A galvanized steel sheet with good adhesion to electron beam cured coating and its manufacturing method

Abstract

This invention discloses a galvanized steel sheet with good adhesion to an electron beam-cured coating, comprising a galvanized steel sheet, at least one surface of which has a composite coating. The composite coating contains the following effective components: an aqueous cationic polymer resin A, comprising 45-75 parts by weight; a compounded organosilane coupling agent B, comprising 15-45 parts by weight; the compounded organosilane coupling agent B is formed by the mixed hydrolysis and condensation of at least one organosilane coupling agent B1 containing an epoxy functional group and at least one organosilane coupling agent B2 containing an amino functional group; a silane coupling agent C containing unsaturated bonds, comprising 3-10 parts by weight; a water-soluble fluorine-containing compound D, wherein the fluorine element comprises 1.5-5 parts by weight; and a water-soluble phosphorus-containing compound E, wherein the phosphorus element comprises 2-5 parts by weight. This invention also discloses a surface treatment agent for galvanized steel sheets and a method for manufacturing a galvanized steel sheet with good adhesion to an electron beam-cured coating.

Description

Technical Field

[0001] This invention relates to a steel sheet with a surface coating, and more particularly to a galvanized steel sheet with a surface coating. Background Technology

[0002] Galvanized color-coated steel sheet (also known as galvanized pre-coated steel sheet) is a composite material made by coating a layer of colored coating onto a galvanized steel sheet. It boasts excellent corrosion resistance, attractive appearance, and ease of processing. Galvanized color-coated steel sheet not only offers outstanding corrosion resistance but also provides a variety of colors and gloss levels. The galvanized layer provides excellent rust protection, suitable for long-term use; the colored coating not only enriches the appearance of home appliances but also enhances their texture. Furthermore, galvanized color-coated steel sheet has excellent formability, facilitating secondary processing such as stamping and bending.

[0003] Radiation-cured color-coated steel sheet production technology, as an improvement on traditional thermosetting processes, is characterized by environmental friendliness, energy saving, and high efficiency, representing an important development direction for future color-coated steel sheet manufacturing. This process utilizes ultraviolet (UV) light or electron beam (EB) energy irradiation as the excitation source for coating curing, enabling solvent-free coatings to achieve instantaneous curing at room temperature. Typically, in the production process of radiation-cured color-coated steel sheets, the thickness and color of the topcoat layer determine the curing method. Since UV curing cannot completely cure the topcoat within a specified time, EB curing is necessary to complete this process.

[0004] While electron beam (EB) irradiation can achieve cross-linking and curing of coatings with specific formulations (usually through free radical polymerization), the high-energy EB irradiation can break chemical bonds in non-radiation-curable coatings, leading to coating degradation and failure. Therefore, if traditional pretreatment processes (such as chemical formation treatment followed by solvent-based primer coating) are used to treat the substrate before radiation curing, the high-energy electron beam will damage the pretreatment layer during the subsequent EB curing process, resulting in reduced adhesion and corrosion resistance between the substrate and the coating, severely impacting product quality. If the substrate is not properly surface-treated before coating and curing, good adhesion and corrosion resistance between the galvanized substrate and the radiation-cured coating cannot be guaranteed.

[0005] In the prior art, existing patent literature covers the above-mentioned fields, for example:

[0006] Chinese patent document CN113522706A, published on October 22, 2021, entitled "Surface-treated color-coated substrate suitable for radiation-cured color-coated steel sheet production process," discloses a surface-treated color-coated substrate suitable for radiation-cured color-coated steel sheet production process. This product possesses excellent surface wear resistance and rust prevention properties and can be directly used in the production of radiation-cured color coating processes. During the EB curing process of the color coating layer, its surface composite protective film effectively resists damage from electron beam irradiation and effectively improves the adhesion and corrosion resistance between the substrate and the radiation-cured coating. However, this surface-treated color-coated substrate does not optimize the deformation and impact resistance of galvanized radiation-cured color-coated steel sheets, nor can it simultaneously provide sufficient corrosion resistance and adhesive bonding properties, thus failing to meet the functional requirements for use as a back coating for galvanized color-coated steel sheets. Summary of the Invention

[0007] One of the objectives of this invention is to provide a galvanized steel sheet with good adhesion to an electron beam cured coating. The composite coating of this steel sheet is adapted to the EB radiation curing process and has excellent corrosion resistance and adhesion properties.

