Hydrophobic / chromium-rich corrosion-resistant composite coating, and its manufacturing method and use

Abstract

This disclosure proposes a hydrophobic / chromium-rich corrosion-resistant composite coating and a method for manufacturing and using the same, and belongs to the technical field of material surface coatings. The manufacturing method includes the steps of: preheating a workpiece; applying a coating slurry to the surface of the preheated workpiece, baking to cure, and sintering to obtain a chromium-rich corrosion-resistant coating on the surface of the workpiece, wherein the coating slurry comprises a solid phase component and a liquid phase component, the solid phase component comprising chromium powder, nickel powder, iron powder, and rare earth compounds, and the liquid phase component comprising Al(H2PO4)3, water glass, ammonium halide, polyvinyl alcohol, and Cr2O3; and spray-coating a superhydrophobic material in one layer onto the surface of the chromium-rich corrosion-resistant coating and curing to obtain a hydrophobic / chromium-rich corrosion-resistant composite coating. This disclosure describes how applying chromizing and superhydrophobic treatments to a workpiece imparts corrosion resistance, wear resistance, and hydrophobic properties to the workpiece, preventing water vapor inside the pipe from remaining on the inner wall of the pipe, thereby avoiding corrosion of the inner wall of the pipe, improving the overall properties of the pipe, and extending its service life.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority to a Chinese patent application filed with the China National Intellectual Property Administration on July 19, 2024, with application number 202410975831.4 and invention title "Hydrophobic / Chromium - rich Corrosion - resistant Composite Coating and Its Manufacturing Method and Use", the entire content of which is incorporated herein by reference.

[0002] This disclosure belongs to the technical field of material surface coatings, and specifically relates to hydrophobic / chromium - rich corrosion - resistant composite coatings and their manufacturing methods and uses.

Background Art

[0003] Thermal corrosion on the inner surface of boiler pipes has conventionally been one of the factors limiting thermal power generation. Especially at the current stage, as operating conditions for thermal power generation, steam temperature and pressure tend to further increase, and it has become an urgent task to improve the heat - resistant corrosion resistance of the inner surface of the pipes.

[0004] The problem of pipe corrosion mainly consists of two parts. One is the corrosion problem caused by gas, and the other is the metal oxidation corrosion problem caused by water vapor. By applying a corrosion - resistant coating on the surface of the pipe, problems such as short pipe life and regular treatment of oxides can be solved, and dangerous events such as pipe rupture can be avoided.

[0005] Currently, the most common corrosion prevention technology involves impregnating alloy surfaces with corrosion-resistant metals such as Al, Si, and Cr. While Cr penetration forms a corrosion-resistant coating on the alloy surface, numerous methods exist for producing Cr-rich coatings, including the powder embedding method, vapor deposition method, and liquid-phase method. In the liquid-phase method, Cr powder is typically added to molten salt and heated at high temperatures to form a Cr-penetrating layer. However, this method can damage the workpiece and the environment due to the high volatilization of the molten salt. The slurry method involves directly applying or spray-coating a slurry onto the workpiece surface and then sintering it at high temperatures to obtain the coating. Coatings obtained using this method exhibit excellent corrosion resistance and good adhesion. Compared to other Cr penetration methods, this method is simpler to operate and suitable for large-scale industrial production.

[0006] However, according to the saturated vapor pressure of water, it was found that liquid water can still be present in the pipes even under high temperature and high pressure conditions. The above corrosion prevention methods can only slow down pipe corrosion to some extent and still cannot fundamentally solve the problem of oxidative corrosion of pipes. [Overview of the project] [Problems that the invention aims to solve]

[0007] This disclosure aims to solve at least one of the technical problems present in the prior art and provides a hydrophobic / chromium-rich corrosion-resistant composite coating, a method for manufacturing the same, and its use. [Means for solving the problem]

[0008] In one aspect of this disclosure, The steps include preheating the workpiece and The process involves applying a coating slurry to the surface of a preheated workpiece, baking it to cure it, and sintering it to obtain a chromium-rich corrosion-resistant coating on the surface of the workpiece, wherein the coating slurry comprises a solid phase component and a liquid phase component, the solid phase component comprising chromium powder, nickel powder, iron powder, and rare earth compounds, and the liquid phase component comprising Al(H2PO4)3, water glass, ammonium halide, polyvinyl alcohol, and Cr2O3, and The present invention provides a method for manufacturing a hydrophobic / chromium-rich corrosion-resistant composite coating, comprising the steps of spray-coating a superhydrophobic material onto the surface of a chromium-rich corrosion-resistant coating, curing it, and obtaining a hydrophobic / chromium-rich corrosion-resistant composite coating.

