Manufacturing method for plated products
The sequential formation of zinc, copper, and aluminum plating layers with a specialized solution and anodic oxidation addresses the challenge of achieving high adhesion and efficient aluminum plating on magnesium alloys, enhancing decorative and functional properties.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- PROTERIAL LTD
- Filing Date
- 2025-03-13
- Publication Date
- 2026-07-22
Smart Images
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Abstract
Description
[Technical Field]
[0001] This invention relates to a method for manufacturing plated products in which a plating is applied to the surface of a substrate made of magnesium or a magnesium alloy. [Background technology]
[0002] Magnesium alloys, for example, are used as lightweight and high-strength materials. Because magnesium alloys are lighter and stronger than aluminum, they are used in a variety of fields. 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 performing electrolytic aluminum plating (for example, Patent Document 1). In the method according to 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. Furthermore, in order to improve the adhesion of the aluminum plating layer, a method has been proposed in which a copper layer and a nickel layer are formed sequentially on the surface of a magnesium alloy, and an aluminum plating film is formed on top of the nickel layer (for example, Patent Document 2). [Prior art documents] [Patent Documents]
[0003] [Patent Document 1] Japanese Patent Publication No. 2004-292858 [Patent Document 2] Japanese Patent Publication No. 2006-161155 [Overview of the project] [Problems that the invention aims to solve]
[0004] Aluminum plating films formed on magnesium or magnesium alloys require high adhesion, while also requiring efficient formation of the aluminum plating film. Therefore, the present invention has been made in view of these problems, and aims to provide a method for manufacturing plated products that can efficiently form an aluminum plating layer with high adhesion to a substrate made of magnesium or a magnesium alloy. [Means for solving the problem]
[0005] To achieve the aforementioned objectives, a method for manufacturing a plated product according to one aspect of the present invention 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 performing a copper plating treatment on the zinc layer to form a copper plating layer on the zinc layer; and an aluminum plating layer forming step of performing an aluminum plating treatment on the copper plating layer to form an aluminum plating layer on the copper plating layer, wherein the aluminum plating solution used to form the aluminum plating layer is dimethyl sulfone And, with respect to 10 moles of dimethyl sulfone, aluminum chloride is added in a ratio of 3.5 moles to 4.2 moles, ammonium chloride in a ratio of 0.1 moles to 0.5 moles, and tetramethylammonium chloride in a ratio of 0.1 moles to 1.5 moles. In the aluminum plating layer formation step, the substrate on which the copper plating layer has been formed by the copper plating layer formation step and the anode electrode are immersed in the aluminum plating solution, the substrate on which the copper plating layer has been formed is used as the cathode electrode, and when a voltage is applied between the cathode electrode and the anode electrode, the current density of the cathode electrode flowing between the cathode electrode and the anode electrode is 15 mA / cm². 2 More than 200mA / cm 2 That is the case.
[0006] The thickness of the copper plating layer is preferably between 1 μm and 30 μm, and it is preferable that the copper plating layer be thicker than the zinc layer. Furthermore, the thickness of the aluminum plating layer is preferably between 1 μm and 100 μm.
[0007] Further, it is desirable to further include an anodic oxidation treatment step of performing anodic oxidation treatment on the aluminum plating layer to form an anodic oxidation film. Furthermore, it is desirable that the total thickness of the aluminum plating layer and the anodic oxidation film is 21 μm or more and 100 μm or less, and the film thickness of the anodic oxidation film is 11 μm or more and 30 μm or less.
[0009] Also, the anode electrode preferably contains an aluminum alloy containing silicon or copper. Also, Preferably, between the copper plating layer formation step and the aluminum plating layer formation step, there is a negative potential application step in which the substrate on which the copper plating layer has been formed is immersed in the aluminum plating solution, and after 1 minute or more has elapsed since immersion, a negative potential is applied to the substrate.
Advantages of the Invention
[0010] According to the plating product and its manufacturing method of the present invention, a plating product of a substrate made of magnesium or magnesium having an aluminum plating layer with high adhesion efficiently can be obtained.
Brief Description of the Drawings
[0011] [Figure 1] It is a schematic cross-sectional view of a plating product manufactured by the manufacturing method of the plating product in the embodiment of the present invention. [Figure 2] It is a flowchart showing the manufacturing method of the plating product in the embodiment of the present invention. [Figure 3] In the manufacturing method of the plating product of the embodiment of the present invention shown in FIG. 2, it is an enlarged cross-sectional view of the surface of the substrate 1 after performing the zinc layer forming step S001. [Figure 4] In the manufacturing method of the plating product of the embodiment of the present invention shown in FIG. 2, it is an enlarged cross-sectional view of the surface of the substrate 1 after performing the copper plating layer forming step S002. [Figure 5] In the manufacturing method of the plating product of the embodiment of the present invention shown in FIG. 2, it is an enlarged cross-sectional view of the surface of the substrate 1 after performing the aluminum plating layer forming step S003.
Modes for Carrying Out the Invention
[0012] Figure 1 shows a schematic cross-sectional view of a plated product obtained by the manufacturing method of a plated product according to an embodiment of the present invention. Figure 1 shows the cross-sectional structure near the surface of magnesium or a magnesium alloy obtained by the manufacturing method of a plated product according to this embodiment. The plated product obtained by the manufacturing method of a plated product according to this embodiment is obtained by sequentially forming a zinc layer 2, a copper plating layer 3, and an aluminum plating layer 4 on a substrate 1 made of magnesium or a magnesium alloy, and then forming an anodic oxide film layer 5 obtained by anodizing the surface of the aluminum plating layer 4, thereby obtaining a plated product with a high aesthetic appeal.
