Alkaline cleaning agent, preparation method of alkaline cleaning agent and die-casting aluminum surface treatment process

Abstract

The invention relates to an alkaline cleaning agent, a preparation method of the alkaline cleaning agent and a die-casting aluminum surface treatment process. The alkaline cleaning agent comprises 5-12% of a nonionic surfactant; 3%-8% of an anionic surfactant; 10%-20% of an inorganic alkali agent; 0.5%-2% of a corrosion inhibitor; 1%-5% of nano silica sol; 0.5%-3% of a silane coupling agent; decontamination, surface activation and corrosion inhibition are synchronously completed in a single cleaning step, a traditional multi-step process (cleaning, acid pickling and passivation) is replaced, and one-step multiple functions are achieved. The rough surface formed by the nano silica sol increases the mechanical meshing force of the coating and the matrix, and mechanical interlocking is achieved; functional groups (such as epoxy groups of KH560) of the silane coupling agent react with the coating resin to form a covalent bond network, so that chemical bonding is realized, and the adhesive force is integrally improved; in addition, a phosphorus-free and heavy metal-free formula reduces the environmental load, and a passivation film (cerous nitrate / phytic acid) and the corrosion inhibitor synergistically prolong the salt mist resistance time to be more than or equal to 120 hours, so that environmental protection and durability are realized.

Description

Technical Field

[0001] This application relates to the technical field of metal surface treatment, and particularly to an alkaline cleaning agent, a preparation method of the alkaline cleaning agent, and a surface treatment process for die-cast aluminum. Background Art

[0002] Traditional alkaline cleaning agents (such as CN113293033A) mainly contain sodium hydroxide and sodium carbonate. Although they can remove dirt, they are prone to corrode the substrate and cannot improve the surface roughness, resulting in insufficient coating adhesion (usually lower than 10 MPa). Summary of the Invention

[0003] In view of this, this application provides an alkaline cleaning agent that can improve the adhesion of die-cast aluminum. The alkaline cleaning agent includes, by mass percentage: Non-ionic surfactant 5% - 12%; Anionic surfactant 3% - 8%; Inorganic base agent 10% - 20%; Corrosion inhibitor 0.5% - 2%; Nanosilica sol 1% - 5%; Silane coupling agent 0.5% - 3%; Deionized water for the balance.

[0004] In one embodiment, the mass ratio of the non-ionic surfactant to the anionic surfactant is (2:1) - (3:1), and the total content of the two accounts for 8% - 18% of the mass of the cleaning agent.

[0005] In one embodiment, the particle size of the nanosilica sol is 10 - 50 nm, and the surface is modified by hydroxylation.

[0006] In one embodiment, the silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0007] In one embodiment, the hydroxylation modification is achieved by in-situ grafting of the silane coupling agent, and the Zeta potential of the sol is -30~-50 mV.

[0008] In one embodiment, the silane coupling agent further includes fluorosilane, and the addition amount of the fluorosilane is 5% - 15% of the total mass of the silane coupling agent.

[0009] In addition, a preparation method of the alkaline cleaning agent is also provided. The alkaline cleaning agent uses the above-mentioned alkaline cleaning agent, and the preparation method includes: Step S1, heating the deionized water to 40~50 °C, and sequentially adding the inorganic base agent and the corrosion inhibitor, and stirring to dissolve; Step S2: Cool down to below 30°C, add non-ionic surfactant and anionic surfactant, and stir until homogeneous. Step S3: Add nano-silica sol and silane coupling agent, and ultrasonically disperse for 20 - 40 minutes. Step S4: Adjust the pH to 10.5 - 12.5, and obtain the finished product after filtration.

[0010] In addition, a surface treatment process for die-cast aluminum is also provided. Applying the above alkaline cleaning agent, the surface treatment process for die-cast aluminum includes the following steps: (1) Immerse the die-cast aluminum workpiece in the cleaning agent and treat at 50 - 60°C for 5 - 15 minutes. (2) Use ultrasonic wave for auxiliary cleaning, with a frequency of 28 - 40 kHz. (3) After water washing, immerse it in a passivation solution containing 0.05% - 0.3% cerium nitrate and 0.5% - 2% phytic acid for 15 minutes. (4) Dry it to form an activated surface with both micro-rough structure and passivation film.

[0011] In one embodiment, in step (2), pulsed ultrasonic wave is used, with a duty cycle of 30% - 50% and a power density of 0.8 - 2.0 W / cm³.

[0012] In addition, an intelligent cleaning system is also provided. Using the above alkaline cleaning agent, the intelligent cleaning system includes a multi-stage circulation filtration module, a pH / temperature automatic control unit, and an ultrasonic generating device. The circulation filtration module includes an activated carbon adsorption layer and a ceramic membrane.

[0013] For the above alkaline cleaning agent, the non-ionic surfactant is 5% - 12%; the anionic surfactant is 3% - 8%; the inorganic base agent is 10% - 20%; the corrosion inhibitor is 0.5% - 2%; the nano-silica sol is 1% - 5%; the silane coupling agent is 0.5% - 3%; the balance is deionized water. It synchronously completes decontamination, surface activation, and corrosion inhibition in a single cleaning step, replacing the traditional multi-step process (cleaning → pickling → passivation), achieving one-step multi-function; the rough surface formed by nano-silica sol increases the mechanical bite force between the coating and the substrate, realizing mechanical interlock; the functional groups of the silane coupling agent (such as the epoxy group of KH560) react with the coating resin to form a covalent bond network, realizing chemical bonding, and overall improving the adhesion; in addition, the phosphorus-free and heavy-metal-free formula reduces the environmental load, and the passivation film (cerium nitrate / phytic acid) and the corrosion inhibitor synergistically extend the salt spray resistance time to ≥120 h, achieving environmental protection and durability. Description of the Drawings

[0014] Figure 1 It is a schematic diagram of the steps of a preparation method of an alkaline cleaning agent provided in an embodiment of the present application.

[0015] The realization, functional features and advantages of the present application will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed Embodiments

[0016] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals indicate the same or similar elements or elements with the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and should not be construed as a limitation to the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts belong to the scope of protection of the present application.

[0017] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation to the scope of the present application: Therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and the individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc. and the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range, which will not be elaborated further.

[0018] The present application provides an alkaline cleaning agent that can improve the adhesion of die-cast aluminum. The alkaline cleaning agent includes, by mass percentage: 5% - 12% of a non-ionic surfactant; 3% - 8% of an anionic surfactant; 10% - 20% of an inorganic base agent; 0.5% - 2% of a corrosion inhibitor; 1% - 5% of nano-silica sol; 0.5% - 3% of a silane coupling agent; and the balance of deionized water.

[0019] In this embodiment, the non-ionic surfactant is selected from at least one of fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether, the anionic surfactant is at least one of sodium dodecylbenzenesulfonate and fatty alcohol polyoxyethylene ether sulfate, the inorganic base agent is a compound selected from sodium hydroxide, sodium carbonate, and sodium silicate, and the corrosion inhibitor is a mixture selected from sodium molybdate and benzotriazole.

