A high-catalytic reactivity passivation solution and passivation method for zinc-aluminum-magnesium plated steel sheets

Abstract

The application discloses a high-catalytic-reactivity passivation solution for zinc-aluminum-magnesium plated steel plates and a passivation method. The passivation solution comprises resin monomers, initiators, polyphenol compounds, water-soluble cross-linking agents, trivalent metal salts for resin polymerization, plated layer passivation metal salts, barrier agents, anti-precipitation agents and other components. All the components have good water solubility and water dispersibility and high reactivity. The polyphenol compounds contain catechol groups which catalyze the polymerization of olefin bonds and enhance the stability of the passivation film. The passivation solution has low film-forming temperature after heating and solidification, high strength, high cross-linking density and excellent barrier performance, can isolate the contact between corrosive media and the metal substrate, thereby preventing or inhibiting the corrosion of water, oxygen and ions through the coating to the battery, and can effectively reduce defects such as passivation spots and insufficient resin solidification. While the resin film is formed on the plated layer surface, the plated layer metal undergoes a passivation reaction to generate a chemical conversion layer, further preventing white scar and black spot defects caused by oxidation defects of the plated layer.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to a highly catalytically active passivation solution and passivation method for zinc-aluminum-magnesium coated steel plates. Background Technology

[0002] Zinc-aluminum-magnesium alloy coatings attracted widespread attention abroad in the 1980s, becoming a key research focus in the fields of hot-dip galvanizing and zinc alloy coatings. Research from domestic and international peers indicates that, compared to traditional hot-dip galvanized steel sheets, hot-dip galvanized aluminum-magnesium alloy coated steel sheets with added Al and Mg exhibit superior corrosion resistance and excellent processing and application properties (formability, weldability, and paintability). They can replace existing hot-dip galvanized or zinc alloy coated steel sheets, showing a very broad market demand prospect. However, because Al and Mg are more reactive than zinc, they are prone to oxidation when exposed to air, producing aluminum and magnesium oxide films. Uneven oxide thickness can also cause white rust defects on the coated steel sheet surface. In particular, magnesium oxidation can darken the coating surface or cause dense black spots across the entire sheet, severely affecting the surface quality of the product. To inhibit the oxidation of zinc-aluminum-magnesium coatings, the coatings need to be surface-treated again. Currently, the surface treatment for galvanized steel sheets usually uses trivalent chromium passivation or silane fingerprint-resistant passivation. Although trivalent chromium passivation is less toxic than hexavalent chromates, it is still harmful to the human body and the environment. Silane-containing passivating agents have the problem of low reactivity, and usually require higher curing temperatures and curing times to cure into a film, which affects production efficiency.

[0003] In the prior art, patent CN113445053B provides a compound corrosion inhibitor for Mg-Al alloys, its preparation method, and its application. This corrosion inhibitor has a simple composition, consisting of 1-100 mmol / L sodium phosphate and 0.1-20 mmol / L sodium dodecyl sulfate in a mass ratio of 2:1-2:4. It achieves a corrosion inhibition efficiency of over 95% for Mg-Al alloys in a 3% sodium chloride medium. However, this method is not suitable as an anti-corrosion method for zinc-aluminum-magnesium alloy coatings. Although low in cost, its composition is relatively simple, its corrosion inhibition ability is limited, and the presence of phosphating agents in the corrosion inhibitor will also have a certain impact on the environment. Patent CN103966590B provides a method for using a single silane coupling agent composite chromium-free passivation solution and passivating the surface coating of galvanized steel wire. This method uses a non-toxic and environmentally friendly passivating agent to improve the corrosion resistance of the steel wire. Its technical drawbacks are that the immersion treatment time is too long and the curing temperature is too high. In summary, current reports on metal surface treatment solutions mainly focus on the formation of oxide films through chemical reactions with metals, while neglecting the role of resin film formation. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, all components of the passivation solution of this invention have good water solubility, are environmentally friendly and non-volatile, have high reactivity, low reaction film formation temperature, high strength, high crosslinking density, and excellent barrier properties. It can isolate corrosive media from contact with the metal substrate, thereby preventing or inhibiting water, oxygen, and ions from permeating the coating and forming corrosion cells. This effectively reduces defects such as passivation spots and insufficient resin curing. Simultaneously, while a resin film forms on the coating surface, the zinc-aluminum-magnesium alloy of the coating undergoes a passivation reaction with the metal salts in the passivation solution to produce a chemical conversion layer. This further prevents oxidation defects in the coating, such as white spots and black patches, which is of great significance for improving the surface quality of the product.

