Method for preparing Ni-Cr-GO composite coating from bimetallic ionic liquid

Abstract

According to the method for preparing the Ni-Cr-GO composite coating through the bimetallic ionic liquid, the bimetallic ionic liquid comprises imidazole fluorocarboxylate, nickel salt and chromium salt, the bimetallic ionic liquid serves as a nickel-chromium source during electroplating, the potential difference between nickel and chromium can be remarkably reduced, and uniform co-deposition of nickel and chromium on the surface of a cathode is facilitated; the bimetallic ionic liquid further comprises graphene oxide which can be co-deposited with nickel and chromium to form a Ni-Cr-GO composite coating, the preparation method of the composite coating is easy to operate, low in cost and good in application prospect, the obtained composite coating is compact in crystallization, uniform in thickness and free of impurities such as pores and bubbles, the bonding strength of the coating and a base body is good, and the service life of the coating is prolonged. And certain corrosion resistance and high temperature resistance are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of electroplating, and in particular to a method for preparing a Ni-Cr-GO composite coating using a bimetallic ion liquid. Background Art

[0002] Ni-Cr composite coating is a corrosion-resistant material with great application prospects in industrial and people's livelihood fields due to its many excellent properties such as wear resistance, high resistance, and high hardness.

[0003] Currently, Ni-Cr and Ni-Cr-GO composite coatings are mainly obtained by electroplating in aqueous solution systems or ionic liquids. Among them, when electroplating is carried out in aqueous solution systems, the electroplating solution produced will pollute the environment, the deposition rate is slow, and the current efficiency is low. When electroplating is carried out in ionic liquids, ionic liquids, as a new type of green solution system, have the advantages of a wide electrochemical window, good conductivity, environmental friendliness, simple electroplating process, and little interference from hydrogen evolution. Good quality metals can be electrodeposited at room temperature with high current efficiency. In addition, due to the simple preparation process of ionic liquids and the low price of raw materials, the use of ionic liquids to prepare electrodeposited alloys has broad prospects.

[0004] In recent years, relevant research on the electrodeposition of metallic nickel and high-value-added nickel alloys such as Ni-Cr in ionic liquids has shown that when graphene or graphene oxide GO is used as the reinforcing phase material of nickel-based composite coatings, Ni-based graphene composite coatings may exhibit better flexibility and corrosion resistance; however, simply adding graphene oxide to ionic liquids does not produce composite materials with excellent performance. How to successfully prepare high-quality, high-performance Ni-Cr-GO composite coatings in ionic liquids is currently an urgent problem that needs to be solved. Summary of the Invention

[0005] In order to solve the technical problems existing in the background technology, the present invention proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid, comprising the following steps:

[0006] S1. Mix imidazolium fluorocarboxylate and acetone, add nickel salt and K3[Cr(C2O4)3] in sequence to obtain a bimetallic ionic liquid, and then mix the bimetallic ionic liquid with graphene oxide to obtain an acidic electroplating solution.

[0007] The following steps are also included:

[0008] S2. Placing the graphite sheet and the pretreated copper sheet in the acidic electroplating solution in step S1 to obtain a Ni-Cr-GO composite coating after electroplating.

[0009] In the present invention, imidazole fluorocarboxylate can react with nickel salt and K3[Cr(C2O4)3] to obtain [NiCr(C2O4)3] nickel-chromium bimetallic coordination anion, which can significantly reduce the potential difference between nickel and chromium and promote the occurrence of co-deposition reaction; the cations in the bimetallic ionic liquid can also complex with water to avoid hydrogen evolution; the anions can complex with graphene oxide to prevent the dendritic growth of graphene oxide during electroplating, thereby obtaining a smooth and uniform composite coating.

[0010] In step S1, the imidazole fluorocarboxylate is one of 1-ethyl-3-methylimidazolium trifluoroacetate ([Emim][TFA]), 1-butyl-3-methylimidazolium trifluoroacetate ([Bmim][TFA]) or 1-methylimidazolium trifluoromethanesulfonate ([1-Mim]OTF).

