Self-repairing chromium-free passivator, preparation method thereof and application of passivator in field of corrosion prevention of alloy workpieces

Abstract

The invention discloses a self-repairing chromium-free passivator, a preparation method thereof and application of the passivator in the field of corrosion prevention of alloy workpieces. The passivating agent is composed of a bifunctional silane coupling agent, a fluoride-free inorganic film-forming agent, an organic film-forming agent, a corrosion inhibition synergistic system, a nano-composite reinforcing system, self-repairing microcapsules, an anti-biological adhesion component and a functional auxiliary agent. The problems that an existing passivating agent contains chromium or fluorine, environmental protection risks exist, the self-repairing function is lost, a base material is corroded, and the process efficiency is low are solved. The passivating agent is free of chromium and fluorine, the adhesive force of the passivating agent and a zincizing / multi-component alloy co-permeation layer is larger than or equal to 7 MPa, the neutral salt mist resistance is larger than or equal to 1700 h, the self-repairing efficiency after a film layer is damaged is larger than or equal to 85%, the single-batch period of the preparation technology is smaller than 1 h, and the passivating agent is suitable for large-scale application in severe scenes such as railways and oceans.

Description

Technical Field

[0001] This invention belongs to the field of self-healing passivating agent technology, specifically relating to a self-healing chromium-free passivating agent, its preparation method, and its application in the field of corrosion protection of alloy workpieces. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Zinc diffusion and multi-alloy co-diffusion technologies have become core anti-corrosion pretreatment methods for steel workpieces in railway, marine, and other fields due to their advantages such as "tight metallurgical bonding and no risk of hydrogen embrittlement." However, existing chromium-free passivation technologies suitable for such workpieces still face the following key technical bottlenecks: 1. Conflict between environmental protection and compatibility: Passivating agents using trivalent chromium salts (such as patents CN111394688A, CN111893473B, CN119800343A, CN118308712A, CN111270231A, etc.), although less toxic than hexavalent chromium, still do not meet the stringent "chromium-free" requirements of EU RoHS 2.0, limiting their application scenarios; while chromium-free passivating agents mostly use fluorinated film-forming agents such as ammonium bifluoride and sodium fluorosilicate (such as patents CN111893473B, CN119800343A), the fluoride ions released during use can easily cause cumulative pollution of soil / water bodies, and react with high magnesium multi-element co-permeable layers (Zn-Al-Mg) to form MgF2 precipitate, causing the film adhesion to drop below 4MPa; in addition, some existing passivating agents require acid washing pretreatment (hydrochloric acid / Sulfuric acid produces acidic wastewater containing heavy metal ions, which is not only costly to treat but also does not meet the environmental protection requirements of "zero discharge".

[0004] 2. Poor corrosion resistance, toughness, and marine compatibility: Chromium-free systems (such as patent CN111270231A) can only withstand neutral salt spray for 500 hours; organic resin systems (such as patent CN110983244A) show long-term corrosion resistance degradation (localized corrosion after >1500 hours); passivating agents for multi-component co-diffusion components (such as patent CN117888097A) can withstand salt spray for 1200 hours, but have poor alkali resistance (weight loss >30% after 168 hours of 5% NaOH immersion); and most existing passivating agents (such as patent CN114703470B) do not take into account marine organism attachment, which will accelerate localized corrosion (refer to patents CN119039818A, CN113292912A).

[0005] 3. Poor stability of nano-components: Although existing passivating agents containing nano-components (such as patent CN113430507B) use nano-components such as nano-SiO2, the dispersion problem has not been solved: the nano-component SiO2 agglomerates after 3 months of storage, and graphene is expensive (>800 yuan / kg) and easy to settle, which limits its large-scale application.

