Nickel-copper-nickel corrosion-resistant composite layer and aluminum terminal

Abstract

Provided in the present disclosure are a nickel-copper-nickel corrosion-resistant composite layer and an aluminum terminal. The nickel-copper-nickel corrosion-resistant composite layer comprises a first nickel layer, a copper layer and a second nickel layer, wherein the first nickel layer is a chemical nickel layer and has a thickness of 1-30 μm; the copper layer has a thickness of 1-15 μm; and the second nickel layer has a thickness of 0.5-30 μm. Further provided in the present disclosure is an aluminum terminal provided with the nickel-copper-nickel corrosion-resistant composite layer. The bottom layer of the nickel-copper-nickel corrosion-resistant composite layer provided in the present disclosure has good salt spray corrosion resistance, and the aluminum terminal provided with the nickel-copper-nickel corrosion-resistant composite layer can resist salt spray for 180 hours or longer.

Description

A nickel-copper-nickel corrosion-resistant composite layer and aluminum terminal

[0001] Related applications

[0002] This application claims priority to the Chinese invention patent application with application number 202310934929.0 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 invention relates to a nickel-copper-nickel corrosion-resistant composite layer and an aluminum terminal, belonging to the technical field of corrosion resistance. Background Art

[0004] Aluminum and its alloys are widely used in power transmission systems in the military, automotive, aerospace and other industries due to their low density, high conductivity and good formability.

[0005] Aluminum and its alloys have the following chemical properties: 1. They readily oxidize in air, forming an oxide film that significantly increases terminal resistance and affects power transmission. 2. Aluminum's standard electrode potential is -1.662V, making it susceptible to potential corrosion when connected to other metals with higher standard electrode potentials (such as copper), resulting in connection failure and, in severe cases, short circuits. The limited corrosion resistance of aluminum and its alloys in corrosive environments has limited their further application.

[0006] 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.

[0007] 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.

[0008] Summary of the Invention

[0009] In order to solve the above technical problems, the purpose of the present disclosure is to provide a corrosion-resistant composite layer, which is based on nickel-copper-nickel, has excellent corrosion resistance, and can meet the corrosion resistance requirements of workpieces under various conditions.

[0010] To achieve the above-mentioned object, the present disclosure provides a nickel-copper-nickel corrosion-resistant composite layer, wherein the nickel-copper-nickel corrosion-resistant composite layer comprises a first nickel layer, a copper layer, and a second nickel layer;

[0011] Wherein, the first nickel layer is a chemical nickel layer, and its thickness is 1-30 μm;

[0012] The thickness of the copper layer is 1-15 μm;

[0013] The thickness of the second nickel layer is 5-30 μm.

[0014] According to a specific embodiment of the present disclosure, illustratively, the thickness of the first nickel layer is 2-15 μm.

[0015] According to a specific embodiment of the present disclosure, illustratively, the thickness of the copper layer is 5-10 μm.

[0016] According to a specific embodiment of the present disclosure, illustratively, the copper layer is selected from any one of calcined copper, alkaline copper, chemical copper, and acid copper.

[0017] According to the specific embodiments of the present disclosure, the copper layer used in the present disclosure has the following advantages:

[0018] Alkali copper electroplating is cyanide copper plating. Cyanide has a strong complexing ability in water, which can greatly increase the cathode polarization of the electroplating process, causing copper ions to accumulate in large quantities at the cathode and then deposit together, increasing the density of the electroplated film. The coating produced by the cyanide system is dense, fast-reacting, and efficient, and can cover the zinc layer with a dense, flat copper layer. In addition, copper is chemically inactive and has low internal stress during electroplating, making it an excellent intermediate coating that is easy to electroplate subsequent metal coatings.

[0019] The electroplated copper layer is electroplated 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 electroplating 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.

[0020] The chemical copper layer is formed by an autocatalytic chemical reaction, resulting in the orderly deposition of copper ions on the substrate. Adding a chemical copper layer between each layer can achieve good bonding strength. The chemical copper layer is an excellent intermediate coating, enhancing the bonding strength of the overall coating. Furthermore, because the preparation process of the chemical copper layer is a simple chemical reaction, the coating thickness and porosity 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 overall coating.

