KR101751453B1 - alkali Conversion Coating Composition of Magnesium and Magnesium Alloy and Surface Treating Method Using The Same - Google Patents

Abstract

The alkaline processing composition for forming a chemical conversion coating on a surface of a magnesium and magnesium alloy material comprises 2 to 10% by weight of a phosphate compound, 1 to 5% by weight of an inorganic metal sol, 0.03 to 0.3% by weight of a vanadium compound, 0.5 to 5% 0.01 to 0.1% by weight of an acrylic resin, and an extra water-soluble solvent. The above-described composition forms a uniform and dense chemical conversion coating film on the surface of magnesium or magnesium alloy material, and imparts corrosion resistance, top adhesion and water resistance to water, and does not cause surface defects in top coating.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline processing composition for magnesium and magnesium alloys, and a surface treatment method of magnesium and magnesium alloys using the composition.

The present invention relates to an alkaline processable composition for magnesium and magnesium alloys and a surface treatment method of magnesium and magnesium alloys using the same. More particularly, the present invention relates to magnesium and magnesium alloys, An alkaline processable composition for an alloy, and a surface treatment method of a magnesium and magnesium alloy material using the same.

 Magnesium is the eighth most abundant metal in the world. It is the lightest metal among practical metals, and has excellent non-strength, machinability and dimensional stability. In addition, the magnesium alloy has an advantage of being applicable to electronic devices and transportation equipment aiming at lightweight because of excellent electromagnetic wave shielding property, heat radiation property and vibration absorption property. Recently, it has been applied as an electronic device such as a computer, a camera, an MP3 player, a mobile phone, a structure for an automobile such as a handle, a cylinder head, a ventilation fan, and a seat frame, and other application fields are expected to increase sharply.

As described above, since the majority of metal material members (aluminum alloy, steel, magnesium alloy, etc.) used for automobiles, motorcycles, household appliances, etc. are required to have corrosion resistance and aesthetic appearance, they are painted after being subjected to various surface treatments. The purpose of the surface treatment is to remove contaminants such as cutting oil and processing oil remaining on the surface of the workpiece to form a dense chemical film to impart corrosion resistance and paint adhesion.

The magnesium alloy member is painted after surface treatment as in the case of steel or aluminum alloy. The magnesium alloy is the most active metal among the practical metals and has a property of being easily corroded. Moreover, since the surface of the magnesium alloy is chemically uneven, the magnesium alloy is an extremely difficult material to form a dense and uniform chemical film.

In order to solve such problems, conventionally, a chemical treatment liquid containing hexavalent chromium having excellent corrosion resistance has been used to secure corrosion resistance and paint adhesion (Japanese Patent Registration No. 10-0869402). However, such hexavalent chromium And its use is regulated because it causes environmental pollution problems. Therefore, recently, a method of imparting corrosion resistance and paint adhesion by forming a dense chemical conversion film using a chromium-free processing solution containing no chromium has been applied.

As the non-chromium conversion treatment method, at least one organometallic compound selected from a metal alkoxide, metal acetylacetonate and metal carboxylate and at least one compound selected from the group consisting of an acid, an alkali and a salt thereof, or a compound having any one of a hydroxyl group, (Japanese Unexamined Patent Publication No. Hei 9-228062) ", a treatment method based on magnesium phosphate treatment, and a method of treating at least one kind of film forming auxiliary selected from zirconium, titanium Phosphate treatment (Japanese Patent Publication No. Hei 7-126858) in which a metal such as zinc is added. However, these chemical conversion treatment compositions are impractical because they require a long treatment time, and require a long time for treatment. However, there is a problem that sufficient corrosion resistance, rust resistance and film adhesion can not be imparted. It is susceptible to influence and the performance is not stable.

In order to solve these problems, the present applicant has obtained a patent registration (10-1559285) for a patent application for a chemical composition for a magnesium or magnesium alloy material. The technique has the advantage of forming a high performance chemical conversion film. However, since the chemical conversion composition has an acidic property, when the process of forming a chemical conversion film is repeated, magnesium is rapidly eluted into the chemical conversion composition. The melting of magnesium leads to the deterioration of the chemical treatment composition, which makes it difficult to continuously form a chemical conversion film having excellent corrosion resistance and water resistance.

The object of the present invention is to overcome such a problem by forming a uniform and dense chemical conversion coating film on the surface of a magnesium or magnesium alloy material and at the same time to provide an alkalizing treatment composition having remarkably low aging characteristics compared to a conventional acidic chemical conversion solution .

