KR102159112B1 - Surface treatment process for magnesium parts and magnesium parts treated by using the same - Google Patents

Abstract

The present invention relates to a surface treatment method of a magnesium member and a magnesium member treated using the same.
A method for treating a surface of a magnesium member according to an embodiment of the present invention includes the steps of combining a first metal material containing magnesium and a second metal material having the same or lower oxidation properties than the first metal material; Degreasing the combined first and second metal materials with an alkali solution; And forming a surface treatment layer using a surface treatment solution containing a zirconium compound on the surfaces of the degreased first metal material and the second metal material.

Description

Surface treatment method of magnesium member and magnesium member treated using the same {SURFACE TREATMENT PROCESS FOR MAGNESIUM PARTS AND MAGNESIUM PARTS TREATED BY USING THE SAME}

The present invention relates to a surface treatment method of a magnesium member and a magnesium member treated using the same. More specifically, it relates to a method for surface treatment of a magnesium member that enables galvanic corrosion control, and a magnesium member capable of controlling galvanic corrosion treated using the same.

Magnesium is the eighth most abundant material on Earth, has a low specific gravity, is harmless to humans, and has the potential to be applied as interior and exterior materials for various products as it has an advantage in weight reduction. In addition, the magnesium alloy has excellent properties such as high vibration damping ability, excellent vibration and shock absorption, excellent electromagnetic shielding properties, light weight, and high specific strength, as well as weight reduction.

However, magnesium alloys have high oxidation properties, and when bonding with dissimilar metals, they are oxidized while protecting other metals by galvanic corrosion. Since most products require a joint part, for product reliability, corrosion resistance performance of the joint part is essential.

To this end, many researchers have conducted studies on electrical insulation that controls galvanic corrosion, but all of the various polymer pads for insulation are not price competitive.

An object of the present invention is to provide a method for surface treatment of a magnesium member and a magnesium member treated using the same. More specifically, a method for surface treatment of a magnesium member that enables galvanic corrosion control and a magnesium member capable of controlling galvanic corrosion treated using the same is provided.

A method for treating a surface of a magnesium member according to an embodiment of the present invention includes the steps of combining a first metal material containing magnesium and a second metal material having the same or lower oxidation properties than the first metal material; Degreasing the combined first and second metal materials with an alkali solution; And forming a surface treatment layer using a surface treatment solution containing a zirconium compound on the surfaces of the degreased first metal material and the second metal material.

In the step of combining a first metal material containing magnesium and a second metal material having the same or lower oxidizability than the first metal material; In, the second metal material having lower oxidation properties than the first metal material is among Al, Fe, Zn, Mg, and combinations thereof It may include at least one.

In the step of degreasing with an alkali solution; In, the alkali solution may include at least one of sodium hydroxide (NaOH), sodium phosphate (Na ₃ PO ₄占12H ₂ O), and mixtures thereof.

In the step of forming a surface treatment layer; In, the surface treatment solution may include a zirconium compound, an inorganic metal sol, and a water-soluble solvent.

In the step of forming a surface treatment layer; In, the zirconium compound may include zirconium oxide.

In the step of forming a surface treatment layer; In, the pH of the surface treatment solution may be 2.5 to 4.

Forming a surface treatment layer; After, the step of painting the surface treatment layer; may further include.

In the step of coating the surface treatment layer; In, the coating may be any one of electrodeposition coating and spray coating.

A magnesium member according to an embodiment of the present invention includes a first metal material containing magnesium; A second metal material that is bonded to the first metal material and has the same or lower oxidizability than the first metal material; And a surface treatment layer formed on the surfaces of the combined first and second metal materials, and the surface treatment layer includes a zirconium compound.

The second metal material may be a rivet having a pair of coupling grooves formed on both sides thereof, and the first metal material may be configured as a pair and coupled to the coupling grooves.

The second metal material may include at least one of Al, Fe, Zn, Mg, and combinations thereof.

The zirconium compound may contain zirconium oxide.

The surface treatment layer may be a ZrO ₂ coating layer.

The thickness of the surface treatment layer may be 20 to 200 nm.

In the method for surface treatment of a magnesium member according to an embodiment of the present invention, a surface-treated magnesium member having high corrosion resistance can be manufactured because there is little chemical treatment without performing pickling and desmuting processes.

