High-potential-corrosion-resistant composite coating as well as preparation method and application thereof

Abstract

The invention discloses a high-potential-corrosion-resistant composite coating as well as a preparation method and application thereof. The high-potential-corrosion-resistant composite coating comprises a metal transition layer, a graphite-like amorphous carbon layer and a SnO2 hole sealing layer which are sequentially formed on the surface of the metal bipolar plate serving as a substrate, wherein the SnO2 hole sealing layer is prepared in an atomic layer deposition mode. According to the high-potential-corrosion-resistant composite coating provided by the invention, the SnO2 layer is deposited on the surface of the amorphous carbon coating, so that the effect of closing amorphous carbon defects is achieved, and the high-potential-corrosion-resistant composite coating has excellent corrosion-resistant protection performance under 1.6 V high-potential corrosion.

Description

Technical Field

[0001] The present invention relates to the technical field of surface protective coatings, and in particular to a high-potential corrosion-resistant composite coating and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFCs) offer advantages such as fast startup, relatively low operating temperatures, rapid environmental response, zero pollution, and high energy efficiency. They hold great promise for applications in new energy vehicles, stationary, and portable power sources. A PEMFC cell typically consists of bipolar plates (BPs), a membrane electrode assembly (MEA), gaskets, and end plates. Among these components, the BPA accounts for 80% of the fuel cell's total mass, nearly all of its volume, and approximately 18%-28% of its manufacturing cost. The BPA is a key functional component in a PEMFC stack, with its primary functions including conducting electrons, distributing chemical fuels, separating individual cells, supporting the membrane electrode assembly, and facilitating water management within the cell. Therefore, it must meet requirements such as easy processing, resistance to electrochemical corrosion, low interfacial resistance, and low cost. Currently, graphite BPAs are widely used in conventional fuel cells, but their bulk and low strength hinder their widespread adoption. Metal plates with excellent properties such as high electrical conductivity, high thermal conductivity, high mechanical strength, low stamping cost and low gas permeability are expected to replace graphite as the main material for bipolar plates.

[0003] The operating environment of proton exchange membrane fuel cells is usually acidic (pH = 2-3), warm and humid (65-90 ° C) environment. Acidic corrosive media at high temperatures will, on the one hand, generate a passivation layer on the surface of the metal bipolar plate, thereby increasing the interfacial contact resistance (ICR) between the metal bipolar plate and the gas diffusion layer (GDLs); on the other hand, the metal bipolar plate is prone to severe corrosion. Both of the above consequences will affect the output power of the battery and cause the battery performance to decline rapidly. Depositing a protective coating on the surface of the metal bipolar plate is an effective means to improve its surface conductivity and corrosion resistance. Commonly used protective coatings include precious metal coatings, metal nitride or carbide coatings, conductive polymer coatings, etc. Amorphous carbon coating is a kind of diamond phase sp 3 and graphite phase sp 2 The hybrid structure coating formed by hybridization, due to the excellent chemical inertness of carbon elements and amorphous structure, has the advantages of corrosion resistance, conductivity and low cost through component structure optimization, and has attracted widespread attention in the field of metal bipolar plate surface protection.

[0004] However, unlike the conventional low-potential (0.6V) steady-state operating condition, the transient potential in the actual operation of the proton exchange membrane fuel cell can be as high as 1.6V, which will cause the performance of the amorphous carbon coating modified metal bipolar plate to degrade rapidly, seriously affecting the battery reliability. The existing scheme can improve the corrosion resistance of the coating at high potential by introducing a metal / carbide multilayer to form a corrosion-resistant continuous metal oxide layer or introducing metal doping to form corrosion-resistant metal oxide particles to fill the pore structure of the amorphous carbon coating. For example, patent CN202411393249.3 discloses a metal bipolar plate coating resistant to high potential corrosion and its preparation method, and patent CN201910511613.4 discloses a metal carbide crystal composite coating and its preparation method, but these methods usually continue to improve the plate ICR and battery energy consumption, and there is a risk of coating peeling and failure due to the difference in volume expansion of each component, which reduces the battery's working efficiency and service life. Therefore, how to break through the coating and application technology that has both excellent corrosion resistance and conductivity at high potential is an urgent problem to be solved in the field of PEMFCs metal bipolar plate surface protection. Summary of the Invention

[0005] The main purpose of the present invention is to provide a high-potential corrosion-resistant composite coating and its preparation method and application, so as to overcome the deficiencies in the prior art.

