Low-temperature low-dregs phosphating agent and preparation method thereof

Abstract

This application relates to the field of chemical production technology, specifically disclosing a low-temperature, low-slag phosphating agent and its preparation method. The low-temperature, low-slag phosphating agent comprises the following raw materials: a main salt component, a composite complexing agent, a synergistic promoter, a corrosion inhibitor and stabilizer, a fluoride, a pH adjuster, and deionized water. The preparation method of the low-temperature, low-slag phosphating agent is as follows: the main salt component is added to deionized water and stirred evenly to obtain a main salt mixture; the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor and stabilizer are added sequentially to the main salt mixture, stirred evenly, ultrasonically dispersed, and the pH adjuster is added to adjust the pH of the system. After stirring evenly, the mixture is allowed to stand and filtered to obtain the low-temperature, low-slag phosphating agent. This low-temperature, low-slag phosphating agent exhibits excellent comprehensive performance, low phosphating sludge content, uniform and dense phosphating film formation, excellent neutral salt spray corrosion resistance, strong adhesion of the phosphating film, and strong bonding force with the metal surface; simultaneously, the product shows good stability at room temperature without stratification or turbidity.

Description

Technical Field

[0001] This application relates to the field of chemical production technology, and more specifically, it relates to a low-temperature, low-slag phosphating agent and its preparation method. Background Technology

[0002] Phosphating is a key pretreatment process for metal surfaces before coating. It significantly improves paint adhesion and substrate corrosion resistance by forming a stable phosphate conversion film on metal surfaces such as steel, zinc, and aluminum. It is widely used in the automotive, home appliance, hardware, and machinery manufacturing industries. Traditional phosphating agents are mostly medium-to-high temperature systems, typically requiring a treatment temperature of 50-70℃. This reliance on continuous heating to maintain process conditions results in high energy consumption and high production costs. Furthermore, the phosphating reaction is intense at medium-to-high temperatures, causing metal ions in the solution to rapidly combine with phosphate ions to form a large amount of insoluble phosphate precipitate. This not only wastes raw materials but also easily adheres to the workpiece surface, forming a sludge deposit. This leads to a rough, porous, and uneven phosphate film, reducing film quality and subsequent coating effects.

[0003] In recent years, low-temperature phosphating technology has gradually developed, but existing low-temperature phosphating agents still have many shortcomings. Most formulations rely on traditional accelerators such as nitrites, which not only pose health and environmental risks but also have limited accelerating efficiency, requiring high acidity to ensure film formation, making it difficult to effectively control the amount of sludge. Some low-temperature phosphating agents improve film performance by adding heavy metals (such as nickel and chromium), but this does not conform to environmental protection trends, and their insufficient complexing ability cannot effectively stabilize ferrous ions in the solution, accelerating sludge formation and bath aging. In addition, existing low-temperature low-sludge phosphating agents generally suffer from slow film formation speed, low film density, insufficient corrosion resistance, and narrow applicability, making it difficult to meet the high-efficiency, stable, and low-maintenance requirements of high-speed automated coating production lines. Therefore, developing a new type of low-temperature low-sludge phosphating agent that forms a film quickly under low-temperature conditions, produces low sludge, forms a dense and corrosion-resistant film, and is environmentally friendly and safe has become an urgent need in the metal surface treatment industry. Summary of the Invention

[0004] To address the technical problems mentioned in the background section, this application provides a low-temperature, low-slag phosphating agent and its preparation method.

[0005] In the first aspect, this application provides a low-temperature, low-slag phosphating agent, which adopts the following technical solution: A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28-35 parts of main salt component, 2.5-5.5 parts of composite complexing agent, 1.2-3.5 parts of synergistic promoter, 0.3-0.9 parts of corrosion inhibitor and stabilizer, 0.2-0.8 parts of fluoride, 0.1-0.5 parts of pH adjuster, and 80-120 parts of deionized water; The main salt components include aminotrimethylenephosphonic acid, sodium zirconium lactate, and ammonium phosphomolybdate.

[0006] Preferably, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 5-8 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 10-12:3-5.

