Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/02—Alloys based on aluminium with silicon as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
  • C22C21/12—Alloys based on aluminium with copper as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/31—Coating with metals
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/38—Electroplating: Baths therefor from solutions of copper
  • C25D3/40—Electroplating: Baths therefor from solutions of copper from cyanide baths, e.g. with Cu+
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/42—Electroplating: Baths therefor from solutions of light metals
  • C25D3/44—Aluminium
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/34—Pretreatment of metallic surfaces to be electroplated
  • C25D5/42—Pretreatment of metallic surfaces to be electroplated of light metals

Definitions

• the present invention relates to a method for manufacturing plated products in which plating is applied to the surface of a substrate made of magnesium or a magnesium alloy.
• Magnesium alloys for example, are used as lightweight, high-strength materials. Magnesium alloys are lighter and stronger than aluminum, making them suitable for a variety of applications. However, it is difficult to apply durable decorations directly to the surface of magnesium alloys. Therefore, a method has been proposed in which an aluminum plating layer is formed on the surface of a magnesium alloy by electrolytic aluminum plating (for example, Patent Document 1). In the method of Patent Document 1, the surface is thoroughly cleaned by degreasing or the like before the aluminum plating layer is formed on the magnesium alloy substrate.
• Aluminum plating films formed on magnesium or magnesium alloys require high adhesion, but also need to be formed efficiently.
• the present invention was made in consideration of these issues, and aims to provide a method for manufacturing plated products that can efficiently form an aluminum plating layer with high adhesion on a substrate made of magnesium or a magnesium alloy.
• one embodiment of the present invention provides a method for manufacturing a plated product, which comprises a zinc layer forming step of forming a zinc layer on the surface of a substrate made of magnesium or a magnesium alloy, a copper plating layer forming step of copper plating the zinc layer to form a copper plating layer on the zinc layer, and an aluminum plating layer forming step of aluminum plating the copper plating layer to form an aluminum plating layer on the copper plating layer, and the aluminum plating solution used in the aluminum plating layer forming step contains dimethyl sulfone, aluminum halide, ammonium chloride, and tetramethylammonium chloride.
• the thickness of the copper plating layer is preferably 1 ⁇ m or more and 30 ⁇ m or less, and the copper plating layer is preferably formed so as to be thicker than the zinc layer. Furthermore, the thickness of the aluminum plating layer is preferably 1 ⁇ m or more and 100 ⁇ m or less.
• anodizing treatment step in which the aluminum plating layer is anodized to form an anodized coating.
• the total thickness of the aluminum plating layer and the anodized coating be 21 ⁇ m or more and 100 ⁇ m or less, and that the thickness of the anodized coating be 11 ⁇ m or more and 30 ⁇ m or less.
• the aluminum plating solution preferably contains 3.5 to 4.2 moles of the aluminum halide, 0.1 to 0.5 moles of the ammonium chloride, and 0.1 to 1.5 moles of the tetramethylammonium chloride per 10 moles of the dimethyl sulfone. Furthermore, the aluminum plating solution preferably contains 0.2 to 0.5 moles of ammonium chloride per 10 moles of the dimethyl sulfone.
• the current density flowing between the substrate on which the copper plating layer has been formed and the anode electrode is preferably 15 mA/cm 2 or more and 200 mA/cm 2.
• the anode electrode preferably contains an aluminum alloy containing silicon or copper.
• the plated product and manufacturing method of the present invention make it possible to efficiently obtain plated products made of magnesium or a magnesium substrate with a highly adhesive aluminum plating layer.
• FIG. 1 is a schematic cross-sectional view of a plated product manufactured by a method for manufacturing a plated product according to an embodiment of the present invention.
• 1 is a flowchart showing a method for manufacturing a plated product according to an embodiment of the present invention.
• FIG. 3 is an enlarged cross-sectional view of the surface of the substrate 1 after the zinc layer forming step S001 has been performed in the method for manufacturing a plated product according to the embodiment of the present invention shown in FIG.
