PATENT DOCUMENT

Publication Number: US-11312107-B2
Application Number: US-201916256825-A
Country: US
Kind Code: B2

Title: Plugging anodic oxides for increased corrosion resistance

Abstract:
This application relates to an enclosure for a portable electronic device. The enclosure includes a metal substrate and a dehydrated anodized layer overlaying the metal substrate. The dehydrated anodized layer includes pores having openings that extend from an external surface of the dehydrated anodized layer and towards the metal substrate, and a metal oxide material that plugs the openings of the pores, where a concentration of the metal oxide material is between about 3 wt % to about 10 wt %.

Claims:
What is claimed is: 
     
       1. An enclosure for a portable electronic device, the enclosure comprising:
 a metal substrate; 
 a dehydrated a nodized layer overlaying the metal substrate, the dehydrated anodized layer comprising:
 an anodic oxidized portion having pores defined by openings that extend from an external surface of the anodic oxidized portion and toward the metal substrate; and 
 a dehydrated portion comprising a metal oxide material that plugs the openings of the pores and is between about 0.5 wt % to about 10 wt % of the dehydrated anodized layer; and 
 
 a hydrated moisture-impermeable barrier overlaying the dehydrated anodized layer. 
 
     
     
       2. The enclosure of  claim 1 , wherein the metal oxide material is between about 3 wt % to about 10 wt % of the dehydrated anodized layer. 
     
     
       3. The enclosure of  claim 1 , wherein the metal oxide material is bonded to pore walls that define the pores. 
     
     
       4. The enclosure of  claim 3 , wherein the dehydrated portion extends from the openings to bottom surfaces of the pores. 
     
     
       5. The enclosure of  claim 3 , wherein a concentration of metal oxide material decreases as a function of a distance from the external surface such that a region of the dehydrated anodized layer away from the external surface has a concentration of the metal oxide material that is less than a concentration of the metal oxide material at the external surface. 
     
     
       6. The enclosure of  claim 1 , wherein the pores further include dye particles disposed therein, and the dye particles impart the dehydrated anodized layer with an L* value of 40 or less as measured using a CIE L*a*b* color space when visible light is incident upon the external surface of the dehydrated anodized layer. 
     
     
       7. The enclosure of  claim 6 , wherein the dehydrated anodized layer has an external surface such as to minimize a light interference effect when the visible light is incident upon the external surface of the dehydrated anodized layer. 
     
     
       8. The enclosure of  claim 1 , wherein the metal substrate is an aluminum alloy and the metal oxide material is alumina (Al 2 O 3 ). 
     
     
       9. The enclosure of  claim 1 , wherein the diffusion and/or moisture-impermeable barrier has a thickness between about 10 nanometers to about 30 nanometers. 
     
     
       10. The enclosure of  claim 1 , wherein the dehydrated portion is formed by an at least partial dehydration of hydrated material formed on the external surface and within the pores of the anodic oxidized portion by an at least partial hydrothermal sealing of the anodic oxidized portion; and
 wherein the hydrated moisture-impermeable barrier is formed upon rehydration of at least a portion of the dehydrated portion. 
 
     
     
       11. The enclosure of  claim 10 , wherein the at least partial dehydration comprises applying at least one of heat and vacuum pressure to the at least partially sealed anodic oxidized portion. 
     
     
       12. The enclosure of  claim 10 , wherein the moisture-impermeable barrier prevents and/or minimizes the diffusion of external contaminants in order to prevent the dehydrated portion from being dissolved. 
     
     
       13. The enclosure of  claim 10 , wherein the moisture-impermeable barrier prevents the flow of corrosion-causing ions through the anodic oxidized portion. 
     
     
       14. The enclosure of  claim 10 , wherein the metal substrate is an aluminum alloy, the hydrated material is boehmite (AlOOH) or bayerite (Al(OH) 3 ), and the metal oxide material is alumina (Al 2 O 3 ). 
     
