A gun black tin-nickel alloy electroplating and electrolytic protection process

Abstract

The present invention discloses a gun-black tin-nickel alloy electroplating and electrolytic protection process. The electroplating process comprises: 240-280 g / L potassium pyrophosphate, 50-60 g / L nickel chloride hexahydrate, 7-9 g / L stannous chloride dihydrate, 1-2 g / L lanthanum chloride or praseodymium chloride, 13-18 g / L potassium thiocyanate, 0.6-1.8 g / L methionine, 20-30 g / L ammonium citrate, 4-6 g / L disodium ethylenediaminetetraacetic acid, a pH range of 7.8-8.2, a plating bath temperature of 35-40°C, a cathode current density of 1-3 A / dm2, and a cathode travel of 3-5 m / min. The electrolytic protection process is as follows: 2-5 g / L cerium chloride, 2-5 g / L sodium molybdate, 15-30 g / L sodium hydroxyethylidene diphosphonate, 100-150 g / L anhydrous potassium carbonate, pH range 11-13, room temperature operation, cathode current density 0.5-1.2 A / dm², using the plated part as the cathode and the titanium plate as the anode, and electrolysis for 60-120 seconds. The prepared gunmetal black tin-nickel alloy plated part was subjected to a neutral salt spray test for 96 hours in accordance with GB / T 10125-2021 "Artificial Atmosphere Corrosion Test Salt Spray Test", and no corrosive products were generated on the surface of the coating. The gunmetal black tin-nickel alloy electroplating and electrolysis process of the present invention improves the corrosion resistance of the coating and solves the high pollution problem of the dichromate electrolytic protection method.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and in particular relates to a gun black tin-nickel alloy electroplating and electrolytic protection process. Background Art

[0002] Gunmetal black tin-nickel alloy coatings offer an elegant appearance and excellent wear resistance, primarily used for decorative coatings on hardware, electronics, and firearms accessories. Previously, dichromate electrolytic protection was commonly used to enhance the corrosion resistance of the coating. However, the use of hexavalent chromium has become increasingly restricted, leading to the development of environmentally friendly post-treatment processes for gunmetal black tin-nickel alloy coatings.

[0003] Traditional gunmetal black tin-nickel alloy coatings contain only tin and nickel, along with other ingredients such as a sulfur blackening agent. Due to the sulfur content, gunmetal black tin-nickel alloy coatings exhibit significantly lower corrosion resistance than silvery-white tin-nickel alloy coatings. Neutral salt spray testing, conducted in accordance with GB / T 10125–2021, "Artificial Atmosphere Corrosion Tests: Salt Spray Test," currently requires that gunmetal black tin-nickel alloy-plated parts remain rust-free for 48 hours. However, production practice demonstrates that gunmetal black tin-nickel alloy-plated parts produced using existing technology typically fail the 48-hour neutral salt spray test without post-treatment protection. Summary of the Invention

[0004] In order to solve the problem of poor corrosion resistance of gunmetal black tin-nickel alloy coating and overcome the high pollution defect of dichromate electrolytic protection method, the present invention provides a gunmetal black tin-nickel alloy electroplating and electrolytic protection process. To achieve the above objectives, the present invention adopts the following technical solutions:

[0005] A gun black tin-nickel alloy electroplating and electrolytic protection process includes two processes: gun black tin-nickel alloy electroplating and electrolytic protection of the coating.

[0006] The gun black tin-nickel alloy electroplating process is as follows: potassium pyrophosphate 240-280g / L, nickel chloride hexahydrate 50-60g / L, stannous chloride dihydrate 7-9g / L, rare earth salt 1-2g / L, potassium thiocyanate 13-18g / L, methionine 0.6-1.8g / L, ammonium citrate 20-30g / L, disodium ethylenediaminetetraacetic acid 4-6g / L, pH range 7.8-8.2, plating tank temperature 35℃-40℃, cathode current density 1-3A / dm2, cathode movement 3-5m / min, using a graphite plate as the anode;

[0007] The rare earth salt includes any one or both of lanthanum chloride and praseodymium chloride;

[0008] The electrolytic protection process of gun black tin-nickel alloy plating is as follows:

[0009] Cerium chloride 2-5 g / L, sodium molybdate 2-5 g / L, sodium hydroxyethylidene diphosphonate 15-30 g / L, anhydrous potassium carbonate 100-150 g / L, pH range 11-13, operation at room temperature, cathode current density 0.5-1.2 A / dm2, use plated parts as cathode, titanium plate as anode, electrolysis for 60-120 s.

[0010] A gunmetal black tin-nickel alloy electroplating process, a gunmetal black tin-nickel alloy plating solution preparation method is as follows:

[0011] (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely;

[0012] (2) Dissolve disodium ethylenediaminetetraacetic acid in water at a mass fraction of 5%, add rare earth salt and stir until completely dissolved, then add the prepared rare earth salt solution into the plating tank and mix evenly;

[0013] (3) Using a thin iron plate as the cathode, electrolyze the prepared plating solution at a current of 0.1 to 0.3 A / dm2 for 1 to 6 hours;

[0014] (4) Dissolve methionine in water and add it to the plating tank and mix evenly. Use hydrochloric acid with a volume ratio of 1:1 to adjust the pH of the plating solution to 7.8-8.2, and add water to the specified volume.

[0015] A gun black tin-nickel alloy electrolytic protection process, the electrolytic protection solution preparation method is as follows:

[0016] (1) Add 4 / 5 of water to the electrolytic protection tank based on the volume of the tank solution, add sodium molybdate, sodium hydroxyethylidene diphosphonate, and anhydrous potassium carbonate under stirring, and stir until the added materials are completely dissolved;

[0017] (2) Dissolve cerium chloride in water at a mass fraction of 10%, add the cerium chloride solution into the electrolytic protection tank under stirring, and stir until the cerium chloride is completely dissolved;

[0018] (3) Adjust the pH of the electrolytic protection solution to 11-13 with 10% potassium hydroxide solution and add water to the specified volume.

[0019] Preferably, during production, ammonia water with a volume ratio of 1:1 is used to adjust the pH of the gun black tin-nickel alloy plating solution to maintain it within the range of 7.8 to 8.2.

