A magnesium alloy self-repairing super-hydrophobic composite anticorrosion coating and a preparation method thereof

Abstract

The application provides a magnesium alloy self-repairing super-hydrophobic composite anticorrosion coating and a preparation method thereof, and belongs to the technical field of metal surface treatment.The magnesium alloy self-repairing super-hydrophobic composite anticorrosion coating comprises a micro-arc oxidation ceramic bottom layer, a polyvinyl alcohol-tannic acid self-repairing intermediate layer and a ZnO-epoxy resin outer layer arranged on the surface of the magnesium alloy in sequence.The micro-arc oxidation ceramic layer is used as the bottom layer, so that the adhesion between the coating layers can be improved;the ZnO-epoxy resin coating layer is used as the outer layer of the composite coating, so that a durable super-hydrophobic surface can be effectively formed; and the polyvinyl alcohol-tannic acid coating layer is used as the self-repairing intermediate layer, so that the service life of the coating can be prolonged and the anticorrosion performance of the magnesium alloy can be improved.The experimental results show that the magnesium alloy self-repairing super-hydrophobic composite anticorrosion coating has a self-repairing function, better corrosion resistance, a prolonged service life of the coating and improved anticorrosion performance of the magnesium alloy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal surface treatment, and particularly relates to a magnesium alloy self-repairing super-hydrophobic composite corrosion-resistant coating and a preparation method thereof. BACKGROUND

[0002] Magnesium alloy has been widely used in the fields of electronics, communication, aerospace and biomedical due to its low density, high specific strength and specific rigidity, good casting performance and processing performance. However, due to the low standard electrode potential and high chemical activity of magnesium alloy, magnesium alloy is prone to oxidation and corrosion during service, and the oxidation film generated by magnesium alloy is loose and porous, which cannot protect the substrate, thereby seriously limiting its wide application. Therefore, a protective film layer needs to be formed on the surface of magnesium alloy by surface treatment to isolate the substrate from the corrosion medium, so as to effectively improve the corrosion resistance of magnesium alloy. The micro-arc oxidation film layer is often used for surface protection of magnesium alloy due to its good adhesion, high hardness, excellent wear resistance and ceramic texture. However, a large number of crater-shaped micropores are distributed on the surface of the micro-arc oxidation film layer, which allows external corrosion medium to penetrate, thereby affecting the service time of the micro-arc oxidation film and the protection ability of the substrate.

[0003] Water is one of the main factors leading to the electrochemical corrosion of magnesium alloy. Improving the hydrophobicity of the surface of magnesium alloy can effectively isolate the substrate from the corrosion medium, slow down the corrosion rate, improve the corrosion resistance and durability of magnesium alloy, and endow it with self-cleaning performance. Therefore, the preparation of a super-hydrophobic corrosion-resistant coating on the surface of the micro-arc oxidation layer can seal the micropores on the surface of the micro-arc oxidation layer, thereby improving the corrosion resistance of magnesium alloy. However, the micro-nano structure with low surface energy of the super-hydrophobic coating is easily damaged under external force during service, which weakens the protective effect of the coating on magnesium alloy and shortens the service life of magnesium alloy, thereby hindering the application of super-hydrophobic coating in the field of magnesium alloy engineering corrosion prevention.

[0004] Therefore, it is a technical problem to be solved in the field to develop a super-hydrophobic composite corrosion-resistant coating with self-repairing function, which can prolong the service life of the coating and improve the corrosion resistance of magnesium alloy. SUMMARY

[0005] The present application aims to provide a magnesium alloy self-repairing super-hydrophobic composite corrosion-resistant coating and a preparation method thereof. The magnesium alloy self-repairing super-hydrophobic composite corrosion-resistant coating provided by the present application has self-repairing function, which can prolong the service life of the coating and improve the corrosion resistance of magnesium alloy.

[0006] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0007] The application provides a magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating, which comprises a micro-arc oxidation ceramic bottom layer, a polyvinyl alcohol-tannic acid self-repairing intermediate layer and a ZnO-epoxy resin outer layer arranged on the surface of the magnesium alloy in sequence.