[0009] The manufacturing method according to claim 1, characterized in that, optionally, the solid-liquid ratio of the solid-phase component to the liquid-phase component is 10:(1~5).

[0010] The chromium powder content is optional, ranging from 40% to 80%. The nickel powder content is 5-30%. The iron powder content is 2-20%. The content of rare earth compounds ranges from 5% to 45%.

[0011] The Al(H2PO4)3 content is optional, ranging from 10% to 30%. The water glass content is 15-25%. The ammonium halide content is 5-10%. The polyvinyl alcohol content is 10-35%. The Cr2O3 content is 10-30%.

[0012] Optionally, the rare earth compound is a rare earth oxide or rare earth chloride, and / or Ammonium halides are either ammonium bromide or ammonium iodide.

[0013] Optionally, the step of spray-coating a superhydrophobic material onto the surface of a chromium-rich corrosion-resistant coating and curing it to obtain a hydrophobic / chromium-rich corrosion-resistant composite coating is: The process involves mixing anhydrous ethanol, HDTMS, and nanoalumina particles, preparing a suspension, stirring, centrifuging, and drying to obtain HDTMS-modified superhydrophobic Al2O3 nanoparticles. The method includes the steps of: dissolving epoxy resin, polydimethylsiloxane, epoxy resin curing agent, and Al2O3 nanoparticles hydrophobized with HDTMS in xylene to prepare a suspension; spray-coating this suspension onto the surface of a chromium-rich corrosion-resistant coating and curing it to obtain a superhydrophobic / chromium-rich corrosion-resistant composite coating.

[0014] Optionally, the workpiece preheating treatment is performed at a temperature of 150-220°C for 30-60 minutes, and / or, The sintering process under inert gas protection is performed at a temperature of 980-1150°C for 8-30 minutes.

[0015] Optionally, the thickness of the chromium-rich corrosion-resistant coating is 5-50 μm, and / or The thickness of the hydrophobic / chromium-rich corrosion-resistant composite coating is 13-64 μm.

[0016] Another aspect of this disclosure proposes a hydrophobic / chromium-rich corrosion-resistant composite coating manufactured by the manufacturing method described above.

[0017] Another aspect of this disclosure proposes the use of a hydrophobic / chromium-rich corrosion-resistant composite coating, wherein the aforementioned hydrophobic / chromium-rich corrosion-resistant composite coating is used on the inner surface of boiler piping. [Effects of the Invention]

[0018] The present disclosure proposes a hydrophobic / chromium-rich corrosion-resistant composite coating, a manufacturing method thereof, and uses thereof. The manufacturing method includes a step of pre-heat treating a workpiece, applying a coating slurry to the surface of the pre-heat treated workpiece, baking and curing it, and performing a sintering treatment to obtain a chromium-rich corrosion-resistant coating on the surface of the workpiece, where the coating slurry includes a solid-phase component and a liquid-phase component, the solid-phase component includes chromium powder, nickel powder, iron powder, and a rare earth compound, and the liquid-phase component includes Al(H2PO4)3, water glass, ammonium halide, polyvinyl alcohol, and Cr2O3; a step of spray coating one layer of a super-hydrophobic material on the surface of the chromium-rich corrosion-resistant coating and performing a curing treatment to obtain a hydrophobic / chromium-rich corrosion-resistant composite coating. This method performs chromizing treatment and super-hydrophobic treatment on the workpiece, thereby imparting hydrophobic properties to the workpiece together with corrosion resistance and wear resistance, preventing water vapor in the pipe from staying on the inner wall of the pipe, thereby avoiding corrosion of the inner wall of the pipe, improving the overall properties of the pipe, and extending its service life.

Brief Description of the Drawings

[0019] [Figure 1] It is a flow block diagram of a manufacturing method of a hydrophobic / chromium-rich corrosion-resistant composite coating according to an embodiment of the present disclosure.

Modes for Carrying Out the Invention

[0020] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the present disclosure will be described in more detail below with reference to the drawings and specific embodiments. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present disclosure without creative labor shall fall within the protection scope of the present disclosure.

[0021] As shown in FIG. 1, in one aspect of the present disclosure, specifically, a manufacturing method S100 of a hydrophobic / chromium-rich corrosion-resistant composite coating is provided, which includes the following steps S110 to S130.

[0022] S110: Preheat the workpiece. Specifically, the workpiece is preheated for 30 to 60 minutes under conditions of a temperature of 150 to 220°C.

[0023] In this embodiment, preheating treatment optimizes the microstructure of the metal workpiece and removes residual stress, thereby reducing workpiece deformation, improving surface quality, and raising the workpiece temperature, which is advantageous for subsequent application of the chromizing slurry to its surface.

