Conductive corrosion-resistant alloy film for titanium bipolar plate and preparation method thereof

Abstract

The present invention relates to the field of functional film technology, and specifically to a conductive corrosion-resistant alloy film for titanium bipolar plates and a preparation method thereof. The film comprises, from bottom to top, a titanium metal substrate, a metal Ti ion implantation layer, a Ti self-healing layer, and a TiNb alloy functional layer. The TiNb alloy functional layer comprises 20 to 45% Ti and 55 to 80% Nb in atomic percentage, and the TiNb alloy functional layer comprises a cubic β-Ti (Nb) solid solution structure. The conductive corrosion-resistant alloy film of the present invention can spontaneously form a dense conductive corrosion-resistant oxide film with high-potential corrosion resistance. At the same time, during long-term service, the film forms local passivation-filled micropores and heals, thereby delaying the penetration of corrosive media, achieving lower contact resistance and corrosion current density without the need to add precious metals, thereby effectively improving the conductivity, corrosion resistance, and durability of the titanium bipolar plate.

Description

Technical Field

[0001] The present invention relates to the technical field of functional films, and in particular to a conductive corrosion-resistant alloy film for titanium metal bipolar plates and a preparation method thereof. Background Art

[0002] As the clean energy with the greatest potential for development in the 21st century, hydrogen energy is an important secondary energy carrier due to its wide availability, green, zero-carbon, high calorific value, and ease of storage and transportation. Proton exchange membrane fuel cells (PEMFCs) and proton exchange membrane water electrolyzers (PEMWEs) are two important pathways for hydrogen energy utilization. Bipolar plates, as key components of PEMFCs and PEMWEs, play a crucial role. Metal bipolar plates offer high mechanical strength, excellent electrical conductivity, impact resistance, low gas permeability, and low cost, making them an ideal alternative to graphite bipolar plates. At present, commonly used metal bipolar plates include titanium (alloy), aluminum alloy and stainless steel. Among them, titanium and titanium alloy have the best corrosion resistance, high electrical conductivity and mechanical strength compared with other metals. Considering the harsh corrosion environment in the fuel cell stack, especially in PEMWE, the metal bipolar plates are in a highly corrosive environment with strong acidity (PH≈2-3), strong oxidizing properties, high potential (2V), humidity and high temperature (60-80℃). Other metals are easily corroded and dissolved, so titanium bipolar plates are a more ideal choice.

[0003] Although titanium metal has excellent corrosion resistance, when it is immersed in acidic, humid and high temperature environment for a long time, an insulating TiO2 passivation film will form on its surface. This passivation film will increase the contact resistance between the titanium metal bipolar plate and the gas diffusion layer, thereby reducing the conductivity. In addition, the perfluorosulfonic acid proton exchange membrane will decay during use, releasing F - and SO4 2- Plasma, where F - Titanium is highly corrosive, and the passivation film will be destroyed and then corroded. The cations generated after corrosion may also poison the proton exchange membrane, forming a vicious cycle. Therefore, the surface protection problem of titanium bipolar plates needs to be solved urgently. The current method is mainly to deposit precious metal films and carbon-based films on titanium substrates. Although precious metal films such as Pt, Au and Ag have excellent electrical conductivity and corrosion resistance, the cost is too high, which limits their large-scale commercial application; metal nitride films generally have columnar crystal growth defects. The corrosive medium can easily reach the substrate through the gaps or pinholes in the columnar crystals and corrode, making it difficult to achieve long-term protection effects; carbon-based films do have excellent electrical conductivity and corrosion resistance, but there is a risk of conversion to CO2 at high potentials, leading to pollution and accelerated corrosion.

[0004] In view of the above-mentioned defects, the inventors of the present invention finally obtained the present invention after a long period of research and practice. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem of how to simultaneously improve the electrical conductivity and high-potential corrosion resistance of titanium alloy bipolar plates, and provide a conductive corrosion-resistant alloy film for titanium metal bipolar plates and a preparation method thereof.

[0006] To achieve the above objectives, the present invention discloses a conductive corrosion-resistant alloy film for titanium bipolar plates, which comprises, from bottom to top, a titanium metal substrate, a metal Ti ion implantation layer, a Ti self-healing layer, and a TiNb alloy functional layer. The TiNb alloy functional layer comprises, by atomic percentage, 20-45% Ti and 55-80% Nb, and the TiNb alloy functional layer comprises a cubic β-Ti(Nb) solid solution structure.