[0020] Preferably, during production, a potassium hydroxide solution with a mass fraction of 10% is used to adjust the pH of the rare earth electrolytic protection solution to maintain it within the range of 11 to 13.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. A gun-black tin-nickel alloy electroplating process of the present invention adds rare earth salts to the plating solution. The prepared gun-black tin-nickel alloy coating contains rare earth metal components, which effectively improves the corrosion resistance of the coating.

[0023] 2. The gun-black tin-nickel alloy electrolytic protection process of the present invention uses rare earth salts and sodium molybdate to prepare the electrolytic protection solution. The process is environmentally friendly, improves the corrosion resistance of the coating, and overcomes the high pollution problem of the dichromate electrolytic protection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present invention, constitute a part of this application, and do not constitute an improper limitation of the present invention. In the drawings:

[0025] Figure 1 Schematic diagram of the coating structure of Example 1, Example 2 and Example 3 of the present invention.

[0026] Figure 2 Schematic diagram of the coating structure of Example 4 and Example 5 of the present invention. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to 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.

[0028] The steel workpiece substrate is pre-treated according to the current degreasing, rust removal and activation processes.

[0029] After the steel workpiece is pre-treated, a pre-nickel plating layer is prepared according to a Watt nickel plating process, and the plating layer thickness is 0.2-2 μm.

[0030] Preferably, the Watt Nickel nickel plating process is as follows: calculated by mass concentration, nickel sulfate hexahydrate 150-200 g / L, sodium chloride 8-10 g / L, boric acid 30-35 g / L, anhydrous sodium sulfate 40-80 g / L, 2-ethylhexyl sulfate sodium salt 0.05-0.15 g / L, pH range 5-5.5, plating tank temperature 18°C-35°C, cathode current density 1-3 A / dm2, cathode movement 3-5 m / min.

[0031] An acid copper plating layer is prepared on the pre-plated nickel layer of the steel workpiece according to the current acid copper plating process, and the thickness of the acid copper plating layer is 8-18 μm.

[0032] Preferably, the acid copper plating process adopts the GAFFA M-8000 acid bright copper plating process of Chaobang Chemical: calculated by mass concentration, copper sulfate pentahydrate 180-210g / L, sulfuric acid 60-80g / L, chloride ion 50-100mg / L, calculated by volume concentration, GAFFA M-8000 Mu cylinder opener 3-8mL / L, GAFFA M-8000 A main brightener 0.3-0.6mL / L, GAFFA M-8000 B auxiliary brightener 0.05-0.3mL / L, plating tank temperature 18°C-30°C, cathode current density 2-6A / dm2, strong and uniform air stirring.

[0033] A bright nickel plating layer is prepared on the acid copper plating layer of the steel workpiece according to the current bright nickel plating process, and the plating layer thickness is 5-12 μm.

[0034] Preferably, the bright nickel plating process adopts the NINFEA 8003 bright nickel plating process of Chaobang Chemical: calculated by mass concentration, the nickel sulfate hexahydrate is 240-320 g / L, the nickel chloride hexahydrate is 45-60 g / L, and the boric acid is 40-50 g / L; calculated by volume concentration, the NINFEA SC-260 bright nickel softener is 15-40 mL / L, the NINFEA AS-250 bright nickel auxiliary agent is 3-7 mL / L, the NINFEA8003 bright nickel main brightening agent is 0.4-0.8 mL / L, and the NINFEA NI-35 bright nickel wetting agent is 0.5-1.5 mL / L; the pH range is 4.2-4.8, the plating tank temperature is 50°C-60°C, the cathode current density is 3-6 A / dm2, and the air is evenly stirred.

[0035] The nickel-phosphorus alloy plating layer is prepared on the bright nickel plating layer of the steel workpiece by adopting the current nickel-phosphorus alloy electroplating process, and the plating layer has a thickness of 1.5 to 1.8 μm.

[0036] Preferably, the nickel-phosphorus alloy coating adopts the EMFASI 8812 nickel-phosphorus alloy electroplating process of Chaobang Chemical: the volume concentration of EMFASI 8812 MU cylinder opener is 450-550 mL / L, the mass concentration of nickel sulfate hexahydrate is 280-340 g / L, the pH range is 2.5-2.7, the operating temperature is 60°C-65°C, the cathode current density is 3-6 A / dm2, and the cathode movement is 3-5 m / min.

[0037] A gun black tin-nickel alloy coating is prepared on the bright nickel coating or the nickel-phosphorus alloy coating of the steel workpiece, and the coating thickness is 0.5-1.5 μm.

[0038] Preferably, the gun black tin-nickel alloy electroplating process is: calculated by mass concentration: 240-280 g / L potassium pyrophosphate, 50-60 g / L nickel chloride hexahydrate, 7-9 g / L stannous chloride dihydrate, 1-2 g / L rare earth salt, 13-18 g / L potassium thiocyanate, 0.6-1.8 g / L methionine, 20-30 g / L ammonium citrate, 4-6 g / L disodium ethylenediaminetetraacetic acid, pH range 7.8-8.2, plating tank temperature 35°C-40°C, cathode current density 1-3 A / dm2, cathode movement 3-5 m / min, and a graphite plate as an anode.

[0039] Preferably, the rare earth salt includes one or both of lanthanum chloride and praseodymium chloride.

[0040] Preferably, during production, the pH of the gun black tin-nickel alloy plating solution is adjusted to within the range of 7.8 to 8.2 using aqueous ammonia at a volume ratio of 1:1.

[0041] Preferably, the gun black tin-nickel alloy plating solution is prepared as follows:

[0042] (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely;

[0043] (2) Dissolve disodium ethylenediaminetetraacetic acid in water at a mass fraction of 5%, add rare earth salt and stir until completely dissolved, then add the prepared rare earth salt solution into the plating tank and mix evenly;

[0044] (3) Using a thin iron plate as the cathode, electrolyze the prepared plating solution at a current of 0.1 to 0.3 A / dm2 for 1 to 6 hours;

[0045] (4) Dissolve methionine in water and add it to the plating tank and mix evenly. Use hydrochloric acid with a volume ratio of 1:1 to adjust the pH of the plating solution to 7.8-8.2, and add water to the specified volume.

[0046] A protective film is prepared on the gun black tin-nickel alloy coating of the prepared steel workpiece according to an electrolytic protection process.

