Multi-claw type silane coupling agent solution for metal surface pretreatment as well as preparation method and application of multi-claw type silane coupling agent solution

Abstract

The invention relates to the technical field of metal surface pretreatment, in particular to a multi-claw type silane coupling agent solution for metal surface pretreatment as well as a preparation method and application of the multi-claw type silane coupling agent solution. According to the multi-claw type silane coupling agent solution for metal surface pretreatment, two or more multi-claw type silane coupling agents are selected, compounding design of different types of silane coupling agents is carried out, an optimal silane coupling agent compounding combination is obtained, and therefore the multi-claw type silane coupling agent solution for metal surface pretreatment is obtained. According to the multi-claw type silane coupling agent solution provided by the invention, the binding force between a metal base material and a subsequent coating can be improved, and the durability and the corrosion resistance of the metal base material are enhanced; the technical problems that a single-claw silane coupling agent is adopted to conduct pretreatment on a metal base material before coating, and after the treated metal base material is coated, the bonding strength of a coating and the metal base body is low are solved.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface pretreatment, and more particularly to a multi-claw silane coupling agent solution for metal surface pretreatment, a preparation method thereof and an application thereof. Background Art

[0002] The process of applying organic coatings to the surface of an object and drying them to form a film is called painting. Various metal materials and their products will always have scale, oil stains, etc. on their surfaces during mechanical processing, heat treatment, storage and transportation. These surface contaminants will seriously affect the density of the coating and the bonding strength with the substrate during the surface treatment process. Therefore, the metal substrate needs to be pretreated before painting.

[0003] The purpose of pretreatment of metal substrates before coating is to remove grease, oil stains, corrosion products, residual impurities, etc. on the surface of the coated object, and to give the coated surface certain chemical and physical properties, so as to increase the adhesion of the coating and increase the protectiveness and decorativeness of the coated object. Therefore, pretreatment before coating is an important step in the construction process of metal substrate coatings, which can ensure the realization of good coating quality. Pretreatment of metal substrates before coating is divided into mechanical method and chemical method according to the treatment method. Chemical method is a method of treatment by chemical reaction, including phosphating, silane coupling agent treatment, etc.

[0004] Phosphating treatment and other methods will produce a large amount of phosphorus-containing wastewater during the treatment process, which causes extremely serious pollution to the environment. With the continuous enhancement of environmental awareness and the increasingly stringent environmental protection requirements, this environmentally unfriendly treatment method faces huge challenges. On the other hand, the phosphating treatment method often performs less than ideal in terms of the bonding strength between the metal and the coating. Insufficient bonding strength may cause the coating to fall off easily, which greatly affects the service life and performance of the product. In practical applications, this may lead to frequent maintenance and replacement costs, reducing production efficiency and economic benefits.

[0005] Using silane coupling agents to treat metal substrates is a relatively new technology. At present, the silane coupling agents used in the disclosed technologies for pretreatment with silane coupling agents are all conventional monoclaw silanes with low crosslinking density; after coating the metal substrate treated with monoclaw silane, the bonding strength between the coating and the metal substrate still needs to be enhanced. Summary of the invention

[0006] The technical problem solved by the present invention is that: after a monoclaw silane coupling agent is used to pretreat a metal substrate before coating, the bonding strength between the coating and the metal substrate still needs to be enhanced after the treated metal substrate is coated.

[0007] As a new type of metal surface pretreatment agent, the multi-claw silane coupling agent solution has a higher cross-linking density. The silanol groups generated after the hydrolysis of the multi-claw terminal silane have obvious bonding advantages with the metal substrate surface, showing great application potential. The present invention obtains the optimal silane coupling agent compound combination by selecting two or more multi-claw silane coupling agents and performing compound design of different types of silane coupling agents, thereby obtaining a multi-claw silane coupling agent solution for metal surface pretreatment. On this basis, the present invention further optimizes the ratio of the silane coupling agent compound combination with different solvents, additives and other components to obtain a more effective multi-claw silane coupling agent solution for metal surface pretreatment.

