CN110468431A - Environmentally friendly chromium-graphene composite coating preparation method - Google Patents

Abstract

The invention discloses a preparation method of a chromium-graphene composite coating. The chromium-graphene composite coating is deposited on a brass substrate through an environment-friendly Cr3 ⁺ electroplating solution, and the electroplating solution includes 100-120g/L chromium chloride , 30~50g/L ammonium formate, 15~20g/L anhydrous sodium acetate, 100~140g/L ammonium chloride, 30~45g/L boric acid, 8~12g/L ammonium bromide, 15~25g/L urea , 0.02‑0.1g/L sodium lauryl sulfate and 1~4g/L saccharin. The graphene sol is added to the Cr ³⁺ electroplating solution, and the chromium-graphene composite coating can be obtained by electrodeposition. The preparation process of the chromium-graphene composite coating will not cause harm to human health and the natural environment, and the preparation process is simple; the hardness and wear resistance of the obtained composite coating are significantly improved, and the corrosion resistance is significantly improved. .

Description

Preparation method of environment-friendly chromium-graphene composite coating

technical field

The invention belongs to the field of environment-friendly chromium plating, and relates to a preparation method of an environment-friendly chromium-graphene composite coating.

Background technique

Chromium coating has high hardness, excellent high temperature resistance, friction resistance, and corrosion resistance, and has a surface that can maintain its reflection ability for a long time, so it has a very wide range of applications in the fields of mechanical parts, electronic products, and daily metal products. application. At present, most of the chromium coatings produced in industry are obtained by depositing Cr ⁶⁺ system electroplating solution, and Cr ⁶⁺ ions have serious pollution to soil and water sources. In addition, Cr ⁶⁺ ions are also harmful to the human body. , studies have shown that Cr ⁶⁺ ions have a carcinogenic effect on the human body and seriously affect human health. With the society's emphasis on environmental issues and human health, the production and application of Cr ⁶⁺ system chromium coatings have been greatly restricted; however, the excellent performance of chromium coatings is indispensable and difficult to replace in industrial production. Metal coating, so it is necessary to find a green and environmentally friendly chromium coating preparation process to replace the original Cr ⁶⁺ electroplating solution system. Cr ³⁺ ion is a kind of non-toxic and pollution-free metal ion, which will not cause harm to the natural environment and human body. Therefore, choosing an environment-friendly Cr ³⁺ electroplating solution system to prepare chromium coating can effectively solve this contradiction. However, compared with the performance of the chromium coating deposited by the Cr ³⁺ system electroplating solution and the chromium coating prepared by the Cr ⁶⁺ system electroplating solution, there is still a certain gap in hardness and friction and wear resistance. There are still some limitations in industrial production and application.

Graphene is the hardest nanomaterial, it has good lubricity and corrosion resistance, and has very important applications in many fields. Composite electroplating technology is used to co-deposit graphene and Cr ³⁺ ions to obtain a chromium-graphene composite coating. This composite process can make graphene highly dispersed and uniformly distributed in the chromium coating matrix, so that the chromium coating Produces the "dispersion strengthening" effect, and can refine the grain of the structure, so that the hardness of the chromium coating is significantly improved. The graphene dispersed in the chromium coating matrix has a lubricating effect, which can reduce the friction coefficient of the coating, thereby improving the friction and wear resistance of the chromium coating. In addition, the latest discovery of graphene is that it has excellent performance in anti-corrosion, and it can be applied in the field of metal anti-corrosion, so the graphene distributed in the chromium coating matrix can improve its corrosion resistance.

The content of graphene in the coating has a great influence on the performance of the composite coating. When the concentration of graphene is low, the performance of the composite coating cannot be fully explored; when the content of graphene is too high, it will cause defects in the coating. Performance deterioration; therefore the addition of graphene is an important parameter for the preparation of chromium-graphene composite coatings.

The application number is CN201480073286.4 titled method for producing a chromium coating and coated objects, the method involves generating a trivalent chromium-based coating on the object, depositing a nickel-phosphorus alloy layer on the object; on the NiP layer An intermediate layer of another metal or metal alloy or ceramic is deposited on it; a chromium layer is deposited on the intermediate layer from a trivalent chromium bath. The coated object is subjected to one or more heat treatments to harden the coating and generate a multiphase layer comprising at least one layer comprising crystalline Ni and crystalline _Ni3P and at least one layer comprising crystalline Cr. The intermediate layer may consist of copper, molybdenum, metal alloys or non-metallic solids such as oxides, nitrides or carbides of metals. The chromium coating produced by this method has high hardness and strong bonding force with the substrate. However, the preparation of Cr ³⁺ system chromium coatings by this process has relatively complicated production steps, high production costs, is not suitable for mass industrial production, and cannot improve the friction and wear resistance of nickel coatings.

