A method for preparing a hydrophobic corrosion protective coating

Abstract

The application 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, magnetically stirring at room temperature after ultrasonic dispersion, and obtaining a mixed emulsion; the mass ratio of the kaolin powder, the PDMS and the nano-silicon dioxide powder is 1:7:1; subsequently, adding a modifier into the mixed emulsion under stirring, stirring at room temperature for a period of time, and obtaining a milky mixed liquid; adding a curing agent into the milky mixed liquid, continuously stirring at room temperature for a period of time, and obtaining a pre-cured mixed emulsion; dropping and coating the pre-cured mixed emulsion on a substrate, curing, and obtaining the hydrophobic anticorrosive coating. The application takes PDMS as a basis, adjusts the hydrophobic performance of the prepared coating by regulating the amount of kaolin and silicon dioxide, studies the relationship between the hydrophobicity and the anticorrosive capacity of the system, and provides theoretical guidance for the preparation of the hydrophobic anticorrosive coating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of anticorrosive coating preparation, in particular to a preparation method of a hydrophobic anticorrosive coating. BACKGROUND

[0002] The adverse effects of metal corrosion on ecology and economy have promoted the research on the development of anticorrosive coatings, and the engineering super-hydrophobic nano-structured coating is a promising self-cleaning and anticorrosive application technology. The working principle of the hydrophobic anticorrosive coating lies in that the metal substrate is isolated from liquid corrosion media such as water, and the propagation path of the liquid corrosion media is prolonged.

[0003] However, the super-hydrophilic surface in the air is generally super-gas-repellent; on the contrary, the super-hydrophobic surface in the air is super-gas-attractive. Therefore, the hydrophobic anticorrosive coating has higher gas-attractive performance than the ordinary coating in the working process, so that another corrosion medium O2 is easier to contact with the metal substrate, and thus the corrosion process may also be accelerated. Therefore, it is necessary to develop an anticorrosive coating with hydrophobic effect. SUMMARY

[0004] To solve the problems in the prior art, the present application provides a preparation method of a hydrophobic anticorrosive coating; the present application obtains a hydrophobic coating with good anticorrosive performance by controlling a single variable.

[0005] To solve the above technical problems, the present application provides the technical solutions as follows.

[0006] The present application provides a preparation method of a hydrophobic anticorrosive coating, comprising:

[0007] Step 1: kaolin powder, polydimethylsiloxane (PDMS) and nanosilica powder are added into ethyl acetate, and after ultrasonic dispersion, magnetic stirring is carried out at room temperature to obtain a mixed emulsion; the mass ratio of the kaolin powder, the PDMS and the nanosilica powder is 1:7:1;

[0008] Step 2: then, a modifier is added into the mixed emulsion under stirring, and stirring is carried out at room temperature for a period of time to obtain a milky mixed liquid;

[0009] Step 3: a curing agent is added into the milky mixed liquid, and continuous stirring is carried out at room temperature for a period of time to obtain a pre-cured mixed emulsion;

[0010] Step 4: the pre-cured mixed emulsion is drop-coated on a substrate, and curing is carried out to obtain a hydrophobic anticorrosive coating.

[0011] Preferably, the particle size of the kaolin powder in step 1 is 1-10 μm. The PDMS is Dow Corning PDMS 184, and the molecular weight of the PDMS is about 25000, and the viscosity of the PDMS after mixing with the curing agent is about 4000 mPa·s. The particle size of the nano-silica powder is 50-200 nm.

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

[0013] In step 1, the ultrasonic dispersion is performed for 30-60 min, and the magnetic stirring is performed for 1-4 h; in step 2, the modifier is 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane, and the amount of the modifier is 2-3 times of the mass of the kaolin.

