Preparation method of Co-Cu-P-Al2O3 nano composite coating with high hardness and excellent corrosion resistance

Abstract

The invention discloses a preparation method of a Co-Cu-P-Al2O3 nano composite coating with high hardness and excellent corrosion resistance, a pulse electroplating method is adopted, cobalt, copper, phosphorus and nano aluminum oxide particles are deposited on the surface of carbon steel at a time, and heat treatment is performed, so that the nano composite coating which can be metallurgically bonded with a carbon steel matrix and is high in hardness and excellent in corrosion resistance is formed. And the service performance of carbon steel is effectively improved. The Co-Cu-P-Al2O3 nano-composite coating capable of forming metallurgical bonding with a carbon steel substrate is obtained by introducing nano aluminum oxide particles and a copper element on the basis of a Co-P coating and carrying out proper heat treatment on the coating, and the coating has the advantages that due to the uniform dispersion and proper heat treatment of nano aluminum oxide in the coating, the coating has the good mechanical property, the mechanical property is good, and the service life of the coating is prolonged. And compared with a Co-P plating layer, the hardness of the plating layer is improved from 656.6 HV to 1153.72 HV.

Description

Technical Field

[0001] The invention belongs to the field of carbon steel surface protection, and specifically relates to a method for preparing a Co-Cu-P-Al2O3 nanocomposite coating which is applied to carbon steel surface protection and can form a metallurgical bond with a carbon steel substrate and has high hardness and excellent corrosion resistance. Background Art

[0002] Carbon steel has become one of the main raw materials in the manufacturing industry due to its advantages such as high hardness, low cost, machinability and recyclability. It is widely used in the production and manufacturing of tools, construction, ships, automobiles, machinery and other industries. However, carbon steel will inevitably suffer from failure problems such as wear and corrosion during its service. Therefore, solving the problems of carbon steel wear and corrosion failure is an urgent need to ensure that carbon steel can serve normally. Since wear and corrosion both start from the surface of carbon steel, surface treatment of carbon steel is a direct and efficient method. Among them, electroplating technology is an effective method that is simple to operate, low in cost and widely applicable to generate a high-hardness, corrosion-resistant coating on the surface of carbon steel.

[0003] Pulse plating is an important type of electroplating technology. Compared with DC plating, pulse plating has more diverse process parameters to adjust, thereby controlling the quality of the coating. Nanocomposite coating is a special coating formed by adding nanoscale (less than 100nm) insoluble solid particles on the basis of traditional composite coating. It overcomes the problem of poor strengthening effect caused by large particle size and uneven dispersion in traditional composite coating and has the advantages of excellent corrosion resistance, wear resistance, high hardness, thermal stability, etc. It is widely used in the fields of carbon steel surface treatment and protection. Among them, Co-P nanocomposite coating has been widely studied in the past decade. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and to provide a method for preparing a Co-Cu-P-Al2O3 nanocomposite coating which can be used for carbon steel surface protection and forms a metallurgical bond with a carbon steel substrate and has high hardness and excellent corrosion resistance.

[0005] The technical purpose of the present invention is achieved through the following technical solutions.

[0006] A method for preparing a Co-Cu-P-Al2O3 nanocomposite coating with high hardness and excellent corrosion resistance is prepared according to the following steps:

[0007] Step 1, placing a carbon steel substrate in an electroplating solution for pulse electroplating, wherein:

[0008] Carbon steel was activated for 5 seconds in an activation solution made of 50 g / L sulfuric acid and 100 g / L hydrochloric acid. After activation, it was cleaned and dried, and then electroplated immediately.