[0007] The thickness of the Ti self-healing layer is 0.1 to 0.3 μm, and the thickness of the TiNb alloy functional layer is 1 to 3 μm.

[0008] The metal matrix is ​​any one of industrial pure titanium, titanium alloy and titanium-based metal.

[0009] The present invention also discloses a method for preparing the conductive corrosion-resistant alloy film for the titanium metal bipolar plate, comprising the following steps:

[0010] S1, substrate pretreatment: the titanium metal substrate is degreased, degreased, and ultrasonically cleaned, then immersed in a passivation film removal solution, and finally dehydrated and dried;

[0011] S2, plasma etching: Place the titanium metal substrate to be plated in a vacuum coating machine and evacuate until the background vacuum is lower than 3×10 -3 Pa, introduce argon gas with a flow rate of 300-500 sccm and a pressure of 2-4 Pa, turn on the substrate bias power supply, and set the substrate negative bias voltage to 600-1000 V to generate glow plasma, and perform high bias glow etching cleaning for 20-30 minutes to remove contaminants and passivation film on the titanium alloy surface to obtain a clean surface;

[0012] S3, preparation of metal ion implantation layer: after the plasma etching in step S2 is completed, the Ti cathode arc target is turned on, and the substrate negative bias voltage is set to 600-1000V. The substrate negative bias voltage is increased in an incremental mode for 20-40 minutes to complete the preparation of the Ti ion implantation layer on the surface of the titanium metal substrate;

[0013] S4, self-healing layer deposition: After the metal ion implantation layer is prepared in step S3, the Ti cathode arc target is turned off, the Ti sputtering target is turned on, the substrate negative bias voltage is 50-300V, and a pure Ti self-healing layer is deposited for 20-40 minutes;

[0014] S5, alloy functional layer deposition: after the Ti self-healing layer deposition in step S4 is completed, the Ti sputtering target and the Nb sputtering target are turned on simultaneously, the gas pressure and the substrate negative bias voltage are kept unchanged, and the TiNb alloy functional layer is deposited for 60 to 300 minutes.

[0015] In the step S1, ultrasonic cleaning includes ultrasonic cleaning with pure water or hydrocarbon solvent, and immersing the passivation film solution is pickling in nitric acid or oxalic acid solution.

[0016] In step S2, the vacuum is pumped until the background vacuum is lower than 3×10 -3 Pa, the flow rate of argon gas is 300-500 sccm, the gas pressure is 2-4 Pa, the negative bias voltage of the substrate is 600-1000 V, and the glow etching cleaning is carried out for 30 minutes under a high bias voltage of 1000 V.

[0017] In step S3, when preparing the metal ion implantation layer, the argon gas flow rate is 100-300 sccm, the gas pressure is 0.2-0.8 Pa, the Ti cathode arc target current is 60-100 A, and the substrate negative bias voltage is increased from 600 V to 1000 V in an incremental mode, increasing by 100 V every 5 minutes, and continuing for 20 minutes under the negative bias voltage of 1000 V.

[0018] In step S4, the Ti sputtering target power is 400-600 W, the gas pressure is 0.2-0.8 Pa, the deposition temperature is 80-250° C., the substrate negative bias voltage is 50-300 V, and the deposition time is 20-40 min.

[0019] In step S5, the power of the Ti sputtering target is 400-800W, and the power of the Nb sputtering target is 400-800W.

[0020] The performance degradation of thin-film modified metal bipolar plates directly affects the durability of the battery stack. The core key technology is to balance the corrosion resistance and electrical conductivity of the metal material. This invention enhances the interfacial bonding between the titanium substrate and the modified thin film by introducing a metallic Ti ion implantation layer. Furthermore, a Ti self-healing layer with strong interfacial fusion properties is designed to further enhance the film's bonding strength. Furthermore, Ti readily forms a passivation film, which can form a self-healing oxide layer in the event of localized corrosive medium infiltration, sealing the pores and slowing down the occurrence of material corrosion. A TiNb alloy functional layer is designed on the top surface, which not only has good electrical conductivity, but also, due to the formation of an oxide film on the surface of the alloy film, a dense, corrosion-resistant oxide film layer improves the corrosion resistance of the entire alloy system, maintaining excellent durability in long-term corrosive environments. Furthermore, the film exhibits good hydrophobic properties.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] 1. The TiNb conductive corrosion-resistant alloy film prepared by the present invention is easy to form a conductive corrosion-resistant oxide film in an acidic environment. The spontaneously formed Nb2O5 has good conductivity and induces the Ti in the TiO2 film lattice to 4+ Convert to Ti 3+ , electrons can be 4+ and Ti 3+ Jumping back and forth between the two, thereby improving the conductivity of the oxide film;

