Micro-arc oxidation electrolyte and micro-arc oxidation method

Abstract

The present application provides a micro-arc oxidation electrolyte and a micro-arc oxidation method. The micro-arc oxidation electrolyte provided by the present application includes silicate, phosphate, pH regulator, potassium fluoride, and silica microcapsules. In the present application, silica microcapsules wrapped with ionic liquid with corrosion inhibition effect are added to the electrolyte, which can not only protect the ionic liquid from burning during the micro-arc oxidation process, but also avoid the leakage of ionic liquid, which can improve the durability of the coating. In addition, the silica microcapsules can be fixed to the surface of the workpiece during the micro-arc oxidation process, and released when the protective film is damaged by corrosion or friction, which can repair the damaged surface and form a lubricating and anti-corrosion film layer. The addition of silica microcapsules gives the protective film formed by micro-arc oxidation the functions of reducing friction, resisting wear, and preventing corrosion. The electrolyte of the present application overcomes the shortcomings of the poor corrosion resistance and wear resistance of the coating obtained by the existing micro-arc oxidation method.

Description

Technical Field

[0001] The present application relates to the technical field of material corrosion protection, and in particular to a micro-arc oxidation electrolyte and a micro-arc oxidation method. Background Art

[0002] Lightweighting is a key trend in the development of high-end shipbuilding and marine engineering equipment, and is of great significance for improving equipment energy efficiency, reducing emissions, and promoting the green and sustainable development of the marine economy. Light alloys such as aluminum, magnesium, and titanium are highly favored for their low density, high specific strength, and good processing properties, and have broad application prospects in the manufacture of lightweight shipbuilding and marine engineering equipment. In shipbuilding, these metals are typically used to manufacture hulls, structural components (support frames, beams, etc.), decks, and some special-purpose equipment and accessories (pump bodies, turbine blades, valves, pipes, etc.). In the field of marine engineering, they are also widely used in the manufacture of equipment and structures such as offshore platforms, deep-sea exploration equipment, and submarine pipelines.

[0003] However, light alloys usually have more active properties and lower surface hardness. Their wear resistance and corrosion resistance cannot meet the requirements of use in harsh marine environments and complex working conditions. Therefore, targeted surface treatment or coating is required. Micro-arc oxidation technology can rely on the instantaneous high temperature and high pressure generated by arc discharge to grow a ceramic film layer with matrix metal oxide and electrolyte compounds / additives as the main components on the surface of light alloys. Compared with traditional anodic oxidation films, micro-arc oxidation films have the advantages of strong coating adhesion, designable coating structure, simple and environmentally friendly process. However, the inevitable high porosity and microcracks of micro-arc oxidation coatings seriously weaken the long-term corrosion resistance of the coating; in addition, the friction coefficient of pure micro-arc oxidation coatings is also relatively high, which limits the application of this technology in the field of light alloy surface protection. Summary of the Invention

[0004] The present application provides a micro-arc oxidation electrolyte and a micro-arc oxidation method to solve the problems of poor corrosion resistance and wear resistance of the coatings obtained by the above-mentioned existing micro-arc oxidation methods. At the same time, it provides an integrated micro-arc oxidation coating with friction reduction, anti-wear and corrosion resistance and in-situ embedded silica microcapsules and a preparation method.

[0005] In a first aspect, the present application provides a micro-arc oxidation electrolyte comprising 5-15 g / L silicate, 5-30 g / L phosphate, 0-5 g / L pH regulator, 0-10 g / L potassium fluoride, and 0.5-10 g / L silica microcapsules.

[0006] The micro-arc oxidation electrolyte provided in this application has the following beneficial effects:

[0007] 1) Adding silicate and phosphate as film-forming agents to the electrolyte will form a ceramic protective film on the surface of the protected workpiece after electrolysis, which will improve the strength and impact resistance of the protective film formed by micro-arc oxidation and extend its service life.

[0008] 2) In the present application, silica microcapsules are added to the electrolyte, which contain ionic liquids that act as corrosion inhibitors. The shell of the silica microcapsules is composed of stable silica. This allows the silica microcapsules to protect the ionic liquid from burning during the micro-arc oxidation process on the one hand, and to prevent leakage of the ionic liquid on the other hand, thereby improving the durability of the coating.

