BACKGROUND

[0001 ] Metal substrates have a variety of applications in electronic devices. However, many metals can be adversely affected in a natural environment, such as via corrosion, wear, etc. As such, these metal substrates are often coated to impart corrosion resistance, electrical resistance, wear resistance, decoration, and a variety of other desirable properties. Coatings can be applied via a variety of techniques, such as chemical vapor deposition, physical vapor deposition, spray coating, dip coating, conversion coating, electroplating, hot melt coating, spin coating, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] FIG. 1 A is a cross-sectional view of a coated metal substrate in

accordance with the present disclosure;

[0003] FIG. 1 B is a cross-sectional view of another coated metal substrate in accordance with the present disclosure;

[0004] FIG. 1 C is a cross-sectional view of another coated metal substrate in accordance with the present disclosure;

[0005] FIG. 1 D is a cross-sectional view of another coated metal substrate in accordance with the present disclosure;

[0006] FIG. 2 is a flow diagram of a method of manufacturing a coated metal substrate for an electronic device in accordance with the present disclosure;

[0007] FIG. 3A is a cross-sectional view of a coated metal substrate at one stage of manufacturing in accordance with the present disclosure; [0008] FIG. 3B is a cross-sectional view of a coated metal substrate at one stage of manufacturing in accordance with the present disclosure;

[0009] FIG. 3C is a cross-sectional view of a coated metal substrate at one stage of manufacturing in accordance with the present disclosure;

[0010] FIG. 3D is a cross-sectional view of a coated metal substrate at one stage of manufacturing in accordance with the present disclosure; and

[0011 ] FIG. 4 is a schematic representation of an electronic device in accordance with the present disclosure.

DETAILED DESCRIPTION

[0012] Metal substrates for electronic devices are often coated with coating(s) to impart corrosion resistance, electrical resistance, wear resistance, decoration, or the like to the metal substrates. However, in some cases, the coating process of one material can have an adverse effect on a previously deposited coating. For example, some coating processes can employ high temperatures for curing polymeric materials. In some cases, the high temperatures used in the curing process of one material can adversely affect a previously deposited coating material. The present disclosure describes coated metal substrates, methods of manufacturing coated metal substrates, and electronic devices having a discrete corrosion resistant and durable coating deposited via ultraviolet electrophoretic deposition (UV ED). UV ED can employ relatively low temperatures to minimize temperature-related defects in the coating materials, composite substrate, and metal substrate.

[0013] In one example, a coated metal substrate for an electronic device can include a metal substrate having a density of from about 1.0 g/cm ³ to about 5.0 g/cm ³ and a thickness of from about 0.3 mm to about 2.0 mm, a base coating on the metal substrate having a thickness of from about 25 pm to about 120 pm, and a first discrete coating positioned at a first discrete location on the metal substrate and contacting the base coating, the first discrete coating having a coating thickness of from about 5 pm to about 50 pm and a pencil hardness of from about H to about 4H, and wherein the first discrete coating can include a photoinitiator and a photocured polymeric material. In a further example, the first discrete location is a chamfered edge of the metal substrate. In an additional example, the photoinitiator can include an onium salt, a pyridinium salt, a transition metal complex, or a combination thereof. In yet an additional example, the photocured polymeric material can include a urethane acrylate, an acrylic acrylate, an epoxy acrylate, polyacrylate copolymer, or a combination thereof. In still an additional example, the first discrete coating can further include a colorant. In a further example, the coated metal substrate can further include a transparent passivation layer between the metal substrate and the first discrete coating.

[0014] In another example, a method of manufacturing a coated metal substrate for an electronic device can include coating a surface of a metal substrate with a base coating having a thickness of from about 25 pm to about 120 pm, wherein the metal substrate has a density of from about 1.0 g/cm ³ to about 5.0 g/cm ³ and a thickness of from about 0.3 mm to about 2.0 mm, removing a first portion of the base coating from the metal substrate at a first discrete location, and depositing a first discrete coating at the first discrete location using ultraviolet electrophoretic deposition (UV ED), the first discrete coating deposited on the metal substrate and also contacting the base coating, wherein the first discrete coating has a coating thickness of from about 5 pm to about 50 pm and a pencil hardness of from about H to about 4H, and wherein the first discrete coating can include a photoinitiator and a photocured polymeric material. In an additional example, the method can further include preliminarily preparing the surface of the metal substrate prior to coating, wherein preparing can include degreasing, passivating, polishing, cleaning, or a combination thereof. In yet an additional example, coating the surface can include powder coating, spray paint coating, electrophoretic deposition coating with thermal curing, or a combination thereof. In a further example, removing the first portion of the base coating can further include forming a chamfer at the first discrete location. In an additional example, the method can further include depositing a transparent passivation layer on the metal substrate at the first discrete location after removing the first portion of the base coating. In yet a further example, depositing the first discrete coating using ultraviolet electrophoretic deposition can be performed at a temperature of from about 15 °C to about 40 °C, and wherein depositing can further include curing the photoinitiator and a photocurable polymeric material at a temperature of from about 60 °C to about 80 °C with UV curing at from about 700 mJ/cm ² to about 1500 mJ/cm ² to generate the photocured polymeric material. In another additional example, the method can further include removing a second portion of the base coating at a second discrete location and depositing a second discrete coating at the second discrete location using UV ED, the second discrete coating deposited on the metal substrate and also contacting the base coating, wherein the second discrete coating has a coating thickness of from about 5 pm to about 50 pm and a pencil hardness of from about H to about 4H, and wherein the second discrete coating can include a colorant, a photoinitiator, and a photocured polymeric material.

