Preparation method and application of magnesium alloy surface SLIPS/LDHs composite film layer
阅读说明：本技术 一种镁合金表面SLIPS/LDHs复合膜层的制备方法及应用 (Preparation method and application of magnesium alloy surface SLIPS/LDHs composite film layer ) 是由 姚文辉 陈勇花 吴量 潘复生 于 2021-07-22 设计创作，主要内容包括：本发明涉及镁合金表面SLIPS/LDHs复合膜层的制备方法,先在镁合金基体上原位生长三元MgAlLa-LDHs膜层,进一步利用LDHs独特的离子交换性能,进行阴离子苯甲酸根的负载,然后采用含氟硅烷对LDHs进行低表面能改性,从而可以实现在其表面进行二甲基硅油的灌注,制备出SLIPS/LDHs复合膜层。复合膜层良好的疏水性可有效隔绝外界腐蚀性离子对镁合金基体的侵蚀。具有缓蚀作用的La离子、苯甲酸根离子及物理流动作用的润滑液,可在镁合金表面三重自修复一体化设计。制备方法简单、成本低,极大提高工业实用性和效率。且复合膜层可显著改善镁合金基体的耐腐蚀性能,从而促进镁合金在航空航天、汽车、电子等领域的广泛应用。(The invention relates to a preparation method of a magnesium alloy surface SLIPS/LDHs composite film, which comprises the steps of firstly growing a ternary MgAlLa-LDHs film on a magnesium alloy substrate in situ, further utilizing the unique ion exchange performance of LDHs to load anion benzoate, and then adopting fluorine-containing silane to modify LDHs with low surface energy, thereby realizing the perfusion of dimethyl silicone oil on the surface of the LDHs film and preparing the SLIPS/LDHs composite film. The good hydrophobicity of the composite film layer can effectively isolate the corrosion of external corrosive ions to the magnesium alloy matrix. La ions with a corrosion inhibition effect, benzoate ions and lubricating liquid with a physical flowing effect can be designed on the surface of the magnesium alloy in a triple self-repairing integrated mode. The preparation method is simple and low in cost, and greatly improves the industrial practicability and efficiency. And the composite film layer can obviously improve the corrosion resistance of the magnesium alloy matrix, thereby promoting the wide application of the magnesium alloy in the fields of aerospace, automobiles, electronics and the like.)
1. A preparation method of a magnesium alloy surface SLIPS/LDHs composite film layer is characterized by comprising the following specific steps:
a. firstly growing an MgAlLa-LDHs film layer on the surface of the magnesium alloy in situ: immersing the cleaned magnesium alloy substrate into the in-situ growth solution, carrying out hydrothermal reaction for 12-16 hours at 110-130 ℃, taking out, and washing with deionized water for multiple times to obtain the magnesium alloy with the MgAlLa-LDHs film; according to the amount concentration of the substances, the in-situ growth liquid is an aqueous solution of 0.02-0.1M of aluminum nitrate, 0.05-0.25M of sodium nitrate and 0.001-0.025M of lanthanum nitrate, and the pH value is 9.5-12;
b. then the magnesium alloy is immersed into 0.1M-0.5M sodium benzoate solution and reacts for 2-4 hours at 50-70 ℃;
c. a fluoride layer: b, immersing the magnesium alloy treated in the step b into an absolute ethyl alcohol solution containing fluorine silane, carrying out fluorination treatment for 2-4 hours, and drying after cleaning to obtain a fluorinated layer;
d. a lubricating liquid layer: and (3) dripping a lubricating liquid onto the surface of the magnesium alloy subjected to c treatment, and obliquely placing at an angle of 10-20 degrees to enable the lubricating liquid to flow out of the surface of the magnesium alloy to form a lubricating liquid layer, so as to finally obtain the magnesium alloy with the SLIPS/LDHs composite film layer.
2. The method for preparing the magnesium alloy surface SLIPS/LDHs composite film layer as recited in claim 1, wherein the in-situ growth liquid is an aqueous solution of 0.05M aluminum nitrate, 0.1M sodium nitrate and 0.001-0.025M lanthanum nitrate, and the pH value is 9.5-12, based on the amount and concentration of the substance.
3. The method for preparing the magnesium alloy surface SLIPS/LDHs composite film layer as recited in claim 1 or 2, wherein the pH of the in-situ growth solution in the step a is 10.8-11.2.
