KR101696082B1 - Surface-treated substrate containing magnesium, and method of surface treatment thereof - Google Patents

Abstract

According to the present invention, a surface-treated magnesium substrate forms a corrosion prevention layer containing a compound expressed as M(OH)_n (wherein, M includes one or more types selected from a group including Na, K, Ma, Ca, and Ba, and n is 1 or 2) on a surface of the magnesium substrate such that corrosion resistance of the substrate is able to be increased. As such, the magnesium substrate is able to usefully be used in building exterior materials; and vehicle interior material, specifically, in electrical and electrical part material fields such as a mobile phone case part, etc., using a magnesium material.

Description

[0001] The present invention relates to a surface-treated magnesium substrate and a method for surface treatment thereof,

The present invention relates to a surface-treated magnesium substrate and a method for treating the surface of the magnesium substrate therefor.

Magnesium is a metal belonging to an ultra-light metal among practical metals, and is environmentally friendly, but has excellent electrochemically active properties. Therefore, when surface treatment is not performed, magnesium is very rapidly corroded in the atmosphere or in a solution.

In recent years, due to the trend toward lighter weight of the industry, the magnesium industry has been attracting attention, and research has been actively conducted to improve such problems of magnesium with the trend of metal casing materials in electric and electronic parts materials such as mobile phone case parts .

As a result, Patent Document 1 discloses nano-sized oxide particles having a Gibbs free energy greater than that of magnesium oxide and a surface-treated magnesium substrate in which oxygen atoms separated from the oxide particles are dispersed to form a cluster structure. Patent Document 2 discloses a magnesium base containing at least one of pores or cracked graphene, graphite, and inorganic nano-particles of an oxide film formed on the surface of a magnesium base.

However, since the above techniques include a coating composed of a metal oxide on a magnesium substrate, the inherent properties of the metal including texture, gloss and the like are deteriorated.

Therefore, in order to put the magnesium substrate into practical use, the surface of the substrate is chemically, electrochemically, or physically treated to improve the corrosion resistance while maintaining the inherent property of the magnesium base material, and economical technology is urgently required.

Korean Patent Publication No. 2013-0000470 Korean Patent Publication No. 2013-0074275

In order to solve such a problem,

It is an object of the present invention to provide a magnesium substrate having improved corrosion resistance.

It is another object of the present invention to provide a method for surface treatment of the substrate.

In order to achieve the above object, the present invention provides, in one embodiment,

A corrosion inhibiting layer formed on the substrate and containing a compound represented by the following general formula (1)

The average CIE color coordinates of any three points included in an arbitrary region (1 cm long x 1 cm long) existing on the corrosion inhibition layer are 76.0? * L? 77.0, -0.4? * A? -1.0 and 5.0? b ≤ 5.6,

A surface-treated magnesium substrate characterized by having a corrosion area of not more than 5% of the total surface area of the substrate when subjected to a 240-hour salt spray test on a magnesium substrate (1 cm x 1 cm x 0.4 T) formed with a corrosion inhibition layer:

[Chemical Formula 1]

M (OH) _n

In Formula 1,

M is at least one selected from the group consisting of Na, K, Mg, Ca and Ba,

n is 1 or 2;

Further, in another embodiment of the present invention,

And immersing the magnesium substrate in a hydroxide solution to form a corrosion inhibition layer containing a compound represented by the following formula (1).

The surface-treated magnesium substrate according to the present invention can effectively improve the corrosion resistance by uniformly forming a corrosion inhibiting layer containing the compound represented by the formula (1) on the surface of the magnesium substrate. In addition, the surface treatment method of the magnesium substrate has an economical advantage because it can densely form the corrosion inhibition layer at a high film density by immersing in a hydroxide solution at a temperature of 100 ° C or lower for a short time.

