A salt and alkali corrosion resistant coated copper-aluminum based grounding alloy material and a preparation method thereof

Abstract

This invention discloses a copper-aluminum based grounding alloy material with a coating resistant to salt and alkali corrosion and its preparation method, belonging to the field of grounding material technology. The technology uses copper and aluminum as the matrix, adding Ni and rare earth oxides to smelt and prepare a copper-aluminum multi-element alloy-based grounding material. Next, flake graphite is exfoliated into two-dimensional multilayer graphene sheets in an aqueous polyurethane medium using a three-roll milling process (TRM). This graphene is then mixed with conductive carbon black and carbon nanotubes to form a conductive network structure coating uniformly mixed with zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional multilayer graphene sheets in the aqueous polyurethane. Finally, this coating is applied to the surface of the copper-aluminum multi-element alloy-based grounding material to obtain a copper-aluminum based grounding alloy material with a coating resistant to salt and alkali corrosion. This invention, by controlling the content of Ni and rare earth oxides and coating its surface with an anti-corrosion coating, achieves good corrosion resistance in saline-alkali soil environments while ensuring good conductivity and mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of grounding materials technology, specifically to a copper-aluminum based grounding alloy material with a coating that is resistant to salt and alkali corrosion and its preparation method, which is suitable for grounding grid systems such as substations, wind turbines, and communication base stations. Background Technology

[0002] The safe and stable operation of power systems highly depends on the long-term reliability of grounding systems. As a critical facility, the grounding system bears the core function of safely conducting grid fault currents and lightning strike currents into the ground, and its performance directly affects the safe operation of transmission lines, substations, and electrical equipment. However, my country's geographical environment is complex and diverse, especially in the acidic red soil areas of the south, the saline-alkali areas of the northwest, and the high-salt coastal areas, where traditional grounding materials (such as carbon steel, galvanized steel, and copper) generally face serious corrosion problems. In saline-alkali soil environments (high soluble salt content, rich in chloride ions, sulfate ions, and carbonate ions, etc.), the continuous high salinity, alkalinity, and frequent alternation of wet and dry soil conditions accelerate the chemical and electrochemical corrosion processes of metal materials, causing surface corrosion of grounding electrodes, reduction of effective cross-section, and deterioration of connection parts. This leads to unstable grounding resistance, decreased current discharge performance, and significantly shortens the service life of grounding devices, posing a lasting hidden danger to the safe and reliable operation of power facilities.

[0003] As a core component in the field of electrical safety, pure copper grounding materials have seen significant progress in material performance optimization in recent years. While traditional copper grounding materials possess good conductivity, their mechanical strength and corrosion resistance still have room for improvement. Leading companies such as Jineng Power have fully replaced pure copper with oxygen-free copper in their high-voltage grounding wire products, significantly improving stability and service life in extreme low-temperature environments. The primary challenge facing pure copper grounding materials is their high cost and resource constraints. As a precious metal, copper's market price fluctuates dramatically, reaching a high of 50,000 yuan / ton in the past five years. This significantly increases the material costs of large-scale grounding projects, especially in long-distance transmission lines and large substation projects, where grounding material costs can account for 15%-20%, placing enormous pressure on project budgets.

[0004] While traditional galvanized steel is inexpensive, in saline-alkali environments, the zinc layer is rapidly consumed and forms porous corrosion products due to the synergistic destructive effect of chloride ions and alkaline substances. This causes the sacrificial anode protection mechanism to fail prematurely, resulting in severely insufficient corrosion resistance. Copper-clad steel, although possessing good conductivity and some corrosion resistance, has a limited copper layer thickness and is easily damaged. Once damaged, it quickly exposes the steel core, accelerating overall corrosion. Furthermore, existing protective measures such as sacrificial anode cathodic protection and coating protection only provide short-term protection in complex soil environments, with limited long-term protective effects, failing to achieve true maintenance-free operation. Therefore, developing new alloy grounding materials that can adapt to complex corrosive environments and provide long-term maintenance-free operation has become an urgent need in the industry. Summary of the Invention

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a copper-aluminum based grounding alloy material with a coating that is resistant to salt and alkali corrosion and its preparation method.

[0006] The technical solution of the present invention is as follows: A method for preparing a copper-aluminum based grounding alloy material with a coating resistant to salt and alkali corrosion includes: first, using copper and aluminum as the matrix, adding Ni and rare earth oxides, and smelting to obtain a copper-aluminum multi-element alloy grounding material; second, using a three-roll milling process to peel flake graphite into two-dimensional multilayer graphene sheets in an aqueous polyurethane medium, then mixing it with conductive carbon black and carbon nanotubes to form a conductive network structure coating; finally, coating the conductive network structure coating onto the surface of the copper-aluminum multi-element alloy grounding material to prepare a copper-aluminum based grounding alloy material with a coating resistant to salt and alkali corrosion.