[0011] In step S1, the molar ratio of the imidazole fluorocarboxylate to acetone is 1:120-200;

[0012] Preferably, the molar ratio of the imidazolium fluorocarboxylate to acetone is 1:150.

[0013] In step S1, the nickel salt is one of NiCl2, NiSO4 or Ni(NO3)2.

[0014] In step S1, the molar ratio of the imidazole fluorocarboxylate, nickel salt, and K3[Cr(C2O4)3] is 1.3-1.8:1:1.

[0015] In step S1, the concentration of graphene oxide in the electroplating solution is 0.05-0.25 g / L;

[0016] Preferably, the concentration of graphene oxide is 0.15 g / L.

[0017] In the present invention, an appropriate amount of graphene oxide can simultaneously increase the deposition rate and hardness of the coating. When the amount of graphene oxide added is too high, the deposition rate decreases relatively.

[0018] In step S2, the electroplating adopts constant current electrodeposition;

[0019] Preferably, the electroplating temperature is 50-70°C;

[0020] Preferably, the current density is 10-30A / dm 2 ;

[0021] Preferably, the electroplating time is 40-100 minutes.

[0022] In the present invention, since the anions in the bimetallic ions, such as trifluoroacetate ions, can complex with graphene oxide, the dendritic growth of graphene oxide is prevented during electroplating, thereby obtaining a smooth and uniform composite coating.

[0023] In step S2, mechanical stirring is also required during the electroplating;

[0024] Preferably, the speed of the mechanical stirring is 250 r / min.

[0025] In the present invention, the solid particles in the electroplating solution can move to the cathode surface under the action of mechanical stirring, thereby promoting the formation of the composite coating.

[0026] Step S1 and step S2 are performed under anhydrous conditions;

[0027] Preferably, steps S1 and S2 are performed under an inert dry atmosphere or vacuum conditions.

[0028] In the present invention, the cations of the biionic metal liquid can complex with water to avoid hydrogen evolution. When operated in an atmospheric environment, steps S1 and S2 can also meet the requirements of anhydrous conditions. Maintaining anhydrous conditions during the operation (the raw materials are anhydrous nickel salt and K3[Cr(C2O4)3]) can further avoid hydrogen evolution. Preferably, when operating in an inert dry atmosphere or vacuum, the side reaction between the electrode and oxygen can be reduced, the current efficiency can be improved, and the obtained nickel plating layer can be brighter and denser.

[0029] Beneficial effects of the present invention:

[0030] (1) Ni-Cr-GO composite coatings were prepared by electroplating using ionic liquid. The coatings had uniform thickness and were tightly bonded to the substrate, exhibiting certain corrosion and high temperature resistance.

[0031] (2) The cations in the bimetallic ionic liquid can complex with water, making it difficult for hydrogen evolution to occur under electroplating conditions, thus ensuring that the coating has a certain hardness;

[0032] (3) The nickel-chromium bimetallic coordination anion [NiCr(C2O4)3] can reduce the potential difference between the two, promote the occurrence of coprecipitation, and obtain a dense crystallized coating;

[0033] (4) The anions in the bimetallic ionic liquid can complex with graphene oxide, preventing the dendritic growth of graphene oxide during electroplating and improving the quality of the composite coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The cyclic voltammograms of [Bmim][TFA] and [Bmim][NiCr(C2O4)3] solutions in Example 1 (scan rate: 50 mV·s-1);

[0035] Figure 2 This is the SEM image of the Ni-Cr-GO composite coating in Example 1;

[0036] Figure 3 is the XRD pattern of the Ni-Cr-GO composite coating in Example 1;

[0037] Figure 4 This is the Raman spectrum of the Ni-Cr-GO composite coating in Example 1. DETAILED DESCRIPTION

[0038] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0040] The technical solution of the present invention is described more clearly and completely below with reference to specific embodiments and comparative examples.