[0006] 4. Lack of self-healing function: Most existing "self-healing" passivating agents do not have a clear repair mechanism (such as patent CN119800343A), and most systems (such as patents CN111270231A and CN117888097A) cannot actively block corrosion after the film layer is damaged. Summary of the Invention

[0007] In summary, existing passivating agents still have shortcomings such as failing to meet environmental standards, being unsuitable for special climates and marine conditions, and some having unstable components and lacking self-healing capabilities. To address these shortcomings, this invention provides a chromium-free passivation system that is "fluorine-free, acid-free, self-healing, highly efficient, and easily mass-producible," balancing environmental friendliness, long-lasting effectiveness, and industrial applicability. The relevant solution is as follows: In a first aspect, the present invention provides a self-healing chromium-free passivating agent, wherein the raw materials of the passivating agent are the following components in parts by weight: The composition includes 8-12 parts of a bifunctional silane coupling agent, 3-5 parts of a fluorine-free inorganic film-forming agent, 12-18 parts of an organic film-forming agent, 3-7 parts of a corrosion-inhibiting synergistic system, 1.5-2.5 parts of a nanocomposite reinforcing system, 1-2 parts of a self-healing functional component, 0.5-1 part of an anti-bioadhesion component, 2-6 parts of a buffer system, and 50-65 parts of deionized water.

[0008] The molecular structure of silane coupling agents is generally YR-Si(OR)3, where Y is an organic functional group, and common functional groups include, but are not limited to, vinyl, amino, epoxy, mercapto, and methacryloyloxysilanes; R is an alkylene chain (such as -CH2CH2CH2-) connecting Y and silicon atoms, which separates the organic group Y and the siloxy group, reducing mutual interference between them, while ensuring the flexibility of the molecular chain. The bifunctional silane coupling agent mentioned in the first aspect above is a combination of silane coupling agents in which the Y group is composed of two different organic functional groups. In a more effective embodiment, the organic functional groups are amino and epoxy. In one example of the above embodiments, the bifunctional silane coupling agent is a mixture of aminosilane (KH-550) and epoxysilane (KH-560) at a dosage ratio of 1:0.8~1.2.

[0009] The aforementioned fluorine-free inorganic film-forming agent preferably uses an inorganic salt containing zirconium and / or lanthanum. Examples of zirconium-containing inorganic salts include zirconium silicate, zirconium phosphate, zirconium nitrate, or zirconium oxide. Examples of lanthanum-containing inorganic salts include lanthanum sulfate, lanthanum nitrate, lanthanum chloride, and lanthanum oxide. In one embodiment verified by this invention, the fluorine-free inorganic film-forming agent is a mixture of zirconium phosphate and zirconium oxide in a mass ratio of 3-4:0.5-1. In this embodiment, the zirconium phosphate (Zr3(PO4)4) has a particle size of 50-100 nm and a purity ≥99.9%, and the lanthanum oxide (La2O3) has a particle size of 20-50 nm and a rare earth purity ≥99.9%.

[0010] The above-mentioned organic film-forming agent is a hydroxyl-modified waterborne acrylic resin with a number-average molecular weight of 3000~5000 Da and a hydroxyl value of 50~80 mgKOH / g.

[0011] The above-mentioned corrosion inhibition synergistic system is a combination of ammonium molybdate and phytic acid in a mass ratio of 2~4:1~3, wherein the purity of ammonium molybdate is ≥99% and the water solubility is >95%, and the phytic acid is an aqueous solution with a mass fraction of 40~60%, wherein the content of phosphoric acid should be ≤0.5%.

[0012] The aforementioned nanocomposite reinforcement system is a combination of silane-modified graphene and nano-silica at a mass ratio of 0.5~1:1~1.5. The silane-modified graphene sheets have a thickness of 0.8~1.2 nm and a modification rate >80%, while the nano-silica has a particle size of 2~5 nm and a specific surface area >200 m² / g. This invention has found that mixing silane-modified graphene and nano-silica can form a "core-shell structure," the passivating agent powder does not agglomerate after storage for more than 6 months, the amount of graphene used is reduced by 50%, and using some silica to replace graphene can further reduce the film defect rate to <0.5%.

