阅读说明：本技术 一种用于提升无磷前处理剂耐蚀性的方法 (Method for improving corrosion resistance of phosphorus-free pretreatment agent ) 是由 张荣金 付海罗 孔繁龙 许能才 陈�光 赵凯利 于 2021-06-16 设计创作，主要内容包括：本发明公开了一种用于提升无磷前处理剂耐蚀性的方法,其特征在于：在无磷前处理前,先采用表面调整剂对金属基材表面进行微观结构的调整,使金属基材表面形成有分布均匀的晶核。本发明通过在无磷前处理前先用表面调整剂对金属基材表面进行处理,有效提升了无磷前处理剂膜层的耐蚀性(使得锆化膜膜层更加致密),进而有效提高了漆膜的耐蚀性,划线单边刻蚀宽度小于2mm；并且还能提高后续漆膜和金属基材的结合力。(The invention discloses a method for improving corrosion resistance of a phosphorus-free pretreatment agent, which is characterized by comprising the following steps of: before the phosphorus-free pretreatment, a surface conditioning agent is adopted to adjust the microstructure of the surface of the metal base material, so that uniformly distributed crystal nuclei are formed on the surface of the metal base material. According to the invention, the surface of the metal substrate is treated by the surface conditioner before the phosphorus-free pretreatment, so that the corrosion resistance of the phosphorus-free pretreatment agent film is effectively improved (the zirconium film is more compact), the corrosion resistance of the paint film is further effectively improved, and the scribing single-side etching width is less than 2 mm; and the binding force between a subsequent paint film and a metal base material can be improved.)

1. A method for improving the corrosion resistance of a phosphorus-free pretreatment agent is characterized by comprising the following steps: before the phosphorus-free pretreatment, a surface conditioning agent is adopted to adjust the microstructure of the surface of the metal base material, so that uniformly distributed crystal nuclei are formed on the surface of the metal base material.

2. The method for improving corrosion resistance of a phosphorus-free pretreatment agent according to claim 1, wherein: each liter of the surface conditioning agent stock solution contains 5-10 g of zirconium salt and 100-150 g of modified silica sol solution.

3. The method for improving corrosion resistance of a phosphorus-free pretreatment agent according to claim 2, wherein: each liter of the surface conditioning agent stock solution also contains 7-10 g of potassium fluoride, 3-5 g of triethanolamine and the balance of water.

4. The method for improving corrosion resistance of a phosphorus-free pretreatment agent according to claim 2, wherein: the zirconium salt is zirconium nitrate pentahydrate.

5. The method for improving corrosion resistance of a phosphorus-free pretreatment agent according to claim 4, wherein: the purity of the zirconium nitrate pentahydrate is more than 98%, and the zirconium ion content in each liter of surface conditioning agent stock solution is not more than 1%.

6. The method for improving corrosion resistance of a phosphorus-free pretreatment agent according to claim 2, wherein: the modified silica sol solution is prepared by the following method: (1) preparing an original silica sol solution; (2) dripping an absolute ethyl alcohol solution containing an epoxy active diluent 748 into the original silica sol solution for reaction to obtain a silica sol solution; (3) removing ethanol and ammonia water in the reaction system; (4) adding a catalyst 4-dimethylamino pyridine and a dehydrating agent dicyclohexyl carbodiimide into the obtained silica sol solution, and stirring for dissolving; (5) dissolving ethylene diamine tetraacetic acid in ultrapure water, then dropwise adding the ethylene diamine tetraacetic acid into the reaction system in the step (4), and reacting at room temperature after dropwise adding; (6) and adding the obtained product into a dialysis bag, and obtaining a modified silica sol solution when the system does not contain 4-dimethylaminopyridine and dicyclohexylcarbodiimide and the solid content is 9-11%.

7. The method for improving corrosion resistance of a phosphorus-free pretreatment agent according to claim 6, wherein: the original silica sol solution is prepared by the following method: dissolving tetraethyl orthosilicate in absolute ethyl alcohol to prepare a TEOS solution, sequentially adding the absolute ethyl alcohol, high-purity water and ammonia water into a reaction container, starting stirring, slowly dropwise adding the TEOS solution into the reaction container, and reacting at room temperature after dropwise adding to obtain the original silica sol solution.

