Method for preparing a high-thickness and tough silane protective coating by a single coating method

Abstract

The present invention relates to coating preparation technology, aiming to provide a method for preparing a high-thickness and tough silane protective coating by a single coating method. First, a zirconium oxide silane composite sol is prepared: a silane mixed solution and an acidic diluent are mixed evenly, an alcohol-water mixed solution is added under stirring conditions, and then benzotriazole is added; continuous stirring and static aging are carried out to obtain a silica sol; it is mixed and dispersed evenly with KH570-modified nano-zirconium oxide to obtain a zirconium oxide silane composite sol; it is used as a one-component coating and is covered on the surface of a metal substrate at one time by spraying or scraping; after curing treatment at 110 °C for 1 h, a silane coating is finally formed on the surface of the metal substrate. The present invention overcomes the problem of insufficient single coating thickness of the existing silane hybrid coating system with silane as the film-forming substance, and avoids the disadvantages of multiple coating and curing of the multiple coating system; the preparation of a high-thickness coating can be achieved by a single coating, which can simplify the coating process and improve production efficiency.

Description

Technical Field

[0001] The present invention relates to coating preparation technology, and particularly to a method for preparing a high-thickness and tough silane protective coating by a single coating method. Background Art

[0002] Attaching a protective coating to the surface of a metal material is an important measure to improve the surface performance of metal components. Current coating attachment technologies mainly include electrochemical deposition, physical vapor deposition, chemical vapor deposition, plasma spraying, electrostatic spraying, sol-gel method, etc. Among them, the sol-gel method can not only keep sensitive materials inside the coating without being damaged, but also provide a certain synergistic effect for the coating. Due to its characteristics such as low energy consumption in the preparation process, flexible composition, low synthesis temperature, and good stoichiometry, it has received extensive attention.

[0003] Since traditional chromium materials cause serious environmental pollution and are toxic, protective coatings prepared with chromium materials as raw materials have been gradually restricted. As a new coating material to replace traditional chromium materials, siloxane materials have the characteristics of environmental friendliness and low toxicity, and have gradually received extensive attention. The general structural formula of the monomer of the commonly used siloxane material in the coating is R n SiX 4-n (1≤n≤3), where R is an organic group and X is an alkoxy group. Since the siloxane protective coating has good adhesion performance on the surface of metal materials, it was initially mostly used as a pretreatment coating in the field of metal anti-corrosion. However, in the prior art, the thickness of the siloxane prepared by the sol-gel method is relatively low, and there are generally problems such as poor mechanical properties, insufficient toughness, and inability to form an effective space barrier, resulting in a decrease in the coating protection efficiency, and it is difficult to play a good protective role for metal materials.

[0004] Compared with pure siloxane coatings, the main feature of hybrid coatings is that while maintaining the toughness of organic materials, the mechanical properties of the coatings are enhanced through doping with inorganic materials. Silane hybrid coatings can be classified into protective coatings with silanes as film-forming substances and protective coatings with resin materials as film-forming substances according to the film-forming substances. For example, Sultan et al. (https: / / doi.org / 10.1016 / j.apsusc.2018.01.203) reported a silane hybrid coating with silanes as film-forming substances. The thickness of the hybrid coating prepared by this method is only 873 nm, which is relatively thin. Patent CN106894013A discloses a method for preparing an anti-corrosion coating on a metal surface with silanes, and a uniform and flat organosilane coating is prepared. However, due to the insufficient thickness of the silane coating, there are micropores, cracks and regions with low crosslinking density inside the coating. Once the coating is damaged, the corrosion rate will be accelerated, which limits the development of the silane film. Patent CN112251706A discloses a silane hybrid coating for the surface of aluminum alloy. By spraying a bonding layer, a zirconia coating and a silane coating on the substrate, a multi-layer protection system is constructed. However, this method requires multiple coatings and high-temperature curing treatments, resulting in a cumbersome preparation process.

