A corrosion-resistant composite layer and a preparation method thereof, an aluminum base material corrosion-resistant treatment method, and a corrosion-resistant aluminum terminal and a preparation method thereof

Abstract

The application provides a kind of corrosion-resistant composite layer and its preparation method, aluminum base material corrosion-resistant treatment method and corrosion-resistant aluminum terminal and its preparation method.The corrosion-resistant composite layer includes: alkali copper layer, cupric pyrolysis layer, silver layer;Wherein, the thickness of the alkali copper layer is 1-10 μm, the thickness of the cupric pyrolysis layer is 2-18 μm, and the thickness of the silver layer is 0.2-25 μm.The aluminum base material corrosion-resistant treatment method includes the step of setting the corrosion-resistant composite layer on the surface of aluminum base material.The surface of the corrosion-resistant aluminum terminal is provided with the corrosion-resistant composite layer.The corrosion-resistant composite layer prepared by the technical scheme provided by the application has good salt spray corrosion resistance, and the aluminum terminal provided with the corrosion-resistant composite layer can realize salt spray resistance for 240 hours.

Description

Technical Field

[0001] This invention relates to a corrosion-resistant composite layer and its preparation method, a corrosion-resistant treatment method for aluminum substrates, and a corrosion-resistant aluminum terminal and its preparation method, belonging to the field of corrosion-resistant technology. Background Technology

[0002] Aluminum and its alloys are widely used in power transmission systems in industries such as military, automotive, and aerospace due to their low density, high conductivity, and good formability. However, their insufficient corrosion resistance in corrosive environments limits their further application. The chemical properties of aluminum and its alloys themselves restrict their applications: 1. They are easily oxidized in air, forming an oxide film that greatly increases terminal resistance and affects power transmission; 2. The standard electrode potential of aluminum is -1.662V, making it prone to potential corrosion when connected to other metals with corrected standard electrode potentials (e.g., copper), leading to connection failure and, in severe cases, short circuits.

[0003] Current electroplating, electroless plating, spraying, and laser surface treatment processes can protect the substrate by coating the surface of aluminum and its alloys with a film. However, the effect of salt spray resistance tests is not ideal. Common aluminum workpieces can only maintain salt spray resistance for 48 hours before corrosion occurs, which greatly limits the service life of aluminum workpieces in assemblies.

[0004] Currently, electroplating manufacturers have limited research and development on aluminum electroplating processes. They often rely on secondary zinc immersion followed by nickel plating to enable further electroplating. The selection of plating solutions varies and the results are generally poor, making it difficult to meet the requirements for electroplating highly corrosion-resistant aluminum workpieces. This is especially true for aluminum workpieces used in harsh environments such as military, aerospace, and automotive industries. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a corrosion-resistant composite layer that exhibits excellent resistance to salt spray corrosion and can be used for corrosion-resistant treatment of aluminum substrates.

[0006] To achieve the above objectives, the present invention first provides a corrosion-resistant composite layer, which includes: an alkali copper layer, a pyrometallurgical copper layer, and a silver layer.

[0007] In the above-mentioned corrosion-resistant composite layer, preferably, the thickness of the alkali copper layer is 1-10 μm, the thickness of the pyrometallurgical copper layer is 2-18 μm, and the thickness of the silver layer is 0.2-25 μm.

[0008] In the above-mentioned corrosion-resistant composite layer, preferably, the pyrocopper layer is disposed between the alkali copper layer and the silver layer, that is, the alkali copper layer, the pyrocopper layer, and the silver layer are disposed in sequence.

[0009] In the above-mentioned corrosion-resistant composite layer, preferably, the thickness of the alkali copper layer is 1-6 μm, more preferably 2-4 μm.

[0010] In the above-mentioned corrosion-resistant composite layer, preferably, the thickness of the copper plating layer is 5-15 μm, more preferably 8-10 μm.

[0011] In the aforementioned corrosion-resistant composite layer, the silver layer can have different thicknesses depending on the corrosion resistance requirements of the applicable location. For example, in the contact area or welding area of ​​the male and female aluminum terminals, these areas have a small contact area with the environment and are considered semi-exposed areas, with lower requirements for corrosion resistance. A thinner silver layer can be used; preferably, the thickness of the thin silver layer is 0.2-3 μm, more preferably 0.5-2 μm. In completely exposed areas where the aluminum terminals have a large contact area with the environment, higher requirements for corrosion resistance necessitate a thicker silver layer. Preferably, the thickness of the thick silver layer is 8-15 μm, more preferably 10-15 μm. In some cases, the thickness of the silver layer can be further controlled to 10-13 μm.

[0012] In the aforementioned corrosion-resistant composite layer, preferably, the corrosion-resistant composite layer further includes a transition layer, which is disposed on the side of the alkali copper layer that does not contact the pyrolytic copper layer. This transition layer is disposed between the alkali copper layer and the substrate requiring corrosion resistance treatment as a transition, and can be achieved using an appropriate surface treatment method.

[0013] In the aforementioned corrosion-resistant composite layer, preferably, the transition layer includes a zinc layer, or a combination of a zinc layer and a secondary zinc plating layer; the zinc layer (or zinc layer and secondary zinc plating layer), alkali copper layer, pyrometallurgical copper layer, and silver layer are sequentially disposed. The zinc layer and the secondary zinc plating layer serve as transition layers for subsequent electroplating layers, ensuring their adhesion. According to a specific embodiment of the present invention, the combination of the zinc layer and the secondary zinc plating layer includes a configuration where the zinc layer and the secondary zinc plating layer are stacked (top to bottom, with the secondary zinc plating layer covering the zinc layer); and a configuration where the zinc layer and the secondary zinc plating layer are located in different regions of the same layer, and in this configuration, a portion of the two layers may overlap.

[0014] The transition layer of the present invention is not limited to a zinc layer or a secondary zinc plating layer. Other metals or alloys can also be used, as long as they can help improve the adhesion of the corrosion-resistant composite layer. For example, other metal transition layers or alloy transition layers can be formed on the surface of the aluminum terminal by surface treatment processes such as spraying or vacuum electroplating.

[0015] In the above-mentioned corrosion-resistant composite layer, preferably, the thickness of the zinc layer is 0.1-10 μm, more preferably 0.5-1 μm.

[0016] In the above-mentioned corrosion-resistant composite layer, preferably, the thickness of the secondary zinc plating layer is 0.1-10 μm, more preferably 1.5-2.5 μm.

[0017] In the above-mentioned corrosion-resistant composite layer, preferably, the zinc layer, the secondary zinc plating layer, the alkali copper layer, the pyrolytic copper layer, and the silver layer are all electroplated layers.

[0018] Preferably, the corrosion-resistant composite layer further includes a chemical copper layer (or chemical copper plating layer).

