece is plated with copper-zinc alloy, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy plating layer 4, and the thickness of the cadmium-iron alloy plating layer is 12 μm.

[0079] 1) Preparation of leveling agent: The leveling agent includes 7.5 g / L of trimercapto-s-triazine, 45 g / L of an organic amine epoxy derivative with a product model of GDX sold by Sefik New Materials Co., Ltd., and 7.5 g / L of sodium hydroxide. According to the formula requirements, sodium hydroxide is dissolved in water, and trimercapto-s-triazine is added, stirred to dissolve, and then the organic amine epoxy derivative is added, and water is added to the required volume to obtain the leveling agent.

[0080] 2) Preparation of stabilizer: The stabilizer includes sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:2.5. Sodium glucoheptanoate and sodium hydrogen succinate are mixed together according to the formula ratio requirements, and stirred evenly to obtain the stabilizer.

[0081] 3) Preparation of complexing agent: The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:1.5:5. Nitrilotriacetic acid, sulfosalicylic acid, and malic acid are mixed together according to the formula ratio and stirred evenly to obtain the complexing agent.

[0082] 4) Prepare brightener: The brightener comprises three components, A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate. 30kg of isopropanol is added to 40kg of water and mixed evenly, 5.5kg of component A, 4kg of component B and 8kg of component C are added, stirred to dissolve, and water is added to 100L to obtain the brightener.

[0083] 5) Preparation of auxiliary agents: The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; 6.5 kg of polyacrylamide with a molecular weight less than 8000, 3.5 kg of a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, 5.5 kg of sodium salt of 2-ethylhexyl sulfate, and 4.5 kg of the D component are added to 70 kg of water, stirred to dissolve, and water is added to 100 L to obtain the auxiliary agent.

[0084] 6) Plating: Cadmium chloride 28g / L, ferrous chloride tetrahydrate 4.7g / L, potassium chloride 135g / L, complexing agent 125g / L, leveling agent 2.0mL / L, brightener 2.0mL / L, auxiliary agent 28mL / L, stabilizer 28g / L, plating solution pH 6.5, plating tank temperature 32℃, cathode current density 1.0A / dm 2 , cathode moves 3m / min.

[0085] 5. Hexavalent chromium military green passivation: After the NdFeB workpiece is plated with cadmium iron alloy, the military green passivation layer 5 is prepared using Chaobang Chemical's OVG-31 military green passivation process.

[0086] OVG-31 military green passivator 100mL / L, passivation solution pH 1.3, passivation temperature 25℃, passivation time 60s, swing plated parts.

[0087] The specific process is "1.5% volume fraction nitric acid polishing → water washing → passivation → water washing → drain after leaving the tank → use high-pressure air to blow away the residual water on the surface of the plated part".

[0088] 6. Drying: After passivation, the NdFeB workpiece was dried at 60°C for 10 minutes.

[0089] Embodiment 3: like Figure 1 As shown, a cyanide-free cadmium-iron alloy plating process for NdFeB suitable for the aerospace field includes pre-treatment of a NdFeB substrate 1, and sequentially preparing a sulfate zinc plating layer 2, a cyanide-free copper-zinc alloy plating layer 3, a cyanide-free cadmium-iron alloy plating layer 4, and a hexavalent chromium black passivation layer 5 on the pre-treated NdFeB substrate 1 from the inside to the outside.

[0090] 1. Pre-treatment: The NdFeB workpiece substrate 1 is subjected to the following steps: "grinding and chamfering → water washing → weak alkaline ultrasonic degreasing → water washing → lactic acid activation → water washing".

[0091] The lactic acid activation process is: lactic acid 40mL / L, operating temperature 35°C, activation time 40s.

[0092] 2. Sulfate zinc plating: After pretreatment, the NdFeB workpiece is subjected to ZL-94 sulfate zinc plating process of Tianjin Fei Ge Group United Chemical Plant to prepare a sulfate zinc plating layer 2, and the thickness of the zinc plating layer is 15 μm.

[0093] Zinc sulfate heptahydrate 350g / L, boric acid 25g / L, ZL-94 brightener 16mL / L, plating solution pH 5.6, plating tank temperature 45℃, cathode current density 2A / dm 2 , cathode moves 4m / min.

[0094] The specific process is "galvanizing → water washing → film removal with 0.5% mass fraction sulfuric acid → water washing".

[0095] 3. Copper-zinc alloy: After the NdFeB workpiece is galvanized, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a cyanide-free copper-zinc alloy coating 3, and the thickness of the copper-zinc alloy coating is 8 μm.