Contents of the invention

In order to solve the above-mentioned technical problems existing in the background technology, the present invention provides a kind of preparation method of the environment-friendly chromium-graphene composite coating that makes the crystal grain refinement in Cr coating, structure compact, hardness higher and corrosion resistance .

In order to achieve the above object, the present invention adopts the following technical solutions:

An electroplating solution for an environment-friendly chromium-graphene composite coating, the electroplating solution for the environment-friendly chromium-graphene composite coating includes CrCl ₃ 6H ₂ O, 30-50g/L with a mass concentration of 100-120g/L HCOONH ₄ and 15-20g/L CH ₃ COONa.

Preferably, the electroplating solution of the environment-friendly chromium-graphene composite coating used in the present invention also includes 100-140 g/L NH ₄ Cl, 30-45 g/L H ₃ BO ₃ , 8-12 g/L NH ₄ Br, 15-25g/L CO(NH ₂ ) ₂ , 0.02-0.1g/L sodium lauryl sulfate and 1-4g/L saccharin.

A method for preparing the electroplating solution of the environmental protection chromium-graphene composite coating as described above, the method may further comprise the steps:

1) Weigh the electroplating solution solute in proportion, and the electroplating solution solute is CrCl ₃ 6H ₂ O, HCOONH ₄ , CH ₃ COONa, NH ₄ Cl, H ₃ BO ₃ , NH ₄ Br, CO(NH ₂ ) ₂ , Sodium Lauryl Sulfate and Saccharin;

2) Dissolve the electroplating solution solute in deionized water, stir evenly with a magnetic stirrer, the stirring speed of the magnetic stirrer is 300～400rpm; the hot water bath is kept to 70±10°C, and the pH is adjusted with 10～20% HCl 3～5, get the electroplating solution of environment-friendly chromium-graphene composite coating.

A kind of preparation method of environment-friendly chromium-graphene composite coating, the preparation method of this environment-friendly chromium-graphene composite coating comprises the following steps:

1) Cut the brass sheet with double-sided film into a sample, tear off one side of the protective film on the brass sheet, put it in acetone solution and vibrate in an ultrasonic instrument;

2) Rinse the sample after shaking with running water first, then clean the sample with deionized water, clamp the middle of the narrow side with crocodile clips, and then place it in an alkaline washing solution at 65°C to 80°C for alkaline washing;

3) After the alkali cleaning, rinse the sample with deionized water, and then place it in the activation solution at 25°C-35°C for 60-100s. During the activation, use the stainless steel plate as the anode, and the sample after alkali washing as the cathode , the cathode and the anode are vertically placed in parallel, the stainless steel plate is connected to the positive pole of the DC power supply; the sample is connected to the negative pole of the DC power supply;

4) Clean the activated sample with deionized water, clamp the middle part of the narrow side with a crocodile clip with a copper rod, and then fix it on the fixture, and then fix the graphite plate with a purity of 99.9% on the On the fixture, ensure that the graphite plate is vertically parallel to the brass sample, and adjust the height of the fixture so that the sample and the graphite plate are immersed in the electroplating solution of the environmentally friendly chromium-graphene composite coating. Add graphene sol to the electroplating solution, and connect the positive and negative electrodes of the DC power supply to the sample copper rod and the graphite copper rod respectively. Switch on the DC power supply for electrodeposition, and the deposition time is 20-40min;

5) After the deposition, the sample is taken out, rinsed with deionized water, and dried to obtain an environmentally friendly chromium-graphene composite coating.

Preferably, the vibration frequency of the ultrasonic instrument in step 1) adopted by the present invention is 40KHz, and the working environment is normal temperature.

Preferably, the alkali washing solution in step 2) used in the present invention is formed by mixing 30-50 g/L NaOH and 6-15 g/L NaH ₂ PO ₄ .

Preferably, the activation solution used in step 3) of the present invention is formed by mixing 10-20 g/L of C ₆ H ₈ O ₇ and 50-80 g/L of C ₆ H ₅ O ₇ (NH ₄ ) ₃ , The current density during activation is 40-60 mA/cm ² .

