A method for preparing an aluminum alloy surface anodization / chemical plating of Ni-P composite coating

Abstract

The application relates to a preparation method of an aluminum alloy surface anodic oxidation / chemical plating Ni-P composite coating, which comprises the following steps: first, carrying out oxidation on a pretreated aluminum alloy base body in a sulfuric acid system electrolyte until an anodic oxidation layer is formed on the surface of the base body; then, carrying out laser scanning on the surface of the anodic oxidation layer; and finally, carrying out plating by using a chemical plating neutral Ni-P layer plating solution to obtain the anodic oxidation / chemical plating Ni-P composite coating. The application has the advantages of simple preparation, cost reduction, improved wear resistance and bonding strength of the composite coating.

Description

Technical Field

[0001] This invention relates to the technical field of electroless plating on the surface of metal materials, and in particular to a method for preparing an anodized / electroless Ni-P composite coating on the surface of aluminum alloy. Background Technology

[0002] Aluminum alloys, due to their numerous excellent properties such as low density, light weight, high strength, and excellent thermal and electrical conductivity, are widely used in many fields with stringent material requirements, including aerospace, automotive manufacturing, and electronics. However, aluminum alloys also have certain shortcomings, the most prominent being their relatively low surface hardness. This characteristic makes aluminum alloys highly susceptible to wear failure under high load conditions or complex and variable service environments. Wear failure can lead to a series of adverse consequences, such as a significant decrease in the dimensional accuracy of parts, a gradual increase in the clearance of precision fits, and in severe cases, structural damage. Therefore, to effectively improve the wear resistance and service reliability of aluminum alloys in practical applications, surface strengthening treatment of aluminum alloys has become an important research direction. This helps to overcome the defect of low surface hardness, further broaden the application range, and improve the performance.

[0003] Currently, commonly used aluminum alloy surface strengthening technologies include electroplating, spraying, physical vapor deposition (PVD), anodizing, micro-arc oxidation, and electroless plating. Among these, anodizing and electroless Ni-P coatings are effective means to improve the wear resistance and corrosion resistance of aluminum alloy surfaces. However, while both single anodized and electroless coatings on aluminum alloy surfaces have their advantages, they also have some drawbacks. For example, anodizing layers have a simple preparation process and fast growth rate, but their microscopic porosity results in relatively low wear and corrosion resistance. Furthermore, the insulating properties of the oxide film limit its application in certain scenarios. While electroless Ni-P coatings offer excellent wear and corrosion resistance, their deposition rate is typically low (10 μm / h), and the coating is mechanically bonded to the substrate, often resulting in insufficient film-substrate adhesion. Additionally, the significant hardness difference between the aluminum alloy substrate and the electroless coating prevents the substrate from effectively supporting the coating, leading to premature coating failure. To address these issues, researchers attempted to prepare anodized / electrochemical Ni-P composite coatings, which combine the advantages of anodizing and electroless plating and are expected to possess superior wear resistance and corrosion resistance.

[0004] However, due to the lack of catalytic activity in anodic oxide films, it is impossible to directly deposit a chemically plated Ni-P layer on aluminum alloy anodic oxide films. Existing technical routes typically involve: first, anodizing the aluminum alloy to generate a porous oxide film on its surface; then, through chemical sensitization and activation steps, introducing noble metal catalytic centers (such as Pd or Ag); finally, chemically plating to deposit a Ni-P coating, forming a composite coating. While this method can achieve chemical plating on the oxide film surface, it suffers from the following problems: 1) The expensive and cumbersome operation of the noble metal activation solution increases production costs; 2) The poor stability and easy deactivation of the activation solution lead to poor repeatability of the chemical plating reaction; 3) The inconvenience of treating noble metal ions and waste liquid poses a potential environmental pollution risk; 4) The uneven distribution of activation particles on the oxide film surface results in poor coating adhesion and localized peeling. Therefore, imparting catalytic activity to the anodic oxide layer without using noble metal activators, and thus preparing anodized / chemically plated Ni-P composite coatings, has become a key problem urgently needing to be solved in this field. Summary of the Invention

[0005] The problem to be solved by the present invention is to provide a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces, which addresses the above-mentioned shortcomings of the prior art. This method has the advantages of simple preparation, reduced cost, and improved wear resistance and bonding strength of the composite coating.

