Multifunctional coating agent and preparation process thereof

Abstract

The invention discloses a multifunctional coating agent and a preparation process thereof, and relates to the technical field of metal treatment agents, the multifunctional coating agent comprises the following components in parts by weight: 350 parts of phosphoric acid, 70.5-91.5 parts of MMoO4 (at) ZnO, 20-28 parts of manganous dihydrogen phosphate and 5-6.3 parts of citric acid; wherein the MMoO4 (at) ZnO contains 70-90 parts of zinc oxide and 0.5-1.5 parts of molybdate, and the preparation method of the MMoO4 (at) ZnO comprises the following steps: respectively obtaining a zinc acetate solution and a molybdate solution, then adding the molybdate solution into the zinc acetate solution, stirring and fully mixing to obtain a mixture, and finally putting the mixture into a drying oven at 60-80 DEG C to be treated for 12-18 hours to obtain the MMoO4 (at) ZnO. And drying and calcining the obtained gel to obtain the MMoO4 (at) ZnO. The zinc phosphate crystal film forming method has the beneficial effects that crystal growth and arrangement are promoted in the film forming process to form a fine, compact and uniform zinc phosphate crystal film, and therefore the corrosion resistance, abrasion resistance and adhesion performance of metal are effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of metal treatment agents, and in particular to a multifunctional coating agent and a preparation process thereof. Background Art

[0002] With the development of metal surface technology and the improvement of life, people have higher and higher requirements for the decorative technology of metal parts, and metal pretreatment is becoming more and more important. Metal pretreatment is not only to make the workpiece surface ready for coating through proper treatment, but also greatly affects the performance of the coating, such as enhancing the adhesion of the coating and improving the corrosion resistance of the coating.

[0003] A film-coating agent is a metal surface treatment agent that reacts with metals to remove rust from the metal surface while forming a water-insoluble, chemically inert protective film that can adhere to the metal surface. This protective film is beneficial for preventing the metal from being oxidized, and is also beneficial for enhancing the adhesion of the sprayed paint film, plastic powder and metal in the subsequent metal surface spraying process. Therefore, it is widely used in the field of metal pre-treatment.

[0004] In the existing technology, due to the need to form a film in a short time, the film layer completed by heating is not stable and is very likely to fall off, which in turn affects the surface treatment effect of the metal and needs to be improved. Summary of the Invention

[0005] In view of this, the first object of this application is to provide a multifunctional film-forming agent to achieve low-temperature film formation and improve film stability. The specific scheme is as follows: A multifunctional film-forming agent comprises 350 parts by weight of phosphoric acid, 70.5-91.5 parts of MMoO4@ZnO, 20-28 parts of Marib salt, and 5-6.3 parts of citric acid; wherein: The MMoO4@ZnO contains 70-90 parts of zinc oxide and 0.5-1.5 parts of molybdate, and the preparation method of the MMoO4@ZnO comprises separately obtaining a zinc acetate solution and a molybdate solution, adding the molybdate solution to the zinc acetate solution, stirring and fully mixing to obtain a mixture, and then placing the mixture in an oven at 60-80°C for 12-18 hours to obtain a gel, followed by drying and calcining to obtain the MMoO4@ZnO.

[0006] Preferably, the zinc acetate solution uses ethanol as a solvent, is prepared by mixing zinc acetate and ethanol at a ratio of 5-8 g: 60-90 ml, and adding citric acid at a rate of 2-4% of the mass of the zinc acetate solution, followed by thorough stirring.

[0007] Preferably, the molybdate solution uses ethanol as a solvent, and is obtained by mixing molybdate and ethanol at a ratio of 3-6 g:40-60 ml, adding 2 mol / L concentrated hydrochloric acid at a ratio of 2-3% of the mass of the molybdate solution, and stirring thoroughly.

[0008] Preferably, the molybdate solution is added dropwise to the zinc acetate solution, and the zinc acetate solution is kept in a stirring state at a stirring speed of 300-500 r / min, and stirring is continued for 1-2 hours after complete addition.

[0009] Preferably, the drying is performed by vacuum drying at 40-60° C. to obtain a dry gel.

