Preparation method and application of antirust coating for marine engine

Abstract

The invention belongs to the technical field of coating compositions, and particularly relates to a preparation method and application of a marine engine antirust coating. The preparation method comprises the following steps: preparing an organic system from an ionic liquid and an organic solvent, adding graphene oxide, a dynamic cross-linking agent and water into the organic system, uniformly mixing, then adjusting the pH value to be acidic, heating, and carrying out a hydrolytic condensation reaction to obtain a dispersion liquid; adding epoxy resin, polydopamine and a ring-opening catalyst into the dispersion liquid, uniformly mixing, adjusting the pH to be alkaline, and heating to carry out a ring-opening reaction; and then adding an anti-rust pigment, concentrating and volatilizing to obtain the marine engine anti-rust coating. According to the application, the anti-rust coating for the marine engine is used for anti-rust treatment of the marine engine. The prepared antirust coating for the marine engine effectively solves the problems of poor ductility, insufficient adhesive force and poor moisture resistance and salt fog resistance of an antirust coating in different degrees when the existing antirust coating is used for dealing with an antirust scene of the marine engine.

Description

Technical Field

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

[0002] A marine engine is the core power device of a ship propulsion system. Diesel engines and gasoline engines are the most common, and they can be divided into three categories: low-speed engines, medium-speed engines, and high-speed engines according to the rotational speed. To improve the service life of marine engines, key components need to be treated against rust.

[0003] An anti-rust coating is a special coating used to protect metal surfaces from corrosion. It is made of a resin-based matrix and added with anti-rust pigments, diluents, fillers, and other modifying additives. The core anti-rust mechanism is that the anti-rust coating adheres to the metal surface to block the erosion of corrosive media in the environment and provide cathodic protection, thereby reducing electrochemical corrosion. However, compared with the conventional anti-rust requirements for metal surfaces, marine engines face many complex situations, so the anti-rust difficulty is greater. This is because marine engines contain complex structural parts such as bolts and flanges that are not easy to coat, which puts higher requirements on the ductility and permeability of the coating. Long-term exposure to the marine atmosphere with high humidity and high salt mist concentration, the penetration of water vapor and inorganic salt impurities easily causes the anti-rust coating to blister, peel off, and electrochemical corrosion of the metal substrate inside the anti-rust coating. In addition, during the operation of marine engines, mechanical vibration and thermal expansion and contraction often occur, and the anti-rust coating is prone to fatigue cracking. The main components of existing anti-rust coatings are resin-based matrices, such as epoxy resins, polyurethanes, or acrylic resins, etc. When used, there are problems such as poor ductility of the anti-rust coating, insufficient adhesion, and poor moisture and salt mist resistance to varying degrees, and it is difficult to cope with the complex use scenarios of marine engines.

[0004] Chinese Patent CN108239458A discloses a phosphoric acid ester-modified acrylic waterborne anti-rust coating with salt mist resistance. By weight percentage, its composition is: 35.0 - 60.0% of a phosphoric acid ester-modified acrylic core-shell emulsion with salt mist resistance, 2.0 - 8.0% of a co-solvent, 12.0 - 25.0% of a filler, 12.0 - 30.0% of an anti-rust pigment, 0.2 - 1.5% of a substrate modifier, 0.5 - 6.0% of an additive, and 12.0 - 35.0% of deionized water; among them, the phosphoric acid ester-modified acrylic core-shell emulsion with salt mist resistance has a glass transition temperature of 30 - 50°C; by weight parts, its composition 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 phosphoric acid diester, 1.0 - 3.0 parts of a neutralizing agent, 0.5 - 2.0 parts of azobisisobutyronitrile, 1.5 - 3.0 parts of an emulsifier, and 40.0 - 60.0 parts of deionized water.

[0005] In this patent, azobisisobutyronitrile is used as a free radical initiator, and monomers in the acrylic core-shell emulsion (mainly soft and hard acrylate monomers) are polymerized by free radical polymerization to obtain an acrylic resin. The acrylic core-shell emulsion has the largest proportion and is the base material of the waterborne anti-rust paint.

[0006] This patent has the following problems: Since the glass transition temperature of the acrylic core-shell emulsion is 30 - 50 °C, and the ambient temperature of marine engines is often above 50 °C. When the temperature is continuously higher than 50 °C for a long time, the molecular chain segments of the acrylic resin will change from the rigid glass state to the flexible high-elastic state, the chain segment movement intensifies, and the coating is prone to softening. This patent uses a neutralizing agent to adjust the pH value to 7 - 8 and then prepares the waterborne anti-rust paint. However, the acrylic resin has an alkali thickening effect, and during long-term storage, the waterborne anti-rust paint will experience swelling and thickening.