[0013] The base material 1 used in the manufacturing method of the plated product in this embodiment may be magnesium or an alloy thereof, and magnesium (Mg)-aluminum (Al)-zinc (Zn) alloys (such as ASTM standard AZ91 and AZ31 materials), Mg-Zn-zirconium (Zr) ternary alloys (such as ASTM standard ZK60 and ZK61 materials), and Mg-Zn-yttrium (Y) ternary alloys are particularly preferred. The overall shape of the base material 1 may be any shape, such as a plate or a round bar. In addition, as long as a zinc layer 2, a copper plating layer 3, and an aluminum plating layer 4 can be formed on the surface of the base material 1, other shapes such as polygonal prisms, spheres, or hemispheres are also acceptable.
[0014] To obtain such plated products, the manufacturing method for plated products in this embodiment can be carried out based on the flowchart shown in Figure 2. As shown in Figure 2, the manufacturing method for plated products 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 part of the vicinity of the surface of the aluminum plating layer is anodized.
[0015] The zinc layer formation step (S001) involves degreasing the surface of the substrate 1 and then performing a well-known zincate treatment to replace the oxide film formed on the surface of the substrate 1, which is made of magnesium or an alloy thereof, with zinc, thereby forming a zinc layer 2 on the surface of the substrate 1. It is preferable to use the well-known double zincate method for the zincate treatment. The double zincate method involves forming a zinc layer 2 on the degreased surface of the substrate 1 by zincate treatment, then removing the zinc layer 2 formed in the previous zincate treatment with nitric acid, and then performing zincate treatment on the surface of the substrate 1 again to form another zinc layer 2. Alternatively, the double zincate method involves forming a zinc layer on the surface of the substrate 1 once using the zincate method, then peeling off the zinc layer with acid, and then forming a zinc layer again using the zincate method. Therefore, the zinc particles forming the zinc layer 2 become denser and finer, resulting in improved adhesion to the substrate and enabling more uniform coating. Figure 3 is an enlarged cross-sectional view of the substrate 1 surface after the zinc layer formation process S001. As shown in Figure 3, when the zinc layer formation process 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, corrosion resistance is increased compared to the state of the substrate 1 alone. Therefore, subsequent surface treatments can be carried out smoothly. Alternatively, in the zinc layer formation process S001, the substrate 1 may be degreased, the oxide film may be removed by etching with acid, and then the zinc plating process may be carried out.
[0016] In this way, a zinc layer 2 can be formed on the surface of a magnesium or magnesium alloy substrate 1 by performing the zinc layer formation step S001. The thickness of the zinc layer formed in the zinc layer formation step (S001) is preferably 0.01 μm or more and 2 μm or less. If the thickness is 0.01 μm or more, almost the entire surface of the substrate 1 is covered by the zinc layer 2, allowing for efficient coating of the substrate 1 by subsequent surface treatments. On the other hand, if the thickness is 2 μm or less, variations in the size of the zinc grains in the zinc layer 2 are less likely to occur, thus suppressing the generation of large surface roughness by subsequent surface treatments.
[0017] Next, the copper plating layer formation process S002 is performed on the substrate 1 on which the zinc layer 2 is formed. In the copper plating layer formation process S002, the substrate 1 on which the zinc layer 2 is formed is immersed in a well-known electrolytic copper plating solution, and a voltage is applied so that the substrate 1 on which the zinc layer 2 is formed becomes the cathode electrode, and copper or platinum becomes the anode electrode, and the copper plating treatment is performed at 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.
[0018] By forming a copper plating layer 3 on the surface of the substrate 1 on which the zinc layer 2 is formed, the surface exposure of the substrate 1, which is magnesium or an alloy thereof, can be minimized. Furthermore, copper has a lower ionization tendency than zinc. Therefore, when moving on to the aluminum plating layer formation process S003, the presence of the copper plating layer 3 makes it easier to handle the substrate 1. Thus, in the method for manufacturing plated products according to the embodiment of the present invention, by performing the copper plating layer formation process S002 after the zinc layer 2 has been formed on the surface of the substrate 1, it is possible to efficiently cover the surface of the substrate 1 with the zinc layer 2 and the copper plating layer 3.
[0019] Furthermore, since the oxide film of the copper plating layer 3 has lower chemical stability than the oxide film of nickel plating, which is a typical metal plating, even if an oxide film is formed on the surface of the copper plating layer 3, the oxide film can be easily removed, enabling the efficient manufacture of plated products having an aluminum plating layer. Furthermore, the copper plating layer 3 has lower internal stress compared to nickel plating. Therefore, the copper plating layer 3 also has the advantage of being less prone to delamination between itself and the plating layer formed on top of it. For these reasons, the copper plating layer 3 was used as the underlayer for the aluminum plating layer in order to improve the production efficiency of plated products having an aluminum plating layer.
[0020] The thickness of the copper plating layer 3 is preferably greater than the thickness of the zinc layer 2. Therefore, the thickness of the copper plating layer 3 is preferably 1 μm or more. If it is 1 μm or more, the copper plating layer 3 is more likely to form on almost the entire surface of the zinc layer 2, and the occurrence of untreated areas in the coating by the copper plating layer can be suppressed. On the other hand, in order to avoid unnecessarily increasing the cycle time of the copper plating layer formation process S002, the thickness of the copper plating layer 3 is preferably 30 μm or less. Furthermore, in the present invention, the copper plating layer formation process 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, but may also be performed by electroless copper plating. Figure 4 is an enlarged cross-sectional view of the substrate 1 surface after the copper plating layer formation process S002. As shown in Figure 4, when the copper plating layer formation process S002 is performed, a zinc layer 2 and a copper plating layer 3 are formed on the surface of the substrate 1.