[0007] Preferably, the composite complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylene phosphonic acid in a mass ratio of 4-9:2-3:1-3.

[0008] Preferably, the synergistic promoter is one or more of hydroxylamine sulfate, sodium m-nitrobenzenesulfonate, and sodium chlorate.

[0009] Preferably, the method for preparing the corrosion inhibitor includes the following preparation steps: (1) Add cerium nitrate and phytic acid to deionized water and stir for 1-2 hours to obtain a rare earth-phytic acid complex solution; (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, ultrasonically disperse for 30-50 min, add polyvinylpyrrolidone, continue stirring for 20-30 min, filter, wash with deionized water, collect the solid product, vacuum dry for 12-18 h, grind and sieve to obtain corrosion inhibitor stabilizer.

[0010] Preferably, the mass ratio of cerium nitrate, phytic acid and deionized water in step (1) is 1-1.2:2-3:20-30.

[0011] Preferably, in step (2), the mass ratio of rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2-5:0.3-1.

[0012] Preferably, the K value of the polyvinylpyrrolidone is in the range of 25-40.

[0013] Preferably, the fluoride is one or more of sodium fluoride, potassium fluoroborate, ammonium fluoride, and ammonium bifluoride.

[0014] Preferably, the pH adjuster is phosphorous acid.

[0015] Secondly, this application also provides a method for preparing a low-temperature, low-slag phosphating agent, using the following technical solution: A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps: Add the main salt component to deionized water and stir until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir for 30-40 minutes, then ultrasonically disperse for 10-15 minutes. Add a pH adjuster to adjust the pH of the system to 2.5-4.0, stir until homogeneous, let stand for 10-15 minutes, and filter to obtain a low-temperature, low-slag phosphating agent.

[0016] In summary, this application has the following beneficial effects: This application utilizes a specific ratio of aminotrimethylenephosphonic acid, sodium zirconium lactate, and ammonium phosphomolybdate to form the main salt component, resulting in a synergistic effect within the main salt system. Aminotrimethylenephosphonic acid efficiently complexes metal ions, inhibiting sludge formation and improving bath stability; sodium zirconium lactate slowly releases zirconium ions, refining the phosphating film grains and enhancing film density and adhesion; ammonium phosphomolybdate, as a low-temperature film-forming promoter, accelerates the cathode reaction rate and lowers the phosphating treatment temperature. This compounded main salt allows for rapid film formation without high temperatures, significantly reducing phosphating sludge production while simultaneously improving film corrosion resistance and adhesion. This gives the phosphating agent the advantages of low-temperature application, low sludge production, and superior film quality, solving the problems of high temperature, excessive sludge, and poor film performance associated with traditional phosphating agents.

[0017] This application optimizes the composition of the composite complexing agent by using sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylene phosphonic acid in a specific ratio. Utilizing the synergistic complexing effect of these three compounds, multiple functional groups work together to increase the binding opportunities and stability with metal ions, effectively chelating metal ions in the system and preventing precipitation. Simultaneously, it refines the phosphate film crystal particles, improving the film density. This application also strictly controls the ratio of cerium nitrate and phytic acid to ensure a complete reaction, generating a structurally stable rare-earth-phytic acid complex. This complex can quickly adsorb onto the metal surface, initially forming a corrosion-inhibiting protective layer. Furthermore, by compounding nano-tungsten disulfide and polyvinylpyrrolidone in a specific ratio, the resulting corrosion inhibitor and stabilizer forms a dense and strongly adherent protective film on the metal surface, possessing both excellent corrosion inhibition performance and system stabilization. This effectively inhibits metal substrate corrosion while preventing delamination and turbidity, ensuring the stable progress of the phosphating reaction.

[0018] This application optimizes the composition of the main salt component, the composition of the composite complexing agent, and precisely controls the preparation method of the corrosion inhibitor and stabilizer. This allows the synergistic effect of each component to overcome the technical shortcomings of existing phosphating agents, such as poor phosphating effect at low temperatures, large amount of sludge, poor film performance, and insufficient stability. The prepared low-temperature, low-sludge phosphating agent can achieve efficient phosphating at a low temperature of 35℃, and has the characteristics of low sludge, high film quality, strong stability, and excellent anti-corrosion performance. It can meet the needs of industrial-scale production and has significant technical advantages and application value. Detailed Implementation

[0019] The present application will be further described in detail below with reference to the embodiments.

