KR100917325B1 - Method of plating nickel on magnesium alloy and nickel plating magnesium alloy - Google Patents

Abstract

A method for plating nickel on a magnesium alloy and a nickel-plated magnesium alloy is provided to form an electronic nickel layer on a magnesium alloy surface without a non-electrolytic nickel plating process by using pyrophosphate nickel plating solution including ammonia solution. A method for plating nickel on a magnesium alloy and a nickel-plated magnesium alloy comprises following steps. A magnesium alloy surface is fat-removed and is pickled. The pickled magnesium alloy surface is dipped in composite solution. The nickel is plated on the magnesium alloy. The composite solution consists of potassium pyrophosphate 200 g/l~350 g/l, nickel sulfate 70 g/l~150 g/l, compound 10 g/l~50 g/l of the fluorine and alkali metal, and ammonia solution 20ml/l~80 ml/l. The concentration of the ammonia solution is 20 ml/l~80 ml/l. The temperature of the composition is 45~65°C.

Description

Method of Plating Nickel on Magnesium Alloy and Nickel plating Magnesium Alloy

The present invention relates to a method of plating nickel on a magnesium alloy of the present invention, and to a nickel plated magnesium alloy, and more particularly, to a nickel pyrophosphate plating solution containing a compound of an alkali metal and fluorine or a compound of ammonia and fluorine, and ammonia water. The present invention relates to a method of plating nickel on a magnesium alloy capable of forming an electric nickel plating layer on a surface of a magnesium alloy without undergoing an electroless nickel plating process, and to a nickel plated magnesium alloy.

Since the 1990s, the improvement of fuel economy has been suggested as the most realistic way to reduce automobile exhaust emissions, which is the main cause of air pollution.In this situation, magnesium alloy is a metal material for structural materials. Since it is the lightest of 2/3, it has started to attract attention as a lightweight material.

Since the electromagnetic shielding ability of magnesium alloy has been proven, the market in the high value-added industry centering on the case of the mobile electronic device is also expanding. Magnesium alloys are currently used in aerospace, transportation machinery, precision instrument parts, and electronics industries due to their excellent material characteristics such as high specific strength, electromagnetic shielding ability, high thermal conductivity, dimensional stability, high machinability, and vibration absorption ability. As a substitute material, the demand is increasing. However, magnesium alloys have very weak properties against wear and corrosion and are therefore only applied to industrially limited fields.

Various surface treatment methods such as anodization, painting, chemical conversion, vacuum deposition, and electroplating have been performed to improve the weak corrosion resistance and wear resistance of magnesium alloys.

Anodization and painting methods do not sufficiently improve wear resistance, and in the case of chemical conversion, they do not secure sufficient corrosion resistance and are used as pretreatment balls for painting. In addition, the method of vacuum deposition has a limited application range due to size and cost problems.

Electroplating can impart not only corrosion resistance and abrasion resistance but also decoration, and is the most realistic and practical method of surface treatment of magnesium in consideration of productivity and cost issues. However, due to the poor corrosion resistance of magnesium, when the magnesium alloy material is rapidly infiltrated into the existing plating bath, the surface of the magnesium alloy material is quickly corroded or dissolved, so plating on the magnesium alloy surface in the conventional plating bath is almost impossible. In addition, in the strong alkali plating bath for suppressing corrosion, since a magnesium oxide film or a magnesium hydroxide film is formed on the surface of the magnesium base material, even if the plating layer is formed, sufficient adhesion between the plating layer and the base material is not secured.

In order to electroplate the magnesium alloy in the existing plating bath, it is possible to protect the magnesium alloy base material from the plating solution, and a base plating having adhesion to the base material should be preceded. Such plating requires electroless nickel directly on the magnesium surface. A plating method and a method of forming a substituted zinc film on the surface of magnesium through zinc casting and electroplating in a cyan nickel plating bath are common.

However, electroless nickel plating has problems such as instability of plating solution, generation of pinhole, deterioration of adhesion force due to aging of solution, low productivity, and cyan nickel plating after zinc treatment forms a dense zinc film in the zinc casting process. There is a problem in that it is not possible to suppress the partial swelling phenomenon, and cyan is being banned as a toxic substance that is gradually prohibited from use.

