High-permeability and low-corrosion die-casting aluminum degreasing agent and preparation method and application thereof

Abstract

The invention belongs to the technical field of metal surface treatment, and discloses a high-permeability and low-corrosion die-casting aluminum degreasing agent as well as a preparation method and application thereof. The die-casting aluminum degreasing agent comprises an active matter and water, the active matters comprise 6 to 10 percent of organic weak acid, 0.5 to 1.5 percent of chitosan oligosaccharide, 0.5 to 1.2 percent of tea polyphenol, 0.7 to 1.8 percent of curcumin, 4 to 6 percent of surfactant, 0.4 to 1.0 percent of cyclodextrin, 0.5 to 0.8 percent of low-foaming additive, 1.0 to 2.0 percent of buffering agent, 0.6 to 1.5 percent of corrosion inhibitor and 0.2 to 0.5 percent of lipase by taking the total mass of the die-casting aluminum degreasing agent as 100 percent; the organic weak acid comprises levulinic acid, lactic acid and acetoacetic acid; the corrosion inhibitor comprises polycarboxylate and hydroxy carboxylate. The die-casting aluminum degreasing agent has excellent removal capacity for common silicone oil / ester release agents on the surface of a die-casting aluminum alloy, is low in corrosivity and does not contain phosphorus or fluorine or other components prone to polluting water.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, and specifically relates to a degreasing agent for die-cast aluminum with strong penetration and low corrosion, its preparation method and application. Background Technology

[0002] Die-cast aluminum alloys are widely used in the automotive, electronics, home appliance, and aerospace industries due to their excellent dimensional accuracy, formability, and mechanical properties. However, during the forming process, contaminants such as mold release agents, lubricants, cutting fluids, or oxide films inevitably adhere to the surface of die-cast aluminum alloys. These residues can severely affect subsequent surface treatment processes such as anodizing, electroplating, spraying, and bonding. Therefore, degreasing and cleaning are crucial steps in the surface pretreatment of die-cast aluminum alloys, and their effectiveness directly determines the subsequent surface quality and protective performance.

[0003] Currently, commonly used industrial degreasing agents are mainly divided into two categories: solvent-based degreasing agents and water-based degreasing agents. Solvent-based degreasing agents have strong cleaning capabilities, but they suffer from problems such as flammability, high toxicity, and environmental pollution, and have been gradually phased out. In contrast, water-based degreasing agents, with surfactants as the main component and supplemented by additives, corrosion inhibitors, and alkaline salts, have become the mainstream due to their safety, environmental friendliness, and ease of handling. However, there is limited research on their compatibility with high-silicon, high-density alloy systems such as die-cast aluminum. Die-cast aluminum alloys have a high silicon content (6-12%) on their surface, making them highly susceptible to "silicon enrichment layers" and "selective corrosion" in alkaline or strong acid environments. Traditional water-based degreasing agents mainly have the following shortcomings: 1) High corrosion risk: Although water-based degreasers are more environmentally friendly than solvent-based ones, alkaline (containing sodium hydroxide) or acidic (containing sulfuric acid) degreasers have a corrosion rate of >0.2g / (m³) on die-cast aluminum alloys. 2 •h), which can easily cause hydrogen embrittlement or surface oxidation, especially on the porous surface of AlSi10MnMg alloy; 2) Difficulty in penetration: The porosity of the die-cast aluminum alloy surface and the segregation of silicon phase (silicon-rich layer thickness is 10-50μm) lead to incomplete cleaning.

[0004] Therefore, it is necessary to develop a degreasing agent that is low in corrosiveness and can effectively degrease die-cast aluminum alloys. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, the purpose of this invention is to provide a highly penetrating, low-corrosion degreasing agent for die-cast aluminum, its preparation method, and its application. The die-cast aluminum degreasing agent of this invention is a weakly acidic water-based degreasing agent. Through the synergistic effect between its components and dosage, it exhibits excellent removal ability against common silicone / ester-based release agents on the surface of die-cast aluminum alloys. It has low corrosiveness and does not contain components such as phosphorus or fluorine that easily pollute water bodies.

