Heat exchanger and method of manufacturing a heat exchanger

Abstract

This invention discloses a heat exchanger and a heat exchanger processing method. The heat exchanger includes an aluminum substrate and a first coating. The first coating is applied to at least a portion of the surface of the aluminum substrate. The first coating includes metal sheets and an adhesive. There are multiple metal sheets, which are dispersed in the adhesive. The metal sheets include zinc sheets. A plane parallel to the thickness direction of the first coating is defined as a first plane, and a plane with an angle θ to the first plane is defined as a second plane, where 0° < θ ≤ 90°. The projections of the multiple metal sheets onto the first plane or the second plane at least partially overlap. The metal sheets form a multi-layered interlaced structure in the first coating. This heat exchanger has good corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of heat exchange, and more specifically, to a heat exchanger and a method for processing the heat exchanger for use in refrigeration, heating, ventilation and air conditioning. Background Technology

[0002] Among related technologies, aluminum heat exchangers have been widely used in the refrigeration, heating, ventilation, and air conditioning (HVAC) field due to their high heat exchange efficiency and lightweight advantages. However, during use, aluminum heat exchangers exposed to air or corrosive environments are at risk of corrosion, affecting their corrosion resistance and service life. Summary of the Invention

[0003] Therefore, the present invention provides a heat exchanger with good corrosion resistance.

[0004] Another aspect of this invention proposes a heat exchanger processing method that can improve the corrosion resistance of the heat exchanger and extend its service life.

[0005] This invention provides a heat exchanger comprising an aluminum substrate and a first coating. The first coating is applied to at least a portion of the surface of the aluminum substrate. The first coating comprises metal sheets and an adhesive. There are multiple metal sheets dispersed in the adhesive. The metal sheets include zinc sheets. A plane parallel to the thickness direction of the first coating is defined as a first plane, and a plane with an angle θ to the first plane is defined as a second plane, where 0° < θ ≤ 90°. The projections of the multiple metal sheets onto the first plane or the second plane at least partially overlap. The metal sheets form a multi-layered staggered structure in the first coating.

[0006] The heat exchanger of this embodiment includes an aluminum substrate. A first coating is applied to at least a portion of the surface of the aluminum substrate. This first coating includes multiple metal sheets dispersed in the binder. The metal sheets include zinc sheets, which have a lower potential than the aluminum substrate. During electrochemical corrosion, the zinc sheets act as sacrificial anodes, providing cathodic protection to the aluminum substrate and are thus corroded first, thereby slowing down the corrosion rate of the heat exchanger. The projections of the multiple metal sheets onto a first or second plane at least partially overlap, forming a multi-layered, interwoven structure in the first coating. This improves the density of the first coating, and the gaps between the metal sheets can be filled with the binder. Therefore, the first coating... It forms an effective barrier layer, which can play a physical isolation role, preventing corrosive media from reaching the aluminum substrate surface and slowing down the corrosion rate of the heat exchanger. Even at the location of defects in the first coating, corrosion will preferentially occur on the first coating. The zinc flakes near the corrosion site can react with the corrosive media to form insoluble zinc salts such as oxides, hydroxides, and carbonates. These substances will fill the small coating losses and act as corrosion inhibitors, thereby delaying further damage to the coating. Furthermore, due to the multi-layered interlaced structure of the first coating, the corrosion is layered corrosion along the coating surface, which further extends the protection of the aluminum substrate, improves the corrosion resistance of the heat exchanger, and increases the service life of the heat exchanger.

[0007] This invention also provides a heat exchanger processing method, the heat exchanger processing method comprising:

[0008] Assemble and weld the aluminum substrate;

[0009] A coating solution is applied to at least a portion of the surface of the aluminum substrate. The coating solution comprises a metal sheet and an adhesive, wherein the metal sheet comprises a zinc sheet, and the metal sheet accounts for 20%-50% of the weight of the coating solution, and the adhesive accounts for 5%-30% of the weight of the metal sheet.

[0010] The heat exchanger is cured to obtain a first coating, wherein the metal sheet forms a multi-layered interlaced structure in the first coating.

[0011] An embodiment of this application discloses a heat exchanger processing method, which involves coating at least a portion of the surface of an aluminum substrate with a coating solution, the coating solution comprising metal sheets and an adhesive, the metal sheets comprising zinc sheets, and after the coating solution is cured, a heat exchanger coated with a first coating is formed. The metal sheets form a multi-layered interlaced structure in the first coating, which helps to slow down the corrosion rate of the aluminum substrate, improve the corrosion resistance of the heat exchanger, and extend the service life of the heat exchanger. Attached Figure Description

[0012] Figure 1 This is a cross-sectional structural diagram of the first coating on the surface of a heat exchanger according to an embodiment of this application;

[0013] Figure 2 This is a cross-sectional structural diagram of the first coating on the surface of a heat exchanger according to another embodiment of this application;

[0014] Figure 3 This is a cross-sectional structural diagram of the first coating on the surface of a heat exchanger according to yet another embodiment of this application;

[0015] Figure 4 This is a cross-sectional structural diagram of the first coating on the surface of a heat exchanger according to another embodiment of this application;

[0016] Figure 5 This is a SEM image of the first coating section of this application;

[0017] Figure 6 This is a SEM image of the first coating surface of this application;

[0018] Figure 7 This is a metallographic schematic diagram of the cross-section of the first surface of the aluminum substrate of this application;

[0019] Figure 8 This is a surface SEM image of the first surface of the aluminum substrate in this application;

[0020] Figure 9 This is a schematic diagram of the structure of an aluminum substrate for a heat exchanger according to an embodiment of this application;

[0021] Figure 10 This is a schematic diagram of the structure of the aluminum substrate of the heat exchanger according to another embodiment of this application;

[0022] Figure label:

[0023] Heat exchanger 100, aluminum substrate 1, first surface 11, first recess 111, first coating 2, metal sheet 21, zinc sheet 211, aluminum sheet 212, passivation layer 3, heat exchange tube 4, first tube 5, fins 6. Detailed Implementation

[0024] To better understand the technical solutions of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are merely a part of the technical solutions of this application, and not all of them. Based on the technical solutions in this application, all other technical solutions obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0026] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0027] It should be noted that the directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this application are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this application. Furthermore, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0028] Embodiments of the present invention are described in detail below, with examples of the embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] This invention is based on the inventor's discovery and understanding of the following facts and problems: Currently, in order to improve the corrosion resistance and service life of heat exchangers in atmospheric environments, heat exchangers are generally treated in some ways, such as applying an anti-corrosion coating after the heat exchanger is formed. However, these coatings still have the risk of corrosion failure when tested in the laboratory and applied in the market. If the coating has defects, it will cause the heat exchanger to corrode faster.

[0030] Analysis suggests several possible reasons: First, during brazing, flux residue may remain on the heat exchanger surface. This flux is difficult to remove, and during coating treatment, areas with flux residue may not adhere properly or have poor adhesion, creating coating defects and corrosion entry points. Second, to improve heat exchanger efficiency, fins are often open-windowed, resulting in numerous cut edges. These edges are often not fully covered by the coating, or if covered, are very thin and defective, creating weak points for corrosion. Corrosive media, such as chloride ions and water vapor, can penetrate the coating and reach the heat exchanger substrate, causing premature blistering or peeling, accelerating localized corrosion, and impacting product lifespan. Third, heat exchangers are prone to dust accumulation, which increases the likelihood of corrosion. If the coating is defective, this dust can also create entry points at these defects, damaging the coating and corroding the heat exchanger's metal substrate.

[0031] In related technologies, commonly used anti-corrosion coatings for heat exchangers, such as electrophoretic organic coatings or chemically reactive coatings, are cathodic protection coatings. Their anti-corrosion mechanism is physical isolation, preventing external corrosive media from contacting the metal substrate and thus avoiding corrosion. However, if these coatings have defects, corrosion may preferentially occur at these defective locations, while areas with intact coatings remain uncorroded, creating a large cathode and small anode corrosion pattern that accelerates the corrosion of the aluminum substrate at the defective locations. If the heat exchange tubes are zinc-sprayed, due to the low potential of the surface zinc layer, corrosion may occur along the surface zinc layer, causing large-area corrosion beneath the coating. This leads to bulging or peeling of the coating around the corrosion points, further accelerating the corrosion of the metal substrate beneath the coating.

