Aluminum alloy surface treatment method with high electrode dot count

Abstract

The application provides an aluminum alloy surface treatment method with high electrode dotting number. The treatment method comprises the following steps: performing pickling treatment on an aluminum alloy plate, adding reagent S5149 and H7274 into the pickling solution, the adding amount of the reagent S5149 and the reagent H7274 is 25 g / L and 12.5 g / L respectively, the pickling treatment temperature is 45-55 DEG C, and the pickling treatment time is 30-60 s; performing deionized water cleaning on the aluminum alloy plate after the pickling treatment, the deionized water temperature is room temperature, and the cleaning time is greater than or equal to 30 s; performing passivation treatment on the aluminum alloy plate after the deionized water cleaning, adding reagent X4591 and H7271 into the passivation treatment solution, the adding amount of the reagent X4591 and the reagent H7271 is 44.3 g / L and 18 g / L respectively, the passivation treatment temperature is 45-55 DEG C, and the passivation treatment time is 3-9 s; performing deionized water cleaning on the aluminum alloy plate after the passivation treatment, the deionized water temperature is room temperature, and the cleaning time is greater than or equal to 30 s; and performing drying on the aluminum alloy plate after the deionized water cleaning.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and more specifically, to a surface treatment method for aluminum alloys with a high number of electrode dots. Background Technology

[0002] Aluminum alloys have excellent application prospects in the field of automotive lightweighting. Currently, OEMs are actively increasing the use of aluminum materials in vehicle bodies to achieve weight reduction and carbon emission control. However, due to significant differences in the basic properties of aluminum alloys and steel, various challenges are frequently encountered in the promotion and application of aluminum alloys. Taking resistance spot welding as an example, due to the high electrical and thermal conductivity of aluminum alloys and the presence of a dense oxide film on their surface, severe chemical reactions occur at the interface between the copper electrode and the aluminum substrate when resistance spot welding is applied. This causes electrode surface contamination, which in turn causes contamination of subsequent weld joints, affecting application. Currently, OEMs mainly keep the electrode caps clean by frequently grinding them. The industry standard is to grind the electrode caps after welding approximately 30 consecutive aluminum alloy joints. This significantly increases the cost of aluminum alloy applications and challenges the continued promotion of aluminum alloy resistance spot welding technology.

[0003] The short lifespan of copper electrodes is due to the chemical reaction at the copper-aluminum interface. This problem arises because the aluminum alloy surface has a dense oxide film with an extremely high melting point and very poor conductivity. This oxide film generates a large amount of contact resistance during welding, which, according to Joule's law and the heat generation formula Q = ηI, results in a significant resistance. 2 Rt (where η is the efficiency coefficient) represents the high-temperature environment created by the resistance heat generated during the welding process between the copper electrode and the aluminum alloy substrate. Under these conditions, aluminum and copper form Cu-Al compounds, and this eutectic reaction causes strong adhesion between the copper electrode and the aluminum substrate, leading to severe burn-off of the copper electrode and affecting the electrode spot count. The electrode spot count is an evaluation criterion in resistance spot welding; a higher spot count indicates better surface quality of the aluminum alloy weld joint under the same welding conditions. Summary of the Invention

[0004] The main objective of this invention is to provide a surface treatment method for aluminum alloys with a high number of electrode spots, in order to solve the problem in the prior art that the surface contamination of aluminum alloy sheets gradually intensifies as the number of continuous resistance spot welding spots increases, resulting in a low number of electrode spots.

[0005] To achieve the above objectives, the present invention provides a surface treatment method for aluminum alloys with a high number of electrode dots, the method comprising the following steps:

[0006] Step S1: Pickling the aluminum alloy sheet by adding reagents S5149 and H7274 to the pickling solution at concentrations of 25 g / L and 12.5 g / L, respectively. The pickling temperature is 45–55 °C and the pickling time is 30–60 s.

[0007] Step S2: Clean the pickled aluminum alloy sheet with deionized water at room temperature for ≥30 seconds.

[0008] Step S3: Passivate the aluminum alloy sheet after cleaning with deionized water. Add agents X4591 and H7271 to the passivation solution at concentrations of 44.3 g / L and 18 g / L, respectively. The passivation temperature is 45–55 °C and the time is 3–9 s.

[0009] Step S4: Clean the passivated aluminum alloy sheet with deionized water at room temperature for ≥30 seconds.