1 is a cross-sectional view showing the structure of a surface-treated magnesium substrate according to the present invention.
2 is an SEM image of the surface morphology of the surface-treated magnesium substrate and the untreated magnesium substrate in one embodiment.
3 is an image showing a transmission electron microscope (TEM) analysis result of the surface-treated magnesium substrate in one embodiment.
4 is an image of the surface of the magnesium substrate after 240 hours of salt spraying in another embodiment.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail.

It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

In the present invention, the term "comprises" or "having ", etc. is intended to specify that there is a feature, number, step, operation, element, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Hereinafter, the present invention will be described in detail with reference to the drawings, and the same or corresponding components are denoted by the same reference numerals regardless of the reference numerals, and a duplicate description thereof will be omitted.

In the present invention, the unit "T" indicates the thickness of the magnesium base material and may be equal to the unit "mm ".

Further, in the present invention, the term "corrosion" refers to a phenomenon in which the magnesium base material is consumed from the surface by chemical or electrochemical erosion and is changed or changed into a non-metallic corrosion product. For example, when magnesium reacts with ambient moisture, oxygen, sulfur, chlorine, etc. to produce products such as dissolution or rust by the action of oxides, emulsions, chlorides, etc., the components and surface morphology and / or structure It means that it changes unevenly.

Further, in the present invention, the term "color coordinate system " means coordinates in the CIE color space, which is a color value defined by CIE (International Commission on Illumination) , a *, b * can be expressed by three coordinate values.

Here, the L * value represents brightness, and when L * = 0, it represents black, and when L * = 100, it represents white. In addition, the a * value indicates whether the color having the corresponding color coordinate deviates to pure red (pure magenta) or pure green, and b * indicates that the color having the corresponding color coordinate is pure yellow Indicates which of the pure blue colors is deviated.

The present invention relates to a surface-treated magnesium substrate and a method for treating the surface of the magnesium substrate therefor.

Magnesium is a metal belonging to an ultra-light metal among practical metals, and is environmentally friendly and electrochemically active. Therefore, when surface treatment is not performed, magnesium is very rapidly corroded in air or in a solution. Accordingly, studies have been actively made to solve such problems of magnesium, but effective techniques for solving such problems while maintaining the inherent properties of magnesium have not been reported yet.

Accordingly, the present invention provides a surface-treated magnesium substrate and a method for treating the surface of the magnesium substrate therefor.

The surface-treated magnesium substrate according to the present invention can improve the corrosion resistance of a magnesium base by uniformly forming a corrosion inhibiting layer containing a compound represented by the general formula (1) on the surface of the magnesium base. In addition, the surface treatment method of the magnesium substrate has an economical advantage because it can densely and uniformly form the corrosion inhibition layer at a high film density by immersing it in a hydroxide solution of 100 DEG C or less for a short time.

Hereinafter, the present invention will be described in more detail.

The present invention, in one embodiment,

Magnesium substrate; And

A corrosion inhibiting layer formed on the substrate and containing a compound represented by the following general formula (1)

The average CIE color coordinates of any three points included in an arbitrary region (1 cm long x 1 cm long) existing on the corrosion inhibition layer are 76.0? * L? 77.0, -0.4? * A? -1.0 and 5.0? b ≤ 5.6,

For the magnesium substrate (1 cm x 1 cm x 0.4 T) with the anti-corrosion layer formed During the 240 hour salt spray test (SST)

Characterized in that the corrosion area is 5% or less of the total surface area of the substrate.

[Chemical Formula 1]

M (OH) _n

In Formula 1,

M is at least one selected from the group consisting of Na, K, Mg, Ca and Ba,

n is 1 or 2;

Specifically, the average CIE color coordinates of the surface-treated substrate may satisfy at least two of the following conditions: 76.0? * L? 77.0, -0.4? * A? -0.0, and 5.0? B? 5.6. More specifically, All the conditions can be satisfied.

The surface-treated magnesium substrate according to the present invention includes a dense and uniform corrosion-preventing layer on the magnesium substrate, so that the corrosion resistance of the substrate can be improved without changing properties inherent to magnesium.