Preferably, the current density of electrodeposition in step 4) used in the present invention is 80-100 mA/cm ² .

Preferably, the added concentration of the graphene sol in step 4) used in the present invention is a; said 5mL/L≤a<20mL/L, preferably a=10mL/L.

An environment-friendly chromium-graphene composite coating prepared based on the aforementioned method for preparing the environment-friendly chromium-graphene composite coating.

Compared with the prior art, the present invention has the advantages of:

1. Significantly improved coating performance: Adding graphene sol to the electroplating solution of Cr ³⁺ system can avoid the agglomeration of graphene. After electrification, Cr ³⁺ ions and graphene co-deposit, and graphene is dispersed and evenly distributed In the chromium coating matrix, a "dispersion strengthening effect" is formed and the grains are refined; compared with the chromium coating without graphene, its hardness is increased from 650HV to 770HV; friction and wear experiments are carried out under the same conditions, when adding When the graphene concentration is 10mL/L, the wear scar width is 306 μm, while the wear scar width of the Cr coating without graphene is 437 μm, which shows that its friction and wear resistance performance is significantly improved; the corrosion resistance of the sample through the polarization curve Performance analysis shows that when the graphene concentration is 10mL/L, the equilibrium potential is the most positive and the corrosion current density is the smallest, indicating that the composite coating has the best corrosion resistance.

2. Simple equipment and low cost: only need ultrasonic instrument, power supply, magnetic stirrer, oven to complete, no need to purchase huge equipment, low energy consumption, suitable for mass industrial production.

3. Environmental protection and no pollution to the environment: the green and environment-friendly Cr ³⁺ electroplating system is adopted, which will not cause harm to the natural environment and human health. The waste liquid is simple in composition and easy to handle.

Description of drawings

Fig. 1 is the schematic diagram of the device that composite electroplating process prepares chromium-graphene composite coating;

Fig. 2 is composite coating deposition step and structural representation;

Fig. 3 is the hardness change curve of the chromium-graphene composite coating of different graphene concentrations;

Figure 4 is the cross-sectional metallography of chromium-graphene composite coatings with different graphene concentrations, where a: pure chromium coating b: Cr+10mL-L graphene sol composite coating c: Cr+50mL/L graphene sol Composite coating;

Figure 5 is the metallography of friction and wear marks of chromium-graphene composite coatings with different graphene concentrations, where a: pure chromium coating b: Cr+10mL/L graphene sol composite coating c: Cr+50mL/L graphene Sol composite coating;

Figure 6 shows the polarization curves of chromium-graphene composite coatings with different graphene concentrations, where a: pure chromium coating b: Cr+10mL/L graphene sol composite coating c: Cr+50mL/L graphene Sol composite coating.

Detailed ways

Example

The invention provides an electroplating solution of an environment-friendly chromium-graphene composite coating. The electroplating solution of the environment-friendly chromium-graphene composite coating comprises CrCl ₃ 6H ₂ O and 38g/L HCOONH with a mass concentration of 106g/L ₄ and 16.4 g/L _of CH3COONa. CrCl ₃ ·6H ₂ O is the main salt, which is used to provide the Cr ³⁺ needed for the metal coating, and the Cr ³⁺ gets electrons to become Cr atoms and adsorb on the surface of the substrate, and a large amount of Cr atoms deposit to form the Cr coating. HCOONH ₄ is a complexing agent, forming complex ions with Cr3+; CH ₃ COONa is a buffering agent, used to stabilize the pH value. High-quality coatings cannot be obtained without any of the main salt, complexing agent, and buffer.

The electroplating solution of the environmentally friendly chromium-graphene composite coating also includes 133g/L NH ₄ Cl, 40g/L H ₃ BO ₃ , 10g/L NH ₄ Br, 20g/L CO(NH ₂ ) ₂ , 0.02 g/L sodium lauryl sulfate and 0.25g/L saccharin. NH ₄ Cl is a conductive agent to improve the conductivity of the electroplating solution; H ₃ BO ₃ buffer is used to increase the electrodeposition rate; NH ₄ Br is used to improve the stability of Cr ³⁺ and prevent oxidation to Cr ⁶⁺ . CO(NH ₂ ) ₂ is used to change the ion state of the coating, adjust the pH of the plating solution, and improve the quality of the coating; sodium lauryl sulfate is a surfactant, which makes the solvent more uniformly dispersed, and reduces the generation of bubbles on the substrate, making graphite The vinyl sol is more evenly dispersed and not easy to agglomerate; saccharin is a brightener, which makes the surface of the coating smooth and bright.

