A concentrated solution of electroless black nickel plating and a preparation method, a plating method and an application thereof

Abstract

The application discloses a kind of chemical plating black nickel concentrated solution, including concentrated solution A, concentrated solution B and concentrated solution C, concentrated solution A includes nickel sulfate, stannous sulfate, zinc sulfate, sodium hypophosphite, sodium citrate, sodium acetate, sodium lactate, sulfur-containing amino acid, stabilizer, ammonia and deionized water, concentrated solution B includes sodium hypophosphite, zinc sulfate, sodium acetate, sodium lactate, stabilizer and deionized water, concentrated solution C includes nickel sulfate, stannous sulfate, sodium citrate, sulfur-containing amino acid, ammonia and deionized water.The application also discloses its preparation method, plating method and application.The black nickel layer prepared from the chemical plating black nickel concentrated solution of the application not only has excellent blackening effect and luster, but also has excellent wear resistance, corrosion resistance and bonding force when directly contacting with metal substrate.The chemical plating bath has long service life and self-regulating control of pH value by continuous supplementing, and the plating speed is stable during the whole plating process.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, specifically to a concentrated solution for electroless black nickel plating, its preparation method, plating method, and application. Background Technology

[0002] Black nickel is often used in certain specialized equipment and fields such as optical instruments and the electronics industry because of its strong extinction ability and extremely high solar energy absorption rate.

[0003] Conventional black nickel is mainly produced by three methods: chemical blackening of the nickel layer, electroplating, and electroless plating. Chemical blackening involves oxidizing the surface nickel layer to blacken it through a post-processing treatment, but this method requires extremely high corrosion resistance of the nickel layer; otherwise, it can lead to problems such as nickel layer detachment. Furthermore, the post-processing blackening operation is difficult to control, making it hard to guarantee uniform color in the same batch of processed workpieces. Electroplating cannot guarantee uniform current, making it difficult to obtain a uniform thickness and color of black nickel when processing irregularly shaped workpieces. Electroless plating effectively solves the above problems (uniform thickness and color), but it also suffers from issues such as poor wear and corrosion resistance, poor adhesion between the nickel layer and the substrate, and poor gloss.

[0004] Chinese patent CN113818014A (publication date 2021.12.21) discloses a surface brightening process for black nickel products. This method involves degreasing, rust removal, activation, hot water preheating, electroless black nickel plating, and post-treatment. The resulting black nickel layer exhibits good color uniformity, adhesion, gloss, and smoothness. However, this method has the following drawbacks: 1) The hot water preheating in the electroless black nickel plating pretreatment increases the cost; 2) The formula uses potassium thiocyanate to enhance adhesion, but this decomposes into highly toxic cyanide under heat; and the post-treatment uses chromic acid, which... 6+ It belongs to Group 1 carcinogens and its use should be strictly controlled according to national laws and regulations; 3) Electricity must be applied during the plating process, and the current must be strictly controlled between 0.2 and 0.5 A / dm². 2 Such stringent production conditions are not feasible for large-scale production in reality.

[0005] Chinese patent CN114481104A (publication date 2022.05.13) discloses a chemical black nickel concentrate and a chemical nickel plating method. However, this method does not fundamentally solve the aforementioned problems of chemical black nickel plating, such as poor corrosion resistance and poor adhesion between the nickel layer and the substrate when in direct contact. Furthermore, based on the data in its embodiments, it can be inferred that its plating rate is very low—less than or equal to 3 μm / h, which will greatly limit production efficiency and does not meet the conditions for large-scale production. Summary of the Invention

[0006] The purpose of this invention is to provide a concentrated solution for electroless black nickel plating, its preparation method, plating method, and application, in order to overcome the shortcomings of the prior art.

[0007] The present invention adopts the following technical solution:

[0008] A chemical black nickel plating concentrate includes concentrate A, concentrate B and concentrate C;

[0009] The concentrated solution A comprises 100-125 g / L nickel sulfate, 20-25 g / L stannous sulfate, 15-20 g / L zinc sulfate, 100-120 g / L sodium hypophosphite, 100-125 g / L sodium citrate, 50-80 g / L sodium acetate, 30-50 g / L sodium lactate, 20-30 g / L sulfur-containing amino acids, 20-25 ppm stabilizer, 150-180 g / L ammonia, and deionized water.

[0010] The concentrated solution B comprises 500-550 g / L sodium hypophosphite, 10-15 g / L zinc sulfate, 30-35 g / L sodium acetate, 20-25 g / L sodium lactate, 150-400 ppm stabilizer, and deionized water.

[0011] The concentrated solution C comprises 400-450 g / L nickel sulfate, 10-20 g / L stannous sulfate, 80-90 g / L sodium citrate, 5-10 g / L sulfur-containing amino acids, 250-300 g / L ammonia, and deionized water.

