Composite plated layer, composite plated steel sheet and method for producing the same

Abstract

The application relates to a composite coating, a composite coating steel plate and a preparation method thereof. The composite coating comprises a zinc-aluminum-magnesium alloy coating, a nickel coating and an oxalate compound coating containing aluminum and magnesium; wherein the nickel coating is attached to at least part of the surface of the zinc-aluminum-magnesium alloy coating, and the oxalate compound coating containing aluminum and magnesium is attached to at least part of the surface of the nickel coating. The application solves the technical problem that after adding magnesium elements in a hot-dip galvanized coating, the zinc-aluminum-magnesium coating is prone to filamentous corrosion under an organic film under certain conditions.

Description

Technical Field

[0001] This application relates to the field of steel rolling, and more particularly to a composite coating, a composite coated steel sheet, and a method for preparing the same. Background Technology

[0002] Hot-dip galvanizing is a process in which molten metal reacts with an iron substrate to create an alloy layer, thus bonding the substrate and the coating. Hot-dip galvanized steel has advantages such as uniform coating, strong adhesion, long service life, simple manufacturing process, and low product price, and is widely used in the manufacture of automobile bodies, home appliances, etc. To improve the protective effect of the hot-dip galvanized coating on the cut edges of the steel sheet and to improve the corrosion resistance of the surface, an appropriate amount of magnesium is added to the hot-dip galvanized coating to obtain a zinc-aluminum-magnesium coating. This can further improve the corrosion resistance by more than 20%, while also providing corrosion resistance to the machined cut edges.

[0003] However, the addition of magnesium to the hot-dip galvanized coating can cause filamentous corrosion under organic film in the zinc-aluminum-magnesium coating under certain conditions. This filamentous corrosion forms a corrosion morphology that extends in a specific direction, affecting the appearance quality of the organic film and, in severe cases, even the corrosion resistance of the coating. Summary of the Invention

[0004] This application provides a composite coating, a composite coated steel plate, and a method for preparing the same, to solve the technical problem that adding magnesium to hot-dip galvanized coatings makes zinc-aluminum-magnesium coatings prone to filamentous corrosion under organic films under certain conditions.

[0005] In a first aspect, this application provides a composite coating comprising a zinc-aluminum-magnesium alloy coating, a nickel coating, and a coating containing an oxalic acid compound of aluminum and magnesium; wherein,

[0006] The nickel plating is attached to at least a portion of the surface of the zinc-aluminum-magnesium alloy plating.

[0007] The coating containing aluminum and magnesium oxalic acid compounds adheres to at least a portion of the surface of the nickel plating.

[0008] Optionally, the chemical composition of the zinc-aluminum-magnesium alloy coating includes: Mg, Al, Ni, and Zn; wherein, by mass fraction,

[0009] The content of Mg is 0.3-2%, the content of Al is 1-3%, and the content of Ni is 0.02-1%.

[0010] Furthermore, the mass fraction of Al and the mass fraction of Mg satisfy the following relationship:

[0011] [Al]-[Mg]>0.5%

[0012] In the formula, [Al] represents the mass fraction of Al, and [Mg] represents the mass fraction of Mg.

[0013] Optionally, the Ni content in the nickel plating is 5% to 50% by mass fraction.

[0014] Optionally, the thickness of the coating containing aluminum and magnesium oxalic acid compounds is 50 to 500 nm.

[0015] Secondly, this application provides a composite coated steel sheet, the composite coated steel sheet comprising a steel substrate and a composite coating as described in any one embodiment of the first aspect, attached to at least a portion of the surface of the steel substrate.

[0016] Thirdly, this application provides a method for preparing the composite coated steel sheet described in any embodiment of the second aspect, the method comprising:

[0017] At least a portion of the surface of a steel substrate is coated with a zinc-aluminum-magnesium plating solution to obtain a zinc-aluminum-magnesium alloy coated steel sheet.

[0018] At least a portion of the surface of the zinc-aluminum-magnesium alloy coated steel sheet is coated with nickel to obtain a first composite coated steel sheet;

[0019] The first composite coated steel sheet was surface treated with sodium oxalate solution to obtain the composite coated steel sheet.

[0020] Optionally, coating at least a portion of the surface of the zinc-aluminum-magnesium alloy coated steel sheet with nickel to obtain the first composite coated steel sheet includes:

[0021] At least a portion of the surface of the zinc-aluminum-magnesium alloy coated steel sheet is electroplated with nickel using an electroplating solution to obtain a first composite coated steel sheet.

