Preparation method of hydrophobic anticorrosive coating

Abstract

The invention discloses a preparation method of a hydrophobic anticorrosive coating, and belongs to the technical field of anticorrosive coating preparation. The method comprises the following steps: adding kaolin powder, PDMS and nano silicon dioxide powder into ethyl acetate, performing ultrasonic dispersion, and then performing magnetic stirring at room temperature to obtain a mixed emulsion; the mass ratio of the kaolin powder to the PDMS to the nano silicon dioxide powder is 1: 7: 1; then respectively adding a modifier into the mixed emulsion under a stirring condition, and stirring for a period of time at room temperature to obtain an emulsified mixed solution; adding a curing agent into the milky mixed solution, and continuously stirring for a period of time at room temperature to obtain a pre-cured mixed emulsion; and dispensing the pre-cured mixed emulsion on a substrate, and curing to obtain the hydrophobic anticorrosive coating. According to the invention, PDMS is taken as the basis, the hydrophobic property of the prepared coating is adjusted by regulating and controlling the dosage of kaolin and silicon dioxide, the relationship between the hydrophobicity and the corrosion resistance of the system is researched, and theoretical guidance is provided for preparation of the hydrophobic corrosion-resistant coating.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-corrosion coating preparation, and in particular to a method for preparing a hydrophobic anti-corrosion coating. Background Art

[0002] The adverse ecological and economic impacts of metal corrosion have driven research into the development of anti-corrosion coatings. Engineered super-hydrophobic nanostructured coatings are a promising self-cleaning and corrosion-resistant technology. Hydrophobic anti-corrosion coatings work by isolating the metal substrate from liquid corrosive media, such as water, and by extending the path for the liquid corrosive media to propagate.

[0003] However, super-hydrophilic surfaces in air are generally super-aerophobic; conversely, super-hydrophobic surfaces in air are super-aerophilic. Therefore, hydrophobic anti-corrosion coatings exhibit a higher affinity for aerophilicity than conventional coatings during operation, allowing another corrosive medium, O₂, to more easily contact the metal substrate, potentially accelerating the corrosion process. Therefore, the development of an anti-corrosion coating that also exhibits a hydrophobic effect is essential. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a method for preparing a hydrophobic anti-corrosion coating; the present invention obtains a hydrophobic coating with good anti-corrosion performance by controlling a single variable.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a hydrophobic anti-corrosion coating, comprising:

[0007] Step 1: adding kaolin powder, polydimethylsiloxane (PDMS), and nano-silica powder to ethyl acetate, ultrasonically dispersing the mixture and magnetically stirring the mixture at room temperature to obtain a mixed emulsion; the mass ratio of the kaolin powder, PDMS, and nano-silica powder is 1:7:1;

[0008] Step 2: Subsequently, the modifiers are added to the mixed emulsion under stirring conditions, and stirred at room temperature for a period of time to obtain an emulsion mixture;

[0009] Step 3: Add the curing agent to the emulsion mixture and stir continuously at room temperature for a period of time to obtain a pre-cured mixed emulsion;

[0010] Step 4: Apply the pre-cured mixed emulsion dropwise onto the substrate and cure it to obtain a hydrophobic anti-corrosion coating.

[0011] Preferably, in step 1, the kaolin powder has a particle size of 1-10 μm. The PDMS is Dow Corning PDMS184, which has a molecular weight of approximately 25,000 and a viscosity of approximately 4,000 mPa·s after mixing with a curing agent. The nano-silica powder has a particle size of 50-200 nm.

[0012] Furthermore, the mass ratio of ethyl acetate to kaolin powder is 60-100:1.

[0013] In the step 1, ultrasonic dispersion is performed for 30-60 minutes, and magnetic stirring is performed for 1-4 hours. In the step 2, the modifier is 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and the amount used is 2-3 times the mass of kaolin.

[0014] Furthermore, in step 3, the mass ratio of the curing agent to PDMS is 1:10.

[0015] Preferably, in step 4, the substrate is a Q235 steel electrode sheet or a glass sheet; the amount of the pre-cured mixed emulsion droplet is 0.5-2 mL / cm 2 .

[0016] Preferably, in step 4, the curing temperature is 70-150° C. and the curing time is 0.5-12 h.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This study briefly analyzes the anti-corrosion mechanisms of different hydrophobic coatings based on their characterization and their varying anti-corrosion capabilities. Nanosilica particles, with PDMS as a binder, form a porous film. As kaolin particles are added, they fill the pores in the film, extending the path for water and oxygen molecules in the air to contact the substrate, increasing the coating's corrosion resistance and further enhancing its corrosion resistance.

