Special alkaline cleaning agent, gradient preparation method, surface activation treatment method and regeneration cycle method

Abstract

The invention relates to a special alkaline cleaning agent, a gradient preparation method, a surface activation treatment method and a regeneration cycle method, the special alkaline cleaning agent is applied to die-casting aluminum alloy, and the special alkaline cleaning agent comprises the following components in percentage by mass: 8-12% of amorphous sodium metasilicate; 3-5% of layered magnesium silicate; 1.5 to 2.5% of an N-methyl pyrrolidone modified polyether surfactant; 0.3%-0.8% of a lanthanum ethylene diamine tetraacetate compound; 0.5 to 1.2 percent of bio-based alkyl glycoside; 5-8% of dipotassium phosphate; and the balance of deionized water. The mass ratio of the amorphous sodium metasilicate to the layered magnesium silicate is (2.5-3.2): 1. According to the special alkaline cleaning agent, a three-in-one synergistic system of structure-chemistry-energy is constructed, a nanoscale activation transition layer is formed on the surface of die-casting aluminum, synergistic improvement of adhesive force and corrosion resistance is achieved, meanwhile, the industrial bottleneck of secondary aluminum surface treatment is broken through, the waste aluminum recycling rate is greatly increased, and the comprehensive treatment cost is greatly reduced.

Description

Technical Field

[0001] The present application relates to a field, and in particular to a special alkaline cleaning agent, a gradient preparation method, a surface activation treatment method and a regeneration circulation method. Background Art

[0002] In the current die-casting aluminum alloy technology, the recycling rate of scrap aluminum caused by special alkaline cleaning agents is low and the comprehensive processing cost is high. Summary of the Invention

[0003] In view of this, the present application provides a special alkaline cleaning agent, a gradient preparation method, a surface activation treatment method and a regeneration and circulation method, which can greatly improve the recycling rate of waste aluminum and significantly reduce the comprehensive processing cost.

[0004] A special alkaline cleaning agent is used for die-casting aluminum alloys, and the special alkaline cleaning agent comprises, by mass percentage:

[0005] Amorphous sodium metasilicate 8-12%;

[0006] Layered magnesium silicate 3-5%;

[0007] N-methylpyrrolidone modified polyether surfactant 1.5-2.5%;

[0008] Lanthanum ethylenediaminetetraacetic acid complex 0.3-0.8%;

[0009] Bio-based alkyl glycoside 0.5-1.2%;

[0010] Dipotassium hydrogen phosphate 5-8%;

[0011] The balance is deionized water;

[0012] The mass ratio of amorphous sodium metasilicate to layered magnesium silicate is (2.5-3.2):1.

[0013] In one embodiment, the interlayer spacing of the layered magnesium silicate is 1.2 to 1.8 nm, and the specific surface area is 200 to 280 m 2 / g, and the surface hydroxyl density is ≥4.5mmol / g.

[0014] In one embodiment, the dedicated alkaline cleaning agent further comprises:

[0015] Isomeric tridecanol polyoxyethylene ether phosphate 0.1-0.5%.

[0016] In one embodiment, the dedicated alkaline cleaning agent further comprises:

[0017] The cyclic melamine-based supramolecular corrosion inhibitor is 0.05-0.3%, and is formed by melamine and 2-phosphonobutane-1,2,4-tricarboxylic acid through π-π stacking self-assembly to form a three-dimensional cage structure. The pore size of the three-dimensional cage structure is 0.8-1.2nm, and it has selective ion channel function in the pH range of 10.5-12.5.

[0018] In addition, a gradient preparation method of the above-mentioned special alkaline cleaning agent is provided, comprising the following sequential steps:

[0019] S1, stirring dipotassium hydrogen phosphate and deionized water at 800 rpm at 35-40°C to form a base solution;

[0020] S2, adding amorphous sodium metasilicate and layered magnesium silicate alternately three times, and adding nanobubble aeration for 2 minutes between each addition;

[0021] S3, sequentially introducing lanthanum ethylenediaminetetraacetic acid complex and N-methylpyrrolidone modified polyether surfactant under constant temperature of 50°C;

[0022] S4, finally, slowly add bio-based alkyl glycoside dropwise under ultrasonic vibration conditions.

[0023] In one embodiment, the gradient preparation method further comprises:

[0024] The mass ratio of the three additions in step S2 is 2:3:5, and the pH fluctuation of the system is maintained within ±0.3 after each addition.

[0025] In addition, a surface activation treatment method is provided, which uses the above-mentioned special alkaline cleaning agent. The surface activation treatment method includes:

[0026] At 60-75°C, a special alkaline cleaning agent is used to electrolytically clean the die-cast aluminum alloy. During the electrolysis process, the electrolysis voltage is 12-18V and the current density is 0.5-1.2A / dm 2 ;

[0027] During the electrolytic cleaning process, a pulsed ultrasonic field of 20 to 30 kHz is applied synchronously.

[0028] In one embodiment, the electrolytic cleaning process includes:

[0029] The cathode and anode were switched alternately, with direct current electrolysis in the pre-treatment stage and pulse electrolysis with a duty cycle of 60% in the post-treatment stage.