[0015] In another example, an electronic device can include a housing carrying electronic components of the electronic device, wherein the housing includes a coated metal substrate including a metal substrate having a density of from about 1.0 g/cm ³ to about 5.0 g/cm ³ and a thickness of from about 0.3 mm to about 2.0 mm, a base coating on the metal substrate having a thickness of from about 25 pm to about 120 pm, and a first discrete coating positioned at a first discrete location on the metal substrate and contacting the base coating, the first discrete coating having a coating thickness of from about 5 pm to about 50 pm and a pencil hardness of from about H to about 4H, and wherein the first discrete coating includes a photoinitiator and a photocured polymeric material. In an additional example, the electronic device can include a display, a personal computer, a laptop computer, a tablet, a media player, a smart device, a keyboard, or a combination thereof.

[0016] In addition to the examples described above, the coated metal substrates, methods of manufacturing coated metal substrates, and electronic devices will be described in greater detail below. It is also noted that when discussing the coated metal substrates, methods of manufacturing coated metal substrates, and electronic devices described herein, these relative discussions can be considered applicable to the other examples, whether or not they are explicitly discussed in the context of that example. Thus, for example, in discussing a discrete coating related to a coated metal substrate, such disclosure is also relevant to and directly supported in the context of the methods of manufacturing coated metal substrates and electronic devices described herein, and vice versa. Metal Substrates

[0017] In further detail, the metal substrates disclosed herein are typically made of a light metal material. The light metals referred to herein generally have a density of from about 0.5 gram per cubic centimeter (g/cm ³ ) to about 8.0 g/cm ³ In some additional examples, the metal substrate can have a density of from about 1.0 g/cm ³ to about 5.0 g/cm ³ . In some specific examples, the metal substrate can have a density of from about 0.5 g/cm ³ to about 2.0 g/cm ³ , about 1 .0 g/cm ³ to about 3.0 g/cm ³ , from about 2.0 g/cm ³ to about 4.0 g/cm ³ , from about 3.0 g/cm ³ to about 5.0 g/cm ³ , from about 4.0 g/cm ³ to about 6.0 g/cm ³ , from about 5.0 g/cm ³ to about 7.0 g/cm ³ , or from about 6.0 g/cm ³ to about 8.0 g/cm ³ . Non-limiting examples of light metal materials for the metal substrate can include magnesium, aluminum, titanium, lithium, zinc, stainless steel, the like, or an alloy thereof. In some specific examples, the metal substrate can include or be made of magnesium or an alloy thereof. In some additional examples, the metal substrate can be made of aluminum or an alloy thereof. In still additional examples, the metal substrate can be made of titanium or an alloy thereof. In some further examples, the metal substrate can be made of lithium or an alloy thereof. In yet further examples examples, the metal substrate can be made of zinc or an alloy thereof. In still further examples, the metal substrate can be made of stainless steel or an alloy thereof.

[0018] The metal substrate can be shaped in a variety of ways to form a frame, housing, support structure, or other suitable component of an electronic device. As such, the metal substrate can be molded, die cast, or otherwise shaped as desired. The metal substrate can typically be relatively thin, such as having a thickness of from about 0.3 millimeters (mm) to about 2.0 mm, although other thicknesses can be employed in some examples. In some specific examples, the metal substrate can have a thickness of from about 0.3 mm to about 0.8 mm, from about 0.5 mm to about 1 .0 mm, from about 0.8 mm to about 1.3 mm, from about 1.0 mm to about 1.5 mm, from about 1.3 mm to about 1.8 mm, or from about 1.5 mm to about 2.0 mm.