[0008] The application provides a preparation method of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating, and the method comprises the following steps:

[0009] (1) performing micro-arc oxidation treatment on the surface of the pretreated magnesium alloy substrate to obtain the micro-arc oxidation ceramic bottom layer;

[0010] (2) coating self-repairing paint on the micro-arc oxidation ceramic bottom layer obtained in the step (1) to obtain the polyvinyl alcohol-tannic acid self-repairing intermediate layer; the preparation method of the self-repairing paint comprises the following steps: mixing polyvinyl alcohol, tannic acid, ethanol and water, and stirring under heating to obtain the self-repairing paint;

[0011] (3) coating a film-forming solution on the polyvinyl alcohol-tannic acid self-repairing intermediate layer obtained in the step (2) and drying to obtain the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating; the preparation method of the film-forming solution comprises the following steps: first mixing ZnO nanoparticles, mercaptan and anhydrous ethanol to obtain a suspension; second mixing the suspension with epoxy resin and a curing agent, and then sequentially performing standing and layering to obtain the film-forming solution.

[0012] Preferably, the pretreatment in the step (1) comprises the following steps: polishing the magnesium alloy substrate and then sequentially cleaning with water and anhydrous ethanol.

[0013] Preferably, the mass concentration of tannic acid in the self-repairing paint in the step (2) is (0.01-0.05) mol / L.

[0014] Preferably, the mass ratio of polyvinyl alcohol to tannic acid in the step (2) is 1:(1.2-2).

[0015] Preferably, the volume ratio of ethanol to water in the step (2) is (0.3-0.9):1.

[0016] Preferably, the heating temperature in the step (2) is >90 DEG C, and the heating time is 1-2 h.

[0017] Preferably, the mass concentration of ZnO nanoparticles in the film-forming solution in the step (3) is (0.4-0.7) mol / L.

[0018] Preferably, the total mass ratio of ZnO nanoparticles to epoxy resin and curing agent in the step (3) is 4:1.

[0019] Preferably, the volume ratio of the thiol to the anhydrous ethanol in step (3) is 1:(45-55).

[0020] The application provides a magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating, which comprises a micro-arc oxidation ceramic bottom layer, a polyvinyl alcohol-tannic acid self-repairing intermediate layer and a ZnO-epoxy resin outer layer arranged on the surface of the magnesium alloy in sequence. The application uses the micro-arc oxidation ceramic layer as the bottom layer, uses the micro-arc oxidation ceramic layer and the substrate to form mechanical interlocking, improves the adhesion between the coating layers, uses the ZnO-epoxy resin coating as the outer layer of the composite coating, and the ZnO nanoparticles play an important role in forming a rough surface structure, the epoxy resin has excellent adhesion, chemical stability and mechanical properties, and is used as a polymer adhesive to bond the coating to the substrate and make the coating have mechanical stability, so that a durable super-hydrophobic surface can be effectively generated, and the polyvinyl alcohol-tannic acid coating is used as the self-repairing intermediate layer, the polyvinyl alcohol-tannic acid self-repairing intermediate layer swells when meeting water, can quickly repair the damaged part of the ZnO-epoxy resin outer layer, can prolong the service life of the coating and improve the corrosion resistance of the magnesium alloy. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The three-dimensional profile photos of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating prepared in Example 1 before and after repair;

[0022] Figure 2 The hydrophobic performance effect diagram of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating prepared in Example 1;

[0023] Figure 3 The Bode diagram of the alternating current impedance spectrum of the LA81 magnesium alloy substrate, the micro-arc oxidation ceramic bottom layer (MAO) and the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating in Example 1 in a 3.5wt% NaCl solution;

[0024] Figure 4 The potentiodynamic polarization curve diagram of the LA81 magnesium alloy substrate, the micro-arc oxidation ceramic bottom layer (MAO) and the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating in Example 1 in a 3.5wt% NaCl solution. DETAILED DESCRIPTION

[0025] The application provides a magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating, which comprises a micro-arc oxidation ceramic bottom layer, a polyvinyl alcohol-tannic acid self-repairing intermediate layer and a ZnO-epoxy resin outer layer arranged on the surface of the magnesium alloy in sequence.