[0019] The present invention successfully prepares a hydrophobic coating with maximum anti-corrosion ability by controlling single variables of kaolin, PDMS and nano-silica powder respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 IR spectra of different coating components (a) mixture of kaolin powder and nano-silica powder, (b) PDMS and (c) the coating prepared in Example 1;

[0021] Figure 2SEM images of different hydrophobic coatings (a) Comparative Example 1, (b) Example 1, (c) Comparative Example 2, (d) Comparative Example 3, (e) Comparative Example 4, (f) Comparative Example 5, and (g) Comparative Example 6; wherein the inset is a picture of the hydrophobic angle of the corresponding coating;

[0022] Figure 3 Impedance results of (a) Comparative Examples 1-3 and Example 1 when immersed in a 3.5 wt % NaCl solution for 5 min; (b) Impedance results of Comparative Examples 1-3 and Example 1 when immersed in a 3.5 wt % NaCl solution for 30 min; (c) Impedance results of Comparative Examples 4-6 when immersed in a 3.5 wt % NaCl solution for 30 min; (d) Impedance results of Comparative Examples 4-6 when immersed in a 3.5 wt % NaCl solution for 30 min;

[0023] Figure 4 Bode plots of (a) Comparative Examples 1-3 and Example 1 when immersed in a 3.5 wt % NaCl solution for 5 min; (b) Bode plots of Comparative Examples 1-3 and Example 1 when immersed in a 3.5 wt % NaCl solution for 30 min;

[0024] Figure 5 (a) Bode plots of Comparative Examples 4-6 when immersed in a 3.5 wt % NaCl solution for 5 min; (b) Bode plots of Comparative Examples 4-6 when immersed in a 3.5 wt % NaCl solution for 30 min;

[0025] Figure 6 (a) Tafel plots of Comparative Examples 1-3 and Example 1 when immersed in a 3.5 wt % NaCl solution for 5 min; (b) Tafel plots of Comparative Examples 1-3 and Example 1 when immersed in a 3.5 wt % NaCl solution for 30 min; (c) Tafel plots of Comparative Examples 4-6 when immersed in a 3.5 wt % NaCl solution for 30 min; (d) Tafel plots of Comparative Examples 4-6 when immersed in a 3.5 wt % NaCl solution for 30 min;

[0026] Figure 7 Optical images of different hydrophobic coatings (a) Comparative Example 1, (b) Example 1, (c) Comparative Example 2, (d) Comparative Example 3, (e) Comparative Example 4, (f) Comparative Example 5, and (g) Comparative Example 6 after 300 hours of neutral salt spray; wherein the inset is a hydrophobic angle image of the corresponding coating;

[0027] Figure 8 The hydrophobic angle images of different hydrophobic coatings are (a) Comparative Example 7, (b) Example 1, and (c) Comparative Example 8;

[0028] Figure 9(a) Impedance results of Comparative Examples 7-8 and Example 1 when immersed in a 3.5 wt % NaCl solution for 5 min; (b) Impedance results of Comparative Examples 7-8 and Example 1 when immersed in a 3.5 wt % NaCl solution for 30 min;

[0029] Figure 10 The hydrophobic angle images of different hydrophobic coatings are (a) Comparative Example 9, (b) Example 1, and (c) Comparative Example 10;

[0030] Figure 11 (a) Impedance results of Comparative Examples 9-10 and Example 1 when immersed in a 3.5 wt % NaCl solution for 5 min; (b) Impedance results of Comparative Examples 9-10 and Example 1 when immersed in a 3.5 wt % NaCl solution for 30 min;

[0031] Figure 12 This is an optical image of the coating prepared in Comparative Example 11;

[0032] Figure 13 These are optical images of the coatings prepared in Comparative Examples 12-15. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0034] Unless otherwise specified, all materials and reagents used in the present invention are commercially available. The PDMS used is Dow Corning PDMS184. The kaolin powder has a particle size of 1-10 μm, and the nano-silica powder has a particle size of 50-200 nm.

[0035] The present invention provides a method for preparing a hydrophobic anti-corrosion coating, and specific embodiments are as follows.

[0036] Example 1

[0037] A method for preparing a hydrophobic and anti-corrosion coating, comprising:

[0038] 0.05 g of kaolin powder, 0.35 g of PDMS, and 0.05 g of nano-silica powder were added to 3.5 mL of ethyl acetate, ultrasonically dispersed for 30 min, and magnetically stirred at room temperature for 2 h to obtain a mixed emulsion; then, 0.10 mL of a modifier (1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane) was added to the mixed emulsion under stirring conditions and stirred at room temperature for 2 h; 2 drops of a curing agent were added to the emulsion mixture and stirred continuously at room temperature for 3 h to obtain a pre-cured mixed emulsion; the pre-cured mixed emulsion was drop-coated on a Q235 steel electrode substrate at a drop-coating amount of 2 mL / cm 2Finally, they were cured in an oven at 70°C for 12 hours to obtain coatings with different hydrophobicity, which were recorded as CK 0.05 SO 0.05 PDMS (CK represents kaolin, SO represents silica).

