JP4714945B2 - Manufacturing method of product made of magnesium or magnesium alloy - Google Patents

Description

The present invention relates to a method for producing a product made of magnesium or a magnesium alloy on which a metal plating film is formed. More specifically, the present invention relates to a method for producing a product made of magnesium or a magnesium alloy in which a metal plating film is directly formed on a conductive anodized film formed on the surface of magnesium or a magnesium alloy.

  Magnesium and magnesium alloys are lightest in practical metals, so they have high specific strength, good heat dissipation, and excellent recyclability compared to resins, so that they are widely used in recent years for electrical equipment and automotive parts. It has become to. Among them, it is suitably used as a casing for electrical equipment that has high performance requirements for reduction in size and weight, and has high requirements for design and recyclability. However, since magnesium and magnesium alloys are easily corroded, surface treatment or coating having corrosion resistance is required. At the same time, it is also desired to cover the surface of magnesium or magnesium alloy with another metal film having excellent appearance and hardness.

  Typical examples of the method of performing metal plating on the surface of magnesium or a magnesium alloy include “Dow method” and “Sakata method”. The “Dow method” is a method in which a complex pretreatment is applied to magnesium or a magnesium alloy, followed by a zinc substitution treatment (zincate treatment), and then strike plating using an aqueous copper cyanide solution. . The “Sakata method” is a method in which an electroless strike plating is performed using an aqueous solution of a nickel salt on magnesium or a magnesium alloy that has been subjected to a complicated pretreatment using an acidic aqueous solution or an alkaline aqueous solution.

  However, the plating film obtained by these plating methods still has insufficient corrosion resistance. This is considered to be because magnesium is most easily corroded among practical metals, and the corrosion resistance cannot be easily improved even after plating. In addition, until the plating film deposited during electrolysis covers the base material made of magnesium or a magnesium alloy, the base material is easily corroded, and it is difficult to obtain a plating film with good adhesion. . Furthermore, these plating methods are not widely used in general because complicated pretreatment may be required. Moreover, since the metal cyanide salt is used in the “Dow method”, it is not preferable from the viewpoint of protecting the surrounding environment and the working environment. In addition, fluoride salts are used by either the “Dow method” or the “Sakata method”. However, in general, when a fluorine ion is contained, waste liquid treatment is often difficult, which is not preferable. . In recent years when the demand for environmental protection has become strict, a plating process that does not use cyanide, fluoride, or the like is desired.

  On the other hand, excellent corrosion resistance can be imparted by anodizing the magnesium or magnesium alloy. As a typical prescription, an anodizing treatment by a prescription called “Dow17 method” or “HAE method” is generally performed, and thereby an anodized film having practically sufficient corrosion resistance can be formed. Also, Japanese Patent Publication No. 11-502567 (WO96 / 28591) (Patent Document 1) describes a method of anodic oxidation of magnesium or a magnesium alloy by immersing in an electrolyte containing ammonia and a phosphate compound. Has been.

  In addition, it is described in the following publication that a certain degree of corrosion resistance can be imparted by chemical conversion treatment of magnesium or a magnesium alloy, and a conductive film can be formed. Japanese Unexamined Patent Publication No. 2000-96255 (Patent Document 2) describes a chemical conversion film containing a certain amount of calcium, manganese, and phosphorus and having an electrical resistivity of 0.1 Ω · cm or less. JP 2000-328261 A (Patent Document 3) discloses that after etching the surface of a magnesium alloy with an acidic aqueous solution having a pH of 1 to 5, it is brought into contact with an alkaline aqueous solution having a pH of 7 to 14 containing an organic phosphorus compound. Subsequently, a surface treatment method of a magnesium alloy that is brought into contact with a chemical conversion treatment liquid is described, and it is described that a product having a small surface resistance value can be obtained.

  In various displays such as plasma displays and mobile phones, it is preferable that electromagnetic waves generated therefrom can be efficiently shielded. Since magnesium and a magnesium alloy have good electrical conductivity, the casing of an electric device using the same can have good electromagnetic shielding properties. Also, in many electrical devices, especially digital electronic devices, it is important to remove electromagnetic noise by grounding to prevent malfunctions. At this time, the casing is made of magnesium or magnesium alloy. If so, it is also possible to ground there.

  However, as described above, surface treatment or coating having corrosion resistance is required for magnesium and magnesium alloys. If magnesium or magnesium alloy is anodized to give corrosion resistance, the insulating film is covered with magnesium or magnesium alloy, and electromagnetic shielding properties are lost, and grounding is impossible. become. For this reason, for example, a method of masking the portion for grounding and then performing anodizing treatment, or anodizing the entire surface and then removing and removing a part of the anodized film has been adopted. However, such a method is complicated in operation and increases the production cost.

  On the other hand, as a film formed by chemical conversion treatment, a film having electrical conductivity has recently been reported, such as a film described in JP 2000-96255 A and JP 2000-328261 A, for example. . However, compared with an anodizing treatment in which a strong oxide film is formed by energizing magnesium or a magnesium alloy, a film formed by a chemical conversion treatment simply immersed in a treatment solution has insufficient corrosion resistance. This problem is particularly important in the case of mobile device casings and the like in recent years because corrosion resistance in various environments is required. For this reason, when a film is formed by chemical conversion treatment, the present situation is that a plurality of layers are further coated thereon to ensure corrosion resistance. However, it is not always easy to apply a uniform coating to a casing of an electric device having a complicated shape, and a cost increase is great if a plurality of coating steps are performed.

  Several attempts have been reported to apply metal plating on the anodized film. For example, in Japanese Patent Application Laid-Open No. 55-18540 (Patent Document 4), magnesium or a magnesium alloy is treated by a known anodic oxidation method to form a primary film, and then AC electrolysis is performed in an aqueous metal salt solution. A method for producing a secondary coating is described. However, in the examples, only the appearance of the obtained film is observed, and specific corrosion resistance evaluation and film composition analysis are not performed. As shown in a comparative example of the present specification shown later, it was difficult to form a metal plating film even when the present inventors tried to electroplate on an anodized film which is an insulating film.

  Japanese Patent Laid-Open No. 2001-152393 (Patent Document 5) discloses a first step of forming an oxide layer by anodizing the surface of a magnesium alloy, and applying a thermosetting resin coating on the oxide layer. A second step of forming a sealing resin layer, a third step of applying a conductive paint on the sealing resin layer to form a conductive resin layer, and a plating treatment on the conductive resin layer A method for anodizing a magnesium alloy comprising a fourth step is described. According to this method, conductivity is imparted by the conductive paint, and subsequent electroplating is possible. However, an operation for forming a plurality of resin layers is necessary after the anodizing treatment, which complicates the operation and increases the manufacturing cost. In addition, the applicant (Tanaka Sangyo Co., Ltd.) of the Japanese Patent Laid-Open No. 2001-152393 is the same as the applicant (Tanaka Sangyo Co., Ltd.) of the Japanese Patent Laid-Open No. 55-18540, which is a published publication 20 years ago. For this reason, it is presumed that a metal plating film having sufficient performance was not obtained by the method described in JP-A-55-18540.