[0096] 1) Preparation of copper-zinc alloy electroplating brightener: Calculated by weight, 820 parts of deionized water were added to a reaction tank, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of IC-125 polyacrylamide were added under stirring, and stirred evenly to obtain the brightener.

[0097] 2) Plating: Polymeric cuprous thiocyanate 18g / L, polymeric zinc thiocyanate 9g / L, polymeric sodium thiocyanate 130g / L, copper-zinc alloy electroplating brightener 10mL / L, plating solution pH 11.5, plating tank temperature 55℃, cathode current density 1.0A / dm 2 The cathode moves at 4 m / min, and a copper-zinc alloy plate with a copper mass fraction of 68% is used as the anode, and the anode moves at 4 m / min.

[0098] 4. Cadmium-plated iron alloy: After the NdFeB workpiece is plated with copper-zinc alloy, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy plating layer 4, and the thickness of the cadmium-iron alloy plating layer is 12 μm.

[0099] 1) Preparation of leveling agent: The leveling agent includes 7.5 g / L of trimercapto-s-triazine, 45 g / L of an organic amine epoxy derivative with a product model of GDX sold by Sefik New Materials Co., Ltd., and 7.5 g / L of sodium hydroxide. According to the formula requirements, sodium hydroxide is dissolved in water, and trimercapto-s-triazine is added, stirred to dissolve, and then the organic amine epoxy derivative is added, and water is added to the required volume to obtain the leveling agent.

[0100] 2) Preparation of stabilizer: The stabilizer includes sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:2.5. Sodium glucoheptanoate and sodium hydrogen succinate are mixed together according to the formula ratio requirements, and stirred evenly to obtain the stabilizer.

[0101] 3) Preparation of complexing agent: The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:1.5:5. Nitrilotriacetic acid, sulfosalicylic acid, and malic acid are mixed together according to the formula ratio and stirred evenly to obtain the complexing agent.

[0102] 4) Prepare brightener: The brightener comprises three components, A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate. 30kg of isopropanol is added to 40kg of water and mixed evenly, 5.5kg of component A, 4kg of component B and 8kg of component C are added, stirred to dissolve, and water is added to 100L to obtain the brightener.

[0103] 5) Preparation of auxiliary agents: The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; 6.5 kg of polyacrylamide with a molecular weight less than 8000, 3.5 kg of a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, 5.5 kg of sodium salt of 2-ethylhexyl sulfate, and 4.5 kg of the D component are added to 70 kg of water, stirred to dissolve, and water is added to 100 L to obtain the auxiliary agent.

[0104] 6) Plating: Cadmium chloride 35g / L, ferrous chloride tetrahydrate 6g / L, potassium chloride 140g / L, complexing agent 140g / L, leveling agent 2.0mL / L, brightener 2.0mL / L, auxiliary agent 28mL / L, stabilizer 35g / L, plating solution pH 7.5, plating tank temperature 20℃, cathode current density 1.0A / dm 2 , cathode moves 3m / min.

[0105] 5. Hexavalent chromium black passivation: After the NdFeB workpiece is plated with cadmium iron alloy, the hexavalent chromium black passivation layer 5 is prepared using the BZ-71 cadmium black passivation process of Chaobang Chemical.

[0106] BZ-71A cadmium black passivation agent 90mL / L, BZ-71B cadmium black passivation agent 90mL / L, passivation solution pH 1.3, passivation temperature 25℃, passivation time 28s, swing plated parts.

[0107] The specific process is "1.5% volume fraction nitric acid polishing → water washing → passivation → water washing → drain after leaving the tank → use high-pressure air to blow away the residual water on the surface of the plated part".

[0108] 6. Drying: After passivation, the NdFeB workpiece was dried at 60°C for 10 minutes.

[0109] Embodiment 4: like Figure 1 As shown, a cyanide-free cadmium-iron alloy plating process for NdFeB suitable for the aerospace field includes pre-treatment of a NdFeB substrate 1, and sequentially preparing a sulfate zinc plating layer 2, a cyanide-free copper-zinc alloy plating layer 3, a cyanide-free cadmium-iron alloy plating layer 4, and a trivalent chromium blue-white passivation layer 5 on the pre-treated NdFeB substrate 1 from the inside to the outside.

[0110] 1. Pre-treatment: The NdFeB workpiece substrate 1 is subjected to “grinding and chamfering → water washing → weak alkaline ultrasonic degreasing → water washing → lactic acid activation → water washing”.

[0111] The lactic acid activation process is: lactic acid 70mL / L, operating temperature 25°C, activation time 25s.