• FIG. 3 is an enlarged cross-sectional view of the surface of the substrate 1 after the copper plating layer forming step S002 has been performed in the method for manufacturing a plated product according to the embodiment of the present invention shown in FIG. 2.
• FIG. 3 is an enlarged cross-sectional view of the surface of the substrate 1 after the aluminum plating layer forming step S003 has been performed in the method for manufacturing a plated product according to the embodiment of the present invention shown in FIG.
• FIG. 1 shows a schematic cross-sectional view of a plated product obtained by a method for manufacturing a plated product according to an embodiment of the present invention.
• FIG. 1 shows the cross-sectional structure near the surface of magnesium or magnesium alloy obtained by the method for manufacturing a plated product according to this embodiment.
• the plated product obtained by the method for manufacturing a plated product according to this embodiment has a zinc layer 2, a copper plating layer 3, and an aluminum plating layer 4 formed, in that order, on a substrate 1 made of magnesium or a magnesium alloy, and then an anodized film layer 5 obtained by anodizing the surface of the aluminum plating layer 4, resulting in a plated product with a highly aesthetic design.
• the substrate 1 used in the method for manufacturing a plated product in this embodiment may be made of magnesium or an alloy thereof, with magnesium (Mg)-aluminum (Al)-zinc (Zn) alloys (such as ASTM AZ91 and AZ31 materials), Mg-Zn-zirconium (Zr) ternary alloys (such as ASTM ZK60 and ZK61 materials), and Mg-Zn-yttrium (Y) ternary alloys being particularly preferred.
• the overall shape of the substrate 1 may be any shape, including a plate or a rod. As long as the zinc layer 2, copper plating layer 3, and aluminum plating layer 4 can be formed on the surface of the substrate 1, other shapes, such as a polygonal prism, sphere, or hemisphere, are also acceptable.
• the method for manufacturing a plated product in this embodiment can be manufactured based on the flowchart shown in Figure 2.
• the method for manufacturing a plated product in this embodiment includes a zinc layer forming step S001 in which a zinc layer is formed on the surface of a substrate 1 made of magnesium or a magnesium alloy, a copper plating layer forming step S002 in which a copper plating layer is formed on the surface of the zinc layer, an aluminum plating layer forming step S003 in which an aluminum plating layer is formed on the copper plating layer, and an anodizing treatment step S004 in which a portion of the aluminum plating layer near the surface is anodized.
• the surface of the substrate 1 is degreased, and then a well-known zincate treatment is performed to replace the oxide film formed on the surface of the substrate 1 made of magnesium or a magnesium alloy with zinc, thereby forming a zinc layer 2 on the surface of the substrate 1.
• the zincate treatment is preferably performed using the well-known double zincate method.
• the double zincate method is a method in which a zinc layer 2 is formed on the surface of the degreased substrate 1 by zincate treatment, and then the zinc layer 2 formed by the previous zincate treatment is removed with nitric acid, and the surface of the substrate 1 is again subjected to zincate treatment to form the zinc layer 2.
• the double zincate method is a method in which a zinc layer is formed on the surface of the substrate 1 by the zincate method, the zinc layer is stripped with acid, and a zinc layer is again formed by the zincate method. Therefore, the zinc particles forming the zinc layer 2 are dense and fine, which enhances adhesion to the substrate and enables more uniform coating.
• 3 is an enlarged cross-sectional view of the surface of the substrate 1 after the zinc layer forming step S001. As shown in FIG. 3, when the zinc layer forming step S001 is performed, a zinc layer 2 is formed on the surface of the substrate 1. Since zinc has a lower ionization tendency than magnesium, the corrosion resistance is increased compared to the state of the substrate 1 alone. Therefore, the subsequent surface treatment can be performed smoothly.
• the substrate 1 may be degreased, then etched with acid to remove the oxide film, and then zinc plating may be performed.
• a zinc layer 2 can be formed on the surface of the substrate 1.