Another object of the present invention is to overcome the above problems, and it is an object of the present invention to overcome the above problems by using an alkaline processing composition to remove contaminants and an oxide layer existing on the surface of a magnesium or magnesium alloy material and then to form a uniform and dense chemical conversion coating, And to provide a surface treatment method of an alloy material.

In order to achieve the above object, the alkaline processing composition for forming a chemical conversion coating on a surface of a magnesium and magnesium alloy material of the present invention comprises 2 to 10% by weight of a phosphate compound, 1 to 5% by weight of an inorganic metal sol, %, A basic compound of 0.5 to 5 wt%, an acrylic resin of 0.01 to 0.1 wt%, and an extra water-soluble solvent.

According to another aspect of the present invention, there is provided a surface treating method for a magnesium and magnesium alloy material, comprising the steps of: performing a degreasing process on magnesium and a magnesium alloy material; subjecting the degreased magnesium and magnesium alloy material to an acidic aqueous solution Performing a desmutting process to remove the smut present in the etched magnesium and magnesium alloy material and a step of removing the smut from the surface of the magnesium and magnesium alloy material by using an alkalizing treatment composition for the magnesium alloy, Thereby forming a chemical conversion film. Wherein the chemical conversion coating comprises 2 to 10 wt% of a phosphate compound, 1 to 5 wt% of an inorganic metal sol, 0.03 to 0.3 wt% of a vanadium compound, 0.5 to 5 wt% of a basic compound, 0.01 to 0.1 wt% of an acrylic resin, It is preferable to use an alkalizing treatment composition for a magnesium and magnesium alloy containing a solvent.

The alkaline processing composition for magnesium and the alloy material of the present invention having such a composition has a low elution property of magnesium ions to prevent the alkalizing composition from aging due to the chemical conversion treatment process so that even if it is reused several times or more, A coating film can be formed. Accordingly, the magnesium material can be provided with high corrosion resistance, excellent paint adhesion, and water resistance, without causing surface defects of the top coat layer formed thereafter.

1 is a graph showing changes in pH of the chemical conversion composition of Example 1 and Comparative Example 11. Fig.
FIG. 2 is a photograph showing an enlarged microstructure of a chemical conversion film formed using the chemical conversion composition of Example 1

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an alkalizing treatment composition for a magnesium and magnesium alloy according to an embodiment of the present invention and a surface treatment method using the same will be described in detail. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are further described in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a part or a combination thereof is described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

On the other hand, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, the alkalizing treatment composition according to one embodiment of the present invention and the surface treatment method using the same will be described in detail.

Alkali-forming treatment compositions for magnesium and magnesium alloys

Since the conventional chemical conversion composition has an acidic property, when the magnesium material is dipped in the solution, the magnesium is continuously eluted from the material to accelerate the deterioration of the chemical treatment composition, while the alkaline chemical treatment composition of the present embodiment, And the reactivity with the magnesium material is well controlled, so that a chemical conversion coating film having excellent characteristics can be formed on the surface of the magnesium material even at room temperature.

The alkalizing agent composition of the present embodiment having the above-mentioned properties has a composition comprising a phosphoric acid compound, an inorganic metal sol, a vanadium compound, a basic compound, an acrylic resin and a water-soluble solvent. As an illustrative example, the alkalizing treatment composition for magnesium and magnesium alloys may comprise 2 to 10% by weight of a phosphoric acid compound, 1 to 5% by weight of an inorganic metal sol, 0.03 to 0.3% by weight of a vanadium compound, 0.5 to 5% From 0.01 to 0.1% by weight of resin and an excess of water-soluble solvent.

In one example, the phosphoric acid compound contained in the alkalizing treatment composition is used for imparting corrosion resistance to the chemical conversion film to be formed and for improving the film adhesion.

Examples of the phosphate compound include ammonium phosphate monobasic, sodium phosphate dibasic, potassium phosphate dibasic, orthophosphoric acid, and the like. The phosphoric acid compound may be used singly or in combination of two or more thereof.

When the content of the phosphoric acid compound to be applied to the chemical conversion composition according to the present invention is less than 2% by weight, formation of a sufficient chemical conversion film is not carried out, and corrosion resistance and paint adhesion are difficult to secure. On the other hand, if the content exceeds 10% by weight, an excessive chemical conversion film is formed on the film to improve the corrosion resistance, but it is difficult to secure the coating adhesion. Therefore, the phosphoric acid compound is preferably used in an amount of 2 to 10% by weight, more preferably 3 to 9% by weight.

