A method for preparing a mechanically robust superhydrophobic anticorrosive coating

Abstract

The application discloses a preparation method of a mechanically robust super-hydrophobic corrosion-resistant coating, and belongs to the technical field of coating preparation.The preparation method comprises the following steps: (1) performing surface pretreatment on a base material; (2) preparing a super-hydrophobic corrosion-resistant coating material; (3) applying the super-hydrophobic corrosion-resistant coating material prepared in the step (2) to the surface of the material prepared in the step (1), and then performing vacuum drying and solidification treatment; and (4) placing the material prepared in the step (3) in a femtosecond laser machine to perform laser line scanning, and obtaining the mechanically robust super-hydrophobic corrosion-resistant coating after the end of the laser line scanning.The super-hydrophobic coating prepared by the method has the advantages of simple preparation, material environmental friendliness, good mechanical robustness, corrosion resistance and excellent self-cleaning property, the combination of the polymer coating and the super-hydrophobic coating provides a double synergistic corrosion-resistant effect for the base, the corrosion-resistant effect is remarkably improved, and the super-hydrophobic coating has good application scenarios in the fields of corrosion resistance, fluid drag reduction and self-cleaning.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating preparation, in particular to a preparation method of a mechanically robust super-hydrophobic anti-corrosion coating. BACKGROUND

[0002] Super-hydrophobic coating refers to a coating with a static water contact angle greater than 150° and a rolling contact angle less than 10°, wherein the two key factors for constructing a super-hydrophobic surface are a low surface energy material and a rough structure. The preparation methods of super-hydrophobic surfaces are thus divided into two categories: one is to construct a rough structure on a material with low surface energy, and the other is to first construct a rough structure and then realize super-hydrophobic performance by grafting a low surface energy material, which has good application prospects in the fields of corrosion prevention, self-cleaning and liquid transportation.

[0003] Application No. 201410641342.1 discloses a super-amphiphobic coating with long-lasting corrosion resistance and wear resistance, wherein the bottom layer is epoxy resin and the surface layer is modified high molecular polymer PVDF. The fluorine-containing high molecular polymer is trapped inside the coating by the reaction between the surface layer and the bottom layer, and the organic fluorine filler is also incorporated into the coating. However, the surface prepared by this patent has enhanced wear resistance, but the preparation method is too complex, and the prepared coating contains a large amount of fluorine and other substances, which are toxic and not suitable for practical application.

[0004] Application No. 201310344505.5 discloses a water-based epoxy resin and a preparation method of a super-amphiphobic coating thereof. The super-amphiphobic coating is prepared by introducing different monomers at two positions respectively based on the special structure of the water-based epoxy resin. However, the coating surface loses the super-amphiphobic property after wear, which destroys the super-amphiphobic microstructure inside the coating and is not suitable for long-term use.

[0005] In summary, the existing super-hydrophobic coating surface exhibits fragile mechanical properties and resistance, which seriously affects the super-hydrophobicity of the material and greatly restricts the application of super-hydrophobic materials in actual life. SUMMARY

[0006] The present application aims to provide a preparation method of a mechanically robust super-hydrophobic anti-corrosion coating which is durable, simple in process and environmentally friendly.

[0007] Technical solution: The preparation method of the mechanically robust super-hydrophobic anti-corrosion coating comprises the following steps:

[0008] (1) Surface pretreatment of the substrate material.

[0009] (2) Preparation of superhydrophobic anticorrosive coating: First, multi-walled carbon nanotubes are mixed with organic solvent to obtain a suspension. Then, polydimethylsiloxane and curing agent are mixed to obtain polydimethylsiloxane polymer. Finally, the suspension is added to the polydimethylsiloxane polymer and mixed evenly to obtain superhydrophobic anticorrosive coating.

[0010] (3) Apply the superhydrophobic anti-corrosion coating obtained in step (2) to the surface of the material obtained in step (1), and then perform vacuum drying and curing treatment.

[0011] (4) The material obtained in step (3) is placed in a femtosecond laser machine for laser line scanning. After the laser line scanning is completed, a superhydrophobic anti-corrosion coating with mechanical robustness is obtained.