[0006] To achieve the aforementioned object of the invention, the technical solutions adopted by the present invention include:

[0007] One aspect of the present invention provides a high-potential corrosion-resistant composite coating, which includes a metal transition layer, a graphite-like amorphous carbon layer and a SnO2 sealing layer formed in sequence on the surface of a metal bipolar plate serving as a substrate; wherein the SnO2 sealing layer is prepared by atomic layer deposition.

[0008] Another aspect of the present invention provides a method for preparing the aforementioned high-potential corrosion-resistant composite coating, comprising:

[0009] providing a metal bipolar plate as a substrate;

[0010] A high-power pulsed magnetron sputtering technology is used to deposit a metal transition layer on the surface of the metal bipolar plate using a metal target as a target material;

[0011] Using DC magnetron sputtering technology and graphite target as target material, a graphite-like amorphous carbon layer is deposited on the surface of the metal transition layer;

[0012] Furthermore, an atomic layer deposition technique is used, with organic tin as a tin source and water vapor as an oxygen source, to deposit a SnO2 sealing layer on the surface of the graphite-like amorphous carbon layer to obtain a high-potential corrosion-resistant composite coating.

[0013] Another aspect of the present invention also provides the use of the aforementioned high-potential corrosion-resistant composite coating in the field of substrate surface protection.

[0014] Another aspect of the present invention provides a bipolar plate for a proton exchange membrane fuel cell, which includes a metal bipolar plate and a protective coating covering the surface of the metal bipolar plate, wherein the protective coating is the aforementioned high-potential corrosion-resistant composite coating.

[0015] Compared with the prior art, the technical solution of the present invention has at least the following advantages:

[0016] The high-potential corrosion-resistant composite coating provided by the present invention seals amorphous carbon defects by depositing a SnO2 layer on the surface of the amorphous carbon coating, thereby significantly improving the density of the composite coating; at the same time, the SnO2 layer process is simple and stable, and the low sealing thickness does not affect the interface bonding strength between the amorphous carbon and the metal matrix; at the same time, based on the high conductivity of the surface SnO2, the overall low ICR level of the plate is achieved, thereby inhibiting the corrosion of the carbon-based coating modified plate under high potential, and improving the performance and service life of the plate; the high-potential corrosion-resistant composite coating provided by the present invention has excellent corrosion protection performance under high potential corrosion of 1.6V. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 A schematic diagram of a high-potential corrosion-resistant composite coating in a typical embodiment of the present invention;

[0019] Figure 2 This is a comparison chart of the coating corrosion performance test results of Example 1 of the present invention and Comparative Examples 1-5;

[0020] Figure 3 This is a comparison chart of the 1.6V high potential corrosion performance test results of the coatings of Example 1 of the present invention and Comparative Examples 1-5;

[0021] Figure 4 1 is a comparison chart of the test results of the coating contact resistance performance of Example 1 of the present invention and Comparative Examples 1-5;

[0022] Figure 5 Photos of the coatings of Examples 1-3 and Comparative Examples 1-2 before and after corrosion;

[0023] Figure 6These are photos of the coatings after corrosion in Example 1 of the present invention and Comparative Example 6. DETAILED DESCRIPTION

[0024] The present invention will be more fully understood by reading the following detailed description. However, it should be understood that the detailed description disclosed below is merely exemplary of the present invention, and that the present invention may be embodied in a variety of forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as a basis for the claims and as a representative basis for teaching those skilled in the art to variously employ the present invention in virtually any appropriately detailed embodiment.

[0025] As one aspect of the technical solution of the present invention, a high-potential corrosion-resistant composite coating is involved, which includes a metal transition layer, a graphite-like amorphous carbon layer and a SnO2 sealing layer formed in sequence on the surface of a metal bipolar plate serving as a substrate; wherein the SnO2 sealing layer is prepared by atomic layer deposition.

[0026] In the present invention, a highly dense and stable SnO2 sealing layer is deposited on the surface of the carbon-based coating by atomic layer deposition, which can reduce the defect density of the composite coating. At the same time, based on the high conductivity of the surface SnO2, a low ICR level of the entire plate is achieved, thereby inhibiting the corrosion of the carbon-based coating modified plate under high potential, and improving the performance and service life of the plate.

[0027] In some embodiments, the metal contained in the metal transition layer includes any one of chromium, titanium, and aluminum, or a combination of two or more thereof.

[0028] In some embodiments, the thickness of the metal transition layer is 100 to 200 μm.

[0029] In some embodiments, the graphite-like amorphous carbon layer has a thickness of 200 to 500 nm.

