Process method for micro-arc oxidation and zinc-iron alloy plating of magnesium alloy workpiece

Abstract

The invention discloses a technological method for micro-arc oxidation and zinc-iron alloy plating of a magnesium alloy workpiece. The technological method comprises the step that a micro-arc oxidation layer, a chemical nickel preplating layer, a chemical copper plating layer, a copper-zinc alloy plating layer, a zinc-iron alloy plating layer, a trivalent chromium passivation film and a graphene modified sealing layer are sequentially prepared on a magnesium alloy matrix from inside to outside. According to the zinc-iron alloy electroplating process, 50-70 g / L of zinc chloride, 2-12 g / L of ferrous chloride tetrahydrate, 180-220 g / L of potassium chloride, 25-32 g / L of boric acid, 8-40 g / L of a coordination agent, 0.1-0.2 mL / L of a brightening agent and 20-30 mL / L of an auxiliary agent are adopted, the pH value of a plating solution is 4.5-5.6, the temperature of a plating tank is 15-30 DEG C, the cathode current density is 1-3 A / dm < 2 >, and cathode movement is 3-5 m / min. The prepared magnesium alloy galvanized iron alloy sample piece is high in corrosion resistance and has a good market prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a process method for micro-arc oxidation and galvanizing of a magnesium alloy workpiece. Background Art

[0002] Magnesium alloy is the lightest metal structural material with many superior properties. It can be widely used in military, automobile, aircraft, mobile phone, computer, electromechanical and other industrial products. It is known as the "green engineering material of the century". However, magnesium alloy has active chemical properties. The ratio of the volume of the generated oxide molecules to the volume of the metal atoms is less than 1. Its surface oxide layer is loose and porous and cannot effectively protect the matrix. For magnesium alloy, the phase containing alloy elements may form local cathode and anode with the magnesium matrix, which aggravates the corrosion tendency. Therefore, magnesium alloy is very susceptible to corrosion if it is not protected. Therefore, obtaining a protective layer through surface treatment is a hot topic in the current research of magnesium alloy.

[0003] There are many methods for magnesium alloy surface treatment, mainly electrophoretic coating, surface plating, micro-arc oxidation, anodizing, chemical conversion film, spraying organic coating and other technologies. [1] At present, electrophoretic coating technology is mainly used to prepare protective layers on the surface of magnesium alloy parts, and other protective technologies need to be further developed and studied.

[0004] The micro-arc oxidation conversion film on the surface of magnesium alloy usually contains more pores. This protective layer alone is not enough to prevent the aluminum alloy substrate from corrosion. [2] .

[0005] There have been some research reports on electroplating nickel and chemical nickel plating on magnesium alloy surfaces. [3-4] The nickel-plated layer and chemical pre-plated nickel layer directly prepared on the surface of magnesium alloy have no electrochemical protection effect on the magnesium alloy substrate, and there is a large potential difference between the two. The electroplated nickel layer and chemical pre-plated nickel layer prepared by the prior art usually contain a certain number of pores. The corrosive medium can pass through the pores of the plating layer to cause galvanic corrosion and destroy the magnesium alloy substrate. Therefore, the corrosion resistance of this plating structure is also poor, which limits its application.

[0006] The inner surface of the pores of the micro-arc oxidation layer on the surface of the magnesium alloy carries a negative charge. The nickel ions in the chemical nickel plating solution can be reduced and deposited in the micropores of the micro-arc oxidation layer without sensitization and activation, forming tiny primary nickel particles. Therefore, chemical nickel plating can be directly performed on the micro-arc oxidation layer of the magnesium alloy workpiece to prepare a chemical pre-plated nickel layer. [5] .

[0007] Chemical copper plating does not require external current, has simple equipment and low production cost, and has therefore been widely used. Its process characteristics are that it is not limited by the surface shape of the plated object. Whether it is a groove, cavity, deep hole, blind hole, etc., any part that can come into contact with the solution can obtain a uniform coating. Its depth capability and throwing power are unmatched by electroplating processes. [6] .

[0008] References: [1]. Fu Haifeng, Lv Dongxian, Tan Huachao, et al., Research status and trends of magnesium alloy surface modification technology [J], Heat Treatment, 2015, 30(3): 1-5. [2]. Liu Fengjuan, Sun Lili, Yu Feng, et al., Preparation of micro-arc oxidation thermal control film on LA141 magnesium-lithium alloy surface [J], Corrosion and Protection, 2022, 43(9): 17-22. [3]. Yu Gang, Yi Xiangrong, Lei Xiping, et al., Study on the formation mechanism and electroplating process of electrodeposited nickel on magnesium alloy [J], Electroplating and Environmental Protection, 2009, 29(1): 21-25. [4]. Zhang Xiaohuan, Feng Lajun, Lu Man, Optimization of chemical nickel-phosphorus plating process and coating performance on magnesium alloy surface [J], Materials Protection, 2022, 55(6): 86-91. [5]. Fu Ming, Li Junming, Composite modification of magnesium alloy surface by micro-arc oxidation / chemical nickel plating [J], Materials Protection, 2022, 52(6): 79-83. [6]. Lin Jianhui, Chen Yong, Chen Gan, et al., Problems and countermeasures of glyoxylic acid chemical copper plating in hole metallization [J], Printed Circuit Information, 2024, 32(5): 216-220. Summary of the invention

[0009] In order to solve the problem of poor corrosion resistance of the existing electroplated protective layer of magnesium alloy, the present invention provides a process for micro-arc oxidation and galvanizing of magnesium alloy workpieces. In order to achieve the above purpose, the present invention adopts the following technical solutions: A process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece, comprising the following steps: (1) Using magnesium alloy pretreatment process to degrease and pickle and activate magnesium alloy workpieces; (2) After the magnesium alloy workpiece is pretreated, a micro-arc oxidation process is used to prepare a micro-arc oxidation layer; (3) A chemical pre-plated nickel layer is prepared by a chemical nickel plating process after micro-arc oxidation of the magnesium alloy workpiece; (4) After the magnesium alloy workpiece is electrolessly nickel-plated, an electroless copper plating process is used to prepare an electroless copper plating layer; (5) After the magnesium alloy workpiece is electrolessly copper-plated, a copper-zinc alloy coating is prepared by a polymerized thiocyanate copper-zinc alloy plating process; (6) After the magnesium alloy workpiece is plated with copper-zinc alloy, a zinc-iron alloy coating is prepared by a potassium chloride zinc-iron alloy plating process; (7) Magnesium alloy workpieces are plated with zinc-iron alloy and then passivated to prepare a trivalent chromium passivation film; (8) Preparation of graphene modified sealing layer after passivation of zinc-iron alloy coating on magnesium alloy workpiece; The potassium chloride zinc-iron alloy plating process includes the following components and process parameters: Zinc chloride 50-70 g / L, ferrous chloride tetrahydrate 2-12 g / L, potassium chloride 180-220 g / L, boric acid 25-32 g / L, complexing agent 8-40 g / L, brightener 0.1-0.2 mL / L, auxiliary agent 20-30 mL / L, plating solution pH 4.5-5.6, plating tank temperature 15-30 ° C, cathode current density 1-3 A / dm 2 , the cathode moves 3-5 m / min, a zinc plate with a mass fraction of ≥99.95% is used as the anode, and the area ratio of the cathode to the anode is 2:1; during production, a 30% mass fraction of ferrous chloride tetrahydrate solution is added to the plating tank to keep its concentration within the process range; The complexing agent includes sodium gluconate and sodium sulfosalicylate, the mass ratio of sodium gluconate to sodium sulfosalicylate is 3:(1-3), and sodium gluconate and sodium sulfosalicylate are mixed according to the ratio and stirred evenly; The brightener comprises o-chlorobenzaldehyde and formic acid, the mass ratio of o-chlorobenzaldehyde to formic acid is 1:(0.8-1.2), and o-chlorobenzaldehyde and formic acid are mixed in the said ratio and stirred until all the solids are dissolved; The auxiliary agent comprises a sulfonated product of fatty alcohol polyoxyethylene ether with model OX-105 and aminosulfonic acid, sodium benzoate, and nicotinic acid. Calculated by weight, the sulfonated product of fatty alcohol polyoxyethylene ether with model OX-105 and aminosulfonic acid is 17 to 23 parts, sodium benzoate is 5 to 7 parts, nicotinic acid is 0.4 to 0.6 parts, and water is 80 to 90 parts. The above three intermediates are added into water according to the weight fractions and stirred until all the solids are dissolved.