[0006] In a first aspect, the present invention provides a degreasing agent for die-cast aluminum, the degreasing agent comprising active ingredients and water; based on 100% of the total mass of the degreasing agent, the active ingredients comprise 6-10% organic weak acid, 0.5-1.5% chitosan oligosaccharide, 0.5-1.2% tea polyphenols, 0.7-1.8% curcumin, 4-6% surfactant, 0.4-1.0% cyclodextrin, 0.5-0.8% low-foaming agent, 1.0-2.0% buffer, 0.6-1.5% corrosion inhibitor, and 0.2-0.5% lipase; the organic weak acid comprises levulinic acid, lactic acid, and acetoacetic acid; the corrosion inhibitor comprises polycarboxylate and hydroxycarboxylate.

[0007] Specifically, this invention uses specific organic weak acids (levulinic acid, lactic acid, and acetoacetic acid) as core active components, providing appropriate acidity and chelating power. This mixed weak acid (acidity coefficient pKa of 3.8-4.8) slowly releases H+. + It gently dissolves the oxide layer (Al2O3 / SiO2) and oil complexes on the surface of die-cast aluminum alloys. By complexing Al / Si ions with carboxyl groups, it promotes oil emulsification and enhances penetration depth (>60μm), while avoiding the risk of hydrogen embrittlement from strong acids (sulfuric acid). The mild acidity is compatible with low-pH processes, ensuring efficient cleaning within a short time (3-8 min) without affecting the integrity of the substrate.

[0008] Specifically, this invention uses chitosan oligosaccharide as a penetration enhancer. Chitosan oligosaccharide molecules (molecular weight <3kDa) carry positively charged amine groups, which interact with the oxide film on the surface of die-cast aluminum alloy to enhance hydrophilicity (contact angle <25°), promote the penetration of weak acid system into the silicon enrichment layer, and significantly improve the problem of oil residue.

[0009] Specifically, this invention employs tea polyphenols and curcumin as a dual passivation antioxidant system; tea polyphenols chelate metal ions and inhibit electrochemical reactions, while curcumin forms a passivation film (EIS impedance > 10) through π-electron transfer. 8 Ω·cm 2 Corrosion current <0.05μA / cm 2 The bisphenol system replaces traditional chromate passivation, achieving a reactive oxygen species (ROS) free radical scavenging rate of >90%. Combined with corrosion inhibitors, it forms a multi-layered protection, mitigating the potential corrosion risk from weak acids.

[0010] Specifically, the addition of lipase in this invention can catalyze the hydrolysis of ester bonds and effectively decompose mold release agents, etc.; through the enzyme-acid synergistic mechanism (Km<0.5mM), it can effectively degrease, and in synergy with weak acids and the envelope, it can efficiently degrade macromolecular esters.

[0011] Specifically, this invention uses polycarboxylate and hydroxycarboxylate as a corrosion inhibition and pH stabilization system: the polycarboxylate and hydroxycarboxylate adsorb to form a protective film, inhibiting ion migration; at the same time, the acidity is maintained through a buffer system, and the pH value of the degreasing tank solution prepared based on the die-cast aluminum degreasing agent of this invention fluctuates by <±0.2 within 30 days.

[0012] Specifically, the present invention adds a low-foaming agent to control foam stability and liquid surface tension, which is beneficial for tank liquid spraying and recycling, and improves operating efficiency.

[0013] This invention, by employing the above-mentioned technical solution, can obtain a weak acid system degreasing agent for die-cast aluminum, which can avoid problems such as alkaline corrosion, whitening, and grain boundary corrosion. Through the synergy of an organic weak acid matrix and natural functional molecules (such as tea polyphenols and curcumin), it achieves surface passivation and anti-oxidation while maintaining the degreasing effect. Through a composite enzyme-acid synergistic decomposition mechanism, it has excellent removal capabilities against common silicone oil and ester-based mold release agents for die-cast aluminum alloys. At the same time, it is low-foaming and the prepared bath solution has high stability, making it suitable for use in continuous production lines and spray cleaning equipment.

[0014] In some embodiments of the present invention, the organic weak acid accounts for 8-10% of the mass percentage of the die-cast aluminum degreasing agent.

[0015] In some embodiments of the present invention, the mass ratio of levulinic acid, lactic acid and acetoacetic acid is (1-3):1:(1-3).

