Method for testing corrosion resistance of 2024 and 6061 aluminum alloy bimetal composite material

Abstract

The application relates to the technical field of layered metal composite materials, in particular to a detection method for the corrosion resistance of 2024 and 6061 aluminum alloy bimetal composite materials, and a preparation method thereof is as follows: S1, sample preparation: cutting a 2024 / 6061 aluminum alloy bimetal composite material sample into a 1cm*1cm*1cm cubic small block, wherein the interface is in the middle of the bimetal composite material; then, oil removal, polishing and polishing are carried out. The application preliminarily judges and determines the regions (matrix material, element diffusion region and cladding material) of the composite material through a metallographic diagram and a scanning diagram, and then combines hardness testing to determine the specific position of the diffusion zone of the bimetal composite material; then, each part is corroded, and the element diffusion region is divided into a region close to the matrix material, a contact region and a region close to the cladding region through a corrosion appearance; and the test of the bimetal composite material is more accurate, and the service time of the bimetal composite material can be fully judged.

Description

Technical Field

[0001] This invention relates to the field of layered metal composite materials technology, and in particular to a method for testing the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials. Background Technology

[0002] With the rapid development of industry and the ever-increasing demands on material performance, traditional single-component materials are no longer sufficient to meet these requirements. Currently, more and more people are focusing on new materials with superior performance and energy-saving and environmentally friendly capabilities to meet the various performance needs of modern society. The reliability and stability of bimetallic composite materials during service are crucial for production and operational safety. However, during use, bimetallic materials may be affected by corrosion, leading to performance degradation, damage, or even failure, thus requiring corrosion performance testing. However, predicting the corrosion performance of bimetallic composite materials is difficult. This invention proposes a method for rapidly, accurately, and reliably evaluating the corrosion resistance of bimetallic composite materials by determining the diffusion band and employing comprehensive characterization techniques, providing a complete methodological system for characterizing the corrosion performance of bimetallic composite materials.

[0003] A technical literature search revealed a paper titled "Influence of Pickling and Passivation on the Corrosion Resistance of Circumferential Welds in 316L / L415 Bimetallic Mechanical Composite Pipes" (DOI 10.11973 / fsyfh-202011009). This paper compares the corrosion resistance of welded samples before and after pickling and passivation of bimetallic composite materials using morphological observation, electrochemical tests, and pitting corrosion tests. However, it does not discuss the different parts of the composite material separately and lacks a clear definition of the element diffusion distance at the interface. Therefore, the corrosion test results are not specific enough, only providing the overall corrosion performance of the bimetallic composite material and not allowing for detailed prediction of its lifespan. A paper titled "Corrosion Resistance of Argon-Free Welded Joints of L415 / 316L Composite Pipes" (DOI 10.13289 / j.issn) in the journal "Materials Heat Treatment" analyzes the corrosion resistance and chemical composition of the joint's inner wall using electrochemical tests, plate experiments, and electron probe microanalysis. Although the article describes testing from welded joints, it does not demonstrate element diffusion and cannot definitively determine the width of the diffusion band. The aforementioned literature reports also fail to specify the corrosion depth of the composite material at a specific time during service. Therefore, it is necessary to invent a comprehensive testing method to fully characterize the corrosion performance of composite materials. To date, there are no literature or patent reports on a complete method for predicting the corrosion performance of bimetallic composite materials.

[0004] Current methods for testing the corrosion performance of bimetallic composite materials are too crude. They fail to identify the different alloy compositions and element diffusion zones within the bimetal, and often test the entire composite material for corrosion. This results in inaccurate test results, which can only provide an overall overview of the corrosion performance and cannot predict the specific corrosion depth of the composite material during service. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for testing the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for testing the corrosion resistance of a bimetallic composite material of 2024 and 6061 aluminum alloys, the preparation method of which is as follows:

[0008] S1. Sample Preparation: Cut the 2024 / 6061 aluminum alloy bimetallic composite sample into 1cm×1cm×1cm cubes, with the interface located in the middle of the bimetallic composite. Then, perform degreasing, grinding, and polishing.

