Electrophoresis anti-corrosion method for engineering machinery battery replacement frame

Abstract

An electrophoresis anti-corrosion method for an engineering machinery battery changing frame relates to the technical field of metal surface treatment and comprises the following steps: S1, pretreatment: a workpiece is sequentially subjected to degreasing, water washing, surface conditioning, chromium-free zirconium treatment, silane treatment and pure water washing; s2, electrophoresis: immersing the workpiece into a thick-film cathode electrophoretic paint tank solution of an electrophoresis tank, and electrifying for electrophoretic deposition; s3, curing is conducted, specifically, the workpiece subjected to electrophoresis is pre-cured firstly, and then complete curing is conducted; in the step S1, the silane agent is one or a combination of epoxy silane, amino silane and sulfydryl silane, and the mass volume concentration of the silane solution is 0.5%-5%; the pH value of a treatment solution for chromium-free zirconium treatment is 3.5-4.5, and the treatment temperature is 20-35 DEG C; the adhesive force of the coating can be remarkably improved, and coating stripping caused by strong vibration is effectively resisted; the corrosion-resistant steel plate is good in corrosion resistance, can effectively resist corrosion of mine mud and chemicals, has the advantages of being environmentally friendly, remarkable in economic benefit and the like, and is particularly suitable for industrial production of large workpieces with complex structures.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, and in particular to an electrophoretic corrosion protection method for battery swapping frames of new energy engineering machinery. Background Technology

[0002] In new energy construction machinery such as electric mining trucks and electric loaders, the battery swapping frame is a key structural component that supports the power battery pack. Its service environment is extremely harsh, requiring it to withstand strong vibrations and impacts, scratches from sand and gravel, and corrosion from highly corrosive media (such as acidic mine mud, de-icing agents, and seawater mist). If the coating fails and leads to frame corrosion, it will cause serious structural safety hazards and economic losses due to downtime.

[0003] Currently, most mainstream corrosion protection processes employ the traditional electrophoresis method of "phosphating / zirconium treatment + cathodic electrophoresis." However, this method has the following drawbacks: 1. Insufficient adhesion: The bonding force between traditional conversion films and the workpiece substrate is limited. Under the continuous strong vibration conditions of engineering machinery, the coating is prone to micro-cracks and peeling off from stress concentration points such as edges and welds. Once damaged, corrosive media quickly penetrate, leading to rapid corrosion of the battery swapping frame.

[0004] 2. Limited corrosion resistance: The conversion film formed by a single pretreatment is not dense enough, and the film thickness uniformity of traditional electrophoretic paint is not well controlled on the surface of complex workpieces, with poor edge coverage, and corrosive media can easily penetrate from weak points.

[0005] 3. Conflict between environmental protection and performance: The performance, especially the adhesion, of environmentally friendly chromium-free zirconium oxide films is usually inferior to that of traditional chromium-containing conversion films, making it difficult to meet the extreme requirements of engineering machinery. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an electrophoretic anti-corrosion method for battery swapping frames of engineering machinery, which can significantly improve the adhesion of the coating and the overall corrosion resistance of the coating, and ensure that the coating can still play a good anti-corrosion role under extremely harsh working conditions.

[0007] The technical solution to the above-mentioned technical problems is: an electrophoretic corrosion protection method for battery swapping frames of engineering machinery, comprising the following steps: S1. Pretreatment: The workpiece is subjected to degreasing, water washing, surface conditioning, chromium-free zirconium treatment, silane treatment, and pure water washing in sequence; S2. Electrophoresis: The workpiece treated in step S1 is immersed in the thick film cathodic electrophoresis paint bath solution in the electrophoresis tank, and electrophoretic deposition is performed by passing an electric current. S3. Curing: The electrophoretic workpiece is first pre-cured, and then fully cured.

[0008] Furthermore, in step S1, the silane treatment uses one or a combination of epoxy silane, amino silane, or mercapto silane, the mass-volume concentration of the silane solution is 0.5%-5%, the treatment temperature is 15-40°C, and the treatment time is 1-5 minutes.