[0012] Furthermore, the stabilizer in concentrate A is one of manganese sulfate, copper sulfate, maleic acid, and potassium iodate; the stabilizer in concentrate B is molybdate, which includes one or two of sodium molybdate and ammonium molybdate; the sulfur-containing amino acids in concentrates A and C are one or more of DL-methionine, L-cysteine, cystine, and homocysteine.

[0013] The above-mentioned method for preparing a concentrated solution for electroless black nickel plating includes the following steps:

[0014] (1) Preparation of concentrated solution A: Weigh each component according to the formula amount, add nickel sulfate, sodium citrate, sodium acetate, sodium lactate and ammonia water to deionized water to dissolve; then add sodium hypophosphite, sulfur-containing amino acids, zinc sulfate and stabilizer to dissolve, and finally add stannous sulfate solution to mix with the above solution evenly to obtain concentrated solution A;

[0015] (2) Preparation of concentrated solution B: Weigh each component according to the formula amount, add sodium hypophosphite, zinc sulfate, sodium acetate, sodium lactate and stabilizer to deionized water to dissolve, and thus obtain concentrated solution B;

[0016] (3) Preparation of concentrated solution C: Weigh each component according to the formula amount, add nickel sulfate, sodium citrate, sulfur-containing amino acids and ammonia water to deionized water to dissolve, then add stannous sulfate solution and mix it evenly with the above solution to obtain concentrated solution C.

[0017] The preparation steps of stannous sulfate solution in concentrate A and concentrate C are as follows: Dissolve the weighed stannous sulfate in deionized water and then add ammonia water dropwise. A white precipitate will appear first, and then gradually disappear as ammonia water is added to obtain stannous sulfate solution. The ammonia water used in the preparation of stannous sulfate solution is not included in the amount of ammonia water specified in concentrate A and concentrate C.

[0018] The above-mentioned method for applying a concentrated electroless black nickel plating solution includes the following steps:

[0019] (1) Bath preparation: Dilute concentrated solution A with deionized water to prepare a chemical plating bath solution of 200-250 ml / l, adjust the pH to 6.5-8.0, and then heat and maintain the temperature at 85-90℃;

[0020] (2) Pre-processing:

[0021] (a) Degreasing and surface hydroxylation: The metal substrate is immersed in a degreasing solution and then taken out and washed with water to remove substances including oxides and grease from the surface of the metal substrate and to form a hydroxyl layer on its surface.

[0022] (b) Formation and densification of self-assembled monolayers: The metal substrate from step (a) is immersed in an ethanol solution containing a grafting agent, then removed, washed with water and dried to obtain a self-assembled monolayer on the metal substrate, and then baked in an inert gas to densify the self-assembled monolayer.

[0023] (c) Activation: First, put the metal substrate with self-assembled monolayer obtained in step (b) into the activation solution, take it out and then put it in the reduction solvent, then take it out and wash it with water for later use.

[0024] (3) Plating: Immerse the pretreated metal substrate from step (2) into the chemical plating bath from step (1) for plating. Maintain a stable temperature of 85-90℃ during the plating process. The plating time is determined according to the required coating thickness. During the plating process, concentrate B and concentrate C are added for replenishment. For every 1g of Ni consumed... 2+ It is necessary to add 10-11 ml of concentrated solution C, and concentrated solution B should be added at a volume ratio of 1-1.2:1 to concentrated solution C. Do not stir or stir during the plating process, and then take it out, wash it with water and dry it.

[0025] Further, in step (1), the pH is adjusted using 50% ammonia water and 200 g / L of hydrogen sulfate ammonia solution. The 50% ammonia water is obtained by mixing ammonia water and deionized water at a volume ratio of 1:1.

[0026] Further, the specific components of the degreasing solution in step (2)a are 30-40 g / L ammonia, 25-35 g / L Na2CO3, 15-30 g / L NaHCO3, 25-40 g / L NaH2PO4, 5-8 g / L Tween-60, 25-35 g / L Na2SiO3, 10-15 g / L H2O2, 0.3-0.8 g / L N-acetylacetanilide and deionized water. The working temperature is 65-75℃, the working time is 5-10 min, and the pH is maintained at 7.0-8.5 with ammonia during the working process.

[0027] Further, in step (2)b, the ethanol solution containing the grafting agent is an ethanol solution containing 10-25 g / L of coupling agent, wherein the coupling agent is one or more of titanate coupling agent, zirconate coupling agent, aluminate coupling agent, bimetallic coupling agent, and boron-containing coupling agent, and its working temperature is 25-35℃, and the working time is 20-30 min; hot air at 35-40℃ is used to blow for 3-5 min to dry the water-washed metal substrate; the inert gas is N2 or Ar, and baking is carried out at 45-55℃ for 20-35 min.

