Cleaning agent for pre-welding treatment of aluminum alloy part as well as preparation method and application of cleaning agent

Abstract

The invention provides a cleaning agent for aluminum alloy part welding pretreatment and a preparation method and application of the cleaning agent. An aluminum alloy part cleaning solution is prepared. The cleaning solution has a strong cleaning effect on oxide skin on the surface of an aluminum alloy workpiece and impurities such as oil stains and dust contaminated in the machining, manufacturing and transporting processes, a nanoscale passive film which does not affect the welding quality is formed after cleaning, and the subsequent protection effect is enhanced. The cleaning agent also has the characteristics of good flowability, permeability and coverage, is low in toxicity and non-irritant, does not contain heavy metals, fluorides and the like, and has better process suitability for manual cleaning and ultrasonic heating cleaning. And waste generated in the cleaning process is easy to treat and does not pollute the environment. And after cleaning, residual liquid is easily removed from the surface of the aluminum alloy workpiece, and no harmful substance is left. The cleaned aluminum alloy workpiece can be directly welded, and long-time waiting or complex post-treatment is not needed.

Description

Technical Field

[0001] This invention belongs to the field of pre-welding cleaning technology for aluminum alloy parts, specifically relating to a cleaning agent for pre-welding treatment of aluminum alloy parts, its preparation method, and its application. Background Technology

[0002] Given its lightweight, corrosion resistance, ease of processing, recyclability, and high specific strength and ductility, aluminum and aluminum alloys are widely used in aerospace, automotive manufacturing, and architectural decoration, among other fields. Based on its excellent mechanical properties and plasticity, aluminum and its alloys are often used in welding and other methods to form various components, playing crucial roles in load distribution and energy transfer. However, due to the high chemical reactivity of aluminum, it readily reacts with oxygen in the air, forming an oxide scale (Al2O3) on its surface during processing, manufacturing, storage, and transportation. This oxide scale has a melting point (approximately 2050℃) much higher than that of pure aluminum (approximately 660℃). During welding, this high-melting-point oxide scale is difficult to melt, hindering the fusion of the filler metal and the base metal, easily leading to defects such as unmelted zones and slag inclusions. Furthermore, the naturally formed oxide scale on the metal surface is characterized by a loose and porous structure, causing problems such as arc deviation and reduced weld density, severely affecting weld quality.

[0003] To address the issue of oxide scale on the surface of aluminum alloy parts affecting welding quality, traditionally, acid pickling solutions prepared with sulfuric acid and nitric acid, or alkaline pickling solutions prepared with sodium hydroxide and sodium carbonate, are used to pickle / alkaline clean the aluminum parts before welding. However, using these cleaning solutions presents challenges such as excessively high reaction rates, which can easily lead to over-corrosion and make it difficult to control process quality; furthermore, acid and alkaline liquids pose significant safety risks, causing adverse effects on occupational health and the environment. Therefore, developing a safe, efficient, and environmentally friendly cleaning solution is of great significance for improving the welding quality of aluminum alloy parts and ensuring production safety.

[0004] Chinese patent CN120119261 A discloses an aluminum alloy welding cleaning agent, its formulation, and its application. In this cleaning agent formulation, ammonium fluoroborate is used as a corrosion inhibitor; this substance is moderately toxic and highly corrosive. Furthermore, cerium nitrate and dopamine are added during the preparation of the diluent, significantly increasing the cost and hindering its widespread industrial application. Chinese patent CN111118513 A discloses an aluminum alloy parts cleaning agent, whose formulation contains hydrofluoric acid (7-12 parts). Therefore, it is evident that the preparation and use of this cleaning agent pose significant safety, environmental, and occupational health risks. Chinese patent CN119843286A discloses a fully synthetic cleaning agent, its preparation method, and its application. This cleaning agent exhibits excellent cleaning effects on residual cutting fluid, wetting paste, and other impurities on aluminum alloy surfaces, but its effect on removing oxide scale on aluminum alloy surfaces is weak, and it cannot form a passivation film with subsequent anti-corrosion effects. Chinese patent CN120041840A discloses an aluminum alloy surface cleaning agent and its preparation method. This cleaning agent has a good cleaning effect on oil stains, oxide scale, dust, and other impurities on aluminum alloy surfaces, but the humic acid, hyperbranched copolymers, and other polymeric compounds included in its formula reduce the fluidity of the liquid, resulting in reduced cleaning efficiency and a complex production process. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] This invention proposes a cleaning agent for pre-welding treatment of aluminum alloy parts, its preparation method and application, to solve the technical problem of improving the cleaning quality and efficiency of removing impurities such as oil, oxide scale and dust from aluminum alloy surfaces.