[0016] In some embodiments of the present invention, the mass ratio of the polycarboxylate to the hydroxycarboxylate is (1-3):(1-3).

[0017] In some embodiments of the present invention, the polycarboxylate includes sodium polyacrylate and / or sodium polyaspartate.

[0018] In some embodiments of the present invention, the hydroxycarboxylate salt includes at least one of sodium citrate, sodium tartrate, and sodium gluconate.

[0019] In some embodiments of the present invention, the active ingredient accounts for 18-25% of the mass percentage of the die-cast aluminum degreasing agent, preferably 20-24%.

[0020] In some embodiments of the present invention, the surfactant includes alkylphenol polyoxyethylene ether and / or betaine.

[0021] In some embodiments of the present invention, the surfactant includes alkylphenol polyoxyethylene ether and betaine.

[0022] In some embodiments of the present invention, the mass ratio of the alkylphenol polyoxyethylene ether to betaine is (1-3):(1-3).

[0023] Specifically, this invention preferably employs a composite surfactant system: a combination of nonionic alkylphenol polyoxyethylene ether and amphoteric betaine to form a dual-interface layer structure, possessing both high detergency and low foaming properties. The alkylphenol polyoxyethylene ether reduces surface tension to <20 mN / m, promoting emulsification; betaine provides pH adaptability, forming a bilayer (critical micelle concentration CMC <0.05%), enhancing oil dispersion and suppressing foam. Synergistically with the low-foaming agent, it ensures a foam-free cleaning process and strengthens weak acid emulsification. Compared to using alkylphenol polyoxyethylene ether or betaine alone, this invention preferably employs a composite surfactant system, which better balances low foaming, strong emulsification, and hard water compatibility, resulting in superior performance (bath solution stability, emulsification / demulsification characteristics, and surface mark control).

[0024] In some embodiments of the present invention, the cyclodextrin is methyl-β-cyclodextrin.

[0025] Specifically, this invention preferably uses methyl-β-cyclodextrin (M-β-CD): the hydrophobic cavity encapsulates oil molecules (encapsulation constant K>200L / mol), mainly forming inclusion complexes with silicone oil-based release agents, wax-based and ester-based oil molecules remaining on the surface of die-cast aluminum, thereby significantly improving the apparent solubility and migration ability of the above-mentioned hydrophobic oils in the water-based system. Its apparent solubility is more than 5 times higher than that of the system without cyclodextrin, effectively reducing the residue of oil in pores and silicon-rich layers; it is suitable for low pH environments, solving the problems of insufficient penetration and oil residue.

[0026] In some embodiments of the present invention, the low-foaming additive includes silicone leveling agents and / or quaternary ammonium salt antistatic agents.

[0027] In some embodiments of the present invention, the low-foaming additives include silicone leveling agents and quaternary ammonium salt antistatic agents.

[0028] In some embodiments of the present invention, the mass ratio of the organosilicon leveling agent to the quaternary ammonium salt antistatic agent is (1-3):(1-3).

[0029] Specifically, the present invention preferably uses a combination of organosilicon leveling agent and quaternary ammonium salt antistatic agent as a low-foaming agent, which can better control foam and avoid silicone spots, and its performance is better than using a single component.

[0030] In some embodiments of the present invention, the buffer includes sodium lactate.

[0031] A second aspect of the present invention provides a method for preparing the degreasing agent for die-cast aluminum described in the first aspect of the present invention, comprising the following steps: The organic weak acid, buffer, and water are mixed to obtain mixture A; Mix the aforementioned mixture A, tea polyphenols, curcumin, and cyclodextrin, and carry out an inclusion reaction to obtain mixture B; The mixture B, surfactant, chitosan oligosaccharide, corrosion inhibitor, low-foaming agent and lipase are mixed, ultrasonically dispersed, aged and filtered to obtain the die-cast aluminum degreasing agent.

[0032] In some embodiments of the present invention, the pH of the mixture A is 1.0-2.0, preferably 1.4-1.5.

[0033] In some embodiments of the present invention, the temperature of the inclusion reaction is 40-60°C.

