A method for improving the protectiveness of passivation film on aluminum alloy surface

Abstract

The invention discloses a method for improving the protectiveness of the passivation film on the surface of aluminum alloy, and belongs to the technical field of metal corrosion and protection. The method comprises the following steps: when generating the passivation film of aluminum alloy, a parallel magnetic field and a vertical magnetic field with an intensity of 0.2 to 0.4 T are simultaneously applied parallel and perpendicular to the surface of the aluminum alloy for 20 to 60 minutes. The generating device of the passivation film of aluminum alloy is a magnetic field generating device, and the magnetic field provided by the magnetic field generating device is a parallel magnetic field parallel to the surface of the aluminum alloy and a vertical magnetic field perpendicular to the surface of the aluminum alloy. The aluminum alloy and the electrode are placed in the passivation medium in the passivation tank, and connected to the electrochemical workstation through a wire. The present invention does not need to change the original passivation process. On the basis of the original passivation effect, a magnetic field generating device such as a permanent magnet or an electromagnet provides a magnetic field parallel to and perpendicular to the surface of the aluminum alloy, which can further improve the compactness, flatness, self-repairing and other protective effects of the passivation film formed on the surface of the aluminum alloy.

Description

Technical Field

[0001] The invention relates to a method for improving the protectiveness of a passivation film on the surface of an aluminum alloy, and belongs to the technical field of metal corrosion and protection. Background Art

[0002] With the development of lightweight materials, aluminum alloys have gradually replaced steel materials in many fields due to their excellent comprehensive properties such as high specific strength, good plasticity and toughness, and good corrosion resistance. They are widely used in the fields of ocean, chemical industry, machinery, etc. The excellent corrosion resistance of aluminum alloys comes from the integrity and density of the passivation film formed on its surface. The dense passivation film can hinder the contact between the external medium and the aluminum matrix, thereby playing a protective role and improving the corrosion resistance of the aluminum alloy. Therefore, processes such as anodizing, chemical oxidation, and electrochemical oxidation, which can form a dense and protective passivation film on the surface of aluminum alloys, are the most commonly used methods for aluminum alloy surface treatment and improving corrosion resistance.

[0003] Therefore, the use of a suitable passivation method can effectively improve the corrosion resistance of aluminum alloys, but these processes often improve the quality of the passivation film by improving the passivation medium, passivating agent, passivation parameters, etc. Once the optimal medium ratio and passivation parameters are found, the process passivation effect cannot be further improved. In order to solve the shortcomings of the existing process, the purpose of the present invention is to provide a method for accelerating the formation of passivation film on the surface of aluminum alloys and improving the protectiveness of the passivation film, without changing the original passivation process, and on the basis of the original passivation effect, further improve the formation rate of the passivation film and the compactness, flatness, self-repairing and other protective effects of the passivation film. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to propose a method for improving the protectiveness of the passivation film on the surface of aluminum alloy, which does not require changing the original passivation process. On the basis of the original passivation effect, the density, flatness, self-repairing and other protective effects of the passivation film formed on the surface of aluminum alloy are further improved.

[0005] At the same time, the present invention provides a corrosion-resistant aluminum alloy.

[0006] At the same time, the present invention provides an application of aluminum alloy in corrosion-resistant lightweight parts.

[0007] At the same time, the present invention provides an application of an aluminum alloy in the fields of ocean, chemical industry and machinery.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] A method for improving the protectiveness of a passive film on an aluminum alloy surface comprises the following steps: when generating the passive film on the aluminum alloy, simultaneously applying a parallel magnetic field and a perpendicular magnetic field with a strength of 0.2 to 0.4 T parallel and perpendicular to the aluminum alloy surface for 20 to 60 minutes.

[0010] The aluminum alloy includes 5083 aluminum alloy, Al-3.0 wt. % Mg alloy, 5052 aluminum alloy, 6061 aluminum alloy, 7075 aluminum alloy or 2024 aluminum alloy.

