Low-corrosion foaming cleaning agent for rust removal and preparation method thereof

Abstract

This invention discloses a low-corrosion, self-healing foam cleaning agent for rust removal and its preparation method, belonging to the field of metal surface treatment technology. It includes independently packaged components A and B. Component A is a metal ion-triggered microcapsule powder, with its core composed of a hydrophobically modified corrosion inhibitor and a self-healing film-forming agent. The capsule wall is a hydrogel formed by the cross-linking of catechol-grafted polyvinyl alcohol and boric acid through dynamic borate ester bonds. Component B is a foam-type rust remover with a pH of 2.0-3.5. During use, component B dissolves the rust layer and releases Fe²⁺. + / Fe³ + Triggering the degradation of the capsule wall enables the targeted release of the capsule core, and a dynamically cross-linked hydrophobic protective film is synergistically formed on the metal surface. This film has self-healing properties. This invention achieves the integration of rust removal and intelligent protection, and has the advantages of low corrosion, high efficiency and long-lasting self-healing protection.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, specifically to a low-corrosion rust removal foam cleaning agent and its preparation method. Background Technology

[0002] Metal corrosion is a common problem in industrial production, seriously affecting the appearance, precision, and service life of equipment. Traditional chemical pickling is widely used for rust removal due to its high efficiency and ease of operation. Its principle is to use acid to react with the rust layer to generate soluble salts, thereby removing the rust products.

[0003] Traditional strong acid rust removal methods have significant drawbacks. While dissolving the rust layer, strong acids can react excessively with the metal substrate, leading to hydrogen embrittlement and excessive corrosion of the substrate, while also generating acid fumes that pollute the environment. The metal surface after rust removal is in an activated state, making it highly susceptible to secondary rusting, usually requiring immediate subsequent rust prevention treatment, increasing the complexity and cost of the process. To reduce acid pickling corrosion, existing technologies often add corrosion inhibitors, but these inhibitors are rapidly consumed in strong acid environments, making it difficult to provide long-term protection after rust removal.

[0004] In recent years, microcapsule-based stimulus-responsive self-healing coating technology has made progress, which can release repair agents when the coating is damaged. However, most existing research focuses on single rust prevention or coating self-healing functions, and there are few technical solutions that combine the rust removal process with intelligent protection mechanisms, failing to utilize the iron ion signals released by the rust layer itself to achieve precise response. Summary of the Invention

[0005] To address the technical deficiencies in the background art, this invention proposes a low-corrosion rust removal foam cleaning agent and its preparation method, solving the aforementioned technical problems and meeting practical needs. The specific technical solution is as follows: A low-corrosion, self-healing foam cleaner for rust removal, comprising individually packaged components A and B; Component A is a metal ion-triggered microcapsule powder, wherein the microcapsule includes a core and a capsule wall covering the core; the core is composed of a hydrophobic modified corrosion inhibitor and a self-healing film-forming agent, and the capsule wall is a metal ion-responsive hydrogel material, characterized in that the capsule wall material is a hydrogel formed by cross-linking of catechol-grafted polyvinyl alcohol and boric acid through dynamic borate ester bonds. The capsule wall material is configured such that, as component B acts on the metal corrosion layer and releases Fe²⁺ in situ. + or Fe³ +Under ionic conditions, the complexation of the catechol groups in the capsule wall material with iron ions competitively destroys the borate ester crosslinking bonds, leading to the degradation of the hydrogel network and achieving the site-specific release of the capsule core. The degradation half-life of the capsule wall material is controlled within the range of 60-240 seconds by adjusting the grafting density of the catechol groups. Component B is a foam-type rust remover, composed of organic acid, foaming agent, penetrant and water, and the pH value of component B is 2.0-3.5.