4. The method for preparing a magnesium alloy surface SLIPS/LDHs composite film as recited in claim 1, wherein the loading of sodium benzoate in step b is performed in a deionized water solution.
5. The method for preparing the magnesium alloy surface SLIPS/LDHs composite film layer as recited in claim 1, wherein the concentration of the fluorine-containing silane is 0.02M-0.05M.
6. The method for preparing the magnesium alloy surface SLIPS/LDHs composite film layer as recited in claim 1, wherein the fluorine-containing silane is perfluorodecyltriethoxysilane or perfluorodecyltrimethoxysilane.
7. The method for preparing the magnesium alloy surface SLIPS/LDHs composite film layer as recited in claim 1, wherein the lubricating fluid is one or more selected from the group consisting of simethicone, Krytox lubricating oil and perfluoropolyether.
8. The method for preparing the magnesium alloy surface SLIPS/LDHs composite film layer as recited in any one of claims 1 to 6, wherein the cleaning in the step a is to clean the magnesium alloy surface with deionized water; or the surface of the magnesium alloy is firstly subjected to water grinding, degreasing and deoiling and then is cleaned by deionized water.
9. The use of the method for preparing a magnesium alloy surface SLIPS/LDHs composite film according to any one of claims 1 to 7 in magnesium alloy surface treatment.
10. The product obtained by the preparation method of the magnesium alloy surface SLIPS/LDHs composite film layer according to any one of claims 1-7 is applied to the fields of aerospace, automobiles, electronic products and the like.
Technical Field
The invention belongs to the technical field of metal surface treatment, and relates to a preparation method and application of a magnesium alloy surface SLIPS/LDHs composite film layer.
Background
The magnesium alloy is used as the lightest metal structure material in the current engineering application, has the excellent performances of small density (about 2/3 of aluminum, 1/4 of iron and 1/3 of titanium), good damping property, good thermal conductivity, high specific rigidity and specific strength, easy cutting processing, higher recycling rate, rich reserves, electromagnetic interference resistance and the like, and has huge application prospect and practical value in the fields of aerospace, automobile industry, medical appliances, electronic communication and the like. However, magnesium has high chemical activity and low electrode potential, which leads to poor corrosion resistance and seriously affects the wide application of magnesium in practice. Therefore, the improvement of the corrosion resistance of the magnesium alloy to expand the application field becomes the key point of the research of domestic and foreign researchers.
Currently, the corrosion resistance of magnesium alloys can be improved by high purification, alloying and surface treatment. The high purification is to reduce the content of harmful elements and impurities as much as possible in the alloy smelting process so as to reduce the number of corrosion-prone phases; alloying is to add alloy elements capable of improving the microstructure and the structure of the magnesium alloy in the smelting process so as to improve the corrosion resistance; the surface treatment is to prepare a film layer on the surface of the magnesium alloy, so that the direct contact between a matrix and a corrosive medium is avoided, and the occurrence of corrosion is reduced. Among them, surface treatment has been widely paid attention to by researchers because of its strong operability, numerous methods and strong functionality. The currently prepared magnesium alloy coating still has the key problems of poor mechanical durability, weak matrix adhesion, low capability of resisting severe environment and the like.
The corrosion resistance of the magnesium alloy can be improved by controlling the change of the structure through heat treatment. In addition, the surface treatment and other processes have the defects of complex operation and high cost, and bring great problems to the treatment of the magnesium alloy. Therefore, efforts should be made to explore processes with the characteristics of simplicity, lower cost and lower pollution.
Disclosure of Invention
The invention aims to solve the technical problem of providing a preparation method of a magnesium alloy surface SLIPS/LDHs composite film layer which is simple, easy for industrial production and capable of realizing triple self-repairing.
In order to solve the problems, the preparation method of the magnesium alloy surface SLIPS/LDHs composite film layer provided by the invention is characterized in that firstly, a MgAlLa-LDHs film layer grows in situ on the surface of the magnesium alloy; loading the benzoate ions of the corrosion inhibitor by virtue of the unique ion exchange performance of LDHs; carrying out low surface energy treatment on the LDHs film layer by using fluorine-containing silane to obtain a fluorinated layer; so that the lubricating liquid is stabilized between MgAlLa-LDHs nano layers by means of a fluoride layer, thereby forming an outermost lubricating liquid layer.
