High-toughness galvanic corrosion protection coating, and preparation method and application thereof

Abstract

The application discloses a high-strength and high-toughness galvanic corrosion protection coating and a preparation method and application thereof, and belongs to the technical field of surface protection. The protection coating comprises an Al2O3-TiO2 composite coating arranged on the surface of a base body. The composite coating contains deposits formed by complete melting of part of original powder materials and serving as a framework for maintaining the overall structure of the composite coating, and deposits formed by partial melting or non-melting of the remaining original powder materials and wrapped in the framework to realize nanometer toughening of the coating. A sealing layer is formed in the surface region of the composite coating, which can reduce the porosity of the coating, improve the toughness and insulation performance of the coating, prevent the entry of corrosive media, form stable hydrophobic properties on the surface of the coating, and improve the corrosion resistance of the coating. The obtained coating has excellent insulation performance and strong impact resistance, and can be used for galvanic corrosion protection at the connecting position of dissimilar metals with relative motion and / or bearing load.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface protection, in particular to a high-toughness galvanic corrosion protection coating and a preparation method and application thereof. BACKGROUND

[0002] With the demand for lightweight of high-end equipment, titanium alloy, aluminum alloy and other lightweight materials are widely used in equipment and pipeline systems, which inevitably exist a large number of dissimilar metal connections. The different corrosion potentials between dissimilar metals exist galvanic current at the contact position, which leads to the widespread existence of galvanic corrosion, increases the dissolution rate of the metal with lower potential, causing local corrosion at the contact, and the dissolution rate of the metal with higher potential is slowed down instead. As a potential, widespread and serious corrosion type, galvanic corrosion can cause accelerated corrosion of low-potential materials such as steel and copper. Its occurrence and development are often accompanied by a variety of local corrosion, such as stress corrosion, pitting corrosion, crevice corrosion, hydrogen embrittlement, etc., thereby accelerating the destruction of equipment and even causing serious losses. Therefore, measures must be taken to intervene in the occurrence of galvanic corrosion at the contact interface of dissimilar metals to ensure the overall reliability and safety of high-end equipment.

[0003] Galvanic corrosion must exist between materials with different corrosion potentials and direct contact between dissimilar materials, and the electrolyte covers or immerses the contact dissimilar materials. Galvanic corrosion protection coating is a protective measure from the perspective of electrical insulation isolation, that is, an insulating coating is coated on the contact surface of dissimilar materials to block the channel for electron movement. The coating can also isolate water, oxygen and other corrosive substances from contacting the substrate. For ordinary parts, an organic insulating coating or a rubber gasket is coated on the contact surface to form electrical insulation isolation. However, for key components that bear load and / or have relative motion, such as natural gas pipeline bends and connection parts, submarine cable joints, electronic components of offshore wind power, circuit interfaces and submarine air inlet components, ceramic coatings with excellent insulation performance, wear resistance and corrosion resistance are required to meet the service requirements. Thermal spraying technology is a typical coating preparation method, which can quickly form an insulating coating with high mechanical strength, good chemical stability and high volume resistivity on the surface of the substrate or component, thereby achieving galvanic corrosion protection.

[0004] Typical insulating ceramic materials include Al2O3, SiO2, ZrO2, CaO, MgO, MgAl2O4, Y2O3, Si3N4, etc. Among them, Al2O3 as a typical insulating ceramic material has the advantages of high temperature stability, sufficient electric breakdown strength, large dielectric constant, excellent radiation resistance and reasonable price, and also has good wear resistance and corrosion resistance, and is a traditional material for insulation. Although high-purity oxides often exhibit better insulating properties, pure Al2O3 coating has the problems of greater brittleness, phase change during spraying process, easy to produce cracks, easy to fall off under the action of transportation, assembly and cold and hot cycle impact, etc.