[0005] To achieve the above-mentioned objective, this invention provides a highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets. The passivation solution comprises the following components in weight fractions (wt%): 10-15% resin monomer, 0.05-0.1% initiator, 0.1-0.2% polyphenolic compound, 0.5-1% water-soluble crosslinking agent, 0.1-0.2% trivalent metal salt for resin polymerization, 2-5% metal salt for coating passivation, 0.1-0.2% barrier agent, 0.5-1% anti-precipitant, pH adjusted with an acid regulator, and the remaining component is water.

[0006] The passivation solution contains an environmentally friendly water-based resin, a water-soluble initiator and crosslinking agent, a water-soluble trivalent metal salt that catalyzes resin polymerization, a reducing polyphenol as the metal chelating agent, an acidic pH adjuster, a chemically converted film-forming metal salt, and an anti-precipitation agent. This passivation solution uses an environmentally friendly water-soluble resin as the film-forming agent. During the drying and curing process, the metal ion-phenolic hydroxyl complex can catalyze the formation of high molecular weight and highly crosslinked polymeric resin from the water-based resin monomers by generating quinone free radicals. The metal ions chelate the hydroxyl and carboxyl groups in the polymeric resin. Polyphenolic compounds contain abundant catechol groups, which can form complexes with trivalent metal salts. These complexes contain three coordinate bonds, thus forming a tripentate coordination structure. This structure can catalyze the catalytic polymerization reaction of olefin bonds while enhancing the physicochemical stability of the passivation film.

[0007] In the above technical solution, the resin monomer is further selected from water-based acrylic derivatives, such as acrylic acid, acrylamide, methacrylic acid, styrene-acrylic emulsion, polyethylene glycol diacrylate, etc., which can be polymerized by free radical initiation.

[0008] Furthermore, the initiator is a water-soluble inorganic peroxide capable of generating hydroxyl radicals, including one of ammonium persulfate, sodium persulfate, potassium persulfate, potassium hydrogen persulfate, etc. Although the peroxide initiator has a high decomposition temperature (50-100°C), limiting its application in low-temperature polymerization reactions, it also avoids the passivation solution from gelling at room temperature due to excessive activity.

[0009] Furthermore, the polyphenolic compound is one of the following: catechol, 3-methylcatechol, 4-methylcatechol, 3,4-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 5,6-dihydroxyindole, catechin, gallic acid, tannic acid, etc.

[0010] Furthermore, the water-soluble crosslinking agent is one of N,N-methylenebisacrylamide, N-hydroxymethylacrylamide, etc.

[0011] Furthermore, the trivalent metal salt used for resin polymerization is one of aluminum sulfate, aluminum nitrate, ferric sulfate, ferric nitrate, cerium acetate, cerium nitrate, etc., and this metal salt can catalyze resin polymerization.

[0012] Furthermore, the passivating metal salt of the coating is one or more of titanium oxysulfate, ammonium metavanadate, sodium metavanadate, sodium molybdate, and sodium fluorozirconate, which can promote the passivation reaction of the zinc-aluminum-magnesium coating.

[0013] Furthermore, the barrier agent is graphene oxide; the anti-precipitation agent is one of polyvinyl alcohol, tragacanth gum, xanthan gum, sodium alginate, bentonite, etc.

[0014] Furthermore, the acidity regulator is one of oxalic acid, 2-aminoethylsulfonic acid, L-lactic acid, succinic acid, nitric acid, sulfuric acid, etc.

[0015] A method for preparing a highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets, the preparation method comprising the following steps:

[0016] ① Add the anti-precipitant to water and stir to dissolve it in hot water at 80℃~90℃ to form a stable colloidal solution;

[0017] ② Add resin monomer, water-soluble crosslinking agent, trivalent metal salt for resin polymerization, metal salt for plating passivation, and barrier agent sequentially to the colloidal solution, and stir to dissolve at room temperature;

[0018] ③ Add the polyphenolic compound and initiator to the solution obtained in step ②, and adjust the pH of the solution to 3-4 with an acidic regulator. After stirring evenly, a passivation solution is obtained.