[0008] To achieve the above objectives, the present invention provides a galvanized steel sheet with good adhesion to an electron beam-cured coating, comprising a galvanized steel sheet, wherein at least one surface of the galvanized steel sheet has a composite coating, the composite coating containing the following effective components:

[0009] Aqueous cationic polymer resin A, in parts by weight 45-75;

[0010] The compounded organosilane coupling agent B has a weight of 15-45 parts; the compounded organosilane coupling agent B is formed by the mixed hydrolysis and condensation polymerization of at least one organosilane coupling agent B1 containing an epoxy functional group and at least one organosilane coupling agent B2 containing an amino functional group.

[0011] Silane coupling agent C containing unsaturated bonds, in parts by weight of 3-10;

[0012] Water-soluble fluorine-containing compound D, wherein the fluorine element is 1.5-5 parts by weight;

[0013] Water-soluble phosphorus-containing compound E, wherein the phosphorus element is present in 2-5 parts by weight.

[0014] In this manner, the galvanized steel sheet of the present invention comprises, from the core outwards: a steel substrate, a galvanized layer, and a composite coating. This composite coating not only ensures excellent inter-process surface damage resistance and rust prevention of the color-coated substrate, but also participates in the cross-linking and curing process of the upper paint film during the subsequent electron beam (EB) radiation curing process, effectively improving the adhesion, processability, and corrosion resistance between the galvanized substrate and the radiation-cured coating. Furthermore, the surface composite coating of this galvanized steel sheet can also be directly used as the back paint of the color-coated steel sheet, exhibiting certain corrosion resistance and adhesion properties.

[0015] In this invention, the inventors control the weight percentage of waterborne cationic polymer resin A in the coating to be between 45 and 75 parts because: when the weight percentage of waterborne cationic polymer resin A is less than 45 parts, the interfacial adhesion between the coating and the upper radiation-cured coating decreases. When the weight percentage of waterborne cationic polymer resin A is greater than 75 parts, the relative proportion of the silane skeleton formed by the compounded organosilane coupling agent B, which plays an electrochemical anti-corrosion role on the galvanized steel surface, decreases, affecting the corrosion resistance of the galvanized surface-treated steel sheet.

[0016] In this invention, the inventors controlled the weight of organosilane coupling agent B in the coating to be between 15 and 45 parts because: when the weight of organosilane coupling agent B is less than 15 parts, the corrosion resistance of the composite coating may decrease; when the weight of organosilane coupling agent B is more than 45 parts, the relative proportion of waterborne cationic polymer resin A, which increases the flexibility of the coating, will decrease, resulting in poor T-bend adhesion and impact resistance of the radiation-cured color-coated steel sheet prepared on the galvanized surface-treated steel sheet.

[0017] In this invention, the unsaturated bonds on the silane coupling agent C, containing unsaturated bonds, participate in the subsequent EB irradiation crosslinking and curing process of the upper radiation-cured coating film. Other alkoxy groups (such as methoxy and ethoxy groups) on the silane coupling agent C, after hydrolysis, form a crosslinking network with the compounded organosilane coupling agent B and are coupled in the composite coating, resulting in good interlayer adhesion between the composite coating and the upper radiation-cured coating film. The inventors control the weight percentage of the silane coupling agent C containing unsaturated bonds in the coating to 3-10 parts because: when the weight percentage of the silane coupling agent C containing unsaturated bonds is less than 3, the relative content of the silane coupling agent C containing unsaturated bonds is low, which is insufficient to ensure adequate adhesion between the composite coating and the upper radiation-cured coating film. When the weight percentage of silane coupling agent C containing unsaturated bonds is higher than 10, the cross-linking polymerization of the brittle organosilane coupling agent will reduce the plasticity of the composite coating, thereby worsening the T-bend adhesion and impact resistance of the radiation-cured color-coated steel sheet prepared on the galvanized surface-treated steel sheet.

[0018] In this invention, the inventors control the weight of fluorine in the water-soluble fluorine compound D in the coating to be between 1.5 and 5 parts because: when the weight of fluorine in the water-soluble fluorine compound D is less than 1.5 parts, the corrosion resistance of the composite coating may decrease, thereby reducing the resistance to under-film corrosion of the radiation-cured color-coated steel sheet prepared on the galvanized surface-treated steel sheet; when the weight of fluorine in the water-soluble fluorine compound D is greater than 5 parts, due to the water-soluble nature of fluorine compounds, residual fluorine compounds that have not fully reacted with the galvanized interface may reduce the water resistance of the composite coating, affecting its resistance to damp heat, and thus reducing the water-boiling resistance of the radiation-cured color-coated steel sheet prepared on the galvanized surface-treated steel sheet.

