Process for galvanizing magnesium alloy parts with zinc-iron alloy in potassium chloride

Abstract

The application discloses a potassium chloride zinc-iron alloy plating process for magnesium alloy parts, and sequentially prepares a chemical zinc deposition layer, a cyanide-free pre-copper plating layer, a pyrophosphate copper plating layer, a zinc-iron alloy plating layer, a passivation film and a graphene modified sealing layer on the magnesium alloy substrate from inside to outside. The potassium chloride zinc-iron alloy plating process is as follows: zinc chloride 50-70 g / L, ferrous chloride tetrahydrate 2-12 g / L, potassium chloride 180-220 g / L, boric acid 25-35 g / L, complexing agent 8-40 g / L, brightener 0.1-0.2 mL / L, auxiliary agent 20-30 mL / L, plating solution pH value 4.5-5.6, plating bath temperature 15-30 DEG C, cathode current density 1-3 A / dm 2 , cathode moving speed 3-5 m / min. The magnesium alloy zinc-iron alloy plated sample prepared by the application and sealed by trivalent chromium blue-white passivation and graphene modified sealing agent has no white rust on the surface after neutral salt spray test for 480 h according to the GB / T 10125-2021 standard, and the plating layer has excellent corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to a potassium chloride zinc plating process for magnesium alloy parts. Background Technology

[0002] Magnesium alloys possess high specific strength and specific stiffness, as well as advantages such as electromagnetic shielding, vibration damping, and good machinability. They are widely used in military, automotive, aircraft, mobile phone, computer, and electromechanical industrial products, and are hailed as "green engineering materials of the century." However, magnesium alloys are chemically reactive, and the oxides formed on their surface are porous and cannot effectively protect the substrate. Therefore, developing highly corrosion-resistant protective layers for magnesium alloys is a research hotspot in the industry.

[0003] There are many methods for surface treatment of magnesium alloys, mainly including electrophoretic coating, surface plating, micro-arc oxidation, anodizing, chemical conversion coating, and spraying organic coatings. [1] However, these surface treatment methods all have certain limitations, and their protective effects need further improvement. Currently, in production applications, electrophoretic coating technology is mainly used to prepare a protective layer on the surface of magnesium alloys. This protective layer has relatively good protective performance for magnesium alloy parts.

[0004] The technology for preparing protective layers on magnesium alloy surfaces through electroplating and electroless plating is still in the research stage. There have been some research reports in the industry on electroplating and electroless nickel plating of magnesium alloys. [2-4] However, the electroplated and electroless nickel plating layers prepared on the surface of magnesium alloys offer no electrochemical protection to the magnesium alloy substrate, and a significant potential difference exists between the substrate and the plating layer. Existing electroplated and electroless nickel plating layers typically contain a certain number of pores, allowing corrosive media to penetrate these pores and cause galvanic corrosion, rapidly damaging the magnesium alloy substrate. Therefore, there are currently no reports of mass production applications of this electroplating technology for magnesium alloys.

[0005] In recent years, hydroxyl graphene-modified sealing agents have made significant progress in improving the corrosion resistance of coatings, and the prepared sealing layers possess self-healing properties. [5] It is used to seal the zinc plating layer and zinc-nickel alloy plating layer that have been passivated by trivalent chromium, thus solving the problem that trivalent chromium passivation does not have self-healing properties.

[0006] References: [1]. Fu Haifeng, Lü Dongxian, Tan Huachao, et al. Research status and trend of magnesium alloy surface modification technology [J]. Heat Treatment, 2015, 30(3): 1-5. [2]. Yu Gang, Yi Xiangrong, Lei Xiping, et al. Study on the formation mechanism of nickel electrodeposition and electroplating process of magnesium alloy [J]. Electroplating and Environmental Protection, 2009, 29(1): 21-25. [3]. Zhang Xiaohuan, Feng Lajun, Lu Man. Optimization of electroless nickel-phosphorus plating process and study on coating performance of magnesium alloy surface [J]. Materials Protection, 2022, 55(6): 86-91. [4]. Xu Gang, Zhang Xiuzhi, Zhang Yishuai. Preparation and performance study of Ni-P / Ni coating on magnesium alloy surface [J]. Surface Technology, 2010, 39(1): 71-73+80. [5]. Guo Chongwu, Lai Huanwen, Xia Liang, Study on the performance of graphene oxide in coating sealant [J], Electroplating & Finishing, 2021, 40(9): 696-700. Summary of the Invention

[0007] To address the poor corrosion resistance of existing electroplated protective layers on magnesium alloys, this invention provides a potassium chloride-zinc-iron alloy plating process for magnesium alloy parts. To achieve the above objective, this invention employs the following technical solution:

[0008] A potassium chloride-zinc-iron alloy plating process for magnesium alloy parts includes the following steps:

[0009] (1) Degreasing and pickling activation of magnesium alloy workpieces;

[0010] (2) After the pretreatment of magnesium alloy workpieces, the existing magnesium alloy chemical zinc deposition process is used to prepare a chemical zinc deposition layer.

[0011] (3) After chemical zinc immersion, magnesium alloy workpieces are prepared with a cyanide-free pre-plated copper layer by polymer thiocyanate copper plating process.

[0012] (4) After the magnesium alloy workpiece is polymerized with thiocyanate and copper is plated, the pyrophosphate copper plating layer is prepared using the current pyrophosphate copper plating process.

[0013] (5) After copper pyrophosphate plating of magnesium alloy workpieces, zinc-iron alloy coating is prepared by potassium chloride plating process.

[0014] (6) After zinc-iron alloy plating, magnesium alloy workpieces are passivated to prepare a passivation film;

[0015] (7) After passivation, magnesium alloy workpieces are sealed to prepare a sealing layer;

[0016] The potassium chloride zinc-iron alloy plating process includes the following components and process parameters:

[0017] Zinc chloride 50–70 g / L, ferrous chloride tetrahydrate 2–12 g / L, potassium chloride 180–220 g / L, boric acid 25–35 g / L, complexing agent 8–40 g / L, brightener 0.1–0.2 mL / L, auxiliary agent 20–30 mL / L, plating bath pH 4.5–5.6, plating bath temperature 15–30℃, cathode current density 1–3 A / dm³ 2 The cathode moves at a speed of 3-5 m / min, and a zinc plate with a mass fraction of 99.9% is used as the anode. The area ratio of the cathode to the anode is 2:1. During production, a 30% ferrous chloride tetrahydrate solution is added to the plating bath to maintain its concentration within the process range.

