KR20020060945A - Conversion Treatment Method for Magnesium Alloy's Electroplating. - Google Patents

Abstract

PURPOSE: A chemical conversion treatment method for electrolytic plating of magnesium alloy is provided to increase application of a magnesium alloy material having the highest specific strength in practical metals by developing a conversion coating forming process required in forming a uniformed coat of electroplating. CONSTITUTION: The chemical conversion treatment method for wet electrolytic plating of magnesium alloy comprises the process of forming a wet electroplating coating film having uniformed current distribution on the surface of magnesium alloy before performing electrolytic plating so as to electrolytic plate magnesium alloy, wherein a composition of a conversion treatment solution for forming the wet electroplating coating film comprises 10 to 45 g/L of Na4P2O7, 10 to 30 g/L of CH3COONa, 5 to 10 g/L of NH3OH, 5 to 10 g/L of HF, 5 to 55 g/L of NaOH and additives, a composition of a conversion treatment solution for forming the wet electroplating coating film comprises 15 to 35 g/L of Mn(H2PO4)2, 5 to 10 g/L of Fe(H2PO4)2, 5 to 20 g/L of NaOH, 3 to 15 g/L of H3PO4, 10 to 30 g/L of Na2CO3 and trace of additives, a composition of a conversion treatment solution for forming the wet electroplating coating film comprises 1 to 5 g/L of NaNO3, 1 to 7 g/L of FeCl2, 3 to 20 g/L of ZnO, 2 to 7 g/L of H3PO4, 50 to 250 g/L of NaOH and additives, and a composition of a conversion treatment solution for forming the wet electroplating coating film comprises 1 to 5 g/L of NaNO3, 3 to 20 g/L of FeCl2, 3 to 20 g/L of ZnO, 25 to 150 g/L of rochelle salt, 1 to 15 g/L of H2SO4, 3 to 15 g/L of H2PO4, 25 to 200 g/L of NaOH and additives.

Description

Chemical conversion method for electroplating of magnesium alloy. {Conversion Treatment Method for Magnesium Alloy's Electroplating.}

Magnesium alloy is the lightest among the practical metals, and has high specific strength and good grinding ability, which makes it easy to machine. Therefore, magnesium alloy is widely used in electric parts such as automobile parts, computer parts, acoustic device parts, information and communication parts, and aircraft parts. In addition, in general, magnesium alloy molded products are mainly manufactured by die casting, extrusion molding, and rolling molding, but recently, thixo-molding using an injection molding machine has been technically established. It becomes possible, and the application range is expanded further.

However, magnesium alloy is a metal having a low standard potential among practical metals, so it is easy to oxidize in the air, and thus has a drawback of being very vulnerable to corrosion resistance as a commercial metal. In order to utilize magnesium alloys, increasing corrosion resistance of magnesium alloys is an important task.

In the conventional magnesium alloy, the chromate treatment is generally performed as a rust preventing treatment for increasing the corrosion resistance. However, since chromate treatment is difficult to set processing conditions, a simpler rust prevention method is required. In addition, chromate treatment has a drawback of discoloration of the surface and the lack of metallic luster, and the liquid used for chromate treatment is increasingly restricted by global environmental regulations due to environmental problems caused by chromium compounds.

Accordingly, the development of non-chromo treatment has been actively made in recent years, but the corrosion resistance and fingerprint resistance is lower than that of the conventional chromate treatment, and the cost of non-chromium liquid is high, resulting in an increase in surface treatment cost. Such film forming treatments such as Chromate treatment and Non-Chromate treatment are limited to interior parts of which appearance is not important or are limited to being used for the ground treatment of painting and painting work.

As the surface treatment method of the magnesium alloy, there is a method of plating on the surface of the magnesium alloy by a dry or wet method in addition to the coating method described above or the appearance after coating. Due to the nature of the magnesium alloy (e.g., adhesion of vacuum deposition and coating failure due to evaporation of a mixture of magnesium alloys in the vacuum chamber), the problem of dry plating becomes difficult.