[0028] Further, in step (2)c, the specific components of the activation solution are 80-100 g / L nickel sulfate, 5-10 g / L sodium acetate, 15-20 g / L malic acid, 10-25 g / L sodium lactate and deionized water, with a working temperature of 25-35℃ and a working time of 5-20 min; the specific components of the reducing solvent are 15-25 g / L potassium borohydride and deionized water, with a working temperature of 65-70℃ and a working time of 5-15 min.

[0029] Furthermore, the stirring method during the plating process in step (3) is air stirring or mechanical stirring. The gas flow rate during air stirring is 3-8 l / min, and the rotation speed during mechanical stirring is 300-500 r / min. Drying is carried out at 35-45℃ for 15-20 min.

[0030] The above-mentioned application of a chemical black nickel plating concentrate on a metal substrate, wherein the metal substrate includes aluminum and its alloys, steel, titanium and its alloys, copper and its alloys, and beryllium and its alloys.

[0031] The beneficial effects of this invention are:

[0032] 1. The black nickel layer prepared by the chemical black nickel plating concentrate of the present invention not only has excellent blackening effect and gloss, but also excellent wear resistance, corrosion resistance and adhesion when in direct contact with metal substrate.

[0033] 2. The electroless black nickel plating concentrate of the present invention achieves long service life and self-regulation of pH value of the electroless plating bath through continuous replenishment, so there is no need to add a pH adjuster; and achieves control over crystal nucleation mode and grain size, thereby controlling the mechanical properties of the black nickel layer.

[0034] 3. The electroless black nickel plating concentrate of the present invention has a relatively stable plating speed and a stable and uniform color throughout the entire plating process.

[0035] 4. The chemical black nickel plating concentrate of the present invention will not exhibit defects such as turbidity or crystallization in extremely harsh environments (such as sub-zero temperatures or temperatures above 40°C).

[0036] 5. During the use of the chemical black nickel plating concentrate of the present invention, even when treating different metal substrates, the pretreatment process can still adopt the same treatment method (self-assembly method, directly forming nickel active points), which not only simplifies the processing flow but also saves the cost increase caused by production line modification.

[0037] 6. The chemical black nickel plating concentrate of this invention only requires one application, which reduces the cost of using the product and improves the ease of operation. Detailed Implementation

[0038] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0039] The ammonia water mentioned below refers to industrial ammonia water, which is an aqueous solution containing 25% to 28% ammonia.

[0040] The water of crystallization in the following compounds is not included in the mass calculation.

[0041] A concentrated solution for electroless black nickel plating, comprising concentrated solution A, concentrated solution B and concentrated solution C;

[0042] The concentrated solution A comprises 100-125 g / L nickel sulfate, 20-25 g / L stannous sulfate, 15-20 g / L zinc sulfate, 100-120 g / L sodium hypophosphite, 100-125 g / L sodium citrate, 50-80 g / L sodium acetate, 30-50 g / L sodium lactate, 20-30 g / L sulfur-containing amino acids, 20-25 ppm stabilizer, 150-180 g / L ammonia, and deionized water; wherein the stabilizer is one of manganese sulfate, copper sulfate, maleic acid, and potassium iodate.

[0043] The concentrated solution B comprises 500-550 g / L sodium hypophosphite, 10-15 g / L zinc sulfate, 30-35 g / L sodium acetate, 20-25 g / L sodium lactate, 150-400 ppm stabilizer, and deionized water; wherein the stabilizer is molybdate, and the molybdate includes one or both of sodium molybdate and ammonium molybdate;

[0044] The concentrated solution C comprises 400-450 g / L nickel sulfate, 10-20 g / L stannous sulfate, 80-90 g / L sodium citrate, 5-10 g / L sulfur-containing amino acids, 250-300 g / L ammonia water, and deionized water.

[0045] The sulfur-containing amino acids in concentrates A and C are one or more of DL-methionine, L-cysteine, cystine, and homocysteine.

[0046] The above-mentioned method for preparing a concentrated solution for electroless black nickel plating includes the following steps:

[0047] (1) Preparation of concentrated solution A: Weigh each component according to the formula amount, add nickel sulfate, sodium citrate, sodium acetate, sodium lactate and ammonia water to deionized water to dissolve; then add sodium hypophosphite, sulfur-containing amino acids, zinc sulfate and stabilizer to dissolve, and finally add stannous sulfate solution to mix with the above solution evenly to obtain concentrated solution A;

[0048] (2) Preparation of concentrated solution B: Weigh each component according to the formula amount, add sodium hypophosphite, zinc sulfate, sodium acetate, sodium lactate and stabilizer to deionized water to dissolve, and thus obtain concentrated solution B;

[0049] (3) Preparation of concentrated solution C: Weigh each component according to the formula amount, add nickel sulfate, sodium citrate, sulfur-containing amino acids and ammonia water to deionized water to dissolve, then add stannous sulfate solution and mix it evenly with the above solution to obtain concentrated solution C.

