Disclosure of Invention
The invention provides a corrosion-resistant wear-resistant composite coating and a preparation method thereof, aiming at the problems of poor corrosion resistance and insufficient surface wear resistance of magnesium alloy. The composite coating is of a double-layer structure and sequentially comprises a polyaniline coating and an iron coating from inside to outside, the outer iron coating provides mechanical strength, and the inner polyaniline coating can prevent iron from directly contacting with magnesium alloy so as to avoid galvanic corrosion. The composite coating can improve the corrosion resistance and the wear resistance of the surface of the magnesium alloy on the basis of ensuring the conductivity through the synergistic effect of iron and polyaniline.
The technical scheme of the invention is as follows:
the composite coating is of a double-layer structure and sequentially comprises a polyaniline coating and an iron coating from inside to outside, wherein the thickness of the iron coating is 40-90 mu m, and the thickness of the polyaniline coating is 60-120 mu m.
The preparation method of the corrosion-resistant wear-resistant composite coating on the surface of the magnesium alloy comprises the following steps:
the first step is as follows: mechanical polishing of magnesium alloy original surface
Sanding the original surface of the magnesium alloy with sand paper, mechanically polishing with an alumina polishing powder, then ultrasonically cleaning in absolute ethyl alcohol, and blow-drying to obtain a polished surface of the magnesium alloy;
the magnesium alloy is a commercial AZ series, ZK series and WE series magnesium alloy plate;
the second step is that: preparation of polyaniline coating on magnesium alloy surface by electrochemical deposition
Performing electrochemical deposition on the polished surface of the magnesium alloy by using a cyclic voltammetry method, selecting a three-electrode system, selecting a working electrode as the magnesium alloy, a counter electrode as a platinum sheet, a reference electrode as a saturated calomel electrode, performing electrochemical deposition at the temperature of 20-30 ℃, wherein an electrolyte is a sodium salicylate solution containing 0.01-0.2M of aniline, the cyclic potential interval is-0.4-1.5V, the scanning rate is 35-85 mV/s, and the cycle number is 10-20, so as to obtain the magnesium alloy with the polyaniline coating on the surface;
the concentration of the sodium salicylate solution is 0.1-0.2M, and the thickness of the polyaniline coating is 60-120 mu M;
preferably, 0.05-0.15M aniline is added into 0.1M sodium salicylate solution to prepare electrolyte, the circulating potential interval is-0.1-1.2V, the scanning speed is 45-75 mV/s, and the circulating frequency is 12-16;
the third step: preparation of iron coating on magnesium alloy surface by magnetron sputtering
Putting the magnesium alloy with the polyaniline coating on the surface obtained in the second step into a cavity of a magnetron sputtering coating machine, selecting high-purity iron as a cathode target source, and controlling the vacuum degree to be 5.0 multiplied by 10-4Starting arc starting sputtering when Pa is reached, wherein the pressure of argon is 0.2-1.0 Pa, the sputtering power is 150-300W, and the coating time is 2-4 h, so that the magnesium alloy with the iron/polyaniline composite coating on the surface is obtained;
the purity of the high-purity iron is 99.9%, and the thickness of the iron coating is 40-90 mu m;
preferably, the argon pressure is 0.4-0.8 Pa, the sputtering power is 180-260W, and the coating time is 2.5-3.5 h.
The surface modification method can prepare the iron/polyaniline composite coating with a double-layer structure on the surface of the magnesium alloy, and the coating has the advantages of conductivity, corrosion resistance and wear resistance and can improve the comprehensive performance of the surface of the magnesium alloy. The electrochemical deposition method has the advantages of high coating efficiency, low equipment cost and small environmental pollution; the magnetron sputtering method has the advantages of uniform and compact film layer, less internal defects, controllable process parameters and good repeatability. Through the optimized combination of the electrochemical deposition and the magnetron sputtering process parameters, the high-quality iron/polyaniline composite coating can be prepared, and meanwhile, the electrical property and the corrosion resistance of the surface of the magnesium alloy are improved, so that the magnesium alloy meets the complex and various use requirements.
The invention organically combines the electrochemical deposition and the magnetron sputtering to form the composite coating method, which has the advantages that:
(1) the inventor obtains the optimal process parameters of electrochemical deposition and magnetron sputtering through a large number of experiments: for electrochemical deposition, a cyclic voltammetry method and a three-electrode system are selected, 0.05-0.15M aniline is added into 0.1M sodium salicylate solution to prepare electrolyte, the cyclic potential range is-0.1-1.2V, the scanning rate is 45-75 mV/s, and the cycle number is 12-16; for magnetron sputtering, the argon pressure is 0.4-0.8 Pa, the sputtering power is 180-260W, and the coating time is 2.5-3.5 h. Within the process parameter range, the iron/polyaniline composite coating which is uniform, compact, high in bonding strength and has a double-layer structure can be prepared.
