A method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles

Abstract

This invention relates to the field of electroplating technology and discloses a method for electroplating a corrosion-resistant zinc-nickel alloy for new energy vehicle battery connectors. The method includes: degreasing, activating, and surface conditioning a substrate of a new energy vehicle battery connector having mounting holes, punched edges, and press-fit contact areas to obtain a surface to be plated; forming a nickel transition layer with a thickness of 0.3 μm-1.5 μm on the surface to be plated; immersing the connector in an alkaline zinc-nickel alloy electroplating solution for segmented pulse electrodeposition within 120 seconds to form a zinc-nickel alloy layer; and then performing passivation and thin-film sealing treatments to obtain a corrosion-resistant zinc-nickel alloy coating. This invention improves the coating uniformity of the inner wall of the mounting holes, punched edges, and press-fit contact areas of the connector through the combination of the nickel transition layer, segmented pulse electrodeposition, passivation treatment, and thin-film sealing treatment, thereby improving corrosion resistance and contact stability.

Description

Technical Field

[0001] This invention relates to the field of electroplating technology, and more specifically, to a method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles. Background Technology

[0002] New energy vehicle power battery systems typically include cells, modules, busbars, connectors, connecting plates, fastening gaskets, grounding connectors, and battery pack structural connectors. These battery connectors are used to achieve electrical or mechanical connections between battery modules, between battery modules and the battery management system, and between the power battery and the vehicle's grounding structure. The reliability of these connections affects the current-carrying stability, grounding stability, and long-term service safety of the power battery system.

[0003] Battery connectors for new energy vehicles typically withstand multiple stresses during use, including vehicle vibration, thermal cycling, humid environments, condensation, salt spray, road de-icing salt, and assembly crimping forces. Some connectors also feature structural characteristics such as mounting holes, punched edges, bending areas, and crimping contact areas. These areas are prone to burrs, oxide films, stress concentrations, or differences in surface activity after processing. If the surface protection of the connector is insufficient, the inner walls of the mounting holes, punched edges, and crimping contact areas can easily become corrosion initiation sites, leading to corrosion propagation, increased contact resistance, localized heating, or decreased connection stability.

[0004] Zinc-nickel alloy coatings are a commonly used type of corrosion-resistant protective coating. Compared with ordinary zinc coatings, zinc-nickel alloy coatings generally have better resistance to salt spray corrosion and have been applied in automotive fasteners, structural parts, and some corrosion-resistant connectors. Existing zinc-nickel alloy electroplating processes typically improve the overall corrosion resistance of the workpiece by controlling the thickness of the zinc-nickel alloy layer, the nickel content of the alloy, passivation treatment, and sealing treatment.

[0005] However, existing zinc-nickel alloy electroplating processes still have shortcomings when used for battery connectors in new energy vehicles. On one hand, there are differences in current density between the inner walls of mounting holes, punched edges, and the press-fit contact area and the planar area in new energy vehicle battery connectors. Conventional constant current electrodeposition tends to result in a thicker plating layer in the planar area, while the plating layer is insufficient in low-current or boundary areas such as the inner walls of holes and punched edges, thus reducing localized protection. On the other hand, insufficient nickel content in the zinc-nickel alloy layer leads to inadequate corrosion resistance, and uneven nickel content distribution increases the differences in corrosion behavior between different areas, easily causing an increase in contact resistance in the press-fit contact area after exposure to salt spray or humid heat environments.

[0006] Furthermore, to improve corrosion resistance, existing processes often employ strong passivation or thick sealing treatments. However, the crimping contact area of ​​new energy vehicle battery connectors needs to maintain low contact resistance. If the sealing film is too thick or the passivation film is too dense, although it can improve the corrosion resistance of exposed areas, it may increase the interfacial resistance of the crimping contact area, which is detrimental to the long-term current flow stability of the connector. For high-strength steel connectors, there may also be a risk of hydrogen absorption during the electroplating process. If proper dehydrogenation treatment is not performed, it may affect the service reliability of the load-bearing connectors.

[0007] Therefore, it is necessary to provide a corrosion-resistant zinc-nickel alloy electroplating method for new energy vehicle battery connectors, so as to improve the uniformity of the plating thickness between the inner wall of the mounting hole, the punched edge and the planar area of ​​the connector, control the nickel content of the zinc-nickel alloy layer and its regional differences, and reduce the risk of increased contact resistance in the crimping contact area while improving corrosion resistance. Summary of the Invention

[0008] The purpose of this invention is to provide a corrosion-resistant zinc-nickel alloy electroplating method for battery connectors in new energy vehicles, so as to solve the above-mentioned technical problems.

[0009] To achieve the above objectives, the present invention provides the following solution:

[0010] A method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles includes the following steps:

[0011] The substrate of the new energy vehicle battery connector is degreased, activated, and surface-conditioned to obtain the surface to be plated; the new energy vehicle battery connector has mounting holes, punched edges, and crimping contact areas.

[0012] A nickel transition layer is formed on the surface to be plated, the thickness of the nickel transition layer being 0.3μm-1.5μm;

[0013] The new energy vehicle battery connector with the nickel transition layer formed thereon is immersed in an alkaline zinc-nickel alloy electroplating solution for 120 seconds for segmented pulse electrodeposition, and a zinc-nickel alloy layer is formed on the surface of the nickel transition layer.

[0014] Passivation treatment is performed on the new energy vehicle battery connector with the zinc-nickel alloy layer to obtain a passivation film layer.

[0015] The new energy vehicle battery connector with the passivation film layer is subjected to thin-film sealing treatment to obtain a corrosion-resistant zinc-nickel alloy coating.

[0016] The alkaline zinc-nickel alloy electroplating solution comprises: zinc ions 6g / L-14g / L, nickel ions 0.6g / L-2.5g / L, sodium hydroxide 90g / L-160g / L, nickel complexing agent 20g / L-70g / L, grain refiner 0.05g / L-1.0g / L, low current area leveling agent 0.02g / L-0.50g / L, wetting agent 0.02g / L-0.30g / L, and water;

[0017] The segmented pulsed electrodeposition includes a low-current pre-deposition stage, a pulsed main deposition stage, and a low-current leveling stage. The current density of the low-current pre-deposition stage is 0.3 A / dm²-0.8 A / dm², and the time is 2 min-6 min. The average current density of the pulsed main deposition stage is 1.5 A / dm²-4.0 A / dm², the pulse frequency is 20 Hz-200 Hz, the duty cycle is 40%-70%, and the time is 12 min-35 min. The current density of the low-current leveling stage is 0.5 A / dm²-1.2 A / dm², and the time is 3 min-8 min. The temperature of the alkaline zinc-nickel alloy electroplating solution is 25℃-40℃.