When the present invention provides the electroplating solution of above-mentioned environment-friendly chromium-graphene composite coating, also provides the preparation method of the electroplating solution of this chromium-retaining-graphene composite coating, the method comprises the following steps:

1) Weigh the electroplating solution solute in proportion. The electroplating solution solute is CrCl ₃ 6H ₂ O, HCOONH ₄ , CH ₃ COONa, NH ₄ Cl, H ₃ BO ₃ , NH ₄ Br, CO(NH ₂ ) ₂ , twelve Sodium Alkyl Sulfate and Saccharin;

2) Dissolve the solute of the electroplating solution in deionized water, stir evenly with a magnetic stirrer, the stirring speed of the magnetic stirrer is 300-400rpm; keep the hot water bath at 70±10°C, adjust the pH=3～3～ with 10～20% HCl 5. Obtain an electroplating solution for an environmentally friendly chromium-graphene composite coating.

Simultaneously, the present invention also provides a kind of preparation method of environment-friendly chromium-graphene composite coating based on the electroplating solution of the above-mentioned environment-friendly chromium-graphene composite coating, see Fig. 1, this environment-friendly chromium-graphene composite coating The preparation method of the layer comprises the following steps:

1) For the convenience of operation, cut a brass sheet with a double-sided film and a thickness of 0.2mm into a sample whose length and width are 30mm and 20mm respectively, tear off one side of the protective film on the brass sheet, put it in an acetone solution and perform it on an ultrasonic instrument. Medium vibration for 5 minutes; the vibration frequency of the ultrasonic instrument is 40KHz, and the working environment is normal temperature;

2) Rinse the sample after shaking with running water first, then clean the sample with deionized water, clamp the middle of the narrow side with crocodile clips, and then place it in an alkaline washing solution at 65°C to 80°C for 5 minutes; The alkali washing solution is made by mixing 50g/L NaOH and 10g/L NaH ₂ PO ₄ . The specific implementation of the alkali washing solution is to first measure 250mL deionized water into a beaker, and put it into a magnet with 200 Stir at a speed of -300rpm, weigh 12.5g NaOH and 2.5g NaH ₂ PO ₄ with a high-precision balance, and pour them into the stirring beaker in turn, and wait for the reagents to dissolve completely.

3) After the alkali cleaning, rinse the sample with deionized water, and then place it in the activation solution at 25°C-35°C for 60-100s. During the activation, use the stainless steel plate as the anode, and the sample after alkali washing as the cathode , the cathode and the anode are vertically placed in parallel, and then respectively connected to the negative and positive poles of the DC power supply; the activation solution is composed of 20g/L C ₆ H ₈ O ₇ and 60g/L C ₆ H ₅ O ₇ (NH ₄ ) ₃ Mixed, the current density during activation is 40mA/cm ² .

4) Clean the activated sample with deionized water, clamp the middle part of the narrow side with a crocodile clip with a copper rod, then fix it on the fixture, and then place a graphite plate with a purity of 99.9% (length, width, thickness: 40× 40×3mm) is fixed on the fixture by the same method to ensure that the graphite plate is vertically parallel to the brass sample, and the height of the fixture is adjusted so that the sample and the graphite plate are immersed in the electroplating solution of the environmentally friendly chromium-graphene composite coating. Add graphene sol in the electroplating solution of environmentally friendly chromium-graphene composite coating, connect the positive and negative electrodes of the DC power supply to the sample copper rod and the graphite copper rod respectively, when the temperature of the electroplating solution is 65°C and the stirring speed is 350rpm 1. When the pH=4, switch on the DC power supply for electrodeposition, the deposition time is 25min, the current density of electrodeposition is 90mA/cm ² , and the coating obtained by electrodeposition is deposited on the surface of the brass sheet. Graphite is the anode, which can form a parallel electric field with the brass plate, and can make the charged ions in the electroplating solution move along the direction of the electric field.