[0019] In the above-mentioned corrosion-resistant composite layer, preferably, the chemical copper layer is disposed on the surface of the alkali copper layer or the surface of the pyrocopper layer, that is, the chemical copper layer can be disposed in the following ways: (1) disposed on the side surface of the alkali copper layer that is not in contact with the pyrocopper layer; (2) disposed between the alkali copper layer and the pyrocopper layer; (3) disposed on the side surface of the pyrocopper layer that is not in contact with the alkali copper layer.

[0020] In the above-mentioned corrosion-resistant composite layer, preferably, the thickness of the chemical copper layer is 3-25 μm, more preferably 5-15 μm.

[0021] Preferably, the corrosion-resistant composite layer further includes an acid copper layer.

[0022] In the above-mentioned corrosion-resistant composite layer, preferably, the acid copper layer is disposed on the surface of the alkali copper layer or the surface of the pyrolytic copper layer, that is, the chemical copper layer can be disposed in the following ways: (1) disposed on the side of the alkali copper layer that does not contact the pyrolytic copper layer; (2) disposed between the alkali copper layer and the pyrolytic copper layer; (3) disposed on the side of the pyrolytic copper layer that does not contact the alkali copper layer.

[0023] In the above-mentioned corrosion-resistant composite layer, preferably, the thickness of the acid copper layer is 1-20 μm, more preferably 3-10 μm.

[0024] Preferably, the corrosion-resistant composite layer further includes a Watt nickel layer.

[0025] In the above-mentioned corrosion-resistant composite layer, preferably, the Watt nickel layer is disposed on the surface of the alkali copper layer or the surface of the pyrocopper layer, that is, the Watt nickel layer can be disposed in the following ways: (1) disposed on the side surface of the alkali copper layer that is not in contact with the pyrocopper layer; (2) disposed between the alkali copper layer and the pyrocopper layer; (3) disposed on the side surface of the pyrocopper layer that is not in contact with the alkali copper layer.

[0026] In the above-mentioned corrosion-resistant composite layer, preferably, the thickness of the Watt nickel layer is 1-20 μm, more preferably 3-9 μm.

[0027] In the aforementioned corrosion-resistant composite layer, preferably, the corrosion-resistant composite layer may simultaneously include two or three of the following: a chemical copper layer, an acid copper layer, and a Watt's nickel layer. Furthermore, their specific locations can be chosen from one, two, or three of the following three positions: the side of the alkali copper layer that does not contact the pyrolytic copper layer, the area between the alkali copper layer and the pyrolytic copper layer, and the side of the pyrolytic copper layer that does not contact the alkali copper layer. When two or three of them are chosen to be in the same location, their order can be arbitrary. For example, when the chemical copper layer, acid copper layer, and Watt's nickel layer are all located between the alkali copper layer and the pyrolytic copper layer, the chemical copper layer can be located between the acid copper layer and the Watt's nickel layer, or the acid copper layer can be located between the chemical copper layer and the Watt's nickel layer, or the Watt's nickel layer can be located between the chemical copper layer and the acid copper layer.

[0028] In a salt spray environment, chloride ions penetrate the coating and corrode the substrate upon contact. The corrosion-resistant composite layer provided by this invention utilizes a combination of alkali copper, pyrometallurgical copper, and silver layers for layered protection. Even when one layer is penetrated, the underlying layer still prevents chloride ions from penetrating, thus providing protection and improving the overall corrosion resistance of the substrate, preventing chloride ions from penetrating the coating and contacting the substrate. Specifically, when a thick silver layer is used, it can achieve 240 hours of salt spray resistance, meeting the corrosion resistance requirements for fully exposed areas of aluminum terminals; when a thin silver layer is used, it can achieve 60 hours of salt spray resistance, meeting the corrosion resistance requirements for semi-exposed areas of aluminum terminals.

[0029] The present invention also provides a method for preparing the above-mentioned corrosion-resistant composite layer, which includes the following steps: forming an alkali copper layer, a pyrocopper layer and a silver layer sequentially on the surface of a substrate by electroplating to obtain the corrosion-resistant composite layer.

[0030] In the above-mentioned method for preparing the corrosion-resistant composite layer, preferably, based on the total volume of the electroplating solution, the electroplating solution used for the alkali copper layer contains: cuprous cyanide: 40-50 g / L, total sodium cyanide: 40-60 g / L, free sodium cyanide: 8-14 g / L, potassium sodium tartrate: 30-45 g / L, sodium hydroxide: 1-3 g / L, and additives (one or a mixture of two or more of polyethylene glycol, fatty amine polyoxyethylene ether (AEO), and OP series octylphenol polyoxyethylene ether): 3-5 mL / L. The remaining component in the electroplating solution is water.

[0031] In the above-mentioned method for preparing the corrosion-resistant composite layer, preferably, the electroplating temperature of the alkaline copper layer is 40-50℃, the anode-cathode area ratio is 1:1-2 (preferably 1:1.5), and the current density is 0.7-1.2A / dm². 2 The electroplating time is 5-15 minutes.

[0032] In the above-mentioned method for preparing the corrosion-resistant composite layer, preferably, based on the total volume of the electroplating solution, the electroplating solution used for the pyrophosphate layer contains: copper pyrophosphate: 50-70 g / L, potassium pyrophosphate: 300-450 g / L, ammonium citrate: 15-30 g / L, and ammonia water: 2-5 mL / L. The remaining component in the electroplating solution is water.

[0033] In the above-mentioned method for preparing the corrosion-resistant composite layer, preferably, the temperature for electroplating the copper plating layer is 40-50℃, and the current density is 0.7-1.2A / dm³. 2 The ratio of anode to cathode area is 1:1-2 (preferably 1:1.5), and the electroplating time is 50-90 min (preferably 70 min).

[0034] In the above-mentioned method for preparing the corrosion-resistant composite layer, preferably, based on the total volume of the electroplating solution, the electroplating solution used for the silver layer contains: silver cyanide: 30-50 g / L, potassium cyanide: 130-150 g / L, free potassium cyanide: 45-60 g / L, potassium carbonate: 15-25 g / L, potassium hydroxide: 4-10 g / L, and additives (one or a mixture of two or more of thiocarbamate, sodium dodecyl sulfonate, and OP series octylphenol polyoxyethylene ether): 20-30 g / L. The remaining component in the electroplating solution is water.

[0035] In the above-mentioned method for preparing the corrosion-resistant composite layer, preferably, the temperature for electroplating the silver layer is 20-25℃, the ratio of anode to cathode area is 1:1-2 (preferably 1:1.5), and the current density is 0.2-0.5A / dm². 2 The electroplating time is 1-90 min (preferably 30-60 min, preferably 40 min).

[0036] In the above-mentioned method for preparing corrosion-resistant composite layers, preferably, the alkali copper layer, pyrocopper layer, silver layer, etc., can be prepared by pulse electroplating process, which can further enhance their original density, thereby making the electroplated layer denser, with fewer pores and stronger salt spray resistance.

[0037] In the above-mentioned method for preparing corrosion-resistant composite layers, preferably, when chemical copper layer, acid copper layer, and Watt's nickel layer are included, these layers can be obtained at an appropriate time and in an appropriate manner.