The inorganic metal sol to be applied to the alkalizing treatment composition according to the present embodiment is applied to ensure corrosion resistance and to form a uniform chemical conversion coating. Examples of the inorganic metal sol include silica sol, alumina sol, titania sol, and zirconia sol. These may be used singly or in a mixture of two or more.

In one example, the GRACE Company as Silica sol Among the inorganic metal sol ^{Ludox ® HS-30, Ludox ®} HS-40, Ludox ® TM, Ludox ® SM, Ludox ® AM, Ludox ® AS, Ludox ® LS, Ludox ® CL- X, Ludox ^® SK, Ludox ^® TMA, Ludox ^® PG, Ludox ^® CL, Ludox ^® CL - P, Ludox ^® DF, Ludox ^® FM, Ludox ^® HSA, SNOWTEX ^® ST - 20L and SNOWTEX ^® ST - 40 from NISSAN CHEMICAL ^{, SNOWTEX ® ST-50, SNOWTEX} ® ST-C, SNOWTEX ® ST-N, SNOWTEX ® ST-O, SNOWTEX ® ST-OL, SNOWTEX ® ST-ZL, SNOWTEX ® ST-PS-M, SNOWTEX ® ST-PS ^{-S, SNOWTEX ® ST-PS-} SO, SNOWTEX ® ST-OUP, SNOWTEX ® ST-UP, S-CHEMTECH 's SS-SOL 30SG, SS-SOL 30E, SS-SOL 30, SS-SOL 30F, SS-SOL SS-SOL 30E, SS-SOL 30OEAC, SS-SOL 30OMAC, SS-SOL 30OPAC, SS-SOL 20EG, SS-SOL 30EK and SS-SOL 30BK). (Ultra-Sol 201A / 60, Ultra-Sol 201A / 280 manufactured by Gerard Kluyskens Co., Inc., Wesol A, Wesol Co., Ltd., WESBOND Co., Ltd.) of the above-mentioned alumina sol (ALUMINASOL ^TM AS-100, ALUMINASOL ^TM AS- C12, Wesol D30), and the like. These may be used singly or in a mixture of two or more.

If the amount of the inorganic metal sol contained in the composition according to the present invention is less than 1% by weight, the non-uniformity and corrosion resistance of the chemical conversion coating may deteriorate. On the other hand, if the content exceeds 5% by weight, There arises a problem accompanied by a decrease in the stability of the treating composition. Therefore, the inorganic metal sol is preferably used in an amount of 1 to 5% by weight, more preferably 1.5 to 4% by weight.

Further, the vanadium compound applied to the alkalizing treatment composition according to the present invention is applied to further improve the corrosion resistance and to give a self-healing effect to the magnesium alloy material.

As the vanadium compound, there can be used a vanadium compound having five valence, four valence or trivalence as the oxidation number of vanadium, and examples thereof include vanadium pentoxide (V ₂ O ₅ ), metavanadic acid (HVO ₃ ) acid, ammonium metavanadate, sodium oxy trichloride vanadium (VOCl ₃₎ oxidation number 5 Cain vanadium compound 3 vanadium oxide, such as (V ₂ O _3), dioxide, vanadium (VO _2), oxy-sulfate, vanadium (VOSO _4), vanadium Oxyacetyl acetate VO (OC (= CH ₂ ) CH ₂ COCH ₃ ) ₂ , vanadium acetylacetate V (OC (= CH ₂ ) CH ₂ COCH ₃ ) ₃ , vanadium chloride (VCl ₃ ) Trivalent or tetravalent vanadium compounds such as tetravalent vanadium compounds. These may be used alone or in combination of two or more.

If the content of the vanadium compound contained in the composition according to the present invention is less than 0.03% by weight, the corrosion resistance and self-healing effect can not be obtained. On the other hand, if the content exceeds 0.3% by weight, There is a problem that occurs. Therefore, the vanadium compound is preferably used in an amount of 0.03 to 0.3% by weight, and more preferably 0.05 to 0.2% by weight.

The basic compound serves to raise the pH of the chemical conversion treatment composition to produce a more stable alkalizing treatment composition, and examples thereof include sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonium hydroxide and lithium hydroxide. These may be used singly or in a mixture of two or more.