[0010] In some embodiments, the polythiocyanate copper-zinc alloy plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 14-20 g / L, polymeric zinc thiocyanate 12-18 g / L, polymeric sodium thiocyanate 140-180 g / L, copper-zinc alloy brightener 8-12 mL / L, plating solution pH 9-10, plating tank temperature 35-45 °C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, a brass angle code-named H59 is used as the anode, the brass angle is placed in the titanium anode blue, the area ratio of the anode to the cathode is >3:1, and the anode moves 3 to 5 m / min.

[0011] In some of the embodiments, the copper-zinc alloy brightener comprises the following components in weight fractions: 6 to 10 parts of N,N'-di-n-propylethylenediamine, 1 to 2 parts of waterborne polyurethane resin, 8 to 12 parts of polyacrylamide with a molecular weight less than 8000, and 77 to 87 parts of deionized water.

[0012] In some embodiments, the magnesium alloy micro-arc oxidation process includes the following components and process parameters: Sodium phosphate 10-14g / L, potassium hydroxide 1.8-2.2g / L, potassium fluorozirconate 2-3g / L, constant current mode, anode current density 6A / dm 2 , pulse frequency 500Hz, duty cycle 20%, oxidation time 8-12min, electrolyte temperature 20-25℃, magnesium alloy workpiece as anode and titanium plate as cathode.

[0013] In some embodiments, the chemical pre-plated nickel layer is prepared by ERANI GG-186 alkaline chemical nickel plating process: ERANI GG-186 A additive 35~45mL / L, ERANI GG-186 B ​​reducing agent 140~160mL / L, operating temperature 85~92℃, plating solution pH 8~9.5.

[0014] In some of the embodiments, the chemical copper plating layer is prepared by using a GG-145 alkaline rapid chemical copper plating process: GG-145A agent 80~120mL / L, GG-145B agent 80~120mL / L, plating solution pH value 12~13, plating tank temperature 45~55℃.

[0015] In some of the embodiments, the trivalent chromium passivation film is prepared using TRIROS 348 zinc iron blue-white passivation agent: TRIROS 348 zinc iron blue-white passivator 135-175 mL / L, passivation solution pH 2.0-2.8, operating temperature 30-60°C, immersion time 30-60s, air stirring.

[0016] In some of the embodiments, the trivalent chromium passivation film is prepared using TRIROS BP-885 trivalent chromium black passivation agent: TRIROS BP-885A agent 40~80mL / L, TRIROS BP-885B agent 30~70mL / L, passivation temperature 20~30℃, passivation solution pH value 2.3~2.7, passivation time 40~120s.

[0017] In some of the embodiments, the graphene-modified sealing layer is prepared using PRODICO 480 graphene-modified sealing agent: Dilute PRODICO 480 graphene modified sealer with water to 2.5-3.2 times to prepare the sealing solution. Immerse the plated parts in the sealing solution for 8-15 seconds. Drain after leaving the tank, and use high-pressure air to blow away the sealing solution remaining on the surface of the plated parts. The sealed plated parts are dried and cured at 70-80°C for 20-35 minutes.

[0018] In some embodiments, the thickness of the chemical copper plating layer is 7-13 μm.

[0019] In some of the embodiments, the copper-zinc alloy coating has a thickness of 5 to 10 μm.

[0020] In some of the embodiments, the thickness of the zinc-iron alloy coating is 10-22 μm.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The process method of micro-arc oxidation and galvanizing of ferroalloy on magnesium alloy workpieces of the present invention significantly improves the scratch resistance of magnesium alloy workpieces on the micro-arc oxidation layer on the surface of magnesium alloy, and overcomes the defect of poor scratch resistance of magnesium alloy matrix; 2. The process method of micro-arc oxidation and galvanized iron alloy plating of the magnesium alloy workpiece of the present invention prepares a chemical pre-plated nickel layer on the micro-arc oxidation layer on the surface of the magnesium alloy, and a good bonding force can be formed between the two, which lays a good foundation for the subsequent preparation of other coatings; 3. The process method of micro-arc oxidation and galvanizing of ferroalloy for magnesium alloy workpieces of the present invention has a deep plating ability and a throwing power that are significantly better than those of the electroplating process. The use of the chemical copper plating process for plating can effectively seal the pores in the micro-arc oxidation layer on the surface of the magnesium alloy, thereby preventing the corrosive medium from passing through the pores to corrode the magnesium alloy substrate. 4. The process method of micro-arc oxidation and galvanizing of a magnesium alloy workpiece of the present invention prepares a copper-zinc alloy coating on a chemical copper coating. The electrode potential of the copper-zinc alloy coating is relatively negative, and the corrosion resistance of the copper-zinc alloy coating is significantly higher than that of the copper coating. This coating structure can effectively prevent the corrosion of the copper coating by the corrosive medium, thus overcoming the defect of low corrosion resistance of the surface coating prepared on the bottom copper coating by the traditional method. 5. The process method of micro-arc oxidation and zinc-iron alloy plating of a magnesium alloy workpiece of the present invention prepares a copper-zinc alloy plating layer on a chemical copper plating layer, and a zinc-iron alloy plating layer prepared on the copper-zinc alloy plating layer. The copper-zinc alloy plating layer has an electrochemical protective effect on the chemical copper plating layer, and the zinc-iron alloy plating layer also has an electrochemical activation effect on the copper-zinc alloy plating layer. The dual electrochemical protection of this plating structure can effectively prevent the corrosive medium from corroding the magnesium alloy substrate; 6. The process method for micro-arc oxidation and galvanized iron alloy plating of magnesium alloy workpieces of the present invention adopts hydroxy graphene modified sealing agent to seal the zinc-iron alloy coating passivated by trivalent chromium. The prepared sealing layer has self-repairing property, which overcomes the defect that the trivalent chromium passivation film does not have self-repairing property, and further enhances the protective effect of the coating structure on the magnesium alloy substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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

[0023] 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.

[0024] A process for micro-arc oxidation and galvanized iron alloy plating of a magnesium alloy workpiece, comprising pre-treatment of the magnesium alloy workpiece, and sequentially preparing a micro-arc oxidation layer, a chemical pre-plated nickel layer, a chemically plated copper layer, a copper-zinc alloy plating layer, a zinc-iron alloy plating layer, a trivalent chromium passivation film, and a graphene-modified sealing layer on a magnesium alloy substrate from the inside to the outside.