[0038] In the above-mentioned method for preparing the corrosion-resistant composite layer, preferably, when a transition layer such as a zinc layer and a secondary zinc plating layer is included, the transition layer is formed first, followed by the formation of the alkali copper layer, the pyrometallurgical copper layer, and the silver layer. The zinc layer and the secondary zinc plating layer can be prepared using conventional electroplating methods.

[0039] In the above-mentioned method for preparing corrosion-resistant composite layers, in order to ensure the electroplating adhesion, other steps can be added to the electroplating process, such as adding acid activation treatment before each step, or adding pure water washing before each step.

[0040] This invention also provides a method for corrosion-resistant treatment of aluminum substrates, which includes the step of depositing the corrosion-resistant composite layer provided by this invention on the surface of the aluminum substrate. The aluminum substrates of this invention include pure aluminum substrates and aluminum alloy substrates.

[0041] In the above-mentioned corrosion-resistant treatment method for aluminum substrates, preferably, the corrosion resistance refers to resistance to salt spray corrosion.

[0042] In the above-mentioned corrosion-resistant treatment method for aluminum substrate, preferably, the surface roughness of the aluminum substrate is less than Ra3.6, more preferably less than Ra0.8.

[0043] The present invention also provides a corrosion-resistant aluminum terminal, wherein a portion or all of the surface of the corrosion-resistant aluminum terminal is provided with the corrosion-resistant composite layer provided by the present invention.

[0044] In the aforementioned corrosion-resistant aluminum terminals, the corrosion-resistant composite layer can cover the entire surface of the aluminum terminal, or it can only cover the surface area that requires corrosion resistance treatment.

[0045] The present invention also provides a method for preparing the above-mentioned corrosion-resistant aluminum terminal, which includes the following steps:

[0046] The front side of the aluminum terminals is rolled and polished.

[0047] The sides of the aluminum terminals are stamped.

[0048] The corrosion-resistant aluminum terminal is obtained by electroplating a zinc layer, a secondary zinc plating layer, an alkali copper layer, a pyrometallurgical copper layer, and a silver layer on the front and sides of the treated aluminum terminal in sequence.

[0049] In the above preparation methods, rolling, polishing, and stamping processes can be applied only to the areas requiring corrosion resistance treatment, and are not limited to the entire surface of the aluminum terminal. This localized treatment facilitates welding and allows for the application of various joining processes such as friction welding, friction stir welding, ultrasonic welding, molecular diffusion welding, and resistance welding, thereby obtaining corrosion-resistant terminals with high reliability and multiple joining capabilities.

[0050] In the above-mentioned method for preparing corrosion-resistant aluminum terminals, preferably, rolling the terminal material can enhance the density of its terminal surface and improve the corrosion resistance of subsequent electroplating treatment.

[0051] In the above-mentioned method for preparing corrosion-resistant aluminum terminals, preferably, polishing the terminal material can enhance the surface smoothness of the terminal and improve the corrosion resistance of subsequent electroplating. Polishing can be performed using methods such as chemical polishing or mechanical polishing.

[0052] In the above-mentioned method for preparing corrosion-resistant aluminum terminals, preferably, the surface roughness of the aluminum terminals after roll forming and polishing is less than Ra 3.6, more preferably less than Ra 0.8.

[0053] In the above-mentioned method for preparing corrosion-resistant aluminum terminals, preferably, the side roughness of the aluminum terminal after roll forming is less than Ra 3.6 (more preferably less than Ra 0.8), and the bright band is greater than 50% (more preferably greater than 98%).

[0054] In the above-mentioned method for preparing corrosion-resistant aluminum terminals, preferably, when a transition layer is provided, a transition layer is first formed on the front and side surfaces of the treated aluminum terminal before electroplating to form an alkaline copper layer.

[0055] The corrosion-resistant composite layer prepared by the technical solution provided by the present invention has good salt spray corrosion resistance. The fully exposed area of ​​the aluminum terminal with the corrosion-resistant composite layer can withstand salt spray for 240 hours, and the semi-exposed area can withstand salt spray for 60 hours. Attached Figure Description

[0056] Figure 1 This is an exemplary overall structural diagram of an aluminum terminal with a corrosion-resistant composite layer provided by the present invention.

[0057] Figure 2 This is a schematic diagram of an exemplary electroplating process for an aluminum terminal with a corrosion-resistant composite layer provided by the present invention.

[0058] Figure 3 This is a schematic diagram of the roll forming process.

[0059] Figure 4 SEM images of conventional aluminum sheets and roll-formed aluminum sheets.

[0060] Figure 5 This is a schematic diagram of the polishing process.

[0061] Figure 6 These are topographic images of the sides of aluminum terminals obtained by conventional stamping and precision stamping.

[0062] Figure 7 This is a diagram showing the condition of the sample after the corrosion resistance test.

[0063] Figure 8 Images of samples showing poor adhesion when directly electroplating copper and silver layers.

[0064] Figure 9 This is an image showing corrosion spots on the side of Comparative Example 8. Detailed Implementation

[0065] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0066] The aluminum terminal provided by this invention includes an aluminum terminal material and an electroplated film layer. The aluminum terminal material has a terminal surface and terminal sides. The electroplated film layer (corrosion-resistant composite layer) includes an alkali copper layer, a pyrometallurgical copper layer, and a silver layer. Furthermore, the electroplated film layer may further include a zinc layer and a secondary zinc plating layer. An exemplary overall structure of the aluminum terminal with the corrosion-resistant composite layer is shown below. Figure 1 As shown, a zinc layer 2, an alkaline copper layer 3, a pyrocopper layer 4, and a silver layer 5 are sequentially provided on the surface of the aluminum substrate 1; if necessary, a secondary zinc plating layer can be further provided between the zinc layer 2 and the alkaline copper layer 3.

[0067] An exemplary electroplating process for aluminum terminals is as follows: Figure 2 As shown: The electroplating process includes the following steps: ultrasonic degreasing, alkaline washing, acid washing, chemical zinc immersion, chemical zinc stripping, secondary zinc immersion, activation, electroplating alkaline copper, electroplating coke copper, pre-plating silver, electroplating silver, post-treatment, pure water washing, and drying; among them, the secondary zinc immersion step can be selected as needed.

[0068] The technical solution of the present invention starts from the design to avoid contact between chloride ions and the substrate. The front side of the material terminal is subjected to roll forming and polishing treatment, and the roughness after treatment is less than Ra 3.6, preferably less than Ra 0.8. The side of the material terminal is processed by precision stamping process, and the bright band after treatment is greater than 50% (preferably greater than 98%) and the roughness is less than Ra 3.6 (preferably less than Ra 0.8).