[0020] The aminotrimethylenephosphonic acid used in the embodiments and comparative examples of this application was purchased from Jinan Jinyu Chemical Co., Ltd.; sodium zirconium lactate was purchased from Hefei Zekenai New Material Technology Co., Ltd.; ammonium phosphomolybdate was purchased from Guangdong Ronghui Chemical Co., Ltd.; hydroxyethylidene diphosphonic acid was purchased from Shandong Yuanlian Chemical Co., Ltd.; aminotrimethylenephosphonic acid was purchased from Wuhan Kemike Biomedical Technology Co., Ltd.; nano tungsten disulfide (brand name: DH-WS2) was purchased from Dinghong (Shanghai) New Material Technology Co., Ltd.; polyvinylpyrrolidone (K value 30) and polyvinylpyrrolidone (K value 60) were both purchased from Shandong Feihong New Material Co., Ltd.

[0021] Examples 1-3 provide a low-temperature, low-slag phosphating agent and its preparation method.

[0022] Example 1 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28 parts of main salt component, 2.5 parts of composite complexing agent, 1.2 parts of synergistic promoter, 0.3 parts of corrosion inhibitor and stabilizer, 0.2 parts of fluoride, 0.1 parts of pH adjuster, and 80 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 5 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 10:3; the composite complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid in a mass ratio of 4:2:1; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0023] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 1 hour at a stirring speed of 200 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1:2:20. (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 30 min at room temperature with an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz. Then add polyvinylpyrrolidone and stir for 20 min at room temperature with a stirring speed of 300 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 12 h at a vacuum degree of -0.09 MPa and a temperature of 60 °C. Grind it through a 300-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2:0.3 and the K value of polyvinylpyrrolidone is 30.

[0024] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 400 rpm for 20 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 300 rpm for 30 minutes at room temperature, then ultrasonically disperse at 120 W and 60 kHz for 10 minutes. Add a pH adjuster to adjust the pH of the system to 2.5, stir at 300 rpm for 30 minutes, and let stand for 10 minutes at room temperature until homogeneous. Remove impurities by passing through a 300-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0025] Example 2 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 32 parts of main salt component, 4.5 parts of composite complexing agent, 2.2 parts of synergistic promoter, 0.6 parts of corrosion inhibitor and stabilizer, 0.6 parts of fluoride, 0.3 parts of pH adjuster, and 90 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 7 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 11:4; the composite complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid in a mass ratio of 7:2.5:2; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0026] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at 300 rpm for 1.5 h at room temperature to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1.1:2.5:25; (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 40 min at room temperature with an ultrasonic power of 110 W and an ultrasonic frequency of 60 kHz. Then add polyvinylpyrrolidone and stir for 25 min at room temperature with a stirring speed of 400 rpm. Pass the mixture through a 400-mesh filter and wash it with deionized water 4 times. Collect the solid product and vacuum dry it for 15 h at a vacuum degree of -0.09 MPa and a temperature of 65 °C. Grind it through a 350-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:4:0.6 and the K value of polyvinylpyrrolidone is 30.

[0027] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 500 rpm for 30 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 400 rpm for 35 minutes at room temperature, then ultrasonically disperse for 12 minutes at an ultrasonic power of 135 W and an ultrasonic frequency of 80 kHz. Add a pH adjuster to adjust the pH of the system to 3.2, stir at 400 rpm for 30 minutes, and let stand for 12 minutes at room temperature until homogeneous. Remove impurities by passing through a 350-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0028] Example 3 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 35 parts of main salt component, 5.5 parts of composite complexing agent, 3.5 parts of synergistic promoter, 0.9 parts of corrosion inhibitor and stabilizer, 0.8 parts of fluoride, 0.5 parts of pH adjuster, and 120 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 8 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 12:5; the composite complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid in a mass ratio of 9:3:3; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0029] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 2 hours at a stirring speed of 400 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1.2:3:30; (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 50 min at room temperature with an ultrasonic power of 120 W and an ultrasonic frequency of 80 kHz. Then add polyvinylpyrrolidone and stir for 30 min at room temperature with a stirring speed of 500 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 18 h at a vacuum degree of -0.09 MPa and a temperature of 70 °C. Grind it through a 400-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:5:1 and the K value of polyvinylpyrrolidone is 30.