[0032] To address this problem, this application provides a novel coating for use in heat exchangers. This coating not only provides simple physical insulation but also offers sacrificial protection and other functions. Furthermore, even at locations with coating defects, corrosion preferentially occurs on the coating, thereby protecting the heat exchanger substrate from corrosion and improving the corrosion resistance of the heat exchanger.

[0033] This application provides a heat exchanger, which includes an aluminum substrate 1 and a first coating 2. The first coating 2 is applied to at least a portion of the surface of the aluminum substrate 1. The first coating 2 includes metal sheets 21 and an adhesive. There are multiple metal sheets 21, which are dispersed in the adhesive. The metal sheets 21 include zinc sheets 211. A plane parallel to the thickness direction of the first coating is defined as a first plane, and a plane with an angle θ with the first plane is defined as a second plane, where 0° < θ ≤ 90°. The projections of the multiple metal sheets 21 on the first plane or the second plane at least partially overlap, and the metal sheets 21 form a multi-layered interlaced structure in the first coating 2.

[0034] Specifically, such as Figure 1-10 As shown, the heat exchanger 100 includes an aluminum substrate 1 and a first coating 2. The first coating 2 is applied to at least a portion of the surface of the aluminum substrate 1. The aluminum substrate 1 can be made of aluminum or an aluminum alloy. The first coating 2 includes multiple metal sheets 21 dispersed in the binder. The metal sheets include zinc sheets 211. The zinc sheets 211 have a lower potential than aluminum or aluminum alloy. During electrochemical corrosion, the zinc sheets 211 act as sacrificial anodes, providing cathodic protection to the aluminum substrate 1 and are the first to be corroded, thus slowing down the corrosion rate of the heat exchanger. Even at locations with defects in the first coating, corrosion preferentially occurs on the first coating. The zinc sheets near the corrosion site can react with the corrosive medium to form insoluble zinc salts such as oxides, hydroxides, and carbonates. These substances fill in small coating losses and act as corrosion inhibitors, thereby delaying further damage to the coating.

[0035] The projections of multiple metal sheets 21 onto a first plane or a second plane at least partially overlap. The first plane is a plane parallel to the thickness direction of the first coating, and the second plane is a plane making an angle θ with the first plane, where 0° < θ ≤ 90°. Alternatively, the projections of the multiple metal sheets 21 onto the plane parallel to the thickness direction of the first coating at least partially overlap, or the projections of the multiple metal sheets 21 onto the plane containing the first coating 2 at least partially overlap. Figure 1-5 As shown, the thickness direction of the first coating 2 is the vertical direction in the figure. On the cross-section of the first coating 2 in the thickness direction, multiple metal sheets 21 are multi-layered in the thickness direction of the first coating, and the multiple metal sheets 21 at least partially overlap in the thickness direction of the first coating, as shown. Figure 6 As shown, the projections of multiple metal sheets 21 onto the plane containing the first coating 2 at least partially overlap, and the multiple metal sheets 21 interweave with each other, thereby improving the density of the first coating.

[0036] The metal sheets 21 form a multi-layered interlaced structure in the first coating, and the gaps between the metal sheets can be filled with an adhesive. Thus, the first coating 2 constitutes an effective barrier layer, which can play a physical isolation role, preventing corrosive media from reaching the surface of the aluminum substrate 1 of the heat exchanger and slowing down the corrosion rate of the heat exchanger. Even at the defective locations of the first coating 2, corrosion will preferentially occur on the first coating. The zinc sheets near the corrosion location can react with the corrosive media to form insoluble zinc salts such as oxides, hydroxides, and carbonates. The corrosive media is air, etc. These substances will fill the small coating losses and act as a corrosion inhibitor, thereby delaying further damage to the first coating. Furthermore, due to the multi-layered interlaced structure of the first coating, the corrosion is a layered corrosion along the coating surface, further extending the protection of the heat exchanger, improving the corrosion resistance of the heat exchanger, and extending the service life of the heat exchanger.

[0037] In some embodiments, such as Figure 9-10 As shown, the aluminum substrate 1 of the heat exchanger includes heat exchange tubes 4, a first tube 5, and fins 6. All three components—heat exchange tubes 4, first tube 5, and fins 6—are made of aluminum or aluminum alloy. The heat exchange tubes 4 include heat exchange channels extending along their length and are connected to the first tube 5 to allow refrigerant circulation within the heat exchanger. The fins 6 can be provided with openings to increase heat exchange with the air and improve heat exchange efficiency. The heat exchange tubes 4 and fins 6 can be welded together, reducing the gap between them and further improving the heat exchange efficiency. The heat exchange tubes 4 can be microchannel flat tubes, round tubes, or elliptical heat exchange tubes.

[0038] The aluminum substrate 1 structure of the heat exchanger can be as follows: Figure 9 As shown, fins 6 are located between adjacent heat exchange tubes 4. Fins 6 are corrugated fins, and both ends of heat exchange tubes 4 are connected to two first tubes 5 respectively; alternatively, as shown... Figure 10As shown, there are multiple fins 6, which are spaced apart along the length of the heat exchange tube 4. The heat exchange tube 4 passes through the through holes or slots on the fins 6 and is connected to the heat exchange tube 4. Both ends of the heat exchange tube 4 are connected to two first tubes 5 respectively. In some embodiments, in the structure of the aluminum substrate 1 of the heat exchanger, the first tube 5 can be a U-shaped tube, with one U-shaped tube connecting an adjacent heat exchange tube 4. There are multiple U-shaped tubes to achieve communication between the first tube 5 and the heat exchange tube 4. The shape of the aluminum substrate 1 of the heat exchanger is not limited.

[0039] The first coating 2 is applied to at least a portion of the surface of at least one of the heat exchange tubes 4, the first tube 5, and the fins 6 of the aluminum substrate 1. The first coating 2 may be applied only to at least a portion of the surface of one of the heat exchange tubes 4, the first tube 5, or the fins 6, or only to locations on the aluminum substrate of the heat exchanger that are prone to corrosion, or the first coating 2 may be applied to all three of the heat exchange tubes 4, the first tube 5, and the fins 6. This provides better protection for the aluminum alloy substrate of the heat exchanger and extends its service life. The specific application of the heat exchanger can be configured accordingly, and no restrictions are imposed here.

[0040] In some embodiments, the aluminum substrate 1 of the heat exchanger also includes other components such as inlet and outlet pipes and mounting brackets, and the first coating may also be applied to at least some of the components to further improve the corrosion resistance of the heat exchanger.

[0041] In some embodiments, the first coating can be applied to heat exchangers with other metal substrates, including stainless steel, iron, copper, etc. Since zinc has a lower potential than other metals, it can provide sacrificial protection for heat exchangers with other metal substrates and improve the corrosion resistance of the heat exchangers.

[0042] In some embodiments, the metal sheet 21 further includes an aluminum sheet 212, a zinc sheet 211 and the aluminum sheet 212 dispersed in the first coating 2, wherein the zinc sheet 211 accounts for 65%-100% of the metal 21 and the aluminum sheet 212 accounts for 0%-35% of the metal sheet.

[0043] The metal sheet 21 also includes an aluminum sheet 212, a zinc sheet 211, and the aluminum sheet 212 are dispersed in the first coating 2. The zinc sheet 211 comprises 65%-100% of the metal sheet, for example, 65%, 70%, 75%, 80%, 90%, or 100%. The aluminum sheet 212 comprises 0%-35% of the metal sheet, for example, 0%, 10%, 15%, 20%, 30%, or 35%. For example, if the zinc sheet 211 comprises 85% of the metal sheet, the corresponding aluminum sheet 212 comprises 15%; if the zinc sheet 211 comprises 100% of the metal sheet, the aluminum sheet 212 comprises 0%.

[0044] Because zinc has a more negative potential than aluminum or aluminum alloys, during electrochemical corrosion, zinc sheet 211 will act as a sacrificial anode to provide cathodic protection for the aluminum substrate and will be corroded first, thus protecting the aluminum substrate 1 of the heat exchanger from corrosion. This can achieve the effect of sacrificial corrosion protection. Therefore, zinc sheet 211 is set to account for a larger proportion of aluminum sheet 212 in the metal sheet, so as to better protect the aluminum substrate 1 of the heat exchanger and improve the corrosion resistance of the heat exchanger.

