WO2019143322A1

WO2019143322A1 - Non-aqueous electrolytes-based electrodeposition on magnesium substrates

Info

Publication number: WO2019143322A1
Application number: PCT/US2018/013935
Authority: WO
Inventors: Chalam Kashyap; Kuan-Ting Wu
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2018-01-17
Filing date: 2018-01-17
Publication date: 2019-07-25

Abstract

In one example, a method is described, which may include providing a magnesium substrate and electrodepositing a zinc layer on the magnesium substrate using a first non-aqueous ionic liquid as an electrolyte.

Description

NON-AQUEOUS ELECTROLYTES-BASED ELECTRODEPOSITION ON

MAGNESIUM SUBSTRATES

BACKGROUND

[0001] Metals such as magnesium or magnesium alloys may be used in housings of various portable electronic devices such as notebook computers, tablet computers, MP3 players, personal digital assistances (PDAs), mobile phones, and the like, because of the mechanical strength. Metallic-appearing coatings such as aluminum coatings may be formed on the magnesium or magnesium alloy substrates to make the electronic devices fashionably and aesthetically appealing to users and to prevent the corrosion. Further, the metallic-appearing coatings may be anodized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Examples are described in the following detailed description and in reference to the drawings, in which:

[0003] FIG. 1 illustrates a flow diagram of an example method for electrodepositing a zinc layer on a magnesium substrate;

[0004] FIG. 2 illustrates a flow diagram of an example method for forming an electronic device housing;

[0005] FIG. 3 illustrates a flow diagram of an example process for electrodepositing zinc and aluminum layers on a magnesium or magnesium alloy substrate;

[0006] FIG. 4 illustrates a schematic representation of an example first electroplating process and an example second electroplating process for depositing a zinc layer and an aluminum layer, respectively; and

[0007] FIG. 5 illustrates a schematic representation of an example electronic device housing.

1 DETAILED DESCRIPTION

[0008] Metals such as magnesium or magnesium alloys may be used for developing structural materials in the aviation industry, electronic industry, automobile industry, and many other areas because of the strength, thermal conductivity, recyclable die-cast thin-walled components, and other characteristics of the magnesium alloys. Further, metallic layers may be coated on the magnesium alloys to protect the magnesium alloys from corrosion and to make the magnesium substrates fashionably and aesthetically appealing to users. For example, aluminum, zinc, copper and the like may be used as the metallic layers on the magnesium alloys. However, the chemical properties of the magnesium alloys may provide poor corrosion resistance, and make the alloys particularly vulnerable to chemical reactions with water. For example, coating the magnesium alloys electrochemically with any metal in aqueous solutions may be complex as the magnesium may tend to react with the water, which may lead to formation of corrosion layers over the magnesium alloys.

[0009] Examples described herein may electrodeposit aluminum and zinc layers on magnesium substrates (e.g. , magnesium alloys) to prevent corrosion of the magnesium substrates. Examples described herein may use non-aqueous electrolytes to electrodeposit the aluminum and zinc layers on a surface of the magnesium substrates. The corrosion rate of the magnesium substrates in the nonaqueous electrolytes may be less than that in the aqueous electrolytes used for zinc layer electrodeposition. Examples described herein may provide a uniform, dense, and defect free zinc layer coatings on the magnesium substrates. The zinc coated magnesium substrates may exhibit a corrosion behaviour substantially similar to that of the pure zinc.

[0010] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present techniques. It will be apparent, however, to one skilled in the art that the present apparatus, devices and systems may be practiced without these specific details. Reference in the specification to "an example" or similar language means that a particular feature, structure, or characteristic described may be included in at least that one example, but not necessarily in other examples. [0011] Examples herein may provide a method for non-aqueous electrolyte- based electrodeposition on magnesium substrates. A zinc layer may be electrodeposited on a magnesium or magnesium alloy substrate using a first nonaqueous ionic liquid in a first electroplating process. Further, an aluminum layer may be electrodeposited on the zinc layer using a second non-aqueous ionic liquid in a second electroplating process. Then, the aluminum layer may be anodized.