8. The method for improving corrosion resistance of a phosphorus-free pretreatment agent according to claim 6, wherein: the specific steps for removing ethanol and ammonia water in the reaction system are as follows: and adding a dimethyl formamide solvent into the silica sol solution obtained by the reaction, and distilling under reduced pressure at 50-60 ℃ to remove ethanol and ammonia water in the system.

9. The method for improving corrosion resistance of a phosphorus-free pretreatment agent according to claim 2, wherein: the pH value of the surface conditioning agent stock solution is 6-8.5.

Technical Field

The invention relates to a method for improving corrosion resistance of a phosphorus-free pretreatment agent, belonging to the technical field of metal working fluid treatment.

Background

With the improvement of the requirement on environmental protection, the metal material surface treatment industry is under greater and greater environmental protection pressure, and in order to reduce the content of nitrogen and phosphorus and the content of heavy metals in wastewater, the green production and use of the surface treatment agent become a necessary trend for industry development. Among them, the ceramic technology and the silane technology have been increasingly used in the industry as typical representatives of the phosphorus-free surface treatment. Compared with the traditional metal surface treatment such as phosphating and passivation technologies, the metal ions in the silane and the vitrification agent have less pollution to the environment, can not cause water eutrophication, and has great advantage in the aspect of environmental protection. Through the continuous development in recent years, the phosphorus-free technology can meet the requirements of most coating industries and has huge potential.

At present, the surface treatment industry has much attention to the improvement of the corrosion resistance of the phosphorus-free technology, and the existing method for improving the corrosion resistance of silane and a vitrification agent has the effects of optimizing the content of inorganic components in the components, introducing new inorganic components to improve the density of a film layer, replacing silane components in a silane product and the like. The cold-rolled thin iron plate is used as a common material in the surface treatment industry, is mainly used in the fields of automobile manufacturing, building industry, ventilation and heat supply facilities, household appliance manufacturing and the like, and has wide research on corrosion resistance, inter-process rust prevention, paint film adhesion and the like. In some coating industries with high quality requirements, the phosphorus-free surface treatment technology still cannot meet the actual use requirements (mainly the corrosion resistance cannot meet the requirements). The corrosion resistance of the final paint film is improved nearly to the limit by the existing improvement technology of the non-phosphorus pretreatment agent formula, so a new method needs to be developed for improving the corrosion resistance.

Disclosure of Invention

The purpose of the invention is as follows: the invention provides a method for improving the corrosion resistance of a phosphorus-free pretreatment agent, aiming at the application scene that the corrosion resistance of a phosphorus-free pretreatment film layer can not meet the high-quality requirement by adjusting the formula of the phosphorus-free pretreatment agent in the prior art.

The technical scheme is as follows: according to the method for improving the corrosion resistance of the phosphorus-free pretreatment agent, before the phosphorus-free pretreatment, the surface of the metal base material is subjected to microstructure adjustment by using the surface conditioning agent, so that crystal nuclei which are uniformly distributed are formed on the surface of the metal base material.

Wherein each liter of the surface conditioning agent stock solution contains 5-10 g of zirconium salt and 100-150 g of modified silica sol solution.

Wherein each liter of the surface conditioning agent stock solution also contains 7-10 g of potassium fluoride, 3-5 g of triethanolamine and the balance of water.

The zirconium salt is zirconium nitrate pentahydrate, the purity of the zirconium nitrate pentahydrate is more than 98%, and the zirconium ion content in each liter of surface conditioner stock solution is not more than 1%; the content of the zirconium salt can control the amount of surface crystal nucleus formation, and a continuous zirconium film cannot be formed on the surface of the metal substrate, and only discontinuous crystal nuclei are formed. The zirconium ions in the surface conditioner are deposited on the surface of the metal substrate, so that the silicon nano-ions complexed with the metal substrate through the EDTA chemical structure are fixed on the surface of the metal substrate and serve as crystal nuclei for subsequent film formation.

