Method for detecting surface defects of an aluminum alloy sheet

Abstract

The present application relates to a kind of detection methods of surface defects of aluminum alloy plate, the surface defects of aluminum alloy plate include the microdefect of depth size is 100 μm below, the detection method includes the following steps: -obtain the sample of aluminum alloy plate to be detected;-using degreasing agent to the sample obtained is carried out degreasing treatment;-after degreasing treatment, the sample is put into the alkaline polishing liquid of pH value 8 to 13 and is carried out electrolytic treatment to enlarge the size of microdefect, sample is connected as anode material with power supply positive pole, cathode material is connected with power supply negative pole;-after electrolytic treatment, the sample is carried out colorant penetration treatment;And-visual observation the surface of sample after colorant penetration treatment, to determine whether there is defect.The detection method of surface defects of aluminum alloy plate according to the present application can quickly and effectively identify the microcrack type defect on the surface of aluminum alloy that cannot be identified by using penetration flaw detection alone.

Description

Technical Field

[0001] This invention relates to the field of metal material testing, and particularly to a method for detecting surface defects in aluminum alloy sheets, and even more particularly to a method for rapidly detecting or identifying micro-defects on the surface of aluminum alloy sheets. Background Technology

[0002] In recent years, with the increasing scarcity of energy and the growing severity of environmental problems, energy conservation and emission reduction have become essential issues for traditional industries. In the automotive manufacturing industry, the main ways to achieve energy conservation and emission reduction in vehicles are through the use of clean energy and the lightweighting of the vehicle body structure. Lightweighting the vehicle body structure further enhances energy conservation and emission reduction on the basis of using clean energy for power. Therefore, lightweighting the vehicle body structure has received significant attention from vehicle manufacturers. The main method to achieve lightweighting is to replace traditional galvanized steel sheets and other materials with lighter aluminum and magnesium alloys in non-load-bearing parts of the body. Currently, the application rate of aluminum alloys in vehicle body structures is gradually increasing, with some high-end vehicles using aluminum alloys accounting for as much as 50-60%.

[0003] Magnesium, aluminum, and other alloy coils are obtained by rolling and heat-treating cast ingots once or multiple times. To facilitate transportation and provide good oxidation resistance, aluminum alloy coils often undergo surface treatments before leaving the factory, including degreasing, Ti-Zr passivation, and oiling. During the rolling process, factors such as bubbles in the cast ingot, slag inclusions, mechanical damage, and over-machining result in surface defects in the aluminum alloy. These defects are difficult to cover up.

[0004] Furthermore, current automotive body pretreatment processes are gradually shifting from steel-aluminum co-phosphating technology to two-step methods (e.g., see US6733896) and Ti-Zr conversion coating methods (e.g., see CN112376038A). Regardless of the two-step method or the Ti-Zr conversion coating method, the oxide film thickness produced on the aluminum alloy surface is only around tens of nanometers. Compared to the tens of micrometers of protective layer obtained by phosphating, its ability to conceal surface defects is very limited. These unmasked defects will generate fine particles on the electrophoretic paint surface during subsequent electrophoretic treatment, affecting paint film quality and increasing the labor and cost of subsequent polishing.

[0005] For the reasons mentioned above, it is essential to adopt a method for rapid detection or identification of board defects that can be applied on the production site. For crack-like defects on the board surface, the most commonly used method on-site is penetrant testing.

[0006] However, in practice, the use of dye penetrant testing is not always very effective, as it may not accurately reveal surface defects in aluminum alloy sheets.

[0007] Therefore, there is a need for a method for detecting surface defects in aluminum alloy sheets that can be applied to production sites and has high accuracy and speed. Summary of the Invention

[0008] To overcome at least one of the aforementioned drawbacks in the prior art, the present invention provides a method for detecting surface defects in aluminum alloy sheets, including micro-defects with a depth dimension of less than 100 μm. The detection method includes the following steps: - obtaining a sample of the aluminum alloy sheet to be tested; - degreasing the obtained sample with a degreasing agent; - immersing the degreased sample in an alkaline polishing solution with a pH value of 8 to 13 for electrolytic treatment to expand the size of the micro-defects, with the sample connected as the anode material to the positive terminal of a power supply and the cathode material connected to the negative terminal of the power supply; - subjecting the electrolytically treated sample to a colorant penetration treatment; and - visually observing the surface of the sample after the colorant penetration treatment to determine whether defects exist on the surface of the aluminum alloy sheet. The method for detecting surface defects in aluminum alloy sheets according to the present invention can quickly and effectively identify micro-crack-like defects on the aluminum alloy surface that cannot be identified by penetrant testing alone.