Base Coatings

[0019] A base coating can be applied to the metal substrate to give the metal substrate its general appearance and other desirable properties, such as corrosion resistance, electrical resistance, wear resistance, etc. In some examples, the base coating can include a single base coating material. In other examples, the base coating can include a plurality of base coating materials or layers. In one example, the base coating can include a primer coating layer, a lower coating layer applied to the primer coating layer, and an upper coating layer applied to the lower coating layer. In some examples, the primer coating can include a polyurethane coating, or the like. The primer coating can have a coating thickness of from about 5 pm to about 20 pm. In some additional examples, the lower coating can include a pigmented polyurethane coating, or the like. The lower coating can have a thickness of from about 10 pm to about 20 pm. A variety of pigments can be used in the lower coating. Non-limiting examples can include carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium

carbonate, a synthetic pigment, a metallic powder, aluminum oxide, an organic powder, an inorganic powder, a plastic bead, a color pigment, the like, or a combination thereof. The upper coating can include a UV curable coating including polyacrylates,

polyurethane, urethane acrylates, acrylic acrylates, epoxy acrylates, the like, or a combination thereof. The upper coating can also include a photoinitiator, such as an onium salt, a pyridinium salt, a transition metal complex, the like, or a combination thereof. The upper coating can have a coating thickness of from about 10 pm to about 25 pm.

[0020] In another example, the base coating can include a powder coating layer. The powder coating layer can generally include a thermoset or thermoplastic polymer powder material. Non-limiting examples of polymers can include a polyester, a polyurethane, a polyester-epoxy, an epoxy, an acrylic, the like, or a combination thereof. In some further examples, the powder coating layer can include a colorant, such as a dye or pigment colorant, to impart a desired color to the base coating. In some examples, the powder coating layer can be applied alone as the base coating. In other examples, the powder coating can be applied together with (e.g. prior to) a primer coating, a lower coating, and an upper coating. Powder coating layers can generally have a coating thickness of from about 20 pm to about 60 pm.

[0021 ] In yet further examples, the base coating can include an

electrophoretically deposited polymer material. In some examples, the

electrophoretically deposited material can be electromagnetically cured. Details regarding this process are described in greater detail with respect to the discrete coating materials. In some other examples, the electrophoretically deposited material can be thermally cured. Where this is the case, the electrophoretically deposited and thermally cured polymer material can include a variety of thermally curable polymeric materials, such as a polyacrylate, an epoxy, a urethane acrylate, an acrylic acrylate, an epoxy acrylate, a polyacrylate copolymer, the like, or a combination thereof. In some additional examples, the electrophoretically deposited material can include a filler. Non limiting examples of fillers can include titanium dioxide, aluminum flakes, pearl, mica, clay, a glass bead, a colored pigment, a dye, the like, or a combination thereof. The electrophoretically deposited material can typically have a thickness of from about 25 pm to about 120 pm.

[0022] Depending on the number and types of layers employed, the base coating can have a variety of thicknesses. In some examples, the base coating can have a thickness of from about 25 pm to about 120 pm. In some specific examples, the base coating can have a thickness of from about 25 pm to about 75 pm, from about 50 pm to about 100 pm, or from about 70 pm to about 120 pm.

Transparent Passivation Layers

[0023] The transparent passivation layer can provide good corrosion resistance while maintain the metallic luster at the discrete location due to its transparent nature. The transparent passivation layer can be formed of a variety of materials. In one example, the transparent passivation layer can include a chelating agent. Non-limiting examples of chelating agents can include ethylenediaminetetraacetic acid (EDTA), ethylenediamine, nitrilotriacetic acid (NTA), diethylenetriaminepenta(methylenephosphonic acid) (DTPPH),

nitrilotris(methylenephosphonic acid) (NTMP), 1 -hydroxyethane-1 ,1 -diphosphonic acid (HEDP), phosphoric acid, the like, or a combination thereof. In some examples, the transparent passivation layer can include an organic acid in combination with aluminum, nickel, chromium, tin, indium, zinc, the like, or a combination thereof. Various

combinations of the previously recited materials can also be employed. The transparent passivation layer can generally have a coating thickness of from about 30 nm to about 3 pm. In some additional examples, the transparent passivation layer can have a coating thickness of from about 30 nm to about 300 nm, from about 150 nm, to about 500 nm, from about 250 nm to about 750 nm, from about 500 nm to about 1 pm, from about 750 nm to about 1.5 pm, from about 1 pm to about 2 pm, from about 1.5 pm to about 2.5 pm, or from about 2 pm to about 3 pm.