[0005] It can be seen that the silane hybrid coatings with silanes as film-forming substances generally have a relatively thin single coating thickness. Since there are usually micropores, cracks and regions with low crosslinking density in the coatings with silanes as film-forming substances, if too much coating is applied at one time during the coating process, a large number of shrinkage holes and cracks will appear on the surface of the coating during high-temperature curing due to uneven stress, resulting in the destruction of the coating integrity. Therefore, the thickness of the existing single-coated silane hybrid coatings usually cannot exceed 10 - 20 μm. In order to obtain a thicker coating, a multi-coating process is usually required in practice to form a multi-layer coating. However, although the multi-layer coating technology can increase the coating thickness, due to the need to go through multiple repeated coating-high temperature curing treatments, there are problems such as a cumbersome preparation process.

[0006] Currently, there are few reports on the related research of silane protective coatings with high thickness that can be formed by only single coating. Therefore, the present invention aims to provide a modified zirconia silane composite sol to solve the above problems and use this sol to achieve the preparation of a high-thickness and tough silane protective coating. Summary of the Invention

[0007] The problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a high-thickness and tough silane protective coating by single coating. While increasing the thickness of the silane protective coating, the toughness of the coating is improved to ensure the integrity of the coating.

[0008] To solve the above problems, the solution of the present invention is:

[0009] Provided is a method for preparing a zirconia silane composite sol, comprising the following steps:

[0010] (1) Take tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane in a molar ratio of 1:2 to 3, mix them evenly to obtain a silane mixed solution A;

[0011] (2) Take absolute ethanol and deionized water in a volume ratio of 8:2, mix them evenly to obtain an alcohol-water mixed solution B;

[0012] (3) Prepare an acidic diluent C with an acid and deionized water, where the hydrogen ion concentration is 0.0005 to 0.05 mol / L;

[0013] (4) Take the silane mixed solution A and the acidic diluent C in a mass ratio of 79.1 to 97.5:2.5 to 20.9, mix them evenly, and continuously stir at 25°C to 70°C for 6 to 10 h;

[0014] (5) Under stirring conditions, continue to add the alcohol-water mixed solution B to the mixed solution obtained in step (4) so that γ-glycidoxypropyltrimethoxysilane accounts for 20% of the total mass of the mixed solution; then add benzotriazole so that the molar ratio of γ-glycidoxypropyltrimethoxysilane to benzotriazole is 1 to 10:1;

[0015] (6) Continuously stir the mixed solution obtained in step (5) until it is clear and transparent; then let it stand and age for 12 h to obtain a silica sol;

[0016] (7) Take the silica sol and KH570-modified nano-zirconia in a mass ratio of 90 to 95:5 to 10, mix and disperse them evenly to obtain a zirconia silane composite sol.

[0017] As a preferred embodiment of the present invention, in steps (1) to (3), the preparation of the solution or diluent is carried out at room temperature, and the stirring speed during mixing is 200 to 300 r / min.

[0018] As a preferred embodiment of the present invention, in step (3), the acid is one of hydrochloric acid, nitric acid or formic acid.

[0019] As a preferred embodiment of the present invention, in step (4), the stirring rate is 500 to 600 r / min.

[0020] As a preferred embodiment of the present invention, in step (7), the stirring speed during dispersion is 600 to 700 r / min.

[0021] As a preferred embodiment of the present invention, in step (7), the KH570-modified nano-zirconia is prepared by the following method:

[0022] Mix absolute ethanol and water in a volume ratio of 3:1, and adjust the pH value of the ethanol solution to 3-4; take an appropriate amount of the ethanol solution, add KH570 at a volume fraction of 2.5%, and mix evenly; heat up to 80 °C and reflux for 2 h under stirring at 400 r / min; based on the mass of KH570, add nano-zirconia powder in a mass ratio of 1:1; heat up to 85 °C and reflux for 30 min under stirring at 400 r / min; after the reaction is completed and cooled to room temperature, centrifuge to remove the supernatant; transfer the obtained solid product to an oven at 80 °C and dry it to obtain modified nano-zirconia in powder form.