[0009] Through research, the inventors discovered that the use of dye penetrant testing agents cannot always effectively identify surface defects in aluminum alloy sheets, mainly for the following reasons. While penetrant testing agents can effectively detect defects on the surface of metal sheets such as aluminum alloys, their detection capability is greatly affected by the surface condition and defect morphology, and is generally only suitable for detecting relatively macroscopic defects, such as those with dimensions in the hundreds of micrometers. Furthermore, the inventors found that the presence of oxide films and grease impurities on the surface of aluminum alloy sheets significantly hinders the penetration of the dye into the cracks. In addition, when the depth of cracks on the aluminum alloy surface is less than 100 μm, especially less than 50 μm, the crack's ability to store dye is poor, resulting in indistinct color development at subsequent defect sites. All of these factors contribute to poor final penetrant testing results. Therefore, this invention creatively employs a detection method combining degreasing and polishing solution electrolysis. Specifically, this invention uses degreasing treatment to remove grease from the surface of the aluminum alloy sheet, ensuring the cleanliness of the aluminum alloy surface. On the other hand, electropolishing is usually used to make the surface of metal sheets smooth and flat (i.e., polishing in the conventional sense). However, the inventors have taken a different approach and creatively used polishing liquid to electrolyze aluminum alloy sheets in order to effectively remove oxides and hydroxides from the surface of the sheet, while further expanding the depth of microcracks, thereby improving the ability of dye penetrant testing agents to identify microcracks on the surface of the sheet.

[0010] According to a preferred embodiment, the alkaline polishing solution comprises Na₂CO₃ at a concentration of 5-150 g / L, Na₃PO₄ at a concentration of 3-60 g / L, NaOH at a concentration of 1-15 g / L, and a complexing agent at a concentration of 0.2-5 g / L. The polishing solution used in this invention is inexpensive, recyclable, and has low environmental pollution.

[0011] According to a preferred embodiment, the complexing agent is an alkanolamine, an organophosphonate, or an aminocarboxylate. This complexing agent is readily available and effective.

[0012] According to a preferred embodiment, the cathode material is stainless steel or graphite plate. This cathode material is readily available.

[0013] According to a preferred embodiment, the distance between the anode material and the cathode material is 3-10 cm, and the current density during the electrolysis process is controlled to be 5-25 A / dm³. 2 The temperature is set between 8-60℃, and the electrolysis time is controlled between 1-30 minutes. The polishing solution electrolysis process of this invention is simple and easy to operate.

[0014] According to a preferred embodiment, the surface defects of the aluminum alloy sheet include micro-defects with a depth dimension of less than 50 μm. Conventional penetrant testing methods are insufficient to effectively identify micro-cracks of this size.

[0015] According to a preferred embodiment, the alkaline polishing solution has a pH of 8.5-9.5 and contains approximately 30 g / L of Na₂CO₃, approximately 8 g / L of Na₃PO₄, approximately 4 g / L of NaOH, and 0.2 g / L of triethanolamine. Triethanolamine is a complexing agent.

[0016] According to a preferred embodiment, the distance between the anode material and the cathode material is approximately 5 cm, and the current density during the electrolysis process is controlled to be approximately 8 A / dm³. 2 The temperature was set at approximately 40°C, and the electrolysis time was controlled to approximately 3 minutes.

[0017] According to a preferred embodiment, the alkaline polishing solution has a pH of 9.5-10.5 and contains approximately 50 g / L of Na₂CO₃, approximately 5 g / L of Na₃PO₄, approximately 6 g / L of NaOH, and 0.5 g / L of sodium diethylenetriaminepentamethylenephosphonate. Sodium diethylenetriaminepentamethylenephosphonate is a complexing agent.

[0018] According to a preferred embodiment, the distance between the anode material and the cathode material is approximately 4 cm, and the current density during the electrolysis process is controlled to be approximately 5 A / dm³. 2The temperature was set at approximately 30°C, and the electrolysis time was controlled at approximately 1.5 minutes.