[0009] S2. Characterizing interfacial element diffusion in bimetallic composites: The element diffusion distance of the bimetallic interface was obtained by characterizing the bimetallic interface using SEM, EDS, and hardness distribution. The bimetallic composite was cut into three parts: 2024 aluminum alloy, diffusion band, and 6061 aluminum alloy.

[0010] S3. Characterize the corrosion morphology of the bimetallic composite material interface: The three cut materials were degreased, ground, polished and etched respectively, and then observed by OM, SEM and AFM. The diffusion zone was divided into three parts by corrosion morphology: the side close to 2024 aluminum alloy, the joint and the side close to 6061 aluminum alloy.

[0011] S4. Polarization curve test: The polarization curve of the composite material was tested using an electrochemical workstation;

[0012] S5. Corrosion rate test: The weight loss of the sample before and after corrosion is calculated.

[0013] Compared with existing technologies, this application uses metallographic images and scanning electron microscope images to make a preliminary judgment on the element diffusion situation and determine the various regions of the composite material (matrix material, element diffusion region, and coating material). Then, it combines hardness testing to determine the specific location of the diffusion zone of the bimetallic composite material. After that, each part is etched and the element diffusion region is divided into the region near the matrix material, the contact region, and the region near the coating material by the corrosion morphology. This makes the testing of the bimetallic composite material more accurate and can fully determine the service life of the bimetallic composite material.

[0014] Preferably, in steps S1 and S3, the degreasing process of the cut material is first performed by grinding on 180# sandpaper, and while ensuring that the surface has a certain roughness, the material is placed in a cleaning agent and ultrasonically cleaned for 10 minutes to remove residual oil stains; grinding is performed on 400#, 600#, 800#, 1000#, 1200#, and 1500# sandpaper respectively; polishing is performed on a polishing machine.

[0015] Furthermore, by using a variety of sandpapers, precise grinding of the corresponding materials can be achieved, and polishing operations can be fully performed to ensure the clarity and smoothness of the cross-section.

[0016] Preferably, in step S2, the location of the interface needs to be determined by SEM, and then the main elements in the metals on both sides of the interface of the bimetallic composite material are scanned to show the diffusion distance of each atom. Finally, the width of the diffusion band is determined by combining the hardness distribution.

[0017] Furthermore, it can clearly obtain information about the width of the diffusion band.

[0018] Preferably, in step S3, the corrosion is carried out using a 3.5% NaCl solution, and the salt immersion treatment time is 8-72 hours. The principle of segmentation is that the corrosion rate of each part of the diffusion zone is not consistent. By observing various tissue morphologies, the specific range of each part can be determined, thereby enabling more precise control over the corrosion of the composite material.

[0019] Furthermore, precise operation can fully ensure accurate control over the corrosion of composite materials.

[0020] Preferably, in step S4, the treated materials are fixed with conductive adhesive to the surface of the material to be tested, and the materials after connecting the wires are embedded to avoid poor conductivity during the test. The concentration of the NaCl solution for salt immersion treatment is 3.5%, and the salt immersion treatment time is 10-60 minutes to improve the stability of the material in salt water. After salt immersion treatment, the material is connected to a three-electrode system for testing.

[0021] Furthermore, a three-electrode system is used to achieve precise testing.

[0022] Preferably, in step S5, a 3.5% NaCl solution is used for corrosion for 72-360 hours. After corrosion, the sample needs to be immersed in a mixed solution of 45-55g CrO3, 2-3g AgNO3, 4-6g Ba(NO3)2 and 250ml deionized water for 15 minutes to remove surface corrosion products. Then, it is rinsed with clean water and dried with a hair dryer.

[0023] Furthermore, it can effectively remove surface impurities and facilitates quick cleaning.

[0024] Preferably, the reference electrode in the three-electrode system is a saturated calomel electrode, and the auxiliary electrode is a Pt sheet.