[0050] The preparation steps of stannous sulfate solution in concentrate A and concentrate C are as follows: Dissolve the weighed stannous sulfate in deionized water and then add ammonia water dropwise. A white precipitate will appear first, and then gradually disappear as ammonia water is added to obtain stannous sulfate solution. The ammonia water used in the preparation of stannous sulfate solution is not included in the amount of ammonia water specified in concentrate A and concentrate C.

[0051] The above-mentioned method for applying a concentrated electroless black nickel plating solution includes the following steps:

[0052] (1) Bath preparation: Dilute concentrated solution A with deionized water to prepare a chemical plating bath solution of 200-250 ml / l, and adjust the pH to 6.5-8.0 with 50% ammonia water (50% ammonia water is obtained by mixing ammonia water and deionized water at a volume ratio of 1:1) and 200 g / l of hydrogen sulfate ammonia solution, then heat and maintain the temperature at 85-90℃;

[0053] (2) Pre-processing:

[0054] (a) Degreasing and surface hydroxylation: The metal substrate is immersed in a degreasing solution at 65-75°C for 5-10 minutes. The specific components of the degreasing solution are 30-40 g / L ammonia, 25-35 g / L Na2CO3, 15-30 g / L NaHCO3, 25-40 g / L NaH2PO4, 5-8 g / L Tween-60, 25-35 g / L Na2SiO3, 10-15 g / L H2O2, 0.3-0.8 g / L N-acetylacetanilide and deionized water. During the process, the pH of the degreasing solution is maintained at 7.0-8.5 with ammonia. After that, the substrate is taken out and washed with water to remove substances including oxides and grease from the surface of the metal substrate and to form a hydroxyl layer on its surface.

[0055] (b) Formation and densification of self-assembled monolayer: The metal substrate from step (a) is immersed in an ethanol solution containing a grafting agent for 20-30 min at 25-35°C. The ethanol solution containing the grafting agent is an ethanol solution containing 10-25 g / L of coupling agent. The coupling agent is one or more of titanate coupling agent, zirconate coupling agent, aluminate coupling agent, bimetallic coupling agent, and boron-containing coupling agent. After that, it is taken out, washed with water and dried (blown with hot air at 35-40°C for 3-5 min) to obtain a self-assembled monolayer on the metal substrate. Then, it is placed in an inert gas of N2 or Ar and baked at 45-55°C for 20-35 min to densify the self-assembled monolayer.

[0056] (c) Activation: The metal substrate with self-assembled monolayer obtained in step (b) is first placed in an activation solution at 25-35°C for 5-20 min. The specific components of the activation solution are 80-100 g / L nickel sulfate, 5-10 g / L sodium acetate, 15-20 g / L malic acid, 10-25 g / L sodium lactate and deionized water. After taking it out, it is placed in a reducing solvent at 65-70°C for 5-15 min. The specific components of the reducing solvent are 15-25 g / L potassium borohydride and deionized water. After that, it is taken out and washed with water for later use.

[0057] (3) Plating: Immerse the pretreated metal substrate from step (2) into the chemical plating bath from step (1) for plating. Maintain a stable temperature of 85-90℃ during the plating process. The plating time is determined according to the required thickness of the plating layer (black nickel layer). During the plating process, concentrate B and concentrate C are added for replenishment. For every 1g of Ni consumed... 2+ 10-11 ml of concentrate C needs to be added, and concentrate B is added at a volume ratio of 1-1.2:1 to concentrate C. No stirring or stirring is required during the plating process. The stirring method is air stirring or mechanical stirring. The gas flow rate is 3-8 l / min when air stirring and the rotation speed is 300-500 r / min when mechanical stirring. After that, take it out, wash it with water, and dry it at 35-45℃ for 15-20 min.

[0058] The above-mentioned application of a chemical black nickel plating concentrate on a metal substrate, wherein the metal substrate includes aluminum and its alloys, steel, titanium and its alloys, copper and its alloys, and beryllium and its alloys.

