Corrosion-resistant composite layer, preparation method therefor, aluminum substrate corrosion-resistance treatment method, corrosion-resistant aluminum terminal and preparation method therefor

Abstract

Provided in the present disclosure are a corrosion-resistant composite layer, a preparation method therefor, an aluminum substrate corrosion-resistance treatment method, a corrosion-resistant aluminum terminal and a preparation method therefor. The corrosion-resistant composite layer comprises: a copper layer prepared by alkaline copper electroplating, a copper layer prepared by copper pyrophosphate electroplating and a silver layer, the thickness of the copper layer prepared by alkaline copper electroplating being 1-10 μm, the thickness of the copper layer prepared by copper pyrophosphate electroplating being 2-18 μm, and the thickness of the silver layer being 0.2-25 μm. The aluminum substrate corrosion-resistance treatment method comprises a step of arranging the corrosion-resistant composite layer on the surface of an aluminum substrate. 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 solutions provided by the present disclosure has good resistance to salt spray corrosion, and the aluminum terminal provided with the corrosion-resistant composite layer can achieve salt spray resistance for 240 hours.

Description

A corrosion-resistant composite layer and its preparation method, an aluminum substrate corrosion-resistant treatment method, and a corrosion-resistant aluminum terminal and its preparation method

[0001] Related applications

[0002] This application claims priority to the Chinese invention patent application with application number 202310935055.0 filed on July 27, 2023, and cites the entire contents disclosed in the above patent application as part of this application. Technical Field

[0003] The present disclosure relates to a corrosion-resistant composite layer and a preparation method thereof, a corrosion-resistant treatment method for an aluminum substrate, and a corrosion-resistant aluminum terminal and a preparation method thereof, and belongs to the technical field of corrosion resistance. Background Art

[0004] 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 has restricted their further application. The chemical properties of aluminum and its alloys limit their application: 1. They are easily oxidized in air to form an oxide film, which greatly increases terminal resistance and affects power transmission. 2. Aluminum has a standard electrode potential of -1.662V, making it susceptible to potential corrosion when connected to other metals with a more positive standard electrode potential (such as copper), resulting in connection failure and, in severe cases, a short circuit.

[0005] Current electroplating, chemical plating, spraying, laser surface treatment and other processes can protect the substrate by coating a film layer on the surface of aluminum and its alloys. However, the results of salt spray resistance tests are not ideal. The salt spray time of common aluminum workpieces can only last for 48 hours before corrosion occurs, which greatly limits the service life of the aluminum workpiece in the assembly.

[0006] Current electroplating manufacturers have done little research and development on aluminum electroplating processes. They only perform secondary zinc deposition followed by nickel plating to proceed to the next electroplating step. The choice of plating solutions varies and the effects are average, making it difficult to meet the requirements for electroplating of highly corrosion-resistant aluminum workpieces, especially for aluminum workpieces used in harsh environments in military, aerospace, automotive and other fields.

[0007] Summary of the Invention

[0008] In order to solve the above technical problems, the purpose of the present disclosure is to provide a corrosion-resistant composite layer, which has excellent salt spray corrosion resistance and can be used for corrosion-resistant treatment of aluminum substrates.

[0009] To achieve the above objectives, the present disclosure first provides a corrosion-resistant composite layer, which includes: an alkali copper layer, a char copper layer, and a silver layer.

[0010] In the above-mentioned corrosion-resistant composite layer, illustratively, the thickness of the alkaline copper layer is 1-10 μm, the thickness of the calcined copper layer is 2-18 μm, and the thickness of the silver layer is 0.2-25 μm.

[0011] In the above-mentioned corrosion-resistant composite layer, illustratively, the charred copper layer is provided between the alkali copper layer and the silver layer, that is, the alkali copper layer, the charred copper layer, and the silver layer are provided in sequence.

[0012] In the above-mentioned corrosion-resistant composite layer, the thickness of the alkaline copper layer is illustratively 1-6 μm, and further illustratively 2-4 μm.

[0013] In the above-mentioned corrosion-resistant composite layer, the thickness of the char copper layer is illustratively 5-15 μm, and further illustratively 8-10 μm.

[0014] In the above-mentioned corrosion-resistant composite layer, the silver layer can have different thicknesses depending on the different 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 semi-exposed areas. The requirements for corrosion resistance are low, and a thinner silver layer can be set. Exemplarily, the thickness of the silver layer (thin silver layer) is 0.2-3μm, and further exemplary is 0.5-2μm; in the completely exposed area where the aluminum terminal has a large contact area with the environment, the requirements for corrosion resistance are high, and a thicker silver layer needs to be set. Exemplarily, the thickness of the silver layer (thick silver layer) is 8-15μm, and further exemplary is 10-15μm. In some cases, the thickness of the silver layer can be further controlled to 10-13μm.

[0015] In the aforementioned corrosion-resistant composite layer, the corrosion-resistant composite layer illustratively further includes a transition layer, which is disposed on the side of the alkali copper layer that is not in contact with the char copper layer. The transition layer is disposed between the alkali copper layer and the substrate requiring corrosion resistance treatment to serve as a transition, and can be achieved using an appropriate surface treatment method.

[0016] In the above-mentioned corrosion-resistant composite layer, illustratively, the transition layer includes a zinc layer, or a combination of a zinc layer and a secondary zinc deposition layer; the zinc layer (or zinc layer, secondary zinc deposition layer), alkali copper layer, char copper layer, and silver layer are arranged in sequence. The zinc layer and the secondary zinc deposition layer serve as transition layers for subsequent electroplating layers, which can ensure their adhesion. According to a specific embodiment of the present disclosure, the combination of the zinc layer and the secondary zinc deposition layer includes a method in which the zinc layer and the secondary zinc deposition layer are superimposed (superimposed up and down, the secondary zinc deposition layer covers the zinc layer); and a method in which the zinc layer and the secondary zinc deposition layer are located in different areas of the same layer, and in this method, a portion of the two can be superimposed on each other.

