1. A simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of an aluminum alloy is characterized by comprising the following specific steps:

1) oil removal: cleaning the aluminum alloy substrate by using alcohol or acetone, soaking for 5-10 min at normal temperature, and removing grease on the surface of the substrate;

2) and (3) activation: placing the aluminum alloy substrate in an activation treatment solution, soaking for 1-10 min at normal temperature, removing oxide skin and dirt on the surface of the aluminum alloy, and increasing surface roughness and surface activity;

3) chemical nickel plating: and (3) putting the aluminum alloy substrate into a chemical nickel plating solution at the temperature of 70-90 ℃ for 60-120 min to form a bright, compact and high-bonding-force nickel-phosphorus plating layer.

2. The simple and easy-to-operate pretreatment process for electroless nickel plating on the surface of the aluminum alloy according to claim 1, wherein in the step 2), the composition and content of the activation treatment solution are as follows: 10-30 g/L of phosphate, 20-40 g/L of carbonate, 1-5 g/L of organic acid or salt thereof, 1-5 g/L of stabilizer, 1-5 g/L of dispersant, 1-10 g/L of corrosion inhibitor, 1-4 g/L of surfactant and the balance of water; the pH value of the activation treatment liquid is 8-10.

3. The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy according to claim 2, wherein in the activation treatment solution, the phosphate is one or more of sodium phosphate, potassium phosphate, ammonium phosphate and sodium hydrogen phosphate; the carbonate is one or more of sodium carbonate, potassium carbonate and sodium bicarbonate; the organic acid or the salt thereof is one or more than two of carboxylic acid and derivatives thereof and alpha-hydroxy acid and derivatives thereof; the stabilizer is one or more than two of metal elements, metal salts of the metal elements and metal oxides of the metal elements; the dispersant is one or more than two of fatty acid, sodium tripolyphosphate and sodium hexametaphosphate; the corrosion inhibitor is one or more than two of nitrite and silicate; the surfactant is one or more of sodium dodecyl benzene sulfonate, OP-10 and glycerin fatty acid.

4. The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy according to claim 3, wherein in the activation treatment solution, one or more than two organic acids selected from lactic acid, malic acid and salicylic acid are compounded; the metal element in the stabilizer is selected from one or more of tin, copper and magnesium; the fatty acid in the dispersant is one or more than two of stearamide, Ethylene Bis Stearamide (EBS) and stearic acid monoglyceride (GMS).

5. The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy according to claim 1, wherein in the step 4), the chemical nickel plating solution comprises the following components in percentage by weight: 10-40 g/L nickel salt, 20-40 g/L phosphate, 10-30 g/L acetate, 10-30 g/L citrate, 4-60 mg/L brightener, 1-10 g/L additive and the balance of water; the pH value of the chemical nickel plating solution is 4-5, the temperature of the chemical nickel plating solution is 70-90 ℃, and the plating time is 1-5 h.

6. The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy according to claim 5, wherein in the chemical nickel plating solution, the nickel salt is selected from one or more of nickel sulfate, nickel chloride and basic nickel carbonate; the phosphate is selected from one or more of sodium hypophosphite, sodium phosphate and diammonium hydrogen phosphate; the acetate is selected from one or more than two of sodium acetate, potassium acetate and sodium diacetate; the citrate is selected from one or more of calcium citrate, sodium citrate and potassium citrate; the brightener is one or more than two of saccharin sodium, copper sulfate, cadmium chloride and 1, 4-butynediol; the additive is one or more than two of aminoacetic acid, iodate and thiourea.

7. The simple and easy-to-handle pretreatment process for electroless nickel plating on the surface of an aluminum alloy according to claim 1, wherein each of the degreasing, activating and electroless nickel plating steps is followed by water washing to remove the residual solution from the previous step.

8. The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy according to claim 1, wherein the thickness of a plating layer after chemical nickel plating is controllable within the range of 5-30 μm, and the performance of the plating layer is equivalent to that of the traditional secondary zinc dipping process.