[0047] Preferably, the electrolytic protection process is as follows:

[0048] Calculated by mass concentration, the cerium chloride is 2-5 g / L, sodium molybdate is 2-5 g / L, sodium hydroxyethylidene diphosphonate is 15-30 g / L, and anhydrous potassium carbonate is 100-150 g / L. The pH range is 11-13. The operation is at room temperature, the cathode current density is 0.5-1.2 A / dm2, the plated part is used as the cathode, the titanium plate is used as the anode, and the electrolysis is carried out for 60-120 s.

[0049] Preferably, during production, a potassium hydroxide solution with a mass fraction of 10% is used to adjust the pH of the rare earth electrolytic protection solution to maintain it within the range of 11 to 13.

[0050] Preferably, the electrolytic protection solution is prepared as follows:

[0051] (1) Add 4 / 5 of water to the electrolytic protection tank based on the volume of the tank solution, add sodium molybdate, sodium hydroxyethylidene diphosphonate, and anhydrous potassium carbonate under stirring, and stir until the added materials are completely dissolved;

[0052] (2) Dissolve cerium chloride in water at a mass fraction of 10%, add the cerium chloride solution into the electrolytic protection tank under stirring, and stir until the cerium chloride is completely dissolved;

[0053] (3) Adjust the pH of the electrolytic protection solution to 11-13 with 10% potassium hydroxide solution and add water to the specified volume.

[0054] Example 1

[0055] like Figure 1 As shown, a gun black tin-nickel alloy electroplating and electrolytic protection process includes preparing a pre-nickel plating layer 2, an acid copper plating layer 3, a bright nickel plating layer 4, a gun black tin-nickel alloy plating layer 5, and an electrolytic protective film 6 on a steel substrate 1 from the inside to the outside.

[0056] 1. Prepare gun black tin-nickel alloy plating solution according to process requirements:

[0057] (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely;

[0058] (2) Dissolve disodium ethylenediaminetetraacetic acid in water at a mass fraction of 5%, add lanthanum chloride and praseodymium chloride at a mass ratio of 1:1, stir until the rare earth salt is completely dissolved, and then add the prepared rare earth salt solution into the plating tank and mix evenly;

[0059] (3) Using a thin iron plate as the cathode, electrolyze the prepared plating solution at a current of 0.1 A / dm2 for 1 hour;

[0060] (4) Dissolve methionine in water and add it to the plating tank and mix evenly. Adjust the pH of the plating solution to 8 with hydrochloric acid at a volume ratio of 1:1, and add water to the specified volume.

[0061] 2. Prepare electrolytic protection solution according to process requirements:

[0062] (1) Add 4 / 5 of water to the electrolytic protection tank based on the volume of the tank solution, add sodium molybdate, sodium hydroxyethylidene diphosphonate, and anhydrous potassium carbonate under stirring, and stir until the added materials are completely dissolved;

[0063] (2) Dissolve cerium chloride in water at a mass fraction of 10%, add the cerium chloride solution into the electrolytic protection tank under stirring, and stir until the cerium chloride is completely dissolved;

[0064] (3) Adjust the pH of the electrolytic protection solution to 12.5 with a 10% potassium hydroxide solution and add water to the specified volume.

[0065] 3. Pre-treatment:

[0066] The steel workpiece substrate 1 is subjected to a pre-treatment process of "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0067] 4. Pre-nickel plating:

[0068] A pre-plated nickel layer 2 is prepared on a pre-treated steel workpiece substrate 1. The thickness of the plating layer 2 is 0.8 μm, and the Watt nickel plating process is adopted: 180 g / L nickel sulfate hexahydrate, 8 g / L sodium chloride, 32 g / L boric acid, 60 g / L anhydrous sodium sulfate, 0.1 g / L sodium 2-ethylhexyl sulfate, pH 5.3, plating tank temperature 25°C, cathode current density 0.8 A / dm2, and air stirring.

[0069] 5. Acid copper plating:

[0070] An acid copper plating layer 3 is prepared on the pre-nickel plating layer 2 of the steel workpiece. The thickness of the plating layer 3 is 15 μm. The GAFFA M-8000 acid bright copper plating process of Chaobang Chemical is adopted: 200 g / L of copper sulfate pentahydrate, 70 g / L of sulfuric acid, 80 mg / L of chloride ions, 6 mL / L of GAFFA M-8000 Mu opener, 0.5 mL / L of GAFFA M-8000 A main brightener, 0.2 mL / L of GAFFA M-8000 B auxiliary brightener, plating tank temperature of 25° C., cathode current density of 5 A / dm2, and strong and uniform air stirring.

[0071] 6. Bright nickel plating:

[0072] A bright nickel plating layer 4 is prepared on the acid copper plating layer 3 of the steel workpiece. The thickness of the plating layer 4 is 6 μm. The NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 280 g / L of nickel sulfate hexahydrate, 50 g / L of nickel chloride hexahydrate, 45 g / L of boric acid, 30 mL / L of NINFEA SC-260 bright nickel softener, 5 mL / L of NINFEA AS-250 bright nickel auxiliary agent, 0.6 mL / L of NINFEA 8003 bright nickel main brightening agent, 1 mL / L of NINFEA NI-35 bright nickel wetting agent, pH of 4.5, plating tank temperature of 55°C, cathode current density of 4 A / dm2, and uniform air stirring.

[0073] 7. Gun-plated black tin-nickel alloy:

[0074] A gun-black tin-nickel alloy coating 5 is formed on the bright nickel coating 4 of the steel workpiece. The coating 5 has a thickness of 1 μm and is prepared using a gun-black tin-nickel alloy electroplating process developed by Chaobang Chemical: 260 g / L potassium pyrophosphate, 55 g / L nickel chloride hexahydrate, 8 g / L stannous chloride dihydrate, 1 g / L lanthanum chloride, 1 g / L praseodymium chloride, 15 g / L potassium thiocyanate, 1.2 g / L methionine, 25 g / L ammonium citrate, 6 g / L disodium ethylenediaminetetraacetic acid, pH 8, plating bath temperature 38°C, cathode current density 2 A / dm2, cathode travel 4 m / min, and a graphite plate as the anode. During production, the pH of the gun-black tin-nickel alloy plating solution is adjusted to within the process range using ammonia water at a volume ratio of 1:1.