In addition, various methods have been proposed to form a dense and cohesive electroplating layer on the surface of magnesium, but most of the methods are complicated by adding other processes in combination with the existing methods, and the industrial application is complicated. Most of these difficult methods were.

In order to solve the problem of electroplating in the existing magnesium alloy, an object of the present invention is to perform electroplating in a general commercial plating bath, and an object of the present invention is to provide a method for directly electroplating nickel on a magnesium base material. .

In order to solve the problem of electroplating in the existing magnesium alloy, an object of the present invention is to provide a nickel-plated magnesium alloy obtained by directly performing electro-nickel plating on a magnesium base material.

In order to achieve the above object, the present invention

(a) degreasing the magnesium alloy surface followed by pickling;

(b) Oxide film on the surface of magnesium alloy is 200 g / l to 350 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), 70 g / l to 150 g / l nickel sulfate (NiSO ₄ ), alkali metal and fluorine Immersing in an electrolyte composition consisting of 10 g / l to 50 g / l of a compound and 20 ml / l to 80 ml / l of ammonia water (NH ₄ OH); And

(c) applying a current of 5 to 200 mA / cm ² to the electrolyte composition and adjusting the pH to 8.5 to 10.5 to provide a method of plating nickel on a magnesium alloy comprising forming a nickel plating on the magnesium alloy.

In order to achieve the above object, the present invention

(a) degreasing the magnesium alloy surface followed by pickling;

(b) 200 g / l to 350 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), 70 g / l to 150 g / l nickel sulfate (NiSO ₄ ), and ammonium fluoride NH ₄ F) dipping in an electrolyte composition solution consisting of 10 g / l to 50 g / l, and 20 ml / l to 80 ml / l of ammonia water (NH ₄ OH); And

(c) applying a current of 5 to 200 mA / cm ² to the electrolyte composition and adjusting the pH to 8.5 to 10.5 to provide a method of plating nickel on a magnesium alloy comprising forming a nickel plating on the magnesium alloy.

In order to achieve the above another object, the present invention

As a result of nickel plating on the magnesium alloy, a composite film containing MgF ₂ and KF is formed at the interface between magnesium and nickel plating,

The composite coating provides a nickel-plated magnesium alloy having a binding energy difference of Mg-F and a binding energy difference of K-F of 2.5 eV to 3.5 eV.

When using a compound of an alkali metal and fluorine or a compound of ammonia and fluorine, and a pyrophosphate nickel plating solution to which ammonia water is added, an electronickel plating layer directly on a magnesium alloy surface without undergoing an electroless nickel plating process Can be formed. Thus, electroless nickel plating processes with low productivity and difficult quality control and solution management can be omitted.

Magnesium alloy with a nickel plating layer according to the present invention has excellent corrosion resistance and adhesion to the base material, and can be applied in a commercial plating solution commonly used according to various purposes, it will be able to expand the application field of the magnesium alloy throughout the industry. .

The present invention comprises the steps of (a) degreasing the surface of the magnesium alloy after pickling; (b) 200 g / l to 350 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), 70 g / l to 150 g / l nickel sulfate (NiSO ₄ ), alkali metals Washing with immersion in an electrolyte composition comprising 10 g / l to 50 g / l of a compound of fluorine or ammonia and fluorine, and 20 ml / l to 80 ml / l of aqueous ammonia (NH ₄ OH); And (c) applying a current of 5 to 200 mA / cm ² to the electrolyte composition and adjusting the pH to 8.5 to 10.5 to form nickel plating on the magnesium alloy. .

The present invention forms an electrolytic nickel plating layer directly on the surface of magnesium without electroless nickel plating by electroplating pretreatment. For this purpose, a compound of alkali metal and fluorine as an additive to a solution composed of potassium pyrophosphate and nickel sulfate, or ammonia and fluorine And ammonia water. That is, a compound of alkali metal and fluorine and ammonia water may be added, and ammonium fluoride (NH ₄ F) and ammonia water may be added.