[0069] A schematic diagram of the roll forming process is shown below. Figure 3 As shown, this is a type of roll forming process, in which two rollers 31 repeatedly roll an aluminum plate 32 sandwiched in between. Roll forming increases the surface density of the aluminum material by applying pressure mechanically, thereby reducing the porosity of the aluminum terminal material surface and improving its compactness. This prepares the material for the subsequent electroplating layer; the fewer the pores in the material, the fewer the pores in the electroplating layer, resulting in higher protective properties. SEM images of conventional aluminum plates and roll-formed aluminum plates are shown below. Figure 4 As shown. In Figure 4 In the diagram, image a shows a conventional aluminum sheet, and image b shows a roll-formed aluminum sheet. (From...) Figure 4 It can be seen that the surface roughness of the aluminum plate is reduced and the flatness is greatly improved through roll forming.

[0070] Polishing process such as Figure 5As shown, the terminal material 41 is processed by placing it in a polishing tank 44 containing a polishing solution 42 and a magnetic needle 43. Magnetic polishing is achieved by generating a magnetic field through an electric current. The magnetic field drives the stainless steel needle (i.e., the magnetic needle 43) to move. During the movement, the magnetic needle 43 rubs against the surface of the terminal material 41, thereby achieving the effect of mechanical polishing and improving the smoothness and flatness of the surface of the terminal material 41.

[0071] Polishing and precision stamping processes are all used to improve the smoothness and flatness of the surface and sides of the terminal material.

[0072] Improving the flatness and smoothness of the terminal material greatly benefits the electroplating film layer. Because of the influence of current, the electroplating process accumulates more film in areas where electrons are concentrated on the workpiece. This results in uneven film thickness on the terminal surface, and even numerous pits, allowing chloride ions in the salt spray to accumulate and penetrate. When the flatness of the terminal material is insufficient, due to the principle of point discharge, the more curved the conductor surface, the more charge accumulates in areas with a relatively small surface area. Uneven protrusions on the material surface will accumulate a large number of electrons, making the protrusions on the electroplated workpiece surface even more prominent, and the depressions even more recessed. This forms pinholes, which easily accumulate salt spray solution, causing chloride ions to penetrate and leading to corrosion. After processing with the process of this invention, the terminal material can be effectively covered with an electroplating film layer, effectively improving its corrosion resistance.

[0073] Alkaline copper electroplating: Alkaline copper electroplating is a cyanide copper plating process. Cyanide has a very strong complexing ability in water, which can greatly increase the cathode polarization of electroplating, causing copper ions to accumulate in large quantities at the cathode and deposit together, increasing the density of the electroplated film. The coating produced by cyanide system electroplating is dense and the reaction is fast and efficient, which can cover the zinc layer with a dense and smooth copper layer. Moreover, copper is chemically inert and has low electroplating internal stress, making it an excellent intermediate coating that is easy to electroplat with subsequent metal coatings.

[0074] The electroplating parameters are as follows: cuprous cyanide: 40-50 g / L, total sodium cyanide: 40-60 g / L, free sodium cyanide: 8-14 g / L, potassium sodium tartrate: 30-45 g / L, sodium hydroxide: 1-3 g / L, additives: 3-5 mL / L, temperature: 40-50℃, anode-cathode area ratio: 1:1.5, current density: 0.7-1.2 A / dm² 2 Electroplating time: 5-15 min; Electroplating coating thickness: preferably 1-6 μm.

[0075] To enhance the density of the coating, the present invention has optimized the process: generally, to meet the requirements of electroplating efficiency and achieve faster production, the current density for electroplating alkaline copper is 4-10 A / dm³. 2The current density directly affects the density of the coating. A high current density weakens cathodic polarization and makes it easier to reach the hydrogen ion evolution overpotential in the solution, causing hydrogen evolution side reactions during electroplating. The evolved hydrogen gas leaves pores in the coating, reducing its density. The alkaline copper electroplating process used in this invention increases the concentration of the main salt cuprous cyanide and free sodium cyanide while reducing the current density, thereby obtaining an alkaline copper coating with excellent electroplating efficiency and density.

[0076] Electroplated copper pyrophosphate: The electroplated copper pyrophosphate layer is made of copper pyrophosphate. Pyrophosphate has a stronger complexing ability in water than cyanide, and its cathodic polarization in the pyrophosphate system is also stronger. This is because [Cu(P₂O₇)₂] in the solution... 6- It carries a greater number of negative charges and has a greater impact on the cathode process, while [Cu(P2O7)2] 6- It is difficult to discharge and requires hydrolysis to form [CuP2O7]. 2- Only then can a copper layer, [CuP2O7], be deposited via electrical discharge. 2- The hydrolysis is relatively slow, thus further increasing cathodic polarization. The pyroplated copper film is denser with fewer pores, effectively preventing chloride ion penetration in salt spray tests and enhancing the corrosion resistance of the workpiece.

[0077] The electroplating parameters are as follows: copper pyrophosphate: 50-70 g / L, potassium pyrophosphate: 300-450 g / L, ammonium citrate: 15-30 g / L, ammonia: 2-5 mL / L, current density: 0.7-1.2 A / dm³ 2 The temperature is 40-50℃, the anode-cathode area ratio is 1:1.5, the electroplating time is 50-90 min, and the electroplating thickness is preferably 5-15 μm. Similarly, to improve the density of the coating, the process used in this invention has been optimized by reducing the current density.

[0078] The present invention, through the combination of alkali copper layer and pyrometallurgical copper layer, can bring the following advantages:

[0079] 1. Enhance the adhesion between plating layers: Alkali copper, as an excellent base coating, has a very good adhesion to the zinc layer of the substrate; if alkali copper is removed and coke copper is plated directly, poor adhesion is likely to occur (e.g., Figure 8 (As shown), this makes the workpiece more susceptible to corrosion.

[0080] 2. Enhanced Salt Spray Effect: Since the surface condition of the substrate has a significant impact on the electroplating layer, it is impossible to directly electroplat a very dense coating on the porous surface of aluminum. This invention preferably adopts a scheme of gradually increasing density. The density of the zinc layer is lower than that of alkali copper, and the density of alkali copper is slightly lower than that of pyrolytic copper. The density of these three layers is gradually increased, so that the final pyrolytic copper layer has the best density. Therefore, the technical solution of this invention preferably uses a combination of 1-6μm alkali copper + 5-15μm pyrolytic copper, which can effectively improve the corrosion resistance of the workpiece.

[0081] When the electroplated alkaline copper layer is too thick, a rough coating can easily occur. Therefore, this invention selects an electroplating thickness of 1-10 μm (preferably 1-6 μm), at which the adhesion and density meet the requirements. The cobalt layer is selected between 2-18 μm; the thicker the coating, the better it can cover its own pores. However, considering the influence of electroplating time, 5-15 μm is preferred.

