SUBSTRATES

BACKGROUND

[0001 ] Generally, magnesium substrates are coated with metallic layers to protect the magnesium substrates from corrosion and to make the surface of magnesium substrates aesthetically appealing to users. For example, layers of metals such as aluminum, zinc, copper, and the like, may be coated on the magnesium substrates by different processes such as electroplating and physical vapor deposition.

BRIEF DESCRIPTION OF DRAWINGS

[0002] The detailed description is provided with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0003] Fig. 1 illustrates a method of waterborne emulsion based electroplating of magnesium substrates, according to an example of the present subject matter.

[0004] Fig 2 illustrates another method of electroplating a zinc layer and an aluminum layer on magnesium substrates, according to an example of the present subject matter.

[0005] Fig. 3 illustrates an example process for electroplating a zinc layer and aluminum layer on magnesium substrates, according to an example of the present subject matter.

[0008] Fig. 4 illustrates a cross-sectional view of a waterborne emulsion based electroplated magnesium substrate, according to an example of the present subject matter.

[0007] Fig. 5 illustrates a method of waterborne emulsion based electroplating of magnesium substrates, according to an example of the present subject matter.

DETAILED DESCRIPTION

[0008] Magnesium substrates are prevalently used as structural components in different industries. The magnesium substrates are generally electroplated with layers of a metal, such as aluminum, zinc, copper, nickel and the like, to prevent corrosion and/ or degradation of the magnesium substrates. However, since magnesium reacts with water in aqueous ionic solutions, electroplating of magnesium substrates is undertaken in non-aqueous ionic solutions. [0009] For electroplating zinc on a magnesium substrate, a non-aqueous ionic solution of zinc ammonium chloride and a mixture of choline chloride and urea is generally utilized. To further electroplate aluminum on the zinc plated magnesium substrate, another non-aqueous ionic solution based on aluminum chloride (AiCh) is used. However, use of AiCIa based non-aqueous ionic solution does not provide sufficient concentration of aluminum (Ai ³⁺ ) ions in the non- aqueous ionic solution, and therefore, deposition rate of aluminum on the magnesium substrates is slow and consumes time. Unavailability of sufficient Ai ³⁺ ions also causes ineffective deposition of aluminum on the magnesium substrates.

[0010] According to an example of the present subject matter, techniques of waterborne emulsion based electroplating of magnesium substrates are described. In an example of the present subject matter, the waterborne emulsion may be used to dispose ions of a metal into a non-aqueous ionic solution, to be deposited on magnesium substrates. The use of waterborne emulsion increases the availability of metal ions in the non-aqueous ionic solution, thereby increasing the deposition rate of metal on the magnesium substrate.

[001 1 ] in an example of the present subject matter, a method of waterborne emulsion based electroplating of magnesium substrates includes cleaning the magnesium substrate to remove impurities. Further, the cleaned magnesium substrate is electroplated with a layer of a first metal in an electrolytic solution in an example, the electrolytic solution may include a non-aqueous ionic solution and a waterborne emulsion, where the waterborne emulsion includes ions of the first metal. During electroplating, the waterborne emulsion may release ions of the first metal in the non-aqueous ionic solution for deposition over the magnesium substrate.

[0012] in an illustrative example, for depositing an aluminum layer on magnesium substrates during electroplating, a waterborne emulsion of at least one of aluminum sulphate, aluminum chloride, aluminum phosphate, and aluminum acetate is utilized. Further, an AlCh based non-aqueous ionic solution is utilized for electroplating the aluminum layer on the magnesium substrate. During electroplating, the waterborne emulsion may release Ai ³⁺ ions into the AlC based non-aqueous ionic solution. Since the waterborne emulsion provides higher availability of Al ³ⁱ ions in the A!C based on-aqueous ionic solution, the aluminum layer is deposited at a higher rate onto the magnesium substrate, as compared to general techniques.