[0034] In some embodiments of the present invention, the inclusion reaction takes 40-60 minutes.

[0035] In some embodiments of the present invention, the frequency of the ultrasonic dispersion is 40-50 kHz.

[0036] In some embodiments of the present invention, the ultrasonic dispersion time is 20-30 min.

[0037] In some embodiments of the present invention, the aging time is 30-40 hours.

[0038] A third aspect of the present invention provides a method for degreasing die-cast aluminum alloys, comprising degreasing the die-cast aluminum alloys with the die-cast aluminum degreasing agent described in the first aspect of the present invention.

[0039] In some embodiments of the present invention, the degreasing method includes the following steps: The die-cast aluminum degreasing agent is mixed with water to obtain a degreasing tank solution; The die-cast aluminum alloy is immersed in the degreasing bath solution for soaking.

[0040] In some embodiments of the present invention, the concentration of the die-cast aluminum degreasing agent in the degreasing bath is 50-60 g / L.

[0041] In some embodiments of the present invention, the pH of the degreasing bath is 1.5-2.5, preferably 1.9-2.0.

[0042] In some embodiments of the present invention, the temperature of the degreasing bath is 20-50°C.

[0043] In some embodiments of the present invention, the soaking time is 3-8 minutes.

[0044] A fourth aspect of the present invention provides the application of the degreasing agent for die-cast aluminum described in the first aspect of the present invention in the surface treatment of die-cast aluminum alloys.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The degreasing agent for die-cast aluminum provided by the present invention significantly improves the degreasing effect (oil removal rate ≥99%) through the synergistic chelation and slow release of acid by organic weak acid matrix (acetopropionic acid, lactic acid, acetoacetic acid), achieving mild acid dissolution and complexation of Al / Si ions, and improving the penetration depth.

[0046] (2) The die-cast aluminum degreasing agent provided by the present invention uses an enzyme-acid synergistic degradation mechanism: lipase is introduced to work synergistically with an organic weak acid matrix to catalyze the hydrolysis of ester bonds in the mold release agent, efficiently decompose the silicone oil mold release agent, and achieve an oil removal rate of ≥99%, thereby effectively solving the problem of incomplete oil removal in traditional methods and improving the performance balance; at the same time, enzyme biocatalysis provides a green alternative to chemical solvents, reducing the environmental burden.

[0047] (3) The degreasing agent for die-cast aluminum provided by the present invention uses M-β-CD to encapsulate macromolecular oil stains (encapsulation constant K>200L / mol, improving solubility by >5 times) and chitosan oligosaccharide low molecular weight permeable micropores (contact angle <25°, coverage >95%), thereby addressing the problem of insufficient permeation and solving the problem of dirt accumulation in porous substrates. Detailed Implementation

[0048] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0049] The silicone leveling agent was purchased from Nagase (China) Co., Ltd., model WynCoat®SL 3455; Quaternary ammonium salt antistatic agent, purchased from Shandong Yousuo Chemical Technology Co., Ltd., model number polyquaternary ammonium salt-47.

[0050] Example 1 A degreasing agent for die-cast aluminum, comprising 20% ​​active ingredient and the remainder deionized water, based on 100% of the total mass of the degreasing agent for die-cast aluminum; The active ingredients include 9% organic weak acid, 1% chitosan oligosaccharide, 0.8% tea polyphenols, 1.2% curcumin, 4% surfactant, 0.6% methyl-β-cyclodextrin, 0.5% low-foaming agent, 1.5% sodium lactate, 1% corrosion inhibitor, and 0.4% lipase. The organic weak acid is a mixture of levulinic acid, lactic acid, and acetoacetic acid in a mass ratio of 1:1:1; the surfactant is a mixture of alkylphenol polyoxyethylene ether (OP-10) and betaine in a mass ratio of 2:1; the low-foaming agent is a mixture of silicone leveling agent and quaternary ammonium salt antistatic agent in a mass ratio of 1:1; the corrosion inhibitor is a mixture of polycarboxylate and hydroxycarboxylate in a mass ratio of 1:1; the polycarboxylate is sodium polyacrylate, and the hydroxycarboxylate is sodium citrate.