The modified silica sol solution is prepared by the following method: (1) preparing an original silica sol solution; (2) dripping an absolute ethyl alcohol solution containing an epoxy active diluent 748 into the original silica sol solution for reaction to obtain a silica sol solution; (3) removing ethanol and ammonia water in the reaction system; (4) adding a catalyst 4-dimethylamino pyridine and a dehydrating agent dicyclohexyl carbodiimide into the obtained silica sol solution, and stirring for dissolving; (5) dissolving ethylene diamine tetraacetic acid in ultrapure water, then dropwise adding the ethylene diamine tetraacetic acid into the reaction system in the step (4), and reacting at room temperature after dropwise adding; (6) and adding the obtained product into a dialysis bag, and when the system does not contain 4-dimethylaminopyridine and dicyclohexylcarbodiimide any more and the solid content is 9-11% (the solid content means that the content of silicon nano-ions in the modified silica sol solution is 9-11%, preferably 10%, and the content of particles in the solution is too high and is easy to agglomerate), obtaining the modified silica sol solution.

Wherein the original silica sol solution is prepared by the following method: dissolving tetraethyl orthosilicate in absolute ethyl alcohol to prepare a TEOS solution, sequentially adding the absolute ethyl alcohol, high-purity water and ammonia water into a reaction container, starting stirring, slowly dropwise adding the TEOS solution into the reaction container, and reacting at room temperature after dropwise adding to obtain the original silica sol solution.

Wherein, the removal of ethanol and ammonia water in the reaction system is specifically as follows: and adding a dimethyl formamide solvent into the silica sol solution obtained by the reaction, and distilling under reduced pressure at 50-60 ℃ to remove ethanol and ammonia water in the system.

Wherein, the concentration of the fluorinion in each liter of the surface conditioning agent stock solution is 0.5-3%, and the concentration of the triethanolamine is 2-4%. The triethanolamine has the advantages that the triethanolamine has the effect of pH adjustment in a system, the potassium fluoride has the effect of a stabilizer in the system, the nucleation rate is controlled, and fluorine ions can perform a complexing reaction with high-valence ions (tetravalent zirconium ions), so that the deposition speed of the zirconium ions on the surface of the metal substrate can be controlled, the more fluorine ions are, the more complexed zirconium ions are, the slower the nucleation speed is, the less fluorine ions are, the less complexed zirconium ions are, the faster the nucleation speed is, the nonuniform nucleation can be caused by the excessively high nucleation speed, and the complexed fluorine ions are released by adjusting the acid-base degree of the microenvironment on the surface of the metal substrate.

Wherein the pH value of the surface conditioning agent stock solution is 6-8.5; and (2) adjusting the pH value of the stock solution by using sodium hydroxide (1-3 g of sodium hydroxide is contained in each liter of the stock solution of the surface conditioner) and nitric acid (2-5 g of nitric acid is contained in each liter of the stock solution of the surface conditioner).

The principle of the method of the invention is as follows: firstly, the surface of the synthesized modified silica sol contains a chemical structure of EDTA (ethylene diamine tetraacetic acid), the chemical structure is easy to complex with metal ions (zirconium ions), when the complexed zirconium ions are deposited on the surface of a metal substrate, silicon nanoparticles are fixed on the metal substrate to form crystal nuclei, on the other hand, the silica sol is further fixedly combined with the metal surface through hydrolysis condensation to form firmer combination points, and the microstructure adjustment of the surface of the metal substrate is realized (namely, a layer of uniformly distributed crystal nuclei is fixed on the surface of the metal substrate); meanwhile, the silica sol is grafted and modified by using an epoxy active diluent 748, wherein the epoxy active diluent 748 is a long carbon chain aliphatic monofunctional diluent, and the molecular structure of the epoxy active diluent contains carbon-carbon double bonds, epoxy bonds and silane components; in the process of forming the film by using the zirconium salt in the phosphorus-free pretreatment agent, zirconium oxide is deposited on the surface of metal, part of groups (carbon-carbon double bonds and epoxy bonds, as the molecular chain of the epoxy active diluent 748 is long) which can have the curing action with a paint film are exposed outside the zirconium film, the microstructure adjustment is carried out on the metal surface, so that the film forming speed of zirconium salt is accelerated, and the density of the film is increased (because the zirconium film is deposited during the nucleation in the initial stage of the non-phosphorus pretreatment process, and the zirconium ions are directly deposited on the basis of crystal nuclei after the surface adjustment, the film forming speed is accelerated, and the problem of insufficient film density caused by nonuniform nucleation exists during the film forming of the non-phosphorus pretreatment process, and the crystal nuclei are uniformly distributed on the surface of the metal substrate after the surface adjustment, so that the film forming in the pretreatment process is more regular and compact); after a paint film, particularly an electrophoretic paint film, is coated, groups exposed outside a zirconium film can generate chemical crosslinking action with the paint film in the curing process of the paint film, and the bonding force between the paint film and a base material is improved in a covalent bond mode.