[0075] 8. Electrolytic protection:

[0076] An electrolytic protective film 6 is prepared on the gunmetal black tin-nickel alloy coating 5 of the steel workpiece using a rare earth cathode electrolytic protection process developed by Chaobang Chemical: 4 g / L cerium chloride, 3 g / L sodium molybdate, 25 g / L sodium hydroxyethylidene diphosphonate, 100 g / L anhydrous potassium carbonate, a pH of 12.5, a cathode current density of 0.8 A / dm², and room temperature operation. The gunmetal black tin-nickel alloy workpiece serves as the cathode and a titanium plate serves as the anode. Electrolysis is performed for 90 seconds, with an area ratio of cathode to anode of 2:1. During production, the pH of the rare earth electrolytic protection solution is adjusted to within the process range using a 10% by mass potassium hydroxide solution.

[0077] 9. Drying:

[0078] The steel workpiece was electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0079] Example 2

[0080] like Figure 1As shown, a gun black tin-nickel alloy electroplating and electrolytic protection process includes preparing a pre-nickel plating layer 2, an acid copper plating layer 3, a bright nickel plating layer 4, a gun black tin-nickel alloy plating layer 5, and an electrolytic protective film 6 on a steel substrate 1 from the inside to the outside.

[0081] 1. Prepare gun black tin-nickel alloy plating solution according to process requirements:

[0082] (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely;

[0083] (2) Dissolve disodium ethylenediaminetetraacetic acid in water at a mass fraction of 5%, add lanthanum chloride and praseodymium chloride at a mass ratio of 2:1, stir until the rare earth salt is completely dissolved, and then add the prepared rare earth salt solution into the plating tank and mix evenly;

[0084] (3) Using a thin iron plate as the cathode, the prepared plating solution was electrolyzed at a current of 0.1 A / dm2 for 2 hours;

[0085] (4) Dissolve methionine in water and add it to the plating tank and mix evenly. Adjust the pH of the plating solution to 8 with hydrochloric acid at a volume ratio of 1:1, and add water to the specified volume.

[0086] 2. Prepare electrolytic protection solution according to process requirements:

[0087] (1) Add 4 / 5 of water to the electrolytic protection tank based on the volume of the tank solution, add sodium molybdate, sodium hydroxyethylidene diphosphonate, and anhydrous potassium carbonate under stirring, and stir until the added materials are completely dissolved;

[0088] (2) Dissolve cerium chloride in water at a mass fraction of 10%, add the cerium chloride solution into the electrolytic protection tank under stirring, and stir until the cerium chloride is completely dissolved;

[0089] (3) Adjust the pH of the electrolytic protection solution to 12.5 with a 10% potassium hydroxide solution and add water to the specified volume.

[0090] 3. Workpiece pre-treatment:

[0091] The steel workpiece substrate 1 is subjected to a pre-treatment process of "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0092] 4. Pre-nickel plating:

[0093] A pre-plated nickel layer 2 is prepared on a pre-treated steel workpiece substrate 1. The thickness of the plating layer 2 is 0.5 μm, and the Watt nickel plating process is adopted: 160 g / L nickel sulfate hexahydrate, 8 g / L sodium chloride, 30 g / L boric acid, 50 g / L anhydrous sodium sulfate, 0.1 g / L sodium 2-ethylhexyl sulfate, pH 5.1, plating tank temperature 20°C, cathode current density 0.8 A / dm2, and air stirring.

[0094] 5. Acid copper plating:

[0095] An acid copper plating layer 3 is prepared on the pre-nickel plating layer 2 of the steel workpiece. The thickness of the plating layer 3 is 15 μm. The GAFFA M-8000 acid bright copper plating process of Chaobang Chemical is adopted: 185 g / L of copper sulfate pentahydrate, 65 g / L of sulfuric acid, 55 mg / L of chloride ions, 4 mL / L of GAFFA M-8000 Mu opener, 0.3 mL / L of GAFFA M-8000 A main brightener, 0.1 mL / L of GAFFA M-8000 B auxiliary brightener, plating tank temperature of 25° C., cathode current density of 3 A / dm2, and strong and uniform air stirring.

[0096] 6. Bright nickel plating:

[0097] A bright nickel plating layer 4 is prepared on the acid copper plating layer 3 of the steel workpiece. The thickness of the plating layer 4 is 5 μm. The NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 260 g / L of nickel sulfate hexahydrate, 45 g / L of nickel chloride hexahydrate, 40 g / L of boric acid, 20 mL / L of NINFEA SC-260 bright nickel softener, 4 mL / L of NINFEA AS-250 bright nickel auxiliary agent, 0.5 mL / L of NINFEA 8003 bright nickel main brightening agent, 0.8 mL / L of NINFEA NI-35 bright nickel wetting agent, pH of 4.3, plating tank temperature of 52°C, cathode current density of 3.5 A / dm2, and uniform air stirring.

[0098] 7. Gun-plated black tin-nickel alloy:

[0099] A gun-black tin-nickel alloy coating 5 is prepared on the bright nickel coating 4 of the steel workpiece. The coating 5 has a thickness of 1 μm and is prepared using the gun-black tin-nickel alloy electroplating process developed by Chaobang Chemical: 240 g / L potassium pyrophosphate, 50 g / L nickel chloride hexahydrate, 7 g / L stannous chloride dihydrate, 1 g / L lanthanum chloride, 0.5 g / L praseodymium chloride, 13 g / L potassium thiocyanate, 0.8 g / L methionine, 20 g / L ammonium citrate, 6 g / L disodium ethylenediaminetetraacetic acid, pH 8, plating tank temperature 40°C, cathode current density 2 A / dm2, cathode movement 4 m / min, a graphite plate as an anode, and in production, ammonia water with a volume ratio of 1:1 is used to adjust the pH of the gun-black tin-nickel alloy plating solution to within the process range.

[0100] 8. Rare earth electrolysis protection:

[0101] An electrolytic protective film 6 is prepared on the gunmetal black tin-nickel alloy coating 5 of the steel workpiece using a rare earth cathode electrolytic protection process developed by Chaobang Chemical: 3 g / L cerium chloride, 4 g / L sodium molybdate, 20 g / L sodium hydroxyethylidene diphosphonate, 120 g / L anhydrous potassium carbonate, a pH of 12.5, a cathode current density of 0.8 A / dm², and room temperature operation. The gunmetal black tin-nickel alloy workpiece serves as the cathode and a titanium plate serves as the anode. Electrolysis is performed for 80 seconds, with an area ratio of cathode to anode of 2:1. During production, the pH of the rare earth electrolytic protection solution is adjusted to within the process range using a 10% by mass potassium hydroxide solution.