[0010] Preferably, the calcination is to first grind the dry gel, then calcine at 550-650°C for 2-3h, and control the calcination starting temperature to be room temperature, and the heating rate to be 5-10°C / min, to obtain MMoO4@ZnO.

[0011] Preferably, the molybdate is composed of sodium molybdate and ammonium molybdate in a mass ratio of 1:2-3.

[0012] The second object of the present invention is to provide a preparation process of a multifunctional film-forming agent, which is used to prepare a multifunctional film-forming agent as described above, comprising fully mixing phosphoric acid, MMoO4@ZnO, Marib salt and citric acid to obtain a prefabricated film-forming agent main material; the prefabricated film-forming agent main material is used to be mixed with clean water and used for spraying film formation before coating the steel surface at room temperature.

[0013] From the above scheme, it can be seen that the present application provides a multifunctional film agent and a preparation process thereof, which has the following beneficial effects: 1. By promoting crystal growth and arrangement during the film formation process to form a small, dense and uniform zinc phosphate crystal film, the corrosion resistance, wear resistance and adhesion performance of the metal are effectively improved; 2. By combining zinc oxide with the corrosion inhibitor, the corrosion inhibitor and the zinc phosphate crystal film are stacked together during the film formation process, so that the generated compound iron molybdate and the zinc phosphate crystal film synergistically promote the deposition effect on the metal surface, thereby achieving an effective protective effect; 3. The corrosion inhibitor promotes the oxidation of zinc and reduces the porosity and defects of the phosphate film, thereby improving the film integrity and protective effect of the phosphate film. The corrosion inhibitor reacts with iron ions to further fill defects and porosity, achieving effective metal protection effect. 4. By forming a layer of fine and dense phosphate film in a short time, the film is dark gray, fine and smooth, with good corrosion resistance, strong adhesion between the phosphate film and the metal substrate, and no dust; 5. By producing very little or no sediment during the phosphating process, the waste of effective ingredients in the phosphating solution caused by sediment is effectively reduced. Workers do not need to clean the sediment and do not need to frequently clean the spraying equipment, which saves working hours, improves production efficiency and reduces labor intensity. 6. No additional accelerator is needed during use, and the phosphating solution can be directly added, which makes the operation simple and easy to maintain; 7. It can be operated at room temperature without heating, which reduces energy consumption, has a long service life, a wide operating range and low overall cost. It is suitable for phosphating treatment of steel products before painting to improve the adhesion of the coating, such as automobile manufacturing, steel doors and windows, instrument housings, household appliance housings, etc., and various steel components in the product manufacturing process of painting, electrophoretic coating or powder electrostatic spraying. DETAILED DESCRIPTION

[0014] The following will be a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0015] It should be mentioned that the multifunctional film agent in the embodiment of the present application is mixed with clean water at a ratio of 12-15:85-88 during use, and the total acidity of the tank liquid is controlled to be 18-22 and the free acidity is 1.5-1.8. Of course, due to the consumption of the multifunctional film agent during use, the concentration will change. Therefore, it is necessary to regularly measure the index concentration and ensure that the corresponding index meets the requirements.

[0016] In the examples of this application, the multifunctional film-forming agent and water were mixed in a ratio of 15:85 and performance testing was performed. If other additives are needed, they can be added as needed, which will not be described here. The amount of additive added in each example should be kept consistent.

[0017] At the same time, the multifunctional film agent in the embodiment of the present application does not need to be heated during use. The metal material is overflow washed with water, neutralized washed with water, overflow washed with water and heated to 40°C for 1-2 minutes, then phosphated for 3-8 minutes, and finally washed with water.

[0018] In the examples of the present application, the corrosion inhibitor is implemented using molybdate, which will not be described in detail here.

[0019] The following is a detailed description of a multifunctional film-forming agent and its preparation process of the present application.

[0020] A multifunctional film-forming agent comprises 350 parts by weight of phosphoric acid, 70.5-91.5 parts by weight of MMoO4@ZnO, 20-28 parts by weight of Marib salt and 5-6.3 parts by weight of citric acid.