[0030] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 600 rpm for 40 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 500 rpm for 40 minutes at room temperature, then ultrasonically disperse at 150 W and 100 kHz for 15 minutes. Add a pH adjuster to adjust the pH of the system to 4.0, stir at 500 rpm for 30 minutes, and let stand for 15 minutes at room temperature until homogeneous. Remove impurities by passing through a 400-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0031] Comparative Example 1 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28 parts of main salt component, 2.5 parts of composite complexing agent, 1.2 parts of synergistic promoter, 0.3 parts of corrosion inhibitor and stabilizer, 0.2 parts of fluoride, 0.1 parts of pH adjuster, and 80 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 5 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 3:10; the composite complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid in a mass ratio of 4:2:1; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0032] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 1 hour at a stirring speed of 200 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1:2:20. (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 30 min at room temperature with an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz. Then add polyvinylpyrrolidone and stir for 20 min at room temperature with a stirring speed of 300 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 12 h at a vacuum degree of -0.09 MPa and a temperature of 60 °C. Grind it through a 300-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2:0.3 and the K value of polyvinylpyrrolidone is 30.

[0033] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 400 rpm for 20 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 300 rpm for 30 minutes at room temperature, then ultrasonically disperse at 120 W and 60 kHz for 10 minutes. Add a pH adjuster to adjust the pH of the system to 2.5, stir at 300 rpm for 30 minutes, and let stand for 10 minutes at room temperature until homogeneous. Remove impurities by passing through a 300-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0034] Comparative Example 2 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28 parts of main salt component, 2.5 parts of composite complexing agent, 1.2 parts of synergistic promoter, 0.3 parts of corrosion inhibitor and stabilizer, 0.2 parts of fluoride, 0.1 parts of pH adjuster, and 80 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 3 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 10:3; the composite complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid in a mass ratio of 4:2:1; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0035] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 1 hour at a stirring speed of 200 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1:2:20. (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 30 min at room temperature with an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz. Then add polyvinylpyrrolidone and stir for 20 min at room temperature with a stirring speed of 300 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 12 h at a vacuum degree of -0.09 MPa and a temperature of 60 °C. Grind it through a 300-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2:0.3 and the K value of polyvinylpyrrolidone is 30.

[0036] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 400 rpm for 20 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 300 rpm for 30 minutes at room temperature, then ultrasonically disperse at 120 W and 60 kHz for 10 minutes. Add a pH adjuster to adjust the pH of the system to 2.5, stir at 300 rpm for 30 minutes, and let stand for 10 minutes at room temperature until homogeneous. Remove impurities by passing through a 300-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0037] Comparative Example 3 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28 parts of main salt component, 2.5 parts of composite complexing agent, 1.2 parts of synergistic promoter, 0.3 parts of corrosion inhibitor and stabilizer, 0.2 parts of fluoride, 0.1 parts of pH adjuster, and 80 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 10 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 10:3; the composite complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid in a mass ratio of 4:2:1; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0038] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 1 hour at a stirring speed of 200 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1:2:20. (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 30 min at room temperature with an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz. Then add polyvinylpyrrolidone and stir for 20 min at room temperature with a stirring speed of 300 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 12 h at a vacuum degree of -0.09 MPa and a temperature of 60 °C. Grind it through a 300-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2:0.3 and the K value of polyvinylpyrrolidone is 30.