(2) The polyaniline coating prepared by the electrochemical deposition method can provide excellent corrosion resistance and good conductivity for the magnesium alloy, and the iron coating prepared by the magnetron sputtering method can improve the mechanical property of the surface of the magnesium alloy. The inner polyaniline coating can prevent the outer iron coating from directly contacting with the magnesium alloy to avoid galvanic corrosion, and the outer iron coating can make up for the defect of poor wear resistance of the inner polyaniline coating. The synergistic effect of iron and polyaniline can improve the corrosion resistance and the surface wear resistance of the magnesium alloy on the basis of ensuring the conductivity of the magnesium alloy. The weight loss of the magnesium alloy after surface modification is reduced by 15.1-34.1% after the magnesium alloy is soaked in 3.5% NaCl solution for 10 days; in addition, the surface abrasion loss is reduced by 8.7 to 62.3 percent.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
The invention relates to a magnesium alloy surface modification method based on an electrochemical deposition and magnetron sputtering composite coating method, which comprises the following steps:
the first step is as follows: mechanical polishing of magnesium alloy original surface
Pretreating the original surface of the magnesium alloy, grinding the magnesium alloy on 500#, 1000#, 1500# and 2000# waterproof abrasive paper respectively to remove surface oxide skin and impurities, then mechanically polishing the ground surface by using 0.3 mu m aluminum oxide polishing powder until surface scratches are removed, finally ultrasonically cleaning the magnesium alloy in absolute ethyl alcohol for 15min, and drying the magnesium alloy by cold air to obtain the polished surface of the magnesium alloy.
The second step is that: preparation of polyaniline coating on magnesium alloy surface by electrochemical deposition
Performing electrochemical deposition on the polished surface of the magnesium alloy by using a cyclic voltammetry method, selecting a three-electrode system, selecting a working electrode as the magnesium alloy, a counter electrode as a platinum sheet, a reference electrode as a saturated calomel electrode, adding a proper amount of aniline into a 0.1M sodium salicylate solution at the electrochemical deposition temperature of 25 ℃, preparing the sodium salicylate solution with the aniline concentration of 0.01-0.2M, using the sodium salicylate solution as an electrolyte, preferably 0.05-0.15M aniline, wherein the cyclic potential range is-0.4-1.5V, preferably-0.1-1.2V, the scanning speed is 35-85 mV/s, preferably 45-75 mV/s, the cycle frequency is 10-20, preferably 12-16, and obtaining the magnesium alloy with the polyaniline coating on the surface.
The third step: preparation of iron coating on magnesium alloy surface by magnetron sputtering
Putting the magnesium alloy with the polyaniline coating on the surface obtained in the second step into a cavity of a magnetron sputtering coating machine, selecting 99.9 percent of high-purity iron as a cathode target source, and controlling the vacuum degree to be 5.0 multiplied by 10-4And starting arc starting sputtering when Pa is reached, wherein the pressure of argon gas is 0.2-1.0 Pa, preferably 0.4-0.8 Pa, the sputtering power is 150-300W, preferably 180-260W, and the coating time is 2-4 h, preferably 2.5-3.5 h, so that the magnesium alloy with the iron/polyaniline composite coating on the surface is obtained.
The microstructure analysis of the iron/polyaniline composite coating on the surface of the magnesium alloy prepared by the surface modification method disclosed by the invention shows that the composite coating has a double-layer structure, the outer layer is an iron coating, the inner layer is a polyaniline coating, the coating is perfectly combined with the magnesium alloy matrix and the coatings, the coating is uniform and compact, and no obvious defect exists in the coating.
The details are described below with reference to specific embodiments.
Example 1:
the first step is as follows: mechanical polishing of magnesium alloy original surface
Pretreating the original surface of the AZ91 magnesium alloy, grinding the surface on 500#, 1000#, 1500# and 2000# water sand paper respectively to remove surface oxide skin and impurities, then mechanically polishing the ground surface by using 0.3 mu m aluminum oxide polishing powder until surface scratches are removed, finally ultrasonically cleaning the surface in absolute ethyl alcohol for 15min, and drying the surface by cold air to obtain the AZ91 magnesium alloy polished surface.
The second step is that: preparation of polyaniline coating on magnesium alloy surface by electrochemical deposition
Performing electrochemical deposition on the polished surface of the AZ91 magnesium alloy by using a cyclic voltammetry method, selecting a three-electrode system, adding a proper amount of aniline into a 0.1M sodium salicylate solution at the electrochemical deposition temperature of 25 ℃ by using a working electrode which is a magnesium alloy with the surface area of 10mm multiplied by 10mm, a counter electrode which is a platinum sheet with the surface area of 10mm multiplied by 10mm and a reference electrode which is a saturated calomel electrode, preparing the sodium salicylate solution with the aniline concentration of 0.05M as an electrolyte, wherein the cyclic potential interval is-0.1-1.2V, the scanning rate is 45mV/s, and the cycle number is 12, thus obtaining the AZ91 magnesium alloy with the polyaniline coating on the surface.