FIG. 1 shows a cross section of a magnesium alloy product according to a process of forming an electroless nickel plating layer after forming an electroless nickel plating layer according to the prior art. When the magnesium alloy is electroplated in a solution composed of potassium pyrophosphate and nickel sulfate, electrodeposition of nickel is not performed due to dissolution of the magnesium alloy by pyrophosphate. However, the addition of compounds of alkali metals and fluorine (e.g., KF, NaF, LiF) or ammonium fluoride (NH ₄ F) to this solution results in the formation of a fluoride film on the surface of the magnesium alloy to inhibit corrosion and dissolution of the magnesium alloy. When the current is applied, the electrodeposition of nickel becomes possible.

Figure 2 shows a cross section of a magnesium alloy output according to the invention. Referring to FIG. 2, there is shown a cross section of a magnesium alloy resultant in which an electrolytic nickel plating layer is formed directly on a magnesium alloy surface without forming an electroless nickel plating layer.

When nickel plating is performed on the magnesium alloy by applying current in an electrolyte solution containing potassium pyrophosphate and nickel sulfate, an alkali metal and fluorine, the plating layer may be cracked before the nickel plating layer sufficiently covers the magnesium base material. Is generated and a large amount of hydrogen gas is generated. At this time, when the ammonia water is added to the solution, it is possible to suppress the occurrence of cracks, and to reduce the amount of hydrogen gas generated, thereby improving the current efficiency. As a result, a good nickel electroplating layer can be formed due to the added ammonia water.

The electrolyte composition for direct nickel plating on the magnesium alloy according to the present invention is a compound of alkali metal and fluorine or ammonium fluoride (NH) in a solution composed of potassium pyrophosphate (K ₄ P ₂ O ₇ ) and nickel sulfate (NiSO ₄ ) F ₄₎ by the addition of 10g / l to 50g / l, ammonia 20ml / l to 80 ml / l is characterized in that formed. As the compound of the alkali metal and fluorine, for example, potassium fluoride (KF), lithium fluoride (LiF), sodium fluoride (NaF), or the like may be used. Unless stated otherwise in the context of the present invention, compounds of alkali metals with fluorine may be replaced with ammonium fluoride.

The content of the compound of the alkali metal and fluorine is 10 g / l to 45 g / l, preferably 30 g / l to 45 g / l. If the compound content of the alkali metal and fluorine is less than 10 g / l, it is not preferable because the magnesium base material cannot be inhibited from dissolving in the electrolyte, and the compound content of the alkali metal and fluorine exceeds 45 g / l. It is not preferable because the fluoride is supersaturated in the plating electrolytic solution and the remaining fluoride which is not dissolved becomes suspended, which degrades the physical properties of the plating.

The concentration of the ammonia water is preferably 20ml / l to 80ml / l. Ammonia water is a necessary configuration in the electrolyte composition of the present invention, and if the concentration of ammonia water is less than 20 ml / l, it is not preferable because cracking occurs in the plating layer. I can't.

It may further comprise the step of performing an activation treatment in hydrofluoric acid (HF) solution before immersing in the composition of step (b). It is preferable to perform the activation treatment with a hydrofluoric acid solution because a chromate coating may be formed on the surface of the magnesium alloy due to the chromic acid pickling process, thereby decreasing the adhesion during nickel plating.

The temperature of the composition in step (c) is preferably adjusted to 45 to 65 ℃. If the temperature of the composition is less than 45 ° C, it is not preferable because it adversely affects the plating properties, and if it is above 65 ° C, potassium pyrophosphate may be decomposed and precipitated in powder form, which is not preferable.

A current of 5 to 200 mA / cm ² is applied to the composition of step (c) and the pH is adjusted to 8.5 to 10.5. It is preferable to apply a current of 5 to 200 mA / cm ² , and the current is 5 mA / cm ^2. If it is applied less than the progress rate of the plating is too slow to achieve efficient plating, when applying a current exceeding 200mA / cm ² is not preferable because it affects the plating properties.

Next, in step (c), the pH is adjusted to about 8.5 to 10.5. Although it is common to apply a pickled magnesium alloy to the electrolytic solution composition and change it to the above pH range, if the pH is lower than 8.5, it is not preferable because potassium pyrophosphate may be decomposed and precipitated in powder form. . On the other hand, when the pH exceeds 10.5, it is not preferable because it adversely affects the plating properties.

According to another embodiment of the present invention, as a result of nickel plated magnesium alloy, a composite film containing MgF ₂ and KF is formed at the interface between magnesium and nickel plating, the binding energy of Mg-F in the composite film ( binding energy) and the binding energy difference between KF is 2.5eV to 3.5eV.