[0006] The above-mentioned objective of this invention is achieved through the following technical solutions: A method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface includes the following steps: first, the pretreated aluminum alloy substrate is oxidized in a sulfuric acid electrolyte until an anodized layer is formed on the surface of the substrate; then, the surface of the anodized layer is scanned with a laser; and finally, a chemically plated neutral Ni-P layer plating solution is applied to obtain the anodized / chemically plated Ni-P composite coating.

[0007] Furthermore, during the oxidation process, the thickness of the anodic oxide layer is 30~120μm.

[0008] Furthermore, during the oxidation process, the oxidation temperature is controlled at -5 to 5°C, the oxidation time at 10 to 70 minutes, and the current density at 2 to 4 A / dm³. 2 The electrolyte in the sulfuric acid system consists of 160~200g / L sulfuric acid.

[0009] Furthermore, during the laser scanning process, the linear energy density of the laser is controlled to be 10~100 J / m.

[0010] Furthermore, during the laser scanning process, the laser pulse frequency is controlled to be 40~60kHz, the laser scanning power is 10~30W, the laser scanning speed is 500~2000mm / s, and the number of laser scans is ≥1.

[0011] Furthermore, during the laser scanning process, the scanning path for each laser scan is one or a combination of several of the following: line-by-line scanning path, grid-interwoven scanning path, concentric circle scanning path, and spiral line scanning path.

[0012] Furthermore, in the electroless plating process, the electroless plating neutral Ni-P layer plating solution is composed of raw materials containing the following concentrations: nickel sulfate: 20~30 g / L, sodium hypophosphite: 20~25 g / L, complexing agent: 15~20 g / L, pH buffer: 10~16 g / L, and ammonia water: to adjust the pH of the plating solution to 7.0±0.5.

[0013] Furthermore, in the electroless plating process, the complexing agent is sodium citrate and the pH buffer is ammonium acetate.

[0014] Furthermore, during the electroless plating process, the plating temperature is controlled at 75~85℃ and the plating time is 1~3h.

[0015] Furthermore, the anodic oxidation / chemical plating Ni-P composite coating includes a substrate, an anodic oxidation layer disposed on the substrate, and a chemical plating layer disposed on the anodic oxidation layer. The surface of the anodic oxidation layer is formed with protrusions by laser scanning, and the chemical plating layer covers the surface of the protrusions and is embedded in the groove formed by two adjacent protrusions.

[0016] In summary, the beneficial technical effects of the present invention are as follows: 1. This invention generates active sites on the surface of the anodic oxide layer by laser scanning, which enables the electroless plating reaction to be initiated directly on the surface of the anodic oxide layer. Since the traditional precious metal colloidal palladium activation is no longer required, it achieves the effects of no precious metals, simplified electroless plating pretreatment, reduced process costs and avoidance of environmental pollution. 2. According to the preferred method of this invention, the linear energy density window for laser scanning activation of the anodic oxide layer is 10~100J / m: when the energy density is below this range, the activation effect is weak; when it is above this range, the anodic oxide layer is prone to overall peeling or breakdown. 3. According to the preferred method of this invention, the sample after laser activation treatment needs to be chemically plated in a near-neutral plating solution system with a pH value of 6.5~7.5. If an acidic or alkaline plating solution is used, it will have a significant erosion effect on the laser-activated area on the sample surface, destroy the nucleation conditions of the chemical plating layer, and thus inhibit the uniform deposition and continuous growth of the plating layer. 4. In the Ni-P composite coating prepared by the present invention, the supporting effect of the anodic oxide layer and the textured features of its surface after laser scanning are utilized to give the surface of the top chemical coating excellent wear resistance and high bonding strength. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the macroscopic structure of the anodic oxide layer obtained in Example 2 of the present invention.

[0018] Figure 2 This is a schematic diagram of the macroscopic structure of the Ni-P composite coating obtained in Example 2 of the present invention.

[0019] Figure 3 This is a schematic diagram of the microstructure of the Ni-P composite coating obtained in Example 2 of the present invention.

[0020] Figure 4 This is a schematic diagram of the macroscopic structure of the anodic oxide layer obtained in Example 3 of the present invention.

[0021] Figure 5 This is a schematic diagram of the macroscopic structure of the Ni-P composite coating obtained in Example 3 of the present invention.

[0022] Figure 6 This is a schematic diagram of the microstructure of the Ni-P composite coating obtained in Example 3 of the present invention.