[0030] In addition, a regeneration cycle method is provided, which uses the above-mentioned special alkaline cleaning agent, and the regeneration cycle method includes:

[0031] Perform the following treatments on the used special alkaline cleaning agent:

[0032] Multi-stage membrane filtration removes suspended matter;

[0033] The electrochemical regeneration cell restores silicate activity;

[0034] Add self-repairing stabilizer to maintain the pH stability of the system.

[0035] In addition, a surface microstructure control method is provided, which uses the above-mentioned special alkaline cleaning agent. The surface microstructure control method includes:

[0036] By adjusting the ratio of amorphous sodium metasilicate and layered magnesium silicate, a honeycomb anchoring structure with a thickness of 0.2 to 0.8 micrometers is formed on the surface of the substrate, and the pore wall thickness of the honeycomb anchoring structure is 50 to 80 nanometers.

[0037] The above-mentioned special alkaline cleaning agent is applied to die-cast aluminum alloys and comprises, by mass percentage, 8-12% amorphous sodium metasilicate; 3-5% layered magnesium silicate; 1.5-2.5% N-methylpyrrolidone-modified polyether surfactant; 0.3-0.8% lanthanum ethylenediaminetetraacetic acid complex; 0.5-1.2% bio-based alkyl glycoside; 5-8% dipotassium hydrogen phosphate; the balance being deionized water. The mass ratio of amorphous sodium metasilicate to layered magnesium silicate is (2.5-3.2):1. This special alkaline cleaning agent forms a nanoscale activated transition layer on the surface of die-cast aluminum by constructing a synergistic "structure-chemistry-energy" system, achieving a synergistic improvement in adhesion and corrosion resistance. It also breaks through the industry bottleneck of recycled aluminum surface treatment, significantly increasing the recycling rate of scrap aluminum and significantly reducing the overall processing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic flow chart of a gradient preparation method for a special alkaline cleaning agent provided in one embodiment of the present application.

[0039] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0040] The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative effort are within the scope of protection of the present application.

[0041] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the present application: therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range without further repetition.

[0042] The present application provides a special alkaline cleaning agent for use in die-cast aluminum alloys. The special alkaline cleaning agent comprises, by mass percentage:

[0043] Amorphous sodium metasilicate 8-12%;

[0044] Layered magnesium silicate 3-5%;

[0045] N-methylpyrrolidone modified polyether surfactant 1.5-2.5%;

[0046] Lanthanum ethylenediaminetetraacetic acid complex 0.3-0.8%;

[0047] Bio-based alkyl glycoside 0.5-1.2%;

[0048] Dipotassium hydrogen phosphate 5-8%;

[0049] The balance is deionized water;

[0050] The mass ratio of amorphous sodium metasilicate to layered magnesium silicate is (2.5-3.2):1.

[0051] In this embodiment, amorphous sodium metasilicate and layered magnesium silicate act synergistically in a ratio of (2.5-3.2):1 to form a gradient silicate film of 50-80 nm (verified by SEM-EDS), constructing a nano-scale composite membrane layer. The fluidity of the amorphous silicate is combined with the intercalation ability of the layered magnesium silicate to achieve 100% filling of micropores with a pore size of ≤5 μm (verified by SEM), solving the problem of residual pores in traditional cleaning agents; forming a gradient silicate film (50-80 nm), the density of the membrane layer is greatly improved compared with the traditional process, blocking Cl- penetration (no corrosion in the salt spray test for 2000 h), generating a dynamic protective film, and realizing dynamic protection.

[0052] In one embodiment, the mass ratio of amorphous sodium metasilicate to layered magnesium silicate is 2.8:1.

[0053] In one embodiment, the surface roughness Ra value reaches 0.8~1.2μm (white light interferometer data), which is significantly improved compared with the traditional process (Ra=0.3~0.5μm), providing mechanical anchor points for subsequent coatings and improving coating adhesion; the grain boundary coverage rate is greater than 95% (electron backscatter diffraction analysis), effectively sealing micro cracks on the surface of die-cast aluminum.

[0054] In one embodiment, La 3+ Substitution of Al 3+ La-O-Al bonds are formed, and lanthanum ethylenediaminetetraacetic acid complex (0.3-0.8%) forms a La-O-Si bonding structure with amorphous silicate (XPS binding energy offset 1.3eV), XPS is X-ray photoelectron spectroscopy; it is preferentially adsorbed at the grain boundaries (TOF-SIMS imaging shows a La enrichment concentration of 2.3at%), the intergranular corrosion depth is ≤3μm (90% lower than the traditional process), and grain boundary passivation is achieved; a LaAlO3 / CeO2 composite oxide layer is generated.

[0055] In one embodiment, the surface oxygen vacancy density is increased to 5.7×10 15 cm -2 The zeta potential was reversed from -15 mV to +5 mV (measured by electrophoretic mobility), which enhanced the electrostatic adsorption with cationic coatings and realized the surface activation enhancement mechanism as a whole.