[0039] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 400 rpm for 20 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 300 rpm for 30 minutes at room temperature, then ultrasonically disperse at 120 W and 60 kHz for 10 minutes. Add a pH adjuster to adjust the pH of the system to 2.5, stir at 300 rpm for 30 minutes, and let stand for 10 minutes at room temperature until homogeneous. Remove impurities by passing through a 300-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0040] Comparative Example 4 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28 parts of main salt component, 2.5 parts of composite complexing agent, 1.2 parts of synergistic promoter, 0.3 parts of corrosion inhibitor and stabilizer, 0.2 parts of fluoride, 0.1 parts of pH adjuster, and 80 parts of deionized water; wherein, the total mass of aminotrimethylene phosphonic acid and sodium zirconium lactate in the main salt component is 5 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylene phosphonic acid to sodium zirconium lactate is 10:3; the composite complexing agent is composed of hydroxyethylidene diphosphonic acid and aminotrimethylene phosphonic acid in a mass ratio of 2:1; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0041] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 1 hour at a stirring speed of 200 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1:2:20. (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 30 min at room temperature with an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz. Then add polyvinylpyrrolidone and stir for 20 min at room temperature with a stirring speed of 300 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 12 h at a vacuum degree of -0.09 MPa and a temperature of 60 °C. Grind it through a 300-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2:0.3 and the K value of polyvinylpyrrolidone is 30.

[0042] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 400 rpm for 20 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 300 rpm for 30 minutes at room temperature, then ultrasonically disperse at 120 W and 60 kHz for 10 minutes. Add a pH adjuster to adjust the pH of the system to 2.5, stir at 300 rpm for 30 minutes, and let stand for 10 minutes at room temperature until homogeneous. Remove impurities by passing through a 300-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0043] Comparative Example 5 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28 parts of main salt component, 2.5 parts of composite complexing agent, 1.2 parts of synergistic promoter, 0.3 parts of corrosion inhibitor and stabilizer, 0.2 parts of fluoride, 0.1 parts of pH adjuster, and 80 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 5 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 10:3; the composite complexing agent is composed of sodium gluconate and aminotrimethylenephosphonic acid in a mass ratio of 4:1; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0044] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 1 hour at a stirring speed of 200 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1:2:20. (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 30 min at room temperature with an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz. Then add polyvinylpyrrolidone and stir for 20 min at room temperature with a stirring speed of 300 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 12 h at a vacuum degree of -0.09 MPa and a temperature of 60 °C. Grind it through a 300-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2:0.3 and the K value of polyvinylpyrrolidone is 30.

[0045] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 400 rpm for 20 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 300 rpm for 30 minutes at room temperature, then ultrasonically disperse at 120 W and 60 kHz for 10 minutes. Add a pH adjuster to adjust the pH of the system to 2.5, stir at 300 rpm for 30 minutes, and let stand for 10 minutes at room temperature until homogeneous. Remove impurities by passing through a 300-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0046] Comparative Example 6 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28 parts of main salt component, 2.5 parts of composite complexing agent, 1.2 parts of synergistic promoter, 0.3 parts of corrosion inhibitor and stabilizer, 0.2 parts of fluoride, 0.1 parts of pH adjuster, and 80 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 5 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 10:3; the composite complexing agent is composed of sodium gluconate and hydroxyethylidene diphosphonic acid in a mass ratio of 4:2; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0047] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 1 hour at a stirring speed of 200 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1:2:20. (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 30 min at room temperature with an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz. Then add polyvinylpyrrolidone and stir for 20 min at room temperature with a stirring speed of 300 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 12 h at a vacuum degree of -0.09 MPa and a temperature of 60 °C. Grind it through a 300-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2:0.3 and the K value of polyvinylpyrrolidone is 30.

[0048] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 400 rpm for 20 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 300 rpm for 30 minutes at room temperature, then ultrasonically disperse at 120 W and 60 kHz for 10 minutes. Add a pH adjuster to adjust the pH of the system to 2.5, stir at 300 rpm for 30 minutes, and let stand for 10 minutes at room temperature until homogeneous. Remove impurities by passing through a 300-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0049] Comparative Example 7 A low-temperature, low-slag phosphating agent comprises the following raw materials in parts by weight: 28 parts of main salt component, 2.5 parts of composite complexing agent, 1.2 parts of synergistic promoter, 0.3 parts of corrosion inhibitor and stabilizer, 0.2 parts of fluoride, 0.1 parts of pH adjuster, and 80 parts of deionized water; wherein, the total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 5 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 10:3; the composite complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylenephosphonic acid in a mass ratio of 4:2:1; the synergistic promoter is hydroxylamine sulfate; the fluoride is potassium fluoroborate; and the pH adjuster is phosphorous acid.

