阅读说明：本技术 一种镁合金漆前表面处理方法 (Surface treatment method for magnesium alloy before painting ) 是由 李卫 蓝花 刘安心 于 2021-08-18 设计创作，主要内容包括：本申请涉及一种镁合金漆前表面处理方法,涉及镁合金表面处理技术领域,其包括以下步骤：将镁合金在5～35℃转化处理液中处理90～180S,以使镁合金的表面形成有机/无机杂化转化膜；其中,有机/无机杂化转化膜由硅烷有机膜和锆盐无机转化膜杂化形成,转化处理液包括锆酸盐和10～25％硅烷,锆酸盐中的锆在转化处理液中的含量为80～300mg/L；有机/无机杂化转化膜的重量为10～150mg/m～(2),厚度为50～1000nm。本申请的处理方法与涂装工艺的配套性良好,可以根据镁合金涂装工艺及涂层特性,调整有机/无机杂化转化膜的主要构成,能显著提高涂层与镁合金的附着力及提高涂层对镁合金的防腐性能。因此,本申请实施例不仅防腐方法简单、而且工艺温度低,无有害物质,有利于节能、环保。(The application relates to a surface treatment method before magnesium alloy painting, which relates to the technical field of magnesium alloy surface treatment and comprises the following steps: treating the magnesium alloy in a conversion treatment solution at 5-35 ℃ for 90-180 seconds to form an organic/inorganic hybrid conversion film on the surface of the magnesium alloy; the organic/inorganic hybrid conversion film is formed by hybridizing a silane organic film and a zirconium salt inorganic conversion film, the conversion treatment liquid comprises zirconate and 10-25% of silane, and the content of zirconium in the zirconate in the conversion treatment liquid is 80-300 mg/L; the weight of the organic/inorganic hybrid conversion film is 10-150 mg/m 2 The thickness is 50-1000 nm. The treatment method has good matching property with the coating process, and can be adjusted according to the magnesium alloy coating process and the coating characteristicsThe main components of the organic/inorganic hybrid conversion film can obviously improve the adhesion of the coating and the magnesium alloy and improve the corrosion resistance of the coating to the magnesium alloy. Therefore, the embodiment of the application has the advantages of simple anticorrosion method, low process temperature and no harmful substances, and is beneficial to energy conservation and environmental protection.)

1. The method for treating the surface of the magnesium alloy before painting is characterized by comprising the following steps of:

treating a magnesium alloy (1) in a conversion treatment liquid at 5-35 ℃ for 90-180S to form an organic/inorganic hybrid conversion film (2) on the surface of the magnesium alloy (1);

the organic/inorganic hybrid conversion film (2) is formed by hybridizing a silane organic film and a zirconium salt inorganic conversion film, the conversion treatment liquid comprises zirconate and 10-25% of silane, and the content of zirconium in the zirconate in the conversion treatment liquid is 80-300 mg/L; the weight of the organic/inorganic hybrid conversion film (2) is 10-150 mg/m²The thickness is 50-1000 nm.

2. The method for surface treatment of magnesium alloy before painting according to claim 1, wherein the silane organic film accounts for 45-75% of the weight of the organic/inorganic hybrid conversion film (2) if the magnesium alloy (1) is painted or powder-sprayed.

3. The method for surface treatment of magnesium alloy before painting according to claim 2, wherein before the magnesium alloy (1) is painted or powder-sprayed, the method comprises the following steps:

and drying the magnesium alloy (1) for 10-15min at 80-120 ℃ to remove the water on the surface of the organic/inorganic hybrid conversion film (2).

4. The method for surface treatment of magnesium alloy before painting according to claim 1, wherein the silane organic film accounts for 15-50% of the weight of the organic/inorganic hybrid conversion film (2) if the magnesium alloy (1) is subjected to electrophoretic coating.

5. The method for surface treatment of magnesium alloy before painting according to claim 4, characterized in that before the magnesium alloy (1) is subjected to the electrophoretic coating, the magnesium alloy (1) does not need to be dried.