[0021] 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.

[0022] According to a specific embodiment of the present disclosure, illustratively, the thickness of the second nickel layer is 10-15 μm.

[0023] According to a specific embodiment of the present disclosure, illustratively, the second nickel layer is selected from any one of nickel sulfamate, chemical nickel, and Watt nickel.

[0024] According to the specific embodiments of the present disclosure, the second nickel layer used in the present disclosure has the following advantages:

[0025] The nickel sulfamate layer is generally obtained by electroplating, with nickel sulfamate as the main salt and nickel chloride as the anode depolarizer. The nickel layer electroplated in this solution system has good ductility. Compared with other electroplated nickel layers, the nickel sulfamate electroplated film is more resilient and has lower internal stress. It can withstand tensile stress in environments with rapid temperature changes without being torn, and still maintains its original density. It can effectively protect the workpiece from corrosion in salt spray tests.

[0026] The electroless nickel layer is obtained by electroless nickel plating. Under the action of catalytic iron ions, hypophosphite ions in the solution catalyze dehydrogenation to form active hydrides, which undergo a reduction reaction with nickel ions in the solution, chemically depositing nickel on the workpiece surface to form the electroless nickel layer. The thickness of the nickel layer deposited by the chemical reaction is very uniform. Because there is no additional current, it is not affected by the current level or the tip discharge effect. There is no internal stress generated by electroplating between the electroless nickel layer and the workpiece, making it truly stress-free. Conventional electroplated layers release internal stress between the coating and the substrate when exposed to temperature, making the underlying coating more susceptible to tearing and losing its protective effect on the workpiece. Since the electroless nickel layer is chemically deposited, it is free of internal stress, meaning it only experiences tensile stress during temperature shock tests. Compared to other electroplated coatings, it is subjected to less stress and is less likely to tear due to stress. It can withstand the effects of temperature shock and still effectively block chloride ion penetration and prevent corrosion in salt spray tests. At the same time, during the deposition process of a typical electroplated film, hydrogen evolution occurs as a side reaction. The generation and overflow of hydrogen will leave microscopic pores in the nickel layer, so the amount of hydrogen evolution directly affects the density of the film. Since electroless nickel plating is a simple chemical reaction, it does not involve the influence of current density and the overpotential of hydrogen atoms on its reaction. The hydrogen generated by the side reaction is far less than that of the electroplated nickel layer. Therefore, the porosity of the electroless nickel layer is lower, the density is better, and it can more effectively prevent the penetration of chloride ions, greatly improving the corrosion resistance of the workpiece.

[0027] 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. Adding Watt nickel between the alkaline copper layer and the coke copper layer or on both sides will generate a potential difference in a corrosive environment, and can act as an anode to be corroded first, thereby protecting other plating layers and enhancing the brightness and corrosion resistance of the overall plating layer itself.

[0028] According to a specific embodiment of the present disclosure, the nickel-copper-nickel corrosion-resistant composite layer may further include a transition layer, which is disposed on a side of the first nickel layer that is not in contact with the copper layer. The transition layer is disposed between the first nickel layer and the substrate requiring corrosion resistance treatment to serve as a transition, and may be achieved using an appropriate surface treatment method.

[0029] According to a specific embodiment of the present disclosure, 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 the zinc layer, the secondary zinc deposition layer), the first nickel layer, the copper layer, and the second nickel layer are arranged in sequence. The zinc layer and the secondary zinc deposition layer serve as transition layers for subsequent electroplating layers, and 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.

[0030] 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.

[0031] According to a specific embodiment of the present disclosure, the thickness of the zinc layer is 0.1-10 μm, and further 0.5-1 μm.

[0032] According to a specific embodiment of the present disclosure, illustratively, the thickness of the secondary zinc deposition layer is 0.1-10 μm, and further illustratively is 1.5-2.5 μm.