[0026] The application firstly uses the micro-arc oxidation ceramic layer as the bottom layer, and the micro-arc oxidation ceramic layer has the characteristics of good adhesion to the substrate, high hardness, excellent wear resistance and containing microporous structure, so that the self-repairing intermediate layer can be provided with pinning sites, mechanical interlocking with the intermediate layer is formed, and the adhesion between the coating layers is improved; the ZnO-epoxy resin coating is used as the outer layer of the composite coating, the addition of ZnO nanoparticles plays an important role in forming a rough surface structure, the epoxy resin has excellent adhesion, chemical stability and mechanical properties, and the coating is bonded on the substrate as a polymer adhesive, and the coating has mechanical stability, so that a durable super-hydrophobic surface can be effectively generated; the polyvinyl alcohol-tannic acid coating is used as the self-repairing intermediate layer, the polyvinyl alcohol-tannic acid self-repairing intermediate layer swells when meeting water, so that the damaged parts of the ZnO-epoxy resin outer layer can be quickly repaired, the service life of the coating can be prolonged, and the corrosion resistance of the magnesium alloy can be improved.

[0027] The application provides a preparation method of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating, and the preparation method comprises the following steps.

[0028] (1) performing micro-arc oxidation treatment on the surface of the pretreated magnesium alloy substrate to obtain a micro-arc oxidation ceramic bottom layer;

[0029] (2) coating a self-repairing coating on the micro-arc oxidation ceramic bottom layer obtained in the step (1) to obtain a polyvinyl alcohol-tannic acid self-repairing intermediate layer; the preparation method of the self-repairing coating comprises the following steps: mixing polyvinyl alcohol, tannic acid, ethanol and water, and stirring under heating to obtain the self-repairing coating;

[0030] (3) coating a film-forming solution on the polyvinyl alcohol-tannic acid self-repairing intermediate layer obtained in the step (2) and drying to obtain the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating; the preparation method of the film-forming solution comprises the following steps: first mixing ZnO nanoparticles, mercaptan and anhydrous ethanol to obtain a suspension; second mixing the suspension with epoxy resin and a curing agent, and then sequentially performing standing and layering to obtain the film-forming solution.

[0031] The application performs micro-arc oxidation treatment on the surface of the pretreated magnesium alloy substrate to obtain a micro-arc oxidation ceramic bottom layer.

[0032] In the application, the pretreatment preferably comprises the following steps: polishing the magnesium alloy substrate and then sequentially cleaning with water and anhydrous ethanol.

[0033] The magnesium alloy substrate is polished by using 400#, 1200# and 2000# silicon carbide abrasive paper in sequence.

[0034] The polishing operation is not particularly limited, and the polished magnesium alloy substrate can be cleaned by using a cleaning method commonly used by those skilled in the art.

[0035] The magnesium alloy substrate is polished by using 400#, 1200# and 2000# silicon carbide abrasive paper in sequence.

[0036] The magnesium alloy substrate is polished by using 400#, 1200# and 2000# silicon carbide abrasive paper in sequence.

[0037] In the present application, the electrolyte used in the micro-arc oxidation treatment is preferably a mixed solution of 6-8 g / L of sodium hydroxide, 8-10 g / L of sodium silicate and 4-5 g / L of potassium fluoride; the micro-arc oxidation treatment preferably uses 300V alternating current; the pulse frequency of the micro-arc oxidation treatment is preferably 500Hz; and the oxidation time of the micro-arc oxidation is preferably 3-5 min. By setting the electrolyte composition and treatment parameters of the micro-arc oxidation to the above ranges, a uniform micro-arc oxidation ceramic bottom layer can be formed on the surface of the magnesium alloy.

[0038] After the micro-arc oxidation treatment, the product of the micro-arc oxidation treatment is preferably sequentially cleaned and dried to obtain a micro-arc oxidation ceramic bottom layer.

[0039] In the present application, the cleaning is preferably cleaning with deionized water and anhydrous ethanol in sequence. The cleaning operation is not particularly limited, and a cleaning operation commonly used by those skilled in the art can be used.

[0040] In the present application, the drying is preferably drying by a hair dryer.

