CN116426793A - A kind of high anti-corrosion zinc-aluminum-magnesium coated steel plate and preparation method thereof - Google Patents

Abstract

The application relates to a high corrosion-resistant zinc-aluminum-magnesium alloy coated steel plate and a preparation method thereof, belonging to the technical field of coating. The technical problem solved by the application is that the zinc-aluminum-magnesium plated steel plate has insufficient corrosion resistance and is easy to appear a phenomenon of surface darkening in the atmosphere. The technical scheme that this application provided to solve above-mentioned technical problem is: by adding Mg, al, si and other elements into the zinc-aluminum-magnesium alloy coating, controlling the mass fraction of the Mg element in the coating to be 3% -8% and the mass fraction of the Al element to be 12% -25%, the volume fraction of the Mg-Zn compound on the surface of the coating is not more than 2%, and the content ratio of the Si element to the Al element in the coating is controlled to be 0.05-0.15, so that the zinc-aluminum-magnesium coating steel plate provided by the application has good corrosion resistance and excellent surface quality.

Description

A kind of high anti-corrosion zinc-aluminum-magnesium coated steel plate and preparation method thereof

technical field

The present application relates to the technical field of coating, in particular to a high-corrosion-resistant zinc-aluminum-magnesium alloy coated steel plate and a preparation method thereof.

Background technique

Zinc-aluminum-magnesium coated steel sheet is a new type of corrosion-resistant alloy coated steel sheet. This coating is developed on the basis of traditional pure zinc coating. Magnesium and aluminum elements are added to the coating, so that the plane corrosion resistance of the coating is the same as that of The corrosion resistance of the notch is significantly improved, and it can be widely used in the manufacture of automobiles, home appliances, and building exterior walls.

However, the corrosion resistance of the current zinc-aluminum-magnesium coating still has room for further improvement. At the same time, when the zinc-aluminum-magnesium-coated steel sheet is used in the atmosphere, the surface color is prone to darkening. Some studies have used surface treatment technology to coat a special organic or inorganic film on the surface of the coating to avoid this phenomenon. However, the film coated on the surface is prone to damage and lose effect, and some application scenarios do not allow surface coating treatment.

Therefore, it is an urgent problem to seek a zinc-aluminum-magnesium coated steel sheet which has excellent corrosion resistance and is not prone to surface darkening in the atmosphere.

Contents of the invention

The present application provides a high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet to solve the technical problems that the zinc-aluminum-magnesium-coated steel sheet has insufficient corrosion resistance and is prone to surface darkening when used in the atmosphere.

In the first aspect, the present application provides a high-corrosion-resistant zinc-aluminum-magnesium coated steel sheet, the steel sheet includes a steel substrate and a zinc-aluminum-magnesium coating, the zinc-aluminum-magnesium coating includes Al elements and Mg elements, and the mass of the Al elements The fraction is between 12% and 25% by weight.

Optionally, the mass fraction of the Mg element is 3% by weight to 8% by weight.

Optionally, the volume fraction of the Mg-Zn compound on the surface of the zinc-aluminum-magnesium coating is not greater than 2%.

Optionally, the zinc-aluminum-magnesium coating further includes Si element, and the content ratio of the Si element to the Al element is 0.02-0.2.

Optionally, the zinc-aluminum-magnesium coating further includes Si element, and the content ratio of the Si element to the Al element is 0.05-0.15.

In a second aspect, the present application provides a method for preparing a high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet, which is used to prepare the high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet described in any one of the first aspect, the method comprising:

Activating the surface of the steel matrix to obtain a steel plate substrate;

Coating a zinc-aluminum-magnesium alloy containing a predetermined chemical composition on the surface of the steel sheet substrate to obtain a coated steel sheet;

The coated steel sheet is subjected to surface treatment.

Optionally, the surface activation includes at least one of the following:

Annealing, pickling and ion etching.

Optionally, the set chemical composition includes the following chemical compositions:

Al: 12% by weight to 25% by weight, Mg: 3% by weight to 8% by weight, Si, Zn.

Optionally, the coating includes at least one of the following:

Electroplating, hot-dip plating, electroless plating, and vapor deposition.

Optionally, the surface treatment method is to deposit zinc atoms on the surface of the coated steel sheet.

