Alloy surface selective micro-arc oxidation method

Abstract

The invention provides an alloy surface selective micro-arc oxidation method which comprises the following steps: pretreating an alloy surface to remove a passivation film on the alloy surface; high-temperature-resistant insulating paint is brushed on the area, not needing micro-arc oxidation, of the pretreated alloy surface, and a high-temperature-resistant insulating hydrophobic coating is formed; carrying out micro-arc oxidation treatment on the alloy on which the high-temperature-resistant insulating hydrophobic coating is formed; and the high-temperature-resistant insulating hydrophobic coating is removed, and the alloy subjected to selective micro-arc oxidation is obtained. According to the selective micro-arc oxidation method for the alloy surface, any area of the surfaces of metals such as aluminum, magnesium and titanium and alloys thereof can be protected, the purpose of selective micro-arc oxidation is achieved, and actual requirements are met.

Description

Technical Field

[0001] The invention relates to the technical field of coating preparation, and specifically provides a method for selective micro-arc oxidation of an alloy surface. Background Art

[0002] Micro-arc oxidation technology is a technology developed on the basis of anodizing. Its working principle is to rely on the matching and adjustment of electrolyte and electrical parameters. Under the instantaneous high temperature and high pressure generated by arc discharge, a modified ceramic coating mainly composed of matrix metal oxide and supplemented by electrolyte components grows on the surface of metals such as aluminum, magnesium, titanium and their alloys. The thickness of this coating is relatively thick, up to hundreds of microns, and its corrosion resistance and wear resistance are often better than traditional anodizing coatings.

[0003] In the actual production process, some special parts of most parts require micro-arc oxidation technology to improve their specific performance, while other parts need to maintain their original state. In order to achieve the above purpose, it is urgent to propose a selective micro-arc oxidation method for alloy surface. Summary of the invention

[0004] In view of this, the present invention provides a method for selective micro-arc oxidation of an alloy surface, so as to perform micro-arc oxidation on a specific area as required.

[0005] The present invention provides a method for selective micro-arc oxidation of an alloy surface, comprising:

[0006] Pre-treating the alloy surface to remove the passivation film on the alloy surface;

[0007] Apply high temperature resistant insulating paint on the pretreated alloy surface area that does not require micro-arc oxidation to form a high temperature resistant insulating hydrophobic coating;

[0008] Micro-arc oxidation treatment is performed on the alloy forming the high temperature resistant insulating hydrophobic coating;

[0009] The high temperature resistant insulating hydrophobic coating on the surface of the alloy after micro-arc oxidation treatment is removed to obtain the alloy after selective micro-arc oxidation.

[0010] Preferably, pre-treating the alloy surface includes grinding and cleaning the alloy surface.

[0011] Further preferably, after applying the high temperature resistant insulating paint, the alloy is air-dried at room temperature or baked at low temperature to form a layer of high temperature resistant insulating hydrophobic coating.

[0012] Further preferably, the micro-arc oxidation treatment adopts a bidirectional pulsed AC voltage, with a forward voltage of 300-420V, a negative voltage of 60-160V, a pulse frequency of 100-1000Hz, a duty cycle of 10-50%, an oxidation time of 10-50min, and an electrolyte composition as follows: Na2SiO3·9H2O: 20-40g / l, (NaPO3)6: 5-15g / l, Na2MoO4: 2-6g / l, KOH: 2-6g / l.

[0013] More preferably, a paint remover is used to remove the high temperature resistant insulating hydrophobic coating on the surface of the alloy.

[0014] The present invention provides a method for selective micro-arc oxidation of an alloy surface. By brushing high-temperature resistant insulating paint on the area on the alloy surface that does not require micro-arc oxidation, the painted part of the alloy can be effectively protected from oxidation during the micro-arc oxidation process, thereby ultimately achieving the purpose of selective micro-arc oxidation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 are photographs of the aluminum alloy parts in Example 1 at different stages, wherein (a) is a photograph before applying high temperature resistant insulating paint, (b) is a photograph after applying high temperature resistant insulating paint to a part of the surface and drying it, (c) is a photograph after micro-arc oxidation, and (d) is a photograph after removing the insulating paint;

[0016] Figure 2 are photographs of the magnesium alloy parts in Example 2 at different stages, wherein (a) is a photograph before applying high temperature resistant insulating paint, (b) is a photograph after applying high temperature resistant insulating paint to a part of the surface and drying it, (c) is a photograph after micro-arc oxidation, and (d) is a photograph after removing the insulating paint;

[0017] Figure 3 These are photographs of the titanium alloy parts in Example 3 at different stages, wherein (a) is a photograph before applying high-temperature resistant insulating paint, (b) is a photograph after applying high-temperature resistant insulating paint to a partial area of ​​the surface and drying it, (c) is a photograph after micro-arc oxidation, and (d) is a photograph after removing the insulating paint. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with specific embodiments.