[0082] The chemical copper plating layer (electrochemical copper plating layer) is formed by the orderly deposition of copper ions on a substrate through a chemical reaction autocatalytic plating method. Adding a chemical copper plating layer between each layer results in good adhesion. The chemical copper plating layer is an excellent intermediate plating layer that enhances the overall adhesion of the plating. Furthermore, because the preparation process of the chemical copper plating layer is a purely chemical reaction, it is not affected by current distribution, which can influence the plating thickness and porosity. Therefore, the chemical copper plating layer has a more uniform thickness, lower porosity, and good corrosion resistance. In this invention, adding this layer enhances the overall corrosion resistance of the plating.

[0083] The parameters for electroless copper plating are as follows: Composition of the electroless plating solution: copper sulfate: 5-20 g / L, sodium hypophosphite: 20-50 g / L, sodium citrate: 5-30 g / L, nickel sulfate: 0.1-5 g / L, potassium ferrocyanide: 0.5-7 mg / L, boric acid: 15-50 g / L; temperature: 60-90℃, pH: 7.8-10.2, plating time: 40-100 min, typical plating rate: 1 μm / 6 min, i.e., 6 min-1 μm, 24 min-4 μm, 48 min-8 μm; the plating thickness can be controlled as needed by adjusting the electroless copper plating parameters.

[0084] The acid copper layer (i.e., acid copper plating) is made by electroplating copper sulfate. It has good adhesion to other plating layers and can serve as an excellent intermediate plating layer. Furthermore, the copper sulfate plating solution used in the preparation of the acid copper layer is stable and low in cost. Adding acid copper between or on both sides of the alkaline copper layer and the pyrolytic copper layer can enhance the overall brightness and corrosion resistance of the plating layer itself.

[0085] The parameters for electroplating acid copper are as follows: Electroplating solution composition: Copper sulfate pentahydrate: 160-250 g / L, sulfuric acid: 25-50 mL / L, chloride ions: 40-120 ppm, additives (sodium polydithiopropane sulfonate, 2-mercaptobenzimidazole, 1,2-ethylidene thiourea, or a mixture of one or more polyamine compounds): 4-15 mL / L; current density: 0.8-2.0 A / dm³ 2 The temperature is 20-30℃, the anode-cathode area ratio is 1:1.5, the electroplating time is 20-80 minutes, and the coating thickness is controlled by adjusting the electroplating parameters as needed.

[0086] Watt's nickel layer (i.e. Watt's nickel plating, bright nickel plating) is a nickel sulfate electroplating layer. It has good adhesion to other plating layers and can be used as an excellent intermediate plating layer. When Watt's nickel is added between or on both sides of alkali copper layer or pyrocopper layer, a potential difference will be generated in the corrosive environment. It can act as an anode and be corroded first, protecting other plating layers and enhancing the overall brightness and corrosion resistance of the plating layer itself.

[0087] The parameters for electroplating Watt's nickel layer are as follows: Electroplating solution composition: Nickel sulfate hexahydrate: 250-350 g / L, Nickel chloride hexahydrate: 60-95 g / L, Boric acid: 40-60 g / L, Additives (sodium dodecyl sulfate, saccharin, butynediol ethoxylate, or one or more of these): 6-12 mL / L; pH: 3-5; Current density: 0.8-2.0 A / dm³ 2 The temperature is 50-60℃, the anode-cathode area ratio is 1:1.5, the electroplating time is 30-70 minutes, and the coating thickness is controlled by adjusting the electroplating parameters as needed.

[0088] The purpose of pre-plating silver is to pre-plat a layer of silver under high current density and dilute solution concentration to enhance the adhesion between electroplated film layers and prepare for the next process.

[0089] The electroplating parameters are as follows:

[0090] Silver cyanide: 30-120 g / L, potassium cyanide: 80-200 g / L, free potassium cyanide: 30-80 g / L, potassium carbonate: 5-30 g / L, potassium hydroxide: 2-20 g / L; temperature: 20-25℃, anode-cathode area ratio: 1:1.5, current density: 0.5-2 A / dm² 2 Electroplating time: approximately 1 minute.

[0091] Electroplated silver: Electroplated silver is a cyanide plating process. It also exhibits strong cathodic polarization, resulting in a denser coating. Cyanide plating effectively hinders the penetration of chloride ions during salt spray testing, enhancing the corrosion resistance of the workpiece. Silver's standard electrode potential is +0.799V. Silver has extremely high chemical inertness, reacting only readily with sulfur in air and hardly reacting with other substances, exhibiting exceptional corrosion resistance. The electroplated silver layer on the workpiece surface effectively improves this corrosion resistance.

[0092] The electroplating parameters are as follows:

[0093] Silver cyanide: 30-50 g / L, potassium cyanide: 130-150 g / L, free potassium cyanide: 45-60 g / L, potassium carbonate: 15-25 g / L, potassium hydroxide: 4-10 g / L, additives: 20-30 g / L; temperature: 20-25℃, anode-to-cathode area ratio: 1:1.5, current density: 0.2-0.5 A / dm² 2Electroplating time: 1-90 min; electroplating thickness is controlled as needed by adjusting electroplating parameters. Similarly, to improve coating density, the process used in this invention has been optimized by reducing current density.

[0094] The corrosion-resistant composite layer provided by this invention features electroplated films such as alkali copper, pyrometallurgical copper, and silver, all exhibiting strong density. These films effectively hinder chloride ion penetration during salt spray testing. Furthermore, the interaction and superposition of the various metal / alloy layers cover the pores present in a single plating layer. Even if chloride ions penetrate one electroplated film layer during salt spray testing, other dense plating layers effectively prevent further penetration, significantly improving the corrosion resistance of the aluminum substrate. Further improvements in corrosion resistance can be achieved by adding zinc layers, secondary zinc plating layers, chemical copper layers, acid copper layers, and Watt's nickel layers.

[0095] Existing aluminum workpieces typically exhibit corrosion resistance to salt spray within 48 hours, making them unsuitable for harsh corrosive environments such as humid or marine environments. The technical solution provided by this invention offers two advantages: First, through rolling, polishing, and stamping processes, aluminum terminal materials with excellent surface finish are manufactured, facilitating subsequent electroplating (resulting in a denser electroplated film). Second, by covering the aluminum with a dense electroplated film layer, and with the interaction between these layers, the penetration of chloride ions during salt spray testing is effectively hindered, thereby preventing corrosion and significantly enhancing the corrosion resistance of the aluminum terminals.

[0096] The aluminum terminals in the embodiments and comparative examples of the present invention can be prepared by referring to the above method.

[0097] Example 1

[0098] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0099] The front side of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8. The side side has been processed by precision stamping, with a bright band of more than 98% and a roughness of less than Ra 0.8. Figure 6 The first image is a side view of conventional stamping, and the second image is a side view of precision stamping. Figure 6 It can be seen that the aluminum terminals obtained by ordinary stamping have a higher proportion of rough bands on their sides, while the aluminum terminals obtained by precision stamping have mostly bright bands on their sides, accounting for more than 98%. The condition of the bright bands was determined by projector detection, and the proportion of bright bands was determined by calculating their length or area. The roughness of the aluminum terminal material before and after polishing was 0.315μm and 0.282μm, respectively. This shows that polishing can significantly reduce surface roughness and improve surface finish. The sampling cutoff wavelength λc of the filter in the roughness test was 0.8mm × 5.