The surface treatment method of a magnesium member according to an embodiment of the present invention does not perform a single treatment agent in consideration of the reactivity of magnesium, but a surface treatment solution used in the surface treatment method of a magnesium member according to an embodiment of the present invention. Since silver can treat Fe, Al, Zn, and Mg at the same time, it can have corrosion resistance up to Mg, which has high oxidation properties, when joints such as bolts are essential.

1 is a diagram showing the oxidation and reduction potentials of metals.
2 is a photograph showing a corrosion state after a salt spray test at a joint including a magnesium alloy and an iron bolt.
3 is a photograph of the appearance of the magnesium plate of Example 1 of the present invention after surface treatment of ZrO ₂ .
4 is a cross-sectional analysis photograph of a magnesium plate of Example 1 of the present invention after surface treatment of ZrO ₂ .
5 is a photograph showing the result of evaluating the properties of electrodeposition coating after performing ZrO ₂ surface treatment on a magnesium plate of Example 1 of the present invention and then electrodeposition coating.
6 is a schematic design diagram of a magnesium member obtained by bonding aluminum rivets to a magnesium plate according to Example 2 of the present invention, after surface treatment of ZrO ₂ and electrodeposition coating.
7 is a photograph showing a salt spray test result of a magnesium member subjected to ZrO ₂ surface treatment of Example 2 of the present invention.
8 is a photograph showing the result of a salt spray test of a member in which aluminum rivets are bonded to a magnesium plate material and a member in which aluminum rivets are bonded to the aluminum plate material in Example 2 of the present invention.
9 is a cross-sectional analysis photograph of a magnesium plate after phosphate surface treatment of a comparative example of the present invention.
10 is a photograph showing the result of evaluating the properties of electrodeposition coating after phosphate surface treatment on a magnesium plate material of a comparative example of the present invention and electrodeposition coating.

In this specification, terms such as first, second and third are used to describe various parts, components, regions, layers and/or sections, but are not limited thereto. These terms are only used to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Accordingly, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention.

In the present specification, parts irrelevant to the description are omitted in order to clearly describe the present invention, and the same reference numerals are attached to the same or similar components throughout the specification.

In the present specification, when a part "includes" a certain component, it means that other components may be further included rather than excluding other components unless otherwise stated.

In this specification, the terminology used is only for referring to specific embodiments, and is not intended to limit the invention. Singular forms as used herein also include plural forms unless the phrases clearly indicate the opposite. The meaning of “comprising” as used in the specification specifies a specific characteristic, region, integer, step, action, element and/or component, and the presence of another characteristic, region, integer, step, action, element and/or component, or It does not exclude additions.

In the present specification, the term "combination of these" included in the expression of the Makushi format refers to one or more mixtures or combinations selected from the group consisting of components described in the expression of the Makushi format, and the components It means to include one or more selected from the group consisting of.

In the present specification, when a part is referred to as being "on" or "on" another part, it may be directly on or on another part, or another part may be involved in between. In contrast, when a part is referred to as being “directly above” another part, no other part is intervened.

Although not defined differently, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms defined in a commonly used dictionary are additionally interpreted as having a meaning consistent with the related technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal meaning unless defined.

In addition, unless otherwise specified,% means% by weight, and 1 ppm is 0.0001% by weight.

Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in a variety of different forms, only these embodiments are intended to complete the disclosure of the present invention, and are common in the technical field to which the present invention pertains. It is provided to fully inform the knowledgeable person of the scope of the invention, and the invention is only defined by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

Therefore, in some embodiments, well-known techniques have not been described in detail in order to avoid obscuring interpretation of the present invention. Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used as meanings that can be commonly understood by those of ordinary skill in the art to which the present invention belongs.

First, FIG. 1 is a diagram showing the oxidation and reduction potentials of metals. As can be seen in FIG. 1, magnesium or magnesium alloy has the lowest oxidation and reduction potential among structural materials, and thus magnesium melts when bonded with other metals. For example, FIG. 2 shows a corrosion state after a salt spray test at a joint including a magnesium alloy and an iron bolt. As can be seen in FIG. 2, corrosion of a magnesium alloy occurs first rather than iron. An embodiment of the present invention is to provide a surface treatment method and a surface-treated magnesium member for maintaining corrosion resistance in a state including a magnesium alloy and a joint member.

