Chemical nickel-plated layer blackening agent and blackening method

Abstract

The invention discloses a chemical nickel-plated layer blackening agent and a blackening method, the chemical nickel-plated layer blackening agent comprises the following components: 400-900g / L of phosphoric acid, 400-900g / L of saturated carboxylic acid, 10-300g / L of an oxidizing agent and 10-100g / L of carbamide, the high-concentration phosphoric acid is used as a main catalyst for a chemical nickel-plated layer (nickel-phosphorus alloy layer) blackening reaction, the complex reaction can be ensured to be stably carried out, and the chemical nickel-plated layer blackening agent can be used for blackening the chemical nickel-plated layer (nickel-phosphorus alloy layer). Meanwhile, due to the high viscosity of phosphoric acid, local peroxidation reaction is prevented, and the defect that in the prior art, a black film layer is generally uneven in color after a nickel-phosphorus alloy layer is blackened is overcome; in addition, saturated carboxylic acid is used as a source of a film-forming substance nitrated carbon chain, so that the defects of poor wear resistance and poor adhesive force of a black film layer after the nickel-phosphorus alloy layer is blackened are overcome; the provided chemical blackening agent for the chemical nickel plating layer has a good blackening effect on a high-phosphorus chemical nickel plating layer, a medium-phosphorus chemical nickel plating layer or a low-phosphorus chemical nickel plating layer. The process is simple to operate, and the formed black film is uniform, has the blackness close to that of carbon black, is well combined with a base material and is not easy to fall off.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, in particular to a chemical nickel plating layer blackening agent and a blackening method. Background Art

[0002] With the development of new energy such as solar energy in modern society, the substantial progress in aerospace technology, and people's diversified requirements for various application scenarios in production and life, the blackening treatment of metal surfaces has many application scenarios.

[0003] Metal surface blackening is mainly used in various fields of materials that are sensitive to light and heat, such as optical instruments, aerospace electronic devices, electronic semiconductor components, and solar cell functional devices. It can not only greatly improve the heat absorption and light absorption efficiency of the device, as well as improve the device's thermal radiation, light scattering and other properties, but also compared with copper, iron, aluminum and other materials, the chemical nickel metal layer (nickel-phosphorus alloy plating) has superior wear resistance, corrosion resistance, and weather resistance.

[0004] The chemical blackening method of nickel layer mainly uses a later blackening treatment to oxidize and blacken the surface nickel layer and finally form black nickel. However, this method has extremely high requirements on the corrosion resistance of the nickel layer, otherwise it will cause problems such as detachment of the nickel layer. At the same time, the later blackening treatment operation is difficult to control, so it is difficult to ensure the uniform color of the workpieces processed in the same batch; the electroplating black nickel method cannot ensure the uniformity of current, so it is difficult to ensure that a black nickel layer with uniform thickness and color can be obtained when processing heterogeneous workpieces (irregularly shaped workpieces); the chemical black nickel plating method can effectively solve the above problems (uniform thickness and uniform color), but it also has problems such as poor wear resistance and corrosion resistance, poor bonding when the nickel layer is in direct contact with the substrate, and poor gloss.

[0005] The plating solution used in the existing chemical nickel plating technology is usually an inorganic nickel salt, hypophosphorous acid or sodium hypophosphite as a reducing agent system; or a black nickel system such as a nickel salt doped with tin, zinc, and copper system. The existing technologies have their own advantages and characteristics, but also have major shortcomings. For example, the nickel plating technology obtained by the chemical nickel plating technology of nickel sulfate and hypophosphorous acid reducing agent system is a single metal silver-white coating. The coating is not suitable for scenes in the optoelectronic field that require light and heat sensitivity (poor adhesion), and the coating has insufficient corrosion resistance and discoloration resistance.

[0006] In summary, there is no stable blackening process for nickel-phosphorus alloy coating that can be applied on an industrial scale. The various blackening methods used in various laboratories have many disadvantages in obtaining blackened films, such as uneven film color, lack of blackness, poor film adhesion and wear resistance, and easy shedding.