[0045] Adding a certain amount of aluminum sheet 212 to the metal sheet 21, where the aluminum sheet 212 has a higher potential than the zinc sheet, allows the first coating to corrode the zinc sheet 211 first, followed by the aluminum sheet 212, during the corrosion process. In a coating of a certain thickness, if it consists entirely of zinc sheet 211, corrosion will directly corrode that thickness of the first coating. However, with the addition of aluminum sheet 212, the zinc sheet 211 corrodes first, followed by the aluminum sheet 212, until the first layer of coating is completely corroded before the next layer is formed. Therefore, adding a certain amount of aluminum sheet 212 to the metal sheet can slow down the corrosion rate of the first coating and extend its service life. However, if too much aluminum sheet 212 is added, and since the heat exchanger 100 is an aluminum substrate, the potential of the aluminum sheet 212 is similar to that of the aluminum substrate 1. In this case, the effect of the first coating 2 in slowing down corrosion will be greatly reduced. Therefore, the proportion of aluminum sheet added should be 0%-35%.

[0046] When the metal sheet 21 also includes an aluminum sheet 212, the projections of the zinc sheet 211 and / or the aluminum sheet 212 on the first plane or the second plane at least partially overlap. That is, the projections of multiple zinc sheets 211 on the first plane or the second plane at least partially overlap, or the projections of multiple zinc sheets 211 and multiple aluminum sheets 212 on the first plane or the second plane at least partially overlap. The zinc sheet 211 and the aluminum sheet 212 form a multi-layered interlaced structure in the first coating. Thus, the first coating constitutes an effective barrier layer, which can slow down the corrosion rate of the heat exchanger and improve the service life of the heat exchanger.

[0047] The metal sheet 21 includes zinc sheet 211 and aluminum sheet 212. The zinc sheet 211 and aluminum sheet 212 are mixed and dispersed in the first coating 2. Compared with zinc-aluminum alloy powder, it is not necessary to smelt zinc and aluminum into zinc-aluminum alloy and then make zinc-aluminum alloy powder. This reduces the metal powder processing steps and lowers the production cost of the metal powder for the coating. Furthermore, the first coating 2 formed by mixing zinc sheet 211 and aluminum sheet 212 has a lower corrosion potential than zinc-aluminum alloy powder, providing better protection for the aluminum substrate 1 of the heat exchanger. This can further improve the corrosion resistance of the heat exchanger and extend its service life.

[0048] In some embodiments, the content of metal sheet 21 in the first coating 2 is greater than 30%, thereby making it easier to form a multi-layered interlaced structure. The gap between zinc sheet 211 and aluminum sheet 212 is filled with amorphous adhesive, forming a very effective barrier layer that effectively prevents corrosive media from reaching the aluminum substrate of the heat exchanger.

[0049] In some embodiments, the zinc sheet 211 has a size of 0.5-40 μm and a thickness of 0.1-3 μm; and / or, the aluminum sheet 212 has a size of 0.5-40 μm and a thickness of 0.1-3 μm.

[0050] Specifically, the zinc sheet 211 has a size of 0.5-40μm. For example, the length of the zinc sheet 211 can be 1μm, 3μm, 10μm, 20μm, 30μm, 35μm, etc., and the width of the zinc sheet 211 can be 1μm, 3μm, 10μm, 20μm, 30μm, 35μm, etc. The thickness of the zinc sheet 211 is 0.1-3μm. For example, the thickness of the zinc sheet 211 can be 0.2μm, 0.3μm, 0.5μm, 1μm, 2μm, 3μm, etc., so that the zinc sheet 211 is generally a sheet-like structure. The sheet-like structure makes it easier to form a multi-layered, interlaced structure in the coating, improving the density of the coating and enhancing the protective effect of the first coating.

[0051] The aluminum sheet 212 has a size of 0.5-40μm. For example, the length of the aluminum sheet 212 can be 1μm, 3μm, 10μm, 20μm, 30μm, 35μm, etc., and the width of the aluminum sheet 212 can be 1μm, 3μm, 10μm, 20μm, 30μm, 35μm, etc. The thickness of the aluminum sheet 212 is 0.1-3μm. For example, the thickness of the aluminum sheet 212 can be 0.2μm, 0.3μm, 0.5μm, 1μm, 2μm, 3μm, etc., making the aluminum sheet 212 generally a sheet-like structure. The sheet-like structure makes it easier to form a multi-layered, interlaced structure in the coating, improving the density of the coating, improving the protective effect of the first coating, and improving the corrosion resistance of the heat exchanger.

[0052] If the zinc sheet 211 or aluminum sheet 212 is too large, the gap between the zinc sheet 211 and aluminum sheet 212 in the first coating 2 will also increase accordingly, which will make the appearance quality of the first coating worse, and the corrosive medium will be more likely to enter the gap and corrode, reducing the life of the first coating. Moreover, if the zinc sheet 211 or aluminum sheet 212 is too large, the adhesion of the first coating will decrease, and the coating will be more likely to fall off from the aluminum substrate 1 of the heat exchanger, thereby reducing the protection of the aluminum substrate of the heat exchanger.

[0053] like Figure 5As shown, in the cross-section along the thickness direction of the first coating 2, the zinc sheet 211 or aluminum sheet 212, due to their smaller thickness dimension, are generally elongated strips. Furthermore, multiple zinc sheets 211 or aluminum sheets 212 are multi-layered along the thickness direction of the first coating. These multi-layered layers interweave, improving the density of the first coating and making it difficult for corrosion to penetrate. Figure 6 As shown, on the surface of the first coating 2, the zinc sheet 211 or aluminum sheet 212 has a sheet-like structure and is interlaced in a plane perpendicular to the thickness direction of the first coating. The density is high in each layer in the thickness direction of the coating. Thus, the zinc sheet 211 and aluminum sheet 212 form an interlaced stacked structure in multiple planes of the first coating. The coating has high density, which prolongs the coating life and makes the corrosion of the first coating layered, improving the protection of the heat exchanger by the coating and increasing the service life of the heat exchanger.

[0054] In some embodiments, the thickness of the first coating is 5 μm-50 μm.

[0055] Specifically, the thickness of the first coating 2 formed on the surface of the heat exchanger 100 is 5μm-50μm. When the thickness of the first coating is less than 5μm, the coating thickness is too small, weakening the corrosion protection of the aluminum substrate of the heat exchanger; if the thickness of the first coating is greater than 50μm, the coating is prone to peeling and detachment, reducing the protection of the aluminum substrate of the heat exchanger. Moreover, if the thickness of the first coating is too large, it will reduce the thermal conductivity of the surface of the aluminum substrate of the heat exchanger, thereby reducing the heat exchange efficiency of the heat exchanger. Therefore, setting the thickness of the first coating to 5μm-50μm can better protect the heat exchanger substrate and extend the service life of the heat exchanger.

[0056] like Figure 1-5 As shown, the thickness of the first coating formed on the surface of the heat exchanger 100 is 5μm-50μm, and the projections of multiple metal sheets 21 on the first plane or the second plane overlap at least partially, forming a multi-layered staggered structure in the first coating. The metal sheets 21 are stacked layer by layer, and the gaps between them can be filled with adhesive, forming an effective barrier layer that can play a physical isolation role, preventing corrosive media from reaching the surface of the heat exchanger, slowing down the corrosion rate of the heat exchanger, and even at the location of defects in the first coating, corrosion will preferentially occur on the first coating. Furthermore, due to the multi-layered staggered structure of the first coating, the corrosion is a layered corrosion along the coating surface, further extending the protection of the heat exchanger, improving the corrosion resistance of the heat exchanger, and extending the service life of the heat exchanger.

[0057] In some embodiments, to thicken the coating and obtain better corrosion resistance, the heat exchanger 100 can be coated with the first coating 2 two or three times. After the first coating is applied and dried, a second coating is applied. After two or three coatings, the thickness of the first coating is correspondingly increased. It should be noted that the maximum thickness of the first coating generally does not exceed 90 μm. When the maximum thickness of the first coating exceeds 90 μm, it will reduce the thermal conductivity of the aluminum substrate surface of the heat exchanger, thereby reducing the heat exchange efficiency of the heat exchanger.