Discrete Coatings

[0024] Discrete coatings can be positioned at a discrete location on the metal substrate and can be in contact with the base coating. More specifically, discrete coatings are generally positioned at a discrete location where a portion of the base coating has been removed to make a deposition site for the discrete coating. In some examples, a single discrete coating can be employed in a single discrete location or a plurality of discrete locations. In other examples, a plurality of discrete coatings can be employed in a plurality of discrete locations. In some specific examples, a discrete location can include a chamfered edge of the metal substrate.

[0025] As described previously, discrete coatings can be deposited using ultraviolet electrophoretic deposition (UV ED), which will be described in greater detail below. As such, the polymeric materials employed in the discrete coatings can be photocurable polymeric materials. Non-limiting examples of photocurable polymeric materials can include a urethane acrylate, an acrylic acrylate, an epoxy acrylate, polyacrylate copolymer, the like, or a combination thereof. Additionally, the discrete coatings can include a photoinitiator. Non-limiting examples can include an onium salt, a pyridinium salt, a transition metal complex (e.g., a ferrocenium salt, etc.), the like, or a combination thereof.

[0026] Discrete coatings can have a variety of thicknesses. In one example, the discrete coating can have a thickness of from about 5 pm to about 50 pm. In some specific examples, the discrete coating can have a thickness of from about 5 pm to about 25 pm, from about 10 pm to about 30 pm, or from about 25 pm to about 50 pm.

[0027] The discrete coating can also be a durable coating having a good pencil hardness. For example, in some cases, the discrete coating can have a pencil hardness of from abut H to about 4H. In some specific examples, the discrete coating can have a pencil hardness of from about H to about 2H, from about 2H to about 3H, or from about 3H to about 4H. In other examples, the discrete coating can have a pencil hardness of from about H to about 3H or from about 2H to about 4H. The“pencil hardness” test is a method that uses pencils of an established hardness grade to be moved over the coating surface at a fixed angle. When the pencil is passed for a specified number of times on the coating surface, a wear factor can be determined that is related to the hardness of the pencil used. See ASTM D 3363, Standard Test Method for Film

Flardness. In more detail, the standard test method includes the following details: Pencil type: 6B-5B-4B-2B-B-HB-F-H-2H-3H^H-5H-6H-7H-8H-9H (brand: Mitsubishi) with 6B being softest and 9H being hardest; Test Protocol: Force loading at 750g; drawing lead sharpened; substrate placed on a level, firm, horizontal surface; starting with the hardest lead, hold the pencil or lead in holder firmly with the lead against the substrate layer at a 45° angle (point away from the operator) and push away from the operator; allow the load weight to apply uniform pressure downward and forward as the pencil is moved to either cut or scratch the substrate or to crumble the edge of the lead (length of stroke to be 1/4 inch (6.5 mm); repeat process down the hardness scale until a pencil is found that will not scratch or gouge the substrate; the hardest pencil that does not scratch or gouge the substrate is then considered the pencil hardness of the substrate.

[0028] Discrete coatings can be transparent, semi-transparent, colored, the like, or a combination thereof, e.g., transparent and colored, semi-transparent and colored, a transparent portion and a semi-transparent portion, etc. In some specific examples, discrete coatings can include a colorant. In some further examples, a first discrete coating does not include a colorant and a second discrete coating can include a colorant. In another example, a first discrete coating can include a first colorant and a second discrete coating can include a second colorant. In still another example, a first discrete coating can include a first amount of a colorant and a second discrete coating can include a second amount of the colorant. Other suitable variations of and amounts of colorants can also be used, as desired. The colorant can be a dye, a pigment, or a combination thereof. Any suitable color of dye or pigment can be used, such as black, white, gray, gold, silver, cyan, magenta, yellow, green, red, blue, purple, orange, brown, bronze, pink, etc.

[0029] FIGs. 1 A-1 D illustrate a few non-limiting examples of coated metal substrates having various discrete coating arrangements. For example, FIG. 1A illustrates a coated metal substrate 100A having a metal substrate 110 with a thickness T1. A base coating 120 having a thickness T2 is on the metal substrate. Additionally, a single discrete coating 130 having a thickness T3 is on the metal substrate at a discrete location 112. The discrete coating is additionally in contact with the base coating.

[0030] FIG. 1 B illustrates a coated metal substrate 100B having a metal substrate 110. A base coating 120 is on the metal substrate. Removal of the base coating at the discrete location 112 formed a chamfered discrete location. A transparent passivation layer 150 is deposited at the chamfered discrete location. A single discrete coating 130 is on the transparent passivation layer and metal substrate at the chamfered discrete location. The discrete coating is also in contact with the base coating.