[0012] Further, in step (1), the substrate material is carbon steel, copper or stainless steel; the surface pretreatment includes sanding treatment and acid etching treatment. The sanding treatment is carried out with SiC sandpaper, and the grit size of the SiC sandpaper is 400, 600, 800, 1000 or 1500 mesh. The acid etching treatment is carried out with dilute hydrochloric acid solution to change the surface roughness of the substrate material.

[0013] Further, in step (2), the mass ratio of the multi-walled carbon nanotubes to the organic solvent is 1-1.5:100; the organic solvent is ethanol, xylene, dichloromethane or acetone; the mass ratio of the polydimethylsiloxane to the curing agent is 5-10:1; and the mass ratio of the suspension to the polydimethylsiloxane polymer is 3-5:10.

[0014] Further, in step (3), the coating thickness is 150±30μm; the vacuum drying parameters are: pressure 0.05-0.1Mpa, time 15-20min, which can remove air inside the coating, reduce pores, and enhance the bonding between the coating and the substrate; the curing parameters are: temperature 75-85℃, time 1-2h.

[0015] Further, in step (4), the process parameters of the laser line scanning are: 1-5 scanning layers, 400-500w power, 200-400mm / s marking speed, and 1000-1500mm / s jumping speed.

[0016] Invention principle: Polydimethylsiloxane (PDMS) is a low surface energy material, and a rough structure is constructed by using low surface energy materials. This invention involves mixing multi-walled carbon nanotubes and polydimethylsiloxane (PDMS) to create a black gel mixture. After solidification, the mixture is placed in a femtosecond laser for cross-scanning. The scanning process creates irregular, columnar microstructures on the surface of the mixture. During the high-temperature laser scanning, silica (SiO2) particles are generated on the surface of the mixture, some of which are embedded in the laser-melted PDMS surface, enhancing the van der Waals forces between the two. These particles, along with the laser-etched columnar structures, form a micro / nano structure. This not only improves the surface roughness of the coating but also enhances its wear resistance and hydrophobicity. Furthermore, the gaps created by the laser scanning allow for better air storage, increasing the stability of the superhydrophobic air layer. Even after the layer has completely lost its hydrophobicity, it can be reprocessed, making it repairable and saving production costs. The combination of the polymer coating and the superhydrophobic coating provides a dual synergistic anti-corrosion effect, significantly improving the corrosion protection.

[0017] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0018] (1) The superhydrophobic coating prepared by the present invention has good mechanical robustness, which is beneficial to improving the corrosion resistance, durability, acid and alkali resistance, salt resistance and temperature resistance of metal substrates in harsh marine environments.

[0019] (2) The present invention has low preparation cost and is environmentally friendly. It can be recycled to prepare superhydrophobic coatings, which makes them re-repairable and has good application prospects. In addition, the preparation process is simple, the preparation cycle is short, and the preparation temperature requirement is low, which greatly simplifies the preparation requirements of superhydrophobic coatings.

[0020] (3) The coating prepared by the present invention has a dual synergistic anti-corrosion effect, which greatly improves the anti-corrosion efficiency and extends the service life of metal. Attached Figure Description

[0021] Figure 1 This is an optical microscope image of the anti-corrosion superhydrophobic coating obtained in Example 1 of the present invention.

[0022] Figure 2 This is a scanning electron microscope (SEM) image of the anti-corrosion superhydrophobic coating prepared in Example 1 of the present invention.

[0023] Figure 3 EDS element diagram of the anti-corrosion superhydrophobic coating obtained in Example 1 of this invention;

[0024] Figure 4 This is a schematic diagram of the non-wear wettability of the anti-corrosion superhydrophobic coating obtained in Example 1 of the present invention;

[0025] Figure 5 This is a schematic diagram of the wettability of the anti-corrosion superhydrophobic coating obtained in Example 1 of the present invention after wear;

[0026] Figure 6 XPS image of the anti-corrosion superhydrophobic coating obtained in Example 1 of this invention;

[0027] Figure 7 EIS test image of the anti-corrosion superhydrophobic coating obtained in Example 1 of this invention;

[0028] Figure 8 This is a polarization curve of the anti-corrosion superhydrophobic coating obtained in Example 1 of the present invention;

[0029] Figure 9 The image shows the contact angle of the anti-corrosion superhydrophobic coated sandpaper obtained in Example 1 of this invention after a wear test.

