Preparation method and application of marine engine anti-rust coating

Abstract

The present invention belongs to the technical field of coating compositions, and specifically relates to a preparation method and application of a marine engine anti-rust coating. The preparation method comprises the following steps: preparing an ionic liquid and an organic solvent into an organic system, adding graphene oxide, a dynamic crosslinking agent and water to the organic system and mixing them, then adjusting the pH to acidic, heating to carry out a hydrolysis condensation reaction, and obtaining a dispersion; adding an epoxy resin, polydopamine and a ring-opening catalyst to the dispersion and mixing them, adjusting the pH to alkaline, and heating to carry out a ring-opening reaction; then adding an anti-rust pigment, concentrating and volatilizing, and obtaining a marine engine anti-rust coating. The application is to use the marine engine anti-rust coating for marine engine anti-rust treatment. The marine engine anti-rust coating prepared by the present invention effectively solves the problems of poor ductility, insufficient adhesion, and poor moisture and salt spray resistance of the existing anti-rust coatings in marine engine anti-rust scenarios.

Description

Technical Field

[0001] The invention belongs to the technical field of coating compositions, and particularly relates to a preparation method and application of a marine engine anti-rust coating. Background Art

[0002] Marine engines are the core power units of ship propulsion systems. Diesel engines and gasoline engines are the most common. They can be divided into three categories according to the speed: low-speed engines, medium-speed engines and high-speed engines. In order to increase the service life of marine engines, key components need to be treated with rust prevention.

[0003] Anti-rust paint is a special coating used to protect metal surfaces from corrosion. It is made of a resin matrix with anti-rust pigments, diluents, fillers, and other modifying additives. The core anti-rust mechanism is that the anti-rust paint adheres to the metal surface to block erosion by corrosive media in the environment and provide cathodic protection, thereby reducing electrochemical corrosion. However, compared with the conventional metal surface rust prevention requirements, marine engines face many complex situations, making rust prevention more difficult. This is because marine engines contain complex structural parts such as bolts and flanges that are difficult to coat, placing higher requirements on the ductility and permeability of the coating. Long-term exposure to the marine atmosphere with high humidity and salt spray concentration, the penetration of water vapor and inorganic salt impurities can easily lead to blistering and peeling of the anti-rust coating, as well as electrochemical corrosion of the metal substrate within the anti-rust coating. In addition, the operation of marine engines is often accompanied by mechanical vibration and thermal expansion and contraction, making the anti-rust coating prone to fatigue cracking. The main components of existing anti-rust coatings are resin matrices, such as epoxy resin, polyurethane or acrylic resin. When used, they all have problems to varying degrees such as poor ductility, insufficient adhesion, and poor moisture and salt spray resistance, making it difficult to cope with the complex usage scenarios of marine engines.

[0004] Chinese patent CN108239458A discloses a salt spray resistant phosphate modified acrylic water-based anti-rust coating, which is composed of: 35.0-60.0% of salt spray resistant phosphate modified acrylic core-shell emulsion, 2.0-8.0% of cosolvent, 12.0-25.0% of filler, 12.0-30.0% of anti-rust pigment, 0.2-1.5% of base material modifier, 0.5-6.0% of auxiliary agent and 12.0-35% of deionized water. .0%; wherein, the salt spray resistant phosphate modified acrylic core-shell emulsion has a glass transition temperature of 30-50°C; its composition, by weight, is: 30.0-50.0 parts of acrylate soft and hard monomers, 1.5-4.0 parts of acrylic acid, 2.0-5.0 parts of long-chain alkyl-acrylate phosphate diester, 1.0-3.0 parts of neutralizer, 0.5-2.0 parts of azobisisobutyronitrile, 1.5-3.0 parts of emulsifier and 40.0-60.0 parts of deionized water.

[0005] In this patent, azobisisobutyronitrile is used as a free radical initiator to produce acrylic resin by free radical polymerization of monomers in acrylic core-shell emulsion (mainly acrylate soft and hard monomers). Acrylic core-shell emulsion accounts for the largest proportion and is the base material of water-based anti-rust coating.