[0020] In this embodiment, a non-ionic surfactant (such as fatty alcohol polyoxyethylene ether) combines with polar groups in the oil stain through the ether bond in the molecule, reducing the oil-water interfacial tension and emulsifying the grease; an anionic surfactant (such as sodium dodecylbenzenesulfonate) adsorbs on the surface of the stain through the anionic group, enhancing the stripping ability, especially effective for silicone oil residues in the release agent; the synergistic decontamination of non-ionic surfactant (5% - 12%) and anionic surfactant (3% - 8%): the non-ionic surfactant provides a mild emulsifying effect, avoiding substrate corrosion (such as pitting corrosion of aluminum) caused by excessive anionic components. The two are compounded to form mixed micelles, synchronously removing polar (oil stain) and non-polar (dust) pollutants, and the removal rate of the release agent is ≥99.5% (detected by FTIR).

[0021] In one embodiment, the inorganic base agent includes sodium hydroxide and sodium silicate. Sodium hydroxide provides a strong alkaline environment (pH 10.5 - 12.5), saponifies the grease and dissolves the natural oxide layer on the aluminum surface (Al 2 O 3 ), and sodium silicate hydrolyzes under alkaline conditions to generate silicic acid colloid, which adsorbs on the aluminum surface to form a protective film, inhibiting the excessive corrosion of the base agent on the substrate. The two constitute the inorganic base agent, rapidly decontaminating through sodium hydroxide and delaying alkaline corrosion through sodium silicate, so that the corrosion rate of aluminum is ≤0.5 g / m²·h (GB / T 18593), and a dynamic pH balance can be achieved.

[0022] In one embodiment, the corrosion inhibitor includes sodium molybdate and benzotriazole (BTA). Sodium molybdate forms a MoO 4 ² - passivation film on the aluminum surface, blocking the corrosion electrochemical reaction. Benzotriazole (BTA) adsorbs on the active sites of the aluminum surface, inhibiting local corrosion (such as intergranular corrosion). Sodium molybdate covers the macroscopic surface, and BTA fills the microscopic defects, so that the corrosion inhibition efficiency is ≥95% (tested by electrochemical impedance spectroscopy).

[0023] In this embodiment, deionized water (conductivity ≤5 μS / cm) avoids the interference of impurity ions with the activities of the corrosion inhibitor and the silane coupling agent.

[0024] In this embodiment, the nano-silica sol provides physical roughness, and the silane coupling agent establishes chemical bonding sites, increasing the coating adhesion to 18 - 22 MPa (ASTM D4541). ASTM D4541 is a test standard. The silane coupling agent can be grafted onto the surface of the nano-silica sol, enhancing its dispersion stability in the solution. Through the synergistic effect of the nano-silica sol and the silane coupling agent, a micro-nano rough surface is formed during the cleaning process, improving the subsequent coating adhesion, and the compounded corrosion inhibitor avoids substrate corrosion.

[0025] In this embodiment, decontamination, surface activation, and corrosion inhibition are synchronously completed in a single cleaning step, replacing the traditional multi-step process (cleaning → pickling → passivation), achieving multi-functionality in one step; the rough surface formed by nano-silica sol increases the mechanical bite force between the coating and the substrate, realizing mechanical interlocking; the functional groups of the silane coupling agent (such as the epoxy group of KH560) react with the coating resin to form a covalent bond network, realizing chemical bonding, and overall improving the adhesion; in addition, the phosphorus-free and heavy-metal-free formula reduces the environmental load, and the passivation film (cerium nitrate / phytic acid) and the corrosion inhibitor synergistically extend the salt spray resistance time to ≥120h, achieving environmental protection and durability.

[0026] In one embodiment, the cross-cut method (ASTM D3359) shows that the coating has no peeling, and the adhesion reaches 20.3 MPa. After SEM (scanning electron microscope) analysis, the surface after cleaning presents a uniform micro-nano structure. After electrochemical testing, the corrosion inhibition efficiency is 95.2%, and the corrosion current density decreases from 1.2×10 -4 A / cm² to 5.6×10 -6 A / cm².

[0027] The above alkaline cleaning agent solves the composite technical problems of cleaning-activation-anti-corrosion of die-cast aluminum, and has outstanding creativity and industrial practicability.

[0028] In one embodiment, "decontamination-activation" integration is achieved through nano-silica sol + silane coupling agent, reducing the process time by 30%, realizing component synergistic innovation; the non-toxic design of the corrosion inhibitor and the passivation solution reduces the COD emission by more than 60% (compared with the chromating process), achieving an environmental protection breakthrough.

[0029] The following are specific examples for experiments respectively.

[0030] Example 1 (basic formula) The components of the alkaline cleaning agent are as follows: Non-ionic surfactant (alkylphenol polyoxyethylene ether) 8%; Anionic surfactant (sodium lauryl polyoxyethylene ether sulfate) 5%; Inorganic base agent (sodium hydroxide 12% + sodium silicate 4%) 16%; Corrosion inhibitor (sodium molybdate 0.8% + benzotriazole 0.4%) 1.2%; Nano-silica sol (hydroxylated, particle size 20 nm) 3%; Silane coupling agent (KH550) 1.5%; Deionized water balance.

[0031] In this example, adhesion: 18.5 MPa (ASTM D4541); salt spray test: no corrosion after 120 h (GB / T 10125); release agent residue rate: 0.3% (detected by FTIR).

[0032] Example 2 Change the mass percentage of the non-ionic surfactant in Example 1 to 5%, and correspondingly adjust the proportion of deionized water. The proportions of the remaining components remain unchanged. In this example, adhesion: 17.2 MPa (slight decrease in detergency), release agent residue rate: 0.5%.

[0033] Example 3 Change the mass percentage of the non-ionic surfactant in Example 1 to 12%, and correspondingly adjust the proportion of deionized water. The proportions of the remaining components remain unchanged. In this example, adhesion: 19.0 MPa, the amount of foam increases, and 0.1% defoamer needs to be added.

[0034] Example 4 Change the mass percentage of the anionic surfactant in Example 1 to 3%, and correspondingly adjust the proportion of deionized water. The proportions of the remaining components remain unchanged. In this example, release agent residue rate: 0.8% (weak removal of silicone oil type), adhesion: 16.8 MPa.

[0035] Example 5 Change the mass percentage of the anionic surfactant in Example 1 to 8%, and correspondingly adjust the proportion of deionized water. The proportions of the remaining components remain unchanged. In this example, release agent residue rate: 0.2%; substrate corrosion rate: 0.5 g / m²·h (corrosion inhibitor needs to be optimized).

[0036] Example 6 Compound and optimize the inorganic base agent in Example 1, change it to sodium hydroxide:sodium silicate = 1:2 (sodium hydroxide 6% + sodium silicate 12%), and the proportions of the remaining components remain unchanged. In this example, the corrosion inhibition property is improved, corrosion rate: 0.2 g / m²·h; pH stability: 12.0 ± 0.3.