[0023] 2. The present invention adopts a multi-layer structure design of metal ion implantation layer / metal self-healing layer / conductive corrosion-resistant functional layer, which not only improves the bonding strength of the modified film on the surface of the titanium metal substrate, but also enhances the high-potential corrosion resistance in the acidic corrosion environment of the proton exchange membrane. The film does not peel off at a high operating voltage of 2.0V, ensuring the conductive corrosion resistance and durability of the metal bipolar plate.

[0024] 3. The present invention uses alloy films prepared from non-precious metal elements to achieve performance indicators such as low contact resistance, low corrosion current density and high water contact angle, greatly reducing the production cost of metal bipolar plates. At the same time, physical vapor deposition technology has the advantages of no gas pollution, environmental friendliness, high density, high film forming efficiency and low film forming temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the conductive corrosion-resistant alloy film structure of the present invention;

[0026] Figure 2 XRD patterns of the conductive corrosion-resistant alloy films in Examples 1-3;

[0027] Figure 3 The contact resistance test results of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Example 1 are shown;

[0028] Figure 4 The water contact angle test results of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Example 1;

[0029] Figure 5 The potentiodynamic polarization curve test results of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Examples 1-2 are shown;

[0030] Figure 6 The constant potential polarization curve test results of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Examples 1-2 are shown;

[0031] Figure 7 The electrochemical impedance spectroscopy test results of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Examples 1-2 are shown;

[0032] Figure 8This is the XPS spectrum of the conductive corrosion-resistant alloy film after corrosion in Example 1.

[0033] The numbers in the figure represent:

[0034] 1-Titanium metal substrate; 2-Metal ion implantation layer; 3-Ti self-healing layer; 4-TiNb alloy functional layer. DETAILED DESCRIPTION

[0035] The above and other technical features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

[0036] Figure 1 Schematic diagram of the method for preparing the conductive corrosion-resistant alloy film in Examples 1-3: 1-Titanium substrate; 2-Metal ion implantation layer; 3-Ti self-healing layer; 4-TiNb alloy functional layer. The titanium bipolar plate material used in the specific embodiment is TC4 titanium alloy.

[0037] Example 1

[0038] A conductive corrosion-resistant alloy film for titanium bipolar plates and a preparation method thereof. The film comprises, from bottom to top, a titanium metal substrate, a metal Ti ion implantation layer, a Ti self-healing layer, and a TiNb alloy functional layer. The specific preparation method is as follows:

[0039] S1, substrate pretreatment: the titanium metal substrate is first degreased and then ultrasonically cleaned in a hydrocarbon solvent and pure water for 10 minutes respectively, then immersed in an oxalic acid solution, heated to 70-80°C, and finally dehydrated and dried;

[0040] S2, plasma etching: Place the titanium metal substrate to be plated in a vacuum coating machine and evacuate until the background vacuum is lower than 3×10 -3 Pa, introduce argon gas at 500 sccm, turn on the substrate bias power supply to generate glow plasma, and perform high bias 1000V glow etching cleaning for 30 minutes to effectively remove contaminants and passivation film on the titanium alloy surface and obtain a clean surface;

[0041] S3, preparation of metal ion implantation layer: after the plasma etching in step S2 is completed, the Ar gas flow rate is adjusted to 120 sccm, the Ti cathode arc target is turned on, the Ti target arc current is set to 80 A, and the substrate negative bias voltage is increased from 600 V to 1000 V in an incremental mode, increasing by 100 V every 5 minutes, and continuing at the negative bias voltage of 1000 V for 20 minutes to complete the preparation of the Ti ion implantation layer on the surface of the titanium metal substrate;

[0042] S4, self-healing layer deposition: After the metal ion implantation layer is prepared in step S3, the Ti cathode arc target is turned off and the Ti sputtering target is turned on. The Ti target power is 600W and the substrate negative bias voltage is 150V. A pure Ti self-healing layer is deposited for 30 minutes.