[0025] Furthermore, this ensures the stable operation of the three-electrode system.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention uses SEM for surface and line scanning to visually observe the distribution changes of elements at the interface of bimetallic composite materials and the diffusion distance of elements, thereby enabling the bimetallic composite materials to be classified into different components.

[0028] 2. This invention observes the corrosion morphology of samples using OM, SEM, and AFM, which can determine the corrosion rate of each part of the element diffusion region, and then divide each part into three parts, laying the foundation for accurate prediction of the corrosion depth of the material.

[0029] 3. This invention can obtain the specific corrosion status of each part of the bimetallic composite material by analyzing the polarization curve and corrosion rate of the sample. It can determine the specific corrosion time and corrosion depth of the bimetallic composite material, and the specific corrosion depth at a specific time during service. This is of great significance for the application of bimetallic composite materials.

[0030] 4. The method for detecting the corrosion resistance of bimetallic composite materials proposed in this invention is accurate, verifiable, and fills a gap in the field. Attached Figure Description

[0031] Figure 1 This is a distance diagram of the diffusion zone in a method for detecting the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials proposed in this invention.

[0032] Figure 2 The diffusion band distance is plotted as a method for detecting the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials proposed in this invention.

[0033] Figure 3 The image shows the corrosion morphology of one side of the 2024 aluminum alloy, which is part of the method for detecting the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials proposed in this invention.

[0034] Figure 4 The corrosion morphology of 6061 aluminum alloy is shown in the figure below, which is a method for detecting the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials proposed in this invention.

[0035] Figure 5 The aluminum alloy test line graph is a method for testing the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials proposed in this invention.

[0036] Figure 6 This is a sample test result data graph of a method for testing the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials proposed in this invention. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] Reference Figure 1-6 A method for testing the corrosion resistance of a bimetallic composite material of 2024 and 6061 aluminum alloys, the preparation method of which is as follows:

[0039] S1. Sample Preparation: The 2024 / 6061 aluminum alloy bimetallic composite material sample was cut into 1cm×1cm×1cm cubes, with the interface located in the middle of the bimetallic composite material. Then, degreasing, grinding, and polishing were performed. The degreasing process after cutting involved grinding on 180# sandpaper, ensuring a certain surface roughness, followed by ultrasonic cleaning in a cleaning agent for 10 minutes to remove residual oil. Grinding was performed on 400#, 600#, 800#, 1000#, 1200#, and 1500# sandpaper respectively. Polishing was performed on a polishing machine.

[0040] S2. Characterizing interfacial element diffusion in bimetallic composites: The bimetallic interface is characterized using SEM, EDS, and hardness distribution to obtain the element diffusion distance. The bimetallic composite is cut into three parts: 2024 aluminum alloy, diffusion band, and 6061 aluminum alloy. The position of the interface needs to be determined by SEM. Then, the main elements in the metals on both sides of the bimetallic composite interface are scanned to show the diffusion distance of each atom. Finally, the width of the diffusion band is determined by combining the hardness distribution.

[0041] S3. Characterizing the corrosion morphology of the bimetallic composite interface: The three cut parts of the material were degreased, ground, polished, and etched respectively. Then, OM, SEM, and AFM were used for observation. The diffusion zone was divided into three parts based on the corrosion morphology: the side near the 2024 aluminum alloy, the joint, and the side near the 6061 aluminum alloy. The degreasing process of the cut material was first carried out on 180# sandpaper. While ensuring a certain roughness, the material was placed in a cleaning agent and ultrasonically cleaned for 10 minutes to remove residual oil. Grinding was carried out on 400#, 600#, 800#, 1000#, 1200#, and 1500# sandpaper respectively. Polishing was carried out on a polishing machine. The etching was carried out with a 3.5% NaCl solution for 8-72 hours. The principle of segmentation is that the corrosion rate of each part of the diffusion zone is different. By observing various microstructures, the specific range of each part can be determined, so as to more accurately control the corrosion of the composite material.

