JP4736084B2 - Manufacturing method of product made of magnesium or magnesium alloy - Google Patents

Description

The present invention relates to a method for producing a product comprising a zinc plating film The formed Mg or magnesium alloy. Moreover, it is related with the manufacturing method of the product in which the metal plating film was further formed on the said zinc plating film.

  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, a frame, a substrate, and the like of an electric device that has high performance requirements for miniaturization and weight reduction and high designability and recyclability. In many electrical devices, especially digital electronic devices, it is important to remove the electromagnetic noise by grounding to prevent malfunction, but at this time, a metal plating film with excellent conductivity is formed. By doing so, the grounding characteristics can be improved. Moreover, the product excellent in an external appearance and hardness can also be obtained by covering the surface of magnesium or a magnesium alloy with another metal film.

  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. . By the zinc substitution treatment, magnesium is oxidized and eluted, and at the same time, zinc ions in the aqueous solution are reduced and deposited. Such a method is described in Patent Document 1, for example. 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 has insufficient adhesion and corrosion resistance to the substrate. 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. However, it is not easy to obtain a plating film having a beautiful appearance. Furthermore, these plating methods are not widely used in general because complicated pretreatment may be required.

  Chemical conversion treatment is widely performed as one of typical surface treatment methods for imparting corrosion resistance to magnesium or a magnesium alloy. Conventionally, a chemical conversion treatment method using a solution containing hexavalent chromium element has been performed, but in recent years, a non-chromium type chemical conversion treatment solution not containing chromium element has been used from the viewpoint of preventing environmental pollution. It has become to. So far, various chemical conversion treatment liquids such as phosphoric acid, oxalic acid, stannic acid, fluoride, and manganese have been reported. Especially, the chemical conversion liquid containing manganese phosphate is said to be excellent in the performance of the film. For example, Patent Document 2 describes a chemical conversion treatment solution for a magnesium-containing metal, which includes an aqueous solution containing calcium ions, manganese ions, phosphate ions, and an oxidation accelerator and having a pH adjusted to 1 to 3. ing. By treating the magnesium-containing metal with the chemical conversion solution, it is said that a film excellent in corrosion resistance, rust prevention, and paint adhesion is formed.

  On the other hand, the anodizing treatment is generally considered to have better corrosion resistance than the chemical conversion treatment, and excellent corrosion resistance can be imparted by subjecting magnesium or a magnesium alloy to anodizing treatment. 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. Patent Document 3 describes a product made of magnesium or a magnesium alloy having a conductive anodic oxide film on the surface, which is immersed in an electrolytic solution made of an alkaline aqueous solution containing ammonia and phosphoric acid and anodized. The product has an anodized film having both electrical conductivity and excellent corrosion resistance on its surface, and is therefore suitable as a casing for electrical equipment.

  Several attempts have been reported to apply metal plating on the anodized film. For example, Patent Document 4 describes a method in which magnesium or a magnesium alloy is treated by a known anodic oxidation method to form a primary film and then subjected to AC electrolysis in a metal salt aqueous solution to form a secondary film. Yes. However, it is difficult to form a metal plating film even if an electroplating is attempted on the anodized film that is an insulating film. Patent Document 5 describes a method in which a molded article made of magnesium or a magnesium alloy is anodized, subjected to a catalyst treatment, and then subjected to electroless plating. However, the palladium used for the catalyst is expensive and the operation is complicated. Moreover, the plating film formed by electroless plating is mainly made of a metal nobler than hydrogen, and it is difficult to form a galvanized film.

Japanese Patent Laid-Open No. 4-31575 JP-A-11-131255 International Publication No. 03/080897 Pamphlet Japanese Patent Laid-Open No. 55-18540 JP 2002-235182 A

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for forming a uniform galvanized film on the surface of a substrate made of magnesium or a magnesium alloy. In addition, a method of forming a metal plating film on the galvanized film thus obtained to form a metal plating film having a beautiful appearance, suppressing occurrence of defects, and having good corrosion resistance and adhesion. It is intended to provide .

The above-mentioned problem is that a base material made of magnesium or a magnesium alloy is immersed in an electrolytic solution containing 0.001 to 1 mol / L of a phosphate group and having a pH of 8 to 14, and an anodized film is formed on the surface of the base material. A method for producing a product comprising magnesium or a magnesium alloy, wherein the zinc plating film is formed by immersing in a zinc plating bath and causing a redox reaction to proceed between the anodized film and zinc ions. Solved by providing. At this time, it is preferable that the electrolyte contains 0.2 to 5 mol / L of ammonia or ammonium ions.
The object is to form an anodic oxide film containing 10 to 60% by weight of magnesium element, 30 to 65% by weight of oxygen element and 1 to 30% by weight of phosphorus element on the surface of a base material made of magnesium or a magnesium alloy. A method of manufacturing a product made of magnesium or a magnesium alloy, wherein the zinc plating film is formed by immersing in a galvanizing bath and advancing a redox reaction between the anodized film and zinc ions. It is also solved by providing.
The above problem is that a substrate made of magnesium or a magnesium alloy is immersed in a chemical conversion treatment solution containing 0.001 to 3 mol / L of a phosphate group and 0.001 to 3 mol / L of a metal ion, and then formed on the surface of the substrate. From magnesium or a magnesium alloy, characterized in that after forming a treatment film, it is immersed in a galvanizing bath and a galvanization film is formed by advancing a redox reaction between the chemical conversion treatment film and zinc ions. This problem can also be solved by providing a manufacturing method for the product. At this time, it is preferable that the metal ions are manganese ions or calcium ions.
The above-mentioned subject forms a chemical conversion treatment film containing 15 to 45% by weight of a phosphorus element, 10 to 45% by weight of an oxygen element and 20 to 60% by weight of a metal element on the surface of a substrate made of magnesium or a magnesium alloy. A method for producing a product made of magnesium or a magnesium alloy, wherein the zinc plating film is formed by dipping in a galvanizing bath and advancing a redox reaction between the chemical conversion film and zinc ions. It is also solved by providing.
In addition, the above-mentioned problem is that, after an anodized film or a chemical conversion film is formed on the surface of a substrate made of magnesium or a magnesium alloy, the zinc ion content is 0.001 to 5 mol / L, and the pH is 8 to 15. A product made of magnesium or a magnesium alloy, wherein the product is formed by immersing in a galvanizing bath and forming a galvanized film by causing an oxidation-reduction reaction to proceed between the anodized film or chemical conversion film and zinc ions. It is also solved by providing a manufacturing method.

In the manufacturing method, it is preferable that a natural electrode potential of the anodized film or the chemical conversion film is lower than a natural electrode potential of the substrate. Moreover, after forming the said zinc plating film | membrane, it is a suitable embodiment of the manufacturing method of this invention which performs electroplating or electroless plating and forms a metal plating film | membrane further.