[0013] The above-mentioned self-healing functional component is a self-made polyurea-encapsulated ammonium molybdate microcapsule. The preparation process is as follows: the aqueous phase is dropped into the oil phase, and a fine emulsion is obtained by high-speed shearing. The mixture is stirred and reacted at 40~60 ℃ for 2~4 h under an inert atmosphere to form a polyurea shell at the interface. The solid part is retained by centrifugation, and the mixture is washed and dried to obtain the polyurea-encapsulated ammonium molybdate microcapsule. The aqueous phase is an aqueous solution of ammonium molybdate (0.6~0.8 g / mL) and ethylenediamine (0.1~0.2 g / mL) (pH 8~9); the oil phase is a mixed solution of ethyl acetate of hexamethylene diisocyanate (0.2~0.4 g / mL), Span-80 (0.02~0.08 g / mL), Tween-80 (0.01~0.03 g / mL), and hexadecane (0.02~0.04 g / mL).

[0014] The preferred anti-bioattachment component is low molecular weight chitosan with a molecular weight of 5000-8000 Da and a degree of deacetylation >90%. The pH buffer and wetting system described above is a mixture of acetate-sodium acetate buffer and sodium dodecylbenzenesulfonate, with a mass ratio of 2~5:0.3~0.8. The acetate-sodium acetate buffer has a concentration of 0.1~0.3 mol / L and a pH of 4.5~5.5. The buffer also includes anionic surfactants, preferably sulfonates, including but not limited to sodium dodecylbenzenesulfonate. α - One of olefin sulfonates and alkyl naphthalene sulfonates, in one embodiment verified by the present invention, the anionic surfactant is sodium dodecylbenzene sulfonate with a purity ≥98% and a surface tension ≤30mN / m.

[0015] In one embodiment of the first aspect described above, the raw materials of the passivating agent are the following components in parts by weight: 8-12 parts of bifunctional silane coupling agent, 3-4 parts of zirconium phosphate, 0.5-1 parts of lanthanum oxide, 12-18 parts of hydroxyl-modified waterborne acrylic resin, 2-4 parts of ammonium molybdate, 1-3 parts of phytic acid, 0.5-1 parts of silane-modified graphene, 1-1.5 parts of nano-silica, 1-2 parts of polyurea-encapsulated ammonium molybdate microcapsules, 0.5-1 parts of low molecular weight chitosan, 2-5 parts of acetate-sodium acetate buffer solution, 0.3-0.8 parts of sodium dodecylbenzenesulfonate, and 50-65 parts of deionized water.

[0016] In this embodiment, the preparation method of the self-healing chromium-free passivating agent includes the following steps: S1: Add water to the continuous reaction vessel, start stirring and add the buffer system until completely dissolved to obtain the wetting solution; S2: Add zirconium phosphate, lanthanum oxide and ammonium molybdate to the wetting solution, heat to 40~60℃, stir for 20~40min to ensure that the solid components are completely dissolved, and obtain the inorganic precursor solution; S3: Reduce the temperature of the above inorganic precursor liquid to 40°C or below, add bifunctional silane coupling agent, hydroxyl-modified waterborne acrylic resin, silane-modified graphene, and nano-silica, and continue stirring to obtain a composite system. S4: Add phytic acid, polyurea-encapsulated ammonium molybdate microcapsules, and low molecular weight chitosan to the above composite system, ultrasonically disperse for 5-20 minutes, heat to 45-55℃, let stand for 10-20 minutes, and filter to obtain the final product.

[0017] In a second aspect, the present invention provides the application of the self-healing chromium-free passivating agent described in the first aspect in the field of corrosion protection of alloy workpieces.

[0018] Furthermore, the aforementioned alloy workpieces are zinc-dipped parts or multi-element alloy co-dipped parts, and their applications include, but are not limited to, rail transit such as railways, power facilities, communication facilities, engineering machinery parts, steel structural components for buildings, ships, offshore facilities, aerospace and other fields.

[0019] In the field of rail transit, the above-mentioned passivating agents can be used for rail embedded parts, bolts, nuts, rail fasteners (such as elastic clips and pads), etc.