[0033] According to a specific embodiment of the present disclosure, illustratively, the corrosion-resistant composite layer further includes a surface layer.

[0034] According to a specific embodiment of the present disclosure, illustratively, the surface layer is a silver layer or a tin layer to achieve a better salt spray effect.

[0035] According to a specific embodiment of the present disclosure, the thickness of the surface layer is exemplarily 2-35 μm, further exemplarily 3-30 μm, and further exemplarily 8-25 μm.

[0036] The nickel-copper-nickel anti-corrosion composite layer provided herein can be obtained by sequentially forming a first nickel layer, a copper layer, and a second nickel layer on the surface of a substrate by appropriate means (electroplating, chemical plating, etc.). When a transition layer is included, the transition layer is first formed on the surface of the substrate, and then the first nickel layer is formed.

[0037] The present disclosure further provides an aluminum terminal, wherein a partial area or the entire area of ​​the surface of the aluminum terminal is provided with the above-mentioned nickel-copper-nickel corrosion-resistant composite layer.

[0038] The method for preparing the aluminum terminal provided in the present disclosure may include the following steps:

[0039] The front surface of the aluminum terminal is rolled and polished;

[0040] Stamping the sides of the aluminum terminals;

[0041] Various layers of nickel-copper-nickel corrosion-resistant composite layers are sequentially formed on the front and side surfaces of the processed aluminum terminal (formed by electroplating, chemical plating, etc.) to obtain an aluminum terminal provided with a nickel-copper-nickel corrosion-resistant composite layer.

[0042] In the above-mentioned aluminum terminal manufacturing method, rolling, polishing, and stamping processes can be performed only on the areas requiring corrosion resistance, not 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.

[0043] In the above-mentioned method for preparing the aluminum terminal, illustratively, by performing a roller-pressing process on the terminal material, the density of the terminal surface can be enhanced, and the corrosion resistance of the subsequent electroplating process can be enhanced.

[0044] In the above-mentioned method for preparing the aluminum terminal, for example, by polishing the terminal material, the smoothness of the terminal surface can be enhanced, and the corrosion resistance of the subsequent electroplating treatment can be enhanced. The polishing treatment can be performed by chemical polishing, mechanical polishing, etc.

[0045] In the above-mentioned method for preparing the aluminum terminal, exemplarily, the front roughness of the aluminum terminal after rolling and polishing is less than Ra 3.6, further exemplarily less than Ra 0.8, that is, the front roughness of the aluminum substrate for preparing the aluminum terminal is less than Ra 3.6, further exemplarily less than Ra 0.8.

[0046] In the above-mentioned method for preparing the 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%), that is, the side roughness of the aluminum substrate used to prepare the aluminum terminal is less than Ra 3.6 (further exemplarily less than Ra 0.8), and the bright band is greater than 50% (exemplarily greater than 98%).

[0047] In the above-mentioned method for preparing the aluminum terminal, illustratively, when a transition layer is provided, before forming the first nickel layer, a transition layer is first formed on the front and side surfaces of the processed aluminum terminal.

[0048] The bottom layer of the nickel-copper-nickel corrosion-resistant composite layer provided by the present disclosure has excellent salt spray corrosion resistance. The aluminum terminal provided with the nickel-copper-nickel corrosion-resistant composite layer can achieve salt spray resistance for more than 180 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG1 is a schematic diagram of an exemplary overall structure of an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer provided by the present disclosure.

[0050] FIG2 is a schematic diagram of an exemplary electroplating process of an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer provided by the present disclosure.

[0051] Figure 3 shows the state of the sample after the 228H corrosion resistance test.

[0052] Figure 4 shows the state of the sample after 120H corrosion resistance test.

[0053] Figure 5 is a diagram of the sample state after 180H corrosion resistance test. DETAILED DESCRIPTION

[0054] 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.

