Rare earth electrolytic protection process of black tin-nickel alloy by electroplating gun and its combined coating

Abstract

The invention discloses a rare earth electrolytic protection process for electroplating gun black tin-nickel alloy and a combined coating, including a bottom coating, a bright nickel coating, a gun black tin-nickel alloy coating, and a rare earth electrolytic protective film, which are prepared sequentially from the inside to the outside on a metal substrate. The rare earth electrolytic protective film is prepared by a rare earth electrolytic protection process: 1 to 8 g / L of rare earth salt, 5 to 50 g / L of HEDP complexing agent, 80 to 160 g / L of anhydrous potassium carbonate, a pH range of 11 to 13, an operating temperature of 15°C to 40°C, and a cathode current density of 0.5 to 1.2 A / dm 2 , using the plated part as the cathode and the titanium plate as the anode, electrolyzing for 30 to 100 seconds, wherein the rare earth salt includes one or two of lanthanum chloride, cerium chloride, and praseodymium chloride. The combined coating is subjected to a neutral salt spray test for 72 hours in accordance with GB / T 10125-2012 "Artificial Atmosphere Corrosion Test Salt Spray Test", and no white corrosion products are generated on the surface of the plated part. The rare earth electrolytic protection process of the present invention replaces the traditional potassium dichromate electrolytic protection process, thereby solving the problem of high pollution of hexavalent chromium.

Description

Technical Field

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

[0002] Gun black tin-nickel alloy coating has an elegant appearance and good wear resistance. It is mainly used to prepare decorative coatings for hardware, electronics and gun accessories. In the past, dichromate electrolytic protection was usually used to improve the corrosion resistance of the coating, but the use of hexavalent chromium has been subject to increasingly stringent restrictions. The industry is developing an environmentally friendly post-treatment protection process for gun black tin-nickel alloy coating. Summary of the invention

[0003] In order to solve the high pollution problem of hexavalent chromium post-treatment protection process, the present invention provides a rare earth electrolytic protection process of black tin-nickel alloy of electroplating gun and its combined coating. In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0004] A rare earth electrolytic protection process for electroplating a gun-black tin-nickel alloy and a combined coating thereof, comprising preparing a bottom coating, a bright nickel coating, a gun-black tin-nickel alloy coating, and a rare earth electrolytic protective film in sequence from the inside to the outside on a metal substrate;

[0005] The rare earth electrolytic protection membrane is prepared by a rare earth electrolytic protection process: rare earth salt 1-8 g / L, HEDP coordination agent 5-50 g / L, anhydrous potassium carbonate 80-160 g / L, pH range 11-13, operating temperature 15°C-40°C, cathode current density 0.5-1.2 A / dm 2 , use the plated part as cathode and the titanium plate as anode, and electrolyze for 30 to 100 seconds;

[0006] The rare earth salt includes one or two of lanthanum chloride, cerium chloride, and praseodymium chloride.

[0007] Preferably, the rare earth electrolytic protection solution is prepared as follows:

[0008] (1) adding 2 / 3 of water to the electrolytic protection tank, then adding HEDP complexing agent and anhydrous potassium carbonate in the amount required by the rare earth electrolytic protection process, and stirring to dissolve;

[0009] (2) preparing the rare earth salt into an aqueous solution with a mass fraction of 10%, adding the prepared rare earth salt solution into the electrolytic protection tank under stirring according to the amount required by the rare earth electrolytic protection process, and stirring until the added material is completely dissolved;

[0010] (3) Use 10% potassium hydroxide solution to adjust the pH of the solution in the electrolytic protection tank to 11-13, and add water to the specified volume.

[0011] Preferably, during production, a 10% by mass potassium hydroxide solution is used to adjust the pH of the rare earth electrolysis protection solution to maintain it within the range of 11 to 13.

[0012] Preferably, the process for electroplating gun black tin-nickel alloy is: potassium pyrophosphate 240-280 g / L, nickel chloride hexahydrate 50-60 g / L, stannous chloride 7-9 g / L, potassium thiocyanate 13-18 g / L, methionine 0.6-1.8 g / L, ammonium citrate 20-30 g / L, pH range 7.8-8.2, plating tank temperature 35°C-40°C, cathode current density 1-3 A / dm 2 , the cathode moves 3 to 5 m / min, and a graphite plate is used as the anode. In production, a 10% by mass potassium hydroxide solution is used to adjust the pH of the gun black tin-nickel alloy plating solution to keep it in the range of 7.8 to 8.2.

[0013] A rare earth electrolytic protection process for electroplating a gun-black tin-nickel alloy and a combined coating thereof. The prepared combined coating comprises a Watt pre-plated nickel layer, an acid copper plating layer, a bright nickel plating layer, a gun-black tin-nickel alloy plating layer, and a rare earth electrolytic protective film, which are sequentially prepared from the inside to the outside on a steel substrate.

[0014] A rare earth electrolytic protection process for electroplating a gun-black tin-nickel alloy and a combined coating thereof. The prepared combined coating comprises a citrate pre-nickel coating, a pyrophosphate copper coating, an acid copper coating, a bright nickel coating, a gun-black tin-nickel alloy coating, and a rare earth electrolytic protective film, which are sequentially prepared from the inside to the outside on a zinc alloy die-casting substrate.

[0015] Preferably, the thickness of the Watt pre-nickel plating layer is 0.2-2 μm.

[0016] Preferably, the thickness of the citrate pre-nickel plating layer is 1 to 9 μm, and the thickness of the pyrophosphate copper plating layer is 5 to 10 μm.