A method for treating a surface of a magnesium member according to an embodiment of the present invention includes the steps of combining a first metal material containing magnesium and a second metal material having the same or lower oxidation properties than the first metal material; Degreasing the combined first and second metal materials with an alkali solution; And forming a surface treatment layer using a surface treatment solution containing a zirconium compound on the surfaces of the degreased first metal material and the second metal material.

The conventional method for treating the surface of the magnesium member includes pickling and desmuting after degreasing. In addition, there is a problem in that it is difficult to proceed as a continuous process because the chemical conversion treatment process after the pickling and desmuting process was performed by a method such as dipping. That is, since the surface treatment process was performed separately from the blanking and molding process, the manufacturing process was complicated, and there was a disadvantage of lowering the production yield.

However, in an embodiment of the present disease, a surface treatment having excellent corrosion resistance may be performed without undergoing such pickling and desmuting processes. More specifically, the step of forming the surface treatment layer may be performed in a continuous process without a separate additional process after the degreasing step, that is, without going through processes such as pickling and desmuting. When performed as a continuous process, the incidence of defects can be remarkably reduced, and productivity can be remarkably improved by simplifying the manufacturing process.

In the conventional method, in a state in which a material such as iron, aluminum, zinc, magnesium, and a magnesium plate is used as a joint member (for example, aluminum rivets, SUS bolts, etc.), the corrosion resistance of a product automobile has not been satisfied. Accordingly, the inventors of the present invention considered that magnesium is very reactive and reacts violently with chemicals, so it is important to minimize the process so as to minimize this reaction. That is, if the oxide film is controlled by performing chemical conversion in two processes of degreasing-surface treatment (coating agent treatment) instead of the conventional degreasing-pickling-dismuting process, it is used for iron and aluminum, which have less oxidation properties than magnesium. Considering that it is possible to secure the properties of the electrodeposition coating of magnesium even with the pretreatment solution for automobiles, a surface treatment method according to an embodiment of the present invention was devised.

First, it includes the step of combining a first metal material containing magnesium and a second metal material having the same or lower oxidation properties than the first metal material.

In this case, the first metal material containing magnesium may be magnesium or a magnesium alloy.

At this time, the second metal material having lower oxidation properties than the first metal material may include at least one of Al, Fe, Zn, and Mg, and combinations thereof.

Next, it includes the step of degreasing the combined first metal material and the second metal material with an alkali solution.

In this case, the alkali solution may include at least one of sodium hydroxide (NaOH), sodium phosphate (Na ₃ PO ₄ ㆍ12H ₂ O), and mixtures thereof. More specifically, the degreasing process may be performed at 40° C. to 60° C. for 1 minute to 5 minutes using an alkaline solution containing 40 g/L to 80 g/L of sodium hydroxide (NaOH). More specifically, sodium hydroxide (NaOH) may be 50g/L to 70g/L. In such a concentration condition, the oil component can be easily removed without discoloration of the magnesium member.

Next, a step of forming a surface treatment layer using a surface treatment solution containing a zirconium compound on the surfaces of the degreased first metal material and the second metal material.

If the magnesium member is surface-treated with a surface treatment solution containing a zirconium compound used for iron, aluminum, etc., adhesion and corrosion resistance of electrodeposition coating can be exhibited even with a thin zirconium-containing film. In addition, in the case of zirconium-based chemical conversion treatment, it is a new concept chemical conversion treatment capable of simultaneously treating aluminum, iron, zinc, and magnesium. The chemical conversion treatment using phosphate, which is a conventional technique, has a disadvantage of heavy metal hazard, and the zirconium-based chemical conversion treatment does not have such a disadvantage.

At this time, the surface treatment solution may include a zirconium compound, an inorganic metal sol, and a water-soluble solvent. More specifically, the surface treatment solution may be a composition comprising 2 to 10% by weight of a zirconium compound, 1 to 5% by weight of an inorganic metal sol, and the balance water-soluble solvent.

At this time, the zirconium compound may include zirconium oxide. More specifically, the zirconium compound may be acidic.

In this case, the inorganic metal sol may include any one or more of silica sol, alumina sol, titania sol, and zirconia sol.

