Magnesium alloy gold plating method with triple electrochemical protection effect and plating layer structure

Abstract

The invention discloses a magnesium alloy gold plating method with triple electrochemical protection effects and a plating layer structure. The process comprises the following steps: sequentially preparing a chemical zinc deposition layer, a cyanide-free copper-tin alloy plating layer, a cyanide-free copper-zinc alloy plating layer, a bright nickel-copper alloy plating layer, a nickel-phosphorus alloy plating layer, a gold plating layer and an anti-discoloration protective film on a magnesium alloy substrate. According to the cyanide-free copper-tin alloy plating process, 18-24 g / L of polycuprous thiocyanate, 0.2-0.6 g / L of stannous oxalate, 130-170 g / L of polysodium thiocyanate, 20-30 g / L of sodium 1-hydroxyethylidene-1, 1-diphosphonate and 8-12 mL / L of a copper-tin alloy plating brightener are adopted, the pH value of a plating solution is 12-13, the temperature of a plating tank is 30-40 DEG C, the cathode current density is 0.5-1.5 A / dm < 2 >, the cathode movement speed is 3-5 m / min, oxygen-free electrolytic copper particles serve as an anode, the copper particles are loaded into a titanium anode basket, the area ratio of the anode to the cathode is larger than 3: 1, and the anode movement speed is 3-5 m / min. And the surface of a plated part is not rusted after the plated part is subjected to an acetate mist test for 200 hours according to the GB / T 10125-2021 standard.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a magnesium alloy gold plating method and a plating layer structure with triple electrochemical protection effects. Background Art

[0002] Magnesium alloy materials have low density and high specific strength, and are particularly suitable for the preparation of aerospace parts. However, magnesium alloys are chemically active, and the oxides generated on their surface are loose and porous, which cannot effectively protect the matrix. The phase containing alloy elements in magnesium alloys can usually form local cathodes and anodes with the magnesium matrix, exacerbating the corrosion tendency through galvanic cell reactions.

[0003] The main surface treatment methods for magnesium alloys include electrophoretic coating, surface plating, micro-arc oxidation, anodizing, chemical conversion film, spraying organic coating and other technologies. [1] However, these surface treatment methods have certain limitations, and the protective effect needs to be further improved. At present, electrophoretic coating technology is mainly used in production applications to prepare a protective layer on the surface of magnesium alloy, which has a relatively good protective effect.

[0004] Magnesium alloy electroplating and chemical plating technology are still in the research stage [2-3] The prepared electroplated nickel layer and chemically plated nickel layer have no electrochemical protective effect on the magnesium alloy substrate. Once galvanic corrosion occurs, the magnesium alloy plated parts will be scrapped quickly. At present, there is no application report of electroplated nickel and chemically plated nickel on magnesium alloy.

[0005] Functional multilayer electroplating technology is very important to break through some difficulties faced in the field of electroplating by integrating the coating structure. The multilayer combination coating not only has mechanical protection, but also has good electrochemical protection function. [4] , which can meet the corrosion resistance requirements of various high-end products.

[0006] The high chemical activity of the magnesium alloy matrix itself has brought certain difficulties to the electroplating of magnesium alloys. There is still a lot of work to be done to realize the application of magnesium alloy electroplating technology.

[0007] 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]. Yu Gang, Yi Xiangrong, Lei Xiping, et al., Research on the formation mechanism and electroplating process of electro-deposited nickel on magnesium alloy [J], Electroplating and Environmental Protection, 2009, 29(1): 21-25. [3]. 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. [4]. Dai Pengmin, Guo Chongwu, Multi-layer nickel plating process suitable for aerospace aluminum alloy parts [J], Electroplating and Finishing, 2024, 43(4): 74-78. Summary of the invention

[0008] In order to solve the problem that the existing electroplated protective layer of magnesium alloy has no electrochemical protection and poor corrosion resistance, the present invention provides a magnesium alloy gold plating method and plating structure with triple electrochemical protection. In order to achieve the above purpose, the present invention adopts the following technical solutions: A method for gold plating a magnesium alloy with triple electrochemical protection comprises the following steps: (1) Degreasing, pickling and activation of magnesium alloy workpieces; (2) After the magnesium alloy workpiece is pre-treated, the chemical zinc deposition layer is prepared by using the current magnesium alloy chemical zinc deposition process; (3) After chemical zinc deposition on magnesium alloy workpiece, a cyanide-free copper-tin alloy coating is prepared by using a polymerized thiocyanate copper-tin alloy plating process; (4) After the magnesium alloy workpiece is polymerized with thiocyanate to plate copper-tin alloy, a cyanide-free copper-zinc alloy coating is prepared by using a polymerized thiocyanate to plate copper-zinc alloy process; (5) After the magnesium alloy workpiece is plated with copper-zinc alloy by polymerization of thiocyanate, a bright nickel-copper alloy coating is prepared by the existing bright nickel-copper alloy plating process; (6) After the magnesium alloy workpiece is plated with bright nickel-copper alloy, the nickel-phosphorus alloy coating is prepared by the current nickel-phosphorus alloy plating process; (7) After the magnesium alloy workpiece is plated with nickel-phosphorus alloy, a gold-plated layer is prepared using the current gold-plating process; (8) After the magnesium alloy workpiece is gold-plated, an electrolytic protection process is used to prepare an anti-discoloration protective film; The polymerized thiocyanate copper-tin alloy plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 18-24 g / L, stannous oxalate 0.2-0.6 g / L, polysodium thiocyanate 130-170 g / L, sodium hydroxyethylidene diphosphonate 20-30 g / L, copper-tin alloy brightener 8-12 mL / L, plating solution pH 12-13, plating tank temperature 30-40 ° C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3-5 m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is greater than 3:1, the anode moves 3-5 m / min, and stannous oxalate is added to the plating tank during plating to keep its concentration within the process range; The copper-tin alloy plating brightener comprises the following components in weight fractions: 30-50 parts of gelatin, 10-20 parts of waterborne polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight less than 8000, 40-60 parts of cobalt acetate, 80-120 parts of ethanol and 780-820 parts of pure water.

[0009] In some of the embodiments, the copper-tin alloy plating brightener is prepared as follows: 780-820 parts of water and 80-100 parts of ethanol are added to a reaction tank by weight, heated to 60-80° C., 40-50 parts of gelatin are added under stirring, stirred until the solid is dissolved, and then 10-20 parts of water-based polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight of less than 8000, and 40-60 parts of cobalt acetate are added, and stirred until the solid is dissolved to obtain the brightener.

[0010] In some embodiments, the gold-plated layer is prepared by BALILOY 300 FC 3N acidic gold-plated cobalt alloy process: BALILOY 300 FC MU cylinder opener 780-820 mL / L, BALILOY CO cobalt salt 18-22 mL / L, potassium gold cyanide 3.6-3.8 g / L, plating solution pH 3.6-4.0, plating tank temperature 30-40 ° C, cathode current density 0.5-1.0 A / dm 2 , the cathode moves 4 to 6 m / min.