  According to the production method of the present invention, a uniform galvanized film can be formed on the surface of a substrate made of magnesium or a magnesium alloy. In particular, a uniform film can be formed even with a molded product having a complicated shape. In addition, a metal plating film may be further formed on the galvanized film thus obtained to form a metal plating film having a beautiful appearance, suppressing occurrence of defects, and having good corrosion resistance and adhesion. it can.

Further, the product obtained by the production method of the present invention, characterized by having an anodized film on the surface of a base material made of magnesium or a magnesium alloy, and having a galvanized film directly on the anodized film, Appearance is beautiful, generation of defects is suppressed, adhesion is good, and corrosion resistance is particularly excellent.

  Hereinafter, the present invention will be described in detail. In the present invention, an anodized film or a chemical conversion film is formed on the surface of a substrate made of magnesium or a magnesium alloy, and then immersed in a galvanizing bath, and oxidized between the anodized film or the chemical conversion film and zinc ions. A method for producing a product made of magnesium or a magnesium alloy, wherein a galvanized film is formed by advancing a reduction reaction.

  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.

  The form of the base material made of magnesium or magnesium alloy used for anodizing treatment or chemical conversion 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 mold release agent remaining in the product volatilizes when heated and may cause swelling in the plating film or 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 treatment as necessary, it is preferable to immerse in an acidic aqueous solution and then perform anodizing treatment or chemical conversion treatment. 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.

  In addition, after treatment with an acidic aqueous solution in this manner, it is also preferable to use an anodizing treatment or a chemical conversion treatment 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 an electrolytic solution and anodized, or is immersed in a chemical conversion solution and subjected to a chemical conversion treatment.

  First, the case of anodizing will be described. The electrolytic solution used for the anodizing treatment is not particularly limited. However, as will be described later, a galvanized film could not be formed by the manufacturing method of the present invention on the anodized film formed by the “Dow 17 method”. The “Dow 17 method” is a method in which anodization is performed using an electrolytic solution containing acidic ammonium fluoride, sodium dichromate and phosphoric acid. On the other hand, a galvanized film could be formed by the production method of the present invention on an anodized film obtained using an electrolytic solution comprising an alkaline phosphoric acid aqueous solution. Therefore, a preferable method is to form the anodized film by immersing the base material in an electrolytic solution composed of an aqueous solution containing 0.001 to 1 mol / L of phosphate radical and having a pH of 8 to 14. By containing an appropriate amount of phosphate groups, an appropriate amount of phosphorus element is included in the anodized film. Moreover, unnecessary elution of magnesium or a magnesium alloy can be prevented by making it alkaline. It is preferable that the electrolytic solution does not substantially contain a heavy metal element. 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.

  The phosphate radicals here are those contained in the electrolyte as free phosphoric acid, phosphate, hydrogen phosphate, dihydrogen phosphate and the like. 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 0.001 mol / L or more. More preferably, it is 0.01 mol / L or more, More preferably, it is 0.05 mol / L or more. In particular, in order to obtain an anodized film excellent in conductivity and corrosion resistance, the content of phosphate radicals is preferably 0.1 mol / L or more, and more preferably 0.15 mol / L or more. More preferably, it is 0.2 mol / L or more. The phosphate group content is preferably 1 mol / L or less, more preferably 0.7 mol / L or less, and even more 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. By making the electrolytic solution alkaline, unnecessary elution of magnesium or magnesium alloy can be prevented.

  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 alkaline level. 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.

  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 supply to be used is not particularly limited, and can be used with either a DC power supply or an AC 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 energized 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 2000 seconds. Preferably it is 50 seconds or more, more preferably 100 seconds or more. Further, it is preferably 1000 seconds or shorter, and more preferably 500 seconds or shorter. When energizing, 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 100 volts or more, more preferably 150 volts or more. Further, it is preferably 500 volts or less, and more preferably 400 volts or less. In the above-described “Dow 17 method” and the like, the applied voltage is often set to less than 100 volts, whereas in the anodic oxidation treatment using an alkaline phosphoric acid aqueous solution, it is preferable to set it to a relatively high voltage. 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 adhesion is easily formed on the entire surface of magnesium or a 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. At the time of washing, it is also preferred to wash using not only water but also other liquids. For example, by washing with an acidic aqueous solution, impurities dissolved in the acid may be removed and the surface of the film may be lightly etched. Since magnesium or a magnesium alloy is unstable in an acidic aqueous solution, it is often preferable to wash with a relatively weak acidic aqueous solution. As the acidic aqueous solution, phosphoric acid aqueous solution, nitric acid aqueous solution, hydrochloric acid aqueous solution, sulfuric acid aqueous solution and the like can be used. On the other hand, by washing with an alkaline aqueous solution, impurities dissolved in alkali may be removed and defects in the film may be repaired. Unlike an acidic aqueous solution, magnesium or a magnesium alloy is relatively stable in an alkali, and thus it is often preferable to wash with a strong alkaline aqueous solution such as sodium hydroxide or potassium hydroxide. Moreover, you may wash | clean with the aqueous solution containing surfactant. In some cases, cleaning may be performed using an organic solvent. After the above washing operation, it is dried. In this way, an anodized film is formed on the surface of the substrate made of magnesium or a magnesium alloy.

The anodic oxide film thus obtained may be an insulating film or a conductive film. For example, when an alkaline phosphoric acid aqueous solution having a phosphate radical content of 0.1 mol / L or more is used as the electrolytic solution, a conductive anodic oxide film can be formed depending on the film thickness to be formed. There is. For example, it is possible to form a conductive anodized film having a resistance value of 10 ⁶ Ω or less measured between two terminals 10 mm apart from each other. 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. The resistance value may be 10 ⁵ Ω or less, or 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.

  The anodized film obtained by the present invention often has a large number of pores that are thought to be derived from sparks during energization on the surface, and is different from the chemical conversion film in this respect. The film thickness of the anodized film is preferably 0.01 to 30 μm. More preferably, it is 0.1 μm or more, and further preferably 0.5 μm or more. In order to leave the anodic oxide film layer with a sufficient thickness even after forming the galvanized layer and obtain a product particularly excellent in corrosion resistance, it is preferably 1 μm or more, more preferably 2 μm or more, More preferably, it is 5 μm or more. Further, it is more preferably 20 μm or less, and further preferably 15 μm or less. Usually, the thicker the anodic oxide film, the better the corrosion resistance, but if it is too thick, the production cost may increase.

  The chemical composition of the anodic oxide film formed in the present invention is not particularly limited, but it is preferable to contain 10 to 60% by weight of magnesium element and 30 to 65% by weight of oxygen element. 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 35% by weight or more, and further preferably 40% by weight or more. Further, it is more preferably 60% by weight or less, and further preferably 55% by weight or less. The oxygen concentration of the anodized film produced by the “Dow 17 method” is often lower than the above range.

