Aluminum alloy surface cleaning agent and preparation method thereof

Abstract

The invention discloses an aluminum alloy surface cleaning agent and a preparation method thereof, the aluminum alloy surface cleaning agent comprises a surfactant, a corrosion inhibitor, salicylic acid, sodium salicylate, benzenesulfonic acid, a hyperbranched copolymer, glycerol and the balance deionized water, the preparation method comprises the following steps: S1, preparing the hyperbranched copolymer; s2, preparing a surface active agent; s3, preparing an acidic mixed solution; S4, preparing a composite cleaning agent; the cleaning agent can effectively remove oxidation films and oil stains on the surface of aluminum alloy, salicylic acid, sodium salicylate and benzenesulfonic acid provide an acid environment for the cleaning agent, the humic acid anionic surfactant can remove the oil stains on the surface of the aluminum alloy, and the corrosion inhibitor can prevent the surface of the aluminum alloy from being excessively corroded in the cleaning process. The hyperbranched copolymer can be attached to the surface of aluminum oxide film fragments, so that the aluminum oxide film is prevented from being attached to the aluminum alloy surface again, and the cleanliness of the cleaned aluminum alloy surface is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of metal surface treatment, and in particular to an aluminum alloy surface cleaning agent and a preparation method thereof. Background Art

[0002] As a widely used metal material, aluminum alloy plays an important role in aerospace, automobile manufacturing, construction and decoration, electronic appliances and other fields due to its light weight, high strength and corrosion resistance. However, during the use of aluminum alloy, its surface is easily contaminated with oil, dust, fingerprints and other dirt, which not only affects the appearance, but also may damage the performance of aluminum alloy. Therefore, aluminum alloy surface cleaning agent came into being and became an important tool to keep the surface of aluminum alloy clean and extend its service life. The application scenarios of aluminum alloy surface cleaning agent are very wide. In the aerospace industry, aluminum alloy parts such as aircraft fuselage structural parts and interior decorative parts need to be cleaned and maintained regularly to resist corrosion in high-altitude environments. In the automobile manufacturing process, aluminum alloy parts such as engine cylinders, wheels, suspension systems, etc. also need to use special cleaning agents to remove oil and dust on the surface.

[0003] Aluminum alloy surface cleaning agents are usually composed of multiple ingredients to deal with different types of dirt. Common ingredients include surfactants, composite penetrants, dispersants, chelating agents, etc. These ingredients can work synergistically to quickly and effectively remove oil, dust and other dirt on the surface of aluminum alloys. The method of use is generally simple. Usually, the aluminum workpiece to be cleaned is immersed in the prepared cleaning solution, taken out after a certain period of immersion, and then rinsed with clean water. However, the existing aluminum alloy surface cleaning agents still have some shortcomings. Some cleaning agents are highly corrosive and can easily damage the aluminum alloy surface, affecting the performance and service life of the aluminum alloy. Summary of the invention

[0004] In view of the technical defects existing in the background technology, the present invention proposes an aluminum alloy surface cleaning agent and a preparation method thereof, which solves the above technical problems and meets the actual needs. The specific technical scheme is as follows: An aluminum alloy surface cleaning agent comprises the following raw materials, measured in weight percentage: 0.5-1% of a surfactant, 0.2-0.4% of a corrosion inhibitor, 1-2% of salicylic acid, 0.1-0.5% of sodium salicylate, 1-2% of benzenesulfonic acid, 1-2% of a hyperbranched copolymer, 7-9% of glycerol and the balance of deionized water.

[0005] As a further technical solution of the present invention, the surfactant is a humic acid anionic surfactant, which is obtained by sulfomethylation reaction of water-soluble humic acid and sodium hydroxymethyl sulfonate, and the molecular weight of the water-soluble humic acid is 5000-10000.

[0006] As a further technical solution of the present invention, the corrosion inhibitor is any one or more of benzotriazole and octadecylamine lauryl phosphate.

[0007] As a further technical solution of the present invention, the hyperbranched copolymer is prepared from maleic anhydride and ethylene glycolamine, and the molecular weight of the hyperbranched copolymer is 4000-5000, and the intrinsic viscosity is 3.8-4 mL / g.