[0018] The zinc-nickel alloy layer has a nickel content of 12wt.%-16wt.% and a thickness of 5μm-12μm; the ratio of the thickness of the zinc-nickel alloy layer on the inner wall of the mounting hole to the thickness of the planar area is ≥0.65; the ratio of the thickness of the zinc-nickel alloy layer on the punched edge to the thickness of the planar area is ≥0.60; and the difference between the nickel content in the press-fit contact area and the nickel content in the planar area is ≤2 percentage points.

[0019] The passivation treatment is performed at a temperature of 20℃-40℃ for 20s-90s; the thin-film sealing treatment is performed at a temperature of 35℃-70℃ for 20s-120s; after the thin-film sealing treatment, the thickness of the sealing film in the press-fit contact area is 20nm-120nm.

[0020] Preferably, the base material of the new energy vehicle battery connector is a steel connecting piece, a steel connecting plate, a steel fastening gasket, a copper alloy connector, or an aluminum alloy connector;

[0021] When the substrate of the new energy vehicle battery connector is a copper alloy connector, micro-etching activation is performed using a persulfate-sulfuric acid system or a hydrogen peroxide-sulfuric acid system before forming the nickel transition layer.

[0022] When the substrate of the new energy vehicle battery connector is an aluminum alloy connector, before forming the nickel transition layer, it undergoes degreasing, alkaline etching, ash removal, zinc replacement, and nickel pre-plating treatment in sequence.

[0023] When the substrate of the new energy vehicle battery connector is a steel connecting piece, a steel connecting plate, or a steel fastening gasket, before forming the nickel transition layer, it is pickled and activated by pickling solution. The pickling solution is a hydrochloric acid solution or sulfuric acid solution with a mass fraction of 5%-15%, and the pickling and activation time is 10s-60s.

[0024] Preferably, the nickel transition layer is an electrodeposited nickel layer, which is prepared using Watt's nickel plating solution, nickel sulfamate plating solution, or semi-bright nickel plating solution.

[0025] When forming the nickel transition layer, the current density is 0.8A / dm²-2.5A / dm², the electroplating time is 1min-5min, and the electroplating temperature is 35℃-60℃.

[0026] After the nickel transition layer is formed, it is washed with water and then immersed in the alkaline zinc-nickel alloy electroplating solution within 60s-120s.

[0027] Preferably, the zinc ions are derived from one or more of zinc oxide, zinc sulfate, and zinc acetate;

[0028] The nickel ions are derived from one or more of nickel sulfate, nickel carbonate, nickel acetate, and nickel aminosulfonate.

[0029] The nickel complexing agent includes at least two of the following: triethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylidene diphosphonate, and gluconate.

[0030] In the nickel complexing agent, the mass ratio of amine complexing agent to carboxylate or phosphonate complexing agent is 1:(0.5-2.5).

[0031] Preferably, the grain refiner comprises one or more of quaternary ammonium salt compounds, pyridinium salt compounds, and polyethyleneimine derivatives;

[0032] The low-current leveling agent includes one or more of polyetheramine, polyoxyethylene ether, and imidazoline derivatives.

[0033] The wetting agent includes one or more of acetylenic diol wetting agents, alkyl glycosides, and polyether wetting agents;

[0034] The mass ratio of the grain refiner, the low-current area leveling agent, and the wetting agent is 1:(0.2-1.5):(0.1-1.0).

[0035] Preferably, during the segmented pulse electrodeposition process, the new energy vehicle battery connector undergoes cathode oscillation or plating solution circulation spraying.

[0036] The oscillation frequency of the cathode is 10 times / min to 40 times / min, and the oscillation amplitude is 20mm to 80mm.

[0037] The spray velocity of the circulating spray of the plating solution is 0.2 m / s-1.2 m / s;

[0038] The low-current pre-deposition stage, the pulsed main deposition stage, and the low-current leveling stage are all performed under the conditions of cathode oscillation or the circulating spray of the plating solution.

[0039] Preferably, the passivation treatment uses a trivalent chromium passivation solution, which comprises 0.5 g / L-5 g / L of trivalent chromium salt, 1 g / L-20 g / L of nitrate, 0.5 g / L-10 g / L of organic carboxylate, 0.1 g / L-3 g / L of film-forming promoter, and water;

[0040] The pH of the trivalent chromium passivation solution is 1.8-3.5;

[0041] After trivalent chromium passivation treatment, the sample is washed with water and dried at 80℃-120℃ for 5min-20min.

[0042] Preferably, the thin-film sealing treatment uses an aqueous sealing solution, which comprises 0.2 g / L-5 g / L hydrolyzed silane, 0.5 g / L-10 g / L nano silica sol, 0.1 g / L-3 g / L molybdate, 0.1 g / L-3 g / L tungstate, and water;

[0043] After the thin-film sealing treatment, the thickness of the sealing film in the press-fit contact area is 20nm-120nm, and the thickness of the sealing film in the non-press-fit exposed area is 80nm-300nm.

[0044] Preferably, when the substrate of the new energy vehicle battery connector is a steel connector with a tensile strength of not less than 1000MPa, a dehydrogenation treatment is performed after the segmented pulse electrodeposition and before the passivation treatment;

[0045] The dehydrogenation treatment is performed at a temperature of 180℃-220℃ for 2-4 hours.

[0046] After the dehydrogenation treatment, the passivation treatment is performed within 30 minutes.

[0047] Preferably, the new energy vehicle battery connector includes a substrate, a nickel transition layer, a zinc-nickel alloy layer, a passivation film layer, and a sealing film layer;

[0048] The nickel content in the zinc-nickel alloy layer is 12 wt.%-16 wt.%;

[0049] The zinc-nickel alloy layer has a thickness of 5μm-12μm;

[0050] After undergoing a neutral salt spray test for 720 hours, the substrate of the new energy vehicle battery connector did not show any red rust.

[0051] After undergoing a neutral salt spray test for 720 hours, the contact resistance growth rate of the crimped contact area of ​​the new energy vehicle battery connector is ≤30%.

[0052] After the new energy vehicle battery connector undergoes 20 cycles of thermal cycling from -40℃ to 85℃, the contact resistance growth rate of the crimped contact area is ≤25%.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] First, this invention forms a nickel transition layer with a thickness of 0.3μm-1.5μm on the surface of the new energy vehicle battery connector to be plated, and then forms a zinc-nickel alloy layer on the surface of the nickel transition layer. The nickel transition layer can improve the bonding state between the substrate and the zinc-nickel alloy layer, reduce the influence of the surface activity differences of steel connectors, copper alloy connectors, or aluminum alloy connectors on the continuity of subsequent zinc-nickel alloy deposition, and enable the zinc-nickel alloy layer to maintain a good adhesion foundation in mounting holes, punched edges, and crimping contact areas.