[0024] Furthermore, the workpiece can be cleaned before preheating. For example, oil stains and dust on the surface of the pipe can be cleaned using alcohol or acetone, and oxide scale can be removed from the surface using a steel brush to increase the specific surface area of ​​the workpiece, thereby enhancing the penetration effect of the metal powder and improving the adhesion of the coating.

[0025] S120: The coating slurry is applied to the surface of the preheated workpiece, and then baked to perform hardening and sintering treatments to obtain a chromium-rich corrosion-resistant coating on the surface of the workpiece. In this embodiment, the coating slurry comprises a solid phase component and a liquid phase component. The solid phase component includes chromium powder, nickel powder, iron powder, and rare earth compounds, while the liquid phase component includes Al(H2PO4)3, water glass, ammonium halide, polyvinyl alcohol, and Cr2O3. Mixing the solid phase component and the liquid phase component in predetermined proportions to form a slurry is advantageous for coating the workpiece surface with each metal powder and forming a corrosion-resistant coating.

[0026] In some arbitrary embodiments, the solid-to-liquid ratio (g:mL) of the solid-phase component to the liquid-phase component is 10:(1~5), for example, the two components are mixed in proportions such as 10:1, 10:2, 10:3, 10:4, 10:5, etc.

[0027] In this embodiment, the mixing form of the solid phase component and the liquid phase component is not particularly limited. The solid phase component may be added directly to the liquid phase component, or the liquid phase component may be injected into the solid phase component and mixed. Of course, each powder in the solid phase component can be mixed in advance. For example, each solid phase component may be ball-milled in a star-type ball mill tank at a rotation speed of 350-400 rpm for 6-24 hours to pre-mix the solid phase component, and then the mixed solid phase component may be further mixed with the liquid phase component.

[0028] In some arbitrary embodiments, the chromium powder content is 40-80%, for example 40%, 50%, 60%, 70%, 80%; the nickel powder content is 5-30%, for example 5%, 10%, 15%, 20%, 25%, 30%; the iron powder content is 2-20%, for example 2%, 7%, 10%, 15%, 17%, 20%; and the rare earth compound content is 5-45%, for example 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%.

[0029] In any form, the rare earth compound may be a rare earth oxide, such as samarium oxide, europium oxide, or yttrium oxide, but of course, the rare earth compound may also be a rare earth chloride, such as lanthanum chloride.

[0030] In the solid phase component of this embodiment, rare earth atoms are provided by adding oxides or chlorides of rare earth elements. During the sintering process, the oxides or chlorides of rare earth elements segregate at the grain boundaries, playing a role in fixing the grain boundaries and refining the grains of the coating. This also prevents Cr atoms from diffusing into deeper parts of the matrix, allowing the coating to grow outward and improving the coating thickness and the concentration of Cr elements within the coating. During use, the oxide film segregates at the grain boundaries, thereby increasing the concentration of Cr along the grain boundaries. 3+ The rapid "short-circuit diffusion" of Cr is suppressed, and the oxidation mechanism of the coating is Cr 3+ Outward diffusion from O 2-The diffusion changes to primarily inward, and the oxide film that grows internally in this way firmly bonds to the matrix, improving the peel-resistant properties of the oxide film and further enhancing the corrosion resistance of the coating.

[0031] Furthermore, the solid phase component of this embodiment contains small amounts of iron and nickel, primarily to accelerate the chromizing rate and lower the chromizing temperature. Chromium forms solid solutions with iron and nickel, respectively, and compared to a single chromizing coating, the co-infiltration of chromium-iron-nickel can significantly improve the abrasion resistance and corrosion resistance of the infiltrated layer.

[0032] In some other arbitrary embodiments, the Al(H2PO4)3 content is 10-30%, for example, 10%, 15%, 20%, 25%, 30%; the water glass content is 15-25%, for example, 15%, 20%, 25%; the ammonium halide content is 5-10%, for example, 5%, 7%, 10%; the polyvinyl alcohol content is 10-35%, for example, 10%, 20%, 25%, 30%, 35%; and the Cr2O3 content is 10-30%, for example, 10%, 15%, 20%, 25%, 30%.

[0033] In any form, ammonium halides are ammonium bromide or ammonium iodide.

[0034] In this embodiment, the liquid phase component, through the synergistic effect of the liquid phase component and the solid phase component, makes it possible to produce a coating of the desired thickness in a single application process. Furthermore, the coating has a smooth surface, a uniform and dense interior, and good corrosion resistance.