[0025] The existing magnesium alloy pretreatment process is used to remove oil, pickle and activate the magnesium alloy workpiece.

[0026] Preferably, the oil removal adopts a weak alkaline ultrasonic oil removal process: Sodium phosphate 20-25g / L, sodium carbonate 20-25g / L, Jintel NP-10 degreasing agent 0.5-1.5g / L, tank temperature 65-75℃, degreasing time 8-12min.

[0027] Preferably, the pickling activation adopts the following pickling activation process: Phosphoric acid 23-28 mL / L, ammonium bifluoride 18-22 g / L, room temperature operation, pickling time 50-70 s.

[0028] After pretreatment of the magnesium alloy workpiece, the micro-arc oxidation layer is prepared by the following magnesium alloy micro-arc oxidation process.

[0029] Preferably, the magnesium alloy micro-arc oxidation process includes the following components and process parameters: Sodium phosphate 10-14g / L, potassium hydroxide 1.8-2.2g / L, potassium fluorozirconate 2-3g / L, constant current mode, anode current density 6A / dm 2, pulse frequency 500Hz, duty cycle 20%, oxidation time 8-12min, electrolyte temperature 20-25℃, magnesium alloy workpiece as anode and titanium plate as cathode.

[0030] The magnesium alloy workpiece is subjected to micro-arc oxidation and then a chemical pre-plated nickel layer is prepared by the current alkaline chemical nickel plating process.

[0031] Preferably, the thickness of the chemical pre-plated nickel layer is 0.5-1.5 μm.

[0032] Preferably, the chemical pre-plated nickel layer is prepared by using the ERANI GG-186 alkaline chemical nickel plating process of Chaobang Chemical: ERANI GG-186 A additive 35~45mL / L, ERANI GG-186 B ​​reducing agent 140~160mL / L, operating temperature 85~92℃, plating solution pH 8~9.5.

[0033] The magnesium alloy workpiece is electrolessly plated with nickel and then the electroless copper layer is prepared by the current electroless copper plating process.

[0034] Preferably, the thickness of the chemical copper plating layer is 7-13 μm.

[0035] Preferably, the chemical copper plating layer is prepared by using the GG-145 alkaline rapid chemical copper plating process of Chaobang Chemical: GG-145A agent 80~120mL / L, GG-145B agent 80~120mL / L, plating solution pH value 12~13, plating tank temperature 45~55℃.

[0036] After the magnesium alloy workpiece is electrolessly copper-plated, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a copper-zinc alloy plating layer.

[0037] Preferably, the copper-zinc alloy coating has a thickness of 5 to 10 μm.

[0038] Preferably, the polythiocyanate copper-zinc alloy plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 14-20 g / L, polymeric zinc thiocyanate 12-18 g / L, polymeric sodium thiocyanate 140-180 g / L, copper-zinc alloy brightener 8-12 mL / L, plating solution pH 9-10, plating tank temperature 35-45 °C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, a brass angle code-named H59 is used as the anode, the brass angle is placed in the titanium anode blue, the area ratio of the anode to the cathode is >3:1, and the anode moves 3 to 5 m / min.

[0039] Preferably, the copper-zinc alloy brightener comprises the following components in weight fractions: 6-10 parts of N,N'-di-n-propylethylenediamine, 1-2 parts of waterborne polyurethane resin, 8-12 parts of polyacrylamide with a molecular weight less than 8000, and 77-87 parts of deionized water.

[0040] After the magnesium alloy workpiece is plated with copper-zinc alloy, the potassium chloride zinc-iron alloy plating process of the present invention is used to prepare a zinc-iron alloy plating layer.

[0041] Preferably, the zinc-iron alloy coating has a thickness of 10 to 22 μm.

[0042] Preferably, the potassium chloride zinc-iron alloy plating process includes the following components and process parameters: Zinc chloride 50-70 g / L, ferrous chloride tetrahydrate 2-12 g / L, potassium chloride 180-220 g / L, boric acid 25-32 g / L, complexing agent 8-40 g / L, brightener 0.1-0.2 mL / L, auxiliary agent 20-30 mL / L, plating solution pH 4.5-5.6, plating tank temperature 15-30 ° C, cathode current density 1-3 A / dm 2 , the cathode moves 3 to 5 m / min, a zinc plate with a mass fraction of ≥99.95% is used as the anode, and the area ratio of the cathode to the anode is 2:1; during production, a 30% mass fraction of ferrous chloride tetrahydrate solution is added to the plating tank to keep its concentration within the process range.

[0043] Preferably, the ligand in the potassium chloride galvanized iron alloy plating process includes sodium gluconate and sodium sulfosalicylate, the mass ratio of sodium gluconate to sodium sulfosalicylate is 3:(1-3), and the sodium gluconate and sodium sulfosalicylate are mixed in the said ratio and stirred evenly.

[0044] Preferably, the brightener in the potassium chloride galvanized iron alloy plating process includes o-chlorobenzaldehyde and formic acid, and the mass ratio of o-chlorobenzaldehyde to formic acid is 1:(0.8-1.2). After mixing o-chlorobenzaldehyde and formic acid in the said ratio, stir until all solids are dissolved.

[0045] Preferably, the auxiliary agents in the potassium chloride galvanized iron alloy plating process include a sulfonation product of a fatty alcohol polyoxyethylene ether with a model number of OX-105 and aminosulfonic acid, sodium benzoate, and nicotinic acid. Calculated by weight, the sulfonation product of a fatty alcohol polyoxyethylene ether with a model number of OX-105 and aminosulfonic acid is 17 to 23 parts, sodium benzoate is 5 to 7 parts, nicotinic acid is 0.4 to 0.6 parts, and water is 80 to 90 parts. The above three intermediates are added to water according to the weight fractions and stirred until all the solids are dissolved.

[0046] Preferably, the potassium chloride zinc-iron alloy plating solution is prepared as follows: a) Add 70% water into the plating tank according to the volume of the plating solution, add zinc chloride, potassium chloride, boric acid, and complexing agent according to the process requirements, and stir to dissolve the above substances; b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solid matter is dissolved; c) Add brightener and auxiliary agent according to the process requirements, stir evenly, adjust the pH of the plating solution to the process range with 10% sodium hydroxide solution or 3% hydrochloric acid, and add water to the specified volume; d) at 0.15A / dm 2 The electrolysis was carried out for 60 min at the current density.

[0047] The magnesium alloy workpiece is plated with galvanized iron alloy and a trivalent chromium passivation film is prepared by a trivalent chromium passivation process.

[0048] Preferably, the trivalent chromium passivation film is prepared using TRIROS 348 zinc-iron blue-white passivation agent developed by Chaobang Chemical: TRIROS 348 zinc iron blue-white passivator 135-175 mL / L, passivation solution pH 2.0-2.8, operating temperature 30-60°C, immersion time 30-60s, air stirring.

[0049] Preferably, the trivalent chromium passivation film is prepared using TRIROS BP-885 trivalent chromium black passivation agent developed by Chaobang Chemical: TRIROS BP-885A agent 40~80mL / L, TRIROS BP-885B agent 30~70mL / L, passivation temperature 20~30℃, passivation solution pH value 2.3~2.7, passivation time 40~120s.