[0008] One of the purposes of the present invention is to provide a multi-claw silane coupling agent solution for metal surface pretreatment.

[0009] The multi-claw silane coupling agent solution for metal surface pretreatment comprises component A, wherein component A comprises two or more multi-claw silane coupling agents; the multi-claw silane coupling agent refers to a silane coupling agent containing two or more hydrolyzable claw-type terminal active groups in the silane molecular chain.

[0010] Although any two or more multi-claw silane coupling agents can achieve a certain improvement in the pretreatment effect after compounding, the effects of different multi-claw silane coupling agents after compounding are not the same. Compared with other multi-claw silane coupling agents, the effect of compounding two or more of 1,3,5-tris (trimethoxysilyl propyl) polyisocyanate, bis [3- (trimethoxysilyl) propyl] ethylenediamine, and bis - (γ-triethoxysilyl propyl) tetrasulfide is significantly better, and the improvement of the adhesion, mechanical properties, and corrosion resistance of the subsequent coating after pretreatment is more significant. Therefore, as a preferred embodiment, the multi-claw silane coupling agent is selected from 1,3,5-tris (trimethoxysilyl propyl) polyisocyanate, bis [3- (trimethoxysilyl) propyl] ethylenediamine, and bis - (γ-triethoxysilyl propyl) tetrasulfide.

[0011] When two or more of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate, bis[3-(trimethoxysilyl)propyl]ethylenediamine and bis-(γ-triethoxysilylpropyl)tetrasulfide are compounded, a better effect can be achieved by compounding in a specific ratio.

[0012] When the multi-claw silane coupling agent is 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate and bis[3-(trimethoxysilyl)propyl]ethylenediamine, the mass ratio of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate to bis[3-(trimethoxysilyl)propyl]ethylenediamine is (1-3):1, preferably (1.5-2):1.

[0013] When the multi-claw silane coupling agent is bis[3-(trimethoxysilyl)propyl]ethylenediamine and bis-(γ-triethoxysilylpropyl)tetrasulfide, the mass ratio of bis[3-(trimethoxysilyl)propyl]ethylenediamine to bis-(γ-triethoxysilylpropyl)tetrasulfide is (0.5-2):1, preferably (1-1.5):1.

[0014] When the multi-claw silane coupling agent is 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate and bis-(γ-triethoxysilylpropyl)tetrasulfide, the mass ratio of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate to bis-(γ-triethoxysilylpropyl)tetrasulfide is (0.5-1.5):1; preferably (0.7-1):1.

[0015] When the multi-claw silane coupling agent is 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate, bis[3-(trimethoxysilyl)propyl]ethylenediamine and bis-(γ-triethoxysilylpropyl)tetrasulfide, the mass ratio of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate, bis[3-(trimethoxysilyl)propyl]ethylenediamine and bis-(γ-triethoxysilylpropyl)tetrasulfide is (0.5-2)(0.5-2):1, preferably (0.8-1.2)(0.6-1):1.

[0016] Conventional silane treatment mostly uses silane solution (equivalent to component A) for direct treatment, and does not add fillers, additives and other ingredients to the silane solution. The present invention further improves the interface bonding, mechanical properties and corrosion resistance between the silane film and the metal surface by adding nanofillers and additives to component A. Therefore, as a preferred embodiment, the multi-claw silane coupling agent solution for metal surface pretreatment also includes component B, and component B includes a solvent, a nanofiller and an additive;

[0017] Taking the total content of component A and component B as 100wt%, the content of each component is as follows:

[0018] Component A 3-15wt%, preferably 8-10wt%;

[0019] Solvent 60-80wt%, preferably 68-72wt%;

[0020] Nano filler 14-26wt%, preferably 18-22wt%;

[0021] The additive is 1 to 3 wt%, preferably 1.5 to 2.5 wt%.

[0022] As a solution, a multi-claw silane coupling agent solution for metal surface pretreatment consists of component A and component B; the content of component A is 3-15wt%, preferably 8-10wt%; the content of component B is 97-85wt%, preferably 92-90wt%.

