Stainless steel polymer adhesive layer

Abstract

The present disclosure relates to stainless steel polymer adhesive layers. Chemical treatment methods have been confirmed as a simple and effective means of improving the adhesion of injection molded polymers to stainless steel surfaces. The method forms an oxide layer on the stainless steel surface, the oxide layer comprising a layered double hydroxide. The layered double hydroxide not only improves the bond strength, but also minimizes leakage of air or water. The method enables the use of stainless steel alloy to bond with injection molded polymer structures in a robust, lightweight and waterproof housing for consumer electronics.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 581,173, filed on September 7, 2023, entitled “Stainless Steel Polymer Adhesion Layer,” the entire disclosure of which is hereby incorporated by reference in its entirety. Technical Field

[0003] The described embodiments generally relate to surface structures on stainless steel surfaces. More specifically, embodiments of the present invention relate to systems and methods for forming interlocking structures at stainless steel surfaces to attach polymeric materials to the stainless steel surfaces. Background Art

[0004] Housings for consumer devices are typically constructed from a combination of metallic and non-metallic materials to provide functional, structural, and visual enhancements. However, metals that exhibit properties that are beneficial for use in consumer devices, such as stainless steel, may lack the natural ability to attach to these non-metallic materials. Techniques for modifying metals to facilitate attachment to non-metallic materials may require considerable time, expense, and effort. In addition, although these techniques can attach non-metallic materials to metallic materials, they may not provide an acceptable amount of tensile strength between stainless steel and non-metallic materials. Summary of the invention

[0005] Various embodiments are disclosed that relate to oxides formed on stainless steel surfaces. Additionally, embodiments are disclosed that relate to techniques for etching surfaces of metal parts including stainless steel. Specifically, various embodiments relate to systems and methods for forming interlocking structures at oxide surfaces of stainless steel parts to attach polymer materials to surfaces of metal parts including stainless steel substrates.

[0006] According to some embodiments, the oxide layer on the stainless steel substrate may include a layered double hydroxide. In some examples, the oxide layer may include an iron-rich precipitate deposited on a porous iron-nickel layer. In some examples, the oxide layer may include a thickness of about 100nm to about 300nm. In some examples, the oxide layer may include a porosity between about 30% and about 80%. In some examples, the iron-rich precipitate may include a microstructure comprising a spherical structure having a diameter between about 20nm and about 100nm. In some examples, the oxide layer may include a first layer and a second layer, the first layer comprising an iron-nickel hydroxide layer having a thickness between about 80nm and about 150nm, the second layer comprising an iron-rich oxide disposed on the first layer, the second layer comprising a spherical structure having a diameter between about 20nm and about 100nm. The oxide layer may also include a porous structure defining pores having a diameter between about 20nm and about 50nm.

[0007] According to some embodiments, the stainless steel-polymer interface may include an oxide layer on a stainless steel substrate, and a polymer. In some examples, the polymer permeates the oxide layer and may form a bond having a bond strength of about 25 MPa or greater. In some embodiments, the oxide layer may include a layered double hydroxide. In some examples, the polymer may include at least one of a glass-filled PBT resin, a polyamide, and an epoxy resin.

[0008] In some examples, the oxide layer may include a surface roughness greater than about 500 nm Sz. In some examples, the oxide layer may include iron-rich precipitates deposited on the porous iron-nickel layer. In some examples, the polymer may include an injection molded polymer. In some examples, the stainless steel-polymer interface may include a polymer having a dynamic viscosity between about 800 Pa·s and about 200 Pa·s.

[0009] According to some embodiments, a method for forming an oxide layer on a stainless steel substrate may include immersing the stainless steel substrate in a caustic solution and applying a cathode potential between the stainless steel substrate and the anode. In some examples, the caustic solution may include a solution of sodium hydroxide or potassium hydroxide between about 1 mole and about 10 moles. In some examples, the cathode potential may include a pulsed potential including a voltage between about 2V and about 5V and a pulse rate of powering on for about 1 minute and about 4 minutes and powering off for about 1 minute and about 4 minutes, the pulse being repeated between about 2 times and about 20 times. In some examples, the caustic solution is between about 50°C and about 90°C. The ratio between the anode and the stainless steel substrate may be between about 2:1 and about 10:1. In some examples, the method may form an oxide layer having a surface roughness between about 500nm and about 1000nm Sz.

