Metal surface anticorrosive paint and preparation method thereof

Abstract

The invention discloses metal surface anticorrosive paint and a preparation method thereof, and relates to the field of metal anticorrosive paint. When the metal surface anticorrosive paint is prepared, modified castor oil and triethylamine hydrochloride react to prepare a castor oil-based cross-linking agent; the preparation method comprises the following steps: carrying out epoxidation reaction on hexafluorobisphenol A and epoxy chloropropane to prepare an epoxy prepolymer; reacting the epoxy prepolymer with protocatechuic acid to obtain modified epoxy resin; the preparation method comprises the following steps: reacting 2-aminobenzothiazole with isocyanate propyl triethoxy silane to prepare modified silane; and uniformly mixing the modified epoxy resin, the modified silane and the mixed solvent, and adding the flatting agent and the castor oil-based cross-linking agent to prepare the metal surface anticorrosive paint. The metal surface anticorrosive paint prepared by the invention has excellent corrosion resistance, antibacterial property and high adhesive force.

Description

Technical Field

[0001] This invention relates to the field of metal anti-corrosion coatings, specifically to a metal surface anti-corrosion coating and its preparation method. Background Technology

[0002] In the medical field, metallic materials are widely used in surgical instruments, implants, diagnostic equipment, and medical furniture. However, in complex service environments, they are susceptible to corrosion from multiple factors, including chloride ions, acidic and alkaline media, microorganisms, and ultraviolet radiation, leading to corrosion failure and significant economic losses and safety hazards. Metal surface coating protection technology, as a low-cost and widely applicable anti-corrosion method, has become a core support for ensuring the long-term service life of metal components. Among these technologies, the research and application of high-performance anti-corrosion coatings have attracted considerable attention.

[0003] Epoxy resins, with their combination of strong adhesion to metal substrates, resistance to chemical corrosion, high crosslinking density, and good mechanical properties, have long been one of the core resin base materials for metal surface coatings. However, when faced with the stringent requirements unique to medical environments, their limitations in corrosion resistance and antibacterial properties become particularly prominent.

[0004] Ordinary epoxy resins rely solely on the dense film formed after curing to provide physical shielding against corrosion. This single mechanism is insufficient for the needs of medical settings. Corrosive ions such as Cl⁻, PO₄³⁻, and organic acids in the medical environment can penetrate through pores to the metal interface, causing pitting and intergranular corrosion. This is especially true for commonly used medical metals like stainless steel and titanium alloys, where ion penetration can damage the surface passivation film and accelerate corrosion failure. Furthermore, epoxy resin molecules themselves lack antibacterial properties, and their dense film structure provides a favorable environment for microbial adhesion and reproduction, posing a potential safety hazard in medical settings.

[0005] Therefore, developing an epoxy resin with high stability, high corrosion resistance, high biocompatibility, and long-lasting antibacterial properties is necessary to overcome application limitations and meet the specialized protection needs of medical metal devices. Summary of the Invention

[0006] The purpose of this invention is to provide a metal surface anti-corrosion coating and its preparation method, so as to solve the problems existing in the prior art.

[0007] To solve the above-mentioned technical problems, the present invention provides the following solution:

[0008] A metal surface anti-corrosion coating is prepared by reacting modified castor oil and triethylamine hydrochloride to obtain a castor oil-based crosslinking agent; epoxidizing hexafluorobisphenol A and epichlorohydrin to obtain an epoxy prepolymer; reacting the epoxy prepolymer and protocatechuic acid to obtain a modified epoxy resin; reacting 2-aminobenzothiazole and propyltriethoxysilane isocyanate to obtain a modified silane; and mixing the modified epoxy resin, modified silane, and mixed solvent evenly, and then adding a leveling agent and a castor oil-based crosslinking agent.

[0009] The modified castor oil is prepared by grafting epichlorohydrin onto castor oil;

[0010] The mixed solvent is prepared by mixing butyl acetate and xylene.

[0011] As an optimization, the epoxy prepolymer is prepared by epoxidation reaction of hexafluorobisphenol A and epichlorohydrin.

[0012] A method for preparing a metal surface anti-corrosion coating, the method comprising the following preparation steps:

[0013] (1) Mix modified castor oil, triethylamine hydrochloride and deionized water in a mass ratio of 1:(0.5~0.7):(0.4~0.5), heat to 55~65℃, stir and react for 3.5~4.5h, dehydrate under reduced pressure, add toluene at 0.9~1.1 times the mass of modified castor oil, heat to 80~90℃ for azeotropic dehydration, heat to 85~95℃, remove toluene under reduced pressure to obtain castor oil-based crosslinking agent;

[0014] (2) The epoxy prepolymer, protocatechuic acid and p-toluenesulfonic acid monohydrate are mixed evenly in a mass ratio of 1:(0.02~0.04):(0.01~0.02). Under nitrogen protection, the temperature is raised to 75~85℃ and the reaction is carried out at a rate of 9~11℃ / h for 4.5~5.5h. After cooling to room temperature, the mixture is extracted with deionized water 2~4 times and the organic phase is taken to obtain the modified epoxy resin.

