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CN-122013170-A - High-sweat strain-resistance chromium-free passivating agent for metal surface treatment and preparation method and application thereof

CN122013170ACN 122013170 ACN122013170 ACN 122013170ACN-122013170-A

Abstract

The invention relates to the technical field of passivating agents, in particular to a chromium-free passivating agent with high sweat strain resistance for metal surface treatment, a preparation method and application thereof. The high-sweat strain-resistance chromium-free passivating agent for metal surface treatment comprises, by mass, 20-30 parts of waterborne polyurethane, 0.1-0.3 part of titanyl sulfate, 0.05-0.15 part of complexing agent, 6-12 parts of silica sol, 3-7 parts of microcapsule emulsion, 0.5-1 part of wetting agent, 0.5-1 part of defoamer and 40-75 parts of deionized water, wherein the microcapsule emulsion contains oil-in-water microcapsules formed by crosslinking and curing glutaraldehyde by taking high-activity isocyanate as a core material and quaternized modified chitosan-sodium alginate as a composite wall material. The passivation film formed by the passivating agent has excellent salt fog resistance, and has the color difference delta E less than or equal to 1.03 in artificial sweat resistance test, the passivating agent is a single-component system, the storage stability is more than or equal to 4 months at 50 ℃, and the phenomena of gelation, abnormal rise of viscosity and the like are avoided.

Inventors

  • HU ZIKANG
  • ZHAN HONG
  • Zhu Zhewen
  • LUO XIAOFENG
  • LU BIAO

Assignees

  • 武汉迪赛环保新材料股份有限公司

Dates

Publication Date
20260512
Application Date
20260210

Claims (10)

  1. 1. The high-sweat strain-resistance chromium-free passivating agent for metal surface treatment is characterized by comprising, by mass, 20-30 parts of waterborne polyurethane, 0.1-0.3 part of titanyl sulfate, 0.05-0.15 part of complexing agent, 6-12 parts of silica sol, 3-7 parts of microcapsule emulsion, 0.5-1 part of wetting agent, 0.5-1 part of defoaming agent and 40-75 parts of deionized water; The microcapsule emulsion comprises oil-in-water microcapsules which are formed by taking high-activity isocyanate as a core material and quaternized modified chitosan-sodium alginate as a composite wall material and curing through glutaraldehyde crosslinking.
  2. 2. The alkaline chromium-free passivating agent according to claim 1, wherein the microcapsule has a particle size of 1-5 μm.
  3. 3. The alkaline chromium-free passivating agent according to claim 1, wherein the mass of the microcapsules in the microcapsule emulsion is 10-40%.
  4. 4. The alkaline chromium-free passivating agent according to claim 1, wherein the high-activity isocyanate is selected from at least one of isophorone diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate.
  5. 5. The alkaline chromium-free passivating agent according to claim 1, wherein the microcapsule emulsion is specifically prepared by the following steps: Adding deionized water, stirring, regulating the pH value to 9.0-10.0 by using ammonia water to form an alkaline water phase, keeping stirring, slowly adding high-activity isocyanate, regulating the rotating speed to 800-1000 r/min, emulsifying at a high speed for 20-30 min to form an oil-in-water emulsion, adding quaternized modified chitosan and sodium alginate into the emulsion, heating to 55-60 ℃, stirring to completely dissolve, keeping the temperature, stirring for a period of time, slowly adding curing agent glutaraldehyde, continuing stirring at a low speed for 2-2.5 hours, and keeping the rotating speed at no more than 300r/min, and maintaining the pH value to 9.0-10.0 in the whole course to obtain the microcapsule emulsion.
  6. 6. The alkaline chromium-free passivating agent according to claim 5, wherein the silica sol has a SiO 2 content of 20% and a SiO 2 particle size of 15-25nm.
  7. 7. The alkaline chromium-free passivating agent according to claim 5, wherein the mass ratio of the sum of the mass of the high-activity isocyanate and the mass of the quaternized modified chitosan and the mass of the sodium alginate is 1 (0.1-0.4).
  8. 8. The alkaline chromium-free passivating agent according to claim 5, wherein the weight ratio of quaternized modified chitosan to sodium alginate is 5:3, and the addition amount of glutaraldehyde is 1% -2% of the total weight of the microcapsule emulsion.
  9. 9. A method for preparing the alkaline chromium-free passivating agent as defined in any one of claims 1-8, comprising the following steps: Preparing microcapsule emulsion; Dissolving a complexing agent in ionized water, adding titanyl sulfate, dispersing uniformly to obtain a titanium-containing complex solution, and regulating the pH value to 8-9 by ammonia water to obtain a solution containing a titanyl sulfate-citric acid complex, wherein the mass ratio of the complexing agent to the titanyl sulfate is 1:2; slowly adding deionized water into aqueous polyurethane, stirring until the aqueous polyurethane is completely dispersed, sequentially adding a solution containing a titanium oxysulfate-citric acid complex and silica sol, stirring to form stable inorganic dispersion liquid, slowly adding the prepared microcapsule emulsion, stirring at a low speed, and finally adding a wetting agent and a defoaming agent, and stirring to obtain the alkaline chromium-free passivating agent.
  10. 10. Use of an alkaline chromium-free passivating agent according to any one of claims 1-8 in the corrosion protection treatment of a metal substrate surface, wherein the alkaline chromium-free passivating agent is coated or sprayed on the metal substrate surface and then baked to form a film at 80-120 ℃.

