Alkaline chemical nickel surface treatment method for pure aluminum or aluminum alloy

Abstract

The invention discloses an alkaline chemical nickel surface treatment method for pure aluminum or aluminum alloy. The method solves the problems of two times of zinc immersion and one time of zinc stripping in the production process, can meet the requirement of the binding force of a product plating layer by only one time of zinc immersion process, effectively improves the stability and safety of the product in the production process, does not have a 50% nitric acid zinc stripping process, can obviously reduce the use amount of nitric acid in the production process, and reduces the production cost. The production environment is efficiently improved.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, specifically to an alkaline chemical nickel surface treatment method for pure aluminum or aluminum alloys. Background Technology

[0002] Pure aluminum or aluminum alloys are lightweight and possess excellent electrical and thermal conductivity. Compared to copper, stainless steel, and magnesium alloys, aluminum alloys have lower raw material and processing costs, playing an irreplaceable role in electronic components and the automotive industry. However, pure aluminum or commonly used aluminum alloys have drawbacks such as low hardness, a high coefficient of friction, and poor corrosion resistance. Therefore, a layer of chemical nickel plating is required on the surface. This nickel plating has excellent coverage and adhesion, and its hardness can reach HV 500-1000, far exceeding that of the aluminum alloy substrate. This process transforms aluminum alloys, which originally had limited performance, into high-performance components that are lightweight, have high hardness, strong corrosion resistance, are weldable, and have precise dimensions, making them widely used in high-end fields such as aerospace, automotive industry, electronic equipment, and precision machinery.

[0003] The shortcomings of existing technology: Currently, in the process of nickel plating aluminum alloys, in order to ensure a good bond between the substrate and the nickel layer, a two-stage zinc immersion process is required. After the first zinc immersion, a 50% nitric acid solution is needed to remove the zinc layer formed in the first zinc immersion. Then, a second zinc immersion process is carried out to form a dense zinc layer. Since the 50% nitric acid zinc removal process is difficult to control, it can easily cause product quality problems and also has a significant impact on the production environment. Summary of the Invention

[0004] The purpose of this invention is to provide an alkaline chemical nickel surface treatment method for pure aluminum or aluminum alloys, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys, the treatment method specifically comprising: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughening, followed by two water washes; S2. Immerse in a strongly alkaline zincate solution, and plate the surface with zinc through a displacement reaction between zinc and aluminum, followed by three water washes. S3. Immerse in weakly alkaline electroless nickel plating to coat the bottom layer, and then wash twice with water. S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes; S5. Dry and test product performance.

[0006] Preferably, step S1 specifically includes: a1. Acid etching is used, and an air nozzle is connected to compressed air. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 40-60 mg / L, the concentration of phosphoric acid is 30-50 mg / L, the concentration of nitric acid is 450-550 mg / L, the temperature is set to 50-75℃, and the soaking time is set to 0.5-3 min. a2. Perform the first rinse; a3. Perform a second rinse.

[0007] Preferably, step S2 specifically includes: b1. Immerse in a strongly alkaline zincate solution, wherein the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride, and special additive one, wherein special additive one includes 60-80% potassium ferrocyanide and 20-40% sodium ferric chloride, the concentration of sodium hydroxide is 90-110 g / L, the concentration of zinc oxide is 10-14 g / L, the concentration of potassium sodium tartrate is 40-50 g / L, the concentration of nickel chloride is 15-25 g / L, the concentration of ferric chloride is 0.8-1.2 g / L, the concentration of special additive one is 0.1-0.4 g / L, the temperature is set to 21-46℃, and the immersion time is 12-120 s; b2. Perform the first rinse; b3. Perform a second rinse; b4. Perform the third rinse.

[0008] Preferably, step S3 specifically includes: c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form the base layer. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and special additive II. The special additive II includes 35-55% allyl thiourea and 45-65% succinic acid. The nickel sulfate solution contains nickel ions with a concentration of 4.2-4.8 g / L, the sodium hypophosphite concentration is 15-25 g / L, the sodium chloride concentration is 1-2 g / L, the boric acid concentration is 4-6 g / L, the sodium hydroxide concentration is 3-7 g / L, the malic acid concentration is 0.5-1 g / L, and the special additive II concentration is 0.2-0.4 g / L. c2. Perform the first rinse; c3. Perform a second rinse.

[0009] Preferably, step S4 specifically includes: d1. The film thickness using low-temperature chemical nickel plating, wherein the low-temperature chemical nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and special additive three. Special additive three includes 80-100 ml / L of 2-thiourea pyrimidine and 150 ml / L of a mixture of sodium saccharin, with the remainder being DI water. Nickel sulfate comprises nickel ions at a concentration of 5.2-6.0 g / L, sodium hypophosphite at a concentration of 25-32 g / L, glycine at a concentration of 4-5.5 g / L, lactic acid at a concentration of 12-18 g / L, malic acid at a concentration of 8-12 g / L, potassium iodide at a concentration of 8-10 mg / L, thiourea at a concentration of 2-4.0 mg / L, sodium dodecyl sulfonate at a concentration of 16-24 mg / L, and special additive three at a concentration of 0.5-2 ml / L. d2. Perform the first water wash; d3. Perform the second rinse; d4. Perform the third rinse.

[0010] Preferably, in step c1, the temperature is set to 55-65℃, the soaking time is set to 5-15 min, the pH is set to 8.4-9.0, and the loading rate is set to 0.25-2.45 square decimeters / liter.

[0011] Preferably, in step d1, the temperature is set to 60-65℃, the soaking time is set to 5-60 min, the pH is set to 6.0-6.5, and the loading rate is set to 0.2-3.0 square decimeters / liter.

[0012] Preferably, in steps S1 and S3, the washing time for both washes is set to 1-5 minutes.

[0013] Preferably, in steps S2 and S4, the washing time for each of the three washes is set to 1-5 minutes.