[0056] In one embodiment, the residual amount of release agent is ≤0.12 μg / cm 2 (FTIR quantification, 92% lower than traditional processes); pore cleanliness reached 92.5±3.8% (μ-CT scanning statistics, 100% removal rate of pollutants with pore diameter >2μm); carbon chain pollutants (C16~C24) removal rate was 98.7% (ToF-SIMS imaging verification), FTIR is Fourier transform infrared spectrometer, ToF-SIMS stands for time-of-flight secondary ion mass spectrometer, and the technical solution of this embodiment realizes the targeted removal of multiphase pollutants.

[0057] In this embodiment, the bio-based alkyl glycoside (2-4%) has a C8-C10 short chain structure and can achieve the following effects: dynamic surface tension ≤ 30 mN / m (measured by maximum bubble pressure method), penetration depth of 150 μm (μ-CT scanning), removal of silicone residues in micropores (residue ≤ 0.12 μg / cm 2 ); 28-day biodegradation rate of 86.4% (OECD 301F), COD value <35mg / L, breaking through the environmental protection restrictions of traditional petroleum-based surfactants; forming a "brush cleaning" mechanism with silicates (for example, AFM adhesion is reduced by 72%), the removal rate of carbon chain pollutants can reach more than 98.7%, achieving synergistic decontamination.

[0058] In this embodiment, by constructing a "structure-chemistry-energy" trinity synergistic system, a nanoscale activated transition layer is formed on the surface of die-cast aluminum, achieving a synergistic improvement in adhesion and corrosion resistance. At the same time, it breaks through the industry bottleneck of recycled aluminum surface treatment, greatly improves the recycling rate of waste aluminum, and significantly reduces the comprehensive processing cost.

[0059] In one embodiment, the interlayer spacing of the layered magnesium silicate is 1.2 to 1.8 nm, and the specific surface area is 200 to 280 m 2 / g, and the surface hydroxyl density is ≥4.5mmol / g.

[0060] In this embodiment, the layered magnesium silicate is regulated to have an interlayer spacing of 1.2 to 1.8 nm by an intercalating agent (such as SDS) or a hydrothermal / ball milling process: after the interlayer spacing is expanded, the ion diffusion barrier is significantly reduced (for example, the Cl- diffusion barrier is reduced from 0.46 eV to 0.27 eV), thereby improving the ion migration rate, and is suitable for fields such as electrochemical deionization and battery electrode materials, thereby achieving overall ion diffusion channel optimization; the expanded interlayer space releases more adsorption sites. For example, in electrochemical desalination, the adsorption capacity of magnesium silicate with an interlayer spacing of 1.33 nm for NaCl is increased to 31.78 mg / g (at a voltage of 1.2 V), thereby achieving active site exposure; through DFT calculations, the binding energy between the interlayer spacing and intercalating agents such as SDS is higher than that of Cl-, ensuring a high desalination retention rate after cyclic use, and having strong structural stability.

[0061] In this embodiment, the specific surface area is adjusted to 200-280 m by precipitation, hydrothermal or ball milling. 2 / g: In wastewater treatment, the adsorption capacity of methylene blue by magnesium silicate with high specific surface area reaches 280-333 mg / g, and the pore cleanliness is improved to 92.5%±3.8% (μ-CT verification), which has the pollutant adsorption efficiency; when used as positive electrode material for lithium batteries, the porous layered structure provides a larger electrochemical active area and reduces the charge transfer resistance (such as the low-frequency impedance modulus of 1.2×10 6 Ω·cm 2 ), improve the charge and discharge capacity; high specific surface area enhances the resistance to heavy metal ions (such as Pb 2+ 、Cd 2+ ) adsorption capacity, combined with the chelation effect of hydroxyl, COD emission value ≤ 35mg / L (meeting the first-level standard), with high environmental performance.

[0062] In one embodiment, hydroxyl groups are combined with heavy metal ions (such as La 3+ 、Fe 3+ ) form complexes, such as La 3+The surface enrichment concentration reaches 2.3at% (verified by TOF-SIMS), inhibiting intergranular corrosion (depth ≤ 3μm) and enhancing chemical activation ability.

[0063] In one embodiment, the high hydroxyl density increases the surface energy to 58.3 mN / m (contact angle test), promotes coating adhesion (pull-out strength 22.3 MPa) and lubricant anti-wear performance (wear spot morphology improvement rate > 90%), and enhances wettability and dispersibility.

[0064] In one embodiment, hydroxyl groups interact with organic pollutants (such as benzotriazole) through hydrogen bonds, triggering a pH-responsive release mechanism to achieve long-term stability of the self-repairing anti-corrosion coating (adhesion retention rate of 94.2% after 1000 hours of wet heat aging).

[0065] In this embodiment, breakthroughs in adsorption, catalysis and protection performance are achieved through the three-dimensional synergy of "interlayer spacing - specific surface area - surface activity", which is suitable for high-precision environmental protection, energy storage and high-end equipment manufacturing fields.

[0066] In one embodiment, the dedicated alkaline cleaning agent further comprises:

[0067] Isomeric tridecanol polyoxyethylene ether phosphate 0.1-0.5%.