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

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

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

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

[0018] The present application simply analyzes the anti-corrosion mechanism of different hydrophobic coatings according to the characterization of different hydrophobic coatings and the different anti-corrosion abilities of the different hydrophobic coatings. The nano-silica particles form a film with multiple pores under the action of the PDMS as a viscous agent. With the increase of the kaolin particles, the kaolin particles fill the pores on the film, thereby prolonging the path of the water molecules and oxygen molecules in the air to contact the substrate, increasing the corrosion resistance time of the coating, and further enhancing the corrosion resistance effect of the coating.

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

[0020] Figure 1 The IR graphs of different coating components (a) the mixture of the kaolin powder and the nano-silica powder, (b) the 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; where the inset is a picture of the hydrophobic angle of the corresponding coating.

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

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

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

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

[0026] Figure 7 Optical pictures of different hydrophobic coatings after 300 hours of neutral salt spray (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; where the inset is a picture of the hydrophobic angle of the corresponding coating.

[0027] Figure 8 Hydrophobic angle pictures of different hydrophobic coatings (a) Comparative Example 7, (b) Example 1, (c) Comparative Example 8.

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

[0029] Figure 10 Hydrophobic angle pictures for different hydrophobic coatings (a) Comparative Example 9, (b) Example 1, (c) Comparative Example 10;

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

[0031] Figure 12 Optical picture of the coating prepared for Comparative Example 11;

[0032] Figure 13 Optical picture of the coating prepared for Comparative Examples 12-15. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and advantages to be solved by the present application more clear, the following will be described in detail with reference to the accompanying drawings and specific examples.

[0034] In the present application, the materials and reagents used, if not specifically mentioned, can be obtained from commercial channels. Among them, PDMS is Dow Corning PDMS 184. The particle size of the kaolin powder is 1-10 μm; the particle size of the nano-silica powder is 50-200 nm.

[0035] The present application provides a preparation method of a hydrophobic anticorrosive coating, and the specific implementation is as follows.

[0036] Example 1

[0037] A preparation method of a hydrophobic anticorrosive 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, and stirred at room temperature for 2 h; 2 drops of a curing agent were added to the emulsion mixture, and continuously stirred 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 sheet substrate, and the drop-coating amount was 2 mL / cm 2, and finally cured in an oven at 70°C for 12h to obtain coatings with different hydrophobicity, denoted as CK 0.05 SO 0.05 PDMS (CK represents kaolin, SO represents silica).

[0039] To further illustrate the beneficial effects of the present application, the following comparative examples were constructed.

[0040] Comparative Example 1

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

[0042] Comparative Example 2

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

[0044] Comparative Example 3

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

[0046] Comparative Example 4

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

[0048] Comparative Example 5

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

[0050] Comparative Example 6

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

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

[0053] In order to determine the composition of the coating, infrared testing was performed on each component in the coating, and the results are as follows. Figure 1shown. Figure 1 (a) is the infrared test result of the mixture of kaolin powder and nano-silica powder, the mixed particles show strong Si-O bond special vibration peaks at 1093 cm -1 and 559 cm -1 , and show kaolin particle specific Al-OH bond special vibration peaks at 906 cm -1 ; Figure 1 (b) is the infrared test result of pure PDMS, the coating shows specific -CH3 bond special vibration peaks at 1258 cm -1 , Si-O bond special vibration peaks at 1010 cm -1 , and specific Si-AC bond special vibration peaks at 786 cm -1 ; Figure 1 (c) is the infrared test result of the coating prepared in Example 1, compared with the pure PDMS coating, the coating shows Si-AC bond special vibration peaks at 788 cm -1 , and shows -CH3 bond special vibration peaks at 1258 cm -1 , which proves that PDMS is perfectly added to the coating, and shows Si-O bond special vibration peaks at 1010 cm -1 , which is stronger than that of the pure PDMS coating, and shows Si-O bond special vibration peaks at 544 cm -1 and Al-OH bond special vibration peaks at 907 cm -1 , which proves that the mixed particles of kaolin and nano-silica are added to the mixed coating.

