A rare earth electrolytic protection solution for coating and electrolytic protection process

Abstract

The invention discloses a rare earth electrolytic protection liquid for plating and an electrolytic protection process. The electrolytic protection process comprises: 1-10 g / L rare earth salt, 5-50 g / L HEDP complexing agent, 80-220 g / L sewage-free sodium carbonate or anhydrous potassium carbonate, pH range of 11-13, operating temperature of 15-40°C, cathode current density of 0.5-1.2 A / dm 2 , using the plated part as the cathode and the inert conductive material as the anode, and electrolyzing for 30 to 120 seconds. The rare earth salt includes one or two of lanthanum chloride, cerium chloride, praseodymium chloride, lanthanum sulfate, cerous sulfate, praseodymium sulfate, lanthanum acetate, cerium acetate, and praseodymium acetate. The electrolytic protection process is used to prepare a rare earth electrolytic protective film on a trivalent chromium plating layer or a bright nickel plating layer to improve the corrosion resistance and anti-discoloration ability of the plating layer. According to GB / T 10125-2012 "Artificial Atmosphere Corrosion Test Salt Spray Test", a neutral salt spray test is carried out. The prepared trivalent chromium white chromium plating layer has no rust on the surface for 120 hours, the prepared trivalent chromium black chromium plating layer has no rust on the surface for 72 hours, and the prepared bright nickel plating layer has no rust for 60 hours. The coating rare earth electrolytic protection solution and electrolytic protection process of the present invention have good market application prospects.

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 solution for plating and an electrolytic protection process. Background Art

[0002] Entering the 21st century, the application of trivalent chromium electroplating has accelerated, and it is mainly used to prepare decorative chrome plating for hardware and electronic accessories. Trivalent chromium plating includes two systems: sulfate trivalent chromium plating and chloride trivalent chromium plating. The prepared coatings include trivalent chromium white chromium plating and trivalent chromium black chromium plating. The trivalent chromium plating layer can only improve its corrosion resistance after post-treatment protection. If it is not post-treated and protected, the surface of the trivalent chromium plating layer cannot form a dense oxide film, and its corrosion resistance is low, and it will lose its luster in the natural environment. In the early days of trivalent chromium plating, the industry used dichromate electrolysis to implement electrolytic protection of the plating layer. Later, post-treatment protection methods such as sealant sealing were developed, but the corrosion resistance and anti-discoloration ability of the sealing method were not ideal. Bright nickel plating process is also widely used in the preparation of surface coatings for hardware and electronic accessories. In the past, chromic acid passivation method and dichromate electrolytic protection method were used to form a protective film on the bright nickel plating layer to improve the corrosion resistance and anti-discoloration ability of the plating layer. However, the use of hexavalent chromium has been subject to increasingly stringent restrictions, and there is a need to develop environmentally friendly post-treatment protection processes for plating to replace hexavalent chromium post-treatment protection. 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 solution and electrolytic protection process for coating. In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0004] A rare earth electrolytic protection solution for coating, comprising the following components: 1-10 g / L rare earth salt, 5-50 g / L HEDP complexing agent, 80-220 g / L alkali metal carbonate, pH range 11-13;

[0005] The rare earth salt includes one or two of lanthanum chloride, cerium chloride, praseodymium chloride, lanthanum sulfate, cerous sulfate, praseodymium sulfate, lanthanum acetate, cerium acetate, and praseodymium acetate.

[0006] In some embodiments, the alkali metal carbonate includes one or both of anhydrous sodium carbonate and anhydrous potassium carbonate.

[0007] In some embodiments, the rare earth electrolytic protection solution is prepared by the following method:

[0008] (1a) adding 4 / 5 of water to the electrolytic cell according to the volume of the electrolytic protection solution, adding HEDP complexing agent and potassium carbonate according to the formula requirements of the rare earth electrolytic protection solution, and stirring to dissolve the above substances;

[0009] (2a) adding rare earth salt under vigorous stirring and stirring until the rare earth salt is completely dissolved;

[0010] (3a) Adjust the pH of the prepared solution to between 11 and 13 with sodium hydroxide or potassium hydroxide solution and add water to the specified volume.