[0030] In some embodiments, the SnO2 sealing layer has a thickness of 10 to 50 nm.

[0031] In some embodiments, the high-potential corrosion-resistant composite coating has a corrosion current density of less than 2×10- 5 A / cm 2 , the deposited contact resistance is less than 4mΩ·cm 2 , after 12 hours of corrosion, the contact resistance is less than 10mΩ·cm 2 .

[0032] As another aspect of the technical solution of the present invention, the preparation method of the aforementioned high-potential corrosion-resistant composite coating involves:

[0033] providing a metal bipolar plate as a substrate;

[0034] A high-power pulsed magnetron sputtering technology is used to deposit a metal transition layer on the surface of the metal bipolar plate using a metal target as a target material;

[0035] Using DC magnetron sputtering technology and graphite target as target material, a graphite-like amorphous carbon layer is deposited on the surface of the metal transition layer;

[0036] Furthermore, an atomic layer deposition technique is used, with organic tin as a tin source and water vapor as an oxygen source, to deposit a SnO2 sealing layer on the surface of the graphite-like amorphous carbon layer to obtain a high-potential corrosion-resistant composite coating.

[0037] In some embodiments, the preparation method specifically includes: using high-power pulsed magnetron sputtering technology to place the metal bipolar plate in a reaction chamber, using a metal target as a target material and an inert gas as a working gas, and depositing a metal transition layer on the surface of the metal bipolar plate, wherein the high-power pulsed magnetron sputtering technology uses a pulse frequency of 500-1000 Hz, a pulse width of 50-100 μs, a pulse voltage of 800-1000 V, a power of 3.0-3.5 kW, a gas pressure of 1.5-2.5 mTorr, a substrate bias voltage of -50 V to -200 V, an inert gas injection amount of 30-55 sccm, a deposition temperature of 70-80°C, and a deposition time of 5-15 min.

[0038] In some preferred embodiments, the metal target includes but is not limited to any one of a high-purity chromium target, a high-purity titanium target, and a high-purity aluminum target, or a combination of two or more thereof.

[0039] In some embodiments, the preparation method specifically includes: using DC magnetron sputtering technology, using a graphite target as a target material, and using an inert gas as a working gas to deposit a graphite-like amorphous carbon layer on the surface of the metal transition layer; wherein the sputtering source power is 0.9 to 1.2 kW, the reaction chamber pressure is 1.5 to 2.5 mTorr, the substrate bias is -50 V to -200 V, the inert gas injection amount is 35 to 55 sccm, the deposition temperature is 70 to 80 ° C, and the deposition time is 60 to 120 min.

[0040] In some embodiments, the preparation method specifically includes: using atomic layer deposition technology, sequentially introducing inert gas, reaction gas containing organic tin, dry gas, water vapor, and dry gas as a deposition cycle, and depositing a SnO2 sealing layer on the surface of the graphite-like amorphous carbon layer; wherein, the time for introducing the inert gas in one deposition cycle is 3-6s, the time for introducing the reaction gas is 6-9s, the time for introducing the dry gas is 2-5s, the time for introducing the water vapor is 1-4s, the time for introducing the dry gas is 2-5s, and the deposition temperature is 200-250°C.

[0041] In some preferred embodiments, the inert gas includes but is not limited to argon.

[0042] In some preferred embodiments, the drying gas includes but is not limited to nitrogen, argon, or a combination of the two.

[0043] In some preferred embodiments, the organic tin includes but is not limited to any one of tetramethyltin and tetrakis(dimethylamino)tin, or a combination of two or more thereof.

[0044] In some preferred embodiments, the SnO2 sealing layer is formed by performing 100-300 deposition cycles on the surface of the graphite-like amorphous carbon layer.

[0045] This invention utilizes atomic layer deposition (ALD) technology for SnO2 pore sealing, characterized by three-dimensional uniformity and atomic-level thickness control, enabling the production of uniform, ultra-thin, high-quality coatings on complex surfaces. Due to the semiconductor properties of SnO2, the thickness of the SnO2 sealing layer is kept within a relatively thin range to ensure the coating's electrical conductivity. Furthermore, the invention optimizes the number of ALD cycles, achieving a coating with both excellent electrical conductivity and corrosion resistance.

[0046] In some embodiments, the preparation method further comprises: etching the surface of the metal bipolar plate before forming the metal transition layer.

[0047] In some preferred embodiments, the etching process includes: using Ar ion etching to etch the metal bipolar plate for 30 to 60 minutes at room temperature; the process conditions used in the etching process include: the reaction chamber pressure is 3.0×10- 5 Torr or less, the argon flow rate is 50 to 100 sccm, the bias voltage is -200 to -500 V, and the Ar ion etching method includes glow etching and / or ion beam etching.