[0017] The transition layer disclosed in the present invention is not limited to the zinc layer or the secondary zinc deposition layer, and other metal or alloy materials can also be used as long as it 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 through surface treatment processes such as spraying and vacuum electroplating.

[0018] In the above-mentioned corrosion-resistant composite layer, the thickness of the zinc layer is exemplarily 0.1-10 μm, and further exemplarily 0.5-1 μm.

[0019] In the above-mentioned corrosion-resistant composite layer, illustratively, the thickness of the secondary zinc deposition layer is 0.1-10 μm, and further illustratively is 1.5-2.5 μm.

[0020] In the above-mentioned corrosion-resistant composite layer, illustratively, the zinc layer, the secondary zinc deposition layer, the alkali copper layer, the char copper layer, and the silver layer are electroplated layers respectively.

[0021] In the above-mentioned corrosion-resistant composite layer, illustratively, the corrosion-resistant composite layer further includes a chemical copper layer (or chemically plated copper layer).

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

[0023] In the above-mentioned corrosion-resistant composite layer, the thickness of the chemical copper layer is illustratively 3-25 μm, and further illustratively 5-15 μm.

[0024] In the above-mentioned corrosion-resistant composite layer, illustratively, the corrosion-resistant composite layer further includes an acid copper layer.

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

[0026] In the above-mentioned corrosion-resistant composite layer, the thickness of the acid copper layer is illustratively 1-20 μm, and further illustratively 3-10 μm.

[0027] In the above-mentioned corrosion-resistant composite layer, illustratively, the corrosion-resistant composite layer further includes a Watt nickel layer.

[0028] In the above-mentioned corrosion-resistant composite layer, illustratively, the Watt nickel layer is arranged on the surface of the alkali copper layer or the surface of the charred copper layer, that is, the Watt nickel layer can be arranged in the following ways: (1) arranged on the side surface of the alkali copper layer that is not in contact with the charred copper layer; (2) arranged between the alkali copper layer and the charred copper layer; (3) arranged on the side surface of the charred copper layer that is not in contact with the alkali copper layer.

[0029] In the above-mentioned corrosion-resistant composite layer, illustratively, the thickness of the Watt nickel layer is 1-20 μm, and further illustratively, 3-9 μm.

[0030] In the above-mentioned corrosion-resistant composite layer, illustratively, the corrosion-resistant composite layer can simultaneously include two or three of the chemical copper layer, the acid copper layer, and the Watt nickel layer, and as for their specific positions, they can be set at any one, two or three of the three positions: the side surface of the alkali copper layer that is not in contact with the coke layer, between the alkali copper layer and the coke layer, and the side surface of the coke layer that is not in contact with the alkali copper layer. When two or three of them choose the same position, their order with respect to each other can be arbitrary. For example, when the chemical copper layer, the acid copper layer, and the Watt nickel layer are all located between the alkali copper layer and the coke layer, the chemical copper layer can be located between the acid copper layer and the Watt nickel layer, the acid copper layer can be located between the chemical copper layer and the Watt nickel layer, or the Watt nickel layer can be located between the chemical copper layer and the acid copper layer.

[0031] In a salt spray environment, chloride ions penetrate the coating and come into contact with the substrate, corroding the substrate. The corrosion-resistant composite layer provided by the present disclosure utilizes an alkali copper layer, a charred copper layer, and a silver layer to provide layered protection. When one coating is penetrated, the other layer below can still block chloride ion penetration, providing protection. This improves the corrosion resistance of the substrate as a whole and prevents chloride ions from penetrating the coating and coming into contact with the substrate. When a thick silver layer is used, salt spray resistance of 240 hours can be achieved, meeting the corrosion resistance requirements of the fully exposed area of ​​the aluminum terminal. When a thin silver layer is used, salt spray resistance of 60 hours can be achieved, meeting the corrosion resistance requirements of the semi-exposed area of ​​the aluminum terminal.

[0032] The present disclosure also provides a method for preparing the above-mentioned corrosion-resistant composite layer, which comprises the following steps: forming an alkali copper layer, a char copper layer, and a silver layer in sequence on the surface of a substrate by electroplating to obtain the corrosion-resistant composite layer.

[0033] In the above-mentioned method for preparing the corrosion-resistant composite layer, the electroplating solution used for the alkaline copper layer, for example, contains, based on the total volume of the electroplating solution, 40-50 g / L of cuprous cyanide, 40-60 g / L of total sodium cyanide, 8-14 g / L of free sodium cyanide, 30-45 g / L of potassium sodium tartrate, 1-3 g / L of sodium hydroxide, and 3-5 mL / L of an additive (one or a mixture of two or more of polyethylene glycol, fatty amine polyoxyethylene ether (AEO), and OP series octylphenol polyoxyethylene ether). The remainder of the electroplating solution is water.

[0034] In the above-mentioned method for preparing the corrosion-resistant composite layer, illustratively, the temperature of the electroplated alkaline copper layer is 40-50°C, the anode-cathode area ratio is 1:1-2 (illustratively 1:1.5), and the current density is 0.7-1.2A / dm 2 , the electroplating time is 5-15min.

[0035] In the above-described method for preparing the corrosion-resistant composite layer, the electroplating solution used for the copper layer, for example, contains, based on the total volume of the electroplating solution, 50-70 g / L of copper pyrophosphate, 300-450 g / L of potassium pyrophosphate, 15-30 g / L of ammonium citrate, and 2-5 mL / L of aqueous ammonia. The remainder of the electroplating solution is water.

[0036] In the above-mentioned method for preparing the corrosion-resistant composite layer, for example, the temperature of the electroplated copper layer is 40-50°C, and the current density is 0.7-1.2A / dm 2 The area ratio of the anode and cathode is 1:1-2 (exemplarily 1:1.5), and the electroplating time is 50-90 min (exemplarily 70 min).