[0039] In order to further illustrate the beneficial effects of the present invention, the following comparative examples are constructed.

[0040] Comparative Example 1

[0041] In this comparative example, the amount of kaolin powder used was 0 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK0SO 0.05 PDMS.

[0042] Comparative Example 2

[0043] In this comparative example, the amount of kaolin powder used was 0.10 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.1 SO 0.05 PDMS.

[0044] Comparative Example 3

[0045] In this comparative example, the amount of kaolin powder used was 0.15 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.15 SO 0.05 PDMS.

[0046] Comparative Example 4

[0047] In this comparative example, the amount of kaolin powder used was 0.20 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.2 SO 0.05 PDMS.

[0048] Comparative Example 5

[0049] In this comparative example, the amount of kaolin powder used was 0.40 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.4 SO 0.05 PDMS.

[0050] Comparative Example 6

[0051] In this comparative example, the amount of kaolin powder used was 0.60 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.6 SO 0.05 PDMS.

[0052] The coatings obtained in the above examples and comparative examples were subjected to performance tests, and the results are as follows.

[0053] In order to determine the components in the coating, infrared tests were carried out on the various components in the coating. The results are as follows Figure 1shown. Figure 1 (a) is the infrared test result of the mixture of kaolin powder and nano-silicon dioxide powder. The mixed particles have an infrared spectrum of 1093 cm -1 559cm -1 There is a strong Si-O bond special vibration peak at 906cm -1 The special vibration peak of Al-OH bond which is unique to kaolin particles is shown at Figure 1 (b) is the infrared test result of pure PDMS. The coating has an infrared wavelength of 1258 cm -1 The unique -CH3 bond special vibration peak is shown at 1010cm -1 The Si-O bond special vibration peak is shown at 786cm -1 The unique Si-AC bond special vibration peak is shown at Figure 1 (c) is the infrared test result of the coating prepared in Example 1. Compared with the pure PDMS coating, the coating has a high infrared spectroscopy at 788 cm -1 The Si-AC bond special vibration peak at 1258 cm -1 The special vibration peak of -CH3 bond at 1010cm -1 The Si-O bond special vibration peak intensity is greater than that of pure PDMS coating, and the 544cm -1 The Si-O bond special vibration peak at 907cm -1 The special vibration peak of Al-OH bond at , proves that kaolin and nano-silica mixed particles are added to the mixed coating.

[0054] In order to study the surface characteristics of different hydrophobic coatings and the wettability of hydrophobic coatings, the coatings were characterized by scanning electron microscopy and hydrophobic angle test. Figure 2 The SEM images and contact angle images of the coatings prepared in Example 1 and Comparative Examples 1-6 are shown in FIG. Figure 2 It can be seen that in (a) (Comparative Example 1), (b) (Example 1), (c) (Comparative Example 2), (d) (Comparative Example 3), (e) (Comparative Example 4), (f) (Comparative Example 5) and (g) (Comparative Example 6), as the amount of kaolin powder added increases, the hydrophobic angles of the coatings are 125°, 130°, 135°, 140°, 145°, 150° and 155°, respectively, and the rolling angles of each coating are all above 25°. However, when the amount of kaolin added reaches more than 0.6g, the hydrophobic angle of the resulting coating remains essentially unchanged. Figure 2From (a), (b), (c), and (d), when the hydrophobic angle is greater than 125° and less than 140°, as the coating particles increase, the particles will block the pores in the coating. It is speculated that the coating's ability to block water molecules and oxygen molecules in the air will also increase. When the contact angle of the coating is greater than 135°, as the coating particles gradually increase, the particles gradually accumulate to form a skeleton structure, thereby forming new pores, which increases the probability of contact between the substrate and water molecules and oxygen molecules in the air. Figure 2 As shown in Figures (e), (f), and (g), as the coating's hydrophobic angle increases, the skeleton structure becomes increasingly distinct. When the skeleton reaches a certain degree of density, it accumulates and forms a lamellar structure, which re-blocks the pores and reduces the probability of contact between the substrate and water and oxygen molecules in the air. To verify this result, an electrochemical workstation was used to analyze the corrosion protection of each coating, thereby indicating the changing probability of the substrate contacting water and oxygen molecules in the air.

