Titanium and titanium alloy surface corrosion-resistant coating and preparation method thereof

Abstract

The invention provides a titanium and titanium alloy surface corrosion-resistant coating and a preparation method thereof.The preparation method comprises the steps that a ceramic coating is prepared on the surface of titanium and titanium alloy through a micro-arc oxidation technology; an organic coating is prepared on the surface of the ceramic coating, and the method comprises the following specific steps that the surface of the ceramic coating is coated with an emulsion in a blade mode and air-dried, the emulsion is deionized water, polyvinyl alcohol, a defoaming agent and PTFE particles, the mass fraction of the polyvinyl alcohol is 1%-10%, the mass fraction of the defoaming agent is 1%, and the concentration of the PTFE particles is 1-10 g / L; the titanium and the titanium alloy which are subjected to emulsion blade coating and air drying are sintered and naturally cooled at the room temperature, the organic coating is obtained, and the organic coating and the ceramic coating are tightly combined to form the corrosion-resistant coating. The titanium and titanium alloy surface corrosion-resistant coating prepared by the preparation method provided by the invention has excellent electrochemical corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of coating preparation, and specifically provides a corrosion-resistant coating on the surface of titanium and titanium alloys and a preparation method thereof. Background Art

[0002] Titanium and its alloys are renowned for their low density, high specific strength, ideal corrosion resistance, exceptional heat resistance, and excellent biocompatibility. Consequently, they are widely used in industries such as aerospace, automotive, chemical, and medical. Despite their inherent corrosion resistance, titanium and its alloys fall short of meeting the requirements of certain specific environmental applications. For example, in high-temperature, high-pressure oil and gas environments, the synergistic effects of various corrosive agents place even higher demands on the corrosion resistance of titanium and its alloys. In seawater corrosive environments, the tribological and other mechanical properties of titanium and its alloys face even greater challenges. In the nuclear energy sector, the requirements for neutron absorption and corrosion resistance are paramount. In aerospace, titanium and its alloys need to be strengthened in terms of mechanical shock and thermal corrosion resistance. In medicine, a good balance between corrosion resistance and biocompatibility is crucial. Therefore, further improving their corrosion resistance is necessary to expand the application areas of titanium and its alloys. Currently, the main methods for improving the corrosion resistance of titanium and its alloys are alloying and applying protective coatings. Micro-arc oxidation is a surface engineering process derived from anodic oxidation (commonly known as plasma electrolytic oxidation). It has the advantages of high operating efficiency, simple operation, and eco-friendliness. It is also conducive to the in-situ growth of ceramic coatings and has strong adhesion to metal surfaces. It is usually used to enhance the corrosion resistance, wear resistance and biocompatibility of light metals such as aluminum, magnesium and titanium. However, although the ceramic coatings generated by micro-arc oxidation technology show excellent performance in corrosion resistance and wear resistance, the improvement in corrosion resistance is limited. It is often necessary to add other technologies to improve its corrosion resistance. In addition, there are a large number of pores and microcracks on the surface of the ceramic coating generated by micro-arc oxidation technology, which provides adhesion space for the organic coating to be scraped on its surface, greatly improving the bonding strength between the organic coating and the substrate, and solving the shortcoming that the organic coating is easy to fall off.

[0003] Therefore, how to combine micro-arc oxidation technology with scraping technology to prepare a surface coating with high corrosion resistance has become an urgent problem to be solved. Summary of the Invention

[0004] In view of this, the present invention provides a corrosion-resistant coating on the surface of titanium and titanium alloys and a preparation method thereof to solve the problems of low corrosion resistance, large self-corrosion current and low self-corrosion potential of titanium and titanium alloys.

[0005] In one aspect, the present invention provides a method for preparing a corrosion-resistant coating on the surface of titanium and titanium alloys, comprising the following steps:

[0006] A ceramic coating is prepared on the surface of titanium and titanium alloys using micro-arc oxidation technology;

[0007] An organic coating is prepared on the surface of the ceramic coating, wherein the preparation method of the organic coating is as follows:

[0008] Applying an emulsion on the surface of the ceramic coating and air-drying the emulsion, wherein the emulsion comprises deionized water + polyvinyl alcohol + defoaming agent + PTFE particles, the mass fraction of polyvinyl alcohol is 1% to 10%, the mass fraction of the defoaming agent is 1%, and the concentration of PTFE particles is 1 to 10 g / L;

[0009] The titanium and titanium alloy after being coated with the emulsion and air-dried are sintered and naturally cooled at room temperature to form the organic coating, wherein the organic coating is closely combined with the ceramic coating to form the corrosion-resistant coating.