[0043] S5, alloy functional layer deposition: After the Ti self-healing layer deposition in step S4 is completed, the Ti sputtering target and the Nb sputtering target are turned on at the same time. The power of the Ti target and the Nb target are 600W and 400W respectively. The gas pressure is kept at 0.6Pa and the substrate negative bias voltage is kept at 150V. The TiNb alloy functional layer is deposited for 160 minutes.

[0044] The total thickness of the conductive corrosion-resistant alloy film obtained in this embodiment is 1.8 μm. The TiNb alloy functional layer contains 44 at.% Ti and 56 at.% Nb. The corrosion current density of the prepared conductive corrosion-resistant alloy film is 0.012 μA / cm 2 , contact resistance is 20.53mΩ·cm 2 The water contact angle is 103.4°, and the corrosion current density is 0.6μA / cm at a high potential of 2.0V. 2 About, maintain excellent durability.

[0045] Example 2

[0046] A conductive corrosion-resistant alloy film for titanium bipolar plates and a preparation method thereof. The film comprises, from bottom to top, a titanium metal substrate, a metal Ti ion implantation layer, a Ti self-healing layer, and a TiNb alloy functional layer. The specific preparation method is as follows:

[0047] S1, substrate pretreatment: the titanium metal substrate is first degreased and then ultrasonically cleaned in a hydrocarbon solvent and pure water for 10 minutes respectively, then immersed in an oxalic acid solution, heated to 70-80°C, and finally dehydrated and dried;

[0048] S2, plasma etching: Place the titanium metal substrate to be plated in a vacuum coating machine and evacuate until the background vacuum is lower than 3×10 -3 Pa, introduce argon gas at 500 sccm, turn on the substrate bias power supply to generate glow plasma, and perform high bias 1000V glow etching cleaning for 30 minutes to effectively remove contaminants and passivation film on the titanium alloy surface and obtain a clean surface;

[0049] S3, preparation of metal ion implantation layer: after the plasma etching in step S2 is completed, the Ar gas flow rate is adjusted to 120 sccm, the Ti cathode arc target is turned on, the Ti target arc current is set to 80 A, and the substrate negative bias voltage is increased from 600 V to 1000 V in an incremental mode, increasing by 100 V every 5 minutes, and continuing at the negative bias voltage of 1000 V for 20 minutes to complete the preparation of the Ti ion implantation layer on the surface of the titanium metal substrate;

[0050] S4, self-healing layer deposition: After the metal ion implantation layer is prepared in step S3, the Ti cathode arc target is turned off and the Ti sputtering target is turned on. The Ti target power is 600W and the substrate negative bias voltage is 150V. A pure Ti self-healing layer is deposited for 30 minutes.

[0051] S5, alloy functional layer deposition: After the Ti self-healing layer deposition in step S4 is completed, the Ti sputtering target and the Nb sputtering target are turned on at the same time. The power of the Ti target and the Nb target are 600W and 600W respectively. The gas pressure is kept at 0.6Pa and the substrate negative bias voltage is kept at 150V. The TiNb alloy functional layer is deposited for 135 minutes.

[0052] The total thickness of the conductive corrosion-resistant alloy film obtained in this embodiment is 1.79 μm. The TiNb alloy functional layer contains 33 at.% Ti and 67 at.% Nb. The corrosion current density of the prepared conductive corrosion-resistant alloy film is 0.047 μA / cm 2 , contact resistance is 17.03mΩ·cm 2 The water contact angle is 102.6°, and the corrosion current density is 0.3μA / cm at a high potential of 2.0V. 2 About, maintain excellent durability.

[0053] Example 3

[0054] A conductive corrosion-resistant alloy film for titanium bipolar plates and a preparation method thereof. The film comprises, from bottom to top, a titanium metal substrate, a metal Ti ion implantation layer, a Ti self-healing layer, and a TiNb alloy functional layer. The specific preparation method is as follows:

[0055] S1, substrate pretreatment: the titanium metal substrate is first degreased and then ultrasonically cleaned in a hydrocarbon solvent and pure water for 10 minutes respectively, then immersed in an oxalic acid solution, heated to 70-80°C, and finally dehydrated and dried;

[0056] S2, plasma etching: Place the titanium metal substrate to be plated in a vacuum coating machine and evacuate until the background vacuum is lower than 3×10 -3Pa, introduce argon gas at 500 sccm, turn on the substrate bias power supply to generate glow plasma, and perform high bias 1000V glow etching cleaning for 30 minutes to effectively remove contaminants and passivation film on the titanium alloy surface and obtain a clean surface;