[0007] Chinese Patent CN 112029327A discloses an anti-rust paint suitable for cast iron parts of automobile engines, which is made of the following components 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 nano-fillers, 0.2 - 0.3 parts of dispersant, 0.6 - 0.8 parts of potassium hydrogen phthalate, 0.3 - 0.5 parts of defoamer, 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 environments with high humidity and high salt mist concentration for a long time, although the waterborne acrylate emulsion used in this patent is more environmentally friendly, its water resistance and salt mist resistance are generally weaker than those of solvent-based resins such as epoxy resins. In addition, dimethylethanolamine is used as a main component (10 - 15 parts), and it is prone to moisture absorption itself, resulting in insufficient weather resistance. Summary of the Invention

[0009] The purpose of the present invention is to provide a preparation method of an anti-rust paint for marine engines to solve the problems that existing anti-rust paints have varying degrees of poor ductility, insufficient adhesion, and poor resistance to humidity and salt mist in the anti-rust coating for marine engine scenarios. The present invention also provides the application of the anti-rust paint for marine engines.

[0010] To achieve the above purpose, the technical solution adopted by the present invention is: The preparation method of the anti-rust paint for marine engines described in the present invention includes the following steps: (1) Prepare an organic system by mixing an ionic liquid and an organic solvent. Add graphene oxide, a dynamic cross-linking agent, and water to the organic system and mix evenly. Then adjust the pH to acidic and raise the temperature for hydrolysis and condensation reaction to obtain a dispersion liquid; (2) Add epoxy resin, polydopamine, and ring-opening catalyst to the dispersion liquid and mix evenly. Adjust the pH to alkaline, and raise the temperature for ring-opening reaction. Subsequently, add anti-rust pigment, concentrate and volatilize to obtain the anti-rust coating for marine engines.

[0011] Among them: 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 from the ionic liquid and the organic solvent according to a volume ratio of 1:(9 - 15).

[0012] The dynamic cross-linking agent is bis-[3-(triethoxysilyl)propyl]-disulfide. The addition ratio of graphene oxide, dynamic cross-linking agent, water, and organic system is (3.8 - 5.5):(1.15 - 1.85):(0.3 - 0.8):(45 - 55), where graphene oxide, dynamic cross-linking agent, and water are in kg, and the organic system is in L. Ultrasonic dispersion is used for mixing for 20 - 35 min.

[0013] In the step (1), the pH is 4.0 - 5.0, the hydrolysis and condensation reaction temperature is 55 - 75 °C, and the hydrolysis and condensation reaction time is 2 - 3.5 h.

[0014] 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.

[0015] 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 min.

[0016] 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.

[0017] The anti-rust pigment is composed of iron oxide red, surface passivator, and graphite. The surface passivator is one of zinc phosphate, aluminum tripolyphosphate, or zinc molybdate. The mass ratio of iron oxide red, surface passivator, and graphite is (10 - 13):2:1, and the mass ratio of anti-rust pigment to epoxy resin is (13 - 16):(40 - 50).

[0018] The concentration and volatilization temperature is 28 - 42 °C. The concentration and volatilization time is 10 - 15 min.

[0019] Application of the anti-rust coating for marine engines of the present invention: The anti-rust coating for marine engines is used for the anti-rust treatment of marine engines. The anti-rust treatment includes the following steps: S1. Clean the surface of the marine engine; S2. Spray the anti-rust coating for marine engines onto the surface of the marine engine; S3. Dry to obtain an anti-rust coating for marine engines.

[0020] Among them: During spraying, the ambient temperature is 25°C and the ambient humidity ≤ 60%; the drying temperature is 40 - 50°C, the drying time is 12 - 18 h, and the dry film thickness of the anti-rust coating for marine engines is 0.2 - 0.3 mm.

[0021] The beneficial effects of the present invention are as follows: (1) In the present invention, under acidic conditions, the triethoxysilyl groups of bis-[3-(triethoxysilyl)propyl]-disulfide hydrolyze to form silanol bonds. Since the selected graphene oxide particles have a two-dimensional sheet structure, the silanol bonds can respectively undergo dehydration condensation with other bis-[3-(triethoxysilyl)propyl]-disulfide molecules or the oxygen-containing functional groups (such as -COOH, -OH) on the surfaces of graphene oxide particles (GO) in different sheets, resulting in a three-dimensional GO structure in which the graphene oxide particles are interconnected by disulfide bonds.