[0021] In the examples of this application, phosphoric acid, Marif salt, and citric acid are all commercially available. MMoO4@ZnO contains 70-90 parts zinc oxide and 0.5-1.5 parts of a corrosion inhibitor, which is molybdate. The preparation method of MMoO4@ZnO includes separately obtaining a zinc acetate solution and a molybdate solution, adding the molybdate solution to the zinc acetate solution, stirring and thoroughly mixing to obtain a mixture, and then placing the mixture in an oven at 60-80°C for 12-18 hours to obtain a gel, which is then dried and calcined to obtain MMoO4@ZnO.

[0022] It should be noted that in the examples of the present application, the zinc acetate solution uses ethanol as the solvent, and is obtained by mixing zinc acetate and ethanol in a ratio of 5-8 g:60-90 ml, adding citric acid at a rate of 2-4% by mass of the zinc acetate solution, and stirring thoroughly. The molybdate solution uses ethanol as the solvent, and is obtained by mixing molybdate and ethanol in a ratio of 3-6 g:40-60 ml, adding 2 mol / L concentrated hydrochloric acid at a rate of 2-3% by mass of the molybdate solution, and stirring thoroughly.

[0023] During the mixing process of the molybdate solution and the zinc acetate solution, the molybdate solution is added dropwise to the zinc acetate solution while the zinc acetate solution is stirred at a speed of 300-500 rpm. Stirring is continued for 1-2 hours after complete addition. Drying is performed at 40-60°C in a vacuum to obtain a xerogel. Calcination is performed by first grinding the xerogel and then calcining it at 550-650°C for 2-3 hours, with the calcination starting temperature controlled at room temperature and the heating rate at 5-10°C / min, to obtain MMoO4@ZnO.

[0024] It should be mentioned that, in order to reduce costs and increase film forming speed, the molybdate in the embodiment of the present application is composed of sodium molybdate and ammonium molybdate in a mass ratio of 1:2-3.

[0025] A process for preparing a multifunctional film-forming agent, for preparing the multifunctional film-forming agent described above, comprises thoroughly mixing phosphoric acid, MMoO4@ZnO, Marib salt, and citric acid to obtain a prefabricated film-forming agent main ingredient. The prefabricated film-forming agent main ingredient is then mixed with clean water and used for spraying and forming a film on a steel surface at room temperature before coating.

[0026] Example 1 A multifunctional coating agent comprises 350 parts by weight of phosphoric acid, 70.5 parts by weight of MMoO4@ZnO, 20 parts by weight of Marib salt and 5 parts by weight of citric acid.

[0027] In the examples of this application, phosphoric acid, Marif salt, and citric acid are all commercially available. MMoO4@ZnO contains 70 parts of zinc oxide and 0.5 parts of a corrosion inhibitor, which is molybdate. The preparation method of MMoO4@ZnO includes separately obtaining a zinc acetate solution and a molybdate solution, adding the molybdate solution to the zinc acetate solution, stirring and thoroughly mixing to obtain a mixture, and then placing the mixture in a 60°C oven for 18 hours to obtain a gel, which is then dried and calcined to obtain MMoO4@ZnO.

[0028] It should be noted that in the examples of the present application, the zinc acetate solution uses ethanol as the solvent, and is obtained by mixing zinc acetate and ethanol at a ratio of 1 g:12 ml, adding citric acid at a ratio of 2% by mass of the zinc acetate solution, and stirring thoroughly. The molybdate solution uses ethanol as the solvent, and is obtained by mixing molybdate and ethanol at a ratio of 3 g:40 ml, adding 2 mol / L concentrated hydrochloric acid at a ratio of 2% by mass of the molybdate solution, and stirring thoroughly.

[0029] During the mixing process of the molybdate solution and the zinc acetate solution, the molybdate solution was added dropwise to the zinc acetate solution while the zinc acetate solution was stirred at a rate of 300 r / min. Stirring was continued for 1 hour after complete addition. Drying was performed under vacuum at 40°C to obtain a xerogel. Calcination was performed by grinding the xerogel and then calcining it at 550°C for 2 hours, starting at room temperature and heating at a rate of 5°C / min, to obtain MMoO4@ZnO.