[0013] The above techniques of waterborne emulsion based electroplating of magnesium substrates are further described with reference to Fig. 1 to Fig. 5. it should be noted that the description and the figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present subject matter. Moreover, ail statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.

[0014] Fig 1 illustrates a method 100 of electroplating a layer of a first metal on a magnesium substrate, according to an example of the present subject matter in an example, the magnesium substrate may be an alloy of magnesium.

[0015] At block 102, the magnesium substrate is cleaned in an example, the magnesium substrate may be cleaned by one of plasma cleaning and particle blasting such as sandblasting. In case of plasma cleaning, impurities and contaminants may be removed from a surface of the magnesium substrate through an ionized gas, such as a plasma in another example, the magnesium substrate may be degreased by treating the magnesium substrate with an aqueous alkaline solution of sodium hydroxide, sodium phosphate, and sodium carbonate, followed by wafer rinsing. In yet another example, the magnesium substrate may be cleaned by acid pickling, where the magnesium substrate may be treated with an aqueous solution containing phosphoric acid, nitric acid, and sulfuric acid.

[0018] At block 104, a layer of a first metal is electroplated on the magnesium substrate in a mixture of a non-aqueous ionic solution and a waterborne emulsion, where the waterborne emulsion is to release ions of the first metal in the non- aqueous ionic solution

[0017] in an example of the present subject matter, the first metal may be aluminum and one or more aluminum layers may be electroplated on the magnesium substrate in an Aids based non-aqueous ionic solution in the example, the AlCb based non-aqueous ionic solution may comprise AiCh and at least one compound from 1-butyl-3-methylimidazolium chloride ([BMIMJCI), 1 - ethyl-3-methyiimidazolium chloride ([EMIMjCI), a!kyl-pyridinium chloride, alkyi- arylimidazo!ium chloride, and BasionicsTM AL-02 Further, the waterborne emulsion may include one or more of aluminum sulphate, aluminum chloride, aluminum phosphate, and aluminum acetate, disposed in the AiCh based non- aqueous ionic solution in operation, the waterborne emulsion may release Ai ³⁺ into the Aids based non-aqueous ionic solution, thereby increasing concentration of the Ai ³⁺ ions in the non-aqueous ionic solution, thereby causing increase in deposition rate of the one or more aluminum layers on the magnesium substrate. Thus, the one or more aluminum layers are effectively deposited on the magnesium substrate

[0018] in another example, another layer of a second metal may be pre coated on the magnesium substrate before electroplating the layer of the first metal. In an example, another layer of the second metal may be electroplated in a second non-aqueous ionic solution. For example, the second metal may be one of zinc, copper, and nickel. In the example, for electroplating one or more layers of zinc, the second non-aqueous ionic solution may comprise zinc ammonium chloride and a mixture of choline chloride and urea.

[0019] in an example, a first electroplating process may be utilized for pre coating another layer of the second metal on the magnesium substrate before electroplating the layer of the first metal. In the example, during the pre-coating of the magnesium substrate, the magnesium substrate may be used as a cathode while a graphite electrode may be used as an anode.

[0020] Further, the layer of the first metal may be electroplated on the pre coated another layer of the second metal through a second electroplating process. In the example, pre-coated magnesium substrate with another layer of the second metal may be used as a cathode while a graphite electrode may be used as an anode. In another example, the layer of the first metal may be directly electroplated on the magnesium substrate through the second electroplating process. In the other example, the magnesium substrate may be used a cathode for electroplating the layer of the first metal directly on the magnesium substrate through a second electroplating process.

[0021 ] Fig. 2 illustrates another method 200 of electroplating a zinc layer and an aluminum layer on the magnesium substrate, according to an example of the present subject matter. Further, Fig. 3 illustrates an example process 300 for electroplating the zinc layer and the aluminum layer on the magnesium substrate, according to an example of the present subject matter. Fig. 2 has been explained in conjunction with Fig. 3 for the ease of understanding.

