A composite coating material for repairing corrosion surface of inner diameter of hydraulic cylinder and a preparation method thereof

Abstract

The application discloses a kind of composite coating material for hydraulic cylinder inner diameter corrosion surface repair and preparation method thereof, belong to metal anticorrosive coating field, can effectively solve the problems such as hydraulic cylinder inner diameter corrosion and severe wear of matched pair sealing ring, with not introducing thermal stress, high repair efficiency, good accessibility advantage.The application adopts layer-by-layer self-assembly method to stably combine corrosion inhibitor on the surface of porous polyether ether ketone nanoparticle material, obtains polyether ether ketone nanoparticle loaded with corrosion inhibitor, then mixes polyether ether ketone nanoparticle loaded with corrosion inhibitor with epoxy resin to obtain uniform, stable modified epoxy resin anticorrosive coating;The modified epoxy resin coating obtained has excellent mechanical properties, corrosion resistance and processability, can effectively inhibit cylinder inner diameter corrosion, and maintain the size accuracy and surface quality of cylinder inner diameter through machining, meet the service requirements of cylinder parts, the repair process is simple and fast, can effectively repair the damage caused by corrosion, reduce maintenance time and cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal anticorrosion coating, and particularly relates to a composite coating material for repairing the corrosion surface of the inner diameter of a hydraulic cylinder body and a preparation method thereof. BACKGROUND

[0002] In the fields of aerospace, automobile industry, etc., the corrosion of the inner diameter of a hydraulic cylinder body is a common problem in hydraulic systems, which may be caused by medium corrosion, friction and wear, etc. Such corrosion may increase the surface roughness of the inner diameter of the cylinder body, change the surface morphology and size, and even cause local wear or crack. In addition, the morphology change caused by corrosion will aggravate the friction and wear of the surface of the sealing ring of the pair, greatly reduce the service life of the sealing ring, and affect the sealing property and service life of the part.

[0003] During daily inspection and maintenance, the damaged sealing ring in the hydraulic cylinder body needs to be replaced in time, and the corrosion surface needs to be derusted. If the corrosion damage is not repaired and checked in time, the hydraulic oil may leak and the oil pressure may drop, the lag effect of the hydraulic cylinder during extension and retraction may be aggravated, and in severe cases, the hydraulic control system may fail, thereby causing a major safety accident.

[0004] At present, the traditional repair methods can be divided into hot repair and cold repair technologies. Common hot repair technologies mainly include laser cladding and flame spraying, etc. The traditional hot repair temperature is higher than the eutectoid transformation temperature of steel, and there are problems such as large heat-affected zone and serious deformation, which are difficult to meet the high-precision and high-performance requirements of the hydraulic cylinder. The cold repair technology, such as micro-pulse cold welding or brush plating, has high repair cost and long processing period. In addition, the sealing size of the inner diameter of the cylinder body is small, and the repair accessibility is poor, so the conventional repair technology cannot directly act on the damaged surface. If a new part is replaced, there is a problem of high updating cost and difficult procurement. Therefore, it is of great significance to develop a composite material coating repair technology for the corrosion surface of the inner diameter of the cylinder body.

[0005] At present, an epoxy resin coating is commonly used to protect the metal substrate. The chemical bonds such as ether or ester bonds contained in the molecular chain of the epoxy resin have good stability and are not easily eroded by common chemical corrosion media, so they have certain corrosion resistance. At the same time, due to the resistance effect of the film-forming material and the high density and sealing property of the material itself, the external corrosion medium can be effectively blocked, the corrosion material can be prevented from penetrating into the material, the dielectric constant is high, the formation of the corrosion circuit can be effectively prevented, and the corrosion medium can be shielded. However, for different working conditions, the performance requirements of the corresponding coating are also quite different, so a single system coating cannot meet the requirements of different environments. SUMMARY

[0006] The application provides a composite coating material for repairing a corroded surface of an inner diameter of a hydraulic cylinder body and a preparation method thereof.