[0031 ] FIG. 1 C illustrates a coated metal substrate 100C having a metal substrate 110. A base coating 120 is on the metal substrate. Removal of the base coating at first discrete location 112 formed a chamfered discrete location. A passivation layer is deposited on the metal substrate at the chamfered discrete location. A first discrete coating 130 is on the passivation layer and the metal substrate at the chamfered discrete location. A second discrete coating 140 is on the metal substrate at a second discrete location 114, which is not a chamfered edge of the metal substrate. It is noted that a transparent passivation layer is not positioned between the metal substrate and the second discrete coating in this example. Flowever, this is not intended to be limiting. A transparent passivation layer may also be included between the metal substrate and the second discrete coating. Both the first discrete coating and the second discrete coating are also in contact with the base coating. The compositions of the first discrete coating and the second discrete coating are different (e.g. one has a colorant and the other does not, one has a different amount of a colorant than the other, multiple individual coatings individually have a different colorant, etc.).

[0032] FIG. 1 D illustrates a coated metal substrate 100D having a metal substrate 110. A base coating 120 is on the metal substrate. Removal of the base coating at the first discrete location 112 forms a first chamfered discrete location. A first passivation layer 150 is deposited on the first chamfered discrete location. A first discrete coating 130 is on the first passivation layer and the metal substrate at the first chamfered discrete location. Removal of the base coating at a second discrete location 114 forms a second chamfered discrete location. A second passivation layer 152 is deposited on the metal substrate at the second chamfered discrete location. A second discrete coating 140 is on the second passivation layer and the metal substrate at a second chamfered discrete location. Both the first discrete coating and the second discrete coating are also in contact with the base coating. The compositions of the first discrete coating and the second discrete coating are different (e.g. one has a colorant and the other does not, one has a different amount of a colorant that the other, multiple individual coatings individually a different colorant, etc.). The compositions of the first and second transparent passivation layers can be the same or different.

Methods of Manufacturing

[0033] The coated metal substrates for electronic devices disclosed herein can be manufactured in a variety of ways. FIG. 2 presents one non-limiting example a method 200 of manufacturing a coated metal substrate for an electronic device. The method can include coating 210 a surface of a metal substrate with a base coating having a thickness of from about 25 pm to about 120 pm, wherein the metal substrate has a density of from about 1.0 g/cm ³ to about 5.0 g/cm ³ and a thickness of from about 0.3 mm to about 2.0 mm. The method can also include removing 220 a first portion of the base coating from the metal substrate at a first discrete location. Additionally, the method can include depositing 230 a first discrete coating at the first discrete location using ultraviolet electrophoretic deposition, the first discrete coating deposited on the metal substrate and also contacting the base coating, wherein the first discrete coating has a coating thickness of from about 5 pm to about 50 pm and a pencil hardness of from about H to about 4H, and wherein the first discrete coating includes a photoinitiator and a photocured polymeric material.

Preparing Metal Substrates

[0034] In further detail, the metal substrate can be coated with a variety of base coatings, such as those described above. Depending on the base coating employed, the surface of the metal substrate can be preliminarily prepared in a variety of ways prior to application of the base coating. Non-limiting examples of surface preparation methods can include degreasing, passivating, polishing, cleaning, or a combination thereof.

[0035] For example, in some cases the surface of the metal substrate can be passivated prior to forming the base coating. In some examples, passivation can include a micro-arc oxidation process. In other examples, passivation can include immersing the metal substrate in molybdates, vanadates, phosphates, chromates, stannates, manganese salts, the like, or a combination thereof for 20-60 seconds to form a passivation layer. A combination of passivation methods can also be employed. In some examples, passivation of the surface of the metal substrate can be performed prior to spray coating, prior to applying a primer coat, or a combination thereof.

[0036] In some additional examples, the surface of the metal substrate can be prepared using a degreasing process. Degreasing can include immersing, scrubbing, the like, or a combination thereof with an alkaline cleaning composition including about 0.3 wt% to about 2.0 wt% sodium caseinate, sodium polyacrylate, sodium

polyoxyethylene alkyl ether carboxylate, sodium dodecyl sulfate, the like, or a

combination thereof. In some further examples, the degreasing process can be performed using an ultrasonic water bath for a time period of from about 30 seconds to about 180 seconds. In some examples, degreasing can be performed prior to polishing, prior to cleaning, prior to electrophoretic deposition of a thermally curable polymer base coating, or a combination thereof. In some additional examples, degreasing can be performed prior to passivating, powder coating, or a combination thereof.