1. A preparation method of a magnesium alloy surface SLIPS/LDHs composite film layer comprises the following specific steps:
a. firstly growing an MgAlLa-LDHs film layer on the surface of the magnesium alloy in situ: immersing the cleaned magnesium alloy substrate into the in-situ growth solution, carrying out hydrothermal reaction for 12-16 hours at 110-130 ℃, taking out, and washing with deionized water for multiple times to obtain the magnesium alloy with the MgAlLa-LDHs film; according to the amount concentration of the substances, the in-situ growth liquid is an aqueous solution of 0.02-0.1M of aluminum nitrate, 0.05-0.25M of sodium nitrate and 0.001-0.025M of lanthanum nitrate, and the pH value is 9.5-12;
b. then the magnesium alloy is immersed into 0.1M-0.5M sodium benzoate solution and reacts for 2-4 hours at 50-70 ℃;
c. a fluoride layer: b, immersing the magnesium alloy treated in the step b into an absolute ethyl alcohol solution containing fluorine silane, carrying out fluorination treatment for 2-4 hours, and drying after cleaning to obtain a fluorinated layer;
d. a lubricating liquid layer: and (3) dripping a lubricating liquid onto the surface of the magnesium alloy subjected to c treatment, and obliquely placing at an angle of 10-20 degrees to enable the lubricating liquid to flow out of the surface of the magnesium alloy to form a lubricating liquid layer, so as to finally obtain the magnesium alloy with the SLIPS/LDHs composite film layer.
Further, the in-situ growth liquid is an aqueous solution of 0.05M of aluminum nitrate, 0.1M of sodium nitrate and 0.001-0.025M of lanthanum nitrate according to the mass concentration of the substances, and the pH value is 9.5-12.
Further, the pH value of the in-situ growth solution in the step a is 10.8-11.2.
Further, the loading of sodium benzoate in step b is carried out in a deionized water solution.
Further, the concentration of the fluorine-containing silane is 0.02M-0.05M.
Further, the fluorine-containing silane is perfluorodecyl triethoxysilane or perfluorodecyl trimethoxysilane.
Further, the lubricating fluid is selected from one or more of simethicone, Krytox lubricating oil and perfluoropolyether;
the Krytox lubricating oil is Krytox series lubricating oil produced by DuPont.
Further, the cleaning in the step a is to clean the surface of the magnesium alloy by using deionized water; or the surface of the magnesium alloy is firstly subjected to water grinding, degreasing and deoiling and then is cleaned by deionized water.
2. The preparation method of any magnesium alloy surface SLIPS/LDHs composite film layer provided by the invention is applied to magnesium alloy surface treatment.
The preparation method of the SLIPS/LDHs composite film with triple self-repairing functions is suitable for various solid substrates except magnesium alloy, such as aluminum alloy, titanium alloy, steel and the like, and has good universality.
The composite film layer with the triple self-repairing SLIPS/LDHs prepared by the preparation method has excellent self-cleaning performance and anti-pollution performance: when the inclination angle is 10-15 degrees, the pollutants on the surface of the magnesium alloy slide along with water drops (5-50 mu L) and are cleaned, and no trace of the water drops or the pollutants is left.
3. The application of the product obtained by the preparation method of any magnesium alloy surface SLIPS/LDHs composite film layer in the fields of aerospace, automobiles, electronic products and the like also belongs to the protection range of the invention.
The invention has the beneficial effects that: the preparation method of the magnesium alloy surface SLIPS/LDHs composite film layer provided by the invention is simple and effective, can realize the integrated design of the triple self-repairing composite film layer on the magnesium alloy surface, simultaneously has the advantages of passive isolation, active protection, intelligent self-repairing and the like of the magnesium alloy, and can further promote the wide application of the magnesium alloy in the fields of aerospace, automobiles, electronics and the like. The film preparation provided by the invention is an in-situ growth method, and the prepared film is firmly combined with a magnesium alloy matrix; MgAlLa-LDHs not only provides a nano container for filling lubricating liquid, but also can simultaneously load anionic corrosion inhibitor benzoate ions and cationic corrosion inhibitor La ions; the filling of the SLIPS lubricating liquid can effectively seal holes on the LDHs film layer, prevent external corrosive ions from corroding the magnesium alloy, and the physical fluidity of the lubricating liquid can provide the film layer with self-repairing performance, so that the corrosion resistance of the magnesium alloy is effectively improved. In general, reagents used in the whole preparation process are low in price and easy to obtain, cannot pollute the environment, and the whole process is simple, green and environment-friendly, can meet the requirements of industrial development and mass production, and further expands the application range of the magnesium alloy.