[0050] After the magnesium alloy workpiece was passivated with trivalent chromium, the graphene-modified sealing layer was prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0051] Dilute PRODICO 480 graphene modified sealer with water to 2.5-3.2 times to prepare the sealing solution. Immerse the plated parts in the sealing solution for 8-15 seconds. Drain after leaving the tank, and use high-pressure air to blow away the sealing solution remaining on the surface of the plated parts. After sealing, dry and cure at 70-80°C for 20-35 minutes.

[0052] Embodiment 1: like Figure 1 As shown, a process method for micro-arc oxidation and galvanized iron alloy plating of a magnesium alloy workpiece includes pre-treatment of a magnesium alloy substrate 1, and sequentially preparing a micro-arc oxidation layer 2, a chemical pre-plated nickel layer 3, a chemically plated copper layer 4, a copper-zinc alloy plating layer 5, a zinc-iron alloy plating layer 6, a trivalent chromium blue-white passivation film 7, and a graphene modified sealing layer 8 on the pre-treated magnesium alloy substrate 1 from the inside to the outside.

[0053] 1. Pre-treatment: The magnesium alloy workpiece substrate 1 is pre-treated by using the current magnesium alloy pre-treatment process.

[0054] 1) Degreasing: The following weak alkaline ultrasonic degreasing process was used: sodium phosphate 20 g / L, sodium carbonate 20 g / L, Jintel NP-10 degreasing agent 1.2 g / L, tank temperature 70°C, and degreasing time 10 min.

[0055] 2) Pickling activation: The following magnesium alloy pickling activation process was adopted: 25 mL / L phosphoric acid, 20 g / L ammonium bifluoride, room temperature operation, and pickling time of 60 s.

[0056] 2. Micro-arc oxidation: After the magnesium alloy workpiece is pre-treated, the micro-arc oxidation layer 2 is prepared by the following magnesium alloy micro-arc oxidation process.

[0057] Sodium phosphate 12g / L, potassium hydroxide 2g / L, potassium fluorozirconate 2.5g / L, constant current mode, anode current density 6A / dm 2 , pulse frequency 500 Hz, duty cycle 20%, oxidation time 10 min, electrolyte temperature 22 °C, magnesium alloy workpiece as anode, and titanium plate as cathode.

[0058] 3. Chemical pre-nickel plating: After micro-arc oxidation, the magnesium alloy workpiece is subjected to ERANI GG-186 alkaline chemical nickel plating process of Chaobang Chemical to prepare a chemical pre-plated nickel layer 3, and the coating thickness is 1 μm.

[0059] ERANI GG-186 A additive 40mL / L, ERANI GG-186 B ​​reducing agent 150mL / L, operating temperature 88℃, plating solution pH 8.2.

[0060] 4. Chemical copper plating: After the magnesium alloy workpiece is pre-plated with nickel, a chemical copper plating layer 4 is prepared by using the GG-145 alkaline rapid chemical copper plating process of Chaobang Chemical, and the coating thickness is 10 μm.

[0061] GG-145A agent 100mL / L, GG-145B agent 100mL / L, plating solution pH is 12.5, plating tank temperature is 50℃.

[0062] 5. Copper-zinc alloy: After the magnesium alloy workpiece is electrolessly copper-plated, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a copper-zinc alloy coating 5, and the coating thickness is 7 μm.

[0063] 1) Preparation of copper-zinc alloy brightener: The copper-zinc alloy brightener comprises the following components in weight fractions: 8 parts of N,N'-di-n-propylethylenediamine, 1.5 parts of waterborne polyurethane resin, 10 parts of polyacrylamide with a molecular weight less than 8000, and 82 parts of deionized water. The three intermediates are added into water and mixed uniformly to obtain the brightener.

[0064] 2) Plating: Polymeric cuprous thiocyanate 17g / L, polymeric zinc thiocyanate 16g / L, polymeric sodium thiocyanate 160g / L, copper-zinc alloy brightener 10mL / L, plating solution pH 9.5, plating tank temperature 40℃, cathode current density 1A / dm 2 , the cathode moves 4m / min, a brass angle code-named H59 is used as the anode, the brass angle is placed in the titanium anode blue, the area ratio of the anode to the cathode is >3:1, and the anode moves 4m / min.

[0065] 6. Galvanized iron alloy: After the magnesium alloy workpiece is plated with copper-zinc alloy, the potassium chloride zinc-iron alloy plating process of the present invention is used to prepare a zinc-iron alloy coating 6, and the coating thickness is 15 μm.

[0066] 1) Preparation of complexing agent: Sodium glucose heptanate and sodium sulfosalicylate are mixed in a mass ratio of 3:2 and stirred evenly to obtain the complexing agent.

[0067] 2) Prepare brightener: The brightener is obtained by mixing o-chlorobenzaldehyde and formic acid in a mass ratio of 1:1 and stirring until all the solids are dissolved.

[0068] 3) Preparation of auxiliary agents: Calculated by weight, 20 parts of the sulfonation product of fatty alcohol polyoxyethylene ether model OX-105 and aminosulfonic acid, 6 parts of sodium benzoate, 0.5 parts of nicotinic acid, and 85 parts of water. Add the above three intermediates into water and stir until the solid matter is completely dissolved to obtain the auxiliary agent.

[0069] 4) Preparation of potassium chloride zinc-iron alloy plating solution: a) Add 70% water into the plating tank according to the volume of the plating solution, add zinc chloride, potassium chloride, boric acid, and complexing agent according to the process requirements, and stir to dissolve the above substances; b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solid matter is dissolved; c) Add brightener and auxiliary agent according to the process requirements, stir evenly, adjust the pH of the plating solution to 5.4 with 10% by mass sodium hydroxide solution or 3% by mass hydrochloric acid, and add water to the specified volume; d) at 0.15A / dm 2 The electrolysis was carried out for 60 min at the current density.

[0070] 5) Plating: Zinc chloride 65g / L, ferrous chloride tetrahydrate 11g / L, potassium chloride 210g / L, boric acid 28g / L, complexing agent 37g / L, brightener 0.15mL / L, auxiliary agent 25mL / L, plating solution pH 5.4, plating tank temperature 25℃, cathode current density 2A / dm 2 , the cathode moves at 4m / min, the anode is made of zinc plate with a mass fraction of ≥99.9%, and the area ratio of the cathode to the anode is 2:1; during production, 30% of ferrous chloride tetrahydrate solution is added to the plating tank to maintain its mass concentration at the required value.

[0071] 7. Passivation: After the magnesium alloy workpiece is plated with galvanized iron alloy, the trivalent chromium blue-white passivation film is prepared using the TRIROS 348 zinc-iron blue-white passivation process of Chaobang Chemical7.

[0072] TRIROS 348 zinc iron blue-white passivator 150mL / L, passivation solution pH 2.4, operating temperature 45℃, immersion time 45s, air stirring.

[0073] The specific process is "film removal with sulfuric acid with a volume fraction of 0.2% → water washing → passivation → water washing → draining after leaving the tank".

[0074] 8. Closure: After the magnesium alloy workpiece is passivated with trivalent chromium, a graphene-modified sealing layer 8 is prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0075] The PRODICO 480 graphene-modified sealer was diluted with water to 2.8 times to prepare the sealing solution. The plated parts were immersed in the sealing solution for 10 seconds, drained after leaving the tank, and the sealing solution remaining on the surface of the plated parts was blown away with high-pressure air. After the plated parts were sealed, they were dried and cured at 75°C for 30 minutes.