[0022] At block 202, a zinc layer is electroplated on a magnesium substrate in a first non-aqueous ionic solution through a first electroplating process. For example, a zinc layer 304 is electroplated on the magnesium substrate 302 in a first non-aqueous ionic solution 308 through a first electroplating process 300A. As described earlier, the magnesium substrate 302 may be an alloy of magnesium.

[0023] As shown in Fig. 3, the first electroplating process 300A may be performed in a first container 308 that may include the first non-aqueous ionic solution 308. The first container 308 may further include the magnesium substrate 302 and a first graphite electrode 310, disposed in the first non-aqueous ionic solution 306. In an example, the magnesium substrate 302 is utilized as a cathode and the first graphite electrode 310 is utilized as an anode for electroplating the zinc layer 304 on the magnesium substrate 302.

[0024] Further, the first non-aqueous ionic solution 306 may comprise zinc ammonium chloride and a mixture of choline chloride and urea. During the first electroplating process 300A, the magnesium substrate 302 and the first graphite electrode 310 may be connected to a first power supply (Vi) such as a battery, where the magnesium substrate 302 is connected to a negative terminal of the first power supply (Vi), while the first graphite electrode 310 is connected to a positive terminal of the first power supply (Vi).

[0025] in operation, upon providing the first power supply (Vi), a predefined current may be passed into the first non-aqueous ionic solution 306, through the magnesium substrate 302 and the first graphite electrode 310 The predefined current dissociates the first non-aqueous ionic solution 306 into zinc ions along with other ions. Since the zinc ions (Zn ²⁺ ) are positively charged, the Zn ²ⁱ ions move toward the cathode, i.e., the magnesium substrate 302. During electroplating, as the cathode receives electrons, the Zn ² * Ions get reduced to zinc and, thus the zinc layer 304 is formed onto the magnesium substrate 302. Thus, the first electroplating process 300A provides a zinc coated magnesium substrate 312.

[0026] Referring to Fig. 2, at block 204, an aluminum layer is electroplated on the zinc layer in a mixture of a second non-aqueous ionic solution and a waterborne emulsion, through a second electroplating process.

[0027] For example, an aluminum layer 314 is electroplated on the zinc layer

304 in a mixture of a second non-aqueous ionic solution 316 and a waterborne emulsion 318, through a second electroplating process 300B, where the waterborne emulsion 318 is to release Al ³ ions in the second non-aqueous ionic solution 316 The electroplating of the aluminum layer 314 on the zinc layer 304 through the second electroplating process 300B has been described below with reference to Fig. 3.

[0028] Referring to Fig. 3, the second electroplating process 300B is performed in a second container 320 that may include the mixture of the second non-aqueous ionic solution 316 and the waterborne emulsion 318. in an example, the second non-aqueous ionic solution 316 may comprise AiCh and at least one compound from 1 -buty!-3-methy!imidazo!ium chloride ([BMIMjCI), 1 -ethyl-3- methyiimidazoiium chloride ([BMIMjCI), aikyl-pyridinium chloride, alkyi- ary!imidazo!ium chloride, and BasionicsTM AL-02. Further, the waterborne emulsion 318 may include at least one of aluminum sulphate, aluminum chloride, aluminum phosphate, and aluminum acetate. [0029] Further, the second container 320 includes the zinc coated magnesium substrate 312 and a second graphite electrode 322 disposed in the mixture of the second non-aqueous ionic solution 316 and the waterborne emulsion 318. In an example, the zinc coated magnesium substrate 312 is utilized as a cathode and the second graphite electrode 322 is utilized as an anode for electroplating the aluminum layer 314 on the zinc layer 304 of the zinc coated magnesium substrate 312.

[0030] Moreover, during the second electroplating process 300B, the zinc coated magnesium substrate 312 and the second graphite electrode 322 may be connected to a second power supply (V ₂ ), such as a battery, where the zinc coated magnesium substrate 312 is connected to a negative terminal of the second power supply (V2), and the second graphite electrode 322 is connected to a positive terminal of the second power supply (V ₂ ).