[0041] Example 1

[0042] This embodiment proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid, and the specific steps are as follows:

[0043] (1) Under vacuum conditions (vacuum degree 0.05 atm), 1-butyl-3-methylimidazolium trifluoroacetate [Bmim][TFA] was dissolved in acetone. Anhydrous NiCl2 and K3[Cr(C2O4)3] were added in sequence at 75°C to prepare a [Bmim][NiCr(C2O4)3] solution. Graphene oxide and boric acid were then added to the [Bmim][NiCr(C2O4)3] solution and ultrasonically stirred. The mixture was stirred for 4 hours with an ultrasonic power of 60 kW and a mechanical stirring rate of 700 r / min, to obtain a plating solution with a pH of 2. The molar ratio of 1-butyl-3-methylimidazolium trifluoroacetate to acetone was 1:200, the molar ratio of 1-butyl-3-methylimidazolium trifluoroacetate, NiCl2, and K3[Cr(C2O4)3] was 1.3:1:1, the boric acid concentration in the plating solution was 3 g / L, and the graphene oxide concentration was 0.15 g / L.

[0044] (2) performing alkaline degreasing and pickling operations on the copper sheet with a 5 wt % sodium hydroxide solution and a 10 wt % nitric acid solution, respectively, and then washing the copper sheet with anhydrous ethanol and deionized water alternately, repeating the washing three times and then drying to obtain a pretreated copper sheet; placing the pretreated copper sheet (cathode) and the graphite sheet (anode) into the electroplating solution prepared in step (1) under a nitrogen atmosphere, with an inter-electrode spacing of 1 cm, and electroplating at 50° C. and 250 r / min under mechanical stirring to ensure that the solid particles can move to the cathode surface under the action of stirring, and controlling the current density to 20 A / dm 2 , constant current electrodeposition was carried out for 90 minutes to obtain a cathode plated piece, and the obtained cathode plated piece was rinsed with ether and deionized water in sequence and dried to obtain a Ni-Cr-GO composite coating.

[0045] Example 2

[0046] This embodiment proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid, and the specific steps are as follows:

[0047] (1) Under vacuum conditions (vacuum degree 0.05 atm), 1-ethyl-3-methylimidazolium trifluoroacetate was dissolved in acetone. At 80°C, vacuum-dried anhydrous NiCl2 and K3[Cr(C2O4)3] were added in sequence to prepare [Emim][NiCr(C2O4)3] solution. Graphene oxide and boric acid were then added to the [Emim][NiCr(C2O4)3] solution and ultrasonically stirred for 3 h. The ultrasonic power was 50 kW and the mechanical stirring rate was 600 r / min, ultimately obtaining an electroplating solution with a pH of 3; wherein the molar ratio of 11-ethyl-3-methylimidazolium trifluoroacetate to acetone was 1:120, the molar ratio of 1-ethyl-3-methylimidazolium trifluoroacetate, NiCl2, and K3[Cr(C2O4)3] was 1.5:1:1, the boric acid concentration in the electroplating solution was 2.5 g / L, and the graphene oxide concentration was 0.06 g / L;

[0048] (2) performing alkaline degreasing and pickling operations on the copper sheet with 8 wt % sodium hydroxide solution and 15 wt % nitric acid solution, respectively, and then washing the copper sheet with anhydrous ethanol and deionized water alternately, repeating the washing three times and then drying to obtain a pretreated copper sheet; placing the pretreated copper sheet (cathode) and the graphite sheet (anode) into the electroplating solution prepared in step (1) under vacuum conditions (vacuum degree 0.05 atm), with an inter-electrode distance of 1 cm, and electroplating at 50° C. and 250 r / min under mechanical stirring to ensure that the solid particles can move to the cathode surface under the action of stirring, and controlling the current density to 15 A / dm 2, constant current electrodeposition was carried out for 70 minutes to obtain a cathode plated piece, and the obtained cathode plated piece was rinsed with ether and deionized water in sequence and dried to obtain a Ni-Cr-GO composite coating.