[0019] The present invention provides a method for selective micro-arc oxidation of an alloy surface, comprising:

[0020] Pre-treating the alloy surface to remove the passivation film on the alloy surface;

[0021] Apply high temperature resistant insulating paint on the pretreated alloy surface area that does not require micro-arc oxidation to form a high temperature resistant insulating hydrophobic coating;

[0022] Micro-arc oxidation treatment is performed on the alloy forming the high temperature resistant insulating hydrophobic coating;

[0023] The high temperature resistant insulating hydrophobic coating on the surface of the alloy after micro-arc oxidation treatment is removed to obtain the alloy after selective micro-arc oxidation.

[0024] The pretreatment of the alloy surface includes the steps of grinding and cleaning the alloy surface, wherein grinding can remove the passivation film on the alloy surface and make the alloy surface flat, and cleaning can remove dirt on the alloy surface.

[0025] After applying the high-temperature resistant insulating paint, the alloy is air-dried at room temperature or baked at low temperature to form a layer of high-temperature resistant insulating hydrophobic coating, wherein the high-temperature resistant insulating hydrophobic coating has the characteristics of high temperature resistance, high pressure resistance, good insulation, strong adhesion, excellent hydrophobicity and acid, alkali and salt resistance, and can isolate the alloy and the electrolyte. The coating will not fall off even under high temperature and high pressure.

[0026] Among them, the micro-arc oxidation treatment adopts a bidirectional pulse AC voltage, the forward voltage is 300-420V, the negative voltage is 60-160V, the pulse frequency is 100-1000Hz, the duty cycle is 10-50%, the oxidation time is 10-50min, and the electrolyte composition is as follows: Na2SiO3·9H2O: 20-40g / l, (NaPO3)6: 5-15g / l, Na2MoO4: 2-6g / l, KOH: 2-6g / l.

[0027] The high temperature resistant insulating hydrophobic coating on the surface of the alloy is removed by using a paint remover, wherein the paint remover can be any paint remover commonly used in the market.

[0028] The selective micro-arc oxidation method for alloy surfaces can protect any area on the surface of metals such as aluminum, magnesium, titanium and their alloys, thereby achieving the purpose of selective micro-arc oxidation. After micro-arc oxidation treatment, a ceramic coating is formed on the area of ​​the alloy surface that is not coated with high-temperature resistant insulating paint, and the alloy substrate area coated with high-temperature resistant insulating paint is isolated from the electrolyte due to the high-temperature resistant insulating hydrophobic coating, and thus micro-arc oxidation cannot be performed due to the lack of conditions for the micro-arc oxidation reaction to occur, thereby protecting the area.

[0029] Example 1

[0030] A method for selective micro-arc oxidation of aluminum alloy surface, the specific steps are as follows:

[0031] (1) Preparation of high temperature resistant insulating hydrophobic coating, the process flow is as follows:

[0032] 1) Parts inspection and drilling: Check whether there are cracks or other defects on the surface of the substrate, make the substrate into a 40×40×2mm square plate and drill holes on the substrate to prepare for subsequent processing;

[0033] 2) Grinding the substrate: Grind the substrate with 180#, 320#, 600#, 800#, 1000# sandpaper;

[0034] 3) Cleaning: Place the polished substrate in alcohol and ultrasonically clean it for 5 minutes to remove surface dirt;

[0035] 4) Weighing: Weigh the substrate using an analytical balance and set aside;

[0036] 5) Apply a layer of high temperature resistant insulating paint on any area of ​​the part surface;

[0037] 6) The parts are completely air-dried at room temperature to form a high temperature resistant insulating hydrophobic coating, and weighed. After the high temperature resistant insulating hydrophobic coating is formed, the weight gain is 0.0988 g;

[0038] (2) Micro-arc oxidation treatment:

[0039] 1) Prepare electrolyte: Prepare electrolyte with sodium silicate Na2SiO3·9H2O (30 g / l), sodium hexametaphosphate (NaPO3)6 (10 g / l), sodium molybdate Na2MoO4 (2 g / l), and potassium hydroxide KOH (2 g / l) as electrolyte, and place it in the electrolytic cell for standby use;