[0007] Preferably, it includes the following steps: S1: Add metals Cu, Al, Ni and rare earth oxides to a graphite crucible, place it in a high-frequency induction furnace, heat it to 1100-1200℃ under N2 atmosphere to completely melt it, stir for 4-6 minutes, then pour it into a mold, cool it and demold it to obtain copper-aluminum multi-element alloy grounding material. S2: Add flake graphite to waterborne polyurethane and stir for 10-30 minutes to obtain mixture A. The obtained mixture A is then exfoliated by a three-roll milling process. After 9-16 cycles of exfoliation, mixture B is obtained. S3: Add conductive carbon black and carbon nanotubes to mixture B, and use a three-roll milling process to peel and mix 3-5 times to obtain a conductive network structure coating. S4: After coating the surface of the copper-aluminum multi-element alloy grounding material obtained in step S1 with the coating obtained in S3, the temperature is increased to 50℃ at 3℃ / min, and then kept at 50℃ for 24h to obtain the product.

[0008] Preferably, in step S1, the copper-aluminum multi-element alloy grounding material contains 85.85-91 wt.% Cu, 7.00-9.00 wt.% Al, 2.00-5.00 wt.% Ni, and 0.01-0.15 wt.% rare earth oxides.

[0009] Preferably, the rare earth element is at least one selected from CeO2, Y2O3, La2O3, Nd2O3, and Sm2O3.

[0010] Preferably, in step S2, the solid content of the waterborne polyurethane is 40-60 wt%.

[0011] Preferably, in step S2, the length dimension of the flake graphite is 10μm-200μm, the thickness is 1μm-10μm, and the mass ratio of flake graphite to waterborne polyurethane is 0.1-10:100.

[0012] Preferably, in step S3, the conductive carbon black has a particle size of 50 nm-200 nm, the carbon nanotubes are 2-10 layers of multi-walled carbon nanotubes, the mass ratio of conductive carbon black to carbon nanotubes added to the waterborne polyurethane is 0.1-2:100, and the mass ratio of conductive carbon black to carbon nanotubes is 1:1-3.

[0013] Preferably, in step S2, the process parameters of the three-roll grinding process are as follows: the rotational speed ratio between the rollers is 1:3:9 for the feed roller N3: center roller N2: discharge roller N1; for the first to fourth cycles of peeling, the gap between each roller is 20-50 μm; for the fifth to eighth cycles of peeling, the gap between each roller is adjusted to 5-20 μm; and after the ninth cycle of peeling, the gap between each roller is adjusted to 0.5-5 μm. Furthermore, it is ensured that during the peeling process, the gap between rollers N3 and N2 is at least twice as large as that between rollers N2 and N1.

[0014] Preferably, in step S3, the process parameters of the three-roll grinding process are as follows: the rotational speed ratio between the rollers is 1:3:9 for the feed roller N3: center roller N2: discharge roller N1, the cyclic peeling is performed 3-5 times, the gap between each roller shaft is adjusted to 0.5-2 μm, and it is ensured that the gap between roller shafts N3 and N2 is at least twice as large as that between roller shafts N2 and N1 during the cyclic peeling process.

[0015] The present invention also discloses a copper-aluminum based grounding alloy material with a coating that is resistant to salt and alkali corrosion, which is prepared by any of the preparation methods described above.

[0016] The beneficial effects of this invention are as follows: This invention uses copper and aluminum as a base, adds nickel and rare earth oxides, and melts them in a high-frequency induction furnace to obtain a copper-aluminum based grounding alloy material. Then, layered flake graphite, conductive carbon black, and carbon nanotubes are exfoliated by three-roll milling in an aqueous polyurethane medium to prepare an anti-corrosion coating. Finally, the coating is applied to the surface of the copper-aluminum based grounding alloy material to obtain a copper-aluminum based grounding alloy material resistant to salt and alkali corrosion. The addition of aluminum reduces the overall corrosion rate of the alloy; nickel plays a triple role in refining grains, enhancing corrosion resistance, and increasing strength; rare earth oxides (such as CeO2 and Y2O3) can hinder the penetration of corrosive media, especially corrosion along grain boundaries; layered flake graphite is milled into multilayer graphene sheets (MLGs) through a three-roll milling process; conductive carbon black and carbon nanotubes are mixed with multilayer graphene sheets to form a conductive network structure of zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional multilayer graphene sheets in aqueous polyurethane. This structure not only improves the conductivity of the coating but also enhances the corrosion resistance of the material. Attached Figure Description

[0017] Figure 1 The images show SEM comparisons of the Cu-9Al-2Ni alloy cross-section before and after etching in 3wt.% NaCl and 0.1 M NaHCO3 solutions after polishing, as shown in Example 1. (a): before etching, (b): after etching. Figure 2 The images are microscopic images of the samples in Example 1, where (a): SEM image of the micro-nano graphite sheets formed after graphite was peeled off by three-roll milling in Example 1, and (b): SEM image of the fracture surface of the grounding material coating in Example 1. Figure 3 Vickers hardness of copper-aluminum based grounding alloys with different Ni contents; Figure 4 This is a schematic diagram of the three-roll mill setup in an embodiment of the present invention. Detailed Implementation

[0018] A method for preparing a copper-aluminum based grounding alloy material with a coating resistant to salt and alkali corrosion involves using copper and aluminum as the base materials, adding nickel and rare earth oxides, and smelting them in a high-frequency induction melting furnace to obtain the copper-aluminum based grounding alloy material; then, flake graphite, conductive carbon black, and carbon nanotubes are peeled off by three-roll milling in an aqueous polyurethane medium to prepare an anti-corrosion coating; finally, the coating is applied to the surface of the copper-aluminum based grounding alloy material to obtain a copper-aluminum based grounding alloy material resistant to salt and alkali corrosion.