[0018] The ligands include sodium gluconate and sodium sulfosalicylate, with a mass ratio of sodium gluconate to sodium sulfosalicylate of 3:(1-3). Sodium gluconate and sodium sulfosalicylate are mixed in the above ratio and stirred until homogeneous.

[0019] The brightening agent includes o-chlorobenzaldehyde and formic acid, with a mass ratio of o-chlorobenzaldehyde to formic acid of 1:(0.8-1.2). The o-chlorobenzaldehyde and formic acid are mixed in the above ratio and stirred until the solids are completely dissolved.

[0020] The auxiliary agent includes a sulfonated product of fatty alcohol polyoxyethylene ether and aminosulfonic acid (model OX-105), sodium benzoate, and nicotinic acid. By weight fraction, the sulfonated product of fatty alcohol polyoxyethylene ether and aminosulfonic acid (model OX-105) is 17-23 parts, sodium benzoate is 5-7 parts, nicotinic acid is 0.4-0.6 parts, and water is 80-90 parts. The above three intermediates are added to water according to the weight fraction and stirred until the solids are completely dissolved.

[0021] In some embodiments, the polymeric thiocyanate copper plating process includes the following components and process parameters:

[0022] Polymeric cuprous thiocyanate 18–24 g / L, polymeric sodium thiocyanate 130–170 g / L, sodium hydroxyethylidene diphosphonate 20–30 g / L, copper plating brightener 8–12 mL / L, plating bath pH 12–13, plating bath temperature 30–40℃, cathode current density 0.5–1.5 A / dm³ 2 The cathode moves at a speed of 3-5 m / min. Oxygen-free electrolytic copper particles are used as the anode. The copper particles are loaded into a titanium anode basket. The area ratio of the anode to the cathode is >3:1. The anode moves at a speed of 3-5 m / min.

[0023] In some embodiments, the copper plating brightener comprises the following components by weight fraction: 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.

[0024] In some embodiments, the pickling and activation process employs the following magnesium alloy pickling and activation process:

[0025] Use 23–28 mL / L phosphoric acid and 18–22 g / L ammonium bifluoride. Operate at room temperature and pickle for 50–70 seconds.

[0026] In some embodiments, the chemical zinc plating layer is prepared using the following magnesium alloy chemical zinc plating process:

[0027] Zinc sulfate heptahydrate 25-35 g / L, potassium pyrophosphate 100-120 g / L, potassium fluoride 6-9 g / L, bath temperature 68-72℃, zinc precipitation time 8-12 min.

[0028] In some embodiments, the passivation film is prepared using the TRIROS 348 zinc-iron blue-white passivation process:

[0029] TRIROS 348 zinc-iron blue-white passivating agent 135-175 mL / L, passivation solution pH 2.0-2.8, operating temperature 30-60℃, immersion time 30-60 s, air agitation.

[0030] In some embodiments, the graphene-modified sealing layer is prepared using PRODICO 480 graphene-modifying sealing agent:

[0031] Prepare a sealing solution by diluting PRODICO 480 graphene modified sealant with water to a ratio of 2.5 to 3.2. Immerse the plated parts in the sealing solution for 8 to 15 seconds, drain them after removal from the tank, and blow off any residual sealing solution on the surface of the plated parts with high-pressure air. After sealing, dry and cure the parts at 70 to 80°C for 20 to 35 minutes.

[0032] In some embodiments, the thickness of the zinc-iron coating is 9–16 μm.

[0033] In some embodiments, the thickness of the cyanide-free pre-plated copper layer is 2–6 μm.

[0034] In some embodiments, the thickness of the copper pyrophosphate plating layer is 10–20 μm.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The potassium chloride zinc-iron alloy plating process of the present invention for magnesium alloy parts involves sequentially preparing a chemical zinc plating layer, a cyanide-free pre-plated copper layer, a pyrophosphate copper plating layer, and a zinc-iron alloy plating layer on a magnesium alloy substrate. The zinc-iron alloy plating layer is an anodic plating layer relative to the copper plating layer. This plating structure can effectively prevent the corrosive medium from eroding towards the magnesium alloy substrate, overcoming the defects of directly plating nickel after chemical zinc plating on the magnesium alloy substrate or chemical nickel plating which does not have an electrochemical protective effect.

[0037] 2. The potassium chloride plating process for zinc-iron alloy on magnesium alloy parts of the present invention has a self-healing sealing layer prepared by a hydroxyl graphene modified sealing agent on the zinc-iron alloy plating layer after trivalent chromium passivation, which overcomes the defect that the trivalent chromium passivation film does not have self-healing properties. Attached Figure Description

[0038] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0039] Figure 1 These are schematic diagrams of the coating structures in Embodiments 1, 2, 3 and 4 of the present invention. Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0041] A potassium chloride zinc-iron alloy plating process for magnesium alloy parts includes pretreatment of the magnesium alloy workpiece and sequential preparation of a chemical zinc plating layer, a cyanide-free pre-plated copper layer, a pyrophosphate copper plating layer, a potassium chloride zinc-iron alloy plating layer, a passivation film, and a graphene-modified sealing layer on the magnesium alloy substrate from the inside out.

[0042] Magnesium alloy workpieces are degreased and acid-washed for activation using a magnesium alloy pretreatment process.

[0043] Preferably, the degreasing process employs a weakly alkaline ultrasonic degreasing process:

[0044] Sodium phosphate 20-25 g / L, sodium carbonate 20-25 g / L, Gintel NP-10 degreasing agent 0.5-1.5 g / L, bath temperature 65-75℃, degreasing time 8-12 min.

[0045] Preferably, the pickling and activation process employs the following pickling and activation process:

[0046] Use 23–28 mL / L phosphoric acid and 18–22 g / L ammonium bifluoride. Operate at room temperature and pickle for 50–70 seconds.

[0047] After pretreatment, magnesium alloy workpieces are prepared with a chemical zinc plating layer using the following magnesium alloy chemical zinc plating process.