[0055] Secondly, this invention employs an alkaline zinc-nickel alloy electroplating solution, controlling zinc ions at 6g / L-14g / L, nickel ions at 0.6g / L-2.5g / L, and sodium hydroxide at 90g / L-160g / L. It also incorporates a nickel complexing agent, a grain refiner, a low-current area leveling agent, and a wetting agent. These components maintain a stable co-deposition state of zinc and nickel ions in the strongly alkaline system, improving the grain structure of the zinc-nickel alloy layer and its coverage in low-current areas, thereby reducing insufficient plating in areas such as the inner walls of mounting holes and punched edges.

[0056] Third, this invention controls the nickel content in the zinc-nickel alloy layer to 12wt.%-16wt.% and the thickness of the zinc-nickel alloy layer to 5μm-12μm. This nickel content range is beneficial for balancing the sacrificial protection performance and salt spray corrosion resistance of the zinc-nickel alloy layer, avoiding insufficient corrosion resistance due to excessively low nickel content, and also preventing adverse changes in alloy deposition stability and corrosion behavior due to nickel content deviating from the appropriate range.

[0057] Fourth, this invention employs a segmented pulsed electrodeposition method consisting of a low-current pre-deposition stage, a pulsed main deposition stage, and a low-current leveling stage. The low-current pre-deposition stage facilitates the formation of a continuous initial deposition layer on the surface to be plated, the inner wall of the mounting hole, the punched edge, and the crimping contact area. The pulsed main deposition stage improves deposition efficiency and stably controls the nickel content in the zinc-nickel alloy layer. The low-current leveling stage compensates for insufficient deposition in low-current areas. The combination of these three electrodeposition stages enhances the coating uniformity in complex areas of new energy vehicle battery connectors.

[0058] Fifth, this invention limits the ratio of the thickness of the zinc-nickel alloy layer on the inner wall of the mounting hole to the thickness of the planar area to be no less than 0.65, and the ratio of the thickness of the zinc-nickel alloy layer on the punched edge to the thickness of the planar area to be no less than 0.60. Furthermore, it limits the difference in nickel content between the press-fit contact area and the planar area to be no more than 2 percentage points. By controlling the aforementioned regional thickness ratios and nickel content differences, the risk of localized corrosion caused by thin plating or fluctuations in alloy composition on the inner wall of the mounting hole, the punched edge, and the press-fit contact area can be reduced, thereby improving the consistency of protection in weak areas of new energy vehicle battery connectors.

[0059] Sixth, this invention performs passivation treatment after the zinc-nickel alloy layer is formed, and further performs thin-film sealing treatment to control the thickness of the sealing film in the press-fit contact area to 20nm-120nm. The passivation film and sealing film can improve the corrosion resistance of the zinc-nickel alloy layer; at the same time, the thin-film sealing control of the press-fit contact area can reduce the risk of increased contact resistance caused by excessively thick sealing film, which is beneficial to maintaining the connection stability of new energy vehicle battery connectors after salt spray, damp heat and thermal cycling.

[0060] Seventh, when the tensile strength of the steel connector is not less than 1000MPa, the present invention performs a dehydrogenation treatment at 180℃-220℃ for 2h-4h after segmented pulse electrodeposition and before passivation. This dehydrogenation treatment can reduce the risk of hydrogen absorption in high-strength steel connectors during electroplating, which is beneficial to improving the long-term service reliability of load-bearing connectors such as connecting plates and fastening gaskets. Detailed Implementation

[0061] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0062] This invention provides a corrosion-resistant zinc-nickel alloy electroplating method for new energy vehicle battery connectors, applicable to connector plates, connecting plates, fastening gaskets, grounding connectors, transition connectors, and structural connectors with corrosion resistance requirements in new energy vehicle power battery systems. The new energy vehicle battery connector has mounting holes, punched edges, and a press-fit contact area. Mounting holes are for bolts or positioning parts to pass through; the punched edge is the boundary area formed after the connector is stamped, sheared, or blanked; the press-fit contact area is the area where the connector is electrically connected or mechanically pressed against the busbar, terminal, grounding part, pressure plate, or fastener after assembly. The flat area is the smooth area on the connector away from the mounting holes, punched edges, and bending transitions, and can be used as a benchmark area for comparing plating thickness and nickel content.

[0063] The substrate for the new energy vehicle battery connector of this invention can be a steel connecting piece, a steel connecting plate, a steel fastening gasket, a copper alloy connector, or an aluminum alloy connector. Different substrates undergo a pretreatment method matching the substrate before forming the nickel transition layer. For steel connecting pieces, steel connecting plates, or steel fastening gaskets, alkaline degreasing, acid pickling activation, and water washing can be used. The alkaline degreasing temperature can be 45℃-70℃, and the treatment time can be 3min-10min; acid pickling activation uses a 5%-15% hydrochloric acid solution or sulfuric acid solution, and the treatment time is 10s-60s. For copper alloy connectors, a persulfate-sulfuric acid system or a hydrogen peroxide-sulfuric acid system can be used for micro-etching activation, and the treatment time is 10s-60s. For aluminum alloy connectors, degreasing, alkaline etching, descaling, zinc replacement, and nickel pre-plating treatments can be performed sequentially to form a surface state suitable for subsequent electrodeposition.

[0064] After pretreatment, a nickel transition layer is formed on the surface to be plated. The nickel transition layer can be prepared using Watt's nickel plating solution, nickel sulfamate plating solution, or semi-bright nickel plating solution. During the formation of the nickel transition layer, the current density is 0.8 A / dm²-2.5 A / dm², the plating time is 1 min-5 min, and the plating temperature is 35℃-60℃. The thickness of the nickel transition layer is controlled to be 0.3 μm-1.5 μm. If the nickel transition layer thickness is less than 0.3 μm, the isolation and transition effect on differences in the substrate surface condition is insufficient; if the nickel transition layer thickness is greater than 1.5 μm, it increases the process cost and may weaken the sacrificial protection effect of the zinc-nickel alloy layer on the steel substrate. Therefore, this invention controls the nickel transition layer thickness within the above range.

[0065] After the nickel transition layer is formed, it is washed with water, and the new energy vehicle battery connector is immersed in an alkaline zinc-nickel alloy electroplating solution for segmented pulse electrodeposition within 120 seconds. Controlling the time of immersion in the alkaline zinc-nickel alloy electroplating solution helps to reduce re-oxidation of the nickel transition layer surface and ensures the bonding stability between the zinc-nickel alloy layer and the nickel transition layer.