[0006] This patent has the following issues: the glass transition temperature of acrylic core-shell emulsions is between 30°C and 50°C, while the ambient temperature of marine engines is often above 50°C. When the temperature is above 50°C for a long time, the acrylic resin molecular segments will transform from a rigid glassy state to a flexible, highly elastic state, intensifying segment motion and causing the coating to soften. This patent uses a neutralizer to adjust the pH to 7-8 to produce a water-based anti-rust coating. However, acrylic resin has an alkali thickening effect, and the water-based anti-rust coating will swell and thicken during long-term storage.

[0007] Chinese patent CN 112029327A discloses an anti-rust coating suitable for cast iron parts of automobile engines. The coating is made of the following ingredients, calculated by weight: 70-80 parts of polyacrylate emulsion, 10-15 parts of dimethylethanolamine, 2.5-2.7 parts of sodium methacrylate, 0.4-0.5 parts of inorganic nanofiller, 0.2-0.3 parts of dispersant, 0.6-0.8 parts of potassium hydrogen phthalate, 0.3-0.5 parts of defoaming agent, 0.2-0.4 parts of azobisisobutyronitrile, 8-10 parts of acetone, and 30-50 parts of deionized water.

[0008] Since marine engines are exposed to high humidity and high salt spray concentrations for a long time, the water-based acrylic emulsion used in this patent is more environmentally friendly, but its water resistance and salt spray resistance are usually weaker than solvent-based resins such as epoxy resins; in addition, dimethylethanolamine is the main component (10 to 15 parts), which is itself hygroscopic and has the problem of insufficient weather resistance. Summary of the Invention

[0009] The purpose of the present invention is to provide a method for preparing a marine engine anti-rust coating to solve the problems of poor ductility, insufficient adhesion, and poor moisture and salt spray resistance of the existing anti-rust coating when used in marine engine anti-rust scenarios; the present invention also provides an application of the marine engine anti-rust coating.

[0010] To achieve the above object, the technical solution adopted by the present invention is:

[0011] The method for preparing the marine engine anti-rust coating of the present invention comprises the following steps:

[0012] (1) An ionic liquid and an organic solvent are prepared into an organic system, graphene oxide, a dynamic crosslinking agent, and water are added to the organic system and mixed, and then the pH is adjusted to acidic, and the temperature is increased to carry out a hydrolysis condensation reaction to obtain a dispersion;

[0013] (2) Add epoxy resin, polydopamine and ring-opening catalyst to the dispersion and mix well, adjust the pH to alkaline, and heat to carry out the ring-opening reaction; then add anti-rust pigment, concentrate and volatilize to obtain marine engine anti-rust coating.

[0014] in:

[0015] The ionic liquid is 1-ethyl-3-methylimidazolium hexafluorophosphate, and the organic solvent is one of acetonitrile, acetone or cyclohexane; the organic system is prepared by mixing the ionic liquid and the organic solvent in a volume ratio of 1:(9-15).

[0016] The dynamic crosslinker is bis-[3-(triethoxysilyl)propyl]-disulfide. The ratio of graphene oxide, dynamic crosslinker, water, and organic system added is (3.8-5.5):(1.15-1.85):(0.3-0.8):(45-55). The graphene oxide, dynamic crosslinker, and water are measured in kg, and the organic system is measured in L. Ultrasonic dispersion is used for mixing for 20-35 minutes.

[0017] In the step (1), the pH is 4.0-5.0, the hydrolysis-condensation reaction temperature is 55-75° C., and the hydrolysis-condensation reaction time is 2-3.5 h.

[0018] The epoxy resin is bisphenol A epoxy resin or bisphenol F epoxy resin, and the ring-opening catalyst is one of 1,8-diazabicycloundec-7-ene, 2,4,6-tris(dimethylaminomethyl)phenol or N,N-dimethylaniline.

[0019] The mass ratio of graphene oxide, epoxy resin, polydopamine, and ring-opening catalyst is (3.8-5.5):(40-50):(4.5-6.5):(0.25-0.35). Ultrasonic dispersion is used for mixing for 20-30 minutes.

[0020] In the step (2), the pH is 8.5-9.5, the ring-opening reaction temperature is 45-75°C, and the ring-opening reaction time is 75-110 min.

[0021] The anti-rust pigment is prepared from red iron oxide, a surface passivator and graphite, the surface passivator is one of zinc phosphate, aluminum tripolyphosphate or zinc molybdate, the mass ratio of red iron oxide, surface passivator and graphite is (10-13):2:1, and the mass ratio of the anti-rust pigment to the epoxy resin is (13-16):(40-50).