[0050] The preparation method of the corrosion inhibitor includes the following steps: (1) Add cerium nitrate and phytic acid to deionized water and stir at room temperature for 1 hour at a stirring speed of 200 rpm to obtain a rare earth-phytic acid complex solution, wherein the mass ratio of cerium nitrate, phytic acid and deionized water is 1:2:20. (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, and ultrasonically disperse it for 30 min at room temperature with an ultrasonic power of 100 W and an ultrasonic frequency of 40 kHz. Then add polyvinylpyrrolidone and stir for 20 min at room temperature with a stirring speed of 300 rpm. Pass the mixture through a 300-mesh filter and wash it three times with deionized water. Collect the solid product and vacuum dry it for 12 h at a vacuum degree of -0.09 MPa and a temperature of 60 °C. Grind it through a 300-mesh sieve to obtain a corrosion inhibitor stabilizer. The mass ratio of the rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2:0.3 and the K value of polyvinylpyrrolidone is 60.

[0051] A method for preparing a low-temperature, low-slag phosphating agent includes the following preparation steps; Add the main salt component to deionized water and stir at 400 rpm for 20 minutes at room temperature until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir at 300 rpm for 30 minutes at room temperature, then ultrasonically disperse at 120 W and 60 kHz for 10 minutes. Add a pH adjuster to adjust the pH of the system to 2.5, stir at 300 rpm for 30 minutes, and let stand for 10 minutes at room temperature until homogeneous. Remove impurities by passing through a 300-mesh filter to obtain a low-temperature, low-slag phosphating agent.

[0052] Performance testing The performance of the low-temperature, low-slag phosphating agents prepared in Examples 1-3 and Comparative Examples 1-7 of this application was determined, and the specific test contents are as follows: The low-temperature, low-slag phosphating agents obtained in Examples 1-3 and Comparative Examples 1-7 were respectively mixed with water at a mass ratio of 1:20 to prepare phosphating working solutions. The metal workpiece surfaces were treated in accordance with the national standard GB / T 6807-2001 "Technical Conditions for Phosphating Treatment of Steel Workpieces Before Coating". Phosphating sludge volume: Take 1 L (V) of phosphating working solution and continuously treat standard test pieces at 35℃ for 1 h; filter the solution with known mass of quantitative filter paper, and pre-dry the filter paper to constant weight (m1); dry the filter residue in an oven at 105℃ to constant weight, and weigh the total mass of filter paper + sludge (m2); calculate the sludge volume according to the formula: Sludge volume (g / L) = (m2−m1) / V; Phosphate film thickness: Tested on standard cold-rolled steel plates in accordance with the national standard GB / T 6462-2025 "Measuring the thickness of metal and oxide coatings by microscopy". Neutral salt spray test: Phosphated test pieces were prepared according to the national standard GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The test solution was 5% NaCl solution, pH 6.5-7.2, the test temperature was 35℃, and continuous spraying was performed. The time when the test piece first showed corrosion was observed and recorded in hours. Phosphating film adhesion: Referring to the national standard GB / T 9286-2021 "Cross-cut test for paints and varnishes", a 1mm × 1mm grid was drawn on the phosphate film surface using a cross-cut tester, for a total of 100 grids; 3M 600 tape was then applied tightly and quickly peeled off; rating was based on the area of ​​peeling. Level 0 / 1: No peeling or very slight peeling; Level 2 and above: Large area peeling or complete peeling; Phosphating agent stability: The low-temperature, low-slag phosphating agents prepared in Examples 1-3 and Comparative Examples 1-7 were placed in sealed containers and kept at room temperature for 72 hours. The appearance changes were observed and rated as four levels: Grade A: no layering, no turbidity; Grade B: no layering, slight turbidity; Grade C: slight layering, obvious turbidity; Grade D: obvious layering, obvious turbidity. The specific test results are shown in Table 1.