[0102] 9. Drying:

[0103] The steel workpiece was electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0104] Example 3

[0105] like Figure 1 As shown, a gun black tin-nickel alloy electroplating and electrolytic protection process includes preparing a pre-nickel plating layer 2, an acid copper plating layer 3, a bright nickel plating layer 4, a gun black tin-nickel alloy plating layer 5, and an electrolytic protective film 6 on a steel substrate 1 from the inside to the outside.

[0106] 1. Prepare gun black tin-nickel alloy plating solution according to process requirements:

[0107] (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely;

[0108] (2) Dissolve disodium ethylenediaminetetraacetic acid in water at a mass fraction of 5%, add lanthanum chloride and praseodymium chloride at a mass ratio of 1:2, stir until the rare earth salt is completely dissolved, and then add the prepared rare earth salt solution into the plating tank and mix evenly;

[0109] (3) Using a thin iron plate as the cathode, electrolyze the prepared plating solution at a current of 0.1 A / dm2 for 1 hour;

[0110] (4) Dissolve methionine in water and add it to the plating tank and mix evenly. Adjust the pH of the plating solution to 8 with hydrochloric acid at a volume ratio of 1:1, and add water to the specified volume.

[0111] 2. Prepare electrolytic protection solution according to process requirements:

[0112] (1) Add 4 / 5 of water to the electrolytic protection tank based on the volume of the tank solution, add sodium molybdate, sodium hydroxyethylidene diphosphonate, and anhydrous potassium carbonate under stirring, and stir until the added materials are completely dissolved;

[0113] (2) Dissolve cerium chloride in water at a mass fraction of 10%, add the cerium chloride solution into the electrolytic protection tank under stirring, and stir until the cerium chloride is completely dissolved;

[0114] (3) Adjust the pH of the electrolytic protection solution to 12.8 with a 10% potassium hydroxide solution and add water to the specified volume.

[0115] 3. Pre-treatment:

[0116] The steel workpiece substrate 1 is subjected to a pre-treatment process of "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0117] 4. Watt nickel plating:

[0118] A pre-plated nickel layer 2 is prepared on a pre-treated steel workpiece substrate 1. The thickness of the plating layer 2 is 0.3 μm, and the Watt nickel plating process is adopted: 190 g / L nickel sulfate hexahydrate, 10 g / L sodium chloride, 35 g / L boric acid, 70 g / L anhydrous sodium sulfate, 0.1 g / L sodium 2-ethylhexyl sulfate, pH 5.5, plating tank temperature 35°C, cathode current density 0.8 A / dm2, and air stirring.

[0119] 5. Acid copper plating:

[0120] An acid copper plating layer 3 is prepared on the pre-nickel plating layer 2 of the steel workpiece. The thickness of the plating layer 3 is 12 μm. The GAFFA M-8000 acid bright copper plating process of Chaobang Chemical is adopted: 200 g / L copper sulfate pentahydrate, 75 g / L sulfuric acid, 90 mg / L chloride ion, 7 mL / L GAFFA M-8000 Mu opener, 0.55 mL / L GAFFA M-8000 A main brightener, 0.25 mL / L GAFFA M-8000 B auxiliary brightener, plating tank temperature of 28° C., cathode current density of 5 A / dm2, and strong and uniform air stirring.

[0121] 6. Bright nickel plating:

[0122] A bright nickel plating layer 4 is prepared on the acid copper plating layer 3 of the steel workpiece. The thickness of the plating layer 4 is 12 μm. The NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 310 g / L of nickel sulfate hexahydrate, 60 g / L of nickel chloride hexahydrate, 50 g / L of boric acid, 35 mL / L of NINFEA SC-260 bright nickel softener, 6 mL / L of NINFEA AS-250 bright nickel auxiliary agent, 0.8 mL / L of NINFEA 8003 bright nickel main brightening agent, 1.5 mL / L of NINFEA NI-35 bright nickel wetting agent, pH 4.7, plating tank temperature 58°C, cathode current density 5 A / dm2, and uniform air stirring.

[0123] 7. Gun-plated black tin-nickel alloy:

[0124] A gun-black tin-nickel alloy coating 5 is prepared on the bright nickel coating 4 of the steel workpiece. The coating 5 has a thickness of 1 μm. The gun-black tin-nickel alloy electroplating process developed by Chaobang Chemical is used: 280 g / L potassium pyrophosphate, 60 g / L nickel chloride hexahydrate, 9 g / L stannous chloride dihydrate, 0.5 g / L lanthanum chloride, 1 g / L praseodymium chloride, 18 g / L potassium thiocyanate, 1.6 g / L methionine, 30 g / L ammonium citrate, 5 g / L disodium ethylenediaminetetraacetic acid, pH 8.2, plating bath temperature 40°C, cathode current density 2 A / dm2, cathode travel 4 m / min, and a graphite plate is used as the anode. During production, the pH of the gun-black tin-nickel alloy plating solution is adjusted to within the process range using ammonia water at a volume ratio of 1:1.

[0125] 8. Electrolytic protection:

[0126] An electrolytic protective film 6 is prepared on the bright nickel coating 5 of the steel workpiece using a rare earth cathode electrolytic protection process developed by Chaobang Chemical: 3.5 g / L cerium chloride, 5 g / L sodium molybdate, 20 g / L sodium hydroxyethylidene diphosphonate, 110 g / L anhydrous potassium carbonate, a pH of 12.8, a cathode current density of 0.8 A / dm², and room temperature operation. A gun-black tin-nickel alloy workpiece serves as the cathode and a titanium plate serves as the anode. Electrolysis is performed for 100 seconds, with an area ratio of 2:1 between the cathode and anode. During production, a 10% by mass potassium hydroxide solution is used to adjust the pH of the rare earth electrolytic protection solution to within the process range.

[0127] 9. Drying:

[0128] The steel workpiece was electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0129] Example 4

[0130] like Figure 2As shown, a gun black tin-nickel alloy electroplating and electrolytic protection process includes preparing a pre-nickel plating layer 2, an acid copper plating layer 3, a bright nickel plating layer 4, a nickel-phosphorus alloy plating layer 5, a gun black tin-nickel alloy plating layer 6, and an electrolytic protective film 7 on a steel substrate 1 from the inside to the outside.