[0049] Example 3

[0050] This embodiment proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid, and the specific steps are as follows:

[0051] (1) Under nitrogen conditions, 1-ethyl-3-methylimidazolium trifluoroacetate was dissolved in acetone, and vacuum-dried anhydrous NiCl2 and K3[Cr(C2O4)3] were added in sequence at 80°C to prepare [Emim][NiCr(C2O4)3] solution, and graphene oxide and boric acid were added to the [Emim][NiCr(C2O4)3] solution, and ultrasonic stirring was performed for 3 hours at an ultrasonic power of 50 kW and a mechanical stirring rate of 600 r / min to finally obtain an electroplating solution with a pH of 3; wherein the molar ratio of 1-ethyl-3-methylimidazolium trifluoroacetate to acetone was 1:120, the molar ratio of 1-ethyl-3-methylimidazolium trifluoroacetate, NiCl2, and K3[Cr(C2O4)3] was 1.8:1:1, the boric acid concentration in the electroplating solution was 3 g / L, and the graphene oxide concentration was 0.10 g / L;

[0052] (2) performing alkaline degreasing and pickling operations on the copper sheet with a 5 wt % sodium hydroxide solution and a 12 wt % nitric acid solution, respectively, and then washing the copper sheet alternately with anhydrous ethanol and deionized water, repeating the washing three times and then drying to obtain a pretreated copper sheet; placing the pretreated copper sheet (cathode) and the graphite sheet (anode) into the electroplating solution prepared in step (1) under an argon atmosphere, with an inter-electrode spacing of 1 cm, and electroplating at 55° C. and 250 r / min under mechanical stirring to ensure that the solid particles can move to the cathode surface under the action of stirring, and controlling the current density to be 15 A / dm 2 , constant current electrodeposition was carried out for 110 minutes to obtain a cathode plated part, and the obtained cathode plated part was rinsed with ether and deionized water in sequence and dried to obtain a Ni-Cr-GO composite coating.

[0053] Example 4

[0054] This embodiment proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid, and the specific steps are as follows:

[0055] (1) Under vacuum conditions (vacuum degree 0.1 atm), 1-butyl-3-methylimidazolium trifluoroacetate was dissolved in acetone, and anhydrous NiCl2 and K3[Cr(C2O4)3] were added in sequence at 75°C to prepare a [Bmim][NiCr(C2O4)3] solution, and graphene oxide and boric acid were added to the [Bmim][NiCr(C2O4)3] solution. The solution was ultrasonically stirred for 4 h at an ultrasonic power of 60 kW and a mechanical stirring rate of 700 r / min to finally obtain an electroplating solution with a pH of 2; wherein the molar ratio of 1-butyl-3-methylimidazolium trifluoroacetate to acetone was 1:150, the molar ratio of 1-butyl-3-methylimidazolium trifluoroacetate, NiCl2, and K3[Cr(C2O4)3] was 1.5:1:1, the boric acid concentration in the electroplating solution was 3 g / L, and the graphene oxide concentration was 0.20 g / L;

[0056] (2) performing alkaline degreasing and pickling operations on the copper sheet with a 5 wt % sodium hydroxide solution and a 10 wt % nitric acid solution, respectively, and then washing the copper sheet with anhydrous ethanol and deionized water alternately, repeating the washing three times and drying to obtain a pretreated copper sheet; placing the pretreated copper sheet (cathode) and the graphite sheet (anode) into the electroplating solution prepared in step (1) in air after drying (water content less than 0.01%), with an inter-electrode spacing of 1 cm, and electroplating at 65° C. and 250 r / min under mechanical stirring to ensure that the solid particles can move to the cathode surface under the action of stirring, and controlling the current density to be 10 A / dm 2 , constant current electrodeposition was carried out for 40 minutes to obtain a cathode plated piece, and the obtained cathode plated piece was rinsed with ether and deionized water in sequence and dried to obtain a Ni-Cr-GO composite coating.

[0057] Example 5

[0058] This embodiment proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid, and the specific steps are as follows:

[0059] (1) Under nitrogen conditions, 1-ethyl-3-methylimidazolium trifluoroacetate was dissolved in acetone, and vacuum-dried anhydrous NiCl2 and K3[Cr(C2O4)3] were added in sequence at 80°C to prepare [Emim][NiCr(C2O4)3] solution, and graphene oxide and boric acid were added to the [Emim][NiCr(C2O4)3] solution, and ultrasonic stirring was performed for 3 hours at an ultrasonic power of 50 kW and a mechanical stirring rate of 600 r / min to finally obtain an electroplating solution with a pH of 3; wherein the molar ratio of 1-ethyl-3-methylimidazolium trifluoroacetate to acetone was 1:140, the molar ratio of 1-ethyl-3-methylimidazolium trifluoroacetate, NiCl2, and K3[Cr(C2O4)3] was 1.8:1:1, the boric acid concentration in the electroplating solution was 3 g / L, and the graphene oxide concentration was 0.25 g / L;