Drawings
In order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation: in order to clearly show the technical scheme and the effect of the invention, the invention is illustrated by the following drawings:
FIG. 1 is a scanning electron micrograph of MgAlLa-LDHs on the surface of the magnesium alloy of example 1;
FIG. 2 is a scanning electron micrograph of a SLIPS/LDHs composite film layer on the surface of the magnesium alloy of example 1;
FIG. 3 is Tafel polarization curves of the magnesium alloy of AZ31, MgAlLa-LDHs film layer and SLIPS/LDHs composite film layer in the example 1 under the same coordinate;
FIG. 4 is a scanning electron micrograph of MgAlLa-LDHs on the surface of the magnesium alloy of example 2;
FIG. 5 is a scanning electron micrograph of a SLIPS/LDHs composite film layer on the surface of the magnesium alloy in example 2;
FIG. 6 is Tafel polarization curves of the magnesium alloy of AZ31, MgAlLa-LDHs film layer and SLIPS/LDHs composite film layer in the example 2 under the same coordinate;
FIG. 7 is a scanning electron micrograph of MgAlLa-LDHs on the surface of the magnesium alloy of example 3;
FIG. 8 is a scanning electron micrograph of a SLIPS/LDHs composite film layer on the surface of the magnesium alloy of example 3;
FIG. 9 is Tafel polarization curves of the magnesium alloy of AZ31, MgAlLa-LDHs film layer and SLIPS/LDHs composite film layer of example 3 under the same coordinate;
FIG. 10 is a scanning electron micrograph of MgAlLa-LDHs on the surface of the magnesium alloy of example 4;
FIG. 11 is a scanning electron micrograph of a SLIPS/LDHs composite film layer on the surface of the magnesium alloy of example 4;
FIG. 12 is Tafel polarization curves of the magnesium alloy of AZ31, MgAlLa-LDHs film layer and SLIPS/LDHs composite film layer of example 4 under the same coordinate;
FIG. 13 is a graph of water contact angle for the sample of example 1;
FIG. 14 is a graph of water contact angle for the sample of example 2;
FIG. 15 is a graph of water contact angle for the sample of example 3;
FIG. 16 is a graph of water contact angle for example 4.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments, but the scope of the present invention is not limited to the above-described embodiments.
Example 1:
a preparation method of a triple self-repairing SLIPS/LDHs composite film layer on the surface of a magnesium alloy comprises the following specific steps:
1. in-situ growth of MgAlLa-LDHs film
The magnesium alloy AZ31 after water grinding is soaked in the degreasing and degreasing aqueous solution (40 g/L of sodium hydroxide, 25g/L of sodium carbonate and 40g/L of sodium phosphate), the temperature is kept at 50 ℃ in a water bath for 60s, then 1M aqueous solution of sodium hydroxide is used for 60 alkali washing for 30s, and then 400g/L nitric acid (rho is 1.42g/ml) is used for polishing at room temperature and 25 ℃ for 1-2 min. And cleaning once with deionized water, and blow-drying with cold air. (Water milling: grinding the magnesium alloy substrate with No. 150, 600, 800, 1200, 2000 sandpaper, respectively, and ultrasonically cleaning with alcohol for 5 minutes, and then drying for later use).
A hydrothermal reaction step: firstly, pouring electrolyte into a reaction kettle inner container, then putting a cleaned magnesium alloy sample into an in-situ growth solution: 0.1M of sodium nitrate, 0.05M of aluminum nitrate and 0.001M of lanthanum nitrate, and the pH value is 10.9; and sealing the reaction kettle, and then putting the reaction kettle into an electric oven for in-situ growth, wherein the reaction temperature is 125 +/-5 ℃, and the constant-temperature reaction time is set to be 12 hours, so as to obtain the magnesium alloy with the surface growing with the ternary MgAlLa-LDHs film layer. The in-situ growth liquid is used in the concentration range of 0.02-0.1M of aluminum nitrate, 0.05-0.25M of sodium nitrate and 0.001-0.025M of lanthanum nitrate, and the pH value is 9.5-12, and in order to compare parameters of other treatment methods more objectively, the examples only show the effects of the in-situ growth liquid under the concentrations of 0.1M of sodium nitrate, 0.05M of aluminum nitrate and 0.001M of lanthanum nitrate.