[0055] A typical structure of an aluminum terminal with a nickel-copper-nickel corrosion-resistant composite layer provided by the present disclosure is shown in Figure 1. The aluminum terminal includes an aluminum substrate 1 and a nickel-copper-nickel corrosion-resistant composite layer provided on the surface of the aluminum substrate 1;

[0056] The nickel-copper-nickel corrosion-resistant composite layer comprises a transition layer 2, a first nickel layer 3, a copper layer 4, a second nickel layer 5, and a surface layer 6, wherein:

[0057] The transition layer 2 can be a zinc layer or a combination of a zinc layer and a secondary zinc deposition layer;

[0058] The first nickel layer 3 is selected from a chemical nickel layer;

[0059] The copper layer 4 is selected from any one of burnt copper, alkaline copper, chemical copper and acid copper;

[0060] The second nickel layer 5 is selected from any one of nickel sulfamate, chemical nickel, and Watt nickel;

[0061] The surface layer 6 is selected from a silver layer or a tin layer.

[0062] The electroplating process of the aluminum terminal disclosed herein may include the following steps: ultrasonic degreasing, alkali washing, pickling, activation, chemical nickel plating (first nickel layer), copper electroplating or chemical copper plating, nickel electroplating or chemical nickel plating, surface electroplating, post-treatment, pure water washing, and drying;

[0063] Wherein, when being provided with transition layer, can carry out chemical zinc precipitation, chemical zinc stripping, secondary zinc precipitation after activation, and the step of secondary zinc precipitation can be selected as needed.In certain embodiments, when being provided with transition layer, can carry out chemical zinc precipitation, chemical zinc stripping, secondary zinc precipitation before activation, and the step of secondary zinc precipitation can be selected as needed.For example, based on demand, this electroplating process may include or not include the step of secondary zinc precipitation.

[0064] An exemplary electroplating process of the aluminum terminal disclosed herein is shown in FIG2 .

[0065] The technical solution disclosed in this disclosure is designed to prevent chloride ions from contacting the substrate. The front of the raw terminal is rolled and polished, resulting in a roughness of less than Ra 3.6, and in an exemplary embodiment, less than Ra 0.8. The side of the raw terminal is processed using a precision stamping process, resulting in a bright band greater than 50%, and in an exemplary embodiment greater than 98%, and a roughness less than Ra 3.6, and in an exemplary embodiment, less than Ra 0.8. In this disclosure, raw terminals are defined as terminals processed from a substrate without a plating layer.

[0066] The roller-pressing process involves repeatedly rolling the aluminum sheet between two rollers. Rolling mechanically applies pressure to increase the surface density of the aluminum, thereby reducing the porosity of the aluminum terminal material and improving its density, preparing it for the next electroplating layer. Less porosity in the material also results in a less porous electroplated film, providing greater protection. Rolling reduces surface roughness and significantly improves flatness.

[0067] The polishing process involves placing the terminal material in a polishing tank containing a polishing solution and magnetic needles. Magnetic polishing uses electricity to generate a magnetic field, which drives the stainless steel needles (i.e., magnetic needles) into motion. During this motion, the magnetic needles rub against the surface of the terminal material, achieving a mechanical polishing effect and improving the surface finish and flatness of the terminal material.

[0068] Polishing and precision stamping processes are all used to improve the smoothness and flatness of the front and side surfaces of the terminal material.

[0069] 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.

[0070] Alkali copper electroplating: 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, additive (polyethylene glycol, fatty amine polyoxyethylene ether (AEO) and OP series octylphenol polyoxyethylene ether, one or a mixture of two or more): 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, coating thickness is selected according to needs.

[0071] 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.

[0072] Copper plating: The plating parameters are as follows: copper pyrophosphate: 50-70g / L, potassium pyrophosphate: 300-450g / L, ammonium citrate: 15-30g / L, ammonia: 2-5mL / L, current density 0.7-1.2A / dm 2 , temperature 40-50℃, anode and cathode area ratio of 1:1.5, electroplating time 50-90min, and coating thickness can be controlled by controlling electroplating parameters as needed.