[0023] Figure 7 This is a schematic diagram of the macroscopic structure of the Ni-P composite coating obtained in Comparative Example 1 of this invention.

[0024] Figure 8 This is a schematic diagram of the macroscopic structure of the Ni-P composite coating obtained in Comparative Example 2 of this invention.

[0025] Figure 9 This is a schematic diagram of the macroscopic structure of the Ni-P composite coating obtained in Comparative Example 3 of this invention. Detailed Implementation

[0026] To make the technical means, creative features, objectives and effects of this invention clearer and easier to understand, the invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0027] Example 1: A method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface disclosed in this invention includes the following steps: first, the pretreated aluminum alloy substrate is oxidized in a sulfuric acid electrolyte until an anodized layer is formed on the surface of the substrate; then, the surface of the anodized layer is scanned with a laser; and finally, a neutral chemically plated Ni-P layer plating solution is applied to obtain the Ni-P composite coating.

[0028] Example 2: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 180 g / L sulfuric acid, with the oxidation temperature controlled at 0℃, the oxidation time at 60 min, and the current density at 3 A / dm³. 2 , refer to Figure 1 This process continues until a 70 μm anodic oxide layer is formed on the surface of the substrate, which is brownish-black in color. S2 uses laser scanning to scan the surface of the anodized layer, controlling the laser's linear energy density to be 25J / m, the laser pulse frequency to be 50kHz, the laser scanning power to be 25W, the laser scanning speed to be 1000mm / s, and the number of laser scans to be 1. The scanning path for each laser scan is a line-by-line scanning path. S3 uses a neutral Ni-P electroless plating solution, which consists of raw materials with the following concentrations: nickel sulfate: 25 g / L, sodium hypophosphite: 23.7 g / L, complexing agent: 17.5 g / L, pH buffer: 15 g / L, and ammonia water to adjust the pH of the plating solution to 7.0 ± 0.1. The plating temperature is controlled at 80℃, and the plating time is 2 hours to obtain the electroless plating layer. Among them, the complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S4 reference Figure 2 Anodizing / chemical plating of Ni-P composite coating was completed on the aluminum alloy surface, resulting in a metallic luster. (Refer to...) Figure 3 The anodic oxidation / chemical plating Ni-P composite coating includes a substrate, an anodic oxidation layer disposed on the substrate, and a chemical plating layer disposed on the anodic oxidation layer. The surface of the anodic oxidation layer is formed with protrusions by laser scanning. The chemical plating layer covers the surface of the protrusions and is embedded in the groove formed by two adjacent protrusions.

[0029] Example 3: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 180 g / L sulfuric acid, with the oxidation temperature controlled at 0℃, the oxidation time at 60 min, and the current density at 3 A / dm³. 2 , refer to Figure 4 This process continues until a 70 μm anodic oxide layer is formed on the surface of the substrate, which is brownish-black in color. S2 uses laser scanning to scan the surface of the anodized layer, controlling the laser's linear energy density to be 35J / m, the laser pulse frequency to be 50kHz, the laser scanning power to be 35W, the laser scanning speed to be 1000mm / s, and the number of laser scans to be 1. The scanning path for each laser scan is a line-by-line scanning path. S3 uses a neutral Ni-P electroless plating solution, which consists of raw materials with the following concentrations: nickel sulfate: 25 g / L, sodium hypophosphite: 23.7 g / L, complexing agent: 17.5 g / L, pH buffer: 15 g / L, and ammonia water to adjust the pH of the plating solution to 7.0 ± 0.1. The plating temperature is controlled at 80℃, and the plating time is 2 hours to obtain the electroless plating layer. Among them, the complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S4 reference Figure 5 Anodizing / chemical plating of Ni-P composite coating was completed on the aluminum alloy surface, resulting in a metallic luster. (Refer to...) Figure 6 The anodic oxidation / chemical plating Ni-P composite coating includes a substrate, an anodic oxidation layer disposed on the substrate, and a chemical plating layer disposed on the anodic oxidation layer. The surface of the anodic oxidation layer is formed with protrusions by laser scanning. The chemical plating layer covers the surface of the protrusions and is embedded in the groove formed by two adjacent protrusions.