  It is preferable that the anodized film contains 1 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. By containing an appropriate amount of the above elements other than magnesium and oxygen, a film having a low natural electrode potential may be formed without impairing the 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 formed as described above may change its chemical composition when a galvanized film is formed.

  Next, the case where chemical conversion treatment is performed will be described. The kind of the chemical conversion treatment liquid used in the present invention is not particularly limited as long as a chemical conversion treatment film is formed. Conventionally used chemical conversion treatment liquid containing chromium element may be used, but it is preferable to use non-chromium type chemical conversion treatment liquid not containing chromium element from the viewpoint of preventing environmental pollution. . As the non-chromium type chemical conversion treatment solution, various chemical conversion treatment solutions such as phosphoric acid type, oxalic acid type, stannic acid type, fluoride type, manganese type, zirconium type and titanium type which have been reported so far are used. Is possible.

  Among them, it is preferable to use a phosphoric acid-based chemical conversion treatment solution because a high-performance chemical conversion treatment film can be obtained. Therefore, it is preferable that the chemical conversion treatment liquid used in the present invention is an aqueous solution containing a phosphate group. The preferred content of phosphate radical is 0.001 to 3 mol / L. If the phosphate radical concentration is too low, the corrosion resistance of the resulting film may be reduced. The concentration of the phosphate radical is more preferably 0.005 mol / L or more, and further preferably 0.01 mol / L or more. In order to obtain a film particularly excellent in corrosion resistance, it is preferably 0.02 mol / L or more. On the other hand, when the phosphate group concentration is too high, the load of the waste liquid increases, and the cost of the chemical conversion treatment liquid may increase. The concentration of the phosphate radical is more preferably 1 mol / L or less, and further preferably 0.5 mol / L or less. At this time, suitable content of the metal ion which becomes a counter ion of phosphate ion is 0.001-3 mol / L. If the concentration of metal ions is too low, the corrosion resistance of the resulting film may be reduced. The concentration of metal ions is more preferably 0.005 mol / L or more, and further preferably 0.01 mol / L or more. On the other hand, when the concentration of metal ions is too high, the load of the waste liquid increases and the cost of the chemical conversion liquid may increase. The concentration of metal ions is more preferably 1 mol / L or less, and even more preferably 0.5 mol / L or less. Here, the content of the metal ion is calculated by using the total number of moles when a plurality of types of metal ions are included.

Moreover, it is preferable that the metal ion contained in the chemical conversion treatment solution used in the present invention is manganese ion or calcium ion because a high-performance chemical conversion coating can be obtained. In particular, in order to obtain a uniform and excellent corrosion resistance film, the content of manganese ions or calcium ions is preferably 0.02 mol / L or more. Here, the content of the manganese ion or calcium ion is calculated using the total weight when both the manganese ion and the calcium ion are included. It is preferable that the chemical conversion treatment solution used in the present invention contains both manganese ions and calcium ions because it is easy to form a uniform and excellent corrosion-resistant film. In this case, the molar ratio (Mn ²⁺ / Ca ²⁺ ) is preferably 5/95 to 90/10, and more preferably 10/90 to 80/20.

  Moreover, it is preferable that pH of the chemical conversion liquid used by this invention is 6 or less. By using an acidic chemical conversion treatment liquid, the surface of the base material can be appropriately etched during chemical conversion treatment, and as a result, a chemical conversion treatment film having excellent corrosion resistance can be obtained. The pH is more preferably 4 or less, and even more preferably 3 or less. On the other hand, if the pH is too low, it may be difficult to form a homogeneous chemical conversion coating, and the pH is preferably 0 or more, more preferably 0.5 or more, and even more preferably 1 or more. .

  The time required for the chemical conversion treatment is preferably 1 second to 60 minutes. In the case of less than 1 second, there is a possibility that the formation of the chemical conversion film is insufficient. More preferably, it is 2 seconds or more, and further preferably 5 seconds or more. On the other hand, if the time required for the chemical conversion treatment is too long, the merit of simplifying the process may be reduced. More preferably, it is 30 minutes or less, More preferably, it is 10 minutes or less.

  The molded product subjected to the chemical conversion treatment as described above is appropriately washed with water and dried. About the method, it is the same as that of the washing | cleaning operation after the above-mentioned anodizing process. In this way, a chemical conversion film is formed on the surface of the molded article made of magnesium or a magnesium alloy. The fact that the chemical conversion film is formed on the surface of the molded product can be understood from the surface shape in which the mesh-like cracks are generated. This is because once the water-containing film is formed, cracks are formed due to volume shrinkage when the water-containing film dries, and it is possible to visually grasp that the chemical conversion treatment film is formed It is. However, such a crack may not be formed when the film of the chemical conversion treatment film is thin. The formed chemical conversion film may or may not have conductivity. About the resistance value of the film surface formed, it is the same as that of the case of the above-mentioned anodic oxide film.

  As described above, it is preferable to use a phosphoric acid-based chemical conversion treatment solution. Therefore, it is preferable that the chemical conversion film formed by the present invention contains a phosphorus element. The phosphorus element content in the chemical conversion film is preferably 15 to 45% by weight. The content of phosphorus element is more preferably 20% by weight or more, and further preferably 25% by weight or more. The phosphorus element content is more preferably 40% by weight or less, and even more preferably 35% by weight or less. Since the phosphorus atom in the chemical conversion treatment film is derived from the phosphate in the chemical conversion treatment solution, it is presumed to be bonded to an oxygen atom. Therefore, it is preferable that an oxygen element is contained in addition to the metal element and the phosphorus element. The content of oxygen element is preferably 10 to 45% by weight. The content of oxygen element is more preferably 15% by weight or more, and further preferably 20% by weight or more. The oxygen element content is more preferably 40% by weight or less, and even more preferably 35% by weight or less. The content of the metal element is preferably 20 to 60% by weight. The content of the metal element is more preferably 25% by weight or more, and further preferably 30% by weight or more. Further, the content of the metal element is more preferably 55% by weight or less, and further preferably 50% by weight or less. Here, when a plurality of metal elements are included, the total content is defined as the metal element content.

  Moreover, as mentioned above, it is preferable that a chemical conversion liquid contains a manganese ion or a calcium ion. Therefore, it is preferable that the chemical conversion film formed by this invention contains a manganese element or a calcium element as a metal element. Here, when both the manganese element and the calcium element are included, the total content is defined as the content of the manganese element or the calcium element. It is preferable that the chemical conversion treatment film formed in the present invention contains both manganese element and calcium element because it is likely to be a conductive film. In this case, the weight ratio (Mn / Ca) of both is preferably 10/90 to 90/10, more preferably 20/80 to 80/20, and even more preferably 30/70 to 70/30. It is.