[0012] Turning now to the figures, FIG. 1 illustrates a flow diagram of an example method 100 for electrodepositing a zinc layer on a magnesium substrate. Example magnesium substrate can be a magnesium alloy substrate. The terms "magnesium substrate" and "magnesium alloy substrate" may be used interchangeably throughout the document. At 102, a magnesium substrate may be provided. For example, the magnesium substrate may represent a material that can be utilized as a structural material in the aviation industry, electronic industry, automobile industry, and the like. At 104, a zinc layer may be electrodeposited on the magnesium substrate using a first non-aqueous ionic liquid as an electrolyte. In one example, the zinc layer may be electrodeposited on the magnesium substrate using a mixture of zinc ammonium chloride and the first non-aqueous ionic liquid. For example, the first non-aqueous ionic liquid may include a mixture of choline chloride and urea.

[0013] Further, an aluminum layer may be electrodeposited on the zinc layer using a second non-aqueous ionic liquid as an electrolyte and then the aluminum layer may be anodized. This is explained in FIG. 2.

[0014] FIG. 2 illustrates a flow diagram of an example method 200 for forming an electronic device housing. Example electronic device housing may be a housing of a mobile phone, personal digital assistant (PDA), notebook computer, tablet computer, MP3, MP4, global positioning system (GPS) navigator, digital camera, convertible device, a personal gaming device, or the like. Further, the electronic device housing may house various electronic components such as a central processing unit (CPU), a graphics processor, a memory element, a display panel, a printed circuit board, means for wireless data exchange, sensors, and the like.

[0015] At 202, a zinc layer may be electrodeposited on a magnesium alloy substrate using a first non-aqueous ionic liquid in a first electroplating process. For example, the zinc layer may be electrodeposited on the magnesium alloy substrate using a mixture of zinc ammonium chloride, choline chloride, and urea as the first non-aqueous ionic liquid in the first electroplating process. In one example, the zinc layer may be electrodeposited on the magnesium alloy substrate with the magnesium alloy substrate serving as a cathode during the first electroplating process. In this example, a graphite may serve as an anode during the first electroplating process.

[0016] At 204, an aluminum layer may be electrodeposited on the zinc layer using a second non-aqueous ionic liquid in a second electroplating process. The second non-aqueous liquid may include aluminum chloride (AlCb) and at least one compound selected from a group consisting of 1 -butyl-3-methylimidazolium chloride ([BMIM]CI), 1 -ethyl-3-methylimidazolium chloride ([EMIM]CI), alkyl- pyridinium chloride, alkyl-arylimidazolium chloride, and basionics™ AL-02. In one example, the aluminum layer may be electrodeposited on the zinc layer with the zinc layer coated magnesium alloy substrate serving as the cathode during the second electroplating process. In this example, a graphite may serve as an anode during the second electroplating process. The first and second electroplating processes are explained in FIG. 4.

[0017] At 206, the aluminum layer may be anodized to form the electronic device housing. For example, the aluminum layer may be anodized at a voltage of about 10-60 volts, a temperature of about 15-30° Celsius, and for about 20-50 minutes.

[0018] FIG. 3 illustrates a flow diagram of an example process 300 for electrodepositing zinc and aluminum layers on a magnesium or magnesium alloy substrate. At 302, a magnesium or magnesium alloy substrate may be cleaned, for instance, using a plasma cleaning. For example, the plasma cleaning may refer to a process of removing impurities and contaminants from a surface of the magnesium or magnesium alloy substrate using an ionized gas called plasma. Plasma cleaning may be performed in a vacuum chamber utilizing gases such as oxygen and/or argon gas.

[0019] At 304, the zinc layer may be electrodeposited on the magnesium or magnesium alloy substrate using a first non-aqueous ionic liquid as the electrolyte. At 306, the aluminum layer may be electrodeposited on the zinc layer using a second non-aqueous ionic liquid as the electrolyte. At 308, the electrodeposited aluminum layer may be anodized, for instance, at a voltage of about 10-60 volts, a temperature of about 15-30° Celsius, and for about 20-50 minutes.