[0011] In some embodiments, the gold-plated layer is prepared by ANG-114 acidic gold-nickel alloy process: ANG-114 M opener solution is used, potassium cyanide is dissolved in hot water and added to the plating tank, the plating tank contains 3-5 g / L gold, 3-5 g / L nickel, the plating solution pH is 4.0-4.5, the plating tank temperature is 35-60°C, and the cathode current density is 1.0-2.5 A / dm 2 , the cathode moves 3 to 5 m / min.

[0012] In some of the embodiments, the gold-plated layer is prepared by AUORO 330 acidic gold-plated iron alloy process: AUORO 330 M cylinder opener 480-520 mL / L, AUORO 330 Fe iron additive 45-55 mL / L, plating solution pH 3.8-4.3, plating tank temperature 35-45°C, cathode current density 1.0-2.5 A / dm 2 , the cathode moves 3 to 5 m / min.

[0013] In some embodiments, the gold-plated layer is prepared by Baliloy 8693 nickel-free gold plating process: Baliloy 8693 MUP opener stock solution is used, potassium gold cyanide is dissolved in hot water and added to the plating tank, the plating tank contains 2-3 g / L gold, the plating solution pH value is 3.8-4.2, the plating tank temperature is 35-45°C, and the cathode current density is 1.0-2.0 A / dm 2 , the cathode moves 3 to 5 m / min.

[0014] In some of the embodiments, the cyanide-free copper-zinc alloy coating is prepared by a polymerized thiocyanate copper-zinc alloy plating process: Polymeric cuprous thiocyanate 18-24 g / L, polymeric zinc thiocyanate 9-13 g / L, polymeric sodium thiocyanate 130-170 g / L, copper-zinc alloy plating brightener 8-12 mL / L, plating solution pH 10-12, plating tank temperature 35-55 ° C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, a brass plate with a copper mass fraction of 68% is used as the anode, the area ratio of the anode to the cathode is >2:1, and the anode moves 3 to 5 m / min.

[0015] In some embodiments, the bright nickel-copper alloy coating is prepared by using Nistar 6070 bright nickel-copper alloy plating process: Nickel sulfate hexahydrate 180-220 g / L, copper sulfate pentahydrate 8-12 g / L, trisodium citrate 50-70 g / L, disodium hydroxyethylidene diphosphonate 20-30 g / L, boric acid 28-35 g / L, sodium chloride 5-8 g / L, NISTAR 6070 brightener 0.3-0.7 mL / L, NISTAR 6071 auxiliary agent 6-10 mL / L, NI-35 wetting agent 0.3-1.0 mL / L, plating solution pH 4.3-4.8, plating tank temperature 50-55 ° C, cathode current density 2.6-3.2 A / dm 2 , the cathode moves 3 to 5 m / min.

[0016] In some of the embodiments, the nickel-phosphorus alloy coating is prepared by PROTEXYER 8713 high corrosion resistant nickel-phosphorus alloy coating process: PROTEXYER 8713 MU tank opener 580~620mL / L, nickel sulfate hexahydrate 280~340g / L, plating solution pH 2.6~2.7, plating tank temperature 60~65℃, cathode current density 3~6A / dm 2 , the cathode moves 3 to 5 m / min.

[0017] In some embodiments, the anti-discoloration protective film is prepared using the ANTITAR 1127 electrolytic protection process: ANTITAR 1127 MUP tank opener 30~40mL / L, ANTITAR 1127 ADDITIVE C additive 70~90mL / L, bath pH 3.3~4.0, operating temperature 55~65℃, cathode current density 0.4~0.8A / dm 2 , electrolysis time 4 to 10 minutes.

[0018] In some of the embodiments, the chemical zinc deposition layer is prepared by the following magnesium alloy chemical zinc deposition process: Zinc sulfate heptahydrate 25-35g / L, potassium pyrophosphate 100-120g / L, potassium fluoride 6-9g / L, bath temperature 68-72℃, zinc precipitation time 8-12min.

[0019] A coating structure prepared by a magnesium alloy gold plating method with triple electrochemical protection includes a magnesium alloy substrate, and a chemical zinc deposition layer, a cyanide-free copper-tin alloy coating, a cyanide-free copper-zinc alloy coating, a bright nickel-copper alloy coating, a nickel-phosphorus alloy coating, a gold plating layer, and an anti-discoloration protective film sequentially prepared on the magnesium alloy substrate.

[0020] In some of the embodiments, the thickness of the gold-plated layer is 0.2-2 μm.

[0021] In some of the embodiments, the thickness of the cyanide-free copper-tin alloy coating is 3-9 μm.

[0022] In some of the embodiments, the thickness of the cyanide-free copper-zinc alloy coating is 3-9 μm.

[0023] In some of the embodiments, the thickness of the nickel-copper alloy plating layer is 10-20 μm.

[0024] In some of the embodiments, the thickness of the nickel-phosphorus alloy coating is 3-7 μm.

[0025] The technical solution is to plate a cyanide-free copper-zinc alloy on the cyanide-free copper-tin alloy plating, a nickel-copper alloy on the cyanide-free copper-zinc alloy plating, and a nickel-phosphorus alloy on the nickel-copper alloy plating. The electrode potential of the cyanide-free copper-zinc alloy plating is more negative than that of the cyanide-free copper-tin alloy plating, the electrode potential of the nickel-copper alloy plating is more negative than that of the cyanide-free copper-zinc alloy plating, and the electrode potential of the nickel-phosphorus alloy plating is more negative than that of the nickel-copper alloy plating. In this plating structure, the outer plating layer is an anodic plating layer relative to the inner plating layer.

[0026] Compared with the prior art, the present invention has the following beneficial effects: 1. The magnesium alloy gold plating method and plating structure with triple electrochemical protection of the present invention, the prepared cyanide-free copper-tin alloy plating has excellent corrosion resistance, and using it as a bottom plating layer has a good protective effect on the magnesium alloy substrate; 2. The magnesium alloy gold plating method and plating structure with triple electrochemical protection of the present invention, the cyanide-free copper-zinc alloy plating has an electrochemical protection effect on the cyanide-free copper-tin alloy plating, the nickel-copper alloy plating has an electrochemical protection effect on the cyanide-free copper-zinc alloy plating, and the nickel-phosphorus alloy plating has an electrochemical protection effect on the nickel-copper alloy plating. This triple electrochemical protection can effectively prevent the corrosive medium from corroding the magnesium alloy substrate; 3. The magnesium alloy gold plating method and plating structure with triple electrochemical protection of the present invention overcome the defects of direct nickel plating after chemical zinc deposition on the magnesium alloy substrate or chemical nickel plating without electrochemical protection; 4. The magnesium alloy gold plating method and coating structure with triple electrochemical protection of the present invention and the coating structure prepared fill the gap of magnesium alloy gold plating in the domestic and international markets. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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 Schematic diagram of the coating structure of Embodiment 1, Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention; Figure 2 This is a picture of a magnesium alloy gold-plated cobalt alloy sample. DETAILED DESCRIPTION

[0028] 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.