     
       15. The enclosure of  claim 10 , wherein, prior to the at least partial dehydration of hydrated material, the at least partially sealed anodic oxidized portion comprises about 25% to 45% by volume of boehmite or bayerite.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Application No. 62/737,687, entitled “PLUGGING ANODIC OXIDES FOR INCREASED CORROSION RESISTANCE,” filed Sep. 27, 2018, the content of which is incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD 
     The described embodiments relate generally to enclosures for portable electronic devices that include metal oxide layers. More particularly, the described embodiments relate to metal oxide layers having dehydrated plugs that impart these enclosures with increased corrosion resistance. 
     BACKGROUND 
     Enclosures for portable electronic devices can include an anodized layer that imparts these enclosures with an aesthetically pleasing appearance. Furthermore, pores of the anodized layer can be sealed such as to impart these enclosures with corrosion protection when these enclosures are exposed to external elements (e.g., moisture, salt, chemicals, debris, etc.). However, over time, these seals are susceptible to dissolving when the anodized layer is exposed to these external elements. Consequently, the metal substrate underlying the anodized layer may become corroded, thereby causing rust to form on these enclosures. Additionally, if these enclosures are dyed, the dissolution of these seals can cause an undesirable iridescent effect of the anodized layer. Accordingly, there is a need to plug anodized layers to prevent corrosion. 
     SUMMARY 
     This paper describes various embodiments that relate generally to enclosures for portable electronic devices that include metal oxide layers. More particularly, the described embodiments relate to metal oxide layers having dehydrated plugs that impart these enclosures with increased corrosion resistance. 
     According to some embodiments, an enclosure for a portable electronic device is described. The enclosure includes a metal substrate and a dehydrated anodized layer overlaying the metal substrate. The dehydrated anodized layer includes pores having openings that extend from an external surface of the dehydrated anodized layer and towards the metal substrate, and a metal oxide material that plugs the openings of the pores, where a concentration of the metal oxide material is between about 3 wt % to about 10 wt %. 
     According to some embodiments, an enclosure for a portable electronic device is described. The enclosure includes an aluminum alloy substrate and a dehydrated anodic layer that overlays the aluminum alloy substrate. The dehydrated anodic layer includes pores having openings, and a moisture-impermeable barrier that includes aluminum oxide, wherein the aluminum oxide plugs the openings of the pores. 
     According to some embodiments, a method for sealing an enclosure for a portable electronic device, the enclosure including a metal substrate and an anodized layer that overlays the metal substrate and includes openings that extend from an external surface of the anodized layer and towards the metal substrate, is described. The method includes sealing the openings of the anodized layer with hydrated material, and forming dehydrated material within pores of the anodized layer by dehydrating the hydrated material, where the dehydrated material plugs the openings of the pores. 
     This Summary is provided merely for purposes of summarizing some example embodiments so as to provide a basic understanding of some aspects of the subject matter described herein. Accordingly, it will be appreciated that the above-described features are merely examples and should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following Detailed Description, Figures, and Claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements. 
         FIG. 1  illustrates perspective views of various portable electronic devices having enclosures that may be processed using the techniques described herein, in accordance with some embodiments. 
         FIGS. 2A-2F  illustrate cross-sectional views of a process for plugging pores of a metal oxide layer, in accordance with some embodiments. 
         FIG. 3  illustrates a magnified cross-sectional view of a metal oxide layer having a plug, in accordance with some embodiments. 
         FIG. 4  illustrates a magnified cross-sectional view of a metal oxide layer having a plug, in accordance with some embodiments. 
         FIG. 5  illustrates a magnified cross-sectional view of a rehydrated metal oxide layer, in accordance with some embodiments. 
         FIGS. 6A-6C  illustrate cross-sectional views of a process for plugging pores of a metal oxide layer that includes dye particles disposed therein, in accordance with some embodiments. 
         FIG. 7A  illustrates a cross-sectional view of a conventional metal oxide layer that is susceptible to corrosion, thereby resulting in a light interference effect, in accordance with some embodiments. 
         FIG. 7B  illustrates a cross-sectional view of a metal oxide layer including a plug that prevents the light interference effect, in accordance with some embodiments. 
         FIG. 8  illustrates a method for forming plugs in a metal part, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Representative applications of methods and apparatus according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
     In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. 
     The embodiments described herein set forth techniques for enhanced sealing of anodized parts. In particular, the techniques described herein set forth techniques for preventing corrosion of metal oxide material of dyed anodized parts when exposed to external contaminants (e.g., oil, salt, debris, etc.), thereby fixing the color of the dyed anodized parts over prolonged usage when utilized as enclosures for portable electronic devices. Additionally, the techniques described herein set forth techniques for forming a rehydrated impermeable barrier that prevents flow of corrosion-causing ions from passing through the anodized layer. 