[0057] S3, preparation of metal ion implantation layer: after the plasma etching in step S2 is completed, the Ar gas flow rate is adjusted to 120 sccm, the Ti cathode arc target is turned on, the Ti target arc current is set to 80 A, and the substrate negative bias voltage is increased from 600 V to 1000 V in an incremental mode, increasing by 100 V every 5 minutes, and continuing at the negative bias voltage of 1000 V for 20 minutes to complete the preparation of the Ti ion implantation layer on the surface of the titanium metal substrate;

[0058] S4, self-healing layer deposition: After the metal ion implantation layer is prepared in step S3, the Ti cathode arc target is turned off and the Ti sputtering target is turned on. The Ti target power is 600W and the substrate negative bias voltage is 150V. A pure Ti self-healing layer is deposited for 30 minutes.

[0059] S5, alloy functional layer deposition: After the Ti self-healing layer deposition in step S4 is completed, the Ti sputtering target and the Nb sputtering target are turned on at the same time. The power of the Ti target and the Nb target are 600W and 800W respectively. The gas pressure is kept at 0.6Pa and the substrate negative bias voltage is kept at 150V. The TiNb alloy functional layer is deposited for 115 minutes.

[0060] The total thickness of the conductive corrosion-resistant alloy film obtained in this embodiment is 1.81 μm. The TiNb alloy functional layer contains 28 at.% Ti and 72 at.% Nb. The corrosion current density of the prepared conductive corrosion-resistant alloy film is 0.105 μA / cm 2 , contact resistance is 11.93mΩ·cm 2 The water contact angle is 105.8°, and the corrosion current density is 0.4μA / cm at a high potential of 2.0V. 2 About, maintain excellent durability.

[0061] Figure 2 The XRD patterns of the conductive corrosion-resistant alloy films in Examples 1-3 (in order to avoid the influence of Ti in the TC4 matrix on the diffraction peak, the sample substrate used was Si wafer). All TiNb alloy films showed the formation of a stable β-Ti(Nb) solid solution structure.

[0062] Comparative Example 1

[0063] This embodiment serves as a comparative example of Example 1, and no TiNb alloy functional layer is deposited on the TC4 titanium alloy substrate.

[0064] Comparative Example 2

[0065] This embodiment is a comparative example of embodiments 1-3. The film does not contain Nb element, and its preparation method includes the following steps:

[0066] S1, substrate pretreatment: the titanium metal substrate is first degreased and then ultrasonically cleaned in a hydrocarbon solvent and pure water for 10 minutes respectively, then immersed in an oxalic acid solution, heated to 70-80°C, and finally dehydrated and dried;

[0067] S2, plasma etching: Place the titanium metal substrate to be plated in a vacuum coating machine and evacuate until the background vacuum is lower than 3×10 -3 Pa, introduce argon gas at 500 sccm, turn on the substrate bias power supply to generate glow plasma, and perform high bias 1000V glow etching cleaning for 30 minutes to effectively remove contaminants and passivation film on the titanium alloy surface and obtain a clean surface;

[0068] S3, preparation of metal ion implantation layer: after the plasma etching in step S2 is completed, the Ar gas flow rate is adjusted to 120 sccm, the Ti cathode arc target is turned on, the Ti target arc current is set to 80 A, and the substrate negative bias voltage is increased from 600 V to 1000 V in an incremental mode, increasing by 100 V every 5 minutes, and continuing at the negative bias voltage of 1000 V for 20 minutes to complete the preparation of the Ti ion implantation layer on the surface of the titanium metal substrate;

[0069] S4, self-healing layer deposition: After the metal ion implantation layer is prepared in step S3, the Ti cathode arc target is turned off, and the Ti sputtering target is turned on. The Ti target power is 600W, the substrate negative bias voltage is 150V, and a pure Ti self-healing layer is deposited for 30 seconds.

[0070] min;

[0071] S5, alloy functional layer deposition: After the Ti self-healing layer deposition in step S4 is completed, the Ti sputtering target is turned on, the Ti target power is 600W, the gas pressure is kept at 0.6Pa and the substrate negative bias voltage is kept at 150V, and the Ti surface functional layer is deposited for 340min.

[0072] The total thickness of the metal film obtained in this comparative example is 1.68 μm, the surface functional layer contains 100 at.% Ti, the film is composed of α-Ti structure, and the corrosion current density of the prepared film is 107 μA / cm 2 .

