Surface treatment method of zinc-nickel coating

Abstract

The invention relates to the technical field of metal coating surface treatment, and discloses a surface treatment method of a zinc-nickel coating, a passivation solution provided by the invention contains composite modified silicon carbide and modified epoxy resin, and the composite modified silicon carbide and the modified epoxy resin form a layer of compact protective film on the surface of the coating. The protective film can effectively prevent external corrosive media from invading, so that the corrosion resistance of the plating layer is improved; the silicon carbide inorganic material selected by the invention has excellent wear resistance, and can effectively prevent the protective film layer from being worn and broken; meanwhile, an alkyl long-chain structure in the composite modified silicon carbide and a polysiloxane structure in the modified epoxy resin have excellent flexibility, so that the protective film layer can better adapt to deformation of a matrix under the action of external force, the risk of cracking of the protective film layer is reduced, and corrosion of the surface of the coating material is delayed.

Description

Technical Field

[0001] The invention relates to the technical field of metal coating surface treatment, and in particular to a surface treatment method for zinc-nickel coating. Background Art

[0002] In recent years, the research and application of electroplated zinc alloys have received extensive attention, especially zinc-cobalt, zinc-iron and zinc-nickel alloy coatings. Among them, zinc-nickel alloy coatings stand out for their excellent corrosion resistance, usually containing 85% to 90% zinc and 10% to 15% nickel. Zinc-nickel alloy coatings not only excel in corrosion resistance, but also have good wear resistance and adhesion. They are widely used in the automotive industry and computer industry, especially in the production of thin plates and complex-shaped parts, which can significantly improve the service life and reliability of products. The superior properties of zinc-nickel alloys make it an important alternative to traditional zinc coatings, meeting the higher requirements of modern industry for protective materials.

[0003] Although zinc-nickel alloy coatings have many advantages, the key to their widespread application lies in the development of environmentally friendly passivation technology. The traditional passivation process mainly relies on hexavalent chromium (Cr(VI)). Although this process has excellent corrosion resistance and self-healing ability, hexavalent chromium is recognized as a highly toxic and carcinogenic substance, and its toxicity is about 100 times that of trivalent chromium. Therefore, the European Union began to restrict and ban the use of hexavalent chromium as early as the last century, and many countries and regions have also introduced relevant regulations to protect human health and environmental safety. In recent years, China has also strengthened its supervision of hexavalent chromium and promoted the research and development of environmentally friendly passivation technology. At present, researchers are exploring new methods such as chromium-free passivation technology and trivalent chromium passivation, in order to reduce the impact on the environment and human health while ensuring the performance of the coating, thereby promoting the wider application of zinc-nickel alloys.

[0004] Chinese patent document CN102312238A discloses a preparation process of zinc-nickel coating and its trivalent chromium passivation process, which includes the following steps: first, pre-plating pretreatment, in which the workpiece is physically polished with a polishing machine, and then the workpiece is cleaned with an alkaline mixed solution, distilled water, and hydrochloric acid solution in sequence, and the alkaline mixed solution is prepared from sodium hydroxide, sodium carbonate, and sodium phosphate; next, the zinc-nickel coating is prepared, and the plating solution is prepared from zinc oxide, sodium hydroxide, nickel sulfate, and ethylenediamine, and the nickel content in the zinc-nickel coating is mainly controlled by adjusting the pulse duty cycle; finally, the zinc-nickel coating is passivated with trivalent chromium, and the passivation solution is prepared from chromium nitrate, oxalic acid, oxalic acid, sodium nitrate, cobalt nitrate, and the additive sodium saccharin. By adopting the above process, although the corrosion resistance of the zinc-nickel coating is improved to a certain extent, the wear resistance of the zinc-nickel coating still needs to be further improved. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a surface treatment method for zinc-nickel coating. By adopting the surface treatment method of the present invention, the invasion of external corrosive media can be effectively blocked, thereby improving the corrosion resistance of the zinc-nickel coating.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] A surface treatment method for zinc-nickel coating comprises the following steps: immersing a workpiece after zinc-nickel electroplating into a passivation solution for passivation treatment, and after the passivation is completed, taking out the workpiece and drying it.