6. The method for treating the surface of the magnesium alloy before painting according to claim 1, wherein before the magnesium alloy (1) is treated in the conversion treatment liquid at the temperature of 5-35 ℃ for 90-180 seconds, the method further comprises the following steps:

performing surface treatment on the magnesium alloy (1) for 20-120 s by adopting a weak acid solution to remove a release agent, an oxide film and impurities on the surface of the magnesium alloy (1);

and (3) washing with water to remove the residual weak acid solution on the surface of the magnesium alloy (1).

7. The method for surface treatment of a magnesium alloy before painting according to claim 6, wherein the weak acid solution is a hydrofluoric acid solution.

8. The method for treating the surface of the magnesium alloy before painting according to claim 7, wherein the pH value of the weak acid solution is 5 to 7.

9. The method for surface treatment of a magnesium alloy as claimed in claim 1, wherein the silane is one or both of vinyltrimethoxysilane and epoxy-alkoxysilane.

10. The magnesium alloy pre-paint surface treatment method according to claim 1, wherein the zirconate is fluorozirconate.

Technical Field

The application relates to the technical field of magnesium alloy surface treatment, in particular to a method for treating the surface of a magnesium alloy before painting.

Background

Along with the requirement for light weight of automobiles is higher and higher, fuel economy is paid attention and is concerned by users, a magnesium alloy forming technology is gradually mature, more and more automobile parts are manufactured by adopting light metal magnesium alloy, the magnesium alloy material is mainly used for the internal parts of automobile bodies in the past, for example, the internal parts such as steering wheel frameworks and the like are shielded by internal decorations, the requirement for corrosion resistance is not high, the existing micro-arc oxidation is adopted to form a protective layer or the corrosion resistance treatment is not carried out, the magnesium alloy material is more and more used for structural parts of automobiles at present, the structural parts are mostly exposed parts, and the corrosion resistance requirement and the appearance requirement (color consistency) are stricter. Therefore, the magnesium alloy parts must be subjected to corrosion prevention treatment.

Coating is one of the main methods for magnesium alloy anticorrosion treatment, and because of the characteristics of magnesium alloy, the prior surface treatment before painting, such as phosphating and passivation, has limited effect although the corrosion resistance and adhesive force of a coating can be improved to a certain extent, and the phosphating and passivation contain heavy metals, such as chromium and other harmful substances and also do not meet the requirement of environmental protection; silane is adopted to carry out pre-painting treatment on the magnesium alloy, and the generated organic film is very thin and not dense and cannot achieve better corrosion resistance. Therefore, the matching performance of the surface treatment before painting and the magnesium alloy coating is poor, and the adhesion between the coating and the magnesium alloy substrate and the corrosion resistance of the coating cannot be effectively improved.

Disclosure of Invention

The embodiment of the application provides a magnesium alloy surface treatment method before painting, which aims to solve the problems that the magnesium alloy surface treatment before painting and a magnesium alloy coating in the related technology are poor in matching performance, and the adhesion between the coating and a magnesium alloy substrate and the corrosion resistance of the coating cannot be effectively improved.

In a first aspect, a method for surface treatment of a magnesium alloy before painting is provided, which comprises the following steps:

treating the magnesium alloy in a conversion treatment liquid at 5-35 ℃ for 90-180 seconds to form an organic/inorganic hybrid conversion film on the surface of the magnesium alloy;

wherein the organic/inorganic hybrid conversion film is composed of a silane organic film and a zirconium salt inorganic filmA conversion film is formed by hybridization, the conversion treatment liquid comprises zirconate and 10-25% of silane, and the content of zirconium in the zirconate in the conversion treatment liquid is 80-300 mg/L; the weight of the organic/inorganic hybrid conversion film is 10-150 mg/m²The thickness is 50-1000 nm.