[0019] The raw material composition of copper-aluminum based grounding alloy material by weight percentage is as follows: Al addition range is 7.00-9.00 wt.%, Ni addition range is 2.00-5.00 wt.%, and rare earth oxides account for 0.01-0.15 wt.%. The introduction of Ni is to form a NiO / Ni(OH)2 protective layer, enhance alkali resistance, refine grains, and reduce grain boundary corrosion. Rare earth oxides (such as CeO2, Y2O3, La2O3, Nd2O3, and Sm2O3) can hinder the penetration of corrosive media, especially corrosion along grain boundaries. The raw material components of the anti-corrosion coating in waterborne polyurethane are as follows by weight percentage: flake graphite is added in the range of 0.1-10.00 wt.%, conductive carbon black is added in the range of 0.10-2.00 wt.%, and carbon nanotubes are added in the range of 0.10-2.00 wt.%. The addition of layered flake graphite, conductive carbon black, and carbon nanotubes is to improve the conductivity of the coating. However, in the existing technology, layered flake graphite is often added directly, and the conductivity is still not satisfactory.

[0020] The preparation method of the coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to the present invention is as follows: (1) Add metals Cu, Al, Ni and one or more rare earth oxides to a graphite crucible in proportion and prepare it by high frequency induction melting. Under N2 atmosphere, heat to 1100-1200℃ to completely melt it, stir for 4-6 min, and then pour it into a mold of the required size and shape. After cooling, demold to obtain copper-aluminum based grounding alloy material. (2) Add layered flake graphite (FG) to waterborne polyurethane and stir for 10-30 min to obtain mixture A. The obtained mixture A is then subjected to a three-roll milling process (TRM, see reference). Figure 4 After peeling for 9-16 cycles, mixture B is obtained. (3) Add some conductive carbon black and carbon nanotubes to the mixture B obtained in step (2), and then grind and peel it together with three rollers for 3-5 times. Finally, a conductive network structure of zero-dimensional carbon black, one-dimensional carbon nanotubes and two-dimensional multilayer graphene sheets is formed in water-based polyurethane as a coating for grounding material.

[0021] (4) After coating the coating obtained in step (3) onto the surface of the alloy material obtained in step (1), the temperature is increased to 50°C at 3°C / min, and then kept at 50°C for 24 hours to obtain a copper-aluminum based grounding alloy material resistant to salt and alkali corrosion.

[0022] This invention relates to a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion, combining the advantages of copper, aluminum, nickel, and other metals in terms of corrosion resistance, conductivity, and mechanical properties. Copper, due to its relatively high electrode potential, generally exhibits good corrosion resistance and also possesses excellent conductivity and ductile processing properties, making it an ideal grounding material. Furthermore, Al and Ni form oxides and hydroxides on the alloy surface, enhancing the alloy's corrosion resistance; the addition of Al and Ni also improves the alloy's strength. Rare earth oxides (such as CeO2, Y2O3, La2O3, Nd2O3, and Sm2O3) can hinder the penetration of corrosive media, particularly along grain boundaries. A conductive network coating, consisting of zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional multilayer graphene sheets, is formed in water-based polyurethane through three-roll milling and peeling. This coating, used as a grounding material coating, further enhances the material's corrosion resistance.

[0023] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0024] Example 1

[0025] A copper-aluminum based grounding alloy material with a coating, resistant to salt and alkali corrosion, is made from copper, al, and ni metals. The anti-corrosion coating is made from water-based polyurethane, layered flake graphite, conductive carbon black, and carbon nanotubes. The specific proportions and steps are as follows: (1) The metal Cu is 89.00 wt.%, the metal Al is 9.00 wt.%, and the metal Ni is 2.00 wt.%. The metal Cu, Al and Ni are added to a graphite crucible in proportion, and the high-frequency induction melting furnace is heated to 1150°C under N2 atmosphere to completely melt it. After stirring for 5 minutes, it is poured into a mold of the required size and shape, cooled and demolded to obtain a copper-aluminum based grounding alloy material; (2) 2.00 wt.% of layered flake graphite (FG) was added to 20 g of waterborne polyurethane and stirred for 10 min to obtain mixture A. The obtained mixture A was peeled by three-roll milling process (TRM) and after 16 cycles of peeling, mixture B was obtained. The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers, from feed roller N3 to center roller N2 to discharge roller N1, is 1:3:9. During the first to fourth cycles of peeling, the gap between rollers N3 and N2 is 48 μm, and the gap between N2 and N1 is 24 μm. During the fifth to eighth cycles of peeling, the gap between rollers N3 and N2 is 12 μm, and the gap between N2 and N1 is 6 μm. After the ninth cycle of peeling, the gap between rollers N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm.