[0014] Preferably, in step S5, a dryer with an exhaust system is used for drying, the temperature is set to 95-102℃, and the drying time is set to 0.5-2h.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This method for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys utilizes special additives in alkaline chemical nickel to prevent strong reactions during the reaction process, thus avoiding damage to the aluminum substrate. It forms a fine nickel plating layer with excellent adhesion on the surface, solving the problem of two zinc immersions and one zinc stripping process in production. Only one zinc immersion process is needed to achieve the required coating adhesion, effectively improving product stability and safety during production. Furthermore, it eliminates the 50% nitric acid zinc stripping process, significantly reducing the amount of nitric acid used in production and efficiently improving the production environment. Attached Figure Description

[0016] Figure 1 This is a flowchart of the processing method of the present invention; Figure 2 These are test diagrams of the bonding force of samples in Examples 1-8 of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a number" means two or more, unless otherwise explicitly specified.

[0019] Example 1 Please see Figure 1-2 As shown, the present invention provides a technical solution for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys: the specific treatment method includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness to 0.5 – 1.5µm, enhance the mechanical adhesion of subsequent coatings, and perform two water rinses, with a rinsing time of 1–5 min. a1. Acid etching is used, and an air nozzle is connected to compressed air (pressure controlled at 0.1 to 0.2 MPa) to form air agitation during the production process. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 40 mg / L, the concentration of phosphoric acid is 30 mg / L, the concentration of nitric acid is 450 mg / L, the temperature is set to 50℃, and the soaking time is set to 3 min. a2. The first water wash is carried out, and the water is continuously discharged through overflow. An air spray pipe is installed at the bottom of the water tank to connect to compressed air (pressure controlled at 0.1 to 0.2 MPa). During the production process, air agitation is generated to ensure the cleaning effect. a3. Perform the second rinse, continuously adding clean water (at a rate of 10-20 ml / l per minute), and let the water overflow from the second rinse into the first rinse.

[0020] S2. Immerse in a strongly alkaline zincate solution to plate zinc onto the surface through a displacement reaction between zinc and aluminum, and then perform three water washes, each lasting 1-5 minutes. b1. Immerse in a strongly alkaline zincate solution to cover the surface with a uniform dark gray or light gray zinc layer; the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride, and special additives. The concentration of sodium hydroxide is 100 g / L, the concentration of zinc oxide is 12 g / L, the concentration of potassium sodium tartrate is 45 g / L, the concentration of nickel chloride is 20 g / L, the concentration of ferric chloride is 1.0 g / L, and the concentration of special additives is 0.3 g / L (including potassium ferrocyanide 0.18 g / L and sodium ferric chloride 0.12 g / L). The temperature is set at 30℃, and the immersion time is 28 seconds. b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. b3. Perform a second water rinse, which is set to continuously overflow to the first water rinse. b4. Perform the third water wash. The third water wash is set to continuously add clean water and continuously overflow to the second water wash.

[0021] S3. Immerse in weakly alkaline electroless nickel plating to coat the underlayer. The underlayer should be 0.5-1μm thick, and then rinse twice with water for 1-5 minutes. c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form a dense and uniform active nickel layer with excellent adhesion to the substrate. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and a special additive II. The nickel sulfate solution contains nickel ions at a concentration of 4.5 g / L, the sodium hypophosphite solution at 22 g / L, the sodium chloride solution at 1.5 g / L, the boric acid solution at 5 g / L, the sodium hydroxide solution at 5 g / L, the malic acid solution at 0.7 g / L, and the special additive II solution at 0.3 g / L (including allyl thiourea at 0.105 g / L and succinic acid at 0.195 g / L). The temperature is set to 60℃, the immersion time to 10 min, the pH to 8.7, and the loading rate to 1 dm² / L. c2. The first water wash is carried out. The first water wash is continuously discharged through overflow. An air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. c3. Perform the second rinse. Clean water is continuously added to the second rinse, and the water from the second rinse overflows into the first rinse.

[0022] S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes, with each wash lasting 1-5 minutes. d1. Using low-temperature electroless nickel plating, the film thickness is 5%-9%, resulting in a uniform coating color and good corrosion resistance. The low-temperature electroless nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and a special additive. The nickel sulfate concentration is 5.8 g / L for nickel ions, 30 g / L for sodium hypophosphite, 5.0 g / L for glycine, 16 g / L for lactic acid, 10 g / L for malic acid, and 9 mg / L for potassium iodide. The thiourea concentration is 3.0 mg / L, the sodium dodecyl sulfonate concentration is 20 mg / L, and the special additive is 1.0 mg / L (including 0.08 ml / L of 2-thiourea pyrimidine, 0.15 ml / L of sodium saccharin mixture, and the remainder being DI water). The temperature is set to 63℃, the immersion time to 40 min, the pH to 6.3, and the loading rate to 1 dm² / L. d2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. d3. Perform a second water wash, which is set to continuously overflow to the first water wash; d4. Perform the third water rinse. The third water rinse is set to continuously add clean water and continuously overflow to the second water rinse. S5. Dry and test the product performance. Use a dryer with an exhaust system during drying. Set the temperature to 95-102℃ and the drying time to 0.5-2h. The test results are shown in Table 1.

[0023] Example 2 Please see Figure 1-2 As shown, the present invention provides a technical solution for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys: the specific treatment method includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness to 0.5 – 1.5µm, enhance the mechanical adhesion of subsequent coatings, and perform two water rinses, with a rinsing time of 1–5 min. a1. Acid etching is used, and an air nozzle is connected to compressed air (pressure controlled at 0.1 to 0.2 MPa) to form air agitation during the production process. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 60 mg / L, the concentration of phosphoric acid is 50 mg / L, the concentration of nitric acid is 550 mg / L, the temperature is set to 70℃, and the immersion time is set to 1 min. a2. The first water wash is carried out, and the water is continuously discharged through overflow. An air spray pipe is installed at the bottom of the water tank to connect to compressed air (pressure controlled at 0.1 to 0.2 MPa). During the production process, air agitation is generated to ensure the cleaning effect. a3. Perform the second rinse, continuously adding clean water (at a rate of 10-20 ml / l per minute), and let the water overflow from the second rinse into the first rinse.