     One attempt at fixing the color of the dyed anodized parts involves sealing the dye particles within pores of the anodized layer. According to some examples, anodized layers of enclosures may be sealed by a hydrothermal sealing process where pores of the anodized layers become plugged by expansion of pore walls during the hydrothermal sealing process. While these enclosures may be dyed a wide spectrum of colors through organic dyeing of the anodized layers, these enclosures remain susceptible to discoloration due to natural ageing based on exposure to external contaminants. Indeed, although these enclosures having dyed particles may be sealed using a hydrothermal sealing process, the hydrothermal seals are susceptible to surface degradation and cosmetic deterioration—notably in conditions of periodic or continuous immersion in water environment (e.g., swimming in pools, surfing in the ocean, etc.). Indeed, even an objectively “good” hydrothermal seal (e.g., having a 1 kHz admittance value of less than 400 times the reciprocal of its thickness when measured within 48 hours after sealing) is susceptible to such surface degradation of its hydrothermal seals. Furthermore, the susceptibility of the hydrothermal seal to degradation is even more noticeable when the enclosures are dyed dark colors (e.g., black) as the outer surface of the enclosures dominates the visual appearance. 
     The embodiments described herein set forth techniques for forming enclosures for portable electronic devices having dehydrated material that plug the pore structures of the metal oxide layer. The plugs for the pore structures of the metal oxide layers as descried herein may be manufactured and shipped to consumers in an intentionally dehydrated state. Beneficially, by shipping these enclosures to consumers in the intentionally dehydrated state, the metal oxide layers of these enclosures demonstrate little to no loss in the dehydrated material that plugs the pore structures and protects the underlying metal substrate from external elements. Indeed, even enclosures that are shipped to consumers with a conventional hydrothermal seal are highly unlikely to encounter the appropriate circumstances which would lead to the formation of a dehydrated plug. For instance, the techniques described herein set forth applying a low vacuum pressure of 3×10 3  to 1×10 −1  Pa for at least 1-2 hours in order to dehydrate the material that makes up the hydrothermal seal. 
     According to some embodiments, an enclosure for a portable electronic device is described. The enclosure includes a metal substrate and a dehydrated anodized layer overlaying the metal substrate. The dehydrated anodized layer includes pores having openings that extend from an external surface of the dehydrated anodized layer and towards the metal substrate, and a metal oxide material that plugs the openings of the pores, where a concentration of the metal oxide material is between about 3 wt % to about 10 wt %. 
     As used herein, the terms anodic film, anodized film, anodic layer, anodized layer, anodic oxide coating, anodic layer, anodic oxidized layer, metal oxide layer, oxide film, oxidized layer, and oxide layer can be used interchangeably and refer to any appropriate oxide layers. The oxide layers are formed on metal surfaces of a metal substrate. The metal substrate can include any of a number of suitable metals or metal alloys. In some embodiments, the metal substrate can include aluminum, and the aluminum is capable of forming an aluminum oxide when oxidized. In some embodiments, the metal substrate can include an aluminum alloy. As used herein, the terms part, layer, segment, and section can also be used interchangeably where appropriate. Additionally, the term “plug” is structurally and functionally distinct from the term “seal.” In particular, the term “plug” may refer to a physical obstruction of an extremity of pore structures by plugging openings of the pore structures. 
     These and other embodiments are discussed below with reference to  FIGS. 1, 2A-2F, 3-5, 6A-6C, 7A-7B, and 8 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
       FIG. 1  illustrates various portable electronic devices that can be processed using the techniques as described herein. The techniques as described herein can be used to process metallic surfaces (e.g., metal oxide layers, etc.) of enclosures of the portable electronic devices.  FIG. 1  illustrates a smartphone  102 , a tablet computer  104 , a smartwatch  106 , and a portable computer  108 . It is well understood that the use of personally identifiable information that is capable of being transmitted, received, and/or managed by these portable electronic devices should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users. 
     According to some embodiments, the metallic surfaces can refer to a metal oxide layer that overlays a metal substrate. In some examples, the metal oxide layer is formed from the metal substrate during an anodization process. The metal oxide layer can function as a protective coating to protect the metal substrate, for example, when these portable devices are dropped, scratched, chipped, or abraded. Additionally, the metal oxide layer can include pore structures that may be plugged such as to external contaminants from reaching the metal substrate. 
     In some examples, such as where the metal substrate includes aluminum or an aluminum alloy, the metal oxide layer can be formed over the metal substrate and can include pore structures (or pores) that are formed through the metal oxide layer and can extend from an external surface of the metal oxide layer and towards a barrier layer that separates the metal oxide layer from the underlying metal substrate. Additionally, according to some embodiments, each of the pore structures of the metal oxide layer can be capable of receiving dye particles which can imbue the metal oxide layer with a specific color associated with the dye particles. In some examples, the metal oxide layer can be imparted with different dye colors based on the dye particles that are deposited within the pore structures. In some examples, the color of the metal oxide layer can be characterized according to L*a*b* color-opponent dimension values. The L* color opponent dimension value is one variable in an L*a*b* color space. In general, L* corresponds to an amount of lightness. L*=0 represents the darkest black while L*=100 represents white. 
       FIGS. 2A-2F  illustrate cross-sectional views of a metal part  200  undergoing various processes for forming a plug therein for increased corrosion resistance, in accordance with some embodiments. In some embodiments, the metal part  200  has a near net shape of a final part, such as the enclosures of the portable electronic devices  102 ,  104 ,  106 , and  108 . 
       FIG. 2A  illustrates the metal part  200  prior to undergoing an anodization process. In particular,  FIG. 2A  illustrates that the metal part  200  corresponds to a metal substrate  204 . The metal substrate  204  may have any thickness that is suitable for providing sufficient hardness and rigidity to protect electronic component(s) that are carried within the portable electronic device. 