[0026] (3) Add 0.50 wt.% conductive carbon black and 0.50 wt.% carbon nanotubes to the mixture B obtained in step (2), and then grind and peel it together three times with three rollers. Finally, form a conductive network structure coating of zero-dimensional carbon black, one-dimensional carbon nanotubes and two-dimensional multilayer graphene sheets in water-based polyurethane as a coating material for grounding.

[0027] The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers is 1:3:9 (feed roller N3: center roller N2: discharge roller N1), the process is repeated 3 times, the gap between rollers N3 and N2 is 2 μm, and the gap between N2 and N1 is 1 μm.

[0028] (4) After coating the coating obtained in step (3) onto the surface of the alloy material obtained in step (1), the temperature is increased to 50°C at 3°C / min, and then kept at 50°C for 24 h to obtain a copper-aluminum based grounding alloy material with coating that is resistant to salt and alkali corrosion.

[0029] Example 2

[0030] Compared to Example 1, the alloy composition is different, and the specific proportions and steps are as follows: (1) The metal Cu is 88.00 wt.%, the metal Al is 9.00 wt.%, and the metal Ni is 3.00 wt.%. The metal Cu, Al and Ni are added to a graphite crucible in proportion, and the high-frequency induction melting furnace is heated to 1150℃ under N2 atmosphere to completely melt it. After stirring for 5 minutes, it is poured into a mold of the required size and shape, cooled and demolded to obtain a copper-aluminum based grounding alloy material; (2) 2.00 wt.% layered flake graphite (FG) was added to 20g of waterborne polyurethane and stirred for 10min to obtain mixture A. The obtained mixture A was peeled by three-roll milling process (TRM) and after 16 cycles of peeling, mixture B was obtained. The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers, from feed roller N3 to center roller N2 to discharge roller N1, is 1:3:9. During the first to fourth cycles of peeling, the gap between rollers N3 and N2 is 48 μm, and the gap between N2 and N1 is 24 μm. During the fifth to eighth cycles of peeling, the gap between rollers N3 and N2 is 12 μm, and the gap between N2 and N1 is 6 μm. After the ninth cycle of peeling, the gap between rollers N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm.

[0031] (3) Add 0.5 wt.% conductive carbon black and 0.5 wt.% carbon nanotubes to the mixture B obtained in step (2), and then grind and peel it together three times with three rollers. Finally, form a conductive network structure coating of zero-dimensional carbon black, one-dimensional carbon nanotubes and two-dimensional multilayer graphene sheets in water-based polyurethane as a coating material for grounding.

[0032] The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers is 1:3:9 (feed roller N3: center roller N2: discharge roller N1), the process is repeated 3 times, the gap between rollers N3 and N2 is 2 μm, and the gap between N2 and N1 is 1 μm.

[0033] (4) After coating the coating obtained in step (3) onto the surface of the alloy material obtained in step (1), the temperature is increased to 50°C at 3°C / min, and then kept at 50°C for 24 h to obtain a copper-aluminum based grounding alloy material with coating that is resistant to salt and alkali corrosion.

[0034] Example 3

[0035] Compared to Example 1, the alloy composition is different, and the specific proportions and steps are as follows: (1) The metal Cu is 87.00 wt.%, the metal Al is 9.00 wt.%, and the metal Ni is 4.00 wt.%. The metal Cu, Al and Ni are added to a graphite crucible in proportion, and the high-frequency induction melting furnace is heated to 1150℃ under N2 atmosphere to completely melt it. After stirring for 5 min, it is poured into a mold of the required size and shape, cooled and demolded to obtain a copper-aluminum based grounding alloy material; (2) 2.00 wt.% layered flake graphite (FG) was added to 20g of waterborne polyurethane and stirred for 10min to obtain mixture A. The obtained mixture A was peeled by three-roll milling process (TRM) and after 16 cycles of peeling, mixture B was obtained. The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers, from feed roller N3 to center roller N2 to discharge roller N1, is 1:3:9. During the first to fourth cycles of peeling, the gap between rollers N3 and N2 is 48 μm, and the gap between N2 and N1 is 24 μm. During the fifth to eighth cycles of peeling, the gap between rollers N3 and N2 is 12 μm, and the gap between N2 and N1 is 6 μm. After the ninth cycle of peeling, the gap between rollers N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm.

[0036] (3) Add 0.50 wt.% conductive carbon black and 0.50 wt.% carbon nanotubes to the mixture B obtained in step (2), and then grind and peel it together three times with three rollers. Finally, form a conductive network structure coating of zero-dimensional carbon black, one-dimensional carbon nanotubes and two-dimensional multilayer graphene sheets in water-based polyurethane as a coating material for grounding.