[0006] As a further technical solution of the present invention, the hydrophobic modified corrosion inhibitor is a reaction product of long-chain alkyl imidazoline quaternary ammonium salt and mercaptobenzothiazole. The molecular structure of the corrosion inhibitor simultaneously contains C12-C18 long-chain alkyl groups and dynamic disulfide bonds. The self-healing film-forming agent is polydimethylsiloxane with dopamine groups modified at the end group. The number average molecular weight of the self-healing film-forming agent is 2000-5000. The mass ratio of the hydrophobic modified corrosion inhibitor to the self-healing film-forming agent in the core is 1:2 to 2:1.

[0007] As a further technical solution of the present invention, the A component microcapsules are prepared by microfluidic technology, and the particle size of the A component microcapsules is monodisperse, with a D50 particle size of 50-150 μm and a capsule wall thickness of 5-20 μm.

[0008] As a further technical solution of the present invention, the organic acid in component B is a composite system of citric acid and gluconic acid, and the mass ratio of citric acid to gluconic acid is 3:1 to 1:3, wherein the total mass fraction of organic acid in component B is 8-15%, the foaming agent is a composite system of alkyl glycoside and cocamidopropyl betaine, and the mass ratio of the two is 2:1 to 1:2, the penetrant is fatty alcohol polyoxyethylene ether, and the mass fraction of the penetrant in component B is 1-3%.

[0009] As a further technical solution of the present invention, the mixing mass ratio of component A to component B is 1:10 to 1:30.

[0010] As a further technical solution of the present invention, when component A and component B are mixed and sprayed onto the metal rust surface, the organic acid in component B dissolves the rust layer and releases Fe²⁺. + or Fe³ + Ions trigger the selective degradation of the microcapsule wall, releasing the core material. The hydrophobic modified corrosion inhibitor and the self-healing film-forming agent in the core synergistically form a dynamically cross-linked hydrophobic protective film on the metal surface. After being artificially scratched in a 3.5wt% NaCl solution and left at room temperature for 2 hours, the contact angle of the scratched area recovers to more than 85% of the initial value.

[0011] As a further technical solution of the present invention, after the hydrophobic protective film is artificially scratched in a 3.5wt% NaCl solution, electrochemical testing shows that the polarization resistance of the repaired protective film recovers to more than 90% of the initial value.

[0012] A method for preparing the above-mentioned low-corrosion rust removal self-healing foam cleaning agent includes the following steps: S001: Preparation of metal ion responsive hydrogel capsule wall material: Polyvinyl alcohol is dissolved in water, and a catechol modifier is added to carry out a grafting reaction. The grafting density is controlled. After the reaction is completed, the catechol-grafted polyvinyl alcohol is purified to obtain catechol-grafted polyvinyl alcohol. Then, the catechol-grafted polyvinyl alcohol is reacted with boric acid crosslinking agent to form a hydrogel with dynamic boric acid ester crosslinking. After freeze drying and grinding, the hydrogel capsule wall material powder is obtained. S002: Preparation of core-capsule composite: Long-chain alkyl imidazoline quaternary ammonium salt and mercaptobenzothiazole are reacted at 60-80℃ for 2-4 hours to introduce dynamic disulfide bonds and obtain a hydrophobic modified corrosion inhibitor. The hydrophobic modified corrosion inhibitor is then mixed with polydimethylsiloxane with dopamine-terminated end groups at a mass ratio of 1:2 to 2:1 and stirred evenly to obtain the core-capsule composite. S003: Preparation of microcapsules: Using microfluidic technology, a monodisperse emulsion was prepared through coaxial annular microchannels, with the capsule core complex from step S002 as the dispersed phase and the hydrogel capsule wall material solution from step S001 as the continuous phase. The flow rate of the dispersed phase was controlled at 0.5-2.0 mL / h and the flow rate of the continuous phase was controlled at 5-20 mL / h. During the preparation process, the capsule wall was cured by ultraviolet light irradiation. After separation, washing, and drying, component A microcapsule powder was obtained. S004: Preparation of Component B: Dissolve organic acid, foaming agent, and penetrant in water in proportion, adjust pH to 2.5-3.5, stir evenly to obtain Component B foam-type rust remover; S005: Package the microcapsule powder of component A and the foam-type rust remover of component B separately.