Japanese National Patent Publication No. 11-502567 JP 2000-96255 A JP 2000-328261 A Japanese Patent Laid-Open No. 55-18540 JP 2001-152393 A

The present invention has been made to solve the above problems, in order to obtain a product consisting of corrosion resistance and adhesion excellent magnesium metal plating film is formed or a magnesium alloy, difficult to pollute the environment, And it aims at providing a low-cost manufacturing method.

The purpose is to immerse magnesium or a magnesium alloy in an electrolyte containing 0.1 to 1 mol / L of phosphate radicals , 0.2 to 5 mol / L of ammonia or ammonium ions, and having a pH of 8 to 14. Then, the surface was anodized and the surface was anodized to contain 10 to 65% by weight of magnesium element, 25 to 60% by weight of oxygen element and 4 to 30% by weight of phosphorus element. After obtaining a magnesium or magnesium alloy having an anodized film with a film thickness of 0.01 to 30 μm on the surface, the resistance value of the film surface measured between two terminals separated is 10 ⁶ Ω or less. Provided is a method for producing a product made of magnesium or a magnesium alloy, which is immersed and electroplated to form a metal plating film directly on the surface of the anodized film. It is achieved by. Since the anodized film formed on the surface of magnesium or magnesium alloy has conductivity, a metal plating film can be formed on the surface by electroplating. When the resistance value on the surface of the film is 10 ⁶ Ω or less, electroplating proceeds smoothly. When the film thickness of the anodized film is 0.01 to 30 μm, the balance between corrosion resistance and electrical conductivity is improved.

  Conventionally, a film obtained by anodizing magnesium or a magnesium alloy is a film mainly composed of an oxide and is an insulator. Rather, it was considered that the corrosion current did not flow through the base material made of magnesium or a magnesium alloy, and that the base material could be prevented from oxidative deterioration because it was an insulator. However, as a result of intensive studies by the present inventor, a film having sufficient electrical conductivity while being an anodized film was found. In addition, it has also been clarified that the excellent corrosion resistance that the anodized film has conventionally had is maintained as it is. As a result, it was possible to provide a product made of magnesium or a magnesium alloy in which a metal plating film was directly formed on the surface of the anodized film having excellent corrosion resistance. In particular, it is possible to provide a casing of an electric device that is excellent in electromagnetic shielding properties, grounding characteristics, and the like.

At this time, it is preferable that the resistance value between the base material made of magnesium or a magnesium alloy and the surface of the metal plating film is 10 ⁴ Ω or less. That the resistance value is 10 ⁴ Ω or less means that the conductivity of the anodic oxide film is not less than a certain value, and electroplating proceeds smoothly .

  In the present invention, the anodic oxide film is composed of a porous layer and a transition layer, and the transition layer is present between the substrate composed of magnesium or a magnesium alloy and the porous layer, and the magnesium content of the transition layer Shows an intermediate value between the magnesium content of the porous layer and the magnesium content of the base material, and the oxygen content of the transition layer is the oxygen content of the porous layer and the oxygen content of the base material It is preferable to show an intermediate value with respect to the content. By having such a transition layer, good conductivity and corrosion resistance can be obtained. The thickness of the transition layer is preferably 0.2 to 5 μm.

Further, the anodized film of the present invention exhibits excellent performance even if it does not contain a heavy metal element as contained in a conventional anodized film.

The metal plating film directly formed on the conductive anodic oxide film is preferably made of a metal selected from the group consisting of zinc, nickel, copper, gold, silver, and chromium, or an alloy of these metals. These metals or alloys can easily form an excellent metal plating film using an alkaline electroplating bath. The thickness of such a metal plating film is preferably 0.1 to 100 μm. Further, on the metal plating film, also preferably formed by forming more other metal plating film, in this case, it is possible to form various types of metal plating layer, depending on the application It is possible to obtain a metal surface having excellent decorativeness and wear resistance.

Preferred embodiments of the present invention, not covered the entire surface of the magnesium or magnesium alloy in the anodized film, not covered the entire surface of the anodized film in the metal plating film, and the surface of the metal plating film provide Reinforced resin coating only part of the Ru to expose the metal plating film of the remaining portion, it is a manufacturing method of the product. By providing an exposed portion of the anodized film in part in this way, it is possible to provide a product with a beautiful appearance and excellent friction resistance by resin coating while ensuring electromagnetic shielding and grounding characteristics It is. Specifically, the product is, in the case inside surface not subjected to resin coating, it is outside the casing surface is a housing for electrical equipment in the resin coating was subjected to a particularly preferred embodiment.

In the production method of the present invention, it is preferable to immerse magnesium or a magnesium alloy in an acidic aqueous solution before anodic oxidation, and then anodic oxidation by immersing in an electrolytic solution. An anodized film having conductivity is easily obtained by subjecting it to an anodizing treatment after appropriate pretreatment.

It is preferable to immerse the surface of the anodic oxide film in an acidic aqueous solution in advance and then perform electroplating by immersing in the plating bath. By doing so, the adhesion between the anodized film and the metal plating film is improved. Moreover, it is also preferable that pH of the said plating bath is 7-14.5. When the pH of the plating bath is in the neutral to alkaline range, the anodic oxide film can be prevented from being eroded by the acid. After forming the metal plating film, it is also preferable that the surface of the metal plating film is further covered with another metal plating film by immersing in another plating bath. In this case, it is possible to employ various plating conditions and form various metal films depending on the purpose.

To obtain a product consisting of corrosion resistance and adhesion excellent magnesium or magnesium alloy metal plating film is formed can provide a suitable manufacturing method.

About the sample in which the anodized film was formed, the cross section of the film was observed with an X-ray microanalyzer, and a photograph showing the cross-sectional shape and a photograph showing the distribution of each element were synthesized. It is the photograph which observed the cross section of the film | membrane with the X-ray microanalyzer about the sample which gave the zinc plating on the anodic oxide film, and showed the cross-sectional shape. It is the photograph which observed the cross section of the film | membrane with the X-ray microanalyzer about the sample which gave the zinc plating on the anodic oxide film, and showed the distribution condition of the magnesium element. It is the photograph which observed the cross section of the film | membrane with the X-ray microanalyzer about the sample which gave galvanization on the anodic oxide film, and showed the distribution condition of the oxygen element. It is the photograph which observed the coating | coated cross section about the sample which gave the galvanization on the anodic oxide film with the X-ray microanalyzer, and showed the distribution condition of the zinc element. For a sample obtained by galvanizing on an anodized film, the cross section of the film was observed with an X-ray microanalyzer, and a photograph showing the cross-sectional shape and a photograph showing the distribution of each element were synthesized. It is the figure which showed the measuring method of the resistance value between a magnesium alloy base material and the surface of a metal plating film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnesium alloy base material 2 Anodizing film 3 Metal plating film 4 Measuring terminal 5 Resistance measuring device

Hereinafter, the present invention will be described in detail. The present invention is a method for producing a product made of magnesium or a magnesium alloy in which a metal plating film is directly formed on a conductive anodized film formed on the surface of magnesium or a magnesium alloy.