[0017] Preferably, the thickness of the acid copper plating layer is 5 to 20 μm, the thickness of the bright nickel plating layer is 5 to 15 μm, and the thickness of the gun black tin-nickel alloy plating layer is 0.5 to 1.5 μm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. A rare earth electrolytic protection process for electroplating gun black tin-nickel alloy and a combined coating thereof of the present invention, wherein a rare earth electrolytic protection process is used to prepare a rare earth electrolytic protective film on a gun black tin-nickel alloy coating, thereby effectively improving the corrosion resistance of the coating;

[0020] 2. The rare earth electrolytic protection process for electroplating gun black tin-nickel alloy and the combined coating of the present invention are environmentally friendly and overcome the high pollution problem of using hexavalent chromium in the traditional post-treatment protection process of gun black tin-nickel alloy coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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:

[0022] Figure 1 It is a schematic diagram of the coating structure of Example 1, Example 2 and Example 3 of the present invention.

[0023] Figure 2 It is a schematic diagram of the coating structure of Example 4 and Example 5 of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be described in detail below in conjunction with specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0025] The steel workpiece or zinc alloy die-casting substrate is pre-treated according to the current degreasing, rust removal and activation processes.

[0026] After the steel workpiece is pre-treated, a Watt pre-plated nickel layer is prepared according to a Watt nickel plating process, and the thickness of the plating layer is 0.2-2 μm.

[0027] Preferably, the Watt nickel plating process is: 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, sodium dodecyl sulfate 0.05-0.1 g / L, pH range 5-5.5, plating tank temperature 18°C-35°C, cathode current density 1-3 A / dm 2 , the cathode moves 3 to 5 m / min.

[0028] After pretreatment, the zinc alloy die casting is subjected to a current citrate nickel plating process to prepare a citrate pre-nickel plating layer, and a current pyrophosphate copper plating process to prepare a pyrophosphate copper plating layer. The thickness of the citrate pre-nickel plating layer is 1 to 9 μm, and the thickness of the pyrophosphate copper plating layer is 5 to 10 μm.

[0029] Preferably, the citrate nickel plating process is: nickel sulfate hexahydrate 180-250 g / L, sodium chloride 10-12 g / L, boric acid 30-35 g / L, magnesium sulfate 30-40 g / L, pH range 7.0-7.2, plating tank temperature 50°C-60°C, cathode current density 1-1.5 A / dm 2 , the cathode moves 4 to 6 m / min.

[0030] Preferably, the pyrophosphate copper plating process adopts the PC-1289 pyrophosphate copper plating process of Chaobang Chemical: 60-90 g / L copper pyrophosphate, 230-280 g / L potassium pyrophosphate, 2-5 mL / L ammonia water, 1-3 mL / L PC-1289 pyrophosphate additive, pH range 8.6-9.0, plating tank temperature 50°C-58°C, cathode current density 1-6 A / dm 2 , air stirring.

[0031] An acid copper coating is prepared on the Watt pre-plated nickel layer of the steel workpiece according to the current acid copper coating process, and an acid copper coating is prepared on the pyrophosphate copper coating of the zinc alloy die casting according to the current acid copper coating process. The acid copper coating has a thickness of 5 to 20 μm.

[0032] Preferably, the acid copper plating process adopts the GAFFA M-8000 acid bright copper plating process of Chaobang Chemical: 180-210 g / L of copper sulfate pentahydrate, 60-80 g / L of sulfuric acid, 50-100 mg / L of chloride ions, 3-8 mL / L of GAFFA M-8000 Mu opener, 0.3-0.6 mL / L of GAFFA M-8000 A main light agent, 0.05-0.3 mL / L of GAFFA M-8000 B auxiliary light agent, 18-30 °C plating tank temperature, 2-7 A / dm 2 , strong and uniform air stirring.

[0033] A bright nickel plating layer is prepared on the acid copper plating layer of the steel workpiece or the zinc alloy die casting according to the current bright nickel plating process, and the plating layer thickness is 5-15 μm.

[0034] Preferably, the bright nickel plating process adopts the NINFEA 8003 bright nickel plating process of Chaobang Chemical: 240-320 g / L of nickel sulfate hexahydrate, 45-60 g / L of nickel chloride hexahydrate, 40-50 g / L of boric acid, 15-40 mL / L of NINFEA SC-260 bright nickel softener, 3-7 mL / L of NINFEA AS-250 bright nickel auxiliary, 0.4-0.8 mL / L of NINFEA 8003 bright nickel main brightener, 0.5-1.5 mL / L of NINFEA NI-35 bright nickel wetting agent, pH range 4.2-4.8, plating tank temperature 50°C-60°C, cathode current density 3-6 A / dm 2 , uniform air stirring.

[0035] A gun black tin-nickel alloy coating is prepared on the bright nickel coating of the steel workpiece or the zinc alloy die casting, the coating thickness is 0.5-1.5 μm, and the coating is prepared by electroplating a gun black tin-nickel alloy process: 240-280 g / L potassium pyrophosphate, 50-60 g / L nickel chloride hexahydrate, 7-9 g / L stannous chloride, 13-18 g / L potassium thiocyanate, 0.6-1.8 g / L methionine, 20-30 g / L ammonium citrate, pH range is 7.8-8.2, plating tank temperature is 35-40°C, cathode current density is 1-3 A / dm 2 , the cathode moves 3 to 5 m / min, a graphite plate is used as the anode, and a 10% by mass potassium hydroxide solution is used to adjust the pH of the gun black tin-nickel alloy plating solution during production.