The embodiment of the application provides a method for treating the surface of a magnesium alloy before painting, which is characterized in that a continuous, uniform and compact organic/inorganic hybrid conversion film is formed on the surface of the magnesium alloy by treating the magnesium alloy in a conversion treatment solution containing silane and zirconate. The specific formation principle of the organic/inorganic hybrid conversion film is as follows: silane is adsorbed on the surface of the magnesium alloy under certain conditions, molecular bond combination is formed between the silane and the magnesium alloy, and the silane is condensed to form a reticular silane organic film; and the hydrolysate of the zirconate is filled in the gaps of the network structure of the silane organic film and hybridized with the silane organic film to form an organic/inorganic hybrid conversion film. And the subsequent coating of the magnesium alloy can obviously improve the adhesion of the coating and the magnesium alloy and improve the corrosion resistance of the coating to the magnesium alloy.

In addition, the magnesium alloy pre-painting surface treatment method provided by the embodiment of the application has good matching performance with a coating process, can adjust the main composition of an organic/inorganic hybrid conversion film according to the magnesium alloy coating process and the coating characteristics, and can obviously improve the adhesion of the coating and the magnesium alloy and improve the corrosion resistance of the coating to the magnesium alloy. After the organic/inorganic hybrid conversion film formed by the surface treatment before the magnesium alloy painting is matched with the coating process, the adhesion force of the formed coating is less than or equal to 2 grades, and the corrosion resistance is excellent. Therefore, the embodiment of the application has the advantages of simple anticorrosion method, low process temperature and no harmful substances, and is beneficial to energy conservation and environmental protection.

In some embodiments, if the magnesium alloy is spray-painted or powder-sprayed, the silane organic film accounts for 45% to 75% of the weight of the organic/inorganic hybrid conversion film.

The powder spraying coating requires that the organic/inorganic hybrid conversion film needs to be dried, the powder spraying adopts electrostatic spraying, the formed coating is thicker than electrophoretic coating, the internal stress of the coating is larger, the thickness of the organic/inorganic hybrid conversion film is too thick, the adhesive property of the coating can be influenced, under the condition that the organic/inorganic hybrid conversion film is compact and the thickness is not too thick, the silane forms a more compact conversion film on the surface of the magnesium alloy, only zirconate hybridization is needed to fill the pores of the reticular structure, and therefore the proportion of the silane organic film is higher.

Therefore, in the embodiment of the application, the weight and the thickness of the organic/inorganic hybrid conversion coating and the proportion of the silane organic coating are controlled by adjusting the proportion of silane and zirconate in the conversion treatment liquid, and the treatment time and the treatment temperature, so as to meet the requirements of a powder spraying coating process, and ensure that the adhesion and the corrosion resistance of the coating are good.

In some embodiments, before the magnesium alloy is painted or powder-sprayed, the method comprises the following steps:

and drying the magnesium alloy at 80-120 ℃ for 10-15min to remove the water on the surface of the organic/inorganic hybrid conversion film.

In some embodiments, if the magnesium alloy is subjected to electrophoretic coating, the silane organic film accounts for 15% to 50% of the weight of the organic/inorganic hybrid conversion film.

The electrophoretic coating is that magnesium alloy is directly coated in an electrophoretic tank by adopting a direct current electric field, and the voltage is generally 200-300V, so that the organic/inorganic hybrid conversion film does not need to be dried before coating. However, since the silane conversion film in the organic/inorganic hybrid conversion film is an organic film, the silane organic film is thicker, which causes poor electroosmosis performance of the electrophoretic coating and affects the appearance and thickness of the electrophoretic coating; if the corrosion resistance of the organic/inorganic hybrid conversion film is not easily affected, the zirconium salt inorganic conversion film needs to be fully hybrid-filled so as to ensure the matching property of the organic/inorganic hybrid conversion film and the electrophoretic coating and the thickness of the electrophoretic coating.

Therefore, in the embodiment of the application, the weight and the thickness of the organic/inorganic hybrid conversion film and the proportion of the silane organic film are controlled by adjusting the proportion of the silane and the zirconate in the conversion treatment liquid, the treatment time and the treatment temperature, so as to meet the requirement of an electrophoretic coating process, and ensure that the coating has good adhesion and corrosion resistance.