9. The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy according to claim 1, wherein the binding force of a plating layer obtained after chemical nickel plating is less than or equal to level 1, and the use requirement is met.

Background

The aluminum alloy has the characteristics of small density, high specific stiffness and specific strength, good electric conductivity and heat conductivity, good casting performance and processability and the like, and is widely applied to the fields of aerospace, traffic and the like. The chemical nickel plating technology is one of the common surface modification technologies for aluminum and aluminum alloy, can form a conductive nickel-phosphorus coating, endows the aluminum alloy with additional functionality, meets the requirements of some special conditions, and can improve the hardness and the wear resistance of the aluminum alloy. Aluminum is used as a metal with active chemical properties, has strong affinity with oxygen, and is easy to form a compact oxide film in an atmospheric environment. The compact oxide film on the surface of the aluminum alloy can cause that the bonding force between the aluminum alloy and the nickel-phosphorus alloy layer is not enough in the chemical nickel plating process, and the coating is easy to foam and fall off. The secondary zinc dipping method is a mature and reliable aluminum alloy surface chemical nickel plating process (publication No. CN106676504A) which is acknowledged at present, but the process is very complicated, parameters needing to be controlled in the process are more, heavy metal zinc discharge waste liquid is difficult to clean, and the overall control difficulty of the process is higher. Some direct chemical nickel plating methods without zinc immersion are developed at present, pretreatment steps comprise oil removal, rust removal, activation, ash removal and the like, and the obtained plating layer has poor binding force with a substrate and cannot meet the requirements in application. Therefore, the development of a pretreatment process for chemical plating of aluminum alloy, which has simple process and convenient operation, is urgently needed, so that the plating layer has good binding force, is uniform and compact and has excellent comprehensive performance.

Disclosure of Invention

Aiming at the problems, the invention aims to provide a simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of an aluminum alloy, which can quickly form a thin uniform loose product film, ensure that after an aluminum alloy matrix is placed in a chemical plating solution, the components of the plating solution can easily penetrate through the product film to reach the matrix for a displacement reaction, realize uniform deposition and growth of the plating layer and solve the problem of complex and tedious secondary zinc dipping pretreatment. Meanwhile, the brightness and compactness of the chemical nickel layer are increased, the thickness of the coating is controllable within the range of 5-30 mu m, the performance of the coating is equivalent to that of the traditional secondary zinc dipping process, the binding force of the coating is not more than 1 grade, and the use requirement is met.

In order to realize the purpose of the invention, the technical scheme of the invention is as follows:

a simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of an aluminum alloy comprises the following specific steps:

1) oil removal: cleaning the aluminum alloy substrate by using alcohol or acetone, soaking for 5-10 min at normal temperature, and removing grease on the surface of the substrate;

2) and (3) activation: placing the aluminum alloy substrate in an activation treatment solution, soaking for 1-10 min at normal temperature, removing oxide skin and dirt on the surface of the aluminum alloy, and increasing surface roughness and surface activity;

3) chemical nickel plating: and (3) putting the aluminum alloy substrate into a chemical nickel plating solution at the temperature of 70-90 ℃ for 60-120 min to form a bright, compact and high-bonding-force nickel-phosphorus plating layer.

The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy comprises the following steps in step 2): 10-30 g/L of phosphate, 20-40 g/L of carbonate, 1-5 g/L of organic acid or salt thereof, 1-5 g/L of stabilizer, 1-5 g/L of dispersant, 1-10 g/L of corrosion inhibitor, 1-4 g/L of surfactant and the balance of water; the pH value of the activation treatment liquid is 8-10.