[0007] To achieve the above object, the application adopts the following technical scheme:

[0008] The composite coating material for repairing a corroded surface of an inner diameter of a hydraulic cylinder body is modified epoxy resin, wherein porous polyether ether ketone nanoparticles are uniformly mixed in the epoxy resin, and the porous polyether ether ketone is coated with an inhibitor.

[0009] The preparation method of the composite coating material comprises the following steps:

[0010] 1) Mix porous polyether ether ketone nanoparticles with a particle size of 150-200 nm and deionized water at a weight ratio of 1:15-1:20, uniformly mix after water bath heat preservation, and obtain a nano polyether ether ketone dispersion liquid;

[0011] 2) uniformly mix the nano polyether ether ketone dispersion liquid and a positively charged polycation electrolyte solution with a concentration of 5 mg / mL, centrifuge and discard the upper solution, and wash the lower precipitate with deionized water;

[0012] 3) uniformly mix the precipitate washed in step 2) and a negatively charged polyanion electrolyte solution with a concentration of 5 mg / mL, centrifuge and discard the upper solution, and wash the lower precipitate with deionized water;

[0013] 4) uniformly mix the precipitate washed in step 3) and a nitrogen-doped carbon quantum dot (N-CQDs) inhibitor solution with a concentration of 5 mg / mL, centrifuge and discard the upper solution, and wash the lower precipitate with deionized water;

[0014] 5) repeat steps 3) and 4) above, dry the final particulate matter in an oven, and obtain porous polyether ether ketone nanoparticles loaded with nitrogen-doped carbon quantum dot inhibitors;

[0015] 6) mix epoxy resin and diluent in proportion, and stir under vacuum for 5-10 min;

[0016] 8) add the porous polyether ether ketone nanoparticles loaded with nitrogen-doped carbon quantum dot inhibitors to the diluted epoxy resin paste material, ultrasonically treat for 1 h, and stir at a stirring speed of 280 r / min under vacuum for 30 min;

[0017] 9) After the stirring is completed, the curing agent is added after the modified material is cooled, and stirring is performed at room temperature for 15 min until the coating is mixed uniformly, and the color is brownish red, thereby obtaining the modified epoxy resin coating material.

[0018] In the above steps, the curing agent is an aromatic modified amine, and the volume dosage is the same as that of the epoxy resin material; the positively charged polycationic electrolyte is polyethyleneimine, and the negatively charged polyanionic electrolyte is sodium polystyrene sulfonate;

[0019] The steps 3) and 4) are repeated to layer-by-layer self-assemble the positively charged polyethyleneimine and the negatively charged polystyrene sulfonate polyelectrolyte multilayer film on the surface of the porous polyether ether ketone nanoparticles, and the nitrogen-doped carbon quantum dot corrosion inhibitor is adsorbed between the polymer films, so that the polyether ether ketone nanoparticles coated with the nitrogen-doped carbon quantum dots, the sodium polystyrene sulfonate, the nitrogen-doped carbon quantum dots, the sodium polystyrene sulfonate and the polyethyleneimine in the order of PEEK / PEI / PSS / N-CQDs / PSS / N-CQDs are obtained, and the porous polyether ether ketone nanoparticles loaded with the corrosion inhibitor are obtained, and the number of repetitions usually depends on the performance requirements of the target;

[0020] The polyether ether ketone is a polymer composed of repeating units containing one ketone bond and two ether bonds in the main chain structure.

[0021] The diluent is prepared from cyclohexanone, butyl acetate and anhydrous dimethylbenzene in a volume ratio of 3:4:3, and the volume ratio of the diluent is usually between 5% and 15%, which can adjust the viscosity of the epoxy resin material, improve the rheological properties, and make the subsequent mixing more uniform.

[0022] The mass of the porous polyether ether ketone particles is not more than 5% of the epoxy resin material.