[0022] The concentration and volatilization temperature is 28-42° C. and the concentration and volatilization time is 10-15 minutes.

[0023] Application of the marine engine anti-rust coating of the present invention: The marine engine anti-rust coating is used for rust prevention treatment of the marine engine, and the rust prevention treatment comprises the following steps:

[0024] S1. Clean the surface of marine engines;

[0025] S2. spraying the marine engine anti-rust paint onto the surface of the marine engine;

[0026] S3, drying to obtain a marine engine anti-rust coating.

[0027] in:

[0028] The ambient temperature during spraying is 25°C and the ambient humidity is ≤60%; the drying temperature is 40~50°C, the drying time is 12~18h, and the dry film thickness of the marine engine anti-rust coating is 0.2~0.3mm.

[0029] The beneficial effects of the present invention are as follows:

[0030] (1) In the present invention, under acidic conditions, the triethoxysilyl group of bis-[3-(triethoxysilyl)propyl]-disulfide is hydrolyzed to form a silanol bond. Since the selected graphene oxide particles have a two-dimensional sheet structure, the silanol bond can be dehydrated and condensed with other bis-[3-(triethoxysilyl)propyl]-disulfide molecules or oxygen-containing functional groups (such as -COOH, -OH) on the surface of graphene oxide particles (GO) of different sheets, thereby obtaining a three-dimensional GO structure in which the graphene oxide particles are interconnected by disulfide bonds.

[0031] Common cross-linking agents such as aromatic diamines or aromatic dithiols containing disulfide bonds are prone to molecular chain folding. As a dynamic covalent bond, the disulfide bond can trigger reversible breakage and reorganization under thermal stress or mechanical stress. At this time, due to the folding of the molecular chain, after the disulfide bond breaks under the action of thermal stress or mechanical stress, the molecular chain tends to accumulate and reorganize in the direction away from the stress point, which can easily lead to uneven film distribution of the anti-rust coating under long-term mechanical vibration and thermal stress, affecting the ductility of the adhesion of the anti-rust coating and prone to local brittle cracking; the bis-[3-(triethoxysilyl)propyl]-disulfide selected by the present invention has unique molecular characteristics, namely triethoxysilyl carbon chains in different directions and with moderate molecular chain length. , connected by disulfide bonds. Since graphene oxide is in the form of two-dimensional sheets, its own mobility is limited. In addition, the bis-[3-(triethoxysilyl)propyl]-disulfide between the sheets can form a steric hindrance to prevent the sheets from agglomerating. Therefore, the bis-[3-(triethoxysilyl)propyl]-disulfide can use the graphene oxide particles as anchor points to reduce the degree of folding and stacking of the molecular chains. Under the mechanical vibration and thermal expansion and contraction of the marine engine, the disulfide bonds in the present invention are mostly broken and reorganized in situ, and dynamic cross-linking can be formed through the microcracks in the coating to repair the damage, further improving the ductility and service life of the rust-proof coating.

[0032] (2) Epoxy resin and polydopamine are then added and fully dispersed in the GO three-dimensional structure. Under the catalysis of the ring-opening catalyst, the epoxy group reacts with the phenolic hydroxyl group in the polydopamine to form an epoxy-polydopamine cross-linked structure. Polydopamine itself contains catechol groups, which can form reversible organic metal complexes with metals. Since polydopamine has a molecular structure that mimics the adhesion protein of mussel silk feet, the epoxy-polydopamine cross-linked structure has good adhesion to a variety of materials such as metals, organics or inorganics, and the adhesion can be maintained in a humid environment; however, the self-adhesiveness of polydopamine easily causes the molecular chains to agglomerate, affecting the uniformity of the coating viscosity; in addition, the cross-linking density of the polydopamine molecule is low, the molecular chain is flexible, and it is easy to break under long-term mechanical stress, resulting in cracks, blistering and even partial shedding of the coating.

[0033] The present invention prepares an epoxy-polydopamine cross-linked structure based on the GO three-dimensional structure, so that the GO three-dimensional structure and the epoxy-polydopamine cross-linked structure form a dynamic interpenetrating network. The dynamic interpenetrating network absorbs external mechanical stress or thermal stress through an energy dissipation mechanism (such as reversible breakage of hydrogen bonds and chain segment slippage), thereby compensating for the defect of insufficient rigidity of polydopamine molecules. The skeleton support of the GO three-dimensional structure fixes the epoxy-polydopamine cross-linked structure and prevents its agglomeration, thereby ensuring the uniformity of the coating viscosity. In addition, the hydrophobicity of the epoxy resin and the hydrophilicity of the polydopamine form a microphase separation structure, which balances the hydrophilicity of the polydopamine and further improves the moisture resistance and salt spray resistance of the rust-proof coating.

