Preparation method of bismuth tungstate nanosheet photocatalytic anticorrosion coating

Abstract

The present application relates to metal material anticorrosion technology, and aims to provide a preparation method of bismuth tungstate nanosheet photocatalytic anticorrosion coating. The method comprises the following steps: dispersing bismuth salt precursor and tungstate precursor, and then performing hydrothermal reaction; precipitating, cleaning and drying to obtain Bi2WO6 nanosheet powder; then mixing and uniformly dispersing with anhydrous ethanol, and then uniformly dispersing with a conductive polymer solution; coating the suspension on the surface of a steel sheet, and then drying at room temperature to form a nanosheet coating; uniformly coating a resin coating solution on the nanosheet coating, and then drying to form a Bi2WO6 nanosheet photocatalytic anticorrosion coating. The semiconductor photocatalytic material is directly loaded on the surface of the steel sheet, the conduction of photo-generated electrons is promoted, and the adverse effect of external current required by traditional photoanode anticorrosion is avoided; the transparent resin is uniformly coated on the surface of the nanosheet layer, and the semiconductor photocatalytic anticorrosion coating is constructed, so that the contact of corrosion substances such as water and oxygen with the surface of the steel sheet is effectively avoided, and the compactness and the shielding and anticorrosion capacity of the coating system are improved.

Description

Technical Field

[0001] This invention belongs to the field of metal material corrosion protection technology, and specifically relates to a method for preparing a bismuth tungstate nanosheet photocatalytic corrosion protection coating. Background Technology

[0002] Steel is the most widely used metallic material in industrial and engineering structures, possessing high strength and ductility. Due to the decrease in system free energy, steel has a strong tendency to decay into rust compounds through corrosion. Traditional protection techniques include coating protection, anodic protection, sacrificial anode cathodic protection, and impressed current cathodic protection. Among these, coating protection mainly uses various anti-corrosion barrier layers to prevent or delay corrosion. These barrier layers are applied using various methods, such as coating with anti-corrosion materials like epoxy resin, silicone resin, and acrylic resin.

[0003] However, traditional anti-corrosion methods have many drawbacks. These technologies consume a lot of materials and energy to maintain the metastable metallic state of steel, resulting in high maintenance costs and a large consumption of human and material resources.

[0004] Therefore, it is necessary to propose a new anti-corrosion technology to solve the problems existing in the current technology. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a photocatalytic anti-corrosion coating of bismuth tungstate nanosheets.

[0006] To solve the above-mentioned technical problems, the solution of the present invention is:

[0007] A method for preparing a bismuth tungstate nanosheet photocatalytic anti-corrosion coating is provided, comprising the following steps:

[0008] (1) Weigh out the bismuth salt precursor and tungstate precursor at a molar ratio of 1:20-30; add them together to an appropriate amount of distilled water, disperse by ultrasonication and stir continuously until homogeneous to obtain mixed solution A.

[0009] (2) Adjust the pH of mixed solution A to 8-10 with alkaline solution, pour it into a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction; after the reaction is completed, cool it naturally to room temperature, and wash and dry the filtered precipitate to obtain Bi2WO6 nanosheet powder.

[0010] (3) The steel sheet was ultrasonically cleaned in deionized water, ethanol and acetone in sequence, and then dried for later use.

[0011] (4) Weigh Bi2WO6 nanosheet powder and anhydrous ethanol at a mass ratio of 1:40-80, mix them and then ultrasonically disperse them evenly to obtain mixture B; take a 5% conductive polymer solution at a mass ratio of Bi2WO6 powder to conductive polymer solution of 1:4-16; add the conductive polymer solution to mixture B and ultrasonically disperse it to form a uniform suspension C.

[0012] (5) The suspension C is coated on the surface of the steel sheet and dried at room temperature to form a Bi2WO6 nanosheet coating; the resin coating liquid is uniformly coated on the Bi2WO6 nanosheet coating of the steel sheet and dried to form a Bi2WO6 nanosheet photocatalytic anti-corrosion coating.

[0013] As a preferred embodiment of the present invention, in step (1), the bismuth salt precursor is any one of Bi(NO3)3·5H2O, Bi(CH3CO2)3, and Bi(NH3)2C6H7O7·H2O; the tungstate precursor is (NH4)6H2W. 12 O 40 Any one of Na2WO4·2H2O and K2WO4.