If the content of the basic compound is less than 0.5% by weight, the pH of the alkaline-treating composition may not be increased to a desired level. If the content of the basic compound exceeds 5% by weight, the pH of the alkaline- There is a problem that a film is not formed. Therefore, the basic compound is preferably used in an amount of 0.5 to 5% by weight.

Also, the acrylic resin applied to the alkalizing treatment composition according to one embodiment of the present invention improves the durability of the chemical conversion film to be formed, thereby forming a more dense chemical conversion film and enhancing the water resistance. The acrylic resin may be an acrylic polyol, an acrylic acid copolymer, a modified acrylic acid copolymer, or a polyacrylate. These may be used singly or in a mixture of two or more.

If the content of the acrylic resin is less than 0.01% by weight, the durability of the formed chemical film is deteriorated to deteriorate the adhesion and the water resistance. When the content exceeds 0.1% by weight, the chemical film is thickened due to the excessive resin, . Therefore, the acrylic resin is preferably used in a range of 0.01 to 0.1% by weight.

In particular, the alkalizing treatment composition according to this embodiment preferably has a pH of 8.5 to 10.5. When the pH of the alkaline processing composition is less than 8.5, the reactivity of the magnesium alloy material becomes large and the chemical conversion coating is actively formed. However, the magnesium ions melt very quickly on the surface of the material, thereby accelerating the aging of the solution. On the other hand, when the pH is above 10.5, the reactivity of the magnesium alloy material is remarkably reduced, so that the formation of the chemical conversion film on the surface of the magnesium material is not performed well.

The alkaline processing composition for magnesium and its alloys having such a composition has a low elution property of magnesium ions, thereby preventing the alkalizing composition from aging due to the chemical conversion treatment process, and thus forming a dense chemical conversion film even if reused several times or more can do. Accordingly, the magnesium material can be provided with high corrosion resistance, excellent paint adhesion, and water resistance, without causing surface defects of the top coat layer formed thereafter.

Hereinafter, a method of surface-treating a magnesium and magnesium alloy material according to an embodiment of the present invention will be described.

The surface treatment method of the magnesium and magnesium alloy materials according to the present invention can be performed by performing the surface cleaning process and the chemical treatment process.

The surface cleaning process is a process for removing contaminants (processing oil, oil, etc.) and an oxide layer existing on the surface of the magnesium alloy before the chemical conversion treatment to help form a uniform and dense chemical conversion film. The following degreasing (alkali degreasing ) Process, a primary washing process, an etching process, a secondary washing process, a hairless process, and a tertiary washing process.

In the surface cleaning process of the present invention, the degreasing process is a step of primarily removing the oil component and the working oil component on the surface of the magnesium alloy prior to the etching process.

The degreasing solution which can be used in the degreasing step is not particularly limited as long as it can remove organic contaminants, but it is preferable to use an alkaline aqueous solution containing a surfactant. The alkali builder of the degreasing liquid may be a hydrate of an alkali metal, a phosphate, a silicate, a carbonate, or the like. As the surfactant, any of a non-ionic surfactant, a cationic surfactant, and an anionic surfactant may be used. Further, a chelating agent may be added to improve the degreasing efficiency.

The temperature and time for bringing the degreasing liquid into contact with the magnesium alloy are not particularly limited, but it is preferably within a range of 30 to 70 ° C for 2 to 10 minutes depending on the degree of contamination on the surface of magnesium. The concentration of the degreasing liquid may also be appropriately set according to the degree of contamination on the surface of the magnesium alloy, the degreasing liquid component, and the like.

The first washing step is a washing step using water to remove the washing liquid applied in the degreasing step. The first flushing may be performed by a method such as dipping, spraying, or submerging. The flushing may be performed using all kinds of water including deionized water, distilled water, pure water, and the like. However, it may be preferably carried out at a temperature range of 25 to 80 캜. This is because, when hot water is used, it becomes flush more efficiently and the composition of dehydration drying improves, so that the inflow of water into the next processing tank is minimized and the treatment liquid can be easily managed. In addition, ultrasonic vibration may be applied to enhance the cleaning effect during the washing step.

In the surface cleaning process of the present invention, the etching process is performed in order to remove the surface of the magnesium alloy which is the object to be processed, when the surface of the magnesium alloy is excessively contaminated by the processing oil or when the oxide film layer is grown. The etching treatment in the etching process is carried out by bringing an acidic aqueous solution into contact with the magnesium alloy material to be treated.