[0037] The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers is 1:3:9 (feed roller N3: center roller N2: discharge roller N1), the process is repeated 3 times, the gap between rollers N3 and N2 is 2 μm, and the gap between N2 and N1 is 1 μm.

[0038] (4) Apply the coating obtained in step (3) to the surface of the alloy material obtained in step (1), then heat it to 50°C at 3°C / min and keep it at 50°C for 24 hours to obtain a copper-aluminum based grounding alloy material resistant to salt and alkali corrosion.

[0039] Example 4

[0040] Compared to Example 1, the alloy composition is different, and the specific proportions and steps are as follows: (1) The metal Cu is 87.90 wt.%, the metal Al is 9.00 wt.%, the metal Ni is 3.00 wt.%, and the rare earth oxide CeO2 is 0.10 wt.%. The metal Cu, Al, Ni and CeO2 are added to the graphite crucible in proportion. The high-frequency induction melting furnace is heated to 1150℃ under N2 atmosphere to completely melt it. After stirring for 5 minutes, it is poured into the mold of the required size and shape. After cooling, it is demolded to obtain the copper-aluminum based grounding alloy material. (2) 2.00 wt.% layered flake graphite (FG) was added to 20g of waterborne polyurethane and stirred for 10 min to obtain mixture A. The obtained mixture A was peeled by three-roll milling process (TRM) and after 16 cycles of peeling, mixture B was obtained. The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers is 1:3:9 for the feed roller N3: center roller N2: discharge roller N1. During the first to fourth cycles of peeling, the gap between rollers N3 and N2 is 48 μm, and the gap between N2 and N1 is 24 μm. During the fifth to eighth cycles of peeling, the gap between N3 and N2 is 12 μm, and the gap between N2 and N1 is 6 μm. After the ninth cycle of peeling, the gap between rollers N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm.

[0041] (3) Add 0.50 wt.% conductive carbon black and 0.50 wt.% carbon nanotubes to the mixture B obtained in step (2), and then grind and peel it together three times with three rollers. Finally, a conductive network structure of zero-dimensional carbon black, one-dimensional carbon nanotubes and two-dimensional multilayer graphene sheets is formed in water-based polyurethane as a coating for grounding material.

[0042] The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers is 1:3:9 (feed roller N3: center roller N2: discharge roller N1), the process is repeated 3 times, the gap between rollers N3 and N2 is 2 μm, and the gap between N2 and N1 is 1 μm.

[0043] (4) Apply the coating obtained in step (3) to the surface of the alloy material obtained in step (1), then heat it to 50°C at 3°C / min and keep it at 50°C for 24 h to obtain a copper-aluminum based grounding alloy material with coating that is resistant to salt and alkali corrosion.

[0044] Comparative Example 1

[0045] Unlike Example 2, steps (2)-(4) are omitted, and nickel is not added in step (1). Specifically, the copper-aluminum based grounding alloy material resistant to salt and alkali corrosion uses Cu and Al as raw materials. The raw material composition by weight percentage is: Cu 91.00 wt.% and Al 9.00 wt.%. Cu and Al are added to a graphite crucible in proportion, and the high-frequency induction melting furnace is heated to 1150°C under N2 atmosphere to completely melt it. After stirring for 5 min, it is poured into a mold of the required size and shape, cooled, and demolded to obtain the copper-aluminum based grounding alloy material resistant to salt and alkali corrosion.

[0046] Comparative Example 2

[0047] Unlike Example 2, steps (2)-(4) are omitted, and the nickel content added in step (1) is 4.00 wt%. Specifically, the copper-aluminum based grounding alloy material resistant to salt and alkali corrosion uses metals Cu, Al, and Ni as raw materials. The raw material components by weight percentage are: metal Cu 87.00 wt.%, metal Al 9.00 wt.%, and metal Ni 4.00 wt.%. Metals Cu, Al, and Ni are added to a graphite crucible in proportion. A high-frequency induction melting furnace is used to heat the material to 1150°C under N2 atmosphere to completely melt it. The mixture is stirred for 5 minutes and then poured into a mold of the required size and shape. After cooling, the material is demolded to obtain the copper-aluminum based grounding alloy material resistant to salt and alkali corrosion.

[0048] Comparative Example 3

[0049] Unlike Example 2, steps (2)-(4) are omitted, and the nickel content added in step (1) is 5.00 wt%. Specifically, the prepared salt and alkali resistant copper-aluminum based grounding alloy material uses metals Cu, Al, and Ni as raw materials. The raw material components by weight percentage are: metal Cu 86.00 wt.%, metal Al 9.00 wt.%, and metal Ni 5.00 wt.%. Metals Cu, Al, and Ni are added to a graphite crucible in proportion. A high-frequency induction melting furnace is used to heat the material to 1150°C under N2 atmosphere to completely melt it. The mixture is stirred for 5 min, then poured into a mold, cooled, and demolded to obtain the salt and alkali resistant copper-aluminum based grounding alloy material.