[0023] The present invention further provides a method for preparing a high-thickness and tough silane protective coating by a single coating method, which is to use the zirconia silane composite sol prepared by the aforementioned method as a one-component coating and cover the surface of the metal substrate by a single coating method; after curing treatment at 110 °C for 1 h, a silane coating is finally formed on the surface of the metal substrate.

[0024] As a preferred embodiment of the present invention, the single coating method refers to covering the surface of the metal substrate with the zirconia silane composite sol at one time by using a spraying or scraping process.

[0025] As a preferred embodiment of the present invention, the thickness of the silane coating is 30-40 μm.

[0026] Description of the invention principle:

[0027] The present invention uses the sol-gel method to prepare a silane sol, and by loading nano-zirconia modified by KH570, it realizes the improvement of the thickness of the silane coating and the toughness of the coating at the same time. The present invention comprehensively considers the influencing factors such as the stoichiometry of silane, reaction temperature, catalyst concentration, benzotriazole, and the addition amount of nano-powder in the synthesis process of the silane sol, and studies and obtains a preparation method that can take into account the thickness and toughness of the silane protective coating.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The present invention uses KH570 to modify nano-zirconia. By introducing a long-chain structure into the silane sol system, on the one hand, it promotes the improvement of the dispersion performance of nano-zirconia in the silane sol system, and on the other hand, it can improve the toughness of the silane protective coating from the perspective of structural design.

[0030] 2. The present invention realizes the preparation of a silane protective coating with both high thickness and excellent toughness by optimizing the composition of the silica sol and the addition amount of the modified nano-zirconia powder.

[0031] 3. The silane composite sol system prepared by the present invention not only overcomes the problem of insufficient single - coating thickness of the existing silane hybrid coating system with silane as the film - forming substance, but also avoids the disadvantages of multiple coatings and multiple curing processes. By single - coating, the preparation of a high - thickness silane protective coating can be achieved, which can simplify the coating process and greatly improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a scanning electron microscope (SEM) photograph of nano - zirconia powder before modification.

[0033] Figure 2 It is a transmission electron microscope (TEM) photograph of nano - zirconia powder after modification.

[0034] Figure 3 It is an element scanning (MAPPING) photograph of nano - zirconia powder after modification.

[0035] Figure 4 It is a scanning electron microscope photograph of the surface of the silane protective coating prepared in Example 3.

[0036] Figure 5 It is a scanning electron microscope photograph of the surface of the silane protective coating prepared in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0038] In the following embodiments:

[0039] KH570 - modified nano - zirconia is prepared by the following method:

[0040] Mix anhydrous ethanol and water in a volume ratio of 3:1, and adjust the pH value of the ethanol solution to 3 - 4; take an appropriate amount of the ethanol solution, add KH570 at a volume fraction of 2.5%, and mix evenly; heat up to 80 °C and reflux for 2 h under stirring at 400 r / min; based on the mass of KH570, add nano - zirconia powder in a mass ratio of 1:1; heat up to 85 °C and reflux for 30 min under stirring at 400 r / min; after the reaction is completed and cooled to room temperature, centrifuge to remove the supernatant; transfer the obtained solid product to an oven at 80 °C for drying to obtain powdery modified nano - zirconia.

[0041] In steps (1) - (3), the preparation of the solution or dilution is carried out at room temperature, and the stirring speed during mixing can be selected within the range of 200 - 300 r / min; in step (8), the stirring speed during dispersion can be selected within the range of 600 - 700 r / min.

[0042] Example 1

[0043] A preparation method of a high-thickness and tough silane protective coating, which successively carries out the following steps:

[0044] (1) Take 0.1 mol of tetraethyl orthosilicate and 0.3 mol of γ-glycidoxypropyltrimethoxysilane according to a molar ratio of 1:2 to obtain a silane mixed solution A;

[0045] (2) Take anhydrous ethanol and deionized water according to a volume ratio of 8:2 to prepare an alcohol-water mixed solution B;

[0046] (3) Prepare an acidic diluent C with a hydrogen ion concentration of 0.05 mol / L by using deionized water and formic acid;