[0011] A coating electrolytic protection process, the electrolytic protection process comprising:

[0012] Rare earth salt 1~10g / L, HEDP complexing agent 5~50g / L, alkali metal carbonate 80~220g / L, pH range 11~13, operating temperature 15℃~40℃, cathode current density 0.5~1.2A / dm 2 , use the plated part as cathode and inert conductive material as anode, and electrolyze for 30 to 120 seconds.

[0013] In some embodiments, the inert conductive material is a titanium plate or a graphite anode plate for electroplating.

[0014] In some of the embodiments, the area ratio of the cathode to the anode is 2:(1-4).

[0015] In some embodiments, the electrolytic protection process comprises the following steps:

[0016] (1b) Pretreatment of workpiece to be plated;

[0017] (2b) preparing a bottom coating and a surface coating;

[0018] (3b) The surface coating of the workpiece is electrolytically protected according to the electrolytic protection process.

[0019] In some of the embodiments, the pH of the rare earth electrolytic protection solution is adjusted with a 10% by mass sodium hydroxide or potassium hydroxide solution.

[0020] In some embodiments, the plating layer includes a trivalent chromium plating layer.

[0021] In some embodiments, the plating layer includes a bright nickel plating layer.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. A rare earth electrolytic protection solution and electrolytic protection process for coating of the present invention adopts a rare earth electrolytic protection process to prepare a rare earth electrolytic protection film on a trivalent chromium coating or a bright nickel coating, thereby effectively improving the corrosion resistance and anti-discoloration ability of the coating;

[0024] 2. The rare earth electrolytic protection solution and electrolytic protection process of the coating of the present invention are environmentally friendly and overcome the high pollution problem of using hexavalent chromium in the traditional coating post-treatment protection process. DETAILED DESCRIPTION

[0025] 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.

[0026] The steel workpiece substrate is pre-treated according to the current degreasing, rust removal and activation processes.

[0027] After the workpiece is pre-treated, a pre-nickel plating layer is prepared according to the Watt nickel plating process, and the thickness of the plating layer is 0.5-3 μm.

[0028] 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 0.5-1 A / dm 2 , air stirring.

[0029] An acid copper plating layer is prepared on the pre-plated nickel layer of the workpiece according to the current acid copper plating process, and the plating layer thickness is 6-15 μm.

[0030] 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.

[0031] A bright nickel plating layer is prepared on the acid copper plating layer of the workpiece according to the current bright nickel plating process, and the plating layer thickness is 3-10 μm.

[0032] 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.

[0033] A trivalent chromium plating layer is prepared on the bright nickel plating layer of the workpiece according to the current trivalent chromium plating process, and the plating layer thickness is 0.05-0.35 μm.

[0034] Preferably, the trivalent chromium plating process adopts the Trich-9551 sulfate trivalent chromium white chromium plating process of Chaobang Chemical: Trich-9551 M cylinder opener 8-12mL / L, Trich-9551 B supplementer 260-300mL / L, Trich-9551 CS conductive salt 260-300g / L, Trich-9551 WA wetting agent 0.5-2.0mL / L, pH range 3.4-3.8, plating tank temperature 50℃-55℃, cathode current density 8-15A / dm 2 , the cathode moves 1 to 3 m / min or is slightly stirred by air.

[0035] Preferably, the trivalent chromium plating process adopts the Trich-7677 sulfate trivalent chromium black chromium plating process of Chaobang Chemical: Trich-7677 S initiator 8-12mL / L, Trich-7677 M cylinder opener 260-300mL / L, Trich-7677 CS conductive salt 260-300g / L, Trich-7677 C stabilizer 3.0-4.0mL / L, Trich-7677 D toner 3.0-8.0mL / L, Trich-7677 WA wetting agent 0.5-2.0mL / L, pH range 3.3-3.7, plating tank temperature 25°C-40°C, cathode current density 8-14A / dm 2 , the cathode moves 1 to 3 m / min or is slightly stirred by air.