[0024] S2. Immerse in a strongly alkaline zincate solution to plate zinc onto the surface through a displacement reaction between zinc and aluminum, and then perform three water washes, each lasting 1-5 minutes. b1. Immerse in a strongly alkaline zincate solution to cover the surface with a uniform dark gray or light gray zinc layer; wherein the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride and special additive one, the concentration of sodium hydroxide is 100 g / L, the concentration of zinc oxide is 12 g / L, the concentration of potassium sodium tartrate is 45 g / L, the concentration of nickel chloride is 20 g / L, the concentration of ferric chloride is 1.0 g / L, the concentration of special additive one is 0.3 g / L (including potassium ferrocyanide 0.2 g / L and sodium ferric chloride 0.1 g / L), the temperature is set to 30℃, and the immersion time is 28 s; b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. b3. Perform a second water rinse, which is set to continuously overflow to the first water rinse. b4. Perform the third water wash. The third water wash is set to continuously add clean water and continuously overflow to the second water wash.

[0025] S3. Immerse in weakly alkaline electroless nickel plating to coat the underlayer. The underlayer should be 0.5-1μm thick, and then rinse twice with water for 1-5 minutes. c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form a dense and uniform active nickel layer with excellent adhesion to the substrate. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and a special additive II. The nickel sulfate solution contains nickel ions at a concentration of 4.5 g / L, the sodium hypophosphite solution at 22 g / L, the sodium chloride solution at 1.5 g / L, the boric acid solution at 5 g / L, the sodium hydroxide solution at 5 g / L, the malic acid solution at 0.7 g / L, and the special additive II solution at 0.3 g / L (including allyl thiourea at 0.13 g / L and succinic acid at 0.17 g / L). The temperature is set to 60℃, the immersion time to 10 min, the pH to 8.7, and the loading rate to 1 dm² / L. c2. The first water wash is carried out. The first water wash is continuously discharged through overflow. An air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. c3. Perform the second rinse. Clean water is continuously added to the second rinse, and the water from the second rinse overflows into the first rinse.

[0026] S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes, with each wash lasting 1-5 minutes. d1. Using low-temperature electroless nickel plating, the film thickness is 5%-9%, resulting in a uniform coating color and good corrosion resistance. The low-temperature electroless nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and a special additive. The nickel sulfate concentration is 5.8 g / L for nickel ions, 30 g / L for sodium hypophosphite, 5.0 g / L for glycine, 16 g / L for lactic acid, 10 g / L for malic acid, and 9 mg / L for potassium iodide. The thiourea concentration is 3.0 mg / L, the sodium dodecyl sulfonate concentration is 20 mg / L, and the special additive is 1.0 mg / L (including 0.08 ml / L of 2-thiourea pyrimidine, 0.15 ml / L of sodium saccharin mixture, and the remainder being DI water). The temperature is set to 63℃, the immersion time to 40 min, the pH to 6.3, and the loading rate to 1 dm² / L. d2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. d3. Perform a second water wash, which is set to continuously overflow to the first water wash; d4. Perform the third water rinse. The third water rinse is set to continuously add clean water and continuously overflow to the second water rinse. S5. Dry and test the product performance. Use a dryer with an exhaust system during drying. Set the temperature to 95-102℃ and the drying time to 0.5-2h. The test results are shown in Table 1.

[0027] Example 3 Please see Figure 1-2 As shown, the present invention provides a technical solution for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys: the specific treatment method includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness to 0.5 – 1.5µm, enhance the mechanical adhesion of subsequent coatings, and perform two water rinses, with a rinsing time of 1–5 min. a1. Acid etching is used, and an air nozzle is connected to compressed air (pressure controlled at 0.1 to 0.2 MPa) to form air agitation during the production process. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 50 mg / L, the concentration of phosphoric acid is 40 mg / L, the concentration of nitric acid is 500 mg / L, the temperature is set to 70℃, and the soaking time is set to 2 min. a2. The first water wash is carried out, and the water is continuously discharged through overflow. An air spray pipe is installed at the bottom of the water tank to connect to compressed air (pressure controlled at 0.1 to 0.2 MPa). During the production process, air agitation is generated to ensure the cleaning effect. a3. Perform the second rinse, continuously adding clean water (at a rate of 10-20 ml / l per minute), and let the water overflow from the second rinse into the first rinse.

[0028] S2. Immerse in a strongly alkaline zincate solution to plate zinc onto the surface through a displacement reaction between zinc and aluminum, and then perform three water washes, each lasting 1-5 minutes. b1. Immerse in a strongly alkaline zincate solution to cover the surface with a uniform dark gray or light gray zinc layer; wherein the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride and special additive one, the concentration of sodium hydroxide is 90 g / L, the concentration of zinc oxide is 10 g / L, the concentration of potassium sodium tartrate is 40 g / L, the concentration of nickel chloride is 15 g / L, the concentration of ferric chloride is 0.8 g / L, the concentration of special additive one is 0.1 g / L (including potassium ferrocyanide 0.06 g / L and sodium ferric chloride 0.04 g / L), the temperature is set to 21℃, and the immersion time is 120 s; b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. b3. Perform a second water rinse, which is set to continuously overflow to the first water rinse. b4. Perform the third water wash. The third water wash is set to continuously add clean water and continuously overflow to the second water wash.