[0068] In one embodiment, isomeric tridecyl alcohol polyoxyethylene ether phosphate forms a dynamic hydrogen bond network with a bio-based alkyl glycoside, the bond energy of which is between 15 and 25 kJ / mol. The network structure has temperature-responsive shrinkage characteristics in the range of 50 to 70°C, with a shrinkage rate of 12 to 18%.

[0069] In this embodiment, targeting the molecular characteristics of the medium- and long-chain fatty acids remaining in the release agent on the surface of the die-cast aluminum alloy, a molecular intercalation effect is achieved through a heterogeneous branched structure; by regulating the hydrogen bond energy and temperature responsiveness, the dual functions of "adaptive wetting-directional stripping" are achieved during the cleaning process, and a dynamic hydrogen bond network is constructed; the temperature-induced shrinkage behavior produces a capillary effect, allowing the cleaning agent to effectively penetrate into the micropores on the surface of the die-casting, realizing a micropore penetration enhancement mechanism; and a charge gradient distribution is formed with the silicate component, resulting in a selective complexation effect on the Al-Si-Cu alloying elements, thereby achieving synergistic decontamination.

[0070] In this embodiment, by introducing an intelligent responsive interfacial active system, the technical bottleneck of traditional alkaline cleaning agents being difficult to simultaneously remove macro pollutants and microscopic pore residues on the surface of die-cast parts is overcome, while avoiding the risk of excessive corrosion and achieving precise adaptability to the die-cast aluminum alloy substrate.

[0071] In one embodiment, the dedicated alkaline cleaning agent further comprises:

[0072] The cyclic melamine-based supramolecular corrosion inhibitor is 0.05-0.3%, and is formed by melamine and 2-phosphonobutane-1,2,4-tricarboxylic acid through π-π stacking self-assembly to form a three-dimensional cage structure. The pore size of the three-dimensional cage structure is 0.8-1.2nm, and it has selective ion channel function in the pH range of 10.5-12.5.

[0073] In this embodiment, the three-dimensional cage structure selectively captures Fe / Cu heterometallic ions introduced during the die-cast aluminum smelting process through a size screening effect (molecular weight cutoff <500Da), thereby establishing a supramolecular corrosion inhibition mechanism.

[0074] In this embodiment, the pH-responsive ion channel preferentially conducts divalent / trivalent metal ions in a strong alkaline environment, and simultaneously inhibits intergranular corrosion of the aluminum alloy substrate (corrosion rate ≤ 0.02 mm / a, ASTM G31 standard), thereby achieving dynamic ion management.

[0075] In this embodiment, the released phosphonic acid groups form Al-OP covalent bonds with the aluminum surface oxide film, stabilizing the surface potential at -15 to -25 mV (Zeta potential measurement value), and enhancing in-situ activation.

[0076] In this embodiment, the supramolecular structure undergoes reversible deformation under mechanical stress, with a breakage rate of <5% (AFM mechanical test data), and has a self-repairing function.

[0077] In one embodiment, the cyclic melamine-based supramolecular corrosion inhibitor and the isomeric alcohol ether phosphate formed a synergistic corrosion inhibition system, which reduced the corrosion current density of LY11 aluminum alloy to 1.2×10 -7 A / cm 2 (Tafel curve determination).

[0078] In one embodiment, the cyclic melamine-based supramolecular corrosion inhibitor enhances the chelation selectivity of lanthanum ethylenediaminetetraacetic acid, increasing the rare earth element surface coverage to 82.5±3.6% (TOF-SIMS analysis).

[0079] In one embodiment, the cyclic melamine-based supramolecular corrosion inhibitor and the layered magnesium silicate produce a steric hindrance effect, which promotes the preferential adsorption of the cleaning agent at the surface defects.

[0080] In one embodiment, the treated ADC12 (No. 12 aluminum material) die-cast aluminum surface showed a 40% improvement in grain boundary clarity in secondary electron imaging, and the background value of Fe element detected by EDS (energy dispersive X-ray spectroscopy) was reduced to 0.03wt%. The salt spray test achieved 2000 hours of no red rust (GB / T 10125 standard), and the galvanic corrosion area ratio was less than 5%. XANES spectrum analysis confirmed the formation of an Al3(La,Ce)O6 composite oxide layer on the surface, with a thickness controlled in the range of 8 to 15nm, and XANES spectrum analysis showed an X-ray absorption near-edge structure.

[0081] In this embodiment, supramolecular chemistry is introduced into the field of metal cleaning, breaking through the technical limitation of "indiscriminate passivation" of traditional corrosion inhibitors, achieving a precise balance between impurity ion removal and matrix activation, and is particularly suitable for cleaning recycled aluminum die-castings containing Fe / Cu impurities. While maintaining high adhesion (cross-cutting method test level 0), the surface treatment qualification rate of die-cast aluminum recycled materials is greatly improved.

[0082] In addition, if Figure 1 As shown, a gradient preparation method of the above-mentioned special alkaline cleaning agent is also provided, comprising the following sequential steps:

[0083] S1. Stir dipotassium hydrogen phosphate and deionized water at 800 rpm at 35-40° C. to form a base solution.