[0011] The device for generating the aluminum alloy passivation film is a magnetic field generating device. The magnetic field generating device provides a parallel magnetic field parallel to the aluminum alloy surface and a vertical magnetic field perpendicular to the aluminum alloy surface. The aluminum alloy and the electrode are placed in the passivation medium in the passivation tank and connected to the electrochemical workstation through a wire.

[0012] The magnetic field generating device includes a permanent magnet or an electromagnet.

[0013] The magnetic field generating device is placed outside the passivation tank; or the magnetic field generating device is wrapped by a protective cover and placed near the aluminum alloy in the passivation tank.

[0014] The material of the protective cover is a material that does not shield the parallel magnetic field and the vertical magnetic field and does not participate in the passivation reaction.

[0015] The aluminum alloy obtained by the method of the present invention.

[0016] Application of the aluminum alloy of the present invention in corrosion-resistant lightweight parts.

[0017] The aluminum alloy of the present invention is applied in the fields of ocean, chemical industry and machinery.

[0018] A method for improving the protectiveness of the passivation film on the surface of aluminum alloy, based on the original passivation process, by applying a magnetic field to improve the density, flatness, self-repairing and other protective effects of the passivation film during the passivation process;

[0019] The external magnetic field can be provided by a magnetic field generating device such as a permanent magnet or an electromagnet. The magnetic field provided is a parallel magnetic field parallel to the surface of the aluminum alloy and a vertical magnetic field perpendicular to the surface of the aluminum alloy. Under the interaction of the parallel magnetic field and the vertical magnetic field, the density, flatness, self-healing and other protective effects of the passivation film formed on the surface of the aluminum alloy are affected.

[0020] The original passivation process can be anodizing, chemical oxidation, electrochemical oxidation and other processes that can form a dense and protective passivation film on the surface of the aluminum alloy. The aluminum alloy and the electrode are placed in the passivation medium in the passivation tank and connected to the passivation power supply through a wire.

[0021] The protective cover is made of glass, plastic or other materials that do not shield the magnetic field and do not participate in the passivation reaction.

[0022] The parallel magnetic field mainly plays the role of increasing the aluminum oxide content in the passivation film on the surface of aluminum alloy, and the vertical magnetic field mainly plays the role of providing magnetohydrodynamic force, reducing the reaction layer, and accelerating the rapid formation of the passivation film. The parallel magnetic field and the vertical magnetic field work synergistically and work together to achieve excellent passivation film density, flatness and self-healing properties, which can greatly improve the corrosion resistance and protection of aluminum alloy and effectively extend the service life of aluminum alloy.

[0023] The present invention is beneficial in that:

[0024] The present invention provides a method for improving the protectiveness of a passivation film on the surface of an aluminum alloy. The method does not require changing the original passivation process. On the basis of the original passivation effect, a magnetic field parallel to and perpendicular to the surface of the aluminum alloy is provided by a magnetic field generating device such as a permanent magnet or an electromagnet, thereby further improving the compactness, flatness, self-repairing and other protective effects of the passivation film formed on the surface of the aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a method for improving the protectiveness of the passivation film on the surface of aluminum alloy by placing a magnetic field generating device outside the passivation tank;

[0026] Figure 2 A schematic diagram of a method for improving the protectiveness of the passivation film on the surface of an aluminum alloy, in which a magnetic field generating device is placed in a passivation tank;

[0027] Figure 3 The constant potential polarization curves (log I-log t) of four aluminum alloys, 5052, 6061, 7075 and 2024, in borate buffer using only the parallel magnetic field method and the present method (magnetic field applied outside the passivation cell), (a) 5052 aluminum alloy; (b) 6061 aluminum alloy; (c) 7075 aluminum alloy; (d) 2024 aluminum alloy;