[0048] In some embodiments, the metal bipolar plate includes but is not limited to any one of a stainless steel bipolar plate, a titanium alloy bipolar plate, and an aluminum alloy bipolar plate.

[0049] As another aspect of the technical solution of the present invention, it involves the application of the aforementioned high-potential corrosion-resistant composite coating in the field of substrate surface protection.

[0050] In some embodiments, the application includes use of the aforementioned high-potential corrosion-resistant composite coating in a proton exchange membrane fuel cell.

[0051] As another aspect of the technical solution of the present invention, it involves a bipolar plate for a proton exchange membrane fuel cell, including a metal bipolar plate and a protective coating covering the surface of the metal bipolar plate, wherein the protective coating is the aforementioned high-potential corrosion-resistant composite coating.

[0052] The present invention is further illustrated by way of examples below, but the invention is not limited to the scope of the examples. The reagents and raw materials used in the following examples are commercially available, and the experimental methods where specific conditions are not specified are generally carried out under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0053] Example 1

[0054] In this embodiment, the preparation method of the high-potential corrosion-resistant composite coating on the surface of the metal bipolar plate is as follows:

[0055] S1. The substrate is TA1 titanium alloy. The titanium alloy bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece bracket, and evacuated to 2.0×10 -5 Torr or less, then under the conditions of argon gas flow rate of 100 sccm and bias voltage of -500 V, turn on the ion source, adjust the output voltage to 1800 V, and use argon plasma to etch the surface of the titanium alloy bipolar plate for 60 minutes;

[0056] S2. Ar gas was introduced into the chamber (the amount of Ar gas was 30 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 1.5 mTorr. The high-power pulse power supply connected to the titanium sputtering target was turned on and the power supply frequency was set to 500 Hz, the pulse width was 50 μs, the pulse voltage was 1000 V, the power was 3.5 kW, the substrate bias was -200 V, and the deposition temperature was 70°C. A titanium transition layer with a thickness of 200 nm was deposited.

[0057] S3. Ar gas was continued to be introduced into the chamber (the amount of Ar gas was 35 sccm), and the chamber pressure was maintained at 1.5 mTorr using DC magnetron sputtering technology. The DC power supply connected to the graphite sputtering target was turned on and the power was set to 1.2 kW, the bias voltage was -200 V, and the deposition temperature was 70 ° C. A graphite-like amorphous carbon layer with a thickness of 500 nm was deposited;

[0058] S4. Place the prepared titanium / amorphous carbon coating into an atomic layer deposition chamber, introduce argon (6s), tetramethyltin (9s), argon (5s), water vapor (4s), and argon (5s) in sequence, with a deposition temperature of 250°C and 300 deposition cycles to obtain a high-potential corrosion-resistant composite coating. Figure 1 As shown, the high-potential corrosion-resistant composite coating includes a Ti transition layer, a graphite-like amorphous carbon layer and a SnO2 sealing layer sequentially formed on the surface of a metal bipolar plate as a substrate.

[0059] According to the test, the corrosion current density at a high potential of 1.6V is 1.1×10 -5 A / cm 2 The contact resistance of the deposited state is 3.9mΩ·cm 2 , the contact resistance after 12h corrosion is 9.1mΩ·cm 2 .

[0060] Example 2

[0061] In this embodiment, the preparation method of the high-potential corrosion-resistant composite coating on the surface of the metal bipolar plate is as follows:

[0062] S1. The base material is 304 stainless steel. The stainless steel bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece bracket, and evacuated to 3.0×10 -5 Torr or less, then, under the conditions of argon flow rate of 50 sccm and bias voltage of -200 V, turn on the ion source, adjust the output voltage to 600 V, and use argon plasma to etch the surface of the stainless steel bipolar plate for 30 minutes;

[0063] S2. Ar gas was introduced into the chamber (the amount of Ar gas was 55 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 2.5 mTorr. The high-power pulse power supply connected to the chromium sputtering target was turned on and the power supply frequency was set to 1000 Hz, the pulse width was 100 μs, the pulse voltage was 800 V, the power was 3.0 kW, the substrate bias was -50 V, and the deposition temperature was 80°C. A chromium transition layer with a thickness of 100 nm was deposited.