  The chemical conversion treatment film may contain various other elements depending on the formulation of the chemical conversion treatment liquid. In addition to the elements described above, sodium, potassium, magnesium, aluminum, zinc, iron, chromium, zirconium, titanium, A film containing an element such as tin, silicon, nitrogen, sulfur, or fluorine can also be formed.

  A galvanized film is formed by immersing the anodic oxide film or chemical conversion film formed as described above in a zinc plating bath and advancing a redox reaction between the anodic oxide film or chemical conversion film and zinc ions. To do. Whereas conventional zinc displacement plating (zincate treatment) directly forms a zinc plating film on the surface of a substrate made of magnesium or a magnesium alloy, the production method of the present invention once forms an anodized film or a chemical conversion treatment film. Then, the point which forms a zinc plating film is a big feature point.

  In displacement plating typified by zincate treatment, electrons are supplied from a base material made of a base metal to ions of the noble metal, and the noble metal is deposited on the surface of the base material. On the other hand, in the method of the present invention, it appears that electrons are supplied from the anodized film or the chemical conversion film to the zinc ions in the zinc plating bath, and zinc is deposited to form a zinc plating film. In particular, zinc ions are reduced to form a plating film without passing an electric current and without containing a reducing agent in the plating bath. Both the anodized film and the chemical conversion film are films of compounds containing metal elements, and are not metals or alloys, but it is surprising that electrons are supplied from these to zinc ions to form a galvanized film.

  As shown in the following examples, in the case of an anodized film using an alkaline phosphoric acid aqueous solution as an electrolyte, a galvanized film is formed regardless of whether the film has conductivity. However, in the case of an anodized film formed by the “Dow 17 method”, a galvanized film could not be formed. When the natural electrode potential of the anodic oxide film in which the galvanized film could be formed was measured, the value was lower than the natural electrode potential of the base material made of magnesium or magnesium alloy. On the other hand, when the natural electrode potential of the anodic oxide film in which formation of the galvanized film was impossible was measured, the value was higher than the natural electrode potential of the base material made of magnesium or magnesium alloy. Therefore, when a film having a lower natural electrode potential than that of the base material is formed, it is estimated that the oxidation-reduction reaction proceeds between the film and zinc ions to form a galvanized film. . As a result, it seems that the film is eluted in preference to the base material and supplies electrons to zinc.

  As shown in the examples below, it was possible to form a galvanized film both with a phosphate-based chemical conversion film and with a chromate treatment. The natural electrode potentials of these chemical conversion coatings were all lower than the natural electrode potential of the substrate. Therefore, the result according to the said estimation was obtained also in the chemical conversion treatment film. From the above, it can be said that the natural electrode potential of the anodized film or the chemical conversion film is preferably lower than the natural electrode potential of the substrate.

  The molded article on which the anodized film or chemical conversion film is formed is immersed in a galvanizing bath to form a galvanized film. As the galvanizing bath, it is also possible to use a commercially available plating solution for zincate treatment. The galvanizing bath is preferably an aqueous solution containing 0.001 to 5 mol / L of zinc ions. If the zinc ion concentration is too low, the plating rate may be slow, or a film having a sufficient film thickness may not be obtained, more preferably 0.01 mol / L or more, and even more preferably 0.05 mol. / L or more. On the other hand, if the zinc ion concentration is too high, uneven film thickness tends to occur and the treatment burden of the waste liquid also increases. Therefore, it is more preferably 1 mol / L or less, and even more preferably 0.5 mol / L or less. is there. The pH of the galvanizing bath is preferably 8-15. Since magnesium or a magnesium alloy is easily dissolved in an acidic aqueous solution, it can be plated while preventing the base material from eluting by keeping the zinc plating bath alkaline. The pH is more preferably 10 or more, and more preferably 14 or less. The galvanizing bath of the present invention preferably contains various phosphoric acids such as orthophosphoric acid, pyrophosphoric acid (diphosphoric acid), triphosphoric acid, metaphosphoric acid, or salts thereof. Among these, it is preferable to contain pyrophosphate.

  When the molded article on which the anodized film or the chemical conversion film is formed is immersed in a galvanizing bath, a galvanized film is formed while bubbles are generated from the surface. In this way, it is possible to form a galvanized film without passing an electric current and without containing a reducing agent in the plating bath. It is possible to form a more uniform film as compared with the case of direct zinc replacement treatment for a molded article made of magnesium or a magnesium alloy. This is considered to be because the anodic oxide film and chemical conversion film formed in the middle cover the influence of the heterogeneous portions and defects on the substrate surface that are likely to occur when casting a molded product. According to the method of the present invention, a uniform film can be formed even on a molded product having a complicated shape.

  The time of immersion in the galvanizing bath is appropriately adjusted according to the composition of the plating bath, the film thickness of the intended galvanized film, and the like. The time for immersion in the galvanizing bath is preferably 1 to 60 minutes. If it is less than 1 minute, the formation of the galvanized film may be insufficient. The immersion time is more preferably 2 minutes or more, and even more preferably 5 minutes or more. On the other hand, if the immersion time is too long, the film thickness may become too thick or the workability may be reduced. The immersion time is more preferably 40 minutes or less, and even more preferably 20 minutes or less.

  The thickness of the formed galvanized film is preferably 0.1 to 8 μm. When the film thickness is less than 0.1 μm, there is a possibility that a portion where the film is not attached may be generated, and there is a possibility that conductivity when electroplating is subsequently performed becomes insufficient. The film thickness is more preferably 0.2 μm or more, and even more preferably 0.4 μm or more. On the other hand, when the film thickness exceeds 8 μm, the adhesiveness may be deteriorated due to the influence of the residual stress and the productivity is also lowered. In particular, in the case of a molded product having a complicated shape, it is important to form a thin and uniform film with good throwing power. Therefore, the film thickness is more preferably 4 μm or less, further preferably 2 μm or less, and optimally 1 μm or less.

  A chemical conversion treatment film is a film | membrane which usually has a film thickness thinner than 1 micrometer. It is possible to form a galvanized film on the order of several μm on a molded article having such a chemical conversion film. In such a case, since the amount of the chemical conversion treatment film alone is not sufficient for reducing the amount of zinc ions, not only the chemical conversion treatment film but also the magnesium or magnesium alloy of the base material is dissolved to form a galvanized film. It is thought that there is. That is, after a certain film thickness is formed, it is presumed that a film is further formed by an oxidation-reduction reaction between a base material made of magnesium or a magnesium alloy and zinc ions. Accordingly, the galvanized film formed in the present invention may be any part as long as it is formed by a redox reaction between the anodized film or the chemical conversion film and zinc ions. There is no. In such a case, it is considered that a galvanized film is formed directly on the base magnesium or magnesium alloy. Even in such a case, it is possible to obtain a metal plating film having a beautiful appearance, suppressing the occurrence of defects, and having good corrosion resistance and adhesion. However, since the base material made of magnesium or a magnesium alloy and the galvanized film are in direct contact with each other, a corrosion current flows due to a potential difference generated between the two and the magnesium is easily oxidized. Accordingly, when a deep scratch that reaches the magnesium base material occurs on the plating film, it may be easily corroded.