When the present invention determines the addition concentration of graphene sol, specific method is: first prepare pure chromium coating with chromium plating solution; Then add the graphene sol of 5mL/L in plating solution, prepare Cr+ A composite coating of 5mL/L graphene sol; add 10mL/L graphene sol to the plating solution to prepare a composite coating of Cr+10mL/L graphene sol; add 15mL/L graphene to the plating solution Sol, prepare the composite coating of Cr+15mL/L graphene sol; Add the graphene sol of 20mL/L in the plating solution, prepare the composite coating of Cr+20mL/L graphene sol; Add in the plating solution 50mL/L graphene sol, a composite coating of Cr+50mL/L graphene sol was prepared; a total of six different types of coatings were prepared. These 6 samples were tested for hardness, friction and wear resistance, and corrosion resistance, and the test results were compared and analyzed. The amount of graphene corresponding to the chromium-graphene composite coating with the best comprehensive performance is the optimal addition of graphene. concentration. Referring to Fig. 3, it can be seen from the abscissa of the peak value of the curve that the amount of graphene added is 10mL/L, and the microhardness corresponding to the ordinate of the coating is 770HV, indicating that the maximum microhardness of adding graphene sol can reach 770HV, which exceeds that of the previous coating. 650HV with graphene coating (starting point in Figure 3). The added concentration of graphene sol is a; 5mL/L≤a<20mL/L, preferably a=10mL/L. Referring to Figure 4, it is the cross-sectional morphology of graphene coatings with different concentrations, indicating that adding an appropriate amount of graphene will not cause its performance to deteriorate, but excessive graphene will cause performance deterioration (≥20mL/L). See Figure 5. Under the same loading force, hard steel balls are used to perform linear reciprocating friction on the coating. This figure shows the appearance after friction. It is generally believed that the narrower the wear scar, the better the friction and wear resistance of the coating. From the figure It can be seen that the wear scar width without graphene coating (a) is 437 microns, and after adding 10mL/L graphene, the wear scar width of composite coating (b) is 306 microns, compared to that without graphene coating The layer is significantly reduced, indicating that the addition of graphene improves the friction resistance. When adding excess graphene (50mL/L), the wear scar width of the corresponding coating (c) increased to 465, and the friction resistance deteriorated.

5) After the deposition, the sample is taken out, rinsed with deionized water, and dried to obtain an environmentally friendly chromium-graphene composite coating.

Based on the method described above, the present invention obtains an environmentally friendly chromium-graphene composite coating, which can replace all Cr coating application scenarios, but the preparation process is more environmentally friendly, safer and greener , the mechanical properties and corrosion resistance of the coating are more excellent. For example, anti-corrosion coatings for auto parts (car skeleton, various parts), plumbing hardware (faucets, valves, metal pipes, towel racks, etc.), bridge metal structures, anti-corrosion coatings for ships, etc.

Referring to Fig. 2, the working principle of the preparation method of the environment-friendly chromium-graphene composite coating provided by the present invention is: after the graphene and ^Cr ion co-deposited uniformly dispersed in the electroplating solution, the graphene will make the Cr coating The "dispersion strengthening" effect is produced in the matrix, and the grains in the Cr coating are refined, the structure is dense, and the hardness is increased; while reducing frictional resistance, it also has excellent corrosion resistance. See Figure 6, the polarization curve of the coating, which represents the difficulty of the coating to corrode. The greater the corrosion potential, the less likely the coating will be corroded, and the better its corrosion resistance. When adding 50mL/L graphene coating, the corrosion potential is the smallest, and the corrosion performance is the worst, because cracks are generated on the coating, which accelerates the corrosion, and the cracks can be seen from the cross-sectional appearance. Adding 10mL/L graphene coating has the largest corrosion potential and the best corrosion performance.

Claims (10)

1. a kind of electroplate liquid of environmental protection chromium-graphene composite coating, it is characterised in that: the environmental protection chromium-graphene composite coating Electroplate liquid include CrCl that mass concentration is 100 ~ 120g/L₃•6H₂O, the HCOONH of 30 ~ 50g/L₄And 15 ~ 20g/L CH₃COONa。

2. the electroplate liquid of environmental protection chromium-graphene composite coating according to claim 1, it is characterised in that: the environmental protection chromium- The electroplate liquid of graphene composite coating further includes the NH of 100 ~ 140g/L₄The H of Cl, 30 ~ 45g/L₃BO₃, 8 ~ 12g/L NH₄Br、 The CO(NH of 15 ~ 25g/L₂)₂, the lauryl sodium sulfate of 0.02-0.1g/L and the saccharin of 1 ~ 4g/L.