[0064] S3. Ar gas was continued to be introduced into the chamber (the amount of Ar gas was 55 sccm), and the chamber pressure was maintained at 2.5 mTorr using DC magnetron sputtering technology. The DC power supply connected to the graphite sputtering target was turned on and the power was set to 0.9 kW, the bias voltage was -50 V, and the deposition temperature was 80 ° C. A graphite-like amorphous carbon layer with a thickness of 200 nm was deposited;

[0065] S4. Place the prepared chromium / amorphous carbon coating into an atomic layer deposition chamber, and introduce argon (3s), tetramethyltin (6s), nitrogen (2s), water vapor (1s), and nitrogen (2s) in sequence. The deposition temperature is 200°C, and the deposition is repeated for 100 cycles to obtain a high-potential corrosion-resistant composite coating.

[0066] According to the test, the corrosion current density at a high potential of 1.6V is 1.3×10 -5 A / cm 2 The contact resistance of the deposited state is 3.9mΩ·cm 2 , the contact resistance after corrosion for 12 hours is 9.2mΩ·cm 2 .

[0067] Example 3

[0068] In this embodiment, the preparation method of the high-potential corrosion-resistant composite coating on the surface of the metal bipolar plate is as follows:

[0069] S1. The base material is 316L stainless steel. The stainless steel bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece holder, and evacuated to 2.5×10 -5 Torr or less, then, under the conditions of argon flow rate of 100 sccm and bias voltage of -350 V, turn on the ion source, adjust the output voltage to 1200 V, and use argon plasma to etch the surface of the stainless steel bipolar plate for 45 minutes;

[0070] S2. Ar gas was introduced into the chamber (the amount of Ar gas was 40 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 2.0 mTorr. The high-power pulse power supply connected to the chromium sputtering target was turned on and the power supply frequency was set to 750 Hz, the pulse width was 75 μs, the pulse voltage was 900 V, the power was 3.5 kW, the substrate bias was -100 V, and the deposition temperature was 75°C. A chromium transition layer with a thickness of 150 nm was deposited.

[0071] S3. Ar gas was continued to be introduced into the chamber (the amount of Ar gas was 45 sccm), and the chamber pressure was maintained at 2.0 mTorr using DC magnetron sputtering technology. The DC power supply connected to the graphite sputtering target was turned on and the power was set to 1.0 kW, the bias voltage was -100 V, and the deposition temperature was 75 ° C. A graphite-like amorphous carbon layer with a thickness of 350 nm was deposited;

[0072] S4. Place the prepared chromium / amorphous carbon coating into an atomic layer deposition chamber, and introduce argon (5s), tetramethyltin (8s), nitrogen (4s), water vapor (3s), and nitrogen (4s) in sequence. The deposition temperature is 250°C, and 200 cycles of deposition are performed to obtain a high-potential corrosion-resistant composite coating.

[0073] According to the test, the corrosion current density at a high potential of 1.6V is 1.2×10 -5 A / cm 2 The contact resistance of the deposited state is 3.8mΩ·cm 2 , the contact resistance after corrosion for 12 hours is 9.3mΩ·cm 2 .

[0074] Example 4

[0075] In this embodiment, the preparation method of the high-potential corrosion-resistant composite coating on the surface of the metal bipolar plate is as follows:

[0076] S1. The substrate is 6061 aluminum alloy. The aluminum alloy bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on a workpiece bracket, and evacuated to 2.5×10 -5 Torr or less, then, under the conditions of argon flow rate of 75 sccm and bias voltage of -300 V, turn on the ion source, adjust the output voltage to 1200 V, and use argon plasma to etch the surface of the aluminum alloy bipolar plate for 30 minutes;

[0077] S2. Ar gas was introduced into the chamber (the amount of Ar gas was 40 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 1.5 mTorr. The high-power pulse power supply connected to the aluminum sputtering target was turned on and the power supply frequency was set to 650 Hz, the pulse width was 65 μs, the pulse voltage was 850 V, the power was 3.0 kW, the substrate bias was -150 V, and the deposition temperature was 70°C. A 200 nm thick aluminum transition layer was deposited.

[0078] S3. Ar gas was continued to be introduced into the chamber (the amount of Ar gas was 35 sccm), and the chamber pressure was maintained at 2.0 mTorr using DC magnetron sputtering technology. The DC power supply connected to the graphite sputtering target was turned on and the power was set to 1.0 kW, the bias voltage was -100 V, and the deposition temperature was 80 ° C. A graphite-like amorphous carbon layer with a thickness of 450 nm was deposited;

[0079] S4. Place the prepared aluminum / amorphous carbon coating into an atomic layer deposition chamber, and introduce argon (5s), tetramethyltin (8s), nitrogen (4s), water vapor (3s), and nitrogen (4s) in sequence. The deposition temperature is 250°C, and the deposition is repeated for 200 cycles to obtain a high-potential corrosion-resistant composite coating.