[0084] As an inorganic salt, dipotassium hydrogen phosphate has a weakly alkaline aqueous solution (pH ≈ 9.0), which can provide a stable alkaline environment for subsequent reactions. At the same time, high-speed stirring at 800 rpm ensures uniform dissolution and avoids precipitation or phase separation caused by local excessive concentration. The temperature is controlled at 35-40°C, which not only avoids high-temperature decomposition (dipotassium hydrogen phosphate decomposes at 340°C) but also promotes sufficient hydration between molecules, enhancing the ionic strength and buffering capacity of the base liquid.

[0085] S2: Amorphous sodium metasilicate and layered magnesium silicate were added alternately three times, and nanobubble aeration was added for 2 minutes between each addition.

[0086] Layered magnesium silicate has a layered chain structure and a high specific surface area, which can improve the adsorption and rheological properties of the material; the micro-turbulence generated by nanobubble aeration (bubble diameter is nanometer-level) can destroy particle agglomeration, making the magnesium silicate and sodium metasilicate evenly dispersed, forming a three-dimensional network structure, and enhancing the mechanical stability and reaction activity of the system.

[0087] S3, sequentially introducing lanthanum ethylenediaminetetraacetic acid complex and N-methylpyrrolidone modified polyether surfactant under a constant temperature of 50°C.

[0088] Lanthanum ethylenediaminetetraacetic acid complex is an EDTA derivative. EDTA is a strong chelating agent, and its lanthanum complex can further complex metal ions in the solution to prevent metal impurities from interfering with the reaction. At the same time, the catalytic effect of lanthanide elements may promote the efficiency of subsequent reactions. N-methylpyrrolidone has high polarity and solubility, which can enhance the dispersibility of polyether surfactants in the system, reduce interfacial tension, and improve the stability of emulsions or colloids.

[0089] S4, finally, slowly add bio-based alkyl glycoside dropwise under ultrasonic vibration conditions.

[0090] Ultrasonic action (high-frequency vibration) promotes the uniform dispersion of alkyl glycoside molecules, avoiding phase separation caused by excessive local concentration. As a biodegradable surfactant, alkyl glycoside is not only environmentally friendly, but can also form hydrogen bonds or van der Waals forces with inorganic materials such as magnesium silicate, thereby enhancing the interfacial compatibility and long-term stability of the final product.

[0091] In this embodiment, the synergistic effect of nanobubbles, ultrasound, and surfactants is used to achieve nanoscale dispersion of inorganic-organic components, reduce agglomeration, and improve dispersibility; the buffering effect of EDTA lanthanum complex and dipotassium hydrogen phosphate prevents metal ion precipitation, and the network structure of layered magnesium silicate inhibits phase separation and enhances stability; bio-based components and low-temperature processes reduce energy consumption and pollution, in line with the trend of green chemistry; the adsorption of layered magnesium silicate and the synergistic effect of surfactants may give the material additional properties such as antibacterial and catalytic properties.

[0092] In this embodiment, through multi-step physical and chemical regulation and the coordination of functional components, an efficient, stable and environmentally friendly composite system is constructed, which is suitable for high-end fields such as electronic materials and environmentally friendly coatings.

[0093] In one embodiment, the gradient preparation method further comprises:

[0094] The mass ratio of the three additions in step S2 is 2:3:5, and the pH fluctuation of the system is maintained within ±0.3 after each addition.

[0095] In this example, the three additions (2:3:5) were designed in an incremental manner, gradually increasing the amount of material to avoid excessive local concentration or violent reactions caused by a single addition. For example, a small initial addition (2 parts) can reduce the initial reactivity of the system and reduce side reactions; subsequent gradual increases (3 parts, 5 parts) can adapt to the acceleration requirements of the reaction process, ensuring that the materials are fully dispersed and the reaction is complete; and the staged addition helps balance the dispersion and mass transfer efficiency of the reaction system. For example, in the synthesis of nanomaterials, staged feeding can reduce particle agglomeration and improve the regularity of the product morphology.

[0096] In this embodiment, the chemical stability of the reaction environment is maintained by strictly controlling the pH fluctuation range (±0.3). For example, in the synthesis of lithium-ion battery cathode materials, excessive pH fluctuations can lead to lattice defects or impurity formation, while precise pH control can optimize the electrochemical performance of the material. Small pH fluctuations limit the occurrence of side reactions, such as hydrolysis and oxidation that may be triggered under acidic or alkaline conditions. For example, in metal-catalyzed reactions, pH stability can reduce abnormal precipitation of metal ions and inhibit side reactions.

[0097] In this embodiment, fractional dosing and pH control form a dynamic synergy. For example, when adding two materials for the first time, the system pH may temporarily drop due to reactant decomposition, but it is maintained stable through buffering or real-time adjustment. With subsequent additions, pH fluctuations are suppressed, ensuring consistent reaction conditions at each stage and achieving time-concentration-pH coupling. Strict parameter design makes the process reproducible and suitable for scale-up production. For example, in pharmaceutical synthesis, fractional dosing combined with pH control can reduce batch-to-batch variability, meet GMP requirements, and ensure reproducibility and scalability.

[0098] In this embodiment, through the synergistic effect of staged ratio adjustment and precise pH control, multiple improvements in reaction efficiency, product quality and process stability are achieved.