[0020] In the field of rail transit, the above-mentioned passivating agents can be used in subway engineering for track bolts, embedded parts and contact wire hardware (such as cable trays and signal equipment).

[0021] In the field of power facilities, the above-mentioned passivating agents can be used in power tower components, cable trays, transmission line fittings, etc.

[0022] In the field of communication equipment, the above-mentioned passivating agents can be used in signal equipment and line fittings (such as clamps and cable reels).

[0023] In the field of engineering machinery parts, the above-mentioned passivating agents can be used in bearings, gears, and internal components of chemical equipment towers (such as float valves and packing).

[0024] In the field of steel structures for construction, the above-mentioned passivating agents can be used for construction scaffolding, hardware (such as steel nails and Maanshan Iron & Steel fasteners), anchor bolts, etc., or bridge bearing plates, embedded U-bolts, anti-fall beam blocks, hanging fence supports, etc.

[0025] In the shipbuilding industry, the aforementioned passivating agents can be used in ship fasteners, anchor chains, etc.

[0026] In the field of offshore facilities, the aforementioned passivating agents can be used for related workpieces in offshore oil fields.

[0027] In the aerospace field, the aforementioned passivating agents can be used in rocket launchers, aircraft fasteners, and other applications.

[0028] In one embodiment of the above application, when the alloy workpiece is a thin-walled workpiece, the passivating agent is used as follows: the alloy workpiece to be treated is immersed in an acid-free activating solution at room temperature for 15-20 seconds, and then transferred to the passivating agent described in the first aspect for immersion at a immersion temperature of 40-50°C for 15-25 minutes. After that, it is dried at 75-85°C for 10-20 minutes to form a passivation film on the surface of the workpiece.

[0029] In another embodiment of the above application, when the alloy workpiece is a thick-walled workpiece, the passivating agent is applied as follows: immerse the workpiece in an acid-free activating solution at room temperature for 15-20 seconds, then spray it 2-3 times with a 5-minute interval between each spray. After spraying, place the workpiece in an environment of 40-60℃ for 10-20 minutes, and then transfer it to a drying equipment to dry at 85-95℃ for 15-25 minutes.

[0030] In another embodiment of the above application, when the alloy workpiece is a complex structure workpiece, the passivating agent is applied as follows: the workpiece to be treated is sprayed with an acid-free activating solution under high pressure (0.1~0.3MPa) for 10~15s, with special attention paid to the weld and blind holes to avoid residue. This can be done by immersing the workpiece in the passivating agent and then spraying the key parts. After spraying, the workpiece is placed in an environment of 40~50℃ and left to stand for 20~30min, and then transferred to a drying equipment and dried at 80~90℃ for 15~20min.

[0031] In the above embodiments, the acid-free activation solution is a solution of sodium silicate (mass fraction 1~3%) and fatty alcohol polyoxyethylene ether-9 (mass fraction 0.3~0.6%).

[0032] Compared with the prior art, the beneficial effects of the present invention are: 1. Significantly improved environmental performance: fluorine-free (zirconium phosphate replaces potassium fluorozirconate), acid-free (acid-free pretreatment replaces acid washing), chemical oxygen demand ≤20mg / L, fluoride ion content <0.001%, compliant with EU RoHS 2.0 and GB / T 38405-2020, and produces no acid washing wastewater, reducing treatment costs by 20%.

[0033] 2. Improved stability and cost optimization: This invention uses silane-modified graphene and nano-silica to form a "core-shell structure". After 6 months of storage, there is no agglomeration, the film defect rate is <0.5%, the amount of graphene used is significantly reduced, and the raw material cost is greatly reduced.

[0034] 3. Enhanced substrate protection and compatibility: Acid-free pretreatment results in a diffusion layer thickness loss of ≤1μm. Zirconium phosphate and lanthanum oxide work synergistically to adapt to the high magnesium co-diffusion layer, improving adhesion to over 7MPa.