[0007] Therefore, the preparation method and related technology of chemical nickel plating blackening agent still need to be further improved. Summary of the invention

[0008] In view of the deficiencies in the above-mentioned prior art, the purpose of the present invention is to provide a blackening agent and a blackening method for a chemical nickel plating layer, which solves the problems of uneven color of the nickel-phosphorus alloy layer after blackening, poor wear resistance of the black film layer, and poor adhesion.

[0009] To achieve the above object, the present invention adopts the following technical solution:

[0010] On the one hand, the present invention provides a chemical nickel plating layer blackening agent, comprising the following components: 400-900 g / L phosphoric acid, 400-900 g / L saturated carboxylic acid, 10-300 g / L oxidant, and 10-100 g / L carbonamide.

[0011] On the basis of this solution, preferably, the chemical nickel plating layer blackening agent also includes 10-100 g / L of a film-forming agent and 1-10 g / L of a surfactant.

[0012] Based on this solution, preferably, the mass fractions of the phosphoric acid, the saturated carboxylic acid, the carbonamide, the film-forming agent and the surfactant are all greater than 95%.

[0013] Based on this solution, preferably, the saturated carboxylic acid is acetic acid, propionic acid or benzoic acid.

[0014] Based on this scheme, preferably, the oxidant is nitric acid, potassium nitrate or sodium nitrate.

[0015] Based on this solution, preferably, when the oxidant is nitric acid, the mass fraction of the nitric acid is greater than 50%; when the oxidant is potassium nitrate or sodium nitrate, the mass fraction of the potassium nitrate or sodium nitrate is greater than 95%.

[0016] Based on this solution, preferably, the film-forming agent is one of chromic acid, potassium chromate, sodium chromate, potassium dichromate, sodium dichromate, molybdic acid or sodium potassium salt of molybdic acid.

[0017] On the other hand, the present invention also provides a method for blackening the chemical nickel plating layer blackening agent according to the first aspect, comprising the following steps:

[0018] S1, adding phosphoric acid, saturated carboxylic acid, oxidant, carbon amide, film-forming agent and surfactant in sequence, stirring evenly, to obtain the chemical nickel plating layer blackening agent;

[0019] S2, immersing the workpiece with chemical nickel plating layer into the chemical nickel plating layer blackening agent, slowly moving the workpiece so that all parts of the workpiece are in uniform contact with the chemical nickel plating layer blackening agent, maintaining a constant temperature, taking out the workpiece, washing it with running water, and drying it to obtain a chemical nickel-phosphorus alloy plating layer.

[0020] Based on this solution, preferably, the constant temperature in step S2 is 18-40°C.

[0021] Based on this solution, preferably, the immersion at a constant temperature in step S2 is for 30-300 seconds.

[0022] Based on this solution, preferably, the phosphorus content in the chemical nickel-phosphorus alloy coating is 3-14%.

[0023] The chemical nickel plating layer blackening agent and blackening method of the present invention have the following beneficial effects compared with the prior art:

[0024] (1) The present invention uses high-concentration phosphoric acid as the main catalyst for the blackening reaction of the chemical nickel plating layer (nickel-phosphorus alloy layer), which can ensure the stable progress of the complex reaction. At the same time, the high viscosity of phosphoric acid prevents the occurrence of local overoxidation reaction, thereby solving the defect of the black film layer with generally uneven color after the nickel-phosphorus alloy layer is blackened in the prior art.

[0025] (2) The present invention also uses saturated carboxylic acid as the source of the nitrated carbon chain of the film-forming substance, thereby solving the disadvantages of poor wear resistance and poor adhesion of the black film layer after the nickel-phosphorus alloy layer is blackened; at the same time, the present invention also adds a small amount of carbon amide to inhibit the volatilization of acidic nitrogen oxide gas in the formula.