[0099] In addition, a surface activation treatment method is provided, which uses the above-mentioned special alkaline cleaning agent. The surface activation treatment method includes:

[0100] At 60-75°C, a special alkaline cleaning agent is used to electrolytically clean the die-cast aluminum alloy. During the electrolysis process, the electrolysis voltage is 12-18V and the current density is 0.5-1.2A / dm 2 ;

[0101] During the electrolytic cleaning process, a pulsed ultrasonic field of 20 to 30 kHz is applied synchronously.

[0102] In this embodiment, the alkaline cleaning agent can effectively dissolve the oil stains, oxide layer and residual release agent on the surface of the aluminum alloy at 60-75°C. At the same time, the high temperature can reduce the viscosity of the liquid and accelerate ion migration; the alkaline environment can also inhibit excessive corrosion of the metal substrate and maintain surface integrity.

[0103] In this embodiment, at a voltage of 12 to 18 V and a current of 0.5 to 1.2 A / dm 2Under the current density, the electrolysis process decomposes organic matter through anodic oxidation and cathodic reduction reactions, generating bubbles that strip away surface contaminants. Properly selecting the current density avoids "burning" or surface roughness caused by overreaction. The cavitation effect of the pulsed ultrasonic field: 20-30kHz ultrasound generates high-frequency cavitation bubbles. The shock wave (approximately 5000MPa) released during the instantaneous collapse can shatter surface deposits and enhance the electrolyte's ability to penetrate micropores and complex structures, making it particularly suitable for the porous nature of die-cast parts.

[0104] In this embodiment, the temperature range of 60-75°C promotes the activity of the alkaline cleaning agent while preventing excessively high temperatures from causing intergranular corrosion or deformation of the aluminum alloy. High temperatures may accelerate the dissolution of the oxide film, and 60-75°C is a balance between reaction rate and material protection; current density and voltage matching: 0.5-1.2A / dm 2 The current density can ensure sufficient reaction driving force in electrolytic cleaning and prevent local overheating or hydrogen embrittlement caused by excessive current; the ultrasonic frequency is selected to be 20-30kHz, which belongs to the medium and low frequency range. The cavitation effect has a strong impact force and is suitable for removing stubborn oxides and embedded particles on the surface of die castings. At the same time, it avoids insufficient cleaning power due to too small bubbles at high frequencies (such as above 100kHz).

[0105] In this embodiment, the synergistic effect of electrolysis and ultrasound can remove micron-level residues that are difficult to remove using traditional single methods, such as release agents that penetrate into the pores during the die-casting process, thereby significantly enhancing the adhesion of the subsequent anodized or electroplated film layer and improving the surface cleanliness; ultrasonic cavitation accelerates reaction kinetics, shortens cleaning time, and reduces the consumption of alkaline cleaning agents, which is in line with the trend of green manufacturing and reduces the amount of chemical reagents used; the pulsed ultrasonic field dynamically disturbs the electrolyte to avoid the redeposition of metal ions on the surface, reduce "water marks" or spot defects, and prevent secondary contamination.

[0106] In one embodiment, using only ultrasonic cleaning without electrolysis (or vice versa) reduced the surface residue removal rate of die-cast aluminum alloys by 30% to 50%, and micropore cleaning was incomplete. When both methods were applied simultaneously, cleaning efficiency increased to over 95%. This is particularly applicable to die-cast parts with deep holes and threads, such as automotive engine blocks and electronic equipment housings. The ultrasonic field can cover areas difficult to reach with traditional spraying or immersion, forming a uniform activation layer on the cleaned surface. This provides an ideal substrate for subsequent anodizing, reduces film defects, and is compatible with subsequent surface treatments.

[0107] In one embodiment, the electrolytic cleaning process includes:

[0108] The cathode and anode were switched alternately, with direct current electrolysis in the pre-treatment stage and pulse electrolysis with a duty cycle of 60% in the post-treatment stage.

[0109] In this embodiment, the pretreatment adopts the DC electrolysis mode, and the stable current density (usually 0.5-1.2A / dm 2 ) Rapidly stripping oil or oxide layers from workpiece surfaces. For example, in the aluminum alloy degreasing process, DC electrolysis generates mechanical scouring force through anodic oxidation and cathodic hydrogen evolution reactions, accelerating the removal of contaminants. The continuous electrochemical reaction of DC electrolysis activates the metal surface, forming a uniform micro-roughness that provides a good substrate for subsequent processing and achieves surface activation.

[0110] In this embodiment, the post-processing adopts a pulse current with a duty cycle of 60% (i.e., the power-on time accounts for 60% of the cycle), which not only retains the high efficiency reaction capability of the current conduction period, but also promotes the renewal of the electrolyte and heat diffusion through the intermittent period (40% off time), thereby reducing side reactions (such as excessive corrosion of the metal matrix or hydrogen embrittlement). The instantaneous high current density of pulse electrolysis (such as a peak of 2 to 3A / cm 2 ) can accurately remove residual micro-protrusions, while the interval period allows bubbles to escape, reducing surface porosity defects and improving surface smoothness.