[0066] The alkaline zinc-nickel alloy electroplating bath comprises 6 g / L-14 g / L zinc ions, 0.6 g / L-2.5 g / L nickel ions, 90 g / L-160 g / L sodium hydroxide, 20 g / L-70 g / L nickel complexing agent, 0.05 g / L-1.0 g / L grain refiner, 0.02 g / L-0.50 g / L low-current leveling agent, 0.02 g / L-0.30 g / L wetting agent, and water. The zinc ions are derived from one or more of zinc oxide, zinc sulfate, and zinc acetate; the nickel ions are derived from one or more of nickel sulfate, nickel carbonate, nickel acetate, and nickel sulfamate. The nickel complexing agent includes at least two of triethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylidene diphosphonate, and gluconate, wherein the mass ratio of amine complexing agent to carboxylate or phosphonate complexing agent is 1:(0.5-2.5). Grain refiners include one or more of quaternary ammonium salts, pyridinium salts, and polyethyleneimine derivatives; low-current leveling agents include one or more of polyetheramines, polyoxyethylene ethers, and imidazoline derivatives; wetting agents include one or more of acetylenic diol wetting agents, alkyl glycosides, and polyether wetting agents.

[0067] Segmented pulsed electrodeposition includes a low-current pre-deposition stage, a pulsed main deposition stage, and a low-current leveling stage. The low-current pre-deposition stage uses a current density of 0.3 A / dm²-0.8 A / dm² for 2-6 minutes, forming a continuous initial deposition layer on the surface to be plated, the inner wall of mounting holes, punched edges, and crimp contact areas. The pulsed main deposition stage uses an average current density of 1.5 A / dm²-4.0 A / dm², a pulse frequency of 20 Hz-200 Hz, a duty cycle of 40%-70%, and a time of 12-35 minutes, forming a zinc-nickel alloy layer with the target thickness and nickel content. The low-current leveling stage uses a current density of 0.5 A / dm²-1.2 A / dm² for 3-8 minutes, improving insufficient deposition in low-current areas such as the inner wall of mounting holes and punched edges. The temperature of the alkaline zinc-nickel alloy plating bath is controlled between 25℃ and 40℃.

[0068] In the segmented pulse electrodeposition process, the cathode of the new energy vehicle battery connector can be oscillated or the plating solution can be circulated and sprayed. The oscillation frequency of the cathode can be 10 times / min to 40 times / min, and the oscillation amplitude can be 20mm to 80mm; the spray velocity of the plating solution circulation can be 0.2m / s to 1.2m / s. By oscillating the cathode or circulating and spraying the plating solution, the concentration polarization near the inner wall of the mounting hole, the punched edge, and the crimping contact area can be reduced, improving the regional consistency of the zinc-nickel alloy layer thickness and nickel content. In the segmented pulse electrodeposition process, the low-current pre-deposition stage, the pulse main deposition stage, and the low-current leveling stage play roles in the initial nucleation, main growth, and low-current compensation deposition of the zinc-nickel alloy layer, respectively.

[0069] In the low-current pre-deposition stage, a current density of 0.3 A / dm²-0.8 A / dm² is used for deposition, allowing a continuous initial deposition layer to form on the inner wall of the mounting hole, the punched edge, and the crimp contact area. This stage features a lower current density, resulting in weaker hydrogen evolution and localized alkalization at the cathode interface. This reduces edge over-plating caused by preferential growth in high-current areas and lowers the risk of incomplete or thin plating in low-current areas due to insufficient initial nucleation.

[0070] The pulsed main deposition stage employs a pulse frequency of 20Hz-200Hz and a duty cycle of 40%-70%. During pulse conduction, the higher instantaneous current is beneficial for increasing the nucleation density and deposition efficiency of the zinc-nickel alloy layer. During pulse intervals, the cathode diffusion layer is restored, and zinc complexes, nickel complexes, and hydroxide ions in the plating bath re-diffuse towards the inner wall of the mounting hole and near the punched edge, thereby reducing concentration polarization caused by continuous constant-current deposition. By alternating between continuous deposition and intermittent replenishment, the metal ion supply state near deep holes, edges, and crimp contact areas can be improved, enabling the zinc-nickel alloy layer to maintain a relatively stable thickness and nickel content in complex structural regions.

[0071] In the low-current leveling stage, deposition continues at a current density of 0.5 A / dm²-1.2 A / dm² to compensate for insufficient deposition in the mounting hole inner wall, punched edges, and low-current shielded areas from the previous stage. Because the current density in this stage is lower than in the pulsed main deposition stage, the continued rapid growth in the planar and edge high-current areas is suppressed, while the relative deposition ratio in the low-current areas increases. This reduces the difference between the mounting hole inner wall thickness and the planar area thickness, and lowers the risk of localized corrosion caused by insufficient plating at the punched edges.

[0072] Following segmented pulse electrodeposition, a zinc-nickel alloy layer is formed on the surface of the nickel transition layer. The nickel content in the zinc-nickel alloy layer is controlled at 12wt.%-16wt.%, and the thickness is controlled at 5μm-12μm. The ratio of the thickness of the zinc-nickel alloy layer on the inner wall of the mounting hole to the thickness in the planar area is not less than 0.65, the ratio of the thickness of the zinc-nickel alloy layer on the punched edge to the thickness in the planar area is not less than 0.60, and the difference in nickel content between the zinc-nickel alloy layer in the crimp contact area and the planar area is not greater than 2 percentage points. By controlling the thickness and nickel content as described above, the corrosion resistance consistency of the mounting hole, punched edge, and crimp contact area of ​​the connector can be improved.

[0073] After forming the zinc-nickel alloy layer, the battery connectors for new energy vehicles undergo passivation treatment to obtain a passivation film. The passivation treatment uses a trivalent chromium passivation solution, which includes 0.5 g / L-5 g / L trivalent chromium salt, 1 g / L-20 g / L nitrate, 0.5 g / L-10 g / L organic carboxylate, 0.1 g / L-3 g / L film-forming promoter, and water. The pH of the trivalent chromium passivation solution is 1.8-3.5, the passivation temperature is 20℃-40℃, and the treatment time is 20 s-90 s. After passivation, the components are washed with water and dried at 80℃-120℃ for 5 min-20 min.

[0074] After passivation, the battery connectors for new energy vehicles undergo thin-film sealing treatment. The thin-film sealing treatment uses an aqueous sealing solution, which includes 0.2 g / L-5 g / L hydrolyzed silane, 0.5 g / L-10 g / L nano-silica sol, 0.1 g / L-3 g / L molybdate, 0.1 g / L-3 g / L tungstate, and water.

[0075] The thin-film sealing process includes a primary thin-film sealing process for the entire component and a secondary sealing process for the non-pressurized exposed areas. The primary thin-film sealing process involves immersing the passivated new energy vehicle battery connector entirely in an aqueous sealing solution at 35℃-55℃ for 20-60 seconds to form an initial sealing film on the surface of the pressurized contact area, the area around the mounting holes, the punched edges, and the non-pressurized exposed areas. Subsequently, a liquid blowing process and a pre-drying process are performed. The liquid blowing process uses compressed air or an air knife to remove residual liquid from the surface of the pressurized contact area. The pre-drying temperature is 60℃-90℃, and the time is 2-8 minutes, so that the initial sealing film reaches a surface-dry state.