[0037] Example 7 Adjust the proportion of nano-silica sol in Example 1 to 5%, and correspondingly adjust the proportion of deionized water. The proportions of the remaining components remain unchanged. In this example, adhesion: 20.1 MPa (Ra = 1.5 μm); dispersion stability: the ultrasonic power needs to be increased to 1.2 W / cm³.

[0038] Example 8 Adjust the proportion of silane coupling agent in Example 1 to 3% (KH560), and correspondingly adjust the proportion of deionized water. The proportions of the remaining components remain unchanged. In this example, adhesion: 21.3 MPa; salt spray resistance: 180 h.

[0039] Comparative Example 1 The proportion of nano-silica sol in Example 1 was adjusted to 0%, and deionized water was added to make up the difference, while the proportions of other components remained unchanged. In this example, the adhesion force was 10.5 MPa (a 43% decrease); the surface roughness Ra = 0.3 μm (no activation layer).

[0040] Comparative Example 2 The proportion of silane coupling agent in Example 1 was adjusted to 0%, and deionized water was added to make up the difference. In this example, the adhesion force was 9.8 MPa (lack of chemical bonding); the salt spray resistance was 48 h (no passivation layer was formed).

[0041] Comparative Example 3 The proportion of non-ionic surfactant in Example 1 was adjusted to 15%, and the proportion of deionized water was adjusted accordingly, while the other components remained unchanged. In this example, there was too much foam (a 300% volume expansion), and it was necessary to stop the machine to defoam; the residual rate of the release agent was 1.2% (the emulsification efficiency decreased).

[0042] Comparative Example 4 The proportion of anionic surfactant in Example 1 was adjusted to 10%, and the proportion of deionized water was adjusted accordingly, while the proportions of other components remained unchanged. In this example, the corrosion rate of the substrate was 1.2 g / m²·h (4 times the standard); the corrosion inhibitor failed (pH > 13).

[0043] Comparative Example 5 The proportion of inorganic base agent in Example 1 was adjusted to 8% (4% sodium hydroxide + 4% sodium silicate), and the proportion of deionized water was adjusted accordingly, while the proportions of other components remained unchanged. In this example, the residual rate of the release agent was 2.5% (the saponification reaction was incomplete); pH = 9.8 (the oxide layer could not be dissolved).

[0044] Comparative Example 6 The proportion of corrosion inhibitor in Example 1 was adjusted to 0.3% (0.2% sodium molybdate + 0.1% benzotriazole), and the proportion of deionized water was adjusted accordingly, while the proportions of other components remained unchanged. In this example, the corrosion rate was 1.0 g / m²·h; pitting corrosion occurred after 24 h in the salt spray test.

[0045] Comparative Example 7 The nano-silica sol in Example 1 was adjusted to 3% of unhydroxylated nano-silica sol, and the proportion of deionized water was adjusted accordingly, while the proportions of other components remained unchanged. In this example, the dispersion stability was such that the precipitation rate was > 50% after 24 h; the adhesion force was 12.0 MPa (particle agglomeration).

[0046] Comparative Example 8 In Example 1, the silane coupling agent was adjusted to 1.5% of KH570 (containing methacryloxy), and the proportion of deionized water was correspondingly adjusted, while the proportions of the remaining components remained unchanged. In this example, the adhesion force was 13.5 MPa (UV curing was required, and the process was not compatible); the coating peeling rate was 15%.

[0047] In one embodiment, the mass ratio of the non-ionic surfactant to the anionic surfactant is (2:1) to (3:1), and the total content of the two accounts for 8% to 18% of the mass of the cleaning agent.

[0048] In this example, the non-ionic surfactant (such as fatty alcohol polyoxyethylene ether) binds to the polar group of the oil stain through an ether bond, reducing the oil-water interfacial tension; the anionic surfactant (such as sodium dodecylbenzenesulfonate) strips the stain through electrostatic repulsion. When the mass ratio is (2:1 to 3:1), the two form mixed micelles with smaller micelle sizes (about 10 to 20 nm), which simultaneously solubilize polar (grease) and non-polar (silicone oil release agent) pollutants. The removal rate of the release agent is increased from 95% of the traditional formula to ≥99.5% (detected by FTIR), achieving the effect of the micelle synergistic effect; at this ratio, the CMC value is reduced by about 30% (measured from 0.05 g / L to 0.035 g / L), enhancing the decontamination efficiency at low concentrations, reducing the total amount of surfactant used (8% to 18%), reducing costs, and optimizing the critical micelle concentration (CMC).

[0049] In this example, the non-ionic surfactant is preferentially adsorbed on the aluminum surface to form a protective film, inhibiting the corrosion of the substrate by the anionic surfactant (such as pitting corrosion and intergranular corrosion). When the mass ratio > 3:1, the non-ionic surfactant is excessive, resulting in a decrease in detergency; when the mass ratio < 2:1, the anionic component is excessive, and the corrosion rate increases from 0.3 g / m²·h to 1.2 g / m²·h (GB / T18593).

[0050] In addition, within the proportion range of this example, the surfactant compounding increases the corrosion inhibition efficiency of the corrosion inhibitor (sodium molybdate / benzotriazole) from 85% to ≥95% (electrochemical impedance test), achieving the technical effect of corrosion inhibition synergy.

[0051] In this example, the mass ratio of the non-ionic surfactant to the anionic surfactant is (2:1) to (3:1), so that the hydrophilic chain (polyoxyethylene group) of the non-ionic surfactant wraps the hydrophobic tail chain of the anionic surfactant, enhancing the stability of the micelles in an alkaline environment and avoiding precipitation or stratification at high temperatures (50 to 60 °C). Within this proportion range, the surfactant compounding forms a stable micelle network, assisting the uniform dispersion of nano-silica sol (Zeta potential -30 to -50 mV) and preventing agglomeration and precipitation.

[0052] In this embodiment, when the proportion of non-ionic surfactant is > 3:1, there is too much foam, and an additional defoaming agent needs to be added; when the proportion of anionic surfactant is too high, there is insufficient foam, which affects the ultrasonic cavitation effect. The ratio (2:1~3:1) balances the amount of foam, increasing the cavitation efficiency of ultrasonic cleaning (28~40kHz) by 20%, and the cleaning coverage rate in the blind hole area increases from 80% to ≥98% (observed by SEM).

[0053] In one embodiment, a detergency comparison was carried out: Example (ratio 2.5:1): the residual amount of release agent was 0.2% (detected by FTIR); Control Group 1 (ratio 1:1): the residual amount was 1.5%, and slight corrosion of the substrate occurred; Control Group 2 (ratio 4:1): the residual amount was 2.8%, and excessive foam led to uneven cleaning.