Has the advantages that: according to the invention, the surface of the metal substrate is treated by the surface conditioner before non-phosphorus pretreatment, so that the corrosion resistance of a non-phosphorus pretreatment agent film (zirconium film) is effectively improved (the zirconium film is more compact), the corrosion resistance of a paint film is further effectively improved, and the scribing single-side etching width is less than 2 mm; and the binding force between a subsequent paint film and a metal base material can be improved.

Drawings

FIG. 1 is an electron micrograph of the modified silica sol solution prepared;

fig. 2 is a partially enlarged view of fig. 1.

Detailed Description

The technical solution of the present invention is further illustrated below with reference to specific examples.

All components in the formula of the surface conditioner are commercially available products: preparing a modified silica sol solution independently; zirconium nitrate pentahydrate, triethanolamine, commercially available, with a purity of 95% +; potassium fluoride, sodium hydroxide, analytically pure, purchased by chemical reagents of national drug group, ltd; nitric acid with a mass fraction of 68% is purchased by chemical reagents of national drug group, ltd.

Example 1

The preparation of the surface conditioning agent of the invention:

every 1 liter of surface conditioning agent is added with the following components by mass and mixed to prepare the water-based paint:

zirconium nitrate pentahydrate: 10g

Modified silica sol solution: 100g

Potassium fluoride: 10g

Triethanolamine: 5g

Adjusting the pH value of the surface conditioning agent to 8.5 by using sodium hydroxide and nitric acid solution;

the balance being deionized water.

Wherein, the preparation of the modified silica sol comprises the following steps: the method mainly comprises the following three steps: the original silica sol, the molecular chain of the grafted epoxy reactive diluent 748, and the chemical structure of the grafted EDTA were prepared. The method specifically comprises the following steps:

(1) preparation of the original silica sol solution: dissolving 2.5mL of tetraethyl orthosilicate (TEOS) in 20mL of absolute ethyl alcohol to prepare a TEOS solution, sequentially adding 80mL of absolute ethyl alcohol, 2mL of high-purity water and 1mL of ammonia water into a reaction container, starting stirring, slowly dropwise adding the TEOS solution into the TEOS solution, and reacting for 12 hours at room temperature after dropwise adding to obtain an original silica sol solution;

(2) dissolving 1mL of epoxy active diluent 748 in 20mL of absolute ethyl alcohol to prepare a diluent solution, slowly dripping the diluent solution into the original silica sol solution, and reacting for 12 hours at room temperature after dripping; adding the silica sol solution obtained by the reaction into 100mL of dimethylformamide solvent, and distilling under reduced pressure at 50 ℃ to remove ethanol and ammonia water in the system;

(3) adding 0.149g of catalyst 4-dimethylaminopyridine and 5.25g of dehydrating agent dicyclohexylcarbodiimide into the solution without ethanol and ammonia water, and stirring and dissolving to obtain a solution A; dissolving 0.292g of ethylenediamine tetraacetic acid into 5mL of ultrapure water, then dropwise adding the solution (ethylenediamine tetraacetic acid solution) into the solution A, reacting for 12h at room temperature after dropwise adding, adding the reacted reactant into a dialysis bag, and obtaining a modified silica sol solution when the system does not contain 4-dimethylaminopyridine and dicyclohexylcarbodiimide and the solid content is about 10%.

The prepared silica sol has the particle size of 23-26 nm, is spherical, and has less agglomeration phenomenon, as shown in figures 1-2.

Example 2

The preparation of the surface conditioning agent of the invention:

every 1 liter of surface conditioning agent is added with the following components by mass and mixed to prepare the water-based paint:

zirconium nitrate pentahydrate: 5g

Modified silica sol solution: 150g

Potassium fluoride: 7g of

Triethanolamine: 3g

Adjusting the pH value of the surface conditioning agent to 6 by using sodium hydroxide and nitric acid solution;

the balance being deionized water.