[0009] 3) During the micro-arc oxidation process, the silica microcapsules added to the electrolyte can adhere to and fix on the workpiece surface together with the film-forming agent. When the protective film is damaged due to corrosion or friction, they are released to repair the damaged surface and form a lubricating anti-corrosion film layer. The addition of silica microcapsules gives the protective film formed by micro-arc oxidation the integrated functions of friction reduction, wear resistance and corrosion resistance.

[0010] Optionally, the concentration of the silica microcapsules is 1 to 10 g / L.

[0011] Optionally, the silicate comprises Na2SiO3·nH2O and potassium silicate;

[0012] Where n=0~12.

[0013] Optionally, the phosphate includes one or more of sodium trimetaphosphate, sodium hexametaphosphate, sodium tripolyphosphate, sodium polyphosphate, sodium phosphate, and potassium polyphosphate.

[0014] Optionally, the pH adjuster includes one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium hydroxide.

[0015] Alternatively, silica microcapsules are prepared as follows:

[0016] a) dissolving an emulsifier in deionized water to form a clear and transparent solution to obtain an aqueous phase;

[0017] b) slowly adding the functional ionic liquid as the oil phase into the water phase and mechanically stirring to emulsify;

[0018] c) adding the silica sol dropwise to the emulsion while maintaining a stirring speed of 200 to 600 r / min, and continuing the reaction for 12 to 48 hours. After the reaction is completed, washing with deionized water until neutral, filtering, and drying to obtain silica microcapsules.

[0019] Optionally, the amount of emulsifier added is 0.5 to 2.5 parts by weight,

[0020] The amount of deionized water added is 95 to 115 parts by weight;

[0021] The amount of functional ionic liquid added is 10 to 30 parts by weight;

[0022] The amount of silica sol added is 15 to 50 parts by weight.

[0023] Optionally, during the emulsification process of the oil phase and the water phase, the stirring speed is 5000 to 15000 rpm and the stirring time is 5 to 15 minutes;

[0024] The silica sol drop acceleration rate is 0.5-1.5 mL / min;

[0025] The drying process is carried out at a constant temperature of 30-55°C until constant weight is achieved.

[0026] In a second aspect, the present application provides a micro-arc oxidation method, comprising the following steps:

[0027] a) pre-treating the substrate to obtain a pre-treated substrate;

[0028] b) placing the pretreated substrate as an anode in an electrolytic cell, adding the micro-arc oxidation electrolyte provided by any one of the first aspects above, and performing micro-arc oxidation treatment;

[0029] c) cleaning and drying the substrate after the micro-arc oxidation treatment to obtain a finished product.

[0030] Optionally, the pre-treatment includes polishing, cleaning, and drying the substrate in sequence;

[0031] During the micro-arc oxidation process, the power supply is bipolar and the current density is 5-10A / dm 2 , duty cycle 10~80%, frequency 200~1000Hz.

[0032] The micro-arc oxidation method provided in the present application, when used in conjunction with the micro-arc oxidation electrolyte of the first aspect described above, can form a dense, stable, and high-strength protective film on the surface of the workpiece, thereby enhancing the protective effect on the workpiece.

[0033] The micro-arc oxidation method provided in this application is also easy to operate and can be promoted for use. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0035] Figure 1A test diagram of the tribological properties of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 provided in one embodiment of the present application;

[0036] Figure 2 Microscopic morphology of the sample coatings provided in Example 1 and Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts also fall within the scope of protection of this application.

[0038] In a first aspect, the present application provides a micro-arc oxidation electrolyte comprising 5-15 g / L silicate, 5-30 g / L phosphate, 0-5 g / L pH regulator, 0-10 g / L potassium fluoride, and 1-10 g / L silica microcapsules.

[0039] The protective layer formed by the electrolyte of the present application after micro-arc oxidation has the following properties:

[0040] (1) Coating appearance: white, uniform, and free of defects;

[0041] (2) Coating adhesion: ≥60MPa, drawing method GB / T5210-2006;

[0042] (3) Coating hardness: ≥500HV, micro Vickers hardness GB / T9790-2021.