[0035] Furthermore, in the liquid phase component of this embodiment, Al(H2PO4)3 acts as a binder, providing high adhesive strength with the metal matrix, and enabling the production of the required coating thickness in a single application process. In addition, this component exhibits good high-temperature toughness and is less prone to cracking during the curing and baking processes.

[0036] Furthermore, in the liquid phase component of this embodiment, the addition of water glass and polyvinyl alcohol modifies the binder, further enhancing the high-temperature toughness and adhesion ability of Al(H2PO4)3 to the metal matrix. In addition, Al(H2PO4)3, being an inorganic binder, can directly volatilize during the slurry baking process and decomposes during the sintering process, generating gas and preventing the formation of holes within the coating. In other words, the polyvinyl alcohol in this embodiment is a substance that can improve the high-temperature toughness and adhesive strength of Al(H2PO4)3.

[0037] Furthermore, in the liquid phase component of this embodiment, NH4I or NH4Br is used as a penetration enhancer, promoting the generation of activated chromium atoms and activated nickel atoms.

[0038] Furthermore, in the liquid phase component of this embodiment, Cr2O3 acts as a curing agent, effectively lowering the curing temperature of the slurry by dehydrating and polycondensing the acidic phosphoric acid in the binder. Additionally, adding an appropriate amount of Cr2O3 can improve the curing performance of Al(H2PO4)3, resulting in a coated layer with a smooth and flat surface and a uniform and dense interior after bake curing.

[0039] In this embodiment, the method of applying the coating slurry to the surface of the workpiece is not particularly limited; for example, the chromizing slurry may be applied to the surface of the workpiece by spray coating or palm brush.

[0040] In this embodiment, the temperatures for the bake curing and sintering processes are not particularly limited. For example, the bake curing may be performed at a temperature of 60 to 300°C for 5 to 15 minutes, and the sintering process may be performed at a temperature of 980 to 1150°C for 8 to 30 minutes.

[0041] In some arbitrary embodiments, bake curing employs a stepwise gradient curing process, for example, pre-baking at 60-85°C for 5-30 minutes, then baking at 100-160°C for 30-60 minutes, and finally medium-temperature curing at 250-300°C for 20-60 minutes. The stepwise curing process ensures that there are no surface quality issues with the coated slurry due to localized stress during the curing process and is also advantageous for improving the adhesion of the coating.

[0042] In several other optional embodiments, inert gas protection is provided throughout the sintering process to prevent oxidation of each component in the slurry in air at high temperatures, and the workpiece is chromized by rapidly heating the temperature and then furnace-cooled. Here, the sintering process is performed at temperatures of 980°C, 1000°C, 1050°C, 1100°C, and 1150°C for 8 minutes, 15 minutes, 20 minutes, and 30 minutes. In this process, the thickness of the slurry to be applied is 0.5 to 1.0 mm, and the thickness of the chromium-rich corrosion-resistant coating obtained on the surface of the workpiece by the process is approximately 5 to 50 μm.

[0043] S130: A chromium-rich corrosion-resistant coating is obtained by spray-coating or applying a superhydrophobic material to the surface of a chromium-rich corrosion-resistant coating and then curing it. The thickness of this composite coating is 13 to 64 μm.

[0044] Specifically, the step of spray-coating or applying a superhydrophobic material to the surface of a chromium-rich corrosion-resistant coating is: The process involves mixing anhydrous ethanol, HDTMS, and nanoalumina particles, preparing a suspension, stirring, centrifuging, and drying to obtain HDTMS-modified superhydrophobic Al2O3 nanoparticles. The method includes the steps of: dissolving epoxy resin, polydimethylsiloxane, epoxy resin curing agent, and Al2O3 nanoparticles hydrophobized with HDTMS in xylene to prepare a suspension; spray-coating this suspension onto the surface of a chromium-rich corrosion-resistant coating and curing it to obtain a superhydrophobic / chromium-rich corrosion-resistant composite coating.

[0045] In some optional embodiments, the volume of anhydrous ethanol is preferably 45-55 mL, for example 45 mL, 50 mL, 55 mL, etc., the volume of hexadecyltrimethoxysilane (HDTMS) is preferably 0.5 mL, 1 mL, 1.5 mL, etc., and the content of nanoalumina particles is preferably 1 g, 2 g, 3 g, etc.

[0046] This embodiment does not particularly limit the method of mixing anhydrous ethanol, HDTMS, and nanoalumina particles. For example, each component may be placed in a constant-temperature magnetic stirrer and stirred for 12 hours to uniformly disperse the alumina particles in a suspension. After obtaining HDTMS-modified superhydrophobic Al2O3 nanoparticles by centrifugation, the formed nanoparticles may be washed with anhydrous ethanol and dried at 120°C for 3 hours to obtain HDTMS-modified superhydrophobic Al2O3 nanoparticles.