[0036] When the outer coating of the workpiece is a bright nickel coating, a rare earth electrolytic protection film is prepared on the bright nickel coating according to a rare earth electrolytic protection process.

[0037] When the outer coating of the workpiece is a trivalent chromium coating, a rare earth electrolytic protection film is prepared on the trivalent chromium coating according to a rare earth electrolytic protection process.

[0038] Preferably, the electrolytic protection solution is prepared by the following method:

[0039] (1a) adding 4 / 5 of water to the electrolytic cell according to the volume of the electrolytic protection solution, adding HEDP complexing agent and alkali metal carbonate according to the formula of the electrolytic protection solution, and stirring to dissolve the above substances;

[0040] (2a) adding rare earth salt under vigorous stirring and stirring until the rare earth salt is completely dissolved;

[0041] (3a) Adjust the pH of the prepared solution to between 11 and 13 with sodium hydroxide or potassium hydroxide solution, and add water to the specified volume;

[0042] The prepared rare earth electrolytic protection solution comprises 1-10 g / L rare earth salt, 5-50 g / L HEDP coordination agent, 80-220 g / L alkali metal carbonate, and a pH range of 11-13.

[0043] The rare earth salt includes one or two of lanthanum chloride, cerium chloride, praseodymium chloride, lanthanum sulfate, cerous sulfate, praseodymium sulfate, lanthanum acetate, cerium acetate, and praseodymium acetate.

[0044] The alkali metal carbonate includes one or both of anhydrous sodium carbonate and anhydrous potassium carbonate.

[0045] Preferably, the rare earth electrolysis protection process is as follows:

[0046] The rare earth salt is 1-10 g / L, the HEDP complexing agent is 5-50 g / L, the alkali metal carbonate is 80-220 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 plated part as cathode, titanium plate or graphite plate for electroplating as anode, and electrolyze for 30 to 120 seconds;

[0047] The area ratio of the cathode to the anode is 2:(1-4).

[0048] The pH of the rare earth electrolytic protection solution is adjusted with a sodium hydroxide or potassium hydroxide solution with a mass fraction of 10%.

[0049] Example 1

[0050] A coating rare earth electrolytic protection liquid and electrolytic protection process, comprising preparing the rare earth electrolytic protection liquid, and sequentially plating watt nickel, acid copper, bright nickel, trivalent chromium and white chromium on a steel substrate from inside to outside, and performing rare earth electrolytic protection.

[0051] 1. Prepare rare earth electrolytic protection solution:

[0052] (1a) Add 4 / 5 of water to the electrolytic cell according to the volume of the electrolytic protection solution, add HEDP complexing agent and potassium carbonate according to the formula requirements of the rare earth electrolytic protection solution, and stir to dissolve the above substances;

[0053] (2a) adding rare earth salt under vigorous stirring and stirring until the rare earth salt is completely dissolved;

[0054] (3a) Adjust the pH of the prepared solution to 12 with potassium hydroxide solution and add water to the specified volume.

[0055] The prepared rare earth electrolytic protection solution includes 2.5 g / L of lanthanum chloride, 3 g / L of cerium chloride, 30 g / L of HEDP complexing agent, and 120 g / L of anhydrous potassium carbonate.

[0056] 2. Pre-treatment:

[0057] The steel workpiece substrate 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".

[0058] 3. Watt nickel plating:

[0059] After the workpiece is pre-treated, a pre-nickel plating layer is prepared on the substrate thereof, the plating layer thickness is 1.5 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, 0.08 g / L sodium dodecyl sulfate, pH is 5.3, plating tank temperature is 25° C., cathode current density is 0.8 A / dm 2 , air stirring.

[0060] 4. Acid copper plating:

[0061] An acid copper coating is prepared on the pre-nickel coating of the workpiece, the coating thickness is 10 μm, and the GAFFAM-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-8000Mu 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 is 25°C, and cathode current density is 5 A / dm 2 , strong and uniform air stirring.

[0062] 5. Bright nickel plating:

[0063] A bright nickel coating is prepared on the acid copper coating of the workpiece, the coating thickness is 6 μm, and the NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 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 agent, 0.6 mL / L NINFEA 8003 bright nickel main brightener, 1 mL / L 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.