[0005] The composite ceramic material can relax stress, reduce crack formation, improve powder wettability, increase coating toughness, and also improve coating microstructure integrity and improve its mechanical, electrical, chemical and other comprehensive properties by adding appropriate reinforcing phase or additives to the initial material. For example, since Cr 3+ has a similar ionic radius to Al 3+ , Al2O3 powder added with Cr2O3 by plasma spraying can easily form Al2O3-Cr2O3 solid solution in the coating, which can effectively stabilize α-Al2O3, and has better heat resistance, corrosion resistance and mechanical properties than pure Al2O3 coating. Adding appropriate amount of TiO2 to the original powder of atmospheric plasma sprayed Al2O3 can improve the deposition efficiency of the coating, promote the metastable γ-Al2O3 to transform into stable α-Al2O3, and at the same time, TiO2 as a solubilizing agent, its dispersion distribution in the brittle Al2O3 matrix plays a role in sealing, stress release and crack reduction, and also can improve the ductility of the coating. At the same time, the Al2O3-TiO2 composite coating has good corrosion resistance and insulating properties, and can effectively prevent the occurrence of galvanic corrosion phenomenon. However, the related parts are at greater risk of bumping, impact and vibration during installation and service, and higher requirements are put forward for the bonding strength, toughness, impact resistance and other properties of the ceramic coating, but the ceramic coating usually has the problems of poor toughness and poor impact resistance, and the coating is easy to crack or even fall off when subjected to external impact, which affects its insulating properties and service life.

[0006] In view of this, the present application is proposed. SUMMARY

[0007] The purpose of the present application is to provide a high-strength and high-toughness galvanic corrosion protection coating and its preparation method and application, in order to solve or improve the above technical problems.

[0008] The present application can be implemented as follows:

[0009] In a first aspect, the present application provides a high-toughness galvanic corrosion protection coating, which comprises an Al2O3-TiO2 composite coating arranged on the surface of a substrate, wherein the Al2O3-TiO2 composite coating contains deposits formed by complete melting of part of the original powder material and serving as a framework to maintain the overall structure of the composite coating, and deposits formed by partial melting or non-melting of the remaining original powder material and wrapped in the framework.

[0010] A sealing layer is formed on the surface region of the Al2O3-TiO2 composite coating.

[0011] In an optional embodiment, the original powder material comprises an Al2O3-TiO2 composite powder, wherein the content of TiO2 is 2-20 wt%.

[0012] In an optional embodiment, the Al2O3-TiO2 composite powder is a nano-agglomerated Al2O3-TiO2 composite powder prepared by a spray granulation method.

[0013] In an optional embodiment, the original powder material further comprises an auxiliary material for modifying the Al2O3-TiO2 composite powder, wherein the auxiliary material contains rare earth oxides.

[0014] In an optional embodiment, the auxiliary material comprises at least one of CeO2, Y2O3, LaO2 and La2O3; preferably, the auxiliary material comprises La2O3; more preferably, the content of La2O3 is 0.5-1.0 wt% of the Al2O3-TiO2 composite powder.

[0015] In an optional embodiment, the high-toughness galvanic corrosion protection coating has at least one of the following characteristics:

[0016] Characteristic one: the thickness of the high-toughness galvanic corrosion protection coating is 100-300 μm;

[0017] Characteristic two: the porosity of the high-toughness galvanic corrosion protection coating is not more than 3%;

[0018] Characteristic three: the fracture toughness of the high-toughness galvanic corrosion protection coating is not less than 2.5 MPa·m 1 / 2 .

[0019] In a second aspect, the present application provides a preparation method of the high-toughness galvanic corrosion protection coating according to any one of the preceding embodiments, which comprises the following steps: preparing an Al2O3-TiO2 composite coating on the surface of a substrate, and then preparing a sealing layer on the surface region of the Al2O3-TiO2 composite coating.

[0020] In an optional embodiment, the Al2O3-TiO2 composite coating is prepared by a thermal spraying method.

[0021] In an optional embodiment, the thermal spraying method comprises any one of low pressure plasma spraying, atmospheric plasma spraying, supersonic plasma spraying and supersonic flame spraying.

[0022] In an optional embodiment, the Al2O3-TiO2 composite coating is prepared by using an atmospheric plasma spraying method.

[0023] In the atmospheric plasma spraying method, the plasma spraying gun current is 450-650 A, the argon flow rate is 35-50 L / min, the hydrogen flow rate is 4-12 L / min, the spraying distance is 90-140 mm, and the powder feeding rate is 20-60 g / min.

[0024] In an optional embodiment, the sealing layer is formed by using a vacuum combined with ultrasonic composite dipping method.

[0025] In an optional embodiment, the preparation of the sealing layer comprises: dipping the Al2O3-TiO2 composite coating into a sealing agent, performing ultrasonic treatment while vacuumizing to -0.10 MPa to -0.01 MPa, until no bubbles are generated on the surface of the Al2O3-TiO2 composite coating.

[0026] In an optional embodiment, the sealing agent comprises at least one of inorganic sealing agent, silicone glass resin sealing agent and epoxy resin sealing agent; preferably, the sealing agent comprises a silicone glass resin sealing agent.