[0022] Optionally, the Ni(II) ion content in the electroplating solution is 100–400 g / L, and the electroplating current density and the electroplating time satisfy the following relationship:

[0023] I·T=20~300A·dm -2 ·s

[0024] In the formula, I represents the current density of electroplating, and T represents the electroplating time.

[0025] Optionally, the molar fraction of the sodium oxalate solution is 0.1–4 M.

[0026] Optionally, the pH value of the sodium oxalate solution is 8.0 to 10.0.

[0027] The technical solutions provided in this application have the following advantages compared with the prior art:

[0028] The composite coating provided in this application significantly improves the coating's atmospheric corrosion resistance through the zinc-aluminum-magnesium alloy coating. The nickel coating disrupts the structure of the aluminum-rich compounds formed by aluminum corrosion, transforming them from needle-like and clustered shapes into planar shapes, thereby reducing the degree of surface filamentous corrosion. The coating containing aluminum and magnesium oxalic acid compounds significantly inhibits the rapid reaction of aluminum and magnesium in the thin liquid film, slowing down the occurrence of filamentous corrosion. In summary, through the interaction of the zinc-aluminum-magnesium alloy coating, the nickel coating, and the coating containing aluminum and magnesium oxalic acid compounds, the technical problem of existing hot-dip galvanized coatings being prone to filamentous corrosion under organic films under certain conditions after the addition of magnesium is achieved is solved. Attached Figure Description

[0029] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A surface morphology diagram of a composite coating provided in an embodiment of this application;

[0032] Figure 2 This application provides an alloy element depth distribution curve for a composite coating according to Embodiment 1.

[0033] Figure 3 This is a schematic flowchart illustrating a method for preparing a composite coated steel sheet, as provided in an embodiment of this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical 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. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0036] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. 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, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0038] Firstly, this application provides a composite coating, please refer to... Figure 1 The surface morphology diagram shown is of the composite coating, which includes a zinc-aluminum-magnesium alloy coating, a nickel coating, and a coating containing an oxalic acid compound of aluminum and magnesium; wherein,

[0039] The nickel plating is attached to at least a portion of the surface of the zinc-aluminum-magnesium alloy plating.

[0040] The coating containing aluminum and magnesium oxalic acid compounds adheres to at least a portion of the surface of the nickel plating.

[0041] In some embodiments, the chemical composition of the zinc-aluminum-magnesium alloy coating includes: Mg, Al, Ni, and Zn; wherein, by mass fraction,

[0042] The content of Mg is 0.3-2%, the content of Al is 1-3%, and the content of Ni is 0.02-1%.

[0043] Furthermore, the mass fraction of Al and the mass fraction of Mg satisfy the following relationship:

[0044] [Al]-[Mg]>0.5%

[0045] In the formula, [Al] represents the mass fraction of Al, and [Mg] represents the mass fraction of Mg.

[0046] In this embodiment, the zinc-aluminum-magnesium alloy coating is adhered to at least a portion of the surface of the steel substrate. The Al element in the coating provides high-quality atmospheric corrosion resistance because, during corrosion, Al can form dense oxides and hydroxides on the surface. If there is no Al in the coating, the adhesion between the coating and the steel plate will be poor, rendering the coating unusable and reducing corrosion resistance. Conversely, excessive Al content in the coating may significantly reduce its weldability, making it prone to cracking after welding. Specifically, the Al content can be 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0047] In the atmosphere, especially in high-humidity atmospheres, a thin liquid film adheres to the surface of zinc-aluminum-magnesium coatings. The oxygen enriched in this film preferentially reacts with the magnesium in the coating, rapidly forming magnesium compounds, while the pH value in the film gradually increases. Under these conditions, the liquid film also allows Al to dissolve. This leads to the reaction of the aluminum-rich phase in the coating with oxygen, hydroxide, and carbonate ions in the liquid film, forming complex aluminum-rich compounds. In the presence of an organic film, this magnesium-aluminum corrosion tends to propagate through weak points in the organic film. This further creates a potential difference between the corrosion head and tail, promoting further corrosion and forming filamentous corrosion morphologies.