[0037] In the above-mentioned method for preparing the corrosion-resistant composite layer, the electroplating solution used for the silver layer illustratively contains, based on the total volume of the electroplating solution, 30-50 g / L of silver cyanide, 130-150 g / L of potassium cyanide, 45-60 g / L of free potassium cyanide, 15-25 g / L of potassium carbonate, 4-10 g / L of potassium hydroxide, and 20-30 g / L of an additive (one or a mixture of two or more of thiocarbamate, sodium lauryl sulfonate, and OP series octylphenol polyoxyethylene ether). The remainder of the electroplating solution is water.

[0038] In the method for preparing the corrosion-resistant composite layer, for example, the temperature of the electroplated silver layer is 20-25°C, the anode-cathode area ratio is 1:1-2 (exemplarily 1:1.5), and the current density is 0.2-0.5A / dm 2 , the electroplating time is 1-90 min (exemplarily 30-60 min, exemplary 40 min).

[0039] In the preparation method of the above-mentioned corrosion-resistant composite layer, for example, the alkali copper layer, the char copper layer, the silver layer, etc. can be subjected to a pulse electroplating process, which can further improve their original density, thereby making the electroplated layer denser, with fewer pores and stronger salt spray resistance.

[0040] In the above-mentioned method for preparing the corrosion-resistant composite layer, illustratively, when a chemical copper layer, an acid copper layer, and a Watt nickel layer are contained, these layers can be obtained by corresponding methods at an appropriate time.

[0041] In the above-mentioned method for preparing the corrosion-resistant composite layer, illustratively, when a transition layer such as a zinc layer and a secondary zinc deposition layer is included, the transition layer is formed first, and then the alkaline copper layer, the char copper layer, the silver layer, etc. are formed. Among them, the zinc layer and the secondary zinc deposition layer can be prepared by conventional electroplating methods.

[0042] In the above-mentioned method for preparing the corrosion-resistant composite layer, in order to ensure its electroplating bonding strength, other steps can be added to the electroplating process, such as adding acid activation treatment before each step, adding pure water washing and cleaning before each step, etc.

[0043] The present disclosure also provides a method for treating an aluminum substrate for corrosion resistance, which includes the step of providing a corrosion-resistant composite layer provided by the present disclosure on the surface of the aluminum substrate. The aluminum substrate disclosed in the present disclosure includes a pure aluminum substrate and an aluminum alloy substrate.

[0044] In the above-mentioned corrosion-resistant treatment method for an aluminum substrate, illustratively, corrosion resistance refers to resistance to salt spray corrosion.

[0045] In the above-mentioned corrosion resistance treatment method for an aluminum substrate, illustratively, the surface roughness of the aluminum substrate is less than Ra3.6, and further illustratively, less than Ra0.8.

[0046] The present disclosure also provides a corrosion-resistant aluminum terminal, wherein a partial area or the entire area of ​​the surface of the corrosion-resistant aluminum terminal is provided with the corrosion-resistant composite layer provided by the present disclosure.

[0047] In the above-mentioned corrosion-resistant aluminum terminal, the corrosion-resistant composite layer may cover the entire surface of the aluminum terminal, or may only cover the surface area that requires corrosion-resistant treatment.

[0048] The present disclosure also provides a method for preparing the corrosion-resistant aluminum terminal, which comprises the following steps:

[0049] The front surface of the aluminum terminal is rolled and polished;

[0050] Stamping the sides of the aluminum terminals;

[0051] A zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a charred copper layer, and a silver layer are sequentially formed on the front and side surfaces of the treated aluminum terminal by electroplating to obtain a corrosion-resistant aluminum terminal.

[0052] In the above-mentioned preparation method, rolling, polishing, and stamping processes can be performed only on the areas requiring corrosion resistance, not on the entire surface of the aluminum terminal. This localized treatment facilitates welding and can be combined with various joining processes, such as friction welding, friction stir welding, ultrasonic welding, molecular diffusion welding, and resistance welding, to produce highly reliable corrosion-resistant terminals that can be used in a variety of connection processes.

[0053] In the above-mentioned method for preparing the corrosion-resistant aluminum terminal, illustratively, by performing a roller-pressing process on the terminal material, the density of the terminal surface can be enhanced, thereby enhancing the corrosion resistance of the subsequent electroplating process.

[0054] In the above-mentioned method for preparing corrosion-resistant aluminum terminals, for example, polishing the terminal material can enhance the smoothness of the terminal surface and improve the corrosion resistance of the subsequent electroplating process. The polishing process can be performed by chemical polishing, mechanical polishing, etc.

[0055] In the method for preparing the corrosion-resistant aluminum terminal, the roughness of the front surface of the aluminum terminal after the rolling and polishing processes is exemplarily less than Ra 3.6, and further exemplarily less than Ra 0.8.

[0056] In the above-mentioned method for preparing the corrosion-resistant aluminum terminal, exemplarily, the side roughness of the aluminum terminal after rolling treatment is less than Ra 3.6 (further exemplarily, less than Ra 0.8), and the bright band is greater than 50% (further exemplarily, greater than 98%).

[0057] In the above-mentioned method for preparing the corrosion-resistant aluminum terminal, illustratively, when a transition layer is provided, the transition layer is first formed on the front and side surfaces of the treated aluminum terminal before the alkaline copper layer is formed by electroplating.

[0058] The corrosion-resistant composite layer prepared by the technical solution provided in the present disclosure has good salt spray corrosion resistance. The fully exposed area of ​​the aluminum terminal provided with the corrosion-resistant composite layer can achieve salt spray resistance for 240 hours, and the semi-exposed area can achieve salt spray resistance for 60 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG1 is a schematic diagram of an exemplary overall structure of an aluminum terminal with a corrosion-resistant composite layer provided by the present disclosure.

[0060] FIG2 is a schematic diagram of an exemplary electroplating process of an aluminum terminal with a corrosion-resistant composite layer provided by the present disclosure.

[0061] FIG3 is a schematic diagram of the roller pressing process.

[0062] Figure 4 shows the SEM images of conventional aluminum sheets and rolled aluminum sheets.