[0010] Other aspects and advantages of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, which illustrate by way of example the principles of the described embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure will be readily understood through the following detailed description in conjunction with the accompanying drawings, in which like reference numerals represent like structural elements, and in which:

[0012] Figure 1 Illustrated are perspective views of various electronic devices having metal surfaces that can be processed using the techniques described herein, according to some embodiments.

[0013] Figure 2 An exploded view of components of an electronic device is illustrated.

[0014] Figure 3A Illustrative images illustrating views of a stainless steel substrate having an oxide layer formed using techniques described herein, according to some embodiments.

[0015] Figure 3B Illustrated is a cross-sectional view of a stainless steel substrate including an oxide layer at the surface formed using the techniques described herein, according to some embodiments.

[0016] FIG. 4A to FIG. 4D Illustrated is a scanning electron microscope image of a cross-section of an exemplary stainless steel substrate having an oxide layer formed using the techniques described herein, according to some embodiments.

[0017] Figure 5 A method of forming a layered double hydroxide oxide layer on a stainless steel substrate according to some embodiments is illustrated.

[0018] Fig. 6AIllustrated is a graph of a stainless steel-polymer interface and the bond strength of the interface according to some embodiments.

[0019] Figure 6B Illustrated is a graph indicating a tensile strength relationship between an etching process and the tensile strength of a treated metal component, according to some examples. DETAILED DESCRIPTION

[0020] Reference will now be made in detail to the representative embodiments illustrated in the accompanying drawings. It should be understood that the following description is not intended to limit the embodiments to a preferred embodiment. On the contrary, it is intended to cover substitutions, modifications and equivalents that may be included in the essence and scope of the described embodiments defined by the appended claims.

[0021] The following disclosure relates to chemical treatment methods that provide effective means for improving the bonding of polymers to stainless steel surfaces. Stainless steel is an attractive metal for certain engineering applications due to its high corrosion resistance and aesthetics. For example, this provides a corrosion-resistant and relatively inexpensive housing for portable electronic devices. In any such application, bonding to other materials such as polymers, glass, and ceramics is desirable. Specifically, injection molded polymers can be used to electrically isolate the various components of the housing while ideally maintaining structural strength. This article provides an example of a chemical method for producing a thin, rough surface oxide on a stainless steel substrate that greatly improves the adhesion of the polymer to the substrate.

[0022] In a specific embodiment, once the final geometry of the stainless steel substrate is ready for adhesive bonding, the stainless steel can be optionally etched to increase the roughness of the stainless steel. After etching, in a chemical process described in more detail below, a surface structure can be created on the stainless steel substrate or surface, onto which a structural polymer such as glass-filled ABS can be injection molded, and the resulting bond strength is high enough to withstand wear while exhibiting a low rate of air leakage through the bond in a leak test.

[0023] References below Figures 1 to 6BThese embodiments and other embodiments are discussed. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for illustrative purposes only and should not be construed as limiting. In addition, as used herein, a system, method, article, assembly, feature, or sub-feature comprising at least one of a first option, a second option, or a third option should be understood to refer to a system, method, article, assembly, feature, or sub-feature comprising one of each listed option (e.g., only one first option, only one second option, only one third option), a plurality of a single listed option (e.g., two or more first options), two options simultaneously (e.g., one first option and one second option), or a combination thereof (e.g., two first options and one second option).

[0024] Stainless steel is often considered the material of choice for consumer-grade portable electronic devices. Stainless steel has desirable properties, such as high specific strength and stiffness, and is relatively easy to process. Stainless steel is a corrosion-resistant alloy of iron, chromium and nickel, and in some instances other metals. Stainless steel, which is completely and infinitely recyclable, is a fairly excellent "green material". Stainless steel can also be used in combination with non-metallic materials such as glass and polymers. For example, the display of a portable electronic device can be bonded to a stainless steel frame of a housing. The stainless steel frame is typically subdivided into various electrically isolated components to prevent electromagnetic interference from an antenna carried within the housing. For example, stainless steel can be used to form a structural band around the edge of the housing so that the display is bonded to one face and the glass is bonded to the opposite face. In addition, electrically insulating cracks can be formed around the periphery of the housing.

