JP2000297386A - Plating method of magnesium alloy member, magnesium alloy plated member, and plating stripping method of the member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnesium alloy plated member which is easy to recycle, and to provide a method capable of reliably peeling a plating film from the member. SOLUTION: After an object to be plated made of a magnesium alloy is subjected to zinc substitution, copper cyanide plating and copper pyrophosphate plating are sequentially performed, and chromium plating is performed thereon.
The magnesium alloy plated member is electrolyzed in an alkaline solution to peel off a plating film from a surface layer of the member. [Effect] The chromium plating layer is securely formed in close contact with the lower layer, and a plating film having excellent corrosion resistance and durability is formed. This coating effectively prevents corrosion of the magnesium alloy member and improves recyclability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for plating a magnesium alloy member, a plated member obtained by the method, and a method for removing a plating film from the plated member.

[0002]

2. Description of the Related Art Magnesium alloy has a specific gravity of about 1.8 Mg.
And / m ^3, utility metals in most small, lightweight metallic material capable of comparable only plastic. Therefore, it is the most suitable material for portable electronic devices and transportation equipment members, and has been particularly noted in recent years. In addition, in terms of recycling, it has a feature that the burden on the global environment is smaller than that of plastic, and its practical application is progressing mainly in home electric appliances. Methods for mass-producing this magnesium alloy include a die casting method and a thixomolding method. The latter method is rapidly spreading from the viewpoint of worker safety and environmental friendliness. Regarding the surface treatment of these magnesium alloys, chemical conversion treatment and anodic oxidation are generally performed from the viewpoint of corrosion resistance, but metal plating is required to impart conductivity, thermal conductivity and wear resistance. Become. A conventional metal plating method for a magnesium alloy is basically to perform zinc substitution, copper plating of a cyanide bath, and electroless nickel plating after a predetermined pretreatment, and further, silver or gold plating,
Alternatively, a method of forming aluminum or the like by dry plating such as evaporation, sputtering, or ion plating is also known.

[0003]

However, the nickel coating formed on the outermost surface by the conventional plating method does not have sufficient corrosion resistance and deteriorates the corrosion resistance of the magnesium alloy material, making it difficult to recycle the magnesium alloy. There's a problem. In addition, other plating materials such as gold and silver are expensive as raw materials for a plating solution, and dry plating has a thickness of several microns, is inferior in abrasion resistance, requires a complicated process, and is expensive. There is. The present invention has been made to solve these problems, and to provide a relatively inexpensive plating method capable of obtaining metal plating with excellent recyclability, a plating member having the plating film, and a method of peeling the plating film. It was done.

[0004]

In order to solve the above-mentioned problems, a method for plating a magnesium alloy member according to the present invention comprises the steps of:
Copper cyanide bath plating and copper pyrophosphate plating are sequentially performed,
The chromium plating is performed on the upper layer.

[0005] A magnesium alloy plated member of the present invention is characterized in that a zinc substitution layer, a strike copper plated layer, an electrolytic plated layer and a hard chromium plated layer are sequentially formed on the surface of the alloy member.

Further, a first aspect of the method of stripping a magnesium alloy plated member of the present invention is to electrolyze a magnesium alloy plated member of the above invention in an alkaline solution to strip a plating film from a surface layer of the member. It is characterized by. The plating stripping method for a magnesium alloy plated member according to a second invention is the plating stripping method according to the first invention,
It is characterized in that a mechanical polishing step is included as a pretreatment for electrolysis.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, various magnesium alloy members can be used as an object to be plated, and their compositions, shapes, uses, and the like are not particularly limited. When plating the magnesium alloy member, a pretreatment is usually performed. As this pretreatment, as shown in FIGS. 1 and 2, mechanical polishing, degreasing, pickling,
Etching and activation processing are mentioned. Examples of the mechanical polishing include buff polishing and barrel polishing. This mechanical polishing is not particularly essential as a pretreatment, but it can effectively remove contaminants, so that the burden of subsequent degreasing treatment can be reduced as shown in FIG. In the subsequent degreasing, oxides and dirt on the surface of the alloy member are removed. In this degreasing, as shown in FIGS. 1 and 2, an organic solvent, an alkaline solution, or the like is used. In such degreasing, a method of immersing the alloy member or rubbing the member by applying a solution to a brush or the like is employed. In addition, as shown in FIG. 2, electrolytic degreasing can be performed using an alkaline solution or the like. The above-described degreasing may be performed by one method, or may be performed by combining a plurality of methods and performing degreasing in a plurality of steps.

