Micro-arc oxidation method for improving galvanic corrosion performance of titanium alloy

Abstract

The invention relates to the technical field of titanium alloy surface engineering, in particular to a micro-arc oxidation method for improving galvanic corrosion performance of titanium alloy, which comprises the following steps: S1, surface treatment: removing oil stain and an oxide layer on the surface of a titanium alloy sample to obtain a first sample; s2, micro-arc oxidation: carrying out micro-arc oxidation treatment on the first sample in an electrolyte, and preparing a uniform and compact oxidation layer on the surface of the first sample to obtain a second sample; and S3, post-treatment: cleaning the second sample, and drying to obtain a final sample. The method is reasonable in design, simple in step, short in treatment period, low in energy consumption, convenient to operate, easy to control and capable of achieving industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy surface engineering, and in particular to a micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy. Background Art

[0002] With the rapid development of economy and society, the demand for energy is increasing day by day. At present, the shallow oil and gas resources in the world are becoming increasingly exhausted, which has forced the energy industry to seek deeper oil and gas resources, including the development of deep wells or ultra-deep wells. However, as the mining depth continues to increase, the underground environment has become more severe, with high temperature, high pressure, high concentration of corrosive environment (CO 2 , H 2 S, Cl - ) and other factors have put forward higher requirements on the performance of materials. Titanium and titanium alloys have been widely used in the field of petrochemicals due to their high specific strength, strong corrosion resistance, good high temperature performance, and excellent fatigue performance.

[0003] In the atmosphere, the surface of titanium alloy is easily oxidized to form TiO 2 The passivation film makes the electrode potential of the titanium alloy more positive, so it has excellent corrosion resistance. During deep well service, titanium alloy will inevitably come into contact with other heterogeneous metals. Due to the large potential difference between different materials, galvanic corrosion is likely to occur, thereby accelerating the failure of the metal. Compared with metals such as carbon steel and stainless steel, the electrode potential of titanium alloy is higher. It generally acts as a cathode without corrosion, while the galvanic corrosion of the anode material will be very serious. Although the passivation film on the surface of the titanium alloy can isolate the contact potential, it is loose and uneven and cannot provide good protection. Therefore, it is necessary to artificially prepare an insulating protective film on the surface of the titanium alloy to avoid the occurrence of galvanic corrosion.

[0004] Micro-arc oxidation, also known as micro-plasma oxidation, is a new surface treatment technology that further increases the voltage to a higher area in the spark discharge zone on the basis of traditional anodic oxidation. By adjusting the matching of electrolyte and electrical parameters, relying on the instantaneous high-temperature sintering effect of the micro-arc zone, an oxide ceramic layer is grown in situ on the substrate material. The oxide ceramic layer prepared by micro-arc oxidation is firmly bonded to the titanium alloy substrate, which can greatly reduce the contact resistance between the titanium alloy and other metals and reduce the tendency of galvanic corrosion. Although micro-arc oxidation has been initially applied in the corrosion protection of titanium alloys, there are still problems such as insufficient density of the oxide film, microscopic pores, and surface "ablation", which affect the service life of the material. Summary of the invention

[0005] The purpose of the present invention is to provide a micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy, so as to solve the technical problems in the prior art that the oxide film is not dense enough, microscopic pores, surface "ablation" and the like still exist, which affect the service life of the material.

[0006] The invention discloses a micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy, comprising the following steps:

[0007] S1. Surface treatment: removing oil stains and oxide layer on the surface of the titanium alloy sample to obtain a first sample;

[0008] S2, micro-arc oxidation: subjecting the first sample to micro-arc oxidation in an electrolyte to form a uniform and dense oxide layer on its surface, thereby obtaining a second sample;

[0009] S3, post-processing: washing and drying the second sample to obtain a final sample.

[0010] Furthermore, the titanium alloy is TA2, TA3 or TA10 titanium alloy.

[0011] Furthermore, the surface treatment in S1 is to remove oil stains and oxide layers on the surface of the titanium alloy sample by using one of grinding and polishing, ultrasonic cleaning or laser cleaning.

[0012] Furthermore, the electrolyte in S2 contains NaCl: 10-20 g / L.

[0013] Furthermore, the electrolyte in S2 also contains Na 2 HPO 4 :2-10g / L, Na 2 B 4 O 7 :4-8g / L, Na 2 SiO 3 :3-6g / L mixed solution with deionized water.

[0014] Furthermore, the micro-arc oxidation in S2 adopts a DC pulse power supply, with the first sample as the anode and the stainless steel as the cathode.

[0015] Furthermore, the process parameters of the S2 micro-arc oxidation are: voltage 300-600V, frequency 400-800HZ, duty cycle 10%-30%, temperature 15-45°C and processing time 3-10min.

[0016] Furthermore, during the S2 micro-arc oxidation process, the electrolyte circulates and is cooled by an external cooling system.