     The metal substrate  204  may be subject to one or more pre-anodization processes. In some examples, the pre-anodization processes of the metal substrate  204  include at least one of polishing, texturizing, buffering, and the like. Beneficially, in this manner, surface(s) of the metal substrate  204  may assume any number of desired surface geometries and surface finishes. In some examples, the metal substrate  204  is a three-dimensional structure having a height, width, and depth, and the metal substrate  204  can have any type of geometry that is suitable for forming an overlaying metal oxide layer, as will be described herein. In particular, the geometry of the metal substrate  204  may be characterized as rectangular, polygonal, circular, beveled edges, angular edges, elliptical, etc. 
       FIG. 2B  illustrates an anodized part  210 , in accordance with some embodiments. For example,  FIG. 2B  illustrates the metal part  200  subsequent to undergoing the anodization process. As illustrated in  FIG. 2B , the metal oxide layer  206  may be formed from the metal substrate  204 . The metal oxide layer  206  may include an external surface  202 , where the external surface  202  of the metal oxide layer  206  is generally parallel to a bottom surface  208  of the metal substrate  204 . In some examples, the metal oxide layer  206  is formed as a result of an electrolytic anodizing process. In particular, during the electrolytic anodizing process, a portion of the metal substrate  204  is converted or consumed by the conversion to the metal oxide layer  206 . 
     According to some examples, the metal oxide layer  206  has a thickness between about 1 micrometer to several tens of micrometers. In some examples, the thickness is between about 5 micrometers to about 15 micrometers. 
     According to some embodiments, the metal oxide layer  206  includes pore structures  212  that extend from the external surface  202  of the anodized part  210  towards the metal substrate  204 . The pore structures  212  may include bottom surfaces  214 . The pore structures  212  are defined by pore walls  216  characterized as having generally columnar shapes that are elongated in a direction generally perpendicular to a central plane of the external surface  202  of the anodized part  210 . The pore structures  212  include openings  218  that may be sealed with hydrated material, and then subsequently plugged with dehydrated material, as described in greater detail herein. 
     According to some examples, the metal substrate  204  may be comprised of aluminum or an aluminum alloy. As a result, the metal oxide layer  206  formed from the metal substrate  204  may be comprised of aluminum oxide. Additionally, the metal substrate  204  can include alloying elements (e.g., copper, zirconium, magnesium, etc.) that may impart increased adhesion between the metal oxide layer and the metal substrate  204 , as described in application Ser. No. 14/830,699 entitled “PROCESSES TO AVOID ANODIC OXIDE DELAMINATION OF ANODIZED HIGH STRENGTH ALUMINUM ALLOYS, which is being incorporated by reference in its entirety for all purposes. 
       FIG. 2C  illustrates a partially-sealed part  220 , in accordance with some embodiments. In some examples, the partially-sealed part  220  represents the anodized part  210  while undergoing a hydrothermal sealing process. During the hydrothermal sealing process, the anodized part  210  is exposed to a sealing solution so as to cause precipitation of hydrated aluminum oxide (e.g., boehmite, etc.). In particular, the hydrothermal sealing process causes swelling of the aluminum oxide of the metal oxide layer  206  while immersed in the sealing solution. Swelling of the aluminum oxide causes the openings  218  to narrow, thereby minimizing external elements from diffusing into the pore structures  212 . Swelling of the openings  218  may also cause oxidized fragments or metal oxide material to be retained within the metal oxide layer  206 . For instance, dye oxide particles may be retained within the pore structures  212 . During the hydrothermal sealing process, the alumina (of aluminum oxide) is converted to a hydrated material  222 , such as aluminum oxide hydroxides (e.g., boehmite, diaspore, etc.) that results in swelling or volume increase of the oxide particles to partially close or partially seal the openings  218  of the pore structures  212 . In some examples, the hydrated material  222  uniformly lines the pore walls  216  of the pore structures  212 . The hydrated material  222  may refer to generally insoluble hydroxide material. 
     In some examples, the hydrothermal sealing solution involves filling in the pore structures  212  by hydrating the amorphous aluminum material of the pore walls  216  to a gel of boehmite and/or bayerite such that the amorphous aluminum material swells and closes the openings  218  of the pore structures  212 . In some examples, the hydrothermal sealing process may be performed in steam, hot water (e.g., at or near boiling temperature with additives to reduce smutting), or at a temperature as low as about 70° C. In some examples, the hydrothermal sealing may be enhanced by using nickel acetate which additional precipitates the metal hydroxides in the pore structures  212 . In some examples, the hydrothermal sealing solution is hot aqueous solution (e.g., greater than 80° C.). In some examples, the metal oxide layer  206  is exposed to a 5 g/l solution of nickel acetate at a temperature of 97° C. for a duration of 25 minutes. 
       FIG. 2D  illustrates a hydrothermally sealed part  230 , in accordance with some embodiments. In some examples, the hydrothermally sealed part  230  represents the anodized part  210  subsequent to completion of the hydrothermal sealing process. In contrast to the partially-sealed part  220 , the openings  218  of the pore structures  212  of the hydrothermally sealed part  230  are sealed such as to prevent external contaminants from diffusing through the pore structures  212  to reach the metal substrate  204 . In some examples, the pore structures  212  include hydrated material  222  (e.g., aluminum oxide hydroxides, etc.) that seals the openings  218 . In particular, the aluminum oxide hydroxides include boehmite, bayerite, diaspore, and the like. In some examples, the aluminum oxide hydroxides has a greater volume than the aluminum oxide. The hydrated material  222  is a structural seal that seals in the openings  218  of the pore structures  212 . According to some embodiments, the hydrothermally sealed part  230  includes uniform levels of hydrated material  222  along the pore walls  216  of the pore structures  212 . In some examples, the hydrated material  222  forms the seal that generally corresponds to the external surface  202  of the anodized part  210 . 
     According to some examples, the hydrothermally sealed part  230  prevents external contaminants (e.g., oils, dirt, etc.) from being absorbed into the pore structures  212 . One example of measuring the quality of the seals of the hydrated material  222  is to perform a dye spot test where the inability of a sealed surface to absorb dye particles is measured. Other tests of seal quality include the quantitative measures of electrochemical impedance spectroscopy (EIS), a simplified variant of EIS performed at a fixed frequency (typically 1 kHz) called “admittance” testing, and acid dissolution testing (ADT). 