[0023] Beneficial effects: the present application provides a composite coating material for repairing the corrosion surface of the inner diameter of a hydraulic cylinder and a preparation method thereof, which has the following advantages compared with the prior art:

[0024] 1. In the present application, the layer-by-layer self-assembly technology is used to adsorb the corrosion inhibitor material, the oppositely charged polyelectrolyte solution is used for alternative deposition, the porous polyether ether ketone nanoparticles loaded with the corrosion inhibitor are prepared, the polyelectrolyte multilayer film with different properties can be obtained by changing the type of polyelectrolyte and the number of depositions, the adhesion of the corrosion inhibitor on the surface of the nanoparticles can be enhanced, the loading capacity and the uniformity of the corrosion inhibitor can be improved, and the corrosion resistance and stability can be enhanced; since the force between the oppositely charged polyelectrolytes is between the van der Waals force and the covalent bond, the corrosion inhibitor molecules enveloped between the polyelectrolytes are not easy to leak in large quantities, and slow release of the corrosion inhibitor can be realized.

[0025] 2、The porous polyether ether ketone nanoparticles are selected as the modified material, are mixed into the epoxy resin matrix and are fully mixed and uniform and solidified, the microstructure of the epoxy resin can be effectively adjusted, the crack propagation phenomenon caused by internal hole / crack damage under the loaded environment is inhibited, and the comprehensive performance of the epoxy resin is improved;And the porous surface structure can effectively absorb the corrosion inhibitor molecules, significantly improve the corrosion resistance of the coating, and release the corrosion inhibitor molecules in the coating micro-damage area to slow down the corrosion phenomenon;

[0026] 3、The nitrogen-doped carbon quantum dots have excellent fluorescence performance, good biocompatibility, high chemical inertness, low toxicity, better specific surface area and rich surface functional groups, such quantum dots can effectively avoid polluting the oil environment in the hydraulic cylinder, and ensure the normal operation of the equipment, are potential green and efficient corrosion inhibitor solutions;The nitrogen-doped carbon quantum dots have lone pair electrons on the surface of the nitrogen-containing groups, and the power supply capacity is stronger than that of oxygen atoms, and physical and chemical adsorption with the metal matrix is easier, so the nitrogen-doped carbon quantum dots can be used as efficient adsorption type corrosion inhibitors;In addition, the distribution of the nitrogen-doped carbon quantum dots in the hydraulic cylinder can be observed by the fluorescence performance of the quantum dots, so that the corrosion / leakage of the hydraulic system can be further grasped, a significant visual signal is provided when oil seepage occurs, the oil seepage problem of the hydraulic cylinder can be found in time, and the reliability and service life of the hydraulic system are greatly improved;

[0027] 4、The modified epoxy resin repair coating material has excellent mechanical properties and corrosion resistance, can effectively inhibit the corrosion of the cylinder bore, and the tensile shear strength reaches 15MPa through detection;The peeling strength is 17.2N / cm;When the coating thickness is 300μm, the charge transfer resistance R ct = 1.2×10 10 Ω, in the micro-damage area of the coating, the composite coating loaded with the corrosion inhibitor can slowly release the corrosion inhibitor molecules, and further slow down the corrosion phenomenon;

[0028] 5、The modified epoxy resin coating has excellent processability, can reduce the friction and wear amount of the coating and the rubber ring when repairing the damaged coating, can maintain the size accuracy and surface quality of the cylinder bore through machining, meets the service requirements of the cylinder parts, the repair process is simple and fast, the damage caused by corrosion can be effectively repaired, and the repair time and cost are reduced. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a schematic diagram of the corrosion prevention mechanism of the modified epoxy resin coating of the application;

[0030] Figure 2 It is a coating repair technology scheme;

[0031] Figure 3The left image is a hydraulic cylinder head cover simulation piece image, and the right image is a hydraulic cylinder head cover simulation piece composite material coating after repair image;

[0032] Figure 4 The micrographs before and after corrosion repair using the coating repair material of the present application;

[0033] Figure 5 The Nyquist diagram of 30CrMnSiNi2A material and metal corrosion repair layer in a NaCl solution with a mass concentration of 3.5%;

[0034] Figure 6 The morphology diagrams of the base material and the corrosion repair layer before and after corrosion: a and b are 30CrMnSiNi2A material, and c and d are repair layer material. DETAILED DESCRIPTION

[0035] The present application will be described in detail below with reference to the accompanying drawings and specific examples: Example 1