Compared with the prior art, the above-mentioned technical solutions provided by the embodiments of the present application have the following advantages:

The method provided in the embodiment of the present application, by reducing the Mg element on the surface of the coating, inhibits the electrochemical reaction of the Mg-Zn compound on the surface of the coating, thereby effectively avoiding the phenomenon of darkening the surface of the steel body. In addition, adding a certain amount of The Al element forms dense oxides and hydroxides on the surface of the coating to inhibit surface corrosion, thereby avoiding the formation of a large number of brittle Al-Fe compounds between Al and the steel substrate, reducing the risk of cracking of the coating, and improving the corrosion resistance of the coating.

Description of drawings

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

In order 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 that need to be used in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, In other words, other drawings can also be obtained from these drawings without paying creative labor.

Fig. 1 is a scanning electron microscope image provided by the embodiment of the present application.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of this application, but not all of them. Based on the embodiments in the present application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present application.

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

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 application; therefore, the described range should be regarded as The description has specifically disclosed all possible subranges as well as individual values within that range. For example, a description of a range from 1 to 6 should be considered to have specifically disclosed subranges, 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 stated ranges, eg 1, 2, 3, 4, 5 and 6, apply regardless of the range. Additionally, whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range.

In the present application, unless otherwise stated, the used orientation words such as "upper" and "lower" specifically refer to the direction of the drawings in the drawings. In addition, in the description of the specification of the present application, the terms "including" and "including" mean "including but not limited to".

In this document, relational terms such as "first" and "second", etc., are only used to distinguish one entity or operation from another, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or sequence. In this article, "and/or" describes the association relationship of associated objects, indicating that there may be three kinds of relationships, for example, A and/or B, which can mean: A exists alone, A and B exist simultaneously, and B exists alone . Among them, A and B can be singular or plural. Herein, "at least one" means one or more, and "plurality" 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 a single item or a plurality of items. For example, "at least one (one) of a, b, or c", or "at least one (one) of a, b, and c" can mean: a, b, c, a-b ( That is, a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

In order to solve the above-mentioned technical problems, the technical solutions provided in the embodiments of the present application provide the following overall ideas:

In the first aspect, the present application provides a high-corrosion-resistant zinc-aluminum-magnesium coated steel sheet, the steel sheet includes a steel substrate and a zinc-aluminum-magnesium coating, the zinc-aluminum-magnesium coating includes Al elements and Mg elements, and the mass of the Al elements The fraction is between 12% and 25% by weight.

In this embodiment, the Al element in the zinc-aluminum-magnesium coating provides high-quality atmospheric corrosion resistance for the coating, because during the corrosion process, the Al element can form dense oxides and dense hydroxides on the surface. If there is no Al in the coating, the bonding force between the coating and the steel plate will be poor, making the coating unusable and reducing the corrosion resistance. When the Al element content in the coating exceeds 12%, a large number of dendritic aluminum-rich crystals will appear in the coating, and the eutectic structure in the coating will be significantly reduced, thereby significantly improving the corrosion resistance of the coating. Therefore, the mass fraction of Al element in the coating should not be lower than 12%. However, if the aluminum element content exceeds 25%, the problem of cracking of the coating will occur, and the corrosion resistance will also be reduced.

In some embodiments, the mass fraction of the Mg element is 3 wt %-8 wt %.

In this embodiment, the Mg element in the zinc-aluminum-magnesium coating can significantly improve the atmospheric corrosion resistance of the coating. The mechanism is that the Mg in the coating will preferentially dissolve into the water film on the surface of the coating in the atmospheric environment. Reacts with dissolved carbon dioxide in the medium to precipitate a dense protective film, which can exist stably in neutral and weakly alkaline environments, and can also promote the electrolytic solution on the surface of the coating to become a weakly alkaline solution, thereby improving the coating. Corrosion resistance. When the Mg element content in the coating exceeds 3%, the coating will preferentially corrode the Mg in the coating during the corrosion process, so that the Mg element can dissolve into the water film on the coating surface to form a dense protective film. However, if the Mg element content is too high, a large amount of coarser Mg-Zn compounds will appear in the coating, which will lead to cracking of the coating and reduce the corrosion resistance and appearance quality of the coating. Therefore, the Mg content in the coating does not exceed 8%.