[0019] In this invention, the inventors control the weight percentage of phosphorus in the water-soluble phosphorus compound E in the coating to be 2-5 parts because: when the weight percentage of phosphorus in the water-soluble phosphorus compound E is less than 2 parts, there is no additive effect, and the corrosion resistance of the composite coating may decrease, thereby reducing the resistance to under-film corrosion of the radiation-cured color-coated steel sheet prepared on the galvanized surface-treated steel sheet. When the weight percentage of phosphorus in the water-soluble phosphorus compound E is greater than 5 parts, it will lead to a decrease in the stability of the aqueous treatment solution used to apply the composite coating.

[0020] Furthermore, in the galvanized steel sheet of the present invention, the waterborne cationic polymer resin A is selected from: waterborne acrylic resin, waterborne epoxy resin, waterborne polyurethane, waterborne polyester resin and waterborne alkyd resin, and the resin dry film formed by compounding at least one of the above resins with copolymerized modified resins, the 100% modulus can be 50-600 MPa, and the elongation at break can be 100-400%.

[0021] Furthermore, in the galvanized steel sheet of the present invention, the organosilane coupling agent B1 containing epoxy functional groups is selected from one or more of the following: 3-glycidyl etheroxypropyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropylmethyldimethoxysilane, 3-glycidyl etheroxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0022] Furthermore, in the galvanized steel sheet of the present invention, the organosilane coupling agent B2 containing an amino functional group is selected from one or more of the following: 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, and bis(3-triethoxysilylpropyl)amine.

[0023] Furthermore, in the galvanized steel sheet of the present invention, the unsaturated bonds in the resin C are one or more of vinyl, acetoxy, acryloyloxy, and methacryloxy.

[0024] Furthermore, in the galvanized steel sheet of the present invention, the water-soluble fluorinated compound D is selected from at least one of fluorinated metal acids, fluorinated metal salts, and fluorides.

[0025] Furthermore, in the galvanized steel sheet of the present invention, the water-soluble phosphorus-containing compound E is selected from at least one of: ammonium dihydrogen phosphate, zinc dihydrogen phosphate, manganese dihydrogen phosphate, phosphoric acid, phytic acid, and hydroxyethylidene diphosphonic acid.

[0026] Furthermore, in the galvanized steel sheet of the present invention, the film weight of the composite coating is 0.5-3 g / m³. 2 .

[0027] In this invention, when the film weight of the composite coating is less than 0.5 g / m³ 2 When the coating is thin, the corrosion resistance of the composite coating decreases, which in turn worsens the corrosion resistance of the radiation-cured color-coated steel sheet prepared on the galvanized steel sheet. When the film weight of the composite coating exceeds 3 g / m²... 2 On the one hand, this will increase the surface treatment cost per unit area. On the other hand, under the same curing conditions, due to the thicker coating, the curing cross-linking may be insufficient, which will lead to a decrease in coating cohesion and wear resistance. Consequently, the T-bend adhesion and corrosion resistance after forming of the radiation-cured color-coated steel sheet prepared on the galvanized surface-treated steel sheet will deteriorate.

[0028] Furthermore, in the galvanized steel sheet of the present invention, the galvanized steel sheet is a hot-dip galvanized steel sheet, an electro-galvanized steel sheet, or a hot-dip galvanized aluminum-magnesium steel sheet with an aluminum content of less than 3 wt%.

[0029] Another object of the present invention is to provide a surface treatment agent for galvanized steel sheets. When the surface treatment agent is applied to the surface of the galvanized steel sheet, a composite coating with excellent corrosion resistance and adhesion properties can be obtained.

[0030] To achieve the above objectives, the present invention provides a surface treatment agent for galvanized steel sheets, which is an aqueous solution containing solids, wherein the solids contain the following active ingredients in parts by weight:

[0031] Aqueous cationic polymer resin A, in parts by weight 45-75;

[0032] The compounded organosilane coupling agent B has a weight of 15-45 parts; the compounded organosilane coupling agent B is formed by the mixed hydrolysis and condensation polymerization of at least one organosilane coupling agent B1 containing an epoxy functional group and at least one organosilane coupling agent B2 containing an amino functional group.

[0033] Silane coupling agent C containing unsaturated bonds, in parts by weight of 3-10;

[0034] Water-soluble fluorine-containing compound D, wherein the fluorine element is 1.5-5 parts by weight;

[0035] Water-soluble phosphorus-containing compound E, wherein the phosphorus element is present in 2-5 parts by weight.