[0131] 1. Prepare gun black tin-nickel alloy plating solution according to process requirements:

[0132] (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely;

[0133] (2) Dissolve disodium ethylenediaminetetraacetic acid in water at a mass fraction of 5%, add lanthanum chloride and stir until completely dissolved, then add the prepared rare earth salt solution into the plating tank and mix evenly;

[0134] (3) Using a thin iron plate as the cathode, the prepared plating solution was electrolyzed at a current of 0.2 A / dm2 for 1 hour;

[0135] (4) Dissolve methionine in water and add it to the plating tank and mix evenly. Adjust the pH of the plating solution to 8 with hydrochloric acid at a volume ratio of 1:1, and add water to the specified volume.

[0136] 2. Prepare electrolytic protection solution according to process requirements:

[0137] (1) Add 4 / 5 of water to the electrolytic protection tank based on the volume of the tank solution, add sodium molybdate, sodium hydroxyethylidene diphosphonate, and anhydrous potassium carbonate under stirring, and stir until the added materials are completely dissolved;

[0138] (2) Dissolve cerium chloride in water at a mass fraction of 10%, add the cerium chloride solution into the electrolytic protection tank under stirring, and stir until the cerium chloride is completely dissolved;

[0139] (3) Adjust the pH of the electrolytic protection solution to 12.8 with a potassium hydroxide solution with a mass fraction of 10%, and add water to the specified volume.

[0140] 3. Pre-treatment:

[0141] The steel substrate 1 is subjected to a pre-treatment process of "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0142] 4. Pre-nickel plating:

[0143] A pre-plated nickel layer 2 is prepared on the pre-treated steel workpiece substrate 1. The thickness of the plating layer 2 is 0.3 μm and is prepared using the Watt nickel plating process: 195 g / L nickel sulfate hexahydrate, 11 g / L sodium chloride, 35 g / L boric acid, 70 g / L anhydrous sodium sulfate, 0.1 g / L sodium 2-ethylhexyl sulfate, pH 5.5, plating tank temperature 35°C, cathode current density 0.8 A / dm2, and air stirring.

[0144] 5. Acid copper plating:

[0145] An acid copper plating layer 3 is prepared on the pre-nickel plating layer 2 of the steel part. The thickness of the plating layer 3 is 14 μm. The GAFFA M-8000 acid bright copper plating process of Chaobang Chemical is adopted: 200 g / L of copper sulfate pentahydrate, 70 g / L of sulfuric acid, 80 mg / L of chloride ions, 6 mL / L of GAFFA M-8000 Mu opener, 0.5 mL / L of GAFFA M-8000 A main brightener, 0.2 mL / L of GAFFA M-8000 B auxiliary brightener, plating tank temperature of 25° C., cathode current density of 4 A / dm2, and strong and uniform air stirring.

[0146] 6. Bright nickel plating:

[0147] A bright nickel plating layer 4 is prepared on the acid copper plating layer 3 of the steel part. The thickness of the plating layer 4 is 6 μm. The NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 280 g / L of nickel sulfate hexahydrate, 50 g / L of nickel chloride hexahydrate, 45 g / L of boric acid, 30 mL / L of NINFEA SC-260 bright nickel softener, 5 mL / L of NINFEA AS-250 bright nickel auxiliary agent, 0.6 mL / L of NINFEA 8003 bright nickel main brightening agent, 1 mL / L of NINFEA NI-35 bright nickel wetting agent, pH of 4.5, plating tank temperature of 55°C, cathode current density of 4 A / dm2, and uniform air stirring.

[0148] 7. Nickel-phosphorus alloy plating

[0149] A nickel-phosphorus alloy coating 5 is prepared on the bright nickel coating 4 of the steel part. The thickness of the coating 5 is 2 μm. The EMFASI 8812 nickel-phosphorus alloy electroplating process of Chaobang Chemical is adopted: EMFASI 8812 MU opener 480 mL / L, nickel sulfate 300 g / L, pH 2.6, operating temperature 62°C, cathode current density 4 A / dm2, and cathode movement 4 m / min.

[0150] 8. Gun-plated black tin-nickel alloy:

[0151] A gun-black tin-nickel alloy coating 6 is formed on the nickel-phosphorus alloy coating 5 of the steel part. The coating 6 has a thickness of 1.2 μm. The gun-black tin-nickel alloy electroplating process developed by Chaobang Chemical is used: 260 g / L potassium pyrophosphate, 55 g / L nickel chloride hexahydrate, 8 g / L stannous chloride dihydrate, 2 g / L lanthanum chloride, 15 g / L potassium thiocyanate, 1.2 g / L methionine, 25 g / L ammonium citrate, 6 g / L disodium ethylenediaminetetraacetic acid, pH 8, plating bath temperature 38°C, cathode current density 2 A / dm², cathode travel 4 m / min, and a graphite plate is used as the anode. During production, the pH of the gun-black tin-nickel alloy plating solution is adjusted to within the process range using ammonia water at a volume ratio of 1:1.

[0152] 9. Electrolytic protection:

[0153] An electrolytic protective film 7 is prepared on the gunmetal black tin-nickel alloy coating 6 of the steel workpiece using a rare earth cathode electrolytic protection process developed by Chaobang Chemical: 5 g / L cerium chloride, 5 g / L sodium molybdate, 30 g / L sodium hydroxyethylidene diphosphonate, 150 g / L anhydrous potassium carbonate, a pH of 12, a cathode current density of 0.8 A / dm², and room temperature operation. The gunmetal black tin-nickel alloy workpiece serves as the cathode and a titanium plate serves as the anode. Electrolysis is performed for 120 seconds, with an area ratio of cathode to anode of 2:1. During production, the pH of the electrolytic protective solution is adjusted to within the process range using a 10% by mass potassium hydroxide solution.

[0154] 10. Drying:

[0155] The steel parts were electrolytically protected and washed with water, and then dried at 80° C. for 25 minutes.

[0156] Example 5

[0157] like Figure 2 As shown, a gun black tin-nickel alloy electroplating process includes preparing a pre-nickel plating layer 2, an acid copper plating layer 3, a bright nickel plating layer 4, a nickel-phosphorus alloy plating layer 5, a gun black tin-nickel alloy plating layer 6, and an electrolytic protective film 7 on a steel substrate 1 from the inside to the outside.

