Water washing treatment agent for zinc-based coating steel before electrophoresis as well as preparation method and application of water washing treatment agent

Abstract

The invention relates to a water washing treatment agent for zinc-based coating steel before electrophoresis as well as a preparation method and application thereof, and belongs to the technical field of metal surface modification. The water washing treatment agent is prepared from the following components in parts by weight: 1 to 2 parts of a film forming agent, 0.1 to 0.25 part of an oxidizing agent, 0.1 to 0.25 part of a surfactant and 0.2 to 0.5 part of a chelating agent. Zinc-based coating steel is subjected to titanium-zirconium treatment, a titanium-zirconium conversion film is formed on the surface, in the washing treatment agent, an oxidizing agent promotes oxidation conversion of the titanium-zirconium conversion film and improves the compactness of an oxidation film, a film-forming agent is adsorbed to the defect position of the titanium-zirconium conversion film to improve the quality of an adsorption film, and a chelating agent can be chelated with the film-forming agent; a complex is formed to be adsorbed and deposited at the defect position of a titanium-zirconium conversion film, surface homogenization is promoted, the surfactant can promote formula solubility and can also promote directional adsorption of a film-forming agent and the like on the liquid-solid (solution / metal) surface, so that external water vapor and corrosive ions are effectively blocked, and the corrosion resistance and filamentous corrosion inhibition performance of zinc-based coating steel are remarkably improved.

Description

Technical Field

[0001] The present application relates to the technical field of metal surface modification, and particularly relates to a pre-electrophoresis water washing treatment agent for zinc-based coated steel, a preparation method thereof, and an application thereof. Background Art

[0002] Zinc-based coated steel plates, including pure galvanized steel plates and zinc-magnesium-aluminum coated steel plates with low aluminum and low magnesium, have been widely used in fields such as automobile manufacturing due to their excellent corrosion resistance, formability, and welding performance. Such materials can not only meet the requirements of the automotive industry for lightweight and high strength, but also show significant advantages in environmental protection performance and service life. Therefore, zinc-based coated steel plates have become one of the ideal choices for dealing with complex working conditions. Although zinc-based coated steel plates have excellent corrosion resistance and mechanical properties, both pure galvanized steel plates and zinc-magnesium-aluminum coated steel plates with low aluminum and low magnesium face potential filiform corrosion problems during the application process after painting. The widespread existence of this phenomenon affects the appearance quality and long-term durability of the materials. Therefore, in order to ensure the wide application of zinc-based coated steel plates in the automotive field, it is urgent to develop a pre-electrophoresis treatment technology with excellent filiform corrosion inhibition effect.

[0003] To further improve the corrosion resistance and filiform corrosion inhibition performance of zinc-based coated steel, it is necessary to further optimize the thin film treatment process and pre-electrophoresis treatment technology. However, the development of pre-electrophoresis treatment technology for zinc-based coated steel plates in China is still imperfect at present, especially in the automotive user side, there is no surface treatment technology that can be applied to inhibit filiform corrosion of zinc-based coated steel wires. Therefore, in order to ensure the efficient application and popularization of zinc-based coated steel in the automotive field, it is necessary to develop a pre-electrophoresis water washing treatment agent for inhibiting filiform corrosion of zinc-based coated steel wires. Summary of the Invention

[0004] The present application provides a pre-electrophoresis water washing treatment agent for zinc-based coated steel, a preparation method thereof, and an application thereof, so as to solve the following technical problem: how to improve the filiform corrosion resistance of zinc-based coated steel.

[0005] In a first aspect, the present application provides a pre-electrophoresis water washing treatment agent for zinc-based coated steel. Calculated by weight parts, the water washing treatment agent includes: a film-forming agent: 1 part to 2 parts, an oxidizing agent: 0.1 part to 0.25 parts, a surfactant: 0.1 part to 0.25 parts, and a chelating agent: 0.2 parts to 0.5 parts.

[0006] Optionally, the pH value of the water washing treatment agent is 6.5 to 7.5.

[0007] Optionally, the film-forming agent is at least one of pyridine, picolinic acid, thiazole, imidazole, benzothiazole, and benzimidazole.

[0008] Optionally, the oxidizing agent is at least one of sodium nitrite, hydrogen peroxide, and potassium permanganate.

[0009] Optionally, the surfactant is an anionic surfactant.

[0010] Optionally, the chelating agent is at least one of disodium ethylenediaminetetraacetate, citric acid, tartaric acid, diethanolamine, and sodium alginate.