[0027] In an optional embodiment, before the preparation of the Al2O3-TiO2 composite coating, the substrate is further subjected to pretreatment.

[0028] In an optional embodiment, the pretreatment comprises: sequentially performing oil removal, sand blasting roughening and preheating on the substrate.

[0029] In a third aspect, the application provides an application of the high-toughness galvanic corrosion protection coating as described in any one of the preceding embodiments, for example, for galvanic corrosion protection at a position where dissimilar metals with relative motion and / or load bearing are connected.

[0030] The beneficial effects of the application include:

[0031] The composite coating provided by the application contains the deposits formed by complete melting of part of the original powder materials as the framework maintaining the overall structure of the composite coating, and the deposits formed by partial melting or non-melting of the remaining original powder materials and wrapped in the framework. The deposits wrapped in the framework structure can realize the nanometer toughening of the coating; the surface area of the composite coating is formed with a sealing layer, which can reduce the porosity of the coating, further improve the toughness and insulation performance of the coating, prevent the entry of corrosive medium and form stable hydrophobic properties on the surface of the coating, and improve the corrosion resistance of the coating. The obtained coating has excellent insulation performance and strong impact resistance, and can be used for galvanic corrosion protection at the connection position of dissimilar metals with relative movement and / or load bearing. BRIEF DESCRIPTION OF DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0033] Figure 1 The scanning electron microscope image of the cross section of the high toughness galvanic corrosion protection coating in Example 1;

[0034] Figure 2 The scanning electron microscope image of the cross section of the protective coating in Comparative Example 1. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the application more clear, the technical solutions in the embodiments of the application will be clearly and completely described below. The specific conditions not mentioned in the embodiments are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not marked with the manufacturer, which are all conventional products that can be purchased on the market.

[0036] The high toughness galvanic corrosion protection coating provided by the application and the preparation method and application thereof will be specifically described below.

[0037] The application provides a high toughness galvanic corrosion protection coating, which comprises an Al2O3-TiO2 composite coating arranged on the surface of a substrate. The Al2O3-TiO2 composite coating contains the deposits formed by complete melting of part of the original powder materials as the framework maintaining the overall structure of the composite coating, and the deposits formed by partial melting or non-melting of the remaining original powder materials and wrapped in the framework. The surface area of the Al2O3-TiO2 composite coating is formed with a sealing layer.

[0038] The deposits formed by complete melting of the above-mentioned part of the original powder material can maintain the overall structure of the coating as a skeleton, and the remaining original powder material that is not completely melted or not melted at all retains its nanostructure and is wrapped by the completely melted powder to achieve nano-toughening of the coating. The sealing process can achieve micro-zone sealing at defects such as internal cracks and pores of the ceramic coating to reduce the porosity of the coating, further improve the toughness and insulation performance of the coating, prevent the entry of corrosive media, and form stable hydrophobic properties on the surface of the coating, further improving the corrosion resistance of the coating.

[0039] In optional embodiments, the original powder material includes Al2O3-TiO2 composite powder. Al2O3 has excellent insulation performance, and TiO2 can improve the deposition efficiency of the coating, promote the transformation of metastable γ-Al2O3 to stable α-Al2O3, and also improve the ductility, density, and comprehensive performance of wear resistance and corrosion resistance of the coating. For reference, the content of TiO2 in the Al2O3-TiO2 composite powder can be 2-20wt%, such as 2wt%, 5wt%, 10wt%, 15wt%, or 20wt%, etc.

[0040] In some preferred embodiments, the above-mentioned Al2O3-TiO2 composite powder can be a nano-agglomerated powder prepared by a spray granulation method, which has high strength and toughness characteristics, can improve the toughness and strength of the ceramic coating, and avoid cracking or even falling off and damage of the ceramic coating during installation and service due to bumps, impacts, and vibrations.

[0041] Further, the above-mentioned original powder material can also include an auxiliary material for modifying the Al2O3-TiO2 composite powder, which contains rare earth oxides. The appropriate addition of the auxiliary material containing rare earth oxides can improve the density of the ceramic coating, disperse the ceramic hard phase to make the coating structure tend to homogenization, reduce the adverse effects of impurities and pores in the composite coating, slow down the initiation and expansion of micro-cracks, and improve the toughness and bonding strength, tribological performance, and thermal shock resistance of the coating.