  Magnesium or a magnesium alloy used as a raw material may be one containing magnesium as a main component, and may be a metal made of magnesium alone or an alloy. Usually, a magnesium alloy is preferably used to impart formability, mechanical strength, ductility, and the like. Examples of magnesium alloys include Mg-Al alloys, Mg-Al-Zn alloys, Mg-Al-Mn alloys, Mg-Zn-Zr alloys, Mg-rare earth elements alloys, Mg-Zn-rare earth elements alloys. Etc. In the examples of the present invention, an Mg—Al—Zn alloy was used, and the obtained anodic oxide film contained an aluminum element. Therefore, it is presumed that the magnesium alloy as the raw material is preferably one containing aluminum among the above-mentioned various alloys.

  The form of magnesium or magnesium alloy used for the anodizing treatment is not particularly limited. A molded product formed by a die casting method, a thixo mold method, a press molding method, a forging method, or the like can be used. At the time of molding, the mold release agent may remain inside the ridges or hollow portions formed near the surface of the molded product. In the case of anodizing, it is easy to reduce the remaining release agent compared to the case of chemical conversion. The release agent remaining in the product volatilizes when heated, and may cause swelling in the resin coating. Here, as a mold release agent used at the time of shaping | molding, the mold release agent which consists of a silicone compound is typical.

  Since a molded product made of magnesium or a magnesium alloy may have dirt on its surface due to organic substances such as a release agent attached during molding, it is preferable to perform a degreasing treatment. As the liquid for degreasing, an aqueous solution containing a surfactant or a chelating agent is preferably used.

  After degreasing as necessary, it is preferable to immerse in an acidic aqueous solution and then immerse in an electrolytic solution to perform anodization. By dipping in an acidic aqueous solution, the surface of magnesium or a magnesium alloy can be appropriately etched to remove an already formed insufficient oxide film and remaining organic contaminants. Although it does not specifically limit as acidic aqueous solution, Phosphoric acid aqueous solution has moderate acidity, and is suitable. When a phosphoric acid aqueous solution is used, magnesium phosphate may be formed on the surface simultaneously with etching. In addition, a degreasing treatment can be performed simultaneously by mixing a surfactant or a chelating agent with an acidic aqueous solution.

  It is also preferable that after the treatment with the acidic aqueous solution, the anodic oxidation treatment is performed after washing with an alkaline aqueous solution. Since a component (smut) that is insoluble in an acidic aqueous solution may adhere to the surface of magnesium or a magnesium alloy, it can be removed. As the alkaline aqueous solution, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferably used.

  After each treatment step such as the degreasing treatment, the acidic aqueous solution treatment, and the alkaline aqueous solution treatment, washing and drying may be performed as necessary. In this way, magnesium or a magnesium alloy that has been pretreated as necessary is immersed in the electrolytic solution and anodized.

  The electrolytic solution used for the anodizing treatment is preferably an alkaline aqueous solution containing phosphate groups, and more specifically, an aqueous solution containing 0.1 to 1 mol / L of phosphate groups and having a pH of 8 to 14. Is preferred. By containing an appropriate amount of phosphate group, an appropriate amount of phosphorus element is included in the anodic oxide film. Moreover, unnecessary elution of magnesium or a magnesium alloy can be prevented by making it alkaline.

  The phosphate group here is one included in the electrolyte as free phosphoric acid, phosphate, hydrogen phosphate, or dihydrogen phosphate. In addition, in the case of polyphosphoric acid obtained by condensation of phosphoric acid or a salt thereof, it is assumed that the phosphoric acid radicals are contained by the number of phosphate radicals obtained by hydrolysis thereof. In the case of a salt, it may be a metal salt or a non-metallic salt such as an ammonium salt. The phosphate group content is preferably 0.1 to 1 mol / L. More preferably, it is 0.15 mol / L or more, and further preferably 0.2 mol / L or more. Further, it is more preferably 0.7 mol / L or less, and further preferably 0.5 mol / L or less.

  The pH of the electrolytic solution is preferably 8-14. More preferably, the pH is 9 or more, and even more preferably 10 or more. Further, the pH is more preferably 13 or less, and even more preferably 12 or less.

  Moreover, it is preferable that electrolyte solution contains 0.2-5 mol / L of ammonia or ammonium ion as those total amounts. As a result, the pH of the electrolytic solution is maintained at an appropriate alkalinity. The content of ammonia or ammonium ions is more preferably 0.5 mol / L or more, and even more preferably 1 mol / L or more. Further, it is more preferably 3 mol / L or less, and further preferably 2 mol / L or less.

  The electrolytic solution used in the anodizing treatment may contain other components as long as the effects of the present invention are not impaired, but preferably does not substantially contain heavy metal elements. Here, the heavy metal element means a metal element having a specific gravity of more than 4 as a simple substance, and chromium, manganese and the like are exemplified as those contained in a typical electrolyte solution in a conventional anodizing treatment. In particular, it is preferable not to contain harmful chromium which has strict emission regulations. It is not usually a problem that a heavy metal contained in the magnesium alloy, for example, zinc, is dissolved in a trace amount and contained in the electrolytic solution. It is also preferable that the electrolytic solution of the present invention does not contain a fluorine element. This is because an aqueous solution containing elemental fluorine often becomes difficult to treat wastewater.

  Anodizing treatment is performed by immersing pretreated magnesium or a magnesium alloy in the electrolytic solution as necessary, and energizing it as an anode. The power source to be used is not particularly limited, and either a DC power source or an AC power source can be used, but it is preferable to use a DC power source. Further, when using a DC power supply, either a constant current power supply or a constant voltage power supply may be used, but it is preferable to use a constant current power supply. A cathode material is not specifically limited, For example, a stainless steel material etc. can be used conveniently. The surface area of the cathode is preferably larger than the surface area of magnesium or magnesium alloy to be anodized, more preferably 2 times or more, and usually 10 times or less.

The current density of the anode surface when using a constant-current power supply as a power source is usually 0.1 to 10 A / dm ^2. Preferably it is 0.2 A / dm ² or more, more preferably 0.5 A / dm ² or more. Further, it is preferably 6 A / dm ² or less, and more preferably 3 A / dm ² or less. The energization time is usually 10 to 1000 seconds. Preferably it is 50 seconds or more, more preferably 100 seconds or more. Further, it is preferably 700 seconds or shorter, and more preferably 500 seconds or shorter. When energizing with a constant current power supply, although the applied voltage at the start of energization is low, the applied voltage increases with time. The applied voltage at the end of energization is usually 50 to 600 volts. Preferably it is 200 volts or more, more preferably 250 volts or more. Further, it is preferably 500 volts or less, and more preferably 400 volts or less. In the “Dow 17 method” and “HAE method” that are conventional anodizing methods, the applied voltage is often set to less than 100 volts, whereas in the present anodizing method, a relatively high voltage is set. It is preferable to set. As a result, the oxidation reaction easily proceeds even in a portion containing impurities such as a silicone release agent, and a film having good conductivity is easily formed on the entire surface of the magnesium or magnesium alloy. Moreover, since oxygen gas is actively generated from the surface of magnesium or a magnesium alloy with the oxidation reaction, the impurities are easily removed during the anodic oxidation treatment. The temperature of the electrolytic solution during energization is usually 5 to 70 ° C. It is preferably 10 ° C or higher. Moreover, it is 50 degrees C or less suitably, More preferably, it is 30 degrees C or less.