[0028] Figure 4 The electrochemical impedance of the passive film formed on the surface of Al-3.0wt.%Mg alloy using only the perpendicular magnetic field method and the present method (applying a magnetic field in the passivation cell);

[0029] Figure 5 The X-ray photoelectron spectroscopy results of the passive film formed on the surface of Al-3.0wt.%Mg alloy using only the method of vertical magnetic field and the present method (magnetic field applied in the passivation cell);

[0030] Figure 6 The atomic force microscopy results of the passive film formed on the surface of Al-3.0wt.%Mg alloy using only the method of perpendicular magnetic field and using the present method (applying magnetic field in the passivation tank): (a) the method of using only the perpendicular magnetic field; (b) using the present method;

[0031] Figure 7The electrochemical impedance of the passivation film formed on the surface of 5083 aluminum alloy by using the method of applying a parallel magnetic field first and then a perpendicular magnetic field and by using the present method (applying a magnetic field outside the passivation cell): (a) using the method of applying a parallel magnetic field first and then a perpendicular magnetic field; (b) using the present method;

[0032] Figure 8 The X-ray photoelectron spectroscopy results of the passivation film formed on the surface of 5083 aluminum alloy by using the method of applying a parallel magnetic field first and then a perpendicular magnetic field and by using the present method (applying a magnetic field outside the passivation cell): (a) using the method of applying a parallel magnetic field first and then a perpendicular magnetic field; (b) using the present method;

[0033] Fig. 9 The atomic force microscopy results of the passive film formed on the surface of 5083 aluminum alloy by using the method of applying a parallel magnetic field first and then a perpendicular magnetic field and by using the present method (applying a magnetic field outside the passivation cell): (a) using the method of applying a parallel magnetic field first and then a perpendicular magnetic field; (b) using the present method;

[0034] Reference numerals:

[0035] 1—magnetic field generating device, 2—parallel magnetic field, 3—vertical magnetic field, 4—passivation cell, 5—passivation medium, 6—aluminum alloy, 7—electrode, 8—conductor, 9—electrochemical workstation, 10—protective cover. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0037] Example 1

[0038] like Figure 1 As shown, the magnetic field generating device 1 is placed outside the passivation tank to apply a magnetic field to the original passivation process.

[0039] The external magnetic field is provided by a Nd-Fe-B permanent magnet magnetic field generating device 1, which provides a parallel magnetic field 2 and a perpendicular magnetic field 3 parallel and perpendicular to the surface of four aluminum alloys 6, 5052, 6061, 7075 and 2024, respectively.

[0040] The Nd-Fe-B permanent magnet magnetic field generating device 1 is placed outside the passivation tank 4 (beaker), and applies a parallel magnetic field 2 and a perpendicular magnetic field 3 with a strength of 0.2 T parallel and perpendicular to the surfaces of four aluminum alloys 6 of 5052, 6061, 7075 and 2024.

[0041] Four aluminum alloys 6 of 5052, 6061, 7075 and 2024 were placed in the passivation medium 5 in the passivation tank 4 (beaker) with a Pt-counter electrode and a saturated calomel-reference electrode 7, respectively, and connected to the electrochemical workstation 9 through a wire 8. The formation, destruction and repair behaviors of the passivation film of the four aluminum alloys 6 of 5052, 6061, 7075 and 2024 were tested by the constant potential polarization curve test method using only the parallel magnetic field 2, and the rest was the same as this method and using this method. The medium is 0.1M H3BO3+0.025MNa2B4O7·10H2O boric acid corrosion inhibitor, and the parameters are: potential 0.2V, time 30min. The test results are as follows Figure 3 As shown, Figure (a) is 5052 aluminum alloy; Figure (b) is 6061 aluminum alloy; Figure (c) is 7075 aluminum alloy; Figure (d) is 2024 aluminum alloy.