[0036] A composite coating material preparation method for the corrosion surface of the inner diameter of a hydraulic cylinder body, the specific steps are as follows:

[0037] (1) A certain amount of epoxy resin material, polyether ether ketone nanoparticles, curing agent, diluent, deionized water, polyethyleneimine solution, polystyrene sodium sulfonate solution, and nitrogen-doped carbon quantum dot corrosion inhibitor solution are weighed;

[0038] (2) The porous polyether ether ketone nanoparticles with a particle size of 150-200 nm are mixed with 200 mL of deionized water at a weight ratio of 1:15-1:20, water bathed at 80°C, uniformly stirred in a magnetic stirrer for 30 min, and dispersed in an ultrasonic disperser for 20 min after stirring;

[0039] (3) 50 ml of the prepared nano polyether ether ketone dispersion liquid is uniformly mixed with 5-10 ml of 5 mg / mL polyethyleneimine (PEI) solution, uniformly stirred in a magnetic stirrer for 30 min, and dispersed in an ultrasonic disperser for 20 min after stirring. Then, centrifuged for 10-20 min with a centrifuge, and after centrifugation, the upper solution was discarded, and the lower particles were washed with deionized water to obtain PEI-coated polyether ether ketone nanoparticles: PEEK / PEI;

[0040] (4) The prepared PEEK / PEI is mixed with 5-10 ml of 5 mg / mL polystyrene sodium sulfonate (PSS) solution, uniformly stirred in a magnetic stirrer for 20 min, and dispersed in an ultrasonic disperser for 20 min after stirring. Then, separated by a centrifuge for 10-20 min, and after centrifugation, the upper solution was discarded, and the lower particles were washed with deionized water to obtain the nanoparticles coated with PSS and PEI in layers: PEEK / PEI / PSS;

[0041] (5) The prepared PEEK / PEI / PSS was mixed with 20-40 ml of 1-5 mg / mL nitrogen-doped carbon quantum dots (N-CQDs, commercially available) corrosion inhibitor solution, uniformly stirred in a magnetic stirrer for 20 min, and dispersed in an ultrasonic disperser for 20 min. The upper layer solution was discarded after centrifugation for 10-20 min, and the lower layer particles were washed with deionized water to prepare polyether ether ketone nanoparticles coated with N-CQDs, PSS and PEI: PEEK / PEI / PSS / N-CQDs;

[0042] (6) Steps 4 and 5 were repeated once respectively, and the final particles were dried in an oven at 60-70°C for 24 h to prepare porous polyether ether ketone nanoparticles loaded with corrosion inhibitor molecules: PEEK / PEI / PSS / N-CQDs / PSS / N-CQDs;

[0043] (7) The epoxy resin and diluent were mixed in proportion, and the diluent was used in an amount of 5 wt%, and vacuum stirring was performed for 5-10 min;

[0044] (8) The diluted epoxy resin paste material was added with the porous polyether ether ketone nanoparticles loaded with corrosion inhibitor molecules, and attention should be paid to the fact that the mass fraction of the modified polyether ether ketone particles should not exceed 5% of the epoxy resin material. The mixed material was ultrasonically treated for 1 h, and then stirred at 65°C and 280 r / min for 30 min.

[0045] (9) After the stirring was completed, the curing agent was added after the modified material was cooled, and the volume was the same as that of the epoxy resin. Vacuum stirring was performed at room temperature for 15 min until the coating was uniformly mixed, the stirring speed was 280 r / min, and the color was brownish red. A modified epoxy resin coating material was prepared.