[0076] After the initial full-part thin-film sealing treatment, the crimping contact area is covered using a masking fixture, a heat-resistant silicone cap, peelable masking tape, or polyimide tape. The edge of the masked part extends 0.5mm-2.0mm beyond the boundary of the crimping contact area to reduce the penetration of the secondary sealing liquid into the crimping contact area. After masking, a secondary sealing treatment is performed on the non-crimping exposed areas. The secondary sealing treatment is carried out by spraying, brushing, dipping, or directional coating, at a temperature of 45℃-70℃ and a treatment time of 20s-90s. After the secondary sealing treatment, the masked part is removed, and the area is dried at 80℃-120℃ for 5min-20min to obtain the sealing film layer.

[0077] A single full-part thin-sealing treatment forms a thin sealing film with a thickness of 20nm-120nm in the crimped contact area to reduce the risk of increased contact resistance in the crimped contact area. After shielding, a secondary sealing treatment is performed on the non-crimped exposed area to achieve a sealing film thickness of 80nm-300nm in the non-crimped exposed area, thereby improving the chloride salt corrosion resistance of the exposed area.

[0078] When the substrate of the battery connector for new energy vehicles is a steel connector with a tensile strength of not less than 1000 MPa, a dehydrogenation treatment is performed after segmented pulse electrodeposition and before passivation. The dehydrogenation treatment temperature is 180℃-220℃, and the time is 2h-4h. After the dehydrogenation treatment, passivation treatment is performed within 30 minutes to reduce the risk of embrittlement caused by hydrogen absorption during the electroplating process of high-strength steel connectors.

[0079] Example 1

[0080] This embodiment provides a method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles, with the object being a steel battery connector plate. The steel battery connector plate has mounting holes, punched edges, and a flat pressing contact area.

[0081] First, the steel battery connecting plate is subjected to alkaline degreasing at 60℃ for 6 minutes. After rinsing with water, it is activated by acid pickling with an 8% hydrochloric acid solution for 30 seconds. Then, it is rinsed with water and surface-conditioning is performed to obtain the surface to be plated. The surface conditioning process uses a weakly acidic complexing wetting solution, comprising 8 g / L sodium citrate, 5 g / L sodium gluconate, 10 g / L ammonium sulfate, 0.10 g / L polyether nonionic wetting agent, and deionized water, with a pH of 4.8. The surface conditioning treatment temperature is 28℃ for 30 seconds. After surface conditioning, it is rinsed with water and then proceeds to the nickel transition layer electrodeposition process within 60 seconds to obtain the surface to be plated.

[0082] Subsequently, a nickel transition layer is formed on the surface to be plated. The nickel transition layer is prepared using Watt's nickel plating solution, which, per 1L of working solution, comprises 240 g / L nickel sulfate hexahydrate, 45 g / L nickel chloride hexahydrate, 35 g / L boric acid, 1.0 g / L sodium saccharin, 0.05 g / L sodium dodecyl sulfate, and water, with a pH of 4.0-4.5. During the formation of the nickel transition layer, the current density is 1.5 A / dm², the plating time is 2 min, and the plating temperature is 50℃, resulting in a nickel transition layer thickness of 0.6 μm. After the nickel transition layer is formed, it is rinsed with water, and within 60 seconds, the steel battery connecting plate is immersed in an alkaline zinc-nickel alloy plating solution.

[0083] Based on 1L of working solution, the alkaline zinc-nickel alloy electroplating solution comprises the following components: zinc oxide 11.20g / L, corresponding to a zinc ion concentration of 9.0g / L; nickel sulfate hexahydrate 5.38g / L, corresponding to a nickel ion concentration of 1.2g / L; sodium hydroxide 125g / L; triethanolamine 20g / L; sodium gluconate 18g / L; benzyltriethylammonium chloride 0.12g / L; dodecyl dimethyl benzyl ammonium chloride 0.08g / L; amino-terminated polyether D-230 0.12g / L; 2,4,7,9-tetramethyl-5-decyn-4,7-diol 0.08g / L; the balance is water.

[0084] Among them, benzyltriethylammonium chloride and dodecyldimethylbenzylammonium chloride are used as quaternary ammonium salt grain refiners with a total concentration of 0.20 g / L; amino-terminated polyether D-230 is used as a polyether amine leveling agent in the low current region with a concentration of 0.12 g / L; and 2,4,7,9-tetramethyl-5-decyn-4,7-diol is used as an alkynyl diol wetting agent with a concentration of 0.08 g / L.

[0085] A steel battery connecting plate with a nickel transition layer was placed in the aforementioned alkaline zinc-nickel alloy electroplating solution and subjected to segmented pulse electrodeposition at 32°C. The low-current pre-deposition stage had a current density of 0.5 A / dm² and a time of 4 min; the pulse main deposition stage had an average current density of 2.5 A / dm², a pulse frequency of 80 Hz, a duty cycle of 55%, and a time of 22 min; the low-current leveling stage had a current density of 0.8 A / dm² and a time of 5 min. Cathode oscillation was used during the electrodeposition process, with an oscillation frequency of 20 times / min and an oscillation amplitude of 40 mm.

[0086] Following segmented pulse electrodeposition, a zinc-nickel alloy layer was formed on the surface of the nickel transition layer. Testing revealed that the thickness of the zinc-nickel alloy layer in the planar region was 8.0 μm, while the thickness inside the mounting hole was 5.8 μm, with a ratio of 0.73 between the inner wall thickness and the planar region thickness. The thickness of the zinc-nickel alloy layer at the punched edge was 5.4 μm, with a ratio of 0.68 between the punched edge thickness and the planar region thickness. The nickel content in the planar region's zinc-nickel alloy layer was 14.0 wt.%, while the nickel content in the press-fit contact region's zinc-nickel alloy layer was 14.2 wt.%, with a difference of 0.2 percentage points between the nickel content in the press-fit contact region and the planar region.

[0087] Subsequently, the steel battery connecting plate with the zinc-nickel alloy layer was subjected to trivalent chromium passivation treatment. The trivalent chromium passivation solution consisted of 2 g / L trivalent chromium salt, 8 g / L nitrate, 4 g / L organic carboxylate, 1 g / L film-forming promoter, and water, with a pH of 2.6. The film-forming promoter specifically used were 0.60 g / L cobalt sulfate, 0.25 g / L nickel sulfate, and 0.15 g / L manganese sulfate. The passivation treatment temperature was 30℃, and the treatment time was 50 s. After passivation, the plate was washed with water and dried at 100℃ for 10 min.

[0088] Then, a thin-film sealing treatment was performed. The aqueous sealing solution consisted of 2 g / L hydrolyzed silane, 4 g / L nano-silica sol, 0.8 g / L molybdate, 0.5 g / L tungstate, and water. The thin-film sealing treatment temperature was 55℃, and the treatment time was 60 s. After treatment, the sealing film thickness in the press-fit contact area was 60 nm, and the sealing film thickness in the non-press-fit exposed area was 160 nm. After drying, a steel battery connection plate with a corrosion-resistant zinc-nickel alloy coating was obtained.