     According to some examples, the hydrothermally sealed part  230  includes between about 8%-12% mass that may be attributed to water, such as a hydrate within boehmite (γ-AlOOH) or bayerite (α-Al(OH)3) or (β-Al(OH)3). In some examples, about 25% of a volume of the metal oxide layer  206  of the hydrothermally sealed part  230  includes a hydrate of bayerite or up to about 45% of a volume of the metal oxide layer  206  of the hydrothermally sealed part  230  includes a hydrate of boehmite. In some examples, the metal oxide layer  206  includes between about 25% to about 45% volume of a hydrate of bayerite or boehmite. 
       FIG. 2E  illustrates a dehydrated part  240 , in accordance with some embodiments. In some examples, the dehydrated part  240  is formed subsequent to exposing the hydrothermally sealed part  230  to a dehydration process. In some examples, the dehydration process includes exposing the hydrothermally sealed part  230  or the partially-sealed part  220  to at least one of heat or by desiccation (e.g., vacuum pressure). As illustrated in  FIG. 2E , the dehydrated part  240  may include dehydrated material  232 , such as γ-alumina (Al 2 O 3 ) that is formed from dehydrating the hydrated material  222 , such as boehmite (γ-AlOOH). The dehydrated material  232  may comprise a plug that plugs the openings  218  of the pore structures  212 . As described herein, the term “plug” may refer to a physical obstruction of the extremity of the pore structures  212 . Although  FIG. 2E  illustrates that the dehydrated part  240  includes dehydrated material  232  that extends throughout the entire length of the pore structures  212 , in other examples, the dehydrated material  232  may only extend partially through the entire length of the pore structures (i.e., not the entire length). In particular, during the dehydration process, the hydrated material  222  (e.g., aluminum oxide hydroxides) that is closer to the external surface  202  may be preferentially dehydrated relative to hydrated material  222  that is closer to the bottom surface  214  of the pore structures  212 . In other words, when subjecting the hydrothermally sealed part  230  to the dehydration process, the hydrated material  222  (e.g., aluminum oxide hydroxide) that is present near the external surface  202  is more likely to be converted to dehydrated material  232 , such as aluminum oxide (Al 2 O 3 ). Therefore, the concentration of dehydrated material  232  included within the pore structures  212  may taper off towards the bottom surfaces  214  of the pore structures  212 . It should be noted that the pore structures  212  may share a combination of an amount of hydrated material  222  and an amount of dehydrated material  232 . 
     In some examples, the dehydrated material  232  is a metal oxide material, such as γ-alumina (Al 2 O 3 ) is characterized as having a fine, lamellar, porous microstructure. In particular, the porous microstructure is consistent with the loss of oxygen atoms  234  from the boehmite lattice. In some examples, the loss of oxygen atoms contributes to a difference in mass between the hydrothermally sealed part  230  and the dehydrated part  240  that is about 5% or less (in some instances 2% or less). In some examples, heating the hydrothermally sealed part  230  drives off about 5+/−2 wt % of water. In some examples, exposing the hydrothermally sealed part to vacuum pressure drives off up to 12 wt % of water. In other words, dehydrating (e.g., heating, vacuum pressure, etc.) the hydrated material  222  of the sealant of the metal oxide layer  206  contributes to a loss of about half of the water content (e.g., hydrate) of the metal oxide layer  206  from the hydrothermal sealing process. In some examples, a concentration of the dehydrated material  232  (e.g., dehydrated boehmite, dehydrated bayerite, etc.) is between about 3 wt % to about 10 wt %. In some examples, a concentration of the dehydrated material  232  is between about 0.5 wt % to about 10 wt %. Moreover, this loss in mass is not recovered, even if the dehydrated part  240  is exposed to a 60% humidity environment for a period of one week. In particular, the dehydrated part  240  would experience a maximum of 1% to 2% loss of water under further heat exposure (e.g., 85° C. at 2 hours) or vacuum pressure. In contrast, conventionally sealed anodic oxide layers when exposed to a dehydration process exhibit a corresponding loss in mass of about 15%. 
     In some embodiments, the loss of moisture is reflected in a difference in mass between the dehydrated part  240  and the hydrothermally sealed part  230 . More particularly, the dehydrated material  232  has a lower physical density than the hydrated material  222 . In some examples, the lower physical density of the dehydrated material  232  may be measured and quantified using a Fourier-Transform Infra-Red Spectroscopy (FTIR) which provides a signal upon the detection of an —OH bond. Indeed, the level of hydration of the hydrated material  222  may be proportionate to the stronger signal for the —OH bond. 
     In some embodiments, the dehydrated material  232  may also differ from the hydrated material  222  in terms of their respective ionic conductivity. In particular, there are fewer mobile ionic species present in the dehydrated material  232  relative to the hydrated material  222 . The difference in mobile ionic species may be quantified using a 1 kHz electrochemical admittance test. In some examples, ionic conductivity was tested for samples of the dehydrated part  240  and the hydrothermally sealed part  230 . All of the samples included a 12 μm thick metal oxide layer. Using the 1 kHz electrochemical admittance test, the plug comprised of the dehydrated material  232  exhibited an admittance of ˜8-12 microSiemens, whereas the hydrated material  222  exhibited an admittance of ˜18-23 microSiemens. 
     It should be noted that despite converting the hydrated material  222  to dehydrated material  232 , the external surface  202  of the dehydrated part  240  may remain smooth. Like the hydrated material  222  of the hydrothermally sealed part  230 , the dehydrated material  232  also provides a reliable barrier to prevent solids and/or liquids from penetrating into the metal substrate  204 . Additionally, the pore structures  212  of the dehydrated part  240  remain plugged subsequent to the dehydration process as the dehydrated material  232  plugs the openings  218  of the pore structures  212 . The dehydrated material  232  corresponds to a plug that physically obstructs the openings  218  of the pore structures  212 . 