[0021] Next, the aluminum plating layer formation process S003 is performed on the substrate 1 on which the copper plating layer 3 is formed. In the aluminum plating layer formation process S003, the substrate 1 on which the copper plating layer 3 is formed is immersed in an electrolytic aluminum plating solution, and a voltage is applied so that the substrate 1 on which the copper plating layer 3 is formed becomes the cathode electrode, and the other side, for example, aluminum, becomes the anode electrode, thereby forming an aluminum plating layer 4 on the substrate 1 on which the copper plating layer 3 is formed.
[0022] In the method for manufacturing plated products according to an embodiment of the present invention, in the aluminum plating layer 4 formation step S003, even if an oxide film is formed on the surface of the copper plating layer 3 as described above, the aluminum plating layer 4 can be formed at the same time as the oxide film is removed. Therefore, in the method for manufacturing plated products according to an embodiment of the present invention, the following aluminum plating solution was used. This aluminum plating solution contains at least (1) dimethyl sulfone, (2) aluminum halide, (3) ammonium chloride, and (4) tetramethylammonium chloride.
[0023] This aluminum plating solution is a mixture of dimethyl sulfone, aluminum halide, ammonium chloride, and tetramethylammonium chloride. In addition to the halogen ions obtained from the aluminum halide mixed with dimethyl sulfone, the chloride ions obtained from ammonium chloride and tetramethylammonium chloride reduce the oxide film of the copper plating layer 3, thereby exhibiting an oxide film removal effect on the copper plating layer 3. In this aluminum plating solution, ammonium chloride or tetramethylammonium chloride mixed in dimethyl sulfone dissociates as shown in Formula 1 below. Here, R is hydrogen (H) or a methyl group (CH3), DM is a dimethyl group, and N is nitrogen. NR4Cl -> NR4 + +Matsu - ...(Formula 1) Furthermore, when aluminum chloride is used as the aluminum halide, some dimethyl sulfone (DMSO2) reacts with aluminum chloride (AlCl3) to form Al(DMSO2)3. 3+ Chloroaluminate (AlCl4) is formed by coordinating four chloride ions to one aluminum ion. ― Chloride ions containing ) are formed.
[0024] As described above, in the aluminum plating solution of this embodiment, 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. As a result, the work required to remove the oxide film can be eliminated, and plated products having an aluminum plating layer can be manufactured efficiently.
[0025] In particular, since aluminum has a lower standard oxidation-reduction potential than hydrogen (-1.66V vs. SHE), if water molecules are attached to the surface of the copper plating layer 3, the growth of the aluminum plating layer will be suppressed in the areas where the molecules are attached. On the other hand, when forming an aluminum plating layer on a metal layer other than the copper plating layer 3, it is usually necessary to remove the oxide film for the reasons mentioned above, and the surface is cleaned after the oxide film removal. An aqueous solution is generally used for this cleaning, but if even a small amount of moisture adheres to the surface on which the aluminum plating layer is to be formed, the formation of the aluminum plating layer will be suppressed in that area, and irregularities will occur on the surface of the aluminum plating layer 4. Although the surface irregularities can be reduced by increasing the thickness of the aluminum plating layer, there are still areas where the adhesion between the aluminum plating layer and the underlying layer is reduced, resulting in a decrease in the adhesion of the aluminum plating layer.
[0026] On the other hand, in the aluminum plating layer formation step S003 in this embodiment, the oxide film formed on the copper plating layer 3 is removed by the aluminum plating solution in the embodiment of the present invention. In other words, the aluminum plating layer formation step S003 can also remove the oxide film, making it possible to omit the oxide film removal step after the formation of the copper plating layer 3. Furthermore, it is possible to eliminate the need for subsequent treatment of exposing the substrate 1 to moisture, enabling the efficient formation of an aluminum plating layer with good adhesion. In this embodiment, it is also possible to perform such an oxide film removal step. For example, even if the oxide film cannot be completely removed, the oxide film removal step may be performed to thin the thickness of the oxide film or to reduce the area covered by the oxide film. In this case, it is not necessary to completely remove the oxide film. By doing so, the reliability of oxide film removal by the aluminum plating solution can be improved. When the oxide film removal step is performed, a cleaning step is required. After the cleaning step, a drying treatment is performed to remove moisture, but at that time, an oxide film may be formed on the copper plating layer 3. Even in such cases, by performing the aluminum plating layer formation step using this aluminum plating solution, it becomes unnecessary to perform oxide film removal again. Therefore, efficiency is improved. Furthermore, the aluminum plating solution used in this embodiment makes it possible to narrow or eliminate the area in which 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 manufacture of plated products with a good design and less surface irregularities on the aluminum plating layer 4. Moreover, when anodizing treatment is performed on the surface of the aluminum plating layer 4, there is a possibility that depressions and pores in the aluminum plating layer 4 caused by the oxide film of the copper plating layer 3 may be enlarged, but the aluminum plating solution used in this embodiment makes it possible to suppress the occurrence of such phenomena.