[0023] The nano filler is mainly used to improve the corrosion resistance, wear resistance and other properties of the silane film. The nano filler can be selected from one or more of nano titanium dioxide, nano silicon dioxide and nano calcium carbonate.

[0024] The nanofillers have a particle size of nanometers, which makes them have unique quantum size effects, surface effects, etc. compared with ordinary fillers (particle sizes are mostly micrometers or larger). Nanofillers have a larger specific surface area, better bonding with the matrix, and more obvious improvement in mechanical properties such as strength of the film-forming material.

[0025] The nanofiller is preferably a small-size filler with a particle size of 1 to 100 nanometers, which has higher filler stability. The nanofiller is preferably a filler with an irregular surface shape, which can form a nanoscale concave-convex rough surface after film formation, providing better interface adhesion for subsequent coating.

[0026] The auxiliary agent is mainly used to improve the performance of the silane coupling agent solution, such as improving the stability of the silane coupling agent solution, preventing foaming, enhancing antioxidant capacity, etc. The auxiliary agent can be selected from one or more of a surfactant, a dispersant, a defoamer, a stabilizer, and an antioxidant.

[0027] Since nanofillers are not easily dispersed in silane coupling agent solutions, the present invention selects suitable surfactants and polymer dispersants through screening and matching experiments of various auxiliary agents containing different functional groups, so that they are adsorbed on the surface of nanofillers, change the properties of the surface of nanofillers, and thus change the interaction between nanofillers and silane coupling agent solutions, and between nanofiller particles, to achieve dispersion of the system. Therefore, the auxiliary agent is preferably selected from ether nonionic emulsifiers and polyacrylic acid sodium salt.

[0028] The solvent plays a role in dissolving, dispersing and promoting the hydrolysis of the multi-claw silane coupling agent in the solution. The solvent can be selected from one or more of water and alcohol. The water is preferably deionized water. The alcohol is preferably selected from ethylene glycol, ethanol, and isopropanol. In specific implementation, the stability and applicability of the solution can be improved by selecting a suitable solvent according to different application requirements and actual conditions.

[0029] The second object of the present invention is to provide a method for preparing the multi-claw silane coupling agent solution containing component B as described in the first object of the invention.

[0030] A method for preparing a multi-claw silane coupling agent solution according to one of the invention objectives comprises: firstly mixing and dispersing the components of the B component according to the content, and then uniformly mixing the A component and the B component according to the content to obtain the multi-claw silane coupling agent solution.

[0031] During the mixing process of component A and component B, the temperature is controlled to be 10°C to 30°C and the pH is 4 to 5. Specifically, the pH can be adjusted to between 4 and 5 by adding acetic acid.

[0032] The mixing and dispersion of the components of the B component can be carried out in a conventional manner; specifically, it can be carried out in a fully automatic oscillating mixer, and the oscillating dispersion time range can be 0.3 to 0.5 hours;

[0033] The mixing of the components A and B can be carried out in a conventional manner; specifically, the mixing can be carried out in a multi-purpose stirring and dispersing machine, and the mixing and stirring speed of the components A and B can range from 300 to 500 r / min, and the time range can range from 0.5 to 1 h.

[0034] The third object of the present invention is to provide an application of the multi-claw silane coupling agent solution described in the first object of the invention and the multi-claw silane coupling agent solution prepared by the preparation method described in the second object of the invention in the field of surface pretreatment of metal substrates. It can be used for the surface pretreatment of various metals including steel, aluminum alloy, etc.

[0035] The method for treating a metal surface with the multi-claw silane coupling agent solution described in the first object of the invention and the multi-claw silane coupling agent solution prepared by the preparation method described in the second object of the invention comprises:

[0036] First, clean the surface of the metal sample to remove impurities such as oil, rust, and oxide layer;

[0037] Then, the multi-claw silane coupling agent solution is evenly coated on the surface of the metal sample;

[0038] Finally, the metal sample coated with the silane solution is dried and cured at a certain temperature and time to form a solid silane film on the surface of the metal sample.

[0039] The cleaning method may be sandpaper polishing, sandblasting, electrolytic polishing, alkaline cleaning agent cleaning, etc., and a suitable cleaning method may be selected according to the properties and surface conditions of the metal material.