[0080] According to the test, the corrosion current density at a high potential of 1.6V is 1.2×10 -5 A / cm 2 The contact resistance of the deposited state is 3.9mΩ·cm 2 , the contact resistance after corrosion for 12 hours is 9.2mΩ·cm 2 .

[0081] Example 5

[0082] In this embodiment, the preparation method of the high-potential corrosion-resistant composite coating on the surface of the metal bipolar plate is as follows:

[0083] S 1. The base material is Ti6A14V titanium alloy. The titanium alloy bipolar plate is ultrasonically cleaned, dried, placed in a vacuum chamber, fixed on the workpiece bracket, and vacuumed to 3.0×10 -5Torr or less, then, under the conditions of argon flow rate of 75 sccm and bias voltage of -400 V, the ion source was turned on, the output voltage was adjusted to 1200 V, and the surface of the titanium alloy bipolar plate was etched by argon plasma for 60 minutes;

[0084] S2. Ar gas was introduced into the chamber (the amount of Ar gas was 50 sccm) and high-power pulsed magnetron sputtering technology was used. The chamber pressure was maintained at 2.5 mTorr. The high-power pulse power supply connected to the titanium sputtering target was turned on and the power supply frequency was set to 850 Hz, the pulse width was 85 μs, the pulse voltage was 950 V, the power was 3.5 kW, the substrate bias was -150 V, and the deposition temperature was 80°C. A titanium transition layer with a thickness of 100 nm was deposited.

[0085] S3. Ar gas was continued to be introduced into the chamber (the amount of Ar gas was 55 sccm), and the chamber pressure was maintained at 2.0 mTorr using DC magnetron sputtering technology. The DC power supply connected to the graphite sputtering target was turned on and the power was set to 1.0 kW, the bias voltage was -150 V, and the deposition temperature was 70 ° C. A graphite-like amorphous carbon layer with a thickness of 250 nm was deposited;

[0086] S4. Place the prepared titanium / amorphous carbon coating into an atomic layer deposition chamber, and introduce argon (5s), tetramethyltin (8s), nitrogen (4s), water vapor (3s), and nitrogen (4s) in sequence. The deposition temperature is 250°C, and 200 cycles of deposition are performed to obtain a high-potential corrosion-resistant composite coating.

[0087] According to the test, the corrosion current density at a high potential of 1.6V is 1.2×10 -5 A / cm 2 The contact resistance of the deposited state is 3.7mΩ·cm 2 , the contact resistance after 12h corrosion is 9.1mΩ·cm 2 .

[0088] Comparative Example 1

[0089] Compared with Example 1, steps S1, S2, and S3 are exactly the same as those in Example 1, except that the SnO2 sealing layer is not deposited.

[0090] Comparative Example 2

[0091] Compared with Example 1, steps S1, S2, and S3 are exactly the same as those in Example 1, except that: in step S4, deposition is performed for 50 cycles.

[0092] Comparative Example 3

[0093] Compared with Example 1, steps S1, S2, and S3 are exactly the same as those in Example 1, except that: in step S4, deposition is performed for 400 cycles.

[0094] Comparative Example 4

[0095] Compared with Example 1, steps S1, S2, and S3 are exactly the same as those of Example 1, except that the deposition temperature in step S4 is 150° C. Due to insufficient temperature, no sealing layer is formed.

[0096] Comparative Example 5

[0097] Compared with Example 1, steps S1, S2, and S3 are exactly the same as those in Example 1, except that the deposition temperature in step S4 is 300° C. The substrate and the amorphous carbon layer are significantly thermally damaged, and the performance is degraded.

[0098] Comparative Example 6

[0099] Compared with Example 1, the difference is that no metal transition layer is deposited. Due to the relationship between bonding strength and stress, the sealing layer cannot be directly bonded to the substrate and cannot form a stable protective layer. Figure 6 As shown, the coating of Comparative Example 6 gradually peeled off from the edge.

[0100] Comparative Example 7

[0101] Compared with Example 1, the difference is that no graphite-like amorphous carbon layer is deposited. The graphite-like amorphous carbon layer is indispensable as a protective main body material, and without the graphite-like amorphous carbon layer, there is no protective effect.