[0034] (3) The ionic liquid used was 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM] + [PF6] - ), due to [EMIM] + The active center of the cation is N + -CH3 is easily affected by the conjugated π electron cloud of the imidazole ring, while [PF6] - Susceptible to the steric hindrance effect of hexafluoride atoms, making [EMIM] + It can react with oxygen lone pair electrons in oxygen-containing functional groups (such as -COOH, -OH) on the surface of graphene oxide or [PF6] - A dynamic reversible electrostatic adsorption effect is formed between the two. Similarly, [PF6] - with [EMIM] + Or the metal surface cation cluster area forms a dynamic reversible electrostatic adsorption effect; In addition [EMIM] + There is a solvation effect with the epoxy resin system (i.e., dynamic interpenetrating network), i.e., [EMIM] +The polar imidazole ring in the graphene oxide can form hydrogen bonds with the epoxy groups and hydroxyl groups in the epoxy resin; the hydroxyl groups and carboxyl groups on the surface of graphene oxide and the amino groups in polydopamine, further reducing the entanglement density of the epoxy resin molecular chains and enhancing the fluidity of the epoxy resin system. This loose ion pairing and solvation effect work together to significantly reduce the viscosity of the epoxy resin system. Macroscopically, it manifests as a decrease in the surface tension of the contact surface between the metal and the anti-rust coating. The ionic liquid drives the slow capillary penetration of graphene oxide (and also the entire epoxy resin system) on the metal surface, forming a rough surface interlocking between graphene oxide and the metal surface oxide layer, effectively solving the problems of insufficient permeability and adhesion of traditional resin-based coatings on some complex surface structures that are difficult to coat in marine engines.

[0035] (4) The ring-opening catalyst in the present invention is selected from one of 1,8-diazabicycloundec-7-ene, 2,4,6-tris(dimethylaminomethyl)phenol or N,N-dimethylaniline: the ring-opening catalysts in the present invention all have a π-π conjugation effect, which enables the nucleophilic atom to attack the oxygen atom in the epoxy group to form a transition intermediate, and the reaction activity is moderate, and no excessive cross-linking will occur, causing the epoxy resin to become brittle; on the other hand, some polyamines such as ethylenediamine and diethylenetriamine contain multiple active hydrogen amino groups in the molecule, and the reaction activity is too high. They can react at room temperature and are prone to excessive cross-linking, resulting in a higher film brittleness of the rust-proof coating; some guanidine and imidazole compounds such as 1,1-dimethylguanidine and 2-ethyl-4-methylimidazole have high curing reaction temperature requirements, and the optimal temperature basically needs to be above 100°C. If the dosage is not well controlled, it is easy to cause insufficient cross-linking. DETAILED DESCRIPTION

[0036] The present invention is described and illustrated in detail below with reference to the embodiments.

[0037] The raw materials used in the following examples and comparative examples are all commercially available products, some of which are produced by the following manufacturers:

[0038] Polydopamine was provided by Xi'an Ruixi Biotechnology Co., Ltd.; bisphenol A epoxy resin, model E-44, was provided by Shandong Deyuan Epoxy Technology Co., Ltd.; bisphenol F epoxy resin, model DF170, was provided by Shandong Deyuan Epoxy Technology Co., Ltd.

[0039] Example 1

[0040] Preparation of anti-rust coating for marine engines

[0041] 55 L of an organic system was prepared at a ratio of 1-ethyl-3-methylimidazolium hexafluorophosphate: acetone = 1:9 (v / v). 4.5 kg of graphene oxide, 1.15 kg of bis-[3-(triethoxysilyl)propyl]-disulfide, and 0.3 kg of deionized water were added to the organic system. The mixture was ultrasonically dispersed for 20 min. Subsequently, dilute hydrochloric acid was added to a pH of 4.2. The mixture was stirred, heated to 65 °C, and subjected to a hydrolysis-condensation reaction for 2 h to obtain a dispersion.