[0054] In another embodiment, when the ratio is 2:1~3:1, the corrosion rate of aluminum is 0.3g / m²·h, and when the ratio is 1:1, the corrosion rate is 1.0g / m²·h (exceeding the standard by 3 times).

[0055] The technical solution of this embodiment, within a specific mass ratio range (2:1~3:1), significantly improves the comprehensive performance (detergency, anti-corrosion, process compatibility) of the cleaning agent by optimizing the micelle synergistic effect, dynamic adsorption film formation, and solution stability. In traditional cleaning agents, if the content of anionic surfactant is increased, the detergency can be enhanced, but the corrosion of the substrate is aggravated; if the content of non-ionic surfactant is increased, the corrosion is reduced, but the detergency is insufficient. The technical solution of this embodiment balances the contradiction between the two, achieving the dual goals of high-efficiency detergency and substrate protection.

[0056] In one embodiment, the particle size of the nano-silica sol is 10~50nm, and the surface is modified by hydroxylation.

[0057] In this embodiment, nano-particles with a particle size of 1050nm can be evenly adsorbed on the aluminum surface, forming a micro-nano composite rough structure (Ra 0.5~1.2μm, observed by SEM), increasing the contact area between the coating and the substrate, and the mechanical anchoring effect increases the adhesion by more than 40% (traditional process: 1012MPa → this invention: 1822MPa), constructing a micro-nano rough surface Among them, when the particle size < 10nm: the particles are prone to agglomerate into micron-sized aggregates, and the roughness is insufficient (Ra≤0.2μm); when the particle size > 50nm: the particle sedimentation rate accelerates, and the dispersion is uneven, resulting in a local adhesion difference > 20%.

[0058] Among them, small-sized nano-particles (10~50nm) can penetrate into the microporous structure of die-cast aluminum (pore diameter about 520μm), completely removing the residual release agent, and the detergency rate in the blind hole area increases from 80% to ≥99% (detected by fluorescence tracer), enhancing the pore penetration ability.

[0059] In this embodiment, hydroxylation modification makes the surface of nano-silica sol rich in active hydroxyl groups, achieving the following functions: (a) enhancing dispersion stability: the hydrogen bond interaction between hydroxyl groups and water increases the Zeta potential of the sol to "-30~-50 mV" (dynamic light scattering test), avoiding particle aggregation (the Zeta potential of the unmodified sol is only -10 mV, and the precipitation rate is >50% within 30 minutes); (b) promoting chemical bonding: the hydroxyl groups and the silanol groups (-Si-OH) generated by the hydrolysis of silane coupling agents (such as KH550) undergo dehydration condensation to form stable Si-O-Si covalent bonds, strengthening the binding force between nano-particles and the matrix (XPS detection shows that the content of Si-O bonds increases by 60%).

[0060] In this embodiment, the hydroxylated nano-silica sol binds to the natural oxide layer (Al 2 O 3 ) on the aluminum surface through Al-O-Si bonds, forming a firm roughened interface, and increasing the peel strength in the coating adhesion test (ASTM D4541) from 12 MPa to 20.3 MPa.

[0061] In this embodiment, the nano-particles with small particle sizes (10~50 nm) have a large specific surface area (80~200 m² / g), providing sufficient active sites for hydroxyl modification, and the hydroxyl density on the surface per square nanometer is ≥5 (determined by titration method), ensuring sufficient reaction with silane coupling agents; in addition, the stability of the hydroxylated nano-silica sol is enhanced in alkaline cleaning agents, and the bath life is extended from 7 days to 30 days (no obvious change in particle size monitored by a laser particle size analyzer), improving the durability.

[0062] In one embodiment, adhesion comparison is carried out (with other conditions being the same): Example (hydroxylated 50 nm silica sol): 20.3 MPa; Control Group 1 (unmodified 50 nm silica sol): 14.2 MPa; Control Group 2 (hydroxylated 100 nm silica sol): 12.5 MPa.

[0063] In one embodiment, dispersion stability comparison is carried out (with other conditions being the same): for the hydroxylated nano-silica sol, the precipitation rate within 30 days is <5%; for the unmodified silica sol, the precipitation rate within 24 hours is >30%.

[0064] In one embodiment, surface morphology analysis is carried out (with other conditions being the same): SEM shows that the hydroxylated nano-particles are evenly distributed, and the roughness Ra = 1.0 μm; in the unmodified group, the particles agglomerate into micron-sized island-like structures, and Ra = 0.3 μm.

[0065] Obviously, in this embodiment, through the collaborative design of particle size control and surface chemical modification, the problems of easy agglomeration of nanomaterials and insufficient interfacial bonding force in traditional cleaning agents are solved, achieving the following core advantages: high adhesion: micro-nano rough surface + chemical bonding, the adhesion is increased by more than 40%; long-term stability: hydroxylation modification inhibits the sedimentation of nanoparticles, and the bath life is extended by 4 times; process compatibility: it is compatible with subsequent processes such as ultrasonic cleaning and passivation, and the yield rate ≥ 98%.

[0066] In one embodiment, the silane coupling agent is γ-aminopropyltriethoxysilane (KH550) or γ-glycidoxypropyltrimethoxysilane (KH560).

[0067] When KH550 is used, the amino group (-NH 2 ) binds to the hydroxyl group (-Al-OH) on the surface of the aluminum substrate through hydrogen bonds and coordination bonds to form a stable interface. The amino group can also react with the carboxyl group (-COOH) or isocyanate group (-NCO) in subsequent coatings (such as epoxy resin and polyurethane) to form a covalent bond network, and the adhesion is increased to 18 - 22 MPa (ASTM D4541).

[0068] When KH560 is used, the epoxy group opens the ring under alkaline conditions and forms an Al-O-Si covalent bond with the hydroxyl group on the aluminum surface; the epoxy group reacts with the amino group or hydroxyl group in the coating (such as electrophoretic paint and acrylic resin) to construct a chemical bridging layer, and the salt spray resistance time is extended from 72 h to ≥ 120 h (GB / T 10125).

[0069] Furthermore, the hydrolysis products (silanols) of KH550 / KH560 condense with the hydroxyl groups (-OH) on the surface of the nano-silica sol to form Si-O-Si bonds, enhancing the dispersion stability of the nanoparticles in the cleaning agent.

[0070] In this embodiment, the nano-silica sol provides physical anchoring points (micro-nano rough surface), and the silane coupling agent establishes chemical bonding sites. The dual action reduces the standard deviation of the coating adhesion from ±3.5 MPa to ±0.8 MPa (statistics of 30 groups of specimens), achieving the technical effect of synergistic enhancement of roughness-chemical bond.

[0071] Compared with the prior art (such as CN114606191A) that uses the silane coupling agent for post-treatment passivation, the present invention integrates it into the cleaning agent to complete "cleaning-activation-bonding" in one step, reducing 2 processes.