Description

High-sweat strain-resistance chromium-free passivating agent for metal surface treatment and preparation method and application thereof Technical Field The invention relates to the technical field of passivating agents, in particular to a chromium-free passivating agent with high sweat strain resistance for metal surface treatment, a preparation method and application thereof. Background In the industrial fields of machine manufacturing, automobile parts, aerospace and the like, the anti-corrosion and rust-proof treatment of the surface of a metal workpiece is a key link for guaranteeing the quality and the service life of a product. In the field of metal surface corrosion prevention treatment, chromium passivator has a long-term dominant role, wherein hexavalent chromium passivator has excellent corrosion resistance and self-repairing capability, but is strictly limited or forbidden by global regulations such as RoHS, REACH and the like due to extremely toxicity, strong carcinogenicity and serious environmental pollution, and trivalent chromium passivator has lower toxicity as a transition scheme and meets the current environmental protection requirement, but still contains heavy metal chromium, lacks self-repairing function, has single film color and limited deep drawing processing adaptability. On the other hand, although the existing acidic chromium-free passivating agents (such as molybdate and fluotitanic/zirconic acid systems) realize chromium-free, the acidic environment is easy to cause pitting or hydrogen embrittlement on a metal matrix, the formed passivation film is insufficient in compactness and adhesion, easy to crack and fall off in the subsequent deep drawing, bending and other forming processing, and poor in artificial sweat resistance and wet heat aging resistance, and meanwhile acidic waste liquid is still generated, so that the environmental protection advantage is limited. The alkaline passivating agent gradually replaces the traditional acidic chromium-containing process due to the advantages of low corrosiveness to the matrix, environmental friendliness and the like. At present, the related art is mainly divided into a chromium-containing two-component system and a chromium-free one-component system. For example, CN116590701a discloses an alkaline zinc-plated black passivating agent of AB two-component, wherein component a comprises 20-35 parts of trivalent chromium salt, 7-15 parts of complexing agent, 5-15 parts of pH regulator, 5-15 parts of auxiliary blackening agent, 10-20 parts of oxidizing agent, 30-40 parts of water, 15-25 parts of main blackening agent, 1-10 parts of film forming promoter, 70-90 parts of water, and A, B parts of black passivating film is formed by mixing in use. The solution realizes blackening passivation under alkaline conditions, but still depends on trivalent chromium salt as a core film forming component, cannot get rid of heavy metal use, does not accord with the development trend of green manufacture and no chromizing, meanwhile, the AB bi-component design needs to be prepared on site, has complex operation, is difficult to be applied to an automatic continuous production line, and the obtained film layer is mainly made of inorganic chromium compounds, has insufficient flexibility and is easy to crack and fall off in subsequent deep drawing or bending processing. On the other hand, CN117867484A discloses an alkaline chromium-free passivating agent with the pH value of 8-10, which is prepared by compounding 8-15% of organic water-based resin, 5-10% of silane coupling agent, 0.02-2% of molybdate water solution, 0.05-3% of alkaline substance and 0.02-2% of functional auxiliary agent. The system realizes chromium-free reaction, and improves the organic-inorganic interface binding force by using the silane coupling agent, but the silane coupling agent is easy to generate hydrolysis and polycondensation reaction in an alkaline water phase, so that the activity of the silane coupling agent is quickly attenuated in the storage process, further the viscosity of the system is increased, the gelation or the film forming performance is reduced, and the requirement of industrial production on long-term shelf life is difficult to meet. In addition, the system lacks an effective crosslinking enhancement mechanism, the obtained passive film has limited compactness, and the protective performance is still insufficient under severe conditions such as artificial sweat and the like. Therefore, the existing alkaline passivation technology still cannot effectively meet multiple requirements of single-component stability, complete no chromization, high crosslinking compactness, high sweat resistance and the like. Disclosure of Invention The invention aims at providing a chromium-free passivating agent with high sweat strain resistance for metal surface treatment, a preparation method and application thereof, aiming at the defects of the prior art. The invention provides a h