[0058] In some embodiments, the binder in the first coating 2 includes a silane coupling agent. The silane coupling agent can disperse the metal sheet 21 in the coating solution, and the silane coupling agent reacts with the metal sheet 21 to form covalent bonds. Specifically, using a silane coupling agent as a binder, silane can be hydrolyzed to generate silanol groups -Si-OH. The silanol hydroxyl groups are adsorbed on the surfaces of the zinc sheet 211 and aluminum sheet 212 in the form of hydrogen bonds, or they can undergo dehydration reactions to form covalent bonds, firmly fixing the coating to the metal surface. The silanol hydrolysis products can also condense with each other to generate -Si-O-Me-Si-O-Si-. In addition, the active functional groups can also cross-link with each other to form a film, connecting the zinc sheet 211 and aluminum sheet 212 into a film, so that the first coating 2 forms a multilayer interwoven structure. Moreover, the first coating 2 formed is relatively dense, and the coating can better adhere to the aluminum substrate 1 of the heat exchanger, further improving the corrosion resistance of the first coating and increasing the service life of the heat exchanger.

[0059] In some embodiments, the binder in the first coating 2 includes an organic carrier, which includes one of a modified epoxy system, an acrylic system, and a polyurethane system. The organic carrier can better disperse the metal sheet 21 in the coating solution. The organic carrier has better corrosion resistance as a binder than silane coupling agents, but it is an oil-based coating solution and has higher environmental protection requirements.

[0060] In some embodiments, the first coating 2 further includes a dispersant, which includes at least one of Tween-20 and polyethylene glycol. The dispersant adsorbs onto the surface of the metal sheet 21, generating charge repulsion or steric hindrance, preventing harmful flocculation of the metal sheet 21, stabilizing the dispersion system, enhancing the dispersion of zinc sheet 211 and aluminum sheet 212 in the coating, and allowing the zinc sheet 211 and aluminum sheet 212 to be uniformly dispersed in the coating, improving the uniformity and reliability of the metal sheet in the coating, thereby improving corrosion resistance.

[0061] Tween-20 can not only effectively adhere to the surfaces of zinc sheet 211 and aluminum sheet 212, reducing the surface tension of metal sheet 21 and playing a good wetting role, but also has a corrosion inhibitory effect on zinc sheet 211, which can improve the corrosion resistance of the first coating.

[0062] Polyethylene glycol, zinc sheet 211 and aluminum sheet 212 are laid in a cross-lay pattern in the coating to make the first coating smoother and denser, thereby improving the uniformity and reliability of the first coating.

[0063] The dispersant can be Tween-20, polyethylene glycol, or a combination of both. When using Tween-20 and polyethylene glycol, not only can the dispersion of zinc flakes 211 and aluminum flakes 212 in the coating solution be improved, but the zinc flakes 211 and aluminum flakes 212 can also be laid out crosswise in the coating, improving the uniformity and reliability of the coating. Furthermore, the corrosion resistance of the coating can be improved, thus extending the service life of the heat exchanger.

[0064] In some embodiments, the first coating 2 further includes a stabilizer, including hexamethylenetetramine.

[0065] Urotropine, as a stabilizer for the coating, can prevent the metal sheet 21 in the coating solution from oxidizing and deteriorating. Adding the stabilizer can extend the storage life of the coating. In some specific embodiments, urotropine includes hexamethylenetetramine, which can slow down the corrosion of the metal sheet 21 in the coating. In particular, when silane coupling agent is used as a binder, adding a certain amount of urotropine can better improve the service life of the first coating, thereby improving the service life of the heat exchanger.

[0066] In some embodiments, the first coating 2 further includes a passivating agent, including sodium molybdate or boric acid. A certain amount of sodium molybdate or boric acid is added to the coating solution of the first coating 2. The sodium molybdate or boric acid forms a dense oxide film on the surfaces of the zinc sheet 211 and the aluminum sheet 212, passivating the surface of the aluminum substrate 1 of the heat exchanger, reducing the corrosion rate of the zinc sheet 211 and the aluminum sheet 212, extending the service life of the first coating, and improving the service life of the heat exchanger.

[0067] In some embodiments, such as Figure 3 As shown, the aluminum substrate 1 of the heat exchanger includes a first surface 11, and the first surface 11 includes a plurality of first recesses 111. A plurality of first recesses 111 are formed on the first surface 11 of the aluminum substrate 1. In the thickness direction of the aluminum substrate 1, the first recesses 111 are lower than the first surface 11.

[0068] A plurality of first recesses 111 are formed on the first surface of the aluminum substrate 1. The first recesses 111 are lower than the first surface 11, which allows the first coating 2 to adhere better to the surface of the aluminum substrate 1 of the heat exchanger. For example, the aluminum substrate 1 includes a heat exchange tube 4, a first tube 5 and fins 6. When a plurality of first recesses 111 are formed on the surface of the first tube 5, the first recesses 111 are lower than the surface of the first tube 5.

[0069] Optionally, the surface of the aluminum substrate 1 of the heat exchanger can be roughened to include a plurality of first recesses 111. After forming a plurality of first recesses 111 on the first surface of the aluminum substrate 1, a first coating 2 is applied to the surface of the aluminum substrate 1. Thus, the first coating 2 can fill the positions of the first recesses 111, improving the adhesion of the first coating 2, increasing the bonding force between the first coating 2 and the aluminum substrate 1, and extending the service life of the first coating.

[0070] Figure 7 The diagram shows the surface of the heat exchange tube 4 on the aluminum substrate 1. The upper surface of the heat exchange tube 4 has been roughened, and multiple first recesses 111 are formed on the first surface of the upper surface. The lower surface has not been roughened and is relatively flat. Figure 8 The image shows the SEM image of the surface of the first surface 11. The surface has a certain roughness. When the surface roughness of the aluminum substrate 1 is 0.8-3.2μm, it can ensure that the first coating 2 has good adsorption to the aluminum substrate 1 of the heat exchanger, and also ensure the smoothness of the outer surface of the aluminum substrate 1 of the heat exchanger, thereby improving the adhesion between the first coating 2 and the aluminum substrate 1 and improving the corrosion resistance of the heat exchanger.

[0071] In some embodiments, the heat exchanger 100 further includes a passivation layer 5 located between the aluminum substrate 1 and the first coating 2.

[0072] Specifically, such as Figure 2 As shown, a passivation layer 5 is formed on the surface of the heat exchanger 100, located between the aluminum substrate 1 and the first coating 2. The passivation layer serves two purposes: firstly, it improves the corrosion resistance life of the aluminum substrate 1 of the heat exchanger; secondly, it enhances the adhesion between the first coating 2 and the aluminum substrate 1, allowing the first coating to adhere better to the aluminum substrate 1, thereby improving the corrosion resistance of the first coating. Furthermore, when the first coating 2 is damaged by external scratches or has defects, residual passivating agent can oxidize the exposed surface of the first coating to form a passivation film, further improving the corrosion resistance of the aluminum substrate.

[0073] In some embodiments, a trivalent chromium passivation layer is added to the surface of the heat exchanger. The trivalent chromium solution includes fluorozirconate and chromium sulfate. The heat exchanger is immersed in the trivalent chromium solution for more than 6 minutes to form a hydrated oxide layer containing Cr-Zr-Al with a thickness of about 50-100 nanometers. The passivation layer 5 is formed by reacting from the surface of the aluminum substrate of the aluminum alloy heat exchanger inward.

[0074] In some embodiments, the passivation treatment may also employ chromium-free passivation, including rare earth conversion, zirconium conversion, silane treatment, etc., on the surface of the aluminum substrate 1 of the heat exchanger to form a passivation layer 5 on the surface of the aluminum substrate 1 of the heat exchanger.

[0075] The passivation treatment is produced by the reaction on the surface of the aluminum substrate 1 of the heat exchanger. The passivation layer 5 formed reacts from the surface of the aluminum substrate of the heat exchanger inward to form a certain thickness, which further improves the corrosion resistance of the aluminum substrate 1 of the heat exchanger and increases the service life of the heat exchanger.

[0076] In some embodiments, after roughening the surface of the aluminum substrate 1 of the heat exchanger, a passivation treatment is added to the surface of the aluminum substrate 1 to form a passivation layer 5 on the outer surface of the aluminum substrate 1 of the heat exchanger, and then a first coating 2 is applied to the surface of the aluminum substrate 1.