[0036] Furthermore, in the surface treatment agent of the present invention, the waterborne cationic polymer resin A is selected from at least one of the following: waterborne acrylic resin, waterborne epoxy resin, waterborne polyurethane, waterborne polyester resin, and waterborne alkyd resin, as well as copolymerized modified resins of the above resins.

[0037] Furthermore, in the surface treatment agent described in this invention, the epoxy-functionalized organosilane coupling agent B1 is selected from one or more of the following: 3-glycidyl etheroxypropyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropylmethyldimethoxysilane, 3-glycidyl etheroxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0038] Furthermore, in the surface treatment agent described in this invention, the organosilane coupling agent B2 containing an amino functional group is selected from one or more of the following: 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, and bis(3-triethoxysilylpropyl)amine.

[0039] Furthermore, in the surface treatment agent described in this invention, the unsaturated bonds in the resin C are one or more of vinyl, acetoxy, acryloyloxy, and methacryloxy.

[0040] Furthermore, in the surface treatment agent described in this invention, the water-soluble fluorinated compound D is selected from at least one of fluorinated metal acids, fluorinated metal salts, and fluorides.

[0041] Furthermore, in the surface treatment agent of the present invention, the water-soluble phosphorus-containing compound E is selected from at least one of: ammonium dihydrogen phosphate, zinc dihydrogen phosphate, manganese dihydrogen phosphate, phosphoric acid, phytic acid, and hydroxyethylidene diphosphonic acid.

[0042] Another object of the present invention is to provide a method for manufacturing a galvanized steel sheet with good adhesion to an electron beam cured coating, which can obtain a galvanized steel sheet with good adhesion to an electron beam cured coating.

[0043] To achieve the above objectives, the present invention provides a method for manufacturing a galvanized steel sheet with good adhesion to an electron beam-cured coating, comprising the steps of:

[0044] The above-mentioned surface treatment agent is applied to the surface of the galvanized steel sheet and cured into a film to form a composite coating on the surface of the galvanized steel sheet.

[0045] Compared with existing technologies, the galvanized steel sheet with good adhesion to electron beam curing coating and its manufacturing method described in this invention have the following advantages and beneficial effects:

[0046] The galvanized steel sheet with good adhesion to electron beam curing coating described in this invention uses water-based cationic polymer resin A and compounded organosilane coupling agent B as the matrix of the composite coating to achieve the effect of preventing physical penetration of corrosive media and inhibiting electrochemical corrosion. This results in a composite coating with excellent corrosion resistance, which can be directly used as the back paint of color-coated steel sheet, and has certain corrosion resistance and adhesion properties.

[0047] In some preferred embodiments, the galvanized steel sheet with good adhesion to the electron beam curing coating described in this invention is selected from an aqueous cationic polymer resin system with both high modulus and high elongation, so that the composite coating has both flexibility and hardness, which can further improve the corrosion resistance of such galvanized surface-treated steel sheet after processing deformation, thereby making the radiation-cured color-coated steel sheet prepared on the galvanized surface-treated steel sheet have good formability and corrosion resistance after forming.

[0048] The galvanized steel sheet with good adhesion to the electron beam cured coating described in this invention uses a silane coupling agent C containing unsaturated bonds. The unsaturated bonds on the organosilane coupling agent C participate in the subsequent EB irradiation crosslinking and curing process of the upper radiation-cured paint film. Other alkoxy groups (such as methoxy and ethoxy groups) on the organosilane coupling agent, after hydrolysis, will form a crosslinking network with the compound organosilane coupling agent and couple to the composite coating. This results in good interlayer adhesion between the composite coating and the upper radiation-cured paint film, giving the radiation-cured color-coated steel sheet prepared on this galvanized surface-treated steel sheet superior adhesion and impact resistance. Detailed Implementation

[0049] The following will further explain and illustrate the galvanized steel sheet with good adhesion to the electron beam curing coating, its manufacturing method, and the surface treatment agent described in this invention, with reference to specific embodiments. However, this explanation and illustration do not constitute an undue limitation on the technical solution of this invention.

[0050] Examples 1-21 and Comparative Examples 1-8

[0051] The galvanized steel sheets with good adhesion to the electron beam-cured coating in Examples 1-21 and Comparative Examples 1-6 of this invention were all prepared using the following steps:

[0052] (1) Apply the surface treatment agent to the surface of the galvanized steel sheet by roller coating or spraying.

[0053] (2) A composite coating is formed on the surface of the galvanized steel sheet by blowing or drying to cure the film.