[0036] A rare earth electrolytic protection film is prepared on the gun black tin-nickel alloy coating of the steel workpiece or the zinc alloy die casting according to a rare earth electrolytic protection process.

[0037] Preferably, the rare earth electrolysis protection process is as follows:

[0038] The rare earth salt is 1-8 g / L, the HEDP complexing agent is 5-50 g / L, the anhydrous potassium carbonate is 80-160 g / L, the pH range is 11-13, the operating temperature is 15° C.-40° C., and the cathode current density is 0.5-1.2 A / dm 2 , use the black tin-nickel alloy workpiece plated with a gun as the cathode and the titanium plate as the anode, and electrolyze for 30 to 100 seconds;

[0039] The rare earth salt includes one or two of lanthanum chloride, cerium chloride, and praseodymium chloride;

[0040] The area ratio of the cathode to the anode is 2:(1-4).

[0041] Preferably, during production, a 10% by mass potassium hydroxide solution is used to adjust the pH of the rare earth electrolysis protection solution to maintain it within the range of 11 to 13.

[0042] Preferably, the rare earth electrolytic protection solution is prepared as follows:

[0043] (1) adding 2 / 3 of water to the electrolytic protection tank, then adding HEDP complexing agent and anhydrous potassium carbonate in the amount required by the rare earth electrolytic protection process, and stirring to dissolve;

[0044] (2) preparing the rare earth salt into an aqueous solution with a mass fraction of 10%, adding the prepared rare earth salt solution into the electrolytic protection tank under stirring according to the amount required by the rare earth electrolytic protection process, and stirring until the added material is completely dissolved;

[0045] (3) Use 10% potassium hydroxide solution to adjust the pH of the solution in the electrolytic protection tank to 11-13, and add water to the specified volume.

[0046] Example 1

[0047] like Figure 1 As shown, a rare earth electrolytic protection process for electroplating gun black tin-nickel alloy and its combined coating include a Watt pre-nickel coating 2, an acid copper coating 3, a bright nickel coating 4, a gun black tin-nickel alloy coating 5, and a rare earth electrolytic protective film 6 prepared in sequence from the inside to the outside on a steel substrate 1.

[0048] 1. Prepare rare earth electrolytic protection solution:

[0049] (1) Add 2 / 3 of water to the electrolytic protection tank, then add HEDP complexing agent and anhydrous potassium carbonate in the amount required by the rare earth electrolytic protection process, and stir to dissolve;

[0050] (2) preparing a rare earth salt into an aqueous solution with a mass fraction of 10%, adding the prepared rare earth salt solution into the electrolytic protection tank under stirring according to the amount required by the rare earth electrolytic protection process, and stirring until the added material is completely dissolved;

[0051] (3) Use 10% potassium hydroxide solution to adjust the pH of the solution in the electrolytic protection tank to 11-13, and add water to the specified volume.

[0052] The prepared rare earth electrolytic protection solution includes 2.5 g / L lanthanum chloride, 2.5 g / L cerium chloride, 30 g / L HEDP complexing agent and 120 g / L anhydrous potassium carbonate.

[0053] 2. Pre-treatment:

[0054] The steel workpiece substrate 1 is subjected to a pre-treatment process of "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathode electrolytic degreasing → water washing → alkaline anode electrolytic degreasing → water washing → activation → water washing".

[0055] 3. Watt nickel plating:

[0056] A Watt pre-plated nickel layer 2 is prepared on a pre-treated steel workpiece substrate 1, and the thickness of the plating layer 2 is 0.8 μm. The plating layer 2 is prepared using a Watt nickel plating process: 180 g / L nickel sulfate hexahydrate, 8 g / L sodium chloride, 32 g / L boric acid, 60 g / L anhydrous sodium sulfate, 0.08 g / L sodium dodecyl sulfate, pH 5.3, plating tank temperature 25°C, cathode current density 0.8 A / dm 2 , air stirring.

[0057] 4. Acid copper plating:

[0058] An acid copper plating layer 3 is prepared on the Watt pre-plated nickel layer 2 of the steel workpiece, and the thickness of the plating layer 3 is 15 μm. The plating layer 3 is prepared using the GAFFA M-8000 acid bright copper plating process of Chaobang Chemical: 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 light agent, 0.2 mL / L of GAFFAM-8000 B auxiliary light agent, plating tank temperature of 25°C, cathode current density of 5 A / dm 2 , strong and uniform air stirring.

[0059] 5. Bright nickel plating:

[0060] A bright nickel coating 4 is prepared on the acid copper coating 3 of the steel workpiece, and the thickness of the coating 4 is 6 μm. The coating 4 is prepared by the NINFEA 8003 bright nickel plating process of Chaobang Chemical: 280 g / L nickel sulfate hexahydrate, 50 g / L nickel chloride hexahydrate, 45 g / L boric acid, 30 mL / L NINFEA SC-260 bright nickel softener, 5 mL / L NINFEA AS-250 bright nickel auxiliary, 0.6 mL / L NINFEA8003 bright nickel main brightener, 1 mL / L NINFEA NI-35 bright nickel wetting agent, pH 4.5, plating tank temperature 55°C, cathode current density 4 A / dm 2 , uniform air stirring.