The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy is characterized in that in the activation treatment solution, phosphate is one or more than two of sodium phosphate, potassium phosphate, ammonium phosphate and sodium hydrogen phosphate; the carbonate is one or more of sodium carbonate, potassium carbonate and sodium bicarbonate; the organic acid or the salt thereof is one or more than two of carboxylic acid and derivatives thereof and alpha-hydroxy acid and derivatives thereof; the stabilizer is one or more than two of metal elements, metal salts of the metal elements and metal oxides of the metal elements; the dispersant is one or more than two of fatty acid, sodium tripolyphosphate and sodium hexametaphosphate; the corrosion inhibitor is one or more than two of nitrite and silicate; the surfactant is one or more of sodium dodecyl benzene sulfonate, OP-10 and glycerin fatty acid.

The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy is characterized in that in the activation treatment solution, organic acid is selected from one or more of lactic acid, malic acid and salicylic acid; the metal element in the stabilizer is selected from one or more of tin, copper and magnesium; the fatty acid in the dispersant is one or more than two of stearamide, Ethylene Bis Stearamide (EBS) and stearic acid monoglyceride (GMS).

The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy comprises the following steps in step 4): 10-40 g/L nickel salt, 20-40 g/L phosphate, 10-30 g/L acetate, 10-30 g/L citrate, 4-60 mg/L brightener, 1-10 g/L additive and the balance of water; the pH value of the chemical nickel plating solution is 4-5, the temperature of the chemical nickel plating solution is 70-90 ℃, and the plating time is 1-5 h.

The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy is characterized in that in the chemical nickel plating solution, nickel salt is selected from one or more of nickel sulfate, nickel chloride and basic nickel carbonate; the phosphate is selected from one or more of sodium hypophosphite, sodium phosphate and diammonium hydrogen phosphate; the acetate is selected from one or more than two of sodium acetate, potassium acetate and sodium diacetate; the citrate is selected from one or more of calcium citrate, sodium citrate and potassium citrate; the brightener is one or more than two of saccharin sodium, copper sulfate, cadmium chloride and 1, 4-butynediol; the additive is one or more than two of aminoacetic acid, iodate and thiourea.

The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy needs to be washed after each step of oil removal treatment, activation treatment and chemical nickel plating so as to remove the residual solution in the previous step.

The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy has the advantages that the thickness of a plating layer after chemical nickel plating is controllable within the range of 5-30 mu m, and the performance of the plating layer is equivalent to that of the traditional secondary zinc dipping process.

The simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy has the advantages that the binding force of a plating layer obtained by chemical nickel plating is less than or equal to level 1, and the use requirement is met.

The design idea of the invention is as follows:

pretreatment of electroless nickel plating is a particularly important process. The surface of the aluminum alloy is easy to form a compact oxide film, and the components of the plating solution are prevented from contacting with a substrate under the film, so that the initial deposition of the plating layer is influenced, and the bonding force between the final plating layer and the substrate is poor. Generally, two methods of completely removing the surface oxide film or forming a new uniform oxide film are adopted in the pretreatment process, wherein the complete removal of the surface oxide film is difficult to realize, and the surface of the aluminum matrix can be immediately oxidized again as long as the surface of the aluminum matrix is contacted with oxygen; the second zinc dipping process is the latter, but the process is too complex. The aluminum belongs to amphoteric metal and is unstable in acidic and alkaline solutions, and the design idea of the invention is to enable the surface of the aluminum alloy in a composite activation solution to quickly form a thin loose product film. On one hand, the product film is not very compact, and plating solution components can penetrate through the product film and contact with a substrate under the film to realize the initial deposition of nickel; on the other hand, the product film is thin, and the isolation effect between the matrix and the coating can not be achieved, so that the subsequent nickel plating process can be stably carried out, uniform deposition is realized, and the coating with good comprehensive performance is obtained.

The invention has the following advantages and beneficial effects:

1. according to the invention, a nickel-phosphorus coating with good uniform binding force can be obtained on the surface of the aluminum alloy by only two procedures of oil removal and activation and soaking in a chemical nickel plating solution at the temperature of 70-90 ℃ for a certain time. The chemical nickel plating process on the surface of the aluminum alloy is simple, convenient to operate, low in cost and high in efficiency.