[0050] Comparative Example 4

[0051] Unlike Example 4, steps (2)-(4) are omitted; specifically, the copper-aluminum based grounding alloy material resistant to salt and alkali corrosion is made from metals Cu, Al and Ni. The raw material components by weight percentage are: metal Cu 87.90 wt.%, metal Al 9.00 wt.%, metal Ni 3.00 wt.%, and rare earth oxide CeO2 0.10 wt.%. Metals Cu, Al, Ni and CeO2 are added to a graphite crucible in proportion, and a high-frequency induction melting furnace is used to heat it to 1150°C under N2 atmosphere to completely melt it. After stirring for 5 minutes, it is poured into a mold of the required size and shape, cooled and demolded to obtain the copper-aluminum based grounding alloy material resistant to salt and alkali corrosion.

[0052] Comparative Example 5

[0053] Compared to Example 2, the conductive coating has a different composition (no conductive carbon black and carbon nanotubes were added), and its specific formulation and steps are as follows: (1) The metal Cu is 88.00 wt.%, the metal Al is 9.00 wt.%, and the metal Ni is 3.00 wt.%. The metal Cu, Al and Ni are added to a graphite crucible in proportion, and the high-frequency induction melting furnace is heated to 1150℃ under N2 atmosphere to completely melt it. After stirring for 5 minutes, it is poured into a mold of the required size and shape, cooled and demolded to obtain a copper-aluminum based grounding alloy material; (2) 2.00 wt.% layered flake graphite (FG) was added to 20g of waterborne polyurethane and stirred for 10min to obtain mixture A. The obtained mixture A was peeled by three-roll milling process (TRM) and after 16 cycles of peeling, mixture B was obtained. The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers, from feed roller N3 to center roller N2 to discharge roller N1, is 1:3:9. During the first to fourth cycles of peeling, the gap between rollers N3 and N2 is 48 μm, and the gap between N2 and N1 is 24 μm. During the fifth to eighth cycles of peeling, the gap between rollers N3 and N2 is 12 μm, and the gap between N2 and N1 is 6 μm. After the ninth cycle of peeling, the gap between rollers N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm.

[0054] (3) After coating the coating obtained in step (2) onto the surface of the alloy material obtained in step (1), the temperature is increased to 50°C at 3°C / min, and then kept at 50°C for 24 h to obtain a copper-aluminum based grounding alloy material with coating that is resistant to salt and alkali corrosion.

[0055] Comparative Example 6 Compared to Example 2, the processing technology for the conductive coating is different (the layered flake graphite was not milled using a three-roll mill), and the specific formulation and steps are as follows: (1) The metal Cu is 88.00 wt.%, the metal Al is 9.00 wt.%, and the metal Ni is 3.00 wt.%. The metal Cu, Al and Ni are added to a graphite crucible in proportion, and the high-frequency induction melting furnace is heated to 1150℃ under N2 atmosphere to completely melt it. After stirring for 5 minutes, it is poured into a mold of the required size and shape, cooled and demolded to obtain a copper-aluminum based grounding alloy material; (2) 2.00 wt.% layered flake graphite (FG), 0.50 wt.% conductive carbon black and 0.50 wt.% carbon nanotubes were added to 20g of waterborne polyurethane and stirred for 10min to obtain an un-grinded and unstripped conductive coating: (3) After coating the coating obtained in step (2) onto the surface of the alloy material obtained in step (1), the temperature is increased to 50°C at 3°C / min, and then kept at 50°C for 24 h to obtain a copper-aluminum based grounding alloy material with coating that is resistant to salt and alkali corrosion.

[0056] Comparative Example 7 Compared to Example 2, the conductive coating has a different composition (no carbon nanotubes were added), and its specific formulation and steps are as follows: (1) The metal Cu is 88.00 wt.%, the metal Al is 9.00 wt.%, and the metal Ni is 3.00 wt.%. The metal Cu, Al and Ni are added to a graphite crucible in proportion, and the high-frequency induction melting furnace is heated to 1150℃ under N2 atmosphere to completely melt it. After stirring for 5 minutes, it is poured into a mold of the required size and shape, cooled and demolded to obtain a copper-aluminum based grounding alloy material; (2) 2.00 wt.% layered flake graphite (FG) was added to 20g of waterborne polyurethane and stirred for 10min to obtain mixture A. The obtained mixture A was peeled by three-roll milling process (TRM) and after 16 cycles of peeling, mixture B was obtained. The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers, from feed roller N3 to center roller N2 to discharge roller N1, is 1:3:9. During the first to fourth cycles of peeling, the gap between rollers N3 and N2 is 48 μm, and the gap between N2 and N1 is 24 μm. During the fifth to eighth cycles of peeling, the gap between rollers N3 and N2 is 12 μm, and the gap between N2 and N1 is 6 μm. After the ninth cycle of peeling, the gap between rollers N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm.

