KR101203087B1 - METHOD OF SURFACE TREATMENT OF Mg ALLOYS GOODS USING PLASMA ELECTROLYSING OXCIDATION SOLUTION - Google Patents

Abstract

Surface treatment method of magnesium alloy product using PEO solution according to the present invention comprises the step of treating the surface of magnesium alloy product step by step using the first anodized solution, the second anodized solution, and the third anodized solution. In the surface treatment method of a magnesium alloy product using a PEO solution containing, sodium hydroxide (NaOH) and sodium metasilicate (Na ₂ SiO ₃ ), sodium citrate (C ₆ H ₅ Na ₃ O ₇ ), rare earth metal powder The first surface treatment step of first treating the surface of magnesium alloy product with the first oxide film treatment solution mixed with water, sodium hydroxide (NaOH) and ammonium fluoride (NH ₄ F), potassium ferricyanide (K _{3 Fe (CN) 6: Potassium Ferricyanide} ) a second surface treatment step of treating the surface of said surface-treated in a primary surface treatment step 2, the magnesium alloy product in a second drive anodized in a mixed solution of water, Sodium (NaOH) and potassium hydroxide (KOH), oxidation acid sodium oxide (NaBO _2: Sodium Metaborate), nitric acid potassium _{(CH 3 COOK: Potassium Acetate)} , the transition metal by a third above the anodized solutions mixed in water And a third surface treatment step of thirdly treating the surface of the magnesium alloy product surface-treated in the second surface treatment step.
Accordingly, the present invention provides magnesium as a first oxide coating solution in which sodium hydroxide (NaOH), sodium metasilicate (Na ₂ SiO ₃ ), sodium citrate (C ₆ H ₅ Na ₃ O ₇ ), and a rare earth metal powder are mixed with water. The surface of the alloy product can be treated primarily to impart tissue density, surface bonding strength and hardness of the magnesium alloy product, and can be applied with sodium hydroxide (NaOH), ammonium fluoride (NH ₄ F) and potassium ferricyanide (K ₃ Fe (CN). ₆ : A second anodized solution in which Potassium Ferricyanide is mixed with water to treat the surface of magnesium alloy secondaryly to reduce pore size, increase film roughness, sodium hydroxide (NaOH) and potassium hydroxide (KOH). ), A third oxide film treatment solution containing sodium borate (NaBO ₂ : Sodium Metaborate), potassium acetate (CH ₃ COOK: Potassium Acetate), and transition metals in water. Pore size reduction, membrane quality and The effect of being able to improve surface roughness easily, etc. is exhibited.

Description

Surface treatment method of magnesium alloy product using POE solution {METHOD OF SURFACE TREATMENT OF Mg ALLOYS GOODS USING PLASMA ELECTROLYSING OXCIDATION SOLUTION}

The present invention relates to a surface treatment method using a PEO solution, which is one of the methods for treating the surface of the magnesium alloy product, and more specifically, magnesium alloy product by treating the surface of the magnesium alloy product step by step with a plurality of anodized solution The present invention relates to a surface treatment method of a magnesium alloy product using a PEO solution that can easily improve the structure density, surface bonding strength, pore size reduction, and surface roughness of an oxide film formed on the surface of the film.

In general, magnesium alloy has excellent dimensional stability, and excellent strength, electromagnetic shielding, and vibration damping are superior to aluminum alloy and steel, and are widely used in automobile and aircraft parts, mobile phone cases, laptop computer cases, and eyeglass frames. The unit is low and its corrosion resistance is poor, so it is surface treated to prevent corrosion.

Therefore, in order to surface-treat the product made of the magnesium alloy, there are anodizing treatment method called anodizing and PEO treatment method called plasma electrolytic oxidation.

Since magnesium alloy is a metal which is well oxidized, a surface treatment process, which is a pretreatment process, is necessary. A product of such magnesium alloy is treated by plasma electrolytic oxidation to form an MgO thin film layer on the surface thereof.