[0030] It should be mentioned that, in order to reduce costs and increase film forming speed, the molybdate in the embodiment of the present application is composed of sodium molybdate and ammonium molybdate in a mass ratio of 1:2.

[0031] A process for preparing a multifunctional film-forming agent, for preparing the multifunctional film-forming agent described above, comprises thoroughly mixing phosphoric acid, MMoO4@ZnO, Marib salt, and citric acid to obtain a prefabricated film-forming agent main ingredient. The prefabricated film-forming agent main ingredient is then mixed with clean water and used for spraying and forming a film on a steel surface at room temperature before coating.

[0032] Example 2 A multifunctional coating agent comprises 350 parts by weight of phosphoric acid, 81 parts by weight of MMoO4@ZnO, 25 parts by weight of Marib salt and 6 parts by weight of citric acid.

[0033] In the examples of this application, phosphoric acid, Marif salt, and citric acid are all commercially available. MMoO4@ZnO contains 80 parts zinc oxide and 1 part molybdate as a corrosion inhibitor. The preparation method of MMoO4@ZnO includes separately obtaining a zinc acetate solution and a molybdate solution, adding the molybdate solution to the zinc acetate solution, stirring and thoroughly mixing to obtain a mixture, and then placing the mixture in a 70°C oven for 15 hours to obtain a gel, which is then dried and calcined to obtain MMoO4@ZnO.

[0034] It should be noted that in the examples of the present application, the zinc acetate solution uses ethanol as the solvent, and is obtained by mixing zinc acetate and ethanol at a ratio of 3 g:35 ml, adding citric acid at a ratio of 3% by mass of the zinc acetate solution, and stirring thoroughly. The molybdate solution uses ethanol as the solvent, and is obtained by mixing molybdate and ethanol at a ratio of 2 g:25 ml, adding 2 mol / L concentrated hydrochloric acid at a ratio of 2.5% by mass of the molybdate solution, and stirring thoroughly.

[0035] During the mixing process of the molybdate solution and the zinc acetate solution, the molybdate solution was added dropwise to the zinc acetate solution while the zinc acetate solution was stirred at a rate of 400 r / min. Stirring was continued for 1.5 hours after complete addition. Drying was performed under vacuum at 50°C to obtain a xerogel. Calcination was performed by first grinding the xerogel and then calcining it at 600°C for 2.5 hours. The calcination starting temperature was controlled at room temperature and the heating rate was increased at 7°C / min to obtain MMoO4@ZnO.

[0036] It should be mentioned that, in order to reduce costs and increase film formation speed, the molybdate in the embodiment of the present application is composed of sodium molybdate and ammonium molybdate in a mass ratio of 1:2.5.

[0037] A process for preparing a multifunctional film-forming agent, for preparing the multifunctional film-forming agent described above, comprises thoroughly mixing phosphoric acid, MMoO4@ZnO, Marib salt, and citric acid to obtain a prefabricated film-forming agent main ingredient. The prefabricated film-forming agent main ingredient is then mixed with clean water and used for spraying and forming a film on a steel surface at room temperature before coating.

[0038] Example 3 A multifunctional film-forming agent comprises 350 parts by weight of phosphoric acid, 91.5 parts by weight of MMoO4@ZnO, 28 parts by weight of Marib salt and 6.3 parts by weight of citric acid.

[0039] In the examples of this application, phosphoric acid, Marif salt, and citric acid are all commercially available. MMoO4@ZnO contains 90 parts zinc oxide and 1.5 parts molybdate as a corrosion inhibitor. The preparation method of MMoO4@ZnO includes separately obtaining a zinc acetate solution and a molybdate solution, adding the molybdate solution to the zinc acetate solution, stirring and thoroughly mixing to obtain a mixture, and then placing the mixture in an 80°C oven for 12 hours to obtain a gel, which is then dried and calcined to obtain MMoO4@ZnO.