[0010] Step S5: Dry the aluminum alloy sheet after cleaning with deionized water.

[0011] Pickling can remove oxide layers and contaminants, and better form a passivation layer on the aluminum alloy surface. The pickling reagent used in the pickling process includes 2.5-3 wt% pickling agent and 9-10 wt% additives. The conductivity of the pickling reagent is 50 ± 5 mS / cm, and the free fluorine content of the pickling reagent is 300 ± 50 ppm.

[0012] Passivation treatment can form a dense oxide film on the surface of aluminum alloys. This film effectively isolates the aluminum alloy from the external environment, reducing corrosion. Simultaneously, passivation treatment can also improve the surface hardness and wear resistance of aluminum alloys, increasing their service life. The passivation reagent used in the passivation treatment includes 4.5–5 wt% of a chromium-free treatment supplement and 1.8–2 wt% of a chromium-free passivation adjuster. The conductivity of the passivation reagent is 1800–2300 μS / cm, and the pH value is 3.8–4.2.

[0013] Among them, agent S5149 is a cleaning agent, such as Gardoclean S5149 from Chemitr GmbH, Germany. Agent H7274 is an additive, such as Gardobond Additive H7274 from Chemitr GmbH, Germany. Agent X4591 is a chromium-free treatment supplement, such as Gardobond X4591 from Chemitr GmbH, Germany. Agent H7271 is a chromium-free passivating modifier, such as GBAH7271 from Chemitr GmbH, Germany.

[0014] Further, by weight percentage, the aluminum alloy sheet in step S1 comprises the following components: Si 0.67%–0.93%, Fe 0.14%–0.20%, Cu 0.07%–0.73%, Mn 0.08%–0.20%, Mg 0.62%–0.83%, with the balance being Al and unavoidable impurities. Preferably, each impurity is less than 0.05%. More preferably, the total amount of impurities is less than 0.15%.

[0015] Furthermore, the surface roughness of the aluminum alloy sheet in step S1 ranges from 0.6 to 1.0 mm.

[0016] During the welding process, surface roughness affects the contact area in the initial stage of resistance spot welding, thereby affecting the contact resistance in the initial stage of welding, and consequently affecting the degree of reaction between the copper electrode and the aluminum substrate at the interface. This invention controls the surface roughness range of the aluminum alloy to ensure that there is a certain contact resistance between the upper and lower plates of the aluminum alloy substrate at the resistance spot welding position, which is conducive to the formation of the resistance spot weld joint. On the other hand, it controls the contact resistance between the aluminum alloy substrate and the copper electrode at the resistance spot welding position to be too large, which helps to reduce the degree of interface reaction and increase the number of electrode spots.

[0017] Furthermore, the pickling etching amount of the aluminum alloy sheet after pickling in step S1 is 0.4–1.0 mg / m². 2 .

[0018] Furthermore, in step S3, the surface Ti and Zr content of the passivated aluminum alloy sheet is 2–8 mg / m². 2 The passivation film thickness is 50–80 nm.

[0019] During the welding process, the dense and uniform passivation layer on the aluminum alloy surface plays a certain role in isolating the reaction between the copper electrode and the aluminum substrate during resistance spot welding, thereby increasing the number of electrode spots. However, when the passivation layer is thin, its isolation effect between the copper electrode and the aluminum substrate is not significant; when the passivation layer is thick, it indirectly increases the contact resistance between the copper electrode and the aluminum substrate, leading to severe electrode adhesion during welding and hindering the control of the interface reaction. Therefore, this invention controls the thickness of the passivation layer on the aluminum alloy surface to minimize the contact between the copper electrode and the aluminum substrate while keeping the contact resistance from becoming too high, thereby increasing the number of electrode spots.

[0020] According to another aspect of the present invention, a welding method for aluminum alloy is provided, using an aluminum alloy sheet obtained by the above-described treatment method, wherein the welding current range for resistance spot welding is 26-38 kA, the pressure range is 3-6 kN, the welding time is 100-300 ms, and the holding time is 100-200 ms.

[0021] According to another aspect of the present invention, a welding joint is provided, wherein the resistance spot welding joint obtained by the above welding method has an excellent number of electrode spots (the number of weld spots corresponding to the area of ​​the contaminated area on the weld spot surface reaching 50% of the surface area of ​​the weld spot), with the number of electrode spots being ≥80.