[0019] A passivation method for treating the surface of zinc-aluminum-magnesium coated steel sheet with the aforementioned passivation solution, wherein the passivation method employs one of the following methods: immersion, roller coating, or brush coating. The passivation solution is dried using one of the following methods: ultraviolet light curing, hot air drying curing, or electromagnetic induction heating of the steel sheet curing; the drying curing temperature is 105–120°C; the curing time varies depending on the passivation treatment method, with immersion and brush coating surface passivation curing time being 1–2 minutes, and roller coating passivation time being 5–10 seconds. When roller coating is used for surface treatment of the coating, the liquid coating amount is 10–15 g / m². 2 Dry film weight 0.8–2 g / m³ 2 .

[0020] Furthermore, the zinc-aluminum-magnesium coated steel sheet has an Al content of 2-55 wt%, a Mg content of 1-5 wt%, and the remainder is zinc and unavoidable impurities.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention uses an environmentally friendly water-based monomer resin as the film-forming agent. An initiator promotes the polymerization of the monomer resin into a film, and a crosslinking agent enhances the crosslinking density and film strength of the resin. Polyphenols promote electron transfer and chelate metal ions, increasing the reaction rate. Polyphenolic compounds contain abundant catechol groups, which can form complexes with trivalent metal salts. These complexes contain three coordinate bonds, thus forming a tridentate coordination structure. This structure can catalyze the catalytic polymerization of olefin bonds while simultaneously enhancing the physicochemical stability of the passivation film. An acidic pH adjuster activates the metal surface, while inorganic metal salts promote the formation of a corrosion-resistant chemical conversion layer. An anti-precipitation agent stabilizes the passivation solution and prevents precipitation. The passivation solution uses an environmentally friendly water-soluble resin as the film-forming agent. During the drying and curing process, a redox reaction occurs between the polyphenols and the initiator, generating semiquinone and hydroxyl radicals that initiate the polymerization of the water-soluble resin monomers. Iron ions chelate the hydroxyl and carboxyl groups in the polymer film and also catalyze the polymerization of acrylic resin. Compared to traditional passivating agents for galvanized steel, the passivation solution of this invention uses all components with good water solubility, is environmentally friendly and non-volatile, has a low reaction film-forming temperature, high strength, and high cross-linking density, which can effectively reduce defects such as passivation spots and insufficient resin curing. It also exhibits good coating adhesion, high catalytic activity, rapid curing performance, resistance to blackening, self-healing properties, and high corrosion resistance. While a resin film forms on the coating surface, the metal undergoes a passivation reaction to generate a chemical conversion layer, further preventing oxidation defects such as white spots and black patches, which is of great significance for improving product surface quality. Furthermore, this passivation solution uses water-soluble resin to form a film on the coating surface, avoiding the use of volatile organic solvents such as alcohols and benzenes that are harmful to the health of operators. Moreover, this passivation solution can reduce the temperature of the hot air blower and the electromagnetic induction heating power in the passivation process of the production line, saving energy. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments, but this does not limit the invention in any way. To avoid redundancy, unless otherwise specified, the raw materials used in the following embodiments are all commercially available products, and the methods used are all conventional methods unless otherwise specified.

[0024] The mass content of each component in the passivation solution for hot-dip galvanized aluminum-magnesium alloy coated steel sheets in Examples 1-6 and Comparative Examples 1-6 is shown in Table 1.

[0025] Table 1. Mass content (g) of each component in the passivation solution

[0026]

[0027] In Examples 1-6 and Comparative Examples 1-6, the method for preparing the passivation solution for hot-dip galvanized aluminum-magnesium alloy coated steel sheets includes the following steps:

[0028] ① Add the anti-precipitant to water and stir to dissolve it in hot water at 80℃~90℃ to form a stable colloidal solution;

[0029] ② Add resin monomer, water-soluble crosslinking agent, trivalent metal salt for resin polymerization, metal salt for plating passivation, and barrier agent sequentially to the colloidal solution, and stir to dissolve at room temperature;

[0030] ③ Add the polyphenolic compound and initiator to the solution obtained in step ②, and adjust the pH of the solution to 3-4 with an acidic regulator. After stirring evenly, a passivation solution is obtained.