[0054] In order to study the surface characteristics of different hydrophobic coatings and the wettability of the hydrophobic coatings, the coatings were characterized by scanning electron microscopy and hydrophobic angle test. Figure 2 SEM images and contact angle pictures of the coatings prepared in Example 1 and Comparative Examples 1-6 are shown in 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 angle of the coating is 125°, 130°, 135°, 140°, 145°, 150° and 155°, respectively, and the rolling angle of each coating is above 25°. However, when the amount of kaolin added is more than 0.6 g, the hydrophobic angle of the obtained coating remains basically unchanged. From Figure 2From (a), (b), (c), (d), when the hydrophobic angle is greater than 125° and less than 140°, with the increase of the coating particles, the particles will block the pores in the coating, it is speculated that the ability of the coating to block the water molecules and oxygen molecules in the air will also increase, when the contact angle of the coating is greater than 135°, with the gradual increase of the particles, the particles gradually accumulate to form a skeleton structure, thereby forming new pores, increasing the probability of the substrate contacting the water molecules and oxygen molecules in the air; from Figure 2 (e), (f), (g), with the increase of the hydrophobic angle of the coating, the skeleton structure gradually becomes clear, and the skeleton structure increases to a certain degree and accumulates to form a sheet structure, thereby re-blocking the pores, reducing the probability of the substrate contacting the water molecules and oxygen molecules in the air. In order to verify this result, an electrochemical workstation is used to represent the corrosion resistance of each coating, thereby representing the trend of the probability of the substrate contacting the water molecules and oxygen molecules in the air.

[0055] In order to determine the corrosion resistance of different hydrophobic coatings, electrochemical tests are performed on Q235 steel electrode pieces coated with different hydrophobic coatings, and the impedance test results are as shown in Figure 3 Figure 3 (a) is the impedance result of the 125°-140° hydrophobic coating when immersed in 3.5wt% NaCl solution for 5min, Figure 3 (b) is the impedance result of the 125°-140° hydrophobic coating when immersed in 3.5wt% NaCl solution for 30min, Figure 3 (c) is the impedance result of the 145°-155° hydrophobic coating when immersed in 3.5wt% NaCl solution for 5min, Figure 3 (d) is the impedance result of the 145°-155° hydrophobic coating when immersed in 3.5wt% NaCl solution for 30min, and the specific data is shown in Table 1.

[0056] Table 1 EIS data of different hydrophobic coatings

[0057]

[0058]

[0059] From Figure 3 and Table 1, for the coating with a hydrophobic angle of 125°-140°, when immersed in 3.5wt% NaCl solution for 5min, the CK 0.05 SO 0.05 PDMS coating has the largest radius of the impedance circle, and the impedance radius is about 4.21×10 4 Ω·cm 2 , which is almost twice that of other hydrophobic coatings, CK 0.1 SO​0.05 The impedance radius of the PDMS coating was 1.48 x 10 4 Ω·cm 2 The impedance radius of the PDMS coating was 1.36 x 10 0.05 Ω·cm 4 The impedance radius of the PDMS coating was almost the same as that of CK 2 SO 0.15 The impedance radius of the PDMS coating was 1.16 x 10 0.05 Ω·cm 4 This indicates that for the coatings with a hydrophobic angle of 125°-140°, the corrosion resistance increases first and then decreases when immersed in 3.5wt% NaCl solution for 5 min, and the coating with a hydrophobic angle of 130° has the best corrosion resistance. When immersed in 3.5wt% NaCl solution for 30 min, CK 2 SO 0.05 The PDMS coating has the largest radius of the impedance circle, and the impedance radius is 3.21 x 10 0.05 Ω·cm 4 The impedance radius of the PDMS coating is smaller than that of CK 2 SO 0.1 The impedance radius of the PDMS coating was 1.31 x 10 0.05 Ω·cm 4 The impedance radius of the PDMS coating is smaller than that of CK 2 SO 0.05 The impedance radius of the PDMS coating was 1.46 x 10 4 Ω·cm 2 The impedance radius of the PDMS coating is larger than that of CK 0.15 SO 0.05 The impedance radius of the PDMS coating was 7.87 x 10 3 Ω·cm 2 It is proved that for the coatings with a hydrophobic angle of 125°-140°, the corrosion resistance is consistent with the rule when immersed in 3.5wt% NaCl solution for 5 min and when immersed in 3.5wt% NaCl solution for 30 min.