[0040] The silane coupling agent solution coating method can be spraying, brushing, dipping, etc. to ensure that the solution can fully cover the metal surface.

[0041] The drying time is generally 12 to 48 hours.

[0042] The curing temperature ranges from 10°C to 150°C.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present invention provides a multi-claw silane coupling agent solution for metal surface pretreatment, which can be used for pretreatment of various metal substrates before coating, and a silane film is formed on the surface of the metal substrate after pretreatment. The obtained silane film has multiple excellent properties, can significantly improve the bonding force between the metal substrate and the coating, and enhance the corrosion resistance and durability of the metal surface coating; the adhesion, corrosion resistance and other properties of the coating are significantly improved compared with the substrate that has not been pretreated.

[0045] The multi-claw silane coupling agent solution provided by the present invention can improve the bonding force between the metal substrate and the subsequent coating, and enhance the durability and corrosion resistance of the metal substrate; specifically, after the metal surface is pretreated by using the multi-claw silane coupling agent solution, the adhesion of the metal coating can reach more than 16.3MPa, the single-side rust width of the neutral salt spray scratch is ≤1mm for 1000h, and the electrochemical impedance value of the seawater immersion for 2000h can reach 1.8×10 9 Ω·cm 2 above.

[0046] The multi-claw silane coupling agent solution of the invention has a simple preparation method, low cost and is easy for industrial production.

[0047] The multi-claw silane coupling agent solution of the present invention is convenient and efficient in pre-treating the metal surface, thereby reducing production costs, improving production efficiency, and meeting the high quality requirements of modern industrial coating for metal surface treatment. When pre-treating the metal surface, it can avoid the generation of a large amount of harmful substances such as phosphorus-containing wastewater, reduce pollution to the environment, and has the characteristics of being environmentally friendly, non-toxic, and pollution-free, meeting modern environmental protection requirements. DETAILED DESCRIPTION

[0048] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0049] The raw materials used in the following examples are all commercially available products.

[0050] 1,3,5-Tris(trimethoxysilylpropyl)polyisocyanate, from NITROCHEMIE (Nitrochemical Group) of Germany, brand name Isocyanurate 88445;

[0051] Bis[3-(trimethoxysilyl)propyl]ethylenediamine, from Sigma-Aldrich (Shanghai) Trading Co., Ltd., brand SigmaAldrich 413365;

[0052] Bis-(γ-triethoxysilylpropyl) tetrasulfide, from Degussa, Germany, brand Si-69;

[0053] Nano titanium dioxide, from Brofos Nanotechnology Co., Ltd., brand Brofos-TiO2-2, purity 99.9%, average particle size 2-3nm; irregular spherical shape;

[0054] Nano calcium carbonate, from Brofos Nanotechnology Co., Ltd., brand Brofos-CaCO3-50, purity 99.9%, average particle size 50nm; irregular spherical shape;

[0055] The surfactant is an ether nonionic emulsifier from Shanghai Bangao Chemical, brand BGF-6 or BGF-7;

[0056] The dispersant is sodium polyacrylate, from Beijing Maier Chemical Technology Co., Ltd., brand HY-1010C; the two-component epoxy coating is from the Marine Chemical Research Institute Co., Ltd., brand HF-07V.

[0057] Example 1

[0058] (1) Preparation of multi-claw silane coupling agent solution

[0059] 68 parts by weight of ethanol, 12 parts by weight of deionized water, 11 parts by weight of nano-titanium dioxide, 3 parts by weight of nano-calcium carbonate, 1 part by weight of a surfactant, and 2 parts by weight of a dispersant were mixed and shaken for 0.3 h to obtain component B; component B was then mixed with 2 parts by weight of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate and 1 part by weight of bis[3-(trimethoxysilyl)propyl]ethylenediamine and stirred for 0.5 h to obtain a uniform and stable multi-claw silane coupling agent solution.