[0035] 4. Dual function of self-repair and anti-biofouling: After the microcapsule is damaged, it releases ammonium molybdate, which forms a repair film within 24 hours, restoring the salt spray resistance to more than 85% of the original performance; chitosan inhibits more than 90% of marine bacteria (pseudomonas) and algae from attaching, thus extending the corrosion resistance life in marine environments by 50%.

[0036] 5. Improved mass production efficiency: The continuous process has a single batch cycle of <1 hour (original plan >2 hours), with a daily production capacity of 1500L, which is suitable for the mass production demand of tens of thousands of railway fasteners per day. Detailed Implementation

[0037] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0038] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0039] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0040] Example 1 In this embodiment, a self-healing chromium-free passivating agent for zinc-plated railway fasteners is provided, comprising the following components (by weight): The composition includes: 10 parts of bifunctional silane coupling agent (KH-550:KH-560=1:1), 3.5 parts of zirconium phosphate, 0.8 parts of lanthanum oxide, 15 parts of hydroxyl-modified waterborne acrylic resin, 3 parts of ammonium molybdate, 2 parts of phytic acid, 0.8 parts of silane-modified graphene, 1.2 parts of nano-silica, 1.5 parts of polyurea-encapsulated ammonium molybdate microcapsules, 0.7 parts of low molecular weight chitosan, 3 parts of acetate-sodium acetate buffer solution, 0.5 parts of sodium dodecylbenzenesulfonate, and 58 parts of deionized water.

[0041] Based on the above-mentioned parts by mass of each raw material, the preparation method of this passivating agent includes the following steps: 1. Add deionized water to the continuous reactor, start stirring (300 r / min), add acetate-sodium acetate buffer to adjust the pH to 4.5~5.5, then add sodium dodecylbenzenesulfonate and stir for 10 min until completely dissolved to obtain a wetting solution. 2. Add zirconium phosphate, lanthanum oxide, and ammonium molybdate to the above system, heat to 50°C, and stir for 30 min (500 r / min) to ensure that the solid components are completely dissolved to obtain the inorganic precursor solution; 3. Cool down to 40℃, then add bifunctional silane coupling agent, hydroxyl-modified waterborne acrylic resin, silane-modified graphene, and nano-silica in sequence, and stir for 60 min (400 r / min) to form a composite system. 4. Add phytic acid, polyurea-encapsulated ammonium molybdate microcapsules, and low molecular weight chitosan to the composite system. Disperse the mixture by first stirring at low speed and then shearing at high speed. Then, keep it at 50°C for 15 minutes and filter it through a 100-mesh filter to obtain a self-healing chromium-free passivating agent (single batch preparation cycle < 1 hour).

[0042] The preparation method of the polyurea-encapsulated ammonium molybdate microcapsules is as follows: First, 12-16 g of ammonium molybdate and 3 g of ethylenediamine are dissolved in 20 mL of deionized water and the pH is adjusted to 8-9 to prepare an aqueous phase. Separately, 8 g of hexamethylene diisocyanate, 1.5 g of Span-80, 0.5 g of Tween-80, and 0.8 g of hexadecane are dissolved in 30 mL of ethyl acetate to prepare an oil phase. Then, the aqueous phase is added dropwise to the oil phase and subjected to high shear at 10000-12000 rpm for 30 minutes to prepare a 50-100 nm fine emulsion. This emulsion is then transferred to a four-necked flask and stirred for 3 hours at 50 °C under nitrogen protection to allow interfacial polymerization and the formation of a polyurea shell. Finally, the mixture is centrifuged at 4000 rpm, washed alternately with ethanol and water, and vacuum dried at 40 °C for 8 hours to obtain nanoscale polyurea-encapsulated ammonium molybdate microcapsules with a particle size of 50-100 nm and a core material content of 30%-40%.