[0055] In order to determine the anti-corrosion ability of different hydrophobic coatings, electrochemical tests were carried out on Q235 steel electrodes coated with different hydrophobic coatings. The impedance test results are shown in Figure 2. Figure 3 As shown, Figure 3 (a) is the impedance result of the 125°-140° hydrophobic coating when immersed in 3.5wt% NaCl solution for 5 minutes. Figure 3 (b) is the impedance result of the 125°-140° hydrophobic coating when immersed in 3.5wt% NaCl solution for 30 min. Figure 3 (c) is the impedance result of the 145°-155° hydrophobic coating when immersed in 3.5wt% NaCl solution for 5 minutes. Figure 3 (d) is the impedance result of the 145°-155° hydrophobic coating when immersed in 3.5wt% NaCl solution for 30 minutes. The specific data are shown in Table 1.

[0056] Table 1 EIS data of different hydrophobic coatings

[0057]

[0058]

[0059] Depend on Figure 3 As shown in Table 1, for the coating with a hydrophobic angle of 125°-140°, when immersed in 3.5wt% NaCl solution for 5 min, CK 0.05 SO 0.05 The PDMS coating has the largest impedance ring radius, which is approximately 4.21×10 4 Ω·cm 2 , almost twice that of other hydrophobic coatings, CK 0.1 SO0.05 The impedance radius of the PDMS coating is 1.48×10 4 Ω·cm 2 , and CK0SO 0.05 The impedance radius of the PDMS coating is 1.36×10 4 Ω·cm 2 Almost the same, both larger than CK 0.15 SO 0.05 The impedance radius of the PDMS coating is 1.16×10 4 Ω·cm 2 This means that for coatings with a hydrophobic angle of 125°-140°, when immersed in 3.5wt% NaCl solution for 5 minutes, the corrosion resistance first increases and then decreases, among which the corrosion resistance of the coating with a hydrophobic angle of 130° is the best. When immersed in 3.5wt% NaCl solution for 30 minutes, CK 0.05 SO 0.05 The PDMS coating has the largest impedance ring radius, which is 3.21×10 4 Ω·cm 2 , CK 0.1 SO 0.05 The impedance radius of the PDMS coating is 1.31×10 4 Ω·cm 2 , less than CK0SO 0.05 The impedance radius of the PDMS coating is 1.46×10 4 Ω·cm 2 , are greater than CK 0.15 SO 0.05 The impedance radius of the PDMS coating is 7.87×10 3 Ω·cm 2 It is shown that for coatings with a hydrophobic angle of 125°-140°, when immersed in a 3.5wt% NaCl solution for 30 min, the anti-corrosion ability is consistent with that when immersed in a NaCl solution for 5 min.

[0060] For the coating with a hydrophobic angle of 145°-155°, CK 0.6 SO 0.05 The PDMS coating has the largest impedance ring radius, which is 2.70×10 4 Ω·cm 2 , less than CK 0.05 SO 0.05 The impedance radius of the PDMS coating is larger than CK 0.4 SO 0.05 The impedance radius of the PDMS coating is 1.32×10 4 Ω·cm 2 , are greater than CK0.2 SO 0.05 The impedance radius of the PDMS coating is 8.36×10 3 Ω·cm 2 This shows that for the coating with a hydrophobic angle of 145°-155°, the corrosion resistance shows an upward trend when immersed in 3.5wt% NaCl solution for 5 minutes, but the corrosion resistance is weaker than that of the coating with a hydrophobic angle of 130°. 0.6 SO 0.05 The PDMS coating has the largest impedance ring radius, which is 8.35×10 3 Ω·cm 2 , less than CK 0.05 SO 0.05 The impedance radius of the PDMS coating is larger than CK 0.4 SO 0.05 The impedance radius of the PDMS coating is 4.07×10 3 Ω·cm 2 , are greater than CK 0.2 SO 0.05 The impedance radius of the PDMS coating is 2.42×10 3 Ω·cm 2 It is shown that for coatings with a hydrophobic angle of 145°-155°, when immersed in NaCl solution for 30 minutes, the anti-corrosion ability is consistent with that when immersed in NaCl solution for 5 minutes.

[0061] For the Bode test of different hydrophobic coatings, the results are as follows Figure 4 、 Figure 5 shown. Figure 4 (a) is the Bode result of the 125°-140° hydrophobic coating when immersed in 3.5wt% NaCl solution for 5 minutes. Figure 4 (b) is the Bode result of the 125°-140° hydrophobic coating when immersed in 3.5wt% NaCl solution for 30 min.

[0062] Figure 5 (a) is the Bode result of the 145°-155° hydrophobic coating when immersed in 3.5wt% NaCl solution for 5 minutes. Figure 5 (b) shows the Bode results of the 145°-155° hydrophobic coating immersed in a 3.5 wt% NaCl solution for 30 min. Like the impedance in the Nyquist plot, the Bode modulus (f = 0.1 Hz) is an important electrochemical parameter for evaluating the anti-corrosion performance of organic coatings.