As an example, the acidic aqueous solution is not particularly limited so long as the contaminants on the surface of the magnesium alloy can be dissolved and removed, and it is preferable to use one or more of sulfuric acid, phosphoric acid, hydrochloric acid, hydrofluoric acid, nitric acid, and carbonic acid in combination. An organic acid may be mixed to improve the etching efficiency. The conditions such as the concentration of the acidic aqueous solution, the temperature, and the contact time with the surface of the magnesium alloy are not limited and are appropriately adjusted according to the degree of contamination of the magnesium alloy, the component of the acidic aqueous solution used, and the like.

The second water washing step is a cleaning step using water to remove the acidic aqueous solution to be applied in the etching step. The second washing may be performed by a method such as dipping, spraying, or submerging, and may be performed using all kinds of water including deionized water, distilled water, pure water, and the like. There is no particular limitation on the temperature range.

In the surface cleaning process of the present invention, the demersal process is performed to remove the smut when the smut remains on the surface of the magnesium alloy after the etching process. The desmutting in the desmutting step can be carried out by contacting the desmutting liquid with the magnesium alloy to be treated.

As an example, the desmut liquid is not particularly limited as long as it can remove the smut remaining on the magnesium surface after the etching process. It is also possible to mix one or two sheets of tartaric acid, ascorbic acid, gluconic acid, citric acid, Aqueous solution (PH12 or higher).

The conditions such as the concentration of the desmut liquid, the temperature, and the contact time with the surface of the magnesium alloy are not particularly limited and may be appropriately adjusted according to the degree of the smut generated after the etching process, the desmut liquid component used, and the like.

The third washing step is a washing step using water to remove the residual desmutting liquid applied in the desmutting step. The third washing may be performed by a method such as dipping, spraying, or submerging. The washing may be performed using all kinds of water including deionized water, distilled water, pure water, etc., and there is no particular limitation on the temperature range.

As another embodiment of the present invention, etching and de-smutting processes may not be performed in a surface cleaning process of magnesium and magnesium alloy materials that are free of contamination or unprocessed in processing oil.

The chemical conversion treatment process according to the present invention is a process for forming a chemical conversion coating on a surface of a magnesium and magnesium alloy material having a cleaned surface using a chemical conversion composition. The alkalizing treatment composition of the present invention comprises 2 to 10 wt% of a phosphoric acid compound, 1 to 5 wt% of an inorganic metal sol, 0.03 to 0.3 wt% of a vanadium compound, 0.5 to 5 wt% of a basic compound, 0.01 to 0.1 wt% of an acrylic resin, And may have a composition comprising an excess of water-soluble solvent. A detailed description of the alkalizing treatment composition is disclosed in the detailed description of the present invention and is omitted in order to avoid redundancy.

At this time, the chemical conversion coating is preferably formed to have a thickness of 0.1 to 2.5 탆. The chemical conversion coating having a thickness of 0.1 탆 or less has a good coating adhesion but a significant deterioration in corrosion resistance and water resistance. When a chemical conversion coating having a thickness of 2.5 탆 or more is formed, corrosion resistance is excellent, but paint adhesion and water resistance are deteriorated . The thickness of the chemical conversion coating can be adjusted by adjusting the temperature and time of the chemical conversion solution.

The magnesium and magnesium alloy materials formed by performing the surface treatment process described above can be used for replacing automobile parts or other steel after top coating. The top coat is preferably an electrodeposition coating so that the moisture on the surface of the magnesium alloy material may be mixed into the paint and thus affecting the drying process.

The drying is not particularly limited, and it is preferable to oven-dry with a hot air heater or an infrared heater, and the drying temperature is preferably in the range of 80 to 160 ^° C for 20 to 60 minutes. In addition, the drying conditions after the electrodeposition coating can be changed according to the type and the characteristics of the electrodeposition coating,

In addition, the type of coating material used for coating is not particularly limited, and any of a water-based or solvent-based coating material may be used. The coating method of the coating material is not limited, and any conventionally known coating method such as spraying, immersion and powder coating can be applied.

Hereinafter, the present invention will be described in more detail with reference to Examples, Experimental Examples and Evaluation Examples of the present invention, but the scope of the present invention is not limited by the following Examples.

 Example 1 and Comparative Examples 1 to 11

An alkaline treating composition containing the ingredients described in the following Table 1 was prepared in 1 L of distilled water and an acidic chemical treating composition containing the ingredients shown in Table 2 was prepared.