[0064] 6. Trivalent chromium white chromium plating:

[0065] A trivalent chromium white chromium coating is prepared on the bright nickel coating of the workpiece, the coating thickness is 0.2 μm, and the Trich-9551 sulfate trivalent chromium plating process of Chaobang Chemical is adopted: Trich-9551 M cylinder opener 10 mL / L, Trich-9551 B supplementer 280 mL / L, Trich-9551 CS conductive salt 280 g / L, Trich-9551 WA wetting agent 1 mL / L, pH is 3.6, plating tank temperature is 52 ° C, cathode current density is 10 A / dm 2 , cathode moves 2m / min.

[0066] 7. Rare earth electrolysis protection:

[0067] A rare earth electrolytic protective film is prepared on the trivalent chromium white chromium coating of the workpiece, using the rare earth electrolytic protective process developed by Chaobang Chemical: 2.5 g / L lanthanum chloride, 3 g / L cerium chloride, 30 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 trivalent chromium-plated workpiece as a cathode and a titanium plate as an anode, and electrolyzing for 60 seconds; using a potassium hydroxide solution with a mass fraction of 10% to adjust the pH of the rare earth electrolytic protection solution, and the area ratio of the cathode to the anode is 2:1.

[0068] 8. Drying:

[0069] The workpiece was rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0070] Example 2

[0071] A coating rare earth electrolytic protection liquid and electrolytic protection process, comprising preparing the rare earth electrolytic protection liquid, and sequentially plating watt nickel, acid copper, bright nickel, trivalent chromium and black chromium on a steel substrate from inside to outside, and performing rare earth electrolytic protection.

[0072] 1. Prepare rare earth electrolytic protection solution:

[0073] (1a) Add 4 / 5 of water to the electrolytic cell according to the volume of the electrolytic protection solution, add HEDP complexing agent and sodium carbonate according to the formula of the electrolytic protection solution, and stir to dissolve the above substances;

[0074] (2a) adding rare earth salt under vigorous stirring and stirring until the rare earth salt is completely dissolved;

[0075] (3a) Adjust the pH of the prepared solution to 12 with sodium hydroxide solution and add water to the specified volume.

[0076] The prepared rare earth electrolytic protection solution includes 3g / L cerous sulfate, 3g / L praseodymium sulfate, 35g / L HEDP complexing agent and 120g / L anhydrous sodium carbonate.

[0077] 2. Workpiece pre-treatment:

[0078] The steel workpiece substrate 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".

[0079] 3. Watt nickel plating:

[0080] After the workpiece is pre-treated, a pre-nickel plating layer is prepared on the substrate thereof, the plating layer thickness is 2 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, 0.05 g / L sodium dodecyl sulfate, pH is 5.1, plating tank temperature is 20°C, cathode current density is 0.8 A / dm 2 , air stirring.

[0081] 4. Acid copper plating:

[0082] An acid copper coating is prepared on the pre-nickel coating of the workpiece, the coating thickness is 12 μm, and the GAFFAM-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-8000Mu 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 is 25°C, and cathode current density is 3 A / dm 2 , strong and uniform air stirring.

[0083] 5. Bright nickel plating:

[0084] A bright nickel coating is prepared on the acid copper coating of the workpiece, the coating thickness is 5 μm, and the NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 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 agent, 0.5 mL / L NINFEA 8003 bright nickel main brightener, 0.8 mL / L NINFEA NI-35 bright nickel wetting agent, pH is 4.3, plating tank temperature is 52°C, cathode current density is 3.5 A / dm 2 , uniform air stirring.

[0085] 6. Trivalent chromium black chromium plating:

[0086] A trivalent chromium black chromium coating is prepared on the bright nickel coating of the workpiece, the coating thickness is 0.2 μm, and the Trich-7677 sulfate trivalent chromium black chromium plating process of Chaobang Chemical is adopted: Trich-7677 S initiator 10 mL / L, Trich-7677 M cylinder opener 280 mL / L, Trich-7677 CS conductive salt 280 g / L, Trich-7677 C stabilizer 3.5 mL / L, Trich-7677 D toner 5 mL / L, Trich-7677 WA wetting agent 1.0 mL / L, pH is 3.5, plating tank temperature is 35°C, cathode current density is 10 A / dm 2 , with slight air agitation.