[0042] 50 kg of bisphenol A epoxy resin, 6.5 kg of polydopamine and 0.33 kg of 1,8-diazabicycloundec-7-ene were added to the dispersion, ultrasonically dispersed for 25 minutes, ammonia water was added until the pH of the dispersion was 9.1, stirring was started, the temperature was raised to 62°C, and the ring-opening reaction was carried out for 90 minutes; red iron oxide, zinc phosphate and graphite were compounded in a mass ratio of 12:2:1 to obtain 15 kg of anti-rust pigment, and then the anti-rust pigment was added to the dispersion, stirred until the color was uniform, and concentrated and volatilized at 28°C for 15 minutes to obtain a marine engine anti-rust coating.

[0043] Example 2

[0044] Preparation of anti-rust coating for marine engines

[0045] A 50 L organic system was prepared at a ratio of 1-ethyl-3-methylimidazolium hexafluorophosphate: acetonitrile = 1:12 (v / v). 3.8 kg of graphene oxide, 1.4 kg of bis-[3-(triethoxysilyl)propyl]-disulfide and 0.4 kg of deionized water were added to the organic system. Ultrasonic dispersion was performed for 28 min. Subsequently, dilute hydrochloric acid was added to pH = 4.0. Stirring was started, the temperature was raised to 75 ° C, and hydrolysis condensation reaction was carried out for 2.5 h to obtain a dispersion.

[0046] 47 kg of bisphenol A epoxy resin, 5.0 kg of polydopamine and 0.25 kg of N,N-dimethylaniline were added to the dispersion, ultrasonically dispersed for 20 minutes, ammonia water was added until the pH of the dispersion was 9.5, stirring was started, the temperature was raised to 45°C, and the ring-opening reaction was carried out for 110 minutes; iron oxide red, aluminum tripolyphosphate and graphite were compounded in a mass ratio of 13:2:1 to obtain 16 kg of anti-rust pigment, and then the anti-rust pigment was added to the dispersion, stirred until the color was uniform, and concentrated and volatilized at 42°C for 10 minutes to obtain a marine engine anti-rust coating.

[0047] Example 3

[0048] Preparation of anti-rust coating for marine engines

[0049] 45 L of an organic system was prepared at a ratio of 1-ethyl-3-methylimidazolium hexafluorophosphate: cyclohexane = 1:15 (v / v), and 5.5 kg of graphene oxide, 1.85 kg of bis-[3-(triethoxysilyl)propyl]-disulfide, and 0.8 kg of deionized water were added to the organic system. The mixture was ultrasonically dispersed for 35 minutes, and then dilute hydrochloric acid was added to pH = 5.0. The mixture was stirred, heated to 55°C, and hydrolysis and condensation reaction was carried out for 3.5 hours to obtain a dispersion.

[0050] Add 40 kg of bisphenol F epoxy resin, 4.5 kg of polydopamine and 0.35 kg of 2,4,6-tris(dimethylaminomethyl)phenol to the dispersion, ultrasonically disperse for 30 minutes, add ammonia water to the dispersion until the pH value is 8.5, start stirring, heat to 75 ° C, and carry out ring-opening reaction for 75 minutes; compound red iron oxide, zinc molybdate and graphite in a mass ratio of 10:2:1 to obtain 13 kg of anti-rust pigment, and then add the anti-rust pigment to the dispersion, stir until the color is uniform, and concentrate and evaporate at 40 ° C for 12 minutes to obtain a marine engine anti-rust coating.

[0051] Example 4

[0052] Marine engine anti-rust treatment

[0053] The surface of the marine engine was cleaned, and then the marine engine antirust coating of Example 1 was sprayed onto the surface of the marine engine at 25°C and an ambient humidity of 60%. After spraying, the surface was dried at 40°C for 18 hours to obtain a marine engine antirust coating with a dry film thickness of 0.20 mm.

[0054] Example 5

[0055] Marine engine anti-rust treatment

[0056] The surface of the marine engine was cleaned, and then the marine engine antirust coating of Example 1 was sprayed onto the surface of the marine engine at 25°C and an ambient humidity of 60%. After spraying, the surface was dried at 45°C for 14 hours to obtain a marine engine antirust coating with a dry film thickness of 0.25 mm.