In some embodiments, the volume fraction of the Mg-Zn compound on the surface of the zinc-aluminum-magnesium coating is not greater than 2%.

In this embodiment, the Mg in the coating mainly exists in the eutectic structure of the coating in the form of Mg-Zn compound, and a very small amount exists in the zinc-rich phase of the coating in the form of solid solution. The main reason why the zinc-aluminum-magnesium coating is prone to surface darkening in the atmosphere is that the Mg-Zn compound in the coating easily reacts electrochemically with the oxygen in the water film under the condition of a wet water film on the coating surface, and the Mg-Zn compound Losing electrons, the Mg element is precipitated into magnesium ions, while oxygen gains electrons to become hydroxide ions. Further, magnesium ions react with hydroxide ions and carbon dioxide in the air in the liquid film to form dark surface oxides, carbon dioxide, etc. salts and hydroxides. Therefore, the Mg-Zn compound on the surface of the coating can only be reduced by reducing the mass percentage of the Mg element on the surface of the coating, so that the volume fraction of the Mg-Zn compound on the surface of the coating should not exceed 2%.

In some embodiments, the zinc-aluminum-magnesium coating further includes Si element, and the content ratio of the Si element to the Al element is 0.02-0.2.

In this embodiment, the Si element can form a ductile Al-Fe-Si phase with Al in the coating and Fe of the steel substrate, avoiding the formation of a large number of brittle Al-Fe compounds between Al and the steel substrate, reducing the risk of cracking of the coating, and improving the quality of the coating. Corrosion resistance. However, if the Si content is too much, a large amount of Mg will combine with Si to form a Mg-Si compound, which will easily lead to blackening of the coating surface. Therefore, the ratio of Si element content to Al element content is not greater than 0.2.

In some embodiments, the zinc-aluminum-magnesium coating further includes Si element, and the content ratio of the Si element to the Al element is 0.05-0.15.

In a second aspect, the present application provides a method for preparing a high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet, which is used to prepare the high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet described in any one of the first aspect, the method comprising:

Activating the surface of the steel matrix to obtain a steel plate substrate;

Coating a zinc-aluminum-magnesium alloy containing a predetermined chemical composition on the surface of the steel sheet substrate to obtain a coated steel sheet;

The coated steel sheet is subjected to surface treatment.

In some embodiments, the surface activation includes at least one of the following:

Annealing, pickling and ion etching.

In this embodiment, annealing can eliminate the rolling stress on the surface of the steel plate base material, eliminate the distorted grain boundaries on the surface, make the surface of the steel plate base material more uniform, and avoid local particularly strong and particularly weak chemical active points. Pickling can clean the high rolling stress layer on the surface of the steel plate, eliminate the distorted grain boundaries on the surface, make the surface of the steel plate base material more uniform, and avoid local particularly strong and particularly weak chemical active points. Ion etching can remove the high rolling stress layer on the surface of the steel plate, eliminate the distorted grain boundaries on the surface, make the surface of the steel plate substrate more uniform, and avoid local particularly strong and particularly weak chemical active points.

In some embodiments, the set chemical composition includes the following chemical composition:

Al: 12% by weight to 25% by weight, Mg: 3% by weight to 8% by weight, Si, Zn.

In this embodiment, the Si element can form a ductile Al-Fe-Si phase with Al in the coating and Fe of the steel substrate, avoiding the formation of a large number of brittle Al-Fe compounds between Al and the steel substrate, reducing the risk of cracking of the coating, and improving the quality of the coating. Corrosion resistance. Mg element can significantly improve the atmospheric corrosion resistance of the coating. Al element can form dense oxides and dense hydroxides on the surface, improving the atmospheric corrosion resistance of the coating.

In some embodiments, the coating includes at least one of the following:

Electroplating, hot-dip plating, electroless plating, and vapor deposition.