[0102] Performance testing:

[0103] The corrosion resistance of the sample was measured using a three-electrode electrochemical test system. The solution was 0.5MH2SO4+5ppmHF solution and the solution temperature was 80℃. The measurement results are as follows: Figure 2 and Figure 3 shown.

[0104] from Figure 2 It can be seen that the corrosion current density of the sample in Example 1 is 1.4×10- 8 A / cm 2 The corrosion current density of the sample in comparative example 1 at a standard working voltage of 0.6 V is 1.5×10 -6 A / cm 2 The corrosion current density of the sample in comparative example 2 at a standard working voltage of 0.6V is 1.6×10 -7 A / cm 2 ;from Figure 3 It can be seen that the corrosion current density of the sample in Example 1 at a high potential of 1.6 V is 1.1×10 -5 A / cm 2 The corrosion current density of the sample in comparative example 1 at a high potential of 1.6 V is 2.9×10-3 A / cm 2 The corrosion current density of the sample in comparative example 2 at a high potential of 1.6 V is 1.7×10 -3 A / cm 2 The corrosion current density of the embodiment is significantly lower than that of the two comparative examples, indicating that the coating prepared in the embodiment of the present invention has better corrosion resistance.

[0105] Apply 1.4MPa assembly preload on the sample surface and test its contact resistance. The results are as follows: Figure 4 As shown, the contact resistance of the deposited state in Example 1 is 3.9 mΩ·cm 2 After 12 hours of corrosion at a high potential of 1.6 V, the contact resistance increased slightly to 9.1 mΩ·cm 2 The contact resistance of the deposited state in comparative example 1 is 2.6 mΩ·cm 2 After 12 hours of corrosion at a high potential of 1.6 V, the contact resistance increased to 85.9 mΩ·cm 2 The contact resistance of the deposited state in comparative example 2 is 3.5 mΩ·cm 2 After 12 hours of corrosion at a high potential of 1.6 V, the contact resistance increased to 44.2 mΩ·cm 2 The contact resistance of the deposited state in comparative example 3 is 10.3 mΩ·cm 2 After 12 hours of corrosion at a high potential of 1.6 V, the contact resistance increased to 13.9 mΩ·cm 2 The contact resistance of the high-potential corrosion-resistant composite coating in Example 1 is lower than that in Comparative Example 3, and the contact resistance after 12 hours of corrosion is lower than that in the three comparative examples, which proves that the initial conductivity of the example is good and that long-term corrosion has less impact on its performance.

[0106] The photos of the samples of Examples 1-3 and Comparative Examples 1-2 before and after corrosion are as follows: Figure 5 As shown, it can be seen that the coatings of Comparative Example 1 and Comparative Example 2 both show obvious corrosion.

[0107] The photos of the samples after corrosion of Example 1 and Comparative Example 6 are as follows: Figure 6 As shown, it can be seen that the coating of Comparative Example 6 exhibits obvious corrosion and peeling.

[0108] It can be seen from the above embodiments and comparative examples that the present invention uses a metal transition layer composite graphite-like carbon layer and a sealing layer as a bipolar plate protective coating, which has a good effect on improving the performance and service life of the battery under high operating potential. If there is no transition layer and a graphite-like carbon layer, the normal protection cannot be achieved, the sealing layer cannot be directly combined with the substrate, and a protective layer cannot be formed.

[0109] In summary, the high-potential corrosion-resistant composite coating provided by the present invention includes a SnO2 sealing layer, wherein the SnO2 sealing layer is prepared by atomic layer deposition technology. By depositing the SnO2 layer on the surface of the graphite-like amorphous carbon layer, the defects are sealed, the defect density in the graphite-like amorphous carbon layer is significantly reduced, the porosity of the coating is reduced, and the density of the coating is improved. Compared with the unsealed coating, the sealing effectively reduces the defects, thereby blocking the diffusion path of the corrosive medium into the interior. The corrosion current density of the coating at a high potential of 1.6V is reduced by 2 orders of magnitude compared with the prior art. At the same time, based on the high conductivity of the surface atomic-level SnO2 (resistivity can reach 3.9×10 -5 Ωcm) to achieve a low ICR level for the entire plate, thereby achieving long-term protection for the metal bipolar plate.

[0110] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0111] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A high potential corrosion resistant composite coating, characterized in that: It includes a metal transition layer, a graphite-like amorphous carbon layer and a SnO2 sealing layer which are sequentially formed on the surface of a metal bipolar plate serving as a substrate; wherein the SnO2 sealing layer is prepared by atomic layer deposition.