[0048] Zinc sulfate heptahydrate 25-35 g / L, potassium pyrophosphate 100-120 g / L, potassium fluoride 6-9 g / L, bath temperature 68-72℃, zinc precipitation time 8-12 min.

[0049] After chemical zinc immersion, magnesium alloy workpieces are prepared with a cyanide-free pre-plated copper layer using the polymeric thiocyanate copper plating process of this invention.

[0050] Preferably, the thickness of the cyanide-free pre-plated copper layer is 2–6 μm.

[0051] Polymeric cuprous thiocyanate 18–24 g / L, polymeric sodium thiocyanate 130–170 g / L, sodium hydroxyethylidene diphosphonate 20–30 g / L, copper plating brightener 8–12 mL / L, plating bath pH 12–13, plating bath temperature 30–40℃, cathode current density 0.5–1.5 A / dm³ 2 The cathode moves at a speed of 3-5 m / min. Oxygen-free electrolytic copper particles are used as the anode. The copper particles are loaded into a titanium anode basket. The area ratio of the anode to the cathode is >3:1. The anode moves at a speed of 3-5 m / min.

[0052] Preferably, the copper plating brightener comprises the following components by weight fraction: 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.

[0053] Preferably, the copper plating brightener is prepared as follows: 770-870 parts by weight of deionized water are added to a reaction vessel, and 60-100 parts of N,N'-di-n-propylethylenediamine, 10-20 parts of waterborne polyurethane resin, and 80-120 parts of polyacrylamide with a molecular weight of less than 8000 are added while stirring. The mixture is stirred until homogeneous to obtain the brightener.

[0054] After cyanide-free copper plating, magnesium alloy workpieces are prepared with pyrophosphate copper plating layer using the existing pyrophosphate copper plating process.

[0055] Preferably, the thickness of the copper pyrophosphate plating layer is 10–20 μm.

[0056] After copper plating with pyrophosphate, magnesium alloy workpieces are coated with zinc-iron alloy using the potassium chloride zinc-iron alloy plating process of this invention.

[0057] Preferably, the thickness of the zinc-iron alloy coating is 9–16 μm.

[0058] Zinc chloride 50–70 g / L, ferrous chloride tetrahydrate 2–12 g / L, potassium chloride 180–220 g / L, boric acid 25–35 g / L, complexing agent 8–40 g / L, brightener 0.1–0.2 mL / L, auxiliary agent 20–30 mL / L, plating bath pH 4.5–5.6, plating bath temperature 15–30℃, cathode current density 1–3 A / dm³ 2 The cathode moves at a speed of 3-5 m / min, and a zinc plate with a mass fraction of 99.9% is used as the anode. The area ratio of the cathode to the anode is 2:1. During production, a 30% ferrous chloride tetrahydrate solution is added to the plating bath to maintain its concentration within the process range.

[0059] The ligands include sodium gluconate and sodium sulfosalicylate, with a mass ratio of sodium gluconate to sodium sulfosalicylate of 3:(1-3). Sodium gluconate and sodium sulfosalicylate are mixed in the above ratio and stirred until homogeneous.

[0060] The brightener includes o-chlorobenzaldehyde and formic acid, with a mass ratio of o-chlorobenzaldehyde to formic acid of 1:(0.8-1.2). The o-chlorobenzaldehyde and formic acid are mixed in the above ratio and stirred until the solids are completely dissolved.

[0061] The auxiliary agent includes a sulfonated product of fatty alcohol polyoxyethylene ether and aminosulfonic acid (model OX-105), sodium benzoate, and nicotinic acid. By weight fraction, the sulfonated product of fatty alcohol polyoxyethylene ether and aminosulfonic acid (model OX-105) is 17-23 parts, sodium benzoate is 5-7 parts, nicotinic acid is 0.4-0.6 parts, and water is 80-90 parts. The above three intermediates are added to water according to the weight fraction and stirred until the solids are completely dissolved.

[0062] The potassium chloride zinc-iron alloy plating solution is prepared according to the following method:

[0063] a) Add 70% water to the plating tank according to the volume of the plating solution, and add zinc chloride, potassium chloride, boric acid and complexing agent according to the process requirements, and stir to dissolve the above substances;

[0064] b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solids dissolve;

[0065] c) Add brightener and auxiliary agents according to 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;

[0066] d) at 0.15A / dm 2 Electrolyze for 60 minutes at the current density.

[0067] Magnesium alloy workpieces are prepared using the TRIROS 348 zinc-iron blue-white passivation process developed by Chaobang Chemical after being plated with zinc-iron alloy.

[0068] TRIROS 348 zinc-iron blue-white passivating agent 135-175 mL / L, passivation solution pH 2.0-2.8, operating temperature 30-60℃, immersion time 30-60 s, air agitation.

[0069] After trivalent chromium passivation, a graphene-modified sealing layer was prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0070] Prepare a sealing solution by diluting PRODICO 480 graphene modified sealant with water to a ratio of 2.5 to 3.2. Immerse the plated parts in the sealing solution for 8 to 15 seconds, drain them after removal from the tank, and blow off any residual sealing solution on the surface of the plated parts with high-pressure air. After sealing, dry and cure the plated parts at 70 to 80°C for 20 to 35 minutes. Example 1

[0071] like Figure 1 As shown, a potassium chloride zinc-iron alloy plating process for magnesium alloy parts includes: pretreatment of magnesium alloy substrate 1, and sequential preparation of chemical zinc plating layer 2, cyanide-free pre-plated copper layer 3, pyrophosphate copper plating layer 4, potassium chloride zinc-iron alloy plating layer 5, trivalent chromium passivation film 6, and graphene modified sealing layer 7 on the pretreated magnesium alloy substrate 1 from the inside out.

[0072] 1. Pre-processing:

[0073] The magnesium alloy workpiece substrate 1 is pretreated using the existing magnesium alloy pretreatment process.

[0074] 1) Degreasing:

[0075] The following weakly alkaline ultrasonic degreasing process was adopted: sodium phosphate 20g / L, sodium carbonate 20g / L, GINET NP-10 degreasing agent 1.2g / L, bath temperature 70℃, and degreasing time 10min.