That is, the electrolyte used in the conventional PEO surface treatment apparatus mainly uses sodium hydroxide (NaOH) solution, the hydroxyl group (OH-) in the sodium hydroxide solution is bonded to the surface layer of the magnesium alloy product, so formed inside the oxide film Plasma is generated by a strong current field formed at, and these energies instantly form oxides to form MgO and Mg (OH) ₂ thin films on the surface layer of the magnesium alloy product.

However, in the past, since sodium hydroxide (NaOH) solution is used as the electrolyte solution used in the PEO surface treatment apparatus, there are limitations in tissue density, surface bonding strength, pore size reduction, and surface roughness of the oxide film formed on the surface of the magnesium alloy product.

The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to affect the structure density, surface bonding strength, decrease the pore size, surface roughness of the oxide film with sodium hydroxide in a number of anodized solution The present invention provides a method for surface-treating a magnesium alloy product using a PEO solution that can form an oxide film on the surface of a magnesium alloy product firmly, densely and uniformly by adding a substance having a high temperature.

In order to achieve the above object, the present invention comprises the step of treating the surface of the magnesium alloy product step by step using a first anodized solution, a second anodized solution, a third anodized solution In the surface treatment method of magnesium alloy product using a solution, sodium hydroxide (NaOH), sodium metasilicate (Na ₂ SiO ₃ ), sodium citrate (C ₆ H ₅ Na ₃ O ₇ ), rare earth metal powder mixed in water A first surface treatment step of first treating the surface of a magnesium alloy product with a first anodized solution, sodium hydroxide (NaOH), ammonium fluoride (NH ₄ F), and potassium ferricyanide (K ₃ Fe (CN)). ₆ : Second surface treatment step of treating the surface of magnesium alloy product surface treated in the first surface treatment step with a second anodized solution mixed with potassium ferricyanide in water, sodium hydroxide (NaOH) And hydroxide Cerium (KOH), sodium borate oxide (NaBO _2: Sodium Metaborate), nitric acid potassium _{(CH 3 COOK: Potassium Acetate)} , a transition metal as the third oxide coating treatment solution was mixed with the water surface at the processing step wherein the secondary surface Provided is a method for surface treatment of a magnesium alloy product using a PEO solution comprising a third surface treatment step of thirdly treating the surface of the treated magnesium alloy product.

Thus, the surface treatment method of the magnesium alloy product using the PEO solution according to the present invention is sodium hydroxide (NaOH) and sodium metasilicate (Na ₂ SiO ₃ ), sodium citrate (C ₆ H ₅ Na ₃ O ₇ ), rare earth The surface treatment of magnesium alloy products is primarily treated with the first anodized solution in which metal powder is mixed with water to impart tissue density, surface bonding strength, and hardness of magnesium alloy products. Sodium hydroxide (NaOH) and ammonium fluoride (NH ₄ F) and potassium ferricyanide (K ₃ Fe (CN) ₆ : Potassis Ferricyanide) is a second oxide film treatment solution mixed with water to reduce the pore size by treating the surface of magnesium alloy products secondly. 3rd oxide film with sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium borate (NaBO ₂ : Sodium Metaborate), potassium acetate (CH ₃ COOK: Potassium Acetate), and transition metal With treatment solution It has the advantage that the surface of the magnesium alloy products processed by car 3 can easily improve the surface roughness, pore size reduction, the film quality and surface roughness.

In particular, the present invention adds a substance which affects the tissue density, surface bonding strength, pore size reduction, and surface roughness of the oxide film together with sodium hydroxide to a plurality of anodized solutions, and the surface treatment is performed step by step. The oxide film can be formed firmly, densely and uniformly on the surface.