  After the energization is finished, the electrolytic solution adhering to the surface of the anodized film is removed by washing. In the cleaning, it is preferable to use not only water but also an acidic aqueous solution. Since the electrolytic solution is alkaline, the adhesion of the coating film is improved when resin coating is performed by washing with an acidic aqueous solution. As the acidic aqueous solution, nitric acid aqueous solution, hydrochloric acid aqueous solution, sulfuric acid aqueous solution and the like can be used. After the washing operation, it is dried. In this way, an anodized film is formed on the surface of magnesium or magnesium alloy.

The magnesium or magnesium alloy thus obtained has a conductive anodic oxide film on the surface whose resistance value on the film surface measured between two terminals 10 mm apart from each other is 10 ⁶ Ω or less. The resistance value is a resistance value (Ω) measured by pressing a terminal against two arbitrary points 10 mm apart from each other on the surface of the anodized film. Since the resistance value of the base material made of magnesium or magnesium alloy is small, the electrical resistance in the thickness direction of the anodized film that exists between the measurement terminal and the base material made of magnesium or magnesium alloy is substantially A value that correlates to is measured. Thus, it becomes possible to form the electroplating film | membrane excellent in adhesiveness on the surface of an anodized film by having electroconductivity. In addition, the resistance value is a preferable value from the viewpoint of electromagnetic shielding properties and grounding characteristics. The resistance value is preferably 10 ⁵ Ω or less, and more preferably 10 ⁴ Ω or less. On the other hand, if the resistance value is too low, the corrosion resistance of the product may be lowered, and is preferably 0.1Ω or more, more preferably 0.2Ω or more. In addition, the resistance value of the surface of the molded article which consists of magnesium or magnesium alloy which is not surface-treated is a value of less than 0.1Ω in the case of AZ91D.

  As shown in FIG. 1, the anodic oxide film obtained by the present invention often has a large number of holes on the surface which are considered to be derived from sparks during energization. This is different from the chemical conversion coating. The film thickness of the anodized film is preferably 0.01 to 30 μm. More preferably, it is 0.1 μm or more, more preferably 1 μm or more, and most preferably 5 μm or more. Further, it is more preferably 20 μm or less, and further preferably 15 μm or less. The thicker the anodic oxide film, the better the corrosion resistance. However, if it is too thick, the electrical conductivity is lowered, which may make the electroplating difficult and increase the production cost.

  The chemical composition of the anodic oxide film formed in the present invention is not particularly limited, but a composition containing 10 to 65% by weight of magnesium element and 25 to 60% by weight of oxygen element is suitable. That is, it is preferable to contain oxidized magnesium, which is a product resulting from anodization of magnesium or a magnesium alloy, as a constituent component. The content of magnesium element is more preferably 15% by weight or more, and further preferably 18% by weight or more. Further, it is more preferably 45% by weight or less, and further preferably 30% by weight or less. The content of oxygen element is more preferably 40% by weight or more. Moreover, it is 55 weight% or less more suitably.

  It is preferable that the anodized film contains 4 to 30% by weight of phosphorus element. The phosphorus element content is more preferably 10% by weight or more, and even more preferably 15% by weight or more. Further, it is more preferably 25% by weight or less. It is also preferable to contain 1 to 20% by weight of aluminum element. The content of aluminum element is more preferably 2% by weight or more. Moreover, it is 10 weight% or less more suitably, More preferably, it is 5 weight% or less. It can be presumed that by containing an appropriate amount of the above-mentioned elements other than magnesium and oxygen, it has good electrical conductivity without impairing corrosion resistance. The anodized film of the present invention may contain elements other than those described above as long as the effects of the present invention are not impaired. However, it is preferable that substantially no heavy metals, particularly chromium elements, are contained except for those originally contained in the raw material magnesium alloy. Moreover, it is preferable not to contain a fluorine element substantially.

  The anodic oxide film does not necessarily have a uniform structure as a whole, and has a porous layer and a transition layer, as will be described later. Further, it has been recognized that the thinner the film thickness, the larger the content of magnesium and the smaller the content of phosphorus element in the whole film. However, since the magnesium element contained in the base material made of magnesium or a magnesium alloy may be picked up as noise when the film thickness becomes small, the measured value indicates that the magnesium content is larger than the actual chemical composition of the film. May be.

  The anodic oxide film formed here has a porous structure having a large number of irregularities on the surface, but the entire surface of the substrate is present at the interface with the substrate made of magnesium or magnesium alloy. A transition layer is formed so as to uniformly cover (see FIG. 1). The transition layer has an intermediate chemical composition that is different from the porous layer and the base material made of magnesium or a magnesium alloy. The transition layer has a lower magnesium content than the substrate but more than the porous layer, and the transition layer has a higher oxygen content than the substrate but less than the porous layer. That is, the transition layer is a homogeneous layer that is less oxidized and does not have a pore structure compared to a porous layer that occupies most of the thickness of the entire anodized film. The presence of this transition layer is considered to have a great influence on conductivity and corrosion resistance. The thickness of the transition layer is preferably 0.2 to 5 μm. The thickness of the transition layer is more preferably 0.5 μm or more, and even more preferably 1 μm or more. On the other hand, the thickness of the transition layer is more preferably 3 μm or less.

  A metal plating film is formed on the anodized film thus formed. Since the anodized film obtained by the present invention has conductivity, a metal plating film can be directly formed on the anodized film by electroplating.

  Before immersing magnesium or a magnesium alloy having an anodized film in a plating bath, it is preferable to immerse in an acidic aqueous solution in advance. By immersing in an acidic aqueous solution, the surface of the anodized film can be appropriately etched to activate the surface. Thereby, while being able to improve the adhesiveness of a metal plating film, the electrical conductivity between a metal plating film and the base material which consists of magnesium or a magnesium alloy can be improved. Although it does not specifically limit as acidic aqueous solution, The dilute aqueous solution of strong acids, such as nitric acid, hydrochloric acid, and a sulfuric acid, is used suitably. Then, after performing water washing and a drying process as needed, it uses for electroplating. Moreover, you may perform surface treatment other than the method of immersing in acidic aqueous solution.

  If necessary, magnesium or a magnesium alloy having an anodized film that has been treated in advance is immersed in a plating bath. The composition of the plating bath used in the present invention is not particularly limited as long as it is an aqueous solution in which a metal that can be precipitated by energization is dissolved as ions. The metal forming the film is not particularly limited, but is preferably a metal selected from the group consisting of zinc, nickel, copper, gold, silver, and chromium, or an alloy of these metals. This is because these metals or alloys are easy to form a good metal plating film using an alkaline electroplating bath.