In addition, the pH of the surface treatment solution may be 2.5 to 4. That is, it may be acidic.

Next, after the step of forming the surface treatment layer, it may further include painting the surface treatment layer.

At this time, the coating may be any one of electrodeposition coating and spray coating.

More specifically, the painting may be treated at room temperature for 1 to 3 minutes.

On the other hand, the magnesium member according to an embodiment of the present invention, a first metal material containing magnesium; A second metal material that is bonded to the first metal material and has the same or lower oxidizability than the first metal material; And a surface treatment layer formed on the surfaces of the combined first and second metal materials, and the surface treatment layer includes a zirconium compound.

The second metal material may be a rivet having a pair of coupling grooves formed on both sides thereof, and the first metal material may be configured as a pair and coupled to the coupling grooves.

The second metal material may include at least one of Al, Fe, Zn, Mg, and combinations thereof.

The zirconium compound may contain zirconium oxide.

The surface treatment layer may be a ZrO ₂ coating layer.

The thickness of the surface treatment layer may be 20 to 200 nm. More specifically, it may be 20 to 100 nm, and more specifically, it may be 20 to 70 nm.

Hereinafter, the present invention will be described in more detail through examples. However, it should be noted that the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by matters described in the claims and matters reasonably inferred therefrom.

Example 1

In order to remove the molding oil and the rolling oil, the magnesium plate was degreased by treating it with a solution of NaOH 60g/L at 40 to 60°C for 2 minutes. Thereafter, the surface was treated with a surface treatment solution having a pH of about 2.4 to 4, wherein the surface treatment solution was a Zr compound, containing 2 to 10% by weight of H ₂ ZrO ₂ , 1 to 5% by weight of inorganic metal sol, and an extra water-soluble solvent. This composition was treated with such a surface treatment solution at room temperature for 2 minutes, and then the coating was performed by applying electricity. Through these experiments, a film-formed magnesium material was prepared.

The reaction formula at this time is as follows.

H ₂ ZrO ₂ + 2H ₂ O -> ZrO ₂ + 6HF

Metal + 3HF -> MeF ₃ + 3/2H ₂

3 is a photograph of the appearance after surface treatment of ZrO ₂ on a magnesium plate, and FIG. 4 is a cross-sectional analysis photograph showing a ZrO ₂ film coated on a magnesium plate (E-form).

As can be seen in Fig. 3, there was no change in appearance even after surface treatment. Meanwhile, as can be seen in FIG. 4, after the ZrO ₂ film treatment, a uniform ceramic film, ZrO ₂ film, was formed on the Mg material, and a uniform film was secured over the entire area. The thickness of this film was very thin, and there was no change in the appearance of the surface or even in microscopic analysis. Its thickness is about 50 nm.

After this surface treatment, the electrodeposition coating used by automobile companies was performed, and accordingly, it was found that the electrodeposition coating properties such as impact resistance, salt hot water resistance, and salt spray resistance were satisfied as shown in FIG. 5.

5 is a photograph showing a result of evaluating the properties of electrodeposition coating after performing electrodeposition coating after ZrO ₂ surface treatment on a magnesium plate.

Example 2

After constructing a joint including aluminum rivets in magnesium or magnesium alloy, electrodeposition coating was performed after degreasing-Zr-based surface treatment. The experiment was performed under the same conditions as in Example 1, except that a member comprising a joint including magnesium or magnesium alloy and aluminum rivets was used instead of the magnesium plate.

6 is a schematic design diagram after degreasing-ZrO ₂ surface treatment-electrode-plating the magnesium member obtained by bonding the magnesium plate and aluminum rivets according to Example 2.

The surface-treated magnesium member was subjected to a salt spray test for 1000 hours. 7 is a photograph of the result after the surface-treated magnesium member was subjected to a salt spray test for 1000 hours.

As can be seen in FIG. 7, the aluminum rivets did not undergo corrosion at all even after 1000 hours of salt spray test, but it was found that corrosion proceeded even in the state in which a polymer pad for galvanic insulation of the SUS bolt was inserted.

In addition, FIG. 8 is a photograph showing the result after performing the salt spray test for 1000 hours, which is the standard of the automobile company, by simulating a product obtained by bonding an aluminum plate and a magnesium plate with aluminum rivets and then performing electrodeposition coating after Zr-based surface treatment .