3. a kind of method for the electroplate liquid for preparing environmentally friendly chromium-graphene composite coating as claimed in claim 1 or 2, feature It is: the described method comprises the following steps:

1) electroplate liquid solute is weighed in proportion, and the electroplate liquid solute is CrCl₃•6H₂O、HCOONH₄、CH₃COONa、NH₄Cl、 H₃BO₃、NH₄Br, CO(NH₂)₂, lauryl sodium sulfate and saccharin；

2) electroplate liquid solute is dissolved in deionized water, with magnetic stirrer uniform stirring, the stirring speed of the magnetic stirrer Degree is 300 ~ 400rpm；Hot bath remains to 70 ± 10 DEG C, adjusts pH=3 ~ 5 with 10 ~ 20% HCl, it is multiple to obtain environmentally friendly chromium-graphene Close the electroplate liquid of coating.

4. a kind of preparation method of environmental protection chromium-graphene composite coating, it is characterised in that: the compound painting of the environmental protection chromium-graphene Layer preparation method the following steps are included:

1) latten(-tin) of two-sided pad pasting is cut into sample, tears on latten(-tin) a wherein surface protective film off, is put into acetone soln It is shaken in ultrasonoscope；

2) sample after shaking first is rinsed with flowing water, then is cleaned up sample with deionized water, clamps narrow side with crocodile clip Centre is subsequently placed in alkali cleaning in 65 DEG C ~ 80 DEG C of alkali wash water；

3) with deionized water that sample wash is clean after alkali cleaning, then be placed in 25 DEG C ~ 35 DEG C activating solutions lower activation 60 ~ Stainless steel plate is made anode when activation by 100s, and the sample after alkali cleaning is cathode, and cathode and anode are placed in parallel vertically, it is described not The steel plate that becomes rusty connects the anode of DC power supply；The cathode of the sample connection DC power supply；

4) sample after activation is cleaned up with deionized water, and clamps the middle part of narrow side with the crocodile clip with copper rod, so After be fixed on fixture, then by purity be that 99.9% graphite plate is fixed on fixture with same method, it is ensured that graphite plate and brass Sample is parallel vertically, alignment jig height, and sample and graphite plate is made to be immersed in the environmentally friendly chromium-stone being prepared such as claim 3 In the electroplate liquid of black alkene composite coating, graphene sol is added in environmentally friendly chromium-graphene composite coating electroplate liquid, by direct current The anode and cathode of power supply are connected respectively on sample copper rod and graphite copper rod, when temperature of electroplating solution is 50 ~ 70 DEG C, mixing speed is DC power supply is connected when 300 ~ 400rpm, pH=3 ~ 5 and carries out electro-deposition, and sedimentation time is 20 ~ 40min；

5) sample is taken out after depositing, is rinsed well with deionized water, it is compound to get environmentally friendly chromium-graphene after drying process Coating.

5. the preparation method of environmental protection chromium-graphene composite coating according to claim 4, it is characterised in that: the step 1) vibration frequency of ultrasonoscope is 40KHz in, and working environment is room temperature.

6. the preparation method of environmental protection chromium-graphene composite coating according to claim 5, it is characterised in that: the step 2) alkali wash water in is by the NaH of the NaOH and 6 ~ 15g/L of 30 ~ 50g/L₂PO₄It mixes.

7. the preparation method of environmental protection chromium-graphene composite coating according to claim 6, it is characterised in that: the step 3) activating solution is the C by 10 ~ 20g/L in₆H₈O₇And the C of 50 ~ 80g/L₆H₅O₇(NH₄)₃It mixes, when the activation Current density is 40 ~ 60mA/cm²。

8. the preparation method of environmental protection chromium-graphene composite coating according to claim 7, it is characterised in that: the step 4) current density of electro-deposition is 80 ~ 100mA/cm in²。

9. environmentally friendly chromium-graphene composite coating preparation method, feature according to claim 4 or 5 or 6 or 7 or 8 exist In: the addition concentration of graphene sol is a in the step 4)；5 mL/L≤a < 20 mL/L, preferably a=10 mL/L.

10. a kind of environmental protection that the preparation method based on environmentally friendly chromium-graphene composite coating as claimed in claim 9 is prepared Chromium-graphene composite coating.