[0013] As a further technical solution of the present invention, the ultraviolet light irradiation in step S003 uses an ultraviolet lamp with a wavelength of 365nm, a light intensity of 10-30 mW / cm², and an irradiation time of 5-15 minutes.

[0014] The beneficial effects of this invention are as follows: The iron ions released by component B dissolving the rust layer trigger the degradation of the microcapsule wall of component A, achieving precise enrichment of corrosion inhibitors and film-forming agents at the rust removal sites and avoiding ineffective consumption; the released hydrophobic modified corrosion inhibitor and self-healing film-forming agent synergistically form a dynamically cross-linked hydrophobic protective film on the metal surface. This film has both excellent shielding performance and self-healing ability; the contact angle and polarization resistance can be quickly restored after scratches, providing long-term rust protection for the metal; by adjusting the grafting density of the capsule wall material, the degradation half-life of the microcapsules can be precisely controlled within 60-240 seconds, matching the rust removal process. Attached Figure Description

[0015] Figure 1 This is a process flow diagram of an embodiment of the present invention. Detailed Implementation

[0016] The embodiments of the present invention will be described below with reference to the accompanying drawings and related examples. The embodiments of the present invention are not limited to the following examples, and the present invention relates to the relevant necessary components in this technical field, which should be regarded as well-known technology in this technical field and can be known and mastered by those skilled in this technical field.

[0017] Example 1 This embodiment provides a low-corrosion rust removal self-healing foam cleaning agent and its preparation method.

[0018] 1. Preparation of Component A: Metal Ion Triggered Microcapsule Powder The preparation of component A microcapsule powder includes three main steps: synthesis of capsule wall material, preparation of capsule core complex, and microcapsule forming.

[0019] 1.1 Preparation of metal ion-responsive hydrogel capsule wall materials 10g of polyvinyl alcohol (PVA, degree of hydrolysis 98.5%, degree of polymerization 1700, commercially available) was dissolved in 100mL of deionized water, heated to 90℃ and stirred until completely dissolved, then cooled to 60℃. 4.5g of 3,4-dihydroxybenzaldehyde (catechol modifier) ​​was added, and the pH was adjusted to 5.0 with 0.1M hydrochloric acid. The reaction was carried out under nitrogen protection for 6 hours. After the reaction, the product was purified by dialysis in deionized water for 48 hours (using a dialysis bag with a molecular weight cutoff of 8000-14000) to remove unreacted small molecules, yielding a catechol-grafted polyvinyl alcohol (PVA-Cat) solution. After freeze-drying, PVA-Cat solid powder was obtained. The grafting density of catechol can be adjusted by controlling the amount of 3,4-dihydroxybenzaldehyde added and the reaction time. In this example, the grafting density was determined to be 12 mol% by 1H NMR spectroscopy.

[0020] The PVA-Cat powder was redissolved in water to prepare a 5 wt% solution. Boric acid was slowly added under stirring, with a boric acid to PVA-Cat mass ratio of 1:12, and the crosslinking reaction was carried out at room temperature for 2 hours. Boric acid formed dynamic borate ester bonds with the catechol groups and hydroxyl groups on the PVA-Cat molecular chain, forming a hydrogel. The resulting hydrogel was freeze-dried at -50°C for 24 hours and then ground through a 200-mesh sieve to obtain a metal ion-responsive hydrogel capsule wall material powder. Simulation tests showed that this capsule wall material exhibited good responsiveness in contact with Fe³⁺. + The degradation half-life of the ions (at a concentration of 0.01 mol / L) is approximately 180 seconds.