[0025] In order for the structural band to give the shell sufficient structural strength, firmness, rigidity, and heat and moisture resistance throughout the life of the shell, the shell needs to form a strong adhesive bond between the metal (e.g., stainless steel) and the non-metallic material (e.g., polymer). In the face of additional insulation cracks (for improving antenna performance) and even smaller adhesion areas (to minimize weight and space), it may be even more challenging to meet these requirements technically. In addition, the growing demand for waterproof shells requires that these adhesive bonds not only maintain strength, but also prevent moisture leakage, even after the shell has been subjected to many strain cycles. In addition, conventional mechanisms such as mechanical fasteners (e.g., rivet guns) for fastening metal to non-metallic materials are generally not used in portable electronic devices because this can eliminate the electrical isolation between metal parts. For example, non-metallic materials (e.g., polymers) are used to electrically isolate different metal parts attached together. In addition, alternative methods for forming polymer adhesion features, such as micro-arc oxidation or by anodizing in fluoride-based electrolytes or caustic solutions, generally produce poor adhesion properties. In practice, these methods produce slightly scalloped structures that fail to provide adequate attachment strength, water resistance, and tensile strength required for portable electronic devices to withstand consumer use in harsh environments. As the housings of portable electronic devices become smaller and / or the design of these housings changes to just a peripheral metal band, the allowable bonding area between metal and non-metal is greatly reduced. Therefore, more emphasis is placed on more robust metal-to-non-metal bonds.

[0026] As used herein, the terms "oxide coating", "oxide layer", "oxide layer", "oxide film", "oxide layer", "porous oxide layer" and "surface oxide layer" may be used interchangeably and may refer to any suitable oxide layer. The oxide layer is formed on the surface of the stainless steel substrate. In some embodiments, the non-metallic layer may include a large portion of non-metallic material mixed or combined with a metallic material so that the non-metallic layer is mainly made of non-metallic material. As used herein, the terms "component", "layer", "segment" and "portion" may also be used interchangeably where appropriate.

[0027] References below Figures 1 to 6B These and other embodiments are discussed. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for illustrative purposes only and should not be construed as limiting.

[0028] Figure 1 Various portable electronic devices that can be processed using the techniques described herein are illustrated.Techniques as described herein can be used to process metal surfaces (eg, stainless steel oxide layers, etc.) of housings of portable devices for consumer use. Figure 1Smartphone 102, tablet computer 104, smart watch 106, and portable computer 108 are illustrated. According to some embodiments, the metal surface may refer to a metal substrate covered by a metal oxide layer. In some examples, the metal oxide layer may be formed from the metal substrate. Specifically, the metal oxide layer may be used as an additional protective coating to protect the metal substrate, for example, when these portable devices are dropped, scratched, chipped, or worn.

[0029] According to some embodiments, non-metallic materials can be attached to the outer surface of the metal surface. Specifically, the multi-layer housing of these portable devices including a combination of metallic materials and non-metallic materials can provide improved structural benefits and electromagnetic interference reduction benefits for the functionality of these portable devices. In one example, these portable devices may include a wireless antenna / transceiver that can receive and send data signals with other electronic devices. However, the metal surface directly covering the wireless antenna can cause a large amount of undesirable electromagnetic interference, which can affect the ability of the portable device to receive and / or send data signals. Non-metallic materials such as polymers are generally non-conductive (i.e., dielectric), so the amount of electromagnetic interference affecting the portable device can be minimized, while still giving the housing of the portable device a sufficient amount of structural rigidity and protective quality.

[0030] Figure 2 An exploded view of a strip 202 is illustrated that may form an electronic device such as Figure 1 202 may include one or more portions that are stainless steel components, such as an outer portion joined to an inner portion, as described herein. For example, the band 202 may include a first stainless steel sidewall component 204, a second stainless steel sidewall component 206, a third stainless steel sidewall component 208 (opposite the first composite sidewall component 204), and a fourth stainless steel sidewall component 210. In some examples, as described herein, by way of non-limiting example, the stainless steel components 204, 206, 208, 210 may be separated and / or joined together by materials that may include electrically inert or electrically insulating materials, such as polymers and / or resins.

[0031] although Figure 2The illustrated embodiment includes a band 202 having a plurality of stainless steel components 204, 206, 208, 210 joined together, but in some embodiments, as described herein, a housing or case for an electronic device may include or may be formed from a single stainless steel component having an interior portion and an exterior portion. Additionally, in some examples, the stainless steel component may form a portion of the housing or case other than the sidewalls, such as a top portion, a bottom portion, or any other portion of the housing or case. The stainless steel components 204, 206, 208, 210 of the band 202 may be formed by a variety of methods and may allow the band 202 to have a detailed shape or design that is specifically tailored to meet one or more needs (such as internal dimensional requirements) without requiring additional features to enhance the structure of the band.