[0011] In a second aspect, the present application provides a method for preparing the water washing treatment agent described in the first aspect, the method comprising:

[0012] Mixing and stirring the film-forming agent and the solvent to obtain a mixed solution;

[0013] Sequentially adding an oxidizing agent, a chelating agent, and a surfactant to the mixed solution to obtain the water washing treatment agent;

[0014] Performing a titanium-zirconium treatment on the zinc-based plated steel to form a titanium-zirconium conversion film on the surface of the zinc-based plated steel, obtaining a zinc-based plated steel with a film;

[0015] Coating the water washing treatment agent on the surface of the zinc-based plated steel with a film to obtain a coated zinc-based plated steel.

[0016] Optionally, the zinc-based plated steel is a pure zinc plated steel and / or a zinc-magnesium-aluminum plated steel.

[0017] Optionally, by weight, the chemical composition of the coating of the zinc-magnesium-aluminum plated steel includes: zinc: 1 part to 3 parts, magnesium: 1 part to 3 parts.

[0018] In a third aspect, the present application provides an application of the water washing treatment agent described in the first aspect, and the water washing treatment agent is applied to the water washing link before electrophoresis of zinc-based plated steel automotive sheets at the user end.

[0019] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0020] The present application provides a pre - electrophoresis water - washing treatment agent for zinc - based coated steel. By weight, the water - washing treatment agent includes: film - forming agent: 1 part - 2 parts, oxidant: 0.1 part - 0.25 parts, surfactant: 0.1 part - 0.25 parts, chelating agent: 0.2 part - 0.5 parts. The zinc - based coated steel is treated with titanium and zirconium, and a titanium - zirconium conversion film is formed on the surface. In the water - washing treatment agent, the oxidant can promote the transformation of titanium and zirconium components in the conversion film into titanium - zirconium oxides, further improving the corrosion resistance of the titanium - zirconium conversion film; the film - forming agent can form a chemical bond adsorption on the oxides of the conversion film to form a dense film layer, effectively blocking water vapor and erosive ions in the environment. At the same time, the film - forming agent can also adsorb at the defects of the conversion film of the zinc - based coated steel to form an organic film layer, and cooperate with the titanium - zirconium conversion film to realize the protection of the zinc - based coated steel; the chelating agent can chelate with the film - forming agent to form a complex that adsorbs and deposits at the defects of the conversion film, promoting surface homogenization and effectively hindering water vapor and erosive ions; the surfactant can promote the solubility of the formulation and also promote the directional adsorption of the film - forming agent, etc. on the liquid - solid (solution / metal) surface. The synergistic effect of the four components promotes the transformation of the titanium - zirconium conversion film into titanium - zirconium oxides, makes up for the defects and improves the film density, effectively blocks external water vapor and erosive ions, significantly improves the corrosion resistance of the zinc - based coated steel, so that the zinc - based coated steel has an excellent effect of inhibiting filiform corrosion, meeting the wide application of the zinc - based coated steel at the automotive user end. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with the present application and, together with the specification, are used to explain the principles of the present application.

[0022] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0023] Figure 1 It is a schematic flow chart of a preparation method of a pre - electrophoresis water - washing treatment agent for zinc - based coated steel provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are a part rather than all of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0025] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and single values within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0026] As used herein, the term "comprising" and the like means "including but not limited to". Relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "a plurality" means two or more; "at least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single items (pieces) or plural items (pieces); for example, "at least one of a, b, or c", or "at least one of a, b, and c" can both mean: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively. The "parts representation method" such as parts by weight, parts by mass, etc. represents the proportional relationship between each component. In the proportional relationships involved herein, the parameters that need to be described by proportion should be understood as the antecedents of the proportion formula in the order of description, and the proportional numbers should be understood as the consequents of the proportion formula. For example, if the weight ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportion formula in the order of description, that is, the weight of substance A: the weight of substance B: the weight of substance C = 1:2:3.

[0027] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used herein can be obtained through market purchase or can be prepared by existing methods.

[0028] In a first aspect, the present application provides a water washing treatment agent for zinc-based coated steel before electrophoresis. Calculated by weight parts, the water washing treatment agent includes: film-forming agent: 1 part to 2 parts, oxidizing agent: 0.1 part to 0.25 parts, surfactant: 0.1 part to 0.25 parts, chelating agent: 0.2 part to 0.5 parts.