[0029] A magnesium alloy gold plating method and plating structure with triple electrochemical protection effects, including magnesium alloy substrate pretreatment, and chemical zinc deposition layer, cyanide-free copper-tin alloy plating layer, cyanide-free copper-zinc alloy plating layer, bright nickel-copper alloy plating layer, nickel-phosphorus alloy plating layer, gold plating layer, and anti-discoloration protective film prepared in sequence on the magnesium alloy substrate.

[0030] The magnesium alloy pretreatment process is used to remove oil, pickle and activate the magnesium alloy workpiece.

[0031] 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.

[0032] 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.

[0033] After pretreatment of the magnesium alloy workpiece, the chemical zinc deposition layer is prepared by the following magnesium alloy chemical zinc deposition process.

[0034] Zinc sulfate heptahydrate 25-35g / L, potassium pyrophosphate 100-120g / L, potassium fluoride 6-9g / L, bath temperature 68-72℃, zinc precipitation time 8-12min.

[0035] After chemical zinc deposition on a magnesium alloy workpiece, the polymerized thiocyanate copper-tin alloy plating process of the invention is adopted to prepare a cyanide-free copper-tin alloy plating layer.

[0036] Preferably, the thickness of the cyanide-free copper-tin alloy plating layer is 3 to 9 μm.

[0037] Polymeric cuprous thiocyanate 18-24 g / L, stannous oxalate 0.2-0.6 g / L, polysodium thiocyanate 130-170 g / L, sodium hydroxyethylidene diphosphonate 20-30 g / L, copper-tin alloy brightener 8-12 mL / L, plating solution pH 12-13, plating tank temperature 30-40 ° C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of the anode to the cathode is >3:1, the anode moves 3 to 5 m / min, and stannous oxalate is added to the plating tank during plating to keep its concentration within the process range.

[0038] Preferably, the copper-tin alloy plating brightener comprises the following components in weight fractions: 30-50 parts of gelatin, 10-20 parts of waterborne polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight less than 8000, 40-60 parts of cobalt acetate, 80-120 parts of ethanol, and 780-820 parts of pure water.

[0039] Preferably, the copper-tin alloy plating brightener is prepared as follows: 780-820 parts of water and 80-120 parts of ethanol are added to a reaction tank by weight, heated to 60-80° C., 30-50 parts of gelatin are added under stirring, stirred until the solid matter is dissolved, and then 10-20 parts of water-based polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight of less than 8000, and 40-60 parts of cobalt acetate are added, and stirred until the solid matter is dissolved to obtain the brightener.

[0040] After the magnesium alloy workpiece is plated with copper-tin alloy without cyanide, the polymerized thiocyanate copper-zinc alloy plating process developed by Chaobang Chemical is used to prepare the cyanide-free copper-zinc alloy coating.

[0041] Preferably, the thickness of the cyanide-free copper-zinc alloy coating is 3 to 9 μm.

[0042] Polymeric cuprous thiocyanate 18-24 g / L, polymeric zinc thiocyanate 9-13 g / L, polymeric sodium thiocyanate 130-170 g / L, copper-zinc alloy plating brightener 8-12 mL / L, plating solution pH 10-12, plating tank temperature 35-55 ° C, cathode current density 0.5-1.5 A / dm2 , the cathode moves 3 to 5 m / min, a brass plate with a copper mass fraction of 68% is used as the anode, the area ratio of the anode to the cathode is >2:1, and the anode moves 3 to 5 m / min.

[0043] The magnesium alloy workpiece is plated with copper-zinc alloy by polymerization of thiocyanate and then the bright nickel-copper alloy coating is prepared by the existing bright nickel-copper alloy plating process.

[0044] Preferably, the thickness of the bright nickel-copper alloy plating layer is 10 to 20 μm.

[0045] Preferably, the bright nickel-copper alloy plating layer is prepared by using the Nistar 6070 bright nickel-copper alloy plating process of Chaobang Chemical: Nickel sulfate hexahydrate 180-220 g / L, copper sulfate pentahydrate 8-12 g / L, trisodium citrate 50-70 g / L, disodium hydroxyethylidene diphosphonate 20-30 g / L, boric acid 28-35 g / L, sodium chloride 5-8 g / L, NISTAR 6070 brightener 0.3-0.7 mL / L, NISTAR 6071 auxiliary agent 6-10 mL / L, NI-35 wetting agent 0.3-1.0 mL / L, plating solution pH 4.3-4.8, plating tank temperature 50-55 ° C, cathode current density 2.6-3.2 A / dm 2 , the cathode moves 3 to 5 m / min.

[0046] The magnesium alloy workpiece is plated with nickel-copper alloy and then the nickel-phosphorus alloy coating is prepared by the current nickel-phosphorus alloy plating process.

[0047] Preferably, the thickness of the nickel-phosphorus alloy coating is 3-7 μm.

[0048] Preferably, the nickel-phosphorus alloy coating is prepared by using the PROTEXYER 8713 high corrosion-resistant nickel-phosphorus alloy coating process of Chaobang Chemical: PROTEXYER 8713 MU tank opener 580~620mL / L, nickel sulfate hexahydrate 280~340g / L, plating solution pH 2.6~2.7, plating tank temperature 60~65℃, cathode current density 3~6A / dm 2 , the cathode moves 3 to 5 m / min.

[0049] The magnesium alloy workpiece is plated with nickel-phosphorus alloy and then a gold-plated layer is prepared using the current gold-plating process.

[0050] Preferably, the thickness of the gold-plated layer is 0.2-2 μm.

[0051] Preferably, the gold-plated layer is prepared by using the BALILOY 300 FC 3N acid gold plating process of SuperBang Chemical: BALILOY 300 FC MU tank opening agent 780~820mL / L, BALILOY CO cobalt salt 18~22mL / L, potassium gold cyanide 3.6~3.8g / L, plating solution pH 3.6~4.0, plating tank temperature 30~40℃, cathode current density 0.4~0.8A / dm 2 , the cathode moves 4 to 6 m / min.

[0052] Preferably, the gold-plated layer is prepared by ANG-114 acidic gold-plated nickel alloy process: ANG-114 M is used as a plating agent. Potassium gold cyanide is dissolved in hot water and added to the plating tank. The plating tank contains 3-5 g / L gold and 3-5 g / L nickel. The pH value of the plating solution is 4.0-4.5. The plating tank temperature is 35-60°C and the cathode current density is 1.0-2.5 A / dm 2 , the cathode moves 3 to 5 m / min.