2. The chemical nickel plating solution for aluminum alloy does not contain zinc and other pollution ions, has less pollution to the environment and is more environment-friendly than the traditional process.

3. The thickness of the coating is controllable within the range of 5-30 mu m, the performance of the coating is equivalent to that of the traditional secondary zinc dipping process, the binding force of the nickel-phosphorus coating formed after the chemical nickel plating process is less than or equal to level 1 (GB/T9286-.

4. The process of the invention is suitable for various brands of aluminum alloy matrixes such as 6061, 2024, 6055, 6063 and the like, and has wide application range.

Drawings

FIG. 1(a) -FIG. 1(b) nickel phosphorous coating thickness profile; wherein: FIG. 1(a) conditions of example 1; FIG. 1(b) conditions of example 2.

FIG. 2(a) -FIG. 2(b) are photographs of the nickel-phosphorus plating adhesion test scribe line; wherein: FIG. 2(a) conditions of example 1; FIG. 2(b) conditions of example 2.

Detailed Description

In the specific implementation process, the simple and easy-to-operate pretreatment process for chemical nickel plating on the surface of the aluminum alloy mainly comprises the following three steps:

1) oil removal: cleaning the aluminum alloy substrate by using alcohol or acetone, soaking for 5-10 min at normal temperature (20-30 ℃), and removing grease on the surface of the substrate;

2) and (3) activation: placing the aluminum alloy substrate in an activation treatment solution, soaking for 1-10 min at normal temperature (20-30 ℃), removing oxide skin and dirt on the surface of the aluminum alloy, and increasing surface roughness and surface activity;

3) chemical nickel plating: and (3) putting the aluminum alloy base material into a chemical nickel plating solution, wherein the temperature is 70-90 ℃, and the time is 60-120 min. Forming a bright, compact and good-binding-force nickel-phosphorus coating;

the three working procedures need to be washed by water after each step of operation so as to remove the residual solution in the previous working procedure; and washing the aluminum alloy substrate subjected to chemical nickel plating with water, drying the aluminum alloy substrate with hot air, and packaging and storing the aluminum alloy substrate. The thickness of the nickel-phosphorus film layer is controllable within the range of 5-30 mu m, the performance of the plating layer is equivalent to that of the traditional secondary zinc dipping process, and the binding force of the nickel-phosphorus plating layer formed by the chemical nickel plating process is less than or equal to level 1.

The technical solution of the present invention will be further specifically described below by way of examples, comparative examples and drawings.

Example 1

In this example, the sample was a wrought 6061 aluminum alloy, which specifically included the following steps:

1) oil removal: removing oil on the surface of the sample by using alcohol, and soaking for 5min at 25 ℃;

2) and (3) activation: the activating treatment solution comprises potassium phosphate 30g/L, sodium carbonate 25g/L, malic acid 1.5g/L, magnesium chloride 2g/L, Ethylene Bis Stearamide (EBS)1g/L, and sodium nitrite (NaNO)₂)2g/L aqueous solution of sodium dodecyl benzene sulfonatePlacing the sample in an activation treatment solution at a pH value of 10, and soaking for 3min at 25 ℃;

3) chemical nickel plating: the chemical nickel plating solution is an aqueous solution of 20g/L nickel sulfate, 20g/L sodium hypophosphite, 30g/L potassium acetate, 10g/L potassium citrate, 40mg/L copper sulfate and 4g/L thiourea, the pH value is 5.4, and a sample is placed in the chemical nickel plating solution and soaked for 1h at the temperature of 80 ℃. The nickel-phosphorus coating prepared by the method is silvery and has a thickness of about 5 μm, as shown in figure 1(a), and the binding force is 0 grade, as shown in figure 2 (a).