[0077] like Figure 4 As shown, the aluminum substrate 1 includes a first surface 11, which includes a plurality of first recesses 111. The first recesses 111 can be formed by roughening the surface of the aluminum substrate 1. Then, a passivation treatment is added to the surface of the aluminum substrate 1 to form a passivation layer 5. The thickness of the passivation layer 5 is about 50-100 nanometers. The passivation layer 5 can be located at the first recesses 111, which can better adhere to the surface of the aluminum substrate 1. Then, a coating solution is applied to the surface of the aluminum substrate 1 to form a first coating 2, which further improves the bonding force between the first coating 2 and the aluminum substrate 1, and improves the corrosion resistance of the aluminum substrate 1 of the heat exchanger, thereby increasing the service life of the heat exchanger.

[0078] This heat exchanger can be applied to a heat exchange system, which includes basic components such as a compressor, heat exchanger 100, and throttling components. The heat exchanger 100 used in the aforementioned embodiment is the same as the heat exchanger 100 used in the previous embodiment. The above-mentioned basic components are connected by pipes to form a closed system. The refrigerant circulates in the system and undergoes state changes, thereby exchanging heat with the outside world to achieve the effect of heat exchange.

[0079] This application also provides a method for processing a heat exchanger, the method comprising:

[0080] Assemble and weld the aluminum substrate;

[0081] Applying a coating solution to an aluminum substrate 1 includes applying the coating solution to at least a portion of the surface of the aluminum substrate. The coating solution includes a metal sheet 21 and an adhesive. The metal sheet includes a zinc sheet 211. The metal sheet accounts for 20%-50% of the weight of the coating solution, and the adhesive accounts for 5%-30% of the weight of the metal sheet.

[0082] After curing, a heat exchanger 100 covered with the first coating 2 is obtained, and the metal sheets form a multi-layered interlaced structure in the first coating 2.

[0083] Specifically, the aluminum substrate 1 is first assembled and welded, as in some embodiments, such as Figure 9-10As shown, the aluminum substrate 1 of the heat exchanger includes heat exchange tubes 4, a first tube 5, and fins 6. The heat exchange tubes 4 include heat exchange channels extending along their length. The heat exchange tubes 4 are connected to the first tube 5 to allow refrigerant flow within the heat exchanger. The heat exchange tubes 4 and fins 6 can be welded together, reducing the gap between the fins 6 and the heat exchange tubes 4 and improving the heat exchange efficiency of the heat exchanger. During heat exchanger fabrication, the heat exchange tubes 4, the first tube 5, and the fins 6 are first assembled, and then the assembled aluminum substrate 1 is welded together to form a single unit.

[0084] After welding the aluminum substrate 1, a coating solution is applied to at least a portion of the surface of the aluminum substrate 1. This includes applying the coating solution to a portion of the surface of the aluminum substrate 1, for example, applying the coating solution to at least a portion of the surface of at least one of the heat exchange tube 4, the first tube 5, and the fins 6, or applying the coating solution to the entire surface of the aluminum substrate 1. Optionally, the coating solution is applied to the outer surface of the aluminum substrate 1. The coating solution includes metal sheets 21 and an adhesive, wherein the metal sheets 21 are dispersed in the adhesive, and the metal sheets include zinc sheets 211, to provide protection for the aluminum substrate 1 of the heat exchanger.

[0085] The metal sheet accounts for 20%-50% of the weight of the coating solution, and the adhesive accounts for 5%-30% of the weight of the metal sheet.

[0086] Specifically, the coating solution includes metal sheets 21 and a binder. The metal sheets 21 are dispersed in the binder, forming a first coating 2 after curing, thereby protecting the heat exchanger and improving its corrosion resistance. The metal sheets 21 are the main component of the coating solution, accounting for 20%-50% of the coating solution's weight. After curing, the first coating 2 containing a certain amount of metal sheets is obtained, better protecting the aluminum substrate 1 of the heat exchanger and improving its corrosion resistance. The binder accounts for 5%-30% of the metal sheets' weight. The binder ensures that the metal sheets 21 are evenly distributed within the binder. By setting the ratio of metal sheets to binder, the metal sheets are evenly distributed in the coating solution, allowing the first coating formed after curing to better protect the aluminum substrate 1, extending the service life of the first coating, and thus extending the service life of the heat exchanger.

[0087] After the coating solution is applied, it is cured to obtain a heat exchanger 100 with the first coating 2. The first coating 2 is formed by curing the coating solution. The heat exchanger 100 includes an aluminum substrate 1 and the first coating 2. The first coating 2 is located on the surface of the aluminum substrate 1, and the metal sheet 21 forms a multi-layered interlaced structure in the first coating 2.

[0088] The surface of the aluminum substrate 1 has a first coating 2, which includes metal sheets 21 and an adhesive. The metal sheets include zinc sheets 211. The zinc sheets have a more negative potential than the aluminum alloy. During electrochemical corrosion, the zinc sheets act as sacrificial anodes to provide cathodic protection to the aluminum substrate and are corroded first, thereby slowing down the corrosion rate of the aluminum substrate 1. The metal sheets 21 form a multi-layered interlaced structure in the first coating, and the gaps between the metal sheets 21 can be filled with the adhesive. Thus, the first coating constitutes an effective barrier layer, which can play a physical isolation role, preventing corrosive media from reaching the surface of the aluminum substrate 1 and slowing down the corrosion of the heat exchanger. The corrosion rate of the aluminum substrate 1 is reduced, and even at locations with defects in the first coating, corrosion preferentially occurs on the first coating. Zinc flakes near the corrosion site can react with the corrosive medium to form insoluble zinc salts such as oxides, hydroxides, and carbonates. These substances fill the small coating losses and act as corrosion inhibitors, thereby delaying further damage to the coating. Furthermore, due to the multi-layered interlaced structure of the first coating, corrosion is a layered corrosion along the coating surface, further extending the protection of the aluminum substrate, improving the corrosion resistance of the heat exchanger, and increasing the service life of the heat exchanger.

[0089] The heat exchanger processing method involves applying a coating solution to at least a portion of the surface of an aluminum substrate. The coating solution includes metal sheets and an adhesive, with the metal sheets including zinc sheets. After the coating solution cures, a heat exchanger covered with a first coating is formed. The metal sheets form a multi-layered, interwoven structure in the first coating. This first coating helps to slow down the corrosion rate of the aluminum substrate, improve the corrosion resistance of the heat exchanger, and extend the service life of the heat exchanger.

[0090] In some embodiments, the binder includes a silane coupling agent, which can disperse the metal sheet 21 in the coating solution. The silane coupling agent reacts with the metal sheet to form covalent bonds. Specifically, when a silane coupling agent is used as a binder, silane can be hydrolyzed to generate silanol groups -Si-OH. The silanol hydroxyl groups are adsorbed on the surface of the metal sheet 21 in the form of hydrogen bonds, or they can undergo a dehydration reaction to form covalent bonds, firmly fixing the first coating to the metal surface. The silanol hydrolysis products can also condense with each other to generate -Si-O-Me-Si-O-Si-. In addition, the active functional groups can also crosslink with each other to form a film, connecting the metal sheet 21 into a film to form a multilayer interwoven structure. Moreover, the formed coating is relatively dense, and the first coating has good corrosion resistance, thereby improving the corrosion resistance of the heat exchanger aluminum substrate.

[0091] In some embodiments, the binder includes an organic carrier, which is one of a modified epoxy system, an acrylic system, and a polyurethane system. This organic carrier can disperse the metal sheet in the coating solution. Organic carriers, when used as binders, offer better corrosion resistance than silane coupling agents; however, they are oil-based coating solutions, thus requiring higher environmental standards.

[0092] In some embodiments, the metal sheet in the coating solution further includes aluminum sheet 212, zinc sheet 211, and aluminum sheet 212 dispersed in the coating solution, wherein zinc sheet 211 accounts for 65%-100% of the metal sheet, and aluminum sheet 212 accounts for 0%-35% of the metal sheet. The addition of a certain amount of aluminum sheet 212 to the metal sheet 21, where the aluminum sheet 212 has a higher potential than the zinc sheet, allows the first coating to corrode the zinc sheet 211 first, followed by the aluminum sheet 212, during the corrosion process. This slows down the corrosion rate of the first coating, extends its service life, and improves the corrosion resistance of the heat exchanger.