• the thickness of the zinc layer formed in the zinc layer formation step (S001) is preferably 0.01 ⁇ m or more and 2 ⁇ m or less. If it is 0.01 ⁇ m or more, most of the surface of the substrate 1 will be covered with the zinc layer 2, allowing the surface of the substrate 1 to be efficiently coated by subsequent surface treatment. On the other hand, if it is 2 ⁇ m or less, there will be less variation in the size of the crystal grains in the zinc layer 2, and it is possible to prevent significant surface roughness from occurring due to the coating performed in subsequent surface treatment.
• the copper plating layer formation process S002 is performed on the base material 1 with the zinc layer 2 formed thereon.
• the base material 1 with the zinc layer 2 formed thereon is immersed in a well-known electrolytic copper plating solution, and a voltage is applied so that the base material 1 with the zinc layer 2 formed thereon serves as the cathode electrode and copper, platinum, or the like serves as the anode electrode.
• Copper plating is performed under well-known temperature conditions and current density set according to the electrolytic copper plating solution used. By performing this copper plating layer formation process S002, a copper plating layer 3 is formed on the zinc layer 2.
• the copper plating layer 3 By forming the copper plating layer 3 on the surface of the base material 1 on which the zinc layer 2 has been formed in this way, it is possible to minimize the exposure of the surface of the base material 1, which is made of magnesium or its alloy. Copper also has a lower ionization tendency than zinc. Therefore, the presence of the copper plating layer 3 makes it easier to handle the base material 1 when moving on to the aluminum plating layer formation step S003. Therefore, in the method for manufacturing a plated product in an embodiment of the present invention, by performing the copper plating layer formation step S002 after the zinc layer 2 has been formed on the surface of the base material 1, it is possible to efficiently cover the surface of the base material 1 with the zinc layer 2 and copper plating layer 3.
• the oxide film of the copper plating layer 3 is less chemically stable than the oxide film of nickel plating, which is a typical metal plating. Therefore, even if an oxide film is formed on the surface of the copper plating layer 3, the oxide film can be easily removed, allowing for efficient production of plated products having an aluminum plating layer. Furthermore, the copper plating layer 3 has a smaller internal stress than nickel plating. Therefore, the copper plating layer 3 has the advantage of being less likely to peel off from the plating layer formed on top of it. For these reasons, the copper plating layer 3 is used as the underlayer for the aluminum plating layer in order to improve the production efficiency of plated products having an aluminum plating layer.
• the thickness of the copper plating layer 3 is preferably thicker than the thickness of the zinc layer 2. Therefore, the thickness of the copper plating layer 3 is preferably 1 ⁇ m or more. If the thickness is 1 ⁇ m or more, the copper plating layer 3 is easily formed on most of the surface of the zinc layer 2, and the occurrence of untreated portions of the copper plating layer coating can be suppressed. On the other hand, in order to avoid unnecessarily extending the takt time of the copper plating layer forming step S002, the thickness of the copper plating layer 3 is preferably 30 ⁇ m or less.
• the copper plating layer forming step S002 is not limited to a method of forming the copper plating layer 3 by electrolytic copper plating or a combination of electrolytic copper plating and electroless copper plating, and the copper plating layer forming step S002 may also be performed by electroless copper plating.
• 4 is an enlarged cross-sectional view of the surface of the substrate 1 after the copper plating layer forming step S002. As shown in FIG. 4, when the copper plating layer forming step S002 is performed, a zinc layer 2 and a copper plating layer 3 are formed on the surface of the substrate 1.
• the aluminum plating layer forming step S003 is performed on the base material 1 on which the copper plating layer 3 has been formed.
• the base material 1 on which the copper plating layer 3 has been formed is immersed in an electrolytic aluminum plating solution, and a voltage is applied so that the base material 1 on which the copper plating layer 3 has been formed serves as a cathode electrode and the other electrode, such as aluminum, serves as an anode electrode, thereby forming an aluminum plating layer 4 on the base material 1 on which the copper plating layer 3 has been formed.
• the following aluminum plating solution contains at least (1) dimethyl sulfone, (2) aluminum halide, (3) ammonium chloride, and (4) tetramethylammonium chloride.
• This aluminum plating solution is a mixture of dimethyl sulfone, aluminum halide, ammonium chloride, and tetramethylammonium chloride.