[0007] (II) Technical Solution

[0008] To address the aforementioned technical problems, this invention proposes a cleaning agent for pre-welding treatment of aluminum alloy parts. This cleaning agent comprises a nonionic surfactant, sodium hydroxide, sodium aluminate, sodium silicate, citric acid, an organic corrosion inhibitor, an inorganic corrosion inhibitor, and a solvent.

[0009] Furthermore, by mass ratio, the cleaning agent contains 1.0–3.0% nonionic surfactant, 1.0–3.0% sodium hydroxide, 1.0–2.0% sodium aluminate, 1.0–2.0% sodium silicate, 0.5–1.0% citric acid, 0.5–1.0% organic corrosion inhibitor, 0.2–0.5% inorganic corrosion inhibitor, with the solvent as the balance.

[0010] Furthermore, the nonionic surfactant is a compound of isooctanol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether.

[0011] Furthermore, in the nonionic surfactant, the mass ratio of isooctanol polyoxyethylene ether to lauryl alcohol polyoxyethylene ether is 6:4.

[0012] Furthermore, the organic corrosion inhibitor is benzoic acid, the inorganic corrosion inhibitor is sodium molybdate, and the solvent is deionized water.

[0013] Furthermore, the present invention also proposes a method for preparing the above-mentioned cleaning agent for pre-welding treatment of aluminum alloy parts, the preparation method comprising the following steps:

[0014] S1. Preparation of isooctanol polyoxyethylene ether

[0015] Isoooctanol was used as an initiator to react with ethylene oxide to generate isoooctanol polyoxyethylene ether;

[0016] S2. Preparation of lauryl alcohol polyoxyethylene ether

[0017] Lauryl alcohol was used as an initiator to react with ethylene oxide to generate lauryl alcohol polyoxyethylene ether;

[0018] S3. Preparation of cleaning agent

[0019] Isooctanol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether were added to a three-necked flask and mixed and stirred at room temperature to obtain a transparent and homogeneous liquid. The reaction temperature was increased to 40-50°C and the stirring speed was increased to 600 rpm. Under the above conditions, sodium hydroxide was added to the obtained liquid and stirred continuously. Sodium aluminate and sodium silicate were added one at a time while maintaining the reaction temperature and stirring. Citric acid was dissolved in deionized water and then added to the reaction system. The pH of the liquid was monitored in real time until it reached 10. Heating was stopped, and after the reaction system cooled to room temperature, benzoic acid and sodium molybdate were added in sequence while stirring at 600 rpm. Deionized water was added, and the reaction liquid was filtered through a membrane to finally obtain a colorless and transparent cleaning agent.

[0020] Further, the specific method of step S1 is as follows: add isooctanol to the reaction vessel and heat to 80°C; add potassium hydroxide, stir at a constant speed and dissolve; close the reaction vessel, purge with nitrogen and replace the air; add ethylene oxide, raise the reaction temperature to 120-130°C, maintain the pressure at 0.8-1.2 MPa, stir at a constant speed, and react for 4-6 hours; after the reaction is completed, cool to 60°C, add dilute hydrochloric acid to adjust the pH value of the liquid to 7; remove unreacted ethylene oxide and byproducts by vacuum distillation to obtain colorless and transparent liquid isooctanol polyoxyethylene ether.