[0047] In some other optional embodiments, the epoxy resin (EP) content is preferably 0.5 to 1.5 g, for example 0.5 g, 1 g, 1.5 g, etc., the polydimethylsiloxane (PDMS) content is preferably 0.5 to 0.7 g, for example 0.5 g, 0.6 g, 0.67 g, 0.7 g, etc., the HDTMS hydrophobized Al2O3 nanoparticle content is preferably 1 to 2 g, for example 1 g, 1.5 g, 2 g, etc., and the volume of xylene is preferably 10 to 30 mL, for example 10 mL, 15 mL, 20 mL, 25 mL, 30 mL, etc.

[0048] In some other arbitrary embodiments, the ratios of EP to PDMS and curing agent are 3:1 and 10:1, respectively. That is, the ratio of EP to epoxy resin curing agent is 3:1, and the ratio of PDMS to curing agent is 10:1.

[0049] In this embodiment, the method for preparing the suspension by dissolving epoxy resin, polydimethylsiloxane, epoxy resin curing agent, and Al2O3 nanoparticles hydrophobized with HDTMS in xylene is not particularly limited. For example, after dissolving each component in xylene, the Al2O3 nanoparticles hydrophobized with HDTMS are added, and the mixture is heated in a 50°C water bath for 1 hour using a constant temperature water bath pot to uniformly disperse and obtain a suspension.

[0050] In some other arbitrary embodiments, the parameters for the process of spray-coating the suspension onto the surface of a chromium-rich corrosion-resistant coating are as follows: the spray gun / matrix distance is 15-20 cm, e.g., 15 cm, 18 cm, 20 cm, and the spray pressure is 0.8 MPa.

[0051] In some other optional embodiments, the curing temperature may preferably be 90 to 110°C, for example 90°C, 95°C, 100°C, or 110°C, and the curing time may be 1 to 3 hours, for example 1 hour, 2 hours, or 3 hours.

[0052] In this embodiment, a hydrophobic film can be formed on the surface of the workpiece by superhydrophobic treatment, preventing water vapor from remaining on the workpiece surface and ensuring that the inner surface of the pipe remains dry. This improves the overall properties such as corrosion resistance and abrasion resistance. Furthermore, this process can also remove fine surface defects and improve its gloss and flatness.

[0053] The manufacturing method of this embodiment is simple and does not require vacuum conditions. Furthermore, the chromizing coating has high manufacturing efficiency, low contamination, adjustable thickness, good wear resistance, and is particularly resistant to high and low temperature corrosion and vapor oxidation. It is also superhydrophobic, preventing metal oxidation corrosion caused by water vapor and fundamentally solving the problem of oxidative corrosion in piping.

[0054] Another aspect of this disclosure proposes a hydrophobic / chromium-rich corrosion-resistant composite coating manufactured by the manufacturing method described above.

[0055] Another aspect of this disclosure proposes the use of a hydrophobic / chromium-rich corrosion-resistant composite coating, wherein the aforementioned hydrophobic / chromium-rich corrosion-resistant composite coating is used on the inner surface of boiler piping.

[0056] The coating of this embodiment has good surface quality, a strong hydrophobic effect on the surface, and excellent corrosion and oxidation resistance, and can be applied to various metal parts that require reinforcement, such as carbon steel, austenitic steel, and high-temperature alloys.

[0057] The manufacturing method for hydrophobic / chromium-rich corrosion-resistant composite coatings is described further below, along with several specific examples. [Examples]

[0058] In this example, we used piping for a large boiler made of carbon steel as an example and applied a hydrophobic / chromium-rich corrosion-resistant composite coating to it. All piping specifications were 55mm outer diameter, 8mm wall thickness, and 4000mm length. The following steps were included:

[0059] S1: Cleaning the surface of the pipes The pipe surfaces were cleaned of oil and dust using alcohol and acetone, and the oxide scale was removed using a steel brush.

[0060] S2: Preheating treatment of piping The piping was preheated to 220°C for 30 minutes.

[0061] S3: Applying slurry to the surface of the pipes The application slurry should be applied in one go to the appropriate thickness using a spray coat (a palm brush or other method may also be used), and should not be applied in multiple layers. The thickness of the slurry layer should be 0.5 mm.