[0019] Other features of the invention will become apparent from the accompanying drawings and from the following description of exemplary embodiments. Attached Figure Description

[0020] The invention will now be specifically described below with reference to the accompanying drawings. The drawings are for illustrative purposes only and should not be construed as limiting the scope of the invention. In the drawings:

[0021] Figure 1 This is a flowchart illustrating a method for detecting surface defects in aluminum alloy sheets according to an exemplary embodiment of the present invention. Detailed Implementation

[0022] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. However, it should be understood that the descriptions of various embodiments are merely illustrative and not intended to limit the technology of the present invention in any way. It should also be understood that the embodiments disclosed herein can be combined in various ways to provide further additional embodiments.

[0023] Unless otherwise specified, all terms used in this specification have the meanings commonly understood by those skilled in the art. For the sake of brevity and / or clarity, well-known functions or structures are not described in detail.

[0024] Unless otherwise specified, the singular forms “a,” “the,” and “the” used in the specification may include plural forms. The terms “comprising,” “including,” and “containing” used in the specification indicate the presence of the claimed feature, but do not exclude the presence of one or more other features.

[0025] In the instruction manual, unless explicitly stated otherwise, the terms "first," "second," "third," etc., are used only to distinguish the use of each step or component and are not intended to restrict the order of the steps or components. Furthermore, subsequent steps or components, such as "second" or "third," may be used even if a prior step or component, such as "first," is not included or employed.

[0026] In this specification, aluminum alloy sheet is used, for example, as automotive aluminum alloy sheet. Typically, such aluminum alloy sheet is a smooth sheet after rolling or stamping. "Micro-defects" on the surface of aluminum alloy sheet refer to defects such as cracks with a depth of less than 100 μm, particularly less than 50 μm, that cannot be effectively identified using conventional penetrant testing methods. The method for detecting surface defects in aluminum alloy sheet according to the present invention will be described in detail below.

[0027] First, cut a sample from the aluminum alloy sheet to be tested. The sample size can be controlled, for example, 5-10cm × 10-20cm. If necessary, the cut edges of the sample can be sanded with 500-4000 grit sandpaper to remove burrs produced by cutting or other processes. Note that care should be taken to avoid damaging the surface of the sample to be tested.

[0028] Then, the obtained sample is degreased using a degreasing agent. The degreasing agent can be, for example, a weakly alkaline degreasing agent, an acidic degreasing agent, an organic solvent, or a mixture of the above. The degreasing temperature can be controlled between 10-80℃, and the time between 0.5-30 minutes. Degreasing removes grease and other impurities from the sample surface; otherwise, these impurities would significantly hinder the penetration of the colorant into the cracks on the sample surface during the subsequent colorant penetration treatment.

[0029] Next, an alkaline polishing solution for electrolysis is prepared. The polishing solution may contain 5-150 g / L Na₂CO₃, 3-60 g / L Na₃PO₄, 1-15 g / L NaOH, and 0.2-5 g / L of a complexing agent. The pH of the polishing solution can be adjusted to 8-13 using a dilute acid solution such as dilute hydrochloric acid. Preferably, the complexing agent is an alkanolamine, organophosphonate, or aminocarboxylate.

[0030] After preparing the polishing solution, place it in the electrolytic cell. A DC power supply can be used for electrolysis. The degreased sample is connected to the positive terminal of the power supply as the anode material, and the cathode material is connected to the negative terminal. Preferably, the cathode material is stainless steel or a graphite plate. The cathode and anode materials are placed parallel to each other, with a distance of 3-10 cm between them. During electrolysis, the current density can be controlled at 5-25 A / dm³. 2 The temperature can be set between 8-60℃, and the electrolysis time can be controlled between 1-30 minutes. The alkaline polishing solution electrolysis process can effectively remove oxides and hydroxides from the surface of aluminum alloy sheet samples and further deepen the microcracks on the sample surface. This enhances the ability of the penetrant to identify microcracks on the sheet surface during subsequent colorant penetration treatment.

[0031] If necessary, the aluminum alloy sheet samples can be rinsed with deionized water after electrolytic treatment to remove any residual electrolyte (i.e., polishing solution) on the sample surface. The rinsed samples then need to be dried. For example, the drying process can be carried out in a drying oven, with the drying temperature set to 5-100℃ and the time controlled to 5-120 minutes.