[0093] In some embodiments, the coating solution further includes Tween-20, which accounts for 15%-25% of the weight of the metal sheet 21.

[0094] Specifically, Tween-20 is a wetting and dispersing agent, accounting for 15%-25% of the weight of the metal sheet. Tween-20 can not only effectively adsorb onto the surface of zinc sheet 211 and aluminum sheet 212, reducing the surface tension of the metal sheet and playing a good wetting role, enhancing the dispersion of zinc sheet 211 and aluminum sheet 212 in the coating solution, but also has a corrosion inhibitory effect on zinc sheet 211, which can improve the corrosion resistance of the coating.

[0095] In some embodiments, the coating solution further includes polyethylene glycol, which accounts for 60%-70% of the weight of the metal sheet.

[0096] Specifically, polyethylene glycol is a wetting and dispersing agent. Polyethylene glycol accounts for 60%-70% of the weight of the metal sheet. Polyethylene glycol can make the zinc sheet 211 and aluminum sheet 212 more evenly distributed in the coating. The zinc sheet 211 and aluminum sheet 212 are laid out crosswise in the coating, making the first coating smoother and denser, and improving the uniformity and reliability of the coating.

[0097] In some embodiments, the coating solution further includes Tween-20 and polyethylene glycol, wherein Tween-20 accounts for 15%-25% of the weight of the metal sheet 21, and polyethylene glycol accounts for 60%-70% of the weight of the metal sheet. Using Tween-20 and polyethylene glycol not only improves the dispersion of zinc sheet 211 and aluminum sheet 212 in the coating solution, but also allows the zinc sheet 211 and aluminum sheet 212 to be laid out cross-laid in the coating, improving the uniformity and reliability of the coating, and further enhancing the corrosion resistance of the coating and extending the service life of the heat exchanger.

[0098] In some embodiments, the coating solution further includes a passivating agent, which accounts for 3%-15% of the weight of the metal sheet 21.

[0099] The passivating agent accounts for 3%-15% of the weight of the metal sheet. The passivating agent includes sodium molybdate or boric acid. When sodium molybdate or boric acid is added to the coating solution, the passivating agent forms a dense oxide film on the surface of zinc sheet 211 and aluminum sheet 212, which passivates the surface of the aluminum substrate 1 of the heat exchanger, reduces the corrosion rate of zinc sheet 211 and aluminum sheet 212, extends the service life of the coating, and thus improves the service life of the heat exchanger.

[0100] In some embodiments, the coating solution further includes a stabilizer, which accounts for 0.2-0.5% of the weight of the metal sheet.

[0101] The stabilizer accounts for 0.2-0.5% of the weight of the metal sheet. Adding a certain amount of stabilizer to the coating solution can extend the storage life of the coating solution, especially when silane coupling agents are used as binders, adding a certain amount of stabilizer can further improve the service life of the coating. Optionally, the stabilizer includes hexamethylenetetramine.

[0102] In some embodiments, the coating solution includes a metal sheet 21, a binder, Tween-20, polyethylene glycol, a passivating agent, and a stabilizer. The metal sheet 21 is the main component of the coating solution. The proportions of the binder, Tween-20, polyethylene glycol, passivating agent, and stabilizer added are based on the weight ratio of the metal sheet. By adding the metal sheet, binder, Tween-20, polyethylene glycol, passivating agent, and stabilizer in the above proportions, the resulting first coating has good density and high corrosion resistance, thus improving the protection of the aluminum substrate of the heat exchanger.

[0103] In some embodiments, before applying the coating solution to the aluminum substrate 1, at least a portion of the surface of the aluminum substrate 1 is roughened, and the surface roughness of the aluminum substrate 1 is 0.8-3.2 μm.

[0104] On the one hand, during the brazing process of the aluminum substrate 1 of the heat exchanger, flux residue may remain on its surface, which is difficult to remove even after cleaning. When the coating solution is applied to the aluminum substrate 1, the coating solution may fail to adhere to areas with flux residue, or the adhesion of the coating solution in these areas may be very poor, causing defects in the first coating and creating corrosion breakthrough points. On the other hand, roughening the surface of the aluminum substrate 1 can increase the adhesion of the first coating 2, allowing the first coating to adhere better to the surface of the aluminum substrate 1 of the heat exchanger. Therefore, before applying the coating solution to the aluminum substrate 1, at least a portion of the surface of the aluminum substrate 1 is roughened.

[0105] like Figure 7 As shown, a portion of the surface of the first surface 11 of the heat exchange tube 4 on the aluminum substrate 1 has been roughened. The upper surface of the heat exchange tube 4 has been roughened, and multiple first recesses 111 are formed on the first surface 11 of the upper surface. The lower surface has not been roughened and is relatively flat. Figure 8The image shows the SEM image of the upper surface of the first surface 11. After roughening treatment, the surface has a certain roughness, forming a micro-nano structure on the surface of the aluminum substrate 1. The first coating 2 can better adhere to the surface of the aluminum substrate, improving the service life of the first coating 2.

[0106] In some embodiments, the outer surface of the heat exchanger can be roughened by sandblasting. The sandblasting abrasive can be aluminum oxide (Al2O3) with a mesh size of 80-150 mesh. The sandblasting distance is 50 mm, which can remove residual flux from the surface of the aluminum substrate 1 of the heat exchanger. After sandblasting, a micro-nano structure is formed on the surface of the aluminum substrate 1, and the roughness of the outer surface of the aluminum substrate 1 is 0.8-3.2 μm. Within this range, it can ensure that the first coating 2 has good adsorption to the aluminum substrate 1 of the heat exchanger, and also ensure the smoothness of the outer surface of the aluminum substrate 1 of the heat exchanger, thereby improving the adhesion between the first coating 2 and the aluminum substrate 1, improving the corrosion resistance of the heat exchanger, and improving the heat exchange efficiency of the heat exchanger.

[0107] Optionally, after roughening the surface of the aluminum substrate 1 of the heat exchanger, the surface of the aluminum substrate 1 of the heat exchanger is cleaned to improve the appearance of the aluminum substrate 1 and to allow the coating solution to adhere better to the aluminum substrate 1 of the heat exchanger.

[0108] like Figure 3-4 As shown, the surface of the aluminum substrate 1 of the heat exchanger includes a first surface 11. After roughening treatment, a rough surface is formed on the first surface 11 of the aluminum substrate 1 of the heat exchanger. The first surface 11 includes a plurality of first recesses 111. After roughening treatment, a coating solution is then applied to the surface of the aluminum substrate 1 of the heat exchanger. At this time, the coating solution can better adhere to the surface of the aluminum substrate 1 of the heat exchanger, improve the adhesion between the coating solution and the aluminum substrate 1 of the heat exchanger, and improve the corrosion protection of the heat exchanger.

[0109] In some embodiments, the aluminum substrate 1 of the heat exchanger includes a heat exchange tube 4, a first tube 5, and fins 6. Optionally, at least a portion of the surface of at least one of the heat exchange tube 4, the first tube 5, and the fins 6 may be roughened. This roughening process may be performed on only at least a portion of the surface of one of the heat exchange tube 4, the first tube 5, and the fins 6, or all of the heat exchange tube 4, the first tube 5, and the fins 6 may be roughened, in order to allow the coating to adhere better to the surface of the aluminum substrate 1 of the heat exchanger.

[0110] In some embodiments, before applying the coating solution to the aluminum substrate 1 or after roughening the surface of the aluminum substrate 1, a trivalent chromium passivation treatment or a chromium-free passivation treatment is performed on the surface of the heat exchanger to form a passivation layer 5 on the outer surface of the heat exchanger.

[0111] Specifically, after welding the aluminum substrate, passivation treatment can be performed on the surface of the heat exchanger before applying the coating solution to the aluminum substrate 1; alternatively, after welding the aluminum substrate, the surface of the aluminum substrate 1 can be roughened before passivation treatment is performed on the surface of the heat exchanger, which further improves the adhesion between the coating solution and the aluminum substrate 1, enhances the corrosion resistance of the aluminum substrate 1 of the heat exchanger, and extends the service life of the heat exchanger.