[0030] The prepared Ni-P composite coating was subjected to tribological wear tests. The test parameters were controlled as follows: lubrication condition: no lubrication; grinding pair: 440C steel ball with a diameter of 10 mm; normal load: 20 N; reciprocating frequency: 5 Hz; amplitude: 5 mm; test time: 10 min. The wear rate of the Ni-P composite coating prepared in this embodiment was measured to be 7.83 × 10⁻⁶. -6 mm 3 / N·m. As a control, the wear rate of a single anodic oxide layer was 3.86 × 10⁻⁶ N·m. -4 mm 3 / N·m, the wear rate of a single Ni-P electroless plating layer is 1.46×10 -4 mm 3 / N·m. Therefore, in the Ni-P composite coating prepared by this invention, the supporting effect of the anodic oxide layer and the textured characteristics of its surface after laser scanning enable the top chemical coating to have excellent wear resistance.

[0031] Example 4: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 160 g / L sulfuric acid, with the oxidation temperature controlled at -5℃, the oxidation time at 50 min, and the current density at 2 A / dm³. 2 This process continues until a 39 μm anodic oxide layer is formed on the surface of the substrate, which is brownish-black in color. S2 uses laser scanning to scan the surface of the anodized layer, controlling the laser's linear energy density to be 22 J / m, the laser pulse frequency to be 60 kHz, the laser scanning power to be 20 W, the laser scanning speed to be 900 mm / s, and the number of laser scans to be 1. The scanning path for each laser scan is a line-by-line scanning path. S3 uses a neutral Ni-P electroless plating solution, which consists of raw materials with the following concentrations: nickel sulfate: 25 g / L, sodium hypophosphite: 20 g / L, complexing agent: 15 g / L, pH buffer: 14 g / L, and ammonia water to adjust the pH of the plating solution to 7.0 ± 0.1. The plating temperature is controlled at 80℃, and the plating time is 1 hour to obtain the electroless plating layer. Among them, the complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S4 completes the anodizing / chemical plating Ni-P composite coating on the aluminum alloy surface, which exhibits a metallic luster. The Ni-P composite coating includes a substrate, an anodized layer disposed on the substrate, and a chemical plating layer disposed on the anodized layer. The surface of the anodized layer is formed with protrusions by laser scanning. The chemical plating layer covers the surface of the protrusions and is embedded in the groove formed by two adjacent protrusions.

[0032] Example 5: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 170 g / L sulfuric acid, with the oxidation temperature controlled at -2℃, the oxidation time at 55 min, and the current density at 3 A / dm³. 2 Until a 65μm anodic oxide layer is formed on the surface of the substrate, the surface of which is brownish-black; S2 uses laser scanning to scan the surface of the anodized layer, controlling the laser's linear energy density to be 26 J / m, the laser pulse frequency to be 55 kHz, the laser scanning power to be 25 W, the laser scanning speed to be 950 mm / s, and the number of laser scans to be 1. The scanning path for each laser scan is a line-by-line scanning path. S3 uses a neutral Ni-P electroless plating solution, which consists of raw materials with the following concentrations: nickel sulfate: 23 g / L, sodium hypophosphite: 22 g / L, complexing agent: 16 g / L, pH buffer: 15 g / L, and ammonia water to adjust the pH of the plating solution to 7.0 ± 0.1. The plating temperature is controlled at 78℃, and the plating time is 2 hours to obtain the electroless plating layer. Among them, the complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S4 completes the anodizing / chemical plating Ni-P composite coating on the aluminum alloy surface, which exhibits a metallic luster. The Ni-P composite coating includes a substrate, an anodized layer disposed on the substrate, and a chemical plating layer disposed on the anodized layer. The surface of the anodized layer is formed with protrusions by laser scanning. The chemical plating layer covers the surface of the protrusions and is embedded in the groove formed by two adjacent protrusions.

[0033] Example 6: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 190 g / L sulfuric acid, with the oxidation temperature controlled at 2℃, the oxidation time at 65 min, and the current density at 3 A / dm³. 2 This process continues until a 75 μm anodic oxide layer is formed on the surface of the substrate, which is brownish-black in color. S2 uses laser scanning to scan the surface of the anodized layer, controlling the laser's linear energy density to be 24 J / m, the laser pulse frequency to be 45 kHz, the laser scanning power to be 25 W, the laser scanning speed to be 1050 mm / s, and the number of laser scans to be 1. The scanning path for each laser scan is a line-by-line scanning path. S3 uses a neutral Ni-P electroless plating solution, which consists of raw materials with the following concentrations: nickel sulfate: 28 g / L, sodium hypophosphite: 24 g / L, complexing agent: 18 g / L, pH buffer: 15 g / L, and ammonia water to adjust the pH of the plating solution to 7.0 ± 0.1. The plating temperature is controlled at 82℃, and the plating time is 2 hours to obtain the electroless plating layer. Among them, the complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S4 completes the anodizing / chemical plating Ni-P composite coating on the aluminum alloy surface, which exhibits a metallic luster. The Ni-P composite coating includes a substrate, an anodized layer disposed on the substrate, and a chemical plating layer disposed on the anodized layer. The surface of the anodized layer is formed with protrusions by laser scanning. The chemical plating layer covers the surface of the protrusions and is embedded in the groove formed by two adjacent protrusions.