[0060] For the coatings with a hydrophobic angle of 145°-155°, CK 0.6 SO 0.05 The PDMS coating has the largest radius of the impedance circle, and the impedance radius is 2.70 x 10 4 Ω·cm 2 The impedance radius of the PDMS coating is smaller than that of CK 0.05 SO 0.05 The impedance radius of the PDMS coating is larger than that of CK 0.4 SO 0.05 The impedance radius of the PDMS coating was 1.32 x 10 4 Ω·cm 2 The impedance radius of the PDMS coating is larger than that of CK0.2 SO 0.05 PDMS coating has the largest impedance radius of 8.36 x 10 3 Ω·cm 2 . This shows that for the coating with hydrophobic angle 145°-155°, the corrosion resistance increases when immersed in 3.5wt% NaCl solution for 5min, but the corrosion resistance is weaker than the coating with hydrophobic angle 130°. When immersed in 3.5wt% NaCl solution for 30min, CK 0.6 SO 0.05 PDMS coating has the largest impedance radius of 8.35 x 10 3 Ω·cm 2 , which is smaller than CK 0.05 SO 0.05 PDMS coating has the largest impedance radius of 8.35 x 10 0.4 SO 0.05 PDMS coating has the largest impedance radius of 4.07 x 10 3 Ω·cm 2 , which is larger than CK 0.2 SO 0.05 PDMS coating has the largest impedance radius of 2.42 x 10 3 Ω·cm 2 . This shows that for the coating with hydrophobic angle 145°-155°, the corrosion resistance is consistent with the rule when immersed in NaCl solution for 5min and 30min.

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

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

[0063] For the coating with hydrophobic angle 125°-140°, CK0.05 SO 0.05 PDMS coating has the largest Bode modulus at f = 0.1 Hz, about 4.45 x 10 4 Ω·cm 2 , almost 4 times of other hydrophobic coatings, CK 0.1 SO 0.05 The modulus value of PDMS coating is 1.65 x 10 4 Ω·cm 2 , almost the same as CK0SO 0.05 The modulus value of PDMS coating is 1.70 x 10 4 Ω·cm 2 , almost the same, both greater than CK 0.15 SO 0.05 The modulus value of PDMS coating is 1.40 x 10 4 Ω·cm 2 . This indicates that for the coatings with hydrophobic angle of 125°-140°, the corrosion resistance increases first and then decreases when immersed in 3.5wt% NaCl solution for 5 min, and the coating with 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 min, CK 0.05 SO 0.05 PDMS coating has the largest modulus value, about 3.20 x 10 4 Ω·cm 2 , CK 0.1 SO 0.05 The modulus value of PDMS coating is 1.95 x 10 4 Ω·cm 2 , and CK0SO 0.05 The modulus value of PDMS coating is 2.01 x 10 4 Ω·cm 2 , almost the same, both greater than CK 0.15 SO 0.05 The impedance radius of PDMS coating is 1.32 x 10 4 Ω·cm 2 . The corrosion law is consistent with the impedance diagram law.