[0089] Example 2

[0090] This embodiment provides a method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles, with the object being a steel fastening gasket. The steel fastening gasket has a central mounting hole, a punched edge, and a bolt crimping contact area.

[0091] This embodiment is basically the same as Embodiment 1, except that: the nickel transition layer thickness is 0.4 μm; the zinc ion concentration in the alkaline zinc-nickel alloy electroplating solution is 8.0 g / L, the nickel ion concentration is 1.0 g / L, the sodium hydroxide concentration is 115 g / L, the triethanolamine concentration is 18 g / L, the sodium gluconate concentration is 16 g / L, and the polyetheramine low-current leveling agent concentration is 0.18 g / L; the current density in the low-current pre-deposition stage is 0.4 A / dm², and the time is 5 min; the average current density in the pulsed main deposition stage is 2.2 A / dm², the pulse frequency is 100 Hz, the duty cycle is 50%, and the time is 20 min; the current density in the low-current leveling stage is 0.7 A / dm², and the time is 6 min. The resulting zinc-nickel alloy layer has a thickness of 7 μm and a nickel content of 13 wt.%. After thin-film sealing treatment, the sealing film thickness in the press-fit contact area is 50 nm, and the sealing film thickness in the non-press-fit exposed area is 140 nm.

[0092] Example 3

[0093] This embodiment provides a method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles, with the copper alloy grounding connector being processed. The copper alloy grounding connector has mounting holes, punched edges, and a grounding crimp contact area.

[0094] First, the copper alloy grounding connector is degreased alkaline at a temperature of 55°C for 5 minutes. After rinsing with water, it is activated by micro-etching using a persulfate-sulfuric acid system for 25 seconds to obtain the surface to be plated.

[0095] A nickel transition layer is formed on the surface to be plated. The nickel transition layer is prepared using a nickel sulfamate electroplating solution with a current density of 1.2 A / dm², an electroplating time of 3 min, an electroplating temperature of 45 °C, and a nickel transition layer thickness of 0.9 μm. After the nickel transition layer is formed, it is washed with water and then immersed in an alkaline zinc-nickel alloy electroplating solution within 90 s.

[0096] Based on 1L of working solution, the alkaline zinc-nickel alloy electroplating solution comprises the following components: zinc ions 10.0g / L, nickel ions 1.5g / L, sodium hydroxide 135g / L, diethylenetriamine 12g / L, sodium gluconate 25g / L, pyridinium salt grain refiner 0.25g / L, polyoxyethylene ether low current zone leveling agent 0.10g / L, alkyl glycoside wetting agent 0.06g / L, with the balance being water.

[0097] A copper alloy grounding connector with a nickel transition layer was placed in the aforementioned alkaline zinc-nickel alloy electroplating solution and subjected to segmented pulse electrodeposition at 30°C. The current density of the low-current pre-deposition stage was 0.6 A / dm², and the time was 3 min; the average current density of the pulsed main deposition stage was 2.8 A / dm², the pulse frequency was 60 Hz, the duty cycle was 60%, and the time was 24 min; the current density of the low-current leveling stage was 0.9 A / dm², and the time was 4 min. A circulating spray of the plating solution was used during the electrodeposition process, with a spray velocity of 0.6 m / s.

[0098] The zinc-nickel alloy layer obtained after electrodeposition has a thickness of 9 μm and a nickel content of 15 wt.%. Subsequently, trivalent chromium passivation and thin-film sealing treatment are performed. The sealing film thickness in the press-fit contact area is 70 nm, and the sealing film thickness in the non-press-fit exposed area is 180 nm, resulting in a copper alloy grounding connector with a corrosion-resistant zinc-nickel alloy coating.

[0099] Example 4

[0100] This embodiment provides a method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles, the object of which is a high-strength steel connecting plate with a tensile strength of not less than 1000MPa.

[0101] This embodiment is basically the same as Embodiment 1, except that a dehydrogenation treatment is performed after segmented pulse electrodeposition and before passivation. The dehydrogenation treatment temperature is 200℃ and the time is 3 hours. After the dehydrogenation treatment is completed, trivalent chromium passivation treatment is performed within 30 minutes. This treatment method reduces the risk of hydrogen absorption generated during the electroplating process of the high-strength steel connecting plate.

[0102] Comparative Example 1

[0103] Comparative Example 1 is basically the same as Example 1, except that: no nickel transition layer is formed, and the steel battery connecting plate is directly put into the alkaline zinc-nickel alloy electroplating solution for segmented pulse electrodeposition after degreasing, acid pickling activation and water washing.

[0104] Comparative Example 2

[0105] Comparative Example 2 is basically the same as Example 1, except that: instead of segmented pulse electrodeposition, constant current electrodeposition is used, with a current density of 2.5 A / dm² and a time of 31 min. The other conditions are the same as in Example 1.

[0106] Comparative Example 3

[0107] Comparative Example 3 is basically the same as Example 1, except that: no low current leveling stage is set, only a low current pre-deposition stage and a pulsed main deposition stage are performed, and the other conditions are the same as those in Example 1.

[0108] Comparative Example 4

[0109] Comparative Example 4 is basically the same as Example 1, except that the film sealing treatment time is extended to 240s, so that the thickness of the sealing film in the press-fit contact area exceeds 120nm. The other conditions are the same as those in Example 1.

[0110] Comparative Example 5

[0111] Comparative Example 5 is basically the same as Example 1, except that the nickel ion concentration and pulse main deposition parameters in the alkaline zinc-nickel alloy electroplating solution are adjusted to control the nickel content in the zinc-nickel alloy layer to 9wt.%-10wt.%, and the other conditions are the same as in Example 1.

[0112] Performance testing methods

[0113] To evaluate the technical effect of the corrosion-resistant zinc-nickel alloy electroplating method for new energy vehicle battery connectors of the present invention, the samples prepared in the examples and comparative examples were tested as follows.

[0114] I. Coating Thickness Inspection. The thickness of the zinc-nickel alloy layer is inspected using an X-ray fluorescence thickness gauge or cross-sectional microscopy. Inspection points are selected in the planar area, the inner wall of the mounting hole, the punched edge, and the press-fit contact area, with no fewer than three inspection points in each area. The average value is taken. The thickness ratio of the inner wall of the mounting hole is equal to the average thickness of the zinc-nickel alloy layer on the inner wall of the mounting hole divided by the average thickness of the zinc-nickel alloy layer in the planar area; the thickness ratio of the punched edge is equal to the average thickness of the zinc-nickel alloy layer on the punched edge divided by the average thickness of the zinc-nickel alloy layer in the planar area.