[0100] The composite corrosion-resistant layer comprises a zinc layer, a secondary zinc plating layer, an alkaline copper layer, a pyrolytic copper layer, and a silver layer, applied to the fully exposed area of ​​the aluminum terminal material surface, with thicknesses of approximately 0.5 μm, approximately 2.0 μm, approximately 2.0 μm, approximately 8 μm, and approximately 15 μm, respectively. After the composite corrosion-resistant layer is formed, the surface roughness of the aluminum terminal is also improved, reduced to 0.243 μm.

[0101] Example 2

[0102] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0103] The front side of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8. The side side has been processed by precision stamping, with a bright band of more than 98% and a roughness of less than Ra 0.8.

[0104] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc plating layer, an alkali copper layer, a pyrometallurgical copper layer, and a silver layer on the fully exposed area of ​​the aluminum terminal material surface, with thicknesses of 0.5μm, 2μm, 2μm, 10μm, and 10μm, respectively.

[0105] Example 3

[0106] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0107] The front side of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8. The side side has been processed by precision stamping, with a bright band of more than 98% and a roughness of less than Ra 0.8.

[0108] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc plating layer, an alkali copper layer, a pyrolytic copper layer, and a silver layer, which are disposed on the semi-exposed area of ​​the aluminum terminal material surface, with thicknesses of 0.5μm, 2μm, 2μm, 2μm, and 0.5μm, respectively.

[0109] Example 4

[0110] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0111] The front side of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8. The side side has been processed by precision stamping, with a bright band of more than 98% and a roughness of less than Ra 0.8.

[0112] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc plating layer, an alkali copper layer, a pyrometallurgical copper layer, and a silver layer on the fully exposed area of ​​the aluminum terminal material surface, with thicknesses of 0.5μm, 2μm, 3μm, 5μm, and 5μm, respectively.

[0113] Example 5

[0114] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0115] The front side of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8. The side side has been processed by precision stamping, with a bright band of more than 98% and a roughness of less than Ra 0.8.

[0116] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc plating layer, an alkali copper layer, a pyrometallurgical copper layer, and a silver layer on the fully exposed area of ​​the aluminum terminal material surface, with thicknesses of 0.5μm, 2μm, 3μm, 5μm, and 20μm, respectively.

[0117] Comparative Example 1

[0118] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the corrosion-resistant composite layer consists only of a zinc layer, a secondary zinc plating layer, and an alkaline copper layer, with thicknesses of 0.5 μm, 2 μm, and 27 μm, respectively.

[0119] The thickness of each comparative example is kept the same as that of Example 1, and the total thickness of each layer remains unchanged.

[0120] Comparative Example 2

[0121] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the corrosion-resistant composite layer consists only of a zinc layer, a secondary zinc plating layer, and a copper plating layer, with thicknesses of 0.5 μm, 2 μm, and 27 μm, respectively.

[0122] Comparative Example 3

[0123] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the corrosion-resistant composite layer consists only of a zinc layer, a secondary zinc plating layer, and a silver layer, with thicknesses of 0.5 μm, 2 μm, and 27 μm, respectively.

[0124] Comparative Example 4

[0125] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the corrosion-resistant composite layer consists only of a zinc layer, a secondary zinc plating layer, a copper plating layer, and a silver layer, with thicknesses of 0.5 μm, 2 μm, 12 μm, and 15 μm, respectively.

[0126] Comparative Example 5

[0127] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the corrosion-resistant composite layer consists only of a zinc layer, a secondary zinc plating layer, an alkali copper layer, and a silver layer, with thicknesses of 0.5 μm, 2 μm, 12 μm, and 15 μm, respectively.

[0128] Comparative Example 6

[0129] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the corrosion-resistant composite layer consists only of a zinc layer, a secondary zinc plating layer, an alkali copper layer, and a pyrolytic copper layer, with thicknesses of 0.5 μm, 2 μm, 2 μm, and 25 μm, respectively.

[0130] Comparative Example 7

[0131] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the corrosion-resistant composite layer consists only of a zinc layer, a secondary zinc plating layer, and a nickel layer, with thicknesses of 0.5 μm, 2 μm, and 27 μm, respectively.

[0132] Comparative Example 8

[0133] This comparative example provides a wire-cut aluminum material: the coating is the same as in Example 1, but it has not undergone precision stamping and polishing.

[0134] Comparative Example 9

[0135] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the coating is the same as that in Example 1 and has not undergone roll forming.

[0136] Comparative Examples 10-12

[0137] These comparative examples each provide an aluminum terminal with a corrosion-resistant composite layer, which differs from Example 3 in that the coating thickness is different from that of Example 3, as shown in Table 1.

[0138] Comparative Example 13

[0139] This comparative example provides a terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the coating thickness is different from that of Example 1, as shown in Table 1.

[0140] Comparative Example 14

[0141] This comparative example provides an aluminum terminal with a transition layer and a conventional electroless nickel layer on its surface.

[0142] Table 1 shows a comparison of the salt spray corrosion resistance test results of the aluminum terminals of the embodiments, the aluminum terminals of the comparative examples, and the wire-cut aluminum material of the comparative example 8.

[0143] Table 1

[0144]

[0145] Salt spray corrosion resistance test:

[0146] The process shall be carried out in accordance with the national standard GB / T 2423.17-2008. Acceptance criteria: No corrosion, pitting, peeling, or blistering shall be observed in the coating; the coating shall be free of spots and color changes.

[0147] Test results:

[0148] The three coatings of alkali copper, pyrometallurgical copper, and silver are layered together, resulting in a better anti-corrosion effect than a single coating.

[0149] example:

[0150] Single coating: Chloride ions can penetrate a single silver layer in a very short time, causing corrosion of the substrate.

[0151] In this invention, chloride ions penetrate the outermost silver layer and then encounter the dense copper layer, thus failing to corrode the substrate. Therefore, the corrosion-resistant composite layer of this invention improves the overall corrosion resistance.

[0152] Compared with conventional electroplating methods (Comparative Example 14, where a 3μm thick electroless nickel layer is electroless plated on the transition layer), conventional salt spray corrosion occurs after 48 hours (as shown in Table 1). The solution provided by the present invention has superior corrosion resistance.

[0153] Comparative Example 8 was fabricated on a wire-cut substrate. In the corrosion resistance test, corrosion pits first appeared on the side of this sample after 72 hours. The corrosion pit details are as follows. Figure 9 As shown.

[0154] The aluminum terminals with a corrosion-resistant composite layer in the exposed area provided in Embodiment 1 of this invention have a salt spray corrosion resistance of up to 240 hours, without any corrosion spots, white rust, or red rust appearing; specifically as follows... Figure 7 As shown, the left figure shows the condition of a conventional coating, which shows that rust and corrosion spots have appeared on the coating. The right figure shows the condition of the coating of Embodiment 1 of the present invention, which shows that no rust or corrosion spots have appeared on the surface of the coating of Embodiment 1 of the present invention.