[0032] The openings or crack areas can separate adjacent stainless steel components of the strip 202. For example, the sidewall component 208 is separated from the sidewall component 210 by the opening 212. The sidewall component 208 is separated from the sidewall component 206 by an additional opening. A non-metallic spacer 214 can fill each opening. In some examples, the non-metallic spacer 214 can include a polymer. According to some examples, the polymer can be at least one of an injection molded glass-filled PBT resin, a polyamide, and an epoxy resin. In some examples, the polymer can be bonded to the stainless steel component using a stainless steel-polymer bonding operation. FIG. 3A to FIG. 6B Further details of stainless steel components and exemplary methods for improving the bond strength of stainless steel-polymer bonds are provided. Figure 3A Further details are provided for an exemplary oxide layer disposed on the surface of a stainless steel substrate.

[0033] Figure 3A An exemplary microscopic image of an example stainless steel substrate having an oxide layer disposed on a surface is illustrated. The oxide layer includes a layered double hydroxide structure. Layered double hydroxide (LDH) is an ionic layered compound having a positively charged layer and an interlayer region having charge compensating anions. Layered double hydroxides typically include mixed metals (e.g., nickel and / or iron) and hydroxide molecules separated by exchangeable anions. In some examples, the oxide layer may include a porous first layer and a second layer disposed on the porous first layer, the second layer including a spherical structure deposited on the surface. The first layer may include an iron-nickel hydroxide layer, and the spherical structure may include an iron-rich oxide material.

[0034] Figure 3BA cross-sectional side view of a stainless steel surface 300 according to an exemplary embodiment is illustrated. As illustrated, the stainless steel surface 300 includes a stainless steel substrate 302 and an oxide layer 304. In some examples, the oxide layer 304 may include a thickness greater than about 100 nm. In some examples, the oxide layer 304 may have a thickness of about 125 nm or more, a thickness of about 150 nm or more, a thickness of about 175 nm or more, a thickness of about 200 nm or more, a thickness of about 225 nm or more, a thickness of about 250 nm or more, or in a thickness range of about 100 nm to about 150 nm, about 150 nm to about 200 nm, about 200 nm to about 250 nm, or about 250 nm to about 300 nm.

[0035] In some examples, the stainless steel surface 300 includes a layered double hydroxide. In some examples, the oxide layer 304 may include a microstructure 306 having a spherical structure 308. The spherical structure 308 may include a layered double hydroxide. In some examples, the oxide layer 304 may include an iron-rich spherical structure 308 precipitate deposited on a porous iron-nickel layer.

[0036] In some examples, the spherical structures 308 may include a diameter of less than about 100 nm. The spherical structures 308 may have a diameter of about 20 nm or more, a diameter of about 40 nm or more, a diameter of about 50 nm or more, a diameter of about 70 nm or more, a diameter of about 80 nm or more, a diameter of about 90 nm or more, or a diameter in the range of about 20 nm to about 100 nm, about 40 nm to about 80 nm, about 50 nm to about 100 nm, or about 60 nm to about 80 nm. In some embodiments, the spherical structures 308 may be at least partially embedded in the porous layer. In some embodiments, the oxide layer may include a porosity between about 30% and about 80%. In some examples, the oxide layer may include a porosity of about 50%. In some embodiments, the porosity of the oxide layer can be 30% or greater, such as about 40% or greater, about 50% or greater, about 60% or greater, about 65% or greater, about 70% or greater, or in the range of about 30% to about 40%, about 40% to about 50%, about 50% to about 60%, about 60% to about 70%, or about 70% to about 80%. In some embodiments, the oxide layer (e.g., oxide layer 304) can include a porous structure, wherein the pores of the porous structure include a diameter of about 20nm to about 50nm. In some examples, the porosity of the oxide layer can be adjusted according to the method of forming the layered double hydroxide film layer on the stainless steel substrate 302.

[0037] In some embodiments, the oxide layer 304 may include a first layer comprising an iron nickel hydroxide layer. The first layer may include a well-adhered layer having a thickness between about 80 nm and about 150 nm. In some embodiments, the first layer may have a thickness of about 80 nm or more, a thickness of about 100 nm or more, a thickness of about 125 nm or more, or in a thickness range of about 80 nm to about 100 nm, about 100 nm to about 120 nm, about 120 nm to about 140 nm, or about 130 nm to about 150 nm. The oxide layer may also include a second layer comprising an iron-rich oxide disposed on the first layer, the second layer having a spherical structure 308 having a diameter between about 20 nm and about 100 nm. The total thickness of the oxide layer 304 may be greater than about 100 nm and between about 100 nm and about 300 nm.