In some embodiments, the magnesium alloy does not need to be dried before the magnesium alloy is subjected to electrocoating.

In some embodiments, before the magnesium alloy is treated in the conversion treatment liquid at 5-35 ℃ for 90-180S, the method further comprises the following steps:

performing surface treatment on the magnesium alloy by adopting a weak acid solution for 20-120 s to remove a release agent, an oxide film and impurities on the surface of the magnesium alloy;

and washing with water to remove the residual weak acid solution on the surface of the magnesium alloy.

In some embodiments, the weak acid solution is hydrofluoric acid.

In some embodiments, the weak acid solution has a pH of 5 to 7.

In some embodiments, one or both of vinyltrimethoxysilane and epoxy-alkoxysilane.

In some embodiments, the zirconate is a fluorozirconate.

The beneficial effect that technical scheme that this application provided brought includes:

the embodiment of the application provides a method for treating the surface of a magnesium alloy before painting, which can solve the defects and problems that the surface treatment before painting in the related technology, such as phosphorization and passivation, contains heavy metals, such as chromium and other harmful substances, does not meet the requirement of environmental protection, and the formed film is thin and not dense, the matching property with a subsequent coating process is poor, the adhesion of a coating is influenced, and the coating cannot achieve better corrosion resistance, such as a simple silane surface treatment technology.

The principle of the embodiment of the application is as follows:

in the embodiment of the application, the magnesium alloy is treated in the conversion treatment liquid containing silane and zirconate, so that a continuous, uniform and compact organic/inorganic hybrid conversion film is formed on the surface of the magnesium alloy. The specific formation principle of the organic/inorganic hybrid conversion film is as follows: silane is adsorbed on the surface of the magnesium alloy under certain conditions, molecular bond combination is formed between the silane and the magnesium alloy, and the silane is condensed to form a reticular silane organic film; and the hydrolysate of the zirconate is filled in the gaps of the network structure of the silane organic film and hybridized with the silane organic film to form an organic/inorganic hybrid conversion film. And the subsequent coating of the magnesium alloy can obviously improve the adhesion of the coating and the magnesium alloy and improve the corrosion resistance of the coating to the magnesium alloy.

In addition, the magnesium alloy pre-painting surface treatment method provided by the embodiment of the application has good matching performance with a coating process, can adjust the main composition of an organic/inorganic hybrid conversion film according to the magnesium alloy coating process and the coating characteristics, and can obviously improve the adhesion of the coating and the magnesium alloy and improve the corrosion resistance of the coating to the magnesium alloy. After the organic/inorganic hybrid conversion film formed by the surface treatment before the magnesium alloy painting is matched with the coating process, the adhesion force of the formed coating is less than or equal to 2 grades, and the corrosion resistance is excellent. Therefore, the embodiment of the application has the advantages of simple anticorrosion method, low process temperature and no harmful substances, and is beneficial to energy conservation and environmental protection.

Therefore, the weight and the thickness of the organic/inorganic hybrid conversion film and the weight ratio of the silane organic film to the organic/inorganic hybrid conversion film can be changed by adjusting the contents of zirconate and silane in the conversion treatment liquid and the treatment temperature and temperature according to the different requirements of the characteristics of different coating processes and the weight and the thickness of the organic/inorganic hybrid conversion film and the weight ratio of the silane organic film to the organic/inorganic hybrid conversion film so as to adapt to different coating processes. Thereby remarkably improving the adhesion of the coating and the magnesium alloy and improving the corrosion resistance of the coating to the magnesium alloy.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a sectional view of a magnesium alloy coating provided in an embodiment of the present application.

In the figure: 1. a magnesium alloy; 2. an organic/inorganic hybrid conversion film; 3. and (4) coating.

Detailed Description

In order to make the objects, 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 with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The embodiment of the application provides a method for treating the surface of a magnesium alloy before painting, which can solve the defects and problems that the surface treatment before painting in the related technology, such as phosphorization and passivation, contains heavy metals, such as chromium and other harmful substances, does not meet the requirement of environmental protection, and the formed film is thin and not dense, the matching property with a subsequent coating process is poor, the adhesion of a coating 3 is influenced, and the coating 3 cannot achieve better corrosion resistance, such as a simple silane surface treatment technology.