As one example, even if the surface-treated magnesium substrate contains a corrosion inhibiting layer on its surface, there is no color change intrinsic to the metal, so that the color deviation from the magnesium substrate, which has not been surface-treated, may be small.

The present invention measured the average CIE color coordinates of any three points included in an arbitrary region (1 cm x 1 cm) existing on the corrosion inhibiting layer of the surface-treated magnesium substrate. As a result, the average CIE color coordinates of the surface-treated magnesium substrate were 76.10? * L? 76.30, -0.70? * A? -0.80, and 5.10? * B? In addition, it was confirmed that the deviation of the CIE color coordinates from the CIE color coordinates of the unmodified magnesium substrate was less than 5%, specifically less than 4%. This means that there is hardly any change in the surface color of the surface-treated magnesium substrate.

In addition, the surface-treated substrate has improved corrosion resistance of the substrate, so that the corrosion area in the 240-hour salt spray test is 5% or less, 4% or less, 3% or less, 2% or less or 1% Can be satisfied.

As an example, the surface-treated magnesium substrate according to the present invention and the magnesium substrate not subjected to the surface treatment were uniformly sprayed with 5 wt% of salt water at 35 ° C using a salt spray tester (SST) And allowed to stand at 35 DEG C for 240 hours, and the surface was observed with naked eyes. As a result, it was confirmed that the magnesium substrate subjected to the surface treatment had a corrosion inhibiting layer on its surface, and the surface change due to salt corrosion was 1% or less of the entire surface area of the substrate. However, , It was confirmed that about 50% or more of the total surface area of the substrate was not uniform and discolored (see Experimental Example 2).

As another example, the corrosion resistance of the substrate was evaluated by subjecting the surface-treated magnesium substrate according to the present invention and the unmodified magnesium substrate to a co-electrification experiment at room temperature (25 ± 2 ° C) and 0.5 wt% As a result, the surface-treated magnesium substrate including the corrosion inhibiting layer showed a corrosion _rate (C _rate ) of about 0.001 mm / yr or less, specifically 0.0001 to 0.001 mm / yr. However, the surface untreated magnesium substrate was found to be about 0.4322 mm / yr (see Experimental Example 3).

From these results, it can be seen that the surface-treated substrate according to the present invention can form a thin and dense corrosion-resistant layer by treating the magnesium substrate at a temperature of 100 DEG C or less for a short period of time, The corrosion resistance is improved.

Hereinafter, each component of the surface-treated magnesium substrate according to the present invention will be described in detail.

Firstly, the magnesium substrate plays a role of determining the basic skeleton and physical properties of the surface-treated magnesium substrate, and may be the magnesium substrate itself before the surface treatment.

The magnesium base material is not limited as long as it is a base material that can be used as a frame in the field of electric and electronic products including magnesium. Specifically, a pure magnesium substrate, an alloy containing magnesium as a main component, or a substrate coated with magnesium on the surface of a substrate containing titanium (Ti) or iron (Fe) as a main component may be used. Herein, the term "main component" is meant to include at least 90 parts by weight, at least 95 parts by weight, at least 96 parts by weight, at least 97 parts by weight, at least 98 parts by weight, or at least 99 parts by weight, based on the total weight of the substrate. For example, the base material containing magnesium as a main component may contain 95 parts by weight of magnesium and 5 parts by weight of metal elements, and the metal element may be aluminum (Al), copper (Cu), zinc (Zn), cadmium (Cd) And nickel (Ni).

Next, the corrosion inhibiting layer is formed on the surface of the magnesium substrate to improve the corrosion resistance of the substrate. At this time, the corrosion inhibiting layer includes a compound represented by the following formula (1) and may be composed of crystals:

[Chemical Formula 1]

M (OH) _n

In the above formula (1), M includes at least one element selected from the group consisting of Na, K, Mg, Ca and Ba, and n is 1 or 2.