[0021] Further, the specific method of step S2 is as follows: add lauryl alcohol to the reaction vessel and heat to 90°C; add potassium hydroxide, stir at a constant speed and dissolve; close the reaction vessel, purge with nitrogen and replace the air; add ethylene oxide, raise the reaction temperature to 140-150°C, maintain the pressure at 1.0-1.5 MPa, stir at a constant speed, and react for 6-8 hours; after the reaction is completed, cool to 60°C, add dilute hydrochloric acid to adjust the pH of the liquid to 7; remove unreacted ethylene oxide and byproducts by vacuum distillation; and obtain a pale yellow liquid lauryl alcohol polyoxyethylene ether.

[0022] Furthermore, the present invention also proposes an application of the above-mentioned cleaning agent for pre-welding treatment of aluminum alloy parts, wherein the cleaning agent is used to clean the aluminum alloy parts.

[0023] Furthermore, the aluminum alloy parts can be manually cleaned by immersing them in a cleaning agent, or ultrasonically heated and cleaned using an ultrasonic cleaning device.

[0024] (III) Beneficial Effects

[0025] This invention proposes a cleaning agent for pre-welding treatment of aluminum alloy parts, its preparation method, and its application. The prepared aluminum alloy cleaning fluid exhibits strong cleaning effects on oxide scale, oil stains acquired during processing, manufacturing, and transportation, as well as dust and other impurities on the surface of aluminum alloy parts. Furthermore, it forms a nanoscale passivation film after cleaning that does not affect welding quality, enhancing subsequent protective effects. In addition, the nonionic surfactants used are isooctanol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether. Due to its branched structure, isooctanol polyoxyethylene ether reduces the regularity of surfactant molecules at the gas-liquid interface, thus reducing foam stability after foaming. This makes it better suited for cleaning scenarios with low foam content, avoiding the impact of excessive foam on ultrasonic cleaning equipment. The branched structure also increases molecular steric hindrance, further enhancing the ability to remove stubborn oil stains and oxide scale.

[0026] This cleaning agent also features good fluidity, penetration, and coverage, and is low in toxicity, non-irritating, and free of heavy metals (such as Cr). 6+ It contains fluorides and other compounds, making it well-suited for both manual and ultrasonic cleaning processes. Waste generated during the cleaning process is easy to dispose of and will not pollute the environment. Residue after cleaning is easily removed from the surface of aluminum alloy parts, leaving no harmful substances. Cleaned aluminum alloy parts can be directly welded without long waiting times or complex post-processing. Attached Figure Description

[0027] Figure 1 This is a process curve diagram of ultrasonic heating cleaning in this invention. Detailed Implementation

[0028] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0029] This embodiment proposes a cleaning agent for pre-welding treatment of aluminum alloy parts. By mass ratio, the cleaning agent comprises the following components: ① a nonionic surfactant (specifically, a compound of isooctanol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether, with a mass ratio of 6:4; its main functions are emulsification, dispersion, and decontamination), accounting for 5.0–10.0%; ② sodium hydroxide (its main function is to remove oxide scale), accounting for 1.0–3.0%; ③ sodium aluminate (its main function is to promote alumina dissolution and synergistically remove oxide scale with sodium hydroxide), accounting for 1.0–2.0%; ④ Sodium silicate (mainly used to disperse oil stains and stabilize suspended solids), accounting for 1.0-2.0%; ⑤ Citric acid (mainly used to adjust the pH value of the cleaning agent, enhance the dispersibility of sodium silicate, and complex metal ions to prevent secondary deposition), accounting for 0.5-1.0%; ⑥ Organic corrosion inhibitor (benzoic acid is selected, mainly used to form a protective film on the surface of aluminum alloy parts to prevent excessive corrosion), accounting for 0.5-1.0%; ⑦ Inorganic corrosion inhibitor (sodium molybdate is selected, mainly used to enhance the corrosion inhibition effect), 0.2-0.5%; ⑧ Solvent (deionized water), balance.