[0064] For the coatings with hydrophobic angle of 145°-155°, CK 0.6 SO 0.05 PDMS coating has the largest Bode modulus value at f = 0.1 Hz, about 2.27 x 10 4 Ω·cm 2 , greater than CK 0.4 SO 0.05 The modulus value of PDMS coating is 1.60 x 104 Ω-cm 2 All are greater than CK 0.2 SO 0.05 The modulus value of PDMS coating is 1.25 x 10 4 Ω-cm 2 This indicates that for the coating with hydrophobic angle 145°-155°, the anticorrosion ability shows an upward trend when immersed in 3.5wt% NaCl solution for 5 min, consistent with the impedance diagram law. When immersed in 3.5wt% NaCl solution for 30 min, CK 0.6 SO 0.05 The PDMS coating has the largest modulus value, which is 1.10 x 10 4 Ω-cm 2 greater than CK 0.4 SO 0.05 The modulus value of PDMS coating is 7.60 x 10 3 Ω-cm 2 , all greater than CK 0.2 SO 0.05 The modulus value of PDMS coating is 6.25 x 10 3 Ω-cm 2 , the anticorrosion 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 3.5wt% sodium chloride solution can be represented by the tafel polarization curve. Generally speaking, the thermodynamic state of the coating is represented by the corrosion potential, reflecting the corrosion resistance of the coating; the kinetic state of the coating is represented by the corrosion current density, reflecting the corrosion rate of the coating. For tafel test of different hydrophobic coatings, the results are shown in Figure 6 . Figure 6 (a) is the tafel result of 125°-140° hydrophobic coating immersed in 3.5wt% NaCl solution for 5 min, Figure 6 (b) is the tafel result of 125°-140° hydrophobic coating immersed in 3.5wt% NaCl solution for 30 min; Figure 6 (c) is the tafel result of 145°-155° hydrophobic coating immersed in 3.5wt% NaCl solution for 5 min, Figure 6 (d) is the tafel result of 145°-155° hydrophobic coating immersed in 3.5wt% NaCl solution for 30 min. Table 2 lists the specific data of corrosion potential (Ecorr), corrosion current (icorr) and corrosion rate (η) in 3.5wt% sodium chloride electrolyte for 5 min and 30 min. Information about Ecorr and icorr can be obtained by the intersection of cathodic and anodic polarization curves.

[0066] Table 2

[0067]

[0068]

[0069] Depend on Figure 6 As shown in Table 2, after soaking for 5 minutes, for CK 0.05 SO 0.05 For PDMS coatings, the highest E corr -369.030mV, minimum I corr 1.45×10 -7 A·cm -2 Prove CK 0.05 SO 0.05 PDMS coatings offer the best corrosion protection. For CK0SO 0.05 For PDMS coatings, its E corr (-391.545mV) is greater than CK 0.1 SO 0.05 PDMS's E corr (-416.480mV), both are greater than CK. 0.15 SO 0.05 PDMS coating E corr (-461.158mV). For CK0SO 0.05 Regarding PDMS coating, its i corr (-2.18×10 -7 A·cm -2 Less than CK 0.1 SO 0.05 PDMS coating i corr (-3.14×10 -7 A·cm -2 ), all smaller than CK 0.15 SO 0.05 PDMS coating i corr (1.19×10 -6 A·cm -2 This indicates that for coatings with a hydrophobic angle of 125°-140°, the corrosion resistance initially increases and then decreases after immersion in a 3.5wt% NaCl solution for 5 minutes, consistent with the trends observed in impedance and Bode. The Tafel polarization curves of coatings with a hydrophobic angle of 125°-140° after immersion in NaCl solution for 30 minutes are shown below. Figure 6 As shown in (b), CK 0.05 SO 0.05 PDMS coating has the largest E corr(-377.511mV) and the smallest i corr (1.91×10 -7 A·cm -2 As for CK0SO 0.05 For PDMS coatings, its E corr (-413.083mV) is greater than CK 0.1 SO 0.05 PDMS's E corr (-435.368mV), all greater than CK. 0.15 SO 0.05 PDMS coating E corr (-500.379mV). For CK0SO 0.05 Regarding PDMS coating, its i corr (2.60×10 -7 A·cm -2 Less than CK 0.1 SO 0.05 PDMS coating i corr (7.47×10 -7 A·cm -2 ), all less than CK 0.15 SO 0.05 PDMS coating i corr (1.57×10 -6 A·cm -2 The results show that for coatings with a hydrophobic angle of 125°-140°, the corrosion resistance first increases and then decreases after immersion in NaCl solution for 30 minutes, consistent with the resistance and Bode patterns.