[0031 ] In operation, upon providing the second power supply (V ₂ ), a predefined current may be passed into the mixture of the second non-aqueous ionic solution 316 and the waterborne emulsion 318, through the zinc coated magnesium substrate 312 and the second graphite electrode 322. The predefined current may then dissociate the second non-aqueous ionic solution 316 info Ai ³⁺ ions along with other ions. Further, the waterborne emulsion 318 also releases A! ³ * ions into the second non-aqueous ionic solution 316

[0032] Since the Al ³⁺ are positively charged, the Al ³⁺ ions move toward the cathode, i.e., the zinc coated magnesium substrate 312. During electroplating, as the cathode receives electrons and the Ai ³⁺ ions get reduced to aluminum. Thus, the aluminum layer 314 is deposited onto the zinc layer 304 of the zinc coated magnesium substrate 312. As the overall concentration of the Al ³⁺ ions in the second non-aqueous ionic solution 316 increases, a higher number of A! ³⁺ ions are reduced onto the zinc layer 304 of the zinc coated magnesium substrate 312. The second electroplating process 300B provides an electroplated magnesium substrate 324, which includes the zinc layer 304 and the aluminum layer 314 that is electroplated on the zinc layer 304. [0033] In an example, a pH value of the mixture of the second non-aqueous ionic solution 316 and the waterborne emulsion 318 may be in a range of about 2 to 4. Therefore, the mixture of the second non-aqueous ionic solution 316 and the waterborne emulsion 318, which is utilized for electroplating the layer of the first metal, is less acidic as compared to the aqueous ionic solution utilized in general techniques. Thereby, corrosion of the magnesium substrate is further prevented and formation of residues during electroplating of the layer of the first etal on the magnesium substrate is minimized

[0034] Fig 4 illustrates a cross-sectional view of an electroplated magnesium substrate 324, according to an example of the present subject matter. In the example, the electroplated magnesium substrate 324 may include a magnesium substrate 302, a zinc layer 304-1 electroplated on surface of the magnesium substrate 302, and an aluminum layer 314-1 electroplated on the zinc layer 304-1 .

[0035] In an example, the zinc layer 304-1 is electroplated on the magnesium substrate 302 in the first non-aqueous ionic solution 306 through the first electroplating process 300A As explained earlier, the first non-aqueous ionic solution 306 may comprise zinc ammonium chloride and a mixture of choline chloride and urea. Also, the first electroplating process 300A may utilize the magnesium substrate 302 as a cathode for electroplating the zinc layer 304-1.

[0036] in the example, the aluminum layer 314-1 may be electroplated on the zinc layer 304-1 in the mixture of the second non-aqueous ionic solution 316 and the waterborne emulsion 318 through the second electroplating process 300B. As explained earlier, the second non-aqueous ionic solution 316 may include Aids and at least one compound from 1-butyi-3-methylimidazoiium chloride ([BMIM]CI), 1-ethyi-3-methyiimidazolium chloride ([EMIMJCI), alkyl- pyridinium chloride, alkyl-arylimidazolium chloride, and BasionicsTM AL-02. Further, the waterborne emulsion 318 may include at least one of aluminum sulphate, aluminum chloride, aluminum phosphate, and aluminum acetate.

[0037] As described earlier, the waterborne emulsion 318 releases aluminum ions (Ai ³⁺ ) in the second non-aqueous ionic solution 316 to increase concentration of the Al ³⁺ ions in the second non-aqueous ionic soiution 318 and, thereby increasing deposition rate of the aluminum layer 314-1 on the zinc layer 304-1. As also explained earlier, the second electroplating process 300B may utilize the zinc coated magnesium substrate 312 as a cathode for electroplating the aluminum layer 314-1.

[0038] Fig. 5 illustrates an example method 500 of producing the electroplated magnesium substrate 324, according to an example of the present subject matter.