[0037] In yet additional examples, the surface of the metal substrate can be prepared using a chemical polishing process. Chemical polishing can include immersing, scrubbing, the like, or a combination thereof with a polishing composition that can include from about 0.2 wt% to about 3.0 wt% hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, the like, or a combination thereof for a period of from about 15 seconds to about 60 seconds. In some examples, chemical polishing can be performed after degreasing. In some further examples, chemical polishing can be performed prior to cleaning, prior to electrophoretic deposition of a thermally curable polymer base coating, or a combination thereof.

[0038] In still additional examples, the surface of the metal substrate can be preliminarily prepared using a cleaning process, such as by immersing, scrubbing, the like, or a combination thereof with deionized water or other suitable cleaning agent. In some additional examples, the cleaning process can be performed using an ultrasonic water bath for a time period of from about 30 seconds to about 180 seconds. In some examples, the cleaning process can be performed after degreasing, after chemical polishing, or a combination thereof. In some examples, the cleaning process can be performed prior to electrophoretic deposition of a thermally curable polymer base coating.

Forming the Base Coating on the Metal Substrate

[0039] The base coating can be applied in a variety of ways. For example, in some cases the base coating can be or include a powder coating. Where this is the case, the powder coating can be electrostatically applied and cured at a temperature of from about 120 °C to about 190°C. In some examples, the powder coating formulation can include an epoxy, a poly(vinyl chloride), a polyamide, a polyester, a polyurethane, an acrylic, a polyphenylene ether, the like, or a combination thereof. Additionally, in some examples, the powder coating formulation can include a high aspect ratio filler, such as talc, clay, graphene, a high aspect ratio pigment, the like, or a combination thereof. The powder coating can generally be applied at a thickness of from about 20 pm to about 60 pm.

[0040] In some additional examples, the base coating can include a plurality of coating layers, such as a primer coating layer, a lower coating layer, and an upper coating layer. Where this is the case, these layers can be individually spray coated, dip coated, or the like. In some examples, the primer layer can include a polyurethane coating, or the like, at a coating thickness of from about 5 pm to about 20 pm. In some examples, the primer coating layer can be cured at a temperature of from about 60 °C to about 80°C for a period of from about 15 to about 40 minutes. The lower coating layer can include a pigmented polyurethane, or the like coated at a coating thickness of from about 5 pm to about 20 pm. Non-limiting examples of pigments can include carbon black, titanium dioxide, clay, mica, talc, barium sulfate, calcium carbonate, a synthetic pigment, a metallic powder, aluminum oxide, an organic powder, an inorganic powder, a plastic bead, a colored pigment, the like, or a combination thereof. In some further examples, the lower coating layer can include a dye. The lower coating layer can be cured at a temperature of from about 60 °C to about 80°C for a period of from about 15 minutes to about 40 minutes. The upper coating layer can include a UV-curable material including polyacrylate, a polyurethane, a urethane acrylate, an acrylic acrylate, and an epoxy acrylate, a polyacrylate copolymer, the like, or a combination thereof coated at a coating thickness of from about 10 pm to about 25 pm. The upper coating can be cured at a temperature of from about 50 °C to about 60°C for a period of from about 10 minutes to about 15 minutes followed by UV curing at about 700 mJ/cm ² to about 1 ,200 mJ/cm ² for a period of about 10 seconds to about 30 seconds. In some specific examples, a top coating layer including a clear polyurethane or polyurethane copolymer can also be applied on the upper coating layer. The top coating layer can be thermally cured at a temperature of from about 60 °C to about 80 °C for period of from about 15 minutes to about 40 minutes.

[0041 ] In still additional examples, the base coating can be applied by

electrophoretic deposition of a thermally curable polymer material. In further detail, the metal substrate can be positioned in an electrolyte solution having an electrolyte concentration of from about 100 mg/L to about 150 mg/L. Non-limiting examples of electrolytes that can be used in the electrolyte solution can include Mg(N03) ₂ , NaCI, CaCh, the like, or a combination thereof. The electrolyte solution can typically have a pH of from about 7.5 to about 9. The temperature of the electrolyte solution can generally be from about 15 °C to about 40 °C. Further, the concentration of the polymer in the electrolyte solution can typically be from about 5 wt% to about 15 wt%.

[0042] The metal substrate can be coupled to an electrode and a voltage of from about 20 V to about 150 V can be applied to the metal substrate. The deposition time and voltage can generally determine the thickness of the electrophoretically deposited polymer material. In some examples, the deposition time can be from about 20 seconds to about 180 seconds. After electrophoretic deposition, the deposited polymer can be thermally cured at a temperature of from about 130 °C to about 180 °C for a period of from about 30 minutes to about 60 minutes.