In this embodiment, the electroplating technology can uniformly coat a single metal or alloy on the steel surface, and a uniform coating can be obtained by selecting appropriate electrolyte salts and adjusting the pH value of the solution. Electroplated coatings are usually less compact than hot dipped coatings, but better than electroless and vapor deposition coatings. By adding an appropriate amount of brightener and dispersant to the electroplating solution, the density of the coating can be increased, thereby improving the corrosion resistance of the coating. Zinc-aluminum-magnesium coating can be realized by traditional electro-galvanizing process technology.

In this embodiment, hot-dip coating is a traditional coating technology, which is to soak the steel plate base material in the zinc-aluminum-magnesium alloy plating solution for a period of time, and then take it out and cool it to room temperature. This technology has strong practicability and can easily obtain zinc-aluminum-magnesium coatings. At the same time, the coatings have better compactness and uniform microstructure, but it is difficult to obtain coatings with a thickness less than 5 microns.

In this embodiment, the electroless plating technology is to soak the steel plate base material in a chemical solution, and the metal ions in the chemical solution are automatically deposited on the surface of the steel plate. This technology can be used to manufacture zinc-aluminum-magnesium alloy coatings. The obtained coating structure is more delicate than electroplating, but the oxygen content in the coating is slightly higher and the corrosion resistance is slightly worse.

In this embodiment, the vapor deposition technique is to deposit high-temperature metal or alloy vapor or ions onto the surface of the steel plate substrate to obtain a coating. This technique is adaptable and can be used for all metal and alloy coating fabrication. A dense coating can be obtained through conditions such as deposition rate, steel plate temperature and other parameters.

In some embodiments, the surface treatment method is to deposit zinc atoms on the surface of the coated steel sheet.

In this embodiment, the purpose of surface treatment is to reduce the volume fraction of Mg-Zn compounds on the surface and increase the proportion of Zn atoms on the surface without affecting the corrosion resistance of the coating. After zinc atoms are further deposited on the surface of the zinc-aluminum-magnesium coating, the zinc atoms can occupy the position of the eutectic structure on the surface of the zinc-aluminum-magnesium coating, so that the volume fraction of the surface Mg-Zn compound is greatly reduced. The method for depositing zinc atoms can be electroplating, vapor deposition, and ion implantation.

The present application will be further described below in conjunction with specific embodiments. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods not indicating specific conditions in the following examples are usually measured according to national standards. If there is no corresponding national standard, proceed according to general international standards, conventional conditions, or the conditions suggested by the manufacturer.

Relevant experiments and effect data:

Preparation Example 1-13, the preparation method comprises:

S1. Surface activating the steel matrix to obtain a steel plate substrate;

S2. Coating a zinc-aluminum-magnesium alloy containing a predetermined chemical composition on the surface of the steel sheet substrate to obtain a coated steel sheet;

S3. Surface treatment is performed on the coated steel sheet.

Fig. 1 is the scanning electron micrograph of the prepared embodiment.

The characteristics of the prepared coatings of Examples 1-13 and Comparative Examples 1-5 are shown in Table 1.

Table 1

The preparation processes of the coatings of Examples 1-13 and Comparative Examples 1-5 are shown in Table 2.

Table 2

Corrosion evaluation was carried out on the zinc-aluminum-magnesium coated steel sheets prepared according to the process parameters in the above examples and comparative examples.

The method of corrosion evaluation is to put the galvanized steel sheet into the cyclic corrosion test box and conduct 18 cycles of cyclic corrosion test. The cyclic corrosion test meets the requirements of Appendix A in ISO1 1997-1:2017, and then measure the mass loss of the coating before and after the test. The corrosion resistance of the coating is evaluated by the mass loss per unit area. The less mass loss, the better the corrosion resistance.

Evaluation of surface darkening tendency of zinc-aluminum-magnesium-coated steel sheets.

The method for evaluating the surface darkening tendency is to soak the zinc-aluminum-magnesium-coated steel sheet in an acidic solution with a pH value of 5 for 60 seconds, then rinse with deionization, and then dry it with a dry air flow, and measure the surface of the zinc-aluminum-magnesium-coated steel sheet. The brightness is L0, and then the sample is placed in a hot and humid environment with a humid and hot temperature of 50°C and a relative humidity of 60% for 120 hours, then take it out and measure the surface brightness L1, subtract L1 from L0, and obtain the brightness change ΔL, the more ΔL The larger the value, the more serious the tendency of the coating to darken.