Referring to fig. 1, the present embodiment provides a method for treating a surface of a magnesium alloy before painting, which forms a continuous, uniform and dense organic/inorganic hybrid conversion coating 2 on the surface of the magnesium alloy 1 by treating the magnesium alloy 1 in a conversion treatment solution containing silane and zirconate. The specific formation principle of the organic/inorganic hybrid conversion film 2 is as follows: silane is adsorbed on the surface of the magnesium alloy 1 under a certain condition, molecular bond combination is formed between the silane and the magnesium alloy 1, and the silane is condensed to form a reticular silane organic film; and zirconium oxide, zirconium hydroxide and other hydrolysate formed by the hydrolysis reaction of zirconate is adsorbed on the surface of the magnesium alloy 1 to form a zirconium salt inorganic conversion film, and the hydrolysate of zirconate is filled in the gaps of the network structure of the silane organic film and hybridized with the silane organic film to form an organic/inorganic hybrid conversion film 2. And the magnesium alloy 1 is coated subsequently, so that the adhesive force of the coating 3 and the magnesium alloy 1 can be obviously improved, and the corrosion resistance of the coating 3 to the magnesium alloy 1 can be improved.

In addition, the magnesium alloy pre-painting surface treatment method provided by the embodiment of the application has good matching performance with a coating process, can adjust the main composition of the organic/inorganic hybrid conversion film 2 according to the coating process of the magnesium alloy 1 and the characteristics of the coating 3, and can obviously improve the adhesion between the coating 3 and the magnesium alloy 1 and improve the corrosion resistance of the coating 3 to the magnesium alloy 1. After the organic/inorganic hybrid conversion film 2 formed by the surface treatment before the painting of the magnesium alloy 1 is matched with the coating process, the adhesion force of the formed coating 3 is less than or equal to 2 grade, and the corrosion resistance is excellent. Therefore, the embodiment of the application has the advantages of simple anticorrosion method, low process temperature and no harmful substances, and is beneficial to energy conservation and environmental protection.

The magnesium alloy surface treatment method before painting provided by the embodiment of the application comprises the following steps: treating the magnesium alloy 1 in a conversion treatment solution at 5-35 ℃ for 90-180 seconds to form an organic/inorganic hybrid conversion film 2 on the surface of the magnesium alloy 1; the organic/inorganic hybrid conversion film 2 is formed by hybridizing a silane organic film and a zirconium salt inorganic conversion film, the conversion treatment liquid is formed by dissolving zirconate and silane in water, the mass fraction of the silane in the conversion treatment liquid is 10-25%, the content of zirconium in the zirconate in the conversion treatment liquid is 80-300 mg/L, and the balance is one or more of hydrofluoric acid, sulfuric acid and hydrochloric acid; the weight of the organic/inorganic hybrid conversion film 2 is 10-150 mg/m²The thickness is 50-1000 nm, and the silane organic film accounts for 15-75% of the weight of the organic/inorganic hybrid conversion film 2.

Aiming at the characteristics of different coating processes and different requirements of the weight and the thickness of the organic/inorganic hybrid conversion film and the weight ratio of the silane organic film to the organic/inorganic hybrid conversion film 2, the weight and the thickness of the organic/inorganic hybrid conversion film 2 and the weight ratio of the silane organic film to the organic/inorganic hybrid conversion film 2 are changed by adjusting the contents of zirconate and silane in the conversion treatment liquid, the treatment temperature and the treatment time so as to adapt to different coating processes. Thereby obviously improving the adhesive force of the coating 3 and the magnesium alloy 1 and improving the corrosion resistance of the coating 3 to the magnesium alloy 1.