[0022] This invention provides a method for treating the surface of 6000 series aluminum alloy with a high number of electrode dots. By controlling the surface roughness and passivation layer thickness of the aluminum alloy sheet, the aluminum alloy sheet can achieve a high number of electrode dots when connected by resistance spot welding.

[0023] According to another aspect of the present invention, an aluminum alloy sheet processed according to the method of the present invention is provided, which has excellent resistance spot welding electrode spot count (the number of weld spots corresponding to the area of ​​the contaminated area on the weld spot surface reaching 50% of the surface area of ​​the weld spot), with an electrode spot count of ≥80 points. This is a significant improvement over the current industry standard of only 30 electrode spot count for OEMs, and meets the requirements for the number of resistance spot welding electrode spot count in subsequent applications of aluminum alloy automotive parts.

[0024] In summary, the beneficial effects of the present invention are at least reflected in the following aspects:

[0025] 1. During the welding process, surface roughness affects the contact area in the initial process of resistance spot welding, thereby affecting the contact resistance in the initial stage of welding, and consequently affecting the degree of reaction between the copper electrode and the aluminum substrate at the interface. This invention controls the surface roughness range of the aluminum alloy to ensure that there is a certain contact resistance between the upper and lower plates of the aluminum alloy substrate at the resistance spot welding position, which is conducive to the formation of resistance spot weld joints. On the other hand, it controls the contact resistance between the aluminum alloy substrate and the copper electrode at the resistance spot welding position to be too large, which helps to reduce the degree of interface reaction and increase the number of electrode spots.

[0026] 2. During the welding process, the dense and uniform passivation layer on the aluminum alloy surface plays a certain role in isolating the reaction between the copper electrode and the aluminum substrate during resistance spot welding, thereby increasing the number of electrode spots. However, when the passivation layer is thin, its isolation effect between the copper electrode and the aluminum substrate is not significant. When the passivation layer is thick, it indirectly increases the contact resistance between the copper electrode and the aluminum substrate, leading to severe electrode adhesion during welding, which is detrimental to controlling the interface reaction. Therefore, this invention controls the thickness of the passivation layer on the aluminum alloy surface to minimize the contact between the copper electrode and the aluminum substrate while keeping the contact resistance from becoming too high, thereby increasing the number of electrode spots.

[0027] 3. This invention is based on the technical equipment optimization of existing aluminum alloy production enterprises. The method controls the aluminum alloy sheet preparation process and passivation process without affecting the original production process, and can be industrialized. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0029] Figure 1 This is a surface SEM image of the aluminum alloy sheet of Embodiment 1 of the present invention.

[0030] Figure 2 This is a surface SEM image of the aluminum alloy sheet after pickling treatment in Embodiment 1 of the present invention.

[0031] Figure 3 This is a surface SEM image of the aluminum alloy sheet after passivation treatment in Embodiment 1 of the present invention.

[0032] Figure 4 This is a schematic diagram showing that the surface contamination rate of the aluminum alloy sheet resistance spot welding of the present invention is 50%. Detailed Implementation

[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] The embodiments of this application provide a surface treatment method for aluminum alloys with a high number of electrode dots. The following description, in conjunction with the accompanying drawings, further illustrates this application, but it is not intended to limit the scope of the invention.

[0035] As described in the background section of this invention, existing technologies for joining aluminum alloy materials using resistance spot welding encounter a problem: the intense interfacial reaction between copper and aluminum results in a low number of consecutive spot welds. This leads to frequent re-grinding, affecting electrode lifespan and increasing costs. Furthermore, it impacts the welding process's cycle time and overall production efficiency. The low number of spot welds is due to the presence of a dense oxide film on the aluminum alloy surface, characterized by extremely high melting point and poor conductivity. This oxide film generates significant contact resistance during welding, which, according to Joule's law and the heat generation formula Q = ηI, results in a high resistance. 2 Rt (η is the efficiency coefficient) A large amount of resistance heat is generated between the copper electrode and the aluminum alloy substrate, forming a high-temperature environment. At high temperatures, aluminum and copper will form a low-melting-point Cu-Al compound. This eutectic reaction will cause strong adhesion between the copper electrode and the surface of the aluminum alloy, resulting in severe burn-off of the copper electrode and affecting the number of electrode dots.

[0036] To address the above problems, this invention provides a surface treatment method for aluminum alloys with a high number of electrode dots, the method comprising the following steps:

[0037] Step S1: Pickling the aluminum alloy sheet by adding reagents S5149 and H7274 to the pickling solution at concentrations of 25 g / L and 12.5 g / L, respectively. The pickling temperature is 45–55 °C and the pickling time is 30–60 s.