[0072] In one embodiment, adhesion tests were conducted: the adhesion of the die-cast aluminum coating treated with KH560 reached 22.1 MPa, an increase of 77% compared to the group without silane addition (12.5 MPa); chemical resistance: the coating treated with KH550 was immersed in 5% NaCl solution for 240 h, and the adhesion retention rate was ≥95% (≤70% for the control group).

[0073] In this embodiment, through the functional group design of specific silane coupling agents (KH550 / KH560), the following core advantages are achieved: high-strength chemical bonding: directionally matching the chemical properties of the coating and the substrate, the adhesion is increased by 40% - 77%; process compatibility: suitable for various subsequent processes such as electrophoresis, spraying, anodic oxidation, etc., without additional treatment; long-term corrosion resistance: the chemical bridging layer blocks the penetration of corrosive media, and the salt spray test is ≥120 h.

[0074] In other words, through precise functional group selection and synergistic effect design, the problems of poor activation effect of traditional cleaning agents and easy peeling of the coating are solved.

[0075] In one embodiment, the hydroxylation modification is achieved by in-situ grafting of silane coupling agents, and the Zeta potential of the sol is -30 to -50 mV.

[0076] In one embodiment, through one-step modification, during the preparation of the cleaning agent, the silane coupling agent (such as KH550 / KH560) directly hydrolyzes to form silanol (-Si-OH), which undergoes an in-situ condensation reaction with the hydroxyl groups (-OH) on the surface of the nano-silica sol to form stable Si-O-Si covalent bonds, reducing 2 pretreatment steps, shortening the preparation time by 40% (from 120 minutes → 70 minutes), and simplifying the process; no additional purchase of modifiers is required, reducing the raw material cost by 15% and lowering the cost; in-situ grafting enables the molecular chains of the silane coupling agent to closely coat the nanoparticles, forming a core-shell structure (observed by TEM), enhancing the binding force between the particles and the aluminum substrate (XPS shows that the content of Al-O-Si bonds increases by 60%), and the adhesion increases from 14.2 MPa to 20.3 MPa (ASTM D4541).

[0077] In this embodiment, the higher the absolute value of the Zeta potential (>30 mV), the stronger the electrostatic repulsion force between the nanoparticles, inhibiting agglomeration. When the potential < -30 mV: the particles are prone to agglomeration, and the precipitation rate within 30 days > 20%; when the potential > -50 mV: excessive dispersion may lead to the exposure of active sites, accelerating the hydrolysis failure of silane.

[0078] In this embodiment, the silane coupling agent forms chemical bonds through in-situ grafting. At the same time, Zeta potential regulation ensures the uniform adsorption of nanoparticles on the aluminum surface, forming a dense micro-nano rough layer (SEM shows Ra = 1.0 μm), reducing the standard deviation of the coating adhesion from ±3.5 MPa to ±0.8 MPa (statistics of 30 groups of specimens).

[0079] In one embodiment, particles with a Zeta potential of -30 to -50 mV remain stable in an alkaline environment, and the bath life is extended from 7 days to 30 days (the decline rate of the cleaning agent activity < 5%), enabling long-term stability to be maintained.

[0080] In one embodiment, a dispersion stability test is carried out: in-situ grafting + Zeta potential -40 mV: the precipitation rate in 30 days < 3%; unmodified silica sol: the precipitation rate in 24 hours > 50%; a bonding strength test is carried out: in-situ grafting group: the content ratio of Al-O-Si bonds is 25% (XPS analysis); pre-treatment modification group: the bond content is only 15%, and the process time-consuming is doubled; an adhesion contrast test is carried out: in-situ grafting + potential -40 mV: 20.3 MPa; traditional pre-treatment modification: 17.8 MPa; unmodified silica sol: 12.5 MPa.

[0081] In one embodiment, through the collaborative design of in-situ grafting modification and Zeta potential regulation, the following core advantages are achieved: process high-efficiency: the modification of nanomaterials is completed by a one-step method, reducing both cost and time; Zeta potential control inhibits agglomeration, and the bath life is extended by 4 times, achieving the effect of dispersion stability; the dual effects of chemical bonding + physical anchoring enhance the adhesion by 60%, strengthening the interface.

[0082] In this embodiment, in-situ grafting is completed synchronously with the preparation of the cleaning agent, realizing process integration; precise control of the Zeta potential ensures the balance between dispersibility and activity, and the residual rate of the release agent ≤ 0.2% (FTIR detection), optimizing the performance; through innovative in-situ modification and dispersion control, the problems of complex traditional nanomaterial modification processes and unstable performance are solved.

[0083] In one embodiment, the silane coupling agent further includes fluorosilane, and the addition amount of fluorosilane is 5% - 15% of the total mass of the silane coupling agent.

[0084] In this embodiment, by introducing the low surface energy characteristics and chemical inertness of fluorine elements, the surface wettability, corrosion resistance, and coating bonding strength of the cleaning agent are significantly improved.

[0085] In one embodiment, the fluorocarbon chain (-CF 2 -CF 3 ) of the fluorosilane forms a superhydrophobic transition layer on the aluminum surface (the contact angle drops from 25° to ≤ 10°), promoting the uniform spreading of subsequent coatings (such as electrophoretic paint, powder coating), reducing wetting defects (such as pinholes, fisheyes), and the coating coverage rate is increased from 90% to ≥ 99% (observed by optical microscope), achieving the technical effect of the low surface energy effect.

[0086] In one embodiment, the silanol group (-Si-OH) of the fluorosilane reacts with the functional groups of the aluminum matrix and KH550 / KH560 to form a fluorine-silicon-aluminum composite interface, and the adhesion force increases from 18 MPa to 22.1 MPa (ASTM D4541). At the same time, the fluorocarbon chains are arranged outward, enhancing the intermolecular forces (van der Waals forces and dipole interactions) between the coating and the matrix, achieving the synergistic effect of chemical bonding.

[0087] In one embodiment, the strong hydrophobicity and chemical inertness of the fluorocarbon chains block the penetration of water molecules and corrosive media (Cl - 、SO 4 ² - ), the salt spray test time is extended from 120 h to ≥200 h (GB / T 10125), and the corrosion current density is reduced to 2.1×10 -6 A / cm² (electrochemical test), achieving the technical effect of the barrier effect.

[0088] In one embodiment, the C-F bond energy of the fluorosilane is high (485 kJ / mol), which resists ultraviolet degradation. After 500 h of QUV aging test (ASTM G154), the adhesion retention rate of the coating is ≥95% (the control group KH550 is only 80%), showing ultraviolet stability.

[0089] In one embodiment, when the addition amount <5%: the coverage rate of the fluorocarbon chains is insufficient, and the improvement of hydrophobicity and corrosion resistance is limited (the contact angle only drops to 15°, and the salt spray test is ≤150 h); when the addition amount >15%: the fluorosilane molecules agglomerate, resulting in microcracks at the coating interface (observed by SEM), the adhesion force drops to 17.5 MPa, and the cost increases significantly; when the addition amount of the fluorosilane is in the range of 5% - 15% of the total mass of the silane coupling agent: the fluorocarbon chains are evenly distributed, forming a dense monolayer (XPS shows that the atomic concentration of the F element is 8% - 12%), and the comprehensive performance is optimal.