[0010] Preferably, preparing a ceramic coating on the surface of titanium or titanium alloy using micro-arc oxidation technology includes:

[0011] Use sandpaper to polish the surface of titanium and titanium alloy to remove rust and make the surface of titanium and titanium alloy smooth;

[0012] The polished titanium and titanium alloy are cleaned, blown dry, and then placed in an electrolyte for micro-arc oxidation treatment to obtain a ceramic coating, wherein the micro-arc oxidation treatment adopts a bidirectional pulsed AC voltage with a forward voltage of 250 to 450 V, a negative voltage of 50 to 150 V, a pulse frequency of 100 to 1000 Hz, a duty cycle of 10 to 50%, and an oxidation time of 10 to 40 minutes.

[0013] More preferably, the method for cleaning the polished titanium and titanium alloy is as follows: cleaning with deionized water and alcohol in an ultrasonic cleaning machine in sequence.

[0014] More preferably, the electrolyte composition is as follows: Na2SiO3·9H2O: 5-30 g / L, KOH: 1-10 g / L.

[0015] More preferably, the ceramic coating on the surface of titanium and titanium alloy is cleaned before preparing the organic coating.

[0016] More preferably, the emulsion is applied for 1 to 5 times, and the emulsion is dried naturally at room temperature after each application cycle.

[0017] More preferably, the particle size of the PTFE particles is 1 μm.

[0018] More preferably, the sintering conditions for the titanium and titanium alloy after the emulsion is applied and air-dried are as follows: sintering temperature: 300-360° C.; sintering time: 10-60 min.

[0019] More preferably, the thickness of the ceramic coating is 2 to 11 μm, and the thickness of the organic coating is 2 to 330 μm.

[0020] The present invention also provides a corrosion-resistant coating on the surface of titanium and titanium alloys, which is prepared by adopting the above-mentioned method for preparing the corrosion-resistant coating on the surface of titanium and titanium alloys.

[0021] Among them, under the condition of immersion in 3.5wt% NaCl solution at room temperature, the self-corrosion current and self-corrosion potential of the corrosion-resistant coating on the surface of titanium and titanium alloy prepared by the method provided by the present invention are better than those of the substrate, and the self-corrosion current is more than half the magnitude of that of the substrate.

[0022] The present invention provides a method for preparing a corrosion-resistant coating on the surface of titanium and titanium alloys. The method comprises the following steps: first preparing a layer of micro-arc oxidation ceramic coating (priming coating) on the surface of titanium and titanium alloys; then, applying an emulsion on the surface of the micro-arc oxidation ceramic coating and air-drying and sintering the coating to form an organic coating (strong corrosion-resistant coating); the organic coating and the ceramic coating are tightly combined to form an integrated corrosion-resistant coating; wherein, by preparing the micro-arc oxidation ceramic coating, the corrosion resistance and wear resistance of the surface of titanium and titanium alloys can be greatly improved; and at the same time, a supporting space is provided for the organic coating, which is beneficial to improving the bonding strength of the organic coating and making the organic coating less likely to crack and fall off, thereby ensuring the sealing effect of the surface of titanium and titanium alloys; and the corrosion resistance of the surface of titanium and titanium alloys can be improved by preparing the organic coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is an experimental flow chart of an embodiment;

[0024] Figure 2 Polarization curves of the samples prepared in Examples 1 to 4 and the samples in Comparative Examples 1 and 2 were obtained by electrochemical testing in a 3.5 wt % NaCl solution at room temperature; DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to specific embodiments.

[0026] The present invention provides a method for preparing a corrosion-resistant coating on the surface of titanium and titanium alloys, comprising:

[0027] A ceramic coating is prepared on the surface of titanium and titanium alloys using micro-arc oxidation technology;

[0028] An organic coating is prepared on the surface of the ceramic coating, wherein the preparation method of the organic coating is as follows:

[0029] A scraping device is used to scrape an emulsion on the surface of the ceramic coating and air-dry it, wherein the emulsion is deionized water + polyvinyl alcohol + defoamer + PTFE particles, the mass fraction of polyvinyl alcohol is 1% to 10%, the mass fraction of the defoamer is 1%, and the concentration of PTFE particles is 1 to 10 g / L. The number of scraping cycles of the emulsion is 1 to 5 times. Preferably, during the process of scraping the emulsion, it is naturally air-dried at room temperature after each 2 scrapings, which is one scraping cycle;

[0030] The titanium and titanium alloy after being coated with the emulsion and air-dried are sintered and naturally cooled at room temperature to form the organic coating, wherein the organic coating is closely combined with the ceramic coating to form the corrosion-resistant coating.

[0031] The method for preparing the corrosion-resistant coating on the surface of titanium and titanium alloys comprises the following steps: first preparing a layer of micro-arc oxidation ceramic coating (priming coating) on the surface of titanium and titanium alloys; then applying emulsion on the surface of the micro-arc oxidation ceramic coating and air-drying and sintering the coating to form an organic coating (strong corrosion-resistant coating); the organic coating and the ceramic coating are tightly combined to form an integrated corrosion-resistant coating; wherein, by preparing the micro-arc oxidation ceramic coating, the corrosion resistance and wear resistance of the surface of titanium and titanium alloys can be greatly improved; and at the same time, a supporting space is provided for the organic coating, which is beneficial to improving the bonding strength of the organic coating and making the organic coating less likely to crack and fall off, thereby ensuring the sealing effect of the surface of titanium and titanium alloys; and the corrosion resistance of the surface of titanium and titanium alloys can be improved by preparing the organic coating.