[0015] (3) Mix 2-aminobenzothiazole and anhydrous tetrahydrofuran at a mass ratio of 1:(6~8), heat to 45~55℃ under nitrogen protection, add propyltriethoxysilane isocyanate, continue stirring for 1.5~2.5h, remove anhydrous tetrahydrofuran by vacuum distillation, and obtain modified silane.

[0016] (4) Mix the modified epoxy resin, modified silane and mixed solvent evenly, and ultrasonically stir for 10-20 minutes at room temperature. Add leveling agent and castor oil-based crosslinking agent, stir for 4-6 minutes at room temperature, adjust the viscosity to 500-1500 mPa·s with mixed solvent, and defoam under vacuum for 10-20 minutes to obtain a metal surface anti-corrosion coating.

[0017] As an optimization, the preparation process of the modified castor oil in step (1) is as follows: castor oil and epichlorohydrin are mixed evenly at a mass ratio of 1:(4~5), methanol with a hydroxyl equivalent of 0.09~0.11 times that of castor oil is added, the temperature is raised to 65~75℃, and 48wt% sodium hydroxide aqueous solution with a hydroxyl equivalent of 0.7~0.8 times that of castor oil is added dropwise at a uniform rate over 1.5~2.5h. The mixture is refluxed under reduced pressure and stirred for 1.5~2.5h, cooled to room temperature, filtered, and the filtrate is washed 3~5 times with deionized water to separate the organic phase. Methanol and epichlorohydrin are removed by vacuum distillation at 75~85℃ to obtain modified castor oil.

[0018] As an optimization, the preparation process of the epoxy prepolymer in step (2) is as follows: Hexafluorobisphenol A and epichlorohydrin are mixed evenly at a molar ratio of 1:(9~11), and anhydrous ethanol of 0.15~0.25 times the mass of hexafluorobisphenol A is added. Under nitrogen protection, the temperature is raised to 45~55℃ and stirred for 15~25 min. 48wt% sodium hydroxide aqueous solution of 0.25~0.3 times the mass of hexafluorobisphenol A is added uniformly over 1~2 h. The temperature is raised to 55~65℃ and stirred for 2~3 h. The mixture is cooled to room temperature, filtered, and the filtrate is washed 2~4 times with deionized water. The mixture is allowed to stand and separate into layers. The organic phase is dried with anhydrous magnesium sulfate for 10~12 h, filtered, and the filtrate is distilled under reduced pressure to remove epichlorohydrin and anhydrous ethanol, thus obtaining the epoxy prepolymer.

[0019] As an optimization, the molar ratio of propyltriethoxysilane isocyanate and 2-aminobenzothiazole in step (3) is 1:1.

[0020] As an optimization, the preparation process of the mixed solvent in step (4) is as follows: butyl acetate and xylene are mixed evenly at a mass ratio of 1:1 to prepare a mixed solvent.

[0021] As an optimization, the leveling agent in step (4) is BSM1333 polyether modified silicone leveling agent, purchased from Qingdao Baisenmao New Materials Co., Ltd.

[0022] As an optimization, the proportions of epoxy resin, modified silane, mixed solvent, leveling agent, and castor oil-based crosslinking agent in step (4) are as follows: by mass, 50-60 parts of modified epoxy resin, 2-4 parts of modified silane, 2-4 parts of mixed solvent, 0.5-1.5 parts of leveling agent, and 8-10 parts of castor oil-based crosslinking agent.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0024] First, epichlorohydrin is grafted onto castor oil to prepare modified castor oil; the modified castor oil and triethylamine hydrochloride are reacted to prepare a castor oil-based crosslinking agent, and a quaternary ammonium salt structure is introduced into the crosslinking agent; the quaternary ammonium salt group destroys the cell membrane bilayer through cation electrostatic adsorption, leading to cytoplasmic leakage and bacterial inactivation, thereby endowing the anti-corrosion coating on the metal surface with long-lasting antibacterial properties.