The third step: preparation of iron coating on magnesium alloy surface by magnetron sputtering
Placing the AZ91 magnesium alloy with polyaniline coating on the surface obtained in the second step into a cavity of a magnetron sputtering coating machine, selecting 99.9% high-purity iron as a cathode target source, and controlling the vacuum degree to be 5.0 multiplied by 10-4Starting arc striking and sputtering when Pa is reached, wherein the argon pressure is 0.4Pa, the sputtering power is 180W, and the film plating time is 2.5h, so that the AZ91 magnesium alloy with the iron/polyaniline composite coating on the surface is obtained.
The sample prepared in example 1 was subjected to structural analysis and performance testing:
(1) microscopic morphology of iron/polyaniline composite coating on surface of AZ91 magnesium alloy
And observing the microscopic morphology of the iron/polyaniline composite coating by adopting a scanning electron microscope. As shown in the attached figure 1, the iron/polyaniline composite coating obtained in example 1 has a double-layer structure, the outer layer is an iron coating with the thickness of about 40 microns, the inner layer is a polyaniline coating with the thickness of about 60 microns, the coating is uniform and compact, and the coating is well combined with an AZ91 magnesium alloy matrix.
(2) Comparison of corrosion properties of AZ91 magnesium alloys before and after surface modification
A soaking test is adopted to analyze the corrosion performance change of the AZ91 magnesium alloy before and after surface modification, the surface area of a sample to be tested is 10mm multiplied by 10mm, the other surfaces are sealed by chloroprene rubber, the testing temperature is 25 ℃, the sample is immersed in 3.5 percent NaCl solution for 10 days, then the sample is taken out and the surface corrosion product is cleaned, and the weight loss is weighed after drying. As can be seen from the attached figure 2, the weight loss of the AZ91 magnesium alloy before and after surface modification in example 1 is increased along with the increase of the soaking time, the change rate of the weight loss is gradually reduced, and the weight loss at the end of soaking reaches a relatively stable state. The final weight loss of the AZ91 magnesium alloy in the 10-day soaking period before and after surface modification is 45.1 +/-1.7 mg/cm2And 32.9. + -. 1.9mg/cm2The iron/polyaniline composite coating reduces the weight loss of the AZ91 magnesium alloy by 27.1 percent and improves the corrosion resistance.
(3) Comparison of surface wear morphology of AZ91 magnesium alloy before and after surface modification
And analyzing the wear resistance change of the AZ91 magnesium alloy before and after surface modification by adopting a scratch test, pressing a diamond pressure head in a rhombohedral cone shape to a certain depth along the normal direction of the surface of the sample, continuously increasing the load from 0 to 10N, simultaneously translating the pressure head on the surface of the sample along the direction vertical to the axial direction, observing the wear morphology by adopting a scanning electron microscope, and measuring the wear loss by using a white light interferometer. As can be seen from FIG. 3, in example 1, the surface of AZ91 magnesium alloy before surface modification had deep grinding marks, wide size, rough shape, and wear loss of (2.42. + -. 0.09). times.106μm3(ii) a After surface modification, AZ91 magnesium alloy has slight grinding scar, narrow size, smooth appearance and abrasion loss of (2.21 +/-0.08) multiplied by 106μm3(ii) a The iron/polyaniline composite coating reduces the abrasion loss of AZ91 magnesium alloy by 8.7%, and improves the surface abrasion resistance.
Example 2:
the first step is as follows: mechanical polishing of magnesium alloy original surface
Pretreating the original surface of the ZK61 magnesium alloy, grinding the original surface on 500#, 1000#, 1500# and 2000# water sand paper respectively to remove surface oxide skin and impurities, then mechanically polishing the ground surface by using 0.3 mu m aluminum oxide polishing powder until surface scratches are removed, finally ultrasonically cleaning the surface in absolute ethyl alcohol for 15min, and drying the surface by cold air to obtain the ZK61 magnesium alloy polished surface.
The second step is that: preparation of polyaniline coating on magnesium alloy surface by electrochemical deposition
Performing electrochemical deposition on the polished surface of the ZK61 magnesium alloy by using cyclic voltammetry, selecting a three-electrode system, adding a proper amount of aniline into a 0.1M sodium salicylate solution at the electrochemical deposition temperature of 25 ℃ by using a working electrode which is a magnesium alloy with the surface area of 10mm multiplied by 10mm, a counter electrode which is a platinum sheet with the surface area of 10mm multiplied by 10mm and a reference electrode which is a saturated calomel electrode, preparing the sodium salicylate solution with the aniline concentration of 0.10M as an electrolyte, wherein the cyclic potential interval is-0.1-1.2V, the scanning rate is 60mV/s, and the cycle number is 14, so as to obtain the ZK61 magnesium alloy with the polyaniline coating on the surface.