[0027] Furthermore, in order to improve the ability of the aluminum plating solution to remove oxide films, in the aluminum plating layer formation step S003, it is preferable to stir the plating solution with a stirring device or to 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 the aluminum plating solution on the surface of the copper plating layer 3. This allows chloride ions and halide ions to be 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. In addition, it is preferable not to apply a voltage to the substrate 1 on which the copper plating layer 3 has been formed for at least 1 second after immersing it in the aluminum plating solution. By applying a negative potential to the substrate 1 on which the copper plating layer 3 has been formed for at least 1 minute after immersion in the aluminum plating solution, more preferably after a period of 3 to 10 minutes, it becomes possible to form the aluminum plating layer 4 with the oxide film formed on the surface of the copper plating layer 3 removed, improving the adhesion and surface smoothness of the aluminum plating layer 4. In this way, by immersing the magnesium or magnesium alloy substrate 1 on which the copper plating layer 3 is formed in the aluminum plating solution while maintaining a state where no voltage is applied for 3 minutes or more, the oxide film of the copper plating layer 3 becomes easier to remove. Also, as the magnesium or magnesium alloy substrate approaches the temperature of the aluminum plating solution, the formation of the aluminum plating layer 4 proceeds more smoothly. Furthermore, by keeping the immersion time to 10 minutes or less, it is possible to suppress the effect of the aluminum plating solution on dissolving the copper plating layer.
[0028] Furthermore, the aluminum plating solution used in the manufacturing method of the 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.
[0029] In order to investigate the effects on ionic species in the aluminum plating solution, the present inventors performed nuclear magnetic resonance (NMR) measurements by changing the addition amounts of ammonium chloride and tetramethylammonium chloride, and analyzed the amount of ions in the aluminum plating solution. 27 From the Al-NMR measurement, it was found that by adding ammonium chloride or tetramethylammonium chloride to an aluminum plating solution composed of dimethyl sulfone and aluminum chloride, the amount of Al(DMSO2)3 3+ in the plating solution decreased. Here, Al(DMSO2)3 3+ is formed by the reaction of dimethyl sulfone and aluminum halide. From this, it is speculated that the chloride ions (Cl - ) dissociated from ammonium chloride or tetramethylammonium chloride cause the following change in Al(DMSO2)3 3+ in the plating solution.
[0030] 4NR4Cl + Al(DMSO2)3 3+ + 3AlCl4 - -> 4NR4 + + 4AlCl3 + 3DMSO2 ··· (Equation 2)
[0031] According to the findings of the present inventors, increasing the concentration of aluminum halide with respect to dimethyl sulfone causes a decrease in the electrical conductivity of the plating solution. When the electrical conductivity decreases, the film formation rate of the aluminum plating layer 4 slows down. On the other hand, the higher the amount of DMSO2, the higher the electrical conductivity of the plating solution. From this, it is preferable to increase the amount of ammonium chloride or tetramethylammonium chloride represented as NR4Cl. That is, without increasing the concentration of aluminum chloride with respect to dimethyl sulfone, by increasing the concentrations of ammonium chloride and tetramethylammonium chloride with respect to dimethyl sulfone, it is preferable to increase the amount of chloride ions. Thereby, it is possible to suppress a decrease in the electrical conductivity in the aluminum plating solution and maintain the film formation efficiency of the aluminum plating layer 4 at a high level, while improving the ability to remove the oxide film of the copper plating layer 3.
[0032] Furthermore, as shown in Equation 2, by adding ammonium chloride or tetramethylammonium chloride, NR4 + NH4 represented by + yaN(CH3) + The amount of NH4 increases in the plating solution. These cations have the effect of suppressing the amplification of 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 the overpotential, which is the potential required to initiate the electrodeposition of aluminum, differs for each type of metal, but NH4 + This is because the ammonium ions represented by [formula] adhere to the surface of the material on which aluminum is electrodeposited, thereby reducing the difference in overpotentials between the surfaces of each material.
[0033] For example, in the plated product of this embodiment, a magnesium or magnesium alloy substrate 1, a zinc layer 2, and a copper plating layer 3 are formed on the aluminum plating layer 4. Preferably, at least the surface of the substrate 1 on which the aluminum plating layer 4 is formed is uniformly covered with the copper plating layer 3. However, the zinc layer 2 may not completely cover the surface of the substrate 1, and in some cases, pores that extend to the surface of the substrate 1 may be formed. In the manufacturing method of plated products in this embodiment, the formation of a copper plating layer 3 on the zinc layer 2 functions to seal the pores in the zinc layer 2. However, since the magnesium of the substrate 1 has a greater ionization tendency than copper, magnesium may dissolve during the copper plating layer formation process S002, and the through-holes in the zinc layer 2 may not be completely sealed by the copper plating layer 3. In such cases, the surface on which the aluminum plating layer 4 is formed will expose 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. In this state, unlike in this embodiment, if a conventional aluminum plating treatment is performed, the growth of the aluminum plating layer 4 will be uneven due to the difference in overvoltage of each metal, and the surface smoothness of the aluminum plating layer 4 will be reduced.
[0034] The aluminum plating solution used in the method for manufacturing plated products in the embodiments of the present invention contains, as described above, NR4 + NH4 represented by + yaN(CH3) + A large amount of cations is present in the aluminum plating solution. When a substrate 1 with a copper plating layer 3 formed on it is immersed in an aluminum plating solution containing such cations, and a voltage is applied so that the cathode side is facing upwards, the NR4 of the aluminum plating solution + Positive ions like these adhere to the entire surface of the substrate 1. As a result, the difference in overpotential between the exposed copper plating layer 3 and the exposed areas of other metals, such as the zinc layer 2 or the magnesium of the substrate 1, becomes smaller. Therefore, if the aluminum plating layer is formed until it reaches a sufficient thickness, the surface smoothness of the aluminum plating layer 4 is expected to be better than that of the aluminum plating layer 4 formed with an aluminum plating solution that does not contain ammonium chloride or tetramethylammonium chloride.