[0042] like Figure 3 As shown in the figure, the passivation process is mainly divided into three stages. In stage 1, the slope of the curve approaches horizontal, and the change of current density is mainly controlled by the dissolution process of the aluminum anode. At this time, a good passivation film with protective effect is not formed. After entering stage 2, the current density drops rapidly, indicating that the passivation film is gradually growing and gradually protecting the alloy matrix, hindering the corrosion process. The current density in stage 3 rises slightly. At this time, the passivation film is dissolved to a certain extent. Some alloys have gradually tended to a certain stable value at this time, indicating that the dissolution rate and growth rate of the passivation film are close to equilibrium at this time, and the passivation film has gradually tended to a steady state.

[0043] In the method of using only parallel magnetic field 2 and using this method, the effect of this method on the four alloys in stage 1 is not obvious. After using this method in stage 2, the dual effect of parallel and perpendicular magnetic fields makes the current density of 5052 and 6061 aluminum alloys 6 decrease faster, forming a more protective passivation film. For 7075 and 2024 aluminum alloys 6, the effect of this method on the rapid formation stage of the passivation film is not obvious.

[0044] In stage 3, the current density of the four aluminum alloys 6 increased slightly, and then gradually stabilized. After using this method, they can all reach a stable state with a lower current density. When only the method of parallel magnetic field 2 is used, the current density of the four aluminum alloys 6 suddenly increases. For 7075 and 2024 aluminum alloys 6, the effect of this method on the passivation film is mainly concentrated in the passivation film dissolution process in stage 3, so that the passivation film generation and dissolution process reach a dynamic balance. It can be seen that after using this method, the rapid formation of the passivation film on the surface of the aluminum alloy 6 can be accelerated, and the passivation film generation and dissolution process can reach a dynamic balance, achieving a re-repairing effect and improving the protectiveness of the passivation film.

[0045] The aluminum alloy of this embodiment is used in corrosion-resistant and lightweight parts.

[0046] The aluminum alloy of this embodiment is used in the fields of ocean, chemical industry and machinery.

[0047] Example 2

[0048] like Figure 2 As shown, the magnetic field generating device 1 is placed in the passivation tank to apply a magnetic field to the original passivation process;

[0049] The external magnetic field is provided by a Nd-Fe-B permanent magnet magnetic field generating device 1, which provides the Al-3.0wt.%Mg alloy 6 with a parallel magnetic field 2 and a perpendicular magnetic field 3 parallel and perpendicular to its surface.

[0050] The passivation process adopts an electrochemical oxidation process, and the Al-3.0wt.% Mg alloy 6, the Pt-counter electrode and the saturated calomel-reference electrode 7 are placed in a passivation medium 5 in a passivation tank 4 (beaker), and connected to an electrochemical workstation 9 through a wire 8. The passivation medium is 0.1M H3BO3+0.025M Na2B4O7·10H2O boric acid corrosion inhibitor, and the passivation parameters are: potential 0V, time 20min.

[0051] The Nd-Fe-B permanent magnet magnetic field generating device 1 is placed in a protective cover 10 (made of glass) that does not shield the magnetic field and does not participate in the passivation reaction, and is placed together in a passivation tank 4 (beaker) to apply a parallel magnetic field 2 and a vertical magnetic field 3 with a strength of 0.4T to the surface of the Al-3.0wt.% Mg alloy 6.

[0052] The impedance, morphology and composition of the passivation film formed on the surface of the Al-3.0wt.%Mg alloy 6 after passivation by the method using only the vertical magnetic field 3 (the rest is the same as the present method) and the present method were tested by an electrochemical workstation 9, an atomic force microscope and an X-ray photoelectron spectroscopy. The test results are shown in FIG. Figure 4 , Figure 5 and Figure 6 As shown, Figure (a) is a method that only uses the vertical magnetic field 3; Figure (b) is a method that simultaneously uses the parallel magnetic field 2 and the vertical magnetic field 3.