[0008] A method for preparing an aluminum alloy surface cleaning agent comprises the following steps: S1, preparing a hyperbranched copolymer, under ice-water bath conditions, adding maleic anhydride to a flask containing ethylene glycolamine, pyridine, and chloroform, reacting for 5-7 hours, distilling off the solvent under reduced pressure to obtain an intermediate, and under heating conditions, adding p-toluenesulfonic acid to the flask to polymerize the intermediate to obtain a hyperbranched copolymer; S2, preparing a surfactant, dissolving a certain amount of water-soluble humic acid in a flask, then adding sodium hydroxymethyl sulfonate, adjusting the pH with sodium hydroxide solution, heating to reflux reaction, cooling to room temperature, centrifuging to remove precipitate, filtering, washing with distilled water until the pH value of the filtrate is about 7, and obtaining a humic acid anionic surfactant; S3. Under heating conditions, salicylic acid and benzenesulfonic acid are dissolved in part of the water to obtain solution 1, sodium salicylate is added to the remaining water, heated and stirred until completely dissolved, 10% dilute hydrochloric acid is added to adjust the pH value to 4-5 to obtain solution 2, and then solution 2 and solution 1 are mixed; S4. Add the hyperbranched copolymer, surfactant, corrosion inhibitor and propylene glycol to the mixed solution of step S3 in sequence, continue stirring, and obtain an aluminum alloy surface cleaning agent after the solid is completely dissolved.

[0009] As a further technical solution of the present invention, in step S1, under nitrogen protection, 9.0-10 g of maleic anhydride is heated into a flask equipped with a stirrer and a drying tube, pyridine and a chloroform solution containing 10-11 g of diethanolamine are heated in an ice-water bath, and reacted in an ice-water bath for 6 hours, and the solvent is evaporated under reduced pressure to obtain a light yellow viscous N, N-dihydroxyethyl maleic acid monoamide monomer, and then 0.20% by mass of p-toluenesulfonic acid is added, and polymerization is carried out at 160° C. to obtain a hyperbranched copolymer.

[0010] As a further technical solution of the present invention, in step S2, water-soluble humic acid and distilled water are added to a three-necked flask, the pH value is adjusted to about 10 with 10% NaOH, and the reaction is refluxed at 100° C. for 5 hours, wherein the mass ratio of the water-soluble humic acid to sodium hydroxymethane sulfonate is 2:1. After cooling to room temperature, the precipitate is removed by centrifugation, the filtrate is filtered, and the filtrate is washed with distilled water until the pH value of the filtrate is about 7, thereby obtaining a humic acid anionic surfactant.

[0011] As a further technical solution of the present invention, in step S4, a surfactant, a corrosion inhibitor, propylene glycol, and a hyperbranched copolymer are quickly added to the mixed solution of step S3. After each of the above components is added, it is quickly stirred for 10-15 minutes and allowed to stand for 5-10 minutes. After all the above components are added, they are quickly stirred for 10 minutes, allowed to stand for 10 minutes, and then quickly stirred in the opposite direction for 10 minutes to obtain an aluminum alloy surface cleaning agent.

[0012] The beneficial effects of the present invention are: The cleaning agent of the present invention can effectively remove the oxide film and oil stains on the surface of the aluminum alloy, wherein the humic acid anionic surfactant can remove the oil stains on the surface of the aluminum alloy, salicylic acid, sodium salicylate and benzenesulfonic acid provide an acidic environment for the cleaning agent, which is helpful for removing the oxide film, the humic acid anionic surfactant itself has carboxyl groups and hydroxyl groups, which can complex the aluminum ions generated in the cleaning process, and avoid the aluminum ions from having adverse effects on the cleaning effect or subsequent processes, the corrosion inhibitor plays a corrosion inhibition role, and can avoid the aluminum alloy surface from being excessively corroded in the cleaning process, and protect the aluminum alloy substrate from being damaged, and the carboxyl groups in the hyperbranched copolymer can react with the hydroxyl groups on the surface of the aluminum oxide film fragments that fall off in the cleaning process, so that the hyperbranched copolymer is attached to the surface of the aluminum oxide film fragments, thereby avoiding the aluminum oxide film from being attached to the aluminum alloy surface again, and ensuring the cleanliness of the aluminum alloy surface after cleaning. DETAILED DESCRIPTION

[0013] The implementation mode of the present invention is described below in conjunction with relevant embodiments. The implementation mode of the present invention is not limited to the following embodiments, and the present invention relates to relevant necessary components in the technical field, which should be regarded as the known technology in the technical field and can be known and mastered by the technical personnel in the technical field.

[0014] An aluminum alloy surface cleaning agent comprises the following raw materials, measured in weight percentage: 0.5-1% of a surfactant, 0.2-0.4% of a corrosion inhibitor, 1-2% of salicylic acid, 0.1-0% of sodium salicylate, 1-2% of benzenesulfonic acid, 1-2% of a hyperbranched copolymer, 7-9% of glycerol and the balance of deionized water.