[0014] As a preferred embodiment of the present invention, in step (1), the ultrasonic power is controlled at 100W and the dispersion time is 30min during ultrasonic dispersion; after ultrasonic dispersion, the stirring time is 1.5h.

[0015] As a preferred embodiment of the present invention, in step (2), the pH value of the mixed solution is adjusted using a 1 mol / L NaOH solution.

[0016] As a preferred embodiment of the present invention, in step (2), during the hydrothermal reaction, the filling ratio in the high-pressure reactor is 60-90%, the reaction temperature is 160℃-200℃, and the reaction time is 10-20h.

[0017] As a preferred embodiment of the present invention, in step (3), the steel sheet refers to sheet-like carbon structural steel Q235; it is ultrasonically cleaned in deionized water, ethanol and acetone for 30 min respectively, and then dried in an oven at 70°C.

[0018] As a preferred embodiment of the present invention, in step (4), the ultrasonic dispersion time is 30 min.

[0019] As a preferred embodiment of the present invention, in step (4), the conductive polymer solution is one of Nafion (perfluorosulfonic acid polymer) ethanol solution, PEDOT (polyethylene dioxythiophene) aqueous solution, and PBI (polybenzimidazole) ethanol solution.

[0020] As a preferred embodiment of the present invention, in step (5), the resin coating liquid is one of transparent epoxy resin, silicone resin, and acrylic resin, with a solid content of 35%.

[0021] As a preferred embodiment of the present invention, in step (5), the coating thickness of the resin coating liquid is controlled to be 20-50 μm; the drying temperature is 150-170°C and the drying time is 0.5-2 h.

[0022] The implementation principle of this invention:

[0023] This invention innovatively proposes a novel Bi2WO4 photocatalytic anti-corrosion coating technology. By combining semiconductor photocatalytic protection technology with coating shielding anti-corrosion technology, a slurry is prepared using semiconductor photocatalytic materials and uniformly coated onto the surface of a steel sheet. A transparent shielding coating is then prepared on top of this slurry, allowing light energy to pass through and be absorbed and utilized by the underlying semiconductor material. Solar energy is collected by mimicking natural photosynthesis and stored in chemical bonds using a light-absorbing semiconductor. Similarly, by coupling an n-type semiconductor photoelectrode to a metal electrode, electrons are received from the photoelectrode when the semiconductor conduction band is above the Fermi level of the material itself. The resulting photoelectrons can be used to inhibit or prevent steel corrosion. These electrons compensate for the corrosion current and shift the potential of the protected metal to a stable region. Thus, the energy required to maintain the metastable metallic state of the steel can be sustainably provided by solar energy, thereby synergistically enhancing the corrosion resistance of the steel sheet.

[0024] Among existing semiconductor photocatalytic materials, Bi₂WO₄, as a typical bismuth-based photocatalytic material, has attracted much attention from researchers due to its advantages such as easy excitation under visible light irradiation, high solar energy utilization, high photocatalytic activity, and photochemical stability. Currently, research on Bi₂WO₄ is limited to applications based on semiconductor photocatalysis; there are no reports on using its photoelectric effect to prepare anti-corrosion materials.

[0025] This invention employs a hydrothermal method to prepare Bi2WO4 nanosheet materials with a larger specific surface area. A conductive polymer solution is used to mix Bi2WO4 powder to prepare a slurry, which is then coated onto the surface of a steel sheet. The conductive polymer strengthens the bond between the Bi2WO4 nanosheets and the steel sheet, while also effectively utilizing its conductivity to conduct photoelectrons to the metal surface. A transparent resin is used as a shielding layer to block corrosive media such as water and oxygen, and the transparency of the resin layer allows visible light to pass through and be absorbed and utilized by the Bi2WO4. The nanosheets of Bi2WO4 can be stacked to form a dense film parallel to the steel sheet surface, further enhancing the coating's shielding capability.

[0026] Compared with the prior art, the technical effects of the present invention are as follows:

[0027] 1. This invention utilizes Bi2WO4 photocatalytic anti-corrosion coating technology to directly load semiconductor photocatalytic materials onto the surface of steel sheets, promoting the conduction of photogenerated electrons and avoiding the adverse effects of traditional photoanodine anti-corrosion requiring external current.