[0043] In the present application, the amount of pH regulator and potassium fluoride can be adjusted according to the material of the substrate. For example, when the substrate is aluminum and its alloys, an alkaline pH regulator needs to be added to remove the oxide film on the surface of the substrate, but potassium fluoride does not need to be added. When the substrate is magnesium and its alloys, the pH regulator does not need to be added, but potassium fluoride needs to be added to promote metal passivation and film growth.

[0044] The micro-arc oxidation electrolyte provided in this application has the following beneficial effects:

[0045] 1) Adding silicate and phosphate as film-forming agents to the electrolyte will form a ceramic protective film (also known as coating) on ​​the surface of the protected workpiece after electrolysis, thereby improving the strength and impact resistance of the protective film formed by micro-arc oxidation and extending its service life.

[0046] 2) In the present application, silica microcapsules are added to the electrolyte, which contain ionic liquids that play a corrosion-inhibiting role. The silica microcapsules can protect the ionic liquid from burning during the micro-arc oxidation process on the one hand, and on the other hand, prevent the leakage of the ionic liquid, thereby improving the durability of the coating.

[0047] 3) During the micro-arc oxidation process, the silica microcapsules added to the electrolyte can adhere to and fix on the surface of the workpiece together with the film-forming agent. When the protective film is damaged due to corrosion or friction, they are released to repair the damaged surface and form a lubricating and anti-corrosion film layer. The addition of silica microcapsules gives the coating formed by micro-arc oxidation the integrated functions of friction reduction, wear resistance and corrosion resistance.

[0048] The electrolyte of the present application can form a protective film with the micro-arc oxidation coating as the main body during the micro-arc oxidation process. The protective film has high hardness and bonding strength, greatly improving the load-bearing capacity and wear resistance of the light alloy surface. The silica microcapsules protect the ionic liquid from burning during the micro-arc oxidation process on the one hand, and prevent the ionic liquid from leaking on the other hand, thereby improving the durability of the coating. The functional ionic liquid is released when the coating is damaged by corrosion or friction, repairing the damaged surface and forming a lubricating anti-corrosion film layer, giving the composite coating the integrated functions of friction reduction, wear resistance and corrosion resistance. Compared with traditional mineral nanocontainers, the silica microcapsules prepared by the present invention have a larger load capacity and lower leakage. Compared with traditional corrosion inhibitors, the functional ionic liquid used in the present invention can simultaneously achieve friction reduction, wear resistance and corrosion resistance.

[0049] Optionally, the concentration of the silica microcapsules is 1 to 10 g / L.

[0050] Optionally, the silicate comprises Na2SiO3·nH2O and potassium silicate;

[0051] Where n=0~12.

[0052] In the present application, the silicate is a water-soluble silicate, Na2SiO3·nH2O, which is a hydrate of sodium silicate, such as sodium silicate nonahydrate, etc. When n=0, it is anhydrous sodium silicate.

[0053] Optionally, the phosphate includes one or more of sodium trimetaphosphate, sodium hexametaphosphate, sodium tripolyphosphate, sodium polyphosphate, sodium phosphate, and potassium polyphosphate.

[0054] In this application, the presence of phosphates and silicates as film-forming agents will not only enhance the conductivity of the solution, generate more discharge center channels, and improve oxidation efficiency, but also form a ceramic film layer after micro-arc oxidation, thereby improving the strength of the protective film after oxidation.

[0055] Optionally, the pH adjuster includes one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium hydroxide.

[0056] In the present application, the pH adjuster is a base, which can be an organic strong base such as a quaternary ammonium base, or an inorganic strong base such as sodium hydroxide or potassium hydroxide.

[0057] Alternatively, silica microcapsules are prepared as follows:

[0058] a) dissolving an emulsifier in deionized water to form a clear and transparent solution to obtain an aqueous phase;

[0059] b) slowly adding the functional ionic liquid as the oil phase into the water phase and mechanically stirring to emulsify;

[0060] c) adding the silica sol dropwise to the emulsion while maintaining a stirring speed of 200 to 600 r / min, and continuing the reaction for 12 to 48 hours. After the reaction is completed, washing with deionized water until neutral, filtering, and drying to obtain silica microcapsules.