[0029] The water washing treatment agent for zinc-based coated steel provided by the embodiments of the present application is mainly used for performing titanium-zirconium treatment on zinc-based coated steel. After the zinc-based coated steel is subjected to titanium-zirconium treatment, a titanium-zirconium conversion film is formed on the surface. The titanium-zirconium treatment film is the main process for the surface treatment of current automotive sheets: The titanium-zirconium conversion film is formed by immersing the metal surface (usually a steel sheet or an aluminum alloy sheet) in a solution containing titanium and zirconium salts, causing a chemical reaction on the metal surface to form a thin film. The main components of this thin film are a composite film of titanium oxide and zirconium oxide. It combines the advantages of titanium and zirconium elements, has good corrosion resistance, wear resistance, and oxidation resistance, and is widely used in aspects such as the protection of automotive sheets, pretreatment of painting, and extension of material life.

[0030] In the water washing treatment agent, the oxidizing agent can promote the transformation of titanium-zirconium components in the conversion film into titanium-zirconium oxides, further enhancing the corrosion resistance of the titanium-zirconium conversion film. The weight parts of the oxidizing agent in the water washing treatment agent for zinc-based coated steel before electrophoresis are 0.1 part to 0.25 parts. When the weight parts are less than 0.1 part, the complete transformation of titanium-zirconium oxides cannot be achieved. When the weight parts are higher than 0.25 parts, it may cause the treatment agent solution to become turbid, affecting the stability of the treatment agent. Exemplarily, the weight parts of the oxidizing agent can be 0.1 part, 0.13 part, 0.16 part, 0.19 part, 0.22 part, 0.25 part, etc.

[0031] The film-forming agent can perform bonding adsorption on the oxides of the conversion film to form a dense film layer, effectively blocking water vapor and erosive ions in the environment. At the same time, the film-forming agent can also adsorb at the defects of the conversion film of the zinc-based coated steel to form an organic film layer, and cooperate with the titanium-zirconium conversion film to achieve the protection of the zinc-based coated steel. The weight parts of the film-forming agent in the water washing treatment agent for zinc-based coated steel before electrophoresis are 1 part to 2 parts. When the weight parts are less than 1 part, the film-forming agent cannot completely make up for the defects of the titanium-zirconium oxide film layer, and the film-forming quality is poor. If the weight parts are higher than 2 parts, the cost increases, and the film-forming is uneven. Exemplarily, the weight parts of the film-forming agent can be 1 part, 1.2 part, 1.4 part, 1.6 part, 1.8 part, 2 part, etc.

[0032] Chelating agents can chelate with film-forming agents to form complexes that adsorb and deposit at the defects of the conversion film, promoting surface homogenization and effectively blocking water vapor and corrosive ions. The weight portion of the chelating agent in the pre-electrophoresis water washing treatment agent for zinc-based coated steel is 0.2 to 0.5 parts. When the weight portion is less than 0.2 parts, the film-forming compactness is poor and the film-forming quality is low. When the weight portion is higher than 0.5 parts, the treatment agent is unstable and the film-forming is uneven. Exemplarily, the weight portion of the chelating agent can be 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.5 parts, etc.

[0033] Surfactants can promote the solubility of each component and also promote the directional adsorption of film-forming agents, etc. on the liquid-solid (solution / metal) surface. The weight portion of the surfactant in the pre-electrophoresis water washing treatment agent for zinc-based coated steel is 0.1 to 0.25 parts. When the weight portion is less than 0.1 part, the treatment agent will become turbid, the treatment agent system is unstable, and at the same time the film-forming quality will also deteriorate. When the weight portion is higher than 0.25 parts, the number of bubbles in the treatment agent increases, affecting the adsorption and wetting of the treatment agent. Exemplarily, the weight portion of the surfactant can be 0.1 part, 0.13 parts, 0.16 parts, 0.19 parts, 0.22 parts, 0.25 parts, etc.

[0034] The synergistic effect of the four components in the pre-electrophoresis water washing treatment agent for zinc-based coated steel promotes the transformation of the titanium-zirconium conversion film into titanium-zirconium oxide, supplements the defects and improves the film compactness, effectively blocks the external water vapor and corrosive ions, significantly improves the corrosion resistance of the zinc-based coated steel, and thus enables the zinc-based coated steel to have an excellent effect of inhibiting filiform corrosion, meeting the wide application of the zinc-based coated steel at the automotive user end.

[0035] In the embodiments of the present application, the pre-electrophoresis water washing treatment agent for zinc-based coated steel further includes 90 to 100 parts by weight of water.

[0036] In some embodiments, the pH value of the water washing treatment agent is 6.5 to 7.5.