[0040] 2) placing the substrate with the high temperature resistant insulating hydrophobic coating in the prepared electrolyte, connecting the substrate to the positive pole of the power supply, and connecting the electrolytic cell to the negative pole of the power supply; adjusting the oxidation power supply parameters to positive voltage of 320V, negative voltage of 80V, frequency of 200Hz, duty cycle of 30%, oxidation time of 5min, and starting oxidation after checking that everything is correct;

[0041] 3) Weighing and measuring after cleaning: The oxidized substrate was rinsed with deionized water and then placed in alcohol for ultrasonic cleaning for 5 minutes. After weighing with an analytical balance, the oxide film thickness of the sample was measured at five different points with an eddy current thickness gauge and the average value was taken. The thickness of the generated oxide film was 6.606 μm.

[0042] (3) Removal of high temperature resistant insulating hydrophobic coating, the process flow is as follows:

[0043] 1) Spray the paint remover on the high temperature resistant insulating hydrophobic coating of the metal parts to remove the high temperature resistant insulating hydrophobic coating;

[0044] 2) After removing the high-temperature resistant insulating hydrophobic coating, the weight loss is 0.0984 g, which is not much different from the weight gain after forming the high-temperature resistant insulating hydrophobic coating. Therefore, it can be explained that the high-temperature resistant insulating hydrophobic coating does not participate in the reaction during the micro-arc oxidation process, and only plays a good protective role for the substrate.

[0045] Example 2

[0046] A method for selective micro-arc oxidation of magnesium alloy surface, the specific steps are as follows:

[0047] (1) Preparation of high temperature resistant insulating hydrophobic coating, the process flow is as follows:

[0048] 1) Parts inspection and drilling: Check whether there are cracks or other defects on the surface of the substrate, make the substrate into a 40×40×2mm square plate and drill holes on the substrate to prepare for subsequent processing;

[0049] 2) Grinding the substrate: Grind the substrate with 180#, 320#, 600#, 800#, 1000# sandpaper;

[0050] 3) Cleaning: Place the polished substrate in alcohol and ultrasonically clean it for 5 minutes to remove surface dirt;

[0051] 4) Weighing: Weigh the substrate using an analytical balance and set aside;

[0052] 5) Apply a layer of high temperature resistant insulating paint on any area of ​​the part surface;

[0053] 6) The parts are completely air-dried at room temperature to form a high temperature resistant insulating hydrophobic coating, and weighed. After the high temperature resistant insulating hydrophobic coating is formed, the weight gain is 0.1215 g;

[0054] (2) Micro-arc oxidation treatment:

[0055] 1) Prepare electrolyte: Prepare electrolyte with sodium silicate Na2SiO3·9H2O (30 g / l), sodium hexametaphosphate (NaPO3)6 (10 g / l), sodium molybdate Na2MoO4 (2 g / l), and potassium hydroxide KOH (2 g / l) as electrolyte, and place it in the electrolytic cell for standby use;

[0056] 2) 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 240V positive voltage, 80V negative voltage, 200Hz frequency, 30% duty cycle, and 5min oxidation time, and start oxidation after checking that everything is correct;

[0057] 3) Weighing and measuring after cleaning: The oxidized substrate was rinsed with deionized water and then placed in alcohol for ultrasonic cleaning for 5 minutes. After weighing with an analytical balance, the oxide film thickness of the sample was measured at five different points with an eddy current thickness gauge to obtain the average value. The thickness of the generated oxide film was 7.932 μm.

[0058] (3) Removal of high temperature resistant insulating hydrophobic coating, the process flow is as follows:

[0059] 1) Spray the paint remover on the high temperature resistant insulating hydrophobic coating of the metal parts to remove the high temperature resistant insulating hydrophobic coating;

[0060] 2) After removing the high-temperature resistant insulating hydrophobic coating, the weight loss is 0.1207 g, which is not much different from the weight gain after forming the high-temperature resistant insulating hydrophobic coating. Therefore, it can be explained that the high-temperature resistant insulating hydrophobic coating does not participate in the reaction during the micro-arc oxidation process, and only plays a good protective role for the substrate.