[0040] It should be noted that in the examples of the present application, the zinc acetate solution uses ethanol as the solvent, and is obtained by mixing zinc acetate and ethanol at a ratio of 8g:90ml, adding citric acid at a ratio of 4% by mass of the zinc acetate solution, and stirring thoroughly. The molybdate solution uses ethanol as the solvent, and is obtained by mixing molybdate and ethanol at a ratio of 1g:10ml, adding 2mol / L concentrated hydrochloric acid at a ratio of 3% by mass of the molybdate solution, and stirring thoroughly.

[0041] During the mixing process of the molybdate solution and the zinc acetate solution, the molybdate solution was added dropwise to the zinc acetate solution while the zinc acetate solution was stirred at a rate of 500 r / min. Stirring was continued for 2 hours after complete addition. Drying was performed at 60°C in a vacuum oven to obtain a xerogel. Calcination was performed by grinding the xerogel and then calcining it at 650°C for 3 hours, starting at room temperature and increasing the temperature at a rate of 10°C / min, to obtain MMoO4@ZnO.

[0042] It should be mentioned that, in order to reduce costs and increase film formation speed, the molybdate in the embodiment of the present application is composed of sodium molybdate and ammonium molybdate in a mass ratio of 1:3.

[0043] A process for preparing a multifunctional film-forming agent, for preparing the multifunctional film-forming agent described above, comprises thoroughly mixing phosphoric acid, MMoO4@ZnO, Marib salt, and citric acid to obtain a prefabricated film-forming agent main ingredient. The prefabricated film-forming agent main ingredient is then mixed with clean water and used for spraying and forming a film on a steel surface at room temperature before coating.

[0044] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that zinc oxide is used instead of MMoO4@ZnO in Comparative Example 1.

[0045] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that in Comparative Example 2, zinc oxide and molybdate are not compounded but directly mixed.

[0046] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that the calcination temperature in Comparative Example 3 is 450°C.

[0047] Performance testing: 1. Film forming speed test: Use a 100mm*100mm metal test piece, control the normal temperature and pressure state, use a spray gun to spray on the surface of the metal test piece, and check every 5 minutes whether the film state meets the dry film forming requirements; 2. Adhesion test: carried out in accordance with GB / T 9286-1998 "Scratch test for paint and varnish films"; 3. Hardness test: carried out in accordance with GB / T 6739-2006 “Paints and varnishes - Determination of film hardness by pencil method”.

[0048] The performance test results are shown in Table 1 below.

[0049] Table 1 Performance test results

[0050] As can be seen from Table 1 above, the MMoO4@ZnO obtained by compounding zinc oxide and molybdate in the present embodiment significantly improves film formation speed and mechanical strength when mixed with phosphoric acid, Marib salt, and citric acid. However, when the drying temperature drops to 450°C, organic matter cannot be completely removed, resulting in the introduction of impurities, which affects the film hardness and adhesion. At the same time, increasing or decreasing the zinc oxide content will affect the crystal structure of the phosphate film, causing changes in the regularity of crystal growth, and further causing the phosphate film structure to become loose and the hardness to decrease. As the hardness decreases, the bonding effect with the metal decreases, resulting in a decrease in adhesion.

[0051] After testing, it was found that the combination of the formulas of the embodiments of the present application, especially the proportion addition of embodiment 2, can break through the existing hardness of the phosphate film and effectively improve the mechanical strength.