[0043] A few specific examples of base coating methods are provided herein as non-limiting examples. In one specific example, the metal substrate can be passivated by micro-arc oxidation. Subsequently a primer coating can be applied, followed by a lower coating and then an upper coating to form the base coating.

[0044] In another specific example, the metal substrate can be passivated by micro-arc oxidation. The metal substrate can be subsequently powder coated. Following the powder coating, a primer coating can be applied. A lower coating can then be applied, followed by an upper coating. The powder coating layer, primer coating layer, lower coating layer, and upper coating layer can form the base coating.

[0045] In yet another specific example, the metal substrate can be degreased, followed by chemical polishing and then cleaning with deionized water. The metal

substrate can then be coated by electrophoretic deposition followed by thermal curing or UV curing of the polymeric material to form the base coating.

[0046] In still another specific example, the metal substrate can be degreased, followed by passivation by micro-arc oxidation. The metal substrate can then be powder coated to form the base coating.

Removing Base Coating Portions

[0047] Discrete portions of the base coating can be removed in a variety of ways. Non-limiting examples can include laser etching, computer numerical control (CNC) cutting, the like, or a combination thereof. In some examples, the removal process can remove the base coating without removing metal from the metal substrate, or with minimal removal of metal from the metal substrate. In other examples, the removal process can also be used to shape the metal substrate, such as to form a chamfer, a bevel, a groove, a fillet, the like, or a combination thereof. In some examples, the removal process can be performed at an edge of the metal substrate, on a sidewall of the metal substrate, elsewhere on the metal substrate, or a combination thereof. In some specific examples, the removal process can be used to form a chamfer at an edge of the metal substrate.

Forming a Transparent Passivation Layer

[0048] The removal of a discrete portion of the base layer exposes the surface of the metal substrate at a discrete location. In some examples, the exposed surface of the metal substrate can include free radicals, surface contaminants, the like, or a

combination thereof that can adversely affect a subsequently deposited material at the discrete location over time. As such, in some examples, it can be desirable to deposit or form a transparent passivation layer to protect the discrete coating from any free radicals, surface contaminants, the like, or a combination thereof on the surface of the metal substrate. In some examples, the transparent passivation layer can include a chelating agent. Non-limiting examples of chelating agents can include

ethylenediaminetetraacetic acid (EDTA), ethylenediamine, nitrilotriacetic acid (NTA), diethylenetriaminepenta(methylenephosphonic acid) (DTPPH), nitrilotris(methylenephosphonic acid) (NTMP), 1 -hydroxyethane-1 ,1 -diphosphonic acid (HEDP), phosphoric acid, the like, or a combination thereof. In some examples, the transparent passivation layer can include an organic acid in combination with aluminum, nickel, chromium, tin, indium, zinc, the like, or a combination thereof. Various

combinations of the previously recited materials can also be employed. In some examples, the transparent passivation layer can be formed by immersing the metal substrate into a transparent passivation chemical bath for a period of from about 30 seconds to about 150 seconds. The transparent passivation layer can generally have a coating thickness of from about 30 nm to about 3 pm. In some additional examples, the transparent passivation layer can have a coating thickness of from about 30 nm to about 300 nm, from about 150 nm, to about 500 nm, from about 250 nm to about 750 nm, from about 500 nm to about 1 pm, from about 750 nm to about 1.5 pm, from about 1 pm to about 2 pm, from about 1.5 pm to about 2.5 pm, or from about 2 pm to about 3 pm. The transparent passivation layer can provide good corrosion resistance while maintain the metallic luster at the discrete location due to its transparent nature.

Depositing Discrete Coatings

[0049] The discrete coating (or coatings) can be applied by ultraviolet

electrophoretic deposition (UV ED). In further detail, the coated metal substrate can be inserted into an electrolyte solution having an electrolyte concentration of from about 100 mg/L to about 150 mg/L. Non-limiting examples of electrolytes that can be used in the electrolyte solution can include Mg(N03) ₂ , NaCI, CaC , the like, or a combination thereof. The electrolyte solution can typically have a pH of from about 7.5 to about 9. The temperature of the electrolyte solution can generally be from about 15 °C to about 40 °C. Further, the concentration of the polymer in the electrolyte solution can typically be from about 5 wt% to about 15 wt%.