  Conversely, when a galvanized layer thinner than that is formed on the surface of the thick anodic oxide film, only a part of the anodic oxide film is dissolved and a galvanized film is formed thereon. Therefore, it has an anodized film on the surface of the base material which consists of magnesium or a magnesium alloy, and has a galvanized film directly on the said anodized film. In such a case, it is possible to obtain a product with a beautiful appearance, suppressed occurrence of defects, good adhesion, and particularly excellent corrosion resistance. The anodized film itself has excellent corrosion resistance, and the anodized film is interposed between the base material magnesium or magnesium alloy and the galvanized film, so that a corrosion current flows and magnesium is oxidized. Can also be suppressed. Therefore, the corrosion rate can be suppressed even when deep scratches that reach the magnesium base material occur on the plating film.

  Here, when a galvanized film is formed on the anodized film, it is considered that the film thickness of the anodized film decreases with the formation of the galvanized film. At this time, the thickness of the remaining anodized film is preferably 0.1 to 30 μm. If the thickness is less than 0.1 μm, the corrosion resistance may decrease, more preferably 0.2 μm or more, and even more preferably 0.5 μm or more. Further, it is more preferably 20 μm or less, and further preferably 15 μm or less.

  It is a preferred embodiment of the present invention to further form a metal plating film on the zinc plating thus formed. In this case, electroless plating can be applied or electroplating can be applied. Since the galvanized film having conductivity is already formed on the surface of the molded product, electroplating can be easily performed thereon. Electroplating is preferable because a film having an arbitrary thickness can be easily formed by a simple operation without using an expensive catalyst such as palladium.

  The metal plating film thus formed 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. Practically, a metal other than zinc is more preferable. As a combination with zinc, it is preferable to first perform copper plating on zinc, thereby improving the smoothness of the plating film surface. On top of that, by forming a film of a metal selected from the group consisting of nickel, chromium, gold, and silver, or an alloy of those metals, a plating film excellent in conductivity, hardness, decorativeness, etc. is formed. Is possible. In particular, it is preferable to use an acidic plating bath having a pH of 6 or less. Even in such a case, it is possible to suppress the occurrence of defects in the obtained plating film, and the significance of adopting the method of the present invention is great. . Examples of metals that are often electroplated using an acidic bath having a pH of 6 or less include nickel, chromium, and copper.

When electroplating, a metal plating film is formed by immersing a molded product made of magnesium or a magnesium alloy having a zinc plating film on the surface in a plating bath, and energizing the molded product as a cathode. The power supply to be used is not particularly limited, and can be used with either a DC power supply or a pulse power supply. In addition, when using a DC power source, either a constant current electrolysis method or a constant voltage electrolysis method may be employed, but it is preferable to employ a constant current electrolysis method. The anode material is not particularly limited, and the same metal as the plating film to be formed, platinum, titanium, stainless steel, or the like can be preferably 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 energization, the plating solution adhering to the surface of the metal plating film is removed by washing and dried to obtain a product having the metal plating film on the surface. In the case of forming a plating film having a plurality of layers, such an operation may be repeated.

  The thickness of the metal plating film formed on the galvanizing film is preferably 0.1 to 100 μm. The thickness of the metal plating film is more preferably 1 μm or more, and further preferably 5 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. The thickness of the metal plating film formed on the galvanizing film is preferably thicker than that of the galvanizing film. The thickness of the metal plating film is more preferably 2 times or more than that of the galvanization film, more preferably 5 times or more, and particularly preferably 10 times or more. When a metal plating film of a plurality of layers is formed, it is the total thickness thereof. In use, a top coat may be applied as necessary.

  In the above, the manufacturing method of the product which consists of magnesium or magnesium alloy of this invention was demonstrated. Conventionally, a method for directly forming galvanizing on an anodized film formed on the surface of a substrate made of magnesium or a magnesium alloy has not been known. Accordingly, the product itself having such a layer structure is novel. That is, it has a anodic oxide film having a thickness of 0.1 to 30 μm on the surface of a substrate made of magnesium or a magnesium alloy, and a galvanized film having a thickness of 0.1 to 8 μm directly on the anodic oxide film The problem of the present invention can also be solved by providing a product made of magnesium or a magnesium alloy characterized by having the following. Although the manufacturing method of such a product is not specifically limited, The above-mentioned method is employ | adopted as a suitable thing.

  A product made of magnesium or a magnesium alloy of the present invention having a metal plating film on the surface is excellent in lightness, strength, designability, conductivity and the like, 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) Natural electrode potential A flat portion of a test piece is cut out, a lead wire is connected, and a portion of a size of 10 mm × 10 mm is removed and masked with an epoxy resin. Soaked in. While bubbling nitrogen, the reference electrode was a saturated calomel electrode, the reference electrode was platinum, and the Lugin tube was brought close to the test piece to measure the natural electrode potential.

(2) Measurement of the resistance value of the surface of the anodized film or chemical conversion film Using a low resistivity meter “Lorestar AP MCP-T400” manufactured by Mitsubishi Chemical Corporation, measured using a two-probe probe “MCP-TP01” did. The resistance value (Ω) was measured by pressing the measuring terminal against the surface of the anodized film or the chemical conversion film at the flat part of the test piece. The probe has measuring terminals arranged at intervals of 10 mm, the terminal is a gold-plated beryllium alloy, the tip shape is a cylindrical shape with a diameter of 2 mm, and the terminal is made of an anodized film or a chemical conversion film. The load pressed against the surface is 240 g per terminal.

(3) Observation and analysis of cross-sectional shape of film A sample was cut into a size of 5 mm × 10 mm from a flat portion of a test piece, embedded in an epoxy resin, and then the cut surface was polished to obtain a mirror surface. An electron micrograph (SEM image) was taken from the cross-sectional direction of the sample using an X-ray microanalyzer “JXA-8100R” manufactured by JEOL Ltd. At the same time, photographs showing the distribution of each element of oxygen (O), magnesium (Mg), phosphorus (P), aluminum (Al), copper (Cu), zinc (Zn), and nickel (Ni) were also taken. Moreover, the film thickness of each film | membrane was measured from this electron micrograph.