Coating adhesion and cracking tendency were evaluated on zinc-aluminum-magnesium-coated steel sheets.

The method for evaluating the bonding force and cracking tendency of the coating is to bend the zinc-aluminum-magnesium-coated steel plate at 90°, the bending diameter is equal to the thickness of the steel plate, and then observe whether there are cracks on the surface of the coating on the outer edge of the bend. If there are cracks visible to the naked eye, it indicates that the coating has poor adhesion and a greater tendency to crack.

Table 3 shows the evaluation results of Examples 1-13 and Comparative Examples 1-5.

table 3

In summary, the zinc-aluminum-magnesium alloy coated steel sheet prepared by the embodiment of the present application has excellent corrosion resistance, and the problem of surface darkening is not easy to occur in the atmosphere.

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 application; therefore, the described range should be regarded as The description has specifically disclosed all possible subranges as well as individual values within that range. For example, a description of a range from 1 to 6 should be considered to have specifically disclosed subranges, 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 stated ranges, eg 1, 2, 3, 4, 5 and 6, apply regardless of the range. Additionally, whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range.

In the present application, unless otherwise stated, the used orientation words such as "upper" and "lower" specifically refer to the direction of the drawings in the drawings. In addition, in the description of the specification of the present application, the terms "including" and "comprising" mean "including but not limited to".

In this document, relational terms such as "first" and "second", etc., are only used to distinguish one entity or operation from another, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or sequence. In this article, "and/or" describes the association relationship of associated objects, indicating that there may be three kinds of relationships, for example, A and/or B, which can mean: A exists alone, A and B exist simultaneously, and B exists alone . Among them, A and B can be singular or plural. Herein, "at least one" means one or more, and "plurality" 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 a single item or a plurality of items. For example, "at least one item (unit) of a, b, or c", or "at least one item (unit) of a, b, and c" can mean: a, b, c, a-b( That is, a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

The above descriptions are only specific implementation manners of the present application, so that those skilled in the art can understand or implement the present 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 the application. Therefore, the present application will not 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 (10)

1. a high corrosion-resistant zinc-aluminum-magnesium coating steel plate, is characterized in that, described steel plate comprises steel substrate and zinc-aluminum-magnesium coating, and described zinc-aluminum-magnesium coating comprises Al element and Mg element, and the massfraction of described Al element is 12% by weight - 25% by weight. 2. The high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet according to claim 1, wherein the mass fraction of the Mg element is 3% by weight to 8% by weight. 3. The high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet according to claim 1 or 2, characterized in that the volume fraction of the Mg-Zn compound on the surface of the zinc-aluminum-magnesium coating is not more than 2%. 4. The high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet according to claim 1 or 2, wherein the zinc-aluminum-magnesium coating also includes Si element, and the ratio of the content of the Si element to the Al element is 0.02 -0.2. 5. The high-corrosion-resistant zinc-aluminum-magnesium-coated steel sheet according to claim 1 or 2, wherein the zinc-aluminum-magnesium coating also includes Si element, and the ratio of the content of the Si element to the Al element is 0.05 -0.15. 6. a preparation method of high corrosion-resistant zinc-aluminum-magnesium-coated steel plate is characterized in that, for preparing the high corrosion-resistant zinc-aluminum-magnesium-coated steel plate described in any one of claim 1-5, said method comprises: Activating the surface of the steel matrix to obtain a steel plate substrate; Coating a zinc-aluminum-magnesium alloy containing a predetermined chemical composition on the surface of the steel sheet substrate to obtain a coated steel sheet; The coated steel sheet is subjected to surface treatment. 7. The preparation method according to claim 6, wherein the surface activation comprises at least one of the following: Annealing, pickling and ion etching. 8. The preparation method according to claim 6, wherein the set chemical composition comprises the following chemical compositions: Al: 12% by weight to 25% by weight, Mg: 3% by weight to 8% by weight, Si, Zn. 9. The preparation method according to claim 6, wherein the coating comprises at least one of the following: Electroplating, hot-dip plating, electroless plating, and vapor deposition. 10. The preparation method according to claim 6, characterized in that, the surface treatment method is to deposit zinc atoms on the surface of the coated steel sheet.

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