[0063] For the coating with a hydrophobic angle of 125°-140°, CK0.05 SO 0.05 The PDMS coating has the largest Bode modulus at f = 0.1 Hz, which is about 4.45 × 10 4 Ω·cm 2 , almost 4 times that of other hydrophobic coatings, CK 0.1 SO 0.05 The modulus of the PDMS coating is 1.65×10 4 Ω·cm 2 With CK0SO 0.05 The modulus of the PDMS coating is 1.70×10 4 Ω·cm 2 Almost the same, both larger than CK 0.15 SO 0.05 The modulus of the PDMS coating is 1.40×10 4 Ω·cm 2 This means that for the coating with a hydrophobic angle of 125°-140°, when immersed in 3.5wt% NaCl solution for 5 minutes, the corrosion resistance shows a trend of first increasing and then decreasing, among which the coating with a hydrophobic angle of 130° has the best corrosion resistance, which is consistent with the impedance diagram. When immersed in 3.5wt% NaCl solution for 30 minutes, CK 0.05 SO 0.05 The PDMS coating has a maximum modulus value of 3.20×10 4 Ω·cm 2 , CK 0.1 SO 0.05 The modulus of the PDMS coating is 1.95×10 4 Ω·cm 2 and CK0SO 0.05 The modulus of the PDMS coating is 2.01×10 4 Ω·cm 2 Almost the same, both larger than CK 0.15 SO 0.05 The impedance radius of the PDMS coating is 1.32×10 4 Ω·cm 2 The anti-corrosion law is consistent with the impedance diagram law.

[0064] For the coating with a hydrophobic angle of 145°-155°, CK 0.6 SO 0.05 The PDMS coating has the largest Bode modulus value at f = 0.1 Hz, which is about 2.27×10 4 Ω·cm 2 , greater than CK 0.4 SO 0.05 The modulus of the PDMS coating is 1.60×104 Ω·cm 2 Both greater than CK 0.2 SO 0.05 The modulus of the PDMS coating is 1.25×10 4 Ω·cm 2 This means that for the coating with a hydrophobic angle of 145°-155°, the corrosion resistance shows an upward trend when immersed in 3.5wt% NaCl solution for 5 minutes, which is consistent with the impedance diagram. 0.6 SO 0.05 The PDMS coating has a maximum modulus value of 1.10×10 4 Ω·cm 2 Greater than CK 0.4 SO 0.05 The modulus value of the PDMS coating is 7.60×10 3 Ω·cm 2 , are greater than CK 0.2 SO 0.05 The modulus value of the PDMS coating is 6.25×10 3 Ω·cm 2 , the anti-corrosion law is consistent with the impedance diagram law.

[0065] The relationship between the corrosion potential (Ecorr) and the corrosion current density (Icorr) of the hydrophobic coating in a 3.5wt% sodium chloride solution can be expressed by the Tafel polarization curve. Generally speaking, the thermodynamic state of the coating is represented by the corrosion potential, which reflects the corrosion resistance of the coating; the kinetic state of the coating is represented by the corrosion current density, which reflects the corrosion rate of the coating. For the Tafel test of different hydrophobic coatings, the results are as follows: Figure 6 shown. Figure 6 (a) is the Tafel result of the 125°-140° hydrophobic coating when immersed in 3.5wt% NaCl solution for 5 minutes. Figure 6 (b) Tafel results of the 125°-140° hydrophobic coating when immersed in 3.5 wt% NaCl solution for 30 min; Figure 6 (c) is the Tafel result of the 145°-155° hydrophobic coating when immersed in 3.5wt% NaCl solution for 5 minutes. Figure 6 (d) Tafel results for the 145°-155° hydrophobic coating when immersed in a 3.5wt% NaCl solution for 30 minutes. Table 2 lists the specific data for the corrosion potential (Ecorr), corrosion current (icorr), and corrosion rate (η) in a 3.5wt% sodium chloride electrolyte for 5 minutes and 30 minutes. Information about Ecorr and icorr can be obtained from the intersection of the cathodic and anodic polarization curves.