[0035] Furthermore, NR4 is formed on the surface where the aluminum plating layer 4 is formed. + In order to facilitate the supply of cations represented by , it is preferable to vibrate the substrate 1 on which the copper plating layer 3 is formed, which serves as the cathode electrode, or to stir the aluminum plating solution while aluminum is being electrodeposited onto the substrate 1 on which the copper plating layer 3 is formed.
[0036] Regarding the aluminum plating solution in the method for manufacturing plated products in the embodiments of the present invention, the blending ratio of dimethyl sulfone, aluminum halide, ammonium chloride, and tetramethylammonium chloride is preferably, for example, 3.5 moles to 4.2 moles of aluminum halide per 10 moles of dimethyl sulfone, and more preferably 3.8 moles to 4.2 moles. Also, 0.1 moles to 0.5 moles of ammonium chloride per 10 moles of dimethyl sulfone, and more preferably 0.2 moles to 0.3 moles. Furthermore, 0.1 moles to 1.5 moles of tetramethylammonium chloride per 10 moles of dimethyl sulfone is desirable, and more preferably 0.3 moles to 1.5 moles.
[0037] By using aluminum halides at a ratio of 4.2 moles or less per 10 moles of dimethyl sulfone, the decrease in the electrical conductivity of the aluminum plating solution is suppressed, contributing to the prevention of a decrease in the diffusion rate of aluminum ions. Furthermore, since the increase in the liquid resistance of the aluminum plating solution can be suppressed, heat generation during aluminum electrodeposition by the aluminum plating solution can be suppressed, preventing deterioration and evaporation of the aluminum plating solution, and thus suppressing the deterioration of the quality of the aluminum plating layer 4. On the other hand, if 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 in the circulation path of the aluminum plating solution. Moreover, if the amount of aluminum halide is 3.8 moles or more, it is possible to further lower the melting point of the aluminum plating solution. In addition, among the aluminum halides, aluminum chloride is preferable. Since the gas generated during aluminum plating is chlorine gas, the chemical effect on the solvent, dimethyl sulfone, can be reduced.
[0038] Furthermore, if the amount of ammonium chloride and tetramethylammonium chloride is 0.1 mole or more per 10 moles of dimethyl sulfone, the increase in chloride ions in the aluminum plating solution will be significant, contributing to an improved ability to remove the oxide film of the copper plating layer 3. Also, NR4 + A supply of cations represented by NH4 is also provided. + As the amount of ammonium ions also increases, the effect of reducing the difference in overvoltage to different metal species appearing on the surface of the substrate 1 forming the aluminum plating layer 4 is also greatly enhanced. Therefore, in the method for manufacturing plated products in this embodiment, it is possible to reduce the influence of surface irregularities and pores in the zinc layer 2 and copper plating layer 3 on the surface smoothness of the aluminum plating layer 4. Furthermore, if the amount of ammonium chloride is 0.2 moles or more per 10 moles of dimethyl sulfone, it is possible to further suppress the blackening of the aluminum plating layer 4.
[0039] Furthermore, by limiting the amount of ammonium chloride to 0.5 moles or less per 10 moles of dimethyl sulfone, the increase in the amount of gas generated from the surface of the cathode electrode during the production of the aluminum film can be suppressed, contributing to the suppression of a decrease in electrodeposition efficiency. Further limiting it to 0.3 moles or less further suppresses gas generation, which is preferable in terms of improving the surface smoothness of the aluminum plating layer 4. Additionally, if the content ratio of tetramethylammonium chloride is 0.1 moles or more per 10 moles of dimethyl sulfone, an effect of increasing the electrical conductivity of the electroplated aluminum solution can be expected. If it is 0.3 moles or more, the electrical conductivity of the electroplated aluminum solution can be further increased, which is more desirable in terms of improving the film formation rate and efficiency. If it is 1.5 moles or less, the Al(DMSO2)3 in the plating solution is preferable. 3+ This method suppresses the decrease in quantity, making it less likely for black deposits (called burning) to occur due to insufficient supply of aluminum ions to the cathode electrode surface to develop, thereby suppressing a decrease in electrodeposition efficiency.
[0040] In the aluminum plating layer formation process using the aluminum plating solution described above, it is preferable, for example, to set the temperature of the aluminum plating solution to 80°C or higher and 110°C or lower. Furthermore, the current density between the anode electrode and cathode electrode immersed in the aluminum plating solution should be 15 mA / cm². 2 More than 200mA / cm 2 It is preferable to carry out the process under the following conditions. The lower limit of the aluminum plating solution temperature should be determined considering the melting point of the aluminum plating solution, preferably 85°C, and more preferably 95°C. On the other hand, by setting the upper limit of the aluminum plating solution temperature to 110°C, deformation of the substrate 1 can be suppressed. If the temperature is 110°C or lower, the activity of the reaction between the aluminum plating layer 5 and the aluminum plating solution can be suppressed, and the increase in the amount of impurities in the aluminum plating layer 4 can be suppressed. Also, the current density should be 15 mA / cm². 2 If the above conditions are met, the film deposition efficiency will be maintained, and NR4 +The effect of the cation represented by this formula covering the substrate 1 on which the copper plating layer, which serves as the cathode electrode, is formed is sufficiently maintained, so it is expected that the pinholes formed in the aluminum plating layer 4 will be reduced. 2 The following conditions suppress the decomposition of nitrogen compounds such as ammonium chloride and tetramethylammonium chloride, making it easier to maintain a stable plating process. The above aluminum plating solution is 100 mA / cm². 2 Even when applying the above current densities, stable plating is possible, thus improving the film deposition rate. The plating time depends on the desired thickness of the aluminum plating layer 4, the temperature of the electrolyte, and the applied current density, but is generally preferably 1 to 90 minutes, and 1 to 60 minutes is more desirable considering production efficiency.