[0060] (2) The copper sheet was subjected to alkaline degreasing and pickling operations with a 5wt% sodium hydroxide solution and a 12wt% nitric acid solution, respectively, and then the copper sheet was alternately washed with anhydrous ethanol and deionized water, and the washing was repeated three times and then dried to obtain a pretreated copper sheet; under a nitrogen atmosphere, the pretreated copper sheet (cathode) and the graphite sheet (anode) were placed in the electroplating solution prepared in step (1), with an inter-electrode spacing of 1 cm, and electroplated at 60°C and 250r / min under mechanical stirring to ensure that the solid particles can move to the cathode surface under the action of stirring, and the current density was controlled to be 10A / dm2, and constant current electroplating was performed for 90min to obtain a cathode plated piece, and the obtained cathode plated piece was rinsed with ether and deionized water in turn, and blown dry to obtain a Ni-Cr-GO composite coating.

[0061] Figure 1 The cyclic voltammograms of [Bmim][TFA] and [Bmim][NiCr(C2O4)3] solutions in Example 1 (scan rate 50 mV·s-1) are shown in FIG. Figure 1 It can be seen that the nickel-chromium bimetallic coordination anions provide a source of nickel and chromium, which can reduce the potential difference between the two and promote the occurrence of codeposition reaction;

[0062] Figure 2 is the SEM image of the Ni-Cr-GO composite coating in Example 1. Figure 2 It can be seen that the coating thickness is uniform, there are no impurities such as pores and bubbles, and the composite coating quality is high;

[0063] Figure 3 is the XRD pattern of the Ni-Cr-GO composite coating in Example 1, Figure 3 It can be seen that the nickel-chromium alloy coating has a crystalline structure with dense crystals, and the addition of graphene oxide causes an interaction between graphene oxide and Ni-Cr, changing the growth and arrangement of the crystals.

[0064] Figure 4 is the Raman spectrum of the Ni-Cr-GO composite coating in Example 1, Figure 4 It can be seen that there are obvious D peaks and G peaks. By analyzing the intensity ratio of these two peaks, it can be seen that in the Ni-Cr-GO composite coating, the carbon atoms of graphene oxide are arranged regularly and have fewer defects.

[0065] Comparative Example 1

[0066] This comparative example proposes a method for preparing a Ni-Cr composite coating using an aqueous solution, the specific steps of which are the same as those in Example 1, except that the "1-butyl-3-methylimidazolium trifluoroacetate dissolved in acetone" in Example 1 is replaced with "deionized water".

[0067] In Comparative Example 1, a water-based electroplating method was used to prepare the Ni-Cr-GO composite coating, but severe hydrogen evolution occurred in the aqueous solution, and the hardness of the product was much lower than that in Example 1.

[0068] Comparative Example 2

[0069] This comparative example proposes a method for preparing a Ni-Cr composite coating using a bimetallic ionic liquid, the specific steps of which are the same as those in Example 1, except that graphene oxide is not added in step (1).

[0070] In Comparative Example 2, the prepared Ni-Cr composite coating does not contain graphene oxide, and its hardness is much lower than that of the Ni-Cr-GO composite coating in Example 1.

[0071] Comparative Example 3

[0072] This comparative example proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid. The specific steps are the same as those in Example 1, except that the "1-butyl-3-methylimidazolium trifluoroacetate" in step (1) is replaced by "2,4,6-trimethylpyridine trifluoroacetate".

[0073] In Comparative Example 3, the pyridinium cation cannot effectively inhibit the discharge of hydrogen ions at the cathode, so that the hydrogen evolution phenomenon still exists, reducing the hardness of the composite coating.