[0155] The aluminum terminal with a corrosion-resistant composite layer in the semi-exposed area provided in Embodiment 3 of the present invention can achieve a salt spray corrosion resistance of 60 hours. Although the corrosion resistance time is not as good as that in Embodiment 1, the test was conducted under complete exposure to a salt spray environment. However, in the actual use of aluminum terminals, this area is not completely exposed to the environment. Therefore, the lower corrosion resistance time obtained in Embodiment 3 compared to Embodiment 1 will not affect the service life of the aluminum terminal. This corrosion-resistant composite layer will still have a good corrosion resistance effect. That is, if the semi-exposed area of ​​the aluminum terminal in Embodiment 1 is provided with the corrosion-resistant composite layer in Embodiment 3, the service life of the corrosion-resistant composite layer in the semi-exposed area will not be lower than the service life of the corrosion-resistant composite layer in the exposed area, and the overall corrosion resistance of the aluminum terminal is also guaranteed.

[0156] Based on this, the present invention can set different corrosion-resistant composite layers at different locations of aluminum terminals according to regional characteristics (whether exposed to the environment, the level of corrosion resistance requirements) and usage needs, thereby reducing costs while ensuring corrosion resistance and service life.

[0157] Thermal shock test: The aluminum terminal was heated to 500℃ and held for 30 minutes, then rapidly cooled to 20℃ using water cooling. Observation revealed that the corrosion-resistant composite layer on the surface of the aluminum terminal was in good condition, with no blistering, indicating good adhesion between the corrosion-resistant composite layer and the aluminum terminal.

[0158] Experiment on the effect of surface roughness and gloss band on corrosion resistance:

[0159] Examples 6, 8, and 15-17: The same corrosion-resistant layer (i.e., the corrosion-resistant composite layer in Example 1) was formed on the surfaces of terminals (including wire-cut materials) with different surface roughnesses (surface roughness before the preparation of the corrosion-resistant layer) and different proportions of bright bands. Salt spray tests were then conducted (according to national standard GB / T 2423.17-2008) to evaluate the influence of surface roughness and the proportion of bright bands on salt spray corrosion resistance. The acceptance criteria were: no corrosion, no surface pitting, peeling, blistering, etc., and no spots or color changes in the coating. The experimental results are shown in Table 2.

[0160] Table 2

[0161]

[0162] According to the experimental data of Example 6, Comparative Example 15 and Comparative Example 16 given in Table 2, it can be seen that under the same conditions, the smaller the surface roughness of the substrate surface, the longer the salt spray resistance time of the aluminum terminal with the corrosion resistant composite layer on the surface, and the better the salt spray corrosion resistance.

[0163] According to the experimental data of Example 6, Comparative Example 17 and Comparative Example 8 given in Table 2, it can be seen that under the same conditions and similar surface roughness, the higher the proportion of bright band on the surface of the substrate, the longer the salt spray resistance time of the aluminum terminal with the corrosion resistant composite layer on the surface, and the better the salt spray corrosion resistance.

[0164] The technical solution of the present invention has the following advantages:

[0165] 1. Low cost and simple process; 2. Excellent performance of the composite layer. When a thicker silver layer is used, it can meet the 240H salt spray corrosion resistance requirement, and when a thinner silver layer is used, it can meet the 60H salt spray corrosion resistance requirement. It can be used in different situations and meet different corrosion resistance requirements; 3. Excellent adhesion of each layer; 4. Although the aluminum terminal surface is provided with a corrosion-resistant composite layer, the conductivity is still very good.

Claims

1. A corrosion-resistant composite layer, comprising: The transition layer includes an alkaline copper layer, a pyrometallurgical copper layer, and a silver layer; the transition layer includes a zinc layer, or a combination of a zinc layer and a secondary zinc plating layer. The thickness of the alkali copper layer is 1-10 μm, the thickness of the pyrometallurgical copper layer is 2-18 μm, and the thickness of the silver layer is 0.2-3 μm or 8-15 μm. The pyrometallurgical copper layer is disposed between the alkali copper layer and the silver layer, and the transition layer is disposed on the side of the alkali copper layer that does not contact the pyrometallurgical copper layer.

2. The corrosion-resistant composite layer according to claim 1, wherein, The thickness of the alkali copper layer is 1-6 μm.

3. The corrosion-resistant composite layer according to claim 1, wherein, The thickness of the copper plating layer is 5-15 μm.

4. The corrosion-resistant composite layer according to claim 3, wherein, The thickness of the zinc layer is 0.1-10 μm.

5. The corrosion-resistant composite layer according to claim 4, wherein, The thickness of the zinc layer is 0.5-1 μm.

6. The corrosion-resistant composite layer according to claim 1, wherein, The thickness of the secondary zinc plating layer is 0.1-10 μm.

7. The corrosion-resistant composite layer according to claim 6, wherein, The thickness of the secondary zinc plating layer is 1.5-2.5 μm.

8. The corrosion-resistant composite layer according to any one of claims 1-7, wherein, The zinc layer, secondary zinc plating layer, alkali copper layer, pyrometallurgical copper layer, and silver layer are all electroplated layers.

9. The corrosion-resistant composite layer according to any one of claims 1-7, wherein, The corrosion-resistant composite layer also includes a chemical copper layer, which is disposed on the surface of the alkali copper layer or the pyrolytic copper layer.

10. The corrosion-resistant composite layer according to claim 9, wherein, The thickness of the chemical copper layer is 3-25 μm.

11. The corrosion-resistant composite layer according to claim 10, wherein, The thickness of the chemical copper layer is 5-15 μm.

12. The corrosion-resistant composite layer according to claim 8, wherein, The corrosion-resistant composite layer also includes a chemical copper layer, which is disposed on the surface of the alkali copper layer or the pyrolytic copper layer.

13. The corrosion-resistant composite layer according to claim 12, wherein, The thickness of the chemical copper layer is 3-25 μm.

14. The corrosion-resistant composite layer according to claim 13, wherein, The thickness of the chemical copper layer is 5-15 μm.

15. The corrosion-resistant composite layer according to any one of claims 1-7 and 10-14, wherein, The corrosion-resistant composite layer also includes an acid copper layer, which is disposed on the surface of the alkali copper layer or the surface of the pyrolytic copper layer.

16. The corrosion-resistant composite layer according to claim 15, wherein, The thickness of the acid copper layer is 1-20 μm.

17. The corrosion-resistant composite layer according to claim 16, wherein, The thickness of the acid copper layer is 3-10 μm.

18. The corrosion-resistant composite layer according to claim 8, wherein, The corrosion-resistant composite layer also includes an acid copper layer, which is disposed on the surface of the alkali copper layer or the surface of the pyrolytic copper layer.