[0061] 6. Gun-plated black tin-nickel alloy:

[0062] A gun black tin-nickel alloy coating 5 is prepared on the bright nickel coating 4 of the steel workpiece, and the coating 5 has a thickness of 1 μm. The coating 5 is prepared by electroplating a gun black tin-nickel alloy: 260 g / L potassium pyrophosphate, 55 g / L nickel chloride hexahydrate, 8 g / L stannous chloride, 15 g / L potassium thiocyanate, 1.2 g / L methionine, 25 g / L ammonium citrate, pH 8, plating tank temperature 38°C, cathode current density 2 A / dm 2 , the cathode moves 4m / min, and a graphite plate is used as an anode. In production, a potassium hydroxide solution with a mass fraction of 10% is used to adjust the pH of the plating solution to within the process range.

[0063] 7. Rare earth electrolysis protection:

[0064] A rare earth electrolytic protective film 6 is prepared on the gun black tin-nickel alloy coating 5 of the steel workpiece. The protective film 6 is prepared using the rare earth cathode electrolytic protection process developed by Chaobang Chemical: 2.5 g / L lanthanum chloride, 2.5 g / L cerium chloride, 30 g / L HEDP complexing agent, 100 g / L anhydrous potassium carbonate, pH 12, cathode current density 0.8 A / dm 2, operated at room temperature, using a black tin-nickel alloy workpiece plated with a gun as the cathode and a titanium plate as the anode, electrolyzing for 60 seconds, the area ratio of the cathode to the anode being 2: 1. In 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 within the process range.

[0065] 8. Drying:

[0066] The steel workpiece is rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0067] Example 2

[0068] like Figure 1 As shown, a rare earth electrolytic protection process for electroplating gun black tin-nickel alloy and its combined coating include a Watt pre-nickel coating 2, an acid copper coating 3, a bright nickel coating 4, a gun black tin-nickel alloy coating 5, and a rare earth electrolytic protective film 6 prepared in sequence from the inside to the outside on a steel substrate 1.

[0069] 1. Prepare rare earth electrolytic protection solution:

[0070] (1) Add 2 / 3 of water to the electrolytic protection tank, then add HEDP complexing agent and anhydrous potassium carbonate in the amount required by the rare earth electrolytic protection process, and stir to dissolve;

[0071] (2) preparing a rare earth salt into an aqueous solution with a mass fraction of 10%, adding the prepared rare earth salt solution into the electrolytic protection tank under stirring according to the amount required by the rare earth electrolytic protection process, and stirring until the added material is completely dissolved;

[0072] (3) Use 10% potassium hydroxide solution to adjust the pH of the solution in the electrolytic protection tank to 11-13, and add water to the specified volume.

[0073] The prepared rare earth electrolytic protection solution includes 2.5 g / L cerium chloride, 2.5 g / L praseodymium chloride, 25 g / L HEDP complexing agent and 130 g / L anhydrous potassium carbonate.

[0074] 2. Workpiece pre-treatment:

[0075] The steel workpiece substrate 1 is subjected to a pre-treatment process of "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathode electrolytic degreasing → water washing → alkaline anode electrolytic degreasing → water washing → activation → water washing".

[0076] 3. Watt nickel plating:

[0077] A Watt pre-plated nickel layer 2 is prepared on a pre-treated steel workpiece substrate 1, and the thickness of the plating layer 2 is 0.5 μm. The plating layer 2 is prepared using a Watt nickel plating process: 160 g / L nickel sulfate hexahydrate, 8 g / L sodium chloride, 30 g / L boric acid, 50 g / L anhydrous sodium sulfate, 0.05 g / L sodium dodecyl sulfate, pH 5.1, plating tank temperature 20°C, cathode current density 0.8 A / dm 2 , air stirring.

[0078] 4. Acid copper plating:

[0079] An acid copper plating layer 3 is prepared on the Watt pre-plated nickel layer 2 of the steel workpiece, and the thickness of the plating layer 3 is 15 μm. The plating layer 3 is prepared using the GAFFA M-8000 acid bright copper plating process of Chaobang Chemical: 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 light agent, 0.1 mL / L of GAFFAM-8000 B auxiliary light agent, plating tank temperature of 25°C, cathode current density of 3 A / dm 2 , strong and uniform air stirring.

[0080] 5. Bright nickel plating:

[0081] A bright nickel coating 4 is prepared on the acid copper coating 3 of the steel workpiece, and the thickness of the coating 4 is 5 μm. The coating 4 is prepared by the NINFEA 8003 bright nickel plating process of Chaobang Chemical: 260 g / L nickel sulfate hexahydrate, 45 g / L nickel chloride hexahydrate, 40 g / L boric acid, 20 mL / L NINFEA SC-260 bright nickel softener, 4 mL / L NINFEA AS-250 bright nickel auxiliary, 0.5 mL / L NINFEA8003 bright nickel main brightener, 0.8 mL / L NINFEA NI-35 bright nickel wetting agent, pH 4.3, plating tank temperature 52°C, cathode current density 3.5 A / dm 2 , uniform air stirring.

[0082] 6. Gun-plated black tin-nickel alloy:

[0083] 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 coating 5 is prepared by electroplating a gun black tin-nickel alloy: 240 g / L potassium pyrophosphate, 50 g / L nickel chloride hexahydrate, 7 g / L stannous chloride, 13 g / L potassium thiocyanate, 0.8 g / L methionine, 20 g / L ammonium citrate, pH 7.8, plating tank temperature 40°C, cathode current density 2 A / dm 2, the cathode moves 4m / min, a graphite plate is used as an anode, and a potassium hydroxide solution with a mass fraction of 10% is used to adjust the pH of the plating solution to within the process range during production.