[0022] 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 be reversibly broken and recombined under thermal stress or mechanical stress. At this time, due to molecular chain folding, after the disulfide bond in the molecular chain is broken under thermal stress or mechanical stress, it tends to stack and recombine in a direction away from the stress point, which easily leads to uneven film distribution of the anti-rust coating under long-term mechanical vibration and thermal stress, affecting the adhesion and ductility of the anti-rust coating and prone to local brittle cracking; the bis-[3-(triethoxysilyl)propyl]-disulfide selected in the present invention has unique molecular characteristics, that is, triethoxysilyl carbon chains with different directions and moderate molecular chain lengths are connected by disulfide bonds. Also, since graphene oxide is in a two-dimensional sheet shape, its own mobility is limited; and the bis-[3-(triethoxysilyl)propyl]-disulfide between the sheets can form steric hindrance to prevent sheet aggregation. Therefore, bis-[3-(triethoxysilyl)propyl]-disulfide can use graphene oxide particles as anchor points to reduce the degree of molecular chain folding and stacking. Under the mechanical vibration and thermal expansion and contraction of marine engines, the disulfide bonds in the present invention mostly undergo in-situ fracture and recombination, and can form dynamic cross-linking at the micro-cracks of the coating to repair damage, further improving the ductility and service life of the anti-rust coating.

[0023] (2) Subsequently, epoxy resin and polydopamine were added and fully dispersed in the three-dimensional structure of GO. Catalyzed by a ring-opening catalyst, the epoxy groups and the phenolic hydroxyl groups in polydopamine underwent a ring-opening reaction to form an epoxy-polydopamine cross-linked structure. Polydopamine itself contains catechol groups, which can form reversible organometallic complexes with metals. Due to the molecular structure of polydopamine mimicking mussel byssal adhesion proteins, the epoxy-polydopamine cross-linked structure has good adhesion to various materials such as metals, organic substances, or inorganic substances, and the adhesion can also be maintained in a humid environment. However, the self-adhesion of polydopamine easily causes molecular chain aggregation, affecting the uniformity of the coating adhesion. In addition, the cross-linking density of polydopamine molecules is relatively low, the molecular chains are flexible, and they are prone to breakage under long-term mechanical stress, resulting in coating cracks, blisters, and even local peeling.

[0024] The present invention prepares an epoxy-polydopamine cross-linked structure based on the three-dimensional structure of GO, enabling the three-dimensional structure of GO and the epoxy-polydopamine cross-linked structure to form a dynamic interpenetrating network. The dynamic interpenetrating network absorbs external mechanical stress or thermal stress through an energy dissipation mechanism (such as reversible hydrogen bond breakage and chain segment slippage), compensating for the deficiency of the rigidity of polydopamine molecules. Through the skeleton support of the three-dimensional structure of GO, the epoxy-polydopamine cross-linked structure is fixed and prevented from aggregating, ensuring the uniformity of the coating adhesion. In addition, the hydrophobicity of epoxy resin and the hydrophilicity of polydopamine form a microphase separation structure, balancing the hydrophilicity of polydopamine and further improving the moisture resistance and salt spray resistance of the anti-rust coating.

[0025] (3) The ionic liquid selected is 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM] + [PF6] - ). Since the active center of the [EMIM] + cation is N + -CH3 is easily affected by the conjugated π electron cloud of the imidazole ring, and [PF6] - is easily affected by the steric hindrance effect of the six fluorine atoms, enabling [EMIM] + to form a dynamic reversible electrostatic adsorption with the oxygen lone pair electrons in the surface oxygen-containing functional groups of graphene oxide (such as -COOH, -OH) or between [PF6] - . Similarly, [PF6] - forms a dynamic reversible electrostatic adsorption with [EMIM] + or the cation aggregation region on the metal surface. In addition, there is a solvation effect between [EMIM] + and the epoxy resin system (i.e., the dynamic interpenetrating network), that is, [EMIM] +The polar imidazole ring in it can form hydrogen bonds with epoxy groups and hydroxyl groups in epoxy resin, hydroxyl groups and carboxyl groups on the surface of graphene oxide, and amino groups in polydopamine, further reducing the entanglement density of epoxy resin molecular chains and enhancing the fluidity of the epoxy resin system. The combined action of this loose ion pairing and solvation effect significantly reduces the viscosity of the epoxy resin system. Macroscopically, it is manifested as a decrease in the surface tension at the contact surface between the metal and the anti-rust coating. The ionic liquid drives the slow capillary penetration of graphene oxide (which is also the entire epoxy resin system) on the metal surface, forming a rough surface interlock 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.