In the composite film, as the fluorine content increases, the corrosion potential increases and the corrosion current density decreases. Corrosion potential increases and corrosion current density decreases due to the effect of the added alkali metal and fluorine compound, which can greatly prevent the dissolution of magnesium alloy in the nickel pyrophosphate solution.

The binding energy of the Mg-F is 686eV to 687eV, and the binding energy of K-F is preferably 683 eV to 684 eV.

The nickel plating process of the magnesium alloy according to the present invention is as follows.

First, pretreatment of magnesium alloy is performed. As a detailed procedure, the magnesium alloy specimen is ultrasonically degreased with acetone, and then pickled for 1 to 2 minutes in an aqueous solution of 180 g / l of chromic acid (CrO ₃ ). Subsequently, the activation treatment may be performed in a hydrofluoric acid solution, specifically, by dipping in a solution of 385 to 420 ml / l of hydrofluoric acid (40%) at room temperature for about 2 to 5 minutes. Thereafter, electrolytic nickel plating directly on the magnesium alloy is electroplated under the following conditions.

The plating time of nickel on the magnesium base material is set according to the thickness of the desired nickel layer. If the thickness of the plating layer is too thin, the current density on the surface is not very uniformly distributed due to the characteristics of the magnesium alloy, so when the thickness of the plating layer is thin, a portion of the magnesium base material is not protected from the nickel plating layer. Therefore, it is preferable to form a nickel plating layer of sufficient thickness until the magnesium base material is completely covered by the nickel plating layer.

By using an alkali metal and fluorine compound and an aqueous solution for nickel pyrophosphate to which ammonia water is added, an electronickel plating layer can be directly formed on the surface of a magnesium alloy without undergoing an electroless nickel plating process. Thus, electroless nickel plating processes with low productivity and difficult quality control and solution management can be omitted.

Nickel pyrophosphate plating process in which an alkali metal and fluorine compound is added according to the present invention can replace the cyan copper plating method after the zinc coating as another base plating method, thereby reducing the burden on the use of toxic harmful substances such as cyan compounds. have.

Magnesium alloy with a nickel plating layer according to the present invention has excellent corrosion resistance and adhesion to the base material, and can be applied in a commercial plating solution commonly used according to various purposes, it will be able to expand the application field of the magnesium alloy throughout the industry. .

Example

Example  One

In order to perform nickel plating directly on the magnesium alloy, the magnesium alloy was pretreated. In detail, the magnesium alloy specimen was ultrasonically degreased in an acetone solution for 3 minutes, and then pickled in a 180 g / l aqueous solution of chromic acid (CrO ₃ ). After pickling, the solution was washed thoroughly to prevent the chromic acid (CrO ₃ ) solution from flowing in the water. 250 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), nickel sulfate (NiSO ₄ ) 90 g / l, potassium fluoride (KF) 30 g / l, nickel ammonia (NH ₄ OH) for nickel plating on magnesium alloy ) The magnesium alloy was immersed in a plating solution of 50 ° C. consisting of a composition of 30 ml / l (molar concentration 0.21 M), and plating was performed for about 30 minutes by applying a current of 10 mA / cm ² . The nickel-plated magnesium alloy by the experiment according to the present embodiment is shown in Figure 3a, the microstructure picture is shown in Figure 4.

Example  2

In order to perform nickel plating directly on the magnesium alloy, the magnesium alloy was pretreated. In detail, the magnesium alloy specimen was ultrasonically degreased in an acetone solution for 3 minutes, and then pickled in a 180 g / l aqueous solution of chromic acid (CrO ₃ ). After the pickling treatment, the water was washed thoroughly so as not to have a chromic acid (CrO ₃ ) solution. 250 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), nickel sulfate (NiSO ₄ ) 100 g / l, potassium fluoride (KF) 45 g / l, nickel ammonia (NH ₄ OH) for nickel plating on magnesium alloy ) The magnesium alloy was immersed in a plating solution of 50 ° C. consisting of a composition of 30 ml / l (molar concentration 0.21 M), and plating was performed for about 30 minutes by applying a current of 10 mA / cm ² .