[0048] Mg in the coating can significantly improve its atmospheric corrosion resistance. The mechanism is that Mg in the coating preferentially dissolves into the water film on the coating surface in the atmosphere. In this water film, it reacts with dissolved carbon dioxide to precipitate a dense protective film. This protective film is stable in neutral and weakly alkaline environments and also promotes the electrolyte solution on the coating surface to become a weakly alkaline solution, thereby improving the coating's corrosion resistance. Within the aforementioned Mg content range, the coating preferentially corrodes the Mg in the coating during corrosion, allowing Mg to dissolve into the water film on the coating surface and form a dense protective film. However, if the Mg content is too high, it will result in more coarse Mg-Zn compounds in the coating. These compounds dissolve rapidly in acidic solutions, inducing filamentary corrosion of the coating under the organic film. Specifically, the Mg content can be 0.3%, 0.5%, 0.7%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0049] Furthermore, when the aluminum content in the coating is higher than the magnesium content, aluminum preferentially reacts with oxygen in the thin liquid film on the coating surface, thus inhibiting the reaction of magnesium. The slower reaction rate of aluminum with oxygen in the thin liquid film also slows down the occurrence of filamentary corrosion. Therefore, the [Al]-[Mg] values ​​can be 0.6%, 0.8%, 1.0%, 1.2%, etc.

[0050] Ni can combine with Al in the coating to form Ni-Al compounds, refining the coating grains, especially inhibiting the growth of Mg-Zn compounds by breaking them down into smaller grains and slowing their dissolution rate, thus reducing the rate of filamentary corrosion. However, excessively high Ni content can cause a significant galvanic reaction with the magnesium in the coating, leading to a decrease in the corrosion resistance of the zinc-aluminum-magnesium coating. Specifically, the Ni content can be 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, etc.

[0051] In some embodiments, the Ni content in the nickel plating is 5% to 50% by mass fraction.

[0052] In this embodiment, since filamentary corrosion occurs on the coating surface, Ni should be concentrated on the coating surface. However, excessive Ni in the nickel coating will reduce the corrosion resistance of Al and Mg in the coating. Specifically, the Ni content in the nickel coating can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. The mass percentage of Ni in the nickel coating can be determined by glow discharge spectroscopy. When testing the Ni content, the glow discharge current is 20mA, the anode diameter is 4mm, and the measurement depth is 100nm. The content of each alloying element within 100nm is calculated as an integral over the depth to obtain the average Ni content within a 100nm depth. This is used as the Ni content on the coating surface. For details, please refer to [link to relevant documentation]. Figure 2 The depth distribution of alloying elements in the composite coating of Example 1 is shown.

[0053] In some embodiments, the thickness of the coating containing the aluminum and magnesium oxalic acid compound is 50–500 nm.

[0054] In this embodiment, coating the nickel plating surface with a layer of oxalic acid compound containing aluminum and magnesium can significantly inhibit the rapid reaction of aluminum and magnesium in the thin liquid film. This is because the solubility of the oxalic acid compound of aluminum and magnesium in the thin liquid film is quite low, thus significantly reducing its reaction kinetics. To achieve the effect of inhibiting the reaction, the thickness of this oxalic acid compound layer cannot be too small. However, if it is too thick, it will cause the zinc-aluminum-magnesium plating surface to appear darker, failing to meet the requirements. Specifically, the thickness of the coating containing the oxalic acid compound of aluminum and magnesium can be 50nm, 80nm, 100nm, 130nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc.

[0055] Secondly, this application provides a composite coated steel sheet, the composite coated steel sheet comprising a steel substrate and a composite coating as described in any one embodiment of the first aspect, attached to at least a portion of the surface of the steel substrate.

[0056] In the embodiments of this application, the composite-coated steel sheet has a composite coating on its surface, exhibiting good resistance to filamentous corrosion in atmospheric exposure environments. The steel substrate is not particularly limited; ordinary steel sheets such as hot-rolled steel sheets and cold-rolled steel sheets can be used. There are also no particular limitations on the type of steel; for example, aluminum-killed steel, ultra-low carbon steel, and high-strength steel can be used.

[0057] Thirdly, this application provides a method for preparing the composite coated steel sheet described in any embodiment of the second aspect; please refer to [link to relevant documentation]. Figure 3 The method includes:

[0058] S1. Coat at least a portion of the surface of the steel substrate with zinc-aluminum-magnesium plating solution to obtain a zinc-aluminum-magnesium alloy coated steel sheet.

[0059] In the embodiments of this application, the zinc-aluminum-magnesium coating is performed by hot-dip galvanizing.

[0060] S2. At least a portion of the surface of the zinc-aluminum-magnesium alloy coated steel sheet is coated with nickel to obtain a first composite coated steel sheet.

[0061] In some embodiments, coating at least a portion of the surface of the zinc-aluminum-magnesium alloy coated steel sheet with nickel to obtain a first composite coated steel sheet includes:

[0062] At least a portion of the surface of the zinc-aluminum-magnesium alloy coated steel sheet is electroplated with nickel using an electroplating solution to obtain a first composite coated steel sheet.