[0076] 2) Acid pickling and activation:

[0077] The following pickling and activation process for magnesium alloys was adopted: 25 mL / L phosphoric acid, 20 g / L ammonium bifluoride, room temperature operation, pickling time 60 s.

[0078] 2. Chemical zinc precipitation:

[0079] After pretreatment, the magnesium alloy workpiece is prepared with a chemical zinc coating layer 2 using the following chemical zinc coating process.

[0080] Zinc sulfate heptahydrate 30 g / L, potassium pyrophosphate 110 g / L, potassium fluoride 7 g / L, bath temperature 70℃, zinc precipitation time 10 min.

[0081] 3. Cyanide-free pre-plated copper:

[0082] After chemical zinc immersion, a cyanide-free pre-plated copper layer 3 is prepared using the polymeric thiocyanate copper plating process of the present invention, with a plating thickness of 4 μm.

[0083] 1) Preparation of copper plating brightener:

[0084] By weight, 820 parts of deionized water were added to a reaction vessel, and 80 parts of N,N'-di-n-propylethylenediamine, 15 parts of waterborne polyurethane resin, and 100 parts of GRO-70 polyacrylamide were added under stirring. The mixture was stirred until homogeneous to obtain the brightener.

[0085] 2) Plating:

[0086] The plating solution contained 21 g / L of polycuprous thiocyanate, 150 g / L of polysodium thiocyanate, 25 g / L of sodium hydroxyethylidene diphosphonate, and 10 mL / L of copper plating brightener. The pH of the plating bath was 12.5, the bath temperature was 35℃, and the cathode current density was 1.0 A / dm³. 2 The cathode moves at a speed of 4 m / min. Oxygen-free electrolytic copper particles are used as the anode. The copper particles are loaded into a titanium anode basket. The area ratio of the anode to the cathode is >3:1. The anode moves at a speed of 4 m / min.

[0087] 4. Copper plating with pyrophosphate:

[0088] After cyanide-free copper pre-plating, magnesium alloy workpieces are coated with pyrophosphate copper plating process to prepare pyrophosphate copper plating layer 4, with a plating thickness of 15μm.

[0089] 5. Galvanized iron alloy:

[0090] After copper plating with pyrophosphate, the magnesium alloy workpiece is coated with zinc-iron alloy using the potassium chloride zinc-iron alloy plating process of the present invention to prepare zinc-iron alloy coating 5 with a coating thickness of 12μm.

[0091] 1) Preparation of the complexing agent:

[0092] The complexing agent is obtained by mixing sodium gluconate and sodium sulfosalicylate in a mass ratio of 3:2 and stirring until homogeneous.

[0093] 2) Preparation of brightening agent:

[0094] o-chlorobenzaldehyde and formic acid are mixed in a mass ratio of 1:1 and stirred until all the solids are dissolved to obtain the brightener.

[0095] 3) Preparation of auxiliary agents:

[0096] The auxiliary agent is obtained by adding 20 parts of the sulfonated 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 according to the weight fractions. The three intermediates are stirred in water until all the solids are dissolved to obtain the auxiliary agent.

[0097] 4) Preparation of potassium chloride zinc-iron alloy plating solution:

[0098] a) Add 70% water to the plating tank according to the volume of the plating solution, and add zinc chloride, potassium chloride, boric acid and complexing agent according to the process requirements, and stir to dissolve the above substances;

[0099] b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solids dissolve;

[0100] c) Add brightener and auxiliary agents according to process requirements, stir evenly, adjust the pH of the plating solution to 5.4 with 10% sodium hydroxide solution or 3% hydrochloric acid, and add water to the specified volume;

[0101] d) at 0.15A / dm 2 Electrolyze for 60 minutes at the current density.

[0102] 5) Plating:

[0103] Zinc chloride 65 g / L, ferrous chloride tetrahydrate 11 g / L, potassium chloride 210 g / L, boric acid 30 g / L, complexing agent 37 g / L, brightener 0.15 mL / L, auxiliary agent 25 mL / L, plating bath pH 5.4, plating tank temperature 25℃, cathode current density 2 A / dm³ 2 The cathode moves at a speed of 4 m / min, and the anode is made of zinc plate with a mass fraction of 99.9%. The area ratio of the cathode to the anode is 2:1. During production, a 30% ferrous chloride tetrahydrate solution is added to the plating tank to maintain its mass concentration at the required value.

[0104] 6. Passivation:

[0105] After zinc-iron alloy plating, magnesium alloy workpieces are treated with the TRIROS 348 zinc-iron blue-white passivation process of Chaobang Chemical to prepare a trivalent chromium passivation film.

[0106] TRIROS 348 zinc-iron blue-white passivating agent 150mL / L, passivation solution pH 2.4, operating temperature 45℃, immersion time 45s, air agitation.

[0107] The specific process is as follows: "removal of film with sulfuric acid of volume fraction of 0.2% → water washing → passivation → water washing → draining after removal from the tank".

[0108] 7. Enclosed:

[0109] After trivalent chromium passivation, a graphene-modified sealing layer 7 was prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0110] Prepare a sealing solution by diluting PRODICO 480 graphene-modified sealant with water to a ratio of 2.8. Immerse the plated parts in the sealing solution for 10 seconds, drain them after removal from the tank, and blow off the residual sealing solution on the surface of the plated parts with high-pressure air. After sealing, dry and cure at 75°C for 30 minutes.

[0111] Example 2:

[0112] like Figure 1 As shown, a potassium chloride zinc-iron alloy plating process for magnesium alloy parts includes: pretreatment of magnesium alloy substrate 1, and sequential preparation of chemical zinc plating layer 2, cyanide-free pre-plated copper layer 3, pyrophosphate copper plating layer 4, potassium chloride zinc-iron alloy plating layer 5, trivalent chromium passivation film 6, and graphene modified sealing layer 7 on the pretreated magnesium alloy substrate 1 from the inside out.

[0113] 1. Pre-processing:

[0114] The magnesium alloy workpiece substrate 1 is pretreated using the existing magnesium alloy pretreatment process.

[0115] 1) Degreasing:

[0116] The following weakly alkaline ultrasonic degreasing process was adopted: sodium phosphate 25g / L, sodium carbonate 25g / L, GINET NP-10 degreasing agent 0.8g / L, bath temperature 65℃, and degreasing time 10min.