The third step: preparation of iron coating on magnesium alloy surface by magnetron sputtering
Putting the ZK61 magnesium alloy with polyaniline coating on the surface obtained in the second step into a cavity of a magnetron sputtering film plating machine, selecting 99.9 percent high-purity iron as a cathode target source, and controlling the vacuum degree to be 5.0 multiplied by 10-4Starting arc striking and sputtering when Pa is reached, wherein the argon pressure is 0.6Pa, the sputtering power is 220W, and the coating time is 3.0h, so that the ZK61 magnesium alloy with the iron/polyaniline composite coating on the surface is obtained.
Through structural analysis and performance detection, the thickness of the outer iron coating in the iron/polyaniline composite coating obtained in example 2 is about 60 micrometers, and the thickness of the inner polyaniline coating is about 80 micrometers; the weight loss of the ZK61 magnesium alloy after being soaked in 3.5 percent NaCl solution for 10 days before and after surface modification is respectively 32.4 +/-1.2 mg/cm2And 27.5. + -. 1.4mg/cm2The weight loss is reduced by 15.1%; in addition, the iron/polyaniline composite coating ensures that the surface abrasion loss of the ZK61 magnesium alloy is from (3.41 +/-0.19) multiplied by 106μm3Down to (1.96 +/-0.12) x 106μm3The abrasion loss decreased by 42.5%.
Example 3:
the first step is as follows: mechanical polishing of magnesium alloy original surface
Pretreating the original surface of WE54 magnesium alloy, grinding on 500#, 1000#, 1500# and 2000# water sand paper respectively to remove surface oxide skin and impurities, then mechanically polishing the ground surface by using 0.3 mu m aluminum oxide polishing powder until surface scratches are removed, finally ultrasonically cleaning in absolute ethyl alcohol for 15min, and blow-drying by cold air to obtain the WE54 magnesium alloy polished surface.
The second step is that: preparation of polyaniline coating on magnesium alloy surface by electrochemical deposition
Performing electrochemical deposition on the WE54 magnesium alloy polished surface by using cyclic voltammetry, selecting a three-electrode system, wherein a working electrode is a magnesium alloy with the surface area of 10mm multiplied by 10mm, a counter electrode is a platinum sheet with the surface area of 10mm multiplied by 10mm, a reference electrode is a saturated calomel electrode, the electrochemical deposition temperature is 25 ℃, adding a proper amount of aniline into 0.1M sodium salicylate solution, preparing the sodium salicylate solution with the aniline concentration of 0.15M as electrolyte, and obtaining the WE54 magnesium alloy with a polyaniline coating on the surface, wherein the cyclic potential range is-0.1-1.2V, the scanning rate is 75mV/s, and the cycle number is 16.
The third step: preparation of iron coating on magnesium alloy surface by magnetron sputtering
Placing the WE54 magnesium alloy with polyaniline coating on the surface obtained in the second step into a cavity of a magnetron sputtering coating machine, selecting 99.9% high-purity iron as a cathode target source, and controlling the vacuum degree to be 5.0 multiplied by 10-4And starting arc striking and sputtering when the pressure is Pa, wherein the pressure of argon is 0.8Pa, the sputtering power is 260W, and the coating time is 3.5h, so that the WE54 magnesium alloy with the iron/polyaniline composite coating on the surface is obtained.
Through structural analysis and performance detection, the thickness of the outer iron coating in the iron/polyaniline composite coating obtained in example 3 is about 90 μm, and the thickness of the inner polyaniline coating is about 120 μm; the weight loss of WE54 magnesium alloy after being soaked in 3.5% NaCl solution for 10 days before and after surface modification is 26.1 +/-0.6 mg/cm2And 17.2. + -. 1.1mg/cm2The weight loss is reduced by 34.1 percent; in addition, the WE54 magnesium alloy surface abrasion quantity is from (2.76 +/-0.09) × 10 by the iron/polyaniline composite coating6μm3Down to (1.04. + -. 0.09) × 106μm3The abrasion loss decreased by 62.3%.
The magnesium alloy with the iron/polyaniline composite coating on the surface prepared by the method has the advantages of conductivity, corrosion resistance and wear resistance, the outer iron coating provides mechanical strength, the inner polyaniline coating can prevent direct contact between iron and the magnesium alloy to avoid galvanic corrosion, and the synergistic effect of the iron coating and the polyaniline coating can improve the comprehensive performance of the surface of the magnesium alloy.
The above description is only for the preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and all equivalent structural changes made by using the contents of the present specification and the drawings, or any other related technical fields, are included in the scope of the present invention.
The invention is not the best known technology.