[0063] In this embodiment, during the preparation of the composite coated steel sheet, a coating process is required on the surface of the hot-dip galvanized aluminum-magnesium coating, where a layer of nickel is coated onto the coating surface. The coating process includes various methods such as electroplating, physical vapor deposition, and ion implantation. Electroplating is preferred.

[0064] In some embodiments, the Ni(II) ion content in the electroplating solution is 100–400 g / L, and the electroplating current density and the electroplating time satisfy the following relationship:

[0065] I·T=20~300A·dm -2 ·s

[0066] In the formula, I represents the current density of electroplating, and T represents the electroplating time.

[0067] In this embodiment, to achieve a Ni element mass fraction of 10-50% on the plating surface, it is necessary to control the electroplating process parameters. The Ni ion content in the electroplating solution cannot be too low, otherwise a nickel plating layer cannot be formed on the plating surface during electroplating. However, if there are too many Ni ions, the electroplating solution itself will become unstable, easily causing precipitation and resulting in uneven Ni deposition on the plating surface, which can easily lead to excess Ni. Specifically, the Ni(II) ion content can be 100 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L, 350 g / L, 400 g / L, etc. In addition, the current density and time during electroplating are also key control factors. The product of these two needs to be within a certain range; too low a value will result in insufficient Ni element deposition on the surface, while too high a value will result in excessive Ni element deposition on the surface. Specifically, the product of the current density and time during electroplating can be 20 A·dm. -2 ·s、50A·dm -2 ·s、70A·dm -2·s、100A·dm -2 ·s、120A·dm -2 ·s、150A·dm -2 ·s、170A·dm -2 ·s、200A·dm -2 ·s、230A·dm -2 ·s、250A·dm -2 ·s、280A·dm -2 ·s、300A·dm -2 ·s etc.

[0068] S3. The first composite coated steel plate is surface treated with sodium oxalate solution to obtain the composite coated steel plate.

[0069] In this embodiment, during the preparation of the composite coated steel sheet, the zinc-aluminum-magnesium coated steel sheet needs to be immersed in a sodium oxalate solution. A sodium oxalate solution is chosen instead of an oxalic acid solution because oxalic acid is too corrosive and would directly damage the coating.

[0070] In some embodiments, the molar fraction of the sodium oxalate solution is 0.1–4 M.

[0071] In this embodiment, the concentration of the sodium oxalate solution cannot be too low, otherwise sufficient aluminum and magnesium-containing oxalic acid compounds cannot be formed on the surface. However, the concentration of the sodium oxalate solution also cannot be too high, otherwise the distribution of the formed aluminum and magnesium-containing oxalic acid compounds will be very uneven, with excessively thick local areas. Specifically, the molar fraction of the sodium oxalate solution can be 0.1M, 0.3M, 0.5M, 0.7M, 0.9M, 1M, 2M, 3M, 4M, etc.

[0072] In some embodiments, the pH value of the sodium oxalate solution is 8.0 to 10.0.

[0073] In the embodiments of this application, the zinc-aluminum-magnesium coating can also form a zinc hydrate compound on its surface in an alkaline sodium oxalate solution. The Gibbs free energy of zinc hydrate (-3160 kJ / mol, room temperature to 100°C) is much lower than that of MgCO3 (-1100 kJ / mol at room temperature to 100°C), indicating that zinc hydrate (Zn5(OH)6(CO3)2) will preferentially form on the coating surface. Zinc hydrate can act as a protective barrier against the formation of filamentous corrosion, and it becomes stable at pH values ​​of 8.0 to 10.0. Too high a pH will cause Al on the coating surface to dissolve, reducing the corrosion resistance of the coating. Too low a pH will prevent the formation of zinc hydrate. Specifically, the pH value of the sodium oxalate solution can be 8.0, 8.5, 9.0, 9.5, 10.0, etc.

[0074] The preparation of the aforementioned composite coated steel sheet includes: obtaining a slab after steel smelting, heating the slab, and then subjecting it to rough rolling, finish rolling, cooling, cold rolling, hot-dip galvanizing with aluminum-magnesium alloy, surface coating with nickel, surface treatment with sodium oxalate solution, and coiling. This preparation method is simple to operate, has low production costs, and is easy to promote and use.

[0075] The method for preparing composite coated steel sheet is based on the above-mentioned composite coated steel sheet. The composition of the composite coated steel sheet can be referred to in the above embodiments. Since the method for preparing composite coated steel sheet adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0076] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then general international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0077] A steel plate with a thickness of 1.50 mm and a width of 1200 mm was used as the substrate, wherein the zinc-aluminum-magnesium alloy coating was applied on both sides at 150 grams per square meter. The characteristics of the composite coatings of Examples 1-13 and Comparative Examples 1-5 of this application are shown in Table 1.