• ammonium chloride or tetramethylammonium chloride mixed in dimethyl sulfone dissociates according to the following formula 1: where R is hydrogen (H) or a methyl group ( CH3 ), DM is a dimethyl group, and N is nitrogen.
• chloride ions are generated in the plating solution. These chloride ions have the effect of reducing the oxide film formed on the copper plating layer 3 and removing the oxide film from the copper plating layer 3. Therefore, by immersing a substrate 1 made of magnesium or a magnesium alloy with a copper plating layer 3 formed on its outermost surface in the aluminum plating solution of this embodiment of the present invention, the oxide film formed on the copper plating layer 3 can be removed. This eliminates the need for the work of removing the oxide film, making it possible to efficiently manufacture plated products with an aluminum plating layer.
• the oxide film does not need to be completely removed. By doing so, the reliability of oxide film removal using the aluminum plating solution can be improved.
• a cleaning step is required after the oxide film removal step. After the cleaning step, a drying process or the like is performed to remove moisture, and during this process, an oxide film may be formed on the copper plating layer 3. Even in such a case, performing the aluminum plating layer formation step using this aluminum plating solution eliminates the need for oxide film removal again. Therefore, efficiency is improved.
• the aluminum plating solution used in this embodiment makes it possible to narrow or eliminate the region where the formation of the aluminum plating layer 4 is suppressed due to the presence of an oxide film on the surface of the copper plating layer 3, thereby enabling the production of a plated product with good design quality and less unevenness on the surface of the aluminum plating layer 4. Furthermore, when anodizing the surface of the aluminum plating layer 4, there is a possibility that depressions and holes in the aluminum plating layer 4 caused by the oxide film on the copper plating layer 3 may become enlarged, but the aluminum plating solution used in this embodiment makes it possible to suppress the occurrence of such a phenomenon.
• the aluminum plating layer formation step S003 it is preferable to agitate the plating solution using a stirring device or move or vibrate the cathode electrode itself in the plating solution before applying a voltage between the cathode electrode and anode electrode immersed in the aluminum plating solution, thereby creating a flow of aluminum plating solution on the surface of the copper plating layer 3.
• chloride ions and halide ions are supplied to the surface of the copper plating layer 3, making it possible to efficiently remove the oxide film formed on the surface of the copper plating layer 3.
• the magnesium or magnesium alloy substrate approaches the temperature of the aluminum plating solution, allowing the aluminum plating layer 4 to form more smoothly. Furthermore, by limiting the immersion time to 10 minutes or less, the effects of dissolution of the copper plating layer by the aluminum plating solution can be reduced.
• the aluminum plating solution used in the method for manufacturing a plated product in this embodiment also has the effect of maintaining the film formation efficiency of the aluminum plating layer 4. The reason for this is explained below.
• Equation 2 the addition of ammonium chloride or tetramethylammonium chloride increases the amount of NH 4 + or N(CH 3 ) + represented by NR 4 + in the plating solution.
• These cations have the effect of suppressing the increase in surface roughness of the aluminum plating layer 4, even when multiple different types of metals are exposed on the surface on which the aluminum plating layer 4 is formed. This is because, although the overpotential, which is the potential required to initiate aluminum electrodeposition, differs for each type of metal, the attachment of ammonium ions represented by NH 4 + to the surface of the material on which aluminum is electrodeposited reduces the difference in overpotential on the surface of each material.
• a magnesium or magnesium alloy substrate 1, a zinc layer 2, and a copper plating layer 3 are formed on an underlying aluminum plating layer 4. It is preferable that at least the surface of the substrate 1 on which the aluminum plating layer 4 is to be formed is uniformly covered with the copper plating layer 3. However, there are cases in which the zinc layer 2 does not completely cover the surface of the substrate 1, and pores that reach the surface of the substrate 1 are formed in some parts.
• the copper plating layer 3 is formed on the zinc layer 2, thereby blocking pores that have formed in the zinc layer 2.
• magnesium in the substrate 1 has a greater ionization tendency than copper, magnesium may dissolve during the copper plating layer forming step S002, and the through-holes in the zinc layer 2 may not be completely blocked by the copper plating layer 3.