[0076] Embodiment 2: like Figure 1 As shown, a process method for micro-arc oxidation and galvanized iron alloy plating of a magnesium alloy workpiece includes pre-treatment of a magnesium alloy substrate 1, and sequentially preparing a micro-arc oxidation layer 2, a chemical pre-plated nickel layer 3, a chemically plated copper layer 4, a copper-zinc alloy plating layer 5, a zinc-iron alloy plating layer 6, a trivalent chromium blue-white passivation film 7, and a graphene modified sealing layer 8 on the pre-treated magnesium alloy substrate 1 from the inside to the outside.

[0077] 1. Pre-treatment: The magnesium alloy workpiece substrate 1 is pre-treated by using the current magnesium alloy pre-treatment process.

[0078] 1) Degreasing: The following weak alkaline ultrasonic degreasing process was used: sodium phosphate 25 g / L, sodium carbonate 25 g / L, Jintel NP-10 degreasing agent 0.8 g / L, tank temperature 65°C, and degreasing time 10 min.

[0079] 2) Pickling activation: The following magnesium alloy pickling activation process was adopted: 28 mL / L phosphoric acid, 22 g / L ammonium bifluoride, room temperature operation, and pickling time of 50 s.

[0080] 2. Micro-arc oxidation: After the magnesium alloy workpiece is pre-treated, the micro-arc oxidation layer 2 is prepared by the following magnesium alloy micro-arc oxidation process.

[0081] Sodium phosphate 14g / L, potassium hydroxide 2.2g / L, potassium fluorozirconate 3g / L, constant current mode, anode current density 6A / dm 2 , pulse frequency 500 Hz, duty cycle 20%, oxidation time 8 min, electrolyte temperature 20 °C, magnesium alloy workpiece as anode, and titanium plate as cathode.

[0082] 3. Chemical pre-nickel plating: After micro-arc oxidation, the magnesium alloy workpiece is subjected to ERANI GG-186 alkaline chemical nickel plating process of Chaobang Chemical to prepare a chemical pre-plated nickel layer 3, and the coating thickness is 1 μm.

[0083] ERANI GG-186 A additive 45mL / L, ERANI GG-186 B ​​reducing agent 160mL / L, operating temperature 85℃, plating solution pH 9.2.

[0084] 4. Chemical copper plating: After the magnesium alloy workpiece is pre-plated with nickel, a chemical copper plating layer 4 is prepared by using the GG-145 alkaline rapid chemical copper plating process of Chaobang Chemical, and the coating thickness is 10 μm.

[0085] GG-145A agent 120mL / L, GG-145B agent 120mL / L, plating solution pH is 12, plating tank temperature is 45℃.

[0086] 5. Copper-zinc alloy: After the magnesium alloy workpiece is electrolessly copper-plated, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a copper-zinc alloy coating 5, and the coating thickness is 7 μm.

[0087] 1) Preparation of copper-zinc alloy brightener: The copper-zinc alloy brightener comprises the following components in weight fractions: 8 parts of N,N'-di-n-propylethylenediamine, 1.5 parts of waterborne polyurethane resin, 10 parts of polyacrylamide with a molecular weight less than 8000, and 82 parts of deionized water. The three intermediates are added into water and mixed uniformly to obtain the brightener.

[0088] 2) Plating: Polymeric cuprous thiocyanate 20g / L, polymeric zinc thiocyanate 18g / L, polymeric sodium thiocyanate 180g / L, copper-zinc alloy brightener 10mL / L, plating solution pH 9, plating tank temperature 40℃, cathode current density 1A / dm 2 , the cathode moves 4m / min, a brass angle code-named H59 is used as the anode, the brass angle is placed in the titanium anode blue, the area ratio of the anode to the cathode is >3:1, and the anode moves 4m / min.

[0089] 6. Galvanized iron alloy: After the magnesium alloy workpiece is plated with copper-zinc alloy, the potassium chloride zinc-iron alloy plating process of the present invention is used to prepare a zinc-iron alloy coating 6, and the coating thickness is 15 μm.

[0090] 1) Preparation of complexing agent: Sodium glucose heptanate and sodium sulfosalicylate are mixed in a mass ratio of 3:2 and stirred evenly to obtain the complexing agent.

[0091] 2) Prepare brightener: The brightener is obtained by mixing o-chlorobenzaldehyde and formic acid in a mass ratio of 1:1 and stirring until all the solids are dissolved.

[0092] 3) Preparation of auxiliary agents: Calculated by weight, 20 parts of the sulfonation product of fatty alcohol polyoxyethylene ether model OX-105 and aminosulfonic acid, 6 parts of sodium benzoate, 0.5 parts of nicotinic acid, and 85 parts of water. Add the above three intermediates into water and stir until the solid matter is completely dissolved to obtain the auxiliary agent.

[0093] 4) Preparation of potassium chloride zinc-iron alloy plating solution: a) Add 70% water into the plating tank according to the volume of the plating solution, add zinc chloride, potassium chloride, boric acid, and complexing agent according to the process requirements, and stir to dissolve the above substances; b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solid matter is dissolved; c) Add brightener and auxiliary agent according to the process requirements, stir evenly, adjust the pH of the plating solution to 4.6 with 10% sodium hydroxide solution or 3% hydrochloric acid, and add water to the specified volume; d) at 0.15A / dm 2 The electrolysis was carried out for 60 min at the current density.

[0094] 5) Plating: Zinc chloride 70g / L, ferrous chloride tetrahydrate 12g / L, potassium chloride 220g / L, boric acid 32g / L, complexing agent 40g / L, brightener 0.15mL / L, auxiliary agent 25mL / L, plating solution pH 4.6, plating tank temperature 15℃, cathode current density 2A / dm 2 , the cathode moves 4m / min, a zinc plate with a mass fraction of ≥99.95% is used as the anode, and the area ratio of the cathode to the anode is 2:1; during production, a 30% mass fraction of ferrous chloride tetrahydrate solution is added to the plating tank to keep its concentration within the process range.

[0095] 7. Passivation: After the magnesium alloy workpiece is plated with galvanized iron alloy, the trivalent chromium blue-white passivation film is prepared using the TRIROS 348 zinc-iron blue-white passivation process of Chaobang Chemical7.

[0096] TRIROS 348 zinc iron blue-white passivator 175mL / L, passivation solution pH 2.2, operating temperature 35℃, immersion time 45s, air stirring.

[0097] The specific process is "film removal with sulfuric acid with a volume fraction of 0.2% → water washing → passivation → water washing → draining after leaving the tank".

[0098] 8. Closure: After the magnesium alloy workpiece is passivated with trivalent chromium, a graphene-modified sealing layer 8 is prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0099] Dilute PRODICO 480 graphene-modified sealer with water to 2.8 times to prepare the sealing solution. Immerse the plated parts in the sealing solution for 10 seconds, drain them after leaving the tank, and use high-pressure air to blow away the sealing solution remaining on the surface of the plated parts. After sealing, dry and cure them at 80°C for 20 minutes.