As a plating bath used in the present invention, a plating bath generally used as an electroplating bath can be employed. However, in order to prevent the anodic oxide film from eluting, it is preferable that the pH of the plating bath is 7 to 14.5. When the pH of the plating bath is in the range from neutral to alkaline, it is possible to prevent the anodic oxide film containing magnesium oxide from being eroded by acid. A more preferable pH of the plating bath is 8 or more and 14 or less. The plating bath may contain other components as long as the effects of the present invention are not impaired, but preferably does not contain cyanide or fluoride. This is because cyanide is highly toxic and easily adversely affects the surrounding environment and work environment, and an aqueous solution containing fluoride often makes it difficult to treat wastewater.

A metal plating film is formed by immersing magnesium or a magnesium alloy having an anodized film on the surface in the plating bath and energizing the magnesium or the magnesium alloy as a cathode. The power source to be used is not particularly limited, and either a DC power source or an AC power source can be used, but it is preferable to use a DC power source. Further, when using a DC power supply, either a constant current power supply or a constant voltage power supply may be used, but it is preferable to use a constant current power supply. The anode material is not particularly limited, and the same metal as the plating film to be formed, platinum, titanium, or the like can be suitably used. The current density of the cathode surface when using a constant current power supply as a power source is usually 0.1 to 10 A / dm ² about. The energization time is usually about 10 to 1000 seconds. The temperature of the electrolytic solution during energization is usually 5 to 70 ° C. By washing after the end of energization, the plating solution adhering to the surface of the metal plating film is removed by washing and dried to obtain a product made of magnesium or a magnesium alloy having the metal plating film on the surface.

  The metal plating film is formed so as to cover the surface of the anodized film. At this time, the surface of the anodized film is considerably eroded and a metal plating layer is formed thereon. It is considered that the surface of the anodized film is eroded when a part of the anodized film is shaved when it is preliminarily immersed in an acidic aqueous solution after anodizing treatment or when metal plating is performed. As described above, since the anodized film has a porous structure with the surface cut off, the metal plating film bites into the pores on the surface of the anodized film and has good adhesion. Layers can be formed (see FIGS. 2-6). At this time, as described above, since the surface of the anodized film is considerably eroded, there is a place where the metal plating film is in contact with or close to the above-described transition layer. For this reason, it is estimated that favorable electroconductivity is ensured through the part. The transition layer is not particularly eroded even when the metal plating treatment is performed. Therefore, it is assumed that the transition layer contributes to the provision of corrosion resistance while ensuring the conductivity between the metal plating layer and the base material made of magnesium or a magnesium alloy.

  The thickness of the metal plating film formed on the surface of the product of the present invention is preferably 0.1 to 100 μm. The thickness of the metal plating film is more preferably 1 μm or more. Further, it is more preferably 50 μm or less. The thickness of the metal plating film is appropriately adjusted depending on the type of metal to be plated and the use.

In the product of the present invention thus obtained, it is preferable that the resistance value between the substrate made of magnesium or a magnesium alloy and the surface of the metal plating film is 10 ⁴ Ω or less. That the resistance value is 10 ⁴ Ω or less means that the conductivity of the anodic oxide film is not less than a certain value, and electroplating proceeds smoothly. In particular, the transition layer in the anodized film has sufficient conductivity. The resistance value between the base material made of magnesium or a magnesium alloy and the surface of the metal plating film is measured by pressing a measuring terminal against both of them. Specifically, as shown in FIG. 7, the film on the back side of the product is shaved to expose the magnesium or magnesium alloy, and the resistance value may be measured between the metal plating film on the front side of the product. Although it is affected by the form of the product, it is possible to grasp the rough resistance value. In the case where a plurality of metal plating layers are provided as will be described later, the measurement may be performed by applying a terminal to the outermost surface of the metal plating layer. Moreover, when resin coating is provided as described later, the resin coating may be removed to expose the metal plating layer, and the measurement may be performed by applying a terminal to the surface. Here, the resistance value is more preferably 10 ² Ω or less, further preferably 10 Ω or less, and most preferably ² Ω or less. On the other hand, when the said resistance value is too small, there exists a possibility that corrosion resistance may become inadequate, and it is 10 ^<-2 > (ohm) or more suitably.

The product of the present invention can be used as it is, but after forming a metal plating film (lower layer), the product is further immersed in another plating bath to make the surface of the metal plating film another metal plating film (upper layer). ) Is also preferable. In the case of plating on the anodized film, there are significant restrictions on the bath composition, such as the pH of the plating bath, and the choice of plating prescription is not necessarily wide. On the other hand, once a metal plating film (lower layer) is formed, it is easy to form various other plating films (upper layers) according to the application.

  As such other plating film (upper layer), all kinds of various films that can be applied by electroplating or electroless plating such as gold, silver, copper, nickel, chromium and other metals or their alloys are formed. Is possible. Further, another plating film may be stacked. The thickness of these other plating films is not particularly limited, and is usually about 1 to 100 μm. As a result, it is possible to form a plating film having performance according to the purpose, such as gloss, smoothness, hardness, and conductivity. For example, it is possible to form a highly decorative mirror surface.

  The use of the product made of magnesium or magnesium alloy of the present invention having a metal plating film on the surface is not particularly limited, and can be used for various electrical equipment, automotive parts, leisure parts, welfare care equipment parts, etc. . In use, the surface of the anodized film may be overcoated as necessary. However, in order to take advantage of the characteristics of the anodized film of the present invention having good electrical conductivity, the entire product is an insulating film. It is preferable not to cover with the coating consisting of.

  The paint used is not particularly limited, and various kinds of paint used for painting a metal surface can be used. A resin coating film can be formed using a solvent-type paint, a water-based paint, a powder paint, or the like. Although it may be a thermosetting paint that requires high-temperature baking after coating, it may be a paint that only needs to volatilize the solvent and water at a relatively low temperature, but the latter, which is easy to operate, is preferably used. In order to make the appearance beautiful, it is preferable to use a transparent resin paint, and an appropriately colored one may be used. The coating method is not particularly limited, and a known method such as spray coating, immersion coating, electrodeposition coating, powder coating, or the like can be employed. In a product made of magnesium or a magnesium alloy of the present invention that preferably has a part that does not have a coating film, powder coating by spray coating or thermal spraying is suitably employed.

  In a preferred embodiment of the present invention, the entire surface of magnesium or a magnesium alloy is covered with an anodized film, the entire surface of the anodized film is covered with the metal plating film, and the surface of the metal plating film is This is a product in which resin coating is applied to only a part and the remaining part of the metal plating film is exposed. Thus, the corrosion resistance of the whole product can be ensured by covering the whole surface of magnesium or magnesium alloy with the anodized film. Moreover, performance, such as hardness, can be provided because the whole surface of the said anodized film is covered with a metal plating film. However, the term “all” used herein means substantially all, and there may be a slight portion where no film is formed, such as a contact portion that is electrically connected to a power source during anodizing treatment or electroplating. . In addition, the resin coating is applied to only a part of the surface of the metal plating film, and the remaining part of the metal plating film is exposed. In addition, it is possible to provide a product with excellent friction resistance.