[0053] Preferably, the gold-plated layer is prepared by AUORO 330 acidic gold-plated iron alloy process: AUORO 330 M opener 480~520mL / L, AUORO 330 Fe iron additive 45~55mL / L, plating solution pH 3.8~4.3, plating tank temperature 35~45℃, cathode current density 1.0~2.5A / dm 2 , the cathode moves 3 to 5 m / min.

[0054] Preferably, the gold-plated layer is prepared using Baliloy 8693 nickel-free gold-plating process: Baliloy 8693 MUP tank opener stock solution is used. Potassium gold cyanide is dissolved in hot water and added to the plating tank. The plating tank contains 2-3 g / L gold, the pH value of the plating solution is 3.8-4.2, the plating tank temperature is 35-45°C, and the cathode current density is 1.0-2.0 A / dm 2 , the cathode moves 3 to 5 m / min.

[0055] After the magnesium alloy workpiece is gold-plated, an anti-discoloration protective film is prepared using the current electrolytic protection process.

[0056] Preferably, the anti-discoloration protective film is prepared by ANTITAR 1127 electrolytic protection process: ANTITAR 1127 MUP tank opener 30~40mL / L, ANTITAR 1127 ADDITIVE C additive 70~90mL / L, bath pH 3.3~4.0, operating temperature 55~65℃, cathode current density 0.4~0.8A / dm 2 , electrolysis time 4 to 10 minutes.

[0057] Embodiment 1: like Figure 1 As shown, a magnesium alloy gold plating method and plating structure with triple electrochemical protection effects include pretreatment of a magnesium alloy substrate 1, and sequentially preparing a chemical zinc deposition layer 2, a cyanide-free copper-tin alloy plating layer 3, a cyanide-free copper-zinc alloy plating layer 4, a bright nickel-copper alloy plating layer 5, a nickel-phosphorus alloy plating layer 6, a gold plating layer 7, and an anti-discoloration protective film 8 on the magnesium alloy substrate 1.

[0058] The appearance of the magnesium alloy gold-plated sample prepared in this embodiment is as follows: Figure 2 shown.

[0059] 1. Pre-treatment: The magnesium alloy workpiece substrate 1 is pre-treated by using the current magnesium alloy pre-treatment process.

[0060] 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.

[0061] 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.

[0062] 2. Chemical zinc precipitation: After the magnesium alloy workpiece is pre-treated, the chemical zinc deposition layer 2 is prepared by the following chemical zinc deposition process.

[0063] Zinc sulfate heptahydrate 30g / L, potassium pyrophosphate 110g / L, potassium fluoride 7g / L, bath temperature 70℃, zinc precipitation time 10min.

[0064] 3. Cyanide-free copper-tin alloy plating: After chemical zinc deposition on the magnesium alloy workpiece, the polymerized thiocyanate copper-tin alloy plating process of the present invention is used to prepare a cyanide-free copper-tin alloy coating 3, and the coating thickness is 6 μm.

[0065] 1) Preparation of copper-tin alloy brightener: Calculated by weight, 800 parts of water and 100 parts of ethanol are added to a reaction tank, heated to 70°C, 40 parts of gelatin are added under stirring, and stirred until the solid is dissolved, and then 15 parts of water-based polyurethane resin, 100 parts of polyacrylamide with a molecular weight of less than 8000, and 50 parts of cobalt acetate are added, and stirred until the solid is dissolved to obtain the brightener.

[0066] 2) Plating: Polymeric cuprous thiocyanate 21g / L, stannous oxalate 0.4g / L, polysodium thiocyanate 150g / L, sodium hydroxyethylidene diphosphonate 25g / L, copper-tin alloy brightener 10mL / L, plating solution pH 12.5, plating tank temperature 35℃, cathode current density 1.0A / dm 2 , the cathode moves 4m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of the anode to the cathode is >3:1, the anode moves 4m / min, and stannous oxalate is added to the plating tank during plating to keep its concentration within the process range.

[0067] 4. Cyanide-free copper-zinc alloy plating: After the magnesium alloy workpiece was plated with copper-tin alloy without cyanide, the polymerized thiocyanate copper-zinc alloy plating process developed by Chaobang Chemical was used to prepare a cyanide-free copper-zinc alloy coating 4, and the coating thickness was 6 μm.

[0068] Polymeric cuprous thiocyanate 21g / L, polymeric zinc thiocyanate 11g / L, polymeric sodium thiocyanate 150g / L, copper-zinc alloy plating brightener 10mL / L, plating solution pH 11, plating tank temperature 45℃, cathode current density 1A / dm 2 , the cathode moves 4m / min, a brass plate with a copper mass fraction of 68% is used as the anode, the area ratio of the anode to the cathode is >2:1, and the anode moves 3-5m / min.

[0069] 5. Bright nickel-copper alloy plating: After the magnesium alloy workpiece is plated with copper-zinc alloy without cyanide, a bright nickel-copper alloy coating 5 is prepared by using the Nistar 6070 bright nickel-copper alloy plating process of Chaobang Chemical, and the coating thickness is 15 μm.

[0070] Nickel sulfate hexahydrate 200g / L, copper sulfate pentahydrate 10g / L, trisodium citrate 60g / L, disodium hydroxyethylidene diphosphonate 25g / L, boric acid 32g / L, sodium chloride 7g / L, NISTAR 6070 brightener 0.5mL / L, NISTAR 6071 auxiliary agent 8mL / L, NI-35 wetting agent 0.7mL / L, plating solution pH 4.5, plating tank temperature 53℃, cathode current density 2.8A / dm 2 , cathode moves 4m / min.

[0071] 6. Nickel-phosphorus alloy plating: After the magnesium alloy workpiece is plated with nickel-copper alloy, the nickel-phosphorus alloy coating 6 is prepared by the PROTEXYER 8713 high corrosion-resistant nickel-phosphorus alloy plating process of Chaobang Chemical, and the coating has a thickness of 5 μm.

[0072] PROTEXYER 8713 MU tank opener 600mL / L, nickel sulfate hexahydrate 320g / L, bath pH 2.6, bath temperature 63℃, cathode current density 4A / dm2 , cathode moves 4m / min.

[0073] 7. Gold plating: After the magnesium alloy workpiece is plated with nickel-phosphorus alloy, a gold-plated layer 7 is prepared by using the BALILOY 300 FC 3N acid gold-cobalt alloy plating process of Chaobang Chemical, and the thickness of the plating layer is 1.5 μm.