[0038] Step S2: Clean the pickled aluminum alloy sheet with deionized water at room temperature for ≥30 seconds.

[0039] Step S3: Passivate the aluminum alloy sheet after cleaning with deionized water. Add agents X4591 and H7271 to the passivation solution at concentrations of 44.3 g / L and 18 g / L, respectively. The passivation temperature is 45–55 °C and the time is 3–9 s.

[0040] Step S4: Clean the passivated aluminum alloy sheet with deionized water at room temperature for ≥30 seconds.

[0041] Step S5: Dry the aluminum alloy sheet after cleaning with deionized water.

[0042] By weight percentage, the aluminum alloy sheet in step S1 comprises the following components: Si 0.67%–0.93%, Fe 0.14%–0.20%, Cu 0.07%–0.73%, Mn 0.08%–0.20%, Mg 0.62%–0.83%, with the balance being Al and unavoidable impurities. Preferably, each impurity is less than 0.05%. More preferably, the total amount of impurities is less than 0.15%.

[0043] This invention relates to a surface treatment process for aluminum alloy sheets, involving pickling, cleaning, passivation, cleaning, and drying. In step S1, the surface roughness of the aluminum alloy sheet ranges from 0.6 to 1.0 mm, and the pickling etching amount of the aluminum alloy sheet after pickling in step S1 is 0.4 to 1.0 mg / m². 2 In step S3, the surface Ti and Zr content of the passivated aluminum alloy sheet is 2-8 mg / m³. 2 The passivation film thickness is 50–80 nm.

[0044] The inventors discovered in their research that extending the number of electrode spots in resistance spot welding can be improved in the following ways. First, by controlling the surface roughness of the aluminum alloy, it can be kept within a suitable range. When the roughness is low, the resistance between the upper and lower aluminum alloy plates is low. To form a weld nugget that meets the required size, a larger welding current is needed, which will also intensify the chemical reaction at the interface between the copper electrode and the aluminum substrate. When the roughness is high, the resistance between the copper electrode and the aluminum substrate is too high, which will also intensify the chemical reaction at the interface. Therefore, controlling the surface roughness of the aluminum alloy within a suitable range will help control the degree of reaction at the interface between the copper electrode and the aluminum substrate, thereby increasing the number of electrode spots. Second, by finely controlling the passivation process, the aluminum alloy surface can be kept within a suitable passivation layer thickness range. When the passivation layer is thin, due to the combined effects of current breakdown and electrode pressure during the welding process, the passivation layer is insufficient to isolate the interface reaction between the copper electrode and the aluminum substrate. When the passivation layer is thick, it will lead to excessive resistance between the copper electrode and the aluminum substrate, resulting in severe heat generation at the interface, which will exacerbate the interface reaction and affect the number of electrode dots.

[0045] Figure 1 The surface SEM of the aluminum alloy sheet of Embodiment 1 of the present invention is shown. Figure 2 The SEM image of the aluminum alloy sheet after pickling treatment in Embodiment 1 of the present invention is shown. It can be seen that the surface morphology of the aluminum alloy sheet has changed significantly, and its surface roughness ranges from 0.6 to 1.0 mm. Figure 3 The diagram shows a surface SEM of an aluminum alloy sheet after passivation treatment according to Embodiment 1 of the present invention. Because the passivation layer is very thin, the surface SEM after passivation treatment is similar to that after pickling treatment.

[0046] SEM, or electron microscope, is a type of microscope that uses the interaction of an electron beam with a sample to acquire images. Compared to traditional optical microscopes, SEM offers higher resolution and magnification, allowing observation of finer sample details. SEM primarily acquires images by scanning the electron beam across the sample surface, rather than observing the sample through transmitted electrons. SEM provides high-quality information on surface morphology and structure, making it suitable for surface observation and analysis of various materials.

[0047] Figure 4 A schematic diagram showing the morphology of an aluminum alloy sheet with a 50% surface contamination rate during resistance spot welding according to the present invention is provided. Here, "the percentage of surface contamination during resistance spot welding of the aluminum alloy sheet" refers to the proportion of surface contamination caused by welding during the resistance spot welding process of the aluminum alloy sheet. Figure 4The white circle represents the surface area of ​​the weld joint, and the black circle represents the area of ​​the contaminated area. The percentage of surface contamination in resistance spot welding of aluminum alloy sheets = contaminated area / weld joint surface area. The number of electrode dots for the spot weld joint in this invention is based on a 50% surface contamination percentage in the resistance spot weld.