[0009] Furthermore, in step S1, the chromium-free zirconium treatment has a treatment solution pH of 3.5-4.5, a treatment temperature of 20-35°C, and a treatment time of 2-5 minutes.

[0010] Furthermore, the thick film cathodic electrophoretic paint in step S2 is a lead-free and tin-free thick film cathodic electrophoretic paint, the electrophoretic deposition voltage is 150-250V, and the film thickness after deposition is 25-35μm.

[0011] Furthermore, the pre-curing temperature in step S3 is 80-100°C, and the time is 8-15 minutes; the complete curing temperature is 170-185°C, and the time is 20-30 minutes.

[0012] Furthermore, in step S2, a zoned anode control system is used to independently regulate the electric field distribution within the electrophoresis tank.

[0013] Furthermore, the aforementioned zoned anode control system independently regulates the electric field distribution within the electrophoresis tank by arranging independent anode systems in different areas of the electrophoresis tank, and can intelligently adjust the current density in different areas according to the shape of the workpiece and the grounding condition.

[0014] Furthermore, after degreasing and before water washing in step S1, an acid pickling process is included to remove welding oxide scale and rust from the surface of the workpiece.

[0015] Furthermore, after the pure water washing in step S1, a process of blowing or draining water is also included to reduce the amount of water carried on the surface of the workpiece entering the electrophoresis tank.

[0016] Due to the adoption of the above structure, the electrophoretic corrosion protection method for battery swapping frames of engineering machinery of the present invention has the following advantages compared with the prior art: 1. Significantly improves coating adhesion: This invention forms a bonding layer on the workpiece substrate primarily based on chemical bonding (covalent bonds) through a combination of "chromium-free zirconium treatment" and "silane treatment". The -Si-O- bonds of the silane layer bond with the metal substrate, and its organic functional groups crosslink with the electrophoretic paint resin, achieving strong chemical bonding throughout the entire process from substrate to coating. The adhesion level can reach 0, effectively resisting coating peeling caused by strong vibration.

[0017] 2. Good corrosion resistance: This invention utilizes the combined action of a composite pretreatment layer and a thick-film electrophoresis layer to create a dense, multi-layered protective barrier. The silane layer effectively seals the micropores of the zirconium oxide film, significantly slowing down the penetration path of corrosive media. Workpieces treated with this process can withstand neutral salt spray tests for over 1200 hours without substrate corrosion, effectively resisting corrosion from mining slurry and chemicals.

[0018] In addition, the present invention employs a zoned anode control system to independently regulate the electric field distribution within the electrophoresis tank. By independently controlling the electric field in different areas of the battery swapping frame, the current distribution is intelligently compensated. The current density is automatically reduced for sharp corners and protrusions, while the electric field is enhanced for grooves and cavities, ensuring uniform film thickness across the entire workpiece surface. This completely solves the problem of excessively thin paint film at edges and welds, significantly improving resistance to stone impacts and scratches. It also ensures that the internal cavities of the frame are also protected by a thick film, preventing corrosion from the inside out.

[0019] 3. Green and environmentally friendly: This invention is completely free of heavy metal pollution such as chromium, making it green and environmentally friendly, and compliant with environmental regulations.

[0020] 4. Low cost The pretreatment temperature and slag volume of this invention are low, reducing energy consumption and waste treatment costs. Furthermore, its high reliability significantly extends the product lifecycle, reduces maintenance and replacement costs, and results in substantial overall economic benefits.

[0021] 5. Good compatibility: This invention can be implemented by upgrading existing mature production lines without the need for disruptive equipment investment, and is particularly suitable for the industrial production of large and complex structural workpieces.