[0025] Secondly, an epoxy prepolymer was prepared by epoxidation reaction of hexafluorobisphenol A and epichlorohydrin; a modified epoxy resin was prepared by reacting the epoxy prepolymer with protocatechuic acid, and a catechol structure was introduced into the modified epoxy resin. The CF bond in hexafluorobisphenol A has strong polarity, and the van der Waals radius of the fluorine atom is small, enabling the formation of a dense hydrophobic layer on the metal surface. Moisture, salt spray, and corrosive media will roll off in droplets, unable to adhere to or penetrate the metal coating surface, thus giving the metal surface anti-corrosion coating excellent anti-corrosion performance. The two ortho-hydroxyl groups in the catechol group can react with Fe on the metal substrate surface. 2+ / Fe 3+ Al 3+ Zn 2+ When metal ions undergo chelation and complexation reactions, a stable five-membered ring chelate complex film is formed. This complex film is chemically stable, insoluble in corrosive media such as water and salt solutions, and adheres tightly to the metal surface, thereby improving the corrosion resistance and adhesion of the anti-corrosion coating on the metal surface. At the same time, the catechol group can inhibit and kill bacteria by disrupting the integrity of bacterial cell membranes, interfering with metabolic processes, and generating reactive oxygen species, further improving the antibacterial properties of the anti-corrosion coating on the metal surface.

[0026] Finally, modified silane was prepared by reacting 2-aminobenzothiazole with propyltriethoxysilane isocyanate. The N and S atoms in the benzothiazole heterocycle possess lone pairs of electrons, which can coordinate with the active anodic sites on the metal substrate surface to form an insoluble benzothiazole-metal complex film. This film covers the metal anodic sites, preventing anodic oxidation and inhibiting metal corrosion from an electrochemical perspective. Simultaneously, the conjugated structure of benzothiazole can adsorb corrosive anions such as Cl⁻ and SO₄²⁻ permeating the paint film through electrostatic interactions, reducing the erosion of the metal substrate by anions and further improving the anti-corrosion performance of the metal surface anti-corrosion coating. The siloxane groups undergo a three-step reaction of hydrolysis-condensation-bonding to achieve chemical bonding between the coating and the metal substrate, replacing the physical adsorption of ordinary coatings. Furthermore, the NH group of the urea bond can form multiple intermolecular hydrogen bonds with the C=O of the epoxy resin, the NH group of the curing agent, and the OH group of the metal surface, promoting the adsorption and spreading of the coating on the metal surface, thereby effectively improving the adhesion of the metal surface anti-corrosion coating, as detailed below:

[0027] . Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1:

[0030] A method for preparing a metal surface anti-corrosion coating, the method comprising the following steps:

[0031] (1) Castor oil and epichlorohydrin were mixed evenly at a mass ratio of 1:4. Methanol with a hydroxyl equivalent of 0.09 times that of castor oil was added. The temperature was raised to 65°C. 48wt% sodium hydroxide aqueous solution with a hydroxyl equivalent of 0.7 times that of castor oil was added dropwise at a uniform rate over 2.5h. The mixture was refluxed under reduced pressure and stirred for 2.5h. The mixture was cooled to room temperature, filtered, and the filtrate was washed three times with deionized water. The organic phase was separated. Methanol and epichlorohydrin were removed by vacuum distillation at 75°C to obtain modified castor oil. Modified castor oil, triethylamine hydrochloride and deionized water were mixed evenly at a mass ratio of 1:0.5:0.4. The mixture was raised to 55°C and stirred for 4.5h. The mixture was dehydrated under reduced pressure. Toluene with a mass ratio of 0.9 times that of modified castor oil was added. The mixture was heated to 80°C for azeotropic dehydration. The mixture was heated to 85°C and dehydrated under reduced pressure to obtain castor oil-based crosslinking agent.

[0032] (2) Mix hexafluorobisphenol A and epichlorohydrin at a molar ratio of 1:9 until homogeneous. Add anhydrous ethanol at 0.15 times the mass of hexafluorobisphenol A. Under nitrogen protection, heat to 45°C and stir for 25 min. Over 2 h, add 48 wt% sodium hydroxide aqueous solution at 0.25 times the mass of hexafluorobisphenol A at a uniform rate. Heat to 55°C and stir for 3 h. Cool to room temperature, filter, wash the filtrate twice with deionized water, allow it to stand and separate into layers, and take the... The organic phase was dried with anhydrous magnesium sulfate for 12 h, filtered, and the filtrate was distilled under reduced pressure to remove epichlorohydrin and anhydrous ethanol to obtain an epoxy prepolymer. The epoxy prepolymer, protocatechuic acid, and p-toluenesulfonic acid monohydrate were mixed evenly at a mass ratio of 1:0.02:0.01. Under nitrogen protection, the mixture was heated to 75 °C and reacted at a rate of 9 °C / h for 5.5 h. After cooling to room temperature, the mixture was extracted twice with deionized water, and the organic phase was collected to obtain the modified epoxy resin.

[0033] (3) Mix 2-aminobenzothiazole and anhydrous tetrahydrofuran at a mass ratio of 1:6. Under nitrogen protection, heat to 45°C and add 2-aminobenzothiazole in equimolar amounts of propyltriethoxysilane isocyanate. Continue stirring for 2.5 h. Remove anhydrous tetrahydrofuran by vacuum distillation to obtain modified silane.