[0038] In some examples, the oxide layer 304 may include a high surface roughness. The surface roughness of the oxide layer may improve bonding at the stainless steel-polymer interface, where the polymer may extend into the oxide layer to form a high bond strength. In some examples, the oxide layer may include a surface roughness between about 500 nm and about 1000 nm Sz. For the present disclosure, Sz is defined as the sum of the maximum peak height value and the maximum pit depth value within the defined area. In other words, Sz is defined as the maximum peak height plus the maximum pit height.

[0039] The surface roughness may be about 500 nm Sz or greater, about 600 nm Sz or greater, about 700 nm Sz or greater, about 800 nm Sz or greater, about 900 nm Sz or greater, or in the range of about 500 nm Sz to about 600 nm Sz, about 600 nm Sz to about 700 nm Sz, about 700 nm Sz to about 800 nm Sz, about 800 nm Sz to about 900 nm Sz, or about 900 nm Sz to about 1000 nm Sz. In some examples, the surface may include a jagged peak-to-valley texture. The spherical structures 308 may be disposed in the valleys, connected to the peaks, or partially embedded in the porous layer portion of the oxide layer 304.

[0040] As explained below, the porous structure of the oxide layer 304 produced by at least the porous iron-nickel layer and the layered double hydroxide microstructure 306 can produce an interlocking structure with a non-metallic material (e.g., a polymer) when the non-metallic material flows into the porous structure and is allowed to harden and transform from a molten state to a solid state.

[0041] FIG. 4A to FIG. 4D Illustrated according to some embodiments having FIG. 3A to FIG. 3B0047] An exemplary microscopic image of an example stainless steel surface of layered double hydroxides similar to those illustrated in , the example stainless steel surface comprising a stainless steel substrate 302 and an oxide layer 304 having layered double hydroxides as spherical structures 308 extending therefrom. FIG. 4A to FIG. 4C A cross-sectional view is illustrated in which the oxide layer exhibits peaks and valleys formed by the etching method described below. FIG. 4A to FIG. 4D As shown, jagged peaks and valleys are shown extending from the oxide layer and providing different angles and features on the stainless steel substrate. The ends of the peaks have corresponding relative distances between them, thereby defining cracks that improve the stainless steel-polymer interface bonding. FIG. 4C to FIG. 4D As shown, in some embodiments, the oxide layer (e.g., oxide layer 304) may include a porous structure, wherein the pores of the porous structure include a diameter of about 20 nm to about 80 nm. In some examples, the porosity of the oxide layer can be adjusted according to a method of forming a layered double hydroxide film layer on a stainless steel surface.

[0042] Figure 5 A method 500 of forming a layered double hydroxide oxide layer on a stainless steel surface is illustrated according to some embodiments. Figure 5 As illustrated, method 500 may begin at frame 502, where a stainless steel substrate may be etched to provide a roughening effect. In some examples, before roughening the surface of the stainless steel, the substrate may be degreased and rinsed. After rinsing, the stainless steel surface may be dried to prepare for etching. The etched surface may be beneficial in providing a rough outer surface of the stainless steel substrate, which may promote the growth of an oxide layer at the roughened area. In some examples, the etching method may provide up to about 15% bonding strength between the oxide layer and the non-metallic material. In other embodiments, the etching method may be omitted and / or replaced with other physical or chemical roughening pretreatment methods.

[0043] At box 504, in some examples, the outer surface of the substrate can be cleaned to remove any liquid or contaminants that may be present, thereby further promoting the formation of an oxide layer on the stainless steel substrate. For example, the outer surface of the stainless steel substrate can be cleaned and rinsed with tap water or deionized water to remove any residues of the etching process. The surface of the stainless steel substrate can then be immersed in a caustic solution. In some examples, the caustic solution can include at least one of sodium hydroxide or potassium hydroxide. The solution can contain between about 1 mole and about 10 moles of sodium hydroxide or potassium hydroxide. In some examples, the caustic solution can include a pH of about 12 to about 14, and a temperature of about 50°C to about 90°C. The caustic solution oxidizes the stainless steel, which produces a porous and generally well-adhered iron-nickel hydroxide layer.