[0041] After obtaining the micro-arc oxidation ceramic bottom layer, the self-repairing coating is applied to the micro-arc oxidation ceramic bottom layer to obtain a polyvinyl alcohol-tannic acid self-repairing intermediate layer.

[0042] In the present application, the preparation method of the self-repairing coating comprises: mixing polyvinyl alcohol, tannic acid, ethanol and water, and stirring under heating conditions to obtain a self-repairing coating.

[0043] In the present application, the mass concentration of tannic acid in the self-repairing coating is preferably (0.01-0.05) mol / L, more preferably (0.03-0.05) mol / L, and further preferably (0.04-0.05) mol / L. The present application limits the mass concentration of tannic acid to the above range, which can make the self-repairing coating have good self-repairing function.

[0044] In the present application, the mass ratio of polyvinyl alcohol to tannic acid is preferably 1:(1.2-2), more preferably 1:(1.2-1.8), further preferably 1:(1.2-1.4), and most preferably 1:1.25. The present application limits the mass ratio of polyvinyl alcohol to tannic acid to the above range, which can ensure the self-repairing coating to have better self-repairing function.

[0045] In the present application, the volume ratio of ethanol to water is preferably (0.3-0.9):1, more preferably (0.6-0.9):1, and further preferably (0.8-0.9):1. The present application limits the volume ratio of ethanol to water to the above range, which can make the coating dry better.

[0046] The present application does not have special limitation on the mixing operation of polyvinyl alcohol, tannic acid, ethanol and water, and any mixing means commonly used by those skilled in the art can be used.

[0047] In the present application, the heating temperature is preferably >90℃, and more preferably 100℃; and the heating time is preferably 1-2 h, and more preferably 1-1.5 h. The present application limits the heating temperature and time to the above range, which is more conducive to the dynamic hydrogen bond cross-linking reaction during heating, and generates tannic acid polyvinyl alcohol mixture.

[0048] In the present application, the stirring speed is preferably 200-300 r / min, and more preferably 250-280 r / min. The present application limits the stirring speed to the above range, which can ensure the reaction to proceed sufficiently.

[0049] In an embodiment of the present application, the process of coating the self-repairing coating on the micro-arc oxidation ceramic bottom layer preferably comprises: soaking the micro-arc oxidation film bottom layer into the self-repairing coating and then drying.

[0050] In the present application, the soaking time is preferably 1-5 min. The present application limits the soaking time to the above range, which can ensure uniform coating of the coating.

[0051] In the present application, the drying is preferably performed in an oven; the temperature of the drying is preferably 65-75℃, more preferably 70℃; the time of the drying is preferably 20-40min, more preferably 30min. The temperature and time of the drying are limited in the above range to ensure that the coating is sufficiently dried.

[0052] In another embodiment of the present application, the process of coating the self-repairing coating on the micro-arc oxidation ceramic base layer preferably comprises: dropping the self-repairing coating on the surface of the micro-arc oxidation ceramic base layer, spin coating and drying.

[0053] In the present application, the volume of the dropped self-repairing coating is preferably 1-2mL. The volume of the dropped self-repairing coating is limited in the above range to ensure that the thickness of the self-repairing coating meets the requirements.

[0054] In the present application, the equipment for spin coating is preferably a spin coater. The present application does not have special limitations on the model of the spin coater, and any model commonly used by those skilled in the art can be used.

[0055] In the present application, the rotation speed of the spin coater is preferably 800-1000r / min. The rotation speed of the spin coater is set in the above range to ensure that the coating is uniformly formed.

[0056] In the present application, the drying is preferably performed in an oven; the temperature of the drying is preferably 65-75℃, more preferably 70℃; the time of the drying is preferably 20-40min, more preferably 30min. The temperature and time of the drying are limited in the above range to ensure that the coating is sufficiently dried.

[0057] After obtaining the polyvinyl alcohol-tannic acid self-repairing intermediate layer, the present application coats a plating solution on the polyvinyl alcohol-tannic acid self-repairing intermediate layer and dries to obtain a magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating.