[0034] (4) Mix butyl acetate and xylene in a mass ratio of 1:1 to prepare a mixed solvent; mix 50 parts modified epoxy resin, 2 parts modified silane and 2 parts mixed solvent evenly by mass, stir ultrasonically at room temperature for 20 min, add 0.5 parts leveling agent and 8 parts castor oil-based crosslinking agent, stir at room temperature for 6 min, adjust the viscosity to 500 mPa·s with mixed solvent, defoam under vacuum for 20 min, and obtain a metal surface anti-corrosion coating.

[0035] Example 2:

[0036] A method for preparing a metal surface anti-corrosion coating, the method comprising the following steps:

[0037] (1) Castor oil and epichlorohydrin were mixed evenly at a mass ratio of 1:4.5. Methanol with a hydroxyl equivalent of 0.1 times that of castor oil was added. The temperature was raised to 70°C. 48wt% sodium hydroxide aqueous solution with a hydroxyl equivalent of 0.75 times that of castor oil was added dropwise at a uniform rate over 2 hours. The mixture was refluxed under reduced pressure and stirred for 2 hours. The mixture was cooled to room temperature, filtered, and the filtrate was washed 4 times with deionized water. The organic phase was separated. Methanol and epichlorohydrin were removed by vacuum distillation at 80°C to obtain modified castor oil. Modified castor oil, triethylamine hydrochloride and deionized water were mixed evenly at a mass ratio of 1:0.6:0.45. The mixture was raised to 60°C and stirred for 4 hours. The mixture was dehydrated under reduced pressure. Toluene with a mass equivalent of 1 times that of modified castor oil was added. The mixture was heated to 85°C for azeotropic dehydration. The mixture was heated to 90°C and dehydrated under reduced pressure to obtain castor oil-based crosslinking agent.

[0038] (2) Mix hexafluorobisphenol A and epichlorohydrin at a molar ratio of 1:10 until homogeneous. Add anhydrous ethanol at 0.2 times the mass of hexafluorobisphenol A. Under nitrogen protection, heat to 50°C and stir for 20 min. Over 1.5 h, add 48 wt% sodium hydroxide aqueous solution at 0.275 times the mass of hexafluorobisphenol A at a uniform rate. Heat to 60°C and stir for 2.5 h. Cool to room temperature, filter, and wash the filtrate three times with deionized water. Allow to stand for separation. The organic phase was dried with anhydrous magnesium sulfate for 11 hours, filtered, and the filtrate was distilled under reduced pressure to remove epichlorohydrin and anhydrous ethanol to obtain an epoxy prepolymer. The epoxy prepolymer, protocatechuic acid, and p-toluenesulfonic acid monohydrate were mixed evenly at a mass ratio of 1:0.03:0.015. Under nitrogen protection, the mixture was heated to 80°C and reacted at a rate of 10°C / h for 5 hours. After cooling to room temperature, the mixture was extracted three times with deionized water, and the organic phase was collected to obtain the modified epoxy resin.

[0039] (3) Mix 2-aminobenzothiazole and anhydrous tetrahydrofuran at a mass ratio of 1:7. Under nitrogen protection, heat to 50°C and add 2-aminobenzothiazole in equimolar amounts of propyltriethoxysilane isocyanate. Continue stirring for 2 hours. Remove anhydrous tetrahydrofuran by vacuum distillation to obtain modified silane.

[0040] (4) Mix butyl acetate and xylene in a mass ratio of 1:1 to prepare a mixed solvent; mix 55 parts modified epoxy resin, 3 parts modified silane and 3 parts mixed solvent in a mass ratio, stir ultrasonically for 15 min at room temperature, add 1 part leveling agent and 9 parts castor oil-based crosslinking agent, stir for 5 min at room temperature, adjust the viscosity to 1000 mPa·s with the mixed solvent, and defoam under vacuum for 15 min to obtain a metal surface anti-corrosion coating.

[0041] Example 3:

[0042] A method for preparing a metal surface anti-corrosion coating, the method comprising the following steps:

[0043] (1) Castor oil and epichlorohydrin were mixed evenly at a mass ratio of 1:5. Methanol with a hydroxyl equivalent of 0.11 times that of castor oil was added. The temperature was raised to 75°C. 48wt% sodium hydroxide aqueous solution with a hydroxyl equivalent of 0.8 times that of castor oil was added dropwise at a uniform rate over 1.5h. The mixture was refluxed under reduced pressure and stirred for 1.5h. The mixture was cooled to room temperature, filtered, and the filtrate was washed 5 times with deionized water. The organic phase was separated. Methanol and epichlorohydrin were removed by vacuum distillation at 85°C to obtain modified castor oil. Modified castor oil, triethylamine hydrochloride and deionized water were mixed evenly at a mass ratio of 1:0.7:0.5. The mixture was raised to 65°C and stirred for 3.5h. The mixture was dehydrated under reduced pressure. Toluene with a mass ratio of 1.1 times that of modified castor oil was added. The mixture was heated to 90°C for azeotropic dehydration. The mixture was heated to 95°C and dehydrated under reduced pressure to obtain castor oil-based crosslinking agent.