[0015] Specifically, the raw materials of the aluminum alloy surface cleaning agent are: 0.5% surfactant, 0.2% corrosion inhibitor, 2% salicylic acid, 0.5% sodium salicylate, 1% benzenesulfonic acid, 2% hyperbranched copolymer, 9% propylene glycol and the balance is deionized water.

[0016] Furthermore, in the above scheme, the surfactant is a humic acid anionic surfactant.

[0017] Among the above-mentioned components of the present invention, the surfactant can remove oil stains on the surface of the aluminum alloy, ensure that the aluminum alloy surface reaches a high degree of cleanliness after cleaning, and provide good surface conditions for subsequent treatment processes. The surfactant itself has carboxyl and hydroxyl groups, which can complex the aluminum ions generated during the cleaning process to avoid the accumulation of aluminum ions in the cleaning solution and prevent them from interfering with the cleaning effect. It also helps to maintain the stability of the cleaning solution.

[0018] Corrosion inhibitors play a role in inhibiting corrosion. During the cleaning process, they can effectively prevent the aluminum alloy surface from being excessively corroded, protect the mechanical properties and surface quality of the aluminum alloy matrix, and extend the service life of aluminum alloy products. Salicylic acid, sodium salicylate, and benzenesulfonic acid provide a suitable acidic environment for the cleaning agent, which helps to remove the oxide film on the surface of the aluminum alloy. Under acidic conditions, the oxide film is more likely to react with the cleaning agent, thereby achieving effective removal.

[0019] The carboxyl groups in the hyperbranched copolymer can react with the hydroxyl groups on the surface of the aluminum oxide film fragments that fall off during the cleaning process, so that the hyperbranched copolymer adheres to the surface of the aluminum oxide film fragments. This can prevent the aluminum oxide film from adhering to the aluminum alloy surface again, ensure the cleanliness and smoothness of the aluminum alloy surface after cleaning, and improve the quality of subsequent surface treatment or processing. As one of the preferred embodiments of the present invention, the humic acid anionic surfactant is obtained by sulfomethylation reaction of water-soluble humic acid and sodium hydroxymethyl sulfonate, and the molecular weight of the water-soluble humic acid is 5000-10000.

[0020] Specifically, after the water-soluble humic acid is reacted with sodium hydroxymethyl sulfonate through a sulfomethylation reaction to form a humic acid anionic surfactant, its decontamination performance is further enhanced, and the oil stains on the surface of the aluminum alloy can be removed efficiently, ensuring that the aluminum alloy surface reaches a high degree of cleanliness after cleaning.

[0021] Water-soluble humic acid itself carries active groups such as carboxyl and hydroxyl. After being converted into humic acid anionic surfactant by sulfomethylation reaction, during the cleaning process, active groups such as carboxyl and hydroxyl can complex the aluminum ions generated during the cleaning process to prevent the accumulation of aluminum ions in the cleaning solution. This not only helps to maintain the stability of the cleaning solution, but also prevents aluminum ions from interfering with the cleaning effect, for example, preventing aluminum ions from re-depositing on the surface of aluminum alloys to form pollution.

[0022] Water-soluble humic acid participates in the reaction as a raw material, which helps to control the molecular structure and performance of the humic acid anionic surfactant. The water-soluble humic acid with a molecular weight of 5000-10000 can make the surfactant have good solubility and dispersibility in the solution, so that it can be evenly distributed in the cleaning liquid and better contact with the aluminum alloy surface being cleaned, thereby improving the cleaning efficiency and effect.

[0023] As one of the preferred embodiments of the present invention, the corrosion inhibitor is any one or more of benzotriazole and octadecyl phosphate.

[0024] Specifically, the corrosion inhibitor is benzotriazole, which can react chemically with the surface of aluminum alloy. The nitrogen atom in the BTA molecule has a lone pair of electrons, which can combine with the active sites on the metal surface to reduce the activity of the metal, so that benzotriazole (BTA) can chemically adsorb with the metal atoms on the surface of the aluminum alloy to form a dense protective film. This protective film can prevent the corrosive substances (such as acidic components) in the cleaning solution from directly contacting the aluminum alloy matrix, thereby effectively inhibiting the corrosion reaction of the aluminum alloy during the cleaning process and reducing the risk of corrosion of the aluminum alloy.