[0042] For example, the auxiliary material can include at least one of CeO2, Y2O3, LaO2, and La2O3. In some more typical embodiments, the auxiliary material can include La2O3. The solid solution strengthening effect produced by the appropriate addition of La can effectively improve the strength and toughness of the coating material. La is beneficial to improve the sintering resistance and high-temperature stability of Al2O3, and the larger radius of La can hinder ion migration and inhibit grain growth, thereby playing a role in refining the grains. The content of the above-mentioned La2O3 can be 0.5-1.0wt% of the Al2O3-TiO2 composite powder, such as 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, or 1wt%, etc.

[0043] In some embodiments, the high-toughness galvanic corrosion protection coating can have a thickness of 100-300 μm, such as 100 μm, 150 μm, 200 μm, 250 μm or 300 μm, etc. In other embodiments, the thickness of the high-toughness galvanic corrosion protection coating can also be set as needed.

[0044] As mentioned above, the protective coating provided by the present application has excellent insulation performance and toughness.

[0045] In some embodiments, the high-toughness galvanic corrosion protection coating provided by the present application has a porosity of not more than 3%, a fracture toughness of not less than 2.5 MPa·m 1 / 2 .

[0046] Correspondingly, the present application provides a preparation method of the above high-toughness galvanic corrosion protection coating, which can include the following steps: preparing an Al2O3-TiO2 composite coating on the surface of the substrate, and then preparing a sealing layer on the surface area of the Al2O3-TiO2 composite coating.

[0047] For reference, the Al2O3-TiO2 composite coating is prepared by thermal spraying. The thermal spraying includes any one of low-pressure plasma spraying, atmospheric plasma spraying, supersonic plasma spraying and supersonic flame spraying.

[0048] As for thermal spraying, it mainly involves feeding powder or wire material into a certain heat source to heat it to a molten or semi-molten state, and using high-speed airflow to spray it onto the surface of the substrate material. The powder particles undergo plastic deformation under the high-speed impact momentum, and the deformed flat particles are stacked together by inlaying hooking, mechanical bonding and partial metallurgical bonding.

[0049] In the present application, the Al2O3-TiO2 composite coating is preferably prepared by atmospheric plasma spraying. Atmospheric plasma spraying has the advantages of no damage to the substrate during the spraying process, easy adjustment of spraying parameters, controllable coating thickness, and high bonding strength, good stability, high preparation efficiency and low cost of the obtained coating.

[0050] It should be noted that prior art usually deposits a metal bonding layer before spraying the ceramic coating to improve the mismatch of the thermal expansion coefficients of the metal substrate and the ceramic surface layer, so as to improve the bonding strength of the coating and the substrate. However, the metal bonding layer introduced due to the significant difference in material composition and structure between the metal bonding layer and the metal substrate will inevitably have a potential difference, and the interface position between the two still has a high risk of galvanic corrosion in the corrosion medium. The present application does not prepare a metal bonding layer before depositing the ceramic coating, but controls the bonding strength between the ceramic coating and the substrate through the spraying process.

[0051] In the present application, the conditions of atmospheric plasma spraying include: the plasma torch current is 450-650 A (such as 450 A, 480 A, 500 A, 520 A, 550 A, 580 A, 600 A, 620 A or 650 A, etc.), the argon flow rate is 35-50 L / min (such as 35 L / min, 38 L / min, 40 L / min, 42 L / min, 45 L / min, 48 L / min or 50 L / min, etc.), the hydrogen flow rate is 4-12 L / min (such as 4 L / min, 6 L / min, 8 L / min, 10 L / min or 12 L / min, etc.), the spraying distance is 90-140 mm (such as 90 mm, 100 mm, 110 mm, 120 mm, 130 mm or 140 mm, etc.), and the powder feeding rate is 20-60 g / min (such as 20 g / min, 30 g / min, 40 g / min, 50 g / min or 60 g / min, etc.).

[0052] The thermal spraying of the original nanostructured powder builds a coating system with nanostructured characteristics on the substrate surface, which usually shows more excellent comprehensive performance than the coating prepared by using traditional micron-sized original powder materials. However, the thermal spraying coating is formed by the high-speed impact of the small droplets of the raw material heated to the molten or semi-molten state by the high-temperature heat source into the center of the jet on the substrate or the surface of the deposited coating, and then rapidly spreads, cools and solidifies and is stacked layer by layer. If the powder particles do not melt, it is difficult to deposit as a coating or the cohesion strength and service performance of the coating is low; if the powder particles completely melt, the nano characteristics of the powder particles will completely disappear, and the coating will no longer have nanostructure characteristics. Therefore, the microstructure and performance of the coating depend on the speed and melting state of the powder particles at the moment of collision with the substrate, which is closely related to the composition, microstructure and particle size of the main sprayed powder, and the spraying process. On the basis of the composition control and nano-agglomerated structure construction of the sprayed nano original powder material, by optimizing the spraying parameters, the temperature and speed of the plasma jet and the residence time of the powder in the plasma jet are adjusted, the melting degree of the powder particles is accurately controlled to form a "double-mode structure", that is, part of the powder particles completely melt and serve as the skeleton to maintain the whole coating, ensuring the effective bonding between the different particle deposits in the coating; part of the particles are limited to melt or not melt and are wrapped by the completely melted particles, and the nanostructure characteristics of the core are retained, realizing the nano-toughening of the coating, so as to obtain a high-quality micro-nano structure coating with higher bonding strength, toughness and compression resistance.