[0100] Embodiment 3: like Figure 1 As shown, a process method for micro-arc oxidation and galvanized iron alloy plating of a magnesium alloy workpiece includes pre-treatment of a magnesium alloy substrate 1, and sequentially preparing a micro-arc oxidation layer 2, a chemical pre-plated nickel layer 3, a chemically plated copper layer 4, a copper-zinc alloy plating layer 5, a zinc-iron alloy plating layer 6, a trivalent chromium black passivation film 7, and a graphene modified sealing layer 8 on the pre-treated magnesium alloy substrate 1 from the inside to the outside.

[0101] 1. Pre-treatment: The magnesium alloy workpiece substrate 1 is pre-treated by using the current magnesium alloy pre-treatment process.

[0102] 1) Degreasing: The following weak alkaline ultrasonic degreasing process was used: sodium phosphate 25 g / L, sodium carbonate 20 g / L, Jintel NP-10 degreasing agent 1.0 g / L, tank temperature 70°C, and degreasing time 10 min.

[0103] 2) Pickling activation: The following magnesium alloy pickling activation process was adopted: 26 mL / L phosphoric acid, 20 g / L ammonium bifluoride, room temperature operation, and pickling time of 60 s.

[0104] 2. Micro-arc oxidation: After the magnesium alloy workpiece is pre-treated, the micro-arc oxidation layer 2 is prepared by the following magnesium alloy micro-arc oxidation process.

[0105] Sodium phosphate 10g / L, potassium hydroxide 1.8g / L, potassium fluorozirconate 2g / L, constant current mode, anode current density 6A / dm 2 , pulse frequency 500 Hz, duty cycle 20%, oxidation time 12 min, electrolyte temperature 25 °C, magnesium alloy workpiece as anode, and titanium plate as cathode.

[0106] 3. Chemical pre-nickel plating: After micro-arc oxidation, the magnesium alloy workpiece is subjected to ERANI GG-186 alkaline chemical nickel plating process of Chaobang Chemical to prepare a chemical pre-plated nickel layer 3, and the coating thickness is 1 μm.

[0107] ERANI GG-186 A additive 35mL / L, ERANI GG-186 B ​​reducing agent 140mL / L, operating temperature 92℃, plating solution pH 9.

[0108] 4. Chemical copper plating: After the magnesium alloy workpiece is pre-plated with nickel, a chemical copper plating layer 4 is prepared by using the GG-145 alkaline rapid chemical copper plating process of Chaobang Chemical, and the coating thickness is 10 μm.

[0109] GG-145A agent 80mL / L, GG-145B agent 80mL / L, plating solution pH is 13, and plating tank temperature is 55℃.

[0110] 5. Copper-zinc alloy: After the magnesium alloy workpiece is electrolessly copper-plated, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a copper-zinc alloy coating 5, and the coating thickness is 7 μm.

[0111] 1) Preparation of copper-zinc alloy brightener: The copper-zinc alloy brightener comprises the following components in weight fractions: 8 parts of N,N'-di-n-propylethylenediamine, 1.5 parts of waterborne polyurethane resin, 10 parts of polyacrylamide with a molecular weight less than 8000, and 82 parts of deionized water. The three intermediates are added into water and mixed uniformly to obtain the brightener.

[0112] 2) Plating: Polymeric cuprous thiocyanate 14g / L, polymeric zinc thiocyanate 12g / L, polymeric sodium thiocyanate 140g / L, copper-zinc alloy brightener 10mL / L, plating solution pH 10, plating tank temperature 45°C, cathode current density 1A / dm 2 , the cathode moves 4m / min, a brass angle code-named H59 is used as the anode, the brass angle is placed in the titanium anode blue, the area ratio of the anode to the cathode is >3:1, and the anode moves 4m / min.

[0113] 6. Galvanized iron alloy: After the magnesium alloy workpiece is plated with copper-zinc alloy, the potassium chloride zinc-iron alloy plating process of the present invention is used to prepare a zinc-iron alloy coating 6, and the coating thickness is 15 μm.

[0114] 1) Preparation of complexing agent: Sodium glucose heptanate and sodium sulfosalicylate are mixed in a mass ratio of 3:2 and stirred evenly to obtain the complexing agent.

[0115] 2) Prepare brightener: The brightener is obtained by mixing o-chlorobenzaldehyde and formic acid in a mass ratio of 1:1 and stirring until all the solids are dissolved.

[0116] 3) Preparation of auxiliary agents: Calculated by weight, 20 parts of the sulfonation product of fatty alcohol polyoxyethylene ether model OX-105 and aminosulfonic acid, 6 parts of sodium benzoate, 0.5 parts of nicotinic acid, and 85 parts of water. Add the above three intermediates into water and stir until the solid matter is completely dissolved to obtain the auxiliary agent.

[0117] 4) Preparation of potassium chloride zinc-iron alloy plating solution: The potassium chloride zinc-iron alloy plating solution is prepared as follows: a) Add 70% water into the plating tank according to the volume of the plating solution, add zinc chloride, potassium chloride, boric acid, and complexing agent according to the process requirements, and stir to dissolve the above substances; b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solid matter is dissolved; c) Add brightener and auxiliary agent according to the process requirements, stir evenly, adjust the pH of the plating solution to 4.8 with 10% by mass sodium hydroxide solution or 3% by mass hydrochloric acid, and add water to the specified volume; d) at 0.15A / dm 2 The electrolysis was carried out for 60 min at the current density.

[0118] 5) Plating: Zinc chloride 50g / L, ferrous chloride tetrahydrate 8g / L, potassium chloride 180g / L, boric acid 25g / L, complexing agent 28g / L, brightener 0.15mL / L, auxiliary agent 25mL / L, plating solution pH 4.8, plating tank temperature 25℃, cathode current density 2A / dm 2 , the cathode moves 4m / min, a zinc plate with a mass fraction of ≥99.95% is used as the anode, and the area ratio of the cathode to the anode is 2:1; during production, a 30% mass fraction of ferrous chloride tetrahydrate solution is added to the plating tank to keep its concentration within the process range.

[0119] 7. Passivation: After the magnesium alloy workpiece is plated with galvanized iron alloy, a trivalent chromium black passivation film is prepared using TRIROS BP-885 trivalent chromium black passivation agent from Chaobang Chemical 7: TRIROS BP-885A agent 60mL / L, TRIROS BP-885B agent 50mL / L, passivation temperature 25℃, passivation solution pH 2.5, passivation time 80s.

[0120] The specific process is "lightening with 1.5% volume fraction nitric acid → water washing → passivation → water washing → draining after leaving the tank".

[0121] 8. Closure: After the magnesium alloy workpiece is passivated with trivalent chromium, the graphene-modified sealing layer 8 is prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0122] Dilute PRODICO 480 graphene-modified sealer with water to 2.8 times to prepare the sealing solution. Immerse the plated parts in the sealing solution for 10 seconds, drain them after leaving the tank, and use high-pressure air to blow away the sealing solution remaining on the surface of the plated parts. After sealing, dry and cure them at 70°C for 35 minutes.

[0123] Embodiment 4: like Figure 1 As shown, a process method for micro-arc oxidation and galvanized iron alloy plating of a magnesium alloy workpiece includes pre-treatment of a magnesium alloy substrate 1, and sequentially preparing a micro-arc oxidation layer 2, a chemical pre-plated nickel layer 3, a chemically plated copper layer 4, a copper-zinc alloy plating layer 5, a zinc-iron alloy plating layer 6, a trivalent chromium black passivation film 7, and a graphene modified sealing layer 8 on the pre-treated magnesium alloy substrate 1 from the inside to the outside.