[0074] BALILOY 300 FC MU tank opener 800mL / L, BALILOY CO cobalt salt 20mL / L, potassium gold cyanide 3.7g / L, plating solution pH 3.8, plating tank temperature 35℃, cathode current density 0.8A / dm 2 , cathode moves 5m / min.

[0075] 8. Electrolytic protection: After the magnesium alloy workpiece is gold-plated, an anti-discoloration protective film 8 is prepared using the ANTITAR 1127 electrolytic protection process of Chaobang Chemical.

[0076] ANTITAR 1127 MUP 40mL / L, ANTITAR 1127 ADDITIVE C 90mL / L, bath pH 4.0, operating temperature 55℃, cathode current density 0.6A / dm 2 , electrolysis time 6min.

[0077] 9. Drying: The magnesium alloy workpiece is dried using conventional drying process after electrolytic protection.

[0078] Embodiment 2: like Figure 1 As shown, a magnesium alloy gold plating method and plating structure with triple electrochemical protection effects include pretreatment of a magnesium alloy substrate 1, and sequentially preparing a chemical zinc deposition layer 2, a cyanide-free copper-tin alloy plating layer 3, a cyanide-free copper-zinc alloy plating layer 4, a bright nickel-copper alloy plating layer 5, a nickel-phosphorus alloy plating layer 6, a gold plating layer 7, and an anti-discoloration protective film 8 on the magnesium alloy substrate 1.

[0079] 1. Pre-treatment: The magnesium alloy workpiece substrate 1 is pre-treated by using the current magnesium alloy pre-treatment process.

[0080] 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.

[0081] 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.

[0082] 2. Chemical zinc precipitation: After the magnesium alloy workpiece is pre-treated, the chemical zinc deposition layer 2 is prepared by the following chemical zinc deposition process.

[0083] Zinc sulfate heptahydrate 35g / L, potassium pyrophosphate 120g / L, potassium fluoride 9g / L, bath temperature 68℃, zinc precipitation time 10min.

[0084] 3. Cyanide-free copper-tin alloy plating: After chemical zinc deposition on the magnesium alloy workpiece, the polymerized thiocyanate copper-tin alloy plating process of the present invention is used to prepare a cyanide-free copper-tin alloy coating 3, and the coating thickness is 6 μm.

[0085] 1) Preparation of copper-tin alloy brightener: Calculated by weight, 800 parts of water and 100 parts of ethanol are added to a reaction tank, heated to 70°C, 40 parts of gelatin are added under stirring, and stirred until the solid is dissolved, and then 15 parts of water-based polyurethane resin, 100 parts of polyacrylamide with a molecular weight of less than 8000, and 50 parts of cobalt acetate are added, and stirred until the solid is dissolved to obtain the brightener.

[0086] 2) Plating: Polymeric cuprous thiocyanate 24g / L, stannous oxalate 0.6g / L, polysodium thiocyanate 170g / L, sodium hydroxyethylidene diphosphonate 25g / L, copper-tin alloy brightener 10mL / L, plating solution pH 12, plating tank temperature 30℃, cathode current density 1.0A / dm 2 , the cathode moves 4m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of the anode to the cathode is >3:1, the anode moves 4m / min, and stannous oxalate is added to the plating tank during plating to keep its concentration within the process range.

[0087] 4. Cyanide-free copper-zinc alloy plating: After the magnesium alloy workpiece was plated with copper-tin alloy without cyanide, the polymerized thiocyanate copper-zinc alloy plating process developed by Chaobang Chemical was used to prepare a cyanide-free copper-zinc alloy coating 4, and the coating thickness was 6 μm.

[0088] Polymeric cuprous thiocyanate 24g / L, polymeric zinc thiocyanate 13g / L, polymeric sodium thiocyanate 170g / L, copper-zinc alloy plating brightener 10mL / L, plating solution pH 11, plating tank temperature 35℃, cathode current density 1A / dm 2 , the cathode moves 4m / min, a brass plate with a copper mass fraction of 68% is used as the anode, the area ratio of the anode to the cathode is >2:1, and the anode moves 4m / min.

[0089] 5. Bright nickel-copper alloy plating: After the magnesium alloy workpiece is plated with copper-zinc alloy without cyanide, a bright nickel-copper alloy coating 5 is prepared by using the Nistar 6070 bright nickel-copper alloy plating process of Chaobang Chemical, and the coating thickness is 15 μm.

[0090] Nickel sulfate hexahydrate 220g / L, copper sulfate pentahydrate 12g / L, trisodium citrate 70g / L, disodium hydroxyethylidene diphosphonate 30g / L, boric acid 32g / L, sodium chloride 7g / L, NISTAR 6070 brightener 0.5mL / L, NISTAR 6071 auxiliary agent 8mL / L, NI-35 wetting agent 0.7mL / L, plating solution pH 4.5, plating tank temperature 50℃, cathode current density 2.8A / dm 2 , cathode moves 4m / min.

[0091] 6. Nickel-phosphorus alloy plating: After the magnesium alloy workpiece is plated with nickel-copper alloy, the nickel-phosphorus alloy coating 6 is prepared by the PROTEXYER 8713 high corrosion-resistant nickel-phosphorus alloy plating process of Chaobang Chemical, and the coating has a thickness of 5 μm.

[0092] PROTEXYER 8713 MU tank opener 620mL / L, nickel sulfate hexahydrate 340g / L, bath pH 2.7, bath temperature 60℃, cathode current density 4A / dm 2 , cathode moves 4m / min.

[0093] 7. Gold plating: After the magnesium alloy workpiece is plated with nickel-phosphorus alloy, a gold-plated layer 7 is prepared using the ANG-114 acidic gold-plated nickel alloy process of Chaobang Chemical, and the thickness of the plating layer is 1.5 μm.

[0094] ANG-114 M tank opening agent stock solution is used. Potassium gold cyanide is dissolved in hot water and added to the plating tank. The plating tank contains 4g / L gold and 4g / L nickel. The pH of the plating solution is 4.3, the plating tank temperature is 50℃, and the cathode current density is 2A / dm 2 , cathode moves 4m / min.

[0095] 8. Electrolytic protection: After the magnesium alloy workpiece is gold-plated, an anti-discoloration protective film 8 is prepared using the ANTITAR 1127 electrolytic protection process of Chaobang Chemical.

[0096] ANTITAR 1127 MUP 30mL / L, ANTITAR 1127 ADDITIVE C 70mL / L, bath pH 3.3, operating temperature 65℃, cathode current density 0.6A / dm 2 , electrolysis time 9min.

[0097] 9. Drying: The magnesium alloy workpiece is dried using conventional drying process after electrolytic protection.