[0066] Table 2

[0067]

[0068]

[0069] Depend on Figure 6 As shown in Table 2, after immersion for 5 minutes, 0.05 SO 0.05 For PDMS coating, it has the largest E corr -369.030mV, minimum I corr 1.45×10 -7 A.cm -2 , proves that CK 0.05 SO 0.05 PDMS coating has the best corrosion resistance. 0.05 For PDMS coating, its E corr (-391.545mV) greater than CK 0.1 SO 0.05 E of PDMS corr (-416.480mV), both greater than CK 0.15 SO 0.05 PDMS-coated E corr (-461.158mV). For CK0SO 0.05 For PDMS coating, its i corr (-2.18×10 -7 A.cm -2 ) is less than CK 0.1 SO 0.05 PDMS coating corr (-3.14×10 -7 A.cm -2 ), are smaller than CK 0.15 SO 0.05 PDMS coating corr (1.19×10 -6 A.cm -2 This means that for the coating with a hydrophobic angle of 125°-140°, when immersed in 3.5wt% NaCl solution for 5 minutes, the corrosion resistance shows a trend of first increasing and then decreasing, which is consistent with the impedance and Bode law. When immersed in NaCl solution for 30 minutes, the Tafel polarization curve of the coating with a hydrophobic angle of 125°-140° is as follows Figure 6 As shown in (b), CK 0.05 SO 0.05 PDMS coating has the largest E corr(-377.511mV) and the minimum i corr (1.91×10 -7 A.cm -2 ). As for CK0SO 0.05 For PDMS coating, its E corr (-413.083mV) greater than CK 0.1 SO 0.05 E of PDMS corr (-435.368mV), both greater than CK 0.15 SO 0.05 PDMS-coated E corr (-500.379mV). For CK0SO 0.05 For PDMS coating, its i corr (2.60×10 -7 A.cm -2 ) is less than CK 0.1 SO 0.05 PDMS coating corr (7.47×10 -7 A.cm -2 ), are smaller than CK 0.15 SO 0.05 PDMS coating corr (1.57×10 -6 A.cm -2 ). It is shown that for coatings with a hydrophobic angle of 125°-140°, when immersed in NaCl solution for 30 minutes, the corrosion resistance shows a trend of first increasing and then decreasing, which is consistent with the impedance and Bode law.

[0070] like Figure 6 As shown in (c), after immersion for 5 minutes, for CK 0.6 SO 0.05 For PDMS coating, its E corr (-390.903mV) greater than CK 0.4 SO 0.05 PDMS-coated E corr (-422.509mV), both greater than CK 0.2 SO 0.05 PDMS-coated E corr (-437.785mV); CK 0.6 SO 0.05 PDMS coating corr (2.07×10 -7 A.cm -2 ) is less than CK 0.4 SO 0.05 PDMS coating corr(4.72×10 -7 A.cm -2 ), are smaller than CK 0.2 SO 0.05 PDMS coating corr (7.60×10 -7 A.cm -2 ). This proves that Tafel's law is consistent with impedance and Bode's law. Figure 6 As shown in (d), after immersion for 30 minutes, the 0.6 SO 0.05 For PDMS coating, its E corr (-408.253mV) greater than CK 0.4 SO 0.05 PDMS-coated E corr (-421.603mV), both greater than CK 0.2 SO 0.05 PDMS-coated E corr (-455.925mV); CK 0.6 SO 0.05 PDMS coating corr (2.21×10 -7 A.cm -2 ) is less than CK 0.4 SO 0.05 PDMS coating corr (3.47×10 -7 A.cm -2 ), are smaller than CK 0.2 SO 0.05 PDMS coating corr (8.11×10 -7 A.cm -2 ). Tafel's law is consistent with impedance and Bode.

[0071] The present invention adjusts the hydrophobicity of the coating by regulating the amount of the substance, but hydrophobicity is not proportional to the corrosion resistance. The inventor has conducted a simple analysis of the corrosion resistance mechanism of different hydrophobic coatings based on the characterization of different hydrophobic coatings and the difference in their corrosion resistance. Nano-silica particles form a porous film under the action of PDMS as a tackifier. At this time, water molecules in the air can penetrate into the substrate through the pores in the film, thereby causing a corrosion effect. As the kaolin particles increase, the kaolin particles will fill the pores in the film, thereby extending the path for water molecules in the air and oxygen molecules to contact the substrate, increasing the corrosion resistance time of the coating and further strengthening the corrosion resistance effect of the coating. When the kaolin particles increase to the same level as the silica particles, the kaolin and silica particles will form a porous skeleton structure under the action of a modifier. This structure increases the possibility of the substrate contacting water molecules and oxygen molecules in the air, thereby reducing the corrosion resistance of the coating. However, once the multi-layered skeleton structure is formed, the skeleton structures will attract and connect to form a large-area sheet structure. At this time, the skeletons will fill the pores in the skeletons, thereby extending the contact path between the substrate and the oxygen molecules and water molecules in the air, and increasing the corrosion resistance of the coating. However, there are still pores in the skeleton filling, so even if the corrosion resistance increases at this time, the corrosion resistance at the best state will be lower than the corrosion resistance at the previous best state. Therefore, when controlling the single variable of kaolin, for coatings with different hydrophobicity, the corrosion resistance of coatings with hydrophobic angles in the range of 125°-140° will first increase and then decrease. The coating with a hydrophobic angle of 130° has the greatest corrosion resistance; the corrosion resistance of coatings with hydrophobic angles in the range of 145°-155° shows a consistent upward trend.