[0070] like Figure 6 As shown in (c), after soaking for 5 minutes, for CK 0.6 SO 0.05 For PDMS coatings, its E corr (-390.903mV) is greater than CK 0.4 SO 0.05 PDMS coating E corr (-422.509mV), all greater than CK. 0.2 SO 0.05 PDMS coating E corr (-437.785mV); CK 0.6 SO 0.05 PDMS coating i corr (2.07×10 -7 A·cm -2 Less than CK 0.4 SO 0.05 PDMS coating i corr(4.72 x 10 -7 A cm -2 ), all less than CK 0.2 SO 0.05 PDMS coating i corr (7.60 x 10 -7 A cm -2 ). This proves that the tafel law is consistent with the impedance, Bode law. As shown in Fig. Figure 6 (d), after 30 min of immersion, for CK 0.6 SO 0.05 PDMS coating, its E corr (-408.253 mV) is greater than CK 0.4 SO 0.05 PDMS coating E corr (-421.603 mV), both are greater than CK 0.2 SO 0.05 PDMS coating E corr (-455.925 mV); CK 0.6 SO 0.05 PDMS coating i corr (2.21 x 10 -7 A cm -2 ) is less than CK 0.4 SO 0.05 PDMS coating i corr (3.47 x 10 -7 A cm -2 ), all less than CK 0.2 SO 0.05 PDMS coating i corr (8.11 x 10 -7 A cm -2 ). The tafel law is consistent with the impedance, Bode.

[0071] The application adjusts the hydrophobicity of the coating by regulating the amount of the material, but the hydrophobicity is not proportional to the corrosion resistance. The inventor analyzes the corrosion resistance mechanism of different hydrophobic coatings according to the characterization of different hydrophobic coatings and their different corrosion resistance. Under the action of PDMS as the adhesive, nano-silicon dioxide particles form a film with multiple pores. At this time, the water molecules in the air can penetrate into the substrate through the pores in the film, thereby causing corrosion effect. With the increase of kaolin particles, the kaolin particles will fill the pores on the film, thereby prolonging the path of water molecules and oxygen molecules in the air contacting the substrate, increasing the corrosion resistance time of the coating, and further enhancing the corrosion resistance effect of the coating. When the kaolin particles increase to the same content as the silicon dioxide particles, the kaolin and silicon dioxide particles will form a skeleton structure with multiple pores under the action of the modifier, which increases the possibility of the substrate contacting the water molecules and oxygen molecules in the air, thereby reducing the corrosion resistance of the coating. However, when the multi-level skeleton structure is formed, the skeleton structures will attract and connect each other to form a large-area sheet structure. At this time, the skeletons will fill the pores in the skeleton, thereby prolonging the path of the substrate contacting the oxygen molecules and water molecules in the air, and increasing the corrosion resistance of the coating. However, the skeleton still has pores, so even if the corrosion resistance increases at this time, the corrosion resistance performance at the time when the corrosion resistance is best will be lower than that at the time when the corrosion resistance is best before. Therefore, under the condition of controlling the single variable of kaolin, for different hydrophobic coatings, the hydrophobic angle of the coating in the range of 125°-140° shows a trend that the corrosion resistance first increases and then decreases, and the coating with a hydrophobic angle of 130° has the maximum corrosion resistance; the corrosion resistance of the coating with a hydrophobic angle in the range of 145°-155° shows a consistent increasing trend.