     Beneficially, intentionally dehydrating the seal of the hydrothermally sealed part  230  may preemptively prevent external contaminants from dissolving the hydroxide (—OH) of the aluminum oxide hydroxide during the normal use of the portable electronic device. When exposed to external contaminants, the external contaminants may consume the hydrated material  222 , thereby reducing a height of the hydrated material  222  relative to a height of the external surface  202  of the pore walls  216 . Consequently, the reduction in the amount of hydrated material  222  present within the pore structures  212  may facilitate the external contaminants to more easily and quickly reach the metal substrate  204 , thereby causing corrosion. Furthermore, a reduction of the height of the hydrated material  222  relative to a height of the external surface  202  of the pore walls  216  may lead to an interference effect, as will be described in greater detail with reference to  FIGS. 7A-7B . Thus, by preemptively dehydrating the seal of hydrated material  222 , there is little to no hydroxide (—OH) that is available to be consumed during the dissolution process. Furthermore, it should be noted that the pore structures  212  remain sealed with the dehydrated material  232 , as illustrated in  FIG. 2E . 
       FIG. 2F  illustrates a rehydrated part  250 , in accordance with some embodiments. In some examples, the rehydrated part  250  corresponds to the dehydrated part  240  undergoing a rehydration process. In particular, the rehydration process may involve introducing water or moisture to at least some of the dehydrated material  232  that plugs the pore structures  212  of the dehydrated part  240 . For instance, if the dehydrated part  240  corresponds to a metallic surface of the smart watch  106  that is exposed to salt water in the ocean during a user&#39;s surfing session, the dehydrated material  232  becomes hydrated. As a result, the dehydrated material  232  is converted to rehydrated material  252 . It should be noted that the rehydrated material  252  still corresponds to a plug that plugs the openings  218  of the pore structures  212  despite the conversion of the dehydrated material  232  to rehydrated material  252 . Indeed, the external surface  202  of the dehydrated part  240  is most susceptible to becoming exposed to moisture. As a result, the dehydrated material  232  closer to the openings  218  of the pore structures  212  and/or the external surface  202  is more preferentially rehydrated than other dehydrated material  232  disposed deeper in the pore structures  212 . The rehydrated material  252  may include hydroxide material. 
     As illustrated in  FIG. 2F , the rehydrated material  252  forms a rehydrated impermeable barrier  254 . In some examples, the rehydrated impermeable barrier  254  is comprised of rehydrated material  252  that extends from the openings  218  and partially along a length of the pore structures  212 . In particular, once the rehydrated impermeable barrier  254  is formed, the rehydrated impermeable barrier  254  acts as a diffusion barrier and/or moisture-impermeable barrier that plugs the openings  218  of the pore structures  212  and prevents moisture from passing through the pore structures  212  to reach underlying dehydrated material  232 . As a result, the rehydrated material  252  does not extend along the entire length of the pore structures  212 . In other words, below the rehydrated impermeable barrier  254  is dehydrated material  232  that lines the pore walls  216  of the pore structures  212 . 
     The rehydrated impermeable barrier  254  may have a thickness that is between about 10 nanometers to about 30 nanometers. In some examples, the rehydrated impermeable barrier  254  plugs the openings  218  of the pore structures  212  and extends only partially along the length of the pore structures  212 . The remaining volume of the pore structures  212  is occupied by the dehydrated material  232 . The dehydrated material  232  (e.g., γ-Al 2 O 3 , etc.) may be characterized as having a fine, lamellar, porous microstructure. In particular, the porous microstructure is consistent with the loss of oxygen atoms  234  from the boehmite lattice. 
     It should be noted that the structure of the rehydrated part  250  is distinguished from the hydrothermally sealed part  230 . In particular, the formation of the rehydrated impermeable barrier  254  makes it more difficult to hydrate the pore walls  216  of the pore structures  212 . In other words, upon formation of the rehydrated impermeable barrier  254 , no additional dehydrated material  232  that is disposed below the rehydrated impermeable barrier  254  will be rehydrated. Beneficially, the rehydrated impermeable barrier  254  may also prevent the dehydrated material  232  that is disposed below the rehydrated impermeable barrier  254  from being dissolved by external contaminants. For instance, the rehydrated impermeable barrier  254  can prevent and/or minimize the diffusion of external contaminants past the rehydrated impermeable barrier  254 . 
     As understood by one of ordinary skill in the art, exposure of the dehydrated part  240  to the same sealing parameters used for forming the hydrothermally sealed part  230  will not result in the formation of a microstructure that is equivalent to the hydrothermally sealed part  230 . Indeed, when the dehydrated part  240  is subject to a forced additional dehydration process, the dehydrated part  240  exhibits little to no loss in mass (i.e., ≤5%) due to moisture loss. In particular, the dehydrated material  232  of the dehydrated part  240  has an inability to lose additional mass during an additional dehydration process relative to the hydrothermally sealed part  230 . In some examples, the dehydrated material  232  of the dehydrated part  240  will lose no more than ˜1%-2% mass when subject to the additional dehydration process (e.g., 100° C. for ˜30 minutes), whereas the hydrated material  222  of the hydrothermally sealed part  230  will lose ˜5% mass when subject to the additional dehydration process (e.g., 100° C. for ˜30 minutes). 
       FIG. 3  illustrates a magnified cross-sectional view of a dehydrated part  300 , in accordance with some embodiments. In some examples,  FIG. 3  illustrates the dehydrated part  300  includes a metal oxide layer  206  having pore structures  212  that extend from the external surface  202  and towards the metal substrate  204 . In some embodiments, the metal oxide layer  206  is separated from the metal substrate  204  by a non-porous barrier layer. 