[0026] (4) In the present invention, the ring-opening catalyst is selected from one of 1,8-diazabicycloundec-7-ene, 2,4,6-tris(dimethylaminomethyl)phenol, or N,N-dimethylaniline: There is a π-π conjugation effect in the ring-opening catalysts in the present invention, enabling the nucleophilic atoms to attack the oxygen atom in the epoxy group to form a transition state intermediate. The reaction activity is moderate and will not cause excessive cross-linking resulting in embrittlement of the epoxy resin. On the other hand, for some polyamines such as ethylenediamine and diethylenetriamine, the amino groups containing multiple active hydrogens in the molecule have too high reaction activity and can react at room temperature, easily causing excessive cross-linking phenomena and resulting in a relatively high film brittleness of the anti-rust coating. For some guanidine and imidazole compounds such as 1,1-dimethylguanidine and 2-ethyl-4-methylimidazole, the curing reaction temperature requirements are relatively high, and the optimal temperature is basically above 100°C. Poor dosage control is likely to lead to insufficient cross-linking. Specific Embodiments

[0027] The present invention will be specifically described and illustrated below in conjunction with examples.

[0028] The raw materials used in the following examples and comparative examples are all commercially available products, and some of the manufacturers are as follows: Polydopamine is provided by Xi'an Ruixi Biotechnology Co., Ltd.; bisphenol A epoxy resin, model E-44, is provided by Shandong Deyuan Epoxy Technology Co., Ltd.; bisphenol F epoxy resin, model DF170, is provided by Shandong Deyuan Epoxy Technology Co., Ltd.

[0029] Example 1 Preparation of anti-rust coating for marine engines Prepare a 55L organic system according to the ratio of 1-ethyl-3-methylimidazolium hexafluorophosphate:acetone = 1:9 (v / v). Add 4.5 kg of graphene oxide, 1.15 kg of bis-[3-(triethoxysilyl)propyl]-disulfide, and 0.3 kg of deionized water to the organic system, ultrasonically disperse for 20 min, then add dilute hydrochloric acid until pH = 4.2, start stirring, heat up to 65°C, and carry out hydrolysis and condensation reaction for 2 h to obtain a dispersion.

[0030] Add 50 kg of bisphenol A epoxy resin, 6.5 kg of polydopamine and 0.33 kg of 1,8-diazabicycloundec-7-ene to the dispersion liquid, ultrasonically disperse for 25 min, add ammonia water until the pH of the dispersion liquid is 9.1, start stirring, heat up to 62 °C, and carry out ring-opening reaction for 90 min; compound at a mass ratio of iron oxide red, zinc phosphate and graphite of 12:2:1 to obtain 15 kg of rust-inhibiting pigment. Subsequently, add the rust-inhibiting pigment to the dispersion liquid, stir until the color is uniform, and concentrate and volatilize at 28 °C for 15 min to obtain the rust-inhibiting coating for marine engines.

[0031] Example 2 Preparation of rust-inhibiting coating for marine engines Prepare 50 L of an organic system according to the ratio of 1-ethyl-3-methylimidazolium hexafluorophosphate: acetonitrile = 1:12 (v / v). Add 3.8 kg of graphene oxide, 1.4 kg of bis-[3-(triethoxysilyl)propyl]-disulfide and 0.4 kg of deionized water to the organic system, ultrasonically disperse for 28 min, then add dilute hydrochloric acid until the pH is 4.0, start stirring, heat up to 75 °C, and carry out hydrolysis and condensation reaction for 2.5 h to obtain a dispersion liquid.

[0032] Add 47 kg of bisphenol A epoxy resin, 5.0 kg of polydopamine and 0.25 kg of N,N-dimethylaniline to the dispersion liquid, ultrasonically disperse for 20 min, add ammonia water until the pH of the dispersion liquid is 9.5, start stirring, heat up to 45 °C, and carry out ring-opening reaction for 110 min; compound at a mass ratio of iron oxide red, aluminum tripolyphosphate and graphite of 13:2:1 to obtain 16 kg of rust-inhibiting pigment. Subsequently, add the rust-inhibiting pigment to the dispersion liquid, stir until the color is uniform, and concentrate and volatilize at 42 °C for 10 min to obtain the rust-inhibiting coating for marine engines.