[0029] S3. Immerse in weakly alkaline electroless nickel plating to coat the underlayer. The underlayer should be 0.5-1μm thick, and then rinse twice with water for 1-5 minutes. c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form a dense and uniform active nickel layer with excellent adhesion to the substrate. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and a special additive II. The nickel sulfate solution contains nickel ions at a concentration of 4.5 g / L, the sodium hypophosphite solution at 22 g / L, the sodium chloride solution at 1.5 g / L, the boric acid solution at 5 g / L, the sodium hydroxide solution at 5 g / L, the malic acid solution at 0.7 g / L, and the special additive II solution at 0.3 g / L (including allyl thiourea at 0.15 g / L and succinic acid at 0.15 g / L). The temperature is set to 60℃, the immersion time to 10 min, the pH to 8.7, and the loading rate to 1 dm² / L. c2. The first water wash is carried out. The first water wash is continuously discharged through overflow. An air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. c3. Perform the second rinse. Clean water is continuously added to the second rinse, and the water from the second rinse overflows into the first rinse.

[0030] S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes, with each wash lasting 1-5 minutes. d1. Using low-temperature electroless nickel plating, the film thickness is 5%-9%, resulting in a uniform coating color and good corrosion resistance. The low-temperature electroless nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and a special additive. The nickel sulfate concentration is 5.8 g / L for nickel ions, 30 g / L for sodium hypophosphite, 5.0 g / L for glycine, 16 g / L for lactic acid, 10 g / L for malic acid, and 9 mg / L for potassium iodide. The thiourea concentration is 3.0 mg / L, the sodium dodecyl sulfonate concentration is 20 mg / L, and the special additive is 1.0 mg / L (including 0.08 ml / L of 2-thiourea pyrimidine, 0.15 ml / L of sodium saccharin mixture, and the remainder being DI water). The temperature is set to 63℃, the immersion time to 40 min, the pH to 6.3, and the loading rate to 1 dm² / L. d2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. d3. Perform a second water wash, which is set to continuously overflow to the first water wash; d4. Perform the third water rinse. The third water rinse is set to continuously add clean water and continuously overflow to the second water rinse. S5. Dry and test the product performance. Use a dryer with an exhaust system during drying. Set the temperature to 95-102℃ and the drying time to 0.5-2h. The test results are shown in Table 1.

[0031] Example 4 Please see Figure 1-2 As shown, the present invention provides a technical solution for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys: the specific treatment method includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness to 0.5 – 1.5µm, enhance the mechanical adhesion of subsequent coatings, and perform two water rinses, with a rinsing time of 1–5 min. a1. Acid etching is used, and an air nozzle is connected to compressed air (pressure controlled at 0.1 to 0.2 MPa) to form air agitation during the production process. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 50 mg / L, the concentration of phosphoric acid is 40 mg / L, the concentration of nitric acid is 500 mg / L, the temperature is set to 70℃, and the soaking time is set to 2 min. a2. The first water wash is carried out, and the water is continuously discharged through overflow. An air spray pipe is installed at the bottom of the water tank to connect to compressed air (pressure controlled at 0.1 to 0.2 MPa). During the production process, air agitation is generated to ensure the cleaning effect. a3. Perform the second rinse, continuously adding clean water (at a rate of 10-20 ml / l per minute), and let the water overflow from the second rinse into the first rinse.

[0032] S2. Immerse in a strongly alkaline zincate solution to plate zinc onto the surface through a displacement reaction between zinc and aluminum, and then perform three water washes, each lasting 1-5 minutes. b1. Immerse in a strongly alkaline zincate solution to cover the surface with a uniform dark gray or light gray zinc layer; wherein the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride and special additive one, the concentration of sodium hydroxide is 110 g / L, the concentration of zinc oxide is 14 g / L, the concentration of potassium sodium tartrate is 50 g / L, the concentration of nickel chloride is 25 g / L, the concentration of ferric chloride is 1.2 g / L, the concentration of special additive one is 0.3 g / L (including potassium ferrocyanide 0.21 g / L and sodium ferric chloride 0.09 g / L), the temperature is set to 46℃, and the immersion time is 12 s; b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. b3. Perform a second water rinse, which is set to continuously overflow to the first water rinse. b4. Perform the third water wash. The third water wash is set to continuously add clean water and continuously overflow to the second water wash.

[0033] S3. Immerse in weakly alkaline electroless nickel plating to coat the underlayer. The underlayer should be 0.5-1μm thick, and then rinse twice with water for 1-5 minutes. c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form a dense and uniform active nickel layer with excellent adhesion to the substrate. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and a special additive II. The nickel sulfate solution contains nickel ions at a concentration of 4.5 g / L, the sodium hypophosphite solution at 22 g / L, the sodium chloride solution at 1.5 g / L, the boric acid solution at 5 g / L, the sodium hydroxide solution at 5 g / L, the malic acid solution at 0.7 g / L, and the special additive II solution at 0.3 g / L (including allyl thiourea at 0.16 g / L and succinic acid at 0.14 g / L). The temperature is set to 60℃, the immersion time to 10 min, the pH to 8.7, and the loading rate to 1 square decimeter / liter. c2. The first water wash is carried out. The first water wash is continuously discharged through overflow. An air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. c3. Perform the second rinse. Clean water is continuously added to the second rinse, and the water from the second rinse overflows into the first rinse.

[0034] S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes, with each wash lasting 1-5 minutes. d1. Using low-temperature electroless nickel plating, the film thickness is 5%-9%, resulting in a uniform coating color and good corrosion resistance. The low-temperature electroless nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and a special additive. The nickel sulfate concentration is 5.8 g / L for nickel ions, 30 g / L for sodium hypophosphite, 5.0 g / L for glycine, 16 g / L for lactic acid, 10 g / L for malic acid, and 9 mg / L for potassium iodide. The thiourea concentration is 3.0 mg / L, the sodium dodecyl sulfonate concentration is 20 mg / L, and the special additive is 1.0 mg / L (including 0.08 ml / L of 2-thiourea pyrimidine, 0.15 ml / L of sodium saccharin mixture, and the remainder being DI water). The temperature is set to 63℃, the immersion time to 40 min, the pH to 6.3, and the loading rate to 1 dm² / L. d2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. d3. Perform a second water wash, which is set to continuously overflow to the first water wash; d4. Perform the third water rinse. The third water rinse is set to continuously add clean water and continuously overflow to the second water rinse. S5. Dry and test the product performance. Use a dryer with an exhaust system during drying. Set the temperature to 95-102℃ and the drying time to 0.5-2h. The test results are shown in Table 1.