2, the surface-treated magnesium substrate according to the present invention confirms that the magnesium hydroxide (Mg (OH) ₂ ) crystals having a plate-like structure having an average size of 10 to 100 nm are tightly laminated to form a corrosion inhibiting layer . This is because the corrosion inhibition layer according to the present invention shows that the crystals containing the compound represented by the general formula (1) are very dense and uniformly laminated so that the film density is high.

Here, the average thickness of the anti-corrosion layer may be 100 nm or less, specifically 10 nm to 100 nm, 20 nm to 100 nm, 50 nm to 95 nm and more specifically 40 nm to 90 nm. In the present invention, by adjusting the average thickness of the corrosion inhibiting layer to the above range, the average thickness of the corrosion inhibiting layer is so thin that the corrosion resistance is not realized, or the cracks of the corrosion inhibiting layer caused by the excessive average thickness, And / or crevice corrosion can be prevented.

Further, in another embodiment of the present invention,

Immersing the magnesium substrate in a hydroxide solution to form a corrosion inhibiting layer containing a compound represented by the following formula (1)

(1 cm x 1 cm x 0.4 T) in which the corrosion inhibiting layer is formed, the corrosion area is 5% or less of the entire surface area of the substrate.

[Chemical Formula 1]

M (OH) _n

In Formula 1,

M is at least one selected from the group consisting of Na, K, Mg, Ca and Ba,

n is 1 or 2;

The surface treatment method of the magnesium substrate according to the present invention can effectively improve the corrosion resistance of the base material by immersing the magnesium base material in the hydroxide solution to uniformly form the corrosion preventive layer on the surface regardless of the shape of the magnesium base material.

At this time, as the hydroxide solution, any solution containing a hydroxyl group (-OH group) can be used without any particular limitation. Specifically, the aqueous solution in which at least one member selected from the group consisting of NaOH, KOH, Mg (OH) ₂ , Ca (OH) ₂ and Ba (OH) ₂ is dissolved can be used.

The surface treatment method according to the present invention can control the film density of the corrosion inhibiting layer formed on the surface of the substrate depending on the immersion conditions, specifically, the density of crystals constituting the corrosion inhibiting layer. Here, since the base material has a different thermal conductivity depending on the thickness, if the thickness of the base material is different, the rate of formation of the anti-corrosion layer formed on the surface may be different even if the base material is immersed under the same conditions. Therefore, it is preferable to control the thickness of the corrosion preventing layer by adjusting the immersion condition according to the thickness of the magnesium base material.

As an example, when the thickness of the magnesium substrate is 0.4 to 0.7 T, the concentration of the hydroxide solution is 5 wt% to 50 wt%, more specifically 10 wt% to 50 wt%; 5% to 30% by weight; 10% to 20% by weight; 30% to 50% by weight; 15% by weight to 45% by weight or 5% by weight to 15% by weight. In addition, the temperature of the hydroxide solution may be 100 ° C or less. Specifically, 50 占 폚 to 100 占 폚, 70 占 폚 to 90 占 폚, 80 占 폚 to 99 占 폚, or 90 占 폚 to 98 占 폚. The immersing time may be from 1 minute to 100 minutes, more specifically from 1 minute to 60 minutes, or from 5 minutes to 40 minutes. The present invention can prevent the corrosion inhibiting layer from being formed sufficiently on the substrate in the above-mentioned condition range, or prevent the corrosion inhibiting layer from being formed at too high speed to lower the density of the film. Further, when the magnesium substrate is surface-treated under the above conditions, there is an economical advantage that the corrosion resistance of the magnesium substrate can be improved in a short time.

On the other hand, in the surface treatment method of the substrate according to the present invention,

Pretreating the surface of the magnesium substrate prior to the step of immersing in the hydroxide solution; And

After the step of immersing in the hydroxide solution, the step of rinsing may further include any one or more of the steps.