[0042] S4. Polarization Curve Test: The polarization curve of the composite material is tested using an electrochemical workstation. The treated material is then fixed with conductive adhesive to the surface of the material to be tested. The material after connecting the wires is then embedded to avoid poor conductivity during the test. The concentration of NaCl solution for salt immersion treatment is 3.5%, and the salt immersion treatment time is 10-60 min to improve the stability of the material in salt water. After salt immersion treatment, the material is connected to a three-electrode system for testing. The reference electrode in the three-electrode system is a saturated calomel electrode, and the auxiliary electrode is a Pt sheet.

[0043] S5. Corrosion rate test: The weight loss of the sample before and after corrosion is calculated. The sample is corroded with a 3.5% NaCl solution for 72-360 hours. After corrosion, the sample needs to be soaked in a mixed solution of 45-55g CrO3, 2-3g AgNO3, 4-6g Ba(NO3)2 and 250ml deionized water for 15 minutes to remove the surface corrosion products. Then rinse with clean water and dry with a hair dryer.

[0044] Example 1:

[0045] A 2024 / 6061 aluminum alloy bimetallic composite material was selected as the test sample, with a 5cm thickness of 2024 aluminum alloy and a 1cm thickness of 6061 aluminum alloy coating. The composite material was cut into 1cm×1cm×1cm cubes (with the composite interface in the center of the sample), and then degreased, ground, and polished. Scanning electron microscopy was then used to analyze the main elements Al, Cu, Mg, and Si in the 2024 and 6061 aluminum alloys. Combined with the hardness distribution at the interface of the bimetallic composite material, the distance of the diffusion bands was determined. The results are shown in the attached figure. Figure 1 Appendix Figure 2The sample was cut according to the diffusion distance of the elements on both sides. The three cut surfaces were then degreased, ground, and polished. The sample was then immersed in a 3.5% NaCl solution for 45 hours, cleaned, and dried. The corrosion morphology of the sample was observed using OM, SEM, and AFM. The results are attached. Figure 3 , Figure 4 As shown; then, by observing the corrosion morphology at the interface, the specific locations of the three parts—the side near the 2024 aluminum alloy, the joint, and the side near the 6061 aluminum alloy—can be determined. The diffusion zone material is cut into three parts, and then the surfaces of the five cut parts are degreased, ground, and polished respectively. Then, the opposite side of the test surface is connected with conductive adhesive and wires and placed in a mold for mounting. After mounting, the test sample is immersed in a 3.5% NaCl solution for 30 minutes. After immersion, the test material is connected to a three-electrode system, in which a saturated calomel electrode is used as the reference electrode, the test sample is used as the working electrode, and a Pt sheet is used as the auxiliary electrode. The results are shown in the attached figure. Figure 5 Appendix Figure 6 As shown, calculations show that the overall corrosion performance of the prepared bimetallic composite material is improved by 85.6%, with the corrosion performance of the coating and diffusion zone being 2.4% higher than that of the matrix.

[0046] Example 2:

[0047] A 2024 / 6061 aluminum alloy bimetallic composite material was selected as the test sample, with a 5cm thickness of 2024 aluminum alloy and a 1cm thickness of 6061 aluminum alloy coating. The layered metal composite material was cut into 1cm×1cm×1cm cubes (with the composite interface in the middle of the sample), and then degreased, ground, and polished. Scanning electron microscopy was then used to perform surface scanning of the main elements Al, Cu, Mg, and Si in the 2024 and 6061 aluminum alloys. Combined with the hardness distribution at the interface of the bimetallic composite material, the distance of the diffusion band was determined. The results are shown in the attached figure. Figure 1 Appendix Figure 2 The sample was cut according to the distance of element diffusion on both sides. The three cut surfaces were then degreased, ground, and polished. A 3.5% NaCl solution was used for corrosion for 300 hours. The sample was then immersed in a mixed solution of 50g CrO3, 2.5g AgNO3, 5g Ba(NO3)2, and 250ml deionized water for 15 minutes to remove surface corrosion products. Finally, the sample was rinsed with clean water and dried with a hair dryer. The weight change of the corroded sample before and after corrosion was measured to obtain the actual corrosion rate. Comparing this with the above predictions accurately yields the specific corrosion performance of the bimetallic composite material.