[0087] 7. Rare earth electrolysis protection:

[0088] A rare earth electrolytic protective film is prepared on the trivalent chromium black chromium coating of the workpiece, using the rare earth electrolytic protective process developed by Chaobang Chemical: 3 g / L lanthanum sulfate, 3 g / L cerium sulfate, 30 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 trivalent chromium-plated workpiece as a cathode and a titanium plate as an anode, and electrolyzing for 80 seconds; using a sodium hydroxide solution with a mass fraction of 10% to adjust the pH of the electrolytic protection solution, and the area ratio of the cathode to the anode is 2:1.

[0089] 8. Drying:

[0090] The workpiece was rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0091] Example 3

[0092] A coating rare earth electrolytic protection solution and electrolytic protection process, comprising preparing the rare earth electrolytic protection solution, and sequentially plating watt nickel, acid copper, bright nickel, and rare earth electrolytic protection on a steel substrate from inside to outside.

[0093] 1. Prepare rare earth electrolytic protection solution:

[0094] (1a) Add 4 / 5 of water to the electrolytic cell according to the volume of the electrolytic protection solution, add HEDP complexing agent and potassium carbonate according to the formula of the electrolytic protection solution, and stir to dissolve the above substances;

[0095] (2a) adding rare earth salt under vigorous stirring and stirring until the rare earth salt is completely dissolved;

[0096] (3a) Adjust the pH of the plating solution to 12 with potassium hydroxide solution and add water to the specified volume.

[0097] The prepared rare earth electrolytic protection solution includes 3g / L cerium chloride, 2.5g / L praseodymium chloride, 30g / L HEDP complexing agent, 120g / L anhydrous potassium carbonate, and pH value is 12.

[0098] 2. Pre-treatment:

[0099] The steel workpiece substrate 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".

[0100] 3. Watt nickel plating:

[0101] After the workpiece is pre-treated, a pre-nickel plating layer is prepared on the substrate thereof, the plating layer thickness is 0.8 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 dodecyl sulfate, pH is 5.5, plating tank temperature is 35° C., cathode current density is 0.8 A / dm 2 , air stirring.

[0102] 4. Acid copper plating:

[0103] An acid copper coating is prepared on the pre-nickel coating of the workpiece, the coating thickness is 8 μm, and the GAFFAM-8000 acid bright copper plating process of Chaobang Chemical is adopted: 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-8000Mu opener, 0.55 mL / L of GAFFA M-8000 A main brightener, 0.25 mL / L of GAFFA M-8000 B auxiliary brightener, the plating tank temperature is 28°C, and the cathode current density is 4 A / dm 2 , strong and uniform air stirring.

[0104] 5. Bright nickel plating:

[0105] A bright nickel coating is prepared on the acid copper coating of the workpiece, the coating thickness is 6 μm, and the NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 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 agent, 0.8 mL / L NINFEA 8003 bright nickel main brightener, 1.5 mL / L NINFEA NI-35 bright nickel wetting agent, pH is 4.7, plating tank temperature is 58°C, cathode current density is 4.5 A / dm 2 , uniform air stirring.

[0106] 6. Rare earth electrolysis protection:

[0107] A rare earth electrolytic protective film was prepared on the bright nickel coating of the workpiece, using the rare earth electrolytic protective process developed by Chaobang Chemical: 3 g / L cerium chloride, 2.5 g / L praseodymium chloride, 30 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 bright nickel-plated workpiece as a cathode and a titanium plate as an anode, and electrolyzing for 100 seconds; using a potassium hydroxide solution with a mass fraction of 10% to adjust the pH required by the electrolytic protection process, and the area ratio of the cathode to the anode is 2:1.