The pretreatment of the surface is a step of treating the surface of the magnesium substrate with an alkaline cleaning liquid to remove contaminants remaining on the surface or polishing the surface before the magnesium substrate is immersed in the hydroxide solution. At this time, the alkaline cleaning liquid is not particularly limited as long as it is commonly used in the art for cleaning the surfaces of metals, metal oxides or metal hydroxides. In addition, the polishing may be performed by buffing, polishing, blasting or electrolytic polishing, but is not limited thereto.

In this step, contaminants and scales present on the surface of the magnesium substrate can be removed, and the rate of formation of the corrosion inhibiting layer can be controlled by changing the surface energy and / or the surface state of the surface, specifically the microstructure of the surface. That is, in the case of the substrate on which the polishing is performed, the thickness of the anti-corrosion layer formed on the substrate surface may be different even if the anti-corrosion layer is formed under the same conditions as the substrate on which the polishing is not performed, Can be different.

In addition, the step of rinsing is a step of removing the hydroxide solution remaining on the surface by rinsing the surface after immersing the substrate in the hydroxide solution. In this step, by removing the hydroxide solution remaining on the surface, the hydroxide solution remaining on a part of the surface may additionally form the corrosion inhibiting layer, thereby preventing the surface from becoming uneven.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples.

However, the following Examples and Experimental Examples are merely illustrative of the present invention, and the present invention is not limited to the following Examples and Experimental Examples.

Example  One.

A magnesium substrate of 1 cm x 1 cm x 0.4 T was immersed in an alkaline cleaning solution to be degreased, and the degreased base was immersed in a 10 wt% NaOH aqueous solution at 95 deg. C for 10 minutes. Thereafter, the substrate was rinsed with distilled water and dried in a drying oven to obtain a surface-treated magnesium substrate.

The CIE color coordinates of the surface-treated magnesium substrate were measured. At this time, the CIE color coordinates were arbitrarily selected from three points in an arbitrary region (1 cm x 1 cm) existing on the substrate, and the results are shown in Table 1 below. The average CIE color coordinates are derived from the measured color coordinates to confirm that the average CIE color coordinates of the surface-treated magnesium substrate are 76.10? * L? 76.30, -0.70? * A? -0.80, and 5.10? * B? 5.35 Respectively.

L * a * b * Point A 76.29 -0.77 5.17 Branch B 76.24 -0.74 5.32 Branch C 76.11 -0.76 5.28 medium 76.21 -0.76 5.26

Example  2.

A surface-treated magnesium substrate was obtained in the same manner as in Example 1 except that the degreased base material in Example 1 was immersed for 20 minutes instead of immersing for 10 minutes.

Comparative Example  One.

A magnesium substrate of 1 cm x 1 cm x 0.4 T was immersed in an alkaline cleaning liquid to be degreased, and the degreased substrate was dried in a drying oven to prepare a magnesium substrate having an untreated surface.

The CIE color coordinates of the prepared untreated magnesium substrate were measured. At this time, the CIE color coordinates were arbitrarily selected from 3 points in an arbitrary region (1 cm x 1 cm) existing on the substrate, and the results are shown in Table 2 below. The average CIE color coordinates are derived from the measured color coordinates to confirm that the average CIE color coordinates of the surface-treated magnesium substrate are 76.60? * L? 76.90, -0.70? * A? -0.80, and 5.10? * B? Respectively.

L * a * b * Point A 76.70 -0.75 5.17 Branch B 76.68 -0.73 5.32 Branch C 76.88 -0.75 5.41 medium 76.75 -0.74 5.30

Comparative Example  2.

A magnesium substrate of 1 cm x 1 cm x 0.4 T was immersed in an alkaline cleaning liquid to be degreased, and the degreased base was immersed in a 10 wt% NaOH aqueous solution at 104 deg. C for 5 minutes. Thereafter, the substrate was rinsed with distilled water and dried in a drying oven to obtain a surface-treated magnesium substrate.

Comparative Example  3.