[0061] In the present application, during the addition of silica sol, the stirring rate affects the particle size of the finally prepared silica microcapsules. The greater the stirring rate, the smaller the particle size of the prepared silica microcapsules. In specific production, the stirring rate can be adjusted as needed.

[0062] In the present application, when the aqueous phase is added in step b), the rate of water addition is controlled to be 2-5 mL / min.

[0063] Optionally, the amount of emulsifier added is 0.5 to 2.5 parts by weight,

[0064] The amount of deionized water added is 95 to 115 parts by weight;

[0065] The amount of functional ionic liquid added is 10 to 30 parts by weight;

[0066] The amount of silica sol added is 15 to 50 parts by weight.

[0067] In the present application, the emulsifier may be a nonionic surfactant and / or a cationic surfactant. For example, the emulsifier used in the present application is a mixture of a nonionic emulsifier OP-10 and a cationic emulsifier cetyl ammonium chloride (CTAC) in a mass ratio of 1:1.

[0068] Functional ionic liquids are ionic liquids with anti-corrosion functions, such as conventional imidazole salts and pyrrole salts ionic liquids, such as benzotriazole ionic liquids, or ionic liquids provided in application documents with application numbers CN202310843741.5, CN202010978771.3, CN201911225370.4, and CN202411572250.2 (however, compared with the ionic liquids provided in the above application documents, conventional ionic liquids have certain anti-corrosion capabilities, but their anti-friction and anti-wear lubrication properties are relatively poor).

[0069] Optionally, during the emulsification process of the oil phase and the water phase, the stirring speed is 5000-15000 rpm, the stirring time is 5-15 min, and the silica sol drop acceleration rate is 0.5-1.5 mL / min;

[0070] The drying process is carried out at a constant temperature of 30-55°C until constant weight is achieved.

[0071] In this application, during the emulsification process of the oil phase and the aqueous phase, the higher the stirring rate, the faster the emulsification. Emulsification at a stirring rate of 5000-15000 rpm not only shortens the emulsification time of the system but also allows the formed emulsion to exist in a more stable form. In addition, since the oil phase and the aqueous phase mix during the emulsification process to form an oil-in-water structure, that is, emulsion droplets are formed with the functional ionic liquid oil phase droplets as the center and surrounded by water molecules, the shear force provided by the stirring process also affects the size of the emulsion droplets. The higher the stirring rate, the smaller the droplets formed, making it easier to prepare silica nano-microcapsules with smaller particle sizes in the later stage.

[0072] In this application, silica sol is a dispersion of nano-scale silica particles in water or a solvent (which can be expressed as SiO2·nH2O). Silica sol can be prepared by acidolysis of sodium silicate or hydrolysis of tetraethoxysilane. After being added to the above-mentioned emulsification system, the silica sol is mixed with the emulsion. The essence of the emulsion is an oil-in-water structure, that is, the small droplets of oily ionic liquid are surrounded by water molecules. Because the silica sol nanoparticles are hydrophilic and disperse in water, the silica sol will disperse in the water around the oily droplets, gradually aggregating into spheres, and encapsulating the oil-phase ionic liquid within the spherical silica nanoparticles, forming a core-shell structure with the ionic liquid as the core and the silica as the shell, namely, silica nanocapsules. During this process, the silica sol should be dispersed as evenly as possible, that is, the addition rate should not be too fast. Otherwise, the added silica sol will be unevenly dispersed and will polymerize itself, which will not only make it difficult to form silica nanocapsules (in this case, solid silica spheres will be produced), but also produce silica particles with larger particle sizes due to the polymerization of the silica sol, resulting in the undesirable consequence of uneven particle size of the produced silica nanocapsules. Therefore, the addition rate of the silica sol should be controlled at a low value, and the silica sol can be added in a controlled manner using a peristaltic pump.

[0073] In a second aspect, the present application provides a micro-arc oxidation method, comprising the following steps:

[0074] a) pre-treating the substrate to obtain a pre-treated substrate;

[0075] b) placing the pretreated substrate as an anode in an electrolytic cell, adding the micro-arc oxidation electrolyte provided by any one of the first aspects above, and performing micro-arc oxidation treatment;

[0076] c) cleaning and drying the substrate after the micro-arc oxidation treatment to obtain a finished product.