[0054] In some specific embodiments, the obtained galvanized steel sheet comprises, from the core outwards: a cold-rolled substrate, front and back galvanized layers, and a composite coating on the front and back.

[0055] It should be noted that Comparative Example 7 is a hot-dip galvanized steel sheet without any surface treatment. The steel sheet consists of the following layers from the core outwards: cold-rolled substrate, front and back galvanized layers, and does not have a composite coating.

[0056] In addition, Comparative Example 8 shows a pretreated hot-dip galvanized color-coated substrate that has undergone a conventional color-coating pretreatment process. The conventional pretreatment process involves spraying a composite film-forming agent with Co and Ni as film-forming elements onto the surface of the substrate, followed by spraying a chromate passivating agent to seal the pretreated layer. The Co and Cr content in the pretreated layer is Co: 3-7 mg / m³. 2 Cr: 15-25 mg / m³ 2 .

[0057] Furthermore, it should be noted that the effective components of the composite coating of the present invention are the same as the effective components of the solid components of the surface treatment agent aqueous solution, therefore the two will not be described separately.

[0058] Table 1-1 lists the composite coatings of galvanized steel sheets in Examples 1-21 and Comparative Examples 1-6, as well as the types and contents of active ingredients in the surface treatment agents used therein.

[0059] Table 1-1.

[0060]

[0061]

[0062]

[0063] *Note: A1 is waterborne polycarbonate-modified polyurethane, A2 is waterborne acrylic resin, A3 is waterborne epoxy resin, A4 is waterborne alkyd resin, and A5 is waterborne polyester resin; B1-1 is 3-glycidyl etheroxypropyltriethoxysilane, B1-2 is 3-glycidyl etheroxypropylmethyldiethoxysilane, B1-3 is 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, B1-4 is 3-glycidyl etheroxypropyltrimethoxysilane, B1-5 is 3-glycidyl etheroxypropylmethyldimethoxysilane, and B1-6 is 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; B2-1 is 3-aminopropyltriethoxysilane, B2-2 is 3-aminopropylmethyldimethoxysilane, and B2-3 is N-2 B2-4 is bis(3-triethoxysilylpropyl)amine, B2-5 is 3-aminopropyltrimethoxysilane, B2-6 is N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, B2-7 is N-(n-butyl)-3-aminopropyltrimethoxysilane; C1 is vinyltriethoxysilane, C2 is 3-acetoxypropyltrimethoxysilane, C3 is 3-methacryloyloxypropyltriethoxysilane, C4 is 3-acryloyloxypropyltrimethoxysilane; D1 is fluorotitanic acid, D2 is ammonium fluorotitanate, D3 is ammonium fluorozirconate; E1 is ammonium dihydrogen phosphate, E2 is phytic acid, E3 is hydroxyethylidene diphosphate, E4 is zinc dihydrogen phosphate, E5 is manganese dihydrogen phosphate, and E6 is phosphoric acid.

[0064] It should be noted that although B1, B2, D, and E in the above embodiments all use a single substance, it is also feasible to use multiple substances that meet the requirements in combination in other embodiments.

[0065] Table 1-2 lists the coating types and composite coating weights of the galvanized steel sheets in Examples 1-21 and Comparative Examples 1-6.

[0066] Table 1-2.

[0067]

[0068]

[0069] Accordingly, to verify the superiority of the galvanized steel sheet with good adhesion to the electron beam curing coating designed in this invention, samples of the galvanized steel sheets prepared in Examples 1-21 and Comparative Examples 1-8 were cut into standard-sized samples and subjected to the following tests to obtain test data for evaluating various properties. The evaluation results are listed in Tables 2-1 and 2-2. The specific test items and methods are as follows:

[0070] (1) Plate corrosion resistance test:

[0071] The plate was subjected to a salt spray test according to ASTM B117, with a test duration of 120 hours. The evaluation criteria are as follows:

[0072] ◎: White rust area ratio is less than or equal to 5%

[0073] ○: White rust area ratio greater than 5% and less than or equal to 10%

[0074] Δ: White rust area ratio greater than 10% and less than or equal to 50%

[0075] ×: White rust area ratio greater than 50%

[0076] (2) Moisture and heat resistance test:

[0077] The stacked wet heat method was used, in which two samples were stacked and a torque of 30 N·m was applied. They were then placed in a wet heat chamber at a temperature of 49℃ and a humidity of 98% for 120 hours. The evaluation criteria are as follows:

[0078] ◎: White rust area ratio is less than or equal to 5%

[0079] ○: White rust area ratio greater than 5% and less than or equal to 5%

[0080] Δ: White rust area ratio greater than 10% and less than or equal to 30%

[0081] ×: White rust area ratio greater than 30%

[0082] (3) Wear resistance test:

[0083] Using the rubber method, a Φ10mm flat rubber sheet is repeatedly rubbed against the surface under a load of 500g, a friction speed of 300m / min, a friction distance of 20mm, and 50 cycles of reciprocating friction. The evaluation criteria are as follows:

[0084] ◎: No change in the surface protective film

[0085] ○: Minor scratches on the protective film

[0086] Δ: Multiple scratches on the protective film

[0087] ×: Protective film completely peeled off

[0088] (4) Adhesion test:

[0089] To determine the bonding performance between the backing paint and the adhesive, the test specimen was cut to a length of 205 mm and a width of 25 mm. At a distance of 50 mm from the end along the length, it was T-bent at a 90-degree right angle. The upper surface of the remaining 155 mm of the specimen at the bend was wiped with a small amount of ethanol using a cotton swab and thoroughly dried. Then, the adhesive (Henkel Microplast UK8103 / UK5400 two-component polyurethane adhesive, mixed in a 5:1 ratio) was evenly applied over the entire width (25 mm). Another specimen with the same 50 mm T-bent was taken, and the remaining 155 mm of the specimen was aligned and attached to the adhesive area. The positions of the upper and lower specimens were adjusted to prevent misalignment, forming a T-shaped test specimen. Pressure (0.7 kPa) was maintained in the fixed mold for 72 hours. The specimen was then removed, and the adhesive on the edges of the specimen was scraped off with a utility knife. At least three parallel specimens were prepared for each sample.

[0090] Adjust the clamped portion of the specimen to be perpendicular to the bonded portion, and then place it in the tensile testing machine clamps for fixation. According to GB / T 2791, set the tensile testing machine parameters, including a tensile rate of 100±10 mm / min, a specimen width of 25 mm, and a peel length of 155 mm. Set the data for the peel length range before and after removal, within 25 mm increments. Start the tensile test. The tensile testing machine recording device records the peel load curve and automatically calculates the peel strength of the specimen.

[0091] The percentage of cohesive failure area is observed, i.e., the percentage of cohesive failure area S = 100% - (percentage of interlaminar failure area of ​​upper sample + percentage of interlaminar failure area of ​​lower sample). The final evaluation criteria for adhesion are as follows:

[0092] ◎: Cohesive failure area S≥80%, and peel strength σ≥4.0 (N / mm)

[0093] ○: 80% > cohesive failure area S ≥ 60%, and peel strength σ ≥ 4.0 (N / mm)

[0094] Δ: 60% > cohesive failure area S ≥ 40%, and peel strength σ ≥ 4.0 (N / mm)

[0095] ×: Cohesion failure area S < 40%

[0096] (5) Compatibility test with electron beam (EB) cured coating:

[0097] Radiation-cured color-coated topcoat was applied and cured on galvanized aluminum-magnesium alloy (GAMA) substrates. The topcoat used was an electron beam (EB) cured coating with a film thickness of 15 μm. Curing conditions included a maximum EB dose of 100 KGy and a maximum voltage of 200 KV. The coated samples underwent adhesion tests including T-bend, cross-cut adhesion, impact, and boiling water tests, as well as corrosion resistance tests including salt spray and under-film corrosion. The adhesion and corrosion resistance test results directly reflect the compatibility of the galvanized aluminum-magnesium alloy substrate with the electron beam radiation curing process and the coating. Specifically:

[0098] 5.1T Bending Adhesion Performance Test: Conducted according to GB / T 13448, section 7. Bending Test standard, with the following evaluation criteria:

[0099] ◎:≤3T

[0100] ○: 4T

[0101] Δ: 5T

[0102] ×:≥6T

[0103] 5.2 Cross-cut adhesion performance test: Conducted according to the cross-cut test standard in GB / T 13448, section 13. The evaluation criteria are as follows:

[0104] ◎: The cross-cut test rating is level 0 as specified in Table 1 of GB / T13448.

[0105] ○: Cross-cut test rating is level 1-2 as specified in Table 1 of GB / T13448.

[0106] Δ: Cross-cut test rating is level 3-4 as specified in Table 1 of GB / T13448.

[0107] ×: The cross-cutting test rating is Level 5 as specified in Table 1 of GB / T13448.