[0032] Preferably, preparing a ceramic coating on the surface of titanium or titanium alloy using micro-arc oxidation technology includes:

[0033] Grinding the surface of titanium and titanium alloys to remove rust and make the surface of titanium and titanium alloys smooth;

[0034] The polished titanium and titanium alloy are cleaned, blown dry and weighed, and then placed in an electrolyte for micro-arc oxidation treatment to obtain a ceramic coating, wherein the micro-arc oxidation treatment adopts a bidirectional pulsed AC voltage, with a forward voltage of 300-400V, a negative voltage of 50-150V, a pulse frequency of 100-1000Hz, a duty cycle of 10-50%, and an oxidation time of 10-40min. Deionized water and alcohol can be used for ultrasonic cleaning.

[0035] Rust removal treatment can remove surface defects of titanium and titanium alloys and thoroughly clean their surfaces, which is beneficial to improving the flatness and molding quality of subsequent ceramic coatings.

[0036] More preferably, the electrolyte composition is as follows: Na2SiO3·9H2O: 5-30 g / L, KOH: 1-10 g / L.

[0037] It is further preferred that before preparing the organic coating, the ceramic coating on the surface of titanium and titanium alloy is cleaned to improve the cleanliness of the surface of the titanium and titanium alloy ceramic coating, which is beneficial to improving the molding quality of the subsequent surface scraping technology to scrape a layer of organic coating on the surface of the titanium and titanium alloy ceramic coating. Preferably, the titanium and titanium alloy ceramic coating is ultrasonically vibrated and cleaned with a cleaning solvent. Compared with other cleaning methods, ultrasonic vibration cleaning has a better cleaning effect. It mainly uses cleaning solvent and water as the medium, and relies on the oscillation generated by ultrasonic waves in the liquid to remove dirt to achieve the cleaning purpose, which is beneficial to achieve thorough cleaning of the surface of the titanium and titanium alloy ceramic coating, so as to improve the molding quality of the subsequent organic coating.

[0038] More preferably, the sintering conditions for the titanium and titanium alloy after the emulsion is applied and air-dried are as follows: sintering temperature: 300-360° C.; sintering time: 10-60 min.

[0039] Among them, the sintering temperature affects the quality of the coating. If the sintering temperature is low, the particles soften and cannot block some smaller pores in the coating, which will affect the stability of the surface state of the bonding coating; if the sintering temperature is high, it will exceed the standard reaction temperature, causing the PTFE particles in the coating to volatilize during the sintering stage, affecting its corrosion resistance. Therefore, 300-360℃ is the optimal sintering temperature.

[0040] In addition, the room temperature natural cooling treatment can directly cool the sintering temperature to room temperature. The cooling process is conducive to closely combining the organic coating and the ceramic coating together to form an integrated coating with corrosion resistance properties superior to that of the substrate.

[0041] Taking into account the small installation gap of certain specific parts, the organic coating can exhibit high corrosion resistance at around 5 μm. However, since the organic coating is relatively soft, as the coating thickness increases, although the corrosion resistance effect can be guaranteed, the coating integrity gradually decreases. Therefore, the thickness of the ceramic coating is controlled to be 2 to 11 μm, and the thickness of the organic coating is controlled to be 2 to 330 μm.

[0042] The present invention also provides a corrosion-resistant coating on the surface of titanium and titanium alloys, which is prepared by adopting the above-mentioned method for preparing the corrosion-resistant coating on the surface of titanium and titanium alloys.

[0043] Among them, under the condition of immersion in 3.5wt% NaCl solution at room temperature, the self-corrosion current and self-corrosion potential of the corrosion-resistant coating on the surface of titanium and titanium alloy prepared by the method provided by the present invention are better than those of the substrate, and the self-corrosion current is more than half the magnitude of that of the substrate.

[0044] Example 1

[0045] A method for preparing a corrosion-resistant coating on the surface of titanium and titanium alloys, such as Figure 1 The specific steps are as follows:

[0046] (1) Preparation of ceramic coating, the process flow is as follows:

[0047] 1) Incoming parts inspection and drilling: Check whether there are cracks or other defects on the surface of the TA1 substrate. Make the TA1 substrate into a 15×20×2mm square plate and drill holes on the top of the substrate to prepare for subsequent processing;

[0048] 2) Polishing the TA1 substrate: Polish the substrate with 180#, 320#, 600#, 800#, and 1000# sandpaper;

[0049] 3) Cleaning: The polished TA1 substrate was ultrasonically cleaned in deionized water and alcohol for 5 minutes to remove surface dirt.