Sodium secondary phosphate Silica sol Vanadium oxysulfate Sodium hydroxide Acrylic resin pH Example 1 3.5 3 0.05 3 0.05 9.5 Comparative Example 1 One 3 0.05 3 0.05 9.5 Comparative Example 2 15 3 0.05 3 0.05 9.5 Comparative Example 3 3.5 0.5 0.05 3 0.05 9.5 Comparative Example 4 3.5 10 0.05 3 0.05 9.5 Comparative Example 5 3.5 3 0.01 3 0.05 9.5 Comparative Example 6 3.5 3 One 3 0.05 9.5 Comparative Example 7 3.5 3 0.05 0.1 0.05 8.0 Comparative Example 8 3.5 3 0.05 10 0.05 11.0 Comparative Example 9 3.5 3 0.05 3 0.005 9.5 Comparative Example 10 3.5 3 0.05 3 0.5 9.5

1st
Sodium Phosphate manganese
acetate Alumina sol Oxy
Vanadium sulfate Selenium sulfide Ammonium fluoride pH Comparative Example 11 2 0.3 3 0.05 0.01 0.1 3

<Experimental Example 1>

(AZ31B plate: ASTM standard product, rolled plate, 70 mm X 140 mm X 0.8 mm AZ31B (high temperature press)) were prepared in the same manner as in Example 1. Subsequently, the surface of the alloy material prepared was subjected to the surface cleaning process under the conditions shown in Table 3. Then, Test samples were prepared by forming the chemical conversion coatings, washing with water, and electrodeposition coating using each of the chemical conversion compositions prepared in each of Examples and Comparative Examples. Conditions for electrodeposition coating were as follows.

[Table 3]

Electrodeposition coating condition

- Curing Condition: 160 ° C x 40min

- Coating thickness: 20 ± 5㎛

- Paints: RF-6900 F-1, F-2 (Noroo Auto Coating)

Evaluation of paint tightness

The surface treatment process, the chemical conversion film formation process and the electrodeposition coating of Experimental Example 1 were carried out by using the alkaline processable compositions of the examples and the comparative examples, respectively, to prepare samples, and the coating adhesion of the samples was evaluated. Here, the coating adhesion was evaluated by the coating adhesion test (ASTM D3359, 1 mm X 1 mm, 100 pieces) by the Cross Cut Test (CCT) method. The evaluation criteria are shown in Table 4 below.

 [Table 4]

Water resistance evaluation

(ASTM D3359, 1 mm x 1 mm, 100 pieces) by Cross Cut Test (CCT) method after 40 days of water resistance test (40 ° C, 240 hours immersion treatment) The evaluation criteria are shown in Table 3.

Corrosion resistance evaluation

The corrosion resistance of each specimen was evaluated by applying a salt spray method according to the method specified in ASTM B117. At this time, the exposures were placed in an X-cut before the brine test. The corrosion rate after coating was evaluated by measuring the expansion width of one side from the X-cut of each specimen after completion of the salt water spraying at 800 hours. The evaluation criteria are as shown in Table 5 below.

[Table 5]

Evaluation results of Examples and Comparative Examples

The coating film adhesion, corrosion resistance, and water resistance were evaluated for each of the specimens prepared by applying the chemical conversion composition of Example 1 and Comparative Examples 1 to 11, and the results are shown in Table 6.

[Table 6]

1) Evaluation of change of physical properties according to phosphate content

As shown in Table 6 above, when the phosphoric acid compound was added (Example 1) as suggested in the present invention, all the physical properties showed better results. On the other hand, when the phosphoric acid compound is added too little (Comparative Example 1), the chemical conversion coating is formed too thin and the corrosion resistance is greatly deteriorated. When too much phosphoric acid compound is added (Comparative Example 2), the chemical conversion coating is too thick, And water resistance. As a result, it has been confirmed that the phosphoric acid compound is very effective in forming a chemical conversion film and is also effective in corrosion resistance and other physical properties when used within the scope of the present invention.

2) Evaluation of physical property change according to inorganic metal sol content

As shown in Table 6, when the inorganic metal sol (alumina sol) was added as suggested in the present invention, as shown in Example 1, all the properties were better than those of the inorganic metal sol (alumina sol). On the contrary, Comparative Example 3, in which too little alumina sol was added as an inorganic metal sol, showed poor results in all properties, and Comparative Example 4, which was added too much, showed poor results in some properties. It has been confirmed that the inorganic metal sol should be used within the range of the present invention in order to obtain a uniform coating because the inorganic metal sol affects the denseness and uniformity of the coating film when forming the chemical conversion coating.