[0073] The chemical copper plating parameters are as follows: composition of the chemical plating solution: copper sulfate: 5-20g / L, sodium hypophosphite: 20-50g / L, sodium citrate: 5-30g / L, nickel sulfate: 0.1-5g / L, potassium ferrocyanide: 0.5-7mg / L, boric acid: 15-50g / L; temperature 60-90°C, pH 7.8-10.2, electroplating time 40-100min, general plating speed 1μm / 6min, i.e.: 6min-1μm, i.e. 24min-4μm, 48min-8μm; the coating thickness can be controlled as needed by controlling the chemical copper plating parameters.

[0074] The parameters for electroplating acid copper are as follows: composition of the electroplating solution: copper sulfate pentahydrate: 160-250 g / L, sulfuric acid: 25-50 mL / L, chloride ion: 40-120 ppm, additives (one or a mixture of two or more of polydisulfide propane sulfonate, 2-mercaptobenzimidazole, 1,2-ethylene thiourea, and polyamine compounds): 4-15 mL / L, current density 0.8-2.0 A / 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.

[0075] Electroless nickel plating: The parameters for the electroless nickel plating are as follows: Based on the total volume of the electroless nickel plating solution, the electroless nickel plating solution contains 15-25 g / L nickel sulfate, 15-25 g / L sodium hypophosphite, 20-30 g / L sodium acetate, 5-10 g / L succinic acid, and 10-20 g / L lactic acid. The remainder of the plating solution is water. The electroless nickel plating temperature is 85-95°C, and the plating time is 20-40 minutes. The electroless nickel plating reaction rate is stable. According to the disclosed method, the typical nickel plating rate is 1 μm / 5 minutes, i.e., 5 minutes to 1 μm, 20 minutes to 4 μm, and 40 minutes to 8 μm.

[0076] Nickel sulfamate layer: Electroplating parameters are as follows: Electroplating solution composition: nickel sulfamate: 300-500g / L, nickel chloride: 10-25g / L, boric acid: 30-40g / L, sulfamate: 100-150g / L, additives: 5-10ml / L, current density: 0.8-1.2A / dm 2 Temperature: 50-60°C, cathode and anode area ratio: 1:1.5, electroplating time: 1-80 minutes (40-60 minutes is an example), and the coating thickness is controlled by controlling the electroplating parameters as needed. Exemplary additives include one or a mixture of two or more of pyridine derivatives, propargyl alcohol derivatives, and saccharin.

[0077] The parameters of the electroplating 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.

[0078] The electroplating of the surface layer can be carried out in a conventional manner in the art, for example:

[0079] Silver electroplating parameters are as follows: Electroplating solution composition: 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, additives (one or a mixture of two or more of thiocarbamate, sodium dodecylsulfonate, OP series octylphenol polyoxyethylene ether): 20-30g / L, temperature: 20-25℃, cathode and anode area ratio of 1:1.5, current density: 0.2-0.5A / dm 2 , electroplating time: 30-60min, the coating thickness is controlled by controlling the electroplating parameters as needed.

[0080] The electroplating parameters of tin are as follows: plating solution composition: stannous sulfate: 10-50g / L, sulfuric acid: 60-190ml / L, gelatin: 1-10g / L, formaldehyde: 5-10ml / L, benzyl acetone: 5-30g / L; temperature: 10-40℃, cathode and anode area ratio: 1:1.5, current density: 0.7-1.2A / dm 2 , electroplating time: 30-120min, the coating thickness is controlled by controlling the electroplating parameters as needed.

[0081] The salt spray corrosion resistance test in each embodiment and comparative example was conducted in accordance with the national standard GB / T 2423.17-2008. Qualified standard: no corrosion, no surface pitting, peeling, blistering, etc., and no spots or color changes on the coating.