[0050] 4) Weighing: Weigh the TA1 substrate using an analytical balance and set aside;

[0051] 5) Prepare electrolyte: Prepare electrolyte with sodium silicate nonahydrate Na2SiO3·9H2O (20 g / L) and potassium hydroxide KOH (3 g / L) as electrolyte, place in electrolytic cell and set aside;

[0052] 6) Micro-arc oxidation: Place the polished TA1 substrate in the prepared electrolyte, connect the TA1 substrate to the positive pole of the power supply, and connect the electrolytic cell to the negative pole of the power supply; adjust the oxidation power supply parameters to a positive voltage of 450V, a negative voltage of 100V, a frequency of 200Hz, a duty cycle of 10%, and an oxidation time of 20min. After checking that everything is correct, start the oxidation;

[0053] 7) Weighing and measuring after cleaning: Rinse the oxidized sample with deionized water and then ultrasonically clean it in alcohol for 5 minutes. After weighing it using an analytical balance, measure the sample thickness and film thickness at five different points using a micrometer and eddy current thickness gauge, and take the average value. Set the sample aside for later use.

[0054] 8) The thickness of the ceramic coating is 9.22 μm and the weight gain is 6.5×10 -3 g, and the unit weight gain is 8.76×10 -6 g·cm -2 ;

[0055] (2) Preparation of organic coating, the process flow is as follows:

[0056] 1) Scrape coating: Place the sample after forming the ceramic coating in the scraper coater and adjust the machine parameters: scrape coating cycle number 2, polyvinyl alcohol mass fraction 3%, PTFE particle concentration (particle size 1μm) 6g / L, add 1% defoamer by mass, mix well and then scrape coat;

[0057] 2) Air drying: After one cycle of scraping, the sample is naturally air-dried at room temperature for 30 minutes, and then scraped again after air drying. Repeat the above steps to achieve the number of scraping cycles corresponding to the scheme;

[0058] 3) Sintering: Heat the resistance furnace to 340°C, place the air-dried sample in the resistance furnace and sinter for 10 minutes, then cool it to room temperature.

[0059] 4) Measure thickness: Measure the thickness of the sample at five different points using a micrometer screw and take the average value. Set the sample aside for later use.

[0060] 4) The thickness of the organic coating is 2 μm and the weight gain is 2.2×10 -3 g, and the unit weight gain is 2.96×10 -6 g·cm -2 ;

[0061] (3) Electrochemical test:

[0062] 1) Use a copper wire with a diameter of 2 mm to connect the prepared sample and use K704N silicone rubber produced by Kraft to seal the sample, leaving 1 cm 2 The exposed area was left to stand for 24 hours.

[0063] 2) An Autolab electrochemical workstation manufactured by Metrohm (Switzerland) was used. A three-electrode system was employed, with the coated sample serving as the working electrode, a saturated calomel bridge electrode serving as the reference electrode, and a platinum electrode serving as the counter electrode. The sample was immersed in a 3.5 wt% NaCl solution at room temperature. Prior to the experiment, the sample was immersed in the solution for 30 minutes. After the open circuit potential (OCP) stabilized, the polarization curve was tested. Potentiodynamic polarization testing was performed at a rate of 1.0 mV / s, scanning from -0.5 V to 1.0 V (relative to the open circuit potential).

[0064] 3) Use Origin software to process the data, draw polarization curves, and calculate the self-corrosion potential and self-corrosion current.

[0065] Example 2

[0066] A method for preparing a corrosion-resistant coating on the surface of titanium and titanium alloys, such as Figure 1 The specific steps are as follows:

[0067] (1) Preparation of ceramic coating, the process flow is as follows:

[0068] 1) Incoming parts inspection and drilling processing: Check whether there are cracks or other defects on the substrate surface, make the TA15 substrate into a 15×20×2mm square plate and drill holes on the TA15 substrate to prepare for subsequent processing;

[0069] 2) Grinding the substrate: Grind the TA15 substrate with 180#, 320#, 600#, 800#, and 1000# sandpaper;

[0070] 3) Cleaning: The polished TA15 substrate was ultrasonically cleaned in deionized water and alcohol for 5 minutes to remove surface dirt.

[0071] 4) Weighing: Weigh the TA15 substrate using an analytical balance and set aside;

[0072] 5) Prepare electrolyte: Prepare electrolyte with sodium silicate nonahydrate Na2SiO3·9H2O (10 g / L) and potassium hydroxide KOH (1.5 g / L) as electrolyte, place in electrolytic cell and set aside;

[0073] 6) Micro-arc oxidation: Place the polished TA15 substrate in the prepared electrolyte, connect the substrate to the positive pole of the power supply, and connect the electrolytic cell to the negative pole of the power supply; adjust the oxidation power supply parameters to 250V positive voltage, 80V negative voltage, 1000Hz frequency, 30% duty cycle, and 15min oxidation time. After checking that everything is correct, start oxidation;

[0074] 7) Weighing and measuring after cleaning: Rinse the oxidized substrate with deionized water and then ultrasonically clean it in alcohol for 5 minutes. After weighing it using an analytical balance, measure the sample thickness and film thickness at five different points using a micrometer and eddy current thickness gauge, and take the average value. Set the sample aside for later use.