The preparation of the modified silica sol solution in example 2 was in accordance with the examples.

Example 3 (electrophoretic paint film Properties)

Testing the plate: a commercially available standard cold-rolled iron plate was used, and the gauge was (150 mm. times.70 mm. times.0.8 mm).

The process flow comprises the following steps:

degreasing and deoiling → washing with tap water → washing with pure water → surface conditioning → phosphorus-free surface treatment → electrophoretic coating → high temperature curing

The brief introduction of each process flow is as follows:

degreasing treatment: the degreasing agent for the commercial heating cold-rolled sheet is adopted, the cold-rolled sheet is soaked for 5 minutes at the temperature of 50 ℃, and manual swing scrubbing and the like are assisted to ensure that the surface is degreased and clean.

And (3) water washing after degreasing: the mixture was rinsed in tap water for 1 minute at room temperature and in pure water for 1 minute.

Surface conditioning: the surface of the plate was adjusted using the diluent prepared with the surface conditioner of example 1, and the plate was immersed in the surface conditioning diluent at room temperature for 1min while intermittently swinging.

Non-phosphorus surface treatment: KR-S210 and KR-S211 (both commercially available products) from Nanjing Kerun were treated at room temperature for 3 min.

Electrophoretic coating: HT8000C water-based cathode electrophoretic paint produced by Xiangjiang Guanxi paint company in the market controls the film thickness of a paint film to be 20-22 mu m. And (3) curing the electrophoresis test plate washed by water at 170 ℃ for 20 minutes, taking out and airing at room temperature.

The using concentration of the surface conditioning agent for the cold-rolled iron plate is 5 per thousand, namely 5g of the surface conditioning agent is added into each kilogram of working solution to obtain diluted treatment solution, the sample is soaked for 1 minute by using the diluted treatment solution, and then the surface treatment process is directly carried out.

Paint film performance:

and synchronously comparing the phosphating agent with the zirconium salt surface treating agent. Example 3 in table 1 is a sample plate after surface conditioning according to the invention.

Comparative example 1 is a sample for phosphating a surface treatment agent, and the process flow is degreasing → washing with tap water → washing with pure water → surface conditioning → phosphating → washing with tap water → washing with pure water 1 → washing with pure water 2 → electrophoretic coating → high temperature curing, wherein the process conditions of the degreasing process and the electrophoretic coating process are the same as those of example 1; surface adjustment and phosphorization are carried out on the surface of a commercial phosphorizing agent and a surface adjusting agent matched with the phosphorization pretreatment, the acid ratio of the phosphorizing agent is controlled to be 10, the total acid point is controlled to be about 35, and the concentration of the surface adjusting agent is 3 per mill; the process conditions for all water washing steps were the same as in example 3.

Comparative example 2 was a zirconium salt surface treatment agent without surface conditioning (the zirconium salt surface treatment agent was identical to the phosphorus-free surface treatment agent used in example 3, and was KR-S210 and KR-S211 of tokyo corporation, south china), and the procedure and the product used were substantially the same as those of example 3, except that comparative example 2 did not undergo the surface conditioning procedure.

The properties of the paint films are described in Table 1.

TABLE 1

The cold-rolled sheet treated by the surface conditioner has excellent adhesion with a paint film, and passes a 30-cycle CCT test. The comprehensive performance, especially the corrosion resistance is obviously improved, and the comprehensive performance is not lower than that of the traditional phosphating treatment.

The properties of the bare film are shown in Table 2

TABLE 2

As can be seen from table 2, the film (the zirconium film formed by the zirconium salt pretreatment agent) after the surface conditioning of the cold-rolled iron plate has good corrosion resistance (the compactness of the film is improved), the corrosion resistance of the bare film is basically equivalent to that of the phosphate film, and the corrosion resistance of the film is obviously improved compared with the corrosion resistance of the film obtained by only using a single zirconium salt pretreatment agent.

The surface conditioning agent does not contain harmful elements such as phosphorus, chromium and the like, and the film forming rate and the film compactness of the zirconium film are obviously improved by adjusting the micro appearance of the cold-rolled iron plate; in addition, the bonding force between the metal base material and the paint film is enhanced in a covalent bond mode through the grafted reactive group, so that the corrosion resistance and the adhesive force of the paint film are comprehensively improved.