[0082] Example 1

[0083] This embodiment provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0084] The front of the aluminum terminal material has been rolled and polished, with a roughness of less than Ra 0.8. The side has been processed through a precision stamping process, with a bright band greater than 98% and a roughness of less than Ra 0.8. The roughness of the aluminum terminal material surface and side before and after polishing is 0.168μm, respectively. This shows that polishing can significantly reduce surface roughness and improve smoothness. The sampling cutoff wavelength of the filter in the roughness test is λc = 0.8mm×5, where 0.8mm is the sampling length and 5 is the amplification factor.

[0085] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), an chemical nickel layer (thickness 10 μm), a charred copper layer (thickness 10 μm), and an aminosulfonic acid nickel layer (thickness 15 μm).

[0086] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 228 hours.

[0087] According to the above test results, it can be seen that the corrosion-resistant composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0088] Example 2

[0089] This embodiment provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0090] 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;

[0091] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 5 μm), an acid copper layer (thickness 8 μm), and a chemical nickel layer (thickness 12 μm).

[0092] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 180 hours.

[0093] According to the above test results, it can be seen that the corrosion-resistant composite layer provided in this embodiment has excellent salt spray corrosion resistance.

[0094] Figure 3 shows the morphology of the aluminum terminals of Examples 1 and 2 after undergoing a 228-hour salt spray test. The left side shows the test piece of Example 1, and the right side shows the test piece of Example 2. As can be seen in Figure 3, the surface of the test piece of Example 1 has not undergone any significant changes, while the surface of the test piece of Example 2 has undergone some changes. While not very obvious, they are still noticeable when compared to Example 1. Therefore, the salt spray resistance of the nickel-copper-nickel corrosion-resistant composite layer of Example 1 is superior to that of Example 2.

[0095] Comparative Example 1

[0096] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0097] 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;

[0098] The corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a charred copper layer (thickness 20 μm), and an aminosulfonic acid nickel layer (thickness 15 μm).

[0099] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 120 hours.

[0100] Figure 4 shows the morphology of the aluminum terminals from Example 1 and Comparative Example 1 after a 120-hour salt spray test. The left side shows the Example 1 test piece, and the right side shows the Comparative Example 1 test piece. As shown in Figure 4, the Example 1 test piece showed no significant changes, while the Comparative Example 1 test piece exhibited blistering and other surface issues, indicating that the salt spray had penetrated the corrosion-resistant layer on the test piece's surface and contacted the test piece's substrate, corroding it.

[0101] According to the above test results, it can be seen that the salt spray corrosion resistance of the corrosion-resistant composite layer provided in this comparative example is relatively poor.

[0102] Comparative Example 2

[0103] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0104] 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;

[0105] The corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 20 μm), and an aminosulfonic acid nickel layer (thickness 15 μm).

[0106] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 108H.

[0107] According to the above test results, it can be seen that the salt spray corrosion resistance of the corrosion-resistant composite layer provided in this comparative example is relatively poor.

[0108] Comparative Example 3

[0109] This comparative example 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 corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), and a chemical nickel layer (thickness 25 μm).

[0112] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 96 hours.

[0113] Figure 5 shows the morphology of the aluminum terminals from Example 2 and Comparative Example 3 after a 120-hour salt spray test. The left side shows the Example 2 test piece, and the right side shows the Comparative Example 3 test piece. As shown in Figure 5, the Example 2 test piece showed no significant changes, while the Comparative Example 3 test piece showed blistering and fading on its surface, indicating that the salt spray had penetrated the corrosion-resistant layer on the test piece's surface, contacted the test piece's substrate, and corroded it.

[0114] According to the above test results, it can be seen that the salt spray corrosion resistance of the corrosion-resistant composite layer provided in this comparative example is relatively poor.

[0115] Comparative Example 4

[0116] This comparative example provides an aluminum terminal with a corrosion-resistant composite layer, wherein:

[0117] 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;

[0118] The corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), an acid copper layer (13 μm), and a chemical nickel layer (thickness 12 μm).

[0119] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 48 hours.

[0120] According to the above test results, it can be seen that the salt spray corrosion resistance of the corrosion-resistant composite layer provided in this comparative example is relatively poor.