[0112] 2. Sulfate zinc plating: After pretreatment, the NdFeB workpiece is subjected to ZL-94 sulfate zinc plating process of Tianjin Fei Ge Group United Chemical Plant to prepare a sulfate zinc plating layer 2, and the thickness of the zinc plating layer is 15 μm.

[0113] Zinc sulfate heptahydrate 430g / L, boric acid 32g / L, ZL-94 brightener 16mL / L, plating solution pH 5.6, plating tank temperature 30℃, cathode current density 2A / dm 2 , cathode moves 4m / min.

[0114] The specific process is "galvanizing → water washing → film removal with 0.5% mass fraction sulfuric acid → water washing".

[0115] 3. Copper-zinc alloy: After the NdFeB workpiece is galvanized, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a cyanide-free copper-zinc alloy coating 3, and the thickness of the copper-zinc alloy coating is 8 μm.

[0116] 1) Preparation of copper-zinc alloy electroplating brightener: Calculated by weight, 820 parts of deionized water were added to a reaction tank, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of IC-213 polyacrylamide were added under stirring, and stirred evenly to obtain the brightener.

[0117] 2) Plating: Polymeric cuprous thiocyanate 23g / L, polymeric zinc thiocyanate 12g / L, polymeric sodium thiocyanate 165g / L, copper-zinc alloy electroplating brightener 10mL / L, plating solution pH 11.8, plating tank temperature 40℃, cathode current density 1.0A / dm 2 The cathode moves at 4 m / min, and a copper-zinc alloy plate with a copper mass fraction of 68% is used as the anode, and the anode moves at 4 m / min.

[0118] 4. Cadmium-plated iron alloy: After the NdFeB workpiece is plated with copper-zinc alloy, the cyanide-free cadmium-iron alloy plating process of the present invention is adopted to prepare a cyanide-free cadmium-iron alloy plating layer 4, and the thickness of the cadmium-iron alloy plating layer is 12 μm.

[0119] 1) Preparation of leveling agent: The leveling agent includes 7.5 g / L of trimercapto-s-triazine, 45 g / L of an organic amine epoxy derivative with a product model of GDX sold by Sefik New Materials Co., Ltd., and 7.5 g / L of sodium hydroxide. According to the formula requirements, sodium hydroxide is dissolved in water, and trimercapto-s-triazine is added, stirred to dissolve, and then the organic amine epoxy derivative is added, and water is added to the required volume to obtain the leveling agent.

[0120] 2) Preparation of stabilizer: The stabilizer includes sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:2.5. Sodium glucoheptanoate and sodium hydrogen succinate are mixed together according to the formula ratio requirements, and stirred evenly to obtain the stabilizer.

[0121] 3) Preparation of complexing agent: The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid, and the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:1.5:5. Nitrilotriacetic acid, sulfosalicylic acid, and malic acid are mixed together according to the formula ratio and stirred evenly to obtain the complexing agent.

[0122] 4) Prepare brightener: The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate. 30kg of isopropanol is added to 40kg of water and mixed evenly, 5.5kg of component A, 4kg of component B and 8kg of component C are added, stirred to dissolve, and water is added to 100L to obtain the brightener.

[0123] 5) Preparation of auxiliary agents: The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; 6.5 kg of polyacrylamide with a molecular weight less than 8000, 3.5 kg of a condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin, 5.5 kg of sodium salt of 2-ethylhexyl sulfate, and 4.5 kg of the D component are added to 70 kg of water, stirred to dissolve, and water is added to 100 L to obtain the auxiliary agent.

[0124] 6) Plating: Cadmium chloride 25g / L, ferrous chloride tetrahydrate 4g / L, potassium chloride 140g / L, complexing agent 100g / L, leveling agent 2.0mL / L, brightener 2.0mL / L, auxiliary agent 28mL / L, stabilizer 25g / L, plating solution pH 8, plating tank temperature 30℃, cathode current density 1.0A / dm 2 , cathode moves 3m / min.

[0125] 5. Trivalent chromium blue-white passivation: After the NdFeB workpiece is plated with cadmium iron alloy, the trivalent chromium blue-white passivation layer 5 is prepared using the TRIROS TCP-185 trivalent chromium blue-white passivation process of Chaobang Chemical.

[0126] TRIROS TCP-185 trivalent chromium blue-white passivator 60mL / L, the pH of the passivation solution is 2.2, the passivation temperature is 25℃, the passivation time is 30s, and the plated parts are swung.

[0127] The specific process is "1.5% volume fraction nitric acid polishing → water washing → passivation → water washing → drain after leaving the tank → use high-pressure air to blow away the residual water on the surface of the plated part".