[0008] In the technical solution of the present invention, the steps of electroplating zinc and nickel on the workpiece are as follows:

[0009] First, the workpiece is treated in an alkaline solution at 55-65°C for 10-15 minutes to remove oil stains; then the workpiece is immersed in distilled water for washing for 5-10 minutes; then it is pickled in a 15wt% hydrochloric acid solution at room temperature for 5-10 minutes; finally, it is immersed in distilled water for washing for 5-10 minutes to obtain a pretreated workpiece.

[0010] The pretreated workpiece is placed in a 25-30°C electroplating solution for electroplating, wherein the electroplating solution includes 120-140 g / L of sodium hydroxide, 6-10 g / L of zinc ions, and 1.2-2.4 g / L of nickel ions. The electroplating time is 30-45 min. The workpiece is removed and repeatedly rinsed with flowing water to obtain a zinc-nickel electroplated workpiece.

[0011] In the technical solution of the present invention, the preparation method of the passivation solution is as follows:

[0012] S1, dispersing silicon carbide in an ethanol aqueous solution, then adding vinyltrimethoxysilane thereto, stirring for reaction, and after the reaction is completed, filtering, washing, and drying to obtain double-bond modified silicon carbide;

[0013] S2, dispersing the double bond modified silicon carbide in deionized water, then adding mercapto polyethylene glycol carboxylic acid thereto, stirring evenly, then adding initiator benzoyl peroxide, heating and stirring to react, after the reaction is completed, filtering, washing and drying to obtain composite modified silicon carbide;

[0014] S3, adding the epoxy resin to the dimethylformamide solvent, stirring evenly, then adding dihydroxy polydimethylsiloxane and a catalyst dibutyltin dilaurate thereto, followed by heating for reaction, and after the reaction is completed, obtaining a modified epoxy resin;

[0015] S4. Add the composite modified silicon carbide into the modified epoxy resin, and stir at a rotation speed of 5000-10000 rpm for 15-30 minutes to obtain a passivation solution.

[0016] Specifically, in step S1, the mass ratio of silicon carbide and vinyltrimethoxysilane is 10-15:1-3. In some embodiments of the present invention, for example, 10:1, 10:2, 10:3, 12:1, 12:2, 12:3, 15:1, 15:2, 15:3 can be selected, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Specifically, in step S1, the stirring reaction temperature is 25-40°C, for example, 25°C, 30°C, 35°C, or 40°C can be selected; the stirring reaction time is 1-3h, for example, 1h, 1.5h, 2h, 2.5h, or 3h can be selected, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0018] Specifically, in step S2, the mass ratio of double bond modified silicon carbide, mercapto polyethylene glycol carboxylic acid and benzoyl peroxide is 10-15:3-6:0.5-1.

[0019] Specifically, in step S2, the temperature of the heating and stirring reaction is 60-70°C, for example, 60°C, 65°C, or 70°C can be selected; the time of the heating and stirring reaction is 3-5h, for example, 3h, 4h, or 5h can be selected, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0020] Specifically, in step S3, the mass ratio of epoxy resin, dimethylformamide, bishydroxypolydimethylsiloxane and dibutyltin dilaurate is 20-30:50:3-6:0.5-1.

[0021] More specifically, the epoxy resin is selected from epoxy resin E44 or epoxy resin E51.

[0022] Specifically, in step S3, the temperature of the heating reaction is 60-80°C, for example, 60°C, 65°C, 70°C, 75°C, and 80°C can be selected; the time of the heating reaction is 2-5h, for example, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, and 5h can be selected, but it is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] Specifically, in step S4, the mass ratio of the composite modified silicon carbide and the modified epoxy resin is 1-5:100, for example, 1:100, 2:100, 3:100, 4:100, 5:100 can be selected, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] In the technical solution of the present invention, the temperature of the passivation treatment is 25-40°C, for example, 25°C, 30°C, 35°C, and 40°C can be selected; the time of the passivation treatment is 3-5min, for example, 3min, 4min, and 5min can be selected, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The passivation solution provided by the present invention contains composite modified silicon carbide and modified epoxy resin, which form a dense protective film on the surface of the coating. This protective film can effectively block the invasion of external corrosive media, thereby improving the corrosion resistance of the coating.