2. Supported corrosion inhibitor
And (2) immersing the magnesium alloy sample of the MgAlLa-LDHs film layer in the step (1) into 0.1M sodium benzoate aqueous solution, wherein the water bath temperature is 60 +/-5 ℃, and the constant-temperature reaction time is set to be 2 hours.
3. Fluorinated layer
A fluorination treatment step: and (3) immersing the magnesium alloy sample treated in the step (2) into 0.02M absolute ethyl alcohol solution of perfluorodecyl triethoxysilane, wherein the water bath temperature is 60 +/-5 ℃, and the constant-temperature reaction time is set to be 2 hours. After the reaction is finished, the mixture is washed clean by water and then dried.
4. Lubricating liquid layer
And (3) adding excessive dimethyl silicon oil drops to the surface of the magnesium alloy sample treated in the step (3), and inclining for 1 hour at an angle of 15 +/-2 degrees to enable redundant lubricating liquid to flow out of the surface of the sample, so as to finally obtain the triple self-repairing SLIPS/LDHs composite film layer magnesium alloy. Further carrying out detection on the structure, the morphology and the like.
FIG. 1 is a scanning electron microscope photograph of the rear surface of a MgAlLa-LDHs film layer grown on a magnesium alloy. FIG. 2 is a scanning electron micrograph of the surface of a magnesium alloy with a SLIPS/LDHs composite film. FIG. 3 is Tafel polarization curves of AZ31 magnesium alloy (AZ31), MgAlLa-LDHs film magnesium alloy (LDHs) and SLIPS/LDHs composite film magnesium alloy (SLIPS) under the same coordinate. The corrosion voltage of the pure AZ31 magnesium alloy is-1491 +/-5 mV, the corrosion voltage of the MgAlLa-LDHs film magnesium alloy is-209 +/-7 mV, the corrosion voltage of the triple self-repairing SLIPS/LDHs composite film AZ31 magnesium alloy prepared in the example 1 is-833 +/-3 mV, the corrosion voltage is improved relative to the magnesium alloy substrate, the corrosion tendency is reduced, and the corrosion speed and the corrosion resistance are directly related to the corrosion current density. The corrosion current density of the pure AZ31 magnesium alloy was 6.74X 10-5Acm-2The corrosion current density of MgAlLa-LDHs film magnesium alloy is 6.87 multiplied by 10-7Acm-2SLIPS/LDHs compositeThe corrosion current density of the film layer is 5.36 multiplied by 10-9Acm-2The corrosion current density of the treated sample was reduced by two and four orders of magnitude, respectively, compared to the sample of pure AZ31 magnesium alloy. The MgAlLa-LDHs film layer and the SLIPS/LDHs composite film layer both have effective corrosion inhibition effect on AZ31 magnesium alloy, and the SLIPS/LDHs composite film layer on the surface of the magnesium alloy has more excellent corrosion resistance and can more effectively protect the magnesium matrix.
Example 2
A preparation method of a triple self-repairing SLIPS/LDHs composite film layer on the surface of a magnesium alloy comprises the following specific steps:
1. in-situ growth of MgAlLa-LDHs film
The magnesium alloy AZ31 after water grinding is soaked in the degreasing and degreasing aqueous solution (40 g/L of sodium hydroxide, 25g/L of sodium carbonate and 40g/L of sodium phosphate), the temperature is kept at 50 ℃ in a water bath for 60s, then 1M aqueous solution of sodium hydroxide is used for 60 alkali washing for 30s, and then 400g/L nitric acid (rho is 1.42g/ml) is used for polishing at room temperature and 25 ℃ for 1-2 min. And cleaning once with deionized water, and blow-drying with cold air.
A hydrothermal reaction step: firstly, pouring electrolyte into a reaction kettle inner container, then putting a cleaned magnesium alloy sample into an in-situ growth solution: 0.1M of sodium nitrate, 0.05M of aluminum nitrate and 0.001M of lanthanum nitrate, and the pH value is 10.9; and sealing the reaction kettle, and then putting the reaction kettle into an electric oven for in-situ growth, wherein the reaction temperature is 125 +/-5 ℃, and the constant-temperature reaction time is set to be 12 hours, so as to obtain the magnesium alloy with the surface growing with the ternary MgAlLa-LDHs film layer.