[0047] (4) Under a stirring rate of 500 r / min, take 79.1 parts by mass of solution A and 20.9 parts by mass of diluent C for mixing, and transfer it to a three-necked flask, and stir for 6 h under the condition of 70 °C;

[0048] (5) Under continuous stirring, weigh 143.9 g of solution B into the three-necked flask so that the mass of γ-glycidoxypropyltrimethoxysilane accounts for 20% of the total mass;

[0049] (6) Weigh 2.4 g of benzotriazole according to a molar ratio of γ-glycidoxypropyltrimethoxysilane to benzotriazole of 10:1 in the system and add it to the three-necked flask;

[0050] (7) After stirring the above solution until it is clear and transparent, stop stirring and age for 12 h to prepare a silica sol;

[0051] (8) Take 95 parts by mass of silica sol and 5 parts by mass of modified nano-zirconia and mix them, and stir and disperse them at a stirring rate of 670 r / min to obtain a zirconia-silane composite sol;

[0052] (9) Adopt a spraying method to coat the zirconia-silane composite sol obtained in step (8) on a metal copper plate at one time, and cure it in an oven at 110 °C for 1 h to obtain a silane coating.

[0053] The silane protective coating prepared by this method has a thickness of about 30 μm and a complete and defect-free surface. The electron microscope photos, transmission electron microscope photos of the nano-zirconia powder before and after modification, and the element distribution photos after modification are as Figure 1 、 Figure 2 and Figure 3 shown.

[0054] Example 2

[0055] A preparation method of a high-thickness and tough silane protective coating, which successively carries out the following steps:

[0056] (1) Take 0.1 mol of tetraethyl orthosilicate and 0.2 mol of γ - glycidoxypropyltrimethoxysilane according to a molar ratio of 1:2.5 to obtain a silane mixed solution A;

[0057] (2) Prepare an alcohol - water mixed solution B by taking anhydrous ethanol and deionized water according to a volume ratio of 8:2;

[0058] (3) Prepare an acidic diluent C with a hydrogen ion concentration of 0.05 mol / L using deionized water and formic acid;

[0059] (4) At a stirring rate of 520 r / min, take 88.5 parts by mass of solution A and 11.5 parts by mass of diluent C for mixing, and transfer it to a three - necked flask, and stir for 6 h at 50 °C;

[0060] (5) Under continuous stirring, weigh 197.2 g of solution B into the three - necked flask so that the mass of γ - glycidoxypropyltrimethoxysilane accounts for 20% of the total mass;

[0061] (6) Weigh 9.9 g of benzotriazole according to a molar ratio of γ - glycidoxypropyltrimethoxysilane to benzotriazole of 3:1 in the system and add it to the three - necked flask;

[0062] (7) After stirring the above solution until it is clear and transparent, stop stirring and age for 12 h to prepare silica sol;

[0063] (8) Take 92 parts by mass of silica sol and 8 parts by mass of modified nano - zirconia for mixing, and stir and disperse at a stirring rate of 630 r / min to obtain a zirconia - silane composite sol;

[0064] (9) By means of spraying, coat the silane composite sol obtained in step (8) on a metal copper plate at one time, and after curing treatment in an oven at 110 °C for 1 h, a silane coating is obtained.

[0065] The silane protective coating prepared by this method has a thickness of about 33 μm and a complete and defect - free surface.

[0066] Example 3

[0067] A preparation method of a high - thickness and tough silane protective coating, which successively carries out the following steps:

[0068] (1) Take 0.1 mol of tetraethyl orthosilicate and 0.3 mol of γ - glycidoxypropyltrimethoxysilane according to a molar ratio of 1:3 to obtain a silane mixed solution A;

[0069] (2) Prepare an alcohol - water mixed solution B by taking anhydrous ethanol and deionized water according to a volume ratio of 8:2;

[0070] (3) Prepare an acidic diluent C with a hydrogen ion concentration of 0.05 mol / L using deionized water and formic acid;

[0071] (4) At a stirring rate of 600 r / min, take 97.5 parts by mass of solution A and 2.5 parts by mass of diluent C, mix them, and transfer the mixture to a three-necked flask. Stir the mixture at 25 °C for 6 h;