[0025] If the aluminum alloy is excessively corroded during the cleaning process, its mechanical properties will be reduced, such as reduced strength and hardness, and its surface quality and appearance will also be affected. Benzotriazole, as a corrosion inhibitor, slows down the corrosion rate, protects the mechanical properties and surface quality of the aluminum alloy matrix, and ensures that the aluminum alloy products can still maintain good performance and appearance after cleaning.

[0026] In the system of the aluminum alloy surface cleaning agent, there are acidic substances such as salicylic acid and benzenesulfonic acid. Although these acidic substances help to remove the oxide film, they may also cause corrosion to the aluminum alloy. Benzotriazole, as a corrosion inhibitor, can stably exist and play a role in this acidic cleaning environment, adapt to the composition of the cleaning agent and the working environment, and provide reliable protection for the aluminum alloy.

[0027] As one of the preferred embodiments of the present invention, the hyperbranched copolymer is prepared from maleic anhydride and ethylene glycolamine, and the molecular weight of the hyperbranched copolymer is 4000-5000, and the intrinsic viscosity is 3.8-4 mL / g.

[0028] The hyperbranched copolymer has a unique molecular structure. The carboxyl groups in its molecules can react with the hydroxyl groups on the surface of the aluminum oxide film fragments that fall off during the cleaning process. The hyperbranched copolymer can firmly adhere to the surface of the aluminum oxide film fragments, so that the hyperbranched copolymer can wrap up the detached aluminum oxide film fragments like a "capture agent" to prevent them from attaching to the aluminum alloy surface again, thereby effectively preventing the formation of an oxide film on the aluminum alloy surface again after cleaning, ensuring the cleaning effect and the cleanliness of the aluminum alloy surface.

[0029] The hyperbranched copolymer has good dispersibility in the solution, which helps to evenly disperse the dirt and aluminum oxide film fragments generated during the cleaning process in the cleaning solution to prevent them from re-depositing. Since the hyperbranched copolymer can prevent the aluminum oxide film fragments from re-attaching, the cleaning process can more thoroughly remove the oxide film on the surface of the aluminum alloy, further improving the cleaning ability of the cleaning agent and ensuring that the aluminum alloy surface reaches a higher cleaning standard.

[0030] Hyperbranched copolymers with specific molecular weight (4000 - 5000) and intrinsic viscosity (3.8 - 4mL / g) have good solubility and dispersibility in the cleaning agent system, allowing them to be evenly distributed in the cleaning solution and interact with other components such as surfactants and corrosion inhibitors to form a stable system, which helps to maintain consistent performance of the cleaning agent and ensure good cleaning results in different batches and usage conditions.

[0031] A method for preparing an aluminum alloy surface cleaning agent comprises the following steps: S1, preparing a hyperbranched copolymer, under ice-water bath conditions, adding maleic anhydride to a flask containing ethylene glycolamine, pyridine, and chloroform, reacting for 5-7 hours, distilling off the solvent under reduced pressure to obtain an intermediate, and under heating conditions, adding p-toluenesulfonic acid to the flask to polymerize the intermediate to obtain a hyperbranched copolymer; S2, preparing a surfactant, dissolving a certain amount of water-soluble humic acid in a flask, then adding sodium hydroxymethyl sulfonate, adjusting the pH with sodium hydroxide solution, heating to reflux reaction, cooling to room temperature, centrifuging to remove precipitate, filtering, washing with distilled water until the pH value of the filtrate is about 7, and obtaining a humic acid anionic surfactant; S3. Under heating conditions, salicylic acid and benzenesulfonic acid are dissolved in part of the water to obtain solution 1, sodium salicylate is added to the remaining water, heated and stirred until completely dissolved, 10% dilute hydrochloric acid is added to adjust the pH value to 4-5 to obtain solution 2, and then solution 2 and solution 1 are mixed; S4. Add the hyperbranched copolymer, surfactant, corrosion inhibitor and propylene glycol to the mixed solution of step S3 in sequence, continue stirring, and obtain an aluminum alloy surface cleaning agent after the solid is completely dissolved.

[0032] In the preparation method of the aluminum alloy surface cleaning agent of the present invention, water-soluble humic acid is combined with sodium hydroxymethyl sulfonate through a sulfomethylation reaction, giving the humic acid a dual function of anionic surfactant, the lipophilic group of humic acid can effectively adsorb and remove oil stains on the surface of the aluminum alloy, and the humic acid itself has carboxyl groups (-COOH) and hydroxyl groups (-OH) that can complex aluminum ions generated during the cleaning process, prevent metal ions from re-depositing on the surface, and improve the cleaning efficiency.