[0027] (2) The present invention first uses vinyltrimethoxysilane to treat silicon carbide, introduces double bonds on the surface of silicon carbide, and then grafts mercapto polyethylene glycol carboxylic acid on silicon carbide through an addition reaction between double bonds and mercapto groups to obtain composite modified silicon carbide, thereby improving the dispersion performance of silicon carbide in modified epoxy resin. At the same time, the carboxyl groups in the composite modified silicon carbide can undergo cross-linking reaction with the epoxy groups in the modified epoxy resin that do not participate in the reaction, thereby making the protective film layer tighter and hindering the corrosive medium from penetrating through the protective film layer to the surface of the coating. In addition, the long chain alkyl structure in the mercapto polyethylene glycol carboxylic acid can increase the steric hindrance effect, further delaying the penetration of the corrosive medium to the surface of the coating.

[0028] (3) The present invention uses dihydroxy polydimethylsiloxane to modify the epoxy resin. By introducing siloxy groups into the epoxy resin, the siloxy groups can be chemically grafted with the hydroxyl groups on the surface of the zinc-nickel coating, thereby improving the bonding strength between the protective film layer and the zinc-nickel coating. At the same time, the siloxy groups also have excellent hydrophobic properties and can effectively prevent the penetration of moisture. They work together with the alkyl long chain structure in the mercapto polyethylene glycol carboxylic acid to delay the corrosion of the coating surface in a humid environment.

[0029] (4) The silicon carbide inorganic material selected in the present invention has excellent wear resistance and can effectively prevent the protective film layer from being worn and cracked; at the same time, the alkyl long chain structure in the composite modified silicon carbide and the polysiloxane structure in the modified epoxy resin have excellent flexibility, so that the protective film layer can better adapt to the deformation of the substrate under the action of external force, reducing the risk of cracking of the protective film layer, thereby delaying the corrosion of the surface of the coating material. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0031] It should be noted that, unless otherwise specified, the chemical reagents involved in the present invention were purchased through commercial channels.

[0032] The silicon carbide used in the embodiments of the present invention was purchased from Henan Sanhui New Materials Co., Ltd. with a mesh size of 4000; mercaptopolyethylene glycol carboxylic acid was purchased from Shanghai Tuoyang Biotechnology Co., Ltd. with a relative molecular mass of 5000; epoxy resin E44 and epoxy resin E51 were purchased from Jinan Qingtian Chemical Technology Co., Ltd.; bishydroxy polydimethylsiloxane with CAS number: 70131-67-8 was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd. with a relative molecular mass of 3000.

[0033] In the embodiment of the present invention, the specific steps of electroplating zinc and nickel on the workpiece are as follows:

[0034] First, the Q345 steel was treated in a 10wt% sodium hydroxide solution at 60°C for 10 minutes to remove oil stains; then the workpiece was immersed in distilled water for washing for 10 minutes; then it was pickled in a 15wt% hydrochloric acid solution at room temperature for 10 minutes; finally, it was immersed in distilled water for washing for 5 minutes to obtain a pretreated workpiece.

[0035] The pretreated workpiece is placed in a 30°C electroplating solution for electroplating. The electroplating solution includes 120 g / L sodium hydroxide, 8 g / L zinc ion content, and 1.6 g / L nickel ion content. The electroplating time is 30 minutes. The workpiece is fished out and rinsed with flowing water to obtain a zinc-nickel electroplated workpiece.

[0036] Example 1

[0037] A surface treatment method for a zinc-nickel coating comprises the following steps:

[0038] The workpiece after zinc-nickel electroplating is immersed in a passivation solution for passivation treatment. The temperature of the passivation treatment is 40° C., and the passivation treatment time is 3 minutes. After the passivation is completed, the workpiece is taken out and dried at 80° C., wherein the preparation method of the passivation solution is as follows:

[0039] S1. Disperse 12 g of silicon carbide in 100 mL of 80 wt% ethanol aqueous solution, then add 2 g of vinyltrimethoxysilane, and stir to react at 25 °C for 3 h. After the reaction is completed, filter, wash, and dry to obtain double-bond modified silicon carbide;

[0040] S2, 10g of double bond modified silicon carbide was dispersed in 100mL of deionized water, and then 3g of mercapto polyethylene glycol carboxylic acid was added thereto, and stirred evenly, followed by adding 0.5g of initiator benzoyl peroxide, and heated and stirred at 60°C for 5h. After the reaction was completed, the composite modified silicon carbide was obtained by filtering, washing and drying;

[0041] S3, adding 20g of epoxy resin E51 to 50g of dimethylformamide solvent, stirring evenly, then adding 3g of dihydroxy polydimethylsiloxane and 0.5g of catalyst dibutyltin dilaurate thereto, then heating at 80°C for 2h, after the reaction is completed, a modified epoxy resin is obtained;

[0042] S4. Add 3 g of the composite modified silicon carbide into 100 g of the modified epoxy resin and stir at a rotation speed of 5000 rpm for 30 min to obtain a passivation solution.