[0062] The method for producing the coating slurry is as follows: As a solid phase component, 60% chromium powder, 15% nickel powder, 5% iron powder, 5% aluminum powder, and 15% yttrium oxide were weighed by mass percentage, and the mixed metal powder was ball milled at a ball milling speed of 350 rpm for 8 hours to obtain the final solid phase component. As a liquid phase component, 25% Al(H2PO4)3, 18% water glass, 7% ammonium iodide, 15% polyvinyl alcohol, and 35% Cr2O3 were weighed by mass percentage, mixed and stirred to obtain the liquid phase component. The solid phase component and the liquid phase component were mixed in a solid-liquid (g:ml) ratio of 10:2 to obtain the final coating slurry.

[0063] S4: Bake curing Metal pipes coated with chromizing material were pre-baked at a low temperature of 60°C for 5 minutes, then baked at a low temperature of 100°C for 55 minutes, and finally cured at a moderate temperature of 250°C for 30 minutes.

[0064] S5: High-speed sintering The piping was rapidly sintered using a high-speed heating method to induce diffusion and chromating, and then air-cooled to room temperature. Here, the heating rate was 1000°C / min, the holding temperature was 980°C, and the holding time was 8 minutes.

[0065] S6: Superhydrophobic treatment A suspension was prepared using 50 mL of anhydrous ethanol, 1 mL of hexadecyltrimethoxysilane (HDTMS), and 2 g of nanoalumina particles. The suspension was stirred with a constant-temperature magnetic stirrer for 12 hours to uniformly distribute the alumina particles. HDTMS-modified superhydrophobic Al2O3 nanoparticles were obtained by centrifugation, and the formed nanoparticles were washed with anhydrous ethanol and dried at 120°C for 3 hours. 1 g of epoxy resin (EP) and 0.67 g of polydimethylsiloxane (PDMS) were completely dissolved in 20 mL of xylene, with the ratios of EP to PDMS and curing agent being 3:1 and 10:1, respectively. Then, 1.5 g of the HDTMS-hydrophobized Al2O3 nanoparticles were added and heated in a 50°C water bath for 1 hour using a constant-temperature water bath pot to uniformly disperse and obtain a suspension. Finally, the suspension was spray-coated onto the surface of a chromium-rich corrosion-resistant coating with a spray gun / matrix distance of 15 cm and a spray pressure of 0.8 MPa. After curing at 100°C for 2 hours, a composite corrosion-resistant coating with a thickness of approximately 13 μm was obtained.

[0066] In the hydrophobic / chromium-rich corrosion-resistant composite coating produced in Example 1, the static water contact angle was 154.1° and the rolling angle was 2.3°. Water droplets could roll freely on the surface of the coating produced in Example 1, and the coating still maintained good superhydrophobicity even after 80 sandpaper abrasion tests (the coating sample was placed face down on sandpaper (2000 mesh) under a 100g load and moved 20cm along a ruler using a horizontal external force; this was defined as one test cycle).

[0067] Furthermore, the charge transfer resistance (RCT) value of the hydrophobic / chromium-rich corrosion-resistant composite coating produced in this Example 1 in a 3.5 wt% sodium chloride solution increased significantly by more than seven orders of magnitude, and the corrosion inhibition rate reached 99.99%. [Examples]

[0068] In this example, we used austenitic steel piping for a large boiler as an example and applied a hydrophobic / chromium-rich corrosion-resistant composite coating to it. All piping specifications were 55mm outer diameter, 8mm wall thickness, and 4000mm length. The following steps were involved.

[0069] S1: Cleaning the surface of the pipes The pipe surfaces were cleaned of oil and dust using alcohol and acetone, and the oxide scale was removed using a steel brush.

[0070] S2: Preheating treatment of piping The piping was preheated to 220°C for 20 minutes.

[0071] S3: Applying slurry to the surface of the pipes The coating slurry should be applied in one go to the appropriate thickness using a spray coating method (a palm brush or other method may also be used), and should not be applied in multiple layers. The coating thickness of the slurry layer should be 0.5 mm.

[0072] The method for producing the coating slurry is as follows: As a solid phase component, 70% chromium powder, 15% nickel powder, 5% iron powder, 5% aluminum powder, and 5% yttrium oxide were weighed by mass percentage and mixed. The mixed metal powder was ball milled at a ball milling speed of 350 rpm for 10 hours to obtain the final solid phase component. As a liquid phase component, 30% Al(H2PO4)3, 25% water glass, 10% ammonium iodide, 15% polyvinyl alcohol, and 20% solidifying agent were weighed by mass percentage, mixed and stirred to obtain the liquid phase component. The solid phase component and the liquid phase component were mixed in a solid-liquid (g:ml) ratio of 10:3 to obtain the final coating slurry.