Wet plating includes electrolytic wet plating using electric energy and electroless plating by chemical reaction. Electroless nickel plating is commonly used as an electroless method. However, the electroless nickel plating solution has a high production cost, and in order to improve the most vulnerable corrosion resistance of magnesium alloy, the electroless nickel plating solution has to be subjected to double or triple electroless nickel plating by changing the phosphorus content (NiP).

The electrolytic wet plating method using electricity is a technology that is developed by our researchers and is pending patent application under domestic patent application No. 2001-12871.

As described above, the present invention obtains a magnesium alloy material which has many advantages among commercial metals and has improved corrosion resistance, which is a disadvantage of magnesium alloy, in order to increase the utilization of magnesium alloy material which has a weak point in acid and especially sodium chloride solution (salt water). Let's do it. During this process, electrochemical plating film is formed on the surface of the magnesium alloy to have a uniform current distribution before the electroplating process, so that the wet electroplating film can be generated smoothly, and the electroplating film itself is corrosion resistant of the magnesium alloy. The aim is to improve this.

The film formation for electroplating of magnesium alloy is the basis of even electroplating, and the formation of the even electroplating film is an important factor in making the corrosion resistance of magnesium vulnerable to corrosion.

By forming electroplating film on magnesium alloy, plating can be performed to increase corrosion resistance, which is vulnerable to magnesium alloy, which brings the advantages of magnesium alloy (high specific strength, light weight, machinability, torsion / warping) to the product. It is to provide a manufactured magnesium alloy that can be applied.

1 is a plating configuration surface-treated in the magnesium alloy according to the present invention.

Figure 2 is a method for forming a copper plating layer on the magnesium alloy according to the present invention by electroplating, after performing a variety of functional and decorative plating (nickel, gold, silver, chromium, rhodium, etc.) after the base copper plating after chemical conversion treatment A block diagram showing the plating process.

<Description of the symbols for the main parts of the drawings>

1: metal base (magnesium alloy) 2: chemical conversion layer

3: copper plating layer

4: nickel plated layer

The present invention relates to a method for forming a chemical conversion coating film for applying a wet electroplating method to a magnesium alloy, and to form a plating film layer for electroplating on a matrix layer of a magnesium alloy, and then plating a copper plating layer by electroplating. It features. The specialization of copper plating by the plating of magnesium alloy is a setting for plating the copper plating because it is commonly used for the base of the existing various plating, and in the present invention, it is possible to plate the copper plating for electroplating by electrolytic method. The chemical conversion film formation method is taken as a main point.

There are two methods of chemical conversion to form a film: phosphate and mixtures of zinc, which can be used individually or in combination to form a high-quality chemical conversion film on the surface of magnesium alloy. Helps to form a high quality plated film can greatly improve the corrosion resistance of the magnesium alloy.

Magnesium alloys are very corrosive to acids and are particularly susceptible to acids with high dissociation, such as nitric acid, making them almost impossible to pickle, which is the basis for pre-plating. As a result of developing a wet electrolytic plating method on a magnesium alloy having such a property, it was found that the formation of a chemical coating film for electroplating prior to plating resulted in a more homogeneous electroplating film. I want to add

In order to surface-treat the magnesium alloy, it is required to undergo degreasing, pickling, and active processes as shown in FIG. 2. The method described in Patent No. 2001-12871, developed and developed by the present researchers, is applied. The active liquid is also changed according to the activation process to form a film.

Hereinafter, embodiments of the present invention will be described.

The degreasing and pickling process was applied in the method of Patent No. 2001-12871, and the composition of the active solution for chemical plating treatment for electroplating is as follows.

Aqueous solution composition Aqueous solution temperature (℃) Immersion time (minutes) pH Na4P2O7 + CH3COONa + NH3OH5HF + NaOH + Additive 45 to 80 1 to 10 8 to 13

Due to the addition of NaOH from above, the color after the active treatment of the magnesium surface brings about an even distribution in white and a shortening time for the formation time of the chemical conversion film. The immersion time and the temperature change of the aqueous solution are applied differently depending on the molded shape of the magnesium alloy.