[0034] Example 7: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 200g / L sulfuric acid, with the oxidation temperature controlled at 5℃, the oxidation time at 70min, and the current density at 4A / dm³. 2 This process continues until an anodic oxide layer of 110 μm is formed on the surface of the substrate, which is brownish-black in color. S2 uses laser scanning to scan the surface of the anodized layer, controlling the laser's linear energy density to be 27 J / m, the laser pulse frequency to be 40 kHz, the laser scanning power to be 30 W, the laser scanning speed to be 1100 mm / s, and the number of laser scans to be 1. The scanning path for each laser scan is a line-by-line scanning path. S3 uses a neutral Ni-P electroless plating solution, which consists of raw materials with the following concentrations: nickel sulfate: 30 g / L, sodium hypophosphite: 25 g / L, complexing agent: 20 g / L, pH buffer: 16 g / L, and ammonia water to adjust the pH of the plating solution to 7.0 ± 0.1. The plating temperature is controlled at 85℃, and the plating time is 3 hours to obtain the electroless plating layer. Among them, the complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S4 completes the anodizing / chemical plating Ni-P composite coating on the aluminum alloy surface, which exhibits a metallic luster. The Ni-P composite coating includes a substrate, an anodized layer disposed on the substrate, and a chemical plating layer disposed on the anodized layer. The surface of the anodized layer is formed with protrusions by laser scanning. The chemical plating layer covers the surface of the protrusions and is embedded in the groove formed by two adjacent protrusions.

[0035] Comparative Example 1: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 180 g / L sulfuric acid, with the oxidation temperature controlled at 0℃, the oxidation time at 60 min, and the current density at 3 A / dm³. 2 This process continues until a 70 μm anodic oxide layer is formed on the surface of the substrate, which is brownish-black in color. S2 uses laser scanning to scan the surface of the anodized layer, controlling the laser's linear energy density to be 250 J / m, the laser pulse frequency to be 50 kHz, the laser scanning power to be 25 W, the laser scanning speed to be 100 mm / s, and the number of laser scans to be 1. The scanning path for each laser scan is a line-by-line scanning path. S3 uses a neutral Ni-P electroless plating solution, which consists of raw materials with the following concentrations: nickel sulfate: 25 g / L, sodium hypophosphite: 23.7 g / L, complexing agent: 17.5 g / L, pH buffer: 15 g / L, and ammonia water to adjust the pH of the plating solution to 7.0 ± 0.1. The plating temperature is controlled at 80℃, and the plating time is 2 hours to obtain the electroless plating layer. Among them, the complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S4 reference Figure 7 Due to the high linear energy density during laser scanning, the anodic oxide layer has been largely removed and the laser has already acted on the aluminum alloy substrate, thus the anodic oxide / chemical plating Ni-P composite coating on the aluminum alloy surface has not been completed.

[0036] Comparative Example 2: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 180 g / L sulfuric acid, with the oxidation temperature controlled at 0℃, the oxidation time at 60 min, and the current density at 3 A / dm³. 2 This process continues until a 70 μm anodic oxide layer is formed on the surface of the substrate, which is brownish-black in color. S2 uses a neutral Ni-P electroless plating solution, which consists of raw materials with the following concentrations: nickel sulfate: 25 g / L, sodium hypophosphite: 23.7 g / L, complexing agent: 17.5 g / L, pH buffer: 15 g / L, and ammonia water to adjust the pH of the plating solution to 7.0 ± 0.1. The plating temperature is controlled at 80℃, and the plating time is 2 hours to obtain the electroless plating layer. Among them, the complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S3 reference Figure 8 Due to the lack of an intermediate laser scanning activation process, it is impossible to effectively deposit a chemical plating layer on the anodic oxide layer. The anodic oxide / chemical plating Ni-P composite coating on the aluminum alloy surface is not completed, and the surface still shows the brownish-black color of the anodic oxide coating.