[0121] Example 3

[0122] This embodiment provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0123] 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;

[0124] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), an chemical nickel layer (thickness 10 μm), a charred copper layer (thickness 10 μm), an aminosulfonic acid nickel layer (thickness 15 μm), and a tin layer (thickness 15 μm).

[0125] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 336 hours.

[0126] According to the above test results, it can be seen that the corrosion-resistant composite layer provided in this embodiment has excellent salt spray corrosion resistance. Compared with Example 1, with the addition of a tin layer as the surface layer, the salt spray resistance time is greatly improved by 47%.

[0127] Example 4

[0128] This embodiment provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0129] 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;

[0130] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 1 μm), an alkaline copper layer (thickness 1 μm), and an aminosulfonic acid nickel layer (thickness 0.5 μm).

[0131] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 52 hours.

[0132] According to the above test results, it can be seen that the corrosion-resistant composite layer provided in this embodiment has excellent salt spray corrosion resistance and is suitable for the welding area of ​​the aluminum terminal or the area that is not directly exposed.

[0133] Comparative Example 5

[0134] This comparative example provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0135] 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;

[0136] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 0.2 μm), an alkaline copper layer (thickness 1 μm), and an aminosulfonate nickel layer (thickness 0.5 μm).

[0137] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 36 hours.

[0138] According to the above test results, it can be seen that the thickness of the corrosion-resistant composite layer provided in this comparative example is relatively low, and the salt spray corrosion resistance cannot reach 48H, which is lower than that of conventional coatings.

[0139] Comparative Example 6

[0140] This comparative example provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0141] 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;

[0142] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 1 μm), an alkaline copper layer (thickness 0.2 μm), and an aminosulfonic acid nickel layer (thickness 0.5 μm).

[0143] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 40 hours.

[0144] According to the above test results, it can be seen that the thickness of the corrosion-resistant composite layer provided in this comparative example is relatively low, and the salt spray corrosion resistance cannot reach 48H, which is lower than that of conventional coatings.

[0145] Comparative Example 7

[0146] This comparative example provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0147] 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;

[0148] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 1 μm), an alkaline copper layer (thickness 1 μm), and an aminosulfonic acid nickel layer (thickness 0.1 μm).

[0149] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 24 hours.

[0150] According to the above test results, it can be seen that the thickness of the corrosion-resistant composite layer provided in this comparative example is relatively low, and the salt spray corrosion resistance cannot reach 48H, which is lower than that of conventional coatings.

[0151] Example 5

[0152] This embodiment provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0153] 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;

[0154] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 1 μm), an alkaline copper layer (thickness 1 μm), and a chemical nickel layer (thickness 0.5 μm).

[0155] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 50 hours.

[0156] According to the above test results, it can be seen that the corrosion-resistant composite layer provided in this embodiment has excellent salt spray corrosion resistance and is suitable for the welding area of ​​the aluminum terminal or the area that is not directly exposed.

[0157] Comparative Example 7

[0158] This comparative example provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0159] 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;

[0160] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 0.2 μm), an alkaline copper layer (thickness 1 μm), and a chemical nickel layer (thickness 0.5 μm).

[0161] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 36 hours.

[0162] According to the above test results, it can be seen that the thickness of the corrosion-resistant composite layer provided in this comparative example is relatively low, and the salt spray corrosion resistance cannot reach 48H, which is lower than that of conventional coatings.

[0163] Comparative Example 8

[0164] This comparative example provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0165] 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;

[0166] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 1 μm), an alkaline copper layer (thickness 0.2 μm), and a chemical nickel layer (thickness 0.5 μm).

[0167] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 38 hours.

[0168] According to the above test results, it can be seen that the thickness of the corrosion-resistant composite layer provided in this comparative example is relatively low, and the salt spray corrosion resistance cannot reach 48H, which is lower than that of conventional coatings.

[0169] Comparative Example 9

[0170] This comparative example provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0171] 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;

[0172] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), a chemical nickel layer (thickness 1 μm), an alkaline copper layer (thickness 1 μm), and a chemical nickel layer (thickness 0.1 μm).