[0053] like Figure 4 As shown, the impedance spectrum radius of the passivation film formed using this method is larger than that of the passivation film formed using only the method of the perpendicular magnetic field 3, indicating that the Al-3.0wt.%Mg alloy 6 formed with the passivation film using this method has better corrosion resistance and the passivation film has better protection.

[0054] like Figure 5As shown, the characteristic peak binding energies of O 1s are 531.1eV, 532.08eV, and 533.1eV, respectively representing Al2O3, Al(OH)3, and H2O. The proportion of Al2O3 in the passivation film formed using this method exceeds that of Al(OH)3, while the proportion of Al2O3 in the passivation film formed using only the method of vertical magnetic field 3 is less than that of Al(OH)3. The higher the oxide content in the aluminum passivation film and the lower the hydroxide content, the better the density and stability of the passivation film. Therefore, the use of this method increases the oxide content in the passivation film of Al-3.0wt.%Mg alloy 6, and improves the density and stability of the passivation film.

[0055] like Figure 6 As shown, compared with the passivation method using only the vertical magnetic field 3, after the Al-3.0wt.%Mg alloy 6 is passivated using this method, the spike-like protrusions on the surface of the passivation film are smaller, the surface is smoother, and the structure is finer. The integrity and density of the passivation film are the key to the excellent corrosion resistance of the passivation film. This shows that the passivation film obtained using the passivation method of the present invention is smoother and denser, and has better corrosion resistance and protection.

[0056] The aluminum alloy of this embodiment is used in corrosion-resistant and lightweight parts.

[0057] The aluminum alloy of this embodiment is used in the fields of ocean, chemical industry and machinery.

[0058] Example 3

[0059] like Figure 1 As shown, the magnetic field generating device 1 is placed outside the passivation tank 4 to apply a magnetic field to the original passivation process.

[0060] The external magnetic field is provided by a Nd-Fe-B permanent magnet magnetic field generating device 1, which provides the 5083 aluminum alloy 6 with a parallel magnetic field 2 and a perpendicular magnetic field 3 parallel and perpendicular to its surface.

[0061] The passivation process adopts an electrochemical oxidation process, and the 5083 aluminum alloy 6, the Pt-counter electrode and the saturated calomel-reference electrode 7 are placed in the passivation medium 5 in the passivation tank 4 (beaker), and connected to the electrochemical workstation 9 (i.e., the passivation power supply) through the wire 8. The passivation medium is 0.1M H3BO3+0.025M Na2B4O7·10H2O boric acid corrosion inhibitor, and the passivation parameters are: potential -0.2V, and the test time is 10min, 20min, 30min, 40min and 60min respectively.

[0062] The Nd-Fe-B permanent magnet magnetic field generating device 1 is placed outside the passivation tank 4 (beaker), and applies a parallel magnetic field 2 and a perpendicular magnetic field 3 with a strength of 0.3 T parallel and perpendicular to the surface of the 5083 aluminum alloy 6.

[0063] The impedance, morphology and composition of the passivation film formed on the surface of 5083 aluminum alloy 6 after passivation by the method of applying a parallel magnetic field for 30 minutes and then a perpendicular magnetic field for 30 minutes (the rest is the same as this method) and the method were tested by electrochemical workstation 9, atomic force microscope and X-ray photoelectron spectroscopy. The test results are as follows: Figure 7 , Figure 8 and Fig. 9 As shown, Figure (a) is a method of applying a parallel magnetic field first and then a perpendicular magnetic field, and the rest is the same as the present method; Figure (b) is a method of using a parallel magnetic field 2 and a perpendicular magnetic field 3 at the same time.