[0030] The preparation method of the above-mentioned cleaning agent specifically includes the following steps:

[0031] S1. Preparation of isooctanol polyoxyethylene ether

[0032] With isooctyl alcohol (C8H) 17 The reaction of OH as an initiator with ethylene oxide (C2H4O) produces isooctanol polyoxyethylene ether (C8H4O). 17 O(CH2CH2O) n H), the reaction process is as follows:

[0033]

[0034] In the reaction formula, n represents the number of moles of ethylene oxide added, typically n = 5 to 10. Taking n = 8 as an example, the structural formula of the reaction product is CH3(CH2)3CH(CH2CH3)CH2O(CH2CH2O)8H. Here, CH2CH3 is a branched chain.

[0035] Taking 1 mol of product as an example, 130.23 g of isooctanol was added to a high-pressure stainless steel reactor equipped with a stirring and heating device, and the temperature was raised to 80°C; 0.56 g of potassium hydroxide was added, and the mixture was stirred at a constant speed to dissolve it; the reactor was closed, nitrogen was introduced, and the air was replaced three times; 300 g of ethylene oxide was added, the reaction temperature was raised to 120-130°C, the pressure was maintained at 0.8-1.2 MPa, and the mixture was stirred at a constant speed of 300 rpm for 4-6 hours; after the reaction was completed, the mixture was cooled to 60°C, and dilute hydrochloric acid was added to adjust the pH of the liquid to 7; unreacted ethylene oxide and byproducts were removed by vacuum distillation (60°C, 0.01 MPa) to obtain a colorless and transparent liquid isooctanol polyoxyethylene ether with a hydroxyl value of 100-120 mg KOH / g.

[0036] S2. Preparation of lauryl alcohol polyoxyethylene ether

[0037] With lauryl alcohol (C16-12 ... 12 H 25 The reaction of OH as an initiator with ethylene oxide (C2H4O) produces lauryl alcohol polyoxyethylene ether (C... 12 H 25 O(CH2CH2O) n H), the reaction process is as follows:

[0038]

[0039] In the reaction formula, n represents the number of moles of ethylene oxide added, typically n = 5 to 15. Taking n = 9 as an example, the structural formula of the reaction product is CH3(CH2). 10 CH2O(CH2CH2O)9H.

[0040] Compared to branched structures, lauryl alcohol polyoxyethylene ether's linear structure possesses characteristics such as regular molecular arrangement and low steric hindrance, making it a key component for efficiently emulsifying oil stains in cleaning fluids for aluminum alloy parts. In actual production, the hydrophilic-lipophilic balance (HLB value) of the product can be flexibly controlled by adjusting the degree of polymerization n, allowing the cleaning agent to adapt to cleaning needs with different levels of contamination (a larger n enhances the emulsification effect on oil stains but weakens penetration). In this embodiment, the HLB value is 12.

[0041] Taking 1 mol of product as an example, 186.33 g of lauryl alcohol was added to a high-pressure stainless steel reactor equipped with a stirring and heating device, and the temperature was raised to 90°C; 0.56 g of potassium hydroxide was added, and the mixture was stirred at a constant speed to dissolve it; the reactor was closed, nitrogen was introduced, and the air was replaced three times; 300 g of ethylene oxide was added, the reaction temperature was raised to 140–150°C, the pressure was maintained at 1.0–1.5 MPa, and the mixture was stirred at a constant speed of 300 rpm for 6–8 hours; after the reaction was completed, the mixture was cooled to 60°C, and dilute hydrochloric acid was added to adjust the pH of the liquid to 7; unreacted ethylene oxide and byproducts were removed by vacuum distillation (60°C, 0.01 MPa); a pale yellow liquid lauryl alcohol polyoxyethylene ether was obtained with a hydroxyl value of 80–100 mg KOH / g.