After the degreasing, as shown in FIG. 1, pickling (acid treatment) can be performed if desired.
Alkali washing (alkali treatment) can also be performed for neutralization. In the case of the above-mentioned mechanical polishing, dirt is sufficiently removed, so that the acid washing (and the alkali washing) can be omitted.
After the above treatment, an etching treatment using an acidic bath is performed. However, in the case where electrolytic degreasing is performed, this etching treatment can be omitted by an electrolytic action (FIG. 2).

Thereafter, activation treatment is performed with an acidic solution containing fluorine ions for the purpose of removing oxides and the like.
After the activation treatment, a zinc substitution treatment is performed. In this treatment, a zinc plating layer is formed on the surface of the alloy member using a bath containing zinc sulfate, pyrophosphate or the like. Generally, an alkaline bath is used for the bath. In this process, the galvanized layer is formed in tight contact with the surface of the alloy member.

After the zinc substitution, the upper layer is subjected to copper plating in a cyanating bath. In this plating, electrolytic plating can be performed using a known cyanation bath. For example, plating is performed using a bath containing copper cyanide or sodium cyanide. The electrolysis conditions at the time of plating are not particularly limited as the present invention, and examples thereof include a current density of 4 to 6 A / dm ² . The thickness of the copper plating layer formed at this time is 2 to 6 μm.
It is desirable that Further, this upper layer is plated with copper pyrophosphate. In this pyrophosphate plating, electrolytic plating is performed using an electrolytic solution or the like containing copper pyrophosphate or potassium pyrophosphate. Although the above-mentioned electrolysis conditions are not particularly limited as the present invention like the above-mentioned copper plating of the cyanide bath, a current density in the range of ^{2 to} 6 A / dm ² can be exemplified. The thickness of the copper plating layer formed by electrolysis using this bath is desirably 6 to 13 μm. According to this copper pyrophosphate plating, a plated layer having no pinholes and having excellent adhesion can be obtained.

By forming these two copper plating layers, chrome plating can be applied directly to the upper layer. The chromium plating layer has excellent corrosion resistance, prevents corrosion of the magnesium alloy, and facilitates recycling. By polishing the chromium plating layer by buffing or the like, not only conductivity and abrasion resistance but also glossy decorative plating can be used. The magnesium alloy member plated according to the above has excellent conductivity, abrasion resistance, and thermal conductivity in addition to excellent corrosion resistance, and has excellent surface properties.

[0012] The magnesium alloy member obtained by the plating method of the present invention is used for recycling after use.
After removing dirt by polishing such as buffing if desired,
It is electrolyzed in an alkaline solution. Sodium carbonate or the like can be used as the alkaline liquid, and the electrolysis conditions at this time can be an electrolysis voltage of 2 to 8 V. This electrolysis reliably removes the copper and chromium plating from the magnesium alloy, making it possible to reuse the magnesium alloy. By performing the above-described polishing prior to the electrolysis, the plating layer can be more reliably separated by the electrolysis.

[0013]

An embodiment of the present invention will be described below. First A
The alloy material containing l, Zn, Mn and the balance magnesium is immersed in an organic solvent containing toluene for 2 to 8 minutes to degrease the solvent, and further immersed in an alkaline bath composed of sodium carbonate for 4 to 10 minutes. Degreased. Then, after performing an acid treatment in an acidic bath composed of phosphoric acid, an alkali treatment was performed in a sodium hydroxide bath. Next, the oxide film was removed (etched) using a chromic anhydride-based solution, and the surface of the material was activated using a phosphoric acid-based solution.

As another test material, buffing was performed using the same alloy material as above, followed by degreasing in the same alkaline bath as above, and etching and activation as above. . In this step, the step before activation was simplified by mechanical polishing compared to the test material, and the entire work time was reduced by about half. The surface properties were not different from those of the test materials.

Next, both test materials were zinc-substituted in an alkaline bath composed of sodium hydroxide, and copper plating was carried out in a cyanide bath containing cuprous cyanide under electrolysis conditions of 4 to 6 A / dm ^2. The layer was formed to a thickness of about 4 μm. Further, in the upper layer, in a pyrophosphate bath containing copper pyrophosphate,
Under electrolytic conditions of ^{2 to} 6 A / dm ² , the thick copper plating layer
m thickness. This upper layer was further subjected to electrolytic conditions of 10 to 40 A / dm ² in an acidic bath containing chromic anhydride.
And electrochromic plating was performed, and the surface was buffed and polished.