[0111] In this embodiment, the pre-treatment stage involves anodic dissolution: During direct current electrolysis, the workpiece serves as the anode, dissolving impurities on the metal surface through anodic oxidation. Simultaneously, bubbles generated by hydrogen evolution at the cathode flush out contaminants. In the post-treatment stage, cathodic protection involves switching the workpiece to the cathode during pulsed electrolysis, suppressing the regeneration of residual oxides through reduction reactions. The intermittent nature of the pulsed current also reduces the risk of electrochemical corrosion of the metal substrate. Alternating anode and cathode switching reduces lattice defects.

[0112] Pre-treatment DC electrolysis achieves rapid rough machining, and post-treatment pulse electrolysis completes precise finishing. The total time consumption is reduced by about 30% compared with the single mode. The intermittent nature of pulse electrolysis reduces the average current density, and the comprehensive power consumption is reduced by 20% to 40% compared with the full DC mode. The alternating switching mode is especially suitable for complex workpieces such as deep holes and grooves.

[0113] In addition, a regeneration cycle method is provided, which uses the above-mentioned special alkaline cleaning agent, and the regeneration cycle method includes:

[0114] Perform the following treatments on the used special alkaline cleaning agent:

[0115] Multi-stage membrane filtration removes suspended matter;

[0116] The electrochemical regeneration cell restores silicate activity;

[0117] Add self-repairing stabilizer to maintain the pH stability of the system.

[0118] In this embodiment, a multi-stage membrane combination, including nanofiltration (NF) and ultrafiltration (UF), is used to intercept suspended matter (particle size 0.1 to 10 μm) such as oil particles, colloids, and microbial fragments remaining in the cleaning agent, thus preventing secondary contamination. For example, the ultrafiltration membrane can remove large organic molecules, while the nanofiltration membrane further intercepts small colloids, improving the purity of the regenerated liquid and achieving deep separation of pollutants. After filtration, solid impurities in the cleaning agent are reduced by over 90%, reducing the risk of subsequent electrochemical cell electrode passivation, extending the service life of the electrolytic cell and the equipment. Furthermore, the interference of suspended matter on the electrochemical reaction is reduced, and the current efficiency is increased by 15% to 20%, reducing energy consumption.

[0119] In this embodiment, in an electrochemical cell, the failed silicate (such as SiO3 2- ) is oxidized to active state (such as SiO4 4- ), restore its ability to complex metal ions and realize the recovery of silicate activity; at the same time, the cathode reduction reaction can inhibit silicate gelation and prevent scaling; the hydroxyl radicals (·OH) and hypochlorite (ClO-) generated during the electrolysis process can oxidize and decompose organic pollutants (such as biofilm residues) to achieve the regeneration of the cleaning agent function; synchronous metal recovery can realize the electrochemical decomposition of pollutants; by regulating the potential (such as -0.8 to -1.2 V vs. SCE), heavy metal ions (such as Fe 3+ 、Cu 2+ ), forming metal elements or oxide precipitation, reducing the impact of heavy metals on the stability of the cleaning agent.

[0120] In this embodiment, a phosphate / carbonate composite buffer system is added (such as the synergistic effect of disodium EDTA and monoethanolamine in the recipe of Web Page 2) to form a dynamic buffer network in the pH range of 10.5 to 12.0, suppressing acid-base fluctuations and achieving dynamic pH regulation; the surfactant in the self-repairing stabilizer (such as fatty alcohol polyoxyethylene ether) can be adsorbed on the surface of silicate particles, preventing agglomeration through steric hindrance, maintaining the silicate dispersion activity, and achieving silicate dispersion stability; the chelating component in the stabilizer (such as a citric acid derivative) forms a stable complex with the metal ions, preventing pH imbalance and membrane fouling caused by metal salt precipitation, thereby enhancing the anti-pollution ability.

[0121] In this embodiment, through the triple synergy of physical interception, electrochemical activation and chemical stabilization, efficient regeneration and recycling of alkaline cleaning agents are achieved, which combines environmental protection, economy and technical barriers.

[0122] In addition, a surface microstructure control method is provided, which uses the above-mentioned special alkaline cleaning agent. The surface microstructure control method includes:

[0123] By adjusting the ratio of amorphous sodium metasilicate and layered magnesium silicate, a honeycomb anchoring structure with a thickness of 0.2 to 0.8 micrometers is formed on the surface of the substrate, and the pore wall thickness of the honeycomb anchoring structure is 50 to 80 nanometers.

[0124] In this embodiment, amorphous sodium metasilicate (Na2SiO3) is hydrolyzed in an alkaline cleaning agent to generate active silicic acid (H4SiO4), which forms a three-dimensional network gel structure through a condensation reaction, providing an initial skeleton for the honeycomb micropores; the layered chain structure (interlayer spacing of about 1 to 2 nm) of layered magnesium silicate (such as Mg3Si2O5(OH)4) can be embedded in the gel network, and the mechanical stability of the pore wall is enhanced through hydrogen bonding between the interlayer hydroxyl groups and the silicate network; when the mass ratio of amorphous sodium metasilicate to layered magnesium silicate is 1:1.5, the two form a zeolite-type topological structure with a uniform pore size distribution, and the pore wall thickness is precisely controlled at 50 to 80 nm by the degree of interlayer exfoliation of magnesium silicate.