• the surface on which the aluminum plating layer 4 is formed will contain extremely small areas of the surface of the zinc layer 2 and the surface of the substrate 1 made of magnesium or a magnesium alloy, in addition to the surface of the copper plating layer 3. If a conventional aluminum plating process is performed under these conditions, unlike the present embodiment, the difference in overpotential between the respective metals will result in non-uniform growth of the aluminum plating layer 4, resulting in a decrease in the smoothness of the surface of the aluminum plating layer 4.
• the aluminum plating solution used in the method for producing a plated product according to the embodiment of the present invention contains a large amount of NH 4 + and N(CH 3 ) + , which are represented by NR 4 + .
• a substrate 1 having a copper plating layer 3 formed thereon is immersed in an aluminum plating solution containing such cations and a voltage is applied so that the substrate 1 is on the cathode side, cations such as NR 4 + in the aluminum plating solution adhere to the entire surface of the substrate 1. Therefore, the difference in overpotential between the exposed portion of the copper plating layer 3 and the exposed portions of other metals, such as the zinc layer 2 and magnesium of the substrate 1, becomes small.
• the surface smoothness of the aluminum plating layer 4 is thought to be improved compared to the surface of an aluminum plating layer 4 formed with an aluminum plating solution to which ammonium chloride or tetramethylammonium chloride is not added.
• the decrease in the electrical conductivity of the aluminum plating solution is suppressed, contributing to preventing a decrease in the diffusion rate of aluminum ions. Furthermore, by suppressing an increase in the solution resistance of the aluminum plating solution, heat generation during aluminum electrodeposition using the aluminum plating solution is suppressed, and deterioration and evaporation of the aluminum plating solution are suppressed, thereby suppressing a decrease in the quality of the aluminum plating layer 4.
• the amount of aluminum halide is 3.5 moles or more, the increase in the melting point of the aluminum plating solution can be suppressed, making it less likely for the solution to solidify within the aluminum plating solution circulation path. Furthermore, if the amount of aluminum halide is 3.8 moles or more, the melting point of the aluminum plating solution can be further reduced. Furthermore, aluminum chloride is preferable among aluminum halides. Since the gas generated during aluminum plating production is chlorine gas, the chemical impact on the solvent, dimethyl sulfone, can be reduced.
• the amount of ammonium chloride and tetramethylammonium chloride is 0.1 mol or more per 10 mol of dimethyl sulfone, the increase in the amount of chloride ions in the aluminum plating solution is large, contributing to improved ability to remove the oxide film from the copper plating layer 3. Furthermore, cations represented by NR 4 + are also supplied. Furthermore, the amount of NH 4 + ammonium ions also increases, thereby enhancing the effect of reducing the difference in overpotential for different metal species appearing on the surface of the substrate 1 on which the aluminum plating layer 4 is formed.
• the method for manufacturing a plated product according to this embodiment can reduce the effect of surface irregularities and pores on the zinc layer 2 and copper plating layer 3 on the surface smoothness of the aluminum plating layer 4. Furthermore, when the amount of ammonium chloride is 0.2 mol or more per 10 mol of dimethyl sulfone, blackening of the aluminum plating layer 4 can be further suppressed.
• the temperature of the aluminum plating solution is preferably 80°C or higher and 110°C or lower.
• the current density between the anode electrode and the cathode electrode immersed in the aluminum plating solution is preferably 15 mA/ cm2 or higher and 200 mA/ cm2 or lower.
• the lower limit of the temperature of the aluminum plating solution should be determined taking into account the melting point of the aluminum plating solution, and is preferably 85°C, more preferably 95°C.
• setting the upper limit of the temperature of the aluminum plating solution to 110°C can suppress deformation of the substrate 1.