[0022] The technical features of an electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to the present invention will be further described below with reference to embodiments. Detailed Implementation

[0023] An electrophoretic corrosion protection method for battery swapping frames in engineering machinery includes the following steps: S1. Pretreatment: The workpiece is subjected to degreasing, pickling, water washing, surface conditioning, chromium-free zirconium plating, silane treatment, pure water washing, and draining in sequence; among which... The pH value of the treatment solution for chromium-free zirconium treatment is 3.5-4.5, the treatment temperature is 20-35°C, and the treatment time is 2-5 minutes. The chromium-free zirconium layer obtained after chromium-free zirconium treatment can form a dense nanoscale conversion film, which is firmly bonded to the workpiece substrate and provides the first anti-corrosion barrier.

[0024] The silane agent used for silane treatment is one or a combination of epoxy silane, amino silane, or mercapto silane. The mass-volume concentration of the silane solution is 0.5%-5%, the treatment temperature is 15-40°C, and the treatment time is 1-5 minutes. The silane agent treated with silane can form a unique -Si-O-Si- network structure. The organic functional groups at its ends are covalently cross-linked with the electrophoretic paint. This chemical bonding force is an order of magnitude stronger than the physical bonding force of traditional phosphating films.

[0025] The pickling process is used to remove welding scale and rust from the surface of the workpiece; the draining process is used to reduce the amount of moisture carried on the surface of the workpiece from entering the electrophoresis tank.

[0026] S2. Electrophoresis: The workpiece treated in step S1 is immersed in the thick-film cathodic electrophoresis paint bath solution, and electrophoretic deposition is performed by applying an electric current; wherein, The thick film cathodic electrophoretic paint is a lead-free and tin-free type. The electrophoretic deposition voltage is 150-250V, and the film thickness after deposition is 25-35μm. With this lead-free and tin-free thick film electrophoretic paint, a film thickness of more than 30μm can be formed in one step. It has excellent penetration power and can fully cover the internal cavity and weld of complex structures, achieving all-round protection without dead angles.

[0027] In this process, a zoned anode control system is used to independently regulate the electric field distribution within the electrophoresis tank. Specifically, independent anode systems are arranged in different areas of the electrophoresis tank, and the current density in different areas can be intelligently adjusted according to the shape of the workpiece and the grounding condition. This invention intelligently compensates for the current distribution by independently controlling the electric field in different areas of the battery swapping frame. It automatically reduces the current density at sharp corners and protrusions, and strengthens the electric field in grooves and cavities, ensuring uniform film thickness across the entire workpiece surface. This completely solves the problem of excessively thin paint film at edges and welds, significantly improving resistance to stone impacts and scratches.

[0028] S3. Curing: The electrophoretic workpiece is first pre-cured at a temperature of 80-100°C for 8-15 minutes to allow the paint film to slowly gel and allow most of the solvent to escape smoothly; then it is fully cured at a temperature of 170-185°C for 20-30 minutes to form a dense and defect-free final coating.

[0029] Specific Application Example 1

[0030] Take the battery swapping frame of an electric loader as an example.

[0031] An electrophoretic corrosion protection method for a battery swapping frame of an electric loader includes the following steps: S1. Preprocessing: S11. Degreasing: Using a combination of spraying and immersion, a neutral and environmentally friendly degreasing agent is used at a temperature of 50°C for 5 minutes to thoroughly remove grease and dirt from the surface of the workpiece. S12. Pickling: Removes welding scale and rust from the surface of the workpiece; S13. Wash with water: Spray with room temperature water for 2 minutes to wash away any residual degreasing agent; S14. Surface conditioning: Use a surface conditioning agent containing titanium salt, pH 8.5-9.5, and soak at room temperature for 1 minute; S15. Chromium-free zirconium treatment: Immerse in chromium-free zirconium solution, the main components of which are fluorozirconic acid and organic acids, with a pH value of 3.8-4.2, a temperature of 30°C, and a time of 3 minutes, to form a uniform nanoscale zirconium conversion film on the surface of the workpiece. S16. Silane treatment: Immerse in a silane solution, which is a 1.5% vol aqueous solution of silane coupling agent KH-560, pH 4.5-5.5, at room temperature for 2 minutes, then remove and drain. S17. Pure water washing: Two-stage countercurrent pure water spraying is used to ensure the cleanliness of the workpiece surface, and the water droplet conductivity is <20μS / cm; S18. Draining: Reduces the amount of moisture carried on the workpiece surface that enters the electrophoresis tank.