[0021] 1.2 Preparation of the core-capsule composite A long-chain alkyl imidazoline quaternary ammonium salt (specifically, dodecyl imidazoline quaternary ammonium salt, commercially available) and mercaptobenzothiazole were added at a molar ratio of 1:1.2 and dissolved in anhydrous ethanol. The mixture was refluxed at 80°C for 3 hours. After the reaction, the solvent was removed by rotary evaporation to obtain a hydrophobically modified corrosion inhibitor. The molecular structure of this corrosion inhibitor simultaneously contains C12 long-chain alkyl groups and dynamic disulfide bonds.

[0022] Another polydimethylsiloxane (PDMS-DOPA) with dopamine-terminated end groups was prepared, with a number-average molecular weight of 3500. This substance was prepared by reacting amino-terminated polydimethylsiloxane with dopamine in the presence of a condensing agent.

[0023] The hydrophobic modified corrosion inhibitor prepared above was mixed with PDMS-DOPA at a mass ratio of 1:1 and stirred at 40°C for 30 minutes until homogeneous to obtain the core-capsule composite.

[0024] 1.3 Preparation of microcapsules Microcapsules were prepared using microfluidic technology. The core-capsule composite obtained in step 1.2 was used as the dispersed phase (inner phase), and an 8 wt% aqueous solution of the hydrogel capsule wall material prepared in step 1.1 was prepared as the continuous phase (outer phase). A coaxial annular microchannel device (inner channel diameter 100 μm, outer channel diameter 300 μm) was used, with the dispersed phase flow rate controlled by an injection pump at 1.2 mL / h and the continuous phase flow rate at 12 mL / h, forming a monodisperse O / W emulsion in the microchannel. After collecting the emulsion droplets, they were irradiated for 12 minutes using a 365 nm UV lamp at a light intensity of 25 mW / cm² to solidify any remaining photocrosslinking groups in the capsule wall and further stabilize the dynamic borate ester bonds, forming microcapsules with a core-shell structure. The resulting microcapsules were washed three times with deionized water and vacuum-dried at room temperature for 24 hours to obtain component A microcapsule powder. The microcapsules were analyzed by a laser particle size analyzer and found to have a D50 particle size of 105 μm, a capsule wall thickness of 12 μm as measured by scanning electron microscopy, and a particle size distribution span of less than 0.3, exhibiting a monodisperse distribution.

[0025] 2. Preparation of Component B: Foam-type Rust Remover The total mass of component B is 100g, prepared according to the following formula: Add 8g of citric acid and 7g of gluconic acid (citric acid to gluconic acid mass ratio approximately 1.14:1, total organic acid mass fraction 15%) to 70g of deionized water and stir to dissolve. Then add 3g of alkyl glycoside (APG0810) and 3g of cocamidopropyl betaine (CAB-35) (mass ratio 1:1, total foaming agent mass fraction 6%), and 2g of fatty alcohol polyoxyethylene ether (AEO-9) as a penetrant (mass fraction 2%). Add deionized water to a total mass of 100g, stir to mix thoroughly, and adjust the pH to 3.0 using citric acid or sodium hydroxide to obtain component B foam-type rust remover.

[0026] 3. Individually packaged and used By packaging the microcapsule powder of component A and the foam-type rust remover of component B separately, a low-corrosion self-healing foam cleaner for rust removal is obtained.

[0027] When using, mix component A and component B at a mass ratio of 1:20. Add the microcapsule powder of component A to the foam-type rust remover of component B, mix thoroughly, and then spray onto the rusted metal surface using a foam spray gun. The organic acid in component B rapidly dissolves the rust layer, releasing Fe²⁺. + or Fe³ + Iron ions complex with the catechol groups in the microcapsule wall, competitively disrupting the original borate ester crosslinks, causing the hydrogel network to degrade within approximately 180 seconds, achieving targeted and timed release of the capsule core. The released hydrophobic modified corrosion inhibitor and self-healing film-forming agent synergistically adsorb onto the metal surface, forming a dynamically crosslinked hydrophobic protective film.