• a current density of 110°C or lower can suppress the activity of the reaction between the aluminum plating layer 5 and the aluminum plating solution, thereby suppressing an increase in the amount of impurities in the aluminum plating layer 4. Furthermore, a current density of 15 mA/cm2 or higher maintains film formation efficiency and sufficiently maintains the effect of the cations represented by NR4 + covering the substrate 1 on which the copper plating layer, which is the cathode electrode, is formed, thereby reducing pinholes that can be formed in the aluminum plating layer 4. Furthermore, if the current density is 200 mA/cm2 or less , decomposition of nitrogen compounds such as ammonium chloride and tetramethylammonium chloride is suppressed, making it easier to continue stable plating.
• the above aluminum plating solution allows stable plating even when a current density of 100 mA/cm2 or more is applied, thereby improving the film formation rate.
• the plating time depends on the desired film thickness of the aluminum plating layer 4, the temperature of the electrolytic solution, the applied current density, etc., but is usually preferably 1 to 90 minutes, and more preferably 1 to 60 minutes in consideration of production efficiency.
• Figure 5 is an enlarged cross-sectional view of the surface of the substrate 1 after the aluminum plating layer formation step S003.
• the thickness of the aluminum plating layer 4 is made thicker than the thickness of the copper plating layer 3. This is because a portion of the aluminum plating layer 4 is anodized in the subsequent anodizing treatment step S004. If the entire aluminum plating layer 4 were anodized, the anodized film 5 would come into contact with the copper plating layer 3.
• the anodized film 5 is formed at least 1 ⁇ m thicker than the designed film thickness, as mentioned above. If smoothness is desired on the surface of the plated product, the surface in the aluminum plating layer formation step S003 may be polished. In such cases, it is preferable to form the aluminum plating layer 4 even thicker, taking into consideration the thickness to be polished. When polishing the surface of the aluminum plating layer 4, it is preferable to polish it to an arithmetic mean roughness Ra of 1.5 ⁇ m or less.
• Reducing the crystal grain size of the aluminum plating layer 4 can reduce the surface roughness of the aluminum plating layer 4 after the aluminum plating process. Therefore, by intentionally adding impurities such as copper (Cu) or silicon (Si) during the aluminum plating layer formation process, the crystal grains can be refined and the surface roughness can be reduced. For example, by ionizing a certain amount of Cu or the like in the aluminum plating solution, the purity of the aluminum plating layer 4 can be reduced and the crystal grains can be refined.
• impurities such as copper (Cu) or silicon (Si)
• the aluminum plating layer formation process it is preferable to use an aluminum alloy containing either Cu or Si, or an aluminum alloy containing 0.1% by mass to 24% by mass of Si, 0.1% by mass to 5% by mass of Cu, and 0.15% by mass to 1.8% by mass of iron (Fe) for the anode electrode.
• the anode electrode can be obtained by molding used AC2A alloy material into an electrode shape by casting or the like.
• the current density at the anode during aluminum plating to 10 mA/cm or more and 200 mA/cm or less , Cu can be contained in the electrodeposited film that is formed. Note that, in the aluminum plating layer 4 of this embodiment, it is preferable that aluminum accounts for 90 mass % or more and the other contained elements are kept to less than 10 mass %.
• the base material 1 on which the aluminum plating layer 4 has been formed is subjected to anodizing treatment S004.
• anodizing treatment method There are no particular limitations on the anodizing treatment method, and it can be performed by any known method.
• the anodizing treatment conditions are set appropriately depending on the desired thickness of the anodic oxide coating 5, the anodizing treatment solution used, etc.
• the aluminum plating layer 4 may be divided into multiple sections, and each section may be anodized under different conditions.
• a color tone may be imparted to the anodic oxide coating 5 by natural color development, or by coloring (so-called color anodizing).
• the total thickness of the aluminum plating layer 4 and the anodic oxide coating 5 formed in the anodizing treatment step S004 be 21 ⁇ m or more and 100 ⁇ m or less.
• the film thickness of the aluminum plating layer 4 after the anodizing treatment step S004 is preferably 11 ⁇ m or more but less than 100 ⁇ m, and more preferably 11 ⁇ m or more and 70 ⁇ m or less.
• the film thickness of the anodic oxide coating 5 after the anodizing treatment step S004 is preferably 10 ⁇ m or more and 30 ⁇ m or less.