[0044] At box 506, the stainless steel surface can be etched while the stainless steel surface is immersed in the hydroxide. In some examples, a cathode potential can be applied to the stainless steel substrate to promote oxide growth. In some examples, a graphite anode can be used. However, the anode material may include stainless steel or any suitable anode material. In one example, etching the stainless steel substrate surface may include applying a voltage between about 2V and about 5V or applying a pulsed or constantly applied current density of about 8 amperes per square decimeter to about 12 amperes (ASD). The potential may be a pulsed or constantly applied potential. In some examples, the pulsed potential may include a pulse rate of about 1 minute to about 4 minutes of power on and about 1 minute to about 4 minutes of power off, and the pulse is repeated about 2 times and about 20 times. In some examples, the ratio between the anode and the stainless steel substrate is between about 2: 1 and about 10: 1. In some examples, the ratio between the anode and the stainless steel substrate is about 5: 1.

[0045] In some examples, the layered double hydroxide attaches to the oxide while it is being formed, thereby etching and roughening the oxide layer to form fine-scale roughness and porosity including the layered double hydroxide spherical structure. The porosity improves the adhesion of the injection molded polymer to the oxide surface.

[0046] In some examples, the stainless steel surface may be rinsed and dried.The outer surface of the stainless steel substrate may be cleaned to remove any liquid or contaminants that may be present, thereby improving the bond strength between the oxide layer and the non-metallic material (eg, polymer).

[0047] In some examples, the treated stainless steel surface can then form a stainless steel-polymer interface. In some examples, the interface can include an oxide layer on the stainless steel substrate and a polymer, wherein the polymer penetrates the oxide layer and forms a bond having a bond strength of about 25 MPa or greater. The stainless steel-polymer interface can include an injection molded polymer. In one example, a structural polymer such as glass-filled ABS can be injection molded with a resulting bond strength of about 32 MPa. As discussed above, reference Figure 3B After forming the oxide layer including the layered double hydroxide, the metal oxide layer may include pores that can be filled with a non-metallic material. For example, the non-metallic material may refer to a polymer material such as polyethylene terephthalate ("PET"), polyaryletherketone ("PAEK"), polyetheretherketone ("PEEK"), injection molded glass-filled PBT resin, polyamide and / or epoxy resin, which can be allowed to flow into the pores and / or the distance between the ends of the plurality of plates of the oxide layer when in a molten state or a liquid state.

[0048] In some examples, the polymer may have any amount of viscosity or surface tension sufficient to attach to the oxide layer. In some examples, the stainless steel-polymer interface comprises a polymer having a viscosity of about 800 Pa·s to about 200 Pa·s measured at about 5000 1 / sec. In some embodiments, the polymer viscosity may be about 500 Pa·s. In some embodiments, the polymer viscosity may be about 200 Pa·s or greater, such as about 300 Pa·s or greater, about 400 Pa·s or greater, about 500 Pa·s or greater, about 600 Pa·s or greater, about 700 Pa·s or greater, or in the range of about 200 Pa·s to about 300 Pa·s, about 300 Pa·s to about 400 Pa·s, about 400 Pa·s to about 500 Pa·s, about 500 Pa·s to about 600 Pa·s, or about 700 Pa·s to about 800 Pa·s. As the polymer material flows around the spherical structure and into the porous oxide structure, the polymer can penetrate through the layered double hydroxide and fill the voids within the oxide structure. After flowing into the porous oxide, the polymer can be allowed to harden. Thereafter, the polymer can transition from a liquid state to a solid state. When the polymer becomes a solid state, it can physically attach and bond to the oxide layer.

[0049] In some examples, the polymer may include at least one of an injection molded glass-filled PBT resin, a polyamide, and / or an epoxy resin. In some examples, the oxide layer and the polymer form a stainless steel-polymer bond that exhibits a bond strength of about 25 MPa or greater. Typically, any failure in the tensile test includes a cohesive failure within the glass reinforced structural polymer, rather than an adhesion failure between the polymer and the oxide layer or between the stainless steel substrate and the oxide layer.

[0050] Fig. 6A Figure illustrating a stainless steel-polymer interface and a configuration that can be used to test the bond strength of the interface according to some embodiments. In some examples, the stainless steel-polymer interface can include an oxide layer on a stainless steel substrate 602, and a polymer 604. The polymer can penetrate the oxide layer and form a bond that exhibits a bond strength of about 25 MPa or greater. The bond strength can be determined by a rod tensile test, in which the polymer is pulled away from the stainless steel substrate and the yield force is recorded. Fig. 6A 6, polymer 604 is bonded to an oxide layer disposed on a stainless steel substrate 602. The polymer may be disposed between a first stainless steel substrate and a second stainless steel substrate, and the first and second substrates may be pulled apart after the polymer has cured until a bond is created. As noted, the polymer penetrates into the oxide layer showing a stronger bond.