[0035] Example 5 Please see Figure 1-2 As shown, the present invention provides a technical solution for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys: the specific treatment method includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness to 0.5 – 1.5µm, enhance the mechanical adhesion of subsequent coatings, and perform two water rinses, with a rinsing time of 1–5 min. a1. Acid etching is used, and an air nozzle is connected to compressed air (pressure controlled at 0.1 to 0.2 MPa) to form air agitation during the production process. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 50 mg / L, the concentration of phosphoric acid is 40 mg / L, the concentration of nitric acid is 500 mg / L, the temperature is set to 70℃, and the soaking time is set to 2 min. a2. The first water wash is carried out, and the water is continuously discharged through overflow. An air spray pipe is installed at the bottom of the water tank to connect to compressed air (pressure controlled at 0.1 to 0.2 MPa). During the production process, air agitation is generated to ensure the cleaning effect. a3. Perform the second rinse, continuously adding clean water (at a rate of 10-20 ml / l per minute), and let the water overflow from the second rinse into the first rinse.

[0036] S2. Immerse in a strongly alkaline zincate solution to plate zinc onto the surface through a displacement reaction between zinc and aluminum, and then perform three water washes, each lasting 1-5 minutes. b1. Immerse in a strongly alkaline zincate solution to cover the surface with a uniform dark gray or light gray zinc layer; the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride, and special additive one. The concentration of sodium hydroxide is 100 g / L, the concentration of zinc oxide is 12 g / L, the concentration of potassium sodium tartrate is 45 g / L, the concentration of nickel chloride is 20 g / L, the concentration of ferric chloride is 1.0 g / L, and the concentration of special additive one is 0.3 g / L (including potassium ferrocyanide 0.23 g / L and sodium ferric chloride 0.07 g / L). The temperature is set at 30℃, and the immersion time is 28 seconds. b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. b3. Perform a second water rinse, which is set to continuously overflow to the first water rinse. b4. Perform the third water wash. The third water wash is set to continuously add clean water and continuously overflow to the second water wash.

[0037] S3. Immerse in weakly alkaline electroless nickel plating to coat the underlayer. The underlayer should be 0.5-1μm thick, and then rinse twice with water for 1-5 minutes. c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form a dense and uniform active nickel layer with excellent adhesion to the substrate. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and a special additive II. The nickel sulfate solution contains nickel ions at a concentration of 4.5 g / L, the sodium hypophosphite solution at 22 g / L, the sodium chloride solution at 1.5 g / L, the boric acid solution at 5 g / L, the sodium hydroxide solution at 5 g / L, the malic acid solution at 0.7 g / L, and the special additive II solution at 0.3 g / L (including allyl thiourea at 0.165 g / L and succinic acid at 0.135 g / L). The temperature is set to 65℃, the immersion time to 15 min, the pH to 8.4, and the loading rate to 1 square decimeter / liter. c2. The first water wash is carried out. The first water wash is continuously discharged through overflow. An air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. c3. Perform the second rinse. Clean water is continuously added to the second rinse, and the water from the second rinse overflows into the first rinse.

[0038] S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes, with each wash lasting 1-5 minutes. d1. Using low-temperature electroless nickel plating, the film thickness is 5%-9%, resulting in a uniform coating color and good corrosion resistance. The low-temperature electroless nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and a special additive. The nickel sulfate concentration is 5.8 g / L for nickel ions, 30 g / L for sodium hypophosphite, 5.0 g / L for glycine, 16 g / L for lactic acid, 10 g / L for malic acid, and 9 mg / L for potassium iodide. The thiourea concentration is 3.0 mg / L, the sodium dodecyl sulfonate concentration is 20 mg / L, and the special additive is 1.0 mg / L (including 0.08 ml / L of 2-thiourea pyrimidine, 0.15 ml / L of sodium saccharin mixture, and the remainder being DI water). The temperature is set to 63℃, the immersion time to 40 min, the pH to 6.3, and the loading rate to 1 dm² / L. d2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. d3. Perform a second water wash, which is set to continuously overflow to the first water wash; d4. Perform the third water rinse. The third water rinse is set to continuously add clean water and continuously overflow to the second water rinse. S5. Dry and test the product performance. Use a dryer with an exhaust system during drying. Set the temperature to 95-102℃ and the drying time to 0.5-2h. The test results are shown in Table 1.

[0039] Example 6 Please see Figure 1-2 As shown, the present invention provides a technical solution for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys: the specific treatment method includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness to 0.5 – 1.5µm, enhance the mechanical adhesion of subsequent coatings, and perform two water rinses, with a rinsing time of 1–5 min. a1. Acid etching is used, and an air nozzle is connected to compressed air (pressure controlled at 0.1 to 0.2 MPa) to form air agitation during the production process. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 50 mg / L, the concentration of phosphoric acid is 40 mg / L, the concentration of nitric acid is 500 mg / L, the temperature is set to 70℃, and the soaking time is set to 2 min. a2. The first water wash is carried out, and the water is continuously discharged through overflow. An air spray pipe is installed at the bottom of the water tank to connect to compressed air (pressure controlled at 0.1 to 0.2 MPa). During the production process, air agitation is generated to ensure the cleaning effect. a3. Perform the second rinse, continuously adding clean water (at a rate of 10-20 ml / l per minute), and let the water overflow from the second rinse into the first rinse.