[0072] (5) Under continuous stirring, weigh 250.9 g of solution B into the three-necked flask so that the mass of γ-glycidoxypropyltrimethoxysilane accounts for 20% of the total mass;

[0073] (6) Weigh 35.7 g of benzotriazole according to the molar ratio of 1:1 of γ-glycidoxypropyltrimethoxysilane to benzotriazole in the system and add it to the three-necked flask;

[0074] (7) After stirring the above solution until it becomes clear and transparent, stop stirring and age it for 12 h to prepare silica sol;

[0075] (8) Take 90 parts by mass of silica sol and 10 parts by mass of modified nano-zirconia, and stir and disperse them at a stirring rate of 700 r / min to obtain a zirconia-silane composite sol;

[0076] (9) Using the spraying method, coat the silane composite sol obtained in step (8) onto a metal copper plate at one time. After curing in an oven at 110 °C for 1 h, a silane coating is obtained.

[0077] The silane protective coating prepared by this method has a thickness of about 40 μm and a surface that is complete and defect-free, indicating that the coating still has good toughness at this thickness. The surface electron microscope photograph of the silane protective coating prepared by this method is as Figure 4 shown.

[0078] Example 4

[0079] A method for preparing a high-thickness and tough silane protective coating, which successively performs the following steps:

[0080] (1) Take 0.1 mol of tetraethyl orthosilicate and 2.5 mol of γ-glycidoxypropyltrimethoxysilane according to a molar ratio of 1:2.5 to obtain a silane mixed solution A;

[0081] (2) Prepare an alcohol-water mixed solution B by mixing absolute ethanol and deionized water according to a volume ratio of 8:2;

[0082] (3) Prepare an acidic diluent C with a hydrogen ion concentration of 0.05 mol / L using deionized water and formic acid;

[0083] (4) At a stirring rate of 550 r / min, 79.4 parts by mass of solution A and 20.6 parts by mass of diluent C were taken and mixed, and then transferred to a three-necked flask, and stirred at 40 °C for 6 h;

[0084] (5) Under continuous stirring, 186.9 g of solution B was weighed into the three-necked flask, so that the mass of γ-glycidoxypropyltrimethoxysilane accounted for 20% of the total mass;

[0085] (6) According to the molar ratio of γ-glycidoxypropyltrimethoxysilane to benzotriazole in the system of 8:1, 3.7 g of benzotriazole was weighed and added to the three-necked flask;

[0086] (7) After the above solution was stirred until clear and transparent, stirring was stopped and aged for 12 h to prepare silica sol;

[0087] (8) 91 parts by mass of silica sol and 9 parts by mass of modified nano-zirconia were taken and mixed, and stirred and dispersed at a stirring rate of 650 r / min to obtain zirconia-silane composite sol;

[0088] (9) By means of spraying, the silane composite sol obtained in step (8) was coated on the metal copper plate at one time, and after curing treatment in an oven at 110 °C for 1 h, a silane coating was obtained.

[0089] The silane protective coating prepared by this method has a thickness of about 35 μm and a surface that is complete and defect-free.

[0090] Example 5

[0091] A preparation method of a high-thickness and tough silane protective coating, which successively carries out the following steps:

[0092] (1) 0.1 mol of tetraethyl orthosilicate and 0.2 mol of γ-glycidoxypropyltrimethoxysilane were taken according to a molar ratio of 1:2 to obtain a silane mixed solution A;

[0093] (2) Absolute ethanol and deionized water were taken according to a volume ratio of 8:2 to prepare an alcohol-water mixed solution B;

[0094] (3) Deionized water and formic acid were used to prepare an acidic diluent C with a hydrogen ion concentration of 0.05 mol / L;

[0095] (4) At a stirring rate of 570 r / min, 88.3 parts by mass of solution A and 11.7 parts by mass of diluent C were taken and mixed, and then transferred to a three-necked flask, and stirred at 25 °C for 6 h;