[0075] 8) The thickness of the ceramic coating is 7.64 μm and the weight gain is 1.4×10 -3 g, the unit weight gain is 1.88×10 -6 g·cm -2 ;

[0076] (2) Preparation of organic coating, the process flow is as follows:

[0077] 1) Scrape coating: Place the sample after forming the ceramic coating in the scraper coater and adjust the machine parameters: scrape coating cycle 3, polyvinyl alcohol mass fraction 5%, PTFE particle concentration (particle size 1μm) 9g / L, add 1% defoamer by mass, mix well and then scrape coat;

[0078] 2) Air drying: After one cycle of scraping, the sample is naturally air-dried at room temperature for 30 minutes, and then scraped again after air drying. Repeat the above steps to achieve the number of scraping cycles corresponding to the scheme;

[0079] 3) Sintering: Heat the resistance furnace to 300°C, place the air-dried sample in the resistance furnace and sinter for 10 minutes, then cool it to room temperature.

[0080] 4) Measurement and weighing: Select five different points on the sample and measure the sample thickness with a screw micrometer to obtain the average value. Place the sample aside for later use.

[0081] 5) The thickness of the organic coating was 74.72 μm and the weight gain was 4.1×10 -3 g, and the unit weight gain is 5.52×10 -6 g·cm -2 ;

[0082] (3) Electrochemical test:

[0083] 1) Use a copper wire with a diameter of 2 mm to connect the prepared sample and use K704N silicone rubber produced by Kraft to seal the sample, leaving 1 cm 2 The exposed area was left to stand for 24 hours.

[0084] 2) An Autolab electrochemical workstation manufactured by Metrohm (Switzerland) was used. A three-electrode system was employed, with the coated sample serving as the working electrode, a saturated calomel bridge electrode serving as the reference electrode, and a platinum electrode serving as the counter electrode. The sample was immersed in a 3.5 wt% NaCl solution at room temperature. Prior to the experiment, the sample was immersed in the solution for 30 minutes. After the open circuit potential (OCP) stabilized, the polarization curve was tested. Potentiodynamic polarization testing was performed at a rate of 1.0 mV / s, scanning from -0.5 V to 1.0 V (relative to the open circuit potential).

[0085] 3) Use Origin software to process the data, draw polarization curves, and calculate the self-corrosion potential and self-corrosion current.

[0086] Example 3

[0087] A method for preparing a corrosion-resistant coating on the surface of titanium and titanium alloys, such as Figure 1 The specific steps are as follows:

[0088] (1) Preparation of ceramic coating, the process flow is as follows:

[0089] 1) Parts inspection and drilling: Check whether there are cracks or other defects on the surface of the TA15 substrate. Make the TA15 substrate into a 15×20×2mm square plate and drill holes on the top of the substrate to prepare for subsequent processing;

[0090] 2) Polishing the TA15 substrate: Polish the substrate with 180#, 320#, 600#, 800#, and 1000# sandpaper;

[0091] 3) Cleaning: The polished TA15 substrate was ultrasonically cleaned in deionized water and alcohol for 5 minutes to remove surface dirt.

[0092] 4) Weighing: Prepare an electrolyte solution of TA15 substrate using sodium silicate nonahydrate Na2SiO3·9H2O (15 g / L) and potassium hydroxide KOH (2 g / L) as electrolyte, place the substrate in an electrolytic cell, and set aside.

[0093] 6) Micro-arc oxidation: Place the polished substrate in the prepared electrolyte, connect the substrate to the positive pole of the power supply, and connect the electrolytic cell to the negative pole of the power supply; adjust the oxidation power supply parameters to 350V positive voltage, 120V negative voltage, 600Hz frequency, 20% duty cycle, and 10min oxidation time. After checking that everything is correct, start oxidation;

[0094] 7) Weighing and measuring after cleaning: Rinse the oxidized sample with deionized water and then ultrasonically clean it in alcohol for 5 minutes. After weighing it using an analytical balance, measure the sample thickness and film thickness at five different points using a micrometer and eddy current thickness gauge, and take the average value. Set the sample aside for later use.