Example 2

In this example, the sample was a wrought 6061 aluminum alloy, which specifically included the following steps:

1) oil removal: removing oil on the surface of the sample by using alcohol, and soaking for 10min at 30 ℃;

2) and (3) activation: the activating treatment liquid is an aqueous solution of 20g/L sodium phosphate, 25g/L potassium carbonate, 1g/L lactic acid, 1g/L magnesium oxide, 2g/L Ethylene Bis Stearamide (EBS), 2g/L sodium hexametaphosphate, 5g/L potassium silicate and 3g/L glycerin fatty acid, the pH value is 9.5, and a sample is placed in the activating treatment liquid and soaked for 4min at the temperature of 30 ℃;

3) chemical nickel plating: the chemical nickel plating solution is an aqueous solution of 30g/L nickel sulfate, 20g/L sodium hypophosphite, 30g/L sodium acetate, 20g/L sodium citrate, 40mg/L saccharin sodium, 10 mg/L1, 4-butynediol and 2g/L thiourea, the pH value is 5.6, and a sample is placed in the chemical nickel plating solution and soaked for 1h at the temperature of 80 ℃. The nickel-phosphorus coating prepared by the method is silver, the thickness is about 7 mu m, and the bonding force is 0 grade, as shown in figure 1(b).

Example 3

In this example, the sample was an extruded 2024 aluminum alloy, which was prepared by the following steps:

1) oil removal: removing oil on the surface of the sample by using alcohol, and soaking for 8min at 25 ℃;

2) and (3) activation: the activating treatment liquid is an aqueous solution of 15g/L sodium phosphate, 30g/L sodium carbonate, 1g/L salicylic acid, 2g/L cadmium chloride, 2g/L stearic acid monoglyceride (GMS), 1g/L sodium silicate and 3g/L glycerin fatty acid, the pH value is 9, and a sample is placed in the activating treatment liquid and soaked for 5min at the temperature of 25 ℃;

3) chemical nickel plating: the chemical nickel plating solution is aqueous solution of 10g/L of basic nickel carbonate, 20g/L of sodium hypophosphite, 30g/L of sodium acetate, 10g/L of potassium citrate, 60mg/L of copper sulfate and 3g/L of thiourea, the pH value is 5.4, and a sample is placed in the chemical nickel plating solution and soaked for 1.5 hours at the temperature of 85 ℃. The nickel-phosphorus coating prepared in this way is silver and has a thickness of about 10 μm.

Example 4

In this example, the sample was an extruded 2024 aluminum alloy, which was prepared by the following steps:

1) oil removal: removing oil on the surface of the sample by using alcohol, and soaking for 10min at 30 ℃;

2) and (3) activation: the activating treatment solution is an aqueous solution of 30g/L potassium phosphate, 30g/L sodium carbonate, 1g/L lactic acid, 1.5g/L copper oxide, 2g/L sodium hexametaphosphate, 3g/L potassium nitrite and 1g/L, OP-101 g/L sodium dodecyl benzene sulfonate, the pH value is 8.5, and the sample is placed in the activating treatment solution and soaked for 4min at the temperature of 30 ℃;

3) chemical nickel plating: the chemical nickel plating solution is an aqueous solution of 15g/L nickel sulfate, 40g/L sodium hypophosphite, 30g/L potassium acetate, 25g/L sodium citrate, 5mg/L cadmium chloride and 2g/L thiourea, the pH value is 5.4, and a sample is placed in the chemical nickel plating solution and soaked for 1.5 hours at the temperature of 85 ℃. The nickel-phosphorus coating prepared in this way is silver and has a thickness of about 10 μm.

Comparative example 1

In this comparative example, the sample was a wrought 6061 aluminum alloy, comprising the following specific steps:

1) oil removal: chemical degreasing is carried out on a sample by using a solution with a formula of 50g/L sodium phosphate, 10g/L sodium hydroxide and 30g/L sodium silicate, the total alkalinity of the solution is 2.0 percent, the working temperature is 65 ℃, and the time is 4 min.