[0046] As shown in Figure 2 , the method for repairing the corrosion surface of the inner diameter of the hydraulic cylinder body using the modified epoxy resin coating material prepared in Example 1 is as follows:

[0047] (1) Preparation: In this scheme, DP420 epoxy resin adhesive was used as the primer, modified epoxy resin material was used as the repair coating, and the repair workpiece was a cylinder head with corroded inner diameter;

[0048] (2) Cleaning treatment: The local corrosion part of the cylinder head was cut open using a wire cutting machine, and the sample surface was cleaned and wiped with acetone; the sample was immersed in ethanol for ultrasonic cleaning and repeatedly cleaned and polished for 10 min until the surface corrosion products were removed; the cylinder head was polished to meet the requirements of a groove bottom surface roughness of less than Ra0.8 and a side surface roughness of less than Ra1.6;

[0049] (3) Preparation of repair coating: using modified epoxy resin material as repair coating, the composition is composed of A / B materials, wherein A material is epoxy resin part, including base resin and other additives, which is the main film forming material, giving the coating basic properties such as mechanical strength, corrosion resistance, etc.; B material is the curing agent part, which reacts with epoxy resin to form a crosslinked network, playing a role in curing and strengthening the structure. Here, the epoxy resin A / B material is mixed according to a volume ratio of 1:1 using an industrial vacuum stirrer, the stirring power is 200W, the stirring speed is 280r / min, and the stirring time is 15min until the epoxy resin coating is mixed uniformly, and the color is brownish red; within 5 minutes of the coating contacting the air, the repair work is completed;

[0050] (4) Adhesive repair: brush adhesive on the damaged part of the cylinder head inner diameter, and ensure uniform brushing to ensure full infiltration with the repaired surface; apply modified epoxy resin material to the damaged part to be repaired, and use a plastic spatula to spread on the surface of the uncured adhesive, and then apply an epoxy resin repair coating on the surface of the cylinder head inner diameter, and the surface of the coating is evenly and tightly coated, the surface is flat and has no obvious texture marks, and a certain processing allowance is left for the epoxy resin repair coating to make its thickness and shape slightly larger than the repaired area, facilitating subsequent processing;

[0051] (5) Heating and curing: place the repaired part in a hot press tank, and cure according to the corresponding curing process of the adhesive and curing agent, heat to 70℃ for 5 hours, and then place at room temperature for 24 hours for secondary curing; the second stage uses 120℃ for 2 hours; among them, the first stage is gentle curing, which reduces thermal stress and thermal expansion; the second stage increases the curing temperature to improve the physicochemical properties and repair quality of the cured repair layer; here, in order to pursue the best repair performance of the coating, the coating curing process of heating and curing is selected; if the convenience and economy of the coating repair are considered, and the repair area and strength requirement are low, the curing can be carried out at room temperature;

[0052] (6) Machining: after the curing process is completed, the repaired part is placed at room temperature for at least 24 hours and then fixed on a lathe for turning processing, and the lathe tool motion parameters are preset through three-dimensional modeling software: spindle speed 1600r / min, feed rate 20m / min, and back engagement amount 0.5mm; remove the excess composite material on the inner surface of the end cover, and grind the cured surface of the excess epoxy resin coating flat; the minimum radius of the coating after processing should be flush with or slightly larger than the minimum radius of the inner surface of the end cover.

[0053] As shown in Figure 1 , the modified epoxy resin coating forms a uniform and dense physical barrier to prevent water (H2O), oxygen (O2) and chloride ions (Cl ⁻) and other corrosive media penetrate into the surface of the metal substrate, this shielding effect reduces the occurrence conditions of the corrosion reaction, delays the oxidation and corrosion of the substrate. At the same time, the modified polyether ether ketone (PEEK) material added in the coating has the effect of reducing friction and lubrication, corrosion prevention and slow release. When a small amount of corrosive medium penetrates through the coating and contacts the substrate under the coating, these corrosion inhibitors can play a role in the corrosion site, inhibit the electrochemical reaction, and prevent further expansion of corrosion.

[0054] As shown in Figure 3 , the repaired end cover surface is smooth, uniform, and dense, which can effectively avoid the contact between the corrosion site and the air and reduce the stress concentration phenomenon.

[0055] As shown in Figure 4 , the micrographs of the material surface before and after repair, the left graph is the metal surface before repair, and obvious corrosion products and local pits can be observed, and the surface topography is relatively rough; the right graph is the coating surface after repair, which shows a relatively uniform and delicate surface without obvious corrosion marks or color difference phenomenon.