[0090] In one embodiment, the hydrophobic chain of the fluorosilane is physically adsorbed on the hydroxylated surface of the nano-silica sol, enhancing the dispersibility of the particles in the alkaline solution (the Zeta potential rises from -40 mV to -25 mV and remains stable).

[0091] In one embodiment, the nano-silica sol constructs a micro-nano rough structure, and the fluorosilane provides a low surface energy, forming a superhydrophobic surface similar to the "lotus leaf effect" (contact angle 150°), reducing the secondary adsorption of pollutants, and the release agent residue rate ≤0.1% (detected by FTIR).

[0092] In this embodiment, the fluorosilane and the silane coupling agent synergistically construct a stable interface, realizing double protection of chemical bonding + physical barrier; 5% - 15% balances the performance and cost, avoiding the process complexity caused by excessive amounts, and realizing precise control of the addition amount.

[0093] In one embodiment, wettability tests were conducted: fluorosilane (10% addition amount): contact angle 8°, no wetting defects in the coating; fluorosilane-free group: contact angle 25°, local pinhole rate 5%; salt spray resistance comparison tests were conducted: fluorosilane group: no substrate corrosion after 200 h; control group (KH560): pitting corrosion occurred after 120 h; adhesion retention rate tests were conducted: after 500 h of QUV aging: fluorosilane group 95%, KH550 group 80%.

[0094] In one embodiment, through the introduction and addition amount optimization of fluorosilane, the following core advantages are achieved: super-wetting surface: coating coverage rate ≥ 99%, defect rate approaching zero; long-term corrosion resistance: salt spray test ≥ 200 h, far exceeding the industry standard; environmental stability: improved anti-ultraviolet aging performance, extending the coating life; through the fluorine-silicon synergistic interface design, the limitations of traditional cleaning agents in wettability and weather resistance are broken through.

[0095] In addition, as Figure 1 shown, a preparation method of an alkaline cleaning agent is also provided. The alkaline cleaning agent uses the above-mentioned alkaline cleaning agent, and this preparation method includes: Step S1, heat deionized water to 40 - 50 °C, and sequentially add inorganic alkali agents and corrosion inhibitors, and stir to dissolve.

[0096] In this embodiment, high temperature accelerates the dissolution efficiency of inorganic alkali agents (such as sodium hydroxide) and corrosion inhibitors (such as sodium molybdate), ensures the uniformity of the solution (dissolution time is shortened by 50%), and at the same time avoids the precipitation of alkali agents at low temperatures later.

[0097] Step S2, cool down to below 30 °C, add non-ionic surfactants and anionic surfactants, and stir until homogeneous.

[0098] Step S3, add nano-silica sol and silane coupling agent, and ultrasonically disperse for 20 - 40 minutes.

[0099] Step S4, adjust the pH to 10.5 - 12.5, and filter to obtain the finished product.

[0100] In this embodiment, the alkali agent is preferentially dissolved, and then nano-materials and silane are added; the alkali agent is preferentially dissolved because dissolving the inorganic alkali agent first forms a high pH environment (pH > 11), which promotes the formation of micelles of subsequent surfactants (CMC is reduced by 30%) and enhances the detergency; adding nano-materials and silane later is to avoid premature gelation of nano-silica sol in a strong alkaline environment (pH > 12), and at the same time, the silane coupling agent is in-situ grafted on the surface of the already dispersed nano-particles to form stable Si - O - Si bonds (the detected bond content increases by 60% by XPS).

[0101] In this embodiment, ultrasonic cavitation is used to break up the agglomerates of nano-silica sol, optimizing its particle size distribution from 100 - 500 nm (before ultrasonic treatment) to 10 - 50 nm (detected by DLS), ensuring the uniform construction of the micro-nano rough surface; after ultrasonic treatment, the Zeta potential of the nano-particles is adjusted from -10 mV to "-30 - -50 mV", enhancing the electrostatic repulsion force, with no precipitation within 30 days (precipitation rate < 5%), and improving the dispersion stability.

[0102] In this embodiment, the pH is 10.5 - 12.5, maintaining an alkaline environment to saponify the grease, while avoiding excessive corrosion of the aluminum substrate due to too high pH (> 13) (corrosion rate ≤ 0.5 g / m²·h); through filtration, undispersed nano-agglomerates and impurities can be removed, ensuring the transparency of the cleaning agent (light transmittance ≥ 95%, NTU ≤ 10), and preventing the risk of hole blockage in the spraying or electrophoresis process.

[0103] In one embodiment, three tests of active retention rate, dispersion uniformity, and cleaning agent stability are carried out respectively, and the results are as follows: Active retention rate: For the low-temperature process in stages: the active retention rate of KH550 is 92%; for the traditional high-temperature mixing: the active retention rate is only 58%.

[0104] Dispersion uniformity: After ultrasonic dispersion, the particle size distribution of nano-silica sol is: 10 - 50 nm (accounting for 95%); Without ultrasonic treatment: the particle size is 100 - 500 nm (accounting for 60%).

[0105] Cleaning agent stability: The cleaning agent is prepared in stages: no precipitation within 30 days, and the demoulding agent removal rate remains 99.3%.

[0106] In this embodiment, through the staged control of temperature, sequential addition, and ultrasonic dispersion optimization, the following core advantages are achieved: High-efficiency activation of components: The active retention rate of silane coupling agent and nano-materials > 90%; Guarantee of uniform dispersion: The particle size of nano-particles is controlled at 10 - 50 nm, and the Zeta potential is -30 - -50 mV; Process stability: The shelf life of the cleaning agent is extended to 30 days, adapting to industrial continuous production. In other words, through precise process design, the problems of component degradation and uneven dispersion in traditional methods are solved.

[0107] In addition, a surface treatment process for die-cast aluminum is also provided, applying the above alkaline cleaning agent. The surface treatment process for die-cast aluminum includes the following steps: (1) Immerse the die-cast aluminum workpiece in the cleaning agent and treat it at 50 - 60 °C for 5 - 15 minutes; (2) Use ultrasonic-assisted cleaning with a frequency of 28 - 40 kHz; (3) After water washing, immerse it in a passivation solution containing 0.05% - 0.3% cerium nitrate and 0.5% - 2% phytic acid and treat it for 15 minutes; (4) Drying to form an activated surface with both micro-rough structure and passivation film.

[0108] In step (1), the alkaline cleaning agent accelerates the saponification reaction at 50 - 60 °C to thoroughly remove the grease, mold release agent (silicone oil type), and oxide layer on the surface of die-cast aluminum. The residual rate of the mold release agent ≤ 0.2% (detected by FTIR). Meanwhile, the nano-silica sol and silane coupling agent form a micro-nano rough activation layer (Ra 0.5 - 1.2 μm), providing a highly active surface for subsequent passivation and coating.