[0053] In the present application, the substrate is also subjected to oil removal, sand blasting roughening and preheating before spraying the coating. Specifically, the substrate can be degreased by using alcohol, acetone or gasoline, and then protected by using a fixture or masking tape on the non-spraying parts. The adsorbed impurities and oxide layer on the surface of the substrate are removed by sand blasting to increase the surface activity and roughness of the substrate, thereby improving the adhesion between the coating and the substrate. Before spraying, the substrate is preheated by plasma jet under the condition of no powder feeding to increase the temperature of the coating and substrate surface contact, reduce the stress caused by the difference in thermal expansion between the substrate and the coating, and enhance the bonding strength between the coating and the substrate. The steps of oil removal, sand blasting and preheating are common techniques in the technical field, and the specific processing parameters are not limited in the present application.

[0054] During thermal spraying, a large number of micropores are formed in the coating due to the synergistic effects of shielding effect, droplet curling and insufficient outgassing of internal adsorbed gas. At the same time, there is a temperature gradient in the interior of the molten powder particles of the brittle ceramic material perpendicular to the coating direction, and the volume shrinkage caused by solidification is constrained by the surrounding conditions, which also forms a network of cracks perpendicular to the deposition direction. The widespread existence of micropores and microcracks in the coating is beneficial to a certain extent for the relaxation, release or even elimination of the residual stress accumulated inside the coating, which can reduce the risk of coating cracking and even falling during service. However, during service, corrosive media are easily adsorbed on the surface of the coating and enter the interior of the coating through the gaps between the microcracks or different particle deposits, and then penetrate and diffuse along the interfacial boundaries between the particles inside the coating, pores and defects, causing chemical or electrochemical corrosion of the coating and the substrate. With the increase of service time, not only will the function of the coating itself degrade, but also the stability of the substrate structure and the mechanical properties may deteriorate, which seriously affects the service life and working reliability. Therefore, the coating must be post-treated.

[0055] Currently, the porosity of the coating is usually reduced by using a sealing agent, i.e. the sealing agent is allowed to penetrate into the interior of the coating by immersion or coating to improve the structural defects. The sealing agent applied to the surface of the coating will quickly penetrate into the pores and cracks of the coating by relying on its own weight and capillary flow and quickly solidify, forming a diffusion barrier to reduce the channels for the accumulation and entry of water vapor and other impurities into the interior of the coating, which is beneficial to improve the corrosion resistance and insulation performance of the coating. However, the coating process usually has the following two problems: first, due to the air resistance in the stagnant pores, it can only reach a certain distance below the surface of the coating, and the sealing effect of the pores in the deep layer of the coating is not good; second, due to the volume shrinkage and escaping gas during the solidification process of the sealing agent, there are structural defects in the interior of the sealing layer itself, which has insufficient corrosion medium blocking ability. Therefore, the problem of structural defects of thermal spraying coatings serving in extreme corrosive environments for a long time cannot be effectively solved.

[0056] Based on this, the application introduces a specific coating surface sealing treatment technology, that is, the sealing layer is formed by adopting a vacuum combined with ultrasonic composite immersion method. The vacuum immersion scheme can significantly improve the penetration depth of the sealing agent, and the ultrasonic immersion can make the treatment liquid penetrate into the material interior more quickly and fully by using the mechanical vibration effect of ultrasonic waves, so as to realize a higher porosity filling rate.

[0057] For reference, the preparation of the sealing layer includes: soaking the Al2O3-TiO2 composite coating in the sealing agent, and performing ultrasonic treatment while vacuumizing to-0.10 MPa to-0.01 MPa, until no bubbles are generated on the surface of the Al2O3-TiO2 composite coating.