[0051] Figure 6BA graph indicating the relationship of tensile strength as a function of processing type of a stainless steel substrate versus the relationship of tensile strength as a function of processing type is illustrated. After the stainless steel is etched, the strength of the stainless steel-polymer bond is much higher. In some examples, the oxide layer may include a layered double hydroxide. The bond strength may be between about 28 MPa and about 35 MPa. In other words, the maximum tensile strength may be between about 32 MPa and about 35 MPa.

[0052] In an exemplary test, metal parts from different methods were attached to a non-metallic layer with a 7 mm x 7 mm surface and tested for tensile strength individually. The non-metallic layer included an injection molded polybutylene terephthalate (PBT) surface. The different metal parts included stainless steel parts that were not etched and parts that had been etched according to the above reference. Figure 5 The method described herein is used to etch stainless steel parts. In exemplary tests, non-etched stainless steel parts exhibited a tensile strength of less than 5 MPa. Etched stainless steel exhibited a tensile strength between about 32 MPa and about 35 MPa.

[0053] To the extent applicable to the present technology, the collection and use of data obtained from various sources may be used to improve the delivery of inspirational content or any other content that may be of interest to the user. The present disclosure contemplates that in some instances, the collected data may include personal information data that uniquely identifies or can be used to contact or locate a specific person. Such personal information data may include demographic data, location-based data, phone numbers, email addresses, ID, home address, data or records related to the user's health or fitness level (e.g., vital sign measurements, medication information, exercise information), date of birth, or any other identifying or personal information.

[0054] The present disclosure recognizes that the use of such personal information data in the present technology can be used to benefit users. For example, the personal information data can be used to deliver targeted content that users are more interested in. Therefore, the use of such personal information data enables users to have planned control over the content delivered. In addition, the present disclosure also anticipates other uses of personal information data that benefit users. For example, health and fitness data can be used to provide insights into the user's overall health status, or can be used as positive feedback to individuals who use technology to pursue health goals.

[0055] The disclosure anticipates that entities responsible for the collection, analysis, disclosure, transmission, storage or other uses of such personal information data will comply with sound privacy policies and / or privacy practices. Specifically, such entities should implement and adhere to the use of privacy policies and privacy practices that are recognized as meeting or exceeding industry or government requirements for maintaining the privacy and security of personal information data. Such policies should be easy for users to access and should be updated as changes in the collection and / or use of data occur. Personal information from users should be collected for legal and reasonable entity purposes and should not be shared or sold outside these legal purposes. In addition, such collection / sharing should be carried out after receiving the user's informed consent. In addition, such entities should consider taking any necessary steps to protect and safeguard access to such personal information data, and ensure that other entities with access to personal information data comply with the privacy policies and procedures of other entities. In addition, such entities can subject themselves to third-party assessments to prove that they comply with widely accepted privacy policies and privacy practices. In addition, policies and practices should be adapted to specific types of personal information data collected and / or accessed, and to applicable laws and standards including considerations of special jurisdictions. For example, in the United States, the collection or acquisition of certain health data may be governed by federal and / or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA); while health data in other countries may be subject to other regulations and policies and should be handled accordingly. Therefore, different privacy practices should be advocated for different types of personal data in each country.

[0056] Regardless of the foregoing, the present disclosure also contemplates implementation schemes in which users selectively block the use or access of personal information data. That is, the present disclosure contemplates that hardware elements and / or software elements may be provided to prevent or block access to such personal information data. For example, with respect to an advertising delivery service, the technology of the present invention may be configured to allow a user to choose to "opt in" or "opt out" at any time during or after registration for the service to participate in the collection of personal information data. In another example, a user may choose not to provide emotion-related data for a target content delivery service. In another example, a user may choose to limit the length of time that emotion-related data is retained, or to completely prohibit the development of basic emotional conditions. In addition to providing "opt-in" and "opt-out" options, the present disclosure also contemplates providing notifications related to access or use of personal information. For example, a user may be notified that the user's personal information data will be accessed when downloading an application, and then the user may be reminded again just before the personal information data is accessed by the application.