[0098] Embodiment 3: like Figure 1 As shown, a magnesium alloy gold plating method and plating structure with triple electrochemical protection effects include pretreatment of a magnesium alloy substrate 1, and sequentially preparing a chemical zinc deposition layer 2, a cyanide-free copper-tin alloy plating layer 3, a cyanide-free copper-zinc alloy plating layer 4, a bright nickel-copper alloy plating layer 5, a nickel-phosphorus alloy plating layer 6, a gold plating layer 7, and an anti-discoloration protective film 8 on the magnesium alloy substrate 1.

[0099] 1. Pre-treatment: The magnesium alloy workpiece substrate 1 is pre-treated by using the current magnesium alloy pre-treatment process.

[0100] 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.

[0101] 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.

[0102] 2. Chemical zinc precipitation: After the magnesium alloy workpiece is pre-treated, the chemical zinc deposition layer 2 is prepared by the following chemical zinc deposition process.

[0103] Zinc sulfate heptahydrate 25g / L, potassium pyrophosphate 100g / L, potassium fluoride 6g / L, bath temperature 72℃, zinc precipitation time 12min.

[0104] 3. Cyanide-free copper-tin alloy plating: After chemical zinc deposition on the magnesium alloy workpiece, the polymerized thiocyanate copper-tin alloy plating process of the present invention is used to prepare a cyanide-free copper-tin alloy coating 3, and the coating thickness is 6 μm.

[0105] 1) Preparation of copper-tin alloy brightener: Calculated by weight, 800 parts of water and 100 parts of ethanol are added to a reaction tank, heated to 70°C, 40 parts of gelatin are added under stirring, and stirred until the solid is dissolved, and then 15 parts of water-based polyurethane resin, 100 parts of polyacrylamide with a molecular weight of less than 8000, and 50 parts of cobalt acetate are added, and stirred until the solid is dissolved to obtain the brightener.

[0106] 2) Plating: Polymeric cuprous thiocyanate 18g / L, stannous oxalate 0.3g / L, polymeric sodium thiocyanate 130g / L, copper-tin alloy brightener 10mL / L, plating solution pH 12.5, plating tank temperature 40℃, cathode current density 1A / dm 2 , the cathode moves 4m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of the anode to the cathode is >3:1, the anode moves 4m / min, and stannous oxalate is added to the plating tank during plating to keep its concentration within the process range.

[0107] 4. Cyanide-free copper-zinc alloy plating: After the magnesium alloy workpiece was plated with copper-tin alloy without cyanide, the polymerized thiocyanate copper-zinc alloy plating process developed by Chaobang Chemical was used to prepare a cyanide-free copper-zinc alloy coating 4, and the coating thickness was 6 μm.

[0108] Polymeric cuprous thiocyanate 18g / L, polymeric zinc thiocyanate 9g / L, polymeric sodium thiocyanate 130g / L, copper-zinc alloy plating brightener 10mL / L, plating solution pH 12, plating tank temperature 55℃, cathode current density 1A / dm 2 , the cathode moves 4m / min, a brass plate with a copper mass fraction of 68% is used as the anode, the area ratio of the anode to the cathode is >2:1, and the anode moves 4m / min.

[0109] 5. Bright nickel-copper alloy plating: After the magnesium alloy workpiece is plated with copper-zinc alloy without cyanide, a bright nickel-copper alloy coating 5 is prepared by using the Nistar 6070 bright nickel-copper alloy plating process of Chaobang Chemical, and the coating thickness is 15 μm.

[0110] Nickel sulfate hexahydrate 180g / L, copper sulfate pentahydrate 8g / L, trisodium citrate 50g / L, disodium hydroxyethylidene diphosphonate 25g / L, boric acid 32g / L, sodium chloride 7g / L, NISTAR 6070 brightener 0.5mL / L, NISTAR 6071 auxiliary agent 8mL / L, NI-35 wetting agent 0.7mL / L, plating solution pH 4.5, plating tank temperature 55℃, cathode current density 2.8A / dm 2 , cathode moves 4m / min.

[0111] 6. Nickel-phosphorus alloy plating: After the magnesium alloy workpiece is plated with nickel-copper alloy, the nickel-phosphorus alloy coating 6 is prepared by the PROTEXYER 8713 high corrosion-resistant nickel-phosphorus alloy plating process of Chaobang Chemical, and the coating has a thickness of 5 μm.

[0112] PROTEXYER 8713 MU tank opener 580mL / L, nickel sulfate hexahydrate 280g / L, bath pH 2.6, bath temperature 65℃, cathode current density 4A / dm 2, cathode moves 4m / min.

[0113] 7. Gold plating: After the magnesium alloy workpiece is plated with nickel-phosphorus alloy, a gold-plated layer 7 is prepared by using the AUORO 330 acidic gold-iron alloy plating process of Chaobang Chemical, and the thickness of the plating layer is 1.5 μm.

[0114] AUORO 330 M opener 500mL / L, AUORO 330 Fe iron additive 50mL / L, bath pH 4, bath temperature 40°C, cathode current density 1.8A / dm 2 , cathode moves 4m / min.

[0115] 8. Electrolytic protection: After the magnesium alloy workpiece is gold-plated, an anti-discoloration protective film 8 is prepared using the ANTITAR 1127 electrolytic protection process of Chaobang Chemical.

[0116] ANTITAR 1127 MUP 34mL / L, ANTITAR 1127 ADDITIVE C 77mL / L, bath pH 3.7, operating temperature 62℃, cathode current density 0.6A / dm 2 , electrolysis time 8min.

[0117] 9. Drying: The magnesium alloy workpiece is dried using conventional drying process after electrolytic protection. Example

[0118] like Figure 1 As shown, a magnesium alloy gold plating method and plating structure with triple electrochemical protection effects include pretreatment of a magnesium alloy substrate 1, and sequentially preparing a chemical zinc deposition layer 2, a cyanide-free copper-tin alloy plating layer 3, a cyanide-free copper-zinc alloy plating layer 4, a bright nickel-copper alloy plating layer 5, a nickel-phosphorus alloy plating layer 6, a gold plating layer 7, and an anti-discoloration protective film 8 on the magnesium alloy substrate 1.

[0119] 1. Pre-treatment: The magnesium alloy workpiece substrate 1 is pre-treated by using the current magnesium alloy pre-treatment process.

[0120] 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.

[0121] 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.

[0122] 2. Chemical zinc precipitation: After the magnesium alloy workpiece is pre-treated, the chemical zinc deposition layer 2 is prepared by the following chemical zinc deposition process.

[0123] Zinc sulfate heptahydrate 33g / L, potassium pyrophosphate 115g / L, potassium fluoride 8g / L, bath temperature 69℃, zinc precipitation time 9min.

[0124] 3. Cyanide-free copper-tin alloy plating: After chemical zinc deposition on the magnesium alloy workpiece, the polymerized thiocyanate copper-tin alloy plating process of the present invention is used to prepare a cyanide-free copper-tin alloy coating 3, and the coating thickness is 6 μm.