[0043] Example 2

[0044] A surface treatment method for a zinc-nickel coating comprises the following steps:

[0045] The workpiece after zinc-nickel electroplating is immersed in a passivation solution for passivation treatment. The temperature of the passivation treatment is 40° C., and the passivation treatment time is 3 minutes. After the passivation is completed, the workpiece is taken out and dried at 80° C., wherein the preparation method of the passivation solution is as follows:

[0046] S1. Disperse 10 g of silicon carbide in 100 mL of 80 wt% ethanol aqueous solution, then add 1 g of vinyltrimethoxysilane, and stir at 40° C. for 1 h. After the reaction is completed, filter, wash, and dry to obtain double-bond modified silicon carbide;

[0047] S2, 15g of double bond modified silicon carbide was dispersed in 100mL of deionized water, and then 6g of mercapto polyethylene glycol carboxylic acid was added thereto, and stirred evenly, followed by adding 1g of initiator benzoyl peroxide, and heated and stirred at 70°C for 3h. After the reaction was completed, the composite modified silicon carbide was obtained by filtering, washing and drying;

[0048] S3, adding 30g of epoxy resin E51 to 50g of dimethylformamide solvent, stirring evenly, then adding 6g of dihydroxy polydimethylsiloxane and 1g of catalyst dibutyltin dilaurate thereto, then heating and reacting at 60°C for 5h, after the reaction is completed, a modified epoxy resin is obtained;

[0049] S4. Add 1 g of the composite modified silicon carbide to 100 g of the modified epoxy resin and stir at a rotation speed of 5000 rpm for 30 min to obtain a passivation solution.

[0050] Example 3

[0051] A surface treatment method for a zinc-nickel coating comprises the following steps:

[0052] The workpiece after zinc-nickel electroplating is immersed in a passivation solution for passivation treatment. The temperature of the passivation treatment is 25° C., and the passivation treatment time is 5 minutes. After the passivation is completed, the workpiece is taken out and dried at 80° C., wherein the preparation method of the passivation solution is as follows:

[0053] S1. Disperse 15 g of silicon carbide in 100 mL of 80 wt% ethanol aqueous solution, then add 3 g of vinyltrimethoxysilane, stir and react at 40° C. for 1 h. After the reaction is completed, filter, wash and dry to obtain double-bond modified silicon carbide;

[0054] S2, 12g of double bond modified silicon carbide was dispersed in 100mL of deionized water, and then 5g of mercapto polyethylene glycol carboxylic acid was added thereto, and stirred evenly, followed by adding 0.8g of initiator benzoyl peroxide, and heated and stirred at 65°C for 4h. After the reaction was completed, the composite modified silicon carbide was obtained by filtering, washing and drying;

[0055] S3, adding 25g of epoxy resin E44 to 50g of dimethylformamide solvent, stirring evenly, then adding 5g of dihydroxy polydimethylsiloxane and 0.8g of catalyst dibutyltin dilaurate thereto, and then heating and reacting at 70°C for 3h. After the reaction is completed, a modified epoxy resin is obtained;

[0056] S4. Add 4 g of the composite modified silicon carbide into 100 g of the modified epoxy resin and stir at a rotation speed of 5000 rpm for 30 min to obtain a passivation solution.

[0057] Example 4

[0058] A surface treatment method for a zinc-nickel coating comprises the following steps:

[0059] The workpiece after zinc-nickel electroplating is immersed in a passivation solution for passivation treatment. The temperature of the passivation treatment is 30° C., and the passivation treatment time is 4 minutes. After the passivation is completed, the workpiece is taken out and dried at 80° C., wherein the preparation method of the passivation solution is as follows:

[0060] S1. Disperse 12 g of silicon carbide in 100 mL of 80 wt% ethanol aqueous solution, then add 2 g of vinyltrimethoxysilane, and stir the mixture at 40° C. for 1 h. After the reaction is completed, filter, wash, and dry to obtain double-bond modified silicon carbide.