[0064] like Figure 7 As shown in the figure, the impedance spectrum radius of the passivation film formed in the first 10min, 20min and 30min parallel magnetic field stage is smaller than the impedance spectrum radius of the passivation film formed by the present method, indicating that the combined effect of the parallel magnetic field and the perpendicular magnetic field makes the passivation film formed on the surface of 5083 aluminum alloy 6 more protective. After applying the parallel magnetic field for 30min, the impedance spectrum radius of the passivation film formed by continuing to apply the perpendicular magnetic field for 10min, 20min and 30min is still smaller than the impedance spectrum radius of the passivation film formed by the present method for the same treatment time (the prior art believes that: the larger the impedance spectrum radius, the better the corrosion resistance), indicating that even if the parallel magnetic field is applied first and then the perpendicular magnetic field is applied, the protectiveness of the passivation film obtained is still less than that of the passivation film obtained by the present method.

[0065] like Figure 8 As shown, the Al2O3 content in the passivation film formed by the method is much higher than that obtained by applying a parallel magnetic field first and then a perpendicular magnetic field. The higher the oxide content in the passivation film, the better the density and stability. Therefore, the use of this method increases the oxide content in the passivation film of 5083 aluminum alloy 6, and improves the density and stability of the passivation film.

[0066] like Fig. 9 As shown, compared with the passivation method of applying a parallel magnetic field first and then a perpendicular magnetic field, after the 5083 aluminum alloy 6 is passivated using this method, the spike-like protrusions on the surface of the passivation film are smaller, the surface is smoother, and the structure is more dense. The integrity and density of the passivation film are the key to the excellent corrosion resistance of the passivation film. This shows that the passivation film obtained using the passivation method of the present invention is smoother and denser, and has better corrosion resistance and protection.

[0067] The aluminum alloy of this embodiment is used in corrosion-resistant and lightweight parts.

[0068] The aluminum alloy of this embodiment is used in the fields of ocean, chemical industry and machinery.

[0069] Finally, it should be noted that the above embodiments are only for illustrating the technical concept and features of the present invention, and do not limit them. Different passivation processes can still be modified according to this technical solution, and the modified technical solution cannot deviate from the spirit of the technical solution of the present invention.

[0070] It should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the previously disclosed embodiments. Therefore, the claims that follow the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0071] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for improving the protectiveness of a passive film on an aluminum alloy surface, characterized in that: The following steps are involved: When generating the aluminum alloy passivation film, a parallel magnetic field and a perpendicular magnetic field with an intensity of 0.2-0.4T are simultaneously applied to the aluminum alloy surface for 20-60 minutes. The parallel magnetic field increases the aluminum oxide content in the passivation film on the surface of the aluminum alloy, and the vertical magnetic field provides magnetohydrodynamic force, reduces the reaction layer, and accelerates the rapid formation of the passivation film.

2. The method according to claim 1, characterized in that The aluminum alloy includes 5083 aluminum alloy, Al-3.0wt.%Mg alloy, 5052 aluminum alloy, 6061 aluminum alloy, 7075 aluminum alloy or 2024 aluminum alloy.

3. The method according to claim 1, characterized in that The device for generating the aluminum alloy passivation film is a magnetic field generating device. The magnetic field generating device provides a parallel magnetic field parallel to the aluminum alloy surface and a vertical magnetic field perpendicular to the aluminum alloy surface. The aluminum alloy and the electrode are placed in the passivation medium in the passivation tank and connected to the electrochemical workstation through a wire.

4. The method according to claim 3, characterized in that The magnetic field generating device includes a permanent magnet or an electromagnet.

5. The method according to claim 3, characterized in that: The magnetic field generating device is placed outside the passivation tank; or the magnetic field generating device is wrapped by a protective cover and placed near the aluminum alloy in the passivation tank.

6. The method according to claim 5, characterized in that The material of the protective cover is a material that does not shield the parallel magnetic field and the vertical magnetic field and does not participate in the passivation reaction.

7. The aluminum alloy obtained according to the method according to any one of claims 1 to 6.

8. Use of the aluminum alloy according to claim 7 in corrosion-resistant lightweight parts.

9. Application of the aluminum alloy according to claim 7 in the fields of ocean, chemical industry and machinery.

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