[0077] The micro-arc oxidation method provided in the present application, when used in conjunction with the micro-arc oxidation electrolyte of the first aspect described above, can form a dense, stable, and high-strength protective film on the surface of the workpiece, thereby enhancing the protective effect on the workpiece.

[0078] The substrate in the present application is a metal element or a metal alloy, such as aluminum, magnesium, titanium or other metal elements or alloys.

[0079] The micro-arc oxidation method provided in this application is also easy to operate and implement, and can be promoted for use.

[0080] Optionally, the pre-treatment includes polishing, cleaning, and drying the substrate in sequence;

[0081] During the micro-arc oxidation process, the power supply is bipolar and the current density is 5-10A / dm 2 , duty cycle 10~80%, frequency 200~1000Hz.

[0082] In the present application, polishing is to sandblast the substrate to remove rust spots on the surface of the substrate, and then polish it with 800 mesh and 1000 mesh sandpaper in sequence to remove the surface passivation film.

[0083] During the sandblasting process, for example, a blasting material with a particle size of 100 to 120 mesh can be used for treatment, and the blasting material can be selected from garnet, corundum, quartz sand, silicon oxide, glass beads, silicon carbide, aluminum oxide and other materials.

[0084] Cleaning: The polished substrate is ultrasonically cleaned (the frequency during the ultrasonic process is 24-30kHz and the ultrasonic time is 15-20 minutes), and then cleaned again with an organic solvent (such as anhydrous ethanol, acetone, etc.);

[0085] Drying: It can be done by heating or drying with hot air.

[0086] Example

[0087] The silicon dioxide microcapsules in the following examples were prepared according to the following method:

[0088] (1) Dissolve 0.7 g of OP-10 and 0.3 g of CTAC (cetyl ammonium chloride) in 100 mL of deionized water to obtain an aqueous phase;

[0089] (2) Dissolve 25 g of sodium silicate in 100 mL of deionized water and adjust the pH to 2.95 with hydrochloric acid to obtain silica sol;

[0090] (3) 20 g of functional ionic liquid (the ionic liquid provided in the public document with application number CN201911225370.4 is used in this application) is slowly added to the aqueous phase, maintaining a stirring speed of 12000 r / min and an emulsification time of 10 min;

[0091] (4) Maintaining the stirring speed at 250 r / min, 60 g of silica sol was added dropwise at a rate of 1 mL / min, the temperature was raised to 70 °C, and the reaction was continued for 48 h. After the reaction was completed, the silica microcapsules were washed with deionized water, filtered, and dried.

[0092] Example 1

[0093] A micro-arc oxidation method is achieved by the following steps:

[0094] S101. The substrate (AZ31 magnesium alloy) is sandblasted with 100-mesh material to remove rust spots on the surface of the substrate, and then polished with 800-mesh and 1000-mesh sandpaper in turn to remove the surface passivation film; the polished substrate is then ultrasonically washed with water, the frequency of the ultrasonic process is 28 kHz, and the ultrasonic time is 15 minutes. After the ultrasonic process is completed, the substrate is cleaned again 2 to 3 times with an organic solvent (such as anhydrous ethanol, acetone, etc.) to obtain a pretreated substrate.

[0095] S102. Place the pretreated substrate as the anode in the electrolytic cell. Weigh the chemicals in the following proportions: 8 g / L silicate (sodium silicate nonahydrate), 12 g / L phosphate (sodium hexametaphosphate), 2 g / L pH adjuster (potassium hydroxide), 4 g / L potassium fluoride, and 5 g / L silica microcapsules. Dissolve them in deionized water in this order. Stirring accelerates dissolution and prevents crystallization. After the chemicals are completely dissolved, pour them into the electrolytic cell for circulation. The water temperature for preparing the electrolyte is controlled below 20° C. When preparing the solution, ensure that the chemicals are accurately weighed, with an error within 0.2%.