Example  3

Ammonia water, the concentration of (NH ₄ OH) was carried out and the same procedure as in Example 1 except that the 20ml / l (molar concentration of 0.14M).

Example  4

Ammonia water, the concentration of (NH ₄ OH) was carried out the same as Example 1 except that the 40ml / l (molar concentration of 0.28M).

Example  5

Ammonia water, the concentration of (NH ₄ OH) was carried out the same as Example 1 except that the 50ml / l (molar concentration of 0.35M).

Example  6

Except that the concentration of ammonia water (NH ₄ OH) is 60ml / l (molar concentration 0.42M) was carried out in the same manner as in Example 1.

Example  7

In order to perform nickel plating directly on the magnesium alloy, magnesium alloy pretreatment was first performed. In detail, the magnesium alloy specimen was ultrasonically degreased in an acetone solution for 3 minutes, and then pickled in a 180g / l aqueous solution of chromic acid (CrO ₃ ). After the pickling treatment, the water was washed thoroughly so as not to have a chromic acid (CrO ₃ ) solution. 250 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), 90 g / l nickel sulfate (NiSO ₄ ), 21.8 g / l sodium fluoride (NaF), nickel ammonia (NH ₄ OH) for nickel plating on magnesium alloy ) The magnesium alloy was immersed in a plating solution of 50 ° C. consisting of 40 ml / l of the composition, and plating was performed for about 30 minutes by applying a current of 10 mA / cm ² . The nickel-plated magnesium alloy by the experiment according to the present embodiment is shown in Figure 3b.

Comparative example  One

Pretreatment was first carried out for nickel plating on the magnesium alloy. As a pretreatment, ultrasonic acetone degreasing was first performed for 3 minutes, followed by pickling in a solution of chromic acid (CrO ₃ ) for about 1 minute. Magnesium alloy is immersed in a plating solution at 50 ° C consisting of 250 g / l of potassium pyrophosphate (K ₄ P ₂ O ₇ ), 90 g / l of nickel sulfate (NiSO ₄ ), and 30 g / l of potassium fluoride (KF). Plating was performed for 30 minutes by applying a current of 10 mA / cm ² .

Comparative example  2

Pretreatment was first carried out for nickel plating on the magnesium alloy. As a pretreatment, ultrasonic acetone degreasing was first performed for 3 minutes, followed by pickling in a solution of chromic acid (CrO ₃ ) for about 1 minute. 50 ° C. consisting of a composition of 200 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), 70 g / l of nickel sulfate (NiSO ₄ ), and 40 ml / l of aqueous ammonia (NH ₄ OH) (molarity 0.28 M) The magnesium alloy was immersed in the plating solution of and the plating was performed for 30 minutes by applying a current of 10 mA / cm ² .

Comparative example  3

Pretreatment was first carried out for nickel plating on the magnesium alloy. As a pretreatment, ultrasonic acetone degreasing was first performed for 3 minutes, followed by pickling in a solution of chromic acid (CrO ₃ ) for about 1 minute. 200 g / l of potassium pyrophosphate (K ₄ P ₂ O ₇ ), 70 g / l of nickel sulfate (NiSO ₄ ), 15 g / l of potassium fluoride (KF) and 40 ml / l of aqueous ammonia (NH ₄ OH) 0.28M) was immersed in a plating solution of 50 ℃ made of a composition of magnesium alloy and the plating was carried out for 30 minutes by applying a current of 10mA / cm ² .

Comparative example  4

Pretreatment was first carried out for nickel plating on the magnesium alloy. As a pretreatment, ultrasonic acetone degreasing was first performed for 3 minutes, followed by pickling in a solution of chromic acid (CrO ₃ ) for about 1 minute. 200 g / l of potassium pyrophosphate (K ₄ P ₂ O ₇ ), 70 g / l of nickel sulfate (NiSO ₄ ), 30 g / l of potassium fluoride (KF) and 10 ml / l of aqueous ammonia (NH ₄ OH) 0.07 M) was immersed in a plating solution of 50 ℃ made of a composition of 50 ° C and the plating was performed for 30 minutes by applying a current of 10 mA / cm ² .