[0041] Figure 5 is an enlarged cross-sectional view of the substrate 1 surface after the aluminum plating layer formation process S003 described above. As shown in Figure 5, after the copper plating layer formation process S002, there is a zinc layer 2 formed on the surface of the substrate 1, a copper plating layer 3 formed on the zinc layer 2, and an aluminum plating layer 4 formed on the copper plating layer 3. In the manufacturing method of the plated product in the embodiment of the present invention, 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 process S004. If the entire aluminum plating layer 4 is anodized, the anodized film 5 will come into contact with the copper plating layer 3. In such a case, as mentioned above, it will cause a decrease in adhesion. Therefore, in the aluminum plating layer formation process S003, the anodized film 5 is formed to be at least 1 μm thicker than the design thickness, as described above. Furthermore, if smoothness is required on the surface of the plated product, the surface after the aluminum plating layer formation process S003 may be polished. In such cases, it is preferable to form the aluminum plating layer 4 even thicker, taking into account the thickness to be polished. When polishing the surface of the aluminum plating layer 4, it is preferable to polish it to a roughness of 1.5 μm or less with an arithmetic mean roughness Ra.
[0042] Furthermore, by reducing the size of the crystal grains of the aluminum plating layer 4, the surface roughness of the aluminum plating layer 4 after aluminum plating can be reduced. Therefore, by intentionally including impurities such as copper (Cu) or silicon (Si) during the aluminum plating layer formation process, the crystal grains can be refined, thereby reducing surface roughness. For example, by ionizing a certain amount of Cu, etc., in the aluminum plating solution, the purity of the aluminum plating layer 4 can be intentionally reduced, thereby refining the crystal grains. For example, in 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% to 24% Si, 0.1% to 5% Cu, and 0.15% to 1.8% iron (Fe) as the anode electrode. For example, the anode electrode can be obtained by shaping used AC2A alloy material into an electrode shape by casting or the like. Furthermore, the current density at the anode electrode during aluminum plating should be 10 mA / cm². 2 More than 200mA / cm 2 By doing the following, Cu can be included in the electrodeposited film. In this embodiment, it is preferable that the aluminum plating layer 4 contains 90% by mass or more aluminum, and that other elements are kept to less than 10% by mass.
[0043] Next, an anodizing treatment S004 is performed on the substrate 1 on which the aluminum plating layer 4 is formed. The anodizing treatment method is not particularly limited and can be carried out by known methods. The anodizing treatment conditions are set appropriately according to the desired thickness of the anodized film 5 and the anodizing solution used. If necessary, the aluminum plating layer 4 may be divided into multiple parts and each part may be subjected to anodizing treatment under different conditions. In addition, the anodizing treatment may impart color to the anodized film 5 by natural color development, or it may be imparted to the anodized film 5 by coloring (so-called color anodizing).
[0044] From the above, it is desirable that the total thickness of the aluminum plating layer 4 and the anodic oxide film 5 after being formed in the anodic oxidation process S004 be 21 μm or more and 100 μm or less. In this case, the film thickness of the aluminum plating layer 4 after the anodic oxidation process S004 is preferably 11 μm or more and less than 100 μm, and more preferably 11 μm or more and 70 μm or less. Furthermore, the film thickness of the anodic oxide film 5 after the anodic oxidation process S004 is preferably 10 μm or more and 30 μm or less. In other words, when performing electroplating, 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 film 5 formed in the anodic oxidation process S004. Note that if the color tone and texture exhibited by aluminum metal are to be utilized, the anodic oxidation process S004 may be omitted. In that case, the aluminum plating layer 4 will be the outermost layer, and the preferred film thickness at this time is preferably 1 μm or more and 100 μm or less, and more preferably 1 μm or more and 70 μm or less.
[0045] As described above, according to this embodiment, the surface of magnesium or magnesium alloy can be given an appearance with excellent decorative properties. 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 part. In the method for manufacturing plated products according to the embodiment of the present invention, good adhesion is ensured, and plated magnesium or magnesium alloy products that can be used in a wider range of applications than conventional methods can be obtained. Furthermore, corrosion resistance and oxidation resistance can be improved, so it is suitable for surface treatment of various exterior parts such as electronic equipment, automotive parts, optical parts, and mechanical parts.