[0124] 1. Pre-treatment: The magnesium alloy workpiece substrate 1 is pre-treated by using the current magnesium alloy pre-treatment process.

[0125] 1) Degreasing: The following weak alkaline ultrasonic degreasing process was used: sodium phosphate 20 g / L, sodium carbonate 25 g / L, Jintel NP-10 degreasing agent 1.0 g / L, tank temperature 70°C, and degreasing time 10 min.

[0126] 2) Pickling activation: The following magnesium alloy pickling activation process was adopted: 24 mL / L phosphoric acid, 19 g / L ammonium bifluoride, room temperature operation, and pickling time of 65 s.

[0127] 2. Micro-arc oxidation: After the magnesium alloy workpiece is pre-treated, the micro-arc oxidation layer 2 is prepared by the following magnesium alloy micro-arc oxidation process.

[0128] Sodium phosphate 13g / L, potassium hydroxide 2.1g / L, potassium fluorozirconate 2.8g / L, constant current mode, anode current density 6A / dm 2 , pulse frequency 500 Hz, duty cycle 20%, oxidation time 9 min, electrolyte temperature 21 °C, magnesium alloy workpiece as anode, and titanium plate as cathode.

[0129] 3. Chemical pre-nickel plating: After micro-arc oxidation, the magnesium alloy workpiece is subjected to ERANI GG-186 alkaline chemical nickel plating process of Chaobang Chemical to prepare a chemical pre-plated nickel layer 3, and the coating thickness is 1 μm.

[0130] ERANI GG-186 A additive 42mL / L, ERANI GG-186 B ​​reducing agent 155mL / L, operating temperature 87℃, and plating solution pH 8.8.

[0131] 4. Chemical copper plating: After the magnesium alloy workpiece is pre-plated with nickel, a chemical copper plating layer 4 is prepared by using the GG-145 alkaline rapid chemical copper plating process of Chaobang Chemical, and the coating thickness is 10 μm.

[0132] GG-145A agent 110mL / L, GG-145B agent 110mL / L, plating solution pH is 12.2, and plating tank temperature is 47°C.

[0133] 5. Copper-zinc alloy: After the magnesium alloy workpiece is electrolessly copper-plated, the polymerized thiocyanate copper-zinc alloy plating process of the present invention is used to prepare a copper-zinc alloy coating 5, and the coating thickness is 7 μm.

[0134] 1) Preparation of copper-zinc alloy brightener: The copper-zinc alloy brightener comprises the following components in weight fractions: 8 parts of N,N'-di-n-propylethylenediamine, 1.5 parts of waterborne polyurethane resin, 10 parts of polyacrylamide with a molecular weight less than 8000, and 82 parts of deionized water. The three intermediates are added into water and mixed uniformly to obtain the brightener.

[0135] 2) Plating: Polymeric cuprous thiocyanate 19g / L, polymeric zinc thiocyanate 17g / L, polymeric sodium thiocyanate 175g / L, copper-zinc alloy brightener 10mL / L, plating solution pH 9.8, plating tank temperature 37°C, cathode current density 1A / dm 2 , the cathode moves 4m / min, a brass angle code-named H59 is used as the anode, the brass angle is placed in the titanium anode blue, the area ratio of the anode to the cathode is >3:1, and the anode moves 4m / min.

[0136] 6. Galvanized iron alloy: After the magnesium alloy workpiece is plated with copper-zinc alloy, the potassium chloride zinc-iron alloy plating process of the present invention is used to prepare a zinc-iron alloy coating 6, and the coating thickness is 15 μm.

[0137] 1) Preparation of complexing agent: Sodium glucose heptanate and sodium sulfosalicylate are mixed in a mass ratio of 3:2 and stirred evenly to obtain the complexing agent.

[0138] 2) Prepare brightener: The brightener is obtained by mixing o-chlorobenzaldehyde and formic acid in a mass ratio of 1:1 and stirring until all the solids are dissolved.

[0139] 3) Preparation of auxiliary agents: Calculated by weight, 20 parts of the sulfonation product of fatty alcohol polyoxyethylene ether model OX-105 and aminosulfonic acid, 6 parts of sodium benzoate, 0.5 parts of nicotinic acid, and 85 parts of water. Add the above three intermediates into water and stir until the solid matter is completely dissolved to obtain the auxiliary agent.

[0140] 4) Preparation of potassium chloride zinc-iron alloy plating solution: a) Add 70% water into the plating tank according to the volume of the plating solution, add zinc chloride, potassium chloride, boric acid, and complexing agent according to the process requirements, and stir to dissolve the above substances; b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solid matter is dissolved; c) Add brightener and auxiliary agent according to the process requirements, stir evenly, adjust the pH of the plating solution to 5.6 with 10% sodium hydroxide solution or 3% hydrochloric acid, and add water to the specified volume; d) at 0.10A / dm 2 The electrolysis was carried out for 90 min at the current density.

[0141] 5) Plating: Zinc chloride 65g / L, ferrous chloride tetrahydrate 11g / L, potassium chloride 210g / L, boric acid 30g / L, complexing agent 36g / L, brightener 0.15mL / L, auxiliary agent 25mL / L, plating solution pH 5.6, plating tank temperature 22℃, cathode current density 2A / dm 2 , the cathode moves 4m / min, a zinc plate with a mass fraction of ≥99.95% is used as the anode, and the area ratio of the cathode to the anode is 2:1; during production, a 30% mass fraction of ferrous chloride tetrahydrate solution is added to the plating tank to keep its concentration within the process range.

[0142] 7. Passivation: After the magnesium alloy workpiece is plated with galvanized iron alloy, a trivalent chromium black passivation film is prepared using TRIROS BP-885 trivalent chromium black passivator produced by Chaobang Chemical7.

[0143] TRIROS BP-885A agent 80mL / L, TRIROS BP-885B agent 70mL / L, passivation temperature 20℃, passivation solution pH 2.7, passivation time 70s.

[0144] The specific process is "lightening with 1.5% volume fraction nitric acid → water washing → passivation → water washing → draining after leaving the tank".

[0145] 8. Closure: After the magnesium alloy workpiece is passivated with trivalent chromium, a graphene-modified sealing layer 8 is prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0146] Dilute PRODICO 480 graphene-modified sealer with water to 2.8 times to prepare the sealing solution. Immerse the plated parts in the sealing solution for 10 seconds, drain them after leaving the tank, and use high-pressure air to blow away the sealing solution remaining on the surface of the plated parts. After sealing, dry and cure them at 77°C for 25 minutes.

[0147] Test Example 1: A neutral salt spray test was carried out in accordance with GB / T 10125-2021 "Salt spray test for corrosion test in artificial atmosphere". The magnesium alloy galvanized iron alloy samples prepared in Example 1 and Example 2 had no white rust on the surface after 480 hours, and the magnesium alloy galvanized iron alloy samples prepared in Example 3 and Example 4 had no white rust on the surface after 438 hours. The prepared coating has excellent corrosion resistance.

[0148] Test Example 2: The coating adhesion was tested according to GB / T 5270-2005 "Review of Test Methods for Adhesion Strength of Electrodeposited and Chemically Deposited Metal Coatings on Metal Substrates". The magnesium alloy galvanized iron alloy samples prepared in Example 1, Example 2, Example 3 and Example 4 were placed in a heating furnace and heated to 150°C for 30 minutes. After being taken out, they were immediately placed in room temperature water for cooling. The coating did not blister or fall off, and the coating adhesion met the standard requirements.