[0061] Example 3

[0062] A method for selective micro-arc oxidation of titanium alloy surface, the specific steps are as follows:

[0063] (1) Preparation of high temperature resistant insulating hydrophobic coating, the process flow is as follows:

[0064] 1) Parts inspection and drilling: Check whether there are cracks or other defects on the surface of the substrate, make the substrate into a 40×40×2mm square plate and drill holes on the substrate to prepare for subsequent processing;

[0065] 2) Grinding the substrate: Grind the substrate with 180#, 320#, 600#, 800#, 1000# sandpaper;

[0066] 3) Cleaning: Place the polished substrate in alcohol and ultrasonically clean it for 5 minutes to remove surface dirt;

[0067] 4) Weighing: Weigh the substrate using an analytical balance and set aside;

[0068] 5) Apply a layer of high temperature resistant insulating paint on any area of ​​the part surface;

[0069] 6) The parts are completely air-dried at room temperature to form a high temperature resistant insulating hydrophobic coating, and weighed. After the high temperature resistant insulating hydrophobic coating is formed, the weight gain is 0.1025 g;

[0070] (2) Micro-arc oxidation treatment:

[0071] 1) Prepare electrolyte: Prepare electrolyte with sodium silicate Na2SiO3·9H2O (30 g / l), sodium hexametaphosphate (NaPO3)6 (10 g / l), sodium molybdate Na2MoO4 (2 g / l), and potassium hydroxide KOH (2 g / l) as electrolyte, and place it in the electrolytic cell for standby use;

[0072] 2) 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 220V positive voltage, 60V negative voltage, 200Hz frequency, 30% duty cycle, and 5min oxidation time, and start oxidation after checking that everything is correct;

[0073] 3) Weighing and measuring after cleaning: The oxidized substrate was rinsed with deionized water and then placed in alcohol for ultrasonic cleaning for 5 minutes. After weighing with an analytical balance, the oxide film thickness of the sample was measured at five different points with an eddy current thickness gauge to obtain the average value. The thickness of the generated oxide film was 12.546 μm.

[0074] (3) Removal of high temperature resistant insulating hydrophobic coating, the process flow is as follows:

[0075] 1) Spray the paint remover on the high temperature resistant insulating hydrophobic coating of the metal parts to remove the high temperature resistant insulating hydrophobic coating;

[0076] 2) After removing the high-temperature resistant insulating hydrophobic coating, the weight loss is 0.1017 g, which is not much different from the weight gain after forming the high-temperature resistant insulating hydrophobic coating. Therefore, it can be explained that the high-temperature resistant insulating hydrophobic coating does not participate in the reaction during the micro-arc oxidation process, and only plays a good protective role for the substrate.

[0077] Figures 1 to 3 Photos of the alloy parts at different stages during the selective micro-arc oxidation process in Examples 1-3 are respectively given. It can be seen from the photos that the purpose of selective micro-arc oxidation can be achieved by brushing high temperature resistant insulating paint.

Claims

1. A method for selective micro-arc oxidation of alloy surface, characterized in that: include: Pre-treating the alloy surface to remove the passivation film on the alloy surface; Apply high temperature resistant insulating paint on the pretreated alloy surface area that does not require micro-arc oxidation to form a high temperature resistant insulating hydrophobic coating; Micro-arc oxidation treatment is performed on the alloy forming the high temperature resistant insulating hydrophobic coating; The high temperature resistant insulating hydrophobic coating on the surface of the alloy after micro-arc oxidation treatment is removed to obtain the alloy after selective micro-arc oxidation.

2. The method for selective micro-arc oxidation of alloy surface according to claim 1, characterized in that: The pretreatment of the alloy surface includes the steps of grinding and cleaning the alloy surface.

3. The method for selective micro-arc oxidation of alloy surface according to claim 1, characterized in that: After applying the high temperature resistant insulating paint, the alloy is air-dried at room temperature or baked at low temperature to form a layer of high temperature resistant insulating hydrophobic coating.

4. The method for selective micro-arc oxidation of alloy surface according to claim 1, characterized in that: The micro-arc oxidation treatment adopts a bidirectional pulse AC voltage, with a forward voltage of 300-420V, a negative voltage of 60-160V, a pulse frequency of 100-1000Hz, a duty cycle of 10-50%, an oxidation time of 10-50min, and an electrolyte composition as follows: Na2SiO3·9H2O: 20-40g / l, (NaPO3)6: 5-15g / l, Na2MoO4: 2-6g / l, KOH: 2-6g / l.

5. The method for selective micro-arc oxidation of alloy surface according to claim 1, characterized in that: The high temperature resistant insulating hydrophobic coating on the alloy surface is removed by a paint remover.

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