[0112] Passivation treatment of the heat exchanger surface includes trivalent chromium passivation or chromium-free passivation on the aluminum substrate 1. Passivation treatment of the heat exchanger surface can improve the corrosion resistance life of the aluminum substrate 1 and enhance the adhesion between the coating solution and the aluminum substrate 1, allowing the coating solution to adhere better to the aluminum substrate 1 and improving the adhesion between the first coating and the outer surface of the aluminum substrate 1, thereby improving the corrosion resistance of the heat exchanger.

[0113] Specifically, during passivation, the aluminum substrate 1 is immersed in a chromium solution for more than 6 minutes to form a layer of Cr-Zr-Al hydrated oxide with a thickness of approximately 50 to 100 nanometers. The chromium solution can be a trivalent chromium solution, for example, a fluorozirconate or a chromium sulfate solution.

[0114] In some embodiments, a chromium-free passivation treatment is performed on the surface of the heat exchanger. The chromium-free passivation compound treatment employs at least one of rare earth conversion, zirconium conversion, or silane to form a passivation layer 5 on the outer surface of the heat exchanger.

[0115] In some embodiments, when applying the coating solution to the aluminum substrate 1, the coating solution is applied to the surface of the aluminum substrate by at least one of spraying, flow coating or dip coating.

[0116] Specifically, when applying the coating solution to the aluminum substrate 1, the coating solution is applied to the surface of the aluminum substrate 1 by at least one of spraying, flow coating, or dip coating. Optionally, the coating solution is applied to the outer surface of the aluminum substrate 1.

[0117] During spraying, the aluminum substrate 100 is placed on the operating table, and the coating solution is sprayed onto the aluminum substrate 100 under certain pressure to form a coating on the surface of the aluminum substrate 1. This method of coating has a higher degree of freedom in coating application, and can be sprayed on the location of the aluminum substrate that needs to be coated, and the operation is more convenient.

[0118] During flow coating, the aluminum substrate 100 is placed on the operating table, and the aluminum substrate 1 is passed through a water curtain containing coating solution by a conveyor belt to form a coating on the surface of the aluminum substrate 1. This method can also be used to coat only the areas of the aluminum substrate 1 that need to be coated, which is convenient to operate.

[0119] During dip coating, the aluminum substrate 100 is immersed in the coating solution, and the entire aluminum substrate 100 is coated. This ensures that every part of the aluminum substrate 100 is covered with the coating solution, thereby better protecting the aluminum substrate 1 and extending the service life of the heat exchanger 100. When the coating solution is applied by dip coating, since the aluminum substrate 1 is coated as a whole with the first coating 2 containing metal sheets 21, the entire outer surface of the heat exchanger has the same corrosion potential. When the heat exchanger 100 comes into contact with the external environment, there are no low corrosion potential areas that will preferentially corrode. This allows the heat exchanger as a whole to resist corrosion from the external environment, rather than corroding in a few small areas with low potential. This greatly reduces the corrosion rate of the heat exchanger in the thickness direction and effectively extends the service life of the heat exchanger 100.

[0120] In some embodiments, when the first coating is applied to the surface of the aluminum substrate 1 by dip coating, the aluminum substrate 1 is made to reciprocate periodically in the coating solution by a swinging device. The direction of movement is perpendicular to the plane where the aluminum substrate 1 is located. The stroke of the swinging device is 1-15cm and the swinging frequency is 5-20 times / min.

[0121] Specifically, during the immersion treatment of the aluminum substrate 1, a oscillating device can be added. This oscillating device allows the aluminum substrate 1 to perform a cyclic reciprocating motion in the coating solution. The direction of motion is perpendicular to the plane of the aluminum substrate, the oscillation stroke is 1-15 cm, and the frequency is 5-20 times / min. This oscillation can expel air between the aluminum substrate 1 and the coating solution during the application of the coating solution, thereby allowing the coating solution to be applied more evenly to the surface of the aluminum substrate 1. The oscillation device improves the adhesion of the coating solution to the aluminum substrate 1. After curing, a first coating 2 is formed on the surface of the aluminum substrate 1, improving the adhesion between the first coating and the aluminum substrate 1 and enhancing the corrosion resistance of the heat exchanger.

[0122] In some embodiments, the aluminum substrate 1 is characterized by being heated and dried after the coating solution is applied, and the heating and drying process is carried out at 180-320°C for 20-40 minutes; and / or, after the coating solution is applied, the aluminum substrate 1 is preheated at 110-150°C, held at that temperature for 5-15 minutes, and then heated to 250°C-320°C for 10-20 minutes.

[0123] Specifically, after applying the coating solution, the aluminum substrate 1 coated with the coating solution is heated and dried at 180-320℃ for 20-40 minutes. For example, the drying temperature can be 180℃, 200℃, 220℃, 300℃, etc., and the drying time can be 20 minutes, 30 minutes, 35 minutes, etc. By setting the drying temperature and time, the aluminum substrate 1 coated with the coating solution is dried, causing the coating solution to solidify and forming a first coating 2 on the surface of the aluminum substrate 1, resulting in a heat exchanger 100 including the first coating 2. During the drying process, the covalent bonds formed by the reaction of the silane coupling agent and the metal sheet 21 can combine, making the formed first coating denser and the coating a whole. This can improve the adhesion of the coating to the aluminum substrate, extend the coating life, and thus improve the life of the heat exchanger 100.

[0124] In some embodiments, after applying the coating solution, the aluminum substrate 1 coated with the coating solution is preheated to a temperature of 110-150°C, held for 5-15 minutes, and then heated to 250°C-320°C for 10-20 minutes.

[0125] For example, the preheating temperature can be 110℃, 120℃, 135℃, or 150℃. After holding at the preheating temperature for 5-15 minutes (5 minutes, 10 minutes, 12 minutes, or 15 minutes respectively), the temperature is then raised to 250℃-320℃ and baked for 10-20 minutes. By holding at the preheating temperature for a period of time before drying, the coating solution can better adhere to the aluminum substrate 1, avoiding excessively rapid temperature rise, which could lead to microcracks in the first coating after curing, affecting the anti-corrosion performance of the first coating 2. After holding at the preheating temperature for 5-15 minutes, the temperature is raised to 250℃-320℃ and baked for 10-20 minutes to dry the aluminum substrate 1 coated with the coating solution, allowing the coating solution to solidify and form the first coating 2 on the surface of the aluminum substrate 1. During the drying process, the covalent bonds formed by the reaction of the silane coupling agent and the metal sheet 21 can combine, making the coating more dense and the coating a whole. This can improve the adhesion of the first coating 2 to the aluminum substrate 1, extend the life of the first coating, and thus improve the life of the heat exchanger 100.

[0126] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0127] Table 1 shows the first coating 2 in several different embodiments. Corrosion resistance refers to the heat exchanger's resistance to general corrosion and intergranular corrosion in the corrosive environment specified in the ASTM G85-A3 SWAAT TEST standard. Specifically, the test environment is as follows: the salt solution is simulated synthetic seawater with a concentration of 42 g / L, the pH value of the solution is 2.8-3.0, and the temperature inside the chamber is set at 49°C; the test cycle is 30 minutes of spraying + 90 minutes of immersion in moisture at 98% RH or higher. The SWAAT corrosion resistance time of the heat exchanger is the time it takes for corrosion penetration to occur in the heat exchanger under this test environment.

[0128] Example 1

[0129] The coating solution of the first coating 2 includes metal sheets 21, binder, dispersant, stabilizer, and passivator. Of the metal sheets 21, zinc sheets 211 comprise 95% and aluminum sheets 212 comprise 5%. The binder is a silane coupling agent, the dispersant is Tween-20 and polyethylene glycol, the stabilizer is hexamethylenetetramine, and the passivator is sodium molybdate. This coating solution is applied to the outer surface of the aluminum substrate 1 to form a heat exchanger 100 including the first coating 2. The heat exchanger has a SWAAT corrosion resistance time of 3200 hours. In contrast, in Comparative Example 1, the aluminum substrate 1 of the heat exchanger was not coated with the first coating 2, and the SWAAT corrosion resistance time was only 1400 hours. This demonstrates that applying the first coating significantly improves the corrosion resistance of the heat exchanger.