(4) Appearance observation of galvanized film The surface of the molded article on which the galvanized film was formed was observed with a stereomicroscope, and the throwing power and uniformity of the galvanized film were evaluated according to the following evaluation criteria.
A: A galvanized film was uniformly formed over the entire surface, and no unevenness in appearance was observed.
B: Undeposited portions were not observed, but unevenness in appearance was observed.
C: An undeposited portion was present in part, and unevenness in appearance was observed in the deposited portion.
D: A galvanized film is not formed.

(5) Observation of appearance of electroplated film The surface of the molded product on which the electroplated film was formed was observed with a stereomicroscope, and the occurrence of appearance defects such as swelling and discoloration was evaluated according to the following evaluation criteria.
A: There was no blistering or discoloration and it had a beautiful appearance.
B: Swelling and discoloration were observed in part.
C: Swelling and discoloration are severe.
D: An electroplating film is not formed.

(6) Evaluation of corrosion resistance A 5% salt spray test is performed on the sample on which the electroplating film is formed in accordance with JIS Z2371, and the occurrence of corrosion and peeling or swelling of the plating film are evaluated according to the following evaluation criteria. did.
A: Even after 96 hours, no corrosion or peeling or swelling of the plating film was observed at all.
B: No occurrence of corrosion or peeling or swelling of the plating film was observed when 8 hours passed, but corrosion or peeling or swelling of the plating film was partially observed after 96 hours.
C: When 8 hours passed, corrosion was partly observed, or peeling or swelling of the plating film was observed.
D: When 8 hours passed, the occurrence of corrosion, or peeling or swelling of the plating film was observed remarkably.

(7) Evaluation of Adhesiveness of Electroplating Film A streak reaching the substrate was formed on the flat portion of the test piece with a cutter so that a square with a side of 2 mm was formed, and this was used as a test object. In accordance with the peeling test method according to JIS H8504, an adhesive tape is applied to the plated surface on which the streaks are formed, and this is peeled off rapidly and strongly, and the plating film is peeled off and swollen according to the following evaluation criteria. evaluated.
A: Plating film peeling and swelling were not observed at all.
B: Peeling and swelling of the plating film were observed in a very small part.
C: Peeling and swelling of the plating film were observed in some places.
D: Peeling and swelling of the plating film were observed remarkably.

Example 1
ASTM No. consisting of 90% magnesium, 9% aluminum and 1% zinc. A mobile phone substrate having an outer dimension of 1200 mm × 40 mm manufactured by a thixomold method using a magnesium alloy of AZ91D as a raw material was used as a test piece. The board is a board for holding various electronic components, which is disposed inside the casing of the mobile phone, and requires grounding performance from the board surface. The substrate is a molded product having a complicated shape having two large rectangular openings in which a liquid crystal display unit is disposed and a flat portion, and a large number of bent portions, through holes, slits, protrusions, and the like. This molded article was immersed in an acidic aqueous solution containing 4% by weight of phosphoric acid and a trace amount of a surfactant, and then washed with ion-exchanged water. Subsequently, the test piece surface was pretreated by immersing in an alkaline aqueous solution containing 10% by weight of potassium hydroxide and then washing with ion-exchanged water. The natural electrode potential of the pretreated test piece was −1.6V.

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. Using a constant current power source, the current density on the anode surface was 1 A / dm ^2, and the current was applied for about 100 seconds. Although the applied voltage was low at the start of energization, it increased to about 220 volts at the end of energization. Gas was generated from the test piece with the start of energization, and this continued until the end of energization. Further, the occurrence of sparks on the surface of the test piece was observed from about 50 seconds after the start of energization, and the generation of active sparks continued until the end of energization. After energization, it was washed with ion exchange water and then dried.

  As a result, an anodized film having a thickness of 2 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. The resistance value of the surface of the anodized film was 0.2Ω. The natural electrode potential of the anodized film was -1.75 V, which was lower than the natural electrode potential of -1.6 V of the magnesium alloy substrate. The anodized film contains 52% by weight of oxygen, 22% by weight of magnesium, 4% by weight of aluminum, and 22% by weight of phosphorus.

The sample on which the anodized film was formed was washed with water and immersed in a galvanizing bath. The galvanizing bath is an aqueous solution having the following composition and a pH of 13.5. It was immersed in a plating bath maintained at 50 to 55 ° C. for 10 minutes. During the immersion, bubbles continuously generated from the surface of the sample, and a galvanized film having a thickness of 0.5 μm was formed. The surface of the obtained galvanized film was observed with a stereomicroscope to evaluate the appearance.
・ Zinc sulfate: 30 g / L
・ Sodium pyrophosphate: 120 g / L
・ Lithium fluoride: 3g / L
・ Sodium carbonate: 5 g / L

The sample on which the galvanized film was formed was washed with water and immersed in a copper plating bath to perform electroplating. The copper plating bath is an aqueous solution having the following composition. It was immersed in a plating bath maintained at 55 ° C. and energized for 5 minutes at a current density of 3 A / dm ² to form a copper plating film having a thickness of 5 μm.
・ Copper cyanide: 50 g / L
-Potassium cyanide: 15 g / L
・ Potassium hydroxide: 15 g / L

The sample on which the copper plating film was formed was washed with water and immersed in a nickel plating bath for electroplating. The nickel plating bath is an aqueous solution having the following composition. It was immersed in a plating bath maintained at 55 ° C. and energized for 10 minutes at a current density of 6 A / dm ² to form a nickel plating film having a thickness of 10 μm.
Nickel sulfate: 280 g / L
・ Nickel chloride: 45g / L
・ Boric acid: 35 g / L
・ Glossing agent G-1 (manufactured by Uemura Kogyo Co., Ltd.): 10 g / L
・ Brightener G-2 (manufactured by Uemura Kogyo Co., Ltd.): 0.3 g / L

  The sample thus formed with nickel plating was washed with water, and the surface of the nickel plating film was observed with a stereomicroscope to evaluate the appearance. Moreover, the corrosion resistance and adhesion of the electroplated film were also evaluated. The above evaluation results are summarized in Table 1. Moreover, the result of having observed the cross section of the obtained film | membrane with the X-ray microanalyzer is shown in FIG.

Example 2
Anodization was performed under the same conditions as in Example 1 except that the same electrolytic solution as in Example 1 was used and the energization time was extended to about 450 seconds. Although the applied voltage was low at the start of energization, it increased to about 370 volts at the end of energization. Gas was generated from the test piece with the start of energization, and this continued until the end of energization. Further, the occurrence of sparks on the surface of the test piece was observed from about 50 seconds after the start of energization, and the generation of active sparks continued until the end of energization. After the end of energization, it was washed in the same manner as in Example 1 and then dried.