[0058] The sealing agent includes at least one of inorganic sealing agent, silicone glass resin sealing agent and epoxy resin sealing agent. The sealing agent has sufficient permeability to fill to a necessary degree, excellent corrosion resistance to resist the erosion of environmental media, can withstand certain mechanical action to ensure that it will not fall off or break due to the collision in the installation process or the vibration in the service, and has stable performance at the working temperature and does not chemically react with the coating or the substrate.

[0059] In some preferred embodiments, the sealing agent includes the silicone glass resin sealing agent. This type of sealing agent has excellent electrical insulation and dielectric properties in a wide temperature and humidity range, and also has good wear resistance, corrosion resistance, stain resistance, permeability and chemical stability, which can well meet the demand for galvanic corrosion protection in complex environments, and also has the advantages of low cost, simple sealing process, strong adhesion, normal temperature curing and good weather resistance.

[0060] In addition, the application also provides an application of the above high-toughness galvanic corrosion protection coating, for example, for galvanic corrosion protection at a position where dissimilar metals connected to bear load and / or have relative motion.

[0061] For example, the galvanic corrosion protection can be performed at a position where dissimilar metals connected to bear load and / or have relative motion in high-end equipment such as aviation, shipbuilding, marine engineering and the like.

[0062] The features and properties of the application are further described in detail below in combination with embodiments.

[0063] Example 1

[0064] The embodiment provides a high-toughness galvanic corrosion protection coating, and a preparation method thereof includes the following steps:

[0065] (1) After the substrate is degreased, sandblasted and preheated, the nano-agglomerated Al2O3-3%TiO2-0.8%La2O3 powder prepared by the spray granulation method is used as the raw powder material to perform the atmospheric plasma spraying on the surface of the substrate. The spraying parameters are as follows: the plasma spraying gun current is 550 A, the argon flow rate is 40 L / min, the hydrogen flow rate is 10 L / min, the spraying distance is 110 mm, and the powder feeding rate is 30 g / min, so as to obtain a coating with a thickness of 200 μm.

[0066] (2) The coating is immersed in the organic silicon glass resin pore sealing agent, vacuumized to-0.09 MPa and subjected to ultrasonic treatment at the same time, until no bubbles are generated on the surface of the coating, so that the pore sealing agent is infiltrated into the submicron-level cracks, pores and other defects of the coating.

[0067] The cross section of the high-strength and high-toughness galvanic corrosion protection coating prepared in the embodiment is observed under a scanning electron microscope, and the results shown in FIG. 1 are obtained. Figure 1 It can be known from FIG. 1 that the high-strength and high-toughness galvanic corrosion protection coating prepared in the embodiment has a uniform coating structure and no obvious cracks. Figure 1

[0068] Example 2

[0069] The embodiment provides a high-strength and high-toughness galvanic corrosion protection coating, and a preparation method thereof includes the following steps.

[0070] (1) After the substrate is degreased, sandblasted and preheated, the nano-agglomerated Al2O3-3%TiO2 powder prepared by the spray granulation method is used as the raw powder material to perform the atmospheric plasma spraying on the surface of the substrate. The spraying parameters are as follows: the plasma spraying gun current is 600 A, the argon flow rate is 42 L / min, the hydrogen flow rate is 8 L / min, the spraying distance is 120 mm, and the powder feeding rate is 45 g / min, so as to obtain a coating with a thickness of 250 μm.

[0071] (2) The coating is immersed in the organic silicon glass resin pore sealing agent, vacuumized to-0.05 MPa and subjected to ultrasonic treatment at the same time, until no bubbles are generated on the surface of the coating, so that the pore sealing agent is infiltrated into the submicron-level cracks, pores and other defects of the coating.

[0072] Example 3

[0073] The embodiment provides a high-strength and high-toughness galvanic corrosion protection coating, and a preparation method thereof includes the following steps.

[0074] ​(1) After degreasing, sandblasting, roughening, and preheating of the substrate, nano-agglomerated Al2O3-13%TiO2 powder prepared by spray granulation was used as the original powder material for atmospheric plasma spraying on the substrate surface. The spraying parameters were: plasma spray gun current of 480A, argon flow rate of 38L / min, hydrogen flow rate of 11L / min, spray distance of 90mm, and powder feed rate of 25g / min, resulting in a coating with a thickness of 150μm.

[0075] (2) Immerse the coating in silicone glass resin sealing agent, and simultaneously perform ultrasonic treatment while drawing a vacuum to -0.08MPa until no bubbles are generated on the coating surface, so that the sealing agent can penetrate into the coating's submicron level cracks, pores and other defects.