[0095] 8) The thickness of the ceramic coating is 10.76 μm and the weight gain is 3.4×10 -3 g, and the unit weight gain is 3.94×10 -6 g·cm -2 ;

[0096] (2) Preparation of organic coating, the process flow is as follows:

[0097] 1) Scrape coating: Place the sample after forming the ceramic coating in the scraper coater and adjust the machine parameters: scrape coating cycle 4, polyvinyl alcohol mass fraction 7%, PTFE particle concentration (particle size 1μm) 3g / L, add 1% defoamer by mass, mix well and then scrape coat;

[0098] 2) Air drying: After one cycle of scraping, the sample is naturally air-dried at room temperature for 30 minutes, and then scraped again after air drying. Repeat the above steps to achieve the number of scraping cycles corresponding to the scheme;

[0099] 3) Sintering: Heat the resistance furnace to 320°C, place the air-dried sample in the resistance furnace and sinter for 10 minutes, then cool it to room temperature;

[0100] 4) Measurement and weighing: Measure the thickness of the sample at five different points using a micrometer screw, take the average value, and weigh it. Set the sample aside for later use.

[0101] 5) The thickness of the organic coating is 83 μm and the weight gain is 7.5×10 -3 g, and the unit weight gain is 8.68×10 -6 g·cm -2 ;

[0102] (3) Electrochemical test:

[0103] 1) Use a copper wire with a diameter of 2 mm to connect the prepared sample and use K704N silicone rubber produced by Kraft to seal the sample, leaving 1 cm 2 The exposed area was left to stand for 24 hours.

[0104] 2) An Autolab electrochemical workstation manufactured by Metrohm (Switzerland) was used. A three-electrode system was employed, with the coated sample serving as the working electrode, a saturated calomel bridge electrode serving as the reference electrode, and a platinum electrode serving as the counter electrode. The sample was immersed in a 3.5 wt% NaCl solution at room temperature. Prior to the experiment, the sample was immersed in the solution for 30 minutes. After the open circuit potential (OCP) stabilized, the polarization curve was tested. Potentiodynamic polarization testing was performed at a rate of 1.0 mV / s, scanning from -0.5 V to 1.0 V (relative to the open circuit potential).

[0105] 3) Use Origin software to process the data, draw polarization curves, and calculate the self-corrosion potential and self-corrosion current.

[0106] Example 4

[0107] A method for preparing a corrosion-resistant coating on the surface of titanium and titanium alloys, such as Figure 1 The specific steps are as follows:

[0108] (1) Preparation of ceramic coating, the process flow is as follows:

[0109] 1) Incoming parts inspection and drilling: Check whether there are cracks or other defects on the surface of the TA1 substrate. Make the TA1 substrate into a 15×20×2mm square plate and drill holes on the top of the substrate to prepare for subsequent processing;

[0110] 2) Polishing the TA1 substrate: Polish the substrate with 180#, 320#, 600#, 800#, and 1000# sandpaper;

[0111] 3) Cleaning: The polished TA1 substrate was ultrasonically cleaned in deionized water and alcohol for 5 minutes to remove surface dirt.

[0112] 4) Weighing: Prepare an electrolyte solution of TA1 substrate using sodium silicate nonahydrate Na2SiO3·9H2O (15 g / L) and potassium hydroxide KOH (2 g / L) as electrolyte, place the substrate in an electrolytic cell, and set aside.

[0113] 6) Micro-arc oxidation: Place the polished TA1 substrate in the prepared electrolyte, connect the substrate to the positive pole of the power supply, and connect the electrolytic cell to the negative pole of the power supply; adjust the oxidation power supply parameters to 400V positive voltage, 150V negative voltage, 1000Hz frequency, 20% duty cycle, and 15min oxidation time. After checking that everything is correct, start the oxidation process;

[0114] 7) Weighing and measuring after cleaning: Rinse the oxidized sample with deionized water and then ultrasonically clean it in alcohol for 5 minutes. After weighing it using an analytical balance, measure the sample thickness and film thickness at five different points using a micrometer and eddy current thickness gauge, and take the average value. Set the sample aside for later use.

[0115] 8) The thickness of the ceramic coating is 2.65 μm and the weight gain is 1.9×10 -3 g, and the unit weight gain is 2.77×10 -6 g·cm -2 ;

[0116] (2) Preparation of organic coating, the process flow is as follows:

[0117] 1) Scrape coating: Place the sample after forming the ceramic coating in the scraper coater and adjust the machine parameters: scrape coating cycle 4, polyvinyl alcohol mass fraction 5%, PTFE particle (particle size 1μm) concentration 6g / L, add 1% defoamer by mass, mix well and then scrape;

[0118] 2) Air drying: After one cycle of scraping, the sample is naturally air-dried at room temperature for 30 minutes, and then scraped again after air drying. Repeat the above steps to achieve the number of scraping cycles corresponding to the scheme;

[0119] 3) Sintering: Heat the resistance furnace to 330°C, place the air-dried sample in the resistance furnace and sinter for 10 minutes, then cool it to room temperature;

[0120] 4) Measurement and weighing: Measure the thickness of the sample at five different points using a micrometer screw, take the average value, and weigh it. Set the sample aside for later use.