[0052] In summary, the present application provides a multifunctional film agent and a preparation process thereof, which effectively improves the corrosion resistance, wear resistance and adhesion performance of the metal by promoting crystal growth and arrangement to form a small, dense and uniform zinc phosphate crystal film during the film forming process. Specifically, by compounding zinc oxide with a corrosion inhibitor, the corrosion inhibitor and the zinc phosphate crystal film are stacked in the film forming process, so that the generated compound iron molybdate and the zinc phosphate crystal film synergistically promote the deposition effect on the metal surface, and thus achieve an effective protective effect. At the same time, the corrosion inhibitor promotes zinc oxide and reduces the porosity and defects of the phosphate film, thereby improving the film integrity and protective effect of the phosphate film, and because the corrosion inhibitor reacts with iron ions, defects and porosity are further filled to achieve an effective metal protection effect. In an embodiment of the present application, by forming a layer of finely crystallized and tightly crystalline phosphate film in a short time, the film is dark gray, the phosphate film is delicate and smooth, has good corrosion resistance, and the phosphate film has strong adhesion to the metal substrate without hanging dust. The phosphating process produces little or no sediment, effectively reducing waste of active ingredients in the phosphating solution due to sediment. Workers also avoid the need to clean sediment or frequent cleaning of spray equipment, saving time, improving production efficiency, and reducing labor intensity. No additional accelerator is required during use; the phosphating solution can be directly replenished, making operation simple and maintenance-friendly. Operating at room temperature, without the need for heating, reduces energy consumption, offers a long service life, a wide operating range, and low overall costs. It is suitable for phosphating steel products prior to painting to improve coating adhesion, such as those used in the automotive industry, steel doors and windows, instrument and meter housings, household appliance housings, and various steel components during the painting, electrophoretic coating, or electrostatic powder spraying process.

[0053] References to "first," "second," "third," "fourth," and the like (if any) herein are intended to distinguish similar objects and are not necessarily intended to describe a particular order or precedence. It should be understood that the numbers used in this manner are interchangeable where appropriate so that the embodiments described herein can be implemented in an order other than that described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions, e.g., a process, method, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, or apparatus.

[0054] It should be noted that the descriptions of "first", "second", etc. in this application are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0055] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A multifunctional film agent, characterized in that: The invention comprises 350 parts by weight of phosphoric acid, 70.5-91.5 parts of MMoO4@ZnO, 20-28 parts of Marib salt and 5-6.3 parts of citric acid; wherein: The MMoO4@ZnO contains 70-90 parts of zinc oxide and 0.5-1.5 parts of molybdate, and the preparation method of the MMoO4@ZnO comprises separately obtaining a zinc acetate solution and a molybdate solution, adding the molybdate solution to the zinc acetate solution, stirring and fully mixing to obtain a mixture, and then placing the mixture in an oven at 60-80°C for 12-18 hours to obtain a gel, followed by drying and calcining to obtain the MMoO4@ZnO.

2. A multifunctional film-forming agent according to claim 1, characterized in that: The zinc acetate solution uses ethanol as a solvent, is prepared by mixing zinc acetate and ethanol at a ratio of 5-8 g:60-90 ml, adding citric acid at a rate of 2-4% of the mass of the zinc acetate solution, and fully stirring.

3. A multifunctional film-forming agent according to claim 1, characterized in that: The molybdate solution uses ethanol as a solvent, is prepared by mixing molybdate and ethanol at a ratio of 3-6 g:40-60 ml, adding 2 mol / L concentrated hydrochloric acid at a ratio of 2-3% of the mass of the molybdate solution, and stirring thoroughly.

4. A multifunctional film-forming agent according to claim 1, characterized in that: The molybdate solution is added to the zinc acetate solution dropwise, and the zinc acetate solution is kept in a stirring state at a stirring speed of 300-500 r / min. Stirring is continued for 1-2 hours after the molybdate solution is completely added.

5. A multifunctional film-forming agent according to claim 1, characterized in that: The drying is performed by vacuum drying at 40-60° C. to obtain a dry gel.

6. A multifunctional film-forming agent according to claim 5, characterized in that: The calcination process comprises the following steps: firstly grinding the dry gel, then calcining at a high temperature of 550-650° C. for 2-3 hours, controlling the starting temperature of the calcination to be room temperature, and heating at a rate of 5-10° C. / min to obtain MMoO4@ZnO.

7. A multifunctional film-forming agent according to claim 1, characterized in that: The molybdate is composed of sodium molybdate and ammonium molybdate in a mass ratio of 1:2-3.

8. A process for preparing a multifunctional film-forming agent, for preparing a multifunctional film-forming agent according to any one of claims 1 to 7, characterized in that: The method comprises fully mixing phosphoric acid, MMoO4@ZnO, Marib salt and citric acid to obtain a main material of a prefabricated film agent; the main material of the prefabricated film agent is used for mixing with clean water and for spraying film formation before coating on steel surfaces at room temperature.

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