[0084] 7. Rare earth electrolysis protection:

[0085] A rare earth electrolytic protective film 6 is prepared on the gun black tin-nickel alloy coating 5 of the steel workpiece. The protective film 6 is prepared using the rare earth cathode electrolytic protection process developed by Chaobang Chemical: 2.5 g / L cerium chloride, 2.5 g / L praseodymium chloride, 25 g / L HEDP complexing agent, 120 g / L anhydrous potassium carbonate, pH 12, cathode current density 0.8 A / dm 2 , operated at room temperature, using a black tin-nickel alloy workpiece plated with a gun as the cathode and a titanium plate as the anode, electrolyzing for 80 seconds, the area ratio of the cathode to the anode being 2: 1. In 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 within the process range.

[0086] 8. Drying:

[0087] The steel workpiece is rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0088] Example 3

[0089] like Figure 1 As shown, a rare earth electrolytic protection process for electroplating gun black tin-nickel alloy and its combined coating include a Watt pre-nickel coating 2, an acid copper coating 3, a bright nickel coating 4, a gun black tin-nickel alloy coating 5, and a rare earth electrolytic protective film 6 prepared in sequence from the inside to the outside on a steel substrate 1.

[0090] 1. Prepare rare earth electrolytic protection solution:

[0091] (1) Add 2 / 3 of water to the electrolytic protection tank, then add HEDP complexing agent and anhydrous potassium carbonate in the amount required by the rare earth electrolytic protection process, and stir to dissolve;

[0092] (2) preparing a rare earth salt into an aqueous solution with a mass fraction of 10%, adding the prepared rare earth salt solution into the electrolytic protection tank under stirring according to the amount required by the rare earth electrolytic protection process, and stirring until the added material is completely dissolved;

[0093] (3) Use 10% potassium hydroxide solution to adjust the pH of the solution in the electrolytic protection tank to 11-13, and add water to the specified volume.

[0094] The prepared rare earth electrolytic protection solution includes 2.5 g / L lanthanum chloride, 2.5 g / L cerium chloride, 28 g / L HEDP complexing agent and 120 g / L anhydrous potassium carbonate.

[0095] 2. Pre-treatment:

[0096] The steel workpiece substrate 1 is subjected to a pre-treatment process of "alkaline chemical degreasing → water washing → rust removal → water washing → alkaline cathode electrolytic degreasing → water washing → alkaline anode electrolytic degreasing → water washing → activation → water washing".

[0097] 3. Watt nickel plating:

[0098] A Watt pre-plated nickel layer 2 is prepared on the pre-treated steel workpiece substrate 1, and the thickness of the plating layer 2 is 0.3 μm. The plating layer 2 is prepared using the Watt nickel plating process: 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 dodecyl sulfate, pH 5.5, plating tank temperature 35°C, cathode current density 0.8 A / dm 2 , air stirring.

[0099] 4. Acid copper plating:

[0100] An acid copper plating layer 3 is prepared on the Watt pre-plated nickel layer 2 of the steel workpiece, and the thickness of the plating layer 3 is 8 μm. The plating layer 3 is prepared using the GAFFA M-8000 acid bright copper plating process of Chaobang Chemical: 200 g / L of copper sulfate pentahydrate, 75 g / L of sulfuric acid, 90 mg / L of chloride ions, 7 mL / L of GAFFA M-8000 Mu opener, 0.55 mL / L of GAFFA M-8000 A main brightener, 0.25 mL / L of GAFFA M-8000 B auxiliary brightener, plating tank temperature of 28°C, cathode current density of 5 A / dm 2 , strong and uniform air stirring.

[0101] 5. Bright nickel plating:

[0102] A bright nickel coating 4 is prepared on the acid copper coating 3 of the steel workpiece, and the thickness of the coating 4 is 12 μm. The coating 4 is prepared by the NINFEA 8003 bright nickel plating process of Chaobang Chemical: 310 g / L nickel sulfate hexahydrate, 60 g / L nickel chloride hexahydrate, 50 g / L boric acid, 35 mL / L NINFEA SC-260 bright nickel softener, 6 mL / L NINFEA AS-250 bright nickel auxiliary, 0.8 mL / L NINFEA 8003 bright nickel main brightener, 1.5 mL / L NINFEA NI-35 bright nickel wetting agent, pH 4.7, plating tank temperature 58°C, cathode current density 5 A / dm 2 , uniform air stirring.

[0103] 6. Gun-plated black tin-nickel alloy:

[0104] A gun black tin-nickel alloy coating 5 is prepared on the bright nickel coating 4 of the steel workpiece, and the coating 5 has a thickness of 1 μm. The coating 5 adopts a gun black tin-nickel alloy electroplating process: 280 g / L potassium pyrophosphate, 60 g / L nickel chloride hexahydrate, 9 g / L stannous chloride, 18 g / L potassium thiocyanate, 1.6 g / L methionine, 30 g / L ammonium citrate, pH 8.2, plating tank temperature 40°C, cathode current density 2 A / dm 2 , the cathode moves 4m / min, and a graphite plate is used as an anode. In production, a potassium hydroxide solution with a mass fraction of 10% is used to adjust the pH of the plating solution to within the process range.

[0105] 7. Rare earth electrolysis protection:

[0106] A rare earth electrolytic protective film 6 is prepared on the bright nickel plating layer 5 of the steel workpiece. The protective film 6 is prepared using the rare earth cathode electrolytic protection process developed by Chaobang Chemical: 2.5 g / L lanthanum chloride, 2.5 g / L praseodymium chloride, 28 g / L HEDP complexing agent, 110 g / L anhydrous potassium carbonate, pH 12, cathode current density 0.8 A / dm 2 , operated at room temperature, using a black tin-nickel alloy workpiece plated with a gun as the cathode and a titanium plate as the anode, electrolyzing for 60 seconds, the area ratio of the cathode to the anode being 2: 1. In 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 within the process range.