[0121] 5) The thickness of the organic coating is 328 μm and the weight gain is 4.2×10 -3 g, and the unit weight gain is 6.13×10 -6 g·cm -2 ;

[0122] (3) Electrochemical test:

[0123] 1) Use a copper wire with a diameter of 2 mm to connect the prepared sample and use K704N silicone rubber produced by Kraft to seal the sample, leaving 1 cm 2 The exposed area was left to stand for 24 hours.

[0124] 2) An Autolab electrochemical workstation manufactured by Metrohm (Switzerland) was used. A three-electrode system was employed, with the coated sample serving as the working electrode, a saturated calomel bridge electrode serving as the reference electrode, and a platinum electrode serving as the counter electrode. The sample was immersed in a 3.5 wt% NaCl solution at room temperature. Prior to the experiment, the sample was immersed in the solution for 30 minutes. After the open circuit potential (OCP) stabilized, the polarization curve was tested. Potentiodynamic polarization testing was performed at a rate of 1.0 mV / s, scanning from -0.5 V to 1.0 V (relative to the open circuit potential).

[0125] 3) Use Origin software to process the data, draw polarization curves, and calculate the self-corrosion potential and self-corrosion current.

[0126] Comparative Example 1

[0127] The specific steps of room temperature electrochemical test of TA1 sample are as follows:

[0128] (1) TA1 pretreatment steps are:

[0129] 1) Incoming parts inspection and drilling processing: Check whether there are cracks or other defects on the surface of the substrate, make the substrate into a 15×20×2mm square plate and drill holes on the top of the substrate to prepare for subsequent processing 5;

[0130] 2) Grinding the substrate: Grind the substrate with 180#, 320#, 600#, 800#, or 1000# sandpaper;

[0131] 3) Cleaning: The polished substrate was ultrasonically cleaned in deionized water and alcohol for 5 minutes to remove surface dirt;

[0132] 4) Weighing: Weigh the substrate using an analytical balance and set aside;

[0133] (2) Electrochemical test:

[0134] 1) Use a copper wire with a diameter of 2 mm to connect the prepared sample and use K704N silicone rubber produced by Kraft to seal the sample, leaving 1 cm 2 The exposed area was left to stand for 24 hours.

[0135] 2) An Autolab electrochemical workstation manufactured by Metrohm (Switzerland) was used. A three-electrode system was employed, with the coated sample serving as the working electrode, a saturated calomel bridge electrode serving as the reference electrode, and a platinum electrode serving as the counter electrode. The sample was immersed in a 3.5 wt% NaCl solution at room temperature. Prior to the experiment, the sample was immersed in the solution for 30 minutes. After the open circuit potential (OCP) stabilized, the polarization curve was tested. Potentiodynamic polarization testing was performed at a rate of 1.0 mV / s, scanning from -0.5 V to 1.0 V (relative to the open circuit potential).

[0136] 3) Use Origin software to process the data, draw polarization curves, and calculate the self-corrosion potential and self-corrosion current.

[0137] Comparative Example 2

[0138] The specific steps of room temperature electrochemical test of TA15 sample are as follows:

[0139] (1) TA15 pretreatment steps are:

[0140] 1) Inspection and drilling of incoming parts: Check whether there are cracks or other defects on the surface of the substrate, make the substrate into a 15×20×2mm square plate and drill holes on the top of the substrate to prepare for subsequent processing;

[0141] 2) Grinding the substrate: Grind the substrate with 180#, 320#, 600#, 800#, or 1000# sandpaper;

[0142] 3) Cleaning: The polished substrate was ultrasonically cleaned in deionized water and alcohol for 5 minutes to remove surface dirt;

[0143] 4) Weighing: Weigh the substrate using an analytical balance and set aside;

[0144] (2) Electrochemical test:

[0145] 1) Use a copper wire with a diameter of 2 mm to connect the prepared sample and use K704N silicone rubber produced by Kraft to seal the sample, leaving 1 cm 2 The exposed area was left to stand for 24 hours.

[0146] 2) An Autolab electrochemical workstation manufactured by Metrohm (Switzerland) was used. A three-electrode system was employed, with the coated sample serving as the working electrode, a saturated calomel bridge electrode serving as the reference electrode, and a platinum electrode serving as the counter electrode. The sample was immersed in a 3.5 wt% NaCl solution at room temperature. Prior to the experiment, the sample was immersed in the solution for 30 minutes. After the open circuit potential (OCP) stabilized, the polarization curve was tested. Potentiodynamic polarization testing was performed at a rate of 1.0 mV / s, scanning from -0.5 V to 1.0 V (relative to the open circuit potential).

[0147] 3) Use Origin software to process the data, draw polarization curves, and calculate the self-corrosion potential and self-corrosion current.