[0063] FIG5 is a schematic diagram of the polishing process.

[0064] Figure 6 shows the morphology of the side of the aluminum terminal obtained by ordinary stamping and precision stamping.

[0065] Figure 7 is a diagram of the sample state after the corrosion resistance test.

[0066] Figure 8 shows a sample with poor adhesion when direct electroplating of the copper and silver layers was performed.

[0067] FIG9 is a picture of corrosion spots appearing on the side of Comparative Example 8. DETAILED DESCRIPTION

[0068] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present disclosure, the technical solution of the present disclosure is now described in detail below, but it should not be understood as limiting the scope of implementation of the present disclosure.

[0069] The aluminum terminal provided by the present disclosure includes an aluminum terminal material and an electroplated film layer, wherein the aluminum terminal material is an unprocessed aluminum substrate in the shape of a terminal without an electroplated film layer. The aluminum terminal material has a terminal surface and a terminal side; the electroplated film layer (corrosion-resistant composite layer) includes: an alkali copper layer, a charred copper layer, and a silver layer, and the electroplated film layer may further include a zinc layer and a secondary zinc deposition layer. An exemplary overall structure of an aluminum terminal with a corrosion-resistant composite layer is shown in FIG1 , wherein a zinc layer 2, an alkali copper layer 3, a charred copper layer 4, and a silver layer 5 are sequentially provided on the surface of the aluminum substrate 1; if necessary, a secondary zinc deposition layer may be further provided between the zinc layer 2 and the alkali copper layer 3.

[0070] Figure 2 shows an exemplary electroplating process for aluminum terminals. The process includes the following steps: ultrasonic degreasing, alkaline cleaning, pickling, chemical zinc deposition, chemical stripping, secondary zinc deposition, activation, alkaline copper electroplating, coke copper electroplating, pre-silver plating, silver electroplating, post-treatment, pure water washing, and drying. The secondary zinc deposition step can be selected as needed. For example, the electroplating process may or may not include the secondary zinc deposition step based on specific requirements.

[0071] The technical solution disclosed in the present invention starts with a design that avoids contact between chloride ions and the substrate. The front of the material terminal is rolled and polished, and the roughness after treatment is less than Ra 3.6, and exemplarily less than Ra 0.8; the side of the material terminal is processed using a precision stamping process, and the bright band after treatment is greater than 50% (exemplarily greater than 98%) and the roughness is less than Ra 3.6 (exemplarily less than Ra 0.8).

[0072] The process diagram of the rolling treatment is shown in Figure 3, which is a method of rolling treatment, that is, the aluminum plate 32 sandwiched in the middle is repeatedly rolled by the upper and lower rolling wheels 31. The rolling treatment increases the surface density of the aluminum material by applying pressure through mechanical means, thereby reducing the porosity of the surface of the aluminum terminal material, improving its density, and preparing for the next step of the electroplating film coverage. The fewer the pores in the material, the fewer the pores in the electroplating film layer, and the higher the protectiveness. The SEM images of conventional aluminum plates and rolled aluminum plates are shown in Figure 4. In Figure 4, Figure a shows a conventional aluminum plate, and Figure b shows a rolled aluminum plate. It can be seen from Figure 4 that through the rolling treatment, the roughness of the aluminum plate surface is reduced and the flatness is greatly improved.

[0073] The polishing process is shown in Figure 5. The polishing process involves placing a terminal material 41 in a polishing tank 44 containing a polishing solution 42 and a magnetic needle 43. Magnetic polishing involves applying electricity to generate a magnetic field, which drives the stainless steel needle (i.e., the magnetic needle 43) into motion. During this motion, the magnetic needle 43 rubs against the surface of the terminal material 41, achieving a mechanical polishing effect and improving the surface finish and flatness of the terminal material 41.

[0074] Polishing and precision stamping processes are all used to improve the smoothness and flatness of the terminal material surface and sides.

[0075] By improving the flatness and smoothness of the terminal material, it can be greatly beneficial to the electroplating film layer. Because of the influence of the current, the electroplating process will accumulate more electroplating film layers at the electron-rich positions of the workpiece, which will cause the thickness of the electroplating film layer on the terminal surface to be uneven, and even a large number of pits to appear, causing the chloride ions in the salt mist to gather and penetrate. When the flatness of the terminal material is insufficient, due to the principle of tip discharge, the more curved the conductor surface is, the more charges will be accumulated in places with smaller relative surface areas. The uneven protrusions on the surface of the material will gather a large number of electrons, making the protruding positions on the surface of the workpiece after electroplating more convex and the concave positions more concave, thus forming small holes that easily gather salt mist solution, causing the penetration of chloride ions, and then causing corrosion. After being processed by the process disclosed in the present invention, the terminal material can effectively cover the electroplating film layer, effectively improving its corrosion resistance.

[0076] Alkali copper electroplating: Alkali copper electroplating is cyanide copper plating. Cyanide has a strong complexing ability in water, which can greatly increase the cathode polarization of electroplating, so that copper ions accumulate in large quantities at the cathode and deposit together, increasing the density of the electroplated film layer. The coating electroplated by the cyanide system is dense and reacts quickly and efficiently, and can cover the zinc layer with a dense and flat copper layer. In addition, copper is chemically inactive and has low internal stress during electroplating, making it an excellent intermediate coating and easy to electroplate subsequent metal coatings.

[0077] 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 ° C, cathode and anode area ratio of 1:1.5, current density: 0.7-1.2 A / dm 2 , electroplating time: 5-15min, electroplating layer thickness: exemplary 1-6μm.