  A particularly preferred embodiment is that the inner surface of the housing is not coated with resin, and the outer surface of the housing is coated with resin on the outer surface of the housing, which is a housing of an electric device. Not only can the appearance be beautiful, but also damage during use can be prevented. On the other hand, since the conductive metal plating film is exposed on the inner surface of the housing, grounding from the electrical wiring can be easily ensured, and electromagnetic waves from the electronic circuit inside the housing can be effectively shielded. it can.

  The product comprising the magnesium or magnesium alloy of the present invention thus obtained is excellent in lightness, strength, conductivity, etc., and can be used for various applications. Mobile phone, personal computer, video camera, still camera, optical disc player, display (CRT, plasma, liquid crystal), housing of electrical equipment such as projectors, automobile parts, leisure parts such as fishing gear, welfare care equipment parts, etc. Can be used for

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these. The test method in this example was performed according to the following method.

(1) Cross-sectional shape observation of anodic oxide film and metal plating film The test piece was cut into a size of 5 mm × 10 mm, embedded in an epoxy resin, and then the cut surface was polished to obtain a mirror surface. An electron micrograph was taken from the cross-sectional direction of the sample using an X-ray microanalyzer “JXA-8900” manufactured by JEOL Ltd. At this time, the state of distribution in the film cross section for each element was also photographed. Moreover, the film thickness of each film | membrane was measured from this electron micrograph.

(2) Chemical composition analysis of anodized film The film composition was analyzed from the cross-sectional direction of the film using an X-ray microanalyzer “JXA-8900” manufactured by JEOL Ltd. Measurements were taken at two locations for each sample. The measurement was performed under the conditions of an acceleration voltage of 15 kV and a sample irradiation current of 2 × 10 ⁻⁸ A. Data analysis was performed with ZAH correction.

(3) Measurement of resistance value on the surface of the anodic oxide film Using a low resistivity meter “Lorestar AP MCP-T400” manufactured by Mitsubishi Chemical Corporation, measurement was performed using a two-probe probe “MCP-TP01”. The resistance value (Ω) was measured by pressing the measurement terminal against the surface of the anodized film at the center of the test piece. The probe has measuring terminals arranged at intervals of 10 mm, the terminal is gold-plated beryllium alloy, the tip shape is a cylindrical shape with a diameter of 2 mm, and the load pressing the terminal against the surface of the anodized film is It is 240 g per terminal.

(4) Measurement of resistance value between the magnesium alloy substrate and the surface of the metal plating film As shown in FIG. 7, the metal plating film 3 and the anodized film 2 on the back surface of the sample are shaved to expose the magnesium alloy substrate 1. The measurement terminal 4 was brought into contact with the exposed surface and the surface of the metal plating film 3 on the opposite side, and the resistance value was measured. The resistance value measuring device 5 is a digital multimeter “R6341B” manufactured by Advantest Corporation.

(5) Evaluation of corrosion resistance After applying acrylic clear coating on the surface of the sample on which the metal plating film was formed, a cross-shaped cut (cross) was made on the surface of the test piece so as to penetrate the resin film and the anodized film. Cut), a 5% salt spray test was conducted in accordance with JIS Z2371. The time when the swelling due to corrosion of the cross cut portion reached 1 mm or more was defined as the corrosion occurrence time.

(6) Evaluation of adhesion of plating film A tape peeling test based on JIS H8504 was performed, and the presence or absence of peeling and swelling of the plating film was observed. Here, the observation results were classified and evaluated as follows.
A: There was no peeling or swelling of the plating film.
B: Peeling or swelling of the plating film partially occurred.
C: Peeling or swelling of the plating film occurred remarkably.

Example 1
ASTM No. consisting of 90% magnesium, 9% aluminum and 1% zinc. An alloy plate having a size of 170 mm × 50 mm × 2 mm manufactured by a thixomold method using a magnesium alloy of AZ91D as a raw material was used as a test piece. The test piece was immersed in an acidic aqueous solution containing 2.2% by weight of phosphoric acid and a small amount of surfactant, and then washed with ion-exchanged water. Subsequently, the test piece surface was pretreated by immersing in an alkaline aqueous solution containing 18% by weight of sodium hydroxide and then washing with ion-exchanged water.

An aqueous solution of phosphoric acid and aqueous ammonia were mixed to prepare an electrolyte solution containing 0.25 mol / L of phosphate groups and 1.5 mol / L of ammonia or ammonium ions in the total amount, and kept at 20 ° C. The electrolyte had a pH of 11. The magnesium alloy test piece subjected to the pretreatment was immersed in this as an anode, and anodizing treatment was performed. As the cathode at this time, a SUS316L plate having a surface area four times that of the anode was used. In order to obtain four types of anodic oxide films, a constant current power source was used, and the current density on the anode surface was 1 A / dm ² , for about 60 seconds, about 150 seconds, about 200 seconds, or about Energized for 400 seconds. Although the applied voltage was low at the start of energization, it increased to about 200 volts, about 250 volts, about 300 volts, or about 350 volts at the end of energization, respectively. After the energization, the ion-exchanged water, nitric acid aqueous solution, and ion-exchanged water were washed in this order and then dried. As a result, an anodized film having a thickness of 1 μm, 3 μm, 5 μm, or 10 μm was formed. The film thickness referred to here is an average distance from the surface of the anodized film to the magnesium alloy surface of the base material in a film having local film thickness unevenness due to a large number of holes.

  FIG. 1 shows the result of observing the cross section of the film with an X-ray microanalyzer for a sample in which the anodized film was formed to a thickness of 10 μm. The photograph on the upper left (described as “SL”) is an electron micrograph observing the cross-sectional shape. About 1/3 below the photograph is a magnesium alloy substrate, about 1/3 the center is an anodized film, and about 1/3 above is an epoxy resin used for embedding treatment. As can be seen from the photograph, in the anodized film, the presence of a large number of holes thought to be derived from sparks during energization was observed on the surface of the anodized film.

  Upper center photo (described as “Mg”), upper right photo (described as “O”), lower left photo (described as “Al”), lower central photo (described as “P”), and lower right photo (Denoted as “Zn”) indicates the distribution of magnesium (Mg), oxygen (O), aluminum (Al), phosphorus (P) and zinc (Zn), respectively. In these figures, the density distribution originally shown by color display is attached to the present specification in black and white display. The right side of FIG. 1 shows a color bar, and it should be noted that the brightness and the element concentration are not always proportional in monochrome display.

  According to these figures, it can be seen that the anodic oxide film is composed of a porous layer occupying most of the anodic oxide film and a transition layer existing between the porous layer and the magnesium alloy substrate. The porous layer contains magnesium, oxygen, aluminum, and phosphorus, and has large and small pores. Further, the oxygen concentration of the transition layer is lower than the oxygen concentration of the porous layer and higher than the oxygen concentration of the magnesium alloy base material. The magnesium concentration of the transition layer is higher than the magnesium concentration of the porous layer and lower than the magnesium concentration of the magnesium alloy substrate.