[0108] 5.3 Impact Adhesion Performance Test: Conducted according to GB / T 13448, section 8. Reverse Impact Test standard, with the following evaluation criteria:

[0109] ◎: The maximum impact energy that causes the coating to not crack or peel off is ≥9J

[0110] ○: The maximum impact energy that causes the coating to not crack or peel off is ≥7-8J.

[0111] Δ: The cross-cut test rating is level 6-7 as specified in Table 1 of GB / T13448.

[0112] ×: The cross-cutting test rating is ≤6 as specified in Table 1 of GB / T13448.

[0113] 5.4 Water Adhesion Resistance Test: Immerse the sample in boiling water for 2 hours. After removal, first evaluate the appearance of blistering or peeling of the coating, then conduct a cross-cut adhesion test according to GB / T 13448, section 13. The evaluation criteria are as follows:

[0114] ◎: The coating shows no blistering or peeling, and its cross-cut test rating is grade 0 as specified in Table 1 of GB / T13448.

[0115] ○: The coating has minor blistering but no peeling, and the cross-cut test rating is level 1-2 as specified in Table 1 of GB / T13448.

[0116] Δ: The coating exhibits extensive blistering without peeling, and its cross-cut test rating is 3-4 as specified in Table 1 of GB / T13448.

[0117] ×: Extensive coating peeling, cross-cut test rating is level 5 as specified in Table 1 of GB / T13448.

[0118] 5.5 Planar Salt Spray Corrosion Resistance Test: Conducted according to ASTM B117, duration 1000 hours, evaluation criteria are as follows:

[0119] ◎: The bubble density grade and bubble size should not exceed grade 2 as specified in Table 21 of GB / T1766.

[0120] ○: The bubble density grade and bubble size should not exceed grade 3 as specified in Table 21 of GB / T1766.

[0121] Δ: The bubble density grade and bubble size should not exceed grade 4 as specified in Table 21 of GB / T1766.

[0122] ×: The bubble density grade and bubble size should not exceed grade 5 as specified in Table 21 of GB / T1766.

[0123] 5.6 Under-film corrosion resistance test: Before the test, use a knife to draw a single straight line parallel to the long side of the sample on the central part of the sample. The line should be no less than 50 mm long and penetrate the coating. The line should be no less than 30 mm from the edge. Then, conduct a salt spray test according to ASTM B117 for 1000 hours. The evaluation criteria are as follows:

[0124] ◎: The average erosion width on one side of the marked area is less than or equal to 5mm

[0125] ○: The average erosion width on one side of the marked area is greater than 5mm and less than or equal to 10mm.

[0126] Δ: The average erosion width on one side of the scribed area is greater than 10mm and less than or equal to 15mm.

[0127] ×: The average erosion width on one side of the marked area is greater than 15mm.

[0128] Tables 2-1 and 2-2 list the evaluation results of various performance tests on the galvanized steel sheet samples of Examples 1-21 and Comparative Examples 1-8 of the present invention.

[0129] Table 2-1.

[0130]

[0131] Table 2-2.

[0132]

[0133]

[0134] As can be seen from Table 2 above, after the galvanized steel sheets in Examples 1-21 were tested, the evaluation results were all “◎” and “○”. When used as a back coating, they all showed good corrosion resistance, wear resistance and adhesion. As a pretreatment layer, they could form good adhesion and corrosion resistance with electron beam (EB) cured coating.

[0135] In summary, the galvanized surface-treated steel sheet provided by this invention can effectively adhere to electron beam (EB) cured coatings. Radiation-cured color-coated steel sheets produced using this galvanized surface-treated steel sheet can meet the requirements for stamping performance, corrosion resistance, and overall resistance. Furthermore, its superior corrosion resistance, abrasion resistance, and adhesion can meet the requirements for back coating, reducing the number of back coating steps.

[0136] It should be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A galvanized steel sheet having good adhesion with an electron beam-cured coating layer, comprising a galvanized steel sheet, characterized by, At least one surface of the galvanized steel sheet has a composite coating, the composite coating containing the following active ingredients: Aqueous cationic polymer resin A, in parts by weight 45-75; The compounded organosilane coupling agent B has a weight of 15-45 parts; the compounded organosilane coupling agent B is formed by the mixed hydrolysis and condensation polymerization of at least one organosilane coupling agent B1 containing an epoxy functional group and at least one organosilane coupling agent B2 containing an amino functional group. Silane coupling agent C containing unsaturated bonds, in parts by weight of 3-10; Water-soluble fluorine-containing compound D, wherein the fluorine element is 1.5-5 parts by weight; Water-soluble phosphorus-containing compound E, wherein the phosphorus element is present in 2-5 parts by weight.