[0073] Comparative Example 3

[0074] This embodiment is a comparative example of embodiments 1-3. The film contains N element, and its preparation method includes the following steps:

[0075] S1, substrate pretreatment: the titanium metal substrate is first degreased and then ultrasonically cleaned in a hydrocarbon solvent and pure water for 10 minutes respectively, then immersed in an oxalic acid solution, heated to 70-80°C, and finally dehydrated and dried;

[0076] S2, plasma etching: Place the titanium metal substrate to be plated in a vacuum coating machine and evacuate until the background vacuum is lower than 3×10 -3 Pa, introduce argon gas at 500 sccm, turn on the substrate bias power supply to generate glow plasma, and perform high bias 1000V glow etching cleaning for 30 minutes to effectively remove contaminants and passivation film on the titanium alloy surface and obtain a clean surface;

[0077] S3, preparation of metal ion implantation layer: after the plasma etching in step S2 is completed, the Ar gas flow rate is adjusted to 120 sccm, the Ti cathode arc target is turned on, the Ti target arc current is set to 80 A, and the substrate negative bias voltage is increased from 600 V to 1000 V in an incremental mode, increasing by 100 V every 5 minutes, and continuing at the negative bias voltage of 1000 V for 20 minutes to complete the preparation of the Ti ion implantation layer on the surface of the titanium metal substrate;

[0078] S4, self-healing layer deposition: After the metal ion implantation layer is prepared in step S3, the Ti cathode arc target is turned off and the Ti sputtering target is turned on. The Ti target power is 600W and the substrate negative bias voltage is 150V. A pure Ti self-healing layer is deposited for 30 minutes.

[0079] S5, alloy functional layer deposition: After the Ti self-healing layer deposition in step S4 is completed, the Ti sputtering target and the Nb sputtering target are turned on at the same time. The power of the Ti target and the Nb target are 600W and 800W respectively, and argon and nitrogen are introduced. The gas pressure is maintained at 0.6Pa and the substrate negative bias voltage is maintained at 150V. The TiNbN alloy functional layer is deposited for 150 minutes.

[0080] The total thickness of the metal film obtained in this comparative example is 1.8 μm, the surface functional layer contains 14 at.% Ti, 36 at.% Nb, and 50 at.% N, and the film is composed of a face-centered cubic TiNbN structure. The corrosion current density of the prepared film is 0.32 μA / cm 2 , but the film has completely failed at a high potential of 2.0V.

[0081] Figure 3 These are the contact resistance test results of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Example 1. As the pressure continues to increase, the contact resistance value gradually decreases to a stable level. The contact resistance values ​​of all TiNb alloy films are smaller than that of the TC4 substrate, indicating that the conductive properties of the titanium alloy are improved.

[0082] Figure 4Graphs showing the water contact angle test results of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Example 1 show that the water contact angles of all TiNb alloy films are greater than 100°, indicating good hydrophobicity.

[0083] Figure 5 The results of the potentiodynamic polarization curve tests of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Examples 1-2 show that the corrosion current density of all TiNb alloy films is much smaller than that of the TC4 substrate and pure Ti film, and the self-corrosion potential of all TiNb alloy films is greater than that of the TC4 substrate and pure Ti film, indicating that all TiNb alloy films have better corrosion resistance and chemical stability than the TC4 substrate and pure Ti film. Among them, Example 1 has the lowest corrosion current density of 0.012 μA / cm 2 .

[0084] Figure 6 The results of the constant potential polarization curves of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Examples 1-2 at low potentials of 0.6V and high potentials of 2.0V are shown. As time goes by, the corrosion current gradually decreases until it stabilizes, indicating that a dense and stable passivation film has formed on the film surface. It can be seen that the film still has a low corrosion current density of less than 1μA / cm at a high potential of 2.0V. 2 , indicating that all TiNb alloy films have excellent durability in strong acidic corrosive solutions.

[0085] Figure 7 The electrochemical impedance spectroscopy test results of the conductive corrosion-resistant alloy films in Examples 1-3 and Comparative Examples 1-2 show that all TiNb alloy films have large and incomplete capacitance arcs, obvious capacitance responses, and the semicircular diameters of the capacitance arcs are larger than those of the TC4 substrate and pure Ti film. Among them, the semicircular diameter of Example 1 is the largest, indicating that Example 1 has the highest charge transfer resistance and the best corrosion resistance.