[0074] Comparative Example 4

[0075] This comparative example proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid. The specific steps are the same as those in Example 1, except that the "1-butyl-3-methylimidazolium trifluoroacetate" in step (1) is replaced with "tetramethylammonium trifluoroacetate".

[0076] In Comparative Example 4, the tetramethylammonium cation has a simple structure and lacks coordination ability, and cannot form a bimetallic coordination anion with the nickel-chromium ion. During electroplating, it is difficult to reduce the potential difference between nickel and chromium, which is not conducive to the occurrence of co-deposition. The nickel-chromium deposition effect in the final composite coating is poor and the hardness is low.

[0077] Comparative Example 5

[0078] This comparative example proposes a method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid. The specific steps are the same as those in Example 1, except that the "1-butyl-3-methylimidazolium trifluoroacetate" in step (1) is replaced with "1-butyl-3-methylimidazolium trifluorosulfate".

[0079] In Comparative Example 5, the anions in 1-butyl-3-methylimidazolium trifluorosulfate cannot form a stable complex structure with graphene oxide, and cannot inhibit the dendritic growth of graphene oxide during electroplating.

[0080] The performance of the composite coatings in the above embodiments and comparative examples was tested. The hardness test was performed using a Vickers hardness tester. After loading, the pressure was maintained for 15 seconds. Ten points were randomly selected, and the lowest and highest values were removed and the average value was taken. Table 1 shows the deposition rate and hardness data of the composite coatings in the embodiments and comparative examples.

[0081] Table 1 Deposition speed and hardness data of composite coatings in various embodiments and comparative examples

[0082]

[0083] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid, characterized in that: The steps are as follows: S1. Mix imidazolium fluorocarboxylate and acetone, add nickel salt and K3[Cr(C2O4)3] in sequence to obtain a bimetallic ionic liquid, and then mix the bimetallic ionic liquid with graphene oxide to obtain an acidic electroplating solution.

2. The method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid according to claim 1, wherein: The following steps are also included: S2. Placing the graphite sheet and the pretreated copper sheet in the acidic electroplating solution of step S1 to obtain a Ni-Cr-GO composite coating after electroplating.

3. The method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid according to claim 1 or 2, characterized in that: In step S1, the imidazole fluorocarboxylate is one of 1-ethyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium trifluoroacetate or 1-methylimidazolium trifluoromethanesulfonate.

4. The method for preparing a Ni-Cr-GO composite coating according to any one of claims 1 to 3, wherein: In step S1, the molar ratio of the imidazole fluorocarboxylate to acetone is 1:120-200; Preferably, the molar ratio of the imidazolium fluorocarboxylate to acetone is 1:

150.

5. The method for preparing a Ni-Cr-GO composite coating according to any one of claims 1 to 4, wherein: In step S1, the nickel salt is one of NiCl2, NiSO4 or Ni(NO3)2.

6. The method for preparing a Ni-Cr-GO composite coating according to any one of claims 1 to 5, wherein: In step S1, the molar ratio of the imidazole fluorocarboxylate, nickel salt, and K3[Cr(C2O4)3] is 1.3-1.8:1:

1.

7. The method for preparing a Ni-Cr-GO composite coating according to any one of claims 1 to 6, wherein: In step S1, the concentration of graphene oxide in the electroplating solution is 0.05-0.25 g / L; Preferably, the concentration of graphene oxide is 0.15 g / L.

8. The method for preparing a Ni-Cr-GO composite coating according to any one of claims 1 to 7, wherein: In step S2, the electroplating adopts constant current electrodeposition; Preferably, the electroplating temperature is 50-70°C; Preferably, the current density is 10-30A / dm 2 ; Preferably, the electroplating time is 40-100 minutes.

9. The method for preparing a Ni-Cr-GO composite coating according to any one of claims 1 to 8, wherein: In step S2, mechanical stirring is also required during the electroplating; Preferably, the speed of the mechanical stirring is 250 r / min.

10. The method for preparing a Ni-Cr-GO composite coating using a bimetallic ionic liquid according to any one of claims 1 to 9, characterized in that: Step S1 and step S2 are performed under anhydrous conditions; Preferably, steps S1 and S2 are performed under an inert dry atmosphere or vacuum conditions.

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