[0061] S2, 12g of double bond modified silicon carbide was dispersed in 100mL of deionized water, and then 5g of mercapto polyethylene glycol carboxylic acid was added thereto, and stirred evenly, followed by adding 0.8g of initiator benzoyl peroxide, and heated and stirred at 65°C for 4h. After the reaction was completed, the composite modified silicon carbide was obtained by filtering, washing and drying;

[0062] S3, adding 28g of epoxy resin E44 to 50g of dimethylformamide solvent, stirring evenly, then adding 5g of dihydroxy polydimethylsiloxane and 1g of catalyst dibutyltin dilaurate thereto, then heating and reacting at 80°C for 2h, after the reaction is completed, a modified epoxy resin is obtained;

[0063] S4. Add 5 g of the composite modified silicon carbide into 100 g of the modified epoxy resin, and stir at a rotation speed of 10,000 rpm for 15 min to obtain a passivation solution.

[0064] Comparative Example 1

[0065] A surface treatment method for a zinc-nickel coating comprises the following steps:

[0066] The workpiece after zinc-nickel electroplating is immersed in a passivation solution for passivation treatment. The temperature of the passivation treatment is 40° C., and the passivation treatment time is 3 minutes. After the passivation is completed, the workpiece is taken out and dried at 80° C., wherein the preparation method of the passivation solution is as follows:

[0067] 3 g of silicon carbide was added to 100 g of epoxy resin E51 and stirred at 5000 rpm for 30 min to obtain a passivation solution.

[0068] Compared with Example 1, in Comparative Example 1, neither the silicon carbide nor the epoxy resin was modified.

[0069] Comparative Example 2

[0070] A surface treatment method for a zinc-nickel coating comprises the following steps:

[0071] The workpiece after zinc-nickel electroplating is immersed in a passivation solution for passivation treatment. The temperature of the passivation treatment is 40° C., and the passivation treatment time is 3 minutes. After the passivation is completed, the workpiece is taken out and dried at 80° C., wherein the preparation method of the passivation solution is as follows:

[0072] S1, adding 20g of epoxy resin E51 to 50g of dimethylformamide solvent, stirring evenly, then adding 3g of dihydroxy polydimethylsiloxane and 0.5g of catalyst dibutyltin dilaurate thereto, then heating at 80°C for 2h, after the reaction is completed, a modified epoxy resin is obtained;

[0073] S2. Add 3 g of silicon carbide to 100 g of modified epoxy resin and stir at 5000 rpm for 30 min to obtain a passivation solution.

[0074] Compared with Example 1, Comparative Example 2 did not perform modification treatment on silicon carbide.

[0075] Comparative Example 3

[0076] A surface treatment method for a zinc-nickel coating comprises the following steps:

[0077] The workpiece after zinc-nickel electroplating is immersed in a passivation solution for passivation treatment. The temperature of the passivation treatment is 40° C., and the passivation treatment time is 3 minutes. After the passivation is completed, the workpiece is taken out and dried at 80° C., wherein the preparation method of the passivation solution is as follows:

[0078] S1. Disperse 12 g of silicon carbide in 100 mL of 80 wt% ethanol aqueous solution, then add 2 g of vinyltrimethoxysilane, and stir to react at 25 °C for 3 h. After the reaction is completed, filter, wash, and dry to obtain double-bond modified silicon carbide;

[0079] S2, 10g of double bond modified silicon carbide was dispersed in 100mL of deionized water, and then 3g of mercapto polyethylene glycol carboxylic acid was added thereto, and stirred evenly, followed by adding 0.5g of initiator benzoyl peroxide, and heated and stirred at 60°C for 5h. After the reaction was completed, the composite modified silicon carbide was obtained by filtering, washing and drying;

[0080] S3. Add 3 g of the composite modified silicon carbide into 100 g of epoxy resin E51, and stir at a rotation speed of 5000 rpm for 30 min to obtain a passivation solution.

[0081] Compared with Example 1, in Comparative Example 3, no modification treatment was performed on the epoxy resin.

[0082] The workpieces prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to performance tests, and the specific steps were as follows:

[0083] Cyclic corrosion mass loss: Cyclic corrosion was carried out in accordance with GMW14872-2018 "Cyclic Corrosion Laboratory Test Standard", and the average mass loss of the workpiece before and after 9 cycles was recorded. According to the mass loss requirements of relevant standards: the standard mass loss of 9±1 cycles is 1.32±0.13g, with 10 samples in each group, and the calculation results are averaged.