19. The corrosion-resistant composite layer according to claim 18, wherein, The thickness of the acid copper layer is 1-20 μm.

20. The corrosion-resistant composite layer according to claim 19, wherein, The thickness of the acid copper layer is 3-10 μm.

21. The corrosion-resistant composite layer according to claim 9, wherein, The corrosion-resistant composite layer also includes an acid copper layer, which is disposed on the surface of the alkali copper layer or the surface of the pyrolytic copper layer.

22. The corrosion-resistant composite layer according to claim 21, wherein, The thickness of the acid copper layer is 1-20 μm.

23. The corrosion-resistant composite layer according to claim 22, wherein, The thickness of the acid copper layer is 3-10 μm.

24. The corrosion-resistant composite layer according to any one of claims 1-7, 10-14, and 16-23, wherein, The corrosion-resistant composite layer also includes a Watt nickel layer, which is disposed on the surface of the alkali copper layer or the pyrolytic copper layer.

25. The corrosion-resistant composite layer according to claim 24, wherein, The thickness of the Watt nickel layer is 1-20 μm.

26. The corrosion-resistant composite layer according to claim 25, wherein, The thickness of the Watt nickel layer is 3-9 μm.

27. The corrosion-resistant composite layer according to claim 8, wherein, The corrosion-resistant composite layer also includes a Watt nickel layer, which is disposed on the surface of the alkali copper layer or the pyrolytic copper layer.

28. The corrosion-resistant composite layer according to claim 27, wherein, The thickness of the Watt nickel layer is 1-20 μm.

29. The corrosion-resistant composite layer according to claim 28, wherein, The thickness of the Watt nickel layer is 3-9 μm.

30. The corrosion-resistant composite layer according to claim 9, wherein, The corrosion-resistant composite layer also includes a Watt nickel layer, which is disposed on the surface of the alkali copper layer or the pyrolytic copper layer.

31. The corrosion-resistant composite layer according to claim 30, wherein, The thickness of the Watt nickel layer is 1-20 μm.

32. The corrosion-resistant composite layer according to claim 31, wherein, The thickness of the Watt nickel layer is 3-9 μm.

33. The corrosion-resistant composite layer according to claim 15, wherein, The corrosion-resistant composite layer also includes a Watt nickel layer, which is disposed on the surface of the alkali copper layer or the pyrolytic copper layer.

34. The corrosion-resistant composite layer according to claim 33, wherein, The thickness of the Watt nickel layer is 1-20 μm.

35. The corrosion-resistant composite layer according to claim 34, wherein, The thickness of the Watt nickel layer is 3-9 μm.

36. A method for preparing the corrosion-resistant composite layer according to any one of claims 1-35, comprising the following steps: An alkaline copper layer, a pyrometallurgical copper layer, and a silver layer are formed on the surface of a substrate through electroplating.

37. The preparation method according to claim 36, wherein, Based on the total volume of the electroplating solution, the electroplating solution used for the alkaline copper layer contains: cuprous cyanide: 40-50 g / L, total sodium cyanide: 40-60 g / L, free sodium cyanide: 8-14 g / L, potassium sodium tartrate: 30-45 g / L, sodium hydroxide: 1-3 g / L, and additives: 3-5 mL / L; the electroplating temperature for the alkaline copper layer is 40-50℃, the anode-to-cathode area ratio is 1:1-2, and the current density is 0.7-1.2 A / dm². 2 The electroplating time is 5-15 minutes.

38. The preparation method according to claim 37, wherein, The ratio of the anode and cathode areas is 1:1.

5.

39. The preparation method according to claim 36, wherein, Based on the total volume of the electroplating solution, the electroplating solution used for the charred copper layer contains: copper pyrophosphate: 50-70 g / L, potassium pyrophosphate: 300-450 g / L, ammonium citrate: 15-30 g / L, and ammonia water: 2-5 mL / L; the electroplating temperature of the charred copper layer is 40-50℃, and the current density is 0.7-1.2 A / dm³. 2 The ratio of anode to cathode area is 1:1-2, and the electroplating time is 50-90 minutes.

40. The preparation method according to claim 39, wherein, The ratio of the anode and cathode areas is 1:1.

5.

41. The preparation method according to claim 39, wherein, The electroplating time is 70 minutes.

42. The preparation method according to claim 36, wherein, Based on the total volume of the electroplating solution, the electroplating solution used for the silver layer contains: silver cyanide: 30-50 g / L, potassium cyanide: 130-150 g / L, free potassium cyanide: 45-60 g / L, potassium carbonate: 15-25 g / L, potassium hydroxide: 4-10 g / L, and additives: 20-30 g / L; the electroplating temperature is 20-25℃, the anode-cathode area ratio is 1:1-2, and the current density is 0.2-0.5 A / dm². 2 The electroplating time is 1-90 minutes.

43. The preparation method according to claim 42, wherein, The ratio of the anode and cathode areas is 1:1.

5.

44. The preparation method according to claim 42, wherein, The electroplating time is 30-60 minutes.

45. The preparation method according to claim 44, wherein, The electroplating time is 40 minutes.

46. ​​A method for treating aluminum substrate with corrosion resistance, comprising the step of forming a corrosion-resistant composite layer as described in any one of claims 1-35 on the surface of the aluminum substrate.

47. The method according to claim 46, wherein, The corrosion resistance mentioned refers to resistance to salt spray corrosion.

48. The method according to claim 46, wherein, The surface roughness of the aluminum substrate is less than Ra 3.

6.

49. The method according to claim 48, wherein, The surface roughness of the aluminum substrate is less than Ra 0.

8.

50. A corrosion-resistant aluminum terminal, wherein, The surface of the corrosion-resistant aluminum terminal is provided with a corrosion-resistant composite layer as described in any one of claims 1-35 in a portion or all of the area.

51. The method for preparing the corrosion-resistant aluminum terminal according to claim 50, comprising the following steps: The front side of the aluminum terminals is rolled and polished. The sides of the aluminum terminals are stamped. The corrosion-resistant aluminum terminal is obtained by electroplating an alkali copper layer, a pyrometallurgical copper layer, and a silver layer on the front and sides of the treated aluminum terminal in sequence.

52. The preparation method according to claim 51, wherein, Before electroplating to form an alkaline copper layer, a transition layer is first formed on the front and sides of the treated aluminum terminal.

53. The preparation method according to claim 51, wherein, The surface roughness of aluminum terminals that have undergone roll forming and polishing is less than Ra 3.

6.

54. The preparation method according to claim 53, wherein, The surface roughness of aluminum terminals after roll forming and polishing is less than Ra 0.

8.

55. The preparation method according to claim 51, wherein, The side roughness of the aluminum terminals after roll forming is less than Ra 3.6, and the bright band is greater than 50%.

56. The preparation method according to claim 55, wherein, The side roughness of the aluminum terminals after roll forming is less than Ra 0.

8.

57. The preparation method according to claim 55, wherein, The bright band of the aluminum terminals after roll forming is greater than 98%.

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