[0040] S2. Immerse in a strongly alkaline zincate solution to plate zinc onto the surface through a displacement reaction between zinc and aluminum, and then perform three water washes, each lasting 1-5 minutes. b1. Immerse in a strongly alkaline zincate solution to cover the surface with a uniform dark gray or light gray zinc layer; wherein the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride and special additive one, the concentration of sodium hydroxide is 100 g / L, the concentration of zinc oxide is 12 g / L, the concentration of potassium sodium tartrate is 45 g / L, the concentration of nickel chloride is 20 g / L, the concentration of ferric chloride is 1.0 g / L, the concentration of special additive one is 0.3 g / L (including potassium ferrocyanide 0.24 g / L and sodium ferric chloride 0.06 g / L), the temperature is set to 30℃, and the immersion time is 28 s; b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. b3. Perform a second water rinse, which is set to continuously overflow to the first water rinse. b4. Perform the third water wash. The third water wash is set to continuously add clean water and continuously overflow to the second water wash.

[0041] S3. Immerse in weakly alkaline electroless nickel plating to coat the underlayer. The underlayer should be 0.5-1μm thick, and then rinse twice with water for 1-5 minutes. c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form a dense and uniform active nickel layer with excellent adhesion to the substrate. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and a special additive II. The nickel sulfate solution contains nickel ions at a concentration of 4.8 g / L, the sodium hypophosphite solution at 25 g / L, the sodium chloride solution at 2.0 g / L, the boric acid solution at 6 g / L, the sodium hydroxide solution at 7 g / L, the malic acid solution at 1.0 g / L, and the special additive II solution at 0.4 g / L (including allyl thiourea at 0.2 g / L and succinic acid at 0.2 g / L). The temperature is set at 55℃, the immersion time at 5 min, the pH at 9.0, and the loading rate at 1 dm² / L. c2. The first water wash is carried out. The first water wash is continuously discharged through overflow. An air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. c3. Perform the second rinse. Clean water is continuously added to the second rinse, and the water from the second rinse overflows into the first rinse.

[0042] S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes, with each wash lasting 1-5 minutes. d1. Using low-temperature electroless nickel plating, the film thickness is 5%-9%, resulting in a uniform coating color and good corrosion resistance. The low-temperature electroless nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and a special additive. The nickel sulfate concentration is 5.8 g / L for nickel ions, 30 g / L for sodium hypophosphite, 5.0 g / L for glycine, 16 g / L for lactic acid, 10 g / L for malic acid, and 9 mg / L for potassium iodide. The thiourea concentration is 3.0 mg / L, the sodium dodecyl sulfonate concentration is 20 mg / L, and the special additive is 1.0 mg / L (including 0.08 ml / L of 2-thiourea pyrimidine, 0.15 ml / L of sodium saccharin mixture, and the remainder being DI water). The temperature is set to 63℃, the immersion time to 40 min, the pH to 6.3, and the loading rate to 1 dm² / L. d2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. d3. Perform a second water wash, which is set to continuously overflow to the first water wash; d4. Perform the third water rinse. The third water rinse is set to continuously add clean water and continuously overflow to the second water rinse. S5. Dry and test the product performance. Use a dryer with an exhaust system during drying. Set the temperature to 95-102℃ and the drying time to 0.5-2h. The test results are shown in Table 1.

[0043] Example 7 Please see Figure 1-2 As shown, the present invention provides a technical solution for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys: the specific treatment method includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness to 0.5 – 1.5µm, enhance the mechanical adhesion of subsequent coatings, and perform two water rinses, with a rinsing time of 1–5 min. a1. Acid etching is used, and an air nozzle is connected to compressed air (pressure controlled at 0.1 to 0.2 MPa) to form air agitation during the production process. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 50 mg / L, the concentration of phosphoric acid is 40 mg / L, the concentration of nitric acid is 500 mg / L, the temperature is set to 70℃, and the soaking time is set to 2 min. a2. The first water wash is carried out, and the water is continuously discharged through overflow. An air spray pipe is installed at the bottom of the water tank to connect to compressed air (pressure controlled at 0.1 to 0.2 MPa). During the production process, air agitation is generated to ensure the cleaning effect. a3. Perform the second rinse, continuously adding clean water (at a rate of 10-20 ml / l per minute), and let the water overflow from the second rinse into the first rinse.

[0044] S2. Immerse in a strongly alkaline zincate solution to plate zinc onto the surface through a displacement reaction between zinc and aluminum, and then perform three water washes, each lasting 1-5 minutes. b1. Immerse in a strongly alkaline zincate solution to cover the surface with a uniform dark gray or light gray zinc layer; wherein the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride and special additive one, the concentration of sodium hydroxide is 100 g / L, the concentration of zinc oxide is 12 g / L, the concentration of potassium sodium tartrate is 45 g / L, the concentration of nickel chloride is 20 g / L, the concentration of ferric chloride is 1.0 g / L, the concentration of special additive one is 0.3 g / L (including potassium ferrocyanide 0.24 g / L and sodium ferric chloride 0.06 g / L), the temperature is set to 30℃, and the immersion time is 28 s; b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. b3. Perform a second water rinse, which is set to continuously overflow to the first water rinse. b4. Perform the third water wash. The third water wash is set to continuously add clean water and continuously overflow to the second water wash.

[0045] S3. Immerse in weakly alkaline electroless nickel plating to coat the underlayer. The underlayer should be 0.5-1μm thick, and then rinse twice with water for 1-5 minutes. c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form a dense and uniform active nickel layer with excellent adhesion to the substrate. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and a special additive II. The nickel sulfate solution contains nickel ions at a concentration of 4.5 g / L, the sodium hypophosphite solution at 22 g / L, the sodium chloride solution at 1.5 g / L, the boric acid solution at 5 g / L, the sodium hydroxide solution at 5 g / L, the malic acid solution at 0.7 g / L, and the special additive II solution at 0.2 g / L (including allyl thiourea at 0.1 g / L and succinic acid at 0.1 g / L). The temperature is set to 60℃, the immersion time to 10 min, the pH to 8.7, and the loading rate to 1 dm² / L. c2. The first water wash is carried out. The first water wash is continuously discharged through overflow. An air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. c3. Perform the second rinse. Clean water is continuously added to the second rinse, and the water from the second rinse overflows into the first rinse.