[0117] 2) Acid pickling and activation:

[0118] The following pickling and activation process for magnesium alloys was adopted: 28 mL / L phosphoric acid, 22 g / L ammonium bifluoride, room temperature operation, pickling time 50 s.

[0119] 2. Chemical zinc precipitation:

[0120] After pretreatment, the magnesium alloy workpiece is prepared with a chemical zinc coating layer 2 using the following chemical zinc coating process.

[0121] Zinc sulfate heptahydrate 35 g / L, potassium pyrophosphate 120 g / L, potassium fluoride 9 g / L, bath temperature 68℃, zinc precipitation time 10 min.

[0122] 3. Cyanide-free pre-plated copper:

[0123] After chemical zinc immersion, a cyanide-free pre-plated copper layer 3 is prepared using the polymeric thiocyanate copper plating process of the present invention, with a plating thickness of 4 μm.

[0124] 1) Preparation of copper plating brightener:

[0125] By weight, 820 parts of deionized water were added to a reaction vessel, 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. The mixture was stirred until homogeneous to obtain the brightener.

[0126] 2) Plating:

[0127] Polymeric cuprous thiocyanate 24 g / L, polymeric sodium thiocyanate 170 g / L, sodium hydroxyethylidene diphosphonate 25 g / L, copper plating brightener 10 mL / L, plating bath pH 12, plating bath temperature 30℃, cathode current density 1.0 A / dm³ 2 The cathode moves at a speed of 4 m / min. Oxygen-free electrolytic copper particles are used as the anode. The copper particles are loaded into a titanium anode basket. The area ratio of the anode to the cathode is >3:1. The anode moves at a speed of 4 m / min.

[0128] 4. Copper plating with pyrophosphate:

[0129] After cyanide-free copper pre-plating, magnesium alloy workpieces are prepared with pyrophosphate copper plating layer 4 using the existing pyrophosphate copper plating process, with a plating thickness of 15μm.

[0130] 5. Galvanized iron alloy:

[0131] After copper plating with pyrophosphate, the magnesium alloy workpiece is coated with potassium chloride zinc-iron alloy using the potassium chloride zinc-iron alloy plating process of the present invention to prepare a potassium chloride zinc-iron alloy coating 5 with a coating thickness of 12μm.

[0132] 1) Preparation of the complexing agent:

[0133] The complexing agent is obtained by mixing sodium gluconate and sodium sulfosalicylate in a mass ratio of 3:2 and stirring until homogeneous.

[0134] 2) Preparation of brightening agent:

[0135] o-chlorobenzaldehyde and formic acid are mixed in a mass ratio of 1:1 and stirred until all the solids are dissolved to obtain the brightener.

[0136] 3) Preparation of auxiliary agents:

[0137] The auxiliary agent is obtained by adding 20 parts of the sulfonated 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 according to the weight fractions. The three intermediates are stirred in water until all the solids are dissolved to obtain the auxiliary agent.

[0138] 4) Preparation of potassium chloride zinc-iron alloy plating solution:

[0139] a) Add 70% water to the plating tank according to the volume of the plating solution, and add zinc chloride, potassium chloride, boric acid and complexing agent according to the process requirements, and stir to dissolve the above substances;

[0140] b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solids dissolve;

[0141] c) Add brightener and auxiliary agents according to 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;

[0142] d) at 0.15A / dm 2 Electrolyze for 60 minutes at the current density.

[0143] 5) Plating:

[0144] Zinc chloride 70 g / L, ferrous chloride tetrahydrate 12 g / L, potassium chloride 220 g / L, boric acid 35 g / L, complexing agent 40 g / L, brightener 0.15 mL / L, auxiliary agent 25 mL / L, plating solution pH 4.6, plating tank temperature 15℃, cathode current density 2 A / dm³ 2 The cathode moves at a speed of 4 m / min, and a zinc plate with a mass fraction of 99.9% is used as the anode. The area ratio of the cathode to the anode is 2:1. During production, a 30% ferrous chloride tetrahydrate solution is added to the plating bath to maintain its concentration within the process range.

[0145] 6. Passivation:

[0146] After zinc-iron alloy plating, magnesium alloy workpieces are treated with the TRIROS 348 zinc-iron blue-white passivation process of Chaobang Chemical to prepare a trivalent chromium passivation film.

[0147] TRIROS 348 zinc-iron blue-white passivating agent 175mL / L, passivation solution pH 2.2, operating temperature 35℃, immersion time 45s, air agitation.

[0148] The specific process is as follows: "removal of film with sulfuric acid of volume fraction of 0.2% → water washing → passivation → water washing → draining after removal from the tank".

[0149] 7. Enclosed:

[0150] After trivalent chromium passivation, a graphene-modified sealing layer 7 was prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0151] Prepare a sealing solution by diluting PRODICO 480 graphene-modified sealant with water to a ratio of 2.8. Immerse the plated parts in the sealing solution for 10 seconds, drain them after removal from the tank, and blow off the residual sealing solution on the surface of the plated parts with high-pressure air. After sealing, dry and cure at 80°C for 20 minutes.

[0152] Example 3:

[0153] like Figure 1 As shown, a potassium chloride zinc-iron alloy plating process for magnesium alloy parts includes: pretreatment of magnesium alloy substrate 1, and sequential preparation of chemical zinc plating layer 2, cyanide-free pre-plated copper layer 3, pyrophosphate copper plating layer 4, potassium chloride zinc-iron alloy plating layer 5, trivalent chromium passivation film 6, and graphene modified sealing layer 7 on the pretreated magnesium alloy substrate 1 from the inside out.

[0154] 1. Pre-processing:

[0155] The magnesium alloy workpiece substrate 1 is pretreated using the existing magnesium alloy pretreatment process.

[0156] 1) Degreasing:

[0157] The following weakly alkaline ultrasonic degreasing process was adopted: sodium phosphate 25g / L, sodium carbonate 20g / L, GINET NP-10 degreasing agent 1.0g / L, bath temperature 70℃, and degreasing time 10min.

[0158] 2) Acid pickling and activation:

[0159] The following pickling and activation process for magnesium alloys was adopted: 26 mL / L phosphoric acid, 20 g / L ammonium bifluoride, room temperature operation, pickling time 60 s.