[0028] Example 2 This embodiment is basically the same as Embodiment 1, except for some raw material ratios and process parameters.

[0029] 1. Preparation of component A microcapsule powder In the preparation of the capsule wall material, the amount of 3,4-dihydroxybenzaldehyde was adjusted to 3g, the reaction time was 4 hours, and the catechol grafting density was determined to be 8 mol%. The mass ratio of boric acid to PVA-Cat was 1:15. This capsule wall material showed good performance in contact with Fe³⁺. + The degradation half-life of ions is approximately 90 seconds.

[0030] In the core-capsule composite, the mass ratio of hydrophobic modified corrosion inhibitor to PDMS-DOPA (number average molecular weight 2000) was adjusted to 2:1.

[0031] In the microcapsule preparation, the dispersed phase flow rate was set to 0.8 mL / h, the continuous phase flow rate was set to 15 mL / h, and the UV irradiation time was 8 minutes. The resulting microcapsules had a D50 particle size of 82 μm and a capsule wall thickness of 9 μm.

[0032] 2. Component B foam-type rust remover Component B, with a total mass of 100g, is prepared according to the following formula: 6g citric acid, 6g gluconic acid (total organic acid mass fraction 12%); 2g alkyl glycoside, 4g cocamidopropyl betaine (mass ratio of the two is 1:2, total foaming agent mass fraction 6%); 1g fatty alcohol polyoxyethylene ether (AEO-7). Adjust the pH to 2.5.

[0033] 3. Packaging and Use Component A and Component B are packaged separately, and the mixing ratio is 1:15 when used. The method of use is the same as in Example 1.

[0034] Example 3 This embodiment is basically the same as Embodiment 1, except for some raw material ratios and process parameters.

[0035] 1. Preparation of component A microcapsule powder In the preparation of the capsule wall material, the amount of 3,4-dihydroxybenzaldehyde was adjusted to 6g, the reaction time was 8 hours, and the catechol grafting density was determined to be 16 mol%. The mass ratio of boric acid to PVA-Cat was 1:10. The degradation half-life of this capsule wall material upon contact with Fe³ ions was approximately 230 seconds.

[0036] In the core-capsule composite, the mass ratio of hydrophobic modified corrosion inhibitor to PDMS-DOPA (number average molecular weight 5000) was adjusted to 1:2.

[0037] In the microcapsule preparation, the dispersed phase flow rate was set to 1.6 mL / h, the continuous phase flow rate was set to 10 mL / h, and the UV irradiation time was 15 minutes. The resulting microcapsules had a D50 particle size of 135 μm and a capsule wall thickness of 18 μm.

[0038] 2. Component B foam-type rust remover Component B, with a total mass of 100g, is prepared according to the following formula: 10g citric acid, 5g gluconic acid (total organic acid mass fraction 15%); 5g alkyl glycoside, 2.5g cocamidopropyl betaine (mass ratio of the two is 2:1, total foaming agent mass fraction 7.5%); 3g fatty alcohol polyoxyethylene ether (AEO-9). Adjust the pH to 3.5.

[0039] 3. Packaging and Use Component A and Component B are packaged separately, and the mixing ratio is 1:25 when used. The method of use is the same as in Example 1.

[0040] Example 4 This embodiment is basically the same as Embodiment 1, except for the organic acid composite system and ratio.

[0041] 1. Preparation of component A microcapsule powder Same as Example 1.

[0042] 2. Component B foam-type rust remover Component B, with a total mass of 100g, is prepared according to the following formula: 4g citric acid, 12g gluconic acid (citric acid to gluconic acid mass ratio 1:3, total organic acid mass fraction 16%); 4g alkyl glycoside, 2g cocamidopropyl betaine (the two mass ratio 2:1, total foaming agent mass fraction 6%); 2g fatty alcohol polyoxyethylene ether (AEO-9). Adjust the pH to 2.8.