1 is an enlarged photograph of a drawing of a surface of a magnesium alloy product subjected to a first surface treatment with a first anodized solution applied to a surface treatment method of a magnesium alloy product using a PEO solution according to the present invention.
FIG. 2 is an enlarged photograph of the surface of a magnesium alloy product subjected to a second surface treatment with a second anodized solution applied to a surface treatment method of a magnesium alloy product using a PEO solution according to the present invention.
FIG. 3 is an enlarged photograph of the surface of a magnesium alloy product subjected to tertiary surface treatment with a third oxide film treatment solution applied to a surface treatment method of a magnesium alloy product using a PEO solution according to the present invention.

Hereinafter, a preferred embodiment of the surface treatment method of the magnesium alloy product using the PEO solution according to the present invention will be described in more detail.

The surface treatment method of the present invention includes treating the surface of a magnesium alloy product step by step using a first anodized solution, a second anodized solution, and a third anodized solution.

Of course, as before, the surface of the magnesium alloy product is sanded, washed, degreased and activated before the surface treatment with the anodized solution, and the surface of the magnesium alloy product is washed, washed with water, washed with water, sealed and dried. The work will proceed.

For example, the overall process for treating the surface of magnesium alloy products is surface sanding → washing → ultrasonic cleaning → activation → 1st washing → 2nd washing → staged surface treatment with 1st, 2nd, 3rd oxide coating solution → 1st washing → 2nd water washing → 3rd warm water washing → sealing → drying.

In this process, the present invention includes a first surface treatment step with a first anodized solution, a second surface treatment step with a second anodized solution, and a third surface treatment step with a third anodized solution .

In the first surface treatment step, the first oxidation of sodium hydroxide (NaOH) and sodium metasilicate (Na ₂ SiO ₃ ), sodium citrate (C ₆ H ₅ Na ₃ O ₇ ), and rare earth metal powder in water The surface treatment of magnesium alloy product is first performed with the coating solution.

In addition, the first oxide film treatment solution is based on the weight of water (distilled water) 0.1 ~ 10.0% by weight of sodium hydroxide (NaOH), 0.1 ~ 1.0% by weight of sodium metasilicate (Na ₂ SiO ₃ ), sodium citrate (C ₆ H ₅ Na ₃ O ₇ ) 0.1 to 2.0% by weight, 0.1 to 1.5% by weight of the rare earth metal powder is mixed with water.

In the second surface treatment step, sodium hydroxide (NaOH), ammonium fluoride (NH ₄ F), and potassium ferricyanide (K ₃ Fe (CN) ₆ : Potassisium Ferricyanide) are mixed with water to prepare a second oxide film treatment solution. The surface of the magnesium alloy product surface-treated in the first surface treatment step is secondly treated.

Furthermore, the second anodized solution is 0.1 to 10.0 wt% sodium hydroxide (NaOH), 0.1 to 3.0 wt% ammonium fluoride (NH ₄ F) based on the weight of water (distilled water), potassium ferricyanide (K ₃ Fe (CN) ₆ : Potassisium Ferricyanide) 0.1 ~ 1.0% by weight is mixed with water.

In the third surface treatment step, sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium borate (NaBO ₂ : Sodium Metaborate), potassium acetate (CH ₃ COOK: Potassium Acetate), a transition metal mixed with water The surface of the magnesium alloy product surface-treated in the second surface treatment step with the trioxide coating solution is subjected to the third treatment.

Furthermore, the third oxide film treatment solution is based on the weight of water (distilled water) 1.0 ~ 10.0% by weight of sodium hydroxide (NaOH), 0.1 ~ 5.0% by weight of potassium hydroxide (KOH), 0.1% sodium borate (NaBO ₂ : Sodium Metaborate) 0.1 ~ 2.0% by weight, potassium acetate (CH ₃ COOK: Potassium Acetate) 0.1 ~ 2.0% by weight, the transition metal 0.1 ~ 2.0% by weight is mixed with water.