[0032] S2. Electrophoresis: The pretreated workpiece was immersed in a lead-free and tin-free thick film cathodic electrophoresis bath with a solid content of 20% and a temperature of 28°C. The DC power supply was turned on, and deposition was carried out at 180V for 3 minutes, with a target film thickness of 30±5μm. S3. Curing: Pre-curing: Treat in a 90°C oven for 10 minutes; Complete curing: Heat to 180°C and hold for 25 minutes to allow the paint film to fully cross-link and cure.

[0033] Performance testing:

[0034] The performance of the workpieces after the above process was tested: Film thickness: The average film thickness is 32 μm, and the film thickness is uniform in the inner and outer cavities and at the edges.

[0035] Adhesion: Cross-cut test, with a cross-cut spacing of 1mm, rating of 0, no peeling.

[0036] Neutral salt spray resistance test: After 1200 hours of testing, the corrosion width on one side of the scratch is <1mm, and there is no blistering or rust in the unscratched area.

[0037] Comparative Example

[0038] The same batch of workpieces was treated using the traditional "chromium-free zirconium leaching + electrophoresis" process (omitting silane treatment). After 800 hours of salt spray testing, significant erosion was observed at the scratched areas, while a small amount of blistering was observed in the unscratched areas.

[0039] The above results show that the process of the present invention significantly improves the overall anti-corrosion performance of the coating.

Claims

1. An electrophoretic corrosion protection method for battery swapping frames in engineering machinery, characterized in that, Includes the following steps: S1. Pretreatment: The workpiece is subjected to degreasing, water washing, surface conditioning, chromium-free zirconium treatment, silane treatment, and pure water washing in sequence; S2. Electrophoresis: The workpiece treated in step S1 is immersed in the thick film cathodic electrophoresis paint bath solution in the electrophoresis tank, and electrophoretic deposition is performed by passing an electric current. S3. Curing: The electrophoretic workpiece is first pre-cured, and then fully cured.

2. The electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to claim 1, characterized in that, The silane treatment in step S1 uses one or a combination of epoxy silane, amino silane, or mercapto silane. The mass-volume concentration of the silane solution is 0.5%-5%, the treatment temperature is 15-40°C, and the treatment time is 1-5 minutes.

3. The electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to claim 1 or 2, characterized in that, In step S1, the chromium-free zirconium treatment has a pH of 3.5-4.5, a treatment temperature of 20-35°C, and a treatment time of 2-5 minutes.

4. The electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to claim 1, characterized in that, The thick film cathodic electrophoretic paint used in step S2 is a lead-free and tin-free thick film cathodic electrophoretic paint, with an electrophoretic deposition voltage of 150-250V and a film thickness of 25-35μm after deposition.

5. The electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to claim 1, characterized in that, The pre-curing temperature in step S3 is 80-100°C, and the time is 8-15 minutes; the complete curing temperature is 170-185°C, and the time is 20-30 minutes.

6. The electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to claim 1, characterized in that, In step S2, a zoned anode control system is used to independently regulate the electric field distribution within the electrophoresis tank.

7. The electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to claim 6, characterized in that, The aforementioned zoned anode control system independently regulates the electric field distribution within the electrophoresis tank by arranging independent anode systems in different areas of the electrophoresis tank, and can intelligently adjust the current density in different areas according to the shape of the workpiece and the grounding condition.

8. The electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to claim 1, characterized in that, After degreasing and before water washing in step S1, an acid pickling process is also included to remove welding oxide scale and rust from the surface of the workpiece.

9. The electrophoretic corrosion protection method for a battery swapping frame of engineering machinery according to claim 1, characterized in that, After the pure water washing in step S1, there is also a process of blowing or draining water to reduce the amount of water carried on the surface of the workpiece entering the electrophoresis tank.