[0096] (5) While continuously stirring, weigh 152.9 g of Solution B into a three-necked flask, such that the mass of γ-glycidoxypropyltrimethoxysilane accounts for 20% of the total mass;

[0097] (6) Weigh 3.4 g of benzotriazole according to the molar ratio of γ-glycidoxypropyltrimethoxysilane to benzotriazole in the system of 7:1 and add it to the three-necked flask;

[0098] (7) After stirring the above solution until it becomes clear and transparent, stop stirring and age for 12 h to prepare silica sol;

[0099] (8) Take 95 parts by mass of silica sol and 5 parts by mass of modified nano-zirconia, and stir and disperse them at a stirring rate of 600 r / min to obtain a zirconia-silane composite sol;

[0100] (9) Using the spraying method, coat the silane composite sol obtained in step (8) onto a metal copper plate at one time, and after curing treatment in an oven at 110 °C for 1 h, a silane coating is obtained.

[0101] The silane protective coating prepared by this method has a thickness of about 32 μm and a surface that is complete and defect-free.

[0102] Example 6

[0103] Replace formic acid in acidic diluent C during the preparation process with hydrochloric acid, and the rest is the same as in Example 3. The coating prepared by this method has a thickness of about 39 μm and a surface that is complete and defect-free.

[0104] Example 7

[0105] Replace formic acid in acidic diluent C during the preparation process with nitric acid, and the rest is the same as in Example 3. The coating prepared by this method has a thickness of about 40 μm and a surface that is complete and defect-free.

[0106] Example 8

[0107] Replace the concentration of 0.05 mol / L in acidic diluent C during the preparation process with 0.005 mol / L, and the rest is the same as in Example 3. The coating prepared by this method has a thickness of about 37 μm and a surface that is complete and defect-free.

[0108] Example 9

[0109] Replace the concentration of 0.05 mol / L in acidic diluent C during the preparation process with 0.0005 mol / L, and the rest is the same as in Example 3. The coating prepared by this method has a thickness of about 35 μm and a surface that is complete and defect-free.

[0110] Example 10

[0111] Replace the spraying method in step (9) of Example 5 with a scraping method, and the rest is the same as Example 5. The coating prepared by this method has a thickness of about 31 μm and a complete and defect-free surface.

[0112] Example 11

[0113] Replace the stirring time of 6 h in step (4) of the preparation process with 7 h, and the rest is the same as Example 3. The coating prepared by this method has a thickness of about 37 μm and a complete and defect-free surface.

[0114] Example 12

[0115] Replace the stirring time of 6 h in step (4) of the preparation process with 9 h, and the rest is the same as Example 3. The coating prepared by this method has a thickness of about 36 μm and a complete and defect-free surface.

[0116] Example 13

[0117] Replace the stirring time of 6 h in step (4) of the preparation process with 10 h, and the rest is the same as Example 3. The coating prepared by this method has a thickness of about 37 μm and a complete and defect-free surface.

[0118] Comparative Example

[0119] Comparative Example 1

[0120] Replace the "molar ratio of 1:2" in step (1) of Example 5 with "molar ratio of 1:1", and the rest is the same as Example 5. When the thickness of the obtained silane coating reaches 20 μm, cracks appear on the surface, resulting in the destruction of the coating integrity. The electron microscope photograph of the coating surface is as Figure 5 shown.

[0121] Comparative Example 2

[0122] Replace the "0.05 mol / L" in step (3) of Example 3 with "0.5 mol / L", and the rest is the same as Example 3. When the acidified water concentration is 0.5 mol / L, cracks visible to the naked eye appear on the coating when the thickness is 20 μm, indicating that the catalyst concentration is too high and the silane sol polycondenses too fast, resulting in uneven stress during the thermal curing process of the coating and cracking.

[0123] Comparative Example 3

[0124] Replace the mass fraction of the modified nano-zirconia added in step (8) of Example 3, "90 parts by mass of silica sol and 10 parts by mass of modified nano-zirconia", with "85 parts by mass of silica sol and 15 parts by mass of modified nano-zirconia", and the rest is the same as Example 3. A large number of shrinkage pores and cracks and other defects appear on the surface of the obtained silane protective coating.