[0009] In the electroplating solution, the components and contents are as follows: sodium citrate is 0.1-0.3 mol / L, sodium hypophosphite is 0.1-0.3 mol / L, copper sulfate is 1-5 g / L, cobalt sulfate heptahydrate is 0.3-0.5 mol / L, potassium sulfate is 0.1-0.5 mol / L, saccharin is 1 g / L, 1,4-butynediol is 1 g / L, 2-ethylhexyl sodium sulfate is 0.1 g / L, polyethylene glycol is 0.1 g / L, boric acid is 30-40 g / L, nano-alumina particles are 10-12 g / L, and the particle size of the nano-alumina particles is 20-30 nm;

[0010] The graphite sheet was used as the anode and the carbon steel substrate was used as the cathode. During electroplating, the plating solution temperature was 60-80 degrees Celsius, the pH was 5±0.1 and stirring was continued. The pulse frequency of the pulse current was adjusted to 200Hz, the duty cycle was 10%, and the average current density was 2A / dm 2 , the electroplating time is 0.5-1 hour;

[0011] Step 2, heat-treating the obtained coating, wherein: placing the coating in a tubular furnace for heat preservation, the atmosphere is an inert protective atmosphere, the temperature is 200-400 degrees Celsius, the heat preservation time is 30-60 minutes, and after the heat treatment is completed, air cooling to room temperature 20-25 degrees Celsius.

[0012] In the technical solution of the present invention, the carbon steel substrate is mechanically polished using 400#, 800#, 1000#, 1500#, and 2000# water-sandpaper in sequence, and then degreased in a degreasing liquid at 70°C for 5 minutes. The degreasing liquid is prepared from 60g / L Na(OH)2, 20g / L Na2CO3, and 40g / L Na3PO4. After completion, it is thoroughly cleaned with distilled water and anhydrous ethanol, and blown dry with cold air from a hair dryer.

[0013] In the technical solution of the present invention, the pH of the electroplating solution is adjusted to 5±0.1 using sodium hydroxide and concentrated sulfuric acid.

[0014] In the technical solution of the present invention, in the electroplating solution, the components and their contents are as follows: 0.3 mol / L sodium citrate, 0.2 mol / L sodium hypophosphite, 5 g / L copper sulfate, 0.5 mol / L cobalt sulfate heptahydrate, 0.1 mol / L potassium sulfate, 1 g / L saccharin, 1 g / L 1,4-butynediol, 0.1 g / L sodium 2-ethylhexyl sulfate, 0.1 g / L polyethylene glycol, 40 g / L boric acid, and 12 g / L nano-alumina particles.

[0015] In the technical solution of the present invention, the temperature of the electroplating solution is 70° C., the stirring speed is 300-500 r / min, and the electroplating time is 1 hour.

[0016] In the technical solution of the present invention, the inert protective atmosphere is nitrogen, helium or argon.

[0017] In the technical solution of the present invention, the coating is placed in a tubular furnace for heat preservation at a temperature of 300-400 degrees Celsius for a heat preservation time of 50-60 minutes.

[0018] The present invention introduces nano-alumina particles and copper elements on the basis of the Co-P coating, and performs appropriate heat treatment on the coating to obtain a Co-Cu-P-Al2O3 nano-composite coating that can form a metallurgical bond with a carbon steel substrate. Due to the uniform dispersion of nano-alumina in the coating and appropriate heat treatment, the hardness of the coating is increased from 656.6HV to 1153.72HV compared with the Co-P coating. Due to the doping of Cu elements, the corrosion current density of the coating is increased from 1.480μA / cm 2 Reduced to 0.810μA / cm 2 ; The corrosion potential is -0.571V compared to the Co-P coating vs。SCE Positive shift is -0.274V vs。SCE This indicates that the corrosion resistance of the coating is significantly improved compared to the Co-P coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a graph showing the morphology and chemical composition characterization results of the Co-Cu-P-Al2O3 nanocomposite coating obtained in Example 1 of the present invention.

[0020] Figure 2 This is a cross-sectional view and line scan characterization result diagram of the Co-Cu-P-Al2O3 nanocomposite coating obtained in Example 1 of the present invention.

[0021] Figure 3 This is a graph showing the morphology and chemical composition characterization results of the Co-Cu-P-Al2O3 nanocomposite coating obtained in Example 2 of the present invention.

[0022] Figure 4 It is a diagram of the morphology characterization results of Examples 3 and 4 of the present invention.

[0023] Figure 5 The morphology and chemical composition characterization results of the Co-P coating obtained in Comparative Example 1 of the present invention.