[0059] The following examples are used to test the adhesion of the parts according to the cross-cut test in section 2.8 and the thermal shock test in section 2.12 of GBT5270-2005 "Review of Test Methods for Adhesion Strength of Electrodeposition and Chemical Deposition of Metallic Coatings on Metallic Substrates". Corrosion resistance is tested according to the neutral salt spray test (NSS test) in section 5.2.2 of GBT10125-2021 "Corrosion Test of Artificial Atmosphere Salt Spray Test". Abrasion resistance is tested according to QBT3820-1999 "Test Method for Abrasion Resistance of Metallic Coatings and Chemically Treated Layers of Light Industrial Products" - that is, calculating the number of milligrams of mass lost per 1000 r when using a hard friction wheel under a load of 1 kg. Gloss and color uniformity are tested according to SJ20891-2003 "Specification for Electroless Nickel-Phosphorus Alloy Coatings". Thickness is measured according to GBT6462-2005 "Metrology of Thickness of Metallic and Oxide Coatings - Microscopic Method".

[0060] The specific components of the degreasing solution in the following examples are 35 g / L ammonia, 30 g / L Na2CO3, 25 g / L NaHCO3, 30 g / L NaH2PO4, 7 g / L Tween-60, 30 g / L Na2SiO3, 15 g / L H2O2, 0.5 g / L N-acetylacetanilide, and deionized water. The specific components of the activating solution are 100 g / L nickel sulfate, 10 g / L sodium acetate, 18 g / L malic acid, 20 g / L sodium lactate, and deionized water. The specific components of the reducing solvent are 20 g / L potassium borohydride and deionized water.

[0061] Example 1

[0062] The chemical black nickel plating concentrate in this embodiment consists of concentrate A, concentrate B and concentrate C.

[0063] The components of concentrate A are as follows: nickel sulfate 100g / L, stannous sulfate 20g / L, zinc sulfate 15g / L, sodium hypophosphite 100g / L, sodium citrate 100g / L, sodium acetate 50g / L, sodium lactate 30g / L, DL-methionine 20g / L, copper sulfate 20ppm, ammonia 150g / L, and deionized water. Weigh each component according to the formula. Dissolve nickel sulfate, sodium citrate, sodium acetate, sodium lactate, and ammonia in deionized water. Then add sodium hypophosphite... Sodium phosphate, DL-methionine, zinc sulfate, and copper sulfate are dissolved, and finally stannous sulfate solution is added and mixed evenly with the above solution. After filtering with filter paper, concentrated solution A is obtained. The preparation steps of stannous sulfate solution are as follows: the weighed stannous sulfate is dissolved in deionized water, and then ammonia water is added dropwise. A white precipitate appears first, and then the white precipitate gradually disappears as ammonia water is continuously added to obtain stannous sulfate solution. The ammonia water used in the preparation of stannous sulfate solution is not included in the amount of ammonia water specified in concentrated solution A.

[0064] The components of concentrated solution B are as follows: 500 g / L sodium hypophosphite, 10 g / L zinc sulfate, 30 g / L sodium acetate, 20 g / L sodium lactate, 150 ppm sodium molybdate, and deionized water. Weigh each component according to the formula, add sodium hypophosphite, zinc sulfate, sodium acetate, sodium lactate, and sodium molybdate to deionized water to dissolve, and filter with filter paper to obtain concentrated solution B.

[0065] The components of concentrated solution C are as follows: 450 g / L nickel sulfate, 10 g / L stannous sulfate, 80 g / L sodium citrate, 5 g / L DL-methionine, 250 g / L ammonia, and deionized water. Weigh each component according to the formula. Dissolve nickel sulfate, sodium citrate, DL-methionine, and ammonia in deionized water. Then add stannous sulfate solution and mix thoroughly. Filter with filter paper to obtain concentrated solution C. The preparation steps of the stannous sulfate solution are as follows: Dissolve the weighed stannous sulfate in deionized water, then add ammonia dropwise. A white precipitate will initially appear, and then gradually disappear as ammonia is added, thus obtaining the stannous sulfate solution. The ammonia used in the preparation of the stannous sulfate solution is not included in the amount of ammonia specified for concentrated solution C.

[0066] Concentrate A was diluted with deionized water to prepare a chemical plating bath solution of 230 ml / l. The pH of the chemical plating bath solution was adjusted to 7.5 using 50% ammonia water (50% ammonia water is obtained by mixing ammonia water and deionized water at a volume ratio of 1:1) and 200 g / l of ammonium hydrogen sulfate solution. The solution was then heated to 85°C and maintained at that temperature.

[0067] The specific plating method is as follows:

[0068] (1) Take an aluminum sheet with dimensions of 100mm*50mm*0.7mm and immerse it in a degreasing solution with a temperature of 70℃ and a pH of 8.5 (the pH of the degreasing solution is maintained at 8.5 with ammonia water during operation) for 8 minutes, then take it out and wash it with water.