[0056] Through detection, the tensile shear strength of the coating reaches 15 MPa; the peeling strength is 17.2 N / cm; as shown in Figure 5 , when the coating thickness is 0.3 mm, the EIS test charge transfer resistance R ct = 1.2 x 10 10 Ω, the charge transfer resistance R ct of the 30CrMnSiNi2A material is 1557 Ω; as shown in Figure 6 , after Tafel test, the epoxy resin coating repair surface has no obvious corrosion deterioration phenomenon, so the coating can effectively protect the actuator end cover from further corrosion and damage, prolong the service life of the equipment, and the repair scheme can significantly reduce the roughness value of the metal surface and maintain good mechanical properties.

[0057] The above examples are only preferred embodiments of the present application; at the same time, for those skilled in the art, according to the idea of the present application, the specific embodiments and application range can be changed, and the contents of the above examples should not be understood as limiting the present application, and some improvements and refinements can be made without departing from the principles of the present application, which should also be regarded as the protection scope of the present application.

Claims

1. A composite coating material for hydraulic cylinder bore corrosion surface repair, characterized by, The composite coating material is a modified epoxy resin, the modified epoxy resin is uniformly mixed with porous polyether ether ketone nanoparticles in the epoxy resin, and the porous polyether ether ketone surface is coated with an inhibitor; The preparation method of the composite coating material comprises the following steps: 1) uniformly mix the porous polyether ether ketone nanoparticles with deionized water at a weight ratio of 1:15 to 1:20 to obtain a nano-polyether ether ketone dispersion; 2) uniformly mix the nano-polyether ether ketone dispersion with a positively charged polycation electrolyte solution, centrifuge, discard the upper solution, and wash the lower precipitate with deionized water; 3) uniformly mix the washed precipitate in step 2) with a negatively charged polyanion electrolyte solution, centrifuge, discard the upper solution, and wash the lower precipitate with deionized water; 4) uniformly mix the washed precipitate in step 3) with a nitrogen-doped carbon quantum dot inhibitor solution, centrifuge, discard the upper solution, and wash the lower precipitate with deionized water; 5) repeat steps 3) and 4) above, layer-by-layer self-assemble the positively charged polycation electrolyte and the negatively charged polyanion electrolyte multilayer film on the surface of the porous polyether ether ketone nanoparticles, and adsorb the nitrogen-doped carbon quantum dot inhibitor between the polymer films, the number of repetitions is determined according to requirements, to obtain porous polyether ether ketone nanoparticles loaded with nitrogen-doped carbon quantum dot inhibitors; 6) uniformly mix the epoxy resin with the porous polyether ether ketone nanoparticles loaded with nitrogen-doped carbon quantum dot inhibitors in a vacuum environment to obtain a modified epoxy resin composite coating material.

2. The composite coating material for hydraulic cylinder bore corrosion surface repair of claim 1, wherein, The main chain structure of the porous polyether ether ketone contains one ketone bond and two ether bonds.

3. The composite coating material for hydraulic cylinder bore corrosion surface repair of claim 1, wherein, The positively charged polycation electrolyte is polyethyleneimine.

4. The composite coating material for hydraulic cylinder bore corrosion surface repair according to claim 1 or 3, characterized in that, The negatively charged polyanion electrolyte is sodium polystyrene sulfonate.

5. The composite coating material for hydraulic cylinder bore corrosion surface repair of claim 1, wherein, The mass of the porous polyether ether ketone is not more than 5% of the mass of the epoxy resin.

6. The composite coating material for hydraulic cylinder bore corrosion surface repair of claim 1, wherein, Before mixing the epoxy resin with the porous polyether ether ketone nanoparticles loaded with nitrogen-doped carbon quantum dot inhibitors, a diluent is added to the epoxy resin to adjust the viscosity of the epoxy resin.

7. The composite coating material for hydraulic cylinder bore corrosion surface repair according to claim 1 or 6, characterized in that, After mixing the epoxy resin with the porous polyether ether ketone nanoparticles loaded with nitrogen-doped carbon quantum dot inhibitors, a curing agent is added.

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