A magnesium substrate of 1 cm x 1 cm x 0.4 T was immersed in an alkaline cleaning liquid to be degreased, and the degreased base was immersed in a 10 wt% NaOH aqueous solution at 104 DEG C for 20 minutes. Thereafter, the substrate was rinsed with distilled water and dried in a drying oven to obtain a surface-treated magnesium substrate.

Experimental Example  One.

The following experiment was conducted to confirm the surface morphology and the average thickness of the anti-corrosion layer provided on the surface-treated magnesium substrate according to the present invention.

The surface morphologies of the magnesium substrates of the surface-treated Examples 1 and 2 and Comparative Example 3 were observed with a scanning electron microscope (SEM) at a magnification of 50,000, and the results are shown in FIG. Transmission electron microscopy (TEM) analysis was performed on the magnesium substrates of Example 2 and Comparative Example 3, and the results of the analysis of Example 2 are shown in FIG.

First, referring to FIG. 2, the magnesium substrate of Examples 1 and 2 surface-treated at 95 占 폚 has a structure in which the corrosion inhibiting layer is densely laminated at a high density of crystals having a plate-like structure having an average size of about 20 to 100 nm, It was found that there is a surface structure in which there is almost no gap. However, the magnesium substrate of Comparative Example 3, which was surface-treated at 104 캜, contained a corrosion inhibiting layer having a surface structure in which tabular crystals having an average size of about 50 to 100 nm were stacked, And 2 magnesium substrates, respectively.

In addition, referring to FIG. 3, it was confirmed that the substrate of Example 2, which was surface-treated at 95 ° C for 20 minutes, had an average thickness of about 60 ± 5 nm. On the other hand, the substrate of Comparative Example 3, which was surface-treated at 104 ° C for 20 minutes, showed that the average thickness of the corrosion-preventive layer was about 100 nm to 200 nm.

From these results, when the temperature at which the magnesium substrate is surface-treated is 100 DEG C or lower, the crystals forming the corrosion inhibiting layer are densely deposited at a slow rate, but when the temperature exceeds 100 DEG C, the crystal laminating speed increases and the dense As shown in FIG.

Experimental Example  2.

In order to evaluate the corrosion resistance of the surface-treated magnesium substrate according to the present invention, the following experiment was conducted.

The magnesium substrate of Comparative Example 1 and magnesium substrate of the surface-treated Example 2 and Comparative Examples 2 and 3, which had not been surface treated, were each subjected to a salt water spray tester (SST, Salt Spray Tester) And the surface of the specimen after 240 hours passed was visually evaluated. The results are shown in Fig.

4, the surface treated specimen of Example 2 in which the corrosion inhibiting layer was formed at 95 캜 for a short time was found to have a corrosion area of about 1% or less of the total surface area, and the surface deformation and discoloration of the specimen did not occur and were uniform . On the contrary, the substrate of Comparative Example 1 which was not surface-treated exhibited corrosion due to salt water, so that about 85% of the total surface area of the substrate was uneven and discolored. Also, the substrates of Comparative Examples 2 and 3 which were surface-treated at 104 占 폚 were also found to have surface deformation and / or discoloration of about 50% or more of the total surface area due to corrosion due to salt water.

From these results, it can be seen that the surface-treated substrate according to the present invention can form a thin and dense corrosion-resistant layer by surface-treating the magnesium substrate at a temperature of 100 ° C or lower for a short period of time, thereby improving the corrosion resistance of the magnesium substrate .

Experimental Example  3.

In order to evaluate the corrosion resistance of the surface-treated magnesium substrate according to the present invention, the following experiment was conducted.

The magnesium substrate of the surface treated Examples 1 and 2 and the magnesium substrate of Comparative Example 1 which was not surface treated were immersed in 0.5 wt% of salt water and after 72 hours passed, the immobilized substrates were subjected to a co-electrification test. The corrosion potentials (I _corr ), corrosion potential (E _corr ) and formula potential (E _pit ) obtained from the tapel area (± 200 mV) of the polarization curve of each specimen were measured by Tafel analysis. ) Were obtained. Corr _rate was also calculated from the values derived using the following equation (1).