[0017] Furthermore, the cleaning in step S3 is performed by ultrasonic cleaning.

[0018] Furthermore, the cleaning agent used in the ultrasonic cleaning is anhydrous ethanol or acetone.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The oxide ceramic layer prepared by the present invention is firmly bonded to the substrate and is uniformly dense.

[0021] 2. By adding a high proportion of NaCl to the electrolyte, the conductivity of the solution can be effectively increased, the formation process of the ceramic layer can be accelerated, and the porosity can be reduced. In addition, NaCl is a commonly used industrial raw material with a low price, which can reduce production costs.

[0022] 3. By directly circulating the electrolyte externally, the solution temperature can be more effectively lowered, avoiding the "ablation" phenomenon caused by the breakdown of the oxide film due to excessive temperature.

[0023] 4. The invention has reasonable design, simple steps, short processing cycle, low energy consumption, convenient operation, easy control, and can realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only represent some embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 This is a low-magnification SEM image of the cross section of the sample after micro-arc oxidation treatment in Example 1 of the present invention.

[0026] Figure 2 This is a high-magnification SEM image of the cross section of the sample after micro-arc oxidation treatment in Example 1 of the present invention.

[0027] Figure 3 This is a side SEM image of the sample after micro-arc oxidation treatment in Example 1 of the present invention.

[0028] Figure 4 This is a low-magnification SEM image of the cross section of the sample after micro-arc oxidation treatment in Example 3 of the present invention.

[0029] Figure 5 This is a high-magnification SEM image of the cross section of the sample after micro-arc oxidation treatment in Example 3 of the present invention.

[0030] Figure 6 This is a side SEM image of the sample after micro-arc oxidation treatment in Example 3 of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0032] Example 1

[0033] This embodiment discloses a micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy, comprising the following steps:

[0034] First, the TA2 titanium alloy was polished on 400#, 800#, 1200#, 1500#, and 2000# SiC sandpapers in turn, and then roughly polished with diamond polishing pastes with particle sizes of 5μm and 1μm, respectively, and finally finely polished with a mixed solution of silicon dioxide suspension (80ml) with a particle size of 0.04μm + hydrogen peroxide (20ml) to obtain the first sample. 2 HPO 4 :5g / L, Na 2 B 4 O 7 :6g / L, Na 2 SiO 3 :5g / L, NaCl:15g / L and deionized water mixed solution for micro-arc oxidation to obtain the second sample. Micro-arc oxidation uses a DC pulse power supply, TA2 as the anode, stainless steel as the cathode, and the electrical parameters are: voltage 400V, frequency 500HZ, duty cycle 20%, temperature 30℃, and processing time 10min. During this process, the electrolyte is circulated with an external cooling device to ensure temperature stability. The second sample is ultrasonically cleaned in anhydrous ethanol and randomly dried to obtain the final product.

[0035] The SEM images of the cross section and side of the sample prepared in Example 1 are as follows: Figure 1-3 As shown. Figure 1 and Figure 2 It can be seen that the density of the samples prepared by micro-arc oxidation is high and there are no obvious holes on the surface. Figure 3 It can be seen that the prepared layer thickness is relatively thick, about 15 μm.

[0036] The final sample was combined with A105N carbon steel to form a galvanic couple for corrosion testing. The results showed that no pitting occurred on the surface of the sample and no obvious corrosion pits, indicating that the prepared ceramic layer can play a good protective role.

[0037] Example 2

[0038] First, the TA3 titanium alloy was ultrasonically cleaned in an acetone solution for 10 minutes and then dried to obtain the first sample. 2 HPO4 :10g / L, Na 2 B 4 O 7 :8g / L, Na 2 SiO 3 :6g / L, NaCl:20g / L and deionized water were used for micro-arc oxidation to obtain the second sample. Micro-arc oxidation uses a DC pulse power supply, TA3 as the anode, stainless steel as the cathode, and the electrical parameters are: voltage 350V, frequency 600HZ, duty cycle 20%, temperature 25℃, and processing time 5min. During this process, the electrolyte is circulated with an external cooling device to ensure temperature stability. The second sample is ultrasonically cleaned in anhydrous ethanol and randomly dried to obtain the final product.

[0039] The final sample was combined with UNS 30400 stainless steel to form a galvanic couple for corrosion testing. The results showed that no pitting occurred on the surface of the sample and no obvious corrosion pits, indicating that the prepared ceramic layer can play a good protective role.