  According to the oxygen (O) concentration distribution at the upper right in FIG. 1, it can be seen that oxygen is not substantially present in the magnesium alloy substrate and is present in the porous layer. And the bright strip-shaped part which exists between a porous layer and a magnesium alloy base material is a transition layer, The part contains oxygen of the intermediate | middle quantity of both of the said. Further, according to the magnesium (Mg) concentration distribution at the center, magnesium is present at a high concentration in the magnesium alloy substrate, and at a lower concentration in the porous layer. And the bright strip-shaped part which exists between a porous layer and a base material is a transition layer, and the part contains the intermediate amount of magnesium of the both. In the color photograph, it was confirmed that even in the transition layer, the portion close to the magnesium alloy substrate was relatively large in magnesium, and the portion close to the porous layer was relatively small in magnesium. That is, it is recognized that the concentration gradually changes even inside the transition layer. The thickness of the transition layer in FIG. 1 is about 2 μm and is formed with a relatively uniform layer thickness regardless of location. Moreover, no pore structure is observed in the transition layer, and it can be seen that a homogeneous layer covers the magnesium alloy substrate.

  About the sample of the thickness of 5 micrometers and 10 micrometers of the obtained anodic oxide film, the film | membrane composition was analyzed from the cross-sectional direction of the film | membrane using the X-ray microanalyzer. The results are shown in Table 1. The resistance values on the surface of the anodized film were 0.1Ω, 0.4Ω, 10Ω, and 1000Ω for the anodized films having film thicknesses of 1, 3, 5, and 10 μm, respectively. Moreover, the naked corrosion resistance (rating number 9.0) in the salt spray test (based on JIS Z2371) was 150, 300, 700, and 1500 hours, respectively. Here, the rating number 9.0 means that the ratio of the corroded area to the total area is 0.07 to 0.10%, and the above time is required until the ratio of such corroded area is reached. Shows time. That is, it can be seen that the thicker the anodic oxide film, the higher the surface resistance value, but the better the corrosion resistance. As will be described later, even if the surface resistance value becomes 1000Ω with a film thickness of 10 μm, electroplating is sufficiently possible. From the viewpoint of corrosion resistance, it is preferable that the film thickness of the anodized film is thicker. .

  The obtained sample on which the anodized film was formed was immersed in a 0.1% nitric acid aqueous solution, washed with water, and electroplated so as to have an average plating thickness of 5 μm. “NZ-65” manufactured by Dipsol Co., Ltd. was used as the plating solution for zinc plating. This is to prepare and use raw materials as shown in Table 2. As the zinc-nickel alloy plating solution, “IZ-250” manufactured by Dipsol Co., Ltd. was used. This is also prepared by using raw materials as shown in Table 2, and a film having a nickel eutectoid rate of 12 to 18% is obtained. For copper plating, “Pyrobright PY-61” manufactured by Uemura Kogyo Co., Ltd. was used. This is mainly composed of copper pyrophosphate. All of these are alkaline plating solutions containing no cyanide or fluoride. In any case, a good metal plating film could be formed with a film thickness of 5 μm. Details of the composition of the plating solution and the plating conditions are summarized in Table 2 below.

  Among the obtained samples, the resistance value between the magnesium alloy substrate and the surface of the zinc film was measured according to the method shown in FIG. 7 for the sample in which the zinc film was formed on the anodized film. In any case where the thickness of the anodized film was 1 μm, 3 μm, 5 μm, and 10 μm, the resistance value was within the range of 1 to 1.5Ω, indicating good conductivity. That is, it was shown that the resistance value in the film thickness direction of the anodized film formed in the present invention is small. At this time, even if the thickness of the anodized film changed, the resistance value did not change much. Moreover, when the resistance value between the magnesium alloy substrate and the surface of the copper film was measured in a sample in which a copper film was formed on the anodized film, the thickness of the anodized film was 1 μm, 3 μm, 5 μm, and 10 μm. In any case, the resistance value was within the range of 0.5 to 1.0Ω, and showed very good conductivity. In this case, it was possible to obtain better conductivity than in the case of galvanization. In the case of copper plating, as in the case of zinc plating, the resistance value did not change much even when the thickness of the anodized film was changed.

  Further, the back surface of the magnesium alloy plate manufactured by the thixomold method, which was subjected to anodizing treatment in this example, was shaved, and the resistance value between the front and back surfaces was measured according to the method shown in FIG. However, the resistance value was about 1Ω. This resistance value is considered to be such a value because of the thin oxide layer formed on the surface of magnesium. That is, when copper plating is performed on the surface of the anodized film according to the method of the present invention, it is possible to obtain better conductivity than a magnesium alloy product that is not particularly subjected to surface treatment.

  About the obtained sample, the corrosion resistance evaluation result by a salt spray test is put together in Table 5, and is shown. It can be seen that the plating film obtained in this example has better corrosion resistance than the comparative examples shown below. In particular, it has been clarified that as the film thickness of the base treatment layer by the anodic oxide film increases, the corrosion resistance becomes better. Moreover, the result of having evaluated the adhesiveness of the film | membrane about the sample which gave copper plating is also put together in Table 5, and is shown. It can be seen that the plating film obtained in this example has better adhesion than the comparative example shown below.

  2 to 6 show the results of observing the cross section of the film with an X-ray microanalyzer for a sample in which an anodic oxide film having a thickness of 10 μm was formed in the same manner as described above and 10 μm of zinc was plated thereon. FIG. 2 is an electron micrograph of the observed cross-sectional shape. This corresponds to the photograph in the upper left of FIG. 6 (described as “SL”). In FIG. 2, about 1/3 below is a magnesium alloy substrate, about 1/3 the center is a galvanized film, and about 1/3 above is an epoxy resin used for embedding. An anodized film exists between the magnesium alloy substrate and the galvanized film. As is apparent from comparison with FIG. 1 in which the sample before galvanization is taken, the surface of the anodized film is considerably eroded, and a metal plating layer is formed thereon. Since the metal plating film bites into the pores on the surface of the anodized film, it is considered that a metal plating layer with good adhesion can be formed.

  FIG. 3 shows a distribution state of magnesium (Mg), FIG. 4 shows a distribution state of oxygen (O), and FIG. 5 shows a distribution state of zinc (Zn). 3 to 5 show the concentration of each element by the density of black and white. The brighter the concentration, the higher the concentration. In FIG. 6, the upper center photo (described as “Mg”), the upper right photo (described as “Zn”), the lower left photo (described as “O”), and the lower central photo (described as “Al”). ) And the lower right photograph (denoted as “P”) show the distribution of magnesium (Mg), zinc (Zn), oxygen (O), aluminum (Al) and phosphorus (P), respectively. These five photographs are originally attached to the present specification in black and white display, in which the density distribution is shown by color display. What is shown on the right side of FIG. 6 is a color bar, and it should be noted that the brightness and the concentration element are not necessarily proportional in the monochrome display.

  As shown in the photograph in the upper center of FIG. 6, it can be seen that the transition layer remains even after the galvanization. Since the surface of the anodized film is considerably eroded, there is a place where the metal plating film is in contact with or close to the aforementioned transition layer. For this reason, it is thought that favorable electroconductivity is ensured through the part. As described above, it is presumed that this is the reason why they have the same degree of conductivity regardless of the thickness of the anodized film. Moreover, since the transition layer covers the magnesium alloy base material uniformly, it is considered that the transition layer contributes to the corrosion resistance of the magnesium alloy base material.