2. The high potential corrosion resistant composite coating according to claim 1, characterized in that: The metal contained in the metal transition layer includes any one of chromium, titanium, and aluminum, or a combination of two or more thereof; and / or the thickness of the metal transition layer is 100 to 200 nm; and / or the thickness of the graphite-like amorphous carbon layer is 200 to 500 nm; and / or the thickness of the SnO2 sealing layer is 10 to 50 nm; And / or, the corrosion current density of the high-potential corrosion-resistant composite coating at a potential of 1.6 V is less than 2×10 -5 A / cm 2 , the deposited contact resistance is less than 4mΩ·cm 2 , after 12 hours of corrosion, the contact resistance is less than 10mΩ·cm 2 .

3. The method for preparing the high-potential corrosion-resistant composite coating according to claim 1 or 2, characterized in that: include: providing a metal bipolar plate as a substrate; A high-power pulsed magnetron sputtering technology is used to deposit a metal transition layer on the surface of the metal bipolar plate using a metal target as a target material; Using DC magnetron sputtering technology and graphite target as target material, a graphite-like amorphous carbon layer is deposited on the surface of the metal transition layer; Furthermore, an atomic layer deposition technique is used, with organic tin as a tin source and water vapor as an oxygen source, to deposit a SnO2 sealing layer on the surface of the graphite-like amorphous carbon layer to obtain a high-potential corrosion-resistant composite coating.

4. The preparation method according to claim 3, characterized in that include: High-power pulse magnetron sputtering technology is used to place the metal bipolar plate in a reaction chamber, use a metal target as the target material, and use an inert gas as the working gas to deposit a metal transition layer on the surface of the metal bipolar plate. The high-power pulse magnetron sputtering technology uses a pulse frequency of 500-1000 Hz, a pulse width of 50-100 μs, a pulse voltage of 800-1000 V, a power of 3.0-3.5 kW, a gas pressure of 1.5-2.5 mTorr, a substrate bias voltage of -50 V to -200 V, an inert gas injection rate of 30-55 sccm, a deposition temperature of 70-80°C, and a deposition time of 5-15 min.

5. The preparation method according to claim 3, characterized in that include: A direct current magnetron sputtering technique is adopted, with a graphite target as the target material and an inert gas as the working gas, to deposit a graphite-like amorphous carbon layer on the surface of the metal transition layer; wherein, the power of the sputtering source is 0.9-1.2 kW, the gas pressure of the reaction chamber is 1.5-2.5 mTorr, the substrate bias voltage is -50 V to -200 V, the inert gas flow rate is 35-55 sccm, the deposition temperature is 70-80°C, and the deposition time is 60-120 min.

6. The preparation method according to claim 3, characterized in that include: Atomic layer deposition technology is used to sequentially introduce inert gas, reaction gas containing organic tin, dry gas, water vapor, and dry gas as one deposition cycle to deposit a SnO2 sealing layer on the surface of the graphite-like amorphous carbon layer; wherein, within one deposition cycle, the time for introducing the inert gas is 3-6s, the time for introducing the reaction gas is 6-9s, the time for introducing the dry gas is 2-5s, the time for introducing the water vapor is 1-4s, the time for introducing the dry gas is 2-5s, and the deposition temperature is 200-250°C.

7. The preparation method according to claim 6, characterized in that Performing 100-300 deposition cycles on the surface of the graphite-like amorphous carbon layer to form the SnO2 sealing layer; And / or, the organic tin comprises any one of tetramethyltin and tetrakis(dimethylamino)tin, or a combination of two or more thereof.

8. The preparation method according to claim 3, characterized in that Also includes: Before forming the metal transition layer, the surface of the metal bipolar plate is first etched; The etching process includes: using Ar ion etching method to etch the metal bipolar plate for 30 to 60 minutes at room temperature; the process conditions used in the etching process include: the reaction chamber pressure is 3.0×10 -5 Torr or less, the argon flow rate is 50 to 100 sccm, the bias voltage is -200 to -500 V, and the Ar ion etching method includes glow etching and / or ion beam etching; And / or, the metal bipolar plate includes any one of a stainless steel bipolar plate, a titanium alloy bipolar plate, and an aluminum alloy bipolar plate.

9. Use of the high-potential corrosion-resistant composite coating according to claim 1 or 2 in the field of substrate surface protection, preferably, the application includes use in proton exchange membrane fuel cells.

10. A bipolar plate for a proton exchange membrane fuel cell, comprising a metal bipolar plate and a protective coating disposed on a surface of the metal bipolar plate, characterized in that: The protective coating is the high-potential corrosion-resistant composite coating according to claim 1 or 2.

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