[0078] In order to enhance the density of the coating, the present invention has carried out process optimization: Generally, in order to meet the requirements of electroplating efficiency and faster production, the current density of electroplating alkaline copper in electroplating plants is 4-10A / dm 2 , far higher than that disclosed herein. Current density directly affects the compactness of the coating. High current density weakens cathodic polarization and makes it easier to reach the overpotential for hydrogen ion precipitation in the solution, causing the hydrogen evolution side reaction during electroplating. The evolved hydrogen gas leaves pores in the coating, reducing the compactness of the coating. The alkaline copper electroplating process used in the present disclosure reduces the current density while increasing the concentration of the main salt, cuprous cyanide, and free sodium cyanide, thereby producing an alkaline copper coating with excellent electroplating efficiency and compactness.

[0079] Electroplated copper: The electroplated copper layer is copper pyrophosphate. The complexing ability of pyrophosphate in water is stronger than that of cyanide. The cathodic polarization effect in the pyrophosphate system is also stronger. Because [Cu(P2O7)2] 6- The more negative charges it carries, the greater the impact on the cathode process. At the same time, [Cu(P2O7)2] 6- Difficult to discharge, needs to be hydrolyzed into [CuP2O7] 2- To discharge and deposit the copper layer, [CuP2O7] 2- The hydrolysis of copper is slow, thus increasing the cathodic polarization again. The copper plating film is denser and has fewer pores, which can effectively prevent the penetration of chloride ions in salt spray tests and enhance the corrosion resistance of the workpiece.

[0080] 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 / dm 2 , temperature 40-50°C, cathode and anode area ratio of 1:1.5, electroplating time 50-90 min, electroplating thickness: exemplarily 5-15 μm. Similarly, to improve the density of the coating, the process used in the present disclosure is optimized to reduce the current density.

[0081] The present disclosure can bring the following advantages by cooperating with the alkali copper layer and the char copper layer:

[0082] 1. Enhance the bonding strength between the plating layers: Alkali copper is an excellent base plating layer and has a good bonding strength with the zinc layer of the substrate. If the alkaline copper is removed and coke copper is directly electroplated, poor adhesion is likely to occur (as shown in Figure 8), making the workpiece more susceptible to corrosion.

[0083] 2. Enhanced salt spray effect: Since the surface state of the substrate has a great influence on the electroplated layer, it is impossible to directly electroplate a very dense coating on the porous surface of the aluminum material. The present disclosure exemplarily adopts a scheme of gradually increasing density. The density of the zinc layer is lower than that of the alkaline copper, and the density of the alkaline copper is slightly lower than that of the coke. The density of these three layers is gradually improved, so that the density of the final coke layer is optimized. Therefore, the technical solution of the present disclosure exemplarily adopts a combination of 1-6μm alkaline copper + 5-15μm coke, which can effectively improve the corrosion resistance of the workpiece.

[0084] When the electroplated alkaline copper layer is thick, the coating is prone to roughness. Therefore, the present disclosure selects a 1-10 μm electroplating thickness (1-6 μm is exemplary). At this coating thickness, both bonding strength and density meet the requirements. The pyrolysis copper layer is selected between 2-18 μm. The thicker the coating, the better it covers its own pores. However, considering the influence of electroplating time, 5-15 μm is selected as an example.

[0085] The chemical copper layer (electroless copper plating) is formed by an autocatalytic chemical reaction, which deposits copper ions in an orderly manner on the substrate. Adding a chemical copper layer between each layer can achieve good bonding strength. The chemical copper layer is an excellent intermediate plating layer, which can enhance the bonding strength of the entire plating layer. At the same time, because the preparation process of the chemical copper layer is a simple chemical reaction, the thickness and porosity of the plating layer are not affected by the current distribution. Therefore, the chemical copper layer has a more uniform thickness, lower porosity, and good corrosion resistance. In the present disclosure, adding this layer can enhance the corrosion resistance of the entire plating layer.

[0086] The chemical copper plating parameters are as follows: composition of the chemical 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°C, pH 7.8-10.2, electroplating time 40-100 min, general plating speed 1 μm / 6 min, i.e.: 6 min-1 μm, i.e. 24 min-4 μm, 48 min-8 μm; the coating thickness can be controlled as needed by controlling the chemical copper plating parameters.

[0087] The acid copper layer (i.e., acid copper plating) is copper sulfate electroplated, has good bonding strength with other plating layers, and can serve as an excellent intermediate plating layer. In addition, the copper sulfate plating solution used in preparing the acid copper layer is stable and low in cost. Adding acid copper between or on both sides of the alkali copper layer and the coke copper can enhance the brightness and corrosion resistance of the overall plating layer itself.

[0088] The parameters for acid copper electroplating are as follows: plating solution composition: copper sulfate pentahydrate: 160-250g / L, sulfuric acid: 25-50mL / L, chloride ion: 40-120ppm, additives (one or more of polydisulfide propane sulfonate, 2-mercaptobenzimidazole, 1,2-ethylene thiourea, polyamine compounds): 4-15mL / L; current density 0.8-2.0A / dm 2 , temperature 20-30℃, anode and cathode area ratio of 1:1.5, electroplating time 20-80min, and coating thickness can be controlled by controlling electroplating parameters as needed.

[0089] Watt nickel layer (i.e. Watt nickel plating, bright nickel plating) is a nickel sulfate electroplating layer, which has good bonding strength with other plating layers and can be used as an excellent intermediate plating layer. When Watt nickel is added between or on both sides of the alkaline copper layer and the coke copper layer, a potential difference will be generated in a corrosive environment. It can act as an anode and be corroded first, thus protecting other plating layers and enhancing the brightness and corrosion resistance of the overall plating layer itself.

[0090] The parameters for the electroplating of the Watt nickel layer are as follows: the composition of the electroplating solution: nickel sulfate hexahydrate: 250-350g / L, nickel chloride hexahydrate: 60-95g / L, boric acid: 40-60g / L, additives (one or more mixtures of sodium lauryl sulfate, saccharin, butynediol ethoxylate): 6-12mL / L; pH 3-5, current density 0.8-2.0A / dm 2 , temperature 50-60℃, anode and cathode area ratio of 1:1.5, electroplating time 30-70min, and coating thickness can be controlled by controlling electroplating parameters as needed.