3) Evaluation of physical property change according to content of vanadium compound

As shown in Table 6, when the vanadium compound (vanadium oxysulfate) was added as suggested in the present invention, all the properties were better than those in Example 1, as shown in Table 1. If the amount of the vanadium compound used is too small, corrosion resistance becomes very poor as in Comparative Example 5. If the content of vanadium compound is too high as in Comparative Example 6, formation of an excessive vanadium coating results in poor water resistance and corrosion resistance A problem has occurred.

4) Salt Assessment of change in physical properties according to the content of the basic compound (sodium hydroxide)

As shown in Table 6, as can be seen in Example 1, the case of adding a ready-made compound salt (sodium hydroxide), as proposed by the present invention showed more satisfactory results in all properties. On the other hand, in Comparative Example 7 in which sodium hydroxide is added in an excessively small amount, magnesium ions are dissolved in the magnesium alloy material to accelerate the aging of the solution, and all the physical properties are deteriorated due to the thick film formed. In Comparative Example 8 in which too much water was added, it was confirmed that the pH of the chemical conversion treatment composition was increased and the reaction did not occur during the chemical conversion treatment, and desired physical properties could not be secured.

5) Evaluation of change of physical properties according to acrylic resin content

As shown in Table 6, when the acrylic resin was added as proposed in the present invention, Example 1 exhibited better results in all properties. In Comparative Example 9 in which the acrylic resin contained in the alkalizing treatment composition is added in an excessively small amount, the water-resistant adhesiveness is lowered. This is because the acrylic resin forms a more dense and durable chemical film on the surface of the magnesium alloy, Because it plays a role of improving. Corrosion resistance and water resistance were lowered. On the other hand, Comparative Example 10, which was added in too much amount, was not able to confirm the effect, and the corrosion resistance and water resistance were all lowered.

PH changes of the chemical conversion compositions of Example 1 and Comparative Example 11

The magnesium alloy material (AZ31B) was treated with the compositions of Example 1 and Comparative Example 11 to measure the pH change of the solution. The measurement results are shown in Fig.

The graph of Fig. 1 shows the pH change when the magnesium alloy material was continuously treated using each of the chemical conversion compositions (Example 1, Comparative Example 11). The X-axis of the graph of Fig. 1 is expressed by converting the magnesium alloy to the amount of solution (m ² / L) per unit area of the treatment. In the case of Comparative Example 11, the pH was drastically increased as the treatment capacity of the magnesium alloy was increased, but in the case of Example 1, the pH was gradually decreased. At this time, in Comparative Example 11, as described in the existing patent, if the pH exceeds 5 or more, the physical properties are lowered and the composition can not be used as a chemical conversion composition.

The aging evaluation of the chemical conversion compositions of Example 1 and Comparative Example 11

A 25 cm x 9 cm AZ31B material was evaluated for the degree of contamination before and after chemical conversion treatment of the two chemical conversion treating compositions (Example 1 and Comparative Example 11). Magnesium alloy materials were each treated in a conversion treatment composition having the compositions of Example 1 and Comparative Example 11 in amounts of 50 sheets, and the degree of contamination of the solution was measured by inductively coupled plasma mass spectrometry (ICP) analysis. The measurement results are shown in Table 7.

[Table 7]

Referring to Table 7, in each of the conversion treatment compositions (Example 1, Comparative Example 11) and Comparative Example 11 in the initial state, 0.15 m ² / L of a solution having a pH of 5 or less and Example 1 had a treatment capacity of 2.0 m ² / L, respectively. As a result of the measurement, it was confirmed that the treatment capacity of Comparative Example 11 was at a level of 0.15 m ² / L, but the concentration of magnesium ions was abruptly increased. However, in Example 1, magnesium ions were not detected even at 2.0 m ² / L .

The initial physical properties of the chemical conversion composition of Comparative Example 11 and Example 1 and the physical properties of the composition after chemical conversion treatment were respectively measured and compared. The results are shown in Table 8.