[0115] II. Nickel Content Detection. The nickel content in the zinc-nickel alloy layer was detected using X-ray fluorescence analysis or energy dispersive spectroscopy. The nickel content was measured in the planar area, the inner wall of the mounting hole, the punched edge, and the press-fit contact area, and the difference in nickel content between the press-fit contact area and the planar area was calculated.

[0116] III. Sealing Membrane Thickness Measurement. The sealing membrane thickness in the press-fit contact area and the non-press-fit exposed area is measured using an ellipsometer, X-ray photoelectron spectroscopy depth analysis, or cross-sectional transmission electron microscopy. At least three measurement points are used for each area, and the average value is taken.

[0117] IV. Neutral Salt Spray Test. The samples were subjected to a neutral salt spray test for 720 hours. After the test, the substrate was observed for red rust, and the number of corrosion spots and the corrosion area ratio were recorded. The corrosion area ratio was calculated as the ratio of the total projected area of ​​the corroded area to the total area of ​​the tested area multiplied by 100%.

[0118] V. Contact Resistance Testing. The four-terminal method is used to test the contact resistance of the crimped contact area. The initial contact resistance R0 is measured before the salt spray test, and the contact resistance R1 is measured after the salt spray test. The contact resistance growth rate is calculated as (R1-R0) / R0×100%.

[0119] VI. Thermal Cycling Test. The thermal cycling conditions are: -40℃ for 1 hour, then heated to 85℃ and held for 1 hour, which constitutes one cycle. A total of 20 cycles are performed. After the thermal cycling, the contact resistance of the crimped contact area is measured, and the coating is observed for blistering, cracking, or peeling.

[0120] The test results can be recorded according to Tables 1 to 4.

[0121] Table 1. Test results of zinc-nickel alloy layer thickness and nickel content

[0122]

[0123] Table 2. Corrosion resistance test results after 720 hours of neutral salt spray test.

[0124]

[0125] Table 3. Contact resistance test results of the crimped contact area

[0126]

[0127] Table 4. Test results of sealing film thickness and coating stability

[0128]

[0129] As shown in Table 1, in Examples 1-4, the thickness ratio of the inner wall of the mounting hole is 0.70-0.73, the thickness ratio of the punched edge is 0.65-0.68, and the difference in nickel content between the press-fit contact area and the planar area is 0.1-0.3 percentage points. This indicates that the present invention, by using a nickel transition layer, an alkaline zinc-nickel alloy electroplating solution, and segmented pulse electrodeposition, can improve the consistency of the plating thickness and nickel content of the inner wall of the mounting hole, the punched edge, and the press-fit contact area.

[0130] Comparative Example 1 did not form a nickel transition layer. Although the ratio of the inner wall thickness of the mounting hole and the ratio of the punched edge thickness were close to the lower limit, the blistering area increased to 0.18% after thermal cycling, and the cross-cut adhesion level dropped to level 1. This indicates that the nickel transition layer has a positive effect on improving the bonding stability between the zinc-nickel alloy layer and the substrate.

[0131] Comparative Example 2 used constant current electrodeposition, which reduced the thickness ratio of the mounting hole inner wall to 0.56 and the thickness ratio of the punched edge to 0.53, while increasing the difference in nickel content between the crimped contact area and the planar area to 2.5 percentage points; at the same time, the contact resistance growth rate after salt spray increased to 45.5%. These results indicate that constant current deposition tends to result in faster deposition in the planar area, while insufficient deposition occurs in areas such as the mounting hole inner wall and punched edge, which is detrimental to the protective consistency of complex structural areas of new energy vehicle battery connectors.

[0132] Comparative Example 3 did not include a low-current leveling stage. The thickness ratio of the inner wall of the mounting hole was 0.61, and the thickness ratio of the punched edge was 0.58, which did not reach the level of the example. This indicates that the low-current leveling stage can compensate for the deposition in the low-current area and improve the problem of insufficient coating on the inner wall of the mounting hole and the punched edge.

[0133] Comparative Example 4 extended the film sealing treatment time, increasing the film thickness in the crimped contact area to 180 nm and in the non-crimped exposed area to 380 nm. Although the corrosion area ratio was low after 720 h of neutral salt spray testing and the coating stability was good after thermal cycling, the initial contact resistance increased to 1.22 mΩ, higher than 0.82 mΩ in Example 1. This indicates that an excessively thick sealing film increases the contact resistance in the crimped contact area, which is detrimental to the current flow stability of the connector.

[0134] In Comparative Example 5, the nickel content of the zinc-nickel alloy layer was 9.5 wt.%-9.8 wt.%, which is lower than the control range of this invention. After 720 hours of neutral salt spray testing, this sample showed numerous corrosion spots, with the corrosion area increasing to 1.10%. The contact resistance growth rate after salt spray increased to 63.8%, indicating that the zinc-nickel alloy layer has insufficient corrosion resistance when the nickel content is too low, making it difficult to meet the long-term corrosion resistance and contact stability requirements of new energy vehicle battery connectors.

[0135] In summary, Examples 1-4, through the combination of a nickel transition layer, an alkaline zinc-nickel alloy electroplating solution, a low-current pre-deposition stage, a pulsed main deposition stage, a low-current leveling stage, trivalent chromium passivation treatment, and thin-film sealing treatment, enable the new energy vehicle battery connector to form a zinc-nickel alloy layer with relatively uniform thickness and nickel content on the inner wall of the mounting hole, the punched edge, and the press-fit contact area. Furthermore, after neutral salt spray testing and thermal cycling, it maintains a low contact resistance growth rate and good coating bonding stability.