[0040] Example 3

[0041] First, the TA10 titanium alloy was cleaned by laser for 15 minutes, then washed and dried to obtain the first sample. 2 HPO 4 :10g / L, Na 2 B 4 O 7 :8g / L, Na 2 SiO 3 :6g / L, NaCl:20g / L and deionized water mixed solution for micro-arc oxidation to obtain the second sample. Micro-arc oxidation uses a DC pulse power supply, TA10 as the anode, stainless steel as the cathode, and the electrical parameters are: voltage 5000V, frequency 800HZ, duty cycle 15%, temperature 40℃, and treatment time 6min. During this process, the electrolyte is circulated with an external cooling device to ensure temperature stability. The second sample is ultrasonically cleaned in anhydrous ethanol and randomly dried to obtain the final product.

[0042] The SEM images of the cross section and side of the sample prepared in Example 1 are as follows: Figure 4-6 As shown. Figure 4 and Figure 5 It can be seen that the density of the samples prepared by micro-arc oxidation is high and there are no obvious holes on the surface. Figure 6 It can be seen that the prepared layer thickness is about 1 μm.

[0043] The final sample was combined with A105N carbon steel to form a galvanic couple for corrosion testing. The results showed that no pitting occurred on the surface of the sample and no obvious corrosion pits, indicating that the prepared ceramic layer can play a good protective role.

[0044] Example 4

[0045] First, the TA2 titanium alloy was ultrasonically cleaned in an acetone solution for 10 minutes and then dried to obtain the first sample. 2 HPO 4 :10g / L, Na 2 B 4 O 7 :8g / L, Na 2 SiO 3 :6g / L, NaCl:20g / L and deionized water were used for micro-arc oxidation to obtain the second sample. Micro-arc oxidation uses a DC pulse power supply, TA2 as the anode, stainless steel as the cathode, and the electrical parameters are: voltage 350V, frequency 600HZ, duty cycle 20%, temperature 25℃, and processing time 5min. During this process, the electrolyte is circulated with an external cooling device to ensure temperature stability. The second sample is ultrasonically cleaned in anhydrous ethanol and randomly dried to obtain the final product.

[0046] The final sample was combined with UNS 30400 stainless steel to form a galvanic couple for corrosion testing. The results showed that no pitting occurred on the surface of the sample and no obvious corrosion pits, indicating that the prepared ceramic layer can play a good protective role.

[0047] By comparing the invention examples 1, 2, 3 and 4, it can be found that the concentration of NaCl mainly affects the conductivity of the solution, and thus affects the rate of micro-arc oxidation. The increase in the rate of micro-arc oxidation helps to reduce the generation of holes. The titanium alloy after micro-arc oxidation, whether it is a galvanic pair with carbon steel or stainless steel, undergoes corrosion tests. The corrosion tests refer to the national standard: GB / T15748-2013, and no obvious corrosion marks appear, indicating that the ceramic layer prepared by this patent can effectively protect the galvanic pair metal.

[0048] The above are the implementation methods listed in this embodiment, but this embodiment is not limited to the above optional implementation methods. Those skilled in the art can arbitrarily combine the above methods to obtain other various implementation methods. Anyone can derive other various forms of implementation methods under the inspiration of this embodiment. The above specific implementation methods should not be understood as limiting the scope of protection of this embodiment. The scope of protection of this embodiment shall be based on the definition in the claims, and the description can be used to interpret the claims.

Claims

1. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloys. Features: The following steps are involved: S1. Surface treatment: removing oil stains and oxide layer on the surface of the titanium alloy sample to obtain a first sample; S2, micro-arc oxidation: subjecting the first sample to micro-arc oxidation in an electrolyte to form a uniform and dense oxide layer on its surface, thereby obtaining a second sample; S3, post-processing: washing and drying the second sample to obtain a final sample.

2. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 1, Features: The titanium alloy is TA2, TA3 or TA10 titanium alloy.

3. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 1, Features: The surface treatment in S1 is to remove oil stains and oxide layers on the surface of the titanium alloy sample by using one of grinding and polishing, ultrasonic cleaning or laser cleaning.

4. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 1, Features: The electrolyte in the S2 contains NaCl: 10-20 g / L.

5. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 4, Features: The electrolyte in S2 also contains Na 2 HPO 4 :2-10g / L, Na 2 B 4 O 7 :4-8g / L, Na 2 SiO 3 :3-6g / L mixed solution with deionized water.

6. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 1, Features: The micro-arc oxidation in S2 adopts a direct current pulse power supply, with the first sample as the anode and the stainless steel as the cathode.

7. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 1, Features: The process parameters of the S2 micro-arc oxidation are: voltage 300-600V, frequency 400-800HZ, duty cycle 10%-30%, temperature 15-45°C and processing time 3-10min.

8. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 1, Features: During the S2 micro-arc oxidation process, the electrolyte circulates and is cooled by an external cooling system.

9. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 1, Features: The cleaning in step S3 is performed by ultrasonic cleaning.

10. A micro-arc oxidation method for improving the galvanic corrosion performance of titanium alloy according to claim 9, Features: The cleaning agent used in the ultrasonic cleaning is anhydrous ethanol or acetone.

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