[0091] The function of pre-silver plating is to pre-plating a layer of silver at a high current density and dilute solution concentration to enhance the bonding strength between the electroplated film layers and prepare for the next step.

[0092] The electroplating parameters are as follows:

[0093] Silver cyanide: 30-120g / L, potassium cyanide: 80-200g / L, free potassium cyanide: 30-80g / L, potassium carbonate: 5-30g / L, potassium hydroxide: 2-20g / L; temperature: 20-25°C, cathode and anode area ratio: 1:1.5, current density: 0.5-2A / dm 2 , electroplating time: about 1min.

[0094] Electroplating silver: Electroplating silver is cyanide silver plating, which also has strong cathodic polarization, making the coating denser. Cyanide silver plating can effectively prevent the penetration of chloride ions in salt spray tests, enhancing the corrosion resistance of the workpiece. The standard electrode potential of silver is +0.799V. Silver is extremely chemically inert, reacting only with sulfur in air and almost no other substances. It has strong corrosion resistance. Electroplating silver on the surface of the workpiece can effectively improve corrosion resistance.

[0095] The electroplating parameters are as follows:

[0096] Silver cyanide: 30-50g / L, potassium cyanide: 130-150g / L, free potassium cyanide: 45-60g / L, potassium carbonate: 15-25g / L, potassium hydroxide: 4-10g / L, additive: 20-30g / L; temperature: 20-25°C, cathode and anode area ratio of 1:1.5, current density: 0.2-0.5A / dm 2 , electroplating time: 1-90min, electroplating thickness is controlled by controlling electroplating parameters as needed. Similarly, in order to improve the density of the coating, the process used in the present disclosure is optimized to reduce the current density.

[0097] In the corrosion-resistant composite layer provided by the present disclosure, the electroplated film layers such as the alkali copper layer, the calcined copper layer, and the silver layer all have a high density, which can effectively prevent the penetration of chloride ions in the salt spray test. Moreover, the metal / alloy layers interact and overlap with each other, so that the pores originally existing in the single plating layer are covered by other electroplated film layers. Even if chloride ions penetrate one electroplated film layer in the salt spray test, there are still other dense plating layers that can effectively prevent further penetration of chloride ions, thereby greatly improving the corrosion resistance of the aluminum substrate. The corrosion resistance can be further improved by adding a zinc layer, a secondary zinc deposition layer, an electroless copper layer, an acid copper layer, a watt nickel layer, etc.

[0098] Existing aluminum workpieces generally exhibit salt spray resistance, corroding after only 48 hours, making them unsuitable for use in harsh corrosive environments such as humid and marine environments. The technical solution provided by this disclosure: on the one hand, through rolling, polishing, and stamping processes, aluminum terminal materials with a superior surface condition are manufactured, facilitating subsequent electroplating (making the subsequent electroplated film layer denser); on the other hand, by covering with dense electroplated layers and the interaction between the electroplated layers, they can effectively hinder the penetration of chloride ions during salt spray testing, thereby inhibiting the occurrence of corrosion and greatly enhancing the corrosion resistance of the aluminum terminals.

[0099] The aluminum terminals of the embodiments and comparative examples of the present disclosure can be prepared by referring to the above method.

[0100] Example 1

[0101] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0102] The front of the aluminum terminal material was rolled and polished to a roughness of less than Ra 0.8. The side was precision stamped to a gloss band greater than 98% and a roughness less than Ra 0.8. The first image (left) in Figure 6 shows the side of the aluminum terminal produced by conventional stamping, while the second image (right) shows the side of the aluminum terminal produced by precision stamping. As shown in Figure 6, the side of the aluminum terminal produced by conventional stamping has a higher proportion of rough bands, while the side of the aluminum terminal produced by precision stamping is essentially glossy, with a proportion greater than 98%. The glossy bands were determined using a projector and the proportion of glossy bands was determined by calculating their length or area. The roughness of the front 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 finish. The filter sampling cutoff wavelength λc used in the roughness test is 0.8mm × 5, where 0.8mm is the sampling length and 5 is the magnification factor.

[0103] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a calcined copper layer, and a silver layer, applied to the fully exposed areas of the aluminum terminal material. The thicknesses are approximately 0.5μm, approximately 2.0μm, approximately 2.0μm, approximately 8 or 10μm, and approximately 15μm, respectively. After the composite corrosion-resistant layer is formed, the surface roughness of the aluminum terminal is also improved, down to 0.243μm.

[0104] Example 2

[0105] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0106] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0107] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a charred copper layer, and a silver layer provided on the fully exposed area of ​​the surface of the aluminum terminal material, with thicknesses of 0.5μm, 2μm, 2μm, 10μm, and 10μm respectively.

[0108] Example 3

[0109] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0110] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0111] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a charred copper layer, and a silver layer arranged in a semi-exposed area on the surface of the aluminum terminal material, with thicknesses of 0.5μm, 2μm, 2μm, 2μm, and 0.5μm respectively.

[0112] Example 4

[0113] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0114] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0115] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a charred copper layer, and a silver layer provided on the fully exposed area of ​​the surface of the aluminum terminal material, with thicknesses of 0.5μm, 2μm, 3μm, 5μm, and 5μm respectively.

[0116] Example 5

[0117] This embodiment provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0118] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8, and the side has been processed by precision stamping, with a bright band greater than 98% and a roughness of less than Ra 0.8;

[0119] The composite corrosion-resistant layer includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, a charred copper layer, and a silver layer provided on the fully exposed area of ​​the surface of the aluminum terminal material, with thicknesses of 0.5μm, 2μm, 3μm, 5μm, and 20μm respectively.

[0120] The present disclosure also provides comparative examples 1-9, the thickness of each comparative example is kept constant with that of Example 1, and the total thickness of each layer (ie, the total thickness of the corrosion-resistant composite layer) remains unchanged.

[0121] Comparative Example 1

[0122] 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 only includes a zinc layer, a secondary zinc deposition layer, and an alkaline copper layer, with thicknesses of 0.5 μm, 2 μm, and 27 μm.

