Method for realizing super-hydrophobic performance of magnesium alloy

Abstract

The invention discloses a method for realizing the super-hydrophobicity of a magnesium alloy, and relates to a method for realizing the super-hydrophobicity of the magnesium alloy. The invention aims to solve the problems that the water resistance, the pollution resistance and the self-cleaning performance of the surface of the existing magnesium alloy are poorer, the service life of a metal base material is short, and the application of the metal base material is limited. The method comprises: 1, magnesium alloy pretreatment; 2, ultrasonic oil removal; 3, etching a micro-arc oxidation part; 4, preparing a super-hydrophobic solution; and 5, preparing the super-hydrophobic coating. The super-hydrophobic performance of the magnesium alloy is achieved, the super-hydrophobic film layer can construct an efficient corrosion protection system by cooperatively regulating and controlling interface wettability and surface chemical characteristics, the contact angle is larger than 150 degrees, the sliding angle is smaller than 10 degrees, excellent waterproofness and self-cleaning capacity are shown, water drops and dirt are prone to slipping off from the surface, the long-term cleaning effect is kept, and the corrosion resistance of the magnesium alloy is improved. Particularly, the method has important application value in the fields of automobiles, aviation, electronic products and the like.

Description

Technical Field

[0001] The present invention relates to a method for superhydrophobicity of magnesium alloys. Background Art

[0002] As a lightweight material, magnesium alloys are widely used in fields such as automobiles, aerospace, and electronic devices. However, due to the easy oxidation and corrosion of the surface of magnesium alloys themselves, their applications are limited. In order to improve the corrosion resistance, wear resistance, and other properties of magnesium alloys, researchers have tried to use micro-arc oxidation (MAO) technology to treat their surfaces. Micro-arc oxidation forms a dense ceramic coating on the metal surface through high-voltage discharge, significantly improving the wear resistance and corrosion resistance of magnesium alloys.

[0003] However, although traditional micro-arc oxidation coatings can provide certain corrosion resistance, due to the generally existing porosity on the coating surface, their waterproofness, anti-fouling property, and self-cleaning performance are poor. Therefore, it is particularly important to develop a surface treatment method that can further enhance the hydrophobicity and self-cleaning ability of the coating.

[0004] The existing technology mainly conducts surface treatment by using low surface energy substances (such as fluorides, silanes, etc.) to enhance their superhydrophobicity, but there are problems such as poor waterproofness, anti-fouling property, and self-cleaning performance, and low service life of the metal substrate. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems that the waterproofness, anti-fouling property, and self-cleaning performance of the existing magnesium alloy surface are poor, and the service life of the metal substrate is low, which limits its application, and to provide a method for realizing the superhydrophobic performance of magnesium alloys.

[0006] A method for realizing the superhydrophobic performance of magnesium alloys is specifically completed according to the following steps:

[0007] I. Pretreatment of magnesium alloy:

[0008] The magnesium alloy is polished to obtain a magnesium alloy with a bright surface;

[0009] II. Ultrasonic degreasing:

[0010] The magnesium alloy with a bright surface is immersed in the degreasing solution, ultrasonically treated for a period of time, taken out, washed several times with water, and dried to obtain a degreased magnesium alloy;

[0011] III. Micro-arc oxidation etching:

[0012] First, the micro-arc oxidation electrolyte is added to a stainless steel cup, then the degreased magnesium alloy is immersed in the micro-arc oxidation electrolyte, and then the stainless steel cup is connected to the negative electrode of the micro-arc oxidation power supply, and the degreased magnesium alloy is connected to the positive electrode of the micro-arc oxidation power supply. At a current density of 10 A / dm 2~20 A / dm 2 Under the conditions of a duty cycle of 40% - 60% and a frequency of 40 Hz - 60 Hz, perform micro-arc oxidation for a period of time to obtain a magnesium alloy after micro-arc oxidation etching;

[0013] IV. Preparation of superhydrophobic aqueous solution:

[0014] Add heptadecafluorodecyltrimethoxysilane to absolute ethanol and perform ultrasonic treatment to obtain a superhydrophobic aqueous solution;

[0015] V. Preparation of superhydrophobic coating:

[0016] Immerse the magnesium alloy after micro-arc oxidation etching into the superhydrophobic aqueous solution, perform ultrasonic treatment for a period of time, and then perform high-temperature heat treatment to achieve the superhydrophobic performance of the magnesium alloy.

[0017] Principle and advantages of the present invention:

[0018] The present invention provides a method for realizing the superhydrophobic performance of magnesium alloy, which has many advantages; firstly, by combining micro-arc oxidation technology with the treatment of heptadecafluorodecyltrimethoxysilane, a coating with excellent superhydrophobicity can be effectively prepared, making the contact angle of the coating surface greater than 150° and the sliding angle less than 10°, showing excellent waterproof and self-cleaning capabilities. Water droplets and dirt are easy to slide off the surface, maintaining a long-term clean effect, and it has important application value especially in the fields of automobiles, aviation, and electronic products; secondly, the dense oxide film formed on the metal surface by micro-arc oxidation technology significantly improves the corrosion resistance of magnesium alloy. Especially in humid or corrosive environments, the coating provides stronger protection and effectively extends the service life of the metal substrate. Description of the drawings

[0019] Figure 1 It is the 3D surface topography of the magnesium alloy after micro-arc oxidation etching obtained in step three of Example 1;

[0020] Figure 2 It is the hydrophobic angle of the magnesium alloy after micro-arc oxidation etching obtained in step three of Example 1 and the magnesium alloys with superhydrophobic performance prepared in Examples 1 - 3;

[0021] Figure 3 It is the corrosion resistance of the magnesium alloy substrate and the magnesium alloys with superhydrophobic performance prepared in Examples 1 - 3. In the figure, 1 is the magnesium alloy substrate, 2 is Example 1, 3 is Example 2, and 4 is Example 3. Specific embodiments

[0022] Specific embodiment one: A method for realizing the superhydrophobic performance of magnesium alloy in this embodiment is specifically completed according to the following steps:

[0023] I. Pretreatment of magnesium alloy:

[0024] The magnesium alloy is polished to obtain a magnesium alloy with a bright surface;

[0025] II. Ultrasonic degreasing:

[0026] The magnesium alloy with a bright surface is immersed in the degreasing solution, ultrasonically treated for a period of time, taken out, washed with water several times, and dried to obtain a degreased magnesium alloy;

[0027] III. Micro-arc oxidation etching:

[0028] First, the micro-arc oxidation electrolyte is added to a stainless steel cup, then the degreased magnesium alloy is immersed in the micro-arc oxidation electrolyte, and then the stainless steel cup is connected to the negative electrode of the micro-arc oxidation power supply, and the degreased magnesium alloy is connected to the positive electrode of the micro-arc oxidation power supply. Under the conditions of a current density of 10 A / dm 2 ~20 A / dm 2 , a duty cycle of 40% - 60% and a frequency of 40 Hz - 60 Hz, micro-arc oxidation is carried out for a period of time to obtain a magnesium alloy after micro-arc oxidation etching;

[0029] IV. Preparation of superhydrophobic aqueous solution:

[0030] Perfluorodecyltrimethoxysilane is added to anhydrous ethanol and ultrasonically treated to obtain a superhydrophobic aqueous solution;

[0031] V. Preparation of superhydrophobic coating:

[0032] The magnesium alloy after micro-arc oxidation etching is immersed in the superhydrophobic aqueous solution, ultrasonically treated for a period of time, and then heat-treated at a high temperature to achieve the superhydrophobic performance of the magnesium alloy.

[0033] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that in Step 1, 60#, 180#, 600#, and 2000# SiC sandpapers are sequentially used to polish the magnesium alloy to obtain a magnesium alloy with a bright surface. Other steps are the same as those in Specific Embodiment 1.

[0034] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that the size of the magnesium alloy described in Step 1 is 150 mm × 30 mm × 5 mm. Other steps are the same as those in Specific Embodiment 1 or 2.

[0035] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that the composition of the degreasing solution described in Step 2 is: potassium hydroxide 20 g / L - 30 g / L, sodium dodecylbenzenesulfonate 2 g / L - 4 g / L, trisodium phosphate 25 g / L - 35 g / L, and the solvent is water. Other steps are the same as those in Specific Embodiments 1 to 3.

[0036] Embodiment 5: The difference between this embodiment and any one of Embodiments 1 to 4 is that: in Step 2, the power of the ultrasonic treatment is 100 W, and the time of the ultrasonic treatment is 10 min to 20 min. Other steps are the same as those in Embodiments 1 to 4.

[0037] Embodiment 6: The difference between this embodiment and any one of Embodiments 1 to 5 is that: in Step 2, the magnesium alloy with a bright surface is immersed in a degreasing solution at a temperature of 50°C to 60°C, ultrasonically treated for a period of time, taken out and washed 3 to 5 times with distilled water, and then dried with a hair dryer to obtain the degreased magnesium alloy. Other steps are the same as those in Embodiments 1 to 5.

[0038] Embodiment 7: The difference between this embodiment and any one of Embodiments 1 to 6 is that: in Step 3, the time of the micro-arc oxidation is 5 min to 10 min. Other steps are the same as those in Embodiments 1 to 6.

[0039] Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is that: the composition of the micro-arc oxidation electrolyte in Step 3 is: sodium bromide 20 g / L to 30 g / L, sodium sulfate 3 g / L to 8 g / L, potassium hydroxide 2 g / L to 4 g / L, sodium dodecylbenzenesulfonate 0.5 g / L to 2 g / L, sodium nitrate 1 g / L to 3 g / L, sodium chloride 3 g / L to 8 g / L, and the solvent is water. Other steps are the same as those in Embodiments 1 to 7.

[0040] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is that: the mass fraction of the super-hydrophobic aqueous solution in Step 4 is 0.5% to 2%; the power of the ultrasonic treatment in Step 4 is 100 W, and the time of the ultrasonic treatment is 10 min to 20 min. Other steps are the same as those in Embodiments 1 to 8.

[0041] Embodiment 10: The difference between this embodiment and any one of Embodiments 1 to 9 is that: the power of the ultrasonic treatment in Step 5 is 100 W, and the time of the ultrasonic treatment is 50 min to 70 min; the temperature of the high-temperature heat treatment in Step 5 is 100°C to 120°C, and the time of the high-temperature heat treatment is 10 min to 40 min. Other steps are the same as those in Embodiments 1 to 9.

[0042] The following examples are used to verify the beneficial effects of the present invention:

[0043] Example 1: A method for realizing the super-hydrophobic performance of a magnesium alloy is specifically completed according to the following steps:

[0044] I. Pretreatment of the magnesium alloy:

[0045] The magnesium alloy was polished successively with 60#, 180#, 600#, and 2000# SiC sandpapers to obtain a magnesium alloy with a bright surface;

[0046] The size of the magnesium alloy described in Step 1 was 150 mm × 30 mm × 5 mm;

[0047] II. Ultrasonic degreasing:

[0048] The magnesium alloy with a bright surface was immersed in a degreasing solution at a temperature of 50°C and ultrasonically treated for 10 min at an ultrasonic power of 100 W, washed 3 times with distilled water, and then dried with an electric hair dryer to obtain a degreased magnesium alloy;

[0049] The composition of the degreasing solution described in Step 2 was: potassium hydroxide 25 g / L, sodium dodecylbenzenesulfonate 3 g / L, trisodium phosphate 30 g / L, and the solvent was water;

[0050] III. Micro-arc oxidation etching:

[0051] First, the micro-arc oxidation electrolyte was added to a stainless steel cup, then the degreased magnesium alloy was immersed in the micro-arc oxidation electrolyte, and then the stainless steel cup was connected to the negative electrode of the micro-arc oxidation power supply, and the degreased magnesium alloy was connected to the positive electrode of the micro-arc oxidation power supply. Under the conditions of a current density of 15 A / dm 2 , a duty cycle of 50%, and a frequency of 50 Hz, micro-arc oxidation was carried out for 5 min to obtain a micro-arc oxidation etched magnesium alloy;

[0052] The composition of the micro-arc oxidation electrolyte described in Step 3 was: sodium bromide 25 g / L, sodium sulfate 5 g / L, potassium hydroxide 3 g / L, sodium dodecylbenzenesulfonate 1 g / L, sodium nitrate 2 g / L, sodium chloride 5 g / L, and the solvent was water;

[0053] IV. Preparation of superhydrophobic aqueous solution:

[0054] Perfluorodecyltrimethoxysilane was added to absolute ethanol and ultrasonically treated for 10 min at an ultrasonic power of 100 W to obtain a superhydrophobic aqueous solution;

[0055] The mass fraction of the superhydrophobic aqueous solution described in Step 4 was 1%;

[0056] V. Preparation of superhydrophobic coating:

[0057] The micro-arc oxidation etched magnesium alloy was immersed in the superhydrophobic aqueous solution and ultrasonically treated for 60 min at an ultrasonic power of 100 W, and then heat-treated at a high temperature to achieve the superhydrophobic performance of the magnesium alloy.

[0058] The temperature of the high-temperature heat treatment described in Step 5 was 120°C, and the time of the high-temperature heat treatment was 20 min.

[0059] Example 2: The difference between this example and Example 1 is that the temperature of the high-temperature heat treatment in Step 5 is 110°C, and the time of the high-temperature heat treatment is 20 min. Other steps and parameters are the same as those in Example 1.

[0060] Example 3: The difference between this example and Example 1 is that the temperature of the high-temperature heat treatment in Step 5 is 100°C, and the time of the high-temperature heat treatment is 20 min. Other steps and parameters are the same as those in Example 1.

[0061] Figure 1 is the 3D surface morphology of the micro-arc oxidation etched magnesium alloy obtained in Step 3 of Example 1;

[0062] Figure 1 shows an obvious surface rough structure, forming many sharp, mountain-like protrusions. This microscopic structure is usually formed during the micro-arc oxidation process through high-voltage discharge, resulting in typical porosity and microstructure changes. The surface is uneven, presenting a complex fine peak-like structure. This highly developed surface topological structure increases the specific surface area, and the mechanical interlocking effect significantly enhances the bonding strength of low-surface-energy substances on the substrate; secondly, the interconnected three-dimensional pore network provides an efficient transmission channel for the directional penetration of functional substances, which is conducive to the formation of a gradient interface bonding layer. Research shows that such a surface structure with multi-scale rough features can significantly improve the Cassie-Baxter state stability of the coating by regulating the behavior of the gas-liquid-solid three-phase contact line, thereby substantially improving the hydrophobic performance.

[0063] Figure 2 is the hydrophobic angle of the micro-arc oxidation etched magnesium alloy obtained in Step 3 of Example 1 and the superhydrophobic magnesium alloys prepared in Examples 1-3;

[0064] Experimental data show that the surface contact angle (CA) of the surface treated only by micro-arc oxidation etching is 52.8° (the micro-arc oxidation etched magnesium alloy obtained in Step 3 of Example 1), indicating that its surface still exhibits hydrophilic characteristics (CA < 90°). After modification with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FDTS), the hydrophobic performance is significantly enhanced: under the condition of heat treatment at 100 °C for 20 min, the CA increases to 130.6°, reaching the hydrophobic state (CA > 90°); when the temperature rises to 110 °C (the same treatment time), the CA further increases to 138.4°, showing high hydrophobicity; finally, under the optimized process at 120 °C, the CA reaches 151.2°, successfully achieving superhydrophobic performance (CA > 150°). Experimental studies show that continuing to increase the drying temperature, the contact angle remains basically constant. This is because the binary azeotropic system formed by 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS, boiling point 247 °C) and absolute ethanol (boiling point 78.5 °C) significantly improves the gas-liquid mass transfer efficiency at the critical temperature of 120 °C. This azeotropic effect strengthens the construction of the superhydrophobic interface through the following synergistic mechanisms: First, the preferential phase change of the low-boiling component ethanol forms a gas stripping effect, accelerating the directional desorption of the unreacted solvent; Second, the FAS monomer fully infiltrates the micro-nano composite structure under the drive of enhanced mass transfer, and realizes the regulation of the surface energy gradient through the condensation reaction of silanol groups; Finally, a dense perfluoroalkyl monolayer is formed on the substrate surface. This thermally induced synergistic modification effect enables low-surface-energy substances to be accurately anchored in the sub-micron pores of the multi-level rough structure, significantly improving the air cushion stability in the Cassie-Baxter state.

[0065] Figure 3 For the corrosion resistance of the magnesium alloy substrate and the superhydrophobic magnesium alloys prepared in Examples 1 to 3, in the figure, 1 is the magnesium alloy substrate, 2 is Example 1, 3 is Example 2, and 4 is Example 3;

[0066] Chemical tests show that the corrosion current density of the bare magnesium alloy substrate is 4.52×10 -4 A / cm 2 , while after surface modification: when the contact angle increases to 130.6° (hydrophobic state), the corrosion current density is significantly reduced to 9.8×10 -6 A / cm 2 , with a decrease of 98.3%; when the contact angle reaches 151.5° (superhydrophobic state), the corrosion current density further decreases to 3.89×10 - 7 A / cm 2, which is three orders of magnitude lower than that of the substrate, and the inhibition efficiency exceeds 99.9%. This phenomenon can be attributed to the dual protection mechanism of the superhydrophobic interface. The first is the physical barrier effect. The micro-nano composite rough structure significantly reduces the effective contact area between the corrosive medium and the substrate by stabilizing the Cassie-Baxter state. The second is the chemical passivation effect. The strong electron shielding characteristics of the perfluoroalkyl chains in the self-assembled monolayer of FDTS hinder the anodic dissolution reaction on the metal surface. It can be seen that the superhydrophobic film layer can construct an efficient corrosion protection system by synergistically regulating the interfacial wettability and surface chemical properties, and the protection efficiency is optimal when the contact angle > 150°. This result provides a theoretical basis for the surface functional design of magnesium alloys.

Claims

1. A method for achieving superhydrophobic properties of magnesium alloys, characterized in that The method is specifically completed according to the following steps: I. Pretreatment of magnesium alloy: The magnesium alloy is polished to obtain a magnesium alloy with a bright surface; II. Ultrasonic degreasing: The magnesium alloy with a bright surface is immersed in the degreasing solution, ultrasonically treated for a period of time, taken out, washed several times with water, and dried to obtain the degreased magnesium alloy; III. Micro-arc oxidation etching: First, add the micro-arc oxidation electrolyte into a stainless steel cup. Then, immerse the degreased magnesium alloy into the micro-arc oxidation electrolyte. Next, connect the stainless steel cup to the negative electrode of the micro-arc oxidation power supply, and connect the degreased magnesium alloy to the positive electrode of the micro-arc oxidation power supply. Perform micro-arc oxidation for a certain period of time under the conditions of a current density of 10 A / dm 2 ~20 A / dm 2 , a duty cycle of 40% - 60%, and a frequency of 40 Hz - 60 Hz to obtain the magnesium alloy after micro-arc oxidation etching; IV. Preparation of superhydrophobic aqueous solution: Perfluorodecyltrimethoxysilane is added to absolute ethanol and ultrasonically treated to obtain a superhydrophobic aqueous solution; V. Preparation of superhydrophobic coating: The magnesium alloy after micro-arc oxidation etching is immersed in the superhydrophobic aqueous solution, ultrasonically treated for a period of time, and then heat-treated at a high temperature to achieve the superhydrophobic performance of the magnesium alloy.

2. The method for realizing superhydrophobic performance of magnesium alloy according to claim 1, wherein In step I, the magnesium alloy is polished successively with 60#, 180#, 600#, and 2000# SiC sandpapers to obtain a magnesium alloy with a bright surface.

3. A method for realizing superhydrophobic performance of magnesium alloy according to claim 1, characterized in that The size of the magnesium alloy described in step I is 150mm×30mm×5mm.

4. A method for achieving superhydrophobic performance of magnesium alloy according to claim 1, characterized in that The composition of the degreasing solution described in step II is: potassium hydroxide 20g / L - 30g / L, sodium dodecylbenzenesulfonate 2g / L - 4g / L, trisodium phosphate 25g / L - 35g / L, and the solvent is water.

5. A method for achieving superhydrophobic performance of magnesium alloy according to claim 1, characterized in that The power of the ultrasonic treatment described in step II is 100W, and the time of the ultrasonic treatment is 10min - 20min.

6. A method for achieving superhydrophobic properties of magnesium alloys according to claim 1, characterized in that In step II, the magnesium alloy with a bright surface is immersed in the degreasing solution at a temperature of 50℃ - 60℃, ultrasonically treated for a period of time, taken out, washed 3 - 5 times with distilled water, and then dried with an electric hair dryer to obtain the degreased magnesium alloy.

7. A method for achieving superhydrophobic properties of magnesium alloys according to claim 1, characterized in that The time of the micro-arc oxidation described in step III is 5min - 10min.

8. A method for achieving superhydrophobic properties of magnesium alloy according to claim 1, characterized in that The composition of the micro-arc oxidation electrolyte described in step III is: sodium bromide 20g / L - 30g / L, sodium sulfate 3g / L - 8g / L, potassium hydroxide 2g / L - 4g / L, sodium dodecylbenzenesulfonate 0.5g / L - 2g / L, sodium nitrate 1g / L - 3g / L, sodium chloride 3g / L - 8g / L, and the solvent is water.

9. A method for realizing superhydrophobic performance of magnesium alloy according to claim 1, characterized in that The mass fraction of the superhydrophobic aqueous solution described in step IV is 0.5% - 2%; the power of the ultrasonic treatment described in step IV is 100W, and the time of the ultrasonic treatment is 10min - 20min.

10. A method for achieving superhydrophobic performance of magnesium alloy according to claim 1, characterized in that The power of the ultrasonic treatment described in step V is 100W, and the time of the ultrasonic treatment is 50min - 70min; the temperature of the high-temperature heat treatment described in step V is 100℃ - 120℃, and the time of the high-temperature heat treatment is 10min - 40min.

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