[0125] 1) Preparation of copper-tin alloy brightener: Calculated by weight, 800 parts of water and 100 parts of ethanol are added to a reaction tank, heated to 70°C, 40 parts of gelatin are added under stirring, and stirred until the solid is dissolved, and then 15 parts of water-based polyurethane resin, 100 parts of polyacrylamide with a molecular weight of less than 8000, and 50 parts of cobalt acetate are added, and stirred until the solid is dissolved to obtain the brightener.

[0126] 2) Plating: Polymerized cuprous thiocyanate 23g / L, stannous oxalate 0.5g / L, sodium polythiocyanate 165g / L, copper-tin alloy brightener 10mL / L, plating solution pH 12.3, plating tank temperature 40℃, cathode current density 1A / dm 2 , the cathode moves 4m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of the anode to the cathode is >3:1, the anode moves 4m / min, and stannous oxalate is added to the plating tank during plating to keep its concentration within the process range.

[0127] 4. Cyanide-free copper-zinc alloy plating: After the magnesium alloy workpiece was plated with copper-tin alloy without cyanide, the polymerized thiocyanate copper-zinc alloy plating process developed by Chaobang Chemical was used to prepare a cyanide-free copper-zinc alloy coating 4, and the coating thickness was 6 μm.

[0128] Polymerized cuprous thiocyanate 23g / L, polyzinc thiocyanate 12g / L, polysodium thiocyanate 160g / L, brightener 10mL / L, plating solution pH 11, plating tank temperature 40℃, cathode current density 1A / dm 2 , the cathode moves 4m / min, a brass plate with a copper mass fraction of 68% is used as the anode, the area ratio of the anode to the cathode is >2:1, and the anode moves 4m / min.

[0129] 5. Bright nickel-copper alloy plating: After the magnesium alloy workpiece is plated with copper-zinc alloy without cyanide, a bright nickel-copper alloy coating 5 is prepared by using the Nistar 6070 bright nickel-copper alloy plating process of Chaobang Chemical, and the coating thickness is 15 μm.

[0130] Nickel sulfate hexahydrate 210g / L, copper sulfate pentahydrate 11g / L, trisodium citrate 65g / L, disodium hydroxyethylidene diphosphonate 28g / L, boric acid 32g / L, sodium chloride 7g / L, NISTAR 6070 brightener 05mL / L, NISTAR 6071 auxiliary agent 8mL / L, NI-35 wetting agent 0.7mL / L, plating solution pH 4.5, plating tank temperature 52℃, cathode current density 2.8A / dm 2 , cathode moves 4m / min.

[0131] 6. Nickel-phosphorus alloy plating: After the magnesium alloy workpiece is plated with nickel-copper alloy, the nickel-phosphorus alloy coating 6 is prepared by the PROTEXYER 8713 high corrosion-resistant nickel-phosphorus alloy plating process of Chaobang Chemical, and the coating has a thickness of 5 μm.

[0132] PROTEXYER 8713 MU tank opener 610mL / L, nickel sulfate hexahydrate 330g / L, bath pH 2.7, bath temperature 62℃, cathode current density 4A / dm 2 , cathode moves 4m / min.

[0133] 7. Gold plating: After the magnesium alloy workpiece is plated with nickel-phosphorus alloy, the gold-plated layer 7 is prepared using the Baliloy 8693 nickel-free gold-plating process of Chaobang Chemical, and the thickness of the plating layer is 1.5 μm.

[0134] Baliloy 8693 MUP tank opener stock solution is used. Potassium gold cyanide is dissolved in hot water and added to the plating tank. The plating tank contains 2.5g / L gold, the plating solution pH is 4, the plating tank temperature is 40℃, and the cathode current density is 1.5A / dm 2 , cathode moves 4m / min.

[0135] 8. Electrolytic protection: After the magnesium alloy workpiece is gold-plated, an anti-discoloration protective film 8 is prepared using the ANTITAR 1127 electrolytic protection process of Chaobang Chemical.

[0136] ANTITAR 1127 MUP 37mL / L, ANTITAR 1127 ADDITIVE C 85mL / L, bath pH 3.7, operating temperature 58℃, cathode current density 0.6A / dm 2 Electrolysis time: 7min.

[0137] 9. Drying: The magnesium alloy workpiece is dried using conventional drying process after electrolytic protection.

[0138] Test Example 1: According to GB / T 10125-2021 "Artificial atmosphere corrosion test salt spray test", the acetic acid salt spray test was carried out. The magnesium alloy gold-plated samples prepared in Example 1, Example 2, Example 3 and Example 4 had no rust on the surface after 200 hours, and the prepared coating had excellent corrosion resistance.

[0139] 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 gold-plated magnesium 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.

[0140] Test Example 3: 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 gold-plated magnesium alloy samples prepared in Example 1, Example 2, Example 3 and Example 4 were tested for 240 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 constant humidity test met the standard requirements.

[0141] 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 method for gold plating magnesium alloy with triple electrochemical protection, characterized in that: The following steps are involved: (1) Degreasing, pickling and activation of magnesium alloy workpieces; (2) After the magnesium alloy workpiece is pre-treated, the chemical zinc deposition layer is prepared by using the current magnesium alloy chemical zinc deposition process; (3) After chemical zinc deposition on magnesium alloy workpiece, a cyanide-free copper-tin alloy coating is prepared by using a polymerized thiocyanate copper-tin alloy plating process; (4) After the magnesium alloy workpiece is polymerized with thiocyanate to plate copper-tin alloy, a cyanide-free copper-zinc alloy coating is prepared by using a polymerized thiocyanate to plate copper-zinc alloy process; (5) After the magnesium alloy workpiece is plated with copper-zinc alloy by polymerization of thiocyanate, a bright nickel-copper alloy coating is prepared by the existing bright nickel-copper alloy plating process; (6) After the magnesium alloy workpiece is plated with bright nickel-copper alloy, the nickel-phosphorus alloy coating is prepared by the current nickel-phosphorus alloy plating process; (7) After the magnesium alloy workpiece is plated with nickel-phosphorus alloy, a gold-plated layer is prepared using the current gold-plating process; (8) After the magnesium alloy workpiece is gold-plated, an electrolytic protection process is used to prepare an anti-discoloration protective film; The polymerized thiocyanate copper-tin alloy plating process includes the following components and process parameters: Polymeric cuprous thiocyanate 18-24 g / L, stannous oxalate 0.2-0.6 g / L, polysodium thiocyanate 130-170 g / L, sodium hydroxyethylidene diphosphonate 20-30 g / L, copper-tin alloy brightener 8-12 mL / L, plating solution pH 12-13, plating tank temperature 30-40 ° C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3-5 m / min, oxygen-free electrolytic copper particles are used as anodes, the copper particles are placed in a titanium anode basket, the area ratio of anode to cathode is greater than 3:1, the anode moves 3-5 m / min, and stannous oxalate is added to the plating tank during plating to keep its concentration within the process range; The copper-tin alloy plating brightener comprises the following components in weight fractions: 30-50 parts of gelatin, 10-20 parts of waterborne polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight less than 8000, 40-60 parts of cobalt acetate, 80-120 parts of ethanol and 780-820 parts of pure water.