[0037] Comparative Example 3: This invention discloses a method for preparing anodized / chemically plated Ni-P composite coatings on aluminum alloy surfaces. The difference from Example 1 is that it includes the following steps: S1 uses 7075-T6 aluminum alloy, which has undergone degreasing and descaling pretreatment, as the substrate. Oxidation is carried out in 180 g / L sulfuric acid, with the oxidation temperature controlled at 0℃, the oxidation time at 60 min, and the current density at 3 A / dm³. 2 This process continues until a 70 μm anodic oxide layer is formed on the surface of the substrate, which is brownish-black in color. S2 uses laser scanning to scan the surface of the anodized layer, controlling the laser's linear energy density to be 25J / m, the laser pulse frequency to be 50kHz, the laser scanning power to be 25W, the laser scanning speed to be 1000mm / s, and the number of laser scans to be 1. The scanning path for each laser scan is a line-by-line scanning path. S3 uses a neutral Ni-P electroless plating solution. This solution consists of raw materials with the following concentrations: nickel sulfate: 25 g / L, sodium hypophosphite: 23.7 g / L, complexing agent: 17.5 g / L, pH buffer: 15 g / L, and dilute sulfuric acid to adjust the pH to 4.5 ± 0.1. The plating temperature is controlled at 80℃, and the plating time is 2 hours to obtain the electroless plating layer. The complexing agent is sodium citrate, and the pH buffer is ammonium acetate. S4 reference Figure 9 Only a few areas on the substrate surface showed a chemically coated layer with a metallic luster. At the same time, due to the corrosive effect of the plating solution, the surface exhibited obvious roughness. The above phenomena indicate that the catalytic activity of the sample after laser scanning was not outstanding in the plating solution system at this pH value.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface, characterized in that: The process includes the following steps: first, the pretreated aluminum alloy substrate is oxidized in a sulfuric acid electrolyte until an anodic oxide layer is formed on the surface of the substrate; then, the surface of the anodic oxide layer is scanned with a laser; and finally, a neutral Ni-P electroless plating solution is used to deposit the anodic oxide / electroless Ni-P composite coating.

2. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 1, characterized in that: During the oxidation process, the thickness of the anodic oxide layer is 30~120μm.

3. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 2, characterized in that: During the oxidation process, the oxidation temperature is controlled at -5 to 5°C, the oxidation time is controlled at 10 to 70 minutes, and the current density is controlled at 2 to 4 A / dm³. 2 The electrolyte in the sulfuric acid system consists of 160~200g / L sulfuric acid.

4. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 1, characterized in that: During the laser scanning process, the linear energy density of the laser is controlled to be 10~100 J / m.

5. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 4, characterized in that: During the laser scanning process, the laser pulse frequency is controlled to be 40~60kHz, the laser scanning power is 10~30W, the laser scanning speed is 500~2000mm / s, and the number of laser scans is ≥1.

6. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 5, characterized in that: During the laser scanning process, the scanning path for each laser scan is one or a combination of several of the following: line-by-line scanning path, grid-interwoven scanning path, concentric circle scanning path, and spiral line scanning path.

7. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 1, characterized in that: In the electroless plating process, the electroless plating neutral Ni-P layer plating solution is composed of raw materials containing the following concentrations: nickel sulfate: 20~30 g / L, sodium hypophosphite: 20~25 g / L, complexing agent: 15~20 g / L, pH buffer: 10~16 g / L, and ammonia water: to adjust the pH of the plating solution to 7.0±0.

5.

8. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 7, characterized in that: In the electroless plating process, the complexing agent is sodium citrate and the pH buffer is ammonium acetate.

9. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 7, characterized in that: During the electroless plating process, the plating temperature is controlled at 75~85℃ and the plating time is 1~3h.

10. The method for preparing an anodized / chemically plated Ni-P composite coating on an aluminum alloy surface according to claim 1, characterized in that: The anodic oxidation / chemical plating Ni-P composite coating includes a substrate, an anodic oxidation layer disposed on the substrate, and a chemical plating layer disposed on the anodic oxidation layer. The surface of the anodic oxidation layer is formed with protrusions by laser scanning. The chemical plating layer covers the surface of the protrusions and is embedded in the groove formed by two adjacent protrusions.

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