[0024] Figure 6 It is the polarization curve diagram of Examples 1 to 4 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0025] The technical scheme of the present invention is further described below in conjunction with specific examples. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art, unless otherwise specified, and can be obtained by those skilled in the art through commercial channels.

[0026] Example 1

[0027] The preparation of the Co-Cu-P-Al2O3 nanocomposite coating in this embodiment is carried out by the following steps:

[0028] (1) Carbon steel (X65 pipeline steel) matrix pretreatment: Use wire cutting to cut X65 pipeline steel into 15×10×5mm 3 The samples were mechanically polished with 400#, 800#, 1000#, 1500#, and 2000# water sandpaper in turn, and then degreased for 5 minutes in a degreasing solution at 70°C. The degreasing solution was prepared from 60g / L Na(OH)2, 20g / L Na2CO3, and 40g / L Na3PO4. After that, they were thoroughly cleaned with distilled water and anhydrous ethanol, and dried with a hair dryer. Finally, they were activated for 5s in an activation solution prepared from 50g / L sulfuric acid and 100g / L hydrochloric acid, and then cleaned and dried after the activation.

[0029] (2) Preparation of electroplating solution: First, add 300 mL of distilled water to a clean 500 mL beaker and heat it to 60°C. Then, according to the concentration of substances described above, add sodium citrate and sodium hypophosphite to the heated distilled water, stir evenly, then add copper sulfate and stir evenly again; then add cobalt sulfate heptahydrate and stir evenly; then add potassium sulfate, saccharin, 1,4-butynediol, sodium 2-ethylhexyl sulfate, polyethylene glycol, and boric acid and stir evenly; then add nano-alumina particles with a particle size of about 20 nm, stir evenly, and then ultrasonically treat the electroplating solution for 10 minutes at an ultrasonic power of 300 w; finally, use distilled water to prepare the electroplating solution to 500 mL and heat it to 70°C, and at this temperature, use sodium hydroxide and concentrated sulfuric acid to adjust the pH of the electroplating solution to 5±0.1. The concentrations of the corresponding substances are: sodium citrate 0.3 mol / L, sodium hypophosphite 0.2 mol / L, copper sulfate 5 g / L, cobalt sulfate heptahydrate 0.5 mol / L, potassium sulfate 0.1 mol / L, saccharin 1 g / L, 1,4-butynediol 1 g / L, 2-ethylhexyl sodium sulfate 0.1 g / L, polyethylene glycol 0.1 g / L, boric acid 40 g / L, and nano-alumina particles 12 g / L.

[0030] (3) Pulse plating: Use an intelligent pulse commutation plating power supply for electroplating. During electroplating, the X65 pipeline steel sample after pretreatment in step (1) is used as the cathode, with a size of 20×20×3 mm 3 The graphite sheet was used as the anode, and the pulse frequency of the pulse current was set to 200 Hz, the duty cycle to 10%, and the average current density to 2 A / dm 2 The electroplating solution prepared in step (2) was placed in a water bath with magnetically controlled stirring and heated to 70°C, and the stirring speed was set to 400 r / min, followed by pulse electroplating for 1 hour.

[0031] (4) The coating obtained in step (3) was placed in a tubular furnace at 400° C. and kept warm for 60 min. Argon gas was introduced for protection during the heat treatment. After the heat treatment, the sample was taken out and air-cooled to room temperature.