[0044] (2) Mix hexafluorobisphenol A and epichlorohydrin at a molar ratio of 1:11 until homogeneous. Add anhydrous ethanol at 0.25 times the mass of hexafluorobisphenol A. Under nitrogen protection, heat to 55°C and stir for 15 min. Over 1 h, add 48 wt% sodium hydroxide aqueous solution at 0.3 times the mass of hexafluorobisphenol A at a uniform rate. Heat to 65°C and stir for 2 h. Cool to room temperature, filter, and wash the filtrate four times with deionized water. Allow to stand and separate the layers. Take the organic... The phase was dried with anhydrous magnesium sulfate for 10 h, filtered, and the filtrate was distilled under reduced pressure to remove epichlorohydrin and anhydrous ethanol to obtain an epoxy prepolymer. The epoxy prepolymer, protocatechuic acid, and p-toluenesulfonic acid monohydrate were mixed evenly at a mass ratio of 1:0.04:0.02. Under nitrogen protection, the temperature was raised to 85℃ and reacted at a rate of 11℃ / h for 4.5 h. After cooling to room temperature, the mixture was extracted four times with deionized water, and the organic phase was collected to obtain the modified epoxy resin.

[0045] (3) Mix 2-aminobenzothiazole and anhydrous tetrahydrofuran at a mass ratio of 1:8. Under nitrogen protection, heat to 55°C and add 2-aminobenzothiazole in 1 molar amount of propyltriethoxysilane isocyanate. Continue stirring for 1.5 h. Remove anhydrous tetrahydrofuran by vacuum distillation to obtain modified silane.

[0046] (4) Mix butyl acetate and xylene in a mass ratio of 1:1 to prepare a mixed solvent; mix 60 parts of modified epoxy resin, 4 parts of modified silane and 4 parts of mixed solvent in a mass ratio, stir ultrasonically for 10 min at room temperature, add 1.5 parts of leveling agent and 10 parts of castor oil-based crosslinking agent, stir at room temperature for 4 min, adjust the viscosity to 1500 mPa·s with mixed solvent, defoam under vacuum for 10 min, and obtain a metal surface anti-corrosion coating.

[0047] Comparative Example 1:

[0048] The preparation method of the anti-corrosion coating for metal surfaces in Comparative Example 1 differs from that in Example 2 in that step (1) is omitted, and the phrase "add 1 part leveling agent and 9 parts castor oil-based crosslinking agent" in step (4) is changed to "add 1 part leveling agent and 9 parts castor oil". The remaining steps are the same as in Example 2.

[0049] Comparative Example 2:

[0050] The preparation method of the anti-corrosion coating for metal surfaces in Comparative Example 2 differs from that in Example 2 only in that step (2) is changed to: mixing 4,4'-dihydroxydiphenylmethane and epichlorohydrin at a molar ratio of 1:10, adding anhydrous ethanol at 0.2 times the mass of 4,4'-dihydroxydiphenylmethane, heating to 50°C under nitrogen protection, stirring for 20 min, and uniformly adding 48wt% sodium hydroxide aqueous solution at 0.275 times the mass of 4,4'-dihydroxydiphenylmethane over 1.5 h, heating to 60°C, and stirring for 2.5 h. The mixture was cooled to room temperature, filtered, and the filtrate was washed three times with deionized water. After standing and separating into layers, the organic phase was dried over anhydrous magnesium sulfate for 11 hours, filtered, and the filtrate was distilled under reduced pressure to remove epichlorohydrin and anhydrous ethanol, yielding the epoxy prepolymer. The epoxy prepolymer, protocatechuic acid, and p-toluenesulfonic acid monohydrate were mixed uniformly at a mass ratio of 1:0.03:0.015. Under nitrogen protection, the mixture was heated to 80°C and reacted at a rate of 10°C / h for 5 hours. After cooling to room temperature, the mixture was extracted three times with deionized water, and the organic phase was collected to obtain the modified epoxy resin. The remaining steps were the same as in Example 2.