[0072] The present invention also studies the long-term corrosion resistance of coatings with different surface hydrophobicity under the neutral salt spray test condition of 3.5wt% sodium chloride. Figure 7 It can be seen that after 300 hours of salt spray exposure, small bubbles and a large amount of red rust corrosion products appeared on the surface of the steel substrate protected by the hydrophobic coating with a surface hydrophobicity of 140° to 155°. The corrosion area was relatively large and tended to spread outward ((d)-(g)). The corrosion degree of the hydrophobic coating with a surface hydrophobicity of 125° to 140° was significantly improved ((a)-(c)). Among them, the surface rust of the coated steel substrate with a surface hydrophobicity of about 130° was less, and there were no small bubbles. At the same time, the adhesion of the coating was still good, indicating that the appropriate surface hydrophobicity can effectively enhance the barrier properties of the hydrophobic coating surface and the bonding strength between the coating and the steel substrate, greatly improving the protective performance of the coating on the steel substrate.

[0073] In order to further illustrate the beneficial effects of the present invention, the present invention also constructs the following comparative example.

[0074] Comparative Example 7

[0075] In this comparative example, the amount of PDMS used was 0.175 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK. 0.05 SO 0.05 PDMS 0.175 .

[0076] Comparative Example 8

[0077] In this comparative example, the amount of PDMS used was 0.7 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK. 0.05 SO 0.05 PDMS 0.7 .

[0078] Comparative Example 9

[0079] In this comparative example, the amount of nano-silicon dioxide powder used was 0 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.05 SOPDMS 0.35 .

[0080] Comparative Example 10

[0081] In this comparative example, the amount of nano-silicon dioxide powder used was 0.1 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.05 SO 0.1 PDMS.

[0082] Comparative Example 11

[0083] In this comparative example, the amount of nano-silicon dioxide powder used was 0.15 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.05 SO 0.1 PDMS.

[0084] Comparative Example 12

[0085] In this comparative example, PDMS was replaced with an equal amount of epoxy resin and kaolin was omitted. The remaining conditions were the same as in Example 1, and the obtained coating was recorded as CK0SO. 0.05 EP.

[0086] Comparative Example 13

[0087] In this comparative example, PDMS was replaced with an equal amount of epoxy resin, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.05 SO 0.05 EP.

[0088] Comparative Example 14

[0089] In this comparative example, PDMS was replaced by an equal amount of epoxy resin, the amount of kaolin was 0.1 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.1 SO 0.05 EP.

[0090] Comparative Example 15

[0091] In this comparative example, PDMS was replaced by an equal amount of epoxy resin, the amount of kaolin was 0.15 g, and the other conditions were the same as in Example 1. The obtained coating was recorded as CK 0.15 SO 0.05 EP.

[0092] The performance of the coating prepared in the above comparative example was compared with the hydrophobic coating prepared in Example 1, and the results are as follows.

[0093] Figure 8 The hydrophobic angle pictures of the coatings prepared by changing the PDMS dosage (Comparative Examples 7-8 and Example 1) show that from left to right, three coatings were prepared using PDMS 0.175g (Comparative Example 7), 0.35g (Example 1), and 0.7g (Comparative Example 8) as variables, and the measured hydrophobic angles were 141.2°, 127.9°, and 119.9°, that is, as the PDMS dosage increased, the hydrophobic angle of the prepared coating gradually decreased.

[0094] In order to determine the anti-corrosion ability of the coating, the coatings prepared in Comparative Example 7, Example 1 and Comparative Example 8 were subjected to electrochemical tests, wherein the impedance test results are as follows: Figure 9 As shown, Figure 9 (a) is the impedance results of different hydrophobic coatings when immersed in 3.5wt% NaCl solution for 5 min. Figure 9 (b) is the impedance results of different hydrophobic coatings when immersed in 3.5wt% NaCl solution for 30 min. The specific data are shown in Table 3.

[0095] Table 3

[0096]

[0097] It can be seen from Table 3 that with the increase of PDMS dosage, the impedance radius first increases and then decreases. When soaking for 5min and 30min, CK 0.05 SO 0.05 The impedance radius of the PDMS coating is the largest, which is 4.21×10 4 Ω·cm 2 and 3.21×10 4 Ω·cm 2 .

[0098] Figure 10In order to change the amount of nano-silica powder (Comparative Examples 9-10 and Example 1) prepared by the hydrophobic angle picture, it can be seen from the figure that from left to right, three coatings are prepared using nano-silica powder 0g (Comparative Example 9), 0.05g (Example 1), and 0.1g (Comparative Example 10) as variables, and the measured hydrophobic angles are 108.5°, 127.9°, and 145.6°, that is, with the increase of the amount of nano-silica powder, the hydrophobic angle of the prepared coating gradually increases.