[0158] 1. Prepare rare earth electrolytic protection solution:

[0159] 1. Prepare gun black tin-nickel alloy plating solution according to process requirements:

[0160] (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely;

[0161] (2) Dissolve disodium ethylenediaminetetraacetic acid in water at a mass fraction of 5%, add praseodymium chloride and stir until completely dissolved, then add the prepared rare earth salt solution into the plating tank and mix evenly;

[0162] (3) Using a thin iron plate as the cathode, the prepared plating solution was electrolyzed at a current of 0.2 A / dm2 for 1 hour;

[0163] (4) Dissolve methionine in water and add it to the plating tank and mix evenly. Adjust the pH of the plating solution to 8 with hydrochloric acid at a volume ratio of 1:1, and add water to the specified volume.

[0164] 2. Prepare electrolytic protection solution according to process requirements:

[0165] (1) Add 4 / 5 of water to the electrolytic protection tank based on the volume of the tank solution, add sodium molybdate, sodium hydroxyethylidene diphosphonate, and anhydrous potassium carbonate under stirring, and stir until the added materials are completely dissolved;

[0166] (2) Dissolve cerium chloride in water at a mass fraction of 10%, add the cerium chloride solution into the electrolytic protection tank under stirring, and stir until the cerium chloride is completely dissolved;

[0167] (3) Adjust the pH of the electrolytic protection solution to 12.8 with a 10% potassium hydroxide solution and add water to the specified volume.

[0168] 2. Pre-treatment:

[0169] The steel substrate 1 is subjected to a pre-treatment process of "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathodic electrolytic degreasing → water washing → alkaline anodic electrolytic degreasing → water washing → activation → water washing".

[0170] 4. Pre-nickel plating:

[0171] A pre-plated nickel layer 2 is prepared on a pre-treated steel workpiece substrate 1. The thickness of the plating layer 2 is 0.3 μm, and the Watt nickel plating process is adopted: 200 g / L nickel sulfate hexahydrate, 10 g / L sodium chloride, 30 g / L boric acid, 75 g / L anhydrous sodium sulfate, 0.1 g / L sodium 2-ethylhexyl sulfate, pH 5.5, plating tank temperature 35°C, cathode current density 0.8 A / dm2, and air stirring.

[0172] 5. Acid copper plating:

[0173] An acid copper plating layer 3 is prepared on the pre-nickel plating layer 2 of the steel part. The thickness of the plating layer 3 is 11 μm. The GAFFA M-8000 acid bright copper plating process of Chaobang Chemical is adopted: 200 g / L copper sulfate pentahydrate, 70 g / L sulfuric acid, 80 mg / L chloride ion, 6 mL / L GAFFA M-8000 Mu opener, 0.5 mL / L GAFFA M-8000 A main brightener, 0.2 mL / L GAFFA M-8000 B auxiliary brightener, plating tank temperature is 25° C., cathode current density is 4 A / dm2, and strong and uniform air stirring is performed.

[0174] 6. Bright nickel plating:

[0175] A bright nickel plating layer 4 is prepared on the acid copper plating layer 3 of the steel part. The thickness of the plating layer 4 is 6 μm. The NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 280 g / L of nickel sulfate hexahydrate, 50 g / L of nickel chloride hexahydrate, 45 g / L of boric acid, 30 mL / L of NINFEA SC-260 bright nickel softener, 5 mL / L of NINFEA AS-250 bright nickel auxiliary agent, 0.6 mL / L of NINFEA 8003 bright nickel main brightening agent, 1 mL / L of NINFEA NI-35 bright nickel wetting agent, pH of 4.5, plating tank temperature of 55°C, cathode current density of 4 A / dm2, and uniform air stirring.

[0176] 7. Nickel-phosphorus alloy plating:

[0177] A nickel-phosphorus alloy coating 5 is prepared on the bright nickel coating 4 of the steel part. The thickness of the coating 5 is 2 μm. The EMFASI 8812 nickel-phosphorus alloy electroplating process of Chaobang Chemical is adopted: EMFASI 8812 MU opener 520 mL / L, nickel sulfate 320 g / L, pH 2.6, operating temperature 62°C, cathode current density 4 A / dm2, and cathode movement 4 m / min.

[0178] 8. Gun-plated black tin-nickel alloy:

[0179] A gunmetal black tin-nickel alloy coating 6 is formed on the nickel-phosphorus alloy coating 5 of the steel component. The coating 6 has a thickness of 1.2 μm. The gunmetal black tin-nickel alloy electroplating process developed by Chaobang Chemical is used: 260 g / L potassium pyrophosphate, 55 g / L nickel chloride hexahydrate, 8 g / L stannous chloride dihydrate, 2 g / L praseodymium chloride, 15 g / L potassium thiocyanate, 1.2 g / L methionine, 25 g / L ammonium citrate, and 6 g / L disodium ethylenediaminetetraacetic acid. The pH is 8, the plating bath temperature is 38°C, the cathode current density is 2 A / dm2, the cathode travel is 4 m / min, and a graphite plate is used as the anode. During production, the pH of the gunmetal black tin-nickel alloy plating solution is adjusted to within the process range using ammonia water at a volume ratio of 1:1.

[0180] 8. Electrolytic protection:

[0181] An electrolytic protective film 7 is prepared on the gunmetal black tin-nickel alloy coating 6 of the steel workpiece using a rare earth cathode electrolytic protection process developed by Chaobang Chemical: 5 g / L cerium chloride, 4 g / L sodium molybdate, 30 g / L sodium hydroxyethylidene diphosphonate, 140 g / L anhydrous potassium carbonate, a pH of 12.8, a cathode current density of 0.8 A / dm², and room temperature operation. The gunmetal black tin-nickel alloy workpiece serves as the cathode and a titanium plate serves as the anode. Electrolysis is performed for 120 seconds, with an area ratio of cathode to anode of 2:1. During production, the pH of the rare earth electrolytic protective solution is adjusted to within the process range using a 10% by mass potassium hydroxide solution.

[0182] 9. Drying:

[0183] After rare earth electrolytic protection and water washing, the steel piece is dried at 80° C. for 25 minutes.