[Equation 1]

In the above equation (1)

E.W is the magnesium atomic weight / exchange electron number = 24.305 / 2;

The density is 1.738 g / cm < ^{3 &} gt ;.

As a result, it can be seen that the surface-treated substrate according to the present invention is excellent in corrosion resistance. More specifically, as a result of conducting a co-rotating polarization test on the surface treated substrates of Examples 1 and 2 and the surface untreated substrate of Comparative Example 1, the substrates of the Examples were found to have a corrosion _rate of less than about 0.001 mm / yr ), And it was confirmed that the corrosion rate gradually decreased as the surface treatment time was longer. On the other hand, in the case of the substrate prepared in Comparative Example 1, the corrosion rate was about 0.4322 mm / yr, and it was confirmed that the corrosion rate was about 430 times higher than that of the surface treated specimen.

From these results, it can be seen that the surface-treated magnesium substrate according to the present invention has an excellent property of preventing corrosion due to the external environment by including a corrosion-resistant layer having a high film density on the surface.

10: Corrosion preventing layer
20: Magnesium substrate

Claims (9)

Magnesium substrate; And
An anticorrosion layer formed on the substrate and having a structure in which crystals of a plate-like structure having an average size of 20 to 100 nm are densely laminated, containing a compound represented by the following formula (1)
The average thickness of the corrosion inhibiting layer is 40 to 90 nm,
The average CIE color coordinates of any three points included in an arbitrary region (1 cm long x 1 cm long) existing on the corrosion inhibition layer are 76.0? * L? 77.0, -0.4? * A? -1.0 and 5.0? b ≤ 5.6,
In a 240-hour salt water spray test on a magnesium substrate (1 cm x 1 cm x 0.4 T) on which a corrosion inhibiting layer was formed,
A surface-treated magnesium substrate characterized in that the corrosion area is 5% or less of the total surface area of the substrate:
[Chemical Formula 1]
M (OH) _n
In Formula 1,
M is at least one selected from the group consisting of Na, K, Mg, Ca and Ba,
n is 1 or 2;
delete The method according to claim 1,
The corrosion-resistant layer comprises a magnesium hydroxide (Mg (OH) ₂ ).
Immersing a magnesium substrate in a hydroxide solution to form a corrosion inhibiting layer having a structure in which crystals of a plate-like structure having an average size of 20 to 100 nm are densely laminated, containing a compound represented by the following formula (1)
The hydroxide solution has a concentration of 5 to 15% by weight, a temperature of 80 to 99 캜,
Immersion is carried out for 10 to 20 minutes,
The average thickness of the formed anti-corrosion layer is 40 to 90 nm,
The average CIE color coordinates of any three points included in an arbitrary region (1 cm x 1 cm) on the corrosion inhibition layer are 76.0? * L? 77.0, -0.4? * A? -1.0 and 5.0? * B ≪ / = 5.6,
In a 240-hour salt water spray test on a magnesium substrate (1 cm x 1 cm x 0.4 T) on which a corrosion inhibiting layer was formed,
Wherein the corrosion area is 5% or less with respect to the total surface area of the substrate.
[Chemical Formula 1]
M (OH) _n
In Formula 1,
M is at least one selected from the group consisting of Na, K, Mg, Ca and Ba,
n is 1 or 2;
5. The method of claim 4,
Wherein the hydroxide solution comprises at least one selected from the group consisting of NaOH, KOH, Mg (OH) ₂ , Ca (OH) ₂ and Ba (OH) ₂ .
delete delete delete 5. The method of claim 4,
Pretreating the surface of the magnesium substrate prior to the step of immersing in the hydroxide solution; And
Further comprising, after the step of immersing the magnesium substrate in the hydroxide solution, rinsing the surface of the magnesium substrate.

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