On the other hand, as a conventional method, a 4 μm-thick strike copper plating is applied to the test material which has been subjected to the above-mentioned activation treatment under electrolytic conditions of 4 to 6 A / dm ² using the same cyanation bath as above. The upper layer was subjected to electrolytic nickel plating having a thickness of 8 to 14 μm. As a comparative example, electrolytic chrome plating having a thickness of 1 to 3 μm was performed on the strike copper plating. However, in this comparative example, pits and pinholes were generated, and there was a problem of corrosion of the material surface.

The above-mentioned invention material and conventional material are described in JIS.
When a corrosion resistance test comprising H8502 was performed, the inventive material showed excellent corrosion resistance as shown below, whereas the conventional material was inferior in corrosion resistance. (Results of Corrosion Resistance Test) JIS H8502 Inventive material for 24 hours by neutral salt spray test. 9.5 or more Conventional material Rating No. 7.5 or more

Next, after buffing the above-mentioned invention material and the conventional material, they are subjected to electrolysis conditions of 2 to 8 V in an alkaline solution comprising sodium carbonate containing cyan and a chelating agent.
And the copper plating layer and the chromium plating layer were peeled off. When the surface of the test material after the plating film was removed was analyzed by an electron beam microanalyzer and Auger electron spectroscopy, neither chromium nor copper was detected in the invention material. On the other hand, in the conventional material, both nickel and copper were detected, and the material was corroded, and smut (oxide) could not be removed. Therefore, in the material of the present invention, no plating component remains on the material surface after the plating film is peeled off, and almost no impurities are mixed during recycling, and recycling can be performed easily. On the other hand, in the conventional material, it is apparent that recycling is not easy because of mixing of oxides and the like.

[0019]

As described above, according to the method of plating a magnesium alloy member of the present invention, after subjecting a plating object made of a magnesium alloy to zinc substitution, copper plating of a cyanide bath and copper pyrophosphate plating are performed. Since the chromium plating is performed successively and the chromium plating is performed on the upper layer, the chromium plating layer on the surface layer is formed in close contact with the lower layer without fail, and a plating film having excellent corrosion resistance and durability is formed.

Further, according to the magnesium alloy plated member of the present invention, since a zinc substitution layer, a strike copper plated layer, an electrolytic plated layer and a hard chromium plated layer are sequentially formed on the surface of the alloy member, the plated layer is more excellent. Corrosion resistance and excellent coating durability. According to the method for stripping a magnesium alloy plated member of the present invention, the plated member is electrolyzed in an alkaline solution to peel a plating film from a surface layer of the member, so that the plated layer is reliably separated from the member surface. In addition, since the obtained members are suppressed from being corroded, they can be easily recycled.

[Brief description of the drawings]

FIG. 1 is a process chart showing an embodiment of the present invention.

FIG. 2 is a process chart showing another embodiment.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C25F 1/00 C25F 1/00 (72) Inventor Isao Nakatsugawa 1-6, Funakoshiminami, Aki-ku, Hiroshima-shi, Hiroshima No. 1 Inside Japan Steel Works Co., Ltd. (72) Inventor Hidenori Takayasu 1-6-1, Funakoshi Minami, Aki-ku, Hiroshima City, Hiroshima Prefecture Inside Japan Steel Works Co., Ltd. (72) Inventor Hideki Yagi 62-1 Hamakata Furama, Hofu City Yamaguchi Prefecture China F-term (reference) in Eka Kogyo Co., Ltd.

Claims (4)

[Claims] 1. A magnesium alloy member, comprising: subjecting an object to be plated made of a magnesium alloy to zinc substitution; sequentially performing copper cyanide plating and copper pyrophosphate plating; and performing chromium plating on an upper layer thereof. Plating method 2. A magnesium alloy plating member, wherein a zinc substitution layer, a strike copper plating layer, an electrolytic plating layer and a hard chromium plating layer are sequentially formed on the surface of the alloy member. 3. A method for removing a plating of a magnesium alloy plating member, comprising: electrolyzing the magnesium alloy plating member according to claim 2 in an alkaline solution to remove a plating film from a surface layer of the member. 4. The method of claim 3, further comprising a mechanical polishing step as a pretreatment for the electrolysis.