[0072] The application also studies the long-term corrosion resistance of different coating surfaces under the condition of neutral salt spray test of 3.5wt% sodium chloride. Figure 7 It can be seen that after 300 hours of salt spray, the steel substrate surface protected by the coating with a surface hydrophobicity of 140° to 155° has small bubbles and a large amount of red rust corrosion products, the corrosion area is relatively large and has a tendency to spread outward ((d)-(g)). The corrosion degree of the coating with a surface hydrophobicity of 125° to 140° is obviously improved ((a)-(c)). Among them, the coating with a surface hydrophobicity of about 130° has less rust on the surface of the steel substrate, and no small bubbles appear, and the adhesion of the coating is still good, which shows that appropriate surface hydrophobicity can effectively enhance the barrier performance of the hydrophobic coating surface and the bonding strength between the coating and the steel substrate, greatly improving the protection performance of the coating on the steel substrate.

[0073] To further illustrate the beneficial effects of the application, the following comparative examples are constructed.

[0074] Comparative Example 7

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

[0076] Comparative Example 8

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

[0078] Comparative Example 9

[0079] In this comparative example, the amount of nanosilica powder was 0 g, and the other conditions were the same as in Example 1, and the coating obtained was designated CK 0.05 SO0PDMS 0.35 .

[0080] Comparative Example 10

[0081] In this comparative example, the amount of nanosilica powder was 0.1 g, and the other conditions were the same as in Example 1, and the coating obtained was designated CK 0.05 SO 0.1 PDMS.

[0082] Comparative Example 11

[0083] In this comparative example, the amount of nanosilica powder was 0.15 g, and the other conditions were the same as in Example 1, and the coating obtained was designated CK 0.05 SO 0.1 PDMS.

[0084] Comparative Example 12

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

[0086] Comparative Example 13

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

[0088] Comparative Example 14

[0089] In the present comparative example, PDMS is replaced by equal amount of epoxy resin, the amount of kaolin is 0.1 g, and the rest of the conditions are the same as in Example 1 to obtain a coating, which is denoted as CK 0.1 SO 0.05 EP.

[0090] Comparative Example 15

[0091] In the present comparative example, PDMS is replaced by equal amount of epoxy resin, the amount of kaolin is 0.15 g, and the rest of the conditions are the same as in Example 1 to obtain a coating, which is denoted as CK 0.15 SO 0.05 EP.

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

[0093] Figure 8 The pictures of the hydrophobic angles of the coatings prepared by changing the amount of PDMS (Comparative Examples 7-8 and Example 1) are shown in the figure, and it can be seen from the figure that three kinds of coatings are prepared by using PDMS 0.175 g (Comparative Example 7), 0.35 g (Example 1), and 0.7 g (Comparative Example 8) as variables, and the measured hydrophobic angles are 141.2°, 127.9°, and 119.9°, respectively, i.e. with the increase of the amount of PDMS, the hydrophobic angle of the prepared coating gradually decreases.

[0094] In order to determine the corrosion resistance of the coating, electrochemical tests are performed on the coatings prepared in Comparative Examples 7, 1 and 8, and the impedance test results are as shown in Figure 9 , 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, and the specific data are shown in Table 3.

[0095] Table 3

[0096]

[0097] As can be seen from Table 3, with the increase of the amount of PDMS, the impedance radius first increases and then decreases, and when immersed for 5 min and 30 min, 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 , respectively.

[0098] Figure 10The hydrophobic angle pictures of the coatings prepared by changing the amount of nano-silica powder (comparative example 9-10 and example 1) are shown in the figure, from left to right, three coatings are prepared by using nano-silica powder 0 g (comparative example 9), 0.05 g (example 1), and 0.1 g (comparative example 10) as variables, and the measured hydrophobic angles are 108.5°, 127.9°, and 145.6°, respectively, 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 corrosion resistance of the coating, electrochemical tests were performed on the coatings prepared in comparative example 9, example 1 and comparative example 10, and the impedance test results are shown in Figure 11 Figure 11 (a) is the impedance result of different hydrophobic coatings when immersed in 3.5wt% NaCl solution for 5 min, Figure 11 (b) is the impedance result of different hydrophobic coatings when immersed in 3.5wt% NaCl solution for 30 min, and the specific data are shown in Table 4.