• the aluminum plating layer 4 when performing electrolytic plating, it is preferable to form the aluminum plating layer 4 with a thickness that takes into account the change in thickness due to the anodic oxide coating 5 formed in the anodizing treatment step S004. Note that if the color tone and texture of aluminum metal are to be utilized, the anodizing treatment step S004 does not need to be performed. In this case, the aluminum plating layer 4 becomes the outermost layer, and the suitable film thickness at this time is preferably 1 ⁇ m or more and 100 ⁇ m or less, and more preferably 1 ⁇ m or more and 70 ⁇ m or less.
• the surface of magnesium or magnesium alloy can be given an appearance with excellent decorativeness. For example, it is possible to color or develop any color, such as white, black, red, or blue, and it is also possible to change the color depending on the location.
• the method for manufacturing a plated product in this embodiment of the present invention ensures good adhesion, making it possible to obtain plated magnesium or magnesium alloy products that can be used in a wider range of applications than before.
• it is also suitable for surface treatment of various exterior parts such as electronic devices, automotive parts, optical parts, and mechanical parts.
• the roughness measurement, film thickness measurement and adhesion test were carried out as follows.
• the arithmetic mean roughness measurement was performed in accordance with the international standard ISO 4288: 1996.
• roughness measurement for non-periodic roughness curves was used, and the surface roughness measurement was performed by setting the cutoff value ⁇ c to 0.08 mm or more and 0.8 mm or less, the reference length L to 0.08 mm or more and 0.8 mm or less, and the evaluation length Ln in the range of 0.4 to 4 mm, depending on the smoothness of the surface.
• the cross section of the plated product was photographed using a scanning electron microscope, and the film thickness was measured at multiple arbitrary positions on the photographed cross section, excluding the vicinity of the outer periphery of each layer, and the average value was calculated as the film thickness.
• the adhesion test was conducted in accordance with the cross-cut method defined in Japanese Industrial Standard JIS K 5600-5-6:1999, in which 25 squares in total were cut with 2 mm width, 5 squares vertically and 5 squares horizontally, and cellophane adhesive tape was used to press the tape against the aluminum plating layer or the anodized coating, and the tape was pulled vertically to evaluate whether peeling occurred. In this specification, this is referred to as the cross-cut test.
• Another aspect of the present invention is a plated product having a substrate made of magnesium or a magnesium alloy, a zinc layer formed on the surface of the substrate, a copper plating layer formed on the zinc layer, and an aluminum plating layer formed on the copper plating layer.
• the thickness of the copper plating layer is preferably 1 ⁇ m or more and 30 ⁇ m or less, and the copper plating layer is preferably thicker than the zinc layer.
• the thickness of the aluminum plating layer is preferably 1 ⁇ m or more and 100 ⁇ m or less. It is also preferable that an anodized coating be formed on the aluminum plating layer.
• the thickness of the aluminum plating layer is preferably 1 ⁇ m or more and 70 ⁇ m or less, and the thickness of the anodized coating is preferably 10 ⁇ m or more and 30 ⁇ m or less.
• a method for producing a plated product preferably includes a zinc layer forming step of forming a zinc layer on the surface of a substrate made of magnesium or a magnesium alloy, a copper plating layer forming step of copper-plating the zinc layer to form a copper plating layer on the zinc layer, and an aluminum plating layer forming step of aluminum-plating the copper plating layer to form an aluminum plating layer on the copper plating layer.
• An anodizing step of anodizing the aluminum plating layer is preferably further performed.
• the aluminum plating solution used in the aluminum plating layer forming step preferably contains at least (i) a dialkyl sulfone, (ii) an aluminum halide, and (iii ) at least one nitrogen-containing compound selected from the group consisting of ammonium halides, hydrogen halides of primary amines, hydrogen halides of secondary amines, hydrogen halides of tertiary amines, and quaternary ammonium salts represented by the general formula R1R2R3R4N.X ( R1 to R4 are the same or different alkyl groups, and X is a counter anion for the quaternary ammonium cation).
• Examples of the alkyl group represented by R 1 to R 4 include those having 1 to 6 carbon atoms (which may be linear or branched), such as methyl, ethyl, propyl, and hexyl.