[0020] The anodized aluminum layer may then be post-treated. At 310, the anodized aluminum layer may be washed. At 312, the anodized aluminum layer may be sealed, for instance, with an additional protection layer. The additional layer may assist in preventing corrosion abrasion and heat resistance of the magnesium or magnesium alloy substrate. At 314, the sealed magnesium or magnesium alloy substrate may be washed. At 316, the sealed magnesium or magnesium alloy substrate may be baked at a temperature of about 60-90° Celsius and for about 20-40 minutes.

[0021] FIG. 4 illustrates a schematic representation of an example first electroplating process 400A and an example second electroplating process 400B for depositing a zinc layer and an aluminum layer, respectively. As shown in FIG. 4, first electroplating process 400A may include a cathode 402, a zinc layer 404. an anode 406, a first plating tank 408, a first non-aqueous ionic liquid 410, and an electrical power supply 412.

[0022] In first electroplating process 400A, the magnesium alloy substrate may be immersed into first non-aqueous ionic liquid 410 inside first plating tank 408. The magnesium alloy substrate may be connected as cathode 402 to electrical power source 412 in first electroplating process 400A. Further, a graphite layer may be immersed into first non-aqueous ionic liquid 410. The graphite may be connected as anode 406 to electrical power source 412. Zinc layer 404 may be electrodeposited on the magnesium alloy substrate (i.e., cathode 402) upon supplying electric power during first electroplating process 400A.

[0023] Further as shown in FIG. 4, second electroplating process 400B may include an aluminum layer 414, a second non-aqueous ionic liquid 416, a second plating tank 418, an anode 420, an electrical power supply 422, and a cathode 424.

[0024] In second electroplating process 400B, aluminum layer 414 may be electrodeposited onto zinc layer 404. In one example, the zinc coated magnesium substrate may be immersed into second non-aqueous ionic liquid 416 inside second plating tank 418. The zinc coated magnesium substrate may be connected as cathode 424 to electrical power source 422 in second electroplating process 400B. Further, a graphite may be connected as anode 420 to electrical power source 422. Aluminum layer 414 may be electrodeposited on zinc layer 404 upon supplying electric power during second electroplating process 400B. Aluminum layer 414 may then be anodized, at 426, thereby forming a stabilized and uniformly anodized surface of the magnesium or magnesium alloy substrate.

[0025] FIG. 5 illustrates a schematic representation of the example electronic device housing 500. Example electronic device housing 500 may include a magnesium substrate 502 and a zinc layer 504 electrodeposited on magnesium substrate 502 using a first non-aqueous ionic liquid. In one example, zinc layer 504 may have a thickness of about 5-20 micrometers.

[0026] Further, electronic device housing 500 may include an aluminum layer 506 electrodeposited on zinc layer 504 using a second non-aqueous ionic liquid. For example, aluminum layer 506 may have a thickness of about 15-70 micrometers. Furthermore, electronic device housing 500 may include an anodized layer 508 disposed on electrodeposited aluminum layer 506. For example, anodized layer 508 may have a thickness of about 5-25 micrometers. As shown in FIG. 5, zinc layer 504, aluminum layer 506, and anodized layer 508 may be formed on the surface of magnesium substrate 502 (i.e., on the surface that may be exposed to the non-aqueous ionic liquids). Even though examples in FIGs. 1 -5 describe about electrodeposition of zinc and aluminum layers on the magnesium or magnesium alloy substrates, examples described herein can also be used for other metallic substrates that may react with the water during the electrodeposition process.

[0027] It may be noted that the above-described examples of the present solution are for the purpose of illustration only. Although the solution has been described in conjunction with a specific implementation thereof, numerous modifications may be possible without materially departing from the teachings and advantages of the subject matter described herein. Other substitutions, modifications and changes may be made without departing from the spirit of the present solution. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0028] The terms "include," "have," and variations thereof, as used herein, have the same meaning as the term "comprise" or appropriate variation thereof. Furthermore, the term "based on", as used herein, means "based at least in part on." Thus, a feature that is described as based on some stimulus can be based on the stimulus or a combination of stimuli including the stimulus.