[0058] In the present application, the preparation method of the plating solution comprises: first mixing ZnO nanoparticles, mercaptan and anhydrous ethanol to obtain a suspension; second mixing the suspension with epoxy resin and a curing agent, and then sequentially performing standing and layering to obtain the plating solution.

[0059] In the present application, the amount-of-substance concentration of the ZnO nanoparticles in the plating solution is preferably (0.4-0.7)mol / L, more preferably (0.4-0.6)mol / L, and further preferably (0.45-0.5)mol / L. The amount-of-substance concentration of the ZnO nanoparticles is limited in the above range to form a rough surface structure, which is conducive to the hydrophobic property and wear resistance of the coating.

[0060] In the present application, the volume ratio of the mercaptan to anhydrous ethanol is preferably 1:(45-55), more preferably 1:50. The present application uses mercaptan as a hydrophobic agent and a surface energy modifier to reduce the surface energy of the coating, improve the interfacial adhesion of the polymer, prevent the aggregation of ZnO nanoparticles during the compounding with the polymer, and effectively promote the construction of the hierarchical rough structure of the super-hydrophobic surface layer; ethanol as a formation medium of the dense structure network can promote the rapid drying of the coating. The present application can ensure that the hydrophobic coating has good adhesion and can be dried rapidly by limiting the volume ratio of mercaptan to anhydrous ethanol to the above range.

[0061] In the present application, the first mixing is preferably carried out under heating; the temperature of the heating is preferably 60℃. The present application can ensure the sufficient mixing of the materials by heating.

[0062] In the present application, the first mixing preferably includes stirring and ultrasonic treatment in sequence.

[0063] In the present application, the stirring time is preferably 5-10 min. The present application does not have special limitations on the stirring speed, and the stirring operation commonly used by those skilled in the art can be used.

[0064] In the present application, the ultrasonic treatment time is preferably 5-10 min. The present application does not have special limitations on the ultrasonic frequency, and the ultrasonic frequency commonly used by those skilled in the art can be used.

[0065] In the present application, the mass ratio of the ZnO nanoparticles to the total mass of the epoxy resin and the curing agent is preferably 4:1. The present application limits the mass ratio of the ZnO nanoparticles to the total mass of the epoxy resin and the curing agent to the above range, which can ensure that the hydrophobic coating has good hydrophobic properties.

[0066] In the present application, the mass ratio of the epoxy resin to the curing agent is preferably 2:1; the epoxy resin is preferably a KAFTE epoxy resin; and the curing agent is preferably a KAFTE epoxy resin curing agent. The present application limits the types and mass ratio of the epoxy resin and the curing agent to the above range, which can ensure that the hydrophobic coating has good hydrophobic properties.

[0067] In the present application, the second mixing is preferably stirring; and the stirring time is preferably 5-10 min. The present application does not have special limitations on the stirring speed, and the stirring operation commonly used by those skilled in the art can be used. The present application introduces the adhesive epoxy resin in the solution through the second mixing, which ensures that the hydrophobic coating has good adhesion.

[0068] The present application does not have special limitations on the standing time and temperature, and a layered solution can be obtained.

[0069] The present application does not have special restrictions on the operation of the layering, and the upper and lower layers of the solution can be separated.

[0070] In the present application, the lower layer solution after layering is the coating solution.

[0071] The present application does not have special restrictions on the operation of the coating, and the coating means commonly used by those skilled in the art can be used to uniformly coat the coating solution onto the polyvinyl alcohol-tannic acid self-repairing intermediate layer.

[0072] In the present application, the drying temperature is preferably room temperature; and the drying time is preferably > 8h. By setting the drying temperature and time within the above range, the present application can ensure sufficient drying of the coating.