[0123] Comparative Example 2

[0124] 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 only includes a zinc layer, a secondary zinc deposition layer, and a charred copper layer, with thicknesses of 0.5 μm, 2 μm, and 27 μm.

[0125] Comparative Example 3

[0126] 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 only includes a zinc layer, a secondary zinc deposition layer, and a silver layer, with thicknesses of 0.5 μm, 2 μm, and 27 μm.

[0127] Comparative Example 4

[0128] 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 only has a zinc layer, a secondary zinc deposition layer, a charred copper layer, and a silver layer, with thicknesses of 0.5 μm, 2 μm, 12 μm, and 15 μm.

[0129] Comparative Example 5

[0130] 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 only includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, and a silver layer, with thicknesses of 0.5 μm, 2 μm, 12 μm, and 15 μm.

[0131] Comparative Example 6

[0132] 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 only includes a zinc layer, a secondary zinc deposition layer, an alkaline copper layer, and a charred copper layer, with thicknesses of 0.5 μm, 2 μm, 2 μm, and 25 μm.

[0133] Comparative Example 7

[0134] 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 only includes a zinc layer, a secondary zinc deposition layer, and a nickel layer, with thicknesses of 0.5 μm, 2 μm, and 27 μm.

[0135] Comparative Example 8

[0136] This comparative example provides a wire-cut aluminum material: the coating is the same as that in Example 1, and no precision stamping and polishing are performed.

[0137] Comparative Example 9

[0138] 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 been subjected to a rolling process.

[0139] Comparative Examples 10-12

[0140] These comparative examples respectively 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.

[0141] Comparative Example 13

[0142] This comparative example provides a terminal with a corrosion-resistant composite layer, which differs from Example 1 in that the thickness of the coating is different from that of Example 1, as shown in Table 1.

[0143] Comparative Example 14

[0144] This comparative example provides an aluminum terminal, the surface of which is provided with a transition layer and a conventional chemical nickel layer.

[0145] Table 1 shows a comparison of the salt spray corrosion resistance test results of the aluminum terminal of the embodiment, the aluminum terminal of the comparative example, and the wire-cut aluminum material of comparative example 8.

[0146] Table 1

[0147] Salt spray corrosion resistance test:

[0148] The test is carried out in accordance with the national standard GB / T 2423.17-2008. Qualified standards: no corrosion, no surface pitting, peeling, blistering, etc., and no spots or color changes on the coating.

[0149] Test results:

[0150] The three coatings of alkaline copper, burnt copper and silver are superimposed on each other, and the anti-corrosion effect is better than that of a single coating.

[0151] example:

[0152] Single coating: Chloride ions penetrate the single silver layer in a very short time, causing corrosion of the substrate.

[0153] The present disclosure discloses that chloride ions penetrate the outermost layer of silver and also face a dense charred copper layer, which prevents them from corroding the substrate. Therefore, the corrosion-resistant composite layer disclosed in the present disclosure improves the overall corrosion resistance.

[0154] Compared with the conventional electroplating method (Comparative Example 14, a 3 μm thick chemical nickel layer is plated on the transition layer by chemical plating), conventional salt spray corrosion occurs after 48 hours (as shown in Table 1), and the solution provided by the present disclosure has better corrosion resistance.

[0155] Comparative Example 8 is based on wire-cut substrate processing. In the corrosion resistance test, corrosion spots first appeared on the side of the sample at 72 hours. The corrosion spot situation is shown in FIG9 .

[0156] The aluminum terminal provided in Example 1 of the present disclosure with a corrosion-resistant composite layer in the exposed area has a salt spray corrosion resistance of up to 240H, and no corrosion spots or white or red rust will appear; as shown in Figure 7, the left figure shows the case of conventional coating, such as the conventional coating of Comparative Example 14. It can be seen that rust and corrosion spots have appeared on the coating, and the right figure shows the case of the coating of Example 1 of the present disclosure. It can be seen that no rust or corrosion spots appear on the surface of the coating of Example 1 of the present disclosure.

[0157] The salt spray corrosion resistance of the aluminum terminal with a corrosion-resistant composite layer in the semi-exposed area provided by Example 3 of the present disclosure can reach 60H. Although it is not as good as Example 1 in terms of corrosion resistance time, the test is carried out in a completely exposed salt spray environment. In the actual use of the aluminum terminal, this area is not completely exposed to the environment. Therefore, the corrosion resistance time obtained by the test of Example 3 is lower than that of Example 1 and does not affect the service life of the aluminum terminal. This part of the corrosion-resistant composite layer will still exert a good corrosion resistance effect. That is, if the semi-exposed area of ​​the aluminum terminal of Example 1 is set with the corrosion-resistant composite layer in Example 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.

[0158] Based on this, the present disclosure can set different corrosion-resistant composite layers at different positions of the aluminum terminal according to regional characteristics (whether exposed to the environment, the level of corrosion resistance requirements) and usage requirements, thereby reducing costs while ensuring corrosion resistance and service life.

[0159] Thermal shock test: The aluminum terminal was heated to 500°C for 30 minutes and then rapidly cooled to 20°C using water cooling. Observation revealed that the corrosion-resistant composite layer on the aluminum terminal surface was in good condition, with no blistering, indicating good adhesion between the corrosion-resistant composite layer and the aluminum terminal.

[0160] Experiment on the influence of surface roughness and bright band on corrosion resistance:

[0161] In Example 6, Comparative Example 8, and Comparative Examples 15-17, the same corrosion-resistant layer (i.e., the corrosion-resistant composite layer described in Example 1) was formed on the surfaces of terminals (including wire-cut materials) with varying surface roughness (pre-corrosion-resistant layer preparation) and varying bright band percentages. Salt spray resistance tests (performed in accordance with the national standard GB / T 2423.17-2008) were then conducted to evaluate the effects of surface roughness and bright band percentage on salt spray corrosion resistance. Acceptance criteria included: no corrosion, no surface pitting, peeling, or blistering, and no spots or color changes in the coating. The experimental results are shown in Table 2.