[0149] Test Example 3: According to GJB 150.9A-2009 "Military Equipment Laboratory Environmental Test Methods Part 10: Mold Test", a mold test was conducted for 28 days. No mold grew on the surface of the magnesium alloy galvanized iron alloy samples prepared in Example 1, Example 2, Example 3 and Example 4, which met the requirements of industry standards.

[0150] Test example 4: According to GB / T 2423.3-2016 "Basic Environmental Test Procedure for Electrical and Electronic Products Test Ca: Steady State Humidity Test Method", a constant humidity test was carried out. The magnesium alloy galvanized iron alloy samples prepared in Example 1, Example 2, Example 3 and Example 4 were tested for 720 hours at a temperature of 40°C and a relative humidity of 93%. There was no visible change in the appearance of the coating, and the coating structure had good resistance to humidity and heat changes.

[0151] 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 process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece, characterized in that: The following steps are involved: (1) Using magnesium alloy pretreatment process to degrease and pickle and activate magnesium alloy workpieces; (2) After the magnesium alloy workpiece is pre-treated, a micro-arc oxidation process is used to prepare a micro-arc oxidation layer; (3) A chemical pre-plated nickel layer is prepared by a chemical nickel plating process after micro-arc oxidation of the magnesium alloy workpiece; (4) After the magnesium alloy workpiece is electrolessly nickel-plated, an electroless copper plating process is used to prepare an electroless copper plating layer; (5) After the magnesium alloy workpiece is electrolessly copper-plated, a copper-zinc alloy coating is prepared by a polymerized thiocyanate copper-zinc alloy plating process; (6) After the magnesium alloy workpiece is plated with copper-zinc alloy, a zinc-iron alloy coating is prepared by a potassium chloride zinc-iron alloy plating process; (7) Magnesium alloy workpieces are plated with zinc-iron alloy and then passivated to prepare a trivalent chromium passivation film; (8) Preparation of graphene modified sealing layer after passivation of zinc-iron alloy coating on magnesium alloy workpiece; The potassium chloride zinc-iron alloy plating process includes the following components and process parameters: Zinc chloride 50-70 g / L, ferrous chloride tetrahydrate 2-12 g / L, potassium chloride 180-220 g / L, boric acid 25-32 g / L, complexing agent 8-40 g / L, brightener 0.1-0.2 mL / L, auxiliary agent 20-30 mL / L, plating solution pH 4.5-5.6, plating tank temperature 15-30 ° C, cathode current density 1-3 A / dm 2 , the cathode moves 3-5 m / min, a zinc plate with a mass fraction of ≥99.95% is used as the anode, and the area ratio of the cathode to the anode is 2:1; during production, a 30% mass fraction of ferrous chloride tetrahydrate solution is added to the plating tank to keep its concentration within the process range; The complexing agent includes sodium gluconate and sodium sulfosalicylate, the mass ratio of sodium gluconate to sodium sulfosalicylate is 3:(1-3), and sodium gluconate and sodium sulfosalicylate are mixed according to the ratio and stirred evenly; The brightener comprises o-chlorobenzaldehyde and formic acid, the mass ratio of o-chlorobenzaldehyde to formic acid is 1:(0.8-1.2), and o-chlorobenzaldehyde and formic acid are mixed in the said ratio and stirred until all the solids are dissolved; The auxiliary agent comprises a sulfonated product of fatty alcohol polyoxyethylene ether with model OX-105 and aminosulfonic acid, sodium benzoate, and nicotinic acid. Calculated by weight, the sulfonated product of fatty alcohol polyoxyethylene ether with model OX-105 and aminosulfonic acid is 17 to 23 parts, sodium benzoate is 5 to 7 parts, nicotinic acid is 0.4 to 0.6 parts, and water is 80 to 90 parts. The above three intermediates are added into water according to the weight fractions and stirred until all the solids are dissolved.

2. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1, characterized in that: The polythiocyanate copper-zinc alloy plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 14-20 g / L, polymeric zinc thiocyanate 12-18 g / L, polymeric sodium thiocyanate 140-180 g / L, copper-zinc alloy brightener 8-12 mL / L, plating solution pH 9-10, plating tank temperature 35-45 °C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3-5 m / min, a brass angle code-named H59 is used as the anode, the brass angle is placed in the titanium anode blue, the area ratio of the anode to the cathode is >3:1, and the anode moves 3-5 m / min; The copper-zinc alloy brightener comprises the following components in weight fractions: 6-10 parts of N,N'-di-n-propylethylenediamine, 1-2 parts of waterborne polyurethane resin, 8-12 parts of polyacrylamide with a molecular weight less than 8000, and 77-87 parts of deionized water.

3. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1, characterized in that: The magnesium alloy micro-arc oxidation process includes the following components and process parameters: Sodium phosphate 10-14g / L, potassium hydroxide 1.8-2.2g / L, potassium fluorozirconate 2-3g / L, constant current mode, anode current density 6A / dm 2 , pulse frequency 500Hz, duty cycle 20%, oxidation time 8-12min, electrolyte temperature 20-25℃, magnesium alloy workpiece as anode and titanium plate as cathode.

4. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1, characterized in that: The chemical pre-plated nickel layer is prepared by using the ERANI GG-186 alkaline chemical nickel plating process: ERANI GG-186 A additive 35~45mL / L, ERANI GG-186 B ​​reducing agent 140~160mL / L, operating temperature 85~92℃, plating solution pH 8~9.

5.

5. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1, characterized in that: The chemical copper plating layer is prepared by using the GG-145 alkaline rapid chemical copper plating process: GG-145A agent 80~120mL / L, GG-145B agent 80~120mL / L, plating solution pH value 12~13, plating tank temperature 45~55℃.

6. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1, characterized in that: The trivalent chromium passivation film is prepared using TRIROS 348 zinc iron blue-white passivation agent: TRIROS 348 zinc iron blue-white passivator 135-175 mL / L, pH value of passivation solution 2.0-2.8, operating temperature 30-60°C, immersion time 30-60s, air stirring; The trivalent chromium passivation film is prepared using TRIROS BP-885 trivalent chromium black passivation agent: TRIROS BP-885A agent 40~80mL / L, TRIROS BP-885B agent 30~70mL / L, passivation temperature 20~30℃, passivation solution pH value 2.3~2.7, passivation time 40~120s.

7. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1, characterized in that: The graphene-modified sealing layer is prepared using PRODICO 480 graphene-modified sealing agent: Dilute PRODICO 480 graphene modified sealer with water to 2.5-3.2 times to prepare the sealing solution. Immerse the plated parts in the sealing solution for 8-15 seconds. Drain after leaving the tank, and use high-pressure air to blow away the sealing solution remaining on the surface of the plated parts. The sealed plated parts are dried and cured at 70-80°C for 20-35 minutes.

8. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1 or 5, characterized in that: The thickness of the chemical copper plating layer is 7-13 μm.

9. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1, characterized in that: The thickness of the copper-zinc alloy coating is 5-10 μm.

10. The process for micro-arc oxidation and galvanizing of a magnesium alloy workpiece according to claim 1, characterized in that: The thickness of the zinc-iron alloy coating is 10-22 μm.

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