[0184] Test Example 1

[0185] A 50 mm × 100 mm × 2 mm A3 steel plate was used to plate a black tin-nickel alloy test sample according to Examples 1-5. A neutral salt spray test was performed for 96 hours in accordance with GB / T 10125-2021 "Artificial atmosphere corrosion test salt spray test". The surface of the test sample was free of rust.

[0186] Test Example 2

[0187] 50 mm × 100 mm × 2 mm A3 steel plates were gun-coated with a black tin-nickel alloy test sample according to Examples 1-5. The coating adhesion was tested using the thermal shock method according to ISO 2819-2017. The test sample was heated to 300°C in a furnace for 30 minutes, then removed and suddenly cooled in room temperature water. The coating showed no blistering or shedding. The test demonstrated that the composite coating prepared by the present invention exhibits excellent adhesion.

[0188] Comparative Example 1

[0189] 1. Prepare gun black tin-nickel alloy plating solution:

[0190] (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely;

[0191] (2) Using a thin iron plate as the cathode, the prepared plating solution was electrolyzed at a current of 0.2 A / dm2 for 1 h;

[0192] (3) Dissolve methionine in water and add it to the plating tank and mix evenly. Adjust the pH of the plating solution to 8 with hydrochloric acid at a volume ratio of 1:1, and add water to the specified volume.

[0193] 2. Gun-plated black tin-nickel alloy test specimens:

[0194] A 50 mm × 100 mm × 2 mm A3 steel sheet was pretreated according to steps 3-6 of Example 1 to prepare a pre-nickel coating, an acid copper coating, and a bright nickel coating. A gunmetal black tin-nickel alloy plating solution prepared in this comparative example was then used to prepare a gunmetal black tin-nickel alloy coating. An electrolytic protective film was then prepared according to step 8 of Example 1. The prepared test specimens were subjected to a neutral salt spray test for 96 hours in accordance with GB / T 10125–2021, "Artificial Atmosphere Corrosion Test Salt Spray Test." Grayish-white corrosion products appeared on the surface. The test showed that the corrosion resistance of the prepared test specimens decreased when rare earth salts were not added to the gunmetal black tin-nickel alloy plating solution.

[0195] Comparative Example 2

[0196] A 50 mm × 100 mm × 2 mm A3 steel sheet was pretreated according to steps 3-7 of Example 1, and a Watt nickel coating, acid copper coating, bright nickel coating, and gunmetal black tin-nickel alloy coating were prepared. No electrolytic protection was performed. The prepared test specimens were subjected to a neutral salt spray test for 96 hours in accordance with GB / T 10125–2021, "Artificial Atmosphere Corrosion Test, Salt Spray Test." Grayish-white corrosion products appeared on the surface. The test showed that even when the gunmetal black tin-nickel alloy coating was prepared according to the present invention without electrolytic protection, its corrosion resistance was reduced.

[0197] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. The scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A gun black tin-nickel alloy electroplating and electrolytic protection process, characterized in that: It includes two processes: gun black tin-nickel alloy electroplating and electrolytic protection of the plating layer: The gun black tin-nickel alloy electroplating process is as follows: potassium pyrophosphate 240-280g / L, nickel chloride hexahydrate 50-60g / L, stannous chloride dihydrate 7-9g / L, rare earth salt 1-2g / L, potassium thiocyanate 13-18g / L, methionine 0.6-1.8g / L, ammonium citrate 20-30g / L, disodium ethylenediaminetetraacetic acid 4-6g / L, pH range 7.8-8.2, plating tank temperature 35℃-40℃, cathode current density 1-3A / dm2, cathode movement 3-5m / min, using a graphite plate as the anode; The rare earth salt includes any one or both of lanthanum chloride and praseodymium chloride; The electrolytic protection process of gun black tin-nickel alloy plating is as follows: Cerium chloride 2-5 g / L, sodium molybdate 2-5 g / L, sodium hydroxyethylidene diphosphonate 15-30 g / L, anhydrous potassium carbonate 100-150 g / L, pH range 11-13, operation at room temperature, cathode current density 0.5-1.2 A / dm2, use plated parts as cathode, titanium plate as anode, electrolysis for 60-120 s.

2. The gun black tin-nickel alloy electroplating and electrolytic protection process according to claim 1, characterized in that: The preparation method of gun black tin-nickel alloy plating solution is as follows: (1) Add 4 / 5 of water to the plating tank based on the volume of the tank solution, add ammonium citrate, nickel chloride hexahydrate, stannous chloride dihydrate, and potassium thiocyanate while stirring, stir to dissolve the added materials, then add potassium pyrophosphate and stir to dissolve completely; (2) Dissolve disodium ethylenediaminetetraacetic acid in water at a mass fraction of 5%, add rare earth salt and stir until completely dissolved, then add the prepared rare earth salt solution into the plating tank and mix evenly; (3) Using a thin iron plate as the cathode, electrolyze the prepared plating solution at a current of 0.1 to 0.3 A / dm2 for 1 to 6 hours; (4) Dissolve methionine in water and add it to the plating tank and mix evenly. Then adjust the pH of the plating solution to 7.8-8.2 with hydrochloric acid at a volume ratio of 1:1, and add water to the specified volume.

3. The gun black tin-nickel alloy electroplating and electrolytic protection process according to claim 1, characterized in that: The preparation method of electrolytic protection solution is as follows: (1) Add 4 / 5 of water to the electrolytic protection tank based on the volume of the tank solution, add sodium molybdate, sodium hydroxyethylidene diphosphonate, and anhydrous potassium carbonate under stirring, and stir until the added materials are completely dissolved; (2) Dissolve cerium chloride in water at a mass fraction of 10%, add the cerium chloride solution into the electrolytic protection tank under stirring, and stir until the cerium chloride is completely dissolved; (3) Adjust the pH of the electrolytic protection solution to 11-13 with 10% potassium hydroxide solution and add water to the specified volume.

4. The gunmetal black tin-nickel alloy electroplating and electrolytic protection process according to claim 1 or 2, characterized in that: During production, ammonia water with a volume ratio of 1:1 is used to adjust the pH of the gun black tin-nickel alloy plating solution to maintain it within the range of 7.8 to 8.

2.

5. The gunmetal black tin-nickel alloy electroplating and electrolytic protection process according to claim 1 or 3, characterized in that: During production, a potassium hydroxide solution with a mass fraction of 10% is used to adjust the pH of the electrolytic protection solution to maintain it within the range of 11 to 13.

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