[0084] Wear weight loss determination: Select a rotation speed of 200r / min and a loading load of 60N. Measure the mass of the sample at the 200th minute and calculate its wear amount. The total number of revolutions of the friction pair is 40,000.

[0085] Salt spray resistance test: Based on GB / T 10125-2012, a neutral salt spray test was carried out. The temperature in the salt spray chamber was 35°C, the corrosion solution was a 5% sodium chloride aqueous solution with a pH of 7.0, and the salt spray time was 960h. The surface of the workpiece was observed for red corrosion products at 240h, 360h, 720h and 960h.

[0086] The test results are shown in Table 1.

[0087] Table 1 Test results of different groups of workpieces

[0088] Mass loss after 9 cycles (g) Weight loss due to abrasion (mg) Salt spray resistance test Example 1 0.76 0.96 No red corrosion on the surface after 960h Example 2 0.83 1.02 No red corrosion on the surface after 960h Example 3 0.72 0.89 No red corrosion on the surface after 960h Example 4 0.69 0.91 No red corrosion on the surface after 960h Comparative Example 1 1.57 2.33 Slight red corrosion appears after 360h Comparative Example 2 1.36 1.84 No red corrosion on the surface after 720h Comparative Example 3 1.24 1.57 No red corrosion on the surface after 720h

[0089] Finally, it should be noted that the above embodiments do not limit the present invention in any form. For those skilled in the art, some modifications and improvements can be made to the present invention. Therefore, any modification or improvement made without departing from the spirit of the present invention belongs to the scope of protection claimed in the present invention.

Claims

1. A surface treatment method for zinc-nickel coating, characterized in that: The method comprises the following steps: immersing the workpiece after zinc-nickel electroplating into a passivation solution for passivation treatment, and after the passivation is completed, taking out the workpiece and drying it, wherein the preparation method of the passivation solution is as follows: S1, dispersing silicon carbide in an ethanol aqueous solution, then adding vinyltrimethoxysilane thereto, stirring for reaction, and after the reaction is completed, filtering, washing, and drying to obtain double-bond modified silicon carbide; S2, dispersing the double bond modified silicon carbide in deionized water, then adding mercapto polyethylene glycol carboxylic acid thereto, stirring evenly, then adding initiator benzoyl peroxide, heating and stirring to react, after the reaction is completed, filtering, washing and drying to obtain composite modified silicon carbide; S3, adding the epoxy resin to the dimethylformamide solvent, stirring evenly, then adding dihydroxy polydimethylsiloxane and a catalyst dibutyltin dilaurate thereto, followed by heating for reaction, and after the reaction is completed, obtaining a modified epoxy resin; S4. Add the composite modified silicon carbide into the modified epoxy resin, and stir at a rotation speed of 5000-10000 rpm for 15-30 minutes to obtain a passivation solution.

2. The surface treatment method of zinc-nickel coating according to claim 1, characterized in that: In step S1, the mass ratio of silicon carbide to vinyltrimethoxysilane is 10-15:1-3.

3. The surface treatment method of zinc-nickel coating according to claim 1, characterized in that: In step S1, the stirring reaction temperature is 25-40° C., and the stirring reaction time is 1-3 h.

4. The surface treatment method of zinc-nickel coating according to claim 1, characterized in that: In step S2, the mass ratio of double bond modified silicon carbide, mercapto polyethylene glycol carboxylic acid and benzoyl peroxide is 10-15:3-6:0.5-1.

5. The surface treatment method of zinc-nickel coating according to claim 1, characterized in that: In step S2, the temperature of the heating and stirring reaction is 60-70° C., and the time of the heating and stirring reaction is 3-5 h.

6. The surface treatment method of zinc-nickel coating according to claim 1, characterized in that: In step S3, the mass ratio of epoxy resin, dimethylformamide, bishydroxypolydimethylsiloxane and dibutyltin dilaurate is 20-30:50:3-6:0.5-1.

7. The surface treatment method of zinc-nickel coating according to claim 1, characterized in that: In step S3, the heating reaction temperature is 60-80° C., and the heating reaction time is 2-5 h.

8. The surface treatment method of zinc-nickel coating according to claim 1, characterized in that: In step S4, the mass ratio of the composite modified silicon carbide to the modified epoxy resin is 1-5:

100.

9. The surface treatment method of zinc-nickel coating according to claim 1, characterized in that: The temperature of the passivation treatment is 25-40°C, and the time of the passivation treatment is 3-5 minutes.