[0069] (2) The aluminum sheet obtained in the above steps is first immersed in an ethanol solution containing 15 g / l aluminate coupling agent (Nanjing Jingtianwei Chemical Co., Ltd., JTW-181) at a temperature of 25°C for 20 min. Then it is taken out, washed with water, and dried with hot air at 40°C for 5 min. Then it is placed in an oven filled with N2 and baked at 50°C for 25 min.

[0070] (3) Immerse the aluminum sheet obtained in the above steps in an activation solution at 30°C for 15 min and a reducing solvent at 65°C for 10 min, then take it out and wash it with water for later use.

[0071] (4) Immerse the aluminum sheet obtained in the above steps into a preheated chemical plating bath for plating (maintain this temperature during the plating process), and during the plating process, according to Ni 2+ The consumption value is replenished using concentrate B and concentrate C, for every 1g of Ni consumed. 2+ 10 ml of concentrate C needs to be added, and concentrate B should be added at a volume ratio of 1.15:1 to concentrate C until the plating time is 90 min. Then take it out, rinse with water and dry at 35℃ for 15 min.

[0072] Repeat steps (1) to (4) until the volume of the added concentrate C is 0.102 times, 0.204 times, 0.306 times, 0.408 times, and 0.51 times the volume of the original electroless plating bath, respectively (i.e., the added nickel ion content is 2 times, 4 times, 6 times, 8 times, and 10 times the nickel ion content in the original electroless plating bath, respectively). This is the electroless plating bath reaching cycles 2, 4, 6, 8, and 10 (2, 4, 6, 8, and 10 MTO). The pH of the electroless plating bath (under cooling) and the corresponding aluminum sheets at 2, 4, 6, 8, and 10 MTO are tested, as shown in the table below:

[0073]

[0074] Example 2

[0075] The electroless black nickel plating concentrate in this embodiment consists of concentrate A, concentrate B and concentrate C.

[0076] The components of concentrate A are as follows: nickel sulfate 125 g / L, stannous sulfate 25 g / L, zinc sulfate 20 g / L, sodium hypophosphite 120 g / L, sodium citrate 120 g / L, sodium acetate 75 g / L, sodium lactate 40 g / L, cystine 25 g / L, manganese sulfate 25 ppm, ammonia 170 g / L, and deionized water. Weigh each component according to the formula. Dissolve nickel sulfate, sodium citrate, sodium acetate, sodium lactate, and ammonia in deionized water. Then add sodium hypophosphite... Sodium phosphate, cystine, zinc sulfate, and manganese sulfate are dissolved, and finally stannous sulfate solution is added and mixed evenly with the above solution. After filtering with filter paper, concentrated solution A is obtained. The preparation steps of stannous sulfate solution are as follows: the weighed stannous sulfate is dissolved in deionized water, and then ammonia water is added dropwise. A white precipitate appears first, and then the white precipitate gradually disappears as ammonia water is continuously added to obtain stannous sulfate solution. The ammonia water used in the preparation of stannous sulfate solution is not included in the amount of ammonia water specified in concentrated solution A.

[0077] The components of concentrated solution B are as follows: sodium hypophosphite 540g / l, zinc sulfate 12g / l, sodium acetate 35g / l, sodium lactate 25g / l, ammonium molybdate 200ppm and deionized water. Weigh each component according to the formula, add sodium hypophosphite, zinc sulfate, sodium acetate, sodium lactate and sodium molybdate to deionized water to dissolve, and filter with filter paper to obtain concentrated solution B.

[0078] The components of concentrated solution C are as follows: 450 g / L nickel sulfate, 15 g / L stannous sulfate, 85 g / L sodium citrate, 8 g / L cystine, 280 g / L ammonia, and deionized water. Weigh each component according to the formula. Dissolve nickel sulfate, sodium citrate, cystine, and ammonia in deionized water. Then add stannous sulfate solution and mix thoroughly. Filter with filter paper to obtain concentrated solution C. The preparation steps of the stannous sulfate solution are as follows: Dissolve the weighed stannous sulfate in deionized water, then add ammonia dropwise. A white precipitate will initially appear, and then gradually disappear as ammonia is added, thus obtaining the stannous sulfate solution. The ammonia used in the preparation of the stannous sulfate solution is not included in the amount of ammonia specified for concentrated solution C.

[0079] Concentrate A was diluted with deionized water to prepare a chemical plating bath solution of 200 ml / L. The pH of the chemical plating bath solution was adjusted to 7.0 using 50% ammonia water (50% ammonia water is obtained by mixing ammonia water and deionized water at a volume ratio of 1:1) and 200 g / L of ammonium hydrogen sulfate solution. The solution was then heated to 90°C and maintained at that temperature.