[0043] 3. Packaging and Use Same as in Example 1, the mass ratio of component A to component B is 1:20.

[0044] Example 5 This embodiment is basically the same as Embodiment 1, except for the organic acid composite system and ratio.

[0045] 1. Preparation of component A microcapsule powder Same as Example 1.

[0046] 2. Component B foam-type rust remover Component B, with a total mass of 100g, is prepared according to the following formula: 12g citric acid, 4g gluconic acid (citric acid to gluconic acid mass ratio 3:1, total organic acid mass fraction 16%); 2g alkyl glycoside, 4g cocamidopropyl betaine (the two mass ratio 1:2, total foaming agent mass fraction 6%); 2g fatty alcohol polyoxyethylene ether (AEO-9). Adjust the pH to 3.2.

[0047] 3. Packaging and Use Same as in Example 1, the mass ratio of component A to component B is 1:20.

[0048] Comparative Example 1 The difference between this comparative example and Example 1 is that the capsule wall material of component A microcapsules is a hydrogel formed by crosslinking ungrafted catechol polyvinyl alcohol with boric acid (i.e., ordinary PVA is used instead of PVA-Cat), which does not have the function of metal ion responsive degradation. The rest of the preparation method is the same as in Example 1.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that the mass ratio of the hydrophobic modified corrosion inhibitor to PDMS-DOPA in the core composite is 1:0 (i.e., it does not contain a self-healing film-forming agent). The rest of the preparation method is the same as in Example 1.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is that the mass ratio of the hydrophobic modified corrosion inhibitor to PDMS-DOPA in the core composite is 0:1 (i.e., no hydrophobic modified corrosion inhibitor is present). The rest of the preparation method is the same as in Example 1.

[0051] Comparative Example 4 The difference between this comparative example and Example 1 is that the catechol grafting density was adjusted during the preparation of the capsule wall material to achieve a degradation half-life of approximately 30 seconds (below 60 seconds). The remaining preparation methods are the same as in Example 1.

[0052] Comparative Example 5 The difference between this comparative example and Example 1 is that the catechol grafting density was adjusted during the preparation of the capsule wall material to achieve a degradation half-life of approximately 300 seconds (higher than 240 seconds). The remaining preparation methods are the same as in Example 1.

[0053] Comparative Example 6 The difference between this comparative example and Example 1 is that component B does not contain any foaming agent or penetrant, and consists only of citric acid, gluconic acid, and water (pH=3.0). When used, it is directly mixed with component A and sprayed, without producing foam.

[0054] Performance Testing and Evaluation The foam cleaning agents prepared in Examples 1-5 and Comparative Examples 1-6 were subjected to performance tests. Before the test, component A and component B were mixed evenly according to their respective proportions. For Examples 1-5 and Comparative Examples 1-5, the foam was sprayed onto the rusted Q235 carbon steel surface using a foam spray gun, while for Comparative Example 6, it was sprayed using a regular spray bottle. The treatment time was 5 minutes for all samples, and then the surface was rinsed with water and allowed to air dry to form a protective film.

[0055] 1. Evaluation of rust removal effect The degree of rust residue on the surface after rust removal was observed visually and by scanning electron microscopy. Evaluation criteria: Excellent (no visible rust on the surface, uniform exposure of the metal substrate); Good (sparse pitting corrosion on the surface, rust removal rate >90%); Poor (obvious rust residue on the surface).

[0056] 2. Self-healing performance evaluation In a 3.5 wt% NaCl solution, the protective film was artificially scratched with a blade (scratch length 1 cm, depth to the metal substrate). After being left at room temperature for 2 hours, the contact angle of the scratched area was tested (using a contact angle measuring instrument).

[0057] Self-healing efficiency is characterized by the contact angle recovery rate (recovered contact angle / initial contact angle × 100%) 2 hours after scratch.