[0128] 6. Drying: After passivation, the NdFeB workpiece was dried at 60°C for 10 minutes.

[0129] Test Example 1: According to GB / T 10125-2021 "Artificial atmosphere corrosion test salt spray test", the acetic acid salt spray test was carried out. The NdFeB cadmium iron alloy hexavalent chromium color passivation sample prepared in Example 1 had no white rust on the surface after 360 hours, the NdFeB cadmium iron alloy hexavalent chromium military green passivation sample prepared in Example 2 had no white rust on the surface after 380 hours, the NdFeB cadmium iron alloy hexavalent chromium black passivation sample prepared in Example 3 had no white rust on the surface after 328 hours, and the NdFeB cadmium iron alloy trivalent chromium blue-white passivation sample prepared in Example 4 had no white rust on the surface after 96 hours. The prepared coatings have excellent corrosion resistance.

[0130] Test Example 2: The NdFeB cadmium-iron alloy samples prepared in Example 1, Example 2, Example 3, and Example 4 were tested for coating adhesion in accordance with GB / T 5270-2005 "Review of test methods for adhesion strength of electrodeposited and chemically deposited metal coatings on metal substrates". The samples were placed in a heating furnace and heated to 250°C for 30 minutes. After being taken out, they were immediately placed in room temperature water for cooling. There was no blistering or shedding of the coating, and the coating adhesion met the standard requirements.

[0131] Test Example 3: The NdFeB cadmium-plated iron alloy samples prepared in Example 1, Example 2, Example 3, and Example 4 were tested for 360 hours at a temperature of 40°C and a relative humidity of 93% in accordance with GB / T 2423.3-2016 "Basic Environmental Test Procedures for Electrical and Electronic Products Test Ca: Steady State Wet Heat Test Method". There was no visible change in the coating, which met the technical requirements of the industry.

[0132] Test example 4: The NdFeB cadmium-plated iron alloy samples prepared in Example 1, Example 2, Example 3, and Example 4 were subjected to a mold test for 28 days in accordance with GJB150.9A-2009 "Military Equipment Laboratory Environmental Test Method Part 10: Mold Test". No mold grew on the surface of the samples, which met the environmental test requirements.

[0133] The technical solutions provided by the embodiments of the present invention are described in detail above. The principles and implementation methods of the embodiments of the present invention are described in detail using specific examples herein. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which are also considered to fall within the protection scope of the present invention.

Claims

1. A cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field, characterized in that: The following steps are involved: (1) Grinding, chamfering, degreasing, and activation of NdFeB workpieces; (2) After the NdFeB workpiece is pre-treated, the sulfate zinc coating is prepared using the current sulfate zinc coating process; (3) After the NdFeB workpiece is zinc plated with sulfate, a cyanide-free copper-zinc alloy coating is prepared by using a polymerized thiocyanate copper-zinc alloy plating process; (4) After the NdFeB workpiece is plated with copper-zinc alloy without cyanide, a cyanide-free cadmium-iron alloy plating process is used to prepare a cyanide-free cadmium-iron alloy coating; (5) After the NdFeB workpiece is plated with cadmium iron alloy, post-treatment is performed to prepare a passivation layer; The cyanide-free cadmium iron alloy plating process includes the following components and process parameters: Cadmium chloride 25-35g / L, ferrous chloride tetrahydrate 4-6g / L, potassium chloride 100-140g / L, complexing agent 100-140g / L, leveling agent 1.5-2.5mL / L, brightener 1.5-2.5mL / L, auxiliary agent 25-30mL / L, stabilizer 25-35g / L, plating solution pH 6-8, plating tank temperature 20-35℃, cathode current density 0.5-1.5A / dm 2 , cathode moves 2-4 m / min; The leveling agent includes 5-10 g / L of trimercapto-s-triazine, 30-60 g / L of organic amine epoxy derivative, and 5-10 g / L of sodium hydroxide; The stabilizer comprises sodium glucoheptanoate and sodium hydrogen succinate, and the mass ratio of sodium glucoheptanoate to sodium hydrogen succinate is 1:(2-3); The complexing agent includes nitrilotriacetic acid, sulfosalicylic acid, and malic acid. The above components are mixed evenly to obtain the complexing agent; the mass ratio of nitrilotriacetic acid, sulfosalicylic acid, and malic acid is 3:(1-2):(4-6); The brightener comprises three components: A, B and C. Component A comprises α-vinyl-N-propanesulfonic acid pyridine inner salt, component B comprises any one or two of 3-methoxy-4-hydroxybenzaldehyde, 3,4-dimethoxybenzaldehyde and 4-methoxybenzaldehyde, and component C comprises any one or two of propargyl alcohol ethoxy ether, propargyl alcohol propoxy ether, N,N-diethylpropargylamine, N,N-diethylpropargylamine formate and N,N-diethylpropargylamine sulfate; wherein component A is 30-80 g / L, component B is 30-80 g / L, component C is 60-100 g / L, and isopropyl alcohol is 280-320 g / L; The auxiliary agent comprises polyacrylamide with a molecular weight less than 8000, sodium salt of 2-ethylhexyl sulfate, a condensate composed of ethylenediamine or dimethylpropylamine and epichlorohydrin, and a D component, wherein the D component is consistent with the C component in the brightener; wherein the polyacrylamide with a molecular weight less than 8000 is 50-80 g / L, the condensate of ethylenediamine or dimethylpropylamine and epichlorohydrin is 20-50 g / L, the sodium salt of 2-ethylhexyl sulfate is 30-80 g / L, and the D component is 30-60 g / L.

2. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field as claimed in claim 1 is characterized in that: The polythiocyanate copper-zinc alloy plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 18-24 g / L, polymeric zinc thiocyanate 9-13 g / L, polymeric sodium thiocyanate 130-170 g / L, copper-zinc alloy electroplating brightener 8-12 mL / L, plating solution pH 10-12, plating tank temperature 35-55 ° C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, a copper-zinc alloy plate with a copper mass fraction of 68% is used as an anode, and the anode moves 3 to 5 m / min; the copper-zinc alloy electroplating brightener comprises the following components by weight: 60 to 100 parts of N,N'-di-n-propylethylenediamine, 10 to 20 parts of water-based polyurethane resin, 80 to 120 parts of polyacrylamide with a molecular weight less than 8000, and 770 to 870 parts of deionized water.

3. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field as claimed in claim 1 is characterized in that: The thickness of the cyanide-free cadmium iron plating layer is 8 to 24 μm.

4. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field as claimed in claim 1 is characterized in that: The thickness of the cyanide-free copper-zinc alloy coating is 6 to 10 μm.

5. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field as claimed in claim 1, characterized in that: The activation adopts lactic acid activation process: Lactic acid 40-80 mL / L, operating temperature 20-35°C, activation time 20-40 s.

6. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field as claimed in claim 1, characterized in that: The sulfate zinc plating layer is prepared by the current sulfate zinc plating process: Zinc sulfate heptahydrate 350-450g / L, boric acid 25-35g / L, ZL-94 brightener 14-18mL / L, plating solution pH 5.0-5.8, plating tank temperature 15-45℃, cathode current density 1-4A / dm 2 , the cathode moves 3 to 5 m / min.

7. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field according to claim 1 or 6, characterized in that: The thickness of the sulfate zinc plating layer is 10 to 20 μm.

8. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field as claimed in claim 1, characterized in that: The passivation layer includes a hexavalent chromium color passivation layer, a hexavalent chromium military green passivation layer, a hexavalent chromium black passivation layer, and a trivalent chromium blue-white passivation layer.

9. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field as claimed in claim 8, characterized in that: The hexavalent chromium color passivation layer is prepared by HC-5 low-chromium color passivation process: the volume concentration of HC-5 high-protection low-chromium color passivator is 2% to 4%, the passivation temperature is 20 to 35° C., the pH value of the passivation solution is 1.3 to 2.0, the passivation time is 5 to 15 seconds, and weak air stirring or workpiece swinging is performed; The hexavalent chromium military green passivation layer is prepared by OVG-31 military green passivation process: OVG-31 military green passivation agent 80-120 mL / L, passivation solution pH value 1.0-1.6, passivation temperature 20-30° C., passivation time 30-90 s, air stirring or swinging the plated piece; The hexavalent chromium black passivation layer is prepared by using the BZ-71 cadmium black passivation process: BZ-71A cadmium black passivation agent 80-100mL / L, BZ-71B cadmium black passivation agent 80-100mL / L, the pH value of the passivation solution is 1.1-1.5, the passivation temperature is 20-35°C, the passivation time is 15-40s, and the plated piece is stirred or swung by air.

10. The cyanide-free cadmium-iron alloy plating process for NdFeB applicable to the aerospace field as claimed in claim 8, characterized in that: The trivalent chromium blue-white passivation layer is prepared by TRIROS TCP-185 trivalent chromium blue-white passivation process: TRIROS TCP-185 trivalent chromium blue-white passivation agent 40-80 mL / L, passivation solution pH value 1.8-2.5, passivation temperature 20-30° C., passivation time 20-40 s, air stirring or swinging the plated piece.

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