[0031] In Examples 1-6 and Comparative Examples 1-6, the passivation methods for treating the surface of the hot-dip galvanized aluminum-magnesium alloy coated steel sheets using passivation solutions were described. For ease of comparison, all passivation methods employed a roller coating method for surface treatment, with a liquid coating amount of 10-15 g / m². 2 Dry film weight 0.8–2 g / m³ 2 Dry with hot air at 105℃ for 10 seconds.

[0032] Example 1

[0033] A highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets is disclosed. The aqueous resin monomer of the passivation solution is acrylamide, the water-soluble crosslinking agent is N,N-methylenebisacrylamide, the metal salt for zinc-aluminum-magnesium coating passivation is sodium molybdate, the pH adjuster is sulfuric acid, the trivalent metal salt for catalyzing resin polymerization is ferric nitrate, the initiator is sodium persulfate, the polyphenol is tannic acid, the barrier agent is graphene oxide, and the anti-precipitation agent is tragacanth gum.

[0034] Example 2

[0035] A highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets is disclosed. The aqueous resin monomer of the passivation solution is acrylic acid, the water-soluble crosslinking agent is N,N-methylenebisacrylamide, the metal salt for zinc-aluminum-magnesium coating passivation is titanium oxysulfate, the pH adjuster is nitric acid, the trivalent metal salt for catalyzing resin polymerization is cerium nitrate, the initiator is ammonium persulfate, the polyphenol is 5,6-dihydroxyindole, the barrier agent is graphene oxide, and the anti-precipitation agent is xanthan gum.

[0036] Example 3

[0037] A highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets is disclosed. The aqueous resin monomer of the passivation solution is styrene-acrylic emulsion, the water-soluble crosslinking agent is N,N-methylenebisacrylamide, the metal salt for zinc-aluminum-magnesium coating passivation is ammonium metavanadate, the pH adjuster is sulfuric acid, the trivalent metal salt for catalyzing resin polymerization is aluminum sulfate, the initiator is sodium fluorozirconate, the polyphenol is catechol, the barrier agent is graphene oxide, and the anti-precipitation agent is polyvinyl alcohol.

[0038] Example 4

[0039] A highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets is disclosed. The aqueous resin monomer of the passivation solution is styrene-acrylic emulsion, the aqueous crosslinking agent is N-hydroxymethylacrylamide, the metal salt for zinc-aluminum-magnesium coating passivation is ammonium metavanadate, the pH adjuster is nitric acid, the trivalent metal salt for catalyzing resin polymerization is ferric nitrate, the initiator is ammonium persulfate, the polyphenol is 2,3-dihydroxybenzoic acid, the barrier agent is graphene oxide, and the anti-precipitation agent is polyvinyl alcohol.

[0040] Example 5

[0041] A highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets is disclosed. The aqueous resin monomer of the passivation solution is methacrylic acid, the aqueous crosslinking agent is N-hydroxymethylacrylamide, the metal salt for zinc-aluminum-magnesium coating passivation is ammonium metavanadate, the pH adjuster is nitric acid, the trivalent metal salt for catalyzing resin polymerization is aluminum sulfate, the initiator is ammonium persulfate, the polyphenol is catechin, the barrier agent is graphene oxide, and the anti-precipitation agent is sodium alginate.

[0042] Example 6

[0043] A highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets is disclosed. The aqueous resin monomer of the passivation solution is methacrylic acid, the aqueous crosslinking agent is N-hydroxymethylacrylamide, the metal salt for zinc-aluminum-magnesium coating passivation is ammonium metavanadate, the pH adjuster is nitric acid, the trivalent metal salt for catalyzing resin polymerization is aluminum sulfate, the initiator is ammonium persulfate, the polyphenol is 4-methylcatechol, the barrier agent is graphene oxide, and the anti-precipitation agent is tragacanth gum.

[0044] Comparative Example 1

[0045] The passivation solution is composed of the following components: acrylic acid as the waterborne resin monomer, no waterborne crosslinking agent is added, titanium oxysulfate is used as the metal salt for passivation of zinc-aluminum-magnesium coating, nitric acid is used as the pH adjuster, cerium nitrate is used as the trivalent metal salt for catalyzing resin polymerization, ammonium persulfate is used as the initiator, 5,6-dihydroxyindole is used as the polyphenol, graphene oxide is used as the barrier agent, and xanthan gum is used as the anti-precipitant.