[0051] The preparation method of the degreasing agent for die-cast aluminum in this embodiment includes the following steps: S1. Dissolve the organic weak acid and sodium lactate in deionized water, stir well, and adjust the pH to 1.4-1.5 to obtain mixture A; S2. Mix the mixture A, tea polyphenols, curcumin and methyl-β-cyclodextrin and carry out an inclusion reaction (45℃, 50min, stirring speed 500rpm) to obtain the mixture B. S3. Mix the mixture B, surfactant, chitosan oligosaccharide, corrosion inhibitor, low-foaming agent and lipase, disperse by ultrasonication (40kHz, 25min), age for 36h, filter to obtain die-cast aluminum degreasing agent.

[0052] A method for degreasing die-cast aluminum alloys includes the following steps: The die-casting aluminum degreasing agent of this embodiment is mixed with water to obtain a degreasing bath solution; the degreasing bath solution contains 55g / L of die-casting aluminum degreasing agent, and the pH of the degreasing bath solution is 1.9-2.0; The AlSi10MnMg alloy sample was immersed in a degreasing bath and soaked at 40°C for 5 minutes, with ultrasonic cleaning as an auxiliary process.

[0053] Example 2 A degreasing agent for die-cast aluminum, comprising 24% active ingredient and the remainder deionized water, based on 100% of the total mass of the degreasing agent for die-cast aluminum; The active ingredients include 9% organic weak acid, 1.5% chitosan oligosaccharide, 1.2% tea polyphenols, 1.8% curcumin, 5% surfactant, 1% methyl-β-cyclodextrin, 0.8% low-foaming agent, 2% sodium lactate, 1.2% corrosion inhibitor, and 0.5% lipase. The organic weak acid is a mixture of levulinic acid, lactic acid, and acetoacetic acid in a mass ratio of 1:1:1; the surfactant is a mixture of alkylphenol polyoxyethylene ether (OP-10) and betaine in a mass ratio of 2:1; the low-foaming agent is a mixture of silicone leveling agent and quaternary ammonium salt antistatic agent in a mass ratio of 1:1; the corrosion inhibitor is a mixture of polycarboxylate and hydroxycarboxylate in a mass ratio of 1:1; the polycarboxylate is sodium polyacrylate, and the hydroxycarboxylate is sodium citrate.

[0054] The preparation method and degreasing method of the die-cast aluminum degreasing agent in this embodiment are the same as those in Example 1.

[0055] Example 3 A degreasing agent for die-cast aluminum, comprising 20% ​​active ingredient and the remainder deionized water, based on 100% of the total mass of the degreasing agent for die-cast aluminum; The active ingredients include 9% organic weak acid, 1% chitosan oligosaccharide, 0.8% tea polyphenols, 1.2% curcumin, 4% surfactant, 0.6% methyl-β-cyclodextrin, 0.5% low-foaming agent, 1.5% sodium lactate, 1% corrosion inhibitor, and 0.4% lipase. The organic weak acid is a mixture of levulinic acid, lactic acid, and acetoacetic acid in a mass ratio of 1:1:1; the surfactant is alkylphenol polyoxyethylene ether (OP-10); the low-foaming agent is a mixture of silicone leveling agent and quaternary ammonium salt antistatic agent in a mass ratio of 1:1; the corrosion inhibitor is a mixture of polycarboxylate and hydroxycarboxylate in a mass ratio of 1:1; the polycarboxylate is sodium polyacrylate, and the hydroxycarboxylate is sodium citrate.

[0056] The preparation method and degreasing method of the die-cast aluminum degreasing agent in this embodiment are the same as those in Example 1.

[0057] Example 4 A degreasing agent for die-cast aluminum, comprising 20% ​​active ingredient and the remainder deionized water, based on 100% of the total mass of the degreasing agent for die-cast aluminum; The active ingredients include 9% organic weak acid, 1% chitosan oligosaccharide, 0.8% tea polyphenols, 1.2% curcumin, 4% surfactant, 0.6% methyl-β-cyclodextrin, 0.5% low-foaming agent, 1.5% sodium lactate, 1% corrosion inhibitor, and 0.4% lipase. The organic weak acid is a mixture of levulinic acid, lactic acid, and acetoacetic acid in a mass ratio of 1:1:1; the surfactant is a mixture of alkylphenol polyoxyethylene ether (OP-10) and betaine in a mass ratio of 2:1; the low-foaming agent is an organosilicon leveling agent; the corrosion inhibitor is a mixture of polycarboxylate and hydroxycarboxylate in a mass ratio of 1:1; the polycarboxylate is sodium polyacrylate, and the hydroxycarboxylate is sodium citrate.