Particularly, in the present invention, the voltage used in the first, second and third surface treatment steps is increased step by step to increase the coating stability and the uniformity of the oxide film. In the first surface treatment step, an anode is used. ) After the magnesium alloy product is connected to the first anodized solution and subjected to a first surface treatment at a voltage of 40 to 60 V. In the second surface treatment step, the magnesium alloy product is connected to an anode. The secondary surface treatment is performed in a second anodized solution at a voltage of 60 to 80 V. In the third surface treatment step, a magnesium alloy product is connected to an anode, and then put in the third anodized solution to be subjected to a voltage of 100. Tertiary surface treatment for 10 to 200 seconds at ~ 120V.

Sodium hydroxide is a basic substance that generates -OH ions because it is contained in the first, second, and third oxide film treatment solution. If it contains less than 0.1% by weight based on the weight of water, the generation of -OH ions is minute. This is because it is difficult to form a magnesium hydroxide (MgOH) oxide film on the surface of the magnesium alloy, even if more than 10.0% by weight based on the weight of water does not affect the rate of change of the production action of the oxide film.

For reference, sodium hydroxide is prepared by causification of sodium carbonate and electrolysis of sodium chloride. It is strongly deliquescent and pure is a colorless transparent crystal, but it is a slightly opaque white solid, usually containing impurities, at room temperature. It is (alpha) type (low temperature type) of, and it transitions to the beta (high temperature type) form of cubic system at 299.6 degreeC.

It dissolves well in water and generates a large amount of heat when dissolved. The aqueous solution has a strong basicity. Solubility in 100g of water is 42g at 0 ° C, 109g at 20 ° C and 347g at 100 ° C. It is soluble but insoluble in ether, acetone and liquid ammonia.

Furthermore, sodium hydroxide solution is used for this dissolution because it dissolves with poorly soluble silicate, phosphate, and sulfate, so it is used for this dissolution. At low temperatures, it produces various halide oxides and at high temperatures sodium halides.

In the present invention, the sodium metasilicate (Na ₂ SiO ₃ ) is to ensure the tissue compactness, when containing more than 1.0% by weight based on the weight of water to reduce the compactness to the roughness of the oxide film formed on the surface of the magnesium alloy product It may adversely affect, and the addition of less than 0.1% by weight is such that the addition amount is small can not affect the securing of tissue density.

For reference, sodium metasilicate is well dissolved in water, and the aqueous solution becomes alkaline by hydrolysis. The concentrated aqueous solution of sodium silicate is called water glass.

In the present invention, the sodium citrate (C ₆ H ₅ Na ₃ O ₇ ) is to give a surface binding force, if containing more than 2.0% by weight based on the weight of water does not proceed to the continuous improvement of the increase in the surface binding force, If the content is less than 0.1% by weight, the added amount is small so as not to affect the surface bonding force.

For reference, sodium citrate is a colorless crystal or white crystalline powder. It has no smell and has a cool salty taste. It is well soluble in water and hardly soluble in ethanol or ether, and aqueous solution shows qualitative reaction of citrate and sodium salt.

In the present invention, the rare earth metal powder is ionized while being dissolved in water, which may not only affect the form and ivory color of the membrane, but also impart hardness, and may not be ionized when added more than 1.5 wt% based on the water weight. This can be an unnecessary impurity, the addition of less than 0.1% by weight is the addition amount is small can not affect the shape of the film and ivory color as well as not give the hardness.

For reference, rare earth metals refer to the entire scandium, yttrium, and lanthanide elements. Oxides of +2, +3, and +4 usually form all trivalent compounds, which are +4 in cerium-terbium praseodymium, In ytterbium, europium, and samarium, there is also +2, and most of them have silver-grey luster, and after the alkali is strong after the alkali metal and the alkaline earth metal, the aqueous solution becomes basic.

In the present invention, the ammonium fluoride (NH ₄ F) is to reduce the pore size, even if it contains more than 3.0% by weight does not significantly affect the reduction of the pore size, when contained less than 0.1% by weight, the addition amount is small and pore size It will not affect the reduction effect.