Comparative Example 1
This is an example of testing a known anodic oxide film forming method called “Dow17 method”. An electrolytic solution containing 360 g / L of acidic ammonium fluoride, 100 g / L of sodium dichromate and 90 mL / L of phosphoric acid was prepared. In this, the magnesium alloy test piece which performed the same pre-processing as Example 1 was immersed as an anode, and it anodized by supplying with electricity using AC power supply. The plating treatment conditions were adjusted within the following ranges to form 1, 3, 5 and 10 μm anodic oxide films.
Temperature: 71-82 (° C)
Current density: 0.5 to 5 (A / dm ² )
Voltage: 95-100 (V)
Time: 2.5-15 (minutes)

Next, after immersing in an aqueous nitric acid solution as in Example 1, galvanizing, zinc-nickel alloy plating, and copper plating were performed under the conditions shown in Table 2. However, at any film thickness of the anodic oxide film, only a slight amount of hydrogen gas was generated from the cathode during energization, and almost no current was energized, and no plating film was formed. This is presumably because the anodized film is an insulating film. Moreover, when the back surface of the obtained sample was shaved and the resistance value between the front and back surfaces was measured according to the method shown in FIG. 7, the resistance value exceeded the measurable range of the measuring instrument, and 10 ⁶ Ω. Exceeded.

Comparative Example 2
This is an example in which a known metal plating film forming method called “Dow method” is tested. The same magnesium alloy test piece as in Example 1 was used as a raw material, and after zincate treatment and copper cyanide strike plating were performed according to the steps shown in Table 3, zinc plating treatment and zinc-nickel alloy plating treatment were performed under the conditions shown in Table 2. And the copper plating process was performed. Table 5 summarizes the evaluation results of the corrosion resistance by the salt spray test and the evaluation results of the adhesion of the plating film.

Comparative Example 3
This is an example in which a known metal plating film forming method called “Sakata method” is tested. The same magnesium alloy test piece as in Example 1 was used as a raw material, and after plating pretreatment and electroless nickel strike plating were performed according to the steps in Table 4, galvanization treatment and zinc-nickel alloy plating were performed under the conditions shown in Table 2. Treatment and copper plating treatment were performed. Table 5 summarizes the evaluation results of the corrosion resistance by the salt spray test and the evaluation results of the adhesion of the plating film.

As described above, direct electroplating can be performed by using a conductive anodic oxide film as a base treatment for each plating. As shown in Table 5, as the thickness of the anodic oxide film increases, the corrosion resistance improves. When the underlying conductive anodic oxide film is 10 μm, the corrosion in the salt spray test occurs in any plating. The generation time is 500 hours or more, and extremely excellent corrosion resistance is exhibited.

  On the other hand, in the samples of Comparative Example 2 (Dow method) and Comparative Example 3 (Sakata method), any of the plated samples corroded within 24 hours, and was more resistant to corrosion than the sample of Example 1. Is significantly inferior. The reason for this is thought to be that galvanic corrosion due to dissimilar metals is likely to occur because the magnesium alloy is directly plated with different metals. Although it is possible to improve the corrosion resistance by increasing the thickness of the upper metal plating film, if the thickness of the metal plating film is about 5 μm, in order to prevent electrolytic corrosion due to dissimilar metals, the metal plating film It is considered that a barrier layer (transition layer) such as that formed in Example 1 is necessary as a base for the above.

Regarding the adhesion of the metal plating film, in the sample of Example 1, when the thickness of the underlying conductive anodic oxide film is as thin as 1 μm, peeling occurs in a part of the plating film , but if it is 3 μm or more No exfoliation or swelling is observed, and very good adhesion is obtained. It has been clarified that excellent adhesion can be obtained when the film thickness of the conductive anodic oxide film is 3 μm or more. However, as described above, the conductive anodic oxide film is extremely porous and uneven. This is because the adhesion is improved by the anchor effect due to the unevenness. In contrast, in the sample of Comparative Example 2 (Dow method), the plating film was completely peeled off. Further, even in the sample of Comparative Example 3 (Sakata method), peeling occurred on a part of the plating film .

Claims (13)

Magnesium or a magnesium alloy is immersed in an electrolytic solution containing 0.1 to 1 mol / L of phosphate radicals, 0.2 to 5 mol / L of ammonia or ammonium ions, and having a pH of 8 to 14. The anode was energized and the surface was anodized to contain 10 to 65% by weight of magnesium element, 25 to 60% by weight of oxygen element and 4 to 30% by weight of phosphorus element . After obtaining magnesium or a magnesium alloy having an anodized film with a film thickness of 0.01 to 30 μm having a resistance value of 10 ⁶ Ω or less measured between the terminals and a thickness of 0.01 to 30 μm on the surface, A method for producing a product made of magnesium or a magnesium alloy, which is plated to form a metal plating film directly on the surface of the anodized film. The method for producing a product according to claim 1, wherein a resistance value between a base material made of magnesium or a magnesium alloy and a surface of the metal plating film is 10 ⁴ Ω or less. The anodized film is composed of a porous layer and a transition layer, the transition layer is present between the porous layer and a base material made of magnesium or a magnesium alloy, and the magnesium content of the transition layer is An intermediate value between the magnesium content of the porous layer and the magnesium content of the base material, and the oxygen content of the transition layer is the oxygen content of the porous layer and the oxygen content of the base material The method for producing a product according to claim 1 or 2, which shows an intermediate value. The method for producing a product according to claim 3, wherein the transition layer has a thickness of 0.2 to 5 μm. The method for producing a product according to any one of claims 1 to 4 , wherein the anodized film contains 1 to 20% by weight of an aluminum element. Wherein the metal plating film, zinc, nickel, copper, gold, silver, metal or method for producing a product according to any of claims 1 to 5 consisting of a metal alloy selected from the group consisting of chromium. The method for producing a product according to any one of claims 1 to 6 , wherein the metal plating film has a thickness of 0.1 to 100 µm. Cover the entire surface of magnesium or magnesium alloy with the anodic oxide film, cover the entire surface of the anodic oxide film with the metal plating film, and apply resin coating to only a part of the surface of the metal plating film to make the remainder The method for producing a product according to any one of claims 1 to 7 , wherein the metal plating film of the portion is exposed. The product manufacturing method according to claim 8 , wherein the product is a housing of an electric device in which resin coating is not applied to an inner surface of the housing and resin coating is applied to an outer surface of the housing. The method for producing a product according to any one of claims 1 to 9 , wherein magnesium or a magnesium alloy is immersed in an acidic aqueous solution in advance and then immersed in the electrolytic solution and anodized. The method for producing a product according to any one of claims 1 to 10 , wherein the surface of the anodized film is immersed in an acidic aqueous solution in advance and then immersed in the plating bath to perform electroplating. The method for producing a product according to any one of claims 1 to 11 , wherein the plating bath has a pH of 7 to 14.5. The method for producing a product according to any one of claims 1 to 12 , wherein after forming the metal plating film, the metal plating film is further immersed in another plating bath to cover the surface of the metal plating film with another metal plating film.

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