[0026] (3) The chemical nickel plating layer blackening agent provided by the present invention makes it possible for this special chemical nickel plating layer (nickel-phosphorus alloy plating layer) blackened film layer to be applied on a large scale, thereby achieving the goal of utilizing the excellent performance of the chemical nickel plating layer (nickel-phosphorus alloy plating layer) while taking into account the special requirements of photothermal sensitive devices or appearance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 , 2 This is a diagram showing the blackening effect of the chemical nickel plating layer blackening agent prepared in an embodiment of the present invention;

[0029] Figure 3 a, Figure 3 b are respectively the SEM and EDS spectra of the blackened chemical nickel plating layer with high phosphorus content obtained in Example 1 of the present invention;

[0030] Figure 4 a, Figure 4b are the SEM and EDS spectra of the chemical nickel plating layer with medium phosphorus content prepared in Example 2 of the present invention after blackening. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The present invention proposes a chemical nickel plating blackening agent and a blackening method. After depositing a 5-20 μm chemical nickel plating layer on the surface of a workpiece made of copper, iron, aluminum, etc., a blackening treatment is performed on the surface chemical nickel layer to obtain a uniform and dense blackened film layer. Figure 1 , 2 , which is a diagram of the blackening effect of the chemical nickel plating layer blackening agent prepared in an embodiment of the present invention; it can be seen that this can not only utilize the excellent performance of the chemical nickel plating layer, but also take into account the special requirements of the photothermal sensitive device, thereby achieving the purpose of greatly improving the light reflection, heat absorption and light absorption efficiency of the device, and the film layer has the properties of corrosion resistance, high temperature resistance, friction resistance, and ultraviolet aging resistance, which greatly improves the stability of the device performance and increases its adaptability to harsh environments.

[0033] Example 1

[0034] A blackening agent for chemical nickel plating layer, comprising the following components:

[0035] Component A, phosphoric acid content per 1L 800g, here use industrial grade phosphoric acid;

[0036] Component B, acetic acid, 250g per 1L, AR grade propionic acid is used here;

[0037] Component C, nitric acid, 100g per 1L, AR grade nitric acid is used here;

[0038] Component D, carbonamide, 50g per 1L, AR grade carbonamide is used here, and it is prepared into a saturated aqueous solution;

[0039] Component F, surfactant, 0.3 g per 1 L, industrial grade potassium perfluorooctane sulfonate is used here, prepared into a saturated aqueous solution;

[0040] The blackening method of the chemical nickel plating layer blackening agent comprises the following steps:

[0041] S1. Add component A first, add component B while stirring continuously, then add component C, and saturated aqueous solutions of components D and F in sequence while stirring continuously, replenish the liquid level with component A to 1L, stir evenly and set aside.

[0042] Among them, the nickel plating method is: take a piece of copper plate, size: 30×2×100mm, after ultrasonic degreasing, pickling, palladium activation, use the following scheme to plate chemical nickel for 60 minutes, nickel sulfate: 28g / 1L; lactic acid: 18g / L; sodium hypophosphite: 32g / L; succinic acid: 12g / L; stabilizer: 1ml / L; phosphorus content adjuster: 2ml / L; 20% ammonia water to adjust the pH value: 4.3; temperature: 92°C; chemically plate a 16μm high-phosphorus chemical nickel layer (phosphorus content 12.3%) on the copper plate.

[0043] S2. At room temperature, immerse the copper plate plated with high-phosphorus chemical nickel in the blackening agent solution of step S1, move slowly, take it out after 100 seconds, wash it with running water, and dry it to obtain a uniformly blackened chemical nickel-phosphorus alloy coating.