For reference, ammonium fluoride is in the form of crystalline powder, has no smell, is easy to react with water, etching of bulbs, CRTs and LCDs, descaling of boilers, automobiles and radiators, carbon steel and metal surface treatment agents, wood preservatives, etc. Used as

In the present invention, the potassium ferricyanide (K ₃ Fe (CN) ₆ : Potassium Ferricyanide) determines the roughness of the thin film, and because it is a toxic material, it does not need to contain more than 1.0 wt% based on the water weight, and 0.1 wt%. If it contains less than%, it becomes insufficient to determine thin film roughness.

For reference, potassium ferricyanide is not poisonous, but potassium cyanide produced by decomposing potassium ferricyanide can be a poison, and is used in pharmaceuticals, photo development, and printing.

In the present invention, the potassium hydroxide (KOH) not only imparts a size reduction to the pore formation, but also affects the color and uniformity of the membrane, and when added to more than 5.0% by weight compared to the sodium hydroxide contained in the sodium hydroxide solution of the magnesium alloy product As the brown color increases in the color of the oxide film formed on the surface, it may adversely affect the uniformity of the surface of the ivory color, and the addition of less than 0.1% by weight is smaller than the total solution in which many other mixtures are mixed. And uniformity cannot be affected.

For reference, it is obtained by electrolysis of aqueous potassium chloride solution as potassium hydroxide. When it is deliquescent, it is absorbed and dissolved when absorbed in air. It absorbs carbon dioxide to become potassium carbonate, and gives a lot of heat when dissolved in water. .

Potassium hydroxide has very similar chemical properties to sodium hydroxide, and is used in the manufacture of various potassium compounds, potassium glass, fuel soap, dyes (such as indigo), synthetic fiber materials (terephthalic acid, etc.), and alkaline batteries and analysis reagents. It is also used in carbon dioxide absorbents.

In the present invention, the sodium borate (NaBO ₂ : Sodium Metaborate) is to give a surface roughness, as a white alkali salt used as a development accelerator, etc., as a powder crystal that is well dissolved in water, 2.0% by weight based on the weight of water It does not need to contain more, and when it contains less than 0.1 weight%, it is insufficient to provide surface roughness.

In the present invention, potassium acetate (CH ₃ COOK: Potassium Acetate) affects the membrane quality and pore size, and when more than 2.0 wt% is added based on the water weight, the pore size increases, which may adversely affect the uniformity and roughness of the membrane. In addition, the addition of less than 0.1% by weight is such that the addition amount is small and cannot affect the pore size of the membrane.

For reference, potassium acetate is an analytical reagent that is soluble in ethanol but not soluble in ether. It is a deliquescent colorless crystal used as a raw material for organic synthesis, and its appearance is colorless to white, easy to dissolve, crystalline or glossy powder. to be.

In the present invention, the transition metal is to improve the surface roughness, it is not necessary to contain more than 2.0% by weight, and if it contains less than 0.1% by weight is small enough to improve the surface roughness.

For reference, a transition metal refers to a metal composed of d-zone elements of the periodic table of the elements, and includes all the group 3 to 12 elements of the periodic table. It acts as an intermediate step of transition to a typical element.

Thus, in the present invention, the surface of the magnesium alloy product is formed on the surface of the magnesium alloy product by interaction of a plurality of materials by treating the surface of the magnesium alloy product step by step using the first, second, and third oxide film treatment solution mixed with different materials. The structure density, surface bonding strength, surface roughness of the oxide film can be improved.

Of course, an example of the overall process to which the surface treatment method according to the present invention is applied is surface sanding → washing with water → ultrasonic cleaning → activation → first washing → second washing → first, second, and third oxide film treatment step by step surface Treatment → 1st washing → 2nd washing → 3rd warm washing → sealing → drying.

Here, it is necessary to degrease the surface of the magnesium alloy product using an alkali-based surfactant before the stepwise surface treatment with the first, second, and third oxide film treatment solution, thereby eliminating the passivation phenomenon in the activation process.