[0057] Example 6

[0058] Marine engine anti-rust treatment

[0059] The surface of the marine engine was cleaned, and then the marine engine antirust coating of Example 1 was sprayed onto the surface of the marine engine at 25°C and an ambient humidity of 60%. After spraying, the surface was dried at 50°C for 12 hours to obtain a marine engine antirust coating with a dry film thickness of 0.30 mm.

[0060] Comparative Example 1

[0061] The ionic liquid was replaced with an equal volume of acetone, and the remaining steps and raw materials were the same as those in Example 1.

[0062] Comparative Example 2

[0063] The bis-[3-(triethoxysilyl)propyl]-disulfide was replaced with γ-aminopropyltriethoxysilane, a commonly used silane coupling agent. The remaining steps and raw materials were the same as those in Example 1.

[0064] Comparative Example 3

[0065] The bis-[3-(triethoxysilyl)propyl]-disulfide was replaced with 2-aminophenyl disulfide, i.e., an aromatic diamine containing a disulfide bond. The remaining steps and raw materials were the same as those in Example 1. The structural formula of 2-aminophenyl disulfide is as follows:

[0066] .

[0067] Comparative Example 4

[0068] Graphene oxide was replaced by nano-silicon dioxide, and the remaining operating steps and raw materials were the same as those in Example 1.

[0069] Comparative Example 5

[0070] Polydopamine was replaced with bisphenol A epoxy resin of equal mass, and the remaining operation steps and raw materials were the same as those in Example 1.

[0071] Comparative Example 6

[0072] The ring-opening catalyst was replaced with an equal mass of ethylenediamine, and the remaining operation steps and raw materials were the same as those in Example 1.

[0073] Comparative Example 7

[0074] The ring-opening catalyst was replaced with an equal mass of 1,1-dimethylguanidine, and the remaining operation steps and raw materials were the same as those in Example 1.

[0075] Implementation effect evaluation

[0076] Preparation of samples: The marine engine antirust coatings in Examples 1 to 3 were evenly applied to clean carbon steel plates (material: Q235, thickness: 1.0 mm) with a dry film thickness of 0.20 mm to obtain samples 1 to 3; similarly, comparative samples 1 to 7 were obtained.

[0077] Based on the GB / T9286-2021 standard, a grid test was designed to test the adhesion of anti-rust coatings. A six-blade cutter was used to create a 2 mm x 2 mm grid on the surface of the specimen. The surface was then peeled with transparent tape (a pressure-sensitive tape based on a transparent polyester film substrate, 19 mm wide, with a peel strength of (10 ± 1) N / 25 mm). The peeled area was then observed. Adhesion grades were categorized according to ISO 0 to ISO 5. ISO0: The cut edge is completely smooth without any peeling; ISO1: There is slight peeling at the intersection of the cut, but no peeling at the grid edge, and the peeling area is ≤5%; ISO2: There is peeling at the cut edge or intersection, but the peeling area does not exceed 15% of the grid area, and the peeling area is 25%-15%; ISO3: The peeling area exceeds 15% but does not exceed 35%, and the peeling area is 15%-35%; ISO4: The peeling area exceeds 35% but does not exceed 65%, and the peeling area is 35%-65%; ISO5: The peeling area exceeds 65%, or most of the grid is completely peeled off, and the peeling area is >65%.

[0078] Based on the standard GB / T1771-2007, a neutral salt spray test was designed to test the salt spray resistance (and moisture resistance) of anti-rust coatings. The specimens were placed in a salt spray chamber and continuously sprayed with a 5 wt.% NaCl solution at 35±2°C and a pH of 6.5-7.2. After 2000 hours, the anti-rust coating was evaluated for blistering. The evaluation criteria used in this invention are a 0-5 scale, based on bubble size and density: Level 0: No bubbles; Level 1: Slightly dispersed bubbles, 0.5 mm or less in diameter; Level 2: A small number of bubbles, 0.5-1 mm in diameter, or less than 5% of the total area; Level 3: Moderate bubbles, 1-3 mm in diameter, or 5%-15% of the total area; Level 4: Numerous bubbles, 3-5 mm in diameter, or 15%-35% of the total area; Level 5: Severe blistering, greater than 5 mm in diameter, or greater than 35% of the total area, accompanied by detachment of the anti-rust coating.