[0042] S3. Preparation of cleaning agent

[0043] Taking the preparation of 100g of cleaning agent as an example, 6.0g of isooctanol polyoxyethylene ether and 4.0g of lauryl alcohol polyoxyethylene ether were added to a three-necked flask and mixed and stirred at 400rpm for 5min at room temperature (25℃±2℃) using a magnetic stirrer to obtain a transparent and uniform liquid; the reaction temperature was increased to 40~50℃ and the stirring rate was increased to 600rpm. Under the same conditions, 2.0 g of sodium hydroxide was slowly added to the resulting liquid and stirred continuously for 10 min. While maintaining the reaction temperature, 1.5 g of sodium aluminate and 1.5 g of sodium silicate were added at once and stirred for 15 min. 0.8 g of citric acid was dissolved in 10 ml of deionized water and then slowly added to the reaction system. The pH of the liquid was monitored in real time until it reached 10 ± 0.2. Heating was stopped, and after the reaction system cooled to room temperature (25℃ ± 2℃), 0.8 g of benzoic acid and 0.3 g of sodium molybdate were added sequentially and stirred at 600 rpm for 20 min. Deionized water was added to bring the total volume to 100.0 g. The reaction liquid was filtered through a 0.45 μm filter membrane to obtain a colorless and transparent cleaning agent.

[0044] The cleaning process of the cleaning agent prepared by this invention is as follows:

[0045] (1) Manual cleaning

[0046] Using an immersion cleaning method, soak the aluminum alloy parts in the cleaning agent, ensuring complete submersion. Immersion time is 5-8 minutes. A soft brush can be used to clean areas with heavy oil stains and numerous impurities to better dissolve and remove oxide scale and impurities from the aluminum alloy surface. After the reaction is complete, visually inspect the aluminum alloy surface; there should be no oil stains or oxide scale residue. After cleaning, allow to air dry or blow dry with compressed air before direct welding.

[0047] (2) Ultrasonic heating cleaning

[0048] The aluminum alloy plate to be treated is placed in an ultrasonic cleaning device, the temperature is adjusted to 40-60℃ (preferably 50℃), the cleaning time is 8-15 minutes (preferably 12 minutes), and the ultrasonic power density is 1.0 W / cm³. 2 A typical ultrasonic heating cleaning process curve is shown below. Figure 1 As shown. After ultrasonic heating, rinse and clean, then air dry or blow dry with compressed air before direct welding.

[0049] The oxide scale removal principle of the cleaning agent prepared in this invention is as follows:

[0050] 1. Stripping and Penetration of Nonionic Surfactants

[0051] Alumina (Al2O3) is a high-hardness oxide (Mohs hardness approximately 9), chemically stable, and difficult to remove using conventional cleaning methods, which are labor-intensive and have long production cycles. The surface energy of alumina differs significantly from that of the aluminum matrix. Based on this characteristic, the hydrophilic-hydrophobic properties of nonionic surfactants are utilized; the hydrophobic ends are adsorbed onto the oxide scale surface through van der Waals forces, while the hydrophilic ends face the water, thus achieving penetration and peeling of the oxide scale.

[0052] 2. Sodium hydroxide reacts with aluminum oxide to produce soluble sodium chlorate and water.

[0053] The reaction process is as follows:

[0054] Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

[0055] 3. Sodium aluminate hydrolyzes in water to produce sodium hydroxide and aluminum hydroxide, replenishing free alkali while increasing the dissolution rate of alumina. The hydrolysis process of sodium aluminate is as follows:

[0056]

[0057] Sodium aluminate and sodium hydroxide work together to increase the dissolution rate of alumina, while avoiding the risk of over-corrosion caused by excessively high concentrations of sodium hydroxide alone.