2. Supported corrosion inhibitor
And (3) immersing the magnesium alloy sample obtained in the step (1) into 0.3M sodium benzoate aqueous solution, wherein the water bath temperature is 60 +/-5 ℃, and the constant-temperature reaction time is set to be 2 hours.
3. Fluorinated layer
A fluorination treatment step: and (3) immersing the magnesium alloy sample in the step (2) into 0.02M absolute ethyl alcohol solution of perfluorodecyl trimethoxy silane, wherein the water bath temperature is 60 +/-5 ℃, and the constant-temperature reaction time is set to be 2 hours. After the reaction is finished, the mixture is washed clean by water and then dried.
4. Lubricating liquid layer
And (3) dropwise adding excessive perfluoropolyether to the surface of the magnesium alloy sample treated in the step (3), and inclining for 1 hour at an angle of 15 +/-2 degrees to enable redundant lubricating liquid to flow out of the surface of the sample, so that the triple self-repairing SLIPS/LDHs composite film layer magnesium alloy is obtained. Further carrying out detection on the structure, the morphology and the like.
FIG. 4 is a scanning electron micrograph of the surface of a MgAlLa-LDHs film grown on a magnesium alloy. FIG. 5 is a scanning electron micrograph of the surface of a magnesium alloy with a SLIPS/LDHs composite film. FIG. 6 is Tafel polarization curves of AZ31 magnesium alloy, MgAlLa-LDHs film magnesium alloy and SLIPS/LDHs composite film magnesium alloy under the same coordinate. Wherein the corrosion voltage of the pure AZ31 magnesium alloy is-1452 +/-3 mV, the corrosion voltage of the MgAlLa-LDHs film layer is-295 +/-7 mV, the corrosion voltage of the triple self-repairing SLIPS/LDHs composite film layer prepared by the embodiment 2 is-836 +/-5 mV, the corrosion voltage is improved, the corrosion tendency is reduced, and the corrosion speed and the corrosion resistance are directly related to the corrosion current density. The corrosion current density of the pure AZ31 magnesium alloy was 6.51X 10-5Acm-2The corrosion current density of MgAlLa-LDHs film layer magnesium alloy is 2.46 multiplied by 10-7Acm-2The corrosion current density of the SLIPS/LDHs composite film layer is 5.27 multiplied by 10-9Acm-2The corrosion current density of the treated sample was reduced by two and four orders of magnitude, respectively, compared to the sample of pure AZ31 magnesium alloy. The MgAlLa-LDHs film layer and the SLIPS/LDHs composite film layer both have effective corrosion inhibition effect on AZ31 magnesium alloy, and the SLIPS/LDHs composite film layer on the surface of the magnesium alloy has more excellent corrosion resistance and can effectively protect the magnesium matrix.
Example 3
A preparation method of a triple self-repairing SLIPS/LDHs composite film layer on the surface of a magnesium alloy comprises the following specific steps:
1. in-situ growth of MgAlLa-LDHs film
Soaking the magnesium alloy AZ31 subjected to water grinding in the degreasing and oil removing aqueous solution (40 g/L of sodium hydroxide, 25g/L of sodium carbonate and 40g/L of sodium phosphate), keeping the temperature of the aqueous solution in a water bath at 50 ℃ for 60s, washing the aqueous solution with 1M of sodium hydroxide 60 in alkali for 30s, and then polishing the aqueous solution with 400g/L of nitric acid at room temperature and 25 ℃ for 1-2 min. And cleaning once with deionized water, and blow-drying with cold air.
A hydrothermal reaction step: firstly, pouring electrolyte into a reaction kettle inner container, then putting a cleaned magnesium alloy sample into an in-situ growth solution: 0.1M of sodium nitrate, 0.05M of aluminum nitrate and 0.001M of lanthanum nitrate, and the pH value is 10.9; and sealing the reaction kettle, and then putting the reaction kettle into an electric oven for in-situ growth, wherein the reaction temperature is 125 +/-5 ℃, and the constant-temperature reaction time is set to be 12 hours, so as to obtain the magnesium alloy with the surface growing with the ternary MgAlLa-LDHs film layer.
2. Supported corrosion inhibitor
And (3) immersing the magnesium alloy sample obtained in the step (1) into 0.3M sodium benzoate aqueous solution, wherein the water bath temperature is 60 +/-5 ℃, and the constant-temperature reaction time is set to be 2 hours.