[0048] The aluminum alloy sheet prepared by the surface treatment method disclosed in this invention can be processed and produced on a conventional production line, and has the characteristic of high electrode spot count during the welding process using resistance spot welding.

[0049] The aluminum alloy sheet is a 6000 series aluminum alloy sheet, which can be welded using the following methods: resistance spot welding with a welding current range of 26-38kA, a pressure range of 3-6kN, a welding time of 100-300ms, and a holding time of 100-200ms.

[0050] The resistance spot welded head obtained by the above welding method of the present invention has an excellent number of electrode spots (the number of weld spots corresponding to the area of ​​the contaminated area on the surface of the weld spot reaching 50% of the surface area of ​​the weld spot), with an electrode spot number of ≥80 spots.

[0051] The present application will be further described in detail below with reference to the embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0052] Example 1

[0053] The aluminum alloy sheet of Embodiment 1 of the present invention is composed of the following components: Si 0.8%, Fe 0.28%, Cu 0.8%, Mn 0.3%, Mg 0.8%, with the balance being Al and unavoidable impurities, wherein each unavoidable impurity is less than 0.05%, and the total amount of impurities is less than 0.15%.

[0054] The surface treatment method for aluminum alloy sheet in Embodiment 1 of the present invention is shown in Table 1, and the treatment method is as follows:

[0055] Step 1: Pickling the aluminum alloy sheet. The pickling solution needs to be supplemented with reagents S5149 and H7274, with addition amounts of 25g / L and 12.5g / L respectively. The pickling temperature is 50℃ and the pickling time is 50s.

[0056] Step 2: Clean the pickled aluminum alloy sheet with deionized water at room temperature for 60 seconds.

[0057] Step 3: Passivate the aluminum alloy sheet after cleaning with deionized water. The passivation solution needs to be supplemented with reagents X4591 and H7271, with addition amounts of 44.3 g / L and 18 g / L respectively. The passivation temperature is 50℃ and the time is 9 seconds.

[0058] Step 4: Clean the passivated aluminum alloy sheet with deionized water at room temperature for 60 seconds.

[0059] Step 5: Dry the aluminum alloy sheet after cleaning with deionized water;

[0060] Step 6: Perform resistance spot welding electrode count test on the passivated plate. The resistance spot welding current is 32kA, the electrode pressure is 4.5kN, the welding time is 120ms, and the holding time is 200ms. The test results show that the electrode count (the number of weld points corresponding to the area of ​​the contaminated area on the weld point surface reaching 50% of the weld point surface area) is 92 points.

[0061] Examples 2-5

[0062] Examples 2 to 5 of the present invention use aluminum alloy sheets with the same composition as those in Example 1. The difference between the examples and Example 1 is that the surface treatment methods of the aluminum alloy sheets are different, as detailed in Table 1.

[0063] Comparative Examples 1-6

[0064] The present invention provides Comparative Examples 1 to 6 for comparative illustration of the effects of the present invention. Comparative Examples 1 to 6 use aluminum alloy sheets with the same composition as Example 1, the difference being that the surface treatment methods of the aluminum alloy sheets are different, as detailed in Table 1.

[0065] Table 1. Processing methods of Examples 1-5 and Comparative Examples 1-6

[0066]

[0067]

[0068] Method for measuring the number of electrode spots on aluminum alloy sheets: Welding tests are conducted on aluminum alloy sheets using specific welding process parameters, with 100 or more spots welded. The surface of the weld spots is photographed using a low-power microscope. As the number of weld spots increases, the aluminum alloy surface gradually becomes contaminated from the inside out. The contaminated areas are marked with black circles, and the overall indentation area of ​​the weld spots is marked with white circles. The proportion of surface contamination on the resistance spot weld of the aluminum alloy sheet can be obtained by dividing the area of ​​the black circle by the area of ​​the white circle.