[0099] In order to determine the anti-corrosion ability of the coating, the coatings prepared in Comparative Example 9, Example 1 and Comparative Example 10 were subjected to electrochemical tests, wherein the impedance test results are as follows: Figure 11 As shown, Figure 11 (a) is the impedance results of different hydrophobic coatings when immersed in 3.5wt% NaCl solution for 5 min. Figure 11 (b) is the impedance results of different hydrophobic coatings when immersed in 3.5wt% NaCl solution for 30 min. The specific data are shown in Table 4.

[0100] Table 4

[0101]

[0102] It can be seen from Table 4 that with the increase of the amount of nano-silica powder, the impedance radius first increases and then decreases. When soaking for 5 minutes and 30 minutes, CK 0.05 SO 0.05 PDMS 0.35 The impedance radius of the coating is the largest, which is 4.21×10 4 Ω·cm 2 and 3.21×10 4 Ω·cm 2 .

[0103] When the amount of nano dioxide powder added is large (Comparative Example 11), cracking occurs on the surface of the prepared coating, such as Figure 12 shown.

[0104] Regardless of whether the substrate is a Q235 steel electrode sheet or a glass sheet, after replacing the PDMS system with a conventional epoxy resin system, the coating obtained by changing the amount of kaolin (Comparative Examples 12-15) has cracks of varying sizes and uneven distribution due to the different viscosities of the epoxy resin and PDMS and the different number of particles they accommodate. Figure 13 As shown in the figure, the impedance data will be messy and measurement will be impossible.

[0105] In summary, the present invention is based on PDMS. By regulating the dosage of kaolin, silica, etc., the hydrophobic properties of the prepared coating are adjusted, the relationship between the hydrophobicity and anti-corrosion ability of the system is studied, and theoretical guidance is provided for the preparation of hydrophobic anti-corrosion coatings.

[0106] The above is a preferred embodiment of the present invention. For ordinary technicians in this technical field, making several improvements and modifications without departing from the principles of the present invention should also be considered as the scope of protection of the present invention.

Claims

1. A method for preparing a hydrophobic anti-corrosion coating, characterized in that: include: Step 1: adding kaolin powder, polydimethylsiloxane (PDMS), and nano-silica powder to ethyl acetate, ultrasonically dispersing the mixture and magnetically stirring the mixture at room temperature to obtain a mixed emulsion; the mass ratio of the kaolin powder, PDMS, and nano-silica powder is 1:7:1; Step 2: then adding a modifier to the mixed emulsion under stirring conditions, and stirring at room temperature for a period of time to obtain an emulsion mixture; Step 3: Add the curing agent to the emulsion mixture and stir continuously at room temperature for a period of time to obtain a pre-cured mixed emulsion; Step 4: Apply the pre-cured mixed emulsion dropwise onto the substrate and cure it to obtain a hydrophobic anti-corrosion coating.

2. The method for preparing a hydrophobic anticorrosive coating according to claim 1, wherein: In the step 1, the particle size of the kaolin powder is 1-10 μm; and the particle size of the nano-silicon dioxide powder is 50-200 nm.

3. The method for preparing a hydrophobic anticorrosive coating according to claim 2, wherein: The molecular weight of the PDMS is about 25,000, and the viscosity thereof is about 4,000 mPa·s after being mixed with the curing agent.

4. The method for preparing a hydrophobic anticorrosive coating according to claim 3, wherein: The mass ratio of the ethyl acetate to the kaolin powder is 60-100:

1.

5. The method for preparing a hydrophobic anticorrosive coating according to claim 4, wherein: In the step 1, ultrasonic dispersion is performed for 30-60 minutes and magnetic stirring is performed for 1-4 hours.

6. The method for preparing a hydrophobic anti-corrosion coating according to claim 5, characterized in that: In the step 2, the modifier is 1H,1H,2H,2H-perfluorodecyltriethoxysilane.

7. The method for preparing a hydrophobic anticorrosive coating according to claim 6, characterized in that: In step 3, the mass ratio of the curing agent to PDMS is 1:

10.

8. The method for preparing a hydrophobic anti-corrosion coating according to claim 7, wherein: In step 4, the substrate is a Q235 steel electrode sheet or a glass sheet; the amount of the pre-cured mixed emulsion droplet is 0.5-2 mL / cm 2 .

9. The method for preparing a hydrophobic anticorrosive coating according to claim 8, characterized in that: In step 4, the curing temperature is 70-150° C. and the curing time is 0.5-12 hours.

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