[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for testing the corrosion resistance of 2024 and 6061 aluminum alloy bimetallic composite materials, characterized in that, Its preparation method is as follows: S1. Sample preparation: Cut the 2024 / 6061 aluminum alloy bimetallic composite material sample into 1cm×1cm×1cm cubes, with the interface in the middle of the bimetallic composite material. Then, degrease, grind and polish the sample. S2. Characterizing interfacial element diffusion in bimetallic composites: The element diffusion distance of the bimetallic interface was obtained by characterizing the bimetallic interface using SEM, EDS, and hardness distribution. The bimetallic composite was cut into three parts: 2024 aluminum alloy, diffusion band, and 6061 aluminum alloy. S3. Characterize the corrosion morphology of the bimetallic composite material interface: The three cut materials were degreased, ground, polished and etched respectively, and then observed by OM, SEM and AFM. Based on the difference in corrosion rate and microstructure characteristics of different regions of the diffusion zone, the diffusion zone was further divided into three parts: the side close to the 2024 aluminum alloy, the joint, and the side close to the 6061 aluminum alloy. S4. Polarization curve test: The polarization curves of the five divided parts were tested using an electrochemical workstation. S5. Corrosion rate test: The corrosion rate of the above five parts is calculated by the weight loss method.

2. The method for testing the corrosion resistance of a 2024 and 6061 aluminum alloy bimetallic composite material according to claim 1, characterized in that: In steps S1 and S3, the degreasing process of the cut material is first performed by grinding on 180# sandpaper. While ensuring that the surface has a certain roughness, the material is placed in the cleaning agent and ultrasonically cleaned for 10 minutes to remove residual oil stains. Grinding is performed on 400#, 600#, 800#, 1000#, 1200#, and 1500# sandpaper respectively. Polishing is performed on a polishing machine.

3. The method for testing the corrosion resistance of a 2024 and 6061 aluminum alloy bimetallic composite material according to claim 1, characterized in that: In step S2, the location of the interface needs to be determined by SEM, and then the main elements in the metals on both sides of the bimetallic composite interface are scanned to show the diffusion distance of each atom. Finally, the width of the diffusion band is determined by combining the hardness distribution.

4. The method for testing the corrosion resistance of a 2024 and 6061 aluminum alloy bimetallic composite material according to claim 1, characterized in that: In step S3, the corrosion is carried out using a 3.5% NaCl solution, and the salt leaching treatment time is 8-72 hours. The principle of segmentation is that the corrosion rate is inconsistent in different parts of the diffusion zone. By observing various microstructures, the specific range of each part can be determined, thus enabling more precise control over the corrosion of composite materials.

5. The method for testing the corrosion resistance of a 2024 and 6061 aluminum alloy bimetallic composite material according to claim 1, characterized in that: In step S4, the treated materials are fixed to the surface of the material to be tested with conductive adhesive. The materials after connecting the wires are then embedded to avoid poor conductivity during testing. The concentration of the NaCl solution for salt immersion treatment is 3.5%, and the salt immersion treatment time is 10-60 minutes to improve the stability of the material in salt water. After salt immersion treatment, the material is connected to a three-electrode system for testing.

6. The method for testing the corrosion resistance of a 2024 and 6061 aluminum alloy bimetallic composite material according to claim 1, characterized in that: In step S5, a 3.5% NaCl solution is used for corrosion for 72-360 hours. After corrosion, the sample needs to be immersed in a mixed solution of 45-55g CrO3, 2-3g AgNO3, 4-6g Ba(NO3)2 and 250ml deionized water for 15 minutes to remove surface corrosion products. Then, it is rinsed with clean water and dried with a hair dryer.

7. The method for testing the corrosion resistance of a 2024 and 6061 aluminum alloy bimetallic composite material according to claim 5, characterized in that: The reference electrode in the three-electrode system is a saturated calomel electrode, and the auxiliary electrode is a Pt sheet.

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