[0053] Table 1 Performance test results of the low-temperature, low-slag phosphating agents prepared in Examples 1-3 and Comparative Examples 1-7 As shown in Table 1, the low-temperature, low-slag phosphating agents prepared in Examples 1-3 of this application exhibit excellent comprehensive performance, with low phosphating sludge content; uniform and dense phosphating film formation; excellent neutral salt spray corrosion resistance; strong adhesion of the phosphating film; and strong bonding with the metal surface. Furthermore, the products demonstrate good stability at room temperature, without stratification or turbidity. The synergistic effect of the formulation and process used in this application achieves low-slag, high-efficiency, and stable phosphating results.

[0054] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A low-temperature, low-slag phosphating agent, characterized in that, The raw materials include the following parts by weight: 28-35 parts of main salt, 2.5-5.5 parts of complexing agent, 1.2-3.5 parts of synergistic promoter, 0.3-0.9 parts of corrosion inhibitor and stabilizer, 0.2-0.8 parts of fluoride, 0.1-0.5 parts of pH adjuster, and 80-120 parts of deionized water; The main salt components include aminotrimethylenephosphonic acid, sodium zirconium lactate, and ammonium phosphomolybdate.

2. The low-temperature, low-slag phosphating agent according to claim 1, characterized in that, The total mass of aminotrimethylenephosphonic acid and sodium zirconium lactate in the main salt component is 5-8 times the mass of ammonium phosphomolybdate, and the mass ratio of aminotrimethylenephosphonic acid to sodium zirconium lactate is 10-12:3-5.

3. The low-temperature, low-slag phosphating agent according to claim 1, characterized in that, The complexing agent is composed of sodium gluconate, hydroxyethylidene diphosphonic acid, and aminotrimethylene phosphonic acid in a mass ratio of 4-9:2-3:1-3.

4. The low-temperature, low-slag phosphating agent according to claim 1, characterized in that, The synergistic promoter is one or more of hydroxylamine sulfate, sodium m-nitrobenzenesulfonate, and sodium chlorate.

5. The low-temperature, low-slag phosphating agent according to claim 1, characterized in that, The method for preparing the corrosion inhibitor includes the following preparation steps: (1) Add cerium nitrate and phytic acid to deionized water and stir for 1-2 hours to obtain a rare earth-phytic acid complex solution; (2) Add nano-tungsten disulfide to the rare earth-phytic acid complex solution, ultrasonically disperse for 30-50 min, add polyvinylpyrrolidone, continue stirring for 20-30 min, filter, wash with deionized water, collect the solid product, vacuum dry for 12-18 h, grind and sieve to obtain corrosion inhibitor stabilizer.

6. The low-temperature, low-slag phosphating agent according to claim 5, characterized in that, In step (1), the mass ratio of cerium nitrate, phytic acid and deionized water is 1-1.2:2-3:20-30.

7. The low-temperature, low-slag phosphating agent according to claim 5, characterized in that, In step (2), the mass ratio of rare earth-phytic acid complex solution, nano-tungsten disulfide and polyvinylpyrrolidone is 100:2-5:0.3-1.

8. The low-temperature, low-slag phosphating agent according to claim 5, characterized in that, The K value of the polyvinylpyrrolidone is in the range of 25-40.

9. The low-temperature, low-slag phosphating agent according to claim 1, characterized in that, The fluoride is one or more of sodium fluoride, potassium fluoroborate, ammonium fluoride, and ammonium bifluoride; the pH adjuster is phosphorous acid.

10. A method for preparing a low-temperature, low-slag phosphating agent as described in any one of claims 1-9, characterized in that, The preparation steps include the following; Add the main salt component to deionized water and stir until homogeneous to obtain a main salt mixture. Add the composite complexing agent, synergistic promoter, fluoride, and corrosion inhibitor to the main salt mixture in sequence. Stir for 30-40 minutes, then ultrasonically disperse for 10-15 minutes. Add a pH adjuster to adjust the pH of the system to 2.5-4.0, stir until homogeneous, let stand for 10-15 minutes, and filter to obtain a low-temperature, low-slag phosphating agent.

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