[0032] Next, the sample undergoes a penetrant treatment, also known as penetrant testing. The standard for penetrant testing methods can be JB / T 6062-1992. The penetrant (also called a penetrant or fluorescent agent) can be commercially available Hongda brand HD-ST type. The penetrant will penetrate into any cracks that may exist on the surface of the aluminum alloy sheet sample. The deeper the crack, the deeper the penetrant penetrates, and the less likely it is to be washed away during subsequent cleaning processes. Because the aforementioned electrolytic process increases the size (depth and width) of microcrack-like defects, the retention capacity of the defect area for the penetrant also increases, resulting in more obvious color development at the defect area. Therefore, it is possible to effectively identify micro-cracks on the aluminum alloy surface that cannot be detected by penetrant testing alone.

[0033] Finally, visually inspect the aluminum alloy sheet samples after the colorant penetration treatment. Smooth, crack-free areas of the sample surface will be covered by the white colorant. If cracks are present on the sample surface, a red color will appear on the white colorant. If no red color is observed on the white colorant, it can be confirmed that there are no defects on the sample surface.

[0034] It should be noted that not all of the above steps are mandatory; one or more of these steps can be omitted, or one or more additional steps can be added as appropriate. For example, if the edges of the obtained sample are smooth and flat, a grinding and deburring step is not necessary.

[0035] The following will further illustrate the method for detecting surface defects in aluminum alloy sheets according to the present invention, in conjunction with the following embodiments and comparative examples.

[0036] Example 1

[0037] First, test samples were cut from aluminum alloy sheets known to have surface micro-defects, with the sample size controlled to approximately 10cm × 10cm. The cut edges of the samples were then polished with 800 and 1000 grit sandpaper to remove burrs produced during cutting and other processes.

[0038] The obtained samples were then degreased using a degreasing agent. The degreasing temperature was controlled at approximately 40°C, and the time was controlled at approximately 10 minutes.

[0039] Next, an alkaline polishing solution is prepared. The polishing solution contains approximately 30 g / L Na₂CO₃, approximately 8 g / L Na₃PO₄, approximately 4 g / L NaOH, and approximately 0.2 g / L triethanolamine. The pH of the polishing solution is adjusted to 8.5-9.5, for example, approximately 9, using a dilute acid solution.

[0040] After preparing the polishing slurry, it was placed in the electrolytic cell. A DC power supply was used as the electrolytic power source. The degreased aluminum alloy sheet sample was connected to the positive terminal of the DC power supply as the anode material, and the cathode material was connected to the negative terminal of the DC power supply. The cathode material and anode material were placed parallel to each other, with the distance between them controlled at approximately 5 cm. The current density during the electrolysis process was controlled at approximately 8 A / dm³. 2 The temperature was controlled at approximately 40°C, and the electrolysis time was controlled at approximately 3 minutes.

[0041] Next, after rinsing the sample with deionized water to remove residual electrolyte from the surface, the sample was dried for about 5 minutes at a temperature of about 50°C.

[0042] Next, the dried aluminum alloy sheet samples were subjected to a coloring and penetration treatment using a colorant.

[0043] Finally, a red color was clearly observed on the surface of the white colorant after the sample was treated with the colorant.

[0044] This demonstrates that the detection method of the present invention successfully detected micro-defects on the surface of aluminum alloy sheets.

[0045] Example 2

[0046] First, test samples were cut from aluminum alloy sheets known to have surface micro-defects, with the sample size controlled to approximately 5cm × 10cm. The cut edges of the samples were then polished with 800 and 1200 grit sandpaper to remove burrs produced during cutting and other processes.

[0047] The obtained samples were then degreased using a degreasing agent. The degreasing temperature was controlled at approximately 25°C, and the time was controlled at approximately 5 minutes.

[0048] Next, an alkaline polishing solution is prepared. The polishing solution contains approximately 50 g / L Na₂CO₃, approximately 5 g / L Na₃PO₄, approximately 6 g / L NaOH, and approximately 0.5 g / L sodium diethylenetriaminepentamethylphosphonate. The pH of the polishing solution is adjusted to 9.5-10.5, for example, approximately 10, using a dilute acid solution.

[0049] After preparing the polishing slurry, it was placed in the electrolytic cell. A DC power supply was used as the electrolytic power source. The degreased aluminum alloy sheet sample was connected to the positive terminal of the DC power supply as the anode material, and the cathode material was connected to the negative terminal of the DC power supply. The cathode material and anode material were placed parallel to each other, with the distance between them controlled at approximately 4 cm. The current density during the electrolysis process was controlled at approximately 5 A / dm³. 2 The temperature was controlled at approximately 30°C, and the electrolysis time was controlled at approximately 1.5 minutes.