[0060] (2) Applied to metal surface pretreatment

[0061] Clean the surface of Q235 steel: use sandpaper to remove rust, and then use organic solvent to clean and remove oil stains;

[0062] The multi-claw silane coupling agent solution prepared in step (1) is uniformly sprayed on the surface of metal Q235 steel; dried at room temperature for 48 hours, and a silane film is formed on the surface of the Q235 steel; the average dry film thickness of the silane film is 2 μm.

[0063] (3) Apply epoxy coating

[0064] A two-component epoxy coating was applied on the surface of the dried silane film and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm. Then, tests related to interface adhesion, salt spray resistance, and electrochemical performance were carried out.

[0065] The interface adhesion test was carried out in accordance with GB / T5210-2006 "Pull-off adhesion test for paints and varnishes", the salt spray resistance test was carried out in accordance with GB / T 1771-2007 "Determination of neutral salt spray resistance of paints and varnishes", and the electrochemical performance related tests were carried out in accordance with GB / T 40299-2021 "Corrosion test of metals and alloys - Practice for electrochemical measurement methods". The test results are shown in Table 1.

[0066] Example 2

[0067] (1) Preparation of multi-claw silane coupling agent solution

[0068] 65 parts by weight of ethanol, 8 parts by weight of deionized water, 10 parts by weight of nano-titanium dioxide, 8.5 parts by weight of nano-calcium carbonate, 1 part by weight of a surfactant, and 1.5 parts by weight of a dispersant were mixed and shaken for 0.4 h to obtain component B; component B was then mixed with 3 parts by weight of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate and 3 parts by weight of bis-(γ-triethoxysilylpropyl)tetrasulfide and stirred for 0.7 h to obtain a uniform and stable multi-claw silane coupling agent solution.

[0069] (2) Applied to metal surface pretreatment

[0070] The surface of Q235 steel was cleaned by sanding to remove rust, and then cleaned with organic solvent to remove oil stains;

[0071] The multi-claw silane coupling agent solution prepared in step (1) is uniformly sprayed on the surface of metal Q235 steel; dried at room temperature for 12 hours, placed in an oven at 80° C. and dried for 6 hours, and a silane film is formed on the surface of the Q235 steel; the average dry film thickness of the silane film is 2 μm.

[0072] (3) Apply epoxy coating

[0073] A two-component epoxy coating was applied to the surface of the dried silane film and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm; then the interface adhesion, salt spray resistance, and electrochemical performance related tests were performed. The test methods for the interface adhesion, salt spray resistance, and electrochemical performance related tests are the same as those in the embodiment. The test results are shown in Table 1.

[0074] Example 3

[0075] (1) Preparation of multi-claw silane coupling agent solution

[0076] 53 parts by weight of ethanol, 15 parts by weight of deionized water, 14 parts by weight of nano-titanium dioxide, 7 parts by weight of nano-calcium carbonate, 0.5 parts by weight of a surfactant, and 0.5 parts by weight of a dispersant were mixed and shaken for 0.5 h to obtain component B; component B was then mixed with 4 parts by weight of bis[3-(trimethoxysilyl)propyl]ethylenediamine and 6 parts by weight of bis-(γ-triethoxysilylpropyl)tetrasulfide and stirred for 0.9 h to obtain a uniform and stable multi-claw silane coupling agent solution.

[0077] (2) Applied to metal surface pretreatment

[0078] The surface of Q235 steel was cleaned by sanding to remove rust, and then cleaned with organic solvent to remove oil stains;

[0079] The multi-claw silane coupling agent solution prepared in step (1) is uniformly sprayed on the surface of metal Q235 steel; dried at room temperature for 12 hours, placed in a 120° C. oven for 2 hours, and a silane film is formed on the surface of the Q235 steel; the average dry film thickness of the silane film is 2 μm.

[0080] (3) Apply epoxy coating

[0081] A two-component epoxy coating was applied to the surface of the dried silane film and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm; then the interface adhesion, salt spray resistance, and electrochemical performance related tests were performed. The test methods for the interface adhesion, salt spray resistance, and electrochemical performance related tests are the same as those in the embodiment. The test results are shown in Table 1.