[0037] The positive effect of the pH value of the water washing treatment agent being 6.5 to 7.5: Oxidants, film-forming agents, and chelating agents need to exist stably in a neutral or weakly alkaline environment, and chelating agents and film-forming agents can react, complex, adsorb, and precipitate to form a film with metal ions in a weakly alkaline environment. Exemplarily, the pH value of the water washing treatment agent can be 6.5, 6.7, 6.9, 7.1, 7.3, 7.5, etc.

[0038] In some embodiments, the film-forming agent is at least one of pyridine, picolinic acid, thiazole, imidazole, benzothiazole, and benzimidazole.

[0039] In some embodiments, the oxidant is at least one of sodium nitrite, hydrogen peroxide, and potassium permanganate.

[0040] In the water washing treatment agent before electrophoresis of zinc-based coated steel, the oxidant can accept electrons to become negative ions, thereby promoting the oxidation reaction of metal ions (such as titanium ions and zirconium ions). During the formation of the titanium-zirconium conversion film, the oxidant can accelerate the formation of titanium and zirconium oxides, enabling more of the titanium-zirconium components in the conversion film to be converted into titanium-zirconium oxides. Titanium-zirconium oxides have higher chemical stability and corrosion resistance than salts / hydroxides of titanium / zirconium. Through the promoting effect of the oxidant, the titanium-zirconium components in the conversion film are more fully converted into titanium-zirconium oxides, thereby enhancing the structural stability and corrosion resistance of the film. Additionally, the oxidant can also regulate the composition of the conversion film to a certain extent, making the distribution of titanium and zirconium oxides in the film more uniform, reducing defects and pores in the film, and further improving the denseness and corrosion resistance of the film.

[0041] In some embodiments, the surfactant is an anionic surfactant.

[0042] Surfactants have the property of reducing the surface tension of the solution, which helps to enhance the solubility and dispersibility of each component in the treatment agent. In the formulation, the surfactant can act as a solvent or co-solvent to ensure that key components such as film-forming agents, oxidants, and chelating agents in the treatment agent can be evenly and stably dispersed in the solvent to form a homogeneous solution. This not only improves the usage efficiency of the treatment agent but also ensures its uniform coverage on the metal surface, thereby enhancing the treatment effect. On the other hand, surfactant molecules have a unique hydrophilic (polar) and hydrophobic (non-polar) group structure. At the liquid-solid interface, surfactant molecules can spontaneously arrange, with the hydrophilic groups facing the aqueous phase (solution) and the hydrophobic groups facing the metal surface. This oriented arrangement not only helps the effective adsorption of components such as film-forming agents on the metal surface but also enables the control of the structure and properties of the adsorption layer by adjusting the type and concentration of the surfactant. Therefore, surfactants play an important role in improving the binding force between the film-forming agent and the metal surface and optimizing the denseness and uniformity of the film. In the examples of the present application, an anionic surfactant is selected as the surfactant in the water washing treatment agent. The anionic surfactant is more likely to complex and react with metal ions, maintaining the stability of the solution while promoting the adsorption and film formation of the treatment solution on the surface of zinc-based coated steel.

[0043] In some embodiments, the chelating agent is at least one of disodium ethylenediaminetetraacetate, citric acid, tartaric acid, diethanolamine, and sodium alginate.

[0044] Chelating agents can undergo chelation reactions with film-forming agents, metallic ions, etc., to form complexes with larger molecular weights. Complexes with larger molecular weights have more adsorption sites and can better adsorb on the surface of zinc-based coated steel to form an adsorption film, making up for defects.

[0045] Figure 1It is a schematic flow chart of a preparation method of a water washing treatment agent for zinc-based coated steel before electrophoresis provided by an embodiment of the present application.

[0046] Please refer to Figure 1 , on the second aspect, the present application provides a preparation method of the water washing treatment agent described in the first aspect, and the method includes:

[0047] S1. Mix and stir a film-forming agent and a solvent to obtain a mixed solution;

[0048] S2. Sequentially add an oxidizing agent, a chelating agent and a surfactant to the mixed solution to obtain the water washing treatment agent;

[0049] S3. Perform titanium-zirconium treatment on the zinc-based coated steel to form a titanium-zirconium conversion film on the surface of the zinc-based coated steel, and obtain a zinc-based coated steel with a film;

[0050] S4. Coat the water washing treatment agent on the surface of the zinc-based coated steel with a film to obtain a coated zinc-based coated steel.

[0051] In the embodiment of the present application, the solvent is water.