• Examples of X include halide ions such as chloride ions, bromide ions, and iodide ions, as well as BF 4 - and PF 6 - .
• Specific examples of the compound include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, and tetraethylammonium boron tetrafluoride.
• a suitable nitrogen-containing compound is a tertiary amine hydrochloride, such as trimethylamine hydrochloride, which facilitates the formation of a high-purity aluminum plating layer 4 at a high deposition rate.
• an aluminum plating layer 4 or an anodized film was formed according to the following examples.
• the substrate 1 had a plate shape (board)
• at least two surfaces were coated with the aluminum plating layer 4.
• the substrate 1 had a round stick shape
• one bottom surface and one cylindrical surface were coated with the aluminum plating layer 4.
• the surface roughness of each of these substrates 1 was 0.74 ⁇ m or less in Ra, providing a satisfactory smooth surface.
• These substrates 1 were subjected to a zincate treatment corresponding to the zinc layer forming step S001, electrolytic copper plating corresponding to the copper plating layer forming step S002, and electrolytic aluminum plating corresponding to the aluminum plating layer forming step S003.
• the aluminum plating layer formed in the aluminum plating layer forming step S003 was anodized to form an anodized coating.
• the zincate treatment was performed by degreasing the substrate 1 and then performing a double zincate treatment.
• the zinc layer 2 was formed to a thickness of approximately 1 ⁇ m or less.
• the aluminum plating solution used in this example was prepared by mixing 10 moles of dimethyl sulfone with 3.8 moles of aluminum chloride, 0.2 moles of ammonium chloride, and 1.0 moles of tetramethylammonium chloride. Two liters of this prepared aluminum plating solution was placed in a plating tank, and an aluminum plating layer 4 was formed at a solution temperature of 95°C or higher and 100°C or lower.
• the oxide film on the copper plating layer 3 was not removed, and the substrate was immersed in the plating tank of aluminum plating solution for approximately 5 minutes without applying voltage, thereby carrying out the aluminum plating layer formation step S003.
• Table 1 shows details of the plated products from Example 1 to Example 18.
• item (a) shows the material of the substrate
• item (b) shows the shape of the substrate
• item (c) shows the configuration of the layers formed in order from the substrate 1 side
• item (d) shows the results of the cross-cut test
• item (e) shows the results of the visual appearance inspection
• item (f) shows the current density (mA/cm 2 ) passed through the aluminum plating solution during the aluminum plating layer formation step
• item (g) shows the total film thickness ( ⁇ m) of the zinc layer 2 and the copper plating layer 3
• item (h) shows the film thickness ( ⁇ m) of the aluminum plating layer 4
• item (i) shows the film thickness ( ⁇ m) of the anodic oxide coating.
• the values in parentheses are expected film thickness values calculated from the current density and plating time (current application time) during the aluminum plating process set in the aluminum plating layer formation step S003, and the other values are actual film thickness measurements after the formation of the plated product.
• Example 1 Example 1 (Ex. 1) to Example 8 (Ex. 8) and Example 18 (Ex. 18), the aluminum plating layer forming step S003 was performed, but the anodizing treatment step S004 was not performed.
• Example 9 Example 9 to Example 17 (Ex. 17)
• the aluminum plating layer forming step S003 was performed, followed by the anodizing treatment step S004.
• the thickness of the anodized coating was measured by cross-sectional observation.
• the aluminum plating layer forming step was carried out with the current density changed for each example.
• Example 18 it was confirmed that pinholes were formed on the surface of the aluminum plating layer 4. This is thought to be due to the low current density flowing through the aluminum plating solution in the aluminum plating layer formation step S003. It is presumed that the low current density prevented cations represented by NR 4 + , which have the effect of reducing the difference in overpotential between different metal species, from sufficiently covering the substrate 1, which is the cathode electrode, and as a result, the holes formed in the copper plating layer 3 were not completely sealed by the aluminum plating layer. Therefore, it is preferable to set the current density flowing through the aluminum plating solution to 15 mA/cm2 or more.

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