[Table 8]

Referring to Table 8, the initial physical properties of the chemical conversion composition of Comparative Example 11 and Example 1 are all excellent, but the physical properties of Comparative Example 11 are equivalent to initial properties up to 0.15 m ² / L, . On the contrary, in the case of Example 1, even the treatment capacity of 2.0 m ² / L was equivalent to the initial physical properties. This is because, in the case of Comparative Example 11, the magnesium ions continuously melt during the continuous treatment of chemical conversion, the pH of the solution was increased and the solution was rapidly aged. In the case of Example 1, magnesium ions did not melt during the conversion treatment, It has been confirmed that aging hardly progresses.

FIG. 2 is a photograph showing an enlarged microstructure of a chemical conversion film formed using the chemical conversion composition of Example 1

As shown in FIG. 2, it was confirmed that the microstructure of the chemical conversion coating formed on the surface of the magnesium alloy material (AZ31B) according to Example 1 of the present invention has a specific structure and a structure similar to that of the Dendrite structure.

Claims (11)

An alkalizing treatment composition applied to form a chemical conversion coating having corrosion resistance on the surfaces of magnesium and magnesium alloy materials,
Wherein the aqueous solution contains 2 to 10 wt% of a phosphoric acid compound, 1 to 5 wt% of an inorganic metal sol, 0.03 to 0.3 wt% of a vanadium compound, 0.5 to 5 wt% of a basic compound, 0.01 to 0.1 wt% An alkalizing agent composition for a magnesium alloy. The method according to claim 1, wherein the phosphoric acid compound is at least one selected from the group consisting of sodium phosphate, ammonium phosphate, potassium phosphate diphosphate and orthophosphoric acid. And an alkalizing agent composition for a magnesium alloy. The alkaline processing composition according to claim 1, wherein the basic compound comprises at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonium hydroxide and lithium hydroxide. The alkalizing agent composition according to claim 1, wherein the inorganic metal sol comprises at least one selected from the group consisting of silica sol, alumina sol, titania sol, and zirconia sol. The method of claim 1, wherein the vanadium compound is selected from the group consisting of vanadium pentoxide (V ₂ O ₅ ), metavanadic acid (HVO ₃ ), ammonium metavanadate, sodium metavanadate, vanadium trichloride (VOCl ₃ ) 3 vanadium oxide V ₂ O _3), dioxide, vanadium (VO _2), oxy-sulfate, vanadium (VOSO _4), vanadium oxy-acetyl acetate _{VO (OC (= CH 2)} CH 2 COCH 3)) 2, vanadium acetylacetate V (OC (= CH ₂ ) CH ₂ COCH ₃ )) ₃ , vanadium chloride (VCl ₃ ), and invened molybdic acid. The alkaline processing composition according to claim 1, wherein the acrylic resin comprises at least one selected from the group consisting of an acrylic polyol, an acrylic acid copolymer, a modified acrylic acid copolymer, and a polyacrylate. The alkalizing agent composition for magnesium and magnesium alloy according to claim 1, which has a value of 8.5 to 10.5 pH. Performing a purification process on the magnesium and magnesium alloy materials; And
Forming a chemical conversion coating on the surfaces of the magnesium and magnesium alloy materials by using an alkalizing treatment composition,
Wherein the chemical conversion coating comprises 2 to 10 wt% of a phosphoric acid compound, 1 to 5 wt% of an inorganic metal sol, 0.03 to 0.3 wt% of a vanadium compound, 0.5 to 5 wt% of a basic compound, 0.01 to 0.1 wt% of an acrylic resin, Wherein the magnesium and magnesium alloys are formed by using an alkalizing treatment composition for magnesium and magnesium alloys containing magnesium and magnesium alloys. 9. The method of claim 8,
Degreasing the magnesium and magnesium alloy materials;
Subjecting the degreased magnesium and magnesium alloy material to a primary washing treatment;
Etching the surfaces of the magnesium and magnesium alloy materials using an acidic aqueous solution;
Subjecting the etched magnesium and magnesium alloy materials to a secondary water washing treatment;
Removing the smuts present in the magnesium and magnesium alloy materials by performing a desmutting process; And
And subjecting the magnesium and magnesium alloy material subjected to the desmutting step to a tertiary water washing treatment. 2. The method for surface treatment of magnesium and magnesium alloy material according to claim 1, 9. The method of claim 8,
Degreasing the magnesium and magnesium alloy materials; And
And subjecting the degreased magnesium and magnesium alloy materials to a primary washing treatment. 2. The method for surface treatment of magnesium and magnesium alloy materials according to claim 1, The surface treatment method of claim 8, wherein the chemical conversion coating is formed to have a thickness of 0.1 to 2.5 탆.

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