[0033] Example 3 Preparation of rust-inhibiting coating for marine engines Prepare 45 L of an organic system according to the ratio of 1-ethyl-3-methylimidazolium hexafluorophosphate: cyclohexane = 1:15 (v / v). Add 5.5 kg of graphene oxide, 1.85 kg of bis-[3-(triethoxysilyl)propyl]-disulfide and 0.8 kg of deionized water to the organic system, ultrasonically disperse for 35 min, then add dilute hydrochloric acid until the pH is 5.0, start stirring, heat up to 55 °C, and carry out hydrolysis and condensation reaction for 3.5 h to obtain a dispersion liquid.

[0034] 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 liquid, ultrasonically disperse for 30 min, add ammonia water until the pH of the dispersion liquid is 8.5, start stirring, heat up to 75 °C, and carry out ring-opening reaction for 75 min; compound at a ratio of the mass ratio of iron oxide red, zinc molybdate and graphite being 10:2:1 to obtain 13 kg of rust-inhibiting pigment. Subsequently, supplement the rust-inhibiting pigment into the dispersion liquid, stir until the color is uniform, and concentrate and volatilize at 40 °C for 12 min to obtain the rust-inhibiting coating for marine engines.

[0035] Example 4 Rust prevention treatment for marine engines Clean the surface of the marine engine, and then spray the rust-inhibiting coating for marine engines in Example 1 onto the surface of the marine engine at 25 °C indoors under the condition that the environmental humidity ≤ 60%; after spraying, dry at 40 °C for 18 h to obtain a rust-inhibiting coating for marine engines, and the dry film thickness is 0.20 mm.

[0036] Example 5 Rust prevention treatment for marine engines Clean the surface of the marine engine, and then spray the rust-inhibiting coating for marine engines in Example 1 onto the surface of the marine engine at 25 °C indoors under the condition that the environmental humidity ≤ 60%; after spraying, dry at 45 °C for 14 h to obtain a rust-inhibiting coating for marine engines, and the dry film thickness is 0.25 mm.

[0037] Example 6 Rust prevention treatment for marine engines Clean the surface of the marine engine, and then spray the rust-inhibiting coating for marine engines in Example 1 onto the surface of the marine engine at 25 °C indoors under the condition that the environmental humidity ≤ 60%; after spraying, dry at 50 °C for 12 h to obtain a rust-inhibiting coating for marine engines, and the dry film thickness is 0.30 mm.

[0038] Comparative Example 1 Replace the ionic liquid with an equal volume of acetone, and the remaining operation steps and raw materials used are the same as in Example 1.

[0039] Comparative Example 2 Replace bis-[3-(triethoxysilyl)propyl]-disulfide with γ-aminopropyltriethoxysilane, a common silane coupling agent, and the remaining operation steps and raw materials used are the same as in Example 1.

[0040] Comparative Example 3 Replace bis-[3-(triethoxysilyl)propyl]-disulfide with 2-aminophenyl disulfide, an aromatic diamine containing a disulfide bond, and the remaining operation steps and raw materials used are the same as in Example 1. The structural formula of 2-aminophenyl disulfide is as follows: 。

[0041] Comparative Example 4 Replace graphene oxide with nano-silica, and the remaining operation steps and raw materials used are the same as in Example 1.

[0042] Comparative Example 5 Replace polydopamine with an equal mass of bisphenol A epoxy resin, and the remaining operation steps and raw materials used are the same as in Example 1.

[0043] Comparative Example 6 Replace the ring-opening catalyst with an equal mass of ethylenediamine, and the remaining operation steps and raw materials used are the same as in Example 1.

[0044] Comparative Example 7 Replace the ring-opening catalyst with an equal mass of 1,1-dimethylguanidine, and the remaining operation steps and raw materials used are the same as in Example 1.

[0045] Evaluation of implementation effects Preparation of specimens: Uniformly coat the marine engine rust-proof coatings in Examples 1 to 3 on clean carbon steel plates (material is Q235, thickness is 1.0 mm), and the dry film thickness is 0.20 mm to obtain Specimens 1 to 3; Similarly, obtain Comparative Specimens 1 to 7.