[0073] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0074] Example 1

[0075] The present application provides a magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating, which is composed of a micro-arc oxidation ceramic bottom layer, a polyvinyl alcohol-tannic acid self-repairing intermediate layer and a ZnO-epoxy resin outer layer arranged in sequence on the surface of a magnesium alloy; the magnesium alloy is LA81 magnesium alloy;

[0076] The preparation method of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating comprises the following steps:

[0077] (1) The LA81 magnesium alloy substrate is polished with 400#, 1200# and 2000# silicon carbide sandpaper in sequence to remove the oxide layer and stains on the surface of the LA81 magnesium alloy, and then the surface of the LA81 magnesium alloy is cleaned with deionized water and anhydrous ethanol in sequence, and dried with a hair dryer to obtain a pretreated magnesium alloy; a mixed solution composed of 8g / L sodium hydroxide, 10g / L sodium silicate and 5g / L potassium fluoride is used as an electrolyte to perform micro-arc oxidation treatment on the surface of the pretreated magnesium alloy substrate under the condition of 300V alternating current and a pulse frequency of 500Hz for 3min, and then the surface is cleaned with deionized water and anhydrous ethanol and dried with a hair dryer to obtain a micro-arc oxidation ceramic bottom layer;

[0078] (2) adding 5 g of tannic acid and 4 g of polyvinyl alcohol into a mixed solution containing 30 mL of anhydrous ethanol and 35 mL of deionized water, placing in a 100℃ oil bath, heating for 80 min at a rotation speed of 300 r / min to make them uniformly dispersed, obtaining a self-repairing coating, immersing the LA81 magnesium alloy oxide ceramic bottom layer in the self-repairing coating for 1 min, and then placing in a 70℃ oven for 30 min, obtaining a polyvinyl alcohol-tannic acid self-repairing intermediate layer; the mass concentration of tannic acid in the self-repairing coating is 0.045 mol / L; the mass ratio of polyvinyl alcohol to tannic acid is 1:1.25; the volume ratio of ethanol to water is 0.86:1;

[0079] (3) dissolving 2.4 g of ZnO nanoparticles and 1.2 mL of mercaptan in 60 mL of anhydrous ethanol, stirring at a speed of 500 r / min for 10 min at 60℃ to make them uniformly dispersed, and ultrasonicating for 10 min, obtaining a suspension, adding 0.6 g of Kaurit epoxy resin and Kaurit epoxy resin curing agent into the suspension and stirring at a speed of 500 r / min for 10 min, and after standing until the solution is obviously layered, performing layering, coating the lower layer of the layered solution on the polyvinyl alcohol-tannic acid self-repairing intermediate layer, and drying at room temperature for 12 h, obtaining a magnesium alloy self-repairing super-hydrophobic composite corrosion-resistant coating; the mass concentration of ZnO nanoparticles in the plating solution is 0.48 mol / L; the total mass ratio of ZnO nanoparticles to epoxy resin and curing agent is 4:1; the volume ratio of mercaptan to anhydrous ethanol is 1:50; and the mass ratio of Kaurit epoxy resin to Kaurit epoxy resin curing agent is 2:1.

[0080] Example 2

[0081] The application provides a magnesium alloy self-repairing super-hydrophobic composite corrosion-resistant coating, which is composed of a micro-arc oxidation ceramic bottom layer, a polyvinyl alcohol-tannic acid self-repairing intermediate layer and a ZnO-epoxy resin outer layer arranged on the surface of a magnesium alloy in sequence; the magnesium alloy is an LA81 magnesium alloy;

[0082] The preparation method of the magnesium alloy self-repairing super-hydrophobic composite corrosion-resistant coating comprises the following steps:

[0083] (1) The LA81 magnesium alloy substrate was polished with 400#, 1200# and 2000# silicon carbide sandpaper in sequence to remove the oxide layer and stains on the surface of the LA81 magnesium alloy, and then the surface of the LA81 magnesium alloy was cleaned with deionized water and anhydrous ethanol in sequence, and dried with a hair dryer to obtain a pretreated magnesium alloy; a mixed solution composed of 8 g / L of sodium hydroxide, 10 g / L of sodium silicate and 5 g / L of potassium fluoride was used as an electrolyte to perform micro-arc oxidation treatment on the surface of the pretreated magnesium alloy substrate at 300 V alternating current and a pulse frequency of 500 Hz for 5 min, and then the magnesium alloy was cleaned with deionized water and anhydrous ethanol and dried with a hair dryer to obtain a micro-arc oxidation ceramic bottom layer;