In addition, after the surface treatment step by step with the first, second, and third oxide film treatment solution, it is sealed, and it is porous with many small pores on the surface of the oxide film. The surface is sealed with an oxide film and smoothed to improve the corrosion resistance and physical properties of the porous film.

Therefore, as a result of surface treatment step by step using the first, second, third oxide film treatment solution as described above, as shown in Figures 1 to 3, a more robust, dense and smooth oxide film can be formed on the surface of the magnesium alloy product there was.

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Claims (5)

In the surface treatment method of a magnesium alloy product using a PEO solution comprising the step of treating the surface of the magnesium alloy product step by step using a first anodized solution, a second anodized solution, a third anodized solution ,
The surface of the magnesium alloy product as the first oxide film treatment solution containing sodium hydroxide (NaOH), sodium metasilicate (Na ₂ SiO ₃ ), sodium citrate (C ₆ H ₅ Na ₃ O ₇ ), and rare earth metal powder The first surface treatment step of treating the first,
Sodium hydroxide (NaOH), ammonium fluoride (NH ₄ F), potassium ferricyanide (K ₃ Fe (CN) ₆ : Potassisium Ferricyanide) in a second oxide film treatment solution mixed with water in the first surface treatment step A second surface treatment step of secondly treating the surface of the surface-treated magnesium alloy product;
Sodium hydroxide (NaOH) and potassium hydroxide (KOH), sodium borate (NaBO ₂ : Sodium Metaborate), potassium acetate (CH ₃ COOK: Potassium Acetate), a third oxide film treatment solution containing a transition metal in water A surface treatment method for a magnesium alloy product using a PEO solution comprising a third surface treatment step of tertiarily treating a surface of a magnesium alloy product surface-treated in a second surface treatment step. The method of claim 1,
In the first surface treatment step, after the magnesium alloy product is connected to the anode (Anode) and put into the first anodized solution, the first surface treatment at a voltage of 40 ~ 60V,
In the second surface treatment step, after the magnesium alloy product is connected to the anode (Anode), the second surface treatment at a voltage of 60 ~ 80V by putting in the second oxide film treatment solution,
In the third surface treatment step, the solution of PEO is characterized in that the third surface treatment is performed for 10 to 200 seconds at a voltage of 100 to 120V by connecting a magnesium alloy product to an anode and then placing the magnesium alloy product in the third anodized solution. Surface treatment method of magnesium alloy product using. The method according to any one of claims 1 and 2,
The first oxide film treatment solution is based on the water weight of sodium hydroxide (NaOH) 0.1 ~ 10.0% by weight, sodium metasilicate (Na ₂ SiO ₃ ) 0.1 ~ 1.0% by weight, sodium citrate (C ₆ H ₅ Na ₃ O ₇ ) A surface treatment method of a magnesium alloy product using a PEO solution, characterized by mixing 0.1 to 2.0% by weight, 0.1 to 1.5% by weight of rare earth metal powder in water. The method according to any one of claims 1 and 2,
The secondary oxide film treatment solution is based on water weight of sodium hydroxide (NaOH) 0.1 ~ 10.0% by weight, ammonium fluoride (NH ₄ F) 0.1 ~ 3.0% by weight, potassium ferricyanide (K ₃ Fe (CN) ₆ : Potassium Ferricyanide) Surface treatment method of magnesium alloy product using PEO solution, characterized by mixing 0.1 to 1.0% by weight in water. The method according to any one of claims 1 and 2,
The third oxide film treatment solution is based on the water weight of sodium hydroxide (NaOH) 1.0 ~ 10.0% by weight, potassium hydroxide (KOH) 0.1 ~ 5.0% by weight, sodium borate (NaBO ₂ : Sodium Metaborate) 0.1 ~ 2.0 weight %, Potassium acetate (CH ₃ COOK: Potassium Acetate) 0.1 to 2.0% by weight, 0.1 to 2.0% by weight of the transition metal surface treatment method of magnesium alloy product using the PEO solution, characterized in that the mixture.

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