[0033] The hyperbranched copolymer synthesized from maleic anhydride and ethylene glycolamine has a steric hindrance effect. The hyperbranched structure provides terminal carboxyl groups (-COOH), which can chemically bond with the hydroxyl groups (-OH) on the surface of the alumina film fragments to form a stable coating layer, preventing the alumina fragments from reattaching to the aluminum alloy surface. Through the synthesis scheme, the intrinsic viscosity (3.8-4 mL / g) and molecular weight (4000-5000) of the hyperbranched copolymer are controlled, the rheological properties of the cleaning agent system are optimized, and the suspension and dispersion ability of particles is enhanced.

[0034] The combination of salicylic acid, sodium salicylate and benzenesulfonic acid forms a weakly acidic environment (pH 4-5). The acidic conditions promote the chemical dissolution of the aluminum oxide film on the surface of the aluminum alloy and improve the stripping efficiency. The salicylic acid / sodium salicylate buffer system can stabilize the pH value and avoid excessive acidity leading to substrate corrosion. The corrosion inhibitor can form a dense protective film on the surface of the aluminum alloy, inhibiting excessive corrosion of the substrate by the acidic environment, and synergistically acting with the carboxyl group of the hyperbranched copolymer to further reduce the corrosion rate of the metal active sites.

[0035] As one of the preferred embodiments of the present invention, in step S1, under nitrogen protection, 9.0-10 g of maleic anhydride is heated into a flask equipped with a stirrer and a drying tube, pyridine and a chloroform solution containing 10-11 g of diethanolamine are heated in an ice-water bath, and reacted in an ice-water bath for 6 hours, and the solvent is evaporated under reduced pressure to obtain a light yellow viscous N, N-dihydroxyethyl maleic acid monoamide monomer, and then 0.20% by mass of p-toluenesulfonic acid is added, and polymerization is carried out at 160° C. to obtain a hyperbranched copolymer.

[0036] In the preparation principle of step S1, an ice-water bath (0-5°C) is used as solvent under nitrogen protection, pyridine and chloroform as solvents, and maleic anhydride (containing two highly reactive carbonyl groups) and diethanolamine (containing an amino group and a hydroxyl group) undergo a nucleophilic addition reaction at low temperature. The amino group (-NH 2 ) attacks the carbonyl carbon of maleic anhydride, opening the ring to form an amide bond (-NH-C=O). The reaction product is N,N-dihydroxyethyl maleic acid monoamide monomer, whose structure contains an unreacted carboxylic acid group (-COOH) and two hydroxyl groups (-OH). p-Toluenesulfonic acid acts as a strong proton acid catalyst to promote the esterification reaction (dehydration condensation) of the carboxyl group (-COOH) in N,N-dihydroxyethyl maleic acid monoamide monomer with the hydroxyl group (-OH) of another monomer. The carboxylic acid is protonated to form an active intermediate, and the hydroxyl oxygen attacks the protonated carboxyl carbon, removing a molecule of water to form an ester bond (-O-CO-). Since the monomer contains two hydroxyl groups and one carboxylic acid group, the esterification reaction can be carried out at multiple sites to form a branched structure.

[0037] Through the above esterification reaction, multiple N, N-dihydroxyethyl maleic acid monoamide monomers are connected to each other to form a hyperbranched copolymer. Due to the characteristics of the reaction conditions and the monomer structure, the polymerization reaction is not a simple linear growth, but a polymer with a branched structure, i.e., a hyperbranched copolymer, is formed. During the polymerization process, the degree of the esterification reaction can be controlled by controlling the reaction conditions (such as temperature, catalyst dosage, etc.), thereby achieving the regulation of the branching degree of the hyperbranched copolymer, and finally obtaining a hyperbranched copolymer with a molecular weight of 4000-5000 and an intrinsic viscosity of 3.8-4mL / g.

[0038] As one of the preferred embodiments of the present invention, in step S2, water-soluble humic acid and distilled water are added to a three-necked flask, the pH value is adjusted to about 10 with 10% NaOH, and the reaction is refluxed at 100° C. for 5 hours, the mass ratio of the water-soluble humic acid to sodium hydroxymethane sulfonate is 2:1, and after cooling to room temperature, the precipitate is removed by centrifugation, filtered, and washed with distilled water until the pH value of the filtrate is about 7, to obtain a humic acid anionic surfactant.