[0125] Comparative Example 4

[0126] The silane protective coating was prepared according to the method reported by Sultan et al. (https: / / doi.org / 10.1016 / j.apsusc.2018.01.203). When the thickness of the coating reached 10 μm, cracks appeared in the coating and the integrity of the film surface was damaged.

[0127] Comparative Example 5

[0128] The silane protective coating was prepared according to the method reported by Varela Caselis (https: / / doi.org / 10.1179 / 1743278211Y.0000000035). After the thickness of the silane protective coating prepared by this method reached 20 μm, cracks appeared in the coating and the integrity of the film surface was damaged.

[0129] Finally, it should also be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of zirconia silane composite sol, characterized in that, it includes the following steps: (1) Take tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane according to a molar ratio of 1:2 to 3, mix them evenly to obtain a silane mixed solution A; (2) Take absolute ethanol and deionized water according to a volume ratio of 8:2, mix them evenly to obtain an alcohol-water mixed solution B; (3) Prepare an acidic diluent C with acid and deionized water, where the hydrogen ion concentration is 0.0005 to 0.05 mol / L; (4) Take the silane mixed solution A and the acidic diluent C according to a mass ratio of 79.1 to 97.5:2.5 to 20.9, mix them evenly, and continuously stir at 25°C to 70°C for 6 to 10 h; (5) Under stirring conditions, continue to add the alcohol-water mixed solution B to the mixed solution obtained in step (4) so that γ-glycidoxypropyltrimethoxysilane accounts for 20% of the total mass of the mixed solution; then add benzotriazole so that the molar ratio of γ-glycidoxypropyltrimethoxysilane to benzotriazole is 1 to 10:1; (6) Continuously stir the mixed solution obtained in step (5) until it is clear and transparent; then let it stand and age for 12 h to obtain a silica sol; (7) Take the silica sol and KH570-modified nano-zirconia according to a mass ratio of 90 to 95:5 to 10, mix and disperse them evenly to obtain a zirconia silane composite sol.

2. The method according to claim 1, characterized in that, in steps (1) to (3), the preparation of the solution or diluent is carried out at room temperature, and the stirring speed during mixing is 200 to 300 r / min.

3. The method according to claim 1, characterized in that, in step (3), the acid is one of hydrochloric acid, nitric acid or formic acid.

4. The method according to claim 1, characterized in that, in step (4), the stirring rate is 500 to 600 r / min.

5. The method according to claim 1, characterized in that, in step (7), the stirring speed during dispersion is 600 to 700 r / min.

6. The method according to claim 1, characterized in that, in step (7), the KH570-modified nano-zirconia is prepared by the following method: Take absolute ethanol and water according to a volume ratio of 3:1 and mix them, adjust the pH value of the ethanol solution to 3 to 4; take an appropriate amount of the ethanol solution, add KH570 according to a volume fraction of 2.5%, and mix evenly; heat up to 80°C and reflux for 2 h under stirring at 400 r / min; based on the mass of KH570, add nano-zirconia powder according to a mass ratio of 1:1; Heat up to 85°C and reflux for 30 min under stirring at 400 r / min; after the reaction is completed and cooled to room temperature, centrifuge to remove the supernatant; Transfer the obtained solid product to an 80°C oven and dry it to obtain a powdery modified nano-zirconia.

7. A method for preparing a high-thickness tough silane protective coating by a single coating method, characterized in that, The zirconium oxide silane composite sol prepared by the method described in any one of claims 1 to 6 is used as a single-component coating and is covered on the surface of the metal substrate in a single coating; after curing treatment at 110 °C for 1 h, a silane coating is finally formed on the surface of the metal substrate.

8. The method according to claim 7, wherein, the single coating means that the zirconium oxide silane composite sol is covered on the surface of the metal substrate at one time by using a spraying or scraping process.

9. The method according to claim 7, wherein, the thickness of the silane coating is 30 to 40 μm.

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