The following is illustrated by three specific examples:

example 1:

in the embodiment 1 of the present application, powder spraying coating needs to be performed on the magnesium alloy 1, and the main implementation steps are as follows:

(1) pre-painting treatment:

s1, performing surface treatment on the magnesium alloy 1 by adopting a hydrofluoric acid solution with the pH value of 5.5 at normal temperature for 20S to remove the release agent, the oxide film and impurities on the surface of the magnesium alloy 1;

s2, washing with water to remove the residual weak acid solution on the surface of the magnesium alloy 1; then washing with deionized water;

s3, treating the magnesium alloy in a conversion treatment liquid at 30 ℃ for 120S to form an organic/inorganic hybrid conversion film 2 on the surface of the magnesium alloy 1; wherein the conversion treatment liquid comprises fluorozirconate and 12% of silane, and the content of zirconium in the zirconate is 260 mg/L;

s4, washing the residual conversion treatment solution on the organic/inorganic hybrid conversion film 2 with water and deionized water to finish the pre-painting treatment; wherein the conductivity of the deionized water washing is less than 20 mu s/cm.

After finishing the pre-painting treatment, drying the magnesium alloy 1 at the drying temperature of 120 ℃ for 10 min; then, the weight of the organic/inorganic hybrid conversion film 2 is detected, and the weight of the organic/inorganic hybrid conversion film 2 is 60mg/m²The thickness is 80nm, and the weight of the silane organic film is 40mg/m²。

(2) Coating:

s1, drying the magnesium alloy for 10min at 100 ℃ to remove the water on the surface of the organic/inorganic hybrid conversion film 2;

s2, performing powder spraying and coating on the magnesium alloy 1 with the organic/inorganic hybrid conversion film 2 to form a coating 3, and drying and curing.

(3) And (3) testing:

the adhesion of the detection coating 3 is grade 1, and the corrosion resistance is good.

The powder spraying coating requires that the organic/inorganic hybrid conversion film 2 needs to be dried, the powder spraying adopts electrostatic spraying, the formed coating 3 is thicker than electrophoretic coating, the internal stress of the coating is larger, and the adhesive force of the coating 3 is influenced because the thickness of the organic/inorganic hybrid conversion film 2 is too thick. Under the condition of ensuring that the organic/inorganic hybrid conversion film 2 is compact and the thickness is not excessively thick, the silane forms a relatively compact conversion film 2 on the surface of the magnesium alloy 1, and only zirconate is required to be hybridized and filled in pores of a net structure, so that the silane organic film is required to have a high proportion.

Therefore, in the embodiment 1 of the present application, the weight and thickness of the organic/inorganic hybrid conversion coating 2 and the ratio of the silane organic coating are controlled by adjusting the ratio of silane to zirconate in the conversion treatment solution, and the treatment time and temperature, so as to satisfy the powder spraying coating process, and make the coating 3 have strong adhesion and good corrosion resistance.

Example 2, the basic content is the same as example 1, except that:

in embodiment 2 of the present application, the magnesium alloy 1 needs to be subjected to anodic electrophoretic coating, and the main implementation steps are as follows:

(1) pre-painting treatment:

s1, performing surface treatment on the magnesium alloy 1 by adopting a hydrofluoric acid solution with the pH value of 6.0 at normal temperature for 30S to remove the release agent, the oxide film and impurities on the surface of the magnesium alloy 1;

s2, washing with water and deionized water to remove residual weak acid solution on the surface of the magnesium alloy 1;

s3, treating the magnesium alloy at 25 ℃ for 150S to form an organic/inorganic hybrid conversion film 2 on the surface of the magnesium alloy 1; wherein the conversion treatment liquid comprises fluorozirconate and 22% of silane, and the content of zirconium in the zirconate is 120 mg/L;

s4, washing the residual conversion treatment solution on the organic/inorganic hybrid conversion film 2 with water and deionized water to finish the pre-painting treatment; wherein the conductivity of deionized water and deionized water washing is less than 20 mu s/cm.