[0096] S103, turn on the power (bipolar), adjust the current density to 8A / dm 2 , duty cycle 20%, frequency 500Hz, processing time 20 to 40 minutes;

[0097] S104, washing the substrate after micro-arc oxidation treatment with deionized water for 2 to 3 times, and then drying it with hot air at a temperature of 50° C. to obtain a treated product.

[0098] Example 2

[0099] A micro-arc oxidation method is achieved by the following steps:

[0100] S201. The substrate (2A12 aluminum alloy) is sandblasted with 100-mesh material to remove rust spots on the surface of the substrate, and then polished with 800-mesh and 1000-mesh sandpaper in turn to remove the surface passivation film; the polished substrate is then ultrasonically washed with water, the frequency of the ultrasonic process is 28 kHz, and the ultrasonic time is 15 minutes. After the ultrasonic process is completed, the substrate is cleaned again 2 to 3 times with an organic solvent (such as anhydrous ethanol, acetone, etc.) to obtain a pretreated substrate.

[0101] S202. Place the pretreated substrate as the anode in an electrolytic cell. Weigh the chemicals in the following proportions: 10 g / L silicate (sodium silicate nonahydrate), 15 g / L phosphate (sodium hexametaphosphate), 2 g / L pH adjuster (potassium hydroxide), and 3 g / L silica microcapsules. Dissolve them in deionized water in this order. Stirring accelerates dissolution and prevents crystallization. After the chemicals are completely dissolved, pour them into the electrolytic cell for circulation. The water temperature for preparing the electrolyte is controlled below 20°C. Ensure accurate weighing of the chemicals during solution preparation, with an error within 0.2%.

[0102] S203, turn on the power (bipolar), adjust the current density to 10A / dm 2 , duty cycle 20%, frequency 500Hz, processing time 20 to 40 minutes;

[0103] S204, washing the substrate after micro-arc oxidation treatment with deionized water for 2 to 3 times, and then drying it with hot air at a temperature of 50 to 60° C. to obtain a finished product.

[0104] Example 3

[0105] A micro-arc oxidation method is achieved by the following steps:

[0106] S301. The substrate (2A12 aluminum alloy) is sandblasted with 100-mesh material to remove rust spots on the surface of the substrate, and then polished with 800-mesh and 1000-mesh sandpaper in sequence to remove the surface passivation film; the polished substrate is then ultrasonically washed with water, the frequency of the ultrasonic process is 28 kHz, and the ultrasonic time is 15 to 20 minutes. After the ultrasonic process is completed, the substrate is cleaned again 2 to 3 times with an organic solvent (such as anhydrous ethanol, acetone, etc.) to obtain a pretreated substrate.

[0107] S302: Place the pretreated substrate as the anode in an electrolytic cell. Weigh the following chemicals: 15 g / L silicate (sodium silicate nonahydrate), 30 g / L phosphate (sodium hexametaphosphate), 5 g / L pH adjuster (potassium hydroxide), 10 g / L potassium fluoride, and 10 g / L silica microcapsules. Dissolve them in deionized water in this order. Stirring accelerates dissolution and prevents crystallization. Once the chemicals are completely dissolved, pour them back into the electrolytic cell for further circulation. The water temperature for preparing the electrolyte is controlled below 20°C. Ensure accurate weighing of the chemicals during solution preparation, with an error within 0.2%.

[0108] S303, turn on the power supply (bipolar), adjust the current density to 5A / dm 2 , duty cycle 80%, frequency 1000Hz, processing time 20 to 40min;

[0109] S304, washing the substrate after micro-arc oxidation treatment with deionized water for 2 to 3 times, and then drying it with hot air at a temperature of 50 to 60°C to obtain a finished product.

[0110] Example 4

[0111] A micro-arc oxidation method is achieved by the following steps:

[0112] S101. The substrate (AZ31 magnesium alloy) is sandblasted with 100-mesh material to remove rust spots on the surface of the substrate, and then polished with 800-mesh and 1000-mesh sandpaper in turn to remove the surface passivation film; the polished substrate is then ultrasonically washed with water, the frequency of the ultrasonic process is 28 kHz, and the ultrasonic time is 15 to 20 minutes. After the ultrasonic process is completed, the substrate is cleaned again 2 to 3 times with an organic solvent (such as anhydrous ethanol, acetone, etc.) to obtain a pretreated substrate.