[0032] (5) Characterization of morphology, chemical composition, hardness, cross section and corrosion resistance: The morphology and chemical composition of the Co-Cu-P-Al2O3 nanocomposite coating obtained in step (4) were characterized using a scanning electron microscope with EDS. Figure 1 As shown, (a) corresponds to the morphology, and (b) corresponds to the chemical composition. Using a Vickers microhardness tester, set the load to 50g, the loading time to 15s, and measure the hardness of the coating 5 times. The average of the measurement results is taken as the hardness of the coating. The average hardness of the Co-Cu-P-Al2O3 nanocomposite coating in Example 1 is 1153.72HV. The CORRTEST CS312M electrochemical workstation was used to measure the potentiodynamic polarization curve of the coating. The traditional three-electrode test system was adopted, and the coating sample was used as the working electrode with an area of ​​1cm 2 The platinum sheet was used as the counter electrode and the saturated calomel electrode (SCE) was used as the reference electrode. During the test, the voltage was -300mV relative to OCP. vs.OCP Sweep to +300mV vs.OCP , the scanning rate is 0.2mV / s, the results are as follows Figure 6 The corrosion potential of the Co-Cu-P-Al2O3 nanocomposite coating in Example 1 is -0.274V vs。SCE , the corrosion current density is 0.810μA / cm 2 The line scan results of the cross-sectional morphology and chemical composition of the coating obtained in Example 1 are as follows: Figure 2 As shown, from the change of Fe element, it can be seen that the left side of the yellow dotted line on the right side of the figure is the carbon steel substrate, and it can be seen that there is no obvious boundary between the coating and the carbon steel substrate; from the line scanning results, it can be seen that between the two yellow dotted lines, the Fe element decreases and the Co element increases, and the Cu element is almost gone, which indicates that after heat treatment, Co diffuses into the carbon steel substrate, thereby forming a metallurgical bond between the Co-Cu-P-Al2O3 nanocomposite coating and the carbon steel substrate.

[0033] Example 2

[0034] The difference between Example 2 and Example 1 is that the heat treatment in step (4) is not included. The other steps and parameters are the same as those in Example 1. The morphology and chemical composition of the obtained Co-Cu-P-Al2O3 coating are as follows: Figure 3 The polarization curve is shown in Figure 6 The average hardness of the Co-Cu-P-Al2O3 coating in Example 2 is 526.40 HV, and the corrosion potential is -0.273 V. vs。SCE , the corrosion current density is 0.319μA / cm 2 .

[0035] Example 3

[0036] The difference between Example 3 and Example 1 is that the heat treatment temperature in step (4) is 200°C. The other steps and parameters are the same as those in Example 1. The morphology of the obtained Co-Cu-P-A12O3 coating is as follows: Figure 4 As shown in FIG. 1 , where (a) corresponds to this embodiment. The polarization curve is shown in FIG. Figure 6 The average hardness of the Co-Cu-P-Al2O3 coating in Example 3 is 772.41 HV, and the corrosion potential is -0.435 V. vs。SCE , the corrosion current density is 1.047μA / cm 2 .

[0037] Example 4

[0038] The difference between Example 7 and Example 1 is that the heat treatment temperature in step (4) is 300°C. The other steps and parameters are the same as those in Example 1. The morphology of the obtained Co-Cu-P-A12O3 coating is as follows: Figure 4 As shown in (b), where (b) corresponds to this embodiment. Figure 6 The average hardness of the Co-Cu-P-Al2O3 coating in Example 7 is 944.34 HV, and the corrosion potential is -0.346 V. vs。SCE , the corrosion current density is 0.873μA / cm 2 .

[0039] Comparative Example 1:

[0040] The difference between this comparative example 1 and Example 1 is that copper sulfate and nano-alumina particles are not added to the electroplating solution in step (2), and the heat treatment process in step (4) is not included. The other steps and parameters are the same as those in Example 1. The morphology and chemical composition of the obtained Co-P coating are as follows: Figure 5 The polarization curve is shown as Figure 6The average hardness of the Co-P coating in Comparative Example 1 is 656.6 HV, and the corrosion potential is -0.571 V. vs。SCE , the corrosion current density is 1.480μA / cm 2 .

[0041] By comparing Examples 1-4, it can be seen that heat treatment effectively improves the hardness of the coating; the Co-Cu-P-Al2O3 nanocomposite coating obtained by Example 1 has improved hardness and corrosion resistance compared to the Co-P coating of Comparative Example 1, and forms a good metallurgical bond with the carbon steel substrate.

[0042] According to the content of the present invention, the process parameters are adjusted to achieve the preparation of the nanocomposite coating, and the performance is basically consistent with the present invention after testing. The above is an exemplary description of the present invention. It should be noted that any simple deformation, modification or equivalent replacement that can be made by other technicians in this field without spending creative labor falls within the protection scope of the present invention without departing from the core of the present invention.