[0051] Comparative Example 3:

[0052] The preparation method of the anti-corrosion coating for metal surfaces in Comparative Example 3 differs from that in Example 2 in that step (2) is changed as follows: Hexafluorobisphenol A and epichlorohydrin are mixed evenly at a molar ratio of 1:10, and anhydrous ethanol of 0.2 times the mass of hexafluorobisphenol A is added. Under nitrogen protection, the mixture is heated to 50°C and stirred for 20 min. Over 1.5 h, 48 wt% sodium hydroxide aqueous solution of 0.275 times the mass of hexafluorobisphenol A is added at a uniform rate. The mixture is heated to 60°C and stirred for 2.5 h. After cooling to room temperature, the mixture is filtered, and the filtrate is washed three times with deionized water. After standing and separating the layers, the organic phase is dried with anhydrous magnesium sulfate for 11 h, filtered, and the filtrate is distilled under reduced pressure to remove epichlorohydrin and anhydrous ethanol, thus obtaining epoxy resin. In step (4), "modified epoxy resin" is changed to "epoxy resin". The remaining steps are the same as in Example 2.

[0053] Comparative Example 4:

[0054] The preparation method of the metal surface anti-corrosion coating in Comparative Example 4 differs from that in Example 2 in that step (3) is omitted, and step (4) is changed to: butyl acetate and xylene are mixed evenly at a mass ratio of 1:1 to prepare a mixed solvent; 55 parts by mass of modified epoxy resin and 3 parts by mass of the mixed solvent are mixed evenly, ultrasonically stirred at room temperature for 15 min, 1 part of leveling agent and 9 parts of castor oil-based crosslinking agent are added, stirred at room temperature for 5 min, the viscosity is adjusted to 1000 mPa·s with the mixed solvent, and defoamed under vacuum for 15 min to obtain the metal surface anti-corrosion coating. The remaining steps are the same as in Example 2.

[0055] Test Example 1

[0056] Corrosion resistance test

[0057] Test Method: The anti-corrosion coatings for the metal surfaces of the examples and comparative examples were applied to the surface of tinplate substrates. Leveling was carried out at room temperature for 10 minutes, repeated twice to achieve a dry film thickness of 40 μm. The coatings were then cured at 25°C for 12 hours, followed by curing at 80°C for 2 hours. After cooling to room temperature, the coatings were left to stand at room temperature for 12 hours to obtain standard samples. A scratch penetrating the substrate was made in the middle of the sample according to GB / T 10125-2021. The scratch was 0.25 mm wide and 200 mm long. The samples were then placed in a salt spray test chamber for salt spray aging testing, using a 50 g / L sodium chloride solution as the spray medium. The test temperature was 35°C, pH=7.0, and spraying was performed continuously for 14 days. The corrosion of the sample surface was observed. The results are shown in Table 1.

[0058] Table 1

[0059]

[0060] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 1 reveals that the anti-corrosion coating for metal surfaces prepared in this invention has excellent anti-corrosion properties.

[0061] By comparison, the corrosion of Examples 1-3 was less severe than that of Comparative Example 2, indicating that the epoxy prepolymer was prepared by epoxidation reaction of hexafluorobisphenol A and epichlorohydrin; the modified epoxy resin was prepared by reaction of epoxy prepolymer and protocatechuic acid; the CF bond in hexafluorobisphenol A has strong polarity and the van der Waals radius of fluorine atoms is small, which can form a dense hydrophobic layer on the metal surface. Moisture, salt spray and corrosive media will roll off in the form of droplets and cannot adhere to or penetrate the metal coating surface, thus giving the anti-corrosion coating of the metal surface excellent anti-corrosion performance.

[0062] By comparison, the corrosion in Examples 1-3 was less severe than that in Comparative Example 3, indicating that the epoxy prepolymer was prepared by epoxidation of hexafluorobisphenol A and epichlorohydrin; the modified epoxy resin was prepared by reacting the epoxy prepolymer with protocatechuic acid; and a catechol structure was introduced into the modified epoxy resin. The two ortho- and phenolic hydroxyl groups in the catechol group can react with Fe on the surface of the metal substrate. 2+ / Fe 3+ Al 3+ Zn 2+ When metal ions undergo chelation and complexation reactions, a stable five-membered ring chelate complex film is formed. This complex film is chemically stable, insoluble in corrosive media such as water and salt solutions, and adheres tightly to the metal surface, thereby improving the anti-corrosion performance of the anti-corrosion coating on the metal surface.

[0063] By comparison, the corrosion in Examples 1-3 was less severe than that in Comparative Example 4, indicating that the modified silane was prepared by reacting 2-aminobenzothiazole and propyltriethoxysilane isocyanate. The N and S atoms in the benzothiazole heterocycle have lone pairs of electrons, which can coordinate and complex with the active anodic sites on the surface of the metal substrate to form an insoluble benzothiazole-metal complex film, covering the metal anodic sites and preventing the oxidation reaction of the anolyte. This inhibits the occurrence of metal corrosion from an electrochemical perspective. At the same time, the conjugated structure of benzothiazole can adsorb corrosive anions such as Cl⁻ and SO₄²⁻ that permeate into the paint film through electrostatic interaction, reducing the erosion of the metal substrate by anions and further improving the anti-corrosion performance of the anti-corrosion coating on the metal surface.