[0029] The present description has been shown and described with reference to the foregoing examples. It is understood, however, that other forms, details, and examples can be made without departing from the spirit and scope of the present subject matter that is defined in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method comprising:

providing a magnesium substrate; and

electrodepositing a zinc layer on the magnesium substrate using a first non-aqueous ionic liquid as an electrolyte.

2. The method of claim 1 , wherein the zinc layer is electrodeposited on the magnesium substrate using zinc ammonium chloride and the first non-aqueous ionic liquid, and wherein the first non-aqueous ionic liquid comprises a mixture of choline chloride and urea.

3. The method of claim 1 , further comprising:

electrodepositing an aluminum layer on the zinc layer using a second nonaqueous ionic liquid as an electrolyte; and

anodizing the aluminum layer.

4. The method of claim 3, wherein the second non-aqueous ionic liquid comprises aluminum chloride and at least one compound selected from a group consisting of 1 -butyl-3-methylimidazolium chloride ([BMIM]CI), 1 -ethyl-3- methylimidazolium chloride ([EMIMJCI), alkyl-pyridinium chloride, alkyl- arylimidazolium chloride, and basionics™ AL-02.

5. A method comprising:

electrodepositing a zinc layer on a magnesium alloy substrate using a first non-aqueous ionic liquid in a first electroplating process;

electrodepositing an aluminum layer on the zinc layer using a second nonaqueous ionic liquid in a second electroplating process; and

anodizing the aluminum layer to form an electronic device housing.

6. The method of claim 5, wherein the zinc layer is electrodeposited on the magnesium alloy substrate using a mixture of zinc ammonium chloride and the first non-aqueous ionic liquid in the first electroplating process, and wherein the first non-aqueous ionic liquid comprises a mixture of choline chloride and urea.

7. The method of claim 5, wherein the second non-aqueous ionic liquid comprises aluminum chloride and at least one compound selected from a group consisting of 1 -butyl-3-methylimidazolium chloride ([BMIM]CI), 1 -ethyl-3- methylimidazolium chloride ([EMIM]CI), alkyl-pyridinium chloride, alkyl- arylimidazolium chloride, and basionics™ AL-02.

8. The method of claim 5, wherein electrodepositing the zinc layer on the magnesium alloy substrate comprises:

electrodepositing the zinc layer on the magnesium alloy substrate with the magnesium alloy substrate serving as a cathode during the first electroplating process.

9. The method of claim 5, wherein electrodepositing the aluminum layer on the zinc layer comprises:

electrodepositing the aluminum layer on the zinc layer with the magnesium alloy substrate serving as the cathode during the second electroplating process.

10. The method of claim 5, wherein the aluminum layer is anodized at a voltage of about 10-60 volts, a temperature of about 15-30° Celsius, and for about 20-50 minutes.

1 1 . The method of claim 5, further comprising:

cleaning the magnesium alloy substrate prior to electrodepositing the zinc layer on the magnesium alloy substrate.

12. The method of claim 5, further comprising:

post-treating the anodized aluminum layer of the magnesium alloy substrate, wherein post-treating the anodized aluminum layer comprises a first washing, sealing, a second washing, and baking the anodized aluminum layer of the magnesium alloy substrate.

13. An electronic device housing comprising:

a magnesium substrate; a zinc layer electrodeposited on the magnesium substrate using a first non-aqueous ionic liquid, wherein the first non-aqueous ionic liquid comprises a mixture of choline chloride and urea;

an aluminum layer electrodeposited on the zinc layer using a second nonaqueous ionic liquid; and

an anodized layer disposed on the electrodeposited aluminum layer.

14. The electronic housing of claim 13, wherein the zinc layer has a thickness of about 5-20 micrometers.

15. The electronic housing of claim 13. wherein the aluminum layer has a thickness of about 15-70 micrometers.