       FIG. 3  illustrates dehydrated material  232  that is dispersed within the pore structures  212  of the dehydrated part  300 . As described herein, during the hydrothermal sealing process, the dehydrated material  232  plugs openings  218  of the pore structures  212 . In some examples, the dehydrated material  232  may uniformly line the pore walls  216  of the pore structures  212 . For example, during the dehydration process, boehmite (γ-AlOOH) is dehydrated to form γ-alumina (Al 2 O 3 ). In some examples, the dehydrated material  232  (e.g., γ-Al 2 O 3 , etc.) may be characterized as having a fine, lamellar, porous microstructure. In particular, the porous microstructure is consistent with the loss of oxygen atoms  304  from the boehmite lattice, as illustrated in  FIG. 3 . Although the loss of oxygen atoms  304  is consistent with a loss in mass of the metal oxide layer  206  (e.g., ≤5%), the structure of hydrated material  222  remains in the form of dehydrated material  232  which may act as a generally impermeable barrier. The generally impermeable barrier acts as a greater barrier to the flow of ions than conventional seals, as will be described in greater detail herein. 
       FIG. 3  illustrates that the dehydrated boehmite, γ-alumina, plugs the pore structures  212  and may extend from the openings  218  of the pore structures  212  and towards the metal substrate  204 . In some examples, during the dehydration process, the hydrothermally sealed part  230  is exposed to at least one of heat or desiccation. In particular, during the dehydration process, the external surface  202  relative to other portions (e.g., sides, metal substrate, etc.) of the hydrothermally sealed part  230  may be exposed to the heat and/or desiccation such as to cause the hydrated material (e.g., boehmite, etc.) that is disposed closer to the openings  218  to be preferentially dehydrated. As a result, the hydrated material  222  closer to the openings  218  is preferentially dehydrated to form the dehydrated material  232  that plugs the openings  218 . 
     In some embodiments, the hydrothermally sealed part  230  may be exposed to heat at a time duration between 1-2 hours at a temperature that is between 65° C. and 85° C. in order to dehydrate the hydroxide sealing material. It should be noted that if the hydrothermally sealed part  230  is heated at a temperature greater than 85° C. then the metal oxide layer  206  may be susceptible to cracking, which may be undesirable in that it may negatively affect the structural rigidity and integrity of the metal oxide layer  206 . Furthermore, it should be noted that heating the hydrothermally sealed part  230  to a temperature of 150° C. or greater may result in aging the metal substrate  204 , which may soften the metal substrate  204 . Therefore, great control should be exercised to control the amount of time and the temperature of which the hydrothermally sealed part  230  is exposed to. In some embodiments, the upper temperature limit may be extended to higher than 85° C. when dehydrating a partially sealed part—e.g., the partially sealed part  400 —as described in detail with reference to  FIG. 4 . Additionally, in some embodiments, the upper temperature limit may be extended to higher than 85° C. when the metal oxide layer  206  is sealed using a process such as zirconia or silicate capping layer, as described by U.S. patent application Ser. No. 15/686,026 entitled “PROTECTING ANODIZED SURFACES DURING MANUFACTURING PROCESSES,” which is being incorporated herein by reference in its entirety for all purposes. 
     In some embodiments, the hydrothermally sealed part  230  may be exposed to vacuum pressure in order to dehydrate the hydrated material  222 . In some examples, the hydrothermally sealed part  230  is exposed to the vacuum pressure at a time range between 30 minutes to 2 hours. In some instances, up to 50% of the moisture included within the hydrated material  222  present in the pore structures  212  is driven off within 30 minutes of applying vacuum pressure to the hydrothermally sealed part  230 . In some examples, the range of vacuum pressure is between about 3×10 3  Pa to about 1×10 −1  Pa. In some examples, the vacuum pressure is applied for a period of at least 1-2 hours, and up to at least 12 hours. 
     In some examples, the longer that the hydrothermally sealed part  230  is exposed to at least one of the heat or vacuum pressure during the dehydration process, the more extensive is the conversion of the hydrated material  222  to dehydrated material  232 . For instance, the extensive conversion of the hydrated material  222  to dehydrated material  232  where the thickness of the dehydrated material  232  is X≥N 1  is indicative of the hydrothermally sealed part  230  being exposed to more than a superficial amount of heat and/or vacuum pressure. For example, if the hydrothermally sealed part  230  is exposed to heat at less than 65° C. for less than 10 minutes may be insufficient to dehydrate the hydrated material  222  to the extent necessary to form the dehydrated material  232  having a thickness that is X≥N 1 . It should be noted that N 1  corresponds to an amount of thickness of the dehydrated material  232  that is sufficient to prevent the aluminum oxide from being dissolved when the hydrothermally sealed part  230  is exposed to external elements (e.g., moisture, salt, debris, etc.). If the amount of thickness of the dehydrated material  232  is less than N 1 , then the hydroxide group (—OH) that makes up the aluminum oxide is susceptible to being consumed. Consequently, the hydrothermally sealed part  230  may be susceptible to corrosion attack. 
     Beneficially, the dehydrated part  300  may exhibit up to a 50% improvement in impedance over conventional hydrothermally sealed anodized parts. Thus, the dehydrated part  300  exhibits resistance to corrosion attack that is common among conventional hydrothermally sealed anodized parts. For instance, the dehydrated part  300  is able to greatly resist corrosion attack to the extent that corrosion defects which would have been observed within 1 year in a conventional hydrothermally sealed anodized part would take about five years to be observed in the dehydrated part  300 . 
     To illustrate this concept,  FIG. 3  illustrates the dehydrated part  300  having dehydrated material  232  that extends throughout the length of the pore structures  212  such that the bottoms  214  of the pore structures  212  also include the dehydrated material.  FIG. 3  illustrates that the thickness of the dehydrated material  232  (as measured from the external surface  202 ) within the pore structures  212  is X=N 2 . It should be noted that the volume of the dehydrated material  232  that generally fills and plugs in the pore structures  212  of the dehydrated part  400  may be the same or generally equivalent to the volume of the hydrated material  222  that generally fills and seals in the pore structures  212  of the hydrothermally sealed metal part  230 . In this manner, the hydrothermally sealed metal part  230  may also be referred to as a fully dehydrated part. 