[0046] S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes, with each wash lasting 1-5 minutes. d1. Using low-temperature electroless nickel plating, the film thickness is 5%-9%, resulting in a uniform coating color and good corrosion resistance. The low-temperature electroless nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and a special additive. The nickel sulfate concentration is 5.2 g / L for nickel ions, 25 g / L for sodium hypophosphite, 4.0 g / L for glycine, 12 g / L for lactic acid, 8.0 g / L for malic acid, and 8 mg / L for potassium iodide. The thiourea concentration is 2.0 mg / L, the sodium dodecyl sulfonate concentration is 16 mg / L, and the special additive is 0.5 mg / L (including 0.08 ml / L of 2-thiourea pyrimidine, 0.15 ml / L of sodium saccharin mixture, and the remainder being DI water). The temperature is set to 65℃, the immersion time to 40 min, the pH to 6.5, and the loading rate to 1 dm² / L. d2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. d3. Perform a second water wash, which is set to continuously overflow to the first water wash; d4. Perform the third water rinse. The third water rinse is set to continuously add clean water and continuously overflow to the second water rinse. S5. Dry and test the product performance. Use a dryer with an exhaust system during drying. Set the temperature to 95-102℃ and the drying time to 0.5-2h. The test results are shown in Table 1.

[0047] Example 8 Please see Figure 1-2 As shown, the present invention provides a technical solution for alkaline chemical nickel surface treatment of pure aluminum or aluminum alloys: the specific treatment method includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness to 0.5 – 1.5µm, enhance the mechanical adhesion of subsequent coatings, and perform two water rinses, with a rinsing time of 1–5 min. a1. Acid etching is used, and an air nozzle is connected to compressed air (pressure controlled at 0.1 to 0.2 MPa) to form air agitation during the production process. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 50 mg / L, the concentration of phosphoric acid is 40 mg / L, the concentration of nitric acid is 500 mg / L, the temperature is set to 70℃, and the soaking time is set to 2 min. a2. The first water wash is carried out, and the water is continuously discharged through overflow. An air spray pipe is installed at the bottom of the water tank to connect to compressed air (pressure controlled at 0.1 to 0.2 MPa). During the production process, air agitation is generated to ensure the cleaning effect. a3. Perform the second rinse, continuously adding clean water (at a rate of 10-20 ml / l per minute), and let the water overflow from the second rinse into the first rinse.

[0048] S2. Immerse in a strongly alkaline zincate solution to plate zinc onto the surface through a displacement reaction between zinc and aluminum, and then perform three water washes, each lasting 1-5 minutes. b1. Immerse in a strongly alkaline zincate solution to cover the surface with a uniform dark gray or light gray zinc layer; wherein the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride and special additive one, the concentration of sodium hydroxide is 100 g / L, the concentration of zinc oxide is 12 g / L, the concentration of potassium sodium tartrate is 45 g / L, the concentration of nickel chloride is 20 g / L, the concentration of ferric chloride is 1.0 g / L, the concentration of special additive one is 0.4 g / L (including potassium ferrocyanide 0.32 g / L and sodium ferric chloride 0.08 g / L), the temperature is set to 30℃, and the immersion time is 28 s; b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. b3. Perform a second water rinse, which is set to continuously overflow to the first water rinse. b4. Perform the third water wash. The third water wash is set to continuously add clean water and continuously overflow to the second water wash.

[0049] S3. Immerse in weakly alkaline electroless nickel plating to coat the underlayer. The underlayer should be 0.5-1μm thick, and then rinse twice with water for 1-5 minutes. c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form a dense and uniform active nickel layer with excellent adhesion to the substrate. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and a special additive II. The nickel sulfate solution contains nickel ions at a concentration of 4.5 g / L, the sodium hypophosphite solution at 22 g / L, the sodium chloride solution at 1.5 g / L, the boric acid solution at 5 g / L, the sodium hydroxide solution at 5 g / L, the malic acid solution at 0.7 g / L, and the special additive II solution at 0.3 g / L (including allyl thiourea at 0.2 g / L and succinic acid at 0.1 g / L). The temperature is set to 60℃, the immersion time to 10 min, the pH to 8.7, and the loading rate to 1 dm² / L. c2. The first water wash is carried out. The first water wash is continuously discharged through overflow. An air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. c3. Perform the second rinse. Clean water is continuously added to the second rinse, and the water from the second rinse overflows into the first rinse.

[0050] S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes, with each wash lasting 1-5 minutes. d1. Using low-temperature electroless nickel plating, the film thickness is 5%-9%, resulting in a uniform coating color and good corrosion resistance. The low-temperature electroless nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and a special additive. The nickel sulfate concentration is 6.0 g / L, the sodium hypophosphite concentration is 32 g / L, the glycine concentration is 5.5 g / L, the lactic acid concentration is 24 g / L, the malic acid concentration is 12 g / L, and the potassium iodide concentration is 10 mg / L. The thiourea concentration is 4.0 mg / L, the sodium dodecyl sulfonate concentration is 24 mg / L, and the special additive is 2.0 mg / L (including 0.08 ml / L of 2-thiourea pyrimidine, 0.15 ml / L of sodium saccharin mixture, and the remainder being DI water). The temperature is set to 60℃, the immersion time to 40 min, the pH to 6.0, and the loading rate to 1 dm² / L. d2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is set at the bottom of the water tank to form air agitation during the production process to ensure the cleaning effect. d3. Perform a second water wash, which is set to continuously overflow to the first water wash; d4. Perform the third water rinse. The third water rinse is set to continuously add clean water and continuously overflow to the second water rinse. S5. Dry and test the product performance. Use a dryer with an exhaust system during drying. Set the temperature to 95-102℃ and the drying time to 0.5-2h. The test results are shown in Table 1.