3. Fluorinated layer
A fluorination treatment step: and (3) immersing the magnesium alloy sample obtained in the step (2) into 0.03M absolute ethyl alcohol solution of perfluorodecyl trimethoxy silane, wherein the water bath temperature is 60 +/-5 ℃, and the constant-temperature reaction time is set to be 2 hours. After the reaction is finished, the mixture is washed clean by water and then dried.
4. Lubricating liquid layer
And (3) dropwise adding excessive perfluoropolyether to the surface of the magnesium alloy sample treated in the step (3), and inclining for 1 hour at an angle of 15 +/-2 degrees to enable redundant lubricating liquid to flow out of the surface of the sample, so that the triple self-repairing SLIPS/LDHs composite film layer magnesium alloy is obtained. Further carrying out detection on the structure, the morphology and the like.
FIG. 7 is a scanning electron micrograph of the surface of a MgAlLa-LDHs film grown on a magnesium alloy. FIG. 8 is a scanning electron micrograph of the surface of a magnesium alloy with a SLIPS/LDHs composite film. FIG. 9 is Tafel polarization curves of AZ31 magnesium alloy, MgAlLa-LDHs film magnesium alloy and SLIPS/LDHs composite film magnesium alloy under the same coordinate. Wherein the corrosion voltage of the pure AZ31 magnesium alloy is-1492 +/-8 mV, the corrosion voltage of the MgAlLa-LDHs film magnesium alloy is-389 +/-6 mV, and the corrosion voltage of the triple self-repairing SLIPS/LDHs composite film prepared by the embodiment 3 is-917 +/-3 mV, so that the corrosion voltage is improved, the corrosion tendency is reduced, and the corrosion speed and the corrosion resistance are directly related to the corrosion current density relative to the magnesium alloy substrate. The corrosion current density of the pure AZ31 magnesium alloy was 6.57×10-5Acm-2The corrosion current density of the MgAlLa-LDHs film layer is 6.82 multiplied by 10-7Acm-2The corrosion current density of the SLIPS/LDHs composite film layer is 3.56 multiplied by 10-9Acm-2The corrosion current density of the treated sample was reduced by two and four orders of magnitude, respectively, compared to the sample of pure AZ31 magnesium alloy. The MgAlLa-LDHs film layer and the SLIPS/LDHs composite film layer both have effective corrosion inhibition effect on AZ31 magnesium alloy, and the SLIPS/LDHs composite film layer on the surface of the magnesium alloy has more excellent corrosion resistance and can effectively protect the magnesium matrix.
Example 4
A preparation method of a triple self-repairing SLIPS/LDHs composite film layer on the surface of a magnesium alloy comprises the following specific steps:
1. in-situ growth of MgAlLa-LDHs film
The magnesium alloy AZ31 after water grinding is soaked in the degreasing and degreasing aqueous solution (40 g/L of sodium hydroxide, 25g/L of sodium carbonate and 40g/L of sodium phosphate), the temperature is kept at 50 ℃ in a water bath for 60s, then 1M aqueous solution of sodium hydroxide is used for 60 alkali washing for 30s, and then 400g/L nitric acid (rho is 1.42g/ml) is used for polishing at room temperature and 25 ℃ for 1-2 min. And cleaning once with deionized water, and blow-drying with cold air.
A hydrothermal reaction step: firstly, pouring electrolyte into a reaction kettle inner container, then putting a cleaned magnesium alloy sample into an in-situ growth solution: 0.1M of sodium nitrate, 0.05M of aluminum nitrate and 0.001M of lanthanum nitrate, and the pH value is 10.9; and sealing the reaction kettle, and then putting the reaction kettle into an electric oven for in-situ growth, wherein the reaction temperature is 125 +/-5 ℃, and the constant-temperature reaction time is set to be 12 hours, so as to obtain the magnesium alloy with the surface growing with the ternary MgAlLa-LDHs film layer.
2. Supported corrosion inhibitor
And (3) immersing the magnesium alloy sample obtained in the step (1) into 0.5M sodium benzoate aqueous solution, wherein the water bath temperature is 60 +/-5 ℃, and the constant-temperature reaction time is set to be 2 hours.
3. Fluorinated layer
A fluorination treatment step: and (3) immersing the magnesium alloy sample obtained in the step (2) into 0.05M absolute ethyl alcohol solution of perfluorodecyl trimethoxy silane, wherein the water bath temperature is 60 +/-5 ℃, and the constant-temperature reaction time is set to be 2 hours. After the reaction is finished, the mixture is washed clean by water and then dried.