[0057] (3) Add 1.00 wt.% of conductive carbon black to the mixture B obtained in step (2), and then grind and peel it together three times with three rollers. Finally, a conductive network structure of zero-dimensional carbon black and two-dimensional multilayer graphene sheets is formed in water-based polyurethane as a coating for grounding material.

[0058] The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers is 1:3:9 (feed roller N3: center roller N2: discharge roller N1), the process is repeated 3 times, the gap between rollers N3 and N2 is 2μm, and the gap between N2 and N1 is 1μm.

[0059] (4) Apply the coating obtained in step (3) to the surface of the alloy material obtained in step (1), then heat it to 50°C at 3°C / min and keep it at 50°C for 24 h to obtain a copper-aluminum based grounding alloy material with coating that is resistant to salt and alkali corrosion.

[0060] Comparative Example 8 Compared to Example 2, the conductive coating has a different composition, and its specific formulation and steps are as follows: (1) The metal Cu is 88.00 wt.%, the metal Al is 9.00 wt.%, and the metal Ni is 3.00 wt.%. The metal Cu, Al and Ni are added to a graphite crucible in proportion, and the high-frequency induction melting furnace is heated to 1150℃ under N2 atmosphere to completely melt it. After stirring for 5 minutes, it is poured into a mold of the required size and shape, cooled and demolded to obtain a copper-aluminum based grounding alloy material; (2) 2.00 wt.% layered flake graphite (FG) was added to 20g of waterborne polyurethane and stirred for 10min to obtain mixture A. The obtained mixture A was peeled by three-roll milling process (TRM) and after 16 cycles of peeling, mixture B was obtained. The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers, from feed roller N3 to center roller N2 to discharge roller N1, is 1:3:9. During the first to fourth cycles of peeling, the gap between rollers N3 and N2 is 48 μm, and the gap between N2 and N1 is 24 μm. During the fifth to eighth cycles of peeling, the gap between rollers N3 and N2 is 12 μm, and the gap between N2 and N1 is 6 μm. After the ninth cycle of peeling, the gap between rollers N3 and N2 is 3 μm, and the gap between N2 and N1 is 1 μm.

[0061] (3) Add 1.00 wt.% of carbon nanotubes to the mixture B obtained in step (2), and then grind and peel it together three times with three rollers. Finally, a conductive network structure of one-dimensional carbon nanotubes and two-dimensional multilayer graphene sheets is formed in water-based polyurethane as a coating for grounding material.

[0062] The specific process parameters for the three-roll grinding process in this step are as follows: the rotational speed ratio between the rollers is 1:3:9 (feed roller N3: center roller N2: discharge roller N1), the process is repeated 3 times, the gap between rollers N3 and N2 is 2μm, and the gap between N2 and N1 is 1μm.

[0063] (4) Apply the coating obtained in step (3) to the surface of the alloy material obtained in step (1), then heat it to 50°C at 3°C / min and keep it at 50°C for 24 h to obtain a copper-aluminum based grounding alloy material with coating that is resistant to salt and alkali corrosion.

[0064] Electrochemical tests were conducted on the grounding materials of Examples 1-8 and Examples 1-4 to compare their corrosion performance.

[0065] The Cu-9Al-2Ni alloy sample obtained in Example 1 was subjected to electron microscopy scanning before and after etching in 3wt.% NaCl and 0.1 M NaHCO3 solutions after the cross-section was polished. The results are shown in the figure. Figure 1 A layer of corrosion products adhered to the surface of the alloy.

[0066] SEM images of the micro / nano graphite sheets formed after graphite exfoliation by three-roll milling in Example 1 are shown below. Figure 2 In (a), the SEM image of the fracture surface of the grounding material coating in Example 1 is shown in Figure (a). Figure 2 As shown in (b), after the flake graphite is peeled off by three-roll milling, it forms micro-nano graphite flakes, which are evenly distributed inside the coating.

[0067] Figure 3 The graph shows the relationship between Vickers hardness and nickel content in grounding materials. As can be seen from the graph, the Vickers hardness of the grounding material increases with the increase of nickel content, indicating that increasing the nickel content is beneficial to improving the mechanical properties of the grounding material.

[0068] The excess working electrode surface was sealed with transparent tape, exposing only a 10mm × 10mm working surface. The open-circuit potential of the working electrode was tested for more than 600s. After the open-circuit voltage stabilized, its potentiodynamic polarization curve was measured. At 25℃, the corrosion rate of the base alloy in a 3.5wt.% NaCl + 0.1 M NaHCO3 electrolyte was tested (electrochemical workstation), and the results are shown in Table 1.

[0069] Table 1 shows the electrochemical corrosion results of copper-aluminum based grounding alloys with different salt and alkali corrosion resistance.