[0043] Example 2 In this embodiment, a self-healing chromium-free passivating agent for multi-element co-permeable marine components is provided. The difference between this passivating agent and the one in Example 1 is that the raw materials and components (by mass) of the passivating agent in this embodiment are as follows: The amount of hydroxyl-modified waterborne acrylic resin was increased to 18 parts (to enhance micropore filling), ammonium molybdate was increased to 4 parts (to strengthen salt spray resistance), low molecular weight chitosan was increased to 1 part (to improve anti-bioadhesion), and polyurea-encapsulated ammonium molybdate microcapsules were increased to 2 parts (to enhance self-healing).

[0044] The remaining components and preparation methods are the same as in Example 1.

[0045] Performance testing I. Testing Methods The performance of the passivating agent in the above embodiments was tested. The metal substrate used in the test was a steel workpiece. The passivating agent was applied to the surface of the steel workpiece by spraying to form a passivation film with a thickness of 3-5 nm.

[0046] 1. Neutral salt spray resistance test The corrosion resistance of the coating was tested using the neutral salt spray test (NSS) method in GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test" 5.2.2. Corrosion signs were observed every 24 hours, and the time of the first corrosion was recorded.

[0047] 2. Adhesion test Referring to GB / T 9286-1998, the passivation film was cut into the substrate by cross-cutting to form a grid pattern, and then adhesive tape was applied for peeling to evaluate the resistance of the passivation film to separation from the substrate.

[0048] 3. Temperature resistance test The temperature cycling test method in GB / T 2423.22-2012 "Environmental Testing - Part 2: Test Methods" adopts the following method for hot and cold cycling: the metal substrate after applying the passivation film is placed at -40℃ (30 min) → room temperature (5 min) → 60℃ (30 min) → room temperature (5 min) as one cycle, and the surface condition of the workpiece is detected after 100 cycles.

[0049] 4. Self-healing performance A 2μm deep scratch was mechanically created on the surface of the passivation film to disrupt its integrity. The scratched area was then subjected to accelerated corrosion using the "1. Neutral salt spray resistance test" to observe whether the scratched area would self-repair. The time of the first corrosion was recorded. After cleaning the corroded area, the workpiece was weighed, and the mass loss of the passivation film layer was recorded.

[0050] 5. Resistance to marine atmospheric corrosion Referring to the marine atmospheric environment simulation method in GB / T 19292.1~4-2018 "Corrosion of metals and alloys, atmospheric corrosion test methods", the corrosion protection performance of the passivation film under real service conditions was evaluated. Salt spray and damp heat cycling were used to record corrosion signs on the sample surface every 24 hours and the time of the first corrosion was recorded.

[0051] 6. Resistance to marine organism attachment Based on the GB / T 5370-2007 standard, observe the signs of bio-attachment on the sample surface, scrape off the attached bio-attachment, dry it and weigh it (g / cm²), compare it with the workpiece without passivating agent, and calculate the bio-attachment rate.

[0052] II. Test Results The passivating agent used for zinc-dipped workpieces in Example 1 above showed no red rust after 1750 h of neutral salt spray resistance testing; adhesion testing (GB / T 9286-1998 cross-cut test) showed that the film layer bond strength with the substrate was as high as 7.2 MPa, and there was no peeling in the cross-cut test; in terms of extreme temperature adaptability, after 100 cycles of thermal cycling from -40℃ to 60℃, the film layer remained intact without cracks; it is particularly noteworthy that it has self-healing ability, when the scratch depth is 2μm, the salt spray resistance can be restored to 1480 h after repair, which is 85% of the original performance; the thickness loss of the zinc-dipped layer after pretreatment is only 0.8μm.