[0064] Test Example 2

[0065] Antibacterial performance test

[0066] Test method: According to GB / T 21866-2008, sterilize the sample plate, place it in a sterile petri dish, and take 5 mL of a 10% concentration. 5A CFU / mL E. coli suspension was added dropwise to the sample plate and blank culture medium. The sample plate was covered with a sterile membrane and incubated under specified conditions for 24 h. The antibacterial rate was calculated as (BC) / B × 100%, where B is the average number of bacteria recovered from the blank control sample after 24 h, and C is the average number of bacteria recovered from the antibacterial coating sample after 24 h (CFU / plate). The results are shown in Table 2.

[0067] Table 2

[0068]

[0069] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 2 reveals that the anti-corrosion coating for metal surfaces prepared in this invention has good antibacterial properties.

[0070] By comparison, the antibacterial rates of Examples 1-3 were higher than those of Comparative Example 1, indicating that the modified castor oil was prepared by grafting epichlorohydrin onto castor oil; the castor oil-based crosslinking agent was prepared by reacting the modified castor oil with triethylamine hydrochloride, and a quaternary ammonium salt structure was introduced into the crosslinking agent; the quaternary ammonium salt group destroyed the cell membrane bilayer through cation electrostatic adsorption, resulting in cytoplasmic leakage and bacterial inactivation, thereby endowing the anti-corrosion coating on the metal surface with long-lasting antibacterial properties.

[0071] By comparison, the antibacterial rates of Examples 1-3 were higher than those of Comparative Example 3, indicating that the epoxy prepolymer was prepared by epoxidation reaction of hexafluorobisphenol A and epichlorohydrin; the epoxy prepolymer was then reacted with protocatechuic acid to prepare a modified epoxy resin, and a catechol structure was introduced into the modified epoxy resin. The catechol group can inhibit and kill bacteria by disrupting the integrity of bacterial cell membranes, interfering with metabolic processes, and generating reactive oxygen species, thereby further improving the antibacterial performance of anti-corrosion coatings on metal surfaces.

[0072] Test Example 3

[0073] Adhesion performance test

[0074] Test method: According to GB / T 9286-2021, use a QFH-A type paint film cross-cut tester to draw 6 straight lines approximately 15 mm long on the sample, with each line spaced 1 mm apart. Draw 6 lines perpendicular to the above straight lines, observe the cut area, and rate according to the standard. The results are shown in Table 3.

[0075] Table 3

[0076]

[0077] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-4 in Table 3 reveals that the anti-corrosion coating for metal surfaces prepared in this invention has good adhesion properties.

[0078] By comparison, the adhesion grades of Examples 1-3 are superior to those of Comparative Example 3, indicating that the epoxy prepolymer prepared by the epoxidation reaction of hexafluorobisphenol A and epichlorohydrin, and the modified epoxy resin prepared by the reaction of the epoxy prepolymer and protocatechuic acid, introduces a catechol structure into the modified epoxy resin; the two ortho-hydroxyl groups in the catechol group can react with Fe on the surface of the metal substrate. 2+ / Fe 3+ Al 3+ Zn 2+ When metal ions undergo chelation and complexation reactions, they adhere tightly to the metal surface, thereby improving the adhesion of anti-corrosion coatings on the metal surface.

[0079] By comparison, the adhesion grades of Examples 1-3 are better than those of Comparative Example 4, indicating that the modified silane is prepared by reacting 2-aminobenzothiazole and propyltriethoxysilane isocyanate; the siloxane group achieves chemical bonding between the coating and the metal substrate through a three-step reaction of hydrolysis-condensation-bonding, replacing the physical adsorption of ordinary coatings. At the same time, the NH of the urea bond can form multiple intermolecular hydrogen bonds with the C=O of the epoxy resin, the NH of the curing agent, and the OH of the metal surface, promoting the adsorption and spreading of the coating on the metal surface, thereby effectively improving the adhesion of the anti-corrosion coating on the metal surface.

[0080] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A metal surface anti-corrosion coating, characterized in that, The metal surface anti-corrosion coating is prepared by reacting modified castor oil and triethylamine hydrochloride to obtain a castor oil-based crosslinking agent; reacting epoxy prepolymer and protocatechuic acid to obtain a modified epoxy resin; reacting 2-aminobenzothiazole and propyltriethoxysilane isocyanate to obtain a modified silane; and mixing the modified epoxy resin, modified silane, and mixed solvent evenly, and then adding a leveling agent and a castor oil-based crosslinking agent. The modified castor oil is prepared by grafting epichlorohydrin onto castor oil; The mixed solvent is prepared by mixing butyl acetate and xylene.

2. The anti-corrosion coating for metal surfaces according to claim 1, characterized in that, The epoxy prepolymer is prepared by epoxidation reaction of hexafluorobisphenol A and epichlorohydrin.