[0058] 4. Sodium silicate (Na₂SiO₃) forms a colloidal solution in water, adsorbing onto the surface of pollutants through electrostatic adsorption and hydrogen bonding, and preventing their re-aggregation based on the principle of electric double-layer repulsion. The cleaning effect of sodium silicate on impurities is as follows:

[0059] Sodium silicate dissolves to form negatively charged silica colloid [SiO2·nH2O]. n- →Adsorption of positively charged solid impurities / oil droplets→Formation of a steric double layer for repulsion→Stable dispersion and expulsion of impurities

[0060] Meanwhile, citric acid and sodium silicate work synergistically to complex metal ions, preventing scale buildup and improving the stability of the cleaning agent. The simplified reaction formula is:

[0061] Al 3+ +3C6H8O7→[Al(C6H5O7)3] 9- +3H +

[0062] Since the complex is soluble, its solubility is greater than that of Al(OH)3 precipitate, thus preventing the deposition of aluminum ions on the metal matrix.

[0063] The oil removal principle of the cleaning agent prepared in this invention is as follows:

[0064] The cleaning agent effectively dissolves both non-saponifiable and saponifiable oils through dispersion, emulsification, and saponification. For non-saponifiable greases, the linear structure of lauryl alcohol polyoxyethylene ether encapsulates oil molecules, forming an oil-in-water emulsion, achieving a "stripping + emulsification" effect. Simultaneously, nonionic surfactants reduce the interfacial tension between oil and water, dispersing the oil into tiny droplets to form an emulsion. For saponifiable greases, the reaction between alkali and ester produces soluble products (carboxylates and alcohols), which are then dissolved in the cleaning agent and discharged. The reaction process is as follows:

[0065] RCOOR' + NaOH → RCOONa + R'OH

[0066] The corrosion protection principle of the cleaning agent prepared by this invention is as follows:

[0067] 1. Sodium molybdate (Na₂MoO₄) hydrolyzes in an alkaline environment (cleaning agent pH≈10) to form molybdate ions (MoO₄). 2- Aluminum ions and molybdate ions form an amorphous aluminum molybdate composite film on the surface of an aluminum substrate. This film, composed of amorphous aluminum molybdate (Al2(MoO4)3) and molybdenum oxide, has excellent physical shielding capabilities and can effectively prevent corrosion from corrosive media (such as moisture and oxygen).

[0068] 2. Benzoic acid ionizes into benzoate ions (C6H5COO) in an alkaline environment. - ), and aluminum ions on the surface of the aluminum alloy react with each other to form an aluminum benzoate complex through "adsorption-polymerization". The reaction process is as follows:

[0069]

[0070] The benzene ring structure endows the film with hydrophobicity, thereby reducing the adsorption of moisture on the metal surface. Furthermore, the aluminum benzoate complex decomposes into carbon dioxide and water at the high welding temperatures, leaving no residue inside the weld. Based on the corrosion inhibitor proposed in this invention, a corrosion-resistant film with a thickness of approximately 50 nm is formed on the aluminum metal surface. This film exhibits strong alkali resistance, a dense structure, and a thickness much smaller than the weld penetration depth (50 nm << 0.5–3 mm), thus providing passivation and corrosion protection without affecting the weld quality.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cleaning agent for pre-welding treatment of aluminum alloy parts, characterized in that, The cleaning agent includes nonionic surfactants, sodium hydroxide, sodium aluminate, sodium silicate, citric acid, organic corrosion inhibitors, inorganic corrosion inhibitors, and solvents.

2. The cleaning agent for pre-welding treatment of aluminum alloy parts as described in claim 1, characterized in that, By mass ratio, the cleaning agent contains 1.0–3.0% nonionic surfactant, 1.0–3.0% sodium hydroxide, 1.0–2.0% sodium aluminate, 1.0–2.0% sodium silicate, 0.5–1.0% citric acid, 0.5–1.0% organic corrosion inhibitor, 0.2–0.5% inorganic corrosion inhibitor, with the solvent as the balance.

3. The cleaning agent for pre-welding treatment of aluminum alloy parts as described in claim 1, characterized in that, The nonionic surfactant is a compound of isooctanol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether.