[0058] The preparation method and degreasing method of the die-cast aluminum degreasing agent in this embodiment are the same as those in Example 1.

[0059] Comparative Example 1 (Traditional Formula) A degreasing agent for die-cast aluminum, comprising 9.0% sulfuric acid, 4% fatty alcohol polyoxyethylene ether (AEO-9), 1% EDTA chelating agent, 0.5% defoamer (conventional silicone oil, non-low-foaming optimized), 1.5% buffer (sodium phosphate), and the balance being deionized water, based on 100% of the total mass of the degreasing agent for die-cast aluminum.

[0060] The degreasing agent for die-cast aluminum in this comparative example is prepared by uniformly mixing all raw material components.

[0061] The degreasing method used in this comparative example is the same as in Example 1.

[0062] Comparative Example 2 The difference from Example 1 is that the content of the organic weak acid is adjusted from 9% to 5%, while the other conditions remain unchanged, and the missing amount is made up by deionized water; the preparation method and degreasing method of the die-cast aluminum degreasing agent are the same as in Example 1.

[0063] Comparative Example 3 The difference from Example 1 is that M-β-CD and chitosan oligosaccharide are missing, while the other conditions remain the same, and the missing amounts are made up by deionized water; the preparation method and degreasing method of the die-cast aluminum degreasing agent are the same as in Example 1.

[0064] Comparative Example 4 The difference from Example 1 is that ammonia water is added to adjust the pH to 2.5 during step S1 of preparing the die-cast aluminum degreasing agent; the pH of the degreasing tank solution in the degreasing method is 2.8.

[0065] Comparative Example 5 The difference from Example 1 is that the "soaking at 40°C for 5 minutes" in the degreasing method is changed to "soaking at 55°C for 12 minutes", while the other conditions are the same; the degreasing agent for die-cast aluminum and the preparation method are the same as in Example 1.

[0066] Comparative Example 6 The difference from Example 1 is that the organic weak acid is replaced with a single levulinic acid, while the other conditions remain the same; the preparation method and degreasing method of the die-cast aluminum degreasing agent are the same as in Example 1.

[0067] Comparative Example 7 The difference from Example 1 is that the corrosion inhibitor is replaced with a single polycarboxylate, while the other conditions remain the same; the preparation method and degreasing method of the die-cast aluminum degreasing agent are the same as in Example 1.

[0068] Comparative Example 8 The difference from Example 1 is that the corrosion inhibitor is replaced with a single hydroxycarboxylate, while the other conditions remain the same; the preparation method and degreasing method of the die-cast aluminum degreasing agent are the same as in Example 1.

[0069] Comparative Example 9 The difference from Example 1 is that chitosan oligosaccharide is missing, while the other conditions remain the same, and the missing amount is made up by deionized water; the preparation method and degreasing method of the die-cast aluminum degreasing agent are the same as in Example 1.

[0070] Comparative Example 10 The difference from Example 1 is that tea polyphenols are missing, while the other conditions remain the same, and the missing amount is made up by deionized water; the preparation method and degreasing method of the die-cast aluminum degreasing agent are the same as in Example 1.

[0071] Comparative Example 11 The difference from Example 1 is that lipase is missing, while the other conditions remain the same, and the missing amount is made up by deionized water; the preparation method of the die-cast aluminum degreasing agent and the degreasing method are the same as in Example 1.

[0072] Product performance testing 1. Oil removal rate evaluation method Objective: To evaluate the effectiveness of degreasing agents for die-cast aluminum in removing surface oil stains, specifically addressing issues of insufficient penetration and weak cleaning.