As can be seen in FIG. 8, it was found that corrosion resistance was secured even when aluminum rivets were bonded to a magnesium plate, as in the case of bonding aluminum rivets to an aluminum plate. This ensures corrosion resistance even when the blister size is less than 3mm.

Comparative example

In order to remove the molding oil and the rolling oil, the magnesium plate was degreased by treating the magnesium plate with a solution of 60 g/L of NaOH at 40 to 60° C. for 2 minutes, and then surface-adjusted and phosphate-treated to form a phosphate film.

9 is a cross-sectional analysis photograph showing a phosphate film coated on a magnesium plate (E-form). As can be seen in FIG. 9, in the phosphate treatment process, the oxide film made of MgO is very thick, so it is difficult to secure adhesion and thus it is difficult to secure corrosion resistance.

10 is a photograph showing the results of evaluating the properties of electrodeposition coating after phosphate treatment on a magnesium plate (E-form) and then electrodeposition coating. Unlike as can be seen in FIG. 5, the result of electrodeposition coating properties such as impact resistance, salt hot water resistance, and salt spray properties was bad, and thus could not be used.

The present invention is not limited to the above embodiments, but may be manufactured in a variety of different forms, and those of ordinary skill in the art to which the present invention pertains, other specific forms without changing the technical spirit or essential features of the present invention. It will be appreciated that it can be implemented with. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not limiting.

Claims (14)

Combining a first metal material containing magnesium and a second metal material having the same or lower oxidizability than the first metal material;
Degreasing the combined first and second metal materials with an alkali solution; And
Forming a surface treatment layer using a surface treatment solution containing a zirconium compound on the surfaces of the degreased first metal material and the second metal material; including,
Combining the first metal material containing magnesium and a second metal material having the same or lower oxidizability than the first metal material;
The second metal material is a rivet with a pair of coupling grooves formed on both sides,
The first metal material is composed of a pair,
A method for treating a surface of a magnesium member by coupling the pair of the first metal materials to the coupling grooves of the second metal material.
The method of claim 1,
Combining a first metal material containing magnesium and a second metal material having the same or lower oxidizability than the first metal material; In,
The second metal material having the same or lower oxidation property than the first metal material includes at least one of Al, Fe, Zn, Mg, and combinations thereof.
The method of claim 1,
Degreasing with the alkaline solution; In,
The alkali solution,
Sodium hydroxide (NaOH), sodium phosphate (Na ₃ PO ₄ ㆍ12H ₂ O), and a method for surface treatment of a magnesium member comprising at least one of a mixture thereof.
The method of claim 1,
Forming the surface treatment layer; In,
The surface treatment solution,
A method for surface treatment of a magnesium member comprising a zirconium compound, an inorganic metal sol and a water-soluble solvent.
The method of claim 1,
Forming the surface treatment layer; In,
The zirconium compound,
Surface treatment method of a magnesium member comprising zirconium oxide.
The method of claim 1,
Forming the surface treatment layer; In,
The pH of the surface treatment solution is,
Surface treatment method of a magnesium member of 2.5 to 4.
The method of claim 1,
Forming the surface treatment layer; afterwards,
Coating the surface treatment layer; surface treatment method of a magnesium member further comprising.
The method of claim 7,
Painting the surface treatment layer; In,
The above painting,
A method for surface treatment of magnesium members, which is either electrodeposition coating or spray coating.
A first metal material containing magnesium;
A second metal material that is combined with the first metal material and has the same or lower oxidizability than the first metal material; And
Including; a surface treatment layer formed on the combined first metal material and the second metal material surface,
The surface treatment layer contains a zirconium compound,
The second metal material,
It is a rivet with a pair of coupling grooves formed on both sides,
The first metal material is composed of a pair of magnesium members each coupled to the coupling groove.
delete The method of claim 9,
The second metal material,
A magnesium member comprising at least one of Al, Fe, Zn, Mg, and combinations thereof.
The method of claim 9,
The zirconium compound,
A magnesium member comprising zirconium oxide.
The method of claim 9,
The surface treatment layer,
Magnesium member as a ZrO ₂ film layer
The method of claim 9,
The thickness of the surface treatment layer is,
Magnesium member of 20 to 200 nm.

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