[0100] Table 4

[0101]

[0102] As can be seen from Table 4, with the increase of the amount of nano-silica powder, the impedance radius first increases and then decreases, and when immersed for 5 min and 30 min, CK 0.05 SO 0.05 PDMS 0.35 coating has the largest impedance radius, which is 4.21×10 4 Ω·cm 2 and 3.21×10 4 Ω·cm 2 , respectively.

[0103] When the amount of nano-silica powder is large (comparative example 11), the surface of the prepared coating will crack, as shown in Figure 12 .

[0104] Regardless of whether the substrate is a Q235 steel electrode sheet or a glass sheet, when the PDMS system is replaced by a conventional epoxy resin system, and the amount of kaolin is changed to obtain the coating (comparative examples 12-15), due to the difference in viscosity of the epoxy resin and PDMS, the number of particles contained is different, and the replaced coating appears cracking of different sizes, uneven distribution, etc., as shown in Figure 13 , thereby causing the impedance data to appear scattered points, which cannot be measured.

[0105] ​In conclusion, the application takes PDMS as the basis, adjusts the hydrophobic property of the prepared coating by regulating the amount of kaolin, silicon dioxide and the like, studies the relationship between the hydrophobicity and the corrosion prevention capability of the system, and provides theoretical guidance for the preparation of the hydrophobic corrosion prevention coating.

[0106] The above is the preferred embodiment of the application, and for those skilled in the art, some improvements and refinements can be made without departing from the principles of the application, which should be considered within the protection scope of the application.

Claims

1. A process for the preparation of a hydrophobic corrosion protective coating, characterized in that, The application relates to a hydrophobic anticorrosive coating preparation method. Step 1: kaolin powder, polydimethylsiloxane (PDMS) and nano-silica powder are added into ethyl acetate, ultrasonic dispersion is carried out, and then magnetic stirring is carried out at room temperature to obtain a mixed emulsion; the mass ratio of the kaolin powder, the PDMS and the nano-silica powder is 1:7:1; the particle size of the kaolin powder is 1-10 mu m; the particle size of the nano-silica powder is 50-200 nm; and the molecular weight of the PDMS is 25000; Step 2: subsequently, a modifier is added into the mixed emulsion under stirring, and stirring is carried out at room temperature for a period of time to obtain an emulsion mixture; Step 3: a curing agent is added into the emulsion mixture, and continuous stirring is carried out at room temperature for a period of time to obtain a pre-cured mixed emulsion; Step 4: the pre-cured mixed emulsion is drop-coated on a substrate, and curing is carried out to obtain a hydrophobic anticorrosive coating.

2. The method for preparing a hydrophobic corrosion protective coating according to claim 1, characterized in that, The viscosity of the PDMS after being mixed with the curing agent is 4000 mPa.s.

3. The method for preparing a hydrophobic corrosion protective coating according to claim 2, characterized in that, The mass ratio of the ethyl acetate and the kaolin powder is 60-100:

1.

4. The method for preparing a hydrophobic corrosion protective coating according to claim 3, characterized in that, In step 1, ultrasonic dispersion is carried out for 30-60 min, and magnetic stirring is carried out for 1-4 h.

5. The method for preparing a hydrophobic corrosion protective coating according to claim 4, characterized in that, In step 2, the modifier is 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane.

6. The method of claim 5, wherein the hydrophobic corrosion protective coating is prepared by, In step 3, the mass ratio of the curing agent and the PDMS is 1:

10.

7. The method of claim 6, wherein the hydrophobic corrosion protective coating is prepared by, In step 4, the substrate is a Q235 steel electrode sheet or a glass sheet; the pre-solidified mixed emulsion drop coating amount is 0.5-2 mL / cm 2 .

8. The method of claim 7, wherein the hydrophobic corrosion protective coating is prepared by, In step 4, the curing temperature is 70-150 DEG C, and the time is 0.5-12 h.

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