[0113] S102. Place the pretreated substrate as the anode in an electrolytic cell. Weigh the following chemicals: 5 g / L silicate (sodium silicate nonahydrate), 5 g / L phosphate (sodium hexametaphosphate), 0 g / L pH adjuster (potassium hydroxide), 0 g / L potassium fluoride, and 0.5 g / L silica microcapsules. Dissolve them in deionized water in this order. Stirring accelerates dissolution and prevents crystallization. After the chemicals are completely dissolved, pour them into the electrolytic cell for circulation. The water temperature for preparing the electrolyte is controlled below 20° C. When preparing the solution, ensure that the chemicals are accurately weighed, with an error within 0.2%.

[0114] S103, turn on the power supply (bipolar), adjust the current density to 5A / dm 2 , duty cycle 10%, frequency 200-1000Hz, processing time 20-40min.

[0115] c) The substrate after micro-arc oxidation treatment is washed with deionized water for 2 to 3 times, and dried with hot air at a temperature of 50 to 60° C. to obtain a finished product.

[0116] Comparative Example 1

[0117] A micro-arc oxidation method is achieved by the following steps:

[0118] The remaining operations were the same as those in Example 1, except that no silica microcapsules were added to the electrolyte. After the micro-arc oxidation was completed, the functional ionic liquid was loaded into the pores of the coating by vacuum impregnation.

[0119] Comparative Example 2

[0120] A micro-arc oxidation method is achieved by the following steps:

[0121] The remaining operations were the same as those in Example 2, except that no silicon dioxide microcapsules were added to the electrolyte, and no functional ionic liquid was impregnated after micro-arc oxidation.

[0122] Experimental Example 1

[0123] The treated finished products of Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to a neutral salt spray resistance test according to the method of GB / T10125-2021 "Artificial atmosphere corrosion test - salt spray test"; the coating adhesion was tested according to GB / T 5210-2006 "Paint and varnish adhesion test by pull-off method"; and the coating hardness was tested according to GB / T 9790-2021 "Vickers and Knoop microhardness test for metal materials, metals and other inorganic coatings". In the neutral salt spray test, the concentration of the salt solution is 5% ± 1%, the pH is between 6.5-7.2, the salt spray chamber temperature is 35°C, and the salt spray deposition is 1-2 mL / 80 cm 2 The actual pH of the salt solution used in the test was about 6.7, and the salt spray deposition was 1.43 mL / 80 cm. 2 / h. The results are shown in Table 1:

[0124] Table 1

[0125] Sex (h) Coating adhesion (MPa) Coating hardness (HV) Example 1 1124 67 536 Example 2 1046 65 542 Example 3 1059 64 533 Example 4 1012 63 527 Comparative Example 1 240 61 501 Comparative Example 2 144 62 489

[0126] As can be seen from the experimental data in Table 1, the coatings obtained by the method of the present application have a salt spray resistance of more than 1000 hours. The salt spray resistance test shows that the coatings obtained after the electrolyte micro-arc oxidation of the present application have good anti-corrosion effects. The coating adhesion test shows that the adhesion of the coatings prepared by the method of the present application is above 60MPa, which shows that the coatings prepared by the method of the present application have strong adhesion. The data in Table 1 also show that the Vickers hardness of the coatings prepared by the method of the present application is greater than 500HV, which shows that the coatings have high hardness and wear resistance.

[0127] Experimental Example 2 Friction Coefficient Test

[0128] The friction coefficient test was conducted on the finished products prepared in Example 1 and Example 2, Comparative Example 1 and Comparative Example 2. The test conditions were: ball-on-disc contact, reciprocating wear, load 10N, frequency 2Hz, amplitude 8mm, and the dual was a 6mm steel ball. The change of the friction coefficient over time was monitored, and the results were as follows: Figure 1 shown.