[0039] Under alkaline conditions, the benzene ring in the water-soluble humic acid reacts with sodium hydroxymethane sulfonate, and the reaction is carried out by heating under reflux at 100°C for 5 hours. Sodium hydroxymethane sulfonate has strong reactivity under alkaline conditions, and its sulfomethyl group can react with the active hydrogen atoms on the benzene ring in the water-soluble humic acid molecule (such as the hydrogen atoms at the ortho-para positions of the phenolic hydroxyl group) to undergo sulfomethylation reaction. The sulfomethyl group (-CH 2 SO 3 - ) acts as a nucleophilic agent in an alkaline environment, attacks the position of the active hydrogen atom in the water-soluble humic acid molecule, undergoes a nucleophilic substitution reaction, introduces sulfomethyl groups into the water-soluble humic acid molecule, and thus forms a humic acid anionic surfactant. The above sulfomethylation reaction introduces sulfomethyl groups into the humic acid molecule, enhances its solubility and dispersibility in water, and also gives it the characteristics of anionic surfactants. After the reaction, the unreacted humic acid (molecular weight is too high or cross-linked part) and by-products (such as humic acid self-polymers) form precipitation due to reduced solubility, which is removed by centrifugation, and washed with distilled water until the filtrate pH is ≈ 7, removes the residual NaOH and reaction by-products, and converts the humic acid anionic surfactant into a free acid form (-SO 3 H), enhancing its dissociation ability and surface activity in water.

[0040] The synthesized humic acid anionic surfactant combines the characteristics of humic acid and anionic surfactants. Humic acid itself has a certain surface activity, and the surface tension of its metal salt is lower than the surface tension of water, which has obvious dispersing and emulsifying effects on oil stains on the surface of aluminum alloys, thereby retaining the efficient decontamination ability of anionic surfactants. Humic acid anionic surfactants can be adsorbed on the surface of oil stains to form a protective film to prevent the oil stains from re-aggregating. The lipophilic group of the surfactant combines with the oil stains, and the hydrophilic group combines with water molecules, so that the oil stains are dispersed into tiny oil droplets.

[0041] As one of the preferred embodiments of the present invention, in step S4, a surfactant, a corrosion inhibitor, propylene glycol, and a hyperbranched copolymer are quickly added to the mixed solution of step S3. After each of the above components is added, it is quickly stirred for 10-15 minutes and allowed to stand for 5-10 minutes. After all the above components are added, they are quickly stirred for 10 minutes and then allowed to stand for 10 minutes, and then quickly stirred in the opposite direction for 10 minutes to obtain an aluminum alloy surface cleaning agent.

[0042] In step S4, a hyperbranched copolymer, a surfactant, a corrosion inhibitor, and propylene glycol are added in sequence. After each component is added, rapid stirring is performed for 10-15 minutes, and then the mixture is allowed to stand for 5-10 minutes. Rapid stirring can break up the agglomerates of the components (such as hyperbranched copolymers and surfactants), promote molecular dispersion, accelerate the miscibility of propylene glycol and water, reduce interfacial tension, and improve dissolution efficiency. The standing stage can eliminate bubbles introduced by stirring, prevent microbubbles from interfering with subsequent mixing, and further dissolve the incompletely dissolved particles.

[0043] After all the above components are added, stir quickly for 10 minutes, let it stand for 10 minutes, stir quickly in the opposite direction for 10 minutes, and let it stand for 10 minutes. The second standing is to make the solution more stable in a more uniform state and make the interaction between the components more sufficient. The rapid stirring in the opposite direction is to break the local ordered structure that may be formed and prevent stratification or precipitation in the solution. By stirring in the opposite direction, the molecular movement in the solution can be made more complex and sufficient, further improving the uniformity and stability of the solution, and finally obtaining an aluminum alloy surface cleaning agent with good performance.

[0044] Example 1 S1. To prepare a hyperbranched copolymer, 9.0-10 g of maleic anhydride was added to a flask equipped with a stirrer and a drying tube under nitrogen protection; pyridine and a chloroform solution containing 10-11 g of ethylene glycolamine were slowly added in an ice-water bath (0-5°C) and stirred continuously; the mixture was reacted in an ice-water bath for 6 hours, and the solvent was removed by vacuum distillation to obtain a light yellow viscous N,N-dihydroxyethyl maleic acid monoamide intermediate; 0.20% by mass of p-toluenesulfonic acid was added to the intermediate, and a polymerization reaction was carried out at 160°C to obtain a hyperbranched copolymer with a molecular weight of 4000-5000 and a characteristic viscosity of 3.8-4 mL / g.