[0039] At block 502, a magnesium substrate 302 is received. In an example, the magnesium substrate 302 may be an alloy of magnesium.

[0040] At block 504, the magnesium substrate 302 is cleaned. In an example, the magnesium substrate 302 may be cleaned through an ionized gas, such as a plasma, and particle blasting such as sandblasting, to remove impurities and contaminants from a surface of the magnesium substrate 302. in another example, the magnesium substrate 302 may be cleaned by add pickling, where the magnesium substrate 302 may be treated with an aqueous solution containing phosphoric acid, nitric acid, and sulfuric acid. In yet another example, the magnesium substrate 302 may be degreased by treating the magnesium substrate 302 with an aqueous alkaline solution of sodium hydroxide, sodium phosphate, and sodium carbonate, followed by water rinsing

[0041 ] At block 506, a zinc layer 304 is electroplated on the magnesium substrate 302 in a first non-aqueous ionic soiution 308 through a first electroplating process 300A. As described earlier, the first non-aqueous ionic soiution 306 may include zinc ammonium chloride and a mixture of choline chloride and urea in an example, the first electroplating process 300A may utilize the magnesium substrate 302 in the first non-aqueous ionic solution 308 as a cathode for electroplating the zinc layer 304 on the magnesium substrate 302.

[0042] At block 508, an aluminum layer 314 is electroplated on the zinc layer 304 in a mixture of a second non-aqueous ionic soiution 316 and a waterborne emulsion 318, through a second electroplating process 300B, where the waterborne emulsion is to release Al ³⁺ ions in the second non-aqueous ionic solution 316. As described earlier, the second non-aqueous ionic solution 316 may include aluminum chloride and at least one compound from 1 -butyl-3- methyiimidazoiium chloride ([BMIMjCI), 1-e!hyl-3-methylimidazolium chloride ([EM!MjCI), aikyi-pyridinium chloride, alkyl-arylimidazolium chloride, and BasionicsTM AL-02. Further, the waterborne emulsion 318 may include at least one of aluminum sulphate, aluminum chloride, aluminum phosphate, and aluminum acetate.

[0043] in an example, the second electroplating process 300B may utilize the zinc coated magnesium substrate 312 as a cathode in the mixture of second non-aqueous ionic solution 316 and the waterborne emulsion 318 for electroplating the aluminum layer 314 on the zinc layer 304. In operation, the waterborne emulsion 318 releases Ai ³⁺ ions in the second non-aqueous ionic solution 316 and thereby increasing overall concentration of the A! ³⁺ ions in the second non-aqueous ionic solution 316. Thereby, increasing deposition rate of the aluminum layer 314 on the zinc layer 304.

[0044] At block 510, the aluminum layer 314 is anodized. In an example, the aluminum layer 314 may be anodized at a voltage of about 10 to 60 volts, a temperature of about 15 °C to 30 °C, and for a time of about 20 to 50 minutes.

[0045] At block 512, the anodized aluminum layer is washed.

[0046] At block 514, the anodized aluminum layer is sealed to form an electroplated magnesium substrate 324. in an example, 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 substrate 302.

[0047] At block 516, the electroplated magnesium substrate 324 is washed. And further, at 518, the electroplated magnesium substrate 324 is baked at a temperature of about 60 to 90 °C and for a time of about 20 to 40 minutes.

[0048] The electroplated magnesium substrate 324 may be used as a structural component in aviation industry, automobile industry, electronic industry, and the like. For instance, the electroplated magnesium substrate 324 may be used for making engine mounts, control hinges, fuel tanks, wings, etc , in an aircraft, and for making wheels, transmission cases, engine blocks, etc., in an automobile. Further, the electroplated magnesium substrate 324 may be utilized for making housings of cameras, laptops, and other portable electronic devices.

[0049] Although examples of present subject matter have been described in language specific to structural features and/or methods, it is to be understood that the present subject matter is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed and explained in the context of a few examples for the present subject matter.