[0053] Example 2 above provides a passivating agent for workpieces in marine environments. Testing showed that it withstood neutral salt spray for up to 1820 hours without producing red rust. In the GB / T 24516-2023 accelerated corrosion test simulating the harsh environment of the South China Sea, it maintained zero corrosion of the substrate for 220 days. This passivating agent also exhibits excellent bioprotective properties, with algae adhesion rates controlled below 10% and shellfish adhesion rates below 5%, significantly superior to similar products. Its bonding strength with the Zn-Al-Mg co-permeation layer reaches 7.5 MPa, and the cross-cut test verified no film detachment, demonstrating its excellent application value in marine engineering equipment, ship corrosion protection, and other fields.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A self-healing chromium-free passivating agent, characterized in that, The passivating agent is composed of the following components in parts by weight: The mixture contains 8-12 parts of a bifunctional silane coupling agent, 3-5 parts of a fluorine-free inorganic film-forming agent, 12-18 parts of an organic film-forming agent, 2-7 parts of a corrosion-inhibiting synergistic system, 0.5-2.5 parts of a nanocomposite reinforcing system, 1-2 parts of a self-healing functional component, 0.5-1 part of an anti-bioadhesion component, 2-6 parts of a buffer system, and 50-65 parts of a solvent.

2. The self-healing chromium-free passivating agent as described in claim 1, characterized in that, The bifunctional silane coupling agent is a mixture of aminosilane and epoxysilane in a dosage ratio of 1:0.8~1.2; The fluorine-free inorganic film-forming agent is a mixture of zirconium phosphate and zirconium oxide in a mass ratio of 3~4:0.5~1; wherein the zirconium phosphate has a particle size of 50~100 nm and a purity ≥ 99.9%, and the lanthanum oxide has a particle size of 20~50 nm and a rare earth purity ≥ 99.9%. The organic film-forming agent is a hydroxyl-modified waterborne acrylic resin with a number-average molecular weight of 3000~5000 Da and a hydroxyl value of 50~80 mgKOH / g.

3. The self-healing chromium-free passivating agent as described in claim 1, characterized in that, The corrosion inhibition synergistic system is a combination of ammonium molybdate and phytic acid in a mass ratio of 2~4:1~3, wherein the purity of ammonium molybdate is ≥ 99.9% and the water solubility is > 95%, and the phytic acid is an aqueous solution with a mass fraction of 40~60%, wherein the content of phosphoric acid should be ≤ 0.5%. The nanocomposite reinforcement system is a combination of silane-modified graphene and nano-silica in a mass ratio of 0.5~1:1~1.5, wherein the silane-modified graphene sheet thickness is 0.8~1.2 nm and the modification rate is >80%, and the nano-silica has a particle size of 2~5 nm and a specific surface area >200 m² / g.

4. The self-healing chromium-free passivating agent as described in claim 1, characterized in that, The self-healing functional component is polyurea-encapsulated ammonium molybdate microcapsules with a particle size of 50-100 nm, and the core material, ammonium molybdate, accounts for 30%-40% of the total composition. The anti-bioattachment component is low molecular weight chitosan with a molecular weight of 5000-8000 Da and a degree of deacetylation >90%; The buffer solution is an acetate-sodium acetate buffer solution with a concentration of 0.1~0.3 mol / L and a pH range of 4.5~5.

5. The buffer solution also includes anionic surfactants, including but not limited to one of sodium dodecylbenzenesulfonate, α-olefin sulfonate, and alkylnaphthalene sulfonate. Further, the anionic surfactant is sodium dodecylbenzenesulfonate with a purity ≥ 98% and a surface tension ≤ 30 mN / m.