[0082] Example 4

[0083] (1) Preparation of multi-claw silane coupling agent solution

[0084] 53 parts by weight of ethanol, 15 parts by weight of deionized water, 14 parts by weight of nano-titanium dioxide, 7 parts by weight of nano-calcium carbonate, 0.5 parts by weight of a surfactant, and 0.5 parts by weight of a dispersant were mixed and shaken for 0.5 hours to obtain component B; component B was then mixed with 4 parts by weight of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate, 3 parts by weight of bis[3-(trimethoxysilyl)propyl]ethylenediamine, and 5 parts by weight of bis-(γ-triethoxysilylpropyl)tetrasulfide and stirred for 1 hour to obtain a uniform and stable multi-claw silane coupling agent solution.

[0085] (2) Applied to metal surface pretreatment

[0086] The surface of Q235 steel was cleaned by sanding to remove rust, and then cleaned with organic solvent to remove oil stains;

[0087] The multi-claw silane coupling agent solution prepared in step (1) is uniformly sprayed on the surface of metal Q235 steel; dried at room temperature for 36 hours, placed in a 150° C. oven for drying for 1 hour, and a silane film is formed on the surface of the Q235 steel; the average dry film thickness of the silane film is 2 μm.

[0088] (3) Apply epoxy coating

[0089] A two-component epoxy coating was applied to the surface of the dried silane film and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm; then the interface adhesion, salt spray resistance, and electrochemical performance related tests were performed. The test methods for the interface adhesion, salt spray resistance, and electrochemical performance related tests are the same as those in the embodiment. The test results are shown in Table 1.

[0090] Comparative Example 1

[0091] Clean the surface of Q235 steel: use sandpaper to remove rust, and then use organic solvent to clean and remove oil stains;

[0092] A 10% KH560 alcohol aqueous solution (KH560 is a monoclaw silane, its chemical name is 3-(2,3-epoxypropoxy)propyltrimethoxysilane, manufacturer Jiangsu Runfeng Synthetic Technology, brand KH560) was brushed on the surface of the cleaned and dried steel plate and dried at room temperature for 48 hours. A silane film was formed on the surface of the Q235 steel; the average dry film thickness of the silane film was 2 μm.

[0093] A two-component epoxy coating was applied to the surface of the dried silane film and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm; then the interface adhesion, salt spray resistance, and electrochemical performance related tests were performed. The test methods for the interface adhesion, salt spray resistance, and electrochemical performance related tests are the same as those in the embodiment. The test results are shown in Table 1.

[0094] Comparative Example 2

[0095] Clean the aluminum alloy surface, use sandpaper to polish to remove rust, and then use organic solvent to clean to remove oil stains;

[0096] Soak the cleaned and dried aluminum alloy in a potassium dichromate solution (the concentration of the potassium dichromate solution is 30 g / L) for 2-3 minutes, then take it out, wash it with water, and dry it for 48 hours;

[0097] After the aluminum substrate was completely dried, two-component epoxy coating was applied and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm. Then, tests on interface adhesion, salt spray resistance, and electrochemical performance were carried out. The test results are shown in Table 1.

[0098] Comparative Example 3

[0099] (1) Preparation of multi-claw silane coupling agent solution

[0100] 68 parts by weight of ethanol, 12 parts by weight of deionized water, 11 parts by weight of nano-titanium dioxide, 3 parts by weight of nano-calcium carbonate, 1 part by weight of a surfactant, and 2 parts by weight of a dispersant were mixed and shaken for 0.3 h to obtain component B; component B was then mixed and stirred with 3 parts by weight of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate for 0.5 h to obtain a uniform and stable multi-claw silane coupling agent solution.

[0101] (2) Applied to metal surface pretreatment

[0102] The surface of Q235 steel was cleaned by sanding to remove rust, and then cleaned with organic solvent to remove oil stains;

[0103] The multi-claw silane coupling agent solution prepared in step (1) is uniformly sprayed on the surface of metal Q235 steel; dried at room temperature for 48 hours, and a silane film is formed on the surface of the Q235 steel; the average dry film thickness of the silane film is 2 μm.