[0076] Example 4

[0077] This embodiment provides a high-strength and tough galvanic corrosion protective coating, the preparation method of which includes the following steps:

[0078] (1) After degreasing, sandblasting, roughening, and preheating of the substrate, atmospheric plasma spraying was performed on the substrate surface using nano-agglomerated Al2O3-3%TiO2-0.6%La2O3 powder as the original powder material. The spraying parameters were: plasma spray gun current of 630A, argon flow rate of 45L / min, hydrogen flow rate of 5L / min, spray distance of 100mm, and powder feed rate of 50g / min, resulting in a coating with a thickness of 280μm.

[0079] (2) Immerse the coating in silicone glass resin sealing agent, and simultaneously perform ultrasonic treatment while drawing a vacuum to -0.08MPa until no bubbles are generated on the coating surface, so that the sealing agent can penetrate into the coating's submicron level cracks, pores and other defects.

[0080] Comparative Example 1

[0081] This comparative example provides a protective coating against galvanic corrosion, prepared using the same method as in Example 2, except that the selected coating material is micron-sized Al2O3-3% TiO2 powder prepared by a melt-crush method. The cross-section of the coating obtained in this comparative example was observed under a scanning electron microscope, as shown below. Figure 2 The results are shown.

[0082] Depend on Figure 2 It can be seen that the coating prepared in this comparative example is relatively loose, with obvious pores and a large number of microcracks.

[0083] Comparative Example 2

[0084] This comparative example provides a protective coating, which is prepared in the same way as in Example 1, except that no surface sealing treatment is performed.

[0085] Comparative Example 3

[0086] The comparative example provides a protective coating, and the preparation method is the same as that of example 1, and the only difference is that the plasma spray gun current is 440 A, the argon flow rate is 32 L / min, and the hydrogen flow rate is 3.8 L / min; the spraying distance and the powder feeding rate are the same as those of example 1. During the spraying process, the original powder material is limitedly melted, the formed coating is relatively loose, and the cohesive strength is insufficient.

[0087] Comparative example 4

[0088] The difference between the comparative example and example 1 is that the preparation process of the sealing layer does not perform ultrasonic treatment.

[0089] Test example

[0090] The protective coatings prepared in examples 1-4 and comparative examples 1-4 are respectively subjected to coating porosity, fracture toughness and volume resistivity tests, and the results are shown in Table 1.

[0091] Among them, the porosity is tested according to ASTM E2109 “Standard Test Methods for Determining Area Percentage Porosity in Thermal Sprayed Coatings”, the fracture toughness is characterized by using the indentation method according to the EVANS model, and the volume resistivity is determined according to GB / T 1410-2006 “Solid Insulating Materials Volume Resistivity and Surface Resistivity Test Method”.

[0092] Table 1 Performance of high-strength and high-toughness galvanic corrosion protective coating

[0093]

[0094] As shown in Table 1, the composite coating provided by the examples has excellent insulation performance and good toughness, which is beneficial to improve the service safety of the equipment and prolong the service life of the dissimilar metal contact part.

[0095] In summary, the scheme provided in the present application has the following advantages:

[0096] (1) The nano-agglomerated Al2O3-TiO2 powder prepared by the spray granulation method is used as the raw material, and the micro-nano structure composite coating is obtained by adjusting the thermal spraying process. Part of the powder is completely melted and maintains the overall structure of the coating as a skeleton, and part of the powder is limitedly melted or not melted and retains its nano structure and is wrapped by the completely melted deposits to realize the nano toughening of the coating, so that a coating with excellent density, toughness and insulation performance is obtained.

[0097] (2) By combining "vacuum + ultrasonic" composite immersion, the penetration depth and sealing efficiency of the organic sealing agent in the coating are improved, the micro-area sealing at the internal micro-cracks and pores of the ceramic coating is realized to reduce the porosity of the coating, and the stable hydrophobic properties are formed on the surface of the coating, which is beneficial to improve the corrosion resistance and insulation performance of the coating, and also has a positive effect on improving the toughness of the coating.

[0098] (3) The atmospheric plasma spraying and "vacuum + ultrasonic" composite immersion process used for coating preparation have the characteristics of high efficiency, low cost and easy operation, and the process is simple and easy to realize automation. The prepared composite coating has excellent toughness and impact resistance, and the coating is not easy to be damaged when subjected to external force impact during installation, welding and service, and has good safety and stability, long service life.