4. Lubricating liquid layer
And (3) dropwise adding excess Krytox lubricating oil (DuPont) to the surface of the magnesium alloy sample treated in the step (3), and inclining for 1 hour at an angle of 15 +/-2 degrees to enable the excess lubricating oil to flow out of the surface of the sample, so that the triple self-repairing SLIPS/LDHs composite film layer magnesium alloy is obtained. Further carrying out detection on the structure, the morphology and the like.
FIG. 10 is a scanning electron micrograph of the surface of a MgAlLa-LDHs film grown on a magnesium alloy. FIG. 11 is a scanning electron micrograph of the surface of a magnesium alloy with a SLIPS/LDHs composite film. FIG. 12 is Tafel polarization curves of AZ31 magnesium alloy, MgAlLa-LDHs film magnesium alloy and SLIPS/LDHs composite film magnesium alloy under the same coordinate. Wherein the corrosion voltage of the pure AZ31 magnesium alloy is-1479 +/-7 mV, the corrosion voltage of the MgAlLa-LDHs film layer is-212 +/-3 mV, and the corrosion voltage of the triple self-repairing SLIPS/LDHs composite film layer prepared by the embodiment 4 is-715 +/-5 mV, so that the corrosion voltage is improved, the corrosion tendency is reduced, and the corrosion speed and the corrosion resistance are directly related to the corrosion current density. The corrosion current density of the pure AZ31 magnesium alloy was 6.52X 10-5Acm-2The corrosion current density of the MgAlLa-LDHs film layer is 8.15 multiplied by 10-7Acm-2The corrosion current density of the SLIPS/LDHs composite film layer is 1.45 multiplied by 10-9Acm-2The corrosion current density of the treated sample was reduced by two and four orders of magnitude, respectively, compared to the sample of pure AZ31 magnesium alloy. The MgAlLa-LDHs film layer and the SLIPS/LDHs composite film layer both have effective corrosion inhibition effect on AZ31 magnesium alloy, and the SLIPS/LDHs composite film layer on the surface of the magnesium alloy has more excellent corrosion resistance and can effectively protect the magnesium matrix.
Performance testing
The samples prepared in examples 1 to 4 were subjected to test tests such as water contact angle and corrosion resistance, and the test methods were as follows:
water contact angle: dropping 5 mu L of water drop on the surface of the magnesium alloy sample, photographing the water drop by a camera and a microscope head, fitting the outline of the water drop by a Young-Laplace method, and calculating the contact angle, wherein the water contact angle test graphs of the embodiments 1 to 4 are respectively shown in sequence in the figures 13 to 16.
Corrosion resistance: the polarization curve of the magnesium alloy specimens in a 3.5 wt.% sodium chloride solution was tested by an electrochemical workstation (Princeton 4000A). The test results are shown in the following table:
table 1 test results of SLIPS/LDHs composite film layers prepared in examples 1-4
The results show that the magnesium alloy surface SLIPS/LDHs composite film prepared by the invention has good hydrophobicity and corrosion resistance and has a wide application prospect. The invention combines the perfusion fluid body type smooth porous surface (SLIPS) on the basis of the nano lamellar sheet structure of Layered Double Hydroxides (LDHs). SLIPS is a novel surface of a super-hydrophobic membrane-like layer, and has good stability, hydrophobicity and self-repairability. A layer of compact and porous LDHs grows in situ on the surface of the magnesium alloy and is used as a good nano container for containing lubricating liquid to construct SLIPS, so that the generated hydrophobicity can further effectively isolate the corrosion of the external corrosive environment on the magnesium alloy matrix, and the corrosion resistance of the magnesium alloy is improved. The invention uses a good nano container of ternary MgAlLa-LDHs to absorb and store lubricating liquid to construct SLIPS; the unique ion exchange performance of the composite material can also provide active defense (adsorbing Cl in corrosive solution) for the membrane layer-Ions) and smart repair (release of interlayer-supported corrosion inhibitor anions). Otherwise, the LDHs film layer is effectively sealed by filling the SLIPS lubricating liquid, so that the corrosion of external corrosive ions to the magnesium alloy is prevented. The two materials supplement each other to finally prepare the SLIPS/LDHs composite film with excellent corrosion resistance.
Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.