[0130] Table 1

[0131]

[0132]

[0133] Example 2

[0134] Unlike Example 1, the dispersant in Example 2 is polyethylene glycol. The corrosion resistance time of the heat exchanger is not much different from that when the dispersant is Tween-20 and polyethylene glycol, and the heat exchanger has good corrosion resistance.

[0135] Example 3

[0136] Unlike Example 1, the binder in Example 3 is a modified epoxy system in an organic carrier, and the passivating agent is boric acid. The corrosion resistance time is not much different from that in Example 1, and the heat exchanger has good corrosion resistance.

[0137] Example 4

[0138] Unlike Example 1, the binder in Example 4 is an acrylic system in an organic carrier, and its corrosion resistance time is not much different from that in Example 1, so the heat exchanger has good corrosion resistance.

[0139] Examples 5-6

[0140] The composition of the coating solution is the same as in Example 1, except for the ratio of zinc and aluminum sheets in the metal sheets of the first coating 2. In Example 5, zinc sheets account for 85% of the metal sheets, and aluminum sheets account for 15%. In Example 6, zinc sheets account for 100% of the metal sheets, and aluminum sheets account for 0%. The corrosion resistance time is not significantly different from that in Example 1, indicating that the heat exchanger exhibits good corrosion resistance. Compared to Comparative Example 2, where zinc sheets account for 60% and aluminum sheets account for 40%, the corrosion resistance of the heat exchanger decreases. It can be concluded that when zinc sheets account for 65%-100% of the metal sheets and aluminum sheets account for 0%-35%, the corrosion resistance of the heat exchanger is better than that outside this range.

[0141] In Examples 1-6, the outer surface of the aluminum substrate 1 of the heat exchanger is covered with a first coating 2. Compared with Comparative Example 1, the surface of the aluminum substrate 1 of the heat exchanger is not covered with the first coating 2, which greatly improves the corrosion resistance of the heat exchanger and increases its service life.

[0142] Table 2 shows examples of further treatment of the surface of the aluminum substrate 1 of the heat exchanger.

[0143] Table 2

[0144]

[0145] Example 7

[0146] The composition of the first coating in Example 1 is the same as that in Example 7. The difference is that a roughening treatment is added to the outer surface of the aluminum substrate. After the roughening treatment is added, the adhesion between the aluminum substrate 1 and the first coating 2 is improved, the SWAAT corrosion resistance time of the heat exchanger is increased, and the corrosion resistance performance of the heat exchanger is improved.

[0147] Example 8

[0148] The composition is the same as the first coating in Example 1. The difference is that in Example 8, a passivation treatment is added to the outer surface of the aluminum substrate to form a passivation layer on the surface of the aluminum substrate. After the passivation treatment is added, the heat exchanger's resistance to SWAAT corrosion increases, which further improves the corrosion resistance of the heat exchanger.

[0149] Example 9

[0150] The composition of the first coating in Example 1 is the same as that in Example 9, the aluminum substrate is roughened and passivated. The addition of roughening and passivation treatments improves the adhesion between the aluminum substrate and the first coating, further increasing the heat exchanger's resistance to SWAAT corrosion and improving the heat exchanger's corrosion resistance.

[0151] It can be seen that after applying the first coating 2 to the surface of the aluminum substrate of the heat exchanger, the corrosion resistance of the heat exchanger is improved. After adding roughening treatment and / or passivation layer to the surface of the aluminum substrate, the corrosion resistance of the heat exchanger can be further improved, and the service life of the heat exchanger can be extended.

[0152] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0153] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A heat exchanger, characterized in that, The heat exchanger includes an aluminum substrate and a first coating. The first coating is applied to at least a portion of the surface of the aluminum substrate. The first coating includes metal sheets and an adhesive. There are multiple metal sheets, which are dispersed in the adhesive. The metal sheets include zinc sheets. A plane parallel to the thickness direction of the first coating is defined as a first plane, and a plane with an angle θ to the first plane is defined as a second plane, where 0° < θ ≤ 90°. The projections of the multiple metal sheets onto the first plane or the second plane at least partially overlap. The metal sheets form a multi-layered staggered structure in the first coating.

2. The heat exchanger according to claim 1, characterized in that, The metal sheet also includes an aluminum sheet, and the zinc sheet and the aluminum sheet are dispersed in the first coating. The zinc sheet accounts for 65%-100% of the metal sheet, and the aluminum sheet accounts for 0%-35% of the metal sheet.

3. The heat exchanger according to claim 2, characterized in that, The zinc sheet has a size of 0.5-40 μm and a thickness of 0.1-3 μm; and / or, the aluminum sheet has a size of 0.5-40 μm and a thickness of 0.1-3 μm.

4. The heat exchanger according to any one of claims 1-3, characterized in that, The thickness of the first coating is 5μm-50μm.

5. The heat exchanger according to any one of claims 1-3, characterized in that, The adhesive includes a silane coupling agent that reacts with the metal sheet to form a covalent bond; or, the adhesive includes an organic carrier that includes one of a modified epoxy system, an acrylic system, and a polyurethane system.

6. The heat exchanger according to any one of claims 1-3, characterized in that, The first coating satisfies one of the following conditions: a) The first coating further includes a dispersant, said dispersant comprising at least one of Tween-20 and polyethylene glycol; b) The first coating further includes a stabilizer, said stabilizer being hexamethylenetetramine; c) The first coating further includes a passivating agent, which includes sodium molybdate or boric acid.

7. The heat exchanger according to any one of claims 1-3, characterized in that, The aluminum substrate includes a first surface, the first surface including a plurality of first recesses, wherein the first recesses are lower than the first surface in the thickness direction of the aluminum substrate; and / or, the aluminum substrate further includes a passivation layer, the passivation layer being located between the aluminum substrate and the first coating.

8. A method for processing a heat exchanger, characterized in that, The heat exchanger processing method includes: Assemble and weld the aluminum substrate; A coating solution is applied to at least a portion of the surface of the aluminum substrate. The coating solution comprises a metal sheet and an adhesive, wherein the metal sheet comprises a zinc sheet, and the metal sheet accounts for 20%-50% of the weight of the coating solution, and the adhesive accounts for 5%-30% of the weight of the metal sheet. The heat exchanger is cured to obtain a first coating, wherein the metal sheet forms a multi-layered interlaced structure in the first coating.

9. The heat exchanger processing method according to claim 8, characterized in that, The coating solution satisfies one of the following conditions: a) The coating solution further includes Tween-20, wherein Tween-20 accounts for 15%-25% of the weight of the metal sheet; b) The coating solution further includes polyethylene glycol, which accounts for 60%-70% of the weight of the metal sheet; c) The coating solution further includes a passivating agent, which accounts for 3%-15% of the weight of the metal sheet; d) The coating solution further includes a stabilizer, which accounts for 0.2-0.5% of the weight of the metal sheet.

10. The heat exchanger processing method according to claim 8, characterized in that, Before applying the coating solution to the aluminum substrate, at least a portion of the surface of the aluminum substrate is roughened, and the surface roughness of the aluminum substrate is 0.8-3.2 μm.

11. The heat exchanger processing method according to claim 8 or 10, characterized in that, Before applying the coating solution to the aluminum substrate or after roughening the surface of the aluminum substrate, a passivation treatment is performed on the surface of the aluminum substrate to form a passivation layer on the surface of the aluminum substrate, the passivation layer being formed by reacting from the surface of the aluminum substrate inward.

12. The heat exchanger processing method according to claim 8, characterized in that, When applying the coating solution to the aluminum substrate, the coating solution is applied to the surface of the aluminum substrate by at least one of spraying, flow coating, or dip coating.

13. The heat exchanger processing method according to claim 12, characterized in that, When the first coating is applied to the surface of the aluminum substrate by dip coating, the aluminum substrate is made to reciprocate periodically in the coating solution by a swinging device. The direction of the movement is perpendicular to the plane of the aluminum substrate. The stroke of the swinging device is 1-15cm and the swinging frequency is 5-20 times / min.

14. The heat exchanger processing method according to any one of claims 8-13, characterized in that, After applying the coating solution, the aluminum substrate is heated and dried at 180-320°C for 20-40 minutes; or, after applying the coating solution, the aluminum substrate is preheated at 110-150°C for 5-15 minutes, then heated to 250-320°C and baked for 10-20 minutes.

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