[0160] 2. Chemical zinc precipitation:

[0161] After pretreatment, the magnesium alloy workpiece is prepared with a chemical zinc coating layer 2 using the following chemical zinc coating process.

[0162] Zinc sulfate heptahydrate 25 g / L, potassium pyrophosphate 100 g / L, potassium fluoride 6 g / L, bath temperature 72℃, zinc precipitation time 12 min.

[0163] 3. Cyanide-free pre-plated copper:

[0164] After chemical zinc immersion, a cyanide-free pre-plated copper layer 3 is prepared using the polymeric thiocyanate copper plating process of the present invention, with a plating thickness of 4 μm.

[0165] 1) Preparation of copper plating brightener:

[0166] By weight, 820 parts of deionized water were added to a reaction vessel, 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. The mixture was stirred until homogeneous to obtain the brightener.

[0167] 2) Plating:

[0168] The plating solution contained 18 g / L of polycuprous thiocyanate, 130 g / L of polysodium thiocyanate, and 10 mL / L of copper plating brightener. The pH of the plating bath was 12.5, the bath temperature was 40℃, and the cathode current density was 1.0 A / dm³. 2The cathode moves at a speed of 4 m / min. Oxygen-free electrolytic copper particles are used as the anode. The copper particles are loaded into a titanium anode basket. The area ratio of the anode to the cathode is >3:1. The anode moves at a speed of 4 m / min.

[0169] 4. Copper plating with pyrophosphate:

[0170] After cyanide-free copper pre-plating, magnesium alloy workpieces are prepared with pyrophosphate copper plating layer 4 using the existing pyrophosphate copper plating process, with a plating thickness of 15μm.

[0171] 5. Galvanized iron alloy:

[0172] After copper plating with pyrophosphate, the magnesium alloy workpiece is coated with zinc-iron alloy using the potassium chloride zinc-iron alloy plating process of the present invention to prepare zinc-iron alloy coating 5 with a coating thickness of 12μm.

[0173] 1) Preparation of the complexing agent:

[0174] The complexing agent is obtained by mixing sodium gluconate and sodium sulfosalicylate in a mass ratio of 3:2 and stirring until homogeneous.

[0175] 2) Preparation of brightening agent:

[0176] o-chlorobenzaldehyde and formic acid are mixed in a mass ratio of 1:1 and stirred until all the solids are dissolved to obtain the brightener.

[0177] 3) Preparation of auxiliary agents:

[0178] The auxiliary agent is obtained by adding 20 parts of the sulfonated 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 according to the weight fractions. The three intermediates are stirred in water until all the solids are dissolved to obtain the auxiliary agent.

[0179] 4) Preparation of potassium chloride zinc-iron alloy plating solution:

[0180] The potassium chloride zinc-iron alloy plating solution is prepared according to the following method:

[0181] a) Add 70% water to the plating tank according to the volume of the plating solution, and add zinc chloride, potassium chloride, boric acid and complexing agent according to the process requirements, and stir to dissolve the above substances;

[0182] b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solids dissolve;

[0183] c) Add brightener and auxiliary agents according to process requirements, stir evenly, adjust the pH of the plating solution to 4.8 with 10% sodium hydroxide solution or 3% hydrochloric acid, and add water to the specified volume;

[0184] d) at 0.15A / dm 2Electrolyze for 60 minutes at the current density.

[0185] 5) Plating:

[0186] Zinc chloride 50 g / L, ferrous chloride tetrahydrate 8 g / L, potassium chloride 180 g / L, boric acid 25 g / L, complexing agent 28 g / L, brightener 0.15 mL / L, auxiliary agent 25 mL / L, plating solution pH 4.8, plating tank temperature 25℃, cathode current density 2 A / dm³ 2 The cathode moves at a speed of 4 m / min, and a zinc plate with a mass fraction of 99.9% is used as the anode. The area ratio of the cathode to the anode is 2:1. During production, a 30% ferrous chloride tetrahydrate solution is added to the plating bath to maintain its concentration within the process range.

[0187] 6. Passivation:

[0188] After zinc-iron alloy plating, magnesium alloy workpieces are treated with the TRIROS 348 zinc-iron blue-white passivation process of Chaobang Chemical to prepare a trivalent chromium passivation film.

[0189] TRIROS 348 zinc-iron blue-white passivating agent 135mL / L, passivation solution pH 2.0, operating temperature 35℃, immersion time 35s, air agitation.

[0190] The specific process is as follows: "removal of film with sulfuric acid of volume fraction of 0.2% → water washing → passivation → water washing → draining after removal from the tank".

[0191] 7. Enclosed:

[0192] After trivalent chromium passivation, a graphene-modified sealing layer was prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0193] Prepare a sealing solution by diluting PRODICO 480 graphene-modified sealant with water to a ratio of 2.8. Immerse the plated parts in the sealing solution for 10 seconds, drain them after removal from the tank, and blow off any remaining sealing solution from the surface of the plated parts with high-pressure air. After sealing, dry and cure at 70°C for 35 minutes.

[0194] Example 4:

[0195] like Figure 1 As shown, a potassium chloride zinc-iron alloy plating process for magnesium alloy parts includes: pretreatment of magnesium alloy substrate 1, and sequential preparation of chemical zinc plating layer 2, cyanide-free pre-plated copper layer 3, pyrophosphate copper plating layer 4, potassium chloride zinc-iron alloy plating layer 5, trivalent chromium passivation film 6, and graphene modified sealing layer 7 on the pretreated magnesium alloy substrate 1 from the inside out.

[0196] 1. Pre-processing:

[0197] The magnesium alloy workpiece substrate 1 is pretreated using the existing magnesium alloy pretreatment process.

[0198] 1) Degreasing:

[0199] The following weakly alkaline ultrasonic degreasing process was adopted: sodium phosphate 20g / L, sodium carbonate 25g / L, GINET NP-10 degreasing agent 1.0g / L, bath temperature 70℃, and degreasing time 10min.

[0200] 2) Acid pickling and activation:

[0201] The following pickling and activation process for magnesium alloys was adopted: 24 mL / L phosphoric acid, 19 g / L ammonium bifluoride, room temperature operation, pickling time 65 s.