[0044] result: Figure 3 (a) and (b) are respectively the SEM and EDS energy spectra of the blackened chemical nickel coating with high phosphorus content obtained in Example 1 of the present invention. It can be seen that the chemical nickel coating blackened in this embodiment has a uniform and dense film layer under an electron microscope, and no corrosion micropores are generated. The energy spectrum shows that the generated black oxide film layer is composed of elements such as carbon, oxygen, phosphorus, nickel, and chromium. The higher content of nickel, phosphorus, and carbon indicates that the black film skeleton is a complex compound composed of these three elements. The higher phosphide in the film layer makes the film layer have a lower friction coefficient, thereby improving the wear resistance of the film layer; due to the presence of chromium compounds in the film layer, the film layer has better corrosion resistance. The film layer is measured using an MN-B blackness meter and the blackness value is 53.2, which is close to the standard value of carbon black of 50; using an RCA paper tape wear tester, using a standard load of 175g, after 1000 cycles, the black film layer is intact.

[0045] Example 2

[0046] A blackening agent for chemical nickel plating layer, comprising the following components:

[0047] Component A, phosphoric acid content per 1L 750g, here use industrial grade phosphoric acid;

[0048] Component B, acetic acid, 250g per 1L, AR grade acetic acid is used here;

[0049] Component C, nitric acid, 80g per 1L, AR grade nitric acid is used here;

[0050] Component D, carbonamide, 50g per 1L, AR grade carbonamide is used here, and it is prepared into a saturated aqueous solution;

[0051] Component E, chromic acid, 20g per 1L, industrial grade chromic acid is used here to prepare a saturated aqueous solution;

[0052] Component F, surfactant, 0.2 g per 1 L, industrial grade potassium perfluorooctane sulfonate is used here, prepared into a saturated aqueous solution;

[0053] The blackening method of the chemical nickel plating layer blackening agent comprises the following steps:

[0054] S1. First add component A, add component B and component C while stirring continuously, then add component D, and saturated aqueous solutions of component E and component F in sequence while stirring continuously, replenish the liquid level with component A to 1L, stir evenly and set aside.

[0055] Among them, the nickel plating method is: take a piece of aluminum alloy plate, size: 30×5×100mm, after ultrasonic degreasing, alkaline etching, acid etching, zinc replacement, use the following scheme to plate chemical nickel for 60 minutes, nickel sulfate: 28g / L; lactic acid: 16g / L; sodium hypophosphite: 30g / L; succinic acid: 12g / L; stabilizer: 1ml / L; 20% ammonia water to adjust the pH value: 4.7; temperature: 92°C; chemically plate the aluminum alloy plate with a 20μm medium-phosphorus chemical nickel layer (phosphorus content 7.6%).

[0056] S2. At room temperature, immerse the aluminum alloy plate coated with a medium-phosphorus chemical nickel layer in the blackening agent solution of step S1, move slowly, take it out after 90 seconds, wash it with running water, and dry it to obtain a uniformly blackened chemical nickel-phosphorus alloy coating.

[0057] result: Figure 4 (a) and (b) are respectively the SEM and EDS energy spectra of the chemical nickel plating with medium phosphorus content obtained in Example 1 of the present invention after blackening. It can be seen that the chemical nickel plating blackened by this embodiment has a uniform and dense film layer under the electron microscope, and no corrosion micropores are generated. The energy spectrum shows that the generated black oxide film layer is composed of carbon, oxygen, phosphorus, nickel, chromium and other elements, among which the higher nickel, phosphorus and carbon content indicates that the black film skeleton is a complex compound composed of these three elements. The higher phosphide in the film layer makes the film layer have a lower friction coefficient, thereby improving the wear resistance of the film layer; due to the presence of chromium compounds in the film layer, the film layer has better corrosion resistance. The film layer is measured using an MN-B blackness meter and the blackness value is 47.5, which is close to the standard value of carbon black 50; using an RCA paper tape wear tester, using a standard load of 175g, after 1000 cycles, the black film layer is intact.