[0069] As can be seen from Table 1 above, the passivated aluminum alloy plates obtained in Examples 1 to 5 of the present invention have ≥80 electrode dots, while the aluminum alloy plates obtained in Comparative Examples 1 to 6 have <80 electrode dots. In Comparative Example 1, the excessive surface roughness of the aluminum alloy resulted in high contact resistance at the interface between the copper electrode and the aluminum substrate during welding, exacerbating the reaction and affecting the number of electrode dots. In Comparative Example 2, the insufficient surface roughness of the aluminum alloy made it difficult for weld nuggets to form at the weld points, requiring a high welding current, which intensified the chemical reaction at the interface and affected the number of electrode dots. In Comparative Example 3, the prolonged pickling time led to excessive cleaning of the original oxide layer on the aluminum alloy surface, resulting in numerous micropits. This would lead to the formation of more granular films during subsequent passivation, increasing the passivation layer thickness and affecting the number of electrode dots. In Comparative Example 4, the short pickling time resulted in a large amount of residual original oxide layer on the aluminum alloy surface, hindering the formation of the subsequent passivation layer and reducing its thickness, thus affecting the number of electrode dots. In Comparative Example 5, the short passivation time resulted in a thin passivation layer on the aluminum alloy surface, affecting the number of electrode dots. In Comparative Example 6, the prolonged passivation time resulted in a thick passivation film on the aluminum alloy surface, affecting the number of electrode dots.

[0070] As can be seen from the above, compared with the comparative example, the embodiments of the present invention achieve a surface roughness range of 0.6-1.0 μm and a surface Ti and Zr content of 2-8 mg / m² by refining the roughness, pickling, and passivation processes of the aluminum alloy sheet. 2 This patented method uses aluminum alloy sheets with a passivation film thickness of 50–80 nm to precisely control the reaction degree between the copper electrode and the aluminum substrate during resistance spot welding, thereby increasing the number of electrode spots. The aluminum alloy sheets prepared according to this method do not require production line modifications and can achieve an excellent number of resistance spot welding electrodes, improving the cycle time in the OEM welding process and increasing production efficiency.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A surface treatment method for aluminum alloys with a high number of electrode dots, characterized in that, The processing method includes the following steps: Step S1: The aluminum alloy sheet is subjected to pickling treatment. Gardoclean S5149 and Gardobond Additive H7274 are added to the pickling solution at concentrations of 25 g / L and 12.5 g / L, respectively. The pickling temperature is 45-55°C, and the pickling time is 30-60 seconds. The aluminum alloy sheet is a 6000 series aluminum alloy sheet. The surface roughness of the aluminum alloy sheet is 0.6-1.0 μm. The pickling etching amount of the aluminum alloy sheet after pickling treatment is 0.4-1.0 mg / m². 2 ; Step S2: Clean the pickled aluminum alloy sheet with deionized water at room temperature for ≥30 seconds. Step S3: The aluminum alloy sheet cleaned with deionized water is passivated. Gardobond X4591 and GBA H7271 are added to the passivation solution at concentrations of 44.3 g / L and 18 g / L, respectively. The passivation treatment temperature is 45-55°C, and the treatment time is 3-9 seconds. The surface Ti and Zr content of the passivated aluminum alloy sheet is 2-8 mg / m³. 2 The passivation film thickness is 50~80nm; Step S4: Clean the passivated aluminum alloy sheet with deionized water at room temperature for ≥30 seconds. Step S5: Dry the aluminum alloy sheet after it has been cleaned with deionized water.

2. The aluminum alloy surface treatment method according to claim 1, characterized in that, The aluminum alloy sheet in step S1, by weight percentage, consists of the following components: Si 0.67%~0.93%, Fe 0.14%~0.20%, Cu 0.07%~0.73%, Mn 0.08%~0.20%, Mg 0.62%~0.83%, with the balance being Al and unavoidable impurities.

3. The aluminum alloy surface treatment method according to claim 2, characterized in that, Each of the impurities is less than 0.05% by weight.

4. The aluminum alloy surface treatment method according to claim 2 or 3, characterized in that, The total amount of the impurities is less than 0.15% by weight.

5. A 6000 series aluminum alloy sheet with a high number of electrode dots, characterized in that, The aluminum alloy sheet is obtained by the processing method according to any one of claims 1 to 4.

6. The aluminum alloy sheet according to claim 5, characterized in that, The aluminum alloy sheet is a 6000 series aluminum alloy sheet.

7. The aluminum alloy sheet according to claim 5, characterized in that, For resistance spot welding joints where the area of ​​contaminated area on the surface of the solder joint reaches 50% of the surface area of ​​the solder joint, the number of electrode dots must be ≥80.

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