[0202] 2. Chemical zinc precipitation:

[0203] After pretreatment, the magnesium alloy workpiece is prepared with a chemical zinc coating layer 2 using the following chemical zinc coating process.

[0204] Zinc sulfate heptahydrate 33 g / L, potassium pyrophosphate 115 g / L, potassium fluoride 8 g / L, bath temperature 69℃, zinc precipitation time 9 min.

[0205] 3. Cyanide-free pre-plated copper:

[0206] After chemical zinc immersion, a cyanide-free pre-plated copper layer 3 is prepared using the polymeric thiocyanate copper plating process of the present invention, with a plating thickness of 4 μm.

[0207] 1) Preparation of copper plating brightener:

[0208] By weight, 820 parts of deionized water were added to a reaction vessel, 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. The mixture was stirred until homogeneous to obtain the brightener.

[0209] 2) Plating:

[0210] The plating solution contained 23 g / L of polycuprous thiocyanate, 165 g / L of polysodium thiocyanate, and 10 mL / L of copper plating brightener. The pH of the plating bath was 12.3, the bath temperature was 40℃, and the cathode current density was 1.0 A / dm³. 2 The cathode moves at a speed of 4 m / min. Oxygen-free electrolytic copper particles are used as the anode. The copper particles are loaded into a titanium anode basket. The area ratio of the anode to the cathode is >3:1. The anode moves at a speed of 4 m / min.

[0211] 4. Copper plating with pyrophosphate:

[0212] After cyanide-free copper pre-plating, a pyrophosphate copper plating layer 4 was prepared on the magnesium alloy workpiece using a pyrophosphate copper plating process, with a copper plating layer thickness of 15μm.

[0213] 5. Galvanized iron alloy:

[0214] After copper plating with pyrophosphate, the magnesium alloy workpiece is coated with zinc-iron alloy using the potassium chloride zinc-iron alloy plating process of the present invention to prepare zinc-iron alloy coating 5 with a coating thickness of 12μm.

[0215] 1) Preparation of the complexing agent:

[0216] The complexing agent is obtained by mixing sodium gluconate and sodium sulfosalicylate in a mass ratio of 3:2 and stirring until homogeneous.

[0217] 2) Preparation of brightening agent:

[0218] o-chlorobenzaldehyde and formic acid are mixed in a mass ratio of 1:1 and stirred until all the solids are dissolved to obtain the brightener.

[0219] 3) Preparation of auxiliary agents:

[0220] The auxiliary agent is obtained by adding 20 parts of the sulfonated 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 according to the weight fractions. The three intermediates are stirred in water until all the solids are dissolved to obtain the auxiliary agent.

[0221] 4) Preparation of potassium chloride zinc-iron alloy plating solution:

[0222] a) Add 70% water to the plating tank according to the volume of the plating solution, and add zinc chloride, potassium chloride, boric acid and complexing agent according to the process requirements, and stir to dissolve the above substances;

[0223] b) Add ferrous chloride tetrahydrate according to the process requirements and stir until the solids dissolve;

[0224] c) Add brightener and auxiliary agents according to 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;

[0225] d) at 0.10 A / dm 2 Electrolyze for 90 minutes at the current density.

[0226] 5) Plating:

[0227] Zinc chloride 65 g / L, ferrous chloride tetrahydrate 11 g / L, potassium chloride 210 g / L, boric acid 28 g / L, complexing agent 36 g / L, brightener 0.15 mL / L, auxiliary agent 25 mL / L, plating bath pH 5.6, plating tank temperature 22℃, cathode current density 2 A / dm³ 2The cathode moves at a speed of 4 m / min, and a zinc plate with a mass fraction of 99.9% is used as the anode. The area ratio of the cathode to the anode is 2:1. During production, a 30% ferrous chloride tetrahydrate solution is added to the plating bath to maintain its concentration within the process range.

[0228] 6. Passivation:

[0229] After zinc-iron alloy plating, magnesium alloy workpieces are treated with the TRIROS 348 zinc-iron blue-white passivation process from Chaobang Chemical to prepare a trivalent chromium passivation film.

[0230] TRIROS 348 zinc-iron blue-white passivating agent 165mL / L, passivation solution pH 2.6, operating temperature 55℃, immersion time 35s, air agitation.

[0231] The specific process is as follows: "removal of film with sulfuric acid of volume fraction of 0.2% → water washing → passivation → water washing → draining after removal from the tank".

[0232] 7. Enclosed:

[0233] After trivalent chromium passivation, a graphene-modified sealing layer was prepared using PRODICO 480 graphene-modified sealing agent developed by Chaobang Chemical.

[0234] Prepare a sealing solution by diluting PRODICO 480 graphene-modified sealant with water to a ratio of 2.8. Immerse the plated parts in the sealing solution for 10 seconds, drain them after removal from the tank, and blow off the residual sealing solution on the surface of the plated parts with high-pressure air. After sealing, dry and cure at 77°C for 25 minutes.

[0235] Experimental Example 1:

[0236] According to GB / T 10125–2021 "Civilized Atmosphere Corrosion Test - Salt Spray Test", the magnesium alloy zinc-plated iron alloy samples prepared in Examples 1, 2, 3 and 4 showed no white rust on the surface after 480 hours, indicating that the prepared coatings have excellent corrosion resistance.

[0237] Experimental Example 2:

[0238] According to GB / T 5270–2005 "Review of Test Methods for Adhesion Strength of Electrodeposited and Chemically Deposited Metallic Coatings on Metal Substrates", the adhesion of the coatings was tested. The magnesium alloy zinc-iron alloy samples prepared in Examples 1, 2, 3 and 4 were heated to 150°C in a heating furnace and held for 30 minutes. After being taken out, they were immediately placed in water at room temperature to cool. No blistering or peeling of the coatings was observed, and the adhesion of the coatings met the standard requirements.

[0239] Experimental Example 3:

[0240] According to GJB 150.9A–2009 "Laboratory Environmental Testing Methods for Military Equipment - Part 10: Mold Test", the magnesium alloy galvanized iron alloy samples prepared in Examples 1, 2, 3 and 4 were tested for mold for 28 days. No mold grew on the surface, which meets the requirements of industry standards.