[0058] Example 3

[0059] A blackening agent for chemical nickel plating layer, comprising the following components:

[0060] Component A, phosphoric acid content per 1L 750g, here use industrial grade phosphoric acid;

[0061] Component B, propionic acid, 250g per 1L, AR grade propionic acid is used here;

[0062] Component C, nitric acid, 50g per 1L, AR grade nitric acid is used here;

[0063] Component D, carbonamide, 50g per 1L, AR grade carbonamide is used here, and it is prepared into a saturated aqueous solution;

[0064] Component E, potassium dichromate, 30g per 1L, industrial grade chromic acid is used here to prepare a saturated aqueous solution;

[0065] The blackening method of the chemical nickel plating layer blackening agent comprises the following steps:

[0066] S1. Add component A first, add component B while stirring continuously, then add component C, and saturated aqueous solutions of components D and E in sequence while stirring continuously, replenish the liquid level with component A to 1L, stir evenly and set aside.

[0067] Among them, the nickel plating method is: take an iron sheet, size: 30×5×100mm, after ultrasonic degreasing, pickling, polishing, acid activation, use the following scheme to plate chemical nickel for 40 minutes, nickel sulfate: 30g / L; lactic acid: 5g / L; glycine: 22g / L; sodium hypophosphite: 28g / L; succinic acid: 10g / L; stabilizer: 1ml / L; 20% ammonia water to adjust the pH value: 4.8; temperature: 90°C; chemically plate a 12μm low-phosphorus chemical nickel layer (phosphorus content 3.8%) on the iron sheet.

[0068] S2. At room temperature, immerse the iron sheet plated with low-phosphorus chemical nickel in the blackening agent solution of step S1, move slowly, take it out after 150 seconds, clean it with running water, and dry it to obtain a uniformly blackened chemical nickel-phosphorus alloy coating. The film layer is measured using an MN-B blackness meter, and the blackness value is 51.2, which is close to the standard value of carbon black 50; using an RCA paper tape wear tester, using a standard load of 175g, after 1000 cycles, the black film layer is intact.

[0069] Example 4

[0070] A blackening agent for chemical nickel plating layer, comprising the following components:

[0071] Component A, phosphoric acid content per 1L 800g, here use industrial grade phosphoric acid;

[0072] Component B, acetic acid, 250g per 1L, AR grade propionic acid is used here;

[0073] Component C, nitric acid, 100g per 1L, AR grade nitric acid is used here;

[0074] Component D, 50 g of carbamide per 1 L, AR grade carbamide is used here to prepare a saturated aqueous solution;

[0075] Component F, surfactant, 10 g per 1 L, industrial grade potassium perfluorooctane sulfonate is used here, prepared into a saturated aqueous solution;

[0076] The blackening method of the chemical nickel plating layer blackening agent comprises the following steps:

[0077] S1. Add component A first, add component B while stirring continuously, then add component C, and saturated aqueous solutions of components D and F in sequence while stirring continuously, replenish the liquid level with component A to the 11L mark, stir evenly and set aside.

[0078] Among them, the nickel plating method is: take a piece of copper plate, size: 30×2×100mm, after ultrasonic degreasing, pickling, palladium activation, use the following scheme to plate chemical nickel for 80 minutes, nickel sulfate: 28g / 1L; lactic acid: 18g / 1L; sodium hypophosphite: 32g / 1L; succinic acid: 12g / 1L; stabilizer: 1ml / 1L; phosphorus content adjuster: 2ml / 1L; 20% ammonia water to adjust the pH value: 4.5; temperature: 94°C; chemically plate a 14μm high-phosphorus chemical nickel layer (phosphorus content 14%) on the copper plate.

[0079] S2. At room temperature, immerse the copper plate plated with high-phosphorus chemical nickel in the solution of the blackening agent in step S1, move slowly, take it out after 100 seconds, clean it with running water, and dry it to obtain a uniformly blackened chemical nickel-phosphorus alloy coating. The film layer is measured using an MN-B blackness meter, and the blackness value is 52.8, which is close to the standard value of carbon black 50; using an RCA paper tape wear tester, using a standard load of 175g, after 1000 cycles, the black film layer is intact.