[0080] The specific plating method is as follows:

[0081] (1) Take a steel sheet with a size of 100mm*50mm*1mm and immerse it in a degreasing solution with a temperature of 70℃ and a pH of 7.5 (the pH of the degreasing solution is maintained at 7.5 with ammonia water during operation) for 8 minutes, and then take it out and wash it with water.

[0082] (2) The steel sheet obtained in the above steps is first immersed in an ethanol solution containing 20 g / l zirconate coupling agent (Nanjing Youpu Chemical Co., Ltd.) at a temperature of 30°C for 25 min. Then it is taken out, washed with water, and dried with hot air at 38°C for 5 min. Then it is placed in an oven filled with N2 and baked at 50°C for 25 min.

[0083] (3) Immerse the steel sheet obtained in the above steps in an activation solution at 30°C for 15 min and a reducing solvent at 65°C for 10 min, then take it out and wash it with water for later use.

[0084] (4) Immerse the steel sheet obtained in the above steps into a preheated chemical plating bath for plating (maintain this temperature during the plating process), and adjust the plating process according to the Ni... 2+ The consumption value is replenished using concentrate B and concentrate C, for every 1g of Ni consumed. 2+ 10 ml of concentrate C needs to be added, and concentrate B is added at a volume ratio of 1.2:1 to concentrate C until the plating time is 90 min. During the entire plating process, air with a flow rate of 5 l / min is used for stirring. After that, take it out, wash it with water, and dry it at 35°C for 15 min.

[0085] Repeat steps (1) to (4) until the volume of the added concentrate C is 0.112 times, 0.224 times, 0.336 times, 0.448 times, and 0.56 times the original volume of the electroless plating bath, respectively (i.e., the added nickel ion content is 2 times, 4 times, 6 times, 8 times, and 10 times the nickel ion content in the original electroless plating bath, respectively). This is the electroless plating bath reaching cycles 2, 4, 6, 8, and 10 (2, 4, 6, 8, and 10 MTO). The pH of the electroless plating bath (under cooling) and the corresponding steel sheets at 2, 4, 6, 8, and 10 MTO are tested, as shown in the table below:

[0086]

[0087]

[0088] As can be seen from the test results of the above two embodiments, the chemical black nickel plating concentrate of the present invention not only achieves a long service life—a service cycle of up to 10 MTO, but also maintains excellent blackening effect, gloss, wear resistance, corrosion resistance, adhesion to the metal substrate when in direct contact, and a relatively stable plating rate—16.5 to 18.5 μm / h throughout the entire plating process. At the same time, the chemical plating bath can achieve self-regulation and control of pH value.

Claims

1. A method for applying a concentrated solution of chemical black nickel plating, characterized in that, The electroless black nickel plating concentrate includes concentrate A, concentrate B and concentrate C; The concentrated solution A comprises 100-125 g / L nickel sulfate, 20-25 g / L stannous sulfate, 15-20 g / L zinc sulfate, 100-120 g / L sodium hypophosphite, 100-125 g / L sodium citrate, 50-80 g / L sodium acetate, 30-50 g / L sodium lactate, 20-30 g / L sulfur-containing amino acids, 20-25 ppm stabilizer, 150-180 g / L ammonia, and deionized water. The concentrated solution B comprises 500-550 g / L sodium hypophosphite, 10-15 g / L zinc sulfate, 30-35 g / L sodium acetate, 20-25 g / L sodium lactate, 150-400 ppm stabilizer, and deionized water. The concentrated solution C comprises 400-450 g / L nickel sulfate, 10-20 g / L stannous sulfate, 80-90 g / L sodium citrate, 5-10 g / L sulfur-containing amino acids, 250-300 g / L ammonia water, and deionized water. The plating method includes the following steps: (1) Bath preparation: Dilute concentrated solution A with deionized water to prepare a chemical plating bath solution of 200-250 ml / l, adjust the pH to 6.5-8.0, and then heat and maintain the temperature at 85-90℃; (2) Pre-processing: (a) Degreasing and surface hydroxylation: The metal substrate is immersed in a degreasing solution and then taken out and washed with water to remove substances including oxides and grease from the surface of the metal substrate and to form a hydroxyl layer on its surface. (b) Formation and densification of self-assembled monolayers: The metal substrate from step (a) is immersed in an ethanol solution containing a grafting agent, then removed, washed with water and dried to obtain a self-assembled monolayer on the metal substrate, and then baked in an inert gas to densify the self-assembled monolayer. (c) Activation: First, place the metal substrate with self-assembled monolayer obtained in step (b) into the activation solution, take it out and then place it in the reduction solvent, then take it out and wash it with water for later use. (3) Plating: Immerse the pretreated metal substrate from step (2) into the chemical plating bath from step (1) for plating. Maintain a stable temperature of 85-90°C during the plating process. The plating time is determined according to the required coating thickness. During the plating process, concentrate B and concentrate C are added for replenishment. For every 1g of Ni consumed... 2+ It is necessary to add 10-11 ml of concentrated solution C, and concentrated solution B should be added at a volume ratio of 1-1.2:1 to concentrated solution C. Do not stir or stir during the plating process, and then take it out, wash it with water and dry it.