[0073] The testing steps are as follows: The surface of the AlSi10MnMg alloy sample was cleaned with alcohol, vacuum dried at 105°C until constant weight, and then weighed on an electronic balance to an accuracy of 0.0001 g. The mass was recorded as m0. A standard oil (such as silicone release agent) was uniformly coated onto the surface of the sample. After vacuum drying at 105°C until constant weight, the sample was weighed on an electronic balance to an accuracy of 0.0001 g. The mass was recorded as m1. The oil-coated samples were cleaned using the degreasing methods described in Examples 1-4 and Comparative Examples 1-11, vacuum dried at 105°C until constant weight, and then weighed on an electronic balance to an accuracy of 0.0001 g. The mass was recorded as m2. The degreasing rate was calculated.

[0074] Oil removal rate = [(m1 - m2) / (m1 - m0)] × 100%.

[0075] 2. Corrosion Rate Evaluation Method Objective: To evaluate the corrosion degree of die-cast aluminum degreasing agents on aluminum substrates, focusing on issues of high corrosion and over-corrosion.

[0076] The testing steps are as follows: The surface of the AlSi10MnMg alloy sample was cleaned with alcohol, dried under vacuum at 105°C until constant weight, and then weighed using an electronic balance to an accuracy of 0.0001 g. The mass was recorded as m0, and the surface area was calculated as A. Samples coated with oil were cleaned using the degreasing methods described in Examples 1-4 and Comparative Examples 1-11, dried under vacuum at 105°C until constant weight, and then weighed using an electronic balance to an accuracy of 0.0001 g. The mass was recorded as m1, and the corrosion rate was calculated.

[0077] Corrosion rate = (m0 - m1) / (A × t); unit is g / (m 2 (t is the soaking time in hours).

[0078] 3. Foaming Amount Evaluation Method Objective: To evaluate the foaming performance of degreasing agents, addressing issues of high foaming and inconvenient operation.

[0079] The testing steps are as follows: Take 100 mL of the degreasing bath liquid from Examples 1-4 and Comparative Examples 1-11 respectively, and place them in 250 mL stoppered graduated cylinders. Shake thoroughly by up and down shaking 30 times (about 15 s). Immediately after shaking, read the highest height of the foam layer (mm) and record it as the foaming amount. Repeat 3 times and take the average value.

[0080] 4. Test method for stability of bath solution Objective: To evaluate the physicochemical stability of the degreasing agent after the bath solution is prepared under actual use conditions, including changes in stratification, precipitation, turbidity and foaming, to ensure performance stability in continuous production or cyclic use.

[0081] The testing steps are as follows: Take 100 mL of the degreasing tank liquid from Examples 1-4 and Comparative Examples 1-11 respectively, place the degreasing tank liquid under constant temperature (25℃) conditions, stir gently for 1-2 minutes every day to simulate the cyclic use of the actual production line, and observe every day whether the degreasing tank liquid shows stratification, precipitation, turbidity, color change or abnormal foaming.

[0082] The test results are shown in Table 1.

[0083] Table 1

[0084] According to Table 1: 1) Regarding degreasing rate: The degreasing rates of Examples 1 (99.9%) and 2 (99.95%) were significantly higher than those of the comparative examples (94.5-98.6%), indicating that the degreasing agent for die-cast aluminum of the present invention has excellent degreasing function. The present invention uses an organic weak acid as a matrix to achieve mild acid dissolution and Al / Si chelation; through enzyme-acid synergistic action (lipase + weak acid), it rapidly decomposes the demolding agent, achieving a degreasing rate ≥99%; through oil stain embedding (M-β-CD) and microporous penetration (chitosan oligosaccharide), the coverage of porous substrates is increased by approximately 30% (for porous die-cast aluminum substrates, the grease residue in the pores can be observed and recorded by visual inspection or by drilling paper towels into the pores). Examples 3 and 4 use a single surfactant or low-foaming additive, and the degreasing rate still reaches over 99.0%, indicating that single use can achieve basic degreasing, but the overall performance is not as good as the compound system. Comparative Example 1 (traditional mineral acid) had the lowest oil removal rate due to the lack of bio-based synergistic effect; Comparative Example 2 had insufficient weak acid, resulting in decreased cleaning power; Comparative Example 3 (lacking penetrant / embedding agent) had decreased penetration and emulsification, leading to a lower oil removal rate; Comparative Examples 4 and 5 (pH or soaking temperature / time not within the range required by this invention) resulted in insufficient acid release or reduced enzyme activity, leading to a lower oil removal rate; Comparative Examples 6-11 all had a significantly lower oil removal rate due to the lack of a certain raw material component.