[0241] Experimental Example 4:

[0242] According to GB / T 2423.3-2016 "Basic Environmental Testing Procedures for Electrical and Electronic Products - Test Ca: Constant Damp Heat Test Method", constant damp heat tests were conducted. The magnesium alloy zinc-plated iron alloy samples prepared in Examples 1, 2, 3 and 4 were tested for 720 hours at a temperature of 40℃ and a relative humidity of 93%. No visible changes were observed in the appearance of the coating, indicating that the coating structure has good weather resistance.

[0243] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these are also considered to fall within the protection scope of the present invention.

Claims

1. A potassium chloride-zinc-iron alloy plating process for magnesium alloy parts, characterized in that, Includes the following steps: (1) Degreasing and pickling activation of magnesium alloy workpieces; (2) After the pretreatment of magnesium alloy workpieces, the existing magnesium alloy chemical zinc deposition process is used to prepare a chemical zinc deposition layer. (3) After chemical zinc immersion, magnesium alloy workpieces are prepared with a cyanide-free pre-plated copper layer by polymer thiocyanate copper plating process. (4) After the magnesium alloy workpiece is polymerized with thiocyanate and copper is plated, the pyrophosphate copper plating layer is prepared using the current pyrophosphate copper plating process. (5) After copper pyrophosphate plating of magnesium alloy workpieces, zinc-iron alloy coating is prepared by potassium chloride plating process. (6) After zinc-iron alloy plating, magnesium alloy workpieces are passivated to prepare a passivation film; (7) After passivation, magnesium alloy workpieces are sealed to prepare a sealing layer; 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 25–35 g / L, complexing agent 8–40 g / L, brightener 0.1–0.2 mL / L, auxiliary agent 20–30 mL / L, plating bath pH 4.5–5.6, plating bath temperature 15–30℃, cathode current density 1–3 A / dm³ 2 The cathode moves at a speed of 3-5 m / min, and a zinc plate with a mass fraction of 99.9% is used as the anode. The area ratio of the cathode to the anode is 2:

1. During production, a 30% ferrous chloride tetrahydrate solution is added to the plating bath to maintain its concentration within the process range. The ligands include sodium gluconate and sodium sulfosalicylate, with a mass ratio of sodium gluconate to sodium sulfosalicylate of 3:(1-3). Sodium gluconate and sodium sulfosalicylate are mixed in the above ratio and stirred until homogeneous. The brightening agent includes o-chlorobenzaldehyde and formic acid, with a mass ratio of o-chlorobenzaldehyde to formic acid of 1:(0.8-1.2). The o-chlorobenzaldehyde and formic acid are mixed in the above ratio and stirred until the solids are completely dissolved. The auxiliary agent includes a sulfonated product of fatty alcohol polyoxyethylene ether and aminosulfonic acid (model OX-105), sodium benzoate, and nicotinic acid. By weight fraction, the sulfonated product of fatty alcohol polyoxyethylene ether and aminosulfonic acid (model OX-105) is 17-23 parts, sodium benzoate is 5-7 parts, nicotinic acid is 0.4-0.6 parts, and water is 80-90 parts. The above three intermediates are added to water according to the weight fraction and stirred until the solids are completely dissolved.

2. The potassium chloride zinc plating process for magnesium alloy parts according to claim 1, characterized in that, The aforementioned polymeric thiocyanate copper plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 18–24 g / L, polymeric sodium thiocyanate 130–170 g / L, sodium hydroxyethylidene diphosphonate 20–30 g / L, copper plating brightener 8–12 mL / L, plating bath pH 12–13, plating bath temperature 30–40℃, cathode current density 0.5–1.5 A / dm³ 2 The cathode moves at a speed of 3-5 m / min. Oxygen-free electrolytic copper particles are used as the anode. The copper particles are loaded into a titanium anode basket. The area ratio of the anode to the cathode is >3:

1. The anode moves at a speed of 3-5 m / min.

3. The potassium chloride zinc plating process for magnesium alloy parts according to claim 2, characterized in that, The copper plating brightener comprises the following components by weight fraction: 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.

4. The potassium chloride zinc plating process for magnesium alloy parts according to claim 1, characterized in that, The pickling and activation process described above employs the following magnesium alloy pickling and activation process: Use 23–28 mL / L phosphoric acid and 18–22 g / L ammonium bifluoride. Operate at room temperature and pickle for 50–70 seconds.

5. The potassium chloride zinc plating process for magnesium alloy parts according to claim 1, characterized in that, The aforementioned chemical zinc plating layer is prepared using the following magnesium alloy chemical zinc plating process: Zinc sulfate heptahydrate 25-35 g / L, potassium pyrophosphate 100-120 g / L, potassium fluoride 6-9 g / L, bath temperature 68-72℃, zinc precipitation time 8-12 min.

6. The potassium chloride zinc plating process for magnesium alloy parts according to claim 1, characterized in that, The passivation film was prepared using the TRIROS 348 zinc-iron blue-white passivation process. TRIROS 348 zinc-iron blue-white passivating agent 135-175 mL / L, passivation solution pH 2.0-2.8, operating temperature 30-60℃, immersion time 30-60 s, air agitation.

7. The potassium chloride zinc plating process for magnesium alloy parts according to claim 1, characterized in that, The sealing layer was prepared using PRODICO 480 graphene-modified sealing agent. Prepare a sealing solution by diluting PRODICO 480 graphene modified sealant with water to a ratio of 2.5 to 3.

2. Immerse the plated parts in the sealing solution for 8 to 15 seconds, drain them after removal from the tank, and blow off any residual sealing solution on the surface of the plated parts with high-pressure air. After sealing, dry and cure the parts at 70 to 80°C for 20 to 35 minutes.

8. The potassium chloride zinc plating process for magnesium alloy parts according to claim 1, characterized in that: The thickness of the potassium chloride zinc iron coating is 9–16 μm.

9. The potassium chloride zinc plating process for magnesium alloy parts according to claim 1, characterized in that: The thickness of the cyanide-free pre-plated copper layer is 2–6 μm.

10. The potassium chloride zinc plating process for magnesium alloy parts according to claim 1, characterized in that: The thickness of the copper pyrophosphate plating layer is 10–20 μm.

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