As a result, an anodized film having a thickness of 12 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. The resistance value of the surface of the anodized film exceeded the measurement limit of 10 ⁷ Ω of the resistivity measuring instrument used for the measurement. The natural electrode potential of the anodic oxide film was -1.68 V, which was lower than the natural electrode potential of -1.6 V of the magnesium alloy substrate. The composition of the anodic oxide film is the same as in Example 1.

  A galvanized film was formed and evaluated in the same manner as in Example 1 for the sample on which the anodic oxide film thus obtained was formed. Further, electroplating was carried out in the same manner as in Example 1, and a copper plating film and a nickel plating film were formed in this order for evaluation. The above evaluation results are summarized in Table 1.

Example 3
Instead of anodizing in Example 1, a chemical conversion treatment was performed. As the chemical conversion treatment liquid, a solution prepared by diluting 75 g of chemical conversion treatment liquid “MC-1000” manufactured by Million Chemical Co., Ltd. with ion-exchanged water was used. Here, the 75 g / L diluted preparation of “MC-1000” has a manganese ion (Mn ²⁺ ) content of 0.038 mol / L and a calcium ion (Ca ²⁺ ) content of 0.148 mol / L. The content of phosphate ions (PO ₄ ³⁻ ) was 0.206 mol / L, and the pH was 1.5. It was immersed in the chemical conversion treatment liquid maintained at 80 ° C. for 3 minutes to form a chemical conversion treatment film.

The resistance value of the surface of the obtained chemical conversion coating exceeded the measurement limit of 10 ⁷ Ω of the resistivity measuring instrument used for the measurement. Moreover, the natural electrode potential of the chemical conversion film was −1.74 V, which was lower than the natural electrode potential of −1.6 V of the magnesium alloy base material. The chemical conversion treatment film contains oxygen 28% by weight, phosphorus 29% by weight, calcium 19% by weight and manganese 24% by weight.

  A galvanized film was formed and evaluated in the same manner as in Example 1 on the sample on which the chemical conversion film thus obtained was formed. Further, electroplating was carried out in the same manner as in Example 1, and a copper plating film and a nickel plating film were formed in this order for evaluation. The above evaluation results are summarized in Table 1. Moreover, the result of having observed the cross section of the obtained film | membrane with the X-ray microanalyzer is shown in FIG.

Example 4
In Example 3, the chemical conversion treatment film was formed in the same manner as in Example 3 except that the temperature of the chemical conversion treatment liquid was changed to 30 ° C. and the immersion time was changed to 15 seconds. The resistance value of the surface of the obtained chemical conversion coating was about 1Ω. Moreover, the natural electrode potential of the chemical conversion film was −1.74 V, which was lower than the natural electrode potential of −1.6 V of the magnesium alloy base material. The composition of the chemical conversion film is the same as in Example 3. A galvanized film was formed and evaluated in the same manner as in Example 1 on the sample on which the chemical conversion film thus obtained was formed. Further, electroplating was carried out in the same manner as in Example 1, and a copper plating film and a nickel plating film were formed in this order for evaluation. The above evaluation results are summarized in Table 1.

Example 5
In Example 3, the chemical conversion treatment was performed in the same manner as in Example 1 except that the chemical conversion treatment liquid “Mugbond MB-C10M” manufactured by Nippon Parkerizing Co., Ltd. was used as the chemical conversion treatment liquid. The said chemical conversion liquid is a chemical conversion liquid for performing what is called chromate prescription. “Mugbond MB-C10M” is an aqueous solution having the following composition, which is diluted with ion-exchanged water at a rate of 75 g / L, and further added with ammonia water (28 wt%) at a rate of 0.7 g / L. did. Chemical conversion treatment was performed by immersing in the chemical conversion solution thus prepared at 50 ° C. for 30 seconds.
-Chromium (IV) anhydride: 10 to 15% by weight
・ Zinc nitrate: 10 to 15% by weight
・ Zinc sulfate: 1 to 5% by weight
-Chromium (III) oxide: 1 to 5% by weight
-Ammonium dichromate: 1 to 5% by weight
-Zinc phosphate: 0.1 to 1% by weight
・ Hydrogen fluoride: 0.1 to 1% by weight
・ Water: remaining weight

The resistance value of the surface of the obtained chemical conversion coating exceeded the measurement limit of 10 ⁷ Ω of the resistivity measuring instrument used for the measurement. Moreover, the natural electrode potential of the chemical conversion film was −1.78 V, which was lower than the natural electrode potential of −1.6 V of the magnesium alloy base material. A galvanized film was formed and evaluated in the same manner as in Example 1 on the sample on which the chemical conversion film thus obtained was formed. Further, electroplating was carried out in the same manner as in Example 1, and a copper plating film and a nickel plating film were formed in this order for evaluation. The above evaluation results are summarized in Table 1.

Comparative Example 1
A magnesium alloy molded article pretreated and dried in the same manner as in Example 1 was evaluated by directly forming a galvanized film in the same manner as in Example 1 without subjecting it to an anodic oxidation treatment. Further, electroplating was carried out in the same manner as in Example 1, and a copper plating film and a nickel plating film were formed in this order for evaluation. The above evaluation results are summarized in Table 1.

Comparative Example 2
In the same manner as in Example 1, a conductive anodic oxide film was formed. The sample on which the anodized film was formed was washed with water and electroplated in the same manner as in Example 1 without being immersed in a galvanizing bath, and a copper plating film and a nickel plating film were formed in this order for evaluation. went. The above evaluation results are summarized in Table 1.

Comparative Example 3
Instead of performing the anodizing treatment with the alkaline phosphoric acid aqueous solution performed in Example 1, anodizing treatment by “Dow 17 method” was performed. An electrolyte solution having the following composition was prepared and kept at 70 to 80 ° C. The electrolyte had a pH of 2.5. A magnesium alloy test piece which had been pretreated in this was immersed as an anode, and anodized. As the cathode at this time, a SUS316L plate having a surface area four times that of the anode was used. A constant current power source was used, and the current density on the anode surface was 2 A / dm ^2, and current was supplied for 240 seconds. Although the applied voltage was low at the start of energization, it increased to about 80 volts at the end of energization. Gas was generated from the test piece with the start of energization, and this continued until the end of energization. After energization, it was washed with ion exchange water and then dried.
・ Ammonium acid fluoride: 300 g / L
・ Sodium dichromate dihydrate: 100 g / L
Phosphoric acid (85% by weight): 90 mL / L

As a result, an anodized film having a thickness of 5 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. The resistance value of the surface of the anodized film exceeded the measurement limit of 10 ⁷ Ω of the resistivity measuring instrument used for the measurement. The natural electrode potential of the anodized film was -1.58 V, which was higher than the natural electrode potential of -1.6 V of the magnesium alloy base material. The anodized film contains 26 wt% magnesium, 26 wt% oxygen, 11 wt% phosphorus, 1 wt% aluminum, 23 wt% fluorine, 9 wt% chromium, and 4 wt% sodium. The sample on which the anodized film was formed was immersed in a galvanizing bath in the same manner as in Example 1, but no galvanized film was formed. Subsequent electroplating was also impossible. Therefore, the electroplating film was not evaluated. The above evaluation results are summarized in Table 1.