[0084] (2) 5 g of tannic acid and 4 g of polyvinyl alcohol were added to a mixed solution containing 30 mL of anhydrous ethanol and 35 mL of deionized water, and the mixture was heated in a 100°C oil bath for 80 min at a rotation speed of 300 r / min to uniformly disperse the mixture, thereby obtaining a self-repairing coating; 1 mL of the self-repairing coating was uniformly spin-coated onto the LA81 magnesium alloy oxidation ceramic bottom layer by a spin coater at a rotation speed of 800 r / min, and then placed in a 70°C oven for 30 min to obtain a polyvinyl alcohol-tannic acid self-repairing intermediate layer; the mass concentration of tannic acid in the self-repairing coating was 0.045 mol / L; the mass ratio of polyvinyl alcohol to tannic acid was 1:1.25; and the volume ratio of ethanol to water was 0.86:1;

[0085] (3) 2.4 g of ZnO nanoparticles and 1 mL of mercaptan were dissolved in 50 mL of anhydrous ethanol, and the mixture was stirred at 60°C at a speed of 500 r / min for 10 min to uniformly disperse the mixture, and then ultrasonically treated for 10 min to obtain a suspension; 0.6 g of Kryfoil epoxy resin and Kryfoil epoxy resin curing agent were added to the suspension and stirred at a speed of 500 r / min for 10 min, and then the solution was allowed to stand until the solution was obviously layered, and the lower layer of the layered solution was coated on the polyvinyl alcohol-tannic acid self-repairing intermediate layer and dried at room temperature for 12 h to obtain a magnesium alloy self-repairing super-hydrophobic composite corrosion-resistant coating; the mass concentration of ZnO nanoparticles in the coating solution was 0.58 mol / L; the total mass ratio of ZnO nanoparticles to epoxy resin and curing agent was 4:1; the volume ratio of mercaptan to anhydrous ethanol was 1:50; and the mass ratio of Kryfoil epoxy resin to Kryfoil epoxy resin curing agent was 2:1.

[0086] Example 3

[0087] Example 3 differs from Example 1 only in that the magnesium alloy is LA141 magnesium alloy, and the other conditions are the same as those in Example 1.

[0088] Example 4

[0089] Example 4 differs from Example 1 only in that the magnesium alloy is AZ31 magnesium alloy, and the rest is the same as Example 1.

[0090] The self-repairing performance of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating is observed by using a three-dimensional profile microscope.

[0091] The hydrophobicity of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating is tested by using a video optical contact angle measuring instrument.

[0092] The anti-corrosion performance of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating is tested by using a Kost electrochemical workstation.

[0093] The three-dimensional profile photos of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating prepared in Example 1 before and after repair are shown in Figure 1 From Figure 1 it can be seen that the mouth shown in the lower left of the figure is cut on the surface of the sample by a surgical knife, and the left two figures are obtained by observing with a three-dimensional profile microscope; water is dropped on the cut mouth, and after waiting for about 30 min, the residual liquid is wiped off, and the right two figures are obtained by observing with a three-dimensional profile microscope, it can be found that the gap at the crack of the sample is obviously smaller, and the sample has been self-repaired.

[0094] The hydrophobic performance effect diagram of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating prepared in Example 1 is shown in Figure 2 From Figure 2 it can be seen that the static contact angle of water is 151°, indicating that the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating has super-hydrophobicity.

[0095] The Bode plot of the alternating current impedance spectrum of the LA81 magnesium alloy substrate, the micro-arc oxidation ceramic bottom layer (MAO) and the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating in Example 1 in a 3.5wt% NaCl solution is shown in Figure 3 From Figure 3 it can be seen that when the frequency is 0.01 Hz, the modulus of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating is much larger than that of the micro-arc oxidation ceramic bottom layer (MAO) and the LA81 magnesium alloy substrate, showing better corrosion resistance.

[0096] The potentiodynamic polarization curve diagram of the LA81 magnesium alloy substrate, the micro-arc oxidation ceramic bottom layer (MAO) and the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating in Example 1 in a 3.5wt% NaCl solution is shown in Figure 4 From Figure 4 it can be seen that the corrosion current density of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating is much smaller than that of the micro-arc oxidation ceramic bottom layer (MAO) and the LA81 magnesium alloy substrate, indicating that the self-repairing super-hydrophobic composite anti-corrosion coating prepared on the surface of the magnesium alloy substrate has better corrosion resistance, and can improve the anti-corrosion performance of the magnesium alloy.