[0070] Table 1 shows that no rare earth oxides were added in Examples 1-3, while in Example 4, rare earth oxides were further added based on Example 2. Furthermore, the performance of Example 4 was superior to Examples 1-3 and Comparative Examples 1-8, indicating that Example 4 had the best performance. This is because the introduction of Ni and rare earth oxides reduced the corrosion current of the copper-aluminum alloy in 3.5 wt.% NaCl and 0.1 M NaHCO3 solutions, thus improving its corrosion resistance. Coating the Cu-9Al-xNi alloy and Cu-9Al-3Ni-0.1CeO2 alloy samples with a conductive coating further improved their corrosion resistance. The different coating components and grinding processes also affected the corrosion resistance of the alloy materials. The coating prepared by three-roll milling to remove flake graphite, conductive carbon black, and carbon nanotubes had the lowest corrosion current density of 6.5 μA / cm. 2 .

[0071] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion, characterized in that, First, copper-aluminum multi-element alloy grounding material is prepared by smelting copper and aluminum as the matrix and adding Ni and rare earth oxides. Second, flake graphite is exfoliated into two-dimensional multilayer graphene sheets in an aqueous polyurethane medium through a three-roll milling process. Then, it is mixed with conductive carbon black and carbon nanotubes to form a conductive network structure coating. Finally, the conductive network structure coating is coated onto the surface of the copper-aluminum multi-element alloy grounding material to obtain a copper-aluminum based grounding alloy material with a coating that is resistant to salt and alkali corrosion.

2. The method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to claim 1, characterized in that, Includes the following steps: S1: Add metals Cu, Al, Ni and rare earth oxides to a graphite crucible, place it in a high-frequency induction furnace, heat it to 1100-1200℃ under N2 atmosphere to completely melt it, stir for 4-6 minutes, then pour it into a mold, cool it and demold it to obtain copper-aluminum multi-element alloy grounding material. S2: Add flake graphite to waterborne polyurethane and stir for 10-30 minutes to obtain mixture A. The obtained mixture A is then exfoliated by a three-roll milling process. After 9-16 cycles of exfoliation, mixture B is obtained. S3: Add conductive carbon black and carbon nanotubes to mixture B, and use a three-roll milling process to peel and mix 3-5 times to obtain a conductive network structure coating. S4: After applying the coating obtained in S3 to the surface of the copper-aluminum multi-element alloy grounding material obtained in step S1, the temperature is raised to 50-70℃ at 3-5℃ / min, and then kept at the temperature for 12-36h to obtain a copper-aluminum based grounding alloy material with coating that is resistant to salt and alkali corrosion.

3. The method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to claim 2, characterized in that, In step S1, the copper-aluminum multi-element alloy grounding material contains 85.85-91 wt.% Cu, 7.00-9.00 wt.% Al, 2.00-5.00 wt.% Ni, and 0.01-0.15 wt.% rare earth oxides.

4. The method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to claim 3, characterized in that, The rare earth element is at least one of CeO2, Y2O3, La2O3, Nd2O3 and Sm2O3.

5. The method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to claim 2, characterized in that, In step S2, the solid content of the waterborne polyurethane is 40-60 wt%.

6. The method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to claim 2, characterized in that, In step S2, the length dimension of the flake graphite is 10μm-200μm, the thickness is 1μm-10μm, and the mass ratio of flake graphite to waterborne polyurethane is 0.1-10:

100.

7. The method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to claim 2, characterized in that, In step S3, the conductive carbon black has a particle size of 50 nm-200 nm, the carbon nanotubes are 2-10 layers of multi-walled carbon nanotubes, and the mass ratio of conductive carbon black to carbon nanotubes added to the waterborne polyurethane is 0.1-2:100, and the mass ratio of conductive carbon black to carbon nanotubes is 1:1-3.

8. The method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to claim 2, characterized in that, In step S2, the specific process parameters of the three-roll grinding process are as follows: the rotational speed ratio between the rollers is 1:3:9 for the feed roller N3: center roller N2: discharge roller N1; for the first 1-4 cycles of peeling, the gap between each roller is 20-50 μm; for the 5th-8th cycles of peeling, the gap between each roller is adjusted to 5-20 μm; and after the 9th cycle of peeling, the gap between each roller is adjusted to 0.5-5 μm. It is also ensured that during the peeling process, the gap between rollers N3 and N2 is at least twice as large as that between rollers N2 and N1.

9. A method for preparing a coated copper-aluminum-based grounding alloy material resistant to salt and alkali corrosion according to claim 2, characterized in that, In step S3, the specific process parameters of the three-roll grinding process are as follows: the rotational speed ratio between the rollers is 1:3:9 for the feed roller N3: center roller N2: discharge roller N1, the cyclic peeling is performed 3-5 times, the gap between each roller shaft is adjusted to 0.5-2 μm, and it is ensured that the gap between roller shafts N3 and N2 is at least twice as large as that between roller shafts N2 and N1 during the cyclic peeling process.

10. A copper-aluminum based grounding alloy material with a coating resistant to salt and alkali corrosion, characterized in that, It is prepared by any one of the preparation methods described in claims 1-9.

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