[0080] As can be seen from the above examples, in the present invention, a small amount of carbonyl amide is added to inhibit the volatilization of acidic nitrogen oxide gas in the formula. In a strong acidic environment, the oxidant nitric acid or nitrate ion will react with the metal nickel in the coating as follows:

[0081] Ni+4HNO3=Ni(NO3)2+2NO2↑+2H2O

[0082] This will release a small amount of nitrogen oxide gas, which will be captured by the added carbamide and the following reaction will occur:

[0083] 2(NH2)2CO+6NO→5N2↑+2CO2↑+4H2O

[0084] 4(NH2)2CO+6NO2→7N2+4CO2↑+8H2O

[0085] The reaction generates harmless gases, thus improving the working environment.

[0086] In summary, the chemical blackening agent for chemical nickel plating provided by the present invention has a good blackening effect on high-phosphorus chemical nickel plating, medium-phosphorus chemical nickel plating or low-phosphorus chemical nickel plating. The process is simple to operate, the resulting black film is uniform, the blackness is close to carbon black, it is well bonded to the substrate and is not easy to fall off. Since the film layer is an inorganic film layer, it has good resistance to high temperature and ultraviolet rays; it is completely applicable to various electronic components that are sensitive to light and heat, and after appropriate post-protection treatment, it can also be used in the decorative metal surface treatment of daily electrical appliances that require a deep black appearance.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A blackening agent for chemical nickel plating, characterized in that: The invention comprises the following components: 400-900 g / L phosphoric acid, 400-900 g / L saturated carboxylic acid, 10-300 g / L oxidant and 10-100 g / L carbonamide.

2. The chemical nickel plating layer blackening agent as claimed in claim 1, characterized in that The chemical nickel plating layer blackening agent also includes 10-100 g / L of a film-forming agent and 1-10 g / L of a surfactant.

3. The chemical nickel plating layer blackening agent as claimed in claim 1, characterized in that, The mass fractions of the phosphoric acid, the saturated carboxylic acid, the carbon amide, the film-forming agent and the surfactant are all greater than 95%.

4. The chemical nickel plating layer blackening agent as claimed in claim 1, characterized in that The saturated carboxylic acid is acetic acid, propionic acid or benzoic acid.

5. The chemical nickel plating layer blackening agent as claimed in claim 1, characterized in that, The oxidant is nitric acid, potassium nitrate or sodium nitrate.

6. The chemical nickel plating layer blackening agent as claimed in claim 4, characterized in that, When the oxidant is nitric acid, the mass fraction of the nitric acid is greater than 50%; when the oxidant is potassium nitrate or sodium nitrate, the mass fraction of the potassium nitrate or sodium nitrate is greater than 95%.

7. The chemical nickel plating layer blackening agent as claimed in claim 1, characterized in that, The film-forming agent is one of chromic acid, potassium chromate, sodium chromate, potassium dichromate, sodium dichromate, molybdic acid or sodium potassium salt of molybdic acid.

8. The method for blackening the chemical nickel plating layer using a blackening agent according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1, adding phosphoric acid, saturated carboxylic acid, oxidant, carbon amide, film-forming agent and surfactant in sequence, stirring evenly, to obtain the chemical nickel plating layer blackening agent; S2, immersing the workpiece with chemical nickel plating layer into the chemical nickel plating layer blackening agent, slowly moving the workpiece so that all parts of the workpiece are in uniform contact with the chemical nickel plating layer blackening agent, maintaining a constant temperature, taking out the workpiece, washing it with running water, and drying it to obtain a chemical nickel-phosphorus alloy plating layer.

9. The blackening method of the chemical nickel plating layer blackening agent as claimed in claim 8, characterized in that: The constant temperature in step S2 is 18-40°C.

10. The blackening method of the chemical nickel plating layer blackening agent according to claim 9, characterized in that: The step S2 is performed by immersing at a constant temperature for 30-300 seconds.

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