[0045] S2. Prepare a humic acid anionic surfactant. Add water-soluble humic acid with a molecular weight of 5000-10000 and distilled water into a three-necked flask and stir to dissolve; add sodium hydroxymethane sulfonate at a mass ratio of 2:1 of water-soluble humic acid: sodium hydroxymethane sulfonate; adjust the pH to 10 with 10% NaOH solution, heat and reflux at 100°C for 5 hours; cool to room temperature, centrifuge to remove precipitate, filter, and wash with distilled water until the filtrate has a pH value of 7 to obtain a humic acid anionic surfactant.

[0046] S3. Prepare an acidic mixed solution: Solution 1: dissolve salicylic acid and benzenesulfonic acid in part of deionized water, heat and stir until completely dissolved; Solution 2: dissolve sodium salicylate in the remaining deionized water, heat and dissolve, then add 10% dilute hydrochloric acid to adjust the pH to 4-5; mix Solution 1 and Solution 2, and stir evenly.

[0047] S4, preparation of composite cleaning agent, add the following components to the mixed solution of S3 in sequence, stir rapidly for 10-15 minutes after each addition, and let stand for 5-10 minutes: humic acid anionic surfactant, benzotriazole, propylene glycol, hyperbranched copolymer. After all components are added, stir rapidly for 10 minutes and let stand for 10 minutes; stir in the reverse direction for 10 minutes, and let stand until the solution is uniform and stable, to obtain the aluminum alloy surface cleaning agent.

[0048] The prepared aluminum alloy surface cleaning agent comprises: 0.5% humic acid anionic surfactant, 0.2% benzotriazole, 2% salicylic acid, 0.5% sodium salicylate, 1% benzenesulfonic acid, 2% hyperbranched copolymer, 9% propylene glycol and the balance is deionized water.

[0049] Comparative Example 1 (without hyperbranched copolymer): In step S4, no hyperbranched copolymer is added, and the rest is the same as in Example 1.

[0050] Comparative Example 2 (without corrosion inhibitor): No benzotriazole was added in step S4, and the rest was the same as in Example 1.

[0051] Comparative Example 3: The dilute hydrochloric acid in step S3 was adjusted to pH=3.0, and the rest was the same as in Example 1.

[0052] The above-mentioned Example 1 and Comparative Examples 1-3 were subjected to performance tests, and the test items included corrosivity, thermal stability, cold stability, and defoaming time.

[0053] Corrosion test: Pour 100 mL of the aluminum alloy surface cleaning agent of Example 1 and Comparative Examples 1-3 into a beaker, take 5 aluminum alloy plates of the same specification and the same surface color and place them in the beakers respectively, soak for 12 hours, take out, wash with deionized water, wipe dry, and observe whether the surface color of the aluminum alloy plate changes.

[0054] Thermal stability: The aluminum alloy surface cleaning agents of Example 1 and Comparative Examples 1-3 were placed in a 45°C oven, kept at a constant temperature for 24 hours, returned to room temperature, and observed for any delamination.

[0055] Cold stability: The aluminum alloy surface cleaning agents of Example 1 and Comparative Examples 1-3 were placed in an environment at 3°C ​​for 24 hours, returned to room temperature, and observed for flocculation.

[0056] Defoaming performance: The time taken by the aluminum alloy surface cleaning agents of Example 1 and Comparative Examples 1-3 to defoam naturally after the foaming ends is observed.

[0057] The test results of the above embodiment 1 and comparative examples 1-4 are shown in the following table:

[0058] In the above test data, in Comparative Example 1, no hyperbranched copolymer is added, and the aluminum alloy plate slightly changes color, while in Example 1, the aluminum alloy plate does not change color after the hyperbranched copolymer is added, which indicates that the hyperbranched copolymer helps prevent the aluminum alloy from being corroded during the cleaning process. In Comparative Example 2, no corrosion inhibitor benzotriazole is added, and the aluminum alloy plate changes color significantly, indicating that the corrosion inhibitor can effectively inhibit the corrosion reaction of the aluminum alloy during the cleaning process and reduce the risk of corrosion of the aluminum alloy. In Comparative Example 4, step S3 uses dilute hydrochloric acid to pH=3.0, and the thermal stability and cold stability become poor, flocculation occurs, and the aluminum alloy plate slightly changes color, which indicates that the pH of the cleaning agent can maintain the stability of the cleaning agent and ensure the degree of corrosiveness of the aluminum alloy. The appropriate pH value range (such as pH=4-5 in Example 1) can ensure that the cleaning agent has good stability and low corrosiveness.