[0162] Table 2

[0163] 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 of the aluminum terminal with the corrosion-resistant composite layer on the surface, and the better the salt spray corrosion resistance;

[0164] According to the experimental data of Example 6, Comparative Example 17, and Comparative Example 8 given in Table 2, it can be seen that when other conditions are the same and the surface roughness is similar, the higher the proportion of the bright band on the substrate surface, the longer the salt spray resistance of the aluminum terminal with a corrosion-resistant composite layer on the surface, and the better the salt spray corrosion resistance.

[0165] The technical solution disclosed in this disclosure has the following advantages:

[0166] 1. Low cost and simple process; 2. The composite layer has excellent performance. 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 applied to different situations and meet different corrosion resistance requirements; 3. The adhesion of each layer is excellent; 4. Although the surface of the aluminum terminal is provided with a corrosion-resistant composite layer, the conductivity is still very good.

Claims

1. A corrosion-resistant composite layer, comprising: Alkali copper layer, burnt copper layer, silver layer; Wherein, the thickness of the alkali copper layer is 1-10 μm, the thickness of the char copper layer is 2-18 μm, and the thickness of the silver layer is 0.2-25 μm; Preferably, the burnt copper layer is disposed between the alkali copper layer and the silver 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 charred copper layer is 5-15 μm.

4. The corrosion-resistant composite layer according to claim 1, wherein: The thickness of the silver layer is 0.2-3 μm or 8-15 μm.

5. The corrosion-resistant composite layer according to any one of claims 1 to 4, wherein: The corrosion-resistant composite layer further comprises a transition layer, wherein the transition layer is arranged on a side of the alkali copper layer that is not in contact with the coke copper layer; Preferably, the transition layer comprises a zinc layer, or a combination of a zinc layer and a secondary zinc deposition layer.

6. The corrosion-resistant composite layer according to claim 5, wherein: The thickness of the zinc layer is 0.1-10 μm, preferably 0.5-1 μm.

7. The corrosion-resistant composite layer according to claim 5, wherein: The thickness of the secondary zinc deposition layer is 0.1-10 μm, preferably 1.5-2.5 μm.

8. The corrosion-resistant composite layer according to any one of claims 1 to 7, wherein: The zinc layer, the secondary zinc deposition layer, the alkali copper layer, the char copper layer and the silver layer are electroplating layers respectively.

9. The corrosion-resistant composite layer according to any one of claims 1 to 8, wherein: The corrosion-resistant composite layer further comprises a chemical copper layer, wherein the chemical copper layer is disposed on the surface of the alkaline copper layer or the surface of the charred copper layer; Preferably, the thickness of the chemical copper layer is 3-25 μm, more preferably 5-15 μm.

10. The corrosion-resistant composite layer according to any one of claims 1 to 9, wherein: The corrosion-resistant composite layer further comprises an acid copper layer, wherein the acid copper layer is disposed on the surface of the alkali copper layer or the surface of the charred copper layer; Preferably, the acid copper layer has a thickness of 1-20 μm, more preferably 3-10 μm.

11. The corrosion-resistant composite layer according to any one of claims 1 to 10, wherein: The corrosion-resistant composite layer further comprises a Watt nickel layer, and the Watt nickel layer is disposed on the surface of the alkali copper layer or the surface of the coke copper layer; Preferably, the thickness of the Watt nickel layer is 1-20 μm, more preferably 3-9 μm.

12. The method for preparing the corrosion-resistant composite layer according to any one of claims 1 to 11, comprising the following steps: Forming an alkaline copper layer, a charred copper layer, and a silver layer on the surface of the substrate by electroplating; Preferably, 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, Additives: 3-5mL / L; the temperature of the electroplated alkaline copper layer is 40-50°C, the anode and cathode area ratio is 1:1-2, preferably 1:1.5, and the current density is 0.7-1.2A / dm 2 , the electroplating time is 5-15min; Preferably, 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, based on the total volume of the electroplating solution; the temperature for electroplating the charred copper layer is 40-50° C., and the current density is 0.7-1.2 A / dm 2 , the anode and cathode area ratio is 1:1-2, preferably 1:1.5, and the electroplating time is 50-90min, preferably 70min; 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: 20-30 g / L; the temperature of the electroplated silver layer is 20-25°C, the anode and cathode area ratio is 1:1-2, preferably 1:1.5, and the current density is 0.2-0.5 A / dm 2 The electroplating time is 1-90 min, preferably 30-60 min, and more preferably 40 min.

13. A method for treating an aluminum substrate against corrosion, comprising the step of providing the corrosion-resistant composite layer according to any one of claims 1 to 11 on the surface of the aluminum substrate; Preferably, the corrosion resistance refers to resistance to salt spray corrosion.

14. The method according to claim 13, wherein: The surface roughness of the aluminum substrate is less than Ra 3.6, preferably less than Ra 0.

8.

15. A corrosion-resistant aluminum terminal, wherein: A partial area or the entire area of ​​the surface of the corrosion-resistant aluminum terminal is provided with the corrosion-resistant composite layer according to any one of claims 1 to 11.

16. The method for preparing the corrosion-resistant aluminum terminal according to claim 15, comprising the following steps: The front surface of the aluminum terminal is subjected to rolling and polishing treatment. Preferably, the front surface roughness of the aluminum terminal subjected to rolling and polishing treatment is less than Ra 3.6, more preferably less than Ra 0.8; The side of the aluminum terminal is subjected to stamping treatment. Preferably, the side roughness of the aluminum terminal after roll pressing 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%; Forming an alkaline copper layer, a charred copper layer, and a silver layer on the front and side surfaces of the treated aluminum terminal in sequence by electroplating to obtain the corrosion-resistant aluminum terminal; Preferably, before forming the alkaline copper layer by electroplating, a transition layer is first formed on the front and side surfaces of the processed aluminum terminal.

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