[0046] In this specification, roughness measurement, film thickness measurement, and adhesion test were performed as follows. Arithmetic mean roughness measurements were performed in accordance with the international standard ISO 4288:1996. In particular, roughness measurements for non-periodic roughness curves were used, and depending on the surface smoothness, the cutoff value λc was set to 0.08 mm or more and 0.8 mm or less, the reference length L was set to 0.08 mm or more and 0.8 mm or less, and the evaluation length Ln was set to a range of 0.4 to 4 mm for surface roughness measurements. Next, for measuring the film thickness, a cross-section of the plated product was photographed using a scanning electron microscope. The film thickness was measured at multiple arbitrary locations, excluding the vicinity of the outer periphery of each layer, from the captured cross-sectional images, and the average value was calculated as the film thickness. Furthermore, for adhesion testing, a cross-cut method was used in accordance with the Japanese Industrial Standard JIS K 5600-5-6:1999. This method involved creating 25 cuts (5 vertically and 5 horizontally) with a width of 2 mm, pressing them onto the aluminum plating layer or anodized film using cellophane adhesive tape, and then pulling them vertically to evaluate whether delamination occurred. In this specification, this method is referred to as the grid test.
[0047] Furthermore, the disclosures in this specification include inventions in the following embodiments, with the aim of obtaining plated products, etc., that can achieve high design quality on a magnesium or magnesium alloy substrate. In order to achieve the aforementioned objectives, another aspect of the present invention provides a plated product comprising a base material made of magnesium or a magnesium alloy, a zinc layer formed on the surface of the base material, a copper plating layer formed on the zinc layer, and an aluminum plating layer formed on the copper plating layer.
[0048] Furthermore, according to this embodiment, the thickness of the copper plating layer is preferably 1 μm or more and 30 μm or less, and the copper plating layer is preferably thicker than the zinc layer. The thickness of the aluminum plating layer is preferably 1 μm or more and 100 μm or less. Furthermore, it is preferable to have an anodic oxide film on the aluminum plating layer. The thickness of the aluminum plating layer is preferably 1 μm or more and 70 μm or less, and the anodic oxide film is preferably 10 μm or more and 30 μm or less.
[0049] In order to achieve the aforementioned objectives, in one other aspect of the present invention, it is preferable that the method for manufacturing a plated product 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 performing a copper plating treatment on the zinc layer to form a copper plating layer on the zinc layer, and an aluminum plating layer forming step of performing an aluminum plating treatment on the copper plating layer to form an aluminum plating layer on the copper plating layer. Furthermore, it is preferable to further perform an anodizing treatment step of performing an anodizing treatment on the aluminum plating layer. The aluminum plating solution used in the aluminum plating layer forming step is (i) dialkyl sulfone, (ii) aluminum halide, and (iii) ammonium halide, a hydrogen halide of a primary amine, a hydrogen halide of a secondary amine, a hydrogen halide of a tertiary amine, and a general formula: R 1 R 2 R 3 R 4 N·X(R 1 ~R 4 It is preferable that it contains at least one nitrogen-containing compound selected from the group consisting of quaternary ammonium salts (where is the same or different alkyl group, and X represents a counteranion for the quaternary ammonium cation). And R 1 ~R 4 Examples of alkyl groups represented by include methyl, ethyl, propyl, and hexyl groups, which have 1 to 6 carbon atoms (they can be linear or branched). X can be a halide ion such as chloride, bromide, or iodide, as well as BF4 - PF6 - Examples include the following. Specific examples of compounds include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, and tetraethylammonium boron tetrafluoride. As for suitable nitrogen-containing compounds, hydrochlorides of tertiary amines, such as trimethylamine hydrochloride, can be cited because they facilitate the formation of a high-purity aluminum plating layer 4 at a fast film formation rate. [Examples]
[0050] Next, an aluminum plating layer 4 or an anodic oxide film was formed according to the following examples. In all embodiments, if the substrate 1 was in the shape of a board, at least two surfaces were coated with the aluminum plating layer 4. If the substrate 1 was in the shape of a round stick, the bottom surface and the cylindrical surface were coated with the aluminum plating layer 4. The surface roughness of all of these substrates 1 was 0.74 μm or less in Ra, indicating a good smooth surface. These substrates 1 were subjected to zincate treatment corresponding to the zinc layer formation step S001, electrolytic copper plating corresponding to the copper plating layer formation step S002, and electrolytic aluminum plating corresponding to the aluminum plating layer formation step S003. Furthermore, as shown in Table 1 below, in some embodiments, the aluminum plating layer formed in the aluminum plating layer formation step S003 was subjected to anodizing treatment to form an anodic oxide film.
[0051] In the zinc layer formation process S001, the zincate treatment was performed by degreasing the substrate 1 followed by a double zincate treatment. The zinc layer 2 was formed with a thickness of approximately 1 μm or less.
[0052] Next, in the copper plating layer formation process S002, the copper plating layer 3 was formed by immersion in a copper plating solution containing copper cyanide, under conditions that the thickness was greater than 8 μm but less than 22 μm.
[0053] Next, 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 mole of tetramethylammonium chloride. Two liters of this prepared aluminum plating solution were placed in a plating tank, and an aluminum plating layer 4 was formed under conditions where the liquid temperature was between 95°C and 100°C. In all examples and comparative examples, after forming the copper plating layer 3 on the substrate 1, the oxide film removal treatment of the copper plating layer 3 was not performed, and the substrate was immersed in the aluminum plating solution in a plating tank for about 5 minutes without applying voltage to perform the aluminum plating layer formation process S003.