[0046] Based on the standard described in GB / T9286-2021, design a cross-cut test to test the adhesion performance of the rust-proof coating: Use a six-blade cutting knife to draw a 2 mm×2 mm grid on the surface of the specimen, and observe the peeling area after peeling with transparent tape (specification is a pressure-sensitive tape with a transparent polyester film substrate, width is 19 mm, and the peel force strength is (10±1) N / 25 mm). The adhesion grade is distinguished according to the standard from ISO0 to ISO5. ISO0: The incision edge is completely smooth without any peeling; ISO1: There is a small amount of peeling at the intersection of the incisions, but there is no peeling at the grid edge, and the peeling area ≤ 5%; ISO2: There is peeling at the incision 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 grids are completely peeled off, and the peeling area > 65%.

[0047] Based on the standard described in GB / T 1771-2007, a neutral salt spray test was designed to test the salt spray resistance (moisture resistance) of the anti-rust coating: The specimen was placed in a salt spray chamber and continuously sprayed with a 5 wt.% NaCl solution at 35 ± 2 °C and pH = 6.5 - 7.2. After 2000 hours of evaluation, the blistering situation of the anti-rust coating was observed. The evaluation criteria designed in the present invention is a 0 - 5 grade system, comprehensively determined from the size and density of the bubbles: Grade 0: No bubbles. Grade 1: Trace dispersed bubbles with a diameter of 0.5 mm or less; Grade 2: A small number of bubbles with a diameter of 0.5 - 1 mm, or a total area less than 5%; Grade 3: Medium-sized bubbles with a diameter of 1 - 3 mm, or a total area of 5% - 15%. Grade 4: A large number of bubbles with a diameter of 3 - 5 mm, or a total area of 15% - 35%. Grade 5: Severe blistering with a diameter greater than 5 mm, or a total area greater than 35%, accompanied by the peeling off of the anti-rust coating.

[0048] According to the standard described in GB / T 6742-2007, a bending test was designed to test the ductility of the anti-rust coating: The specimen was bent 180° within 1 second around cylinders with different diameters (3 mm and 6 mm), and the cracking or peeling of the coating was observed. No cracks and peeling were considered qualified.

[0049] Specific test data of the anti-rust coating performance are shown in Table 1.

[0050]

[0051] It can be seen from Table 1 that after the anti-rust coating was formed by coating with the marine engine anti-rust paint of the present invention, 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 use effect of the present invention.

Claims

1. A preparation method of an anti-rust coating for marine engines, characterized in that, It includes the following steps: (1) Prepare an organic system by mixing an ionic liquid and an organic solvent. Add graphene oxide, a dynamic cross-linking agent, and water to the organic system and mix well. Then adjust the pH to acidic and raise the temperature for a hydrolysis condensation reaction to obtain a dispersion; (2) Add an epoxy resin, polydopamine, and a ring-opening catalyst to the dispersion and mix well. Adjust the pH to basic and raise the temperature for a ring-opening reaction; then add an anti-rust pigment, concentrate and volatilize to obtain an anti-rust coating for marine engines.

2. The preparation method of the anti-rust coating for marine engines according to claim 1, wherein, 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 from the ionic liquid and the organic solvent according to a volume ratio of 1:(9 - 15).

3. The preparation method of the marine engine rust-proof paint according to claim 1, characterized in that, The dynamic cross-linking agent is bis-[3-(triethoxysilyl)propyl]-disulfide, and the addition ratio of graphene oxide, the dynamic cross-linking agent, water, and the organic system is (3.8 - 5.5):(1.15 - 1.85):(0.3 - 0.8):(45 - 55), with graphene oxide, the dynamic cross-linking agent, and water in kg and the organic system in L.

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

5. The preparation method of the anti-rust coating for marine engines according to claim 1, characterized in that, 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.

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

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

8. The preparation method of the marine engine rust-proof paint according to claim 1, characterized in that, The anti-rust pigment is prepared from iron oxide red, a surface passivator, and graphite. The surface passivator is one of zinc phosphate, aluminum tripolyphosphate, or zinc molybdate. The mass ratio of iron oxide red, the 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).

9. Application of the marine engine rust-proof coating prepared by the preparation method of the marine engine rust-proof coating according to any one of claims 1-8, characterized in that, Use the anti-rust coating for marine engines for the anti-rust treatment of marine engines. The anti-rust treatment includes the following steps: S1. Clean the surface of the marine engine; S2. Spray the anti-rust coating for marine engines onto the surface of the marine engine; S3. Dry to obtain an anti-rust coating for marine engines.

10. Use of the marine engine rust preventive paint according to claim 9, characterized in that, The drying temperature is 40 - 50 °C, the drying time is 12 - 18 h, and the dry film thickness of the anti-rust coating for marine engines is 0.2 - 0.3 mm.

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