After finishing the pre-painting treatment, drying the magnesium alloy 1 at the drying temperature of 120 ℃ for 10 min; then, the weight of the organic/inorganic hybrid conversion film 2 is detected, and the weight of the organic/inorganic hybrid conversion film 2 is 100mg/m²300nm in thickness and 45mg/m in weight of the silane organic film²。

(2) Coating:

and (3) carrying out anodic electrophoretic coating on the magnesium alloy 1 with the formed organic/inorganic hybrid conversion film 2 to form a coating 3, and drying and curing.

(3) And (3) testing:

the adhesion of the coating 3 is detected to be 2 grade, and the corrosion resistance is good.

Example 3, the basic content is the same as example 1, except that:

in the embodiment 3 of the present application, the magnesium alloy 1 needs to be subjected to cathodic electrophoretic coating, and the main implementation steps are as follows:

(1) pre-painting treatment:

s1, performing surface treatment on the magnesium alloy 1 at normal temperature by adopting a hydrofluoric acid solution with the pH value of 5.5 for 2min to remove the release agent, the oxide film and impurities on the surface of the magnesium alloy 1;

s2, washing with water and deionized water to remove residual weak acid solution on the surface of the magnesium alloy 1;

s3, treating the magnesium alloy in a conversion treatment liquid at 30 ℃ for 150S to form an organic/inorganic hybrid conversion film 2 on the surface of the magnesium alloy 1; wherein the conversion treatment liquid comprises fluorozirconate and 22% of silane, and the content of zirconium in the zirconate is 180 mg/L;

s4, washing the residual conversion treatment solution on the organic/inorganic hybrid conversion film 2 with water and deionized water to finish the pre-painting treatment; wherein the conductivity of deionized water and deionized water washing is less than 20 mu s/cm.

After finishing the pre-painting treatment, drying the magnesium alloy 1 at the drying temperature of 120 ℃ for 10 min; then, the weight of the organic/inorganic hybrid conversion film 2 is detected, and the weight of the organic/inorganic hybrid conversion film 2 is 130mg/m²400nm thick, 65mg/m weight of silane organic film²。

(2) Coating:

and (3) carrying out anodic electrophoretic coating on the magnesium alloy 1 with the formed organic/inorganic hybrid conversion film 2 to form a coating 3, and drying and curing.

(3) And (3) testing:

the adhesion of the detection coating 3 is grade 1, and the corrosion resistance is good.

The electrophoretic coating is that the magnesium alloy 1 is directly coated in an electrophoretic bath by adopting a direct current electric field, and the voltage is generally 200-300V, so that the organic/inorganic hybrid conversion film 2 does not need to be dried before coating. However, since the silane conversion film in the organic/inorganic hybrid conversion film 2 is an organic film, the thicker silane organic film will cause the poorer electroosmosis performance of the electrophoretic coating, and affect the appearance and thickness of the electrophoretic coating; if the organic/inorganic hybrid conversion film 2 is not compact and the corrosion resistance is easily affected, the zirconium salt inorganic conversion film needs to be fully hybrid-filled to ensure the matching property of the organic/inorganic hybrid conversion film and the electrophoretic coating and the thickness of the electrophoretic coating.

Therefore, in the embodiments 2 and 3 of the present application, the weight, thickness and ratio of the organic/inorganic hybrid conversion film 2 and the silane organic film can be controlled by adjusting the ratio of silane and zirconate in the conversion treatment solution, and the treatment time and temperature, so as to satisfy the electrophoretic coating process and make the adhesion and corrosion resistance of the coating 3 good.

As can be seen from the coating adhesion tests of the 3 embodiments, the surface treatment method before painting in the embodiment of the application has the advantages that the adhesion of the coating 3 is less than or equal to 2 grade, the anticorrosion performance of the coating 3 is good, the matching performance with the coating process is good, and the anticorrosion requirement of the coating 3 is met.

In the description of the present application, it should be noted that the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Unless expressly stated or limited otherwise, the terms "mounted," "connected," and "connected" are intended to be inclusive and mean, for example, that they may be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

It is noted that, in the present application, relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

The above description is merely exemplary of the present application and is presented to enable those skilled in the art to understand and practice the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.