[0028] 2. This invention constructs a semiconductor photocatalytic anti-corrosion coating by uniformly coating a transparent resin on the surface of Bi2WO4 nanosheets, which effectively prevents corrosive substances such as water and oxygen from contacting the steel sheet surface. Furthermore, the addition of nanosheets further enhances the density and shielding anti-corrosion capabilities of the coating system.

[0029] 3. This invention utilizes the shielding effect of photocatalytic electron injection into steel sheets and coatings to synergistically enhance the anti-corrosion capability of the coating. Attached Figure Description

[0030] Figure 1 The image shows a scanning electron microscope (SEM) image of the Bi2WO6 nanosheets prepared in Example 1.

[0031] Figure 2 The image shows a scanning electron microscope (SEM) image of the Bi2WO6 nanosheets prepared in Example 1.

[0032] Figure 3 This is a scanning electron microscope image of the Bi2WO6 nanosheet coating prepared on the metal surface in Example 1. Detailed implementation method:

[0033] The present invention will now be described in further detail with reference to specific embodiments. The embodiments provided will enable those skilled in the art to gain a more comprehensive understanding of the present invention, but will not limit the invention in any way.

[0034] I. Implementation Examples

[0035] In this invention, the preparation method of the bismuth tungstate nanosheet photocatalytic anti-corrosion coating includes the following steps:

[0036] (1) Weigh out the bismuth salt precursor and the tungstate precursor in a molar ratio of 1:20-30; wherein the bismuth salt precursor may be any one of Bi(NO3)3·5H2O, Bi(CH3CO2)3, or Bi(NH3)2C6H7O7·H2O; and the tungstate precursor may be (NH4)6H2W. 12 O 40 Any one of Na2WO4·2H2O and K2WO4.

[0037] The two types of precursors were added to an appropriate amount of distilled water and dispersed using an ultrasonic dispersion device with a power of 100W for 30 minutes. After ultrasonic dispersion, the mixture was stirred continuously for 1.5 hours to obtain a homogeneous mixed solution A.

[0038] (2) Adjust the pH of mixed solution A to 8-10 with 1 mol / L NaOH solution, pour it into a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction; control the filling ratio in the high-pressure reactor to be 60-90%, the reaction temperature to be 160℃-200℃, and the reaction time to be 10-20 h. After the reaction is completed, allow it to cool naturally to room temperature, and wash and dry the filtered precipitate to obtain Bi2WO6 nanosheet powder;

[0039] Figure 1 and Figure 2 These are scanning electron microscope (SEM) images of Bi2WO6 nanosheets. The difference between the two images is the different shooting angles of the nanosheets. Figure 1 It is a side structure. Figure 2 This refers to the surface morphology of a single Bi2WO6 sheet.

[0040] (3) The steel sheet is ultrasonically cleaned in deionized water, ethanol and acetone for 30 minutes in sequence, and then dried in an oven at 70°C. The steel sheet can be made of sheet-like carbon structural steel Q235.

[0041] (4) Weigh Bi2WO6 nanosheet powder and anhydrous ethanol at a mass ratio of 1:40-80, mix them, and then ultrasonically disperse for 30 min to obtain a uniform mixture B. Add 5% (by mass) of the conductive polymer solution to mixture B at a mass ratio of Bi2WO6 powder to conductive polymer solution of 1:4-16, and ultrasonically disperse to form a uniform suspension C. The conductive polymer solution can be one of Nafion (perfluorosulfonic acid polymer) ethanol solution, PEDOT (polyvinyl dioxythiophene) aqueous solution, or PBI (polybenzimidazole) ethanol solution.

[0042] (5) The suspension C is coated on the surface of the steel sheet and dried at room temperature to form a Bi2WO6 nanosheet coating; the resin coating liquid is uniformly coated on the Bi2WO6 nanosheet coating of the steel sheet and dried to form a Bi2WO6 nanosheet photocatalytic anti-corrosion coating.

[0043] The resin coating liquid is a transparent material, which can be selected from epoxy resin, silicone resin, and acrylic resin, with a solid content of 35%. The coating thickness of the resin coating liquid is controlled to be 20-50 μm; the drying temperature is 150-170℃, and the drying time is 0.5-2 hours.

[0044] Bi2WO4 nanosheet photocatalytic anti-corrosion coatings were successfully prepared through eight examples. The experimental data of each example are shown in Table 1 below.