[0046] Comparative Example 2

[0047] The passivation solution is composed of the following components: waterborne resin monomer is methacrylic acid, waterborne crosslinking agent is N,N-methylenebisacrylamide, no zinc-aluminum-magnesium plating passivation metal salt is added, pH adjuster is sulfuric acid, trivalent metal salt for catalyzing resin polymerization is ferric sulfate, initiator is sodium persulfate, polyphenol is 2,3-dihydroxybenzoic acid, barrier agent is graphene oxide, and anti-precipitant is polyvinyl alcohol.

[0048] Comparative Example 3

[0049] The passivation solution is composed of the following components: acrylamide as the aqueous resin monomer, N-hydroxymethylacrylamide as the aqueous crosslinking agent, ammonium metavanadate as the metal salt for passivation of zinc-aluminum-magnesium coating, oxalic acid as the pH adjuster, ferric nitrate as the trivalent metal salt for catalyzing resin polymerization, no initiator added, tannic acid as the polyphenol, graphene oxide as the barrier agent, and tragacanth gum as the anti-precipitant.

[0050] Comparative Example 4

[0051] The passivation solution is composed of the following components: waterborne resin monomer is styrene-acrylic emulsion, waterborne crosslinking agent is N-hydroxymethylacrylamide, passivation metal salt for zinc-aluminum-magnesium coating is ammonium metavanadate, pH adjuster is nitric acid, no catalytic resin polymerization trivalent metal salt is added, initiator is potassium persulfate, polyphenol is catechin, barrier agent is graphene oxide, and anti-precipitation agent is xanthan gum.

[0052] Comparative Example 5

[0053] The passivation solution is composed of the following components: polyethylene glycol diacrylate as the aqueous resin monomer, N,N-methylenebisacrylamide as the aqueous crosslinking agent, sodium silicate as the passivation metal salt for zinc-aluminum-magnesium plating, L-lactic acid as the pH adjuster, cerium nitrate as the trivalent metal salt to catalyze resin polymerization, sodium persulfate as the initiator, gallic acid as the polyphenol, graphene oxide as the barrier agent, and no anti-precipitation agent.

[0054] Comparative Example 6

[0055] The passivation solution is composed of the following components: polyethylene glycol diacrylate as the aqueous resin monomer, N,N-methylenebisacrylamide as the aqueous crosslinking agent, sodium molybdate as the passivation salt for zinc-aluminum-magnesium plating, L-lactic acid as the pH adjuster, cerium nitrate as the trivalent metal salt to catalyze resin polymerization, sodium persulfate as the initiator, gallic acid as the polyphenol, polyvinyl alcohol as the anti-precipitant, and no graphene oxide barrier agent is added.

[0056] The stability of the surface treatment solution for hot-dip galvanized aluminum-magnesium alloy coated steel plates was determined by testing Examples 1-6 and Comparative Examples 1-6. The test method was as follows: the prepared passivation solution was placed in a well-ventilated indoor area, and the time for stable storage of the liquid (without color change, precipitation, coagulation, or other adverse phenomena) was observed. The results are shown in Table 2 (the shelf life of the coating treatment solution is currently 90 days).

[0057] The corrosion resistance, blackening resistance, fingerprint resistance, water resistance, and heat resistance of the surface coating of hot-dip galvanized aluminum-magnesium alloy coated steel sheets were determined using Examples 1-6 and Comparative Examples 1-6. The results are shown in Table 3.

[0058] The corrosion resistance was tested according to the methods and conditions specified in GB / T10125, and the corrosion results were evaluated according to GB12335-90 (expressed as the percentage of the corroded area to the total area after 72h and 120h). A smaller corroded area is better (currently, the general requirement is that the NSST / 72h corrosion area ≤ 5%).

[0059] Resistance to blackening is determined by the color difference before and after the NSST / 120h test. If no obvious color change is observed on the surface, i.e., the color difference value is ≤2, then the resistance to blackening is good.

[0060] Fingerprint resistance is determined by the change in color difference before and after applying Vaseline to the sample surface: if the change is less than 1, it is grade A; if the change is greater than 1 but less than 2, it is grade B; if the change is greater than 2 but less than 4, it is grade C; and if the change is greater than 4, it is grade D. Currently, the fingerprint resistance of coatings is generally grade B or higher.

[0061] Water resistance is determined by dropping 100°C deionized water onto the sample: if the sample shows no watermarks at all, it is grade A; if there are slight watermarks, it is grade B; and if there are obvious watermarks, it is grade C. Currently, the water resistance of coatings is generally grade A or B.