[0050] Next, after rinsing the sample with deionized water to remove residual electrolyte from the surface, the sample was dried for about 5 minutes at a temperature of about 65°C.

[0051] Next, the dried aluminum alloy sheet samples were subjected to a coloring and penetration treatment using a colorant.

[0052] Finally, a red color was clearly observed on the surface of the white colorant after the sample was treated with the colorant.

[0053] This demonstrates that the detection method of the present invention successfully detected micro-defects on the surface of aluminum alloy sheets.

[0054] Comparative Example 1

[0055] First, a sample to be tested is cut from an aluminum alloy sheet known to have surface micro-defects. The sample size is controlled to be approximately 5cm × 10cm. The cut edges of the sample are polished with 500-4000 grit sandpaper to remove burrs produced by cutting and other processes.

[0056] The obtained samples were then degreased using a degreasing agent. The degreasing temperature was controlled at approximately 50°C, and the time was controlled at approximately 20 minutes.

[0057] Next, an alkaline polishing solution is prepared. The polishing solution contains approximately 80 g / L Na₂CO₃, approximately 20 g / L Na₃PO₄, approximately 10 g / L NaOH, and approximately 1 g / L polyacrylamide. The pH of the polishing solution is adjusted to approximately 11 using a dilute acid solution.

[0058] After preparing the alkaline polishing solution, instead of electrolytic treatment, the degreased sample is chemically treated by placing the sample in the prepared polishing solution and treating it at 30°C for 8 minutes.

[0059] Next, after rinsing the sample with deionized water to remove the residual polishing liquid on the surface, the sample was dried for about 20 minutes at a temperature of about 50°C.

[0060] Next, the dried aluminum alloy sheet samples were subjected to a coloring and penetration treatment using a colorant.

[0061] Finally, only white colorant was observed on the surface of the sample after the colorant penetration treatment, and no red colorant was observed.

[0062] This indicates that if the aluminum alloy sheet sample is not electrolyzed with a polishing solution as in this invention, micro-defects on the surface of the aluminum alloy sheet cannot be effectively identified.

[0063] Comparative Example 2

[0064] First, test samples were cut from aluminum alloy sheets known to be free of surface defects, with the sample size controlled to approximately 5cm × 10cm. The cut edges of the samples were then polished with 800 and 1200 grit sandpaper to remove burrs produced during cutting and other processes.

[0065] The obtained samples were then degreased using a degreasing agent. The degreasing temperature was controlled at approximately 25°C, and the time was controlled at approximately 5 minutes.

[0066] Next, an alkaline polishing solution is prepared. The polishing solution contains approximately 50 g / L Na₂CO₃, approximately 5 g / L Na₃PO₄, approximately 6 g / L NaOH, and approximately 0.5 g / L sodium diethylenetriaminepentamethylphosphonate. The pH of the polishing solution is adjusted to approximately 10 using a dilute acid solution.

[0067] After preparing the polishing slurry, it was placed in the electrolytic cell. A DC power supply was used as the electrolytic power source. The degreased aluminum alloy sheet sample was connected to the positive terminal of the DC power supply as the anode material, and the cathode material was connected to the negative terminal of the DC power supply. The cathode material and anode material were placed parallel to each other, with the distance between them controlled at approximately 4 cm. The current density during the electrolysis process was controlled at approximately 5 A / dm³. 2 The temperature was controlled at approximately 30°C, and the electrolysis time was controlled at approximately 1.5 minutes.

[0068] Next, after rinsing the sample with deionized water to remove residual electrolyte from the surface, the sample was dried for about 5 minutes at a temperature of about 65°C.

[0069] Next, the dried aluminum alloy sheet samples were subjected to a coloring and penetration treatment using a colorant.

[0070] Finally, only white developer was observed on the surface of the sample after the colorant penetration treatment, with no red development. This indicates that no defects were detected on the surface of the aluminum alloy sheet.