Thereafter, a chemical conversion film is formed by electroplating pretreatment by the method as described below.

Chemical film treatment method 1)

Aqueous solution composition Aqueous solution temperature (℃) Immersion time (minutes) pH Mn (H2PO4) 2 + Fe (H2PO4) 2 + NaOH + H3PO4 + Na2CO3 + Additive 40 to 85 3 to 15 7-10

Chemical film treatment method 2)

Aqueous solution composition Aqueous solution temperature (℃) Immersion time (minutes) pH NaNO3 + FeCl2 + ZnO + H3PO4 + NaOH + Additive 15-75 0.5-20 5.5 to 8

Chemical film treatment method 3)

Mixed and complex treatment methods of the above-mentioned chemical conversion treatment methods 1) and 2)

Aqueous solution composition Aqueous solution temperature (℃) Immersion time (minutes) pH NaNO3 + FeCl2 + ZnO + Lotel salt + H2SO4 + H3PO4 + NaOH + Additive 15 to 85 0.5-20 5.5 to 10

As such, the diversification of the treatment method of the chemical coating film shows that the method according to the manufacturing method and shape of the magnesium alloy is organically applied. Before the treatment of the chemical conversion coating, it is possible to shorten the chemical coating treatment time by applying hot water at a temperature of 80 to 90 DEG C according to the characteristics of the product.

Thereafter, copper plating of the wet electrolytic method is performed on the magnesium alloy on which the chemical conversion film is formed.

At this time, the composition of the plating solution used in the electroplating of copper at this time is appropriate to the method disclosed in Patent 2001-12871, it is also possible to apply the existing copper plating solution if necessary.

Reliability experiments presented below are test specimens 1 and 2 manufactured by the method proposed in Patent No. 2001-12871. Experimental specimens 3 and 4 were subjected to chemical treatment method 1. Experimental specimens 5 and 6 were chemically treated. Applying Method 2, Experimental Specimens 7 and 8 were fabricated by applying the chemical treatment method 3. Experimental specimens 1,2 and 3 to 8 were differentiated during copper plating. The copper plating solution and the plating conditions were kept constant, but only the plating time was applied to the test specimens 3-8 only 70% of the time compared to the time applied to the test specimens 1,2.

Table 1

Test specimen Adhesion Pencil lead test (H) Give test Tape testing Example One ○ ○ 3 2 ○ ○ 3 3 ○ ○ 3 4 ○ ○ 3 5 ○ ○ 3 6 ○ ○ 3 7 ○ ○ 3 8 ○ ○ 3

○) Excellent △: Normal ×: Easily peeled off

Table 1 is a joule test and a tape test of the copper plated product after the formation of the chemical conversion coating on the magnesium alloy of the present invention as a prescribed condition.

What is clearly shown here was uniform gloss without any discoloration of plating in any of Examples 1-8. In addition, as a general adhesive test method, the tape was scratched with a tungsten knife horizontally and vertically at intervals of 1 mm, and no peeling phenomenon was found. The string test cuts the plating vertically, and the test piece is fixed to the plated surface at an angle of 45 degrees. (At this time, the coating film should not be peeled off.) As shown in Table 1, the results of the string test are all excellent. Appeared.

Table 2

3% NaOH amount (period) Psalm Number One 2 3 4 5 6 7 8 1 day ○ ○ ○ ○ ○ ○ ○ ○ 2 day ○ ○ ○ ○ ○ ○ ○ ○ 3 day ○ ○ ○ ○ ○ ○ ○ ○ 4 day ○ ○ ○ ○ ○ ○ ○ ○ 5 day ○ ○ ○ ○ ○ ○ ○ ○

○) Excellent corrosion resistance ×: Easily eluted

Table 2 shows that after the plating under the conditions of the present invention, all 8 specimens which were tested by immersion in a 3% NaOH aqueous solution to check the corrosion resistance did not progress. Also, no change in gloss and color was seen.