[0079] According to the standard GB / T6742-2007, a bending test is designed to test the ductility of the anti-rust coating: the sample is bent 180° around a cylinder of different diameters (3mm and 6mm) within 1 second, and the cracking or peeling of the coating is observed. The sample is qualified if there is no cracking or peeling.

[0080] Specific anti-rust coating performance test data are shown in Table 1.

[0081]

[0082] As can be seen from Table 1, after the marine engine anti-rust coating of the present invention is applied to form an anti-rust coating, the anti-rust coating meets the requirements of ductility, adhesion, moisture resistance, and salt spray resistance. Replacing any one of the ionic liquid, graphene oxide, bis-[3-(triethoxysilyl)propyl]-disulfide, polydopamine, and ring-opening catalyst in the present invention cannot achieve the same effect as the present invention.

Claims

1. A method for preparing a marine engine anti-rust coating, characterized in that: The following steps are involved: (1) An ionic liquid and an organic solvent are prepared into an organic system, graphene oxide, a dynamic crosslinking agent, and water are added to the organic system and mixed, and then the pH is adjusted to acidic, and the temperature is increased to carry out a hydrolysis condensation reaction to obtain a dispersion; (2) adding epoxy resin, polydopamine and ring-opening catalyst to the dispersion and mixing them evenly, adjusting the pH to alkaline, and heating to carry out the ring-opening reaction; then adding anti-rust pigment, concentrating and volatilizing, and obtaining the marine engine anti-rust coating; The ionic liquid is 1-ethyl-3-methylimidazolium hexafluorophosphate, the dynamic crosslinking agent is bis-[3-(triethoxysilyl)propyl]-disulfide, and the ring-opening catalyst is one of 1,8-diazabicycloundec-7-ene, 2,4,6-tris(dimethylaminomethyl)phenol or N,N-dimethylaniline.

2. The method for preparing the marine engine anti-rust coating according to claim 1, characterized in that: The organic solvent is one of acetonitrile, acetone or cyclohexane; the organic system is prepared by the ionic liquid and the organic solvent in a volume ratio of 1: (9-15).

3. The method for preparing the marine engine anti-rust coating according to claim 1, characterized in that: The addition ratio of graphene oxide, dynamic crosslinking agent, water and organic system is (3.8~5.5):(1.15~1.85):(0.3~0.8):(45~55), graphene oxide, dynamic crosslinking agent and water are measured in kg, and the organic system is measured in L.

4. The method for preparing the marine engine anti-rust coating according to claim 1, characterized in that: In step (1), the pH is 4.0-5.0, the hydrolysis-condensation reaction temperature is 55-75° C., and the hydrolysis-condensation reaction time is 2-3.5 h.

5. The method for preparing the marine engine anti-rust coating according to claim 1, characterized in that: The epoxy resin is bisphenol A epoxy resin or bisphenol F epoxy resin.

6. The method for preparing the marine engine anti-rust coating according to claim 5, characterized in that: The mass ratio of graphene oxide, epoxy resin, polydopamine and ring-opening catalyst is (3.8~5.5):(40~50):(4.5~6.5):(0.25~0.35).

7. The method for preparing the marine engine anti-rust coating according to claim 1, characterized in that: In step (2), the pH is 8.5-9.5, the ring-opening reaction temperature is 45-75°C, and the ring-opening reaction time is 75-110 min.

8. The method for preparing the marine engine anti-rust coating according to claim 1, characterized in that: The anti-rust pigment is prepared from red iron oxide, a surface passivator and graphite. The surface passivator is one of zinc phosphate, aluminum tripolyphosphate or zinc molybdate. The mass ratio of red iron oxide, surface passivator and graphite is (10~13):2:

1. The mass ratio of the anti-rust pigment to the epoxy resin is (13~16):(40~50).

9. An application of a marine engine antirust coating prepared by the method for preparing a marine engine antirust coating according to any one of claims 1 to 8, characterized in that: The marine engine anti-rust coating is used for the anti-rust treatment of the marine engine. The anti-rust treatment includes the following steps: S1. Clean the surface of marine engines; S2. spraying the marine engine anti-rust paint onto the surface of the marine engine; S3, drying to obtain a marine engine anti-rust coating.

10. The use of the marine engine anti-rust coating according to claim 9, characterized in that: The drying temperature is 40~50℃, the drying time is 12~18h, and the dry film thickness of the marine engine anti-rust coating is 0.2~0.3mm.

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