[0054] Table 1 shows the details of the plated products from Example 1 to Example 18. In Table 1, item (a) indicates the material of the substrate, item (b) indicates the shape of the substrate, item (c) indicates the composition of the layers formed sequentially from the substrate 1 side, item (d) indicates the results of the grid test, item (e) indicates the results of the visual inspection, and item (f) indicates the current density (mA / cm²) flowed through the aluminum plating solution during the aluminum plating layer formation process. 2 ), item (g) shows the total film thickness (μm) of the zinc layer 2 and copper plating layer 3, item (h) shows the film thickness (μm) of the aluminum plating layer 4, and item (i) shows the film thickness (μm) of the anodic oxide coating. In Table 1, "-" indicates that no test or film thickness measurement was performed. In item (b), "Board" indicates that the substrate is flat, and "Round Stick" indicates that the substrate is cylindrical. In item (d), ○ indicates that no peeling was observed in the grid test, and in item (e), ○ indicates that no pinholes were observed in the plated product visually and no peeling was observed when touched with a finger. On the other hand, in item (e), △ indicates that no peeling was observed when touched with a finger, but pinholes were observed. In item (h), the values inside parentheses are estimated film thickness values obtained from the current density and plating time (current application time) during the aluminum plating process set in aluminum plating layer formation process S003, while the others are actual measured film thickness values after the plated product has been formed.
[0055] Examples 1 through 8, and Example 18, were performed up to the aluminum plating layer formation step S003, but the anodizing treatment step S004 was omitted. On the other hand, Examples 9 through 17 were performed after the aluminum plating layer formation step S003, followed by the anodizing treatment step S004. For Examples 12, 15, and 16, the thickness of the anodic oxide film was measured by cross-sectional observation. Then, the aluminum plating layer formation process was carried out by changing the current density for each embodiment.
[0056] [Table 1]
[0057] According to the results in Table 1, the grid test results were good in Examples 1 to 5 and Examples 14 to 18, and no peeling was observed. Furthermore, in all examples and comparative examples, no peeling from the substrate 1 was observed even when touched by hand. From these results, it can be seen that by performing the aluminum plating layer formation process S003 with the aluminum plating solution in this example, it was possible to form an aluminum plating layer with good adhesion without removing the oxide film formed on the copper plating layer 3. Although the grid test was not performed in Examples 6 to 13, it is presumed that they have similar adhesion to Examples 3 and 4 because they were performed under the same conditions as Examples 3 and 4 (copper plating layer formed on the substrate, and the same current density during aluminum plating layer formation).
[0058] In Example 18, it was confirmed that pinholes were formed on the surface of the aluminum plating layer 4. This is thought to be because the current density flowing through the aluminum plating solution in the aluminum plating layer formation process S003 is low. Due to the low current density, NR4 has the effect of reducing the difference in overvoltage between different metal species. + It is presumed that the cations represented by the formula were unable to adequately cover the substrate 1, which is the cathode electrode, and as a result, the pores created in the copper plating layer 3 could not be 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 higher. [Explanation of symbols]
[0059] 1: Substrate, 2: Zinc layer, 3: Copper plating layer, 4: Aluminum plating layer, 5: Anodized layer, S001: Zinc layer formation process, S002: Copper plating layer formation process, S003: Aluminum plating layer formation process, S004: Anodized process
Claims
1. A zinc layer formation step in which a zinc layer is formed on the surface of a substrate made of magnesium or a magnesium alloy, A copper plating layer formation step involves performing a copper plating treatment on the zinc layer to form a copper plating layer on the zinc layer, The process includes an aluminum plating layer formation step, in which an aluminum plating treatment is performed on the copper plating layer to form an aluminum plating layer on the copper plating layer. The aluminum plating solution used in the aluminum plating layer formation process contains dimethyl sulfone and, per 10 moles of dimethyl sulfone, aluminum chloride in an amount of 3.5 moles to 4.2 moles, ammonium chloride in an amount of 0.1 moles to 0.5 moles, and tetramethylammonium chloride in an amount of 0.1 moles to 1.5 moles. In the aluminum plating layer formation step, the substrate on which the copper plating layer has been formed in the copper plating layer formation step and the anode electrode are immersed in the aluminum plating solution, the substrate on which the copper plating layer has been formed serves as the cathode electrode, and when a voltage is applied between the cathode electrode and the anode electrode, the current density of the cathode electrode flowing between the cathode electrode and the anode electrode is 15 mA / cm². ２ 200mA / cm or more ２ A method for manufacturing plated products, characterized by the following:
2. The thickness of the copper plating layer is 1 μm or more and 30 μm or less. The method for manufacturing a plated product according to claim 1, characterized in that the copper plating layer is formed to be thicker than the zinc layer.
3. The method for manufacturing a plated product according to claim 2, characterized in that the thickness of the aluminum plating layer is 1 μm or more and 100 μm or less.
4. The method for manufacturing a plated product according to claim 1, further comprising an anodizing step of performing an anodizing treatment on the aluminum plating layer to form an anodized film.
5. The method for manufacturing a plated product according to claim 4, wherein the total thickness of the aluminum plating layer and the anodic oxide film is 21 μm or more and 100 μm or less, and the thickness of the anodic oxide film is 11 μm or more and 30 μm or less.
6. The method for producing a plated product according to claim 1, wherein the aluminum plating solution contains 0.2 moles or more and 0.5 moles or less of ammonium chloride per 10 moles of dimethyl sulfone.
7. The method for manufacturing a plated product according to claim 1, characterized in that the anode electrode includes an aluminum alloy containing silicon or copper.
8. The method for manufacturing a plated product according to claim 1, characterized in that the aluminum plating layer formation step involves immersing the substrate on which the copper plating layer is formed in the aluminum plating solution, and applying a negative potential to the substrate after 1 minute or more has elapsed since immersion.