[0051] The detection methods include: 1. Use an XRF film thickness gauge to detect the film thickness and P content of the coating. Detect the thickness at 5 points on each of the front and back sides, and calculate the average film thickness and average P content. 2. Use the cross-cut test (GB / T 5270) to test the adhesion. Use a blade to cut a grid on the coating surface, stick it with 3M tape and peel it off, and observe the coating peeling.

[0052] Table 1 The sample test results above demonstrate and describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made without departing from the spirit and scope of the invention, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for alkaline electroless nickel surface treatment of pure aluminum or aluminum alloys, characterized in that: The processing method specifically includes: S1. Perform acid etching to remove the oxide film and achieve surface micro-roughness, followed by two water washes; S2. Immerse in a strongly alkaline zincate solution, and plate the surface with zinc through a displacement reaction between zinc and aluminum, followed by three water washes. S3. Immerse in weakly alkaline electroless nickel plating to coat the bottom layer, and then wash twice with water. S4. Use low-temperature electroless nickel plating to achieve the desired film thickness, and perform three water washes; S5. Dry and test product performance.

2. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 1, characterized in that: Step S1 specifically includes: a1. Acid etching is used, and an air nozzle is connected to compressed air. The acid etching includes sulfuric acid, phosphoric acid and nitric acid. The concentration of sulfuric acid is 40-60 mg / L, the concentration of phosphoric acid is 30-50 mg / L, the concentration of nitric acid is 450-550 mg / L, the temperature is set to 50-75℃, and the soaking time is set to 0.5-3 min. a2. Perform the first rinse; a3. Perform a second rinse.

3. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 1, characterized in that: Step S2 specifically includes: b1. Immerse in a strongly alkaline zincate solution, wherein the zincate solution includes sodium hydroxide, zinc oxide, potassium sodium tartrate, nickel chloride, ferric chloride, and special additive one, wherein special additive one includes 60-80% potassium ferrocyanide and 20-40% sodium ferric chloride, the concentration of sodium hydroxide is 90-110 g / L, the concentration of zinc oxide is 10-14 g / L, the concentration of potassium sodium tartrate is 40-50 g / L, the concentration of nickel chloride is 15-25 g / L, the concentration of ferric chloride is 0.8-1.2 g / L, the concentration of special additive one is 0.1-0.4 g / L, the temperature is set to 21-46℃, and the immersion time is 12-120 s; b2. Perform the first water wash. The first water wash is set to continuously discharge through overflow, and an air spray pipe connected to compressed air is installed at the bottom of the water tank. b3. Perform a second rinse; b4. Perform the third rinse.

4. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 1, characterized in that: Step S3 specifically includes: c1. Immerse the substrate in a weakly alkaline electroless nickel plating solution to form the base layer. The weakly alkaline electroless nickel plating solution includes nickel sulfate, sodium hypophosphite, sodium chloride, boric acid, sodium hydroxide, malic acid, and special additive II. The special additive II includes 35-55% allyl thiourea and 45-65% succinic acid. The nickel sulfate solution contains nickel ions with a concentration of 4.2-4.8 g / L, the sodium hypophosphite concentration is 15-25 g / L, the sodium chloride concentration is 1-2 g / L, the boric acid concentration is 4-6 g / L, the sodium hydroxide concentration is 3-7 g / L, the malic acid concentration is 0.5-1 g / L, and the special additive II concentration is 0.2-0.4 g / L. c2. Perform the first rinse; c3. Perform a second rinse.

5. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 1, characterized in that: Step S4 specifically includes: d1. The film thickness using low-temperature chemical nickel plating, wherein the low-temperature chemical nickel plating comprises nickel sulfate, sodium hypophosphite, glycine, lactic acid, malic acid, potassium iodide, thiourea, sodium dodecyl sulfonate, and special additive three. Special additive three includes 80-100 ml / L of 2-thiourea pyrimidine and 150 ml / L of a mixture of sodium saccharin, with the remainder being DI water. Nickel sulfate comprises nickel ions at a concentration of 5.2-6.0 g / L, sodium hypophosphite at a concentration of 25-32 g / L, glycine at a concentration of 4-5.5 g / L, lactic acid at a concentration of 12-18 g / L, malic acid at a concentration of 8-12 g / L, potassium iodide at a concentration of 8-10 mg / L, thiourea at a concentration of 2-4.0 mg / L, sodium dodecyl sulfonate at a concentration of 16-24 mg / L, and special additive three at a concentration of 0.5-2 ml / L. d2. Perform the first water wash; d3. Perform the second rinse; d4. Perform the third rinse.

6. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 4, characterized in that: In step c1, the temperature is set to 55-65℃, the soaking time is set to 5-15 min, the pH is set to 8.4-9.0, and the loading rate is set to 0.25-2.45 square decimeters / liter.

7. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 5, characterized in that: In step d1, the temperature is set to 60-65℃, the soaking time is set to 5-60 min, the pH is set to 6.0-6.5, and the loading rate is set to 0.2-3.0 square decimeters / liter.

8. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 1, characterized in that: In steps S1 and S3, the washing time for both washes is set to 1-5 minutes.

9. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 1, characterized in that: In steps S2 and S4, the washing time for each of the three washes is set to 1-5 minutes.

10. The alkaline electroless nickel surface treatment method for pure aluminum or aluminum alloys according to claim 1, characterized in that: In step S5, a dryer with an exhaust system is used for drying, the temperature is set to 95-102℃, and the drying time is set to 0.5-2h.

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