  As can be seen from Table 1, in Examples 1-5, an anodized film or a chemical conversion film was formed on a magnesium alloy substrate and then immersed in a galvanizing bath to form a galvanized film, followed by electroplating. It was possible to obtain an excellent metal plating film. Moreover, in these Examples, corrosion resistance and adhesiveness were also favorable, and Examples 1 and 2 in which an anodized film was formed were particularly excellent in corrosion resistance and adhesiveness. On the other hand, in Comparative Example 1 in which the magnesium alloy base material was directly immersed in a galvanizing bath to form galvanizing and subsequently electroplated, all of the appearance, corrosion resistance and adhesion of the metal plating film were insufficient. It was. Further, in Comparative Example 2 in which direct electroplating was performed after the formation of the conductive anodic oxide film, the appearance was insufficient. Furthermore, when an anodic oxide film was formed by the Dow 17 method, the galvanized film could not be formed even when immersed in a galvanizing bath. Therefore, it was impossible to perform subsequent electroplating.

  FIG. 1 shows an image obtained by photographing and analyzing the cross section of the film formed in Example 1, and FIG. 2 shows an image obtained by photographing and analyzing the cross section of the film formed in Example 3. The bottom is a magnesium alloy base material on which a film is formed. As can be seen from the SEM image, the magnesium alloy substrate of FIG. 2 was observed to have irregularities on the polished surface. The sample used for photographing was polished and smoothed in a wet state, but in Example 3, it is considered that magnesium was eluted from the polished surface into water during polishing. Also in the sample of FIG. 2, such unevenness was no longer observed at a portion about 15 μm away from the film. Therefore, it is considered that the magnesium film in the vicinity of the film is oxidized and eluted when the zinc film directly contacts and the corrosion current flows. The reason why the magnesium concentration at the upper end of the base material appears to be low in the magnesium distribution photograph in FIG. 2 is thought to be because regular reflection is reduced due to the unevenness. In contrast, the polished surface of the magnesium alloy substrate of FIG. 1 was flat. From this, it can be said that Example 1 in which the galvanized film is formed on the surface of the base material via the anodized film has better corrosion resistance than Example 3 in which the base material and the galvanized film are in direct contact. . In particular, it can be said that the corrosion resistance is excellent when a deep scratch that reaches the magnesium alloy base material occurs on the plating film.

  In FIG. 1, in the SEM image, it can be confirmed that a dark-colored anodic oxide film is present on the magnesium alloy substrate in a thickness of about 1 to 2 μm. In this portion, the magnesium concentration is lowered in the magnesium distribution photograph, and the presence of oxygen is recognized in the oxygen distribution photograph. However, the presence of phosphorus was not observed in the phosphorus distribution photograph. From the inventor's knowledge so far, it is known that the anodized film formed in Example 1 contains a sufficiently observable amount of phosphorus, so that when zinc ions are reduced. In addition, it seems that phosphorus is selectively eluted. That is, it is considered that the phosphorus concentration is lower than that of the original anodized film. On the other hand, in FIG. 2, the presence of the chemical conversion coating was not recognized.

  From the zinc distribution photograph of FIG. 1, it can be seen that a thin and uniform galvanized film having a thickness of about 0.5 μm is formed on the anodized film. On the other hand, as shown in FIG. 2, when the galvanized film is formed after forming the chemical conversion film, the galvanized unevenness seems to be large. It can be seen that a copper plating film and a nickel plating film are formed on the formed galvanizing without any problem in both FIG. 1 and FIG. The top of the photo is the epoxy resin used for embedding.

For the film formed in Example 1, the film cross section was observed with an X-ray microanalyzer, and a photograph showing the cross-sectional shape (SEM image) and a photograph showing the distribution of each element were synthesized. For the film formed in Example 3, the cross section of the film was observed with an X-ray microanalyzer, and a photograph showing the cross-sectional shape (SEM image) and a photograph showing the distribution of each element were synthesized.

Claims (9)

A base material made of magnesium or a magnesium alloy is immersed in an electrolytic solution containing 0.001 to 1 mol / L of a phosphate group and having a pH of 8 to 14, and an anodic oxide film is formed on the surface of the base material. A method for producing a product made of magnesium or a magnesium alloy, wherein the zinc plating film is formed by dipping in a plating bath and causing an oxidation-reduction reaction to proceed between the anodized film and zinc ions. Product manufacturing method according to claim 1, wherein said electrolyte contains 0.2~5mol / L ammonia or ammonium ions. Zinc plating after forming an anodic oxide film containing 10 to 60% by weight of magnesium element, 30 to 65% by weight of oxygen element and 1 to 30% by weight of phosphorus element on the surface of a substrate made of magnesium or magnesium alloy A method for producing a product made of magnesium or a magnesium alloy, wherein a galvanized film is formed by dipping in a bath and causing a redox reaction to proceed between the anodized film and zinc ions. A base material made of magnesium or a magnesium alloy is immersed in a chemical conversion treatment solution containing 0.001 to 3 mol / L of phosphate radicals and 0.001 to 3 mol / L of metal ions to form a chemical conversion treatment film on the surface of the base material. Then, it is immersed in a galvanizing bath, and a galvanized film is formed by causing a redox reaction between the chemical conversion film and zinc ions to produce a product made of magnesium or a magnesium alloy Method. The method for producing a product according to claim 4 , wherein the metal ions are manganese ions or calcium ions. Zinc plating after forming a chemical conversion treatment film containing 15 to 45% by weight of phosphorus element, 10 to 45% by weight of oxygen element and 20 to 60% by weight of metal element on the surface of a substrate made of magnesium or magnesium alloy A method for producing a product made of magnesium or a magnesium alloy, wherein a galvanized film is formed by dipping in a bath and causing a redox reaction to proceed between the chemical conversion film and zinc ions. After forming an anodized film or a chemical conversion film on the surface of a substrate made of magnesium or a magnesium alloy , a zinc plating bath having a zinc ion content of 0.001 to 5 mol / L and a pH of 8 to 15 is used. A method for producing a product made of magnesium or a magnesium alloy, comprising immersing and forming a galvanized film by advancing a redox reaction between the anodized film or chemical conversion film and zinc ions. The method for producing a product according to any one of claims 1 to 7 , wherein a natural electrode potential of the anodized film or the chemical conversion film is lower than a natural electrode potential of the substrate. The method for producing a product according to any one of claims 1 to 8 , wherein after forming the galvanized film, electroplating or electroless plating is performed to further form a metal plated film.