[0073] S4: Bake curing Metal pipes coated with chromizing material were pre-baked at a low temperature of 70°C for 5 minutes, then baked at a low temperature of 120°C for 55 minutes, and finally cured at a medium temperature of 300°C for 30 minutes.

[0074] S5: High-speed sintering The piping was rapidly sintered using a high-speed heating method to induce diffusion and chromating, and then air-cooled to room temperature. The heating rate was 1000°C / min, the holding temperature was 1080°C, and the holding time was 20 minutes.

[0075] S6: Superhydrophobic treatment Using a spray-coating process similar to that of Example 1, a superhydrophobic material was directly spray-coated or applied as a single layer to the surface of the manufactured chromium-rich corrosion-resistant coating, and then cured to obtain a composite corrosion-resistant coating with a thickness of approximately 43 μm.

[0076] In the hydrophobic / chromium-rich corrosion-resistant composite coating produced in Example 2, the static water contact angle was 155.6° and the rolling angle was 1.8°. Water droplets could roll freely on the surface of the coating produced in Example 2, and the coating still maintained good superhydrophobicity even after 80 sandpaper abrasion tests (the coating sample was placed face down on sandpaper (2000 mesh) under a 100g load and moved 20cm along a ruler using a horizontal external force; this was defined as one test cycle).

[0077] Furthermore, the charge transfer resistance (RCT) value of the hydrophobic / chromium-rich corrosion-resistant composite coating produced in this Example 2 increased by more than seven orders of magnitude in a 3.5 wt% sodium chloride solution, and the corrosion inhibition rate reached 99.99%. [Examples]

[0078] In this example, we used piping for a large boiler made of high-temperature alloy as an example and applied a hydrophobic / chromium-rich corrosion-resistant composite coating to it. All piping specifications were 55mm outer diameter, 8mm wall thickness, and 4000mm length. The following steps were included:

[0079] S1: Cleaning the surface of the pipes Alcohol and acetone were used to remove oil stains and dust from the surface of the pipes, and a steel brush was used to remove oxide scale from the surface.

[0080] S2: Preheating treatment of piping The piping was preheated to 220°C for 50 minutes.

[0081] S3: Applying slurry to the surface of the pipes The coating slurry should be applied in one go to the appropriate thickness using a spray coating method (a palm brush or other method may also be used), and should not be applied in multiple layers. The coating thickness of the slurry layer should be 1.0 mm.

[0082] The method for producing the coating slurry is as follows: As a solid phase component, 70% chromium powder, 5% nickel powder, 5% iron powder, 5% aluminum powder, and 15% yttrium oxide were weighed by mass percentage, and the mixed metal powder was ball milled at a ball milling speed of 350 rpm for 12 hours to obtain the final solid phase component. As a liquid phase component, 30% Al(H2PO4)3, 20% water glass, 5% ammonium iodide, 15% polyvinyl alcohol, and 30% solidifying agent were weighed by mass percentage, mixed and stirred to obtain the liquid phase component. The solid phase component and the liquid phase component were mixed in a solid-liquid (g:ml) ratio of 10:5 to obtain the final coating slurry.

[0083] S4: Bake curing Metal pipes coated with chromizing material were pre-baked at a low temperature of 80°C for 10 minutes, then baked at a low temperature of 150°C for 30 minutes, and finally cured at a medium temperature of 300°C for 20 minutes.

[0084] S5: High-speed sintering The piping was rapidly sintered using a high-speed heating method to induce diffusion and chromating, and then air-cooled to room temperature. The heating rate was 1000°C / min, the holding temperature was 1150°C, and the holding time was 30 minutes.

[0085] S6: Superhydrophobic treatment A superhydrophobic material was directly spray-coated or applied as a single layer to the surface of the chromium-rich corrosion-resistant coating manufactured using a spray-coating process similar to that of Example 1, and then cured to obtain a composite corrosion-resistant coating with a thickness of approximately 64 μm.

[0086] In the hydrophobic / chromium-rich corrosion-resistant composite coating produced in Example 3, the static water contact angle was 154.5° and the rolling angle was 2.7°. Water droplets could roll freely on the surface of the coating produced in Example 3, and the coating still maintained good superhydrophobicity even after 80 sandpaper abrasion tests (the coating sample was placed face down on sandpaper (2000 mesh) under a 100g load and moved 20cm along a ruler using a horizontal external force; this was defined as one test cycle).

[0087] Furthermore, the charge transfer resistance (RCT) value of the hydrophobic / chromium-rich corrosion-resistant composite coating produced in this Example 3 increased by more than seven orders of magnitude in a 3.5 wt% sodium chloride solution, and the corrosion inhibition rate reached 99.99%.