[0136] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles, characterized in that, Includes the following steps: The substrate of the new energy vehicle battery connector is degreased, activated, and surface-conditioned to obtain the surface to be plated; the new energy vehicle battery connector has mounting holes, punched edges, and crimping contact areas. A nickel transition layer is formed on the surface to be plated, the thickness of the nickel transition layer being 0.3μm-1.5μm; The new energy vehicle battery connector with the nickel transition layer formed thereon is immersed in an alkaline zinc-nickel alloy electroplating solution for 120 seconds for segmented pulse electrodeposition, and a zinc-nickel alloy layer is formed on the surface of the nickel transition layer. Passivation treatment is performed on the new energy vehicle battery connector with the zinc-nickel alloy layer to obtain a passivation film layer. The new energy vehicle battery connector with the passivation film layer is subjected to thin-film sealing treatment to obtain a corrosion-resistant zinc-nickel alloy coating. The alkaline zinc-nickel alloy electroplating solution comprises: zinc ions 6g / L-14g / L, nickel ions 0.6g / L-2.5g / L, sodium hydroxide 90g / L-160g / L, nickel complexing agent 20g / L-70g / L, grain refiner 0.05g / L-1.0g / L, low current area leveling agent 0.02g / L-0.50g / L, wetting agent 0.02g / L-0.30g / L, and water; The segmented pulsed electrodeposition includes a low-current pre-deposition stage, a pulsed main deposition stage, and a low-current leveling stage. The current density of the low-current pre-deposition stage is 0.3 A / dm²-0.8 A / dm², and the time is 2 min-6 min. The average current density of the pulsed main deposition stage is 1.5 A / dm²-4.0 A / dm², the pulse frequency is 20 Hz-200 Hz, the duty cycle is 40%-70%, and the time is 12 min-35 min. The current density of the low-current leveling stage is 0.5 A / dm²-1.2 A / dm², and the time is 3 min-8 min. The temperature of the alkaline zinc-nickel alloy electroplating solution is 25℃-40℃. The zinc-nickel alloy layer has a nickel content of 12wt.%-16wt.% and a thickness of 5μm-12μm; the ratio of the thickness of the zinc-nickel alloy layer on the inner wall of the mounting hole to the thickness of the planar area is ≥0.65; the ratio of the thickness of the zinc-nickel alloy layer on the punched edge to the thickness of the planar area is ≥0.60; and the difference between the nickel content in the press-fit contact area and the nickel content in the planar area is ≤2 percentage points. The passivation treatment is performed at a temperature of 20℃-40℃ for 20s-90s; the thin-film sealing treatment is performed at a temperature of 35℃-70℃ for 20s-120s; after the thin-film sealing treatment, the thickness of the sealing film in the press-fit contact area is 20nm-120nm.

2. The method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to claim 1, characterized in that, The base material of the new energy vehicle battery connector is a steel connecting piece, a steel connecting plate, a steel fastening gasket, a copper alloy connector, or an aluminum alloy connector. When the substrate of the new energy vehicle battery connector is a copper alloy connector, micro-etching activation is performed using a persulfate-sulfuric acid system or a hydrogen peroxide-sulfuric acid system before forming the nickel transition layer. When the substrate of the new energy vehicle battery connector is an aluminum alloy connector, before forming the nickel transition layer, it undergoes degreasing, alkaline etching, descaling, zinc replacement and nickel pre-plating treatments in sequence. When the substrate of the new energy vehicle battery connector is a steel connecting piece, a steel connecting plate, or a steel fastening gasket, before forming the nickel transition layer, it is pickled and activated by pickling solution. The pickling solution is a hydrochloric acid solution or sulfuric acid solution with a mass fraction of 5%-15%, and the pickling and activation time is 10s-60s.

3. The method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to claim 1, characterized in that, The nickel transition layer is an electrodeposited nickel layer, which is prepared using Watt's nickel plating solution, nickel aminosulfonate plating solution, or semi-bright nickel plating solution. When forming the nickel transition layer, the current density is 0.8A / dm²-2.5A / dm², the electroplating time is 1min-5min, and the electroplating temperature is 35℃-60℃. After the nickel transition layer is formed, it is washed with water and then immersed in the alkaline zinc-nickel alloy electroplating solution within 60s-120s.

4. The method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to claim 1, characterized in that, The zinc ions are derived from one or more of zinc oxide, zinc sulfate, and zinc acetate. The nickel ions are derived from one or more of nickel sulfate, nickel carbonate, nickel acetate, and nickel aminosulfonate. The nickel complexing agent includes at least two of the following: triethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylidene diphosphonate, and gluconate. In the nickel complexing agent, the mass ratio of amine complexing agent to carboxylate or phosphonate complexing agent is 1:(0.5-2.5).

5. The method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to claim 1, characterized in that, The grain refiner includes one or more of quaternary ammonium salt compounds, pyridinium salt compounds, and polyethyleneimine derivatives; The low-current leveling agent includes one or more of polyetheramine, polyoxyethylene ether, and imidazoline derivatives. The wetting agent includes one or more of acetylenic diol wetting agents, alkyl glycosides, and polyether wetting agents; The mass ratio of the grain refiner, the low-current area leveling agent, and the wetting agent is 1:(0.2-1.5):(0.1-1.0).

6. The method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to claim 1, characterized in that, During the segmented pulse electrodeposition process, the new energy vehicle battery connector undergoes cathode oscillation or plating solution circulation spraying. The oscillation frequency of the cathode is 10 times / min to 40 times / min, and the oscillation amplitude is 20mm to 80mm. The spray velocity of the circulating spray of the plating solution is 0.2 m / s-1.2 m / s; The low-current pre-deposition stage, the pulsed main deposition stage, and the low-current leveling stage are all performed under the conditions of cathode oscillation or the circulating spray of the plating solution.

7. The method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to claim 1, characterized in that, The passivation treatment uses a trivalent chromium passivation solution, which comprises 0.5 g / L-5 g / L of trivalent chromium salt, 1 g / L-20 g / L of nitrate, 0.5 g / L-10 g / L of organic carboxylate, 0.1 g / L-3 g / L of film-forming promoter, and water; The pH of the trivalent chromium passivation solution is 1.8-3.5; The trivalent chromium passivation treatment is followed by water washing and drying at 80℃-120℃ for 5min-20min.

8. The method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to claim 1, characterized in that, The thin-film sealing treatment uses an aqueous sealing solution, which includes 0.2 g / L-5 g / L hydrolyzed silane, 0.5 g / L-10 g / L nano silica sol, 0.1 g / L-3 g / L molybdate, 0.1 g / L-3 g / L tungstate, and water. After the thin-film sealing treatment, the thickness of the sealing film in the press-fit contact area is 20nm-120nm, and the thickness of the sealing film in the non-press-fit exposed area is 80nm-300nm.

9. The method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to claim 1, characterized in that, When the substrate of the new energy vehicle battery connector is a steel connector with a tensile strength of not less than 1000MPa, a dehydrogenation treatment is performed after the segmented pulse electrodeposition and before the passivation treatment. The dehydrogenation treatment is performed at a temperature of 180℃-220℃ for 2-4 hours. After the dehydrogenation treatment, the passivation treatment is performed within 30 minutes.

10. A method for electroplating corrosion-resistant zinc-nickel alloy for battery connectors in new energy vehicles according to any one of claims 1-9, characterized in that, The resulting new energy vehicle battery connector includes a substrate, a nickel transition layer, a zinc-nickel alloy layer, a passivation film layer, and a sealing film layer. The nickel content in the zinc-nickel alloy layer is 12 wt.%-16 wt.%; The zinc-nickel alloy layer has a thickness of 5μm-12μm; After undergoing a neutral salt spray test for 720 hours, the substrate of the new energy vehicle battery connector did not show any red rust. After undergoing a neutral salt spray test for 720 hours, the contact resistance growth rate of the crimped contact area of ​​the new energy vehicle battery connector is ≤30%. After the new energy vehicle battery connector undergoes 20 cycles of thermal cycling from -40℃ to 85℃, the contact resistance growth rate of the crimped contact area is ≤25%.

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