[0108] 7. Drying:

[0109] The workpiece was rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0110] Example 4

[0111] A coating rare earth electrolytic protection liquid and electrolytic protection process, comprising preparing the rare earth electrolytic protection liquid, and sequentially plating watt nickel, acid copper, bright nickel, and rare earth electrolytic protection on a steel substrate from the inside to the outside.

[0112] 1. Prepare rare earth electrolytic protection solution:

[0113] (1a) Add 4 / 5 of water to the electrolytic cell according to the volume of the electrolytic protection solution, add HEDP complexing agent and sodium carbonate according to the formula requirements of the rare earth electrolytic protection solution, and stir to dissolve the above substances;

[0114] (2a) adding rare earth salt under vigorous stirring and stirring until the rare earth salt is completely dissolved;

[0115] (3a) Adjust the pH of the plating solution to 12 with sodium hydroxide solution and add water to the specified volume;

[0116] The prepared rare earth electrolytic protection solution includes 4 g / L lanthanum acetate, 2 g / L praseodymium acetate, 35 g / L HEDP complexing agent and 120 g / L anhydrous sodium carbonate.

[0117] 2. Pre-treatment:

[0118] 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".

[0119] 3. Watt nickel plating:

[0120] After the workpiece is pre-treated, a pre-nickel plating layer is prepared on the substrate thereof, the plating layer thickness is 1 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, 0.08 g / L sodium dodecyl sulfate, pH is 5.3, plating tank temperature is 25° C., cathode current density is 0.8 A / dm 2 , air stirring.

[0121] 4. Acid copper plating:

[0122] An acid copper coating is prepared on the pre-nickel coating of the workpiece, the coating thickness is 14 μm, and the GAFFAM-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-8000Mu 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 is 25°C, and cathode current density is 4 A / dm 2 , strong and uniform air stirring.

[0123] 5. Bright nickel plating:

[0124] A bright nickel coating is prepared on the acid copper coating of the workpiece, the coating thickness is 8 μm, and the NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 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 agent, 0.6 mL / L NINFEA 8003 bright nickel main brightener, 1 mL / L 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.

[0125] 6. Rare earth electrolysis protection:

[0126] A rare earth electrolytic protective film was prepared on the bright coating of the workpiece using the rare earth electrolytic protective process developed by Chaobang Chemical: 4 g / L lanthanum acetate, 2 g / L praseodymium acetate, 35 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 bright nickel-plated workpiece as a cathode and a graphite plate as an anode, and electrolyzing for 70 seconds; using a 10% by mass sodium hydroxide solution to adjust the pH of the rare earth electrolysis protection solution, and the area ratio of the cathode to the anode is 2:1.

[0127] 7. Drying:

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

[0129] Example 5

[0130] A coating rare earth electrolytic protection liquid and electrolytic protection process, comprising preparing the rare earth electrolytic protection liquid, and sequentially plating watt nickel, acid copper, bright nickel, and rare earth electrolytic protection on a steel substrate from the inside to the outside.

[0131] 1. Prepare rare earth electrolytic protection solution:

[0132] (1a) Add 4 / 5 of water to the electrolytic cell according to the volume of the electrolytic protection solution, add HEDP complexing agent and potassium carbonate according to the formula requirements of the rare earth electrolytic protection solution, and stir to dissolve the above substances;

[0133] (2a) adding rare earth salt under vigorous stirring and stirring until the rare earth salt is completely dissolved;

[0134] (3a) Adjust the pH of the plating solution to 12 with potassium hydroxide solution and add water to the specified volume;

[0135] The prepared rare earth electrolytic protection solution includes 3 g / L of lanthanum sulfate, 2.5 g / L of praseodymium chloride, 30 g / L of HEDP complexing agent, and 120 g / L of anhydrous potassium carbonate.

[0136] 2. Workpiece pre-treatment:

[0137] The steel workpiece substrate 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".

[0138] 3. Watt nickel plating:

[0139] After the workpiece is pre-treated, a pre-nickel plating layer is prepared on the substrate thereof, the plating layer thickness is 2.5 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, 0.05 g / L sodium dodecyl sulfate, pH is 5.1, plating tank temperature is 20°C, cathode current density is 0.8 A / dm 2 , air stirring.