[0099] The above is only the preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A high-strength and tough protective coating against galvanic corrosion, characterized in that, The high-strength and tough galvanic corrosion protective coating includes an Al2O3-TiO2 composite coating disposed on the surface of the substrate. The Al2O3-TiO2 composite coating contains deposits formed by the complete melting of a portion of the original powder material, which serve as a skeleton to maintain the overall structure of the composite coating, and deposits formed by the partial melting or non-melting of the remaining original powder material, which are encapsulated within the skeleton. A sealing layer is formed on the surface area of ​​the Al2O3-TiO2 composite coating; The original powder material includes Al2O3-TiO2 composite powder, wherein the content of TiO2 is 2-20 wt%; the Al2O3-TiO2 composite powder is nano-agglomerated Al2O3-TiO2 composite powder prepared by spray granulation method; The preparation of the high-strength and tough galvanic corrosion protective coating includes: preparing the Al2O3-TiO2 composite coating on the surface of the substrate, and then preparing the sealing layer on the surface region of the Al2O3-TiO2 composite coating; The Al2O3-TiO2 composite coating was prepared by atmospheric plasma spraying. The atmospheric plasma spraying conditions included: plasma spray gun current of 450-650A, argon flow rate of 35-50L / min, hydrogen flow rate of 4-12L / min, spray distance of 90-140mm, and powder feeding rate of 20-60g / min. The sealing layer is formed by a vacuum combined with ultrasonic composite impregnation method. The preparation of the sealing layer includes: immersing the Al2O3-TiO2 composite coating in a sealing agent, evacuating to -0.10MPa to -0.01MPa while performing ultrasonic treatment until no bubbles are generated on the surface of the Al2O3-TiO2 composite coating.

2. The high-strength and tough galvanic corrosion protective coating according to claim 1, characterized in that, The original powder material also includes auxiliary materials for modifying the Al2O3-TiO2 composite powder, wherein the auxiliary materials contain rare earth oxides.

3. The high-strength and tough galvanic corrosion protective coating according to claim 2, characterized in that, The excipients include at least one of CeO2, Y2O3, LaO2, and La2O3.

4. The high-strength and tough galvanic corrosion protective coating according to claim 3, characterized in that, The excipients include La2O3.

5. The high-strength and tough galvanic corrosion protective coating according to claim 4, characterized in that, The content of La2O3 is 0.5-1.0 wt% of the Al2O3-TiO2 composite powder.

6. The high-strength and tough galvanic corrosion protective coating according to any one of claims 1-5, characterized in that, The high-strength and tough galvanic corrosion protective coating has at least one of the following characteristics: Feature 1: The thickness of the high-strength and tough galvanic corrosion protective coating is 100-300μm; Feature 2: The porosity of the high-strength and tough galvanic corrosion protective coating does not exceed 3%; Feature 3: The fracture toughness of the high-strength and tough galvanic corrosion protective coating is not less than 2.5 MPa·m. 1 / 2 .

7. A method for preparing a high-strength and tough galvanic corrosion protective coating as described in any one of claims 1-6, characterized in that, Includes the following steps: An Al2O3-TiO2 composite coating is prepared on the surface of the substrate, and then a sealing layer is prepared on the surface region of the Al2O3-TiO2 composite coating; The Al2O3-TiO2 composite coating was prepared by atmospheric plasma spraying. The atmospheric plasma spraying conditions included: plasma spray gun current of 450-650A, argon flow rate of 35-50L / min, hydrogen flow rate of 4-12L / min, spray distance of 90-140mm, and powder feeding rate of 20-60g / min. The sealing layer is formed by a vacuum combined with ultrasonic composite impregnation method. The preparation of the sealing layer includes: immersing the Al2O3-TiO2 composite coating in a sealing agent, evacuating to -0.10MPa to -0.01MPa while performing ultrasonic treatment until no bubbles are generated on the surface of the Al2O3-TiO2 composite coating.

8. The preparation method according to claim 7, characterized in that, The sealing agent includes at least one of inorganic sealing agents, organosilicon glass resin sealing agents, and epoxy resin sealing agents.

9. The preparation method according to claim 8, characterized in that, The sealing agent includes an organosilicon glass resin sealing agent.

10. The preparation method according to claim 7, characterized in that, Before preparing the Al2O3-TiO2 composite coating, the substrate is also pretreated. Pretreatment includes: sequentially degreasing, sandblasting roughening, and preheating the substrate.

11. The application of a high-strength and tough galvanic corrosion protective coating as described in any one of claims 1-6, characterized in that, The high-strength and tough galvanic corrosion protective coating is used to protect dissimilar metals from galvanic corrosion at load-bearing and / or relatively moving connection points.

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