[0062] Heat resistance is determined by the change in color difference before and after baking the sample at 350℃ for 30 minutes: if the change in color difference is less than 2, it is Grade A; if the change in color difference is greater than 2 but less than 4, it is Grade B; if the change in color difference is greater than 4 but less than 8, it is Grade C; and if the change in color difference is greater than 8, it is Grade D. Currently, organic coatings have poor heat resistance and are generally Grade C or D.

[0063] Table 2. Results of passivation solution stability test

[0064] Treatment fluid Settling time (d) Treatment fluid Stable number of days (d) Example 1 ≥90 Comparative Example 1 ≥90 Example 2 ≥90 Comparative Example 2 ≥90 Example 3 ≥90 Comparative Example 3 ≥90 Example 4 ≥90 Comparative Example 4 ≥90 Example 5 ≥90 Comparative Example 5 ≤7 Example 6 ≥90 Comparative Example 6 ≥90

[0065] Table 3. Performance of Passivation Solution

[0066]

[0067]

[0068] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A highly catalytically active passivation solution for zinc-aluminum-magnesium coated steel sheets, characterized in that, The passivation solution contains the following components by mass: 120g resin monomer, 1g initiator, 2g polyphenol compound, 6g water-soluble crosslinking agent, 2g trivalent metal salt for resin polymerization, 25g metal salt for plating passivation, 1.5g barrier agent, 5g anti-precipitant, and 1000g water, with pH adjusted by an acidic regulator. The resin monomer is one of acrylic acid, acrylamide, methacrylic acid, styrene-acrylic emulsion, and polyethylene glycol diacrylate; the initiator is one of ammonium persulfate, sodium persulfate, potassium persulfate, and potassium peroxymonosulfate. The polyphenolic compound is one of the following: catechol, 3-methylcatechol, 4-methylcatechol, 3,4-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, 5,6-dihydroxyindole, catechin, gallic acid, and tannic acid. The water-soluble crosslinking agent is one of N,N-methylenebisacrylamide and N-hydroxymethylacrylamide; The trivalent metal salt used for resin polymerization is one of aluminum sulfate, aluminum nitrate, ferric sulfate, ferric nitrate, cerium acetate, and cerium nitrate; the passivation metal salt for coating is one or more of titanium oxysulfate, ammonium metavanadate, sodium metavanadate, sodium molybdate, and sodium fluorozirconate. The barrier agent is graphene oxide; the anti-precipitant is one of polyvinyl alcohol, tragacanth gum, xanthan gum, sodium alginate, and bentonite; the acid regulator is one of oxalic acid, 2-aminoethylsulfonic acid, L-lactic acid, succinic acid, nitric acid, and sulfuric acid.

2. A method for preparing the passivation solution as described in claim 1, characterized in that, The preparation method includes the following steps: (1) Add the anti-precipitant to water and stir to dissolve it in hot water at 80℃~90℃ to form a stable colloidal solution; (2) Add resin monomer, water-soluble crosslinking agent, trivalent metal salt for resin polymerization, metal salt for plating passivation and barrier agent to the colloidal solution in sequence, and stir to dissolve at room temperature; (3) Add the polyphenolic compound and initiator to the solution obtained in step (2), and adjust the pH of the solution to 3-4 with an acidic regulator. After stirring evenly, a passivation solution is obtained.

3. A passivation method for treating the surface of zinc-aluminum-magnesium coated steel sheet using the passivation solution as described in claim 1, characterized in that, The passivation method employs one of the following methods: immersion, roller coating, or brush coating.

4. The passivation method according to claim 3, characterized in that, The passivation solution is dried using one of the following methods: ultraviolet light curing, hot air drying curing, or electromagnetic induction heating of the steel plate. The drying curing temperature is 105℃~120℃. The curing time for immersion and brush coating passivation is 1~2 min, and the time for roller coating passivation is 5~10 s. When roller coating is used for surface treatment of the coating, the liquid coating amount is 10~15 g / m². 2 Dry film weight 0.8~2 g / m 2 .

5. The passivation method according to claim 3, characterized in that, The zinc-aluminum-magnesium coated steel sheet has an Al content of 2-55 wt%, a Mg content of 1-5 wt%, and the remainder is zinc and unavoidable impurities.

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