[0045] Table 1. Data Table of Embodiments

[0046]

[0047]

[0048] II. Electrochemical Corrosion Test

[0049] 1. Experimental Materials and Apparatus

[0050] Electrochemical testing employed a three-electrode system: a 1cm × 0.5cm platinum electrode as the counter electrode; an Ag / AgCl electrode as the reference electrode; a pre-prepared steel sheet with an anti-corrosion coating as the working electrode; an electrolyte containing 3.5wt% NaCl solution; a 300W xenon lamp; and a CHI750E electrochemical workstation.

[0051] 2. Experimental Procedure

[0052] The three electrodes were placed simultaneously in the electrolytic cell and connected to the electrode clamps of the electrochemical workstation. The xenon lamp was turned on to irradiate the working electrodes, and then the power switch of the electrochemical workstation was turned on. The open circuit potential (OCP) was measured without applying a bias voltage using general test control software.

[0053] III. Comparison with existing anti-corrosion technologies

[0054] Under the same test conditions, the open-circuit potential of the uncoated steel sheet was -0.4 eV, the corrosion potential of the epoxy resin coating was -0.58 eV, the corrosion potential of the silicone resin layer was -0.5 eV, and the corrosion potential of the acrylic resin layer was -0.51 eV. In comparison, the open-circuit potential of the coating with photocatalytic material added in this invention reaches -0.6 to -0.9 eV.

[0055] This shows that the coating with added photocatalyst improves the corrosion resistance of the steel sheet.

[0056] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for preparing a bismuth tungstate nanosheet photocatalytic anti-corrosion coating, characterized in that, Includes the following steps: (1) Weigh out the bismuth salt precursor and tungstate precursor in a molar ratio of 1:20-30; add them together to an appropriate amount of distilled water, disperse by ultrasonication and stir continuously until homogeneous to obtain mixed solution A; The salt precursor is any one of Bi(NO3)3·5H2O, Bi(CH3CO2)3, and Bi(NH3)2C6H7O7·H2O; the tungstate precursor is (NH4)6H2W. 12 O 40 Any one of Na2WO4·2H2O and K2WO4; (2) Adjust the pH of mixed solution A to 8-10 with alkaline solution, pour it into a high-pressure reactor lined with polytetrafluoroethylene for hydrothermal reaction; the filling ratio in the high-pressure reactor is 60-90%, the reaction temperature is 160℃-200℃, and the reaction time is 10-20h; after the reaction is completed, cool naturally to room temperature, and wash and dry the filtered precipitate to obtain Bi2WO6 nanosheet powder; (3) Clean the steel sheet in deionized water, ethanol and acetone in turn for 30 min each, and then dry it in an oven at 70℃ for later use. (4) Weigh Bi2WO6 nanosheet powder and anhydrous ethanol at a mass ratio of 1:40-80, mix them and then ultrasonically disperse them evenly to obtain mixture B; take a 5% conductive polymer solution at a mass ratio of Bi2WO6 powder to conductive polymer solution of 1:4-16; add the conductive polymer solution to mixture B and ultrasonically disperse it to form a uniform suspension C. (5) The suspension C is coated on the surface of the steel sheet and dried at room temperature to form a Bi2WO6 nanosheet coating; then the resin coating liquid is uniformly coated on the Bi2WO6 nanosheet coating of the steel sheet and dried to form a Bi2WO6 nanosheet photocatalytic anti-corrosion coating with a transparent shielding layer; the solid content of the resin coating liquid is 35%, and it is one of transparent epoxy resin, silicone resin and acrylic resin materials; the coating thickness is controlled to be 20~50μm, the drying temperature is 150~170℃, and the time is 0.5~2h.

2. The method according to claim 1, characterized in that, In step (1), the ultrasonic power is controlled at 100 W and the dispersion time is 30 min during ultrasonic dispersion; after ultrasonic dispersion, the stirring time is 1.5 h.

3. The method according to claim 1, characterized in that, In step (2), the pH value of the mixed solution is adjusted using a 1 mol / L NaOH solution.

4. The method according to claim 1, characterized in that, In step (3), the steel sheet refers to sheet-like carbon structural steel Q235.

5. The method according to claim 1, characterized in that, In step (4), the ultrasonic dispersion time is 30 min.

6. The method according to claim 1, characterized in that, In step (4), the conductive polymer solution is one of Nafion ethanol solution, PEDOT aqueous solution, and PBI ethanol solution.

Images