Comparative example  5

Pretreatment was first carried out for nickel plating on the magnesium alloy. As a pretreatment, ultrasonic acetone degreasing was first performed for 3 minutes, followed by pickling in a solution of chromic acid (CrO ₃ ) for about 1 minute. Magnesium alloy was immersed in a plating solution at 50 ° C. consisting of 200 g / l of potassium pyrophosphate (K ₄ P ₂ O ₇ ) and 70 g / l of nickel sulfate (NiSO ₄ ) and applied with a current of 10 mA / cm ² . Minute plating was performed.

Evaluation and Results

Surface photo

The magnesium alloy pictures obtained according to Examples 1 and 6 are shown in FIGS. 3A and 3B, and the microstructure pictures according to FIG. 3A are shown in FIG. 4. A microstructure photograph of the magnesium alloy obtained according to Comparative Example 1 is shown in FIG. 5. Referring to FIG. 4, a magnesium surface having a dense nickel plated layer is formed, but referring to FIG. 5, a dense nickel plated layer is not formed and a crack is severely formed on the surface.

Nickel plated layer  Corrosion Resistance Experiment

In order to evaluate the corrosion resistance of the nickel plated layer formed on the magnesium surface, the polarization test was performed on the test specimens according to Example 1 and Comparative Example 5 in a 3.5 wt% NaCl aqueous solution according to ASTM G3-89, and the measurement results are shown in FIG. Shown. Corrosion potential is -243mV to Example No. 1 and the corrosion current density is 1.11 × 10 ^{- 6} were measured by, and the corrosion potential -1100mV according to Comparative Example 5 Corrosion current density is 2.03 × 10 ^- was determined to be ^6. These results indicate that the corrosion resistance of the nickel-plated magnesium alloy was improved in the solution of increasing the concentration of fluorine compound and ammonia water according to Example 1, which formed a dense nickel plated layer to protect magnesium on the magnesium surface. Means that.

In solution  Corrosion Resistance Measurement of Magnesium

Impedance and coin polarization experiments were performed at the equilibrium potential for the magnesium alloy material in the plating solution according to Example 1, Example 2, and Comparative Example 3, and the results are shown in FIGS. 7A and 7B, respectively. As a result of impedance measurement shown in FIG. 7A, the polarization resistance (R _p ) according to Example 1 was 602.2 ohm · m ² , and the polarization resistance (R _p ) according to Example 2 was 665.0 ohm · m ² , according to Comparative Example 3 Polarization resistance (R _p ) was measured to be 80.07 ohm · m ² . It can be seen that the polarization resistance increased due to the increase in fluorine concentration. In addition, as a result of the polarization test according to FIG. 7B, the corrosion potential according to Example 2 is −740.5 mV, the corrosion current density is 1.2 × 10 ⁻⁶ , the corrosion potential according to Example 1 is −800 mV, and the corrosion current density is 3.2 × 10 ^The corrosion potential of ^-5 and Comparative Example 3 was -1040.5 mV, and the corrosion current density was 4.1 × 10 ^-4 . The decrease in the corrosion current density, the increase in the corrosion potential, and the increase in the polarization resistance indicate that the corrosion resistance of the magnesium base material is improved by increasing the concentration of fluorine in the plating solution.

Impedance Measurement in Plating Process

The impedances according to Examples 1, 3 to 6, Comparative Example 1, and Comparative Example 4 were measured, which was measured at -80 mV (-80 mV vs OCP (equilibrium potential)) for the equilibrium potential where plating proceeded in solution. It measured about magnesium base material. The measurement results are shown in FIG. 8. Referring to FIG. 8, in Examples 1 and 3 to 6, the charge transfer resistance of nickel plating was greatly decreased, but in Comparative Example 1 and Comparative Example 4, the charge transfer resistance of nickel plating was higher than that of Example. The result was not greatly reduced. Therefore, it can be seen that the charge transfer resistance for the nickel reduction reaction is greatly reduced as the ammonia water concentration is increased.

XPS Binding Energy Energy )

The binding energy of Mg-F and K-F on the nickel-plated magnesium alloy surface prepared according to Examples 1 to 3 was measured, and these are shown in FIGS. 9A to 9C, respectively.

Referring to FIG. 9A, the binding energy of Mg-F was measured as 686.3 (eV), and the binding energy of K-F was measured as 683.7 (eV). The difference in binding energy between Mg-F and K-F was calculated to be 2.6 (eV).