[0086] Figure 8 The XPS spectrum of the conductive corrosion-resistant alloy film after corrosion in Example 1, Ti 4+ (TiO2) peak and Nb 5+ The (Nb2O5) peak is the highest, indicating that the surface of the corroded sample is mainly composed of a large amount of Nb2O5 and TiO2 oxide films, and these two oxide films are dense, with high stability and excellent corrosion resistance.

[0087] The above description is merely a preferred embodiment of the present invention and is intended to be illustrative rather than restrictive of the present invention. Those skilled in the art will appreciate that many changes, modifications, and even equivalents may be made to the present invention within the spirit and scope of the claims, all of which fall within the scope of protection of the present invention.

Claims

1. A method for preparing a conductive corrosion-resistant alloy film for titanium bipolar plates, characterized in that: The following steps are involved: S1, substrate pretreatment: the titanium metal substrate is degreased, degreased, and ultrasonically cleaned, then immersed in a passivation film removal solution, and finally dehydrated and dried; S2, plasma etching: Place the titanium metal substrate to be plated in a vacuum coating machine, evacuate the vacuum, introduce argon gas, turn on the substrate bias power supply, generate glow plasma, and perform high-bias glow etching cleaning to remove contaminants and passivation film on the titanium alloy surface to obtain a clean surface; S3, preparation of metal ion implantation layer: after the plasma etching in step S2 is completed, the Ti cathode arc target is turned on to complete the preparation of the Ti ion implantation layer on the surface of the titanium metal substrate; S4, self-healing layer deposition: after the metal ion implantation layer is prepared in step S3, the Ti cathode arc target is turned off, and the Ti sputtering target is turned on to deposit a pure Ti self-healing layer; S5, alloy functional layer deposition: after the Ti self-healing layer deposition in step S4 is completed, the Ti sputtering target and the Nb sputtering target are turned on simultaneously, the gas pressure and the substrate negative bias voltage are kept constant, and the TiNb alloy functional layer is deposited for 60 to 300 minutes; In step S3, when preparing the metal ion implantation layer, the argon gas flow rate is 100-300 sccm, the gas pressure is 0.2-0.8 Pa, the Ti cathode arc target current is 60-100 A, and the substrate negative bias voltage is increased from 600 V to 1000 V in an incremental mode, increasing by 100 V every 5 minutes, and continuing at the negative bias voltage of 1000 V for 20 minutes; In step S4, the Ti sputtering target power is 400-600 W, the gas pressure is 0.2-0.8 Pa, the deposition temperature is 80-250° C., the substrate negative bias voltage is 50-300 V, and the deposition time is 20-40 min; In step S5, the Ti sputtering target power is 400-800 W, and the Nb sputtering target power is 400-800 W.

2. The method for preparing a conductive corrosion-resistant alloy film for a titanium bipolar plate according to claim 1, wherein: In the step S1, ultrasonic cleaning includes ultrasonic cleaning with pure water or hydrocarbon solvent, and immersing the passivation film solution is pickling in nitric acid or oxalic acid solution.

3. The method for preparing a conductive corrosion-resistant alloy film for a titanium bipolar plate according to claim 1, wherein: In step S2, the vacuum is pumped until the background vacuum is lower than 3×10 -3 Pa, the flow rate of argon gas is 300~500 sccm, the gas pressure is 2~4 Pa, the substrate negative bias voltage is 600~1000 V, and glow etching cleaning is performed at a high bias voltage of 1000 V for 30 min.

4. A conductive corrosion-resistant alloy film for titanium bipolar plates prepared by the preparation method according to any one of claims 1 to 3, characterized in that: From bottom to top, it includes a titanium metal substrate, a metal Ti ion implantation layer, a Ti self-healing layer and a TiNb alloy functional layer. The TiNb alloy functional layer includes 20-45% Ti and 55-80% Nb in atomic percentage. The TiNb alloy functional layer includes a cubic β-Ti(Nb) solid solution structure.

5. The conductive corrosion-resistant alloy film for titanium bipolar plates according to claim 4, characterized in that: The thickness of the Ti self-healing layer is 0.1-0.3 μm, and the thickness of the TiNb alloy functional layer is 1-3 μm.

6. The conductive corrosion-resistant alloy film for titanium bipolar plates according to claim 4, characterized in that: The metal matrix is ​​industrial pure titanium or titanium alloy.

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