2) And (3) activation: the density is 1.42g/cm³The nitric acid is activated at 20 ℃ for 3 min.

3) Primary zinc dipping: the sample after the activation treatment was immersed in a solution described in patent publication No. CN 106676504A: 500g/L of sodium hydroxide, 100g/L of zinc oxide, 20g/L of potassium sodium tartrate and 1g/L of ferric trichloride, and the working temperature is 20 ℃ and the time is 50 s.

4) Removing the zinc-impregnated layer: and removing the primary zinc-dipped layer by using a nitric acid solution with the volume ratio of 1:1 at 25 ℃.

5) Secondary zinc dipping: the samples were soaked as described in patent publication No. CN 106676504A: 120g/L of sodium hydroxide, 20g/L of zinc oxide, 2g/L of potassium sodium tartrate and 1g/L of sodium nitrate. The working temperature was 25 ℃ and the time was 30 s.

6) Chemical nickel plating: the solution and the operation conditions are the same as those of the process 1.

Comparative example 2

In this comparative example, the sample was a wrought 6061 aluminum alloy, comprising the following specific steps:

1) oil removal: the chemical degreasing is carried out on the solution with the formula of 40g/L sodium phosphate, 20g/L sodium hydroxide and 30g/L sodium silicate for the sample, the total alkalinity of the solution is 2.0 percent, the working temperature is 65 ℃, and the time is 5 min.

2) And (3) activation: the density is 1.42g/cm³The nitric acid is activated at 20 ℃ for 4 min.

3) Primary zinc dipping: the sample after the activation treatment was immersed in a solution described in patent publication No. CN 106676504A: 500g/L of sodium hydroxide, 100g/L of zinc oxide, 20g/L of potassium sodium tartrate and 1g/L of ferric trichloride, and the working temperature is 20 ℃ and the time is 50 s.

4) Removing the zinc-impregnated layer: and removing the primary zinc-dipped layer by using a nitric acid solution with the volume ratio of 1:1 at 25 ℃.

5) Secondary zinc dipping: the sample was immersed in an aqueous zinc-immersing solution containing 120g/L of sodium hydroxide, 20g/L of zinc oxide, 2g/L of potassium sodium tartrate and 1g/L of sodium nitrate as described in patent publication No. CN 106676504A. The working temperature was 25 ℃ and the time was 30 s.

6) Chemical nickel plating: the solution and the operation conditions are the same as those of the process 2.

The results were as follows:

1. state of nickel-phosphorus coating

The films prepared according to the above examples 1-4 and comparative examples 1-2 were uniform and had complete coatings. The thickness of the nickel-phosphorus coating in the embodiment 1-4 is controllable in the range of 5-30 μm through the reaction time.

2. Nickel-phosphorus coating binding force

According to GB/T9286-1998 standard, the nickel-phosphorus coatings prepared by the processes of the examples 1 to 4 and the comparative examples 1 to 2 are cut at a constant speed at a 2mm interval by using a QFH type single-edge Baige cutter under a stable pressure until an aluminum substrate is exposed, and the coatings are cut in parallel at an angle of 90 degrees to form a grid. Cleaning the surface with a soft brush, and pasting the coating layer with a 3M adhesive tape in parallel, tearing the adhesive tape at an angle of approximately 60 degrees within 0.5-1.0 s, and checking the state of the cut part. Wherein the adhesive force of all samples is 0 grade, and the use requirement is met.

The results show that the bright chemical nickel plating process with simple surface process of the aluminum alloy is superior to the traditional secondary zinc dipping process in the thickness of the plating layer and the binding force of the plating layer. Meanwhile, the process is simple, convenient to operate, low in cost and small in environmental pollution, and is a new surface treatment method which is more environment-friendly than the traditional process.