[0140] 4. Acid copper plating:

[0141] An acid copper coating is prepared on the pre-nickel coating of the workpiece, the coating thickness is 9 μm, and the GAFFAM-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-8000Mu 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 is 25°C, and cathode current density is 3.5 A / dm 2 , strong and uniform air stirring.

[0142] 5. Bright nickel plating:

[0143] A bright nickel coating is prepared on the acid copper coating of the workpiece, the coating thickness is 9 μm, and the NINFEA 8003 bright nickel plating process of Chaobang Chemical is adopted: 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 agent, 0.5 mL / L NINFEA 8003 bright nickel main brightener, 0.8 mL / L NINFEA NI-35 bright nickel wetting agent, pH is 4.3, plating tank temperature is 52°C, cathode current density is 3.5 A / dm 2 , uniform air stirring.

[0144] 6. Rare earth electrolysis protection:

[0145] A rare earth electrolytic protective film was prepared on the bright nickel coating of the workpiece, using the rare earth electrolytic protective process developed by Chaobang Chemical: 3 g / L lanthanum sulfate, 2.5 g / L praseodymium chloride, 30 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 bright nickel-plated workpiece as a cathode and a titanium plate as an anode, and electrolyzing for 120 seconds; using a potassium hydroxide solution with a mass fraction of 10% to adjust the pH of the rare earth electrolysis protection solution, and the area ratio of the cathode to the anode is 2:1.

[0146] 7. Drying:

[0147] The workpiece was rare earth electrolytically protected and washed with water and then dried at 80° C. for 25 minutes.

[0148] Test Example 1

[0149] The combined coating of trivalent chromium and white chromium plating on the steel part prepared in Example 1 was subjected to a neutral salt spray test for 120 hours in accordance with the standard GB / T 10125-2012 "Artificial atmosphere corrosion test salt spray test", and no rust was found on the surface.

[0150] Test Example 2

[0151] The combined coating of trivalent chromium and black chromium on the steel part prepared in Example 2 was subjected to a neutral salt spray test for 72 hours in accordance with the standard GB / T 10125-2012 "Artificial atmosphere corrosion test salt spray test", and no rust was found on the surface.

[0152] Test Example 3

[0153] The bright nickel composite coating of the steel parts prepared in Examples 3-5 was subjected to a neutral salt spray test for 60 hours according to GB / T 10125-2012 "Artificial atmosphere corrosion test salt spray test" standard, and no rust was found on the surface.

[0154] Test Example 4

[0155] In this test example, a weather resistance test was conducted on the samples prepared in Example 1, Example 2, Example 3, Example 4 and Example 5. The samples were placed in an outdoor natural environment for 1 year, and no obvious changes were observed in the gloss and color of the coating.

[0156] Comparative Example 1

[0157] A trivalent chromium white chromium coating was prepared according to the process described in Example 1, but rare earth electrolytic protection was not performed. The prepared white chromium composite coating was subjected to a neutral salt spray test for 120 hours according to GB / T 10125-2012 "Artificial atmosphere corrosion test salt spray test" standard, and white corrosion products appeared on its surface.

[0158] Comparative Example 2

[0159] The trivalent chromium black chromium coating was prepared according to the process described in Example 2, but rare earth electrolytic protection was not performed. The prepared black chromium composite coating was subjected to a neutral salt spray test for 72 hours according to GB / T 10125-2012 "Artificial atmosphere corrosion test salt spray test" standard, and white corrosion products appeared on its surface.

[0160] Comparative Example 3

[0161] A bright nickel plating layer was prepared according to the process described in Example 3, but no rare earth electrolytic protection was performed. The prepared bright nickel composite plating layer was subjected to a neutral salt spray test for 60 hours according to GB / T 10125-2012 "Artificial atmosphere corrosion test salt spray test" standard, and white corrosion products appeared on its surface.

[0162] Comparative Example 4

[0163] The samples prepared in Comparative Examples 1, 2 and 3 were placed in an outdoor natural environment for one year, and a mist-like oxide film appeared on the surface of the coating.