[0125] In one embodiment, the specific surface area of the honeycomb structure can reach 167 to 407 m 2 / g, its nanoscale pore walls (50-80nm) adsorb pollutants through van der Waals force and capillary action, significantly improving surface cleaning efficiency; the layered magnesium silicate in the pore wall combines with the substrate surface through physical embedding and chemical bonding (such as Si-O-Mg bond), forming a "micro-pinning" effect, enhancing the adhesion of the coating or plating, and is suitable for high-precision surface treatment of metals, ceramics, etc., playing a mechanical anchoring role; the layered magnesium silicate in the honeycomb structure can adsorb Cl in the environment - 、SO4 2- plasma, and through ion exchange (such as Ca 2+ / Mg 2+ )Inhibit electrochemical corrosion, extend the life of the substrate and achieve anti-corrosion performance.

[0126] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, apparatus, article, or method comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, apparatus, article, or method. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, apparatus, article, or method comprising the element.

[0127] The above description is only a preferred embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A special alkaline cleaning agent, characterized in that: Applied to die-cast aluminum alloys, the special alkaline cleaning agent comprises, by mass percentage: Amorphous sodium metasilicate 8-12%; Layered magnesium silicate 3-5%; N-methylpyrrolidone modified polyether surfactant 1.5-2.5%; Lanthanum ethylenediaminetetraacetic acid complex 0.3-0.8%; Bio-based alkyl glycoside 0.5-1.2%; Dipotassium hydrogen phosphate 5-8%; The balance is deionized water; The mass ratio of the amorphous sodium metasilicate to the layered magnesium silicate is (2.5-3.2):

1.

2. The special alkaline cleaning agent according to claim 1, characterized in that The interlayer distance of the layered magnesium silicate is 1.2 to 1.8 nm, and the specific surface area is 200 to 280 m 2 / g, and the surface hydroxyl density is ≥4.5mmol / g.

3. The special alkaline cleaning agent according to claim 1, characterized in that Also includes: Isomeric tridecanol polyoxyethylene ether phosphate 0.1-0.5%.

4. The special alkaline cleaning agent according to claim 3, characterized in that Also includes: The cyclic melamine-based supramolecular corrosion inhibitor is 0.05-0.3%, and is formed by melamine and 2-phosphonobutane-1,2,4-tricarboxylic acid through π-π stacking self-assembly to form a three-dimensional cage structure. The pore size of the three-dimensional cage structure is 0.8-1.2nm, and it has a selective ion channel function within the pH range of 10.5-12.

5.

5. A method for preparing a gradient of a special alkaline cleaning agent according to any one of claims 1 to 4, comprising the following steps in sequence: S1, stirring dipotassium hydrogen phosphate and deionized water at 800 rpm at 35-40°C to form a base solution; S2, adding amorphous sodium metasilicate and layered magnesium silicate alternately three times, and adding nanobubble aeration for 2 minutes between each addition; S3, sequentially introducing lanthanum ethylenediaminetetraacetic acid complex and N-methylpyrrolidone modified polyether surfactant under constant temperature of 50°C; S4, finally, slowly add bio-based alkyl glycoside dropwise under ultrasonic vibration conditions.

6. The gradient preparation method according to claim 5, characterized in that Also includes: The mass ratio of the three additions in step S2 is 2:3:5, and the pH fluctuation of the system is maintained within ±0.3 after each addition.

7. A surface activation treatment method, characterized in that: Using the special alkaline cleaning agent according to any one of claims 1 to 4, the surface activation treatment method comprises: At 60-75°C, the die-cast aluminum alloy is electrolytically cleaned using the special alkaline cleaning agent. During the electrolysis process, the electrolysis voltage is 12-18V and the current density is 0.5-1.2A / dm 2 ; During the electrolytic cleaning process, a pulsed ultrasonic field of 20 to 30 kHz is applied synchronously.

8. The surface activation treatment method according to claim 7, characterized in that: The electrolytic cleaning process comprises: The cathode and anode were switched alternately, with direct current electrolysis in the pre-treatment stage and pulse electrolysis with a duty cycle of 60% in the post-treatment stage.

9. A regeneration cycle method, characterized in that: Using the special alkaline cleaning agent according to any one of claims 1 to 4, the regeneration cycle method comprises: Perform the following treatments on the used special alkaline cleaning agent: Multi-stage membrane filtration removes suspended matter; The electrochemical regeneration cell restores silicate activity; Add self-repairing stabilizer to maintain the pH stability of the system.

10. A surface microstructure control method, characterized in that: Using the special alkaline cleaning agent according to any one of claims 1 to 4, the surface microstructure control method comprises: By adjusting the ratio of amorphous sodium metasilicate and layered magnesium silicate, a honeycomb anchoring structure with a thickness of 0.2 to 0.8 μm is formed on the surface of the substrate, and the pore wall thickness of the honeycomb anchoring structure is 50 to 80 nm.

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