[0088] This disclosure proposes a hydrophobic / chromium-rich corrosion-resistant composite coating, as well as a method for manufacturing and using the same, which has the following beneficial effects compared to the prior art.

[0089] Firstly, this disclosure, by combining chromizing treatment and surface hydrophobic treatment, imparts not only wear resistance and corrosion resistance but also hydrophobic properties to the surface of a workpiece, thereby preventing oxidative corrosion of metals due to water vapor and fundamentally solving the problem of oxidative corrosion of piping.

[0090] Secondly, the chromatizing process of this disclosure is highly efficient, produces minimal contamination, and allows for adjustment of the coating thickness.

[0091] The embodiments described above are merely illustrative examples for illustrating the principles of the Disclosure, but the Disclosure is not limited thereto. Those skilled in the art can make various modifications and improvements without departing from the spirit and essence of the Disclosure, and such modifications and improvements will also be considered within the scope of the Disclosure.

Claims

1. A method for manufacturing a hydrophobic / chromium-rich corrosion-resistant composite coating, The steps include preheating the workpiece and The process involves applying a coating slurry to the surface of a preheated workpiece, baking it to cure it, and then sintering it to obtain a chromium-rich corrosion-resistant coating on the surface of the workpiece, wherein the coating slurry comprises a solid phase component and a liquid phase component, the solid phase component comprising chromium powder, nickel powder, iron powder, and a rare earth compound, and the liquid phase component comprising Al(H) ２ PO ４ ) ３ , water glass, ammonium halides, polyvinyl alcohol, and Cr ２ O ３ Steps including, A manufacturing method characterized by comprising the step of spray-coating a superhydrophobic material in one layer onto the surface of the chromium-rich corrosion-resistant coating and curing it to obtain a hydrophobic / chromium-rich corrosion-resistant composite coating.

2. The manufacturing method according to claim 1, characterized in that the solid-liquid ratio of the solid-phase component to the liquid-phase component is 10:(1 to 5).

3. The chromium powder content is 40-80%, The nickel powder content is 5-30%. The iron powder content is 2-20%, The manufacturing method according to claim 1, characterized in that the content of the rare earth compound is 5 to 45%.

4. The Al(H ２ PO ４ ) ３ The content is 10-30%, The water glass content is 15-25%, The ammonium halide content is 5-10%, The polyvinyl alcohol content is 10-35%. The content of the Cr ２ O ３ is 10 to 30%, and the manufacturing method according to claim 1 is characterized by this.

5. The aforementioned rare earth compound is a rare earth oxide or a rare earth chloride, and / or The manufacturing method according to claim 1, characterized in that the ammonium halide is ammonium bromide or ammonium iodide.

6. The step of applying a superhydrophobic material as a spray coat to the surface of the aforementioned chromium-rich corrosion-resistant coating, followed by a curing treatment, to obtain a hydrophobic / chromium-rich corrosion-resistant composite coating is as follows: Anhydrous ethanol, HDTMS, and nanoalumina particles are mixed to prepare a suspension, stirred, centrifuged, and dried to obtain HDTMS-modified superhydrophobic aluminum. ２ O ３ Steps to obtain nanoparticles, Epoxy resin, polydimethylsiloxane, epoxy resin curing agent, and Al hydrophobized with HDTMS ２ O ３ A manufacturing method according to any one of claims 1 to 5, characterized by comprising the steps of: dissolving nanoparticles in xylene to prepare a suspension; spray-coating the suspension onto the surface of a chromium-rich corrosion-resistant coating; and curing it to obtain a superhydrophobic / chromium-rich corrosion-resistant composite coating.

7. The preheating treatment of the workpiece is performed at a temperature of 150 to 220°C for 30 to 60 minutes, and / or, The manufacturing method according to any one of claims 1 to 5, characterized in that the sintering treatment under inert gas protection is performed at a temperature of 980 to 1150°C for a duration of 8 to 30 minutes.

8. The thickness of the chromium-rich corrosion-resistant coating is 5 to 50 μm, and / or The manufacturing method according to any one of claims 1 to 5, characterized in that the thickness of the hydrophobic / chromium-rich corrosion-resistant composite coating is 13 to 64 μm.

9. A hydrophobic / chromium-rich corrosion-resistant composite coating, A hydrophobic / chromium-rich corrosion-resistant composite coating characterized by being manufactured by the manufacturing method described in any one of claims 1 to 8.

10. The use of a hydrophobic / chromium-rich corrosion-resistant composite coating, The hydrophobic / chromium-rich corrosion-resistant composite coating described in claim 9 is characterized by being used on the inner surface of boiler piping.

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