[0107] 8. Drying:

[0108] The steel workpiece is rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0109] Example 4

[0110] like Figure 2 As shown, a rare earth electrolytic protection process for electroplating gun-black tin-nickel alloy and its combined coating include a citrate pre-nickel coating 2, a pyrophosphate copper coating 3, an acid copper coating 4, a bright nickel coating 5, a gun-black tin-nickel alloy coating 6, and a rare earth electrolytic protective film 7 prepared in sequence from the inside to the outside on a zinc alloy die-casting substrate 1.

[0111] 1. Prepare rare earth electrolytic protection solution:

[0112] (1) Add 2 / 3 of water to the electrolytic protection tank, then add HEDP complexing agent and anhydrous potassium carbonate in the amount required by the rare earth electrolytic protection process, and stir to dissolve;

[0113] (2) preparing a rare earth salt into an aqueous solution with a mass fraction of 10%, adding the prepared rare earth salt solution into the electrolytic protection tank under stirring according to the amount required by the rare earth electrolytic protection process, and stirring until the added material is completely dissolved;

[0114] (3) Use 10% potassium hydroxide solution to adjust the pH of the solution in the electrolytic protection tank to 11-13, and add water to the specified volume.

[0115] The prepared rare earth electrolytic protection solution includes 5g / L cerium chloride, 28g / L HEDP complexing agent and 160g / L anhydrous potassium carbonate.

[0116] 2. Pre-treatment:

[0117] The zinc alloy die casting substrate 1 is subjected to a pre-treatment process of "chemical wax removal → water washing → ultrasonic wax removal → water washing → chemical oil removal → water washing → descaling → water washing → acid salt activation → water washing".

[0118] 3. Nickel plating with citrate:

[0119] A citrate pre-plated nickel layer 2 is prepared on a pre-treated zinc alloy die-casting substrate 1. The thickness of the plating layer 2 is 5 μm. The citrate nickel plating process is used: 200 g / L nickel sulfate hexahydrate, 10 g / L sodium chloride, 30-35 g / L boric acid, 30 g / L magnesium sulfate, pH range 7.0, plating tank temperature 52°C, cathode current density 1.2 A / dm 2 , the cathode moves 4 to 6 m / min.

[0120] 4. Pyrophosphate copper plating:

[0121] A pyrophosphate copper plating layer 3 is prepared on the citrate pre-nickel plating layer 2 of the zinc alloy die casting, the thickness of the plating layer 3 is 7 μm, and the PC-1289 pyrophosphate copper plating process of Chaobang Chemical is adopted: 60-90 g / L of copper pyrophosphate, 230-280 g / L of potassium pyrophosphate, 2-5 mL / L of ammonia water, 1-3 mL / L of PC-1289 pyrophosphate copper additive, pH range of 8.6-9.0, plating tank temperature of 50°C-58°C, cathode current density of 1-6 A / dm 2 , air stirring.

[0122] 5. Acid copper plating:

[0123] An acid copper plating layer 4 is prepared on the pyrophosphate copper plating layer 3 of the zinc alloy die casting. The thickness of the plating layer 4 is 14 μm. The plating layer 4 is prepared by using the GAFFA M-8000 acid bright copper plating process of Chaobang Chemical: 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, and cathode current density of 5 A / dm 2 , strong and uniform air stirring.

[0124] 6. Bright nickel plating:

[0125] A bright nickel plating layer 5 is prepared on the acid copper plating layer 4 of the zinc alloy die casting, the thickness of the plating layer 5 is 6 μm, and the bright nickel plating process of NINFEA 8003 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 NINFEA8003 bright nickel main brightener, 1 mL / L of NINFEA NI-35 bright nickel wetting agent, pH is 4.5, plating tank temperature is 55° C., cathode current density is 4 A / dm 2 , uniform air stirring.

[0126] 7. Gun-plated black tin-nickel alloy:

[0127] A gun black tin-nickel alloy coating 6 is prepared on the bright nickel coating 5 of the zinc alloy die casting, the coating 6 has a thickness of 1.2 μm, and is prepared by electroplating a gun black new nickel alloy process: 260 g / L potassium pyrophosphate, 55 g / L nickel chloride hexahydrate, 8 g / L stannous chloride, 15 g / L potassium thiocyanate, 1.2 g / L methionine, 25 g / L ammonium citrate, pH 8, plating tank temperature 38°C, cathode current density 2 A / dm 2 , the cathode moves 4m / min, and a graphite plate is used as an anode. In production, a potassium hydroxide solution with a mass fraction of 10% is used to adjust the pH of the plating solution to within the process range.

[0128] 8. Rare earth electrolysis protection:

[0129] A rare earth electrolytic protective film 7 is prepared on the gun black tin-nickel alloy coating 6 of the zinc alloy die casting. The protective film 7 is prepared using the rare earth cathode electrolytic protection process developed by Chaobang Chemical: 5 g / L cerium chloride, 28 g / L HEDP complexing agent, 160 g / L anhydrous potassium carbonate, pH 12, and cathode current density 0.8 A / dm 2 , operated at room temperature, using a black tin-nickel alloy workpiece plated with a gun as the cathode and a titanium plate as the anode, electrolyzing for 100 seconds, the area ratio of the cathode to the anode being 2: 1. In production, a 10% potassium hydroxide solution is used to adjust the pH of the rare earth electrolytic protection solution to within the process range.