[0058] 3. Corrosion rate test The metal corrosion rate (unit: mm / a) was determined by immersing the treated sample in a 3.5 wt% NaCl solution for 72 hours using the weight loss method.

[0059] Test Results Summary

[0060] Results Analysis The test results show that: Examples 1-5 all exhibited excellent rust removal effects, good self-healing properties, and extremely low corrosion rates. Among them, Examples 1-3 showed "excellent" rust removal effects, self-healing efficiencies of over 85%, and corrosion rates of less than 0.003 mm / a, indicating that within the preferred technical solution range of this invention, the product performance is even more outstanding.

[0061] Comparative Example 1 uses a non-responsive capsule wall material, which has a good rust removal effect, but because it cannot achieve targeted release, the self-healing efficiency is significantly reduced and the corrosion rate is increased.

[0062] Comparative Examples 2 and 3 lacked self-healing film-forming agents or hydrophobic modified corrosion inhibitors, resulting in a significant reduction in the integrity, hydrophobicity, and self-healing ability of the formed protective films, and a significantly higher corrosion rate than the examples.

[0063] The degradation half-life of the capsule wall in Comparative Examples 4 and 5 deviated from the 60-240 seconds range specified in this invention, resulting in premature or delayed release of the capsule core, which affected the formation of the protective film and the self-repair effect.

[0064] Comparative Example 6 did not use foam, resulting in a decreased rust removal effect (due to the long wall-hanging time and full effect of foam), and its self-healing efficiency and corrosion resistance were lower than those of Example 1, which used foam.

[0065] In summary, this invention achieves integrated spot rust removal and self-healing protection through the synergistic effect of metal ion-responsive microcapsules and foam-type rust remover, resulting in excellent rust removal and self-healing protection effects.

[0066] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-corrosion, self-healing foam cleaning agent for rust removal, characterized in that, Includes individually packaged components A and B; Component A is a metal ion-triggered microcapsule powder, wherein the microcapsule includes a core and a capsule wall covering the core; the core is composed of a hydrophobic modified corrosion inhibitor and a self-healing film-forming agent, and the capsule wall is a metal ion-responsive hydrogel material, characterized in that the capsule wall material is a hydrogel formed by cross-linking of catechol-grafted polyvinyl alcohol and boric acid through dynamic borate ester bonds. The capsule wall material is configured such that, as component B acts on the metal corrosion layer and releases Fe²⁺ in situ. + or Fe³ + Under ionic conditions, the complexation of the catechol groups in the capsule wall material with iron ions competitively destroys the borate ester crosslinking bonds, leading to the degradation of the hydrogel network and achieving the site-specific release of the capsule core. The degradation half-life of the capsule wall material is controlled within the range of 60-240 seconds by adjusting the grafting density of the catechol groups. Component B is a foam-type rust remover, composed of organic acid, foaming agent, penetrant and water, and the pH value of component B is 2.0-3.

5.

2. The low-corrosion rust removal self-healing foam cleaning agent according to claim 1, characterized in that, The hydrophobic modified corrosion inhibitor is a reaction product of long-chain alkyl imidazoline quaternary ammonium salt and mercaptobenzothiazole. The molecular structure of the corrosion inhibitor simultaneously contains C12-C18 long-chain alkyl groups and dynamic disulfide bonds. The self-healing film-forming agent is polydimethylsiloxane with dopamine groups modified at the end groups. The number average molecular weight of the self-healing film-forming agent is 2000-5000. The mass ratio of the hydrophobic modified corrosion inhibitor to the self-healing film-forming agent in the core is 1:2 to 2:

1.

3. The low-corrosion rust removal self-healing foam cleaning agent according to claim 1, characterized in that, The microcapsules of component A are prepared by microfluidic technology. The microcapsules of component A have a monodisperse particle size distribution, a D50 particle size of 50-150 μm, and a capsule wall thickness of 5-20 μm.