[0104] (3) Apply epoxy coating

[0105] A two-component epoxy coating was applied to the surface of the dried silane film and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm; then the interface adhesion, salt spray resistance, and electrochemical performance related tests were performed. The test methods for the interface adhesion, salt spray resistance, and electrochemical performance related tests are the same as those in the embodiment. The test results are shown in Table 1.

[0106] Comparative Example 4

[0107] (1) Preparation of multi-claw silane coupling agent solution

[0108] 65 parts by weight of ethanol, 8 parts by weight of deionized water, 10 parts by weight of nano-titanium dioxide, 8.5 parts by weight of nano-calcium carbonate, 1 part by weight of a surfactant, and 1.5 parts by weight of a dispersant were mixed and shaken for 0.4 h to obtain component B; component B was then mixed and stirred with 6 parts by weight of bis[3-(trimethoxysilyl)propyl]ethylenediamine for 0.7 h to obtain a uniform and stable multi-claw silane coupling agent solution.

[0109] (2) Applied to metal surface pretreatment

[0110] The surface of Q235 steel was cleaned by sanding to remove rust, and then cleaned with organic solvent to remove oil stains;

[0111] The multi-claw silane coupling agent solution prepared in step (1) is uniformly sprayed on the surface of metal Q235 steel; dried at room temperature for 12 hours, placed in an oven at 80° C. and dried for 6 hours, and a silane film is formed on the surface of the Q235 steel; the average dry film thickness of the silane film is 2 μm.

[0112] (3) Apply epoxy coating

[0113] A two-component epoxy coating was applied to the surface of the dried silane film and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm; then the interface adhesion, salt spray resistance, and electrochemical performance related tests were performed. The test methods for the interface adhesion, salt spray resistance, and electrochemical performance related tests are the same as those in the embodiment. The test results are shown in Table 1.

[0114] Comparative Example 5

[0115] (1) Preparation of multi-claw silane coupling agent solution

[0116] 53 parts by weight of ethanol, 15 parts by weight of deionized water, 14 parts by weight of nano-titanium dioxide, 7 parts by weight of nano-calcium carbonate, 0.5 parts by weight of a surfactant, and 0.5 parts by weight of a dispersant were mixed and shaken for 0.5 h to obtain component B; component B was then mixed and stirred with 10 parts by weight of bis-(γ-triethoxysilylpropyl) tetrasulfide for 0.9 h to obtain a uniform and stable multi-claw silane coupling agent solution.

[0117] (2) Applied to metal surface pretreatment

[0118] The surface of Q235 steel was cleaned by sanding to remove rust, and then cleaned with organic solvent to remove oil stains;

[0119] The multi-claw silane coupling agent solution prepared in step (1) is uniformly sprayed on the surface of metal Q235 steel; dried at room temperature for 12 hours, placed in a 120° C. oven for 2 hours, and a silane film is formed on the surface of the Q235 steel; the average dry film thickness of the silane film is 2 μm.

[0120] (3) Apply epoxy coating

[0121] A two-component epoxy coating was applied to the surface of the dried silane film and cured at room temperature for 7 days to form a coating dry film with an average thickness of 50 μm; then the interface adhesion, salt spray resistance, and electrochemical performance related tests were performed. The test methods for the interface adhesion, salt spray resistance, and electrochemical performance related tests are the same as those in the embodiment. The test results are shown in Table 1.

[0122] Table 1

[0123]

[0124] Comparative Examples 1-5 use the existing method or a single multi-claw silane coupling agent solution to pretreat the metal surface, while Example 1-4 uses the multi-claw silane coupling agent solution of the present invention to pretreat the metal surface; compared with Comparative Examples 1-5, the difference between Example 1-4 is that the solution for pretreating the metal surface is different. It can be concluded from Table 1 that compared with Comparative Examples 1-5, the adhesion of the coating of Example 1-4 is increased by at least 20.7%, the width of the single-side rust of the neutral salt spray scratch after 1000h is reduced by at least 56.5%, and the electrochemical impedance value after 2000h seawater immersion is increased by at least 17.4 times. Therefore, it can be concluded that compared with the existing method or a single multi-claw silane coupling agent solution to pretreat the metal surface, the multi-claw silane coupling agent solution of the present invention to pretreat the metal surface can significantly improve the adhesion and corrosion resistance of the coating.