       FIG. 4  illustrates a magnified cross-sectional view of a partially dehydrated part  400  subsequent to the completion of the dehydration process, in accordance with some embodiments. In particular, the dehydration process may be stopped and the partially dehydrated part  400  intentionally released from the dehydration environment and dehydration process before generally all of the hydrated material  222  is converted to dehydrated material  232 . The partially dehydrated part  400  may be released from the dehydration environment so long as the thickness of the dehydrated material  232  as measured from the external surface  202  is X≥N 1 , which is sufficient for the partially dehydrated part  400  to resist corrosion attack from external elements. In some examples, the partially dehydrated part  400  includes dehydrated material  232  that only partially extends throughout the length of the pore structures  212 . In some examples, the amount of the dehydrated material  232  may be more heavily concentrated towards the openings  218  of the pore structures  212  and less concentrated towards the bottom surfaces  214  of the pore structures  212 . As illustrated in  FIG. 4 , the bottom surfaces  214  of the pore structures  212  may include a combination of dehydrated material  232  and hydrated material  222 . Unlike the dehydrated part  300 , the partially dehydrated part  400  does not include generally uniform dispersion of the loss of oxygen atoms  404  from the boehmite lattice. 
     As illustrated in  FIG. 4 , the thickness of the dehydrated material  232  is X≥N 1 , which is sufficient for the dehydrated part  4  to resist corrosion attack from external elements. In some examples, the thickness of the dehydrated material is between about 10 nm to about 30 nm. In other examples, the thickness of the dehydrated material is between about 10 nm to about 50 nm. 
       FIG. 4  illustrates dehydrated material  232  (e.g., aluminum oxide, etc.) that is dispersed within the pore structures  212 . As described herein, during the hydrothermal sealing process, the dehydrated material  232  plugs the openings  218  of the pore structures  212 . In some examples, the dehydrated material  232  partially lines the pore walls  216  of the pore structures  212 . In some examples, the boehmite (γ-AlOOH) is dehydrated to form γ-alumina (Al 2 O 3 ). In some examples, the dehydrated material  232  (e.g., γ-Al 2 O 3 , etc.) may be characterized as having a fine, lamellar, porous microstructure. In particular, the porous microstructure is consistent with the loss of oxygen atoms  404  from the boehmite lattice, as illustrated in  FIG. 4 . In contrast to the dehydrated part  300 , the thickness of the dehydrated material  232  of the partially-dehydrated part  400  extends to a thickness of X=N 3 , where N 3 &lt;N 2 . 
       FIG. 5  illustrates a magnified cross-sectional view of a rehydrated part  500  that corresponds to the rehydrated part  250  as illustrated in  FIG. 2F , in accordance with some embodiments. As illustrated in  FIG. 5 , the rehydrated part  500  includes a rehydrated impermeable barrier  502  formed from the rehydrated material  252 . The rehydrated material  252  includes rehydrated hydroxide particles  252 . The rehydrated impermeable barrier  502  has a thickness that is X≥N 1 , which is to mean that the rehydrated impermeable barrier  502  is sufficient to prevent the dehydrated material  508  disposed below the rehydrated impermeable barrier  502  from being dissolved when exposed to external contaminants. The rehydrated impermeable barrier  502  may have a thickness that is between about 10 nanometers to about 30 nanometers. In some examples, the rehydrated impermeable barrier  254  extends only partially along the length of the pore structures  212 . In some examples, the dehydrated material  232  (e.g., γ-Al 2 O 3 , etc.) may be characterized as having a fine, lamellar, porous microstructure. In particular, the porous microstructure is consistent with the loss of oxygen atoms  506  from the boehmite lattice. In some examples, the rehydrated impermeable barrier  502  is comprised of rehydrated material  504  that extends only partially along a length of the pore structures  212  from the openings  218  of the pore structures  212 . In some embodiments, the rehydrated material  504  plugs the openings  218  of the pore structures  212 . 
     In some examples, the rehydrated impermeable barrier  502  may be more resilient than the hydrated material  222  in resisting corrosion when exposed to external contaminants. This may be because the rehydrated impermeable barrier  254  starts from the external surface  202  and plugs the outer region, thereby inhibiting further, deeper rehydration of the dehydrated material  232 . In effect, the rehydration process is almost irreversible. Moreover, the rehydrated impermeable barrier  502  provides a greater barrier than the hydrated material  222  in preventing the flow of ions through the metal oxide layer  206 . Rather, the conventional hydrothermally sealed anodized parts have a hydrated gel-like state where the water provides a medium for ion flow. 
       FIGS. 6A-6C  illustrate cross-sectional views of a dyed part  600  undergoing various processes for forming an enhanced seal for increased corrosion resistance, in accordance with some embodiments. In some embodiments, the dyed part  600  has a near net shape of a final part, such as the enclosures of the portable electronic devices  102 ,  104 ,  106 , and  108 . In some examples, the resulting dyed part  600  may correspond to any one of the metallic surfaces of the portable electronic devices  102 ,  104 ,  106 , and  108 . 
       FIG. 6A  illustrates the dyed part  600  while undergoing a hydrothermal sealing process, in accordance with some embodiments.  FIG. 6A  illustrates that the dyed part  600  includes dye particles  602  that are disposed within the pore structures  212 . During the hydrothermal sealing process, hydrated material  222  acts to seal the openings  218  of the pore structures  212 , thereby sealing the dye particles  602  within the pore structures  212 . In some examples, the hydrated material  222  uniformly lines the pore walls  216  of the pore structures  212 . 
     According to some examples, the dyed part  600  may be dyed a wide spectrum of colors through organic dyeing of the metal oxide layer  206 . In some examples, the colors may be tuned by adjusting the parameters of the composition of the dye bath, such as concentration of the dye particles  602 , pH level, time, and/or temperature of the dye bath. However, by maintaining a constant bath composition, the pH level, time, and/or temperature may be adjusted in order to fine-tune the dyed color