[0164] 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.

[0165] The invention discloses a rare earth electrolytic protection liquid for plating and an electrolytic protection process. The electrolytic protection process comprises: 1-10 g / L rare earth salt, 5-50 g / L HEDP complexing agent, 80-220 g / L sewage-free sodium carbonate or anhydrous potassium carbonate, pH range of 11-13, operating temperature of 15-40°C, cathode current density of 0.5-1.2 A / dm 2 , using the plated part as the cathode and the inert conductive material as the anode, and electrolyzing for 30 to 120 seconds. The rare earth salt includes one or two of lanthanum chloride, cerium chloride, praseodymium chloride, lanthanum sulfate, cerous sulfate, praseodymium sulfate, lanthanum acetate, cerium acetate, and praseodymium acetate. The electrolytic protection process is used to prepare a rare earth electrolytic protective film on a trivalent chromium plating layer or a bright nickel plating layer to improve the corrosion resistance and anti-discoloration ability of the plating layer. According to GB / T 10125-2012 "Artificial Atmosphere Corrosion Test Salt Spray Test", a neutral salt spray test is carried out. The prepared trivalent chromium white chromium plating layer has no rust on the surface for 120 hours, the prepared trivalent chromium black chromium plating layer has no rust on the surface for 72 hours, and the prepared bright nickel plating layer has no rust for 60 hours. The coating rare earth electrolytic protection solution and electrolytic protection process of the present invention have good market application prospects.

Claims

1. A rare earth electrolytic protection process for coating, characterized in that: It includes the following components: rare earth salt 1-10 g / L, HEDP complexing agent 5-50 g / L, alkali metal carbonate 80-220 g / L, pH range 11-13; The rare earth salt includes one or two of lanthanum chloride, cerium chloride, praseodymium chloride, lanthanum sulfate, cerous sulfate, praseodymium sulfate, lanthanum acetate, cerium acetate, and praseodymium acetate; The parameters of the electrolytic protection process implemented by the coating electrolytic protection solution are: Operating temperature 15℃~40℃, cathode current density 0.5~1.2A / dm 2 , use the plated part as cathode and inert conductive material as anode, and electrolyze for 30 to 120 seconds.

2. The rare earth electrolytic protection process for coating as claimed in claim 1, characterized in that: The alkali metal carbonate includes one or both of anhydrous sodium carbonate and anhydrous potassium carbonate.

3. The rare earth electrolytic protection process for coating as claimed in claim 1, characterized in that: The rare earth electrolytic protection solution is prepared by the following method: (1a) adding 4 / 5 of water to the electrolytic cell according to the volume of the electrolytic protection solution, adding HEDP complexing agent and potassium carbonate according to the formula requirements of the rare earth electrolytic protection solution, and stirring to dissolve the above substances; (2a) adding rare earth salt under vigorous stirring and stirring until the rare earth salt is completely dissolved; (3a) Adjust the pH of the prepared solution to between 11 and 13 with sodium hydroxide or potassium hydroxide solution and add water to the specified volume.

4. The rare earth electrolytic protection process for coating as claimed in claim 1, characterized in that: The inert conductive material is a titanium plate or a graphite anode plate for electroplating.

5. The rare earth electrolytic protection process for coating as claimed in claim 1, characterized in that: The area ratio of the cathode to the anode is 2:(1-4).

6. The rare earth electrolytic protection process for coating as claimed in claim 1, characterized in that: The electrolytic protection process comprises the following steps: (1b) Pretreatment of workpiece to be plated; (2b) preparing a bottom coating and a surface coating; (3b) The surface coating of the workpiece is electrolytically protected according to the electrolytic protection process.

7. The rare earth electrolytic protection process for coating as claimed in claim 1, characterized in that: The pH of the rare earth electrolytic protection solution is adjusted with a sodium hydroxide or potassium hydroxide solution with a mass fraction of 10%.

8. The electrolysis process implemented by the rare earth electrolysis protection process for coating according to any one of claims 1 to 7 is characterized in that: The plating layer comprises a trivalent chromium plating layer and a bright nickel plating layer.