Claims

1. A multi-claw silane coupling agent solution for metal surface pretreatment, characterized in that: The multi-claw silane coupling agent solution comprises component A, and the component A comprises two or more multi-claw silane coupling agents; the multi-claw silane coupling agent refers to a silane coupling agent containing two or more hydrolyzable claw-type terminal active groups in the silane molecular chain.

2. The multi-claw silane coupling agent solution according to claim 1, characterized in that: The multi-claw silane coupling agent is selected from 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate, bis[3-(trimethoxysilyl)propyl]ethylenediamine, and bis-(γ-triethoxysilylpropyl)tetrasulfide.

3. The multi-claw silane coupling agent solution according to claim 2, characterized in that: When the multi-claw silane coupling agent is 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate and bis[3-(trimethoxysilyl)propyl]ethylenediamine, the mass ratio of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate to bis[3-(trimethoxysilyl)propyl]ethylenediamine is (1-3):1, preferably (1.5-2):1; or / and, When the multi-claw silane coupling agent is bis[3-(trimethoxysilyl)propyl]ethylenediamine and bis-(γ-triethoxysilylpropyl)tetrasulfide, the mass ratio of bis[3-(trimethoxysilyl)propyl]ethylenediamine to bis-(γ-triethoxysilylpropyl)tetrasulfide is (0.5-2):1, preferably (1-1.5):1; or / and, When the multi-claw silane coupling agent is 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate and bis-(γ-triethoxysilylpropyl)tetrasulfide, the mass ratio of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate to bis-(γ-triethoxysilylpropyl)tetrasulfide is (0.5-1.5):1; preferably (0.7-1):1; or / and, When the multi-claw silane coupling agent is 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate, bis[3-(trimethoxysilyl)propyl]ethylenediamine and bis-(γ-triethoxysilylpropyl)tetrasulfide, the mass ratio of 1,3,5-tris(trimethoxysilylpropyl)polyisocyanate, bis[3-(trimethoxysilyl)propyl]ethylenediamine and bis-(γ-triethoxysilylpropyl)tetrasulfide is (0.5-2):(0.5-2):1, preferably (0.8-1.2):(0.6-1):

1.

4. The multi-claw silane coupling agent solution according to any one of claims 1 to 3, characterized in that: The multi-claw silane coupling agent solution further comprises a component B, wherein the component B comprises a solvent, a nanofiller and an auxiliary agent; Taking the total content of component A and component B as 100wt%, the content of each component is as follows:

5. The multi-claw silane coupling agent solution according to claim 4, characterized in that: The nano filler is selected from one or more of nano titanium dioxide, nano silicon dioxide and nano calcium carbonate.

6. The multi-claw silane coupling agent solution according to claim 4, characterized in that: The auxiliary agent is selected from at least one of a surfactant, a dispersant, a defoamer, a stabilizer, and an antioxidant.

7. The multi-claw silane coupling agent solution according to claim 4, characterized in that: The solvent is selected from one or more of water and alcohol; the water is preferably deionized water; the alcohol is preferably selected from ethylene glycol, ethanol, and isopropanol.

8. A method for preparing a multi-claw silane coupling agent solution according to any one of claims 4 to 7, characterized in that: The preparation method comprises firstly mixing and dispersing the components of the B component according to the content, and then uniformly mixing the A component and the B component according to the content to obtain the multi-claw silane coupling agent solution.

9. The preparation method according to claim 8, characterized in that: During the mixing process of component A and component B, the temperature is controlled at 10°C to 30°C and the pH is controlled at 4 to 5.

10. Use of the multi-claw silane coupling agent solution according to any one of claims 1 to 7 or the multi-claw silane coupling agent solution prepared by the preparation method according to claim 8 or 9 in the field of surface pretreatment of metal substrates.

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