[0109] In step (2), the ultrasonic cavitation effect generates micro-jet flow to remove the residual contaminants in the micropores (pore diameter 5 - 20 μm) of die-cast aluminum. The cleaning coverage rate in the blind hole area is increased from 80% to ≥ 98% (observed by SEM), avoiding the uneven adhesion of the coating caused by residues (the standard deviation is reduced from ±3.5 MPa to ±0.8 MPa). In step (3), the functions of cerium nitrate (0.05% - 0.3%): Rare earth cerium ions (Ce³ + ) adsorb and hydrolyze on the aluminum surface to form a CeO 2 ·nH 2 O colloidal film, filling the microscopic defects and inhibiting the initiation of pitting corrosion. The salt spray test time is extended from 72 h to ≥ 150 h (GB / T 10125); the functions of phytic acid (0.5% - 2%): The six phosphate groups of phytic acid form multi-toothed chelation bonds with the aluminum surface, and at the same time form a stable composite passivation film by complexing with Ce³ + , reducing the corrosion current density to 1.5×10 -6 A / cm² (tested by electrochemical impedance spectroscopy); the function of the passivation time (15 minutes): Short-time treatment avoids brittle cracking caused by too thick film layer, and the film thickness is controlled within 50 - 100 nm (measured by ellipsometer), balancing the corrosion resistance and the coating adhesion.

[0110] In the above integrated process, cleaning and passivation are carried out continuously, replacing the traditional multi-step process (cleaning → pickling → passivation). The treatment time is shortened from 60 minutes to 20 minutes, and the energy consumption is reduced by 40%; the use of toxic components such as chromates and phosphates is abandoned, the COD of the wastewater ≤ 50 mg / L (GB 8978), and the biodegradation rate ≥ 90% (OECD 301B), meeting the RoHS and REACH regulations and containing no harmful substances.

[0111] In one embodiment, the mold release agent removal rate, salt spray test experiment, and process efficiency experiment are carried out, and the results are as follows: Mold release agent removal rate: Example: Residual amount 0.18% (detected by FTIR); Traditional alkaline cleaning agent: Residual amount 1.5%.

[0112] Salt spray test comparison: Example: No substrate corrosion after 150h; Chromating process: Pitting occurred after 120h, and hexavalent chromium residue was present.

[0113] Process efficiency: Integrated process: Total time consumption is 20 minutes; Traditional multi-step process: 60 minutes.

[0114] In this example, through the integrated cleaning-passivation process design, the following core advantages are achieved: High-efficiency decontamination and activation: The synergistic effect of ultrasonic assistance + nanomaterials, the cleaning rate of blind holes ≥ 98%; Long-term corrosion resistance: Salt spray test of cerium-phytate composite passivation film ≥ 150h; Green manufacturing: Chromium-free and phosphorus-free, the wastewater treatment cost is reduced by 30%.

[0115] In one example, pulsed ultrasonic waves are used in step (2), with a duty cycle of 30% - 50% and a power density of 0.8 - 2.0 W / cm³.

[0116] In one example, the duty cycle is 40%.

[0117] In one example, the power density is 1.5 W / cm³.

[0118] In this example, the duty cycle is controlled at 30% - 50%. The pulsed ultrasound reduces the micro-impact damage (such as pitting and micro-cracks) to the aluminum substrate caused by the continuous collapse of cavitation bubbles through the intermittent working cycle (on / off time ratio), while maintaining sufficient cavitation intensity; When the duty cycle < 30%: The cavitation energy is insufficient, and the cleaning rate of blind holes drops to 85%; When the duty cycle > 50%: It is close to the continuous ultrasound mode, and the substrate corrosion rate increases from 0.3 g / m·h to 0.8 g / m·h (GB / T 18593).

[0119] In one example, the power density is 0.8 - 2.0 W / cm³. In this range, the cavitation bubble density and collapse energy reach an equilibrium, which can not only remove stubborn stains (such as silicone release agents) but also avoid the peeling of the nano-activation layer caused by too high power.

[0120] In one example, the intermittent cavitation of pulsed ultrasound generates a directional micro-jet, which penetrates into the blind hole structure with an aspect ratio > 5:1. The pollutant removal rate is increased from 80% to ≥ 99% (fluorescent tracer detection). When the duty cycle is 40%, the energy consumption is reduced by 35% compared with continuous ultrasound, while the release agent removal rate remains ≥ 99.5% (FTIR detection).

[0121] In one example, the pulse interval allows cavitation bubbles to regenerate after collapse, avoiding the intergranular corrosion of the aluminum substrate caused by local overheating (> 80°C). The surface roughness Ra is controlled at 0.5 - 1.2 μm (SEM observation), which can reduce cavitation corrosion.

[0122] In one embodiment, the retention rate of the bonding layer of nano-silica sol and silane coupling agent in pulse mode is ≥95% (XPS analysis), while continuous ultrasound results in 20% peeling of the activation layer, achieving the effect of the activation layer retention rate.

[0123] Blind hole cleaning comparison tests were carried out respectively: Pulse ultrasound (duty cycle 40%, 1.5 W / cm³): Cleaning rate 99.2%; Continuous ultrasound (same power): Cleaning rate 88.5%, and micro-cracks appeared on the substrate.

[0124] Energy consumption and efficiency tests were carried out respectively: Pulse mode: Energy consumption 0.8 kW·h / m², demoulding agent removal rate 99.6%; Continuous mode: Energy consumption 1.2 kW·h / m², removal rate 99.5%.

[0125] Substrate damage assessment tests were carried out respectively: Pulse ultrasound: Corrosion rate 0.3 g / m²·h, Ra = 1.0 μm; Continuous ultrasound: Corrosion rate 0.9 g / m²·h, Ra = 1.8 μm.

[0126] In this embodiment, through the optimization of pulse ultrasonic parameters, the following core advantages are achieved: High-efficiency and low-damage cleaning: Blind hole cleaning rate ≥99%, substrate corrosion rate reduced by 70%; Energy consumption savings: Energy consumption per unit area reduced by 35%, meeting the requirements of green manufacturing; Compatibility with complex structures: Meeting the industrialized high-efficiency processing of die-cast aluminum with porous and deep grooves. By optimizing the cavitation effect and energy input, the cleaning efficiency is significantly improved, the risk of substrate damage is reduced, and the cleaning effect of complex structures (such as blind holes and micro-grooves) is enhanced.

[0127] In addition, an intelligent cleaning system is also provided, which uses the above alkaline cleaning agent. The intelligent cleaning system includes a multi-stage circulation filtration module, a pH / temperature automatic control unit and an ultrasonic generating device. The multi-stage circulation filtration module includes an activated carbon adsorption layer and a ceramic membrane.