[0130] 9. Drying:

[0131] The zinc alloy die casting is rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0132] Example 5

[0133] like Figure 2As shown, a rare earth electrolytic protection process for electroplating gun-black tin-nickel alloy and its combined coating include a citrate and nickel coating 2, a pyrophosphate copper coating 3, an acid copper coating 4, a bright nickel coating 5, a gun-black tin-nickel alloy coating 6, and a rare earth electrolytic protective film 7 prepared in sequence from the inside to the outside on a zinc alloy die-casting substrate 1.

[0134] 1. Prepare rare earth electrolytic protection solution:

[0135] (1) Add 2 / 3 of water to the electrolytic protection tank, then add HEDP complexing agent and anhydrous potassium carbonate in the amount required by the rare earth electrolytic protection process, and stir to dissolve;

[0136] (2) preparing a rare earth salt into an aqueous solution with a mass fraction of 10%, adding the prepared rare earth salt solution into the electrolytic protection tank under stirring according to the amount required by the rare earth electrolytic protection process, and stirring until the added material is completely dissolved;

[0137] (3) Use 10% potassium hydroxide solution to adjust the pH of the solution in the electrolytic protection tank to 11-13, and add water to the specified volume.

[0138] The prepared rare earth electrolytic protection solution includes 6g / L cerium chloride, 30g / L HEDP complexing agent and 140g / L anhydrous potassium carbonate.

[0139] 2. Pre-treatment:

[0140] The zinc alloy die casting substrate 1 is subjected to a pre-treatment process of "chemical wax removal → water washing → ultrasonic wax removal → water washing → chemical oil removal → water washing → descaling → water washing → acid salt activation → water washing".

[0141] 3. Nickel plating with citrate:

[0142] A citrate pre-plated nickel layer 2 is prepared on a pre-treated zinc alloy die-casting substrate 1. The thickness of the plating layer 2 is 4 μm and the citrate nickel plating process is adopted: 240 g / L nickel sulfate hexahydrate, 12 g / L sodium chloride, 35 g / L boric acid, 38 g / L magnesium sulfate, pH range 7.2, plating tank temperature 58°C, cathode current density 1.5 A / dm 2 , cathode moves 5m / min.

[0143] 4. Pyrophosphate copper plating:

[0144] A pyrophosphate copper plating layer 3 is prepared on the citrate pre-nickel plating layer 2 of the zinc alloy die casting. The thickness of the plating layer 3 is 9 μm. The PC-1289 pyrophosphate copper plating process of Chaobang Chemical is used for preparation: 85 g / L copper pyrophosphate, 270 g / L potassium pyrophosphate, 4 mL / L ammonia water, 2.5 mL / L PC-1289 pyrophosphate copper additive, pH range 8.9, plating tank temperature 56°C, cathode current density 4 A / dm2 , air stirring.

[0145] 5. Acid copper plating:

[0146] An acid copper plating layer 4 is prepared on the pyrophosphate copper plating layer 3 of the zinc alloy die casting. The thickness of the plating layer 4 is 11 μm. The plating layer 4 is prepared by the GAFFA M-8000 acid bright copper plating process of Chaobang Chemical: 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, and cathode current density of 4 A / dm 2 , strong and uniform air stirring.

[0147] 6. Bright nickel plating:

[0148] A bright nickel plating layer 5 is prepared on the acid copper plating layer 4 of the zinc alloy die casting, the thickness of the plating layer 5 is 8 μm, and the bright nickel plating process of NINFEA 8003 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 NINFEA8003 bright nickel main brightener, 1 mL / L of NINFEA NI-35 bright nickel wetting agent, pH is 4.5, plating tank temperature is 55°C, cathode current density is 4 A / dm 2 , uniform air stirring.

[0149] 7. Gun-plated black tin-nickel alloy:

[0150] A gun black tin-nickel alloy coating 6 is prepared on the bright nickel coating 5 of the zinc alloy die casting, the coating 6 has a thickness of 1.2 μm, and is prepared by electroplating a gun black tin-nickel alloy process: 260 g / L potassium pyrophosphate, 55 g / L nickel chloride hexahydrate, 8 g / L stannous chloride, 15 g / L potassium thiocyanate, 1.2 g / L methionine, 25 g / L ammonium citrate, pH 8, plating tank temperature 38°C, cathode current density 2 A / dm 2 , the cathode moves 4m / min, and a graphite plate is used as an anode. In production, a potassium hydroxide solution with a mass fraction of 10% is used to adjust the pH of the plating solution to within the process range.

[0151] 8. Rare earth electrolysis protection:

[0152] A rare earth electrolytic protective film 7 is prepared on the bright coating of the zinc alloy die casting 6. The protective film 7 is prepared using the rare earth cathode electrolytic protection process developed by Chaobang Chemical: 2.5 g / L cerium chloride, 2.5 g / L praseodymium chloride, 25 g / L HEDP complexing agent, 140 g / L anhydrous potassium carbonate, pH 12, cathode current density 0.8 A / dm 2 , operated at room temperature, using a black tin-nickel alloy workpiece plated with a gun as the cathode and a titanium plate as the anode, electrolyzing for 100 seconds, the area ratio of the cathode to the anode being 2: 1. In production, a 10% potassium hydroxide solution is used to adjust the pH of the rare earth electrolytic protection solution to within the process range.