[0078]

[0079]

[0080] The preparation process parameters of the composite coated steel sheets of Examples 1-13 and Comparative Examples 1-5 of this application are shown in Table 2.

[0081] Table 2. Preparation process parameters of composite coated steel plates

[0082]

[0083]

[0084] Test for resistance to filamentous corrosion:

[0085] Anti-filamentary corrosion evaluation experiments were conducted on the composite coated steel sheets prepared according to the process parameters in Examples 1-13 and Comparative Examples 1-5 and the preparation method in accordance with the embodiments of this application.

[0086] A 20-micron thick layer of epoxy resin was coated onto the surface of the composite coating. Then, scratches were made on the surface of the organic film, with a scratch width of 1 mm and a scratch depth reaching the steel substrate. 5 μL of acetic acid solution with a concentration of 1 mol / dm³ was injected into the scratched areas.3 The samples were then placed in a constant temperature and humidity environment (22℃, 86% RH) and stored for 4 weeks. The growth length of filamentary corrosion on the sample surface was then evaluated according to GB / T 30789.9. Longer growth indicates a greater susceptibility to filamentary corrosion.

[0087] The method for evaluating the corrosion resistance of the coating is to place the composite-coated steel sheet in a cyclic corrosion test chamber and conduct 18 cycles of cyclic corrosion testing. The cyclic corrosion test meets the requirements of Annex A of ISO 11997-1:2017. Then, the mass loss of the coating before and after the test is measured, and the corrosion resistance of the composite coating is evaluated by the mass loss per unit area. The experimental evaluation results are shown in Table 3.

[0088] Table 3 Evaluation results of the composite coating's resistance to filamentous corrosion and its corrosion resistance.

[0089]

[0090]

[0091] As shown in Table 3, the composite coating surface provided in the embodiments of this application has excellent resistance to filamentous corrosion.

[0092] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A composite coating, characterized by, The composite coating includes a zinc-aluminum-magnesium alloy coating, a nickel coating, and a coating containing an oxalic acid compound of aluminum and magnesium; wherein, The nickel plating is attached to at least a portion of the surface of the zinc-aluminum-magnesium alloy plating. The coating containing the aluminum and magnesium oxalic acid compound adheres to at least a portion of the surface of the nickel plating; The chemical composition of the zinc-aluminum-magnesium alloy coating includes: Mg, Al, Ni, and Zn; wherein, by mass fraction, The content of Mg is 0.3-2%, the content of Al is 1-3%, and the content of Ni is 0.02-1%. Furthermore, the mass fraction of Al and the mass fraction of Mg satisfy the following relationship: [Al]-[Mg]>0.5% In the formula, [Al] represents the mass fraction of Al, and [Mg] represents the mass fraction of Mg; The nickel plating layer contains 5-50% Ni by mass fraction. The coating containing aluminum and magnesium oxalic acid compounds has a thickness of 50~500 nm.

2. A composite plated steel sheet, characterized by, The composite coated steel sheet includes a steel substrate and the composite coating of claim 1 attached to at least a portion of the surface of the steel substrate.

3. A method of producing the composite plated steel sheet according to claim 2, characterized by, The method includes: At least a portion of the surface of a steel substrate is coated with a zinc-aluminum-magnesium plating solution to obtain a zinc-aluminum-magnesium alloy coated steel sheet. At least a portion of the surface of the zinc-aluminum-magnesium alloy coated steel sheet is coated with nickel to obtain a first composite coated steel sheet; The first composite coated steel sheet was surface treated with sodium oxalate solution to obtain the composite coated steel sheet.

4. The method of claim 3, wherein, The zinc-aluminum-magnesium alloy coated steel sheet At least a portion of the surface is coated with nickel to obtain a first composite-plated steel sheet, comprising: At least a portion of the surface of the zinc-aluminum-magnesium alloy coated steel sheet is electroplated with nickel using an electroplating solution to obtain a first composite coated steel sheet.

5. The method of claim 4, wherein, The Ni(II) ion content in the electroplating solution is 100~400 g / L, and the electroplating current density and the electroplating time satisfy the following relationship: I T=20~300 A dm -2 s In the formula, I represents the current density of electroplating, and T represents the electroplating time.

6. The method of claim 3, wherein, The molar fraction of the sodium oxalate solution is 0.1~4 M.

7. The method according to claim 3 or 6, characterized in that, The pH value of the sodium oxalate solution is 8.0~10.0.

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