4. The low-corrosion rust removal self-healing foam cleaning agent according to claim 1, characterized in that, The organic acid in component B is a composite system of citric acid and gluconic acid, with a mass ratio of citric acid to gluconic acid of 3:1 to 1:

3. The total mass fraction of organic acid in component B is 8-15%. The foaming agent is a composite system of alkyl glycoside and cocamidopropyl betaine, with a mass ratio of 2:1 to 1:

2. The penetrant is fatty alcohol polyoxyethylene ether, with a mass fraction of 1-3% in component B.

5. The low-corrosion rust removal self-healing foam cleaning agent according to claim 1, characterized in that, The mixing mass ratio of component A to component B is 1:10 to 1:

30.

6. The low-corrosion rust removal self-healing foam cleaning agent according to claim 1, characterized in that, When the mixture of component A and component B is sprayed onto the rusted metal surface, the organic acid in component B dissolves the rust layer and releases Fe²⁺. + or Fe³ + Ions trigger the selective degradation of the microcapsule wall and release the core material. The hydrophobic modified corrosion inhibitor and the self-healing film-forming agent in the core synergistically form a dynamically cross-linked hydrophobic protective film on the metal surface. After being artificially scratched in a 3.5wt% NaCl solution and left at room temperature for 2 hours, the contact angle of the scratched area recovers to more than 85% of the initial value.

7. The low-corrosion rust removal self-healing foam cleaning agent according to claim 6, characterized in that, After the hydrophobic protective film was artificially scratched in a 3.5wt% NaCl solution, electrochemical testing showed that the polarization resistance of the repaired protective film recovered to more than 90% of its initial value.

8. A method for preparing the low-corrosion rust-removing foam cleaning agent according to any one of claims 1-7, characterized in that, Includes the following steps: S001: Preparation of metal ion responsive hydrogel capsule wall material: Polyvinyl alcohol is dissolved in water, and a catechol modifier is added to carry out a grafting reaction. The grafting density is controlled. After the reaction is completed, the catechol-grafted polyvinyl alcohol is purified to obtain catechol-grafted polyvinyl alcohol. Then, the catechol-grafted polyvinyl alcohol is reacted with boric acid crosslinking agent to form a hydrogel with dynamic boric acid ester crosslinking. After freeze drying and grinding, the hydrogel capsule wall material powder is obtained. S002: Preparation of core-capsule composite: Long-chain alkyl imidazoline quaternary ammonium salt and mercaptobenzothiazole are reacted at 60-80℃ for 2-4 hours to introduce dynamic disulfide bonds and obtain a hydrophobic modified corrosion inhibitor. The hydrophobic modified corrosion inhibitor is then mixed with polydimethylsiloxane with dopamine-terminated end groups at a mass ratio of 1:2 to 2:1 and stirred evenly to obtain the core-capsule composite. S003: Preparation of microcapsules: Using microfluidic technology, a monodisperse emulsion was prepared through coaxial annular microchannels, with the capsule core complex from step S002 as the dispersed phase and the hydrogel capsule wall material solution from step S001 as the continuous phase. The flow rate of the dispersed phase was controlled at 0.5-2.0 mL / h and the flow rate of the continuous phase was controlled at 5-20 mL / h. During the preparation process, the capsule wall was cured by ultraviolet light irradiation. After separation, washing, and drying, component A microcapsule powder was obtained. S004: Preparation of Component B: Dissolve organic acid, foaming agent, and penetrant in water in proportion, adjust pH to 2.5-3.5, stir evenly to obtain Component B foam-type rust remover; S005: Package the microcapsule powder of component A and the foam-type rust remover of component B separately.

9. The preparation method according to claim 8, characterized in that, The ultraviolet light irradiation in step S003 uses an ultraviolet lamp with a wavelength of 365nm, a light intensity of 10-30 mW / cm², and an irradiation time of 5-15 minutes.

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