[0071] As can be seen, except that the sample to be tested is an aluminum alloy sheet known to be free of surface defects, the other process steps and parameters of Comparative Example 2 are basically the same as those of Example 2. Consistent with actual conditions, Comparative Example 2 identified no defects on the surface of the aluminum alloy sheet. This further demonstrates the effectiveness of the detection method of the present invention. By using the specific polishing liquid composition and electrolysis control parameters defined in this invention, the electrolysis process will not generate new defects that are not present on the surface of the aluminum alloy sheet sample, thus preventing distortion of the detection results.

[0072] In summary, the present invention employs a combined degreasing and alkaline polishing solution electrolysis process, which can effectively remove grease and other impurities from the surface of aluminum alloy sheets, ensuring the cleanliness of the aluminum alloy surface. In addition, alkaline polishing solution electrolysis can effectively remove oxides and hydroxides from the surface of aluminum alloy sheets, and can further extend the depth of microcracks, thereby improving the ability of penetrant testing agents to identify microcracks on the surface of aluminum alloy sheets.

[0073] The detection method of the present invention is low in cost, the electrolyte used can be recycled and reused multiple times, it has little environmental pollution, the process is simple and feasible, and the detection results are intuitive and clear. It has great application prospects in the detection and identification of surface defects, especially micro-defects, of aluminum alloy plates.

[0074] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A method for detecting surface defects in aluminum alloy sheets, wherein the surface defects of the aluminum alloy sheets include micro-defects with a depth dimension of less than 100 μm, the detection method comprising the following steps: - Obtain a sample of the aluminum alloy sheet to be tested; - The obtained samples were degreased using a degreasing agent; - The degreased sample is placed in an alkaline polishing solution with a pH of 8 to 13 for electrolytic treatment to expand the size of micro-defects. The sample is connected to the positive terminal of the power supply as the anode material, and the cathode material is connected to the negative terminal of the power supply. - The electrolyzed sample is then subjected to a colorant permeation treatment; and - Visually inspect the surface of the sample after colorant penetration treatment to determine whether there are any defects on the surface of the aluminum alloy sheet. The alkaline polishing solution contains Na2CO3 at a concentration of 5-150 g / L, Na3PO4 at a concentration of 3-60 g / L, NaOH at a concentration of 1-15 g / L, and a complexing agent at a concentration of 0.2-5 g / L.

2. The method for detecting surface defects in aluminum alloy sheets according to claim 1, characterized in that, The complexing agent is an alcohol amine, an organophosphonate, or an aminocarboxylate.

3. The method for detecting surface defects in aluminum alloy sheets according to any one of claims 1-2, characterized in that, The cathode material is stainless steel or graphite plate.

4. The method for detecting surface defects in aluminum alloy sheets according to any one of claims 1-2, characterized in that, The distance between the anode and cathode materials is set to 3-10 cm, and the current density during electrolysis is controlled to be 5-25 A / dm³. 2 The temperature is set between 8 and 60°C, and the electrolysis time is controlled between 1 and 30 minutes.

5. A method for detecting surface defects in aluminum alloy sheets according to any one of claims 1-2, characterized in that, Surface defects in aluminum alloy sheets include micro-defects with a depth dimension of less than 50 μm.

6. The method for detecting surface defects in aluminum alloy sheets according to claim 2, characterized in that, The alkaline polishing solution has a pH of 8.5-9.5 and contains approximately 30 g / L of Na2CO3, approximately 8 g / L of Na3PO4, approximately 4 g / L of NaOH, and 0.2 g / L of triethanolamine.

7. The method for detecting surface defects in aluminum alloy sheets according to claim 6, characterized in that, The distance between the anode and cathode materials is approximately 5 cm, and the current density during electrolysis is controlled to be approximately 8 A / dm³. 2 The temperature was set at approximately 40°C, and the electrolysis time was controlled to approximately 3 minutes.

8. The method for detecting surface defects in aluminum alloy sheets according to claim 2, characterized in that, The alkaline polishing solution has a pH of 9.5-10.5 and contains approximately 50 g / L of Na2CO3, approximately 5 g / L of Na3PO4, approximately 6 g / L of NaOH, and 0.5 g / L of sodium diethylenetriaminepentamethylphosphonate.

9. The method for detecting surface defects in aluminum alloy sheets according to claim 8, characterized in that, The distance between the anode and cathode materials is approximately 4 cm, and the current density during electrolysis is controlled to be approximately 5 A / dm³. 2 The temperature was set at approximately 30°C, and the electrolysis time was controlled to approximately 1.5 min.

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