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An aluminum alloy surface cleaning agent, characterized in that: The invention comprises the following raw materials in weight percentage: 0.5-1% of surfactant, 0.2-0.4% of corrosion inhibitor, 1-2% of salicylic acid, 0.1-0.5% of sodium salicylate, 1-2% of benzenesulfonic acid, 1-2% of hyperbranched copolymer, 7-9% of glycerol and the balance of deionized water.

2. The aluminum alloy surface cleaning agent according to claim 1, characterized in that: The surfactant is a humic acid anionic surfactant, which is obtained by sulfomethylation reaction of water-soluble humic acid and sodium hydroxymethyl sulfonate, and the molecular weight of the water-soluble humic acid is 5000-10000.

3. The aluminum alloy surface cleaning agent according to claim 1, characterized in that: The corrosion inhibitor is any one or more of benzotriazole and octadecylamine lauryl phosphate.

4. The aluminum alloy surface cleaning agent according to claim 1, characterized in that: The hyperbranched copolymer is prepared from maleic anhydride and ethylene glycol amine, and has a molecular weight of 4000-5000 and an intrinsic viscosity of 3.8-4 mL / g.

5. The method for preparing an aluminum alloy surface cleaning agent according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, preparing a hyperbranched copolymer, under ice-water bath conditions, adding maleic anhydride to a flask containing ethylene glycolamine, pyridine, and chloroform, reacting for 5-7 hours, distilling off the solvent under reduced pressure to obtain an intermediate, and under heating conditions, adding p-toluenesulfonic acid to the flask to polymerize the intermediate to obtain a hyperbranched copolymer; S2, preparing a surfactant, dissolving a certain amount of water-soluble humic acid in a flask, then adding sodium hydroxymethyl sulfonate, adjusting the pH with sodium hydroxide solution, heating to reflux reaction, cooling to room temperature, centrifuging to remove precipitate, filtering, washing with distilled water until the pH value of the filtrate is about 7, and obtaining a humic acid anionic surfactant; S3. Under heating conditions, salicylic acid and benzenesulfonic acid are dissolved in part of the water to obtain solution 1, sodium salicylate is added to the remaining water, heated and stirred until completely dissolved, 10% dilute hydrochloric acid is added to adjust the pH value to 4-5 to obtain solution 2, and then solution 2 and solution 1 are mixed; S4. Add the hyperbranched copolymer, surfactant, corrosion inhibitor and propylene glycol to the mixed solution of step S3 in sequence, continue stirring, and obtain an aluminum alloy surface cleaning agent after the solid is completely dissolved.

6. The method for preparing an aluminum alloy surface cleaning agent according to claim 5, characterized in that: In step S1, under nitrogen protection, 9.0-10 g of maleic anhydride is heated into a flask equipped with a stirrer and a drying tube, pyridine and a chloroform solution containing 10-11 g of diethanolamine are heated in an ice-water bath, and reacted in an ice-water bath for 6 hours, and the solvent is evaporated under reduced pressure to obtain a light yellow viscous N, N-dihydroxyethyl maleic acid monoamide monomer, and then 0.20% by mass of p-toluenesulfonic acid is added, and polymerization is carried out at 160° C. to obtain a hyperbranched copolymer.

7. The method for preparing an aluminum alloy surface cleaning agent according to claim 5, characterized in that: In step S2, water-soluble humic acid and distilled water are added to a three-necked flask, the pH value is adjusted to about 10 with 10% NaOH, and the reaction is heated to reflux at 100° C. for 5 hours, the mass ratio of the water-soluble humic acid to sodium hydroxymethyl sulfonate is 2:1, and after cooling to room temperature, the precipitate is removed by centrifugation, the filtrate is filtered, and the filtrate is washed with distilled water until the pH value of the filtrate is about 7, thereby obtaining a humic acid anionic surfactant.

8. The method for preparing an aluminum alloy surface cleaning agent according to claim 5, characterized in that: In step S4, the surfactant, corrosion inhibitor, propylene glycol and hyperbranched copolymer are quickly added to the mixed solution of step S3. After each component is added, it is quickly stirred for 10-15 minutes and allowed to stand for 5-10 minutes. After all the components are added, they are quickly stirred for 10 minutes, allowed to stand for 10 minutes, and then quickly stirred in the opposite direction for 10 minutes to obtain an aluminum alloy surface cleaning agent.

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