[0052] In some embodiments, the zinc-based coated steel is a pure zinc coated steel and / or a zinc-magnesium-aluminum coated steel.

[0053] In some embodiments, by weight, the chemical composition of the coating of the zinc-magnesium-aluminum coated steel includes: zinc: 1 part to 3 parts, magnesium: 1 part to 3 parts.

[0054] The preparation product of the preparation method of the water washing treatment agent for zinc-based coated steel before electrophoresis is the above-mentioned water washing treatment agent for zinc-based coated steel before electrophoresis. Since the preparation method of the water washing treatment agent for zinc-based coated steel before electrophoresis adopts some or all of the technical solutions of the embodiment of the water washing treatment agent for zinc-based coated steel before electrophoresis, it has at least all the beneficial effects brought by the technical solutions of the embodiment of the water washing treatment agent for zinc-based coated steel before electrophoresis, and will not be elaborated here one by one.

[0055] Based on a general inventive concept, the present application provides an application of the water washing treatment agent described in any one of the above embodiments, and the water washing treatment agent is applied to the water washing link before electrophoresis of zinc-based coated steel automotive sheets at the user end.

[0056] The water washing treatment agent provided by the embodiment of the present application is mainly applied to the pre-treatment link of automobile painting, coated on the surface of zinc-based coated steel. Specifically, it is applied to the water washing link after titanium-zirconium treatment and before electrophoresis in the pre-treatment link of painting. The coating method can be any one of spraying, dipping and roll coating.

[0057] In some embodiments, the use temperature of the water washing treatment agent for zinc-based coated steel before electrophoresis is 30°C to 50°C, and the water washing treatment time is 30 s to 2 min. These treatment process conditions vary due to different treatment processes in different automobile factories.

[0058] After being treated with the water washing treatment agent for zinc-based coated steel before electrophoresis, a nano-level protective film layer is formed on the surface of the zinc-based coated steel.

[0059] The following further elaborates the present application in conjunction with specific embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are generally determined according to national standards / industry standards; if there are no corresponding national standards / industry standards, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0060] The content (parts by weight) of each component of the water washing treatment agent for zinc-based coated steel before electrophoresis in Examples 1 to 10 is shown in Table 1.

[0061] Table 1 Content (parts by weight) of each component of the water washing treatment agent for zinc-based coated steel before electrophoresis in the examples

[0062] Group Water Oxidizing agent Film-forming agent Chelating agent Surfactant Example 1 100 0.25 2 0.5 0.25 Example 2 100 0.1 1 0.2 0.1 Example 3 100 0.25 1 0.5 0.25 Example 4 100 0.1 2 0.3 0.1 Example 5 100 0.25 1 0.3 0.25 Example 6 100 0.25 2 0.5 0.25 Example 7 100 0.25 2 0.5 0.25 Example 8 100 0.25 2 0.5 0.25 Example 9 100 0.25 2 0.5 0.25 Example 10 100 0.25 2 0.5 0.25

[0063] In Examples 1 to 5, the oxidant is sodium nitrite, the film-forming agent is benzothiazole, the chelating agent is disodium ethylenediaminetetraacetate, and the surfactant is sodium dodecyl sulfate. The difference between Examples 1 to 5 lies in the different parts by weight of different components.

[0064] In Example 6, different from Example 1, the oxidant is hydrogen peroxide.

[0065] In Example 7, different from Example 1, the film-forming agent is benzimidazole.

[0066] In Example 8, different from Example 1, the chelating agent is sodium alginate.

[0067] In Example 9, different from Example 1, the surfactant is sodium dodecylbenzenesulfonate.

[0068] In Example 10, different from Example 1, the oxidant is sodium nitrite and the chelating agent is tartaric acid.

[0069] A stability test is carried out on the water washing treatment agent for zinc-based coated steel before electrophoresis. The test method is: place the prepared water washing treatment agent for zinc-based coated steel before electrophoresis in a well-ventilated and cool indoor environment, observe the specific situations such as liquid color change, precipitation, and aggregation, record the time when adverse phenomena occur, and the results are shown in Table 2 (the generally recognized shelf life of the water washing treatment agent in the industry needs to be greater than 90 days).

[0070] Table 2 Stability test results of the water washing treatment agent for zinc-based coated steel before electrophoresis

[0071] Group Stable time Example 1 ≥180 days Example 2 ≥180 days Example 3 ≥180 days Example 4 ≥180 days Example 5 ≥180 days Example 6 ≥180 days Example 7 ≥180 days Example 8 ≥180 days Example 9 ≥180 days Example 10 ≥180 days

[0072] The water washing pretreatment agent for zinc-based coating steel obtained in Examples 1 to 10 was placed in a water washing tank. The zinc-based coating steel was coated with the water washing pretreatment agent by dipping for 30 s, and then dried with hot air to obtain the treated sheet.