3. A method for preparing an anti-corrosion coating for metal surfaces, characterized in that, The preparation method of the anti-corrosion coating for metal surfaces includes the following preparation steps: (1) Mix modified castor oil, triethylamine hydrochloride and deionized water in a mass ratio of 1:(0.5~0.7):(0.4~0.5), heat to 55~65℃, stir and react for 3.5~4.5h, dehydrate under reduced pressure, add toluene at 0.9~1.1 times the mass of modified castor oil, heat to 80~90℃ for azeotropic dehydration, heat to 85~95℃, remove toluene under reduced pressure to obtain castor oil-based crosslinking agent; (2) The epoxy prepolymer, protocatechuic acid and p-toluenesulfonic acid monohydrate are mixed evenly in a mass ratio of 1:(0.02~0.04):(0.01~0.02). Under nitrogen protection, the temperature is raised to 75~85℃ and the reaction is carried out at a rate of 9~11℃ / h for 4.5~5.5h. After cooling to room temperature, the mixture is extracted with deionized water 2~4 times and the organic phase is taken to obtain the modified epoxy resin. (3) Mix 2-aminobenzothiazole and anhydrous tetrahydrofuran at a mass ratio of 1:(6~8), heat to 45~55℃ under nitrogen protection, add propyltriethoxysilane isocyanate, continue stirring for 1.5~2.5h, remove anhydrous tetrahydrofuran by vacuum distillation, and obtain modified silane. (4) Mix the modified epoxy resin, modified silane and mixed solvent evenly, and ultrasonically stir for 10-20 minutes at room temperature. Add leveling agent and castor oil-based crosslinking agent, stir for 4-6 minutes at room temperature, adjust the viscosity to 500-1500 mPa·s with mixed solvent, and defoam under vacuum for 10-20 minutes to obtain a metal surface anti-corrosion coating.

4. The method for preparing the anti-corrosion coating for metal surfaces according to claim 3, characterized in that, The preparation process of the modified castor oil in step (1) is as follows: castor oil and epichlorohydrin are mixed evenly at a mass ratio of 1:(4~5), methanol with a hydroxyl equivalent of 0.09~0.11 times that of castor oil is added, the temperature is raised to 65~75℃, and 48wt% sodium hydroxide aqueous solution with a hydroxyl equivalent of 0.7~0.8 times that of castor oil is added dropwise at a uniform rate over 1.5~2.5h. The mixture is refluxed under reduced pressure and stirred for 1.5~2.5h, cooled to room temperature, filtered, and the filtrate is washed 3~5 times with deionized water to separate the organic phase. Methanol and epichlorohydrin are removed by vacuum distillation at 75~85℃ to obtain modified castor oil.

5. The method for preparing the anti-corrosion coating for metal surfaces according to claim 3, characterized in that, The preparation process of the epoxy prepolymer in step (2) is as follows: Hexafluorobisphenol A and epichlorohydrin are mixed evenly at a molar ratio of 1:(9~11), and anhydrous ethanol of 0.15~0.25 times the mass of hexafluorobisphenol A is added. Under nitrogen protection, the temperature is raised to 45~55℃ and stirred for 15~25 min. 48wt% sodium hydroxide aqueous solution of 0.25~0.3 times the mass of hexafluorobisphenol A is added uniformly over 1~2 h. The temperature is raised to 55~65℃ and stirred for 2~3 h. The mixture is cooled to room temperature, filtered, and the filtrate is washed 2~4 times with deionized water. The mixture is allowed to stand and separate into layers. The organic phase is dried with anhydrous magnesium sulfate for 10~12 h, filtered, and the filtrate is distilled under reduced pressure to remove epichlorohydrin and anhydrous ethanol, thus obtaining the epoxy prepolymer.

6. The method for preparing the anti-corrosion coating for metal surfaces according to claim 3, characterized in that, The molar ratio of propyltriethoxysilane isocyanate and 2-aminobenzothiazole in step (3) is 1:

1.

7. The method for preparing the anti-corrosion coating for metal surfaces according to claim 3, characterized in that, The preparation process of the mixed solvent in step (4) is as follows: butyl acetate and xylene are mixed evenly at a mass ratio of 1:1 to prepare a mixed solvent.

8. The method for preparing the anti-corrosion coating for metal surfaces according to claim 3, characterized in that, The leveling agent used in step (4) is BSM1333 polyether modified silicone leveling agent.

9. The method for preparing the anti-corrosion coating for metal surfaces according to claim 3, characterized in that, The proportions of epoxy resin, modified silane, mixed solvent, leveling agent, and castor oil-based crosslinking agent in step (4) are as follows: by mass, 50-60 parts of modified epoxy resin, 2-4 parts of modified silane, 2-4 parts of mixed solvent, 0.5-1.5 parts of leveling agent, and 8-10 parts of castor oil-based crosslinking agent.

Images