[0148] The corrosion resistance of the samples prepared in Examples 1 to 4 and the samples in Comparative Examples 1 and 2 was evaluated by electrochemical testing. Figure 1Polarization curves of the samples prepared in Examples 1 to 4 and the samples of Comparative Examples 1 and 2 in 3.5 wt% NaCl solution at room temperature are given. Table 1 shows the self-corrosion potential and self-corrosion current calculated from the polarization curves using the Tafel extrapolation method for the samples prepared in Examples 1 to 4 and the samples of Comparative Examples 1 and 2. Figure 1 As shown in Table 1, in the electrochemical test in 3.5wt% NaCl solution at room temperature, the polarization curve of the coating prepared by the method proposed in the present invention is generally located in the upper left corner, and its self-corrosion potential is higher and its self-corrosion current is smaller, indicating that its corrosion resistance is better. Its self-corrosion potential is -0.239~0.171V, and its self-corrosion current is 2.52×10 -9 ~2.67×10 -8 A / cm 2 , which is about 3.52% to 43.66% of the substrate, while the polarization curves of Comparative Examples 1 and 2 are located in the lower right corner, and their corrosion resistance is worse than that of the coating prepared by the method proposed in the present invention.

[0149] The following table is a comparison table of the self-corrosion potential and self-corrosion current of the samples prepared in Examples 1 to 4 and the samples of Comparative Examples 1 and 2.

[0150] Table 1

[0151]

Claims

1. A method for preparing a corrosion-resistant coating on the surface of titanium and titanium alloys, characterized in that: The steps include: A ceramic coating is prepared on the surface of titanium and titanium alloys using micro-arc oxidation technology; An organic coating is prepared on the surface of the ceramic coating, wherein the preparation method of the organic coating is as follows: Applying an emulsion on the surface of the ceramic coating and air-drying the emulsion, wherein the emulsion comprises deionized water + polyvinyl alcohol + defoaming agent + PTFE particles, the mass fraction of polyvinyl alcohol is 1% to 10%, the mass fraction of the defoaming agent is 1%, and the concentration of PTFE particles is 1 to 10 g / L; The titanium and titanium alloy after being coated with the emulsion and air-dried are sintered and naturally cooled at room temperature to form the organic coating, wherein the organic coating is closely combined with the ceramic coating to form the corrosion-resistant coating.

2. The method for preparing the corrosion-resistant coating on the surface of titanium and titanium alloy according to claim 1, characterized in that: The use of micro-arc oxidation technology to prepare a ceramic coating on the surface of titanium and titanium alloys includes: Use sandpaper to polish the surface of titanium and titanium alloy to remove rust and make the surface of titanium and titanium alloy smooth; The polished titanium and titanium alloy are cleaned, blown dry, and then placed in an electrolyte for micro-arc oxidation treatment to obtain a ceramic coating, wherein the micro-arc oxidation treatment adopts a bidirectional pulsed AC voltage with a forward voltage of 250 to 450 V, a negative voltage of 50 to 150 V, a pulse frequency of 100 to 1000 Hz, a duty cycle of 10 to 50%, and an oxidation time of 10 to 40 minutes.

3. The method for preparing the corrosion-resistant coating on the surface of titanium and titanium alloy according to claim 2, characterized in that: The method for cleaning polished titanium and titanium alloys is as follows: use deionized water and alcohol to clean in an ultrasonic cleaning machine.

4. The method for preparing the corrosion-resistant coating on the surface of titanium and titanium alloy according to claim 2, characterized in that: The electrolyte composition is as follows: Na2SiO3·9H2O: 5-30 g / L, KOH: 1-10 g / L.

5. The method for preparing the corrosion-resistant coating on the surface of titanium and titanium alloy according to claim 1, characterized in that: Before preparing the organic coating, the ceramic coating on the surface of titanium and titanium alloy is cleaned.

6. The method for preparing corrosion-resistant coating on titanium and titanium alloy surfaces according to claim 1, characterized in that: The number of cycles for scraping the emulsion is 1 to 5 times, and it is naturally air-dried at room temperature after each scraping cycle.

7. The method for preparing corrosion-resistant coating on titanium and titanium alloy surfaces according to claim 1, characterized in that: The particle size of the PTFE particles is 1 μm.

8. The method for preparing corrosion-resistant coating on the surface of titanium and titanium alloy according to claim 1, characterized in that: The sintering conditions for titanium and titanium alloys after the emulsion is applied and air-dried are as follows: sintering temperature: 300-360° C.; sintering time: 10-60 min.

9. The method for preparing corrosion-resistant coating on titanium and titanium alloy surfaces according to claim 1, characterized in that: The thickness of the ceramic coating is 2 to 11 μm, and the thickness of the organic coating is 2 to 330 μm.

10. A corrosion-resistant coating on the surface of titanium and titanium alloys, characterized by: The titanium and titanium alloy surface corrosion-resistant coating is prepared by the method for preparing the corrosion-resistant coating on the surface of titanium and titanium alloy according to any one of claims 1 to 9.

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