Referring to Figure 9b, the binding energy of Mg-F was measured as 686.8 (eV), the binding energy of K-F was measured to 683.9 (eV). The difference in binding energy between Mg-F and K-F was calculated to be 2.9 (eV).

Referring to Figure 9c, the binding energy of Mg-F was measured as 686.6 (eV), the binding energy of K-F was measured to 683.5 (eV). The difference in binding energy between Mg-F and K-F was calculated as 3.1 (eV).

FIG. 1 shows a cross section of a magnesium alloy product according to a process of forming an electroless nickel plating layer after forming an electroless nickel plating layer according to the prior art.

FIG. 2 shows a cross section of a magnesium alloy resultant in which an electrolytic nickel plated layer was formed directly on a magnesium alloy surface without forming an electroless nickel plated layer in accordance with the present invention.

3A and 3B show photographs of a magnesium alloy resultant having a nickel plated layer formed in accordance with the present invention.

Figure 4 shows a micrograph of a magnesium alloy with a nickel plated layer formed in accordance with an embodiment of the present invention.

5 shows a micrograph of a magnesium alloy having a nickel plating layer formed according to a comparative example of the present invention.

Figure 6 shows the results in 3.5% by weight aqueous solution of NaCl for the evaluation of the corrosion resistance of the nickel plating layer according to the present invention.

7a and 7b show the results of impedance test at the equipotential polarization test and the equilibrium potential in the plating solution according to the fluoride concentration.

Figure 8 shows the impedance measurement results for the magnesium base material in the process of plating the nickel plated layer according to the present invention.

9A to 9C illustrate binding energy of magnesium alloy components in which a nickel plating layer is formed according to an embodiment of the present invention.

Claims (10)

(a) degreasing the magnesium alloy surface followed by pickling; (b) 200 g / l to 350 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), 70 g / l to 150 g / l nickel sulfate (NiSO ₄ ), alkali metals Immersing in a composition solution consisting of 10 g / l to 50 g / l of a compound with fluorine, and 20 ml / l to 80 ml / l of aqueous ammonia (NH ₄ OH); And (c) applying a current of 5 to 200 mA / cm ² to the composition and adjusting the pH to 8.5 to 10.5 to form nickel plating on the magnesium alloy. 2. The method of claim 1, wherein the content of the compound of alkali metal and fluorine is 20 g / l to 45 g / l. The method of claim 1, wherein the concentration of the ammonia water is 20 ml / l to 80 ml / l. The method of claim 1, further comprising the step of performing an activation treatment in hydrofluoric acid (HF) solution before immersing in the composition of step (b). 2. The method of claim 1, wherein the temperature of the composition in step (c) is controlled to 45 to 65 ℃ nickel plating method for the magnesium alloy. The method of claim 1, wherein the compound of alkali metal and fluorine is lithium fluoride (LiF), sodium fluoride (NaF) or potassium fluoride (KF). (a) degreasing the magnesium alloy surface followed by pickling; (b) 200 g / l to 350 g / l potassium pyrophosphate (K ₄ P ₂ O ₇ ), 70 g / l to 150 g / l nickel sulfate (NiSO ₄ ), and ammonium fluoride NH ₄ F) dipping in a composition solution consisting of 20 g / l to 50 g / l, and 20 ml / l to 80 ml / l of ammonia water (NH ₄ OH); And (c) applying a current of 5 to 200 mA / cm ² to the composition to adjust the pH to 8.5 to 10.5, thereby forming nickel plating on the magnesium alloy. As a nickel plated product of magnesium alloy, a composite film containing MgF ₂ and KF is formed at the interface between magnesium and nickel plating, Nickel-plated magnesium alloy, characterized in that the binding energy (binding energy) of Mg-F and the binding energy of K-F in the composite film is 2.6eV to 3.1eV. The nickel-plated magnesium alloy of claim 8, wherein the corrosion current density decreases and the corrosion potential and polarization resistance increase as the content of fluorine increases in the composite film. The nickel-plated magnesium alloy of claim 8, wherein the binding energy of Mg-F is 686.3 eV to 686.8 eV, and the binding energy of K-F is 683.5 eV to 683.9 eV.

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