Table 3

5% NaOH amount (period) Psalm Number One 2 3 4 5 6 7 8 1 day ○ ○ ○ ○ ○ ○ ○ ○ 2 day ○ ○ ○ ○ ○ ○ ○ ○ 3 day ○ ○ ○ ○ ○ ○ ○ ○ 4 day ○ ○ ○ ○ ○ ○ ○ ○ 5 day ○ ○ ○ ○ ○ ○ ○ ○

○) Excellent corrosion resistance ×: Easily eluted

Table 3 shows the corrosion resistance by immersing in 5% NaCl solution. Likewise, no progress of corrosion was seen in all eight cases, and no change in color and gloss was found.

The embodiments of the present invention as described above do not limit the present invention, and modifications within the scope of the foregoing description are included in the technical scope of the present invention as a whole.

The present invention, as described above, to obtain a magnesium alloy material that has many advantages among commercial metals, but also to improve the utilization of the magnesium alloy material, which has a drawback that is weak in acid and in particular sodium chloride solution (salt water), which is a disadvantage of magnesium alloy. To this end, by forming an electroplating film having a uniform current distribution on the surface of the magnesium alloy, the wet electroplating is smoothly generated, and the film itself by the electroplating chemical conversion treatment improves the corrosion resistance of the magnesium alloy. It works.

That is, the magnesium alloy is expected to be used as a material actively used in the industry because it can take advantage of the high specific strength by supplementing the disadvantages of the corrosion of the magnesium alloy.

It is expected to be actively used as a durable material of magnesium alloy. In particular, due to the recent development of the IT industry, the materials of cases, housings, and durable frames of portable information and communication devices have to be thin, light, warped, and rigid. Since magnesium alloy material is eligible, the utilization of magnesium alloy material with corrosion resistance is expected to increase rapidly.

The film formation that enables electroplating of magnesium alloy can apply electroplating of various methods to magnesium alloy, so it is possible to apply existing plating technology to magnesium alloy, so the surface treatment method of magnesium alloy material is also diversified. can see.

Claims (5)

A chemical conversion treatment method for wet electroplating of magnesium alloy, in which an electroplating film is formed on the surface of a magnesium alloy to give a uniform current distribution before electroplating the magnesium alloy. The composition of the active treatment liquid as an electrochemical conversion film forming pretreatment according to claim 1 is 10 to 45 g / l Na 4 P 2 O 7, 10 to 30 g / l CH 3 COONa, 5 to 10 g / l NH 3 OH, 5 to 10 g / l HF, 5 to 55g / l, consisting of NaOH and additives, composition of active treatment solution for chemical conversion for wet electroplating of magnesium alloy The composition of the chemical conversion treatment liquid for forming the wet electroplating film according to claim 1 is 15 to 35 g / l Mn (H 2 PO 4) 2, 5 to 10 g / l Fe (H 2 PO 4) 2, + 5 to 20 g / l NaOH , + 3 ~ 15g / l H3PO4, + 10 ~ 30g / l Na2CO3 with trace amount of additives, method for composition of chemical conversion treatment for wet electroplating of magnesium alloy. The composition of the chemical conversion treatment liquid for forming a wet electroplating film according to claim 1 is 1 to 5 g / l NaNO 3, 1 to 7 g / l FeCl 2, 3 to 20 g / l ZnO, 2 to 7 g / l H 3 PO 4, 50 Composition method of chemical conversion treatment for wet electroplating of magnesium alloy with ~ 250g / l NaOH and additives The composition of the chemical conversion treatment liquid for forming a wet electroplating film according to claim 1 is 1-5 g / l NaNO 3, 3-20 g / l FeCl 2, 3-20 g / l ZnO, 25-150 g / l Rossel salt, Method of composition of chemical conversion treatment for wet electroplating of magnesium alloy, consisting of 1 ~ 15g / l H2SO4, 3 ~ 15g / l H3PO4 + 25 ~ 200g / l NaOH and additives.