[0050] The coated metal substrate can be coupled to an electrode and a voltage of from about 20 V to about 150 V can be applied to the coated metal substrate to deposit the discrete coating at the discrete location where the base coating was previously removed. The deposition time and voltage can generally determine the thickness of the electrophoretically deposited polymer material. In some examples, the deposition time can be from about 20 seconds to about 120 seconds.

[0051 ] After the polymer is deposited on the coated metal substrate, the deposited polymer can be baked on the coated metal substrate at a temperature of from about 60 °C to about 80 °C for a period of from about 20 minutes to about 40 minutes. Subsequently, the deposited polymer can be cured via ultraviolet electromagnetic radiation at from about 700 mJ/cm ² to about 1500 mJ/cm ² for a period of from about 10 seconds to about 30 seconds.

[0052] It is noted that this process can be repeated as many times as desired to prepare multiple discrete coatings at multiple discrete locations. For example, a first removal process can prepare a first discrete location for deposition of a first discrete coating material. The first discrete location can be passivated to prepare the metal substrate for deposition of the first discrete coating material. The first discrete coating material can then be deposited by UV ED. A second removal process can then be employed to prepare a second discrete location for deposition of a second discrete coating material. The second discrete location can be passivated to prepare the metal substrate for deposition of the second discrete coating material. The second discrete coating material can then be deposited by UV ED. The process can be continued in like manner to prepare as many discrete coatings as desired. In this example, the first and/or second discrete location can be transparently passivated.

[0053] One non-limiting example of a method of manufacturing a coated metal substrate is presented in FIGs. 3A-3D. More specifically, coated metal substrate 300 is illustrated in FIG. 3A as including a base coating 320 on a metal substrate 310. FIG. 3B illustrates the coated metal substrate after the removal process, which removed a portion of the base coating and prepared a chamfered edge of the metal substrate at the discrete location 312 for depositing the discrete coating. As presented in FIG. 3C, a transparent passivation layer can be formed at the discrete location to provide corrosion resistance and to maintain the metallic luster at the discrete location. Turning to FIG. 3D, the discrete coating 320 has been deposited and cured at the discrete location to form the final coated metal substrate.

Electronic Devices

[0054] The coated metal substrates described herein can be used in a variety of electronic devices. For example, the metal substrates can be used as a cover, a frame, a support structure, the like, or a combination thereof for a variety of electronic devices. For example, the coated metal substrates can be used with a display, a personal computer, a laptop computer, a tablet, a media player, a smart device, a keyboard, the like, or a combination thereof.

[0055] One non-limiting example of an electronic device in accordance with the present disclosure is presented in FIG. 4. In this example, the electronic device 490 is a laptop computer. The coated metal substrate 400 forms a keyboard frame for the laptop computer. The base coating 410 provides the general appearance of the keyboard frame. Flowever, an edge of the keyboard frame that was cut for placement of a click pad 480 has been modified to include a discrete coating 430 to give this region of the keyboard frame an appearance distinct from the base coating, such as a glossy appearance, a metallic luster, a different color, the like, or a combination thereof. It is noted that while FIG. 4 illustrates a single discrete coating about a click pad, this is not intended to be limiting. For example, individual discrete coatings can be deposited about a click pad, a touch screen, a touch pad, a fingerprint scanner, a keyboard, individual keyboard keys, a sidewall, other suitable or desirable location, or a

combination thereof.

Definitions

[0056] It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise.

[0057] As used herein, the term“about” is used to provide flexibility to a numerical range endpoint by providing that a given value may be“a little above” or“a little below” the endpoint. The degree of flexibility of this term can be dictated by the particular variable and would be within the knowledge of those in the field technology determine based on experience and the associated description herein.

[0058] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience.

However, these lists should be construed as though individual members of the list are individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary.

[0059] Concentrations, dimensions, amounts, and other numerical data may be presented herein in a range format. It is to be understood that such range format is used merely for convenience and brevity and should be interpreted flexibly to include the numerical values explicitly recited as the limits of the range, but also all the individual numerical values or sub-ranges encompassed within that range as if individual numerical values and sub-ranges are explicitly recited. For example, an atomic ratio range of about 1 at% to about 20 at% should be interpreted to include the explicitly recited limits of about 1 at% and about 20 at%, but also to include individual atomic percentages such as 2 at%, 11 at%, 14 at%, and sub-ranges such as 10 at% to 20 at%, 5 at% to 15 at%, etc.

[0060] The terms, descriptions, and figures used herein are set forth by way of illustration and are not meant as limitations. Many variations are possible within the disclosure, which is intended to be defined by the following claims -- and equivalents -- in which all terms are meant in the broadest reasonable sense unless otherwise indicated.