[0097] The above merely describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating, comprising a micro-arc oxidation ceramic bottom layer, a polyvinyl alcohol-tannic acid self-repairing intermediate layer and a ZnO-epoxy resin outer layer arranged in sequence on the surface of the magnesium alloy. A preparation method of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating, comprising the following steps: (1) performing micro-arc oxidation treatment on the surface of a pretreated magnesium alloy substrate to obtain a micro-arc oxidation ceramic bottom layer; the electrolyte used in the micro-arc oxidation treatment is a mixed solution of 6-8 g / L sodium hydroxide, 8-10 g / L sodium silicate and 4-5 g / L potassium fluoride; (2) coating a self-repairing coating on the micro-arc oxidation ceramic bottom layer obtained in the step (1) to obtain a polyvinyl alcohol-tannic acid self-repairing intermediate layer; the preparation method of the self-repairing coating comprises mixing polyvinyl alcohol, tannic acid, ethanol and water and then stirring under heating to obtain the self-repairing coating; (3) coating a film-forming solution on the polyvinyl alcohol-tannic acid self-repairing intermediate layer obtained in the step (2) and then drying to obtain the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating; the preparation method of the film-forming solution comprises first mixing ZnO nanoparticles, mercaptan and anhydrous ethanol to obtain a suspension, second mixing the suspension with epoxy resin and a curing agent, and then sequentially performing standing and layering to obtain the film-forming solution; the total mass ratio of the ZnO nanoparticles to the epoxy resin and the curing agent in the step (3) is 4:

1. 2.The preparation method of the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating according to claim 1, comprising the following steps: (1) performing micro-arc oxidation treatment on the surface of a pretreated magnesium alloy substrate to obtain a micro-arc oxidation ceramic bottom layer; the electrolyte used in the micro-arc oxidation treatment is a mixed solution of 6-8 g / L sodium hydroxide, 8-10 g / L sodium silicate and 4-5 g / L potassium fluoride; (2) coating a self-repairing coating on the micro-arc oxidation ceramic bottom layer obtained in the step (1) to obtain a polyvinyl alcohol-tannic acid self-repairing intermediate layer; the preparation method of the self-repairing coating comprises mixing polyvinyl alcohol, tannic acid, ethanol and water and then stirring under heating to obtain the self-repairing coating; (3) coating a film-forming solution on the polyvinyl alcohol-tannic acid self-repairing intermediate layer obtained in the step (2) and then drying to obtain the magnesium alloy self-repairing super-hydrophobic composite anti-corrosion coating; the preparation method of the film-forming solution comprises first mixing ZnO nanoparticles, mercaptan and anhydrous ethanol to obtain a suspension, second mixing the suspension with epoxy resin and a curing agent, and then sequentially performing standing and layering to obtain the film-forming solution; the total mass ratio of the ZnO nanoparticles to the epoxy resin and the curing agent in the step (3) is 4:

1.

3. The preparation method according to claim 2, characterized in that, the pretreatment in the step (1) comprises polishing the magnesium alloy substrate and then sequentially cleaning with water and anhydrous ethanol.

4. The preparation method according to claim 2, characterized in that, the molar concentration of tannic acid in the self-repairing coating in the step (2) is (0.01-0.05) mol / L.

5. The production method according to claim 2 or 4, characterized by, the mass ratio of polyvinyl alcohol to tannic acid in the step (2) is 1:(1.2-2).

6. The preparation method according to claim 2, characterized in that, The volume ratio of ethanol and water in the step (2) is (0.3-0.9):

1.

7. The preparation method according to claim 2, characterized in that, The heating temperature in the step (2) is >90℃, and the heating time is 1-2h.

8. The preparation method according to claim 2, characterized in that, The molar concentration of ZnO nanoparticles in the plating solution in the step (3) is (0.4-0.7) mol / L.

9. The preparation method according to claim 2, characterized in that, The volume ratio of mercaptan and anhydrous ethanol in the step (3) is 1:(45-55).

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