[0128] In this embodiment, the multi-stage circulation filtration module can provide long-term cleaning ability, specifically as follows: Activated carbon adsorption layer: Activated carbon efficiently removes organic pollutants (such as demoulding agent residues and grease decomposition products) in the cleaning agent through physical adsorption and chemical bonding. The adsorption capacity is ≥200 mg / g (GB / T 12496), reducing the COD value of the cleaning agent from 500 mg / L to ≤50 mg / L (GB 11914-89), and extending the bath life from 7 days to ≥30 days.

[0129] Ceramic membrane filtration (pore size 0.1 - 0.5 μm): The ceramic membrane intercepts nano-silica sol aggregates (particle size > 100 nm) and particulate pollutants, preventing them from depositing on the workpiece surface and causing coating defects, while maintaining the effective concentration of nano-materials (suspension rate ≥95%), ensuring the stable performance of the cleaning agent.

[0130] Synergistic effect of activated carbon adsorption layer and ceramic membrane filtration: The combination of activated carbon and ceramic membrane achieves dual-effect filtration of organic matter and particulate matter, increases the recycling rate of the cleaning agent from 50% to ≥90%, and reduces the waste liquid discharge by 60%.

[0131] In this embodiment, the pH / temperature automatic control unit can improve the process stability, as follows: Real-time pH monitoring and adjustment: Through the linkage of the pH sensor and the automatic dosing module, the pH value of the cleaning agent is stabilized within the range of 10.5 - 12.5, avoiding the corrosion of the aluminum substrate caused by pH fluctuations (corrosion rate ≤0.3 g / m²·h) or the hydrolysis failure of the silane coupling agent (activity retention rate ≥90%).

[0132] Precise temperature control (±1°C): Maintain the temperature of the cleaning tank at 50 - 60°C, which not only ensures the saponification reaction efficiency of the mold release agent but also prevents the accelerated degradation of the surfactant at high temperatures (>65°C). The fluctuation of the mold release agent removal rate is reduced from ±15% to ±3%.

[0133] Data traceability and early warning: The system automatically records pH / temperature data and predicts the life of the bath solution, triggers a replacement prompt in advance, and reduces the unplanned downtime by 30%.

[0134] Adaptability of multi-frequency ultrasonic waves (28 - 50 kHz): The low-frequency (28 kHz) cavitation effect is strong, suitable for removing large stains; the high-frequency (50 kHz) has good penetration and is suitable for the microporous structure of die-cast aluminum (pore diameter 5 - 20 μm). The cleaning rate of blind holes is increased from 85% to ≥98%.

[0135] Energy-saving mode design: Automatically adjust the power density (0.8 - 2.0 W / cm³) according to the stain degree of the workpiece, reduce the unit energy consumption by 25% (from 1.2 kW·h / m² → 0.9 kW·h / m²), and at the same time maintain the mold release agent removal rate ≥99.5%.

[0136] In this embodiment, multi-frequency (28 - 50 kHz) ultrasonic waves match different structured workpieces, the cleaning rate of blind holes is increased from 85% to ≥98%, the power density is dynamically adjusted (0.8 - 2.0 W / cm³), and the energy consumption is reduced by 25% (from 1.2 → 0.9 kW·h / m²).

[0137] In this embodiment, through the deep integration of circulating filtration, dynamic control and Internet of Things technology, the cleaning process has achieved high efficiency, greenness and intelligence. Its core values are reflected in: efficient resource utilization: the life of the cleaning agent is extended by 4 times, and both costs and energy consumption are reduced; zero process defects: the adhesion consistency reaches the top level in the industry; environmental compliance: the wastewater is nearly pollution-free and complies with global environmental regulations; compatibility with Industry 4.0: intelligent management enables digital production and promotes industry upgrading.

[0138] It should be noted that in this text, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, apparatus, article or method comprising a series of elements not only includes those elements but also other elements not expressly listed, or further includes elements inherent to such process, apparatus, article or method. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, apparatus, article or method comprising such element.

[0139] The above are only the preferred embodiments of the present application, and do not limit the patent scope of the present application accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present application, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present application.

Claims

1. An alkaline cleaning agent, characterized in that: Included by mass percentage: Nonionic surfactant 5%~12%; Anionic surfactant 3%~8%; Inorganic alkali agent 10%~20%; Corrosion inhibitor 0.5%~2%; Nano silica sol 1%~5%; Silane coupling agent 0.5%~3%; Deionized water balance.

2. The alkaline cleaning agent according to claim 1, characterized in that The mass ratio of the nonionic surfactant to the anionic surfactant is (2:1) to (3:1), and the total content of the two accounts for 8% to 18% of the mass of the cleaning agent.

3. The alkaline cleaning agent according to claim 1, characterized in that The particle size of the nano silica sol is 10-50 nm, and the surface is modified by hydroxylation.

4. The alkaline cleaning agent according to claim 1, characterized in that The silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidyloxypropyltrimethoxysilane.

5. The alkaline cleaning agent according to claim 2, characterized in that The hydroxylation modification is achieved by in-situ grafting of a silane coupling agent, and the Zeta potential of the sol is -30 to -50 mV.

6. The alkaline cleaning agent according to claim 1, characterized in that The silane coupling agent also includes fluorine-containing silane, and the added amount of the fluorine-containing silane is 5% to 15% of the total mass of the silane coupling agent.

7. A method for preparing an alkaline cleaning agent, characterized in that: The alkaline cleaning agent is the alkaline cleaning agent according to any one of claims 1 to 6, and the preparation method comprises: Step S1, heating deionized water to 40-50° C., adding an inorganic alkali agent and a corrosion inhibitor in sequence, and stirring to dissolve; Step S2, cooling to below 30° C., adding a nonionic surfactant and an anionic surfactant, and stirring until homogeneous; Step S3, adding nano silica sol and silane coupling agent, and ultrasonically dispersing for 20 to 40 minutes; Step S4, adjusting the pH to 10.5-12.5, and filtering to obtain the finished product.

8. A die-cast aluminum surface treatment process, characterized in that: Using the alkaline cleaning agent described in any one of claims 1 to 6, the die-cast aluminum surface treatment process comprises the following steps: (1) Immerse the die-cast aluminum workpiece in the cleaning agent and treat it at 50~60℃ for 5~15 minutes; (2) Ultrasonic cleaning is used with a frequency of 28-40 kHz; (3) After washing with water, immerse in a passivation solution containing 0.05%~0.3% cerium nitrate and 0.5%~2% phytic acid for 15 minutes; (4) Drying to form an activated surface with both a micro-rough structure and a passivation film.

9. The die-cast aluminum surface treatment process according to claim 8, characterized in that: In step (2), pulsed ultrasound is used with a duty cycle of 30% to 50% and a power density of 0.8 to 2.0 W / cm³.

10. An intelligent cleaning system, characterized in that: Using the alkaline cleaning agent described in any one of claims 1 to 6, the intelligent cleaning system includes a multi-stage circulation filtration module, a pH / temperature automatic control unit and an ultrasonic generating device, and the circulation filtration module includes an activated carbon adsorption layer and a ceramic membrane.

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