5. The self-healing chromium-free passivating agent as described in claim 1, characterized in that, The passivating agent is composed of the following components in parts by weight: 8-12 parts of bifunctional silane coupling agent, 3-4 parts of zirconium phosphate, 0.5-1 part of lanthanum oxide, 12-18 parts of hydroxyl-modified waterborne acrylic resin, 2-4 parts of ammonium molybdate, 1-3 parts of phytic acid, 0.5-1 part of silane-modified graphene, 1-1.5 parts of nano-silica, 1-2 parts of polyurea-encapsulated ammonium molybdate microcapsules, 0.5-1 part of low molecular weight chitosan, 2-5 parts of acetate-sodium acetate buffer solution, 0.3-0.8 parts of sodium dodecylbenzenesulfonate, and 50-65 parts of deionized water; the preparation method of the self-healing chromium-free passivating agent includes the following steps: S1: Add water to the continuous reaction vessel, start stirring and add the buffer system until completely dissolved to obtain the wetting solution; S2: Add zirconium phosphate, lanthanum oxide and ammonium molybdate to the wetting solution, heat to 40~60 ℃, stir for 20~40 min to ensure that the solid components are completely dissolved, and obtain the inorganic precursor solution. S3: Reduce the temperature of the above inorganic precursor liquid to 40 ℃ or below, add bifunctional silane coupling agent, hydroxyl-modified waterborne acrylic resin, silane-modified graphene, and nano-silica, and continue stirring to obtain a composite system. S4: Add phytic acid, polyurea-encapsulated ammonium molybdate microcapsules, and low molecular weight chitosan to the above composite system, ultrasonically disperse for 5-20 min, heat to 45-55 ℃ and age for 10-20 min, then filter to obtain the final product.

6. The application of the self-healing chromium-free passivating agent according to any one of claims 1-5 in the field of corrosion protection of alloy workpieces, characterized in that, The alloy workpiece is a zinc-dipped part or a multi-element alloy co-dipped part, and its application fields include, but are not limited to, railways, rail transit, power facilities, communication facilities, engineering machinery parts, steel structure parts for buildings, ships, offshore facilities or aerospace fields.

7. The application of the self-healing chromium-free passivating agent as described in claim 6 in the field of corrosion protection of alloy workpieces, characterized in that, In the railway sector, the passivating agent is used in rail embedded parts, bolts, nuts, and rail fasteners; In the field of rail transit, the passivating agent is used in track bolts, embedded parts and contact wire fittings in subway engineering, and further, in cable trays and signal equipment; In the field of power facilities, the passivating agent is used in power tower components, cable trays, or transmission line fittings; In the field of communication equipment, the passivating agent is used in signal equipment and line fittings, and further, in clamps and cable reels; In the field of engineering machinery parts, the passivating agent is used in bearings, gears, internal components of chemical equipment towers, and further, in float valves and packings; In the field of steel structures for building construction, the passivating agent is used in building scaffolding, hardware, anchor bolts or bridge bearing plates, embedded U-bolts, anti-fall beam blocks, and hanging fence supports. In the marine industry, the passivating agent is used in marine fasteners and anchor chains; In the field of offshore facilities, the passivating agent is used in related workpieces in offshore oil fields; In the aerospace field, the passivating agent is used in rocket launchers and aircraft fasteners.

8. The application as described in claim 6, characterized in that, When the alloy workpiece is a thin-walled workpiece, the passivating agent is applied as follows: the alloy workpiece to be treated is immersed in an acid-free activating solution at room temperature for 15-20 seconds, and then transferred to the passivating agent described in the first aspect for immersion at a temperature of 40-50 ℃ for 15-25 min. After that, it is dried at 75-85 ℃ for 10-20 min to form a passivation film on the surface of the workpiece. When the alloy workpiece is a thick-walled workpiece, the passivating agent is applied as follows: immerse in an acid-free activating solution at room temperature for 15-20 seconds, then spray 2-3 times with a 5-minute interval between each spray. After spraying, place the workpiece in an environment of 40-60 ℃ for 10-20 minutes, then transfer it to a drying equipment and dry it at 85-95 ℃ for 15-25 minutes. When the alloy workpiece is a complex structure, the passivating agent is applied as follows: The workpiece to be treated is sprayed with an acid-free activating solution at a high pressure of 0.1~0.3 MPa for 10~15 s. Special attention is paid to the weld and blind holes to avoid residue. The workpiece can be soaked in the passivating agent and then sprayed with the key parts. After spraying, the workpiece is placed in an environment of 40~50 ℃ and left to stand for 20~30 min. Then it is transferred to a drying equipment and dried at 80~90 ℃ for 15~20 min.

9. The application as described in claim 8, characterized in that, The acid-free activation solution is 1-3%. wt. Sodium silicate and 0.3~0.6% wt. AEO-9 solution.