[0129] pass Figure 1The results show that as the friction test progressed, the friction coefficients of Examples 1 and 2 rose to below 0.2 at 100 seconds and then remained below 0.2, demonstrating the excellent wear resistance of the coatings obtained by micro-arc oxidation using the electrolyte of the present application. The friction coefficients of Comparative Examples 1 and 2 reached 0.6 and 0.9, respectively, indicating that the coatings obtained by micro-arc oxidation using the electrolyte without the addition of silica microcapsules had poorer wear resistance.

[0130] Experimental Example 3 Coating Micromorphology

[0131] The microscopic morphology of the micro-arc oxidation samples and the composite film samples of the treated products of Example 1 and Comparative Example 2 were observed using a JEOL-6700F scanning electron microscope (SEM). Figure 2 shown.

[0132] Figure 2 (a) is an electron microscope image of the microscopic morphology of the sample of Example 1, and (b) is an electron microscope image of the microscopic morphology of the sample of Comparative Example 2.

[0133] pass Figure 2 As can be seen from the SEM image, a large amount of silica microcapsule particles are deposited on the surface of the coating of Example 1, while there are none on the surface of the coating of Comparative Example 2.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A magnesium alloy or aluminum alloy micro-arc oxidation electrolyte, characterized in that: Including silicate 5~15g / L, phosphate 5~30g / L, pH adjuster 0~5g / L, potassium fluoride 0~10g / L, silica microcapsule 0.5~10g / L; The silica microcapsules were prepared as follows: a) dissolving an emulsifier in deionized water to form a clear and transparent solution to obtain an aqueous phase; b) Use the functional ionic liquid as the oil phase, slowly add the water phase, and mechanically stir to emulsify; c) adding silica sol dropwise to the emulsion while maintaining a stirring speed of 200-600 r / min, and continuing the reaction for 12-48 hours. After the reaction is complete, washing with deionized water until neutral, filtering, and drying to obtain silica microcapsules; During the emulsification process of the oil phase and the water phase, the stirring speed is 5000~15000rpm and the stirring time is 5~15min; The silica sol drop acceleration rate is 0.5~1.5mL / min; The drying process is carried out at a constant temperature of 30-55°C until constant weight is reached; The emulsifier is a mixture of OP-10 and CTAC; The functional ionic liquid is an ionic liquid with anti-corrosion function; The silica sol is a dispersion of nano-scale silicon dioxide particles in water.

2. The magnesium alloy or aluminum alloy micro-arc oxidation electrolyte according to claim 1, characterized in that: The concentration of silica microcapsules is 1~10g / L.

3. The magnesium alloy or aluminum alloy micro-arc oxidation electrolyte according to claim 1, characterized in that The silicate includes Na2SiO3·nH2O and potassium silicate; Where n=0~12.

4. The magnesium alloy or aluminum alloy micro-arc oxidation electrolyte according to claim 1, characterized in that The phosphate includes one or more of sodium trimetaphosphate, sodium hexametaphosphate, sodium tripolyphosphate, sodium polyphosphate, sodium phosphate, and potassium polyphosphate.

5. The magnesium alloy or aluminum alloy micro-arc oxidation electrolyte according to claim 1, characterized in that The pH regulator includes one or more of sodium hydroxide, potassium hydroxide, and quaternary ammonium hydroxide.

6. The magnesium alloy or aluminum alloy micro-arc oxidation electrolyte according to claim 1, characterized in that The amount of emulsifier added is 0.5 to 2.5 parts by weight; The amount of deionized water added is 95 to 115 parts by weight; The amount of functional ionic liquid added is 10 to 30 parts by weight; The amount of silica sol added is 15 to 50 parts by weight.

7. A micro-arc oxidation method, characterized in that: The steps include: a) pre-treating the substrate to obtain a pre-treated substrate; b) placing the pretreated substrate as an anode in an electrolytic cell, adding the micro-arc oxidation electrolyte provided by any one of claims 1 to 6, and performing micro-arc oxidation treatment; c) Cleaning and drying the substrate after micro-arc oxidation treatment to obtain a finished product.

8. The micro-arc oxidation method according to claim 7, characterized in that: The pre-treatment includes polishing, cleaning and drying the substrate in sequence; During the micro-arc oxidation process, the power supply is bipolar and the current density is 5-10A / dm 2 , duty cycle 10~80%, frequency 200~1000Hz.

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