2. The method for gold plating a magnesium alloy having triple electrochemical protection according to claim 1, characterized in that: The copper-tin alloy plating brightener is prepared as follows: Calculated by weight, 780-820 parts of water and 80-120 parts of ethanol are added to a reaction tank, heated to 60-80°C, 40-50 parts of gelatin are added under stirring, stirred until the solid matter is dissolved, and then 10-20 parts of waterborne polyurethane resin, 80-120 parts of polyacrylamide with a molecular weight of less than 8000, and 40-60 parts of cobalt acetate are added, stirred until the solid matter is dissolved to obtain the brightener.

3. The method for gold plating a magnesium alloy having triple electrochemical protection according to claim 1, characterized in that: The gold-plated layer is prepared by BALILOY 300 FC 3N acidic gold-plated cobalt alloy process: BALILOY 300 FC MU cylinder opener 780-820mL / L, BALILOY CO cobalt salt 18-22mL / L, potassium gold cyanide 3.6-3.8g / L, plating solution pH 3.6-4.0, plating tank temperature 30-40°C, cathode current density 0.5-1.0A / dm 2 , cathode moves 4-6m / min; The gold-plated layer is prepared by ANG-114 acidic gold-plated nickel alloy process: ANG-114 M cylinder opening agent stock solution is used, potassium cyanide is dissolved in hot water and added to the plating tank, the plating tank contains 3-5g / L gold, 3-5g / L nickel, the plating solution pH value is 4.0-4.5, the plating tank temperature is 35-60°C, and the cathode current density is 1.0-2.5A / dm 2 , cathode moves 3-5m / min; The gold-plated layer is prepared by AUORO 330 acidic gold-plated iron alloy process: AUORO 330 M cylinder opener 480-520 mL / L, AUORO 330 Fe iron additive 45-55 mL / L, plating solution pH 3.8-4.3, plating tank temperature 35-45°C, cathode current density 1.0-2.5 A / dm 2 , cathode moves 3-5m / min; The gold-plated layer is prepared by Baliloy 8693 nickel-free gold plating process: Baliloy 8693 MUP opener stock solution is used, potassium gold cyanide is dissolved in hot water and added to the plating tank, the plating tank contains 2-3 g / L gold, the plating solution pH value is 3.8-4.2, the plating tank temperature is 35-45°C, and the cathode current density is 1.0-2.0 A / dm 2 , the cathode moves 3 to 5 m / min.

4. The method for gold plating a magnesium alloy having triple electrochemical protection according to claim 1, characterized in that: The cyanide-free copper-zinc alloy coating is prepared by using a polymerized thiocyanate copper-zinc alloy plating process: Polymeric cuprous thiocyanate 18-24 g / L, polymeric zinc thiocyanate 9-13 g / L, polymeric sodium thiocyanate 130-170 g / L, copper-zinc alloy plating brightener 8-12 mL / L, plating solution pH 10-12, plating tank temperature 35-55 ° C, cathode current density 0.5-1.5 A / dm 2 , the cathode moves 3 to 5 m / min, a brass plate with a copper mass fraction of 68% is used as the anode, the area ratio of the anode to the cathode is >2:1, and the anode moves 3 to 5 m / min.

5. The method for gold plating a magnesium alloy having triple electrochemical protection according to claim 1, characterized in that: The bright nickel-copper alloy coating is prepared by using the Nistar 6070 bright nickel-copper alloy plating process: Nickel sulfate hexahydrate 180-220 g / L, copper sulfate pentahydrate 8-12 g / L, trisodium citrate 50-70 g / L, disodium hydroxyethylidene diphosphonate 20-30 g / L, boric acid 28-35 g / L, sodium chloride 5-8 g / L, NISTAR 6070 brightener 0.3-0.7 mL / L, NISTAR 6071 auxiliary agent 6-10 mL / L, NI-35 wetting agent 0.3-1.0 mL / L, plating solution pH 4.3-4.8, plating tank temperature 50-55 ° C, cathode current density 2.6-3.2 A / dm 2 , the cathode moves 3 to 5 m / min.

6. The method for gold plating a magnesium alloy having triple electrochemical protection according to claim 1, characterized in that: The nickel-phosphorus alloy coating is prepared by using the PROTEXYER 8713 high corrosion resistant nickel-phosphorus alloy plating process: PROTEXYER 8713 MU tank opener 580~620mL / L, nickel sulfate hexahydrate 280~340g / L, plating solution pH 2.6~2.7, plating tank temperature 60~65℃, cathode current density 3~6A / dm 2 , the cathode moves 3 to 5 m / min.

7. The magnesium alloy gold plating method with triple electrochemical protection according to claim 1, characterized in that: The anti-discoloration protective film is prepared by ANTITAR 1127 electrolytic protection process: ANTITAR 1127 MUP tank opener 30~40mL / L, ANTITAR 1127 ADDITIVE C additive 70~90mL / L, bath pH 3.3~4.0, operating temperature 55~65℃, cathode current density 0.4~0.8A / dm 2 , electrolysis time 4 to 10 minutes.

8. The method for gold plating a magnesium alloy having triple electrochemical protection according to claim 1, characterized in that: The chemical zinc deposition layer is prepared by the following magnesium alloy chemical zinc deposition process: Zinc sulfate heptahydrate 25-35g / L, potassium pyrophosphate 100-120g / L, potassium fluoride 6-9g / L, bath temperature 68-72℃, zinc precipitation time 8-12min.

9. A coating structure prepared by a magnesium alloy gold plating method with triple electrochemical protection, characterized in that: The invention comprises a magnesium alloy substrate, and a chemical zinc deposition layer, a cyanide-free copper-tin alloy plating layer, a cyanide-free copper-zinc alloy plating layer, a bright nickel-copper alloy plating layer, a nickel-phosphorus alloy plating layer, a gold plating layer, and an anti-discoloration protective film which are sequentially prepared on the magnesium alloy substrate.

10. The coating structure prepared by the method for gold plating on magnesium alloy with triple electrochemical protection according to claim 9, characterized in that: The thickness of the gold-plated layer is 0.2-2 μm, the thickness of the cyanide-free copper-tin alloy plating layer is 3-9 μm, the thickness of the cyanide-free copper-zinc alloy plating layer is 3-9 μm, the thickness of the nickel-copper alloy plating layer is 10-20 μm, and the thickness of the nickel-phosphorus alloy plating layer is 3-7 μm.

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