2. The plating method of the concentrated solution for electroless black nickel plating according to claim 1, characterized in that, The stabilizer in concentrate A is one of manganese sulfate, copper sulfate, maleic acid, and potassium iodate; the stabilizer in concentrate B is molybdate, which includes one or two of sodium molybdate and ammonium molybdate; the sulfur-containing amino acids in concentrates A and C are one or more of DL-methionine, L-cysteine, cystine, and homocysteine.

3. A method for applying a concentrated solution of electroless black nickel plating according to claim 1 or 2, characterized in that, The concentrated solution for electroless black nickel plating is prepared by the following steps: (1) Preparation of concentrated solution A: Weigh each component according to the formula amount, add nickel sulfate, sodium citrate, sodium acetate, sodium lactate and ammonia water to deionized water to dissolve; then add sodium hypophosphite, sulfur-containing amino acids, zinc sulfate and stabilizer to dissolve, and finally add stannous sulfate solution to mix with the above solution evenly to obtain concentrated solution A; (2) Preparation of concentrated solution B: Weigh each component according to the formula amount, add sodium hypophosphite, zinc sulfate, sodium acetate, sodium lactate and stabilizer to deionized water to dissolve, and thus obtain concentrated solution B; (3) Preparation of concentrated solution C: Weigh each component according to the formula, add nickel sulfate, sodium citrate, sulfur-containing amino acids and ammonia water to deionized water to dissolve, then add stannous sulfate solution and mix it evenly with the above solution to obtain concentrated solution C; The preparation steps of stannous sulfate solution in concentrate A and concentrate C are as follows: Dissolve the weighed stannous sulfate in deionized water and then add ammonia water dropwise. A white precipitate will appear first, and then gradually disappear as ammonia water is added to obtain the stannous sulfate solution. The ammonia water used in the preparation of stannous sulfate solution is not included in the amount of ammonia water specified in concentrate A and concentrate C.

4. A method for applying a concentrated solution of electroless black nickel plating according to claim 1 or 2, characterized in that, In step (1), the pH is adjusted using 50% ammonia water and 200g / l hydrogen sulfate ammonia solution. The 50% ammonia water is obtained by mixing ammonia water and deionized water in a volume ratio of 1:

1.

5. A method for applying a concentrated solution of electroless black nickel plating according to claim 1 or 2, characterized in that, The specific components of the degreasing solution in step (2)a are 30-40 g / L ammonia, 25-35 g / L Na2CO3, 15-30 g / L NaHCO3, 25-40 g / L NaH2PO4, 5-8 g / L Tween-60, 25-35 g / L Na2SiO3, 10-15 g / L H2O2, 0.3-0.8 g / L N-acetylacetanilide and deionized water. The working temperature is 65-75℃ and the working time is 5-10 min. During the working process, the pH is maintained at 7.0-8.5 with ammonia.

6. A method for applying a concentrated solution of electroless black nickel plating according to claim 1 or 2, characterized in that, In step (2)b, the ethanol solution containing the grafting agent is an ethanol solution containing 10-25 g / L of coupling agent. The coupling agent is one or more of titanate coupling agents, zirconate coupling agents, aluminate coupling agents, bimetallic coupling agents, and boron-containing coupling agents. The working temperature is 25-35℃ and the working time is 20-30 min. Hot air at 35-40℃ is blown for 3-5 min to dry the water-washed metal substrate. The inert gas is N2 or Ar, and baking is carried out at 45-55℃ for 20-35 min.

7. A method for applying a concentrated solution of electroless black nickel plating according to claim 1 or 2, characterized in that, The specific components of the activation solution in step (2)c are 80-100 g / L nickel sulfate, 5-10 g / L sodium acetate, 15-20 g / L malic acid, 10-25 g / L sodium lactate and deionized water, with a working temperature of 25-35℃ and a working time of 5-20 min; the specific components of the reducing solvent are 15-25 g / L potassium borohydride and deionized water, with a working temperature of 65-70℃ and a working time of 5-15 min.

8. A method for applying a concentrated solution of electroless black nickel plating according to claim 1 or 2, characterized in that, Step (3) The stirring method during the plating process is air stirring or mechanical stirring. The gas flow rate during air stirring is 3-8 l / min, and the rotation speed during mechanical stirring is 300-500 r / min. Dry at 35-45℃ for 15-20 min.

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