[0057] In addition, it is the intention of the present disclosure that personal information data should be managed and processed in a manner that minimizes the risk of unintentional or unauthorized access or use. Once the data is no longer needed, the risk can be minimized by limiting the collection of data and deleting the data. In addition, and when applicable, including in certain health-related applications, data de-identification can be used to protect the privacy of users. De-identification can be facilitated by removing specific identifiers (e.g., date of birth, etc.), controlling the amount or specificity of stored data (e.g., collecting location data at the city level rather than at the address level), controlling how the data is stored (e.g., aggregating data between users), and / or other methods when appropriate.

[0058] Thus, while the present disclosure broadly covers the use of personal information data to implement one or more of the various disclosed embodiments, the present disclosure also contemplates that various embodiments may also be implemented without requiring access to such personal information data. That is, various embodiments of the present technology will not fail to function properly due to the lack of all or a portion of such personal information data. For example, content may be selected and delivered to a user by inferring preferences based on non-personal information data or an absolute minimum amount of personal information, such as content requested by a device associated with the user, other non-personal information available to a content delivery service, or publicly available information.

[0059] For the purpose of illustration, the foregoing description uses specific nomenclature to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that specific details are not required in order to practice the embodiments. Therefore, for the purpose of illustration and description, the foregoing description of the specific embodiments described herein is presented. They are not intended to be exhaustive or to limit the embodiments to the precise form disclosed. It will be apparent to those of ordinary skill in the art that, in view of the above teachings, many modifications and variations are feasible.

Claims

1. An oxide layer on a stainless steel substrate, the oxide layer comprising a layered double hydroxide; The oxide layer comprises an iron-rich precipitate deposited on the porous iron-nickel layer.

2. The oxide layer of claim 1, wherein the oxide layer comprises a surface roughness between about 500 nm and about 1000 nm Sz. 3 . The oxide layer of claim 1 , wherein the oxide layer comprises a thickness of about 100 nm to about 300 nm.

4. The oxide layer of claim 1, wherein the oxide layer comprises a porosity between about 30% and about 80%.

5. The oxide layer of claim 1, wherein the iron-rich precipitates comprise a microstructure comprising spherical structures having a diameter between about 20 nm and about 100 nm.

6. The oxide layer of claim 1, wherein the oxide layer comprises a first layer comprising an iron nickel hydroxide layer having a thickness between about 80 nm and about 150 nm; and The oxide layer also includes a second layer including an iron-rich oxide disposed on the first layer, the second layer including spherical structures having a diameter between about 20 nm and about 100 nm.

7. The oxide layer of claim 1, wherein the oxide layer further comprises a porous structure defining pores having a diameter between about 20 nm and about 50 nm.

8. A stainless steel-polymer interface, the stainless steel-polymer interface comprising: Oxide layer on stainless steel substrate; and a polymer extending into the oxide layer; wherein the polymer extending into the oxide layer forms a bond comprising a bond strength of about 25 MPa or greater.

9. The stainless steel-polymer interface of claim 8, wherein the oxide layer comprises a layered double hydroxide.

10. The stainless steel-polymer interface of claim 8, wherein the polymer comprises glass-filled PBT resin, polyamide, or epoxy resin.

11. The stainless steel-polymer interface of claim 8, wherein the oxide layer comprises a surface roughness greater than about 500 nm Sz.

12. The stainless steel-polymer interface of claim 8, wherein the oxide layer comprises iron-rich precipitates deposited on a porous iron-nickel layer.

13. The stainless steel-polymer interface of claim 8, wherein the polymer comprises an injection molded polymer.

14. The stainless steel-polymer interface of claim 8, wherein the polymer comprises a dynamic viscosity of about 800 Pa·s to about 200 Pa·s.

15. A method for forming an oxide layer on a stainless steel substrate, the method comprising: etching the stainless steel substrate by immersing the stainless steel substrate in a caustic solution; as well as A cathodic potential was applied between the stainless steel substrate and the anode.

16. The method of claim 15, wherein the caustic solution comprises a solution of between about 1 molar and about 10 molar sodium hydroxide or potassium hydroxide.

17. The method of claim 15, wherein the cathode potential comprises a pulsed potential comprising a voltage between about 2 V and about 5 V and a pulse rate between about 1 minute and about 4 minutes on and between about 1 minute and about 4 minutes off, the pulse being repeated between about 2 times and about 20 times.

18. The method of claim 15, wherein the caustic solution is between about 50°C and about 90°C.

19. The method of claim 15, wherein the ratio between the anode and the stainless steel substrate is between about 2:1 and about 10:

1.

20. The method of claim 15, wherein the oxide layer comprises a surface roughness between about 500 nm and about 1000 nm Sz.

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