[0085] 2) Corrosion rate: Example 1 (0.012 g / (m) 2 ·h)) and Example 2 (0.015g / (m 2 The concentration of ·h) was significantly lower than that of control example 1 (0.22 g / (m)). 2 The study demonstrated that the synergistic protection of bisphenol passivation (tea polyphenols + curcumin) and corrosion inhibitors effectively solved the problems of high corrosion and over-corrosion. Comparative Example 1 (sulfuric acid) showed the highest corrosion rate due to a lack of passivation protection; Comparative Example 4 (high pH) showed insufficient release of weak acid, weakening the bisphenol passivation effect and increasing the corrosion rate; Comparative Example 5 (excessively high soaking temperature) showed decreased enzyme activity, leading to over-corrosion, resulting in a high degreasing rate but also an increased corrosion rate; Comparative Example 6 (monoacetylpropionic acid) showed a relatively high corrosion rate, with both penetration and passivation decreasing.

[0086] 3) Foaming amount: The foaming amount of Examples 1-4 (6-14mm) was significantly lower than that of Comparative Example 1 (20mm), indicating that the degreasing agent for die-cast aluminum of the present invention can effectively control foam stability through the synergistic effect of low-foaming additive and surfactant. Examples 3 and 4 used only a single surfactant or low-foaming additive, and the foaming amount was increased compared with the composite system.

[0087] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A degreasing agent for die-cast aluminum, characterized in that, The die-cast aluminum degreasing agent comprises active ingredients and water; based on the total mass of the die-cast aluminum degreasing agent as 100%, the active ingredients comprise 6-10% organic weak acids, 0.5-1.5% chitosan oligosaccharides, 0.5-1.2% tea polyphenols, 0.7-1.8% curcumin, 4-6% surfactants, 0.4-1.0% cyclodextrin, 0.5-0.8% low-foaming agent, 1.0-2.0% buffer, 0.6-1.5% corrosion inhibitor, and 0.2-0.5% lipase; the organic weak acids comprise levulinic acid, lactic acid, and acetoacetic acid; the corrosion inhibitor comprises polycarboxylates and hydroxycarboxylates.

2. The degreasing agent for die-cast aluminum according to claim 1, characterized in that, The active ingredient accounts for 18-25% of the mass percentage of the die-cast aluminum degreasing agent.

3. The degreasing agent for die-cast aluminum according to claim 1, characterized in that, The surfactants include alkylphenol polyoxyethylene ethers and / or betaine.

4. The degreasing agent for die-cast aluminum according to claim 1, characterized in that, The low-foaming additives include silicone leveling agents and / or quaternary ammonium salt antistatic agents.

5. The degreasing agent for die-cast aluminum according to claim 1, characterized in that, The buffer includes sodium lactate.

6. A method for preparing a degreasing agent for die-cast aluminum as described in any one of claims 1-5, characterized in that, Includes the following steps: The organic weak acid, buffer, and water are mixed to obtain mixture A; Mix the aforementioned mixture A, tea polyphenols, curcumin, and cyclodextrin, and carry out an inclusion reaction to obtain mixture B; The mixture B, surfactant, chitosan oligosaccharide, corrosion inhibitor, low-foaming agent and lipase are mixed, ultrasonically dispersed, aged and filtered to obtain the die-cast aluminum degreasing agent.

7. The preparation method according to claim 6, characterized in that, The inclusion reaction is carried out at a temperature of 40-60°C; and / or the inclusion reaction is carried out for a time of 40-60 min.

8. The preparation method according to claim 6, characterized in that, The aging time is 30-40 hours.

9. A method for degreasing die-cast aluminum alloys, characterized in that, This includes degreasing die-cast aluminum alloys using the die-cast aluminum degreasing agent described in any one of claims 1-5.

10. The application of a degreasing agent for die-cast aluminum as described in any one of claims 1-5 in the surface treatment of die-cast aluminum alloys.

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