4. The cleaning agent for pre-welding treatment of aluminum alloy parts as described in claim 1, characterized in that, In the nonionic surfactant, the mass ratio of isooctanol polyoxyethylene ether to lauryl alcohol polyoxyethylene ether is 6:

4.

5. The cleaning agent for pre-welding treatment of aluminum alloy parts as described in claim 1, characterized in that, The organic corrosion inhibitor is benzoic acid, the inorganic corrosion inhibitor is sodium molybdate, and the solvent is deionized water.

6. A method for preparing a cleaning agent for pre-welding treatment of aluminum alloy parts as described in any one of claims 1 to 5, characterized in that, The preparation method includes the following steps: S1. Preparation of isooctanol polyoxyethylene ether Isoooctanol was used as an initiator to react with ethylene oxide to generate isoooctanol polyoxyethylene ether; S2. Preparation of lauryl alcohol polyoxyethylene ether Lauryl alcohol was used as an initiator to react with ethylene oxide to generate lauryl alcohol polyoxyethylene ether; S3. Preparation of cleaning agent Isooctanol polyoxyethylene ether and lauryl alcohol polyoxyethylene ether were added to a three-necked flask and mixed and stirred at room temperature to obtain a transparent and homogeneous liquid. The reaction temperature was increased to 40-50°C and the stirring rate was increased to 600 rpm. Under the above conditions, sodium hydroxide was added to the obtained liquid and stirred continuously. Sodium aluminate and sodium silicate were added at one time while maintaining the reaction temperature and stirring. Citric acid was dissolved in deionized water and then added to the reaction system. The pH of the liquid was monitored in real time until it reached 10 using a pH meter. Stop heating and wait for the reaction system to cool to room temperature. Then add benzoic acid and sodium molybdate in sequence while stirring at 600 rpm. Add deionized water and filter the reaction liquid through a membrane to obtain a colorless and transparent cleaning agent.

7. The method for preparing the cleaning agent for pre-welding treatment of aluminum alloy parts as described in claim 6, characterized in that, The specific method for step S1 is as follows: add isooctanol to the reactor and heat to 80°C; add potassium hydroxide, stir at a constant speed and dissolve; close the reactor, purge with nitrogen and replace the air; add ethylene oxide, raise the reaction temperature to 120-130°C, maintain the pressure at 0.8-1.2 MPa, stir at a constant speed, and react for 4-6 hours; after the reaction is complete, cool to 60°C, add dilute hydrochloric acid to adjust the pH of the liquid to 7; remove unreacted ethylene oxide and byproducts by vacuum distillation to obtain colorless and transparent liquid isooctanol polyoxyethylene ether.

8. The method for preparing the cleaning agent for pre-welding treatment of aluminum alloy parts as described in claim 6, characterized in that, The specific method for step S2 is as follows: add lauryl alcohol to the reactor and heat to 90°C; add potassium hydroxide, stir at a constant speed and dissolve; close the reactor, purge with nitrogen and replace the air; add ethylene oxide, raise the reaction temperature to 140-150°C, maintain the pressure at 1.0-1.5 MPa, stir at a constant speed, and react for 6-8 hours; after the reaction is complete, cool to 60°C, add dilute hydrochloric acid to adjust the pH of the liquid to 7; remove unreacted ethylene oxide and byproducts by vacuum distillation; obtain a pale yellow liquid lauryl alcohol polyoxyethylene ether.

9. The application of the cleaning agent for pre-welding treatment of aluminum alloy parts as described in any one of claims 1 to 5, characterized in that, Use the cleaning agent to clean aluminum alloy parts.

10. The application of the cleaning agent for pre-welding treatment of aluminum alloy parts as described in claim 9, characterized in that, Aluminum alloy parts can be manually cleaned by immersing them in a cleaning agent, or ultrasonically heated and cleaned using an ultrasonic cleaning device.

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