Claims

1. A method for preparing a Co-Cu-P-Al2O3 nanocomposite coating with high hardness and excellent corrosion resistance, characterized in that: Prepare according to the following steps: Step 1: placing a carbon steel substrate in an electroplating solution for pulse electroplating, wherein: Carbon steel is activated in an activation solution of 50 g / L sulfuric acid and 100 g / L hydrochloric acid for 5 seconds. After activation, it is cleaned and dried, and then electroplated immediately. The components and contents of the electroplating solution are as follows: 0.1-0.3 mol / L sodium citrate, 0.1-0.3 mol / L sodium hypophosphite, 1-5 g / L copper sulfate, 0.3-0.5 mol / L cobalt sulfate heptahydrate, 0.1-0.5 mol / L potassium sulfate, 1 g / L saccharin, 1 g / L 1,4-butynediol, 0.1 g / L sodium 2-ethylhexyl sulfate, 0.1 g / L polyethylene glycol, 30-40 g / L boric acid, 10-12 g / L nano-alumina particles, and a particle size of 20-30 nm. The graphite sheet was used as the anode and the carbon steel substrate was used as the cathode. When electroplating was performed, the plating solution temperature was 60-80 degrees Celsius, the pH was 5±0.1 and stirring was continued. The pulse frequency of the pulse current was adjusted to 200 Hz, the duty cycle was 10%, and the average current density was 2A / dm 2 , electroplating time is 0.5-1 hour; Step 2: heat-treating the obtained coating, wherein: placing the coating in a tubular furnace for insulation, the atmosphere is an inert protective atmosphere, the temperature is 200-400 degrees Celsius, the insulation time is 30-60 minutes, and after the heat treatment is completed, air cooling to room temperature 20-25 degrees Celsius.

2. The method for preparing a Co-Cu-P-Al2O3 nanocomposite coating with high hardness and excellent corrosion resistance according to claim 1, characterized in that: The carbon steel substrate was mechanically polished using 400#, 800#, 1000#, 1500#, and 2000# water sandpaper in sequence, and then degreased in a degreasing solution at 70°C for 5 minutes. The degreasing solution was prepared by 60g / L Na(OH)2, 20g / L Na2CO3, and 40g / L Na3PO4. After completion, it was thoroughly cleaned with distilled water and anhydrous ethanol, and blown dry with cold air from a hair dryer.

3. The method for preparing a Co-Cu-P-Al2O3 nanocomposite coating with high hardness and excellent corrosion resistance according to claim 1, characterized in that: The pH of the plating solution was adjusted to 5 ± 0.1 using sodium hydroxide and concentrated sulfuric acid.

4. The method for preparing a Co-Cu-P-Al2O3 nanocomposite coating with high hardness and excellent corrosion resistance according to claim 1, characterized in that: In the electroplating solution, the components and their contents are as follows: 0.3 mol / L sodium citrate, 0.2 mol / L sodium hypophosphite, 5 g / L copper sulfate, 0.5 mol / L cobalt sulfate heptahydrate, 0.1 mol / L potassium sulfate, 1 g / L saccharin, 1 g / L 1,4-butynediol, 0.1 g / L sodium 2-ethylhexyl sulfate, 0.1 g / L polyethylene glycol, 40 g / L boric acid, and 12 g / L nano-alumina particles.

5. The method for preparing a Co-Cu-P-Al2O3 nanocomposite coating with high hardness and excellent corrosion resistance according to claim 1, characterized in that: The temperature of the electroplating solution is 70°C, the stirring speed is 300-500 r / min, and the electroplating time is 1 h.

6. The method for preparing a Co-Cu-P-Al2O3 nanocomposite coating with high hardness and excellent corrosion resistance according to claim 1, characterized in that: The inert protective atmosphere is nitrogen, helium or argon.

7. The method for preparing a Co-Cu-P-Al2O3 nanocomposite coating with high hardness and excellent corrosion resistance according to claim 1, characterized in that: Place the coating in a tubular furnace and keep it warm at 300-400 degrees Celsius for 50-60 minutes.

8. A Co-Cu-P-Al2O3 nanocomposite coating obtained according to the preparation method according to any one of claims 1 to 7.

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