[0073] The corrosion resistance of the above-treated zinc-based coating steel plate and the filamentary corrosion inhibition performance of the zinc-based coating steel plate after electrophoretic coating were tested, and the results are shown in Table 3.

[0074] Among them, the corrosion resistance was tested according to the methods and conditions specified in GB / T 10125, and then the corrosion results were evaluated according to the provisions of GB 12335-90 (expressed as the percentage of the corrosion area to the total area after 72 h and 120 h). Among them, the smaller the corrosion area, the better (currently, generally, the NSST / 72 h corrosion area ≤ 5%). The filamentary corrosion inhibition performance was determined according to the filament situation before and after the scratched sample after electrophoresis was induced by acetic acid solution, and the filament emergence time was recorded. Generally, it is considered that the filamentary corrosion inhibition time needs to be greater than 30 days.

[0075] Table 3 Performance test results of the sheet treated with the water washing pretreatment agent for zinc-based coating steel before electrophoresis

[0076]

[0077]

[0078] It can be seen from the data in Tables 1 to 2 that the content (parts by weight) of each component of the water washing pretreatment agent for zinc-based coating steel in the examples is within the required range of the present invention. The water washing pretreatment agent for zinc-based coating steel has good stability and a shelf life of more than 180 days.

[0079] It can be seen from the data in Table 3 that the zinc-based coating steel treated with the water washing pretreatment agent provided by the present application has good corrosion resistance, especially excellent filamentary corrosion resistance.

[0080] One or more technical solutions in the embodiments of the present invention at least further have the following technical effects or advantages:

[0081] The water washing pretreatment agent provided in the embodiments of the present invention does not contain toxic heavy metal ions and harmful solvents, and is environmentally friendly. The treatment process is simple and has low energy consumption, meeting the requirements of green manufacturing and sustainable development.

[0082] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but rather to the broadest scope consistent with the principles and novel features claimed in the present application.

Claims

1. A pre-electrophoresis water washing treatment agent for zinc-based coated steel, calculated by weight, the water washing treatment agent comprises: Film-forming agent: 1 part to 2 parts, oxidizing agent: 0.1 part to 0.25 parts, surfactant: 0.1 part to 0.25 parts, chelating agent: 0.2 parts to 0.5 parts.

2. The water-washing treatment agent according to claim 1, wherein The pH value of the water washing treatment agent is 6.5 to 7.

5.

3. The water-washing treatment agent according to claim 1, wherein The film-forming agent is at least one of pyridine, picolinic acid, thiazole, imidazole, benzothiazole, and benzimidazole.

4. The water-washing treatment agent according to claim 1, wherein, The oxidizing agent is at least one of sodium nitrite, hydrogen peroxide, and potassium permanganate.

5. The water washing treatment agent according to claim 1, characterized in that, The surfactant is an anionic surfactant.

6. The water-washing treatment agent according to claim 1, wherein The chelating agent is at least one of disodium ethylenediaminetetraacetate, citric acid, tartaric acid, diethanolamine, and sodium alginate.

7. A preparation method of the water washing treatment agent according to any one of claims 1 to 6, the method comprising: Mixing the film-forming agent with a solvent and stirring to obtain a mixed solution; Sequentially adding an oxidizing agent, a chelating agent, and a surfactant to the mixed solution to obtain the water washing treatment agent; Performing titanium-zirconium treatment on the zinc-based plated steel to form a titanium-zirconium conversion film on the surface of the zinc-based plated steel to obtain a zinc-based plated steel with a film; Coating the water washing treatment agent on the surface of the zinc-based plated steel with a film to obtain a zinc-based plated steel with a coating.

8. The method according to claim 7, wherein The zinc-based plated steel is a pure zinc plated steel and / or a zinc-magnesium-aluminum plated steel.

9. The method according to claim 8, characterized in that, By weight, the chemical composition of the coating of the zinc-magnesium-aluminum plated steel includes: zinc: 1 part to 3 parts, magnesium: 1 part to 3 parts.

10. An application of the water washing treatment agent according to any one of claims 1 to 6, the water washing treatment agent is applied to the water washing link before electrophoresis of the zinc-based plated steel automotive sheet at the user end.

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