[0153] 9. Drying:

[0154] The zinc alloy die casting is rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0155] Test Example 1

[0156] The gun black tin-nickel alloy composite coating prepared in Examples 1-5 was subjected to a neutral salt spray test for 72 hours in accordance with GB / T 10125-2012 “Artificial atmosphere corrosion test salt spray test”, and no surface corrosion was observed.

[0157] Test Example 2

[0158] The coating adhesion test was carried out on the samples prepared in Example 1, Example 2 and Example 3. The coating adhesion was tested by the thermal shock method according to ISO2819-2017 standard. The plated parts were heated to 300°C in a heating furnace for 30 minutes. After being taken out, they were suddenly cooled in water at room temperature. No bubbling or falling off occurred on the coating.

[0159] The samples prepared in Example 4 and Example 5 were tested for coating adhesion. The coating adhesion was determined by a thermal shock test method in accordance with JB 2111-1977 “Test Method for Bonding Strength of Metal Coverings”. The workpiece was heated to 190° C. in a heating furnace for 30 min, then taken out and suddenly cooled in water at room temperature. No bubbling or shedding occurred on the coating.

[0160] Experiments show that the combined coating prepared by the present invention has good bonding strength.

[0161] Test Example 3

[0162] The samples prepared in Examples 1-5 were placed in an outdoor natural environment for one year, and no obvious changes were observed in the gloss and color of the coating.

[0163] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. 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, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A rare earth electrolytic protection process for electroplating gun black tin-nickel alloy, characterized in that: The method comprises preparing a bottom coating, a bright nickel coating, a gun black tin-nickel alloy coating, and a rare earth electrolytic protective film on a metal substrate in sequence from the inside to the outside; The rare earth electrolytic protection membrane is prepared by a rare earth electrolytic protection process: rare earth salt 1-8 g / L, HEDP coordination agent 5-50 g / L, anhydrous potassium carbonate 80-160 g / L, pH range 11-13, operating temperature 15°C-40°C, cathode current density 0.5-1.2 A / dm 2 , use the plated part as cathode and the titanium plate as anode, and electrolyze for 30 to 100 seconds; The rare earth salt includes one or two of lanthanum chloride, cerium chloride, and praseodymium chloride.

2. The rare earth electrolytic protection process for electroplating gun black tin-nickel alloy as claimed in claim 1, characterized in that: The preparation method of rare earth electrolytic protection solution is as follows: (1) adding 2 / 3 of water to the electrolytic protection tank, then adding HEDP complexing agent and anhydrous potassium carbonate in the amount required by the rare earth electrolytic protection process, and stirring to dissolve; (2) preparing the rare earth salt into an aqueous solution with a mass fraction of 10%, adding the prepared rare earth salt solution into the electrolytic protection tank under stirring according to the amount required by the rare earth electrolytic protection process, and stirring until the added material is completely dissolved; (3) Use 10% by mass potassium hydroxide solution to adjust the pH of the solution prepared in the electrolytic protection tank to 11-13, and add water to the specified volume.

3. The rare earth electrolytic protection process for black tin-nickel alloy of electroplating gun as claimed in claim 1, characterized in that: In 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 keep it within the range of 11-13.

4. The rare earth electrolytic protection process for electroplating gun black tin-nickel alloy as claimed in claim 1, characterized in that: The process of electroplating gun black tin-nickel alloy is: potassium pyrophosphate 240-280g / L, nickel chloride hexahydrate 50-60g / L, stannous chloride 7-9g / L, potassium thiocyanate 13-18g / L, methionine 0.6-1.8g / L, ammonium citrate 20-30g / L, pH range 7.8-8.2, plating tank temperature 35℃-40℃, cathode current density 1-3A / dm 2 The cathode moves 3 to 5 m / min, and a graphite plate is used as the anode. In production, a 10% potassium hydroxide solution is used to adjust the pH of the gun black tin-nickel alloy plating solution to keep it in the range of 7.8 to 8.

2.

5. The composite coating prepared by the rare earth electrolytic protection process of electroplating gun black tin-nickel alloy as described in claim 1, wherein the prepared composite coating comprises a Watt pre-plated nickel layer, an acid copper plating layer, a bright nickel plating layer, a gun black tin-nickel alloy plating layer, and a rare earth electrolytic protective film prepared in sequence from the inside to the outside on a steel substrate.

6. The composite coating prepared by the rare earth electrolytic protection process for electroplating gun black tin-nickel alloy according to claim 1, wherein the composite coating comprises a citrate pre-nickel plating layer, a pyrophosphate copper plating layer, an acid copper plating layer, a bright nickel plating layer, a gun black tin-nickel alloy plating layer, and a rare earth electrolytic protective film, which are sequentially prepared from the inside to the outside on a zinc alloy die-casting substrate.

7. The combined coating prepared by the rare earth electrolytic protection process of the electroplating gun black tin-nickel alloy as claimed in claim 5, characterized in that: The thickness of the Watt pre-plated nickel layer is 0.2-2 μm.

8. The combined coating prepared by the rare earth electrolytic protection process of the black tin-nickel alloy of the electroplating gun as claimed in claim 6, characterized in that: The thickness of the citrate pre-nickel plating layer is 1 to 9 μm, and the thickness of the pyrophosphate copper plating layer is 5 to 10 μm.

9. The combined coating prepared by the rare earth electrolytic protection process of the electroplating gun black tin-nickel alloy as claimed in claim 5 or 6, characterized in that: The thickness of the acid copper plating layer is 5 to 20 μm, the thickness of the bright nickel plating layer is 5 to 15 μm, and the thickness of the gun black tin-nickel alloy plating layer is 0.5 to 1.5 μm.

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