[0173] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 24 hours.

[0174] According to the above test results, it can be seen that the thickness of the corrosion-resistant composite layer provided in this comparative example is relatively low, and the salt spray corrosion resistance cannot reach 48H, which is lower than that of conventional coatings.

[0175] Example 6

[0176] This embodiment provides an aluminum terminal having a nickel-copper-nickel corrosion-resistant composite layer, wherein:

[0177] 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;

[0178] The nickel-copper-nickel corrosion-resistant composite layer includes a primary zinc deposition layer (thickness 1 μm), a secondary zinc deposition layer (thickness 2 μm), an chemical nickel layer (thickness 20 μm), a charred copper layer (thickness 10 μm), and an aminosulfonic acid nickel layer (thickness 20 μm).

[0179] The aluminum terminal was subjected to a salt spray resistance test, and the salt spray resistance time was measured to be 224 hours.

[0180] According to the above test results, it can be seen that the corrosion-resistant composite layer provided in this embodiment has a relatively high thickness and has excellent salt spray corrosion resistance.

Claims

1. A nickel-copper-nickel corrosion-resistant composite layer, characterized in that: The nickel-copper-nickel corrosion-resistant composite layer comprises a first nickel layer, a copper layer, and a second nickel layer; Wherein, the first nickel layer is a chemical nickel layer, and its thickness is 1-30 μm; The thickness of the copper layer is 1-15 μm; The thickness of the second nickel layer is 0.5-30 μm.

2. The nickel-copper-nickel corrosion-resistant composite layer according to claim 1, characterized in that: The thickness of the first nickel layer is 2-15 μm.

3. The nickel-copper-nickel corrosion-resistant composite layer according to claim 1, characterized in that: The copper layer has a thickness of 5-10 μm.

4. The nickel-copper-nickel corrosion-resistant composite layer according to claim 1 or 3, characterized in that: The copper layer is selected from any one of calcined copper, alkaline copper, chemical copper and acid copper.

5. The nickel-copper-nickel corrosion-resistant composite layer according to claim 1, characterized in that: The thickness of the second nickel layer is 10-15 μm.

6. The nickel-copper-nickel corrosion-resistant composite layer according to claim 1 or 5, characterized in that: The second nickel layer is selected from any one of nickel sulfamate, chemical nickel, and Watt nickel.

7. The nickel-copper-nickel corrosion-resistant composite layer according to claim 1, characterized in that: The nickel-copper-nickel corrosion-resistant composite layer further comprises a transition layer, wherein the transition layer is arranged on a side of the first nickel layer that is not in contact with the copper layer; Preferably, the transition layer comprises a zinc layer, or a combination of a zinc layer and a secondary zinc deposition layer.

8. The nickel-copper-nickel corrosion-resistant composite layer according to claim 7, characterized in that: The thickness of the zinc layer is 0.1-10 μm, preferably 0.5-1 μm; Preferably, the thickness of the secondary zinc deposition layer is 0.1-10 μm, more preferably 1.5-2.5 μm.

9. The nickel-copper-nickel corrosion-resistant composite layer according to claim 1, characterized in that: The nickel-copper-nickel corrosion-resistant composite layer also includes a surface layer; preferably, the surface layer is a silver layer or a tin layer; more preferably, the thickness of the surface layer is 2-35 μm, preferably 8-25 μm.

10. An aluminum terminal, characterized in that: A partial area or the entire area of ​​the surface of the aluminum terminal is provided with the nickel-copper-nickel corrosion-resistant composite layer according to any one of claims 1-9.

11. The aluminum terminal according to claim 10, characterized in that: The front surface roughness of the aluminum substrate for preparing the aluminum terminal is less than Ra 3.6; preferably less than Ra 0.8; Preferably, the side roughness of the aluminum substrate used to prepare the aluminum terminal is less than Ra 3.6, preferably less than Ra 0.8, and the bright band is greater than 50%, preferably greater than 98%.

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