2. The galvannealed steel sheet according to claim 1, characterized in that, The waterborne cationic polymer resin A is selected from at least one of the following: waterborne acrylic resin, waterborne epoxy resin, waterborne polyurethane, waterborne polyester resin, and waterborne alkyd resin, as well as copolymerized modified resins of the above resins.

3. The galvanized steel sheet according to claim 1, characterized in that, The organosilane coupling agent B1 containing an epoxy functional group is selected from one or more of the following: 3-glycidyl etheroxypropyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropylmethyldimethoxysilane, 3-glycidyl etheroxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

4. The galvanized steel sheet according to claim 1, characterized in that, The amino-functionalized organosilane coupling agent B2 is selected from one or more of the following: 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, and bis(3-triethoxysilylpropyl)amine.

5. The galvanized steel sheet according to claim 1, characterized in that, The unsaturated bonds in resin C are one or more of vinyl, acetoxy, acryloyloxy, and methacryloyloxy.

6. The galvanized steel sheet according to claim 1, characterized in that, The water-soluble fluorinated compound D is selected from at least one of fluorinated metal acids, fluorinated metal salts, and fluorides.

7. The galvanized steel sheet according to claim 1, characterized in that, The water-soluble phosphorus-containing compound E is selected from at least one of: ammonium dihydrogen phosphate, zinc dihydrogen phosphate, manganese dihydrogen phosphate, phosphoric acid, phytic acid, and hydroxyethylidene diphosphonic acid.

8. The galvanized steel sheet according to claim 1, characterized in that, The film weight of the composite coating is 0.5-3 g / m 2 .

9. The galvanized steel sheet according to claim 1, characterized in that, The galvanized steel sheet is a hot-dip galvanized steel sheet, an electro-galvanized steel sheet, or a hot-dip galvanized aluminum-magnesium steel sheet with an aluminum content of less than 3wt%.

10. A surface treatment agent for a galvanized steel sheet, characterized by, It is an aqueous solution containing solids, wherein the solids contain the following active ingredients in parts by weight: Aqueous cationic polymer resin A, in parts by weight 45-75; The compounded organosilane coupling agent B has a weight of 15-45 parts; the compounded organosilane coupling agent B is formed by the mixed hydrolysis and condensation polymerization of at least one organosilane coupling agent B1 containing an epoxy functional group and at least one organosilane coupling agent B2 containing an amino functional group. Silane coupling agent C containing unsaturated bonds, in parts by weight of 3-10; Water-soluble fluorine-containing compound D, wherein the fluorine element is 1.5-5 parts by weight; Water-soluble phosphorus-containing compound E, wherein the phosphorus element is present in 2-5 parts by weight.

11. The surface treatment agent according to claim 10, wherein The polymer resin A is selected from at least one of the following: waterborne acrylic resin, waterborne epoxy resin, waterborne polyurethane, waterborne polyester resin, and waterborne alkyd resin, as well as copolymerized modified resins of the above resins.

12. The surface treatment agent according to claim 10, wherein The organosilane coupling agent B1 containing an epoxy functional group is selected from one or more of the following: 3-glycidyl etheroxypropyltriethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropylmethyldimethoxysilane, 3-glycidyl etheroxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

13. The surface treatment agent according to claim 10, wherein The amino-functionalized organosilane coupling agent B2 is selected from one or more of the following: 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, and bis(3-triethoxysilylpropyl)amine.

14. The surface treatment agent according to claim 10, wherein The unsaturated bonds in resin C are one or more of vinyl, acetoxy, acryloyloxy, and methacryloyloxy.

15. The surface treatment agent according to claim 10, wherein The water-soluble fluorinated compound D is selected from at least one of fluorinated metal acids, fluorinated metal salts, and fluorides.

16. The surface treatment agent according to claim 10, wherein The water-soluble phosphorus-containing compound E is selected from at least one of: ammonium dihydrogen phosphate, zinc dihydrogen phosphate, manganese dihydrogen phosphate, phosphoric acid, phytic acid, and hydroxyethylidene diphosphonic acid.

17. A method of manufacturing a galvanized steel sheet having good adhesion with an electron beam-cured coating layer, characterized by, Including the following steps: The surface treatment agent as described in any one of claims 10-16 is applied to the surface of a galvanized steel sheet and cured into a film to form a composite coating on the surface of the galvanized steel sheet.

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