[0030] Figure 10 The contact angle diagram of the anti-corrosion superhydrophobic coating prepared in Example 1 of the present invention after sand abrasion test;

[0031] Figure 11 The images show the droplet bounce patterns of the anti-corrosion superhydrophobic coating obtained in Example 1 of this invention, before and after scratching. Detailed Implementation

[0032] The present invention will now be further described in conjunction with specific embodiments and accompanying drawings.

[0033] Example 1: The mechanically robust superhydrophobic anticorrosive coating of the present invention and its preparation method include the following steps:

[0034] (1) Surface pretreatment of the substrate material: The carbon steel substrate is sanded with 1500-mesh SiC sandpaper for 20 seconds, cleaned in ethanol, and ultrasonically cleaned with deionized water at 20°C for 10 minutes. It is then chemically etched in dilute hydrochloric acid solution to change its surface roughness, and then placed in deionized water for ultrasonic cleaning.

[0035] (2) Preparation of superhydrophobic anticorrosive coating: First, multi-walled carbon nanotubes and ethanol were mixed at a mass ratio of 1.5:100. After stirring with a glass rod, the mixture was ultrasonically dispersed for 15 min and ultrasonically dispersed for 5 min to obtain a suspension. Then, polydimethylsiloxane and Dow Corning 184 curing agent were prepared at a mass ratio of 10:1 and stirred evenly with a magnetic stirrer to obtain polydimethylsiloxane polymer. Finally, the suspension was added to the polydimethylsiloxane polymer at a mass ratio of 5:10. The mixture was stirred evenly with a glass rod and ultrasonically dispersed for 20 min and ultrasonically dispersed for 10 min to obtain the superhydrophobic anticorrosive coating.

[0036] (3) The superhydrophobic anti-corrosion coating is uniformly coated on the carbon steel substrate obtained in step (1) with a coating thickness of 150±30μm; then vacuum dried for 15min at a pressure of 0.05MPa, and then dried at a constant temperature of 75℃ for 1h to obtain the cured coating.

[0037] (4) The cured coating obtained in step (3) is placed in a femtosecond laser machine for laser line scanning of 5 layers with parameters of power 400w, marking speed 200mm / s and jump speed 1000mm / s, thus obtaining a superhydrophobic anti-corrosion coating with mechanical robustness.

[0038] To verify the durability of the preparation method, four samples were prepared using the method described in Example 1. The contact angles of these samples were measured after immersion in a 3.5 wt% sodium chloride corrosive solution for 24 h, 72 h, and 168 h. The results are shown in Table 1. Table 1 shows that the average initial contact angle of the prepared samples was 162°. After immersion in the 3.5 wt% sodium chloride corrosive solution for 168 h, the contact angle of the coating remained above 155°, demonstrating good stability.

[0039] Table 1. Contact angles of the samples obtained in Example 1

[0040] Sample No. 1 2 3 4 Initial contact angle 162° 163° 164° 161° Contact angle after 24h immersion in 3.5wt% sodium chloride solution 159° 160° 161° 158° Contact angle after 72h immersion in 3.5wt% sodium chloride solution 158° 159° 160° 156° Contact angle after 168h immersion in 3.5wt% sodium chloride solution 155° 156° 157° 155°

[0041] like Figure 1 As shown, this is an optical microscope image of the coating prepared in Example 1: It can be observed that after being scanned by laser lines, the surface of the mixture forms an irregular microstructure resembling columns, and gaps are formed between them.

[0042] like Figure 2 As shown, this is a SEM image of the coating prepared in Example 1: It can be observed that after line scanning, many papillary particles and irregular columnar structures are attached to its surface, which increases the surface roughness of the coating.

[0043] like Figure 3 The image shown is an EDS elemental diagram of the coating prepared in Example 1, which proves that the papillary particles on its surface are silicon after laser line scanning.

[0044] like Figure 4 and Figure 5 The diagram shows the wettability of the coating prepared in Example 1 before and after wear. It can be observed that water droplets do not easily adhere to the coating surface after wear, indicating that it still has excellent superhydrophobic properties after wear.

[0045] like Figure 6 As shown: XPS elemental diagram of the coating prepared in Example 1: It proves that the papillary particles on its surface after laser line scanning are divalent silicon.

[0046] like Figure 7 The image shown is an EIS test image of the coating prepared in Example 1. It can be observed that the impedance modulus of Example 1 is 10. 11 The power of this power is significantly higher than that of Comparative Example 1 and the bare substrate, demonstrating its excellent corrosion resistance.

[0047] like Figure 8 The following is a polarization curve of the coating prepared in Example 1: It can be observed that the self-corrosion current of Example 1 is significantly lower than that of Comparative Example 1 and the bare substrate, and the self-corrosion potential is significantly higher than that of Comparative Example 1 and the bare substrate. In the polarization curve characterization method: the higher the self-corrosion potential, the better the corrosion resistance; the lower the self-corrosion current, the better the corrosion resistance.

[0048] like Figure 9 As shown: This is a wear contact angle diagram of the coated sandpaper prepared in Example 1. It can be observed that after being worn for 500cm with 1500-grit sandpaper, its contact angle is less than 150°. Compared with other existing coatings, which are worn for 300cm and have a contact angle less than 150°, this proves that it has excellent mechanical robustness.

[0049] like Figure 10 As shown: This is a wear contact angle diagram of the coated sandpaper prepared in Example 1. It can be observed that after a long period of sand impact, its contact angle still remains at 150° upward, until it is lower than 150° after 55 minutes of impact, which proves that it has excellent mechanical robustness.

[0050] like Figure 11 As shown: the droplet bounce diagrams of the coating prepared in Example 1 before and after scratching are shown. It can be observed that after scratching, water droplets do not easily adhere to the coating surface and still maintain good superhydrophobic properties, proving that it still maintains excellent water repellency and mechanical robustness after scratching.

[0051] Example 2: The mechanically robust superhydrophobic anticorrosive coating of the present invention and its preparation method include the following steps:

[0052] (1) Surface pretreatment of the substrate material: The carbon steel substrate is sanded with 1500-mesh SiC sandpaper for 20 seconds, cleaned in ethanol, and ultrasonically cleaned with deionized water at 20°C for 10 minutes. It is then chemically etched in dilute hydrochloric acid solution to change its surface roughness, and then placed in deionized water for ultrasonic cleaning.

[0053] (2) Preparation of superhydrophobic anticorrosive coating: First, multi-walled carbon nanotubes and ethanol were mixed at a mass ratio of 1.5:100, stirred with a glass rod, and then ultrasonically dispersed for 15 min and 10 min to obtain a suspension. Then, polydimethylsiloxane and Dow Corning 184 curing agent were prepared at a mass ratio of 5:1 and stirred evenly with a magnetic stirrer to obtain polydimethylsiloxane polymer. Finally, the suspension was added to the polydimethylsiloxane polymer at a mass ratio of 4:10, stirred evenly with a glass rod, and ultrasonically dispersed for 20 min and 10 min to obtain the superhydrophobic anticorrosive coating.

[0054] (3) The superhydrophobic anti-corrosion coating is uniformly coated on the carbon steel substrate obtained in step (1) with a coating thickness of 150±30μm; then vacuum dried for 15min at a pressure of 0.05MPa, and then dried at a constant temperature of 75℃ for 1h to obtain the cured coating.

[0055] (4) The cured coating obtained in step (3) is placed in a femtosecond laser machine for laser line scanning of 5 layers with parameters of power 400w, marking speed 400mm / s and jump speed 1000mm / s, thus obtaining a superhydrophobic anti-corrosion coating with mechanical robustness.

[0056] To verify the durability of the preparation method, four samples were prepared using the method described in Example 2. The contact angles of these samples were measured after immersion in a 3.5 wt% sodium chloride corrosive solution for 24 h, 72 h, and 168 h. The results are shown in Table 2. Table 2 shows that the average initial contact angle of the prepared samples was 158°. After immersion in the 3.5 wt% sodium chloride corrosive solution for 168 h, the contact angle of the coating remained above 150°, demonstrating good stability. However, compared to Example 1, the contact angle showed a significant decrease, indicating that the reduced suspension ratio decreased the content of multi-walled carbon nanotubes in the coating, leading to easier penetration of corrosive ions into the coating interior and affecting its superhydrophobicity.

[0057] Table 2. Contact angle of the sample obtained in Example 2

[0058] Sample No. 1 2 3 4 Initial contact angle 158° 159° 160° 158° Contact angle after 24h immersion in 3.5wt% sodium chloride solution 156° 158° 159° 156° Contact angle after 72h immersion in 3.5wt% sodium chloride solution 155° 156° 156° 154° Contact angle after 168h immersion in 3.5wt% sodium chloride solution 152° 154° 155° 152°

[0059] Example 3: The preparation method of the mechanically robust superhydrophobic anticorrosive coating of the present invention includes the following steps:

[0060] (1) Surface pretreatment of the substrate material: The carbon steel substrate is sanded with 1500-mesh SiC sandpaper for 20 seconds, cleaned in ethanol, and ultrasonically cleaned with deionized water at 20°C for 10 minutes. It is then chemically etched in dilute hydrochloric acid solution to change its surface roughness, and then placed in deionized water for ultrasonic cleaning.

[0061] (2) Preparation of superhydrophobic anticorrosive coating: First, multi-walled carbon nanotubes and ethanol were mixed at a mass ratio of 1.5:100. After stirring with a glass rod, the mixture was ultrasonically dispersed for 15 min and ultrasonically dispersed for 5 min to obtain a suspension. Then, polydimethylsiloxane and Dow Corning 184 curing agent were prepared at a mass ratio of 5:1 and stirred evenly with a magnetic stirrer to obtain polydimethylsiloxane polymer. Finally, the suspension was added to the polydimethylsiloxane polymer at a mass ratio of 3:10. The mixture was stirred evenly with a glass rod and ultrasonically dispersed for 20 min and ultrasonically dispersed for min to obtain the superhydrophobic anticorrosive coating.

[0062] (3) The superhydrophobic anti-corrosion coating is uniformly coated on the carbon steel substrate surface in step one, with a coating thickness of 150±30μm; then vacuum dried for 15min at a pressure of 0.05MPa, and then dried at a constant temperature of 75℃ for 1h to obtain the cured coating.

[0063] (4) The cured coating obtained in step (3) is placed in a femtosecond laser machine for laser line scanning of 5 layers with parameters of power 500w, marking speed 400mm / s and jump speed 1500mm / s, thus obtaining a superhydrophobic anti-corrosion coating with mechanical robustness.

[0064] To verify the durability of the preparation method, four samples were prepared using the method described in Example 3. The contact angles were measured after immersion in a 3.5 wt% sodium chloride corrosive solution for 24 h, 72 h, and 168 h. The results are shown in Table 3. Table 3 shows that the average initial contact angle of the prepared samples was 157°. After immersion in the 3.5 wt% sodium chloride corrosive solution for 168 h, the contact angle of the coating remained above 150°, demonstrating good stability. However, compared to Examples 1 and 2, the contact angle showed a significant decrease. This indicates that the reduced suspension ratio decreased the content of multi-walled carbon nanotubes in the coating, leading to easier penetration of corrosive ions into the coating interior and affecting its superhydrophobicity.

[0065] Table 3. Contact angles of the samples obtained in Example 3

[0066] Sample No. 1 2 3 4 Initial contact angle 156° 158° 159° 157° Contact angle after 24h immersion in 3.5wt% sodium chloride solution 155° 156° 158° 155° Contact angle after 72h immersion in 3.5wt% sodium chloride solution 153° 154° 155° 153° Contact angle after 168h immersion in 3.5wt% sodium chloride solution 150° 152° 153° 151°

[0067] Comparative Example 1: The difference from Example 1 is that in step (2), the mass ratio of multi-walled carbon nanotubes to ethanol is 0.5:100.

[0068] To verify the durability of the preparation method, four samples were prepared using the method in Comparative Example 1. The contact angles were measured after immersion in a 3.5 wt% sodium chloride corrosive solution for 24 h, 72 h, and 168 h. The results are shown in Table 4. Table 4 shows that the average initial contact angle of the prepared samples was 155°, a decrease of 7° compared to Example 1. This indicates that the reduced content of multi-walled carbon nanotubes makes it easier for corrosive ions to penetrate the coating, thus affecting its hydrophobicity. After immersion in the 3.5 wt% sodium chloride corrosive solution for 168 h, the contact angles of the coatings were generally below 150°, indicating that the superhydrophobicity was no longer present.

[0069] Table 4 shows the contact angles of the samples obtained in Comparative Example 1.

[0070] Sample No. 1 2 3 4 Initial contact angle 155° 156° 154° 158° Contact angle after 24h immersion in 3.5wt% sodium chloride solution 153° 154° 153° 156° Contact angle after 72h immersion in 3.5wt% sodium chloride solution 150° 152° 150° 153° Contact angle after 168h immersion in 3.5wt% sodium chloride solution 148° 149° 147° 149°

[0071] Comparative Example 2: The difference from Example 1 is that in step (4), the parameters of the laser line scan are: power 600w, marking speed 500mm / s, and jumping speed 2000mm / s.

[0072] To verify the durability of the preparation method, four samples were prepared using the method in Comparative Example 2. The contact angles of these samples were measured after immersion in a 3.5 wt% sodium chloride corrosive solution for 24 h, 72 h, and 168 h. The results are shown in Table 5. Table 5 shows that the average initial contact angle of the prepared samples was 154°. After immersion in the 3.5 wt% sodium chloride corrosive solution for 168 h, the contact angle of the coating was below 145°, indicating a loss of superhydrophobicity. This demonstrates that when laser parameters reach a certain limit, line scanning can affect the durability of the coating.

[0073] Table 5 shows the contact angles of the samples obtained in Comparative Example 2.

[0074] Sample No. 1 2 3 4 Initial contact angle 154° 155° 153° 156° Contact angle after 24h immersion in 3.5wt% sodium chloride solution 153° 154° 152° 154° Contact angle after 72h immersion in 3.5wt% sodium chloride solution 151° 152° 150° 152° Contact angle after 168h immersion in 3.5wt% sodium chloride solution 143° 144° 142° 144°

Claims

1. A method for preparing a superhydrophobic anticorrosive coating with mechanical robustness, characterized in that, Includes the following steps: (1) Surface pretreatment of the substrate material; (2) Preparation of superhydrophobic anticorrosive coating: First, multi-walled carbon nanotubes are mixed with an organic solvent to obtain a suspension. Then, polydimethylsiloxane and a curing agent are mixed to obtain a polydimethylsiloxane polymer. Finally, the suspension is added to the polydimethylsiloxane polymer and mixed evenly to obtain a superhydrophobic anticorrosive coating. The mass ratio of the multi-walled carbon nanotubes to the organic solvent is 1-1.5:

100. The mass ratio of the suspension to the polydimethylsiloxane polymer is 3-5:

10. (3) Apply the superhydrophobic anticorrosive coating obtained in step (2) to the surface of the material obtained in step (1), and then perform vacuum drying and curing treatment; the coating thickness is 150±30μm; (4) The material obtained in step (3) is placed in a femtosecond laser machine for laser line scanning. After the laser line scanning is completed, a superhydrophobic anti-corrosion coating with mechanical robustness is obtained. The process parameters of the laser line scanning are: 1-5 line scanning layers, power of 400-500W, marking speed of 200-400mm / s, and jumping speed of 1000-1500mm / s.

2. The preparation method according to claim 1, characterized in that, In step (1), the substrate material is carbon steel, copper, or stainless steel.

3. The preparation method according to claim 1, characterized in that, In step (1), the surface pretreatment includes abrasive treatment and acid etching treatment.

4. The preparation method according to claim 1, characterized in that, In step (2), the organic solvent is ethanol, xylene, dichloromethane or acetone.

5. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of polydimethylsiloxane to curing agent is 5-10:

1.

6. The preparation method according to claim 1, characterized in that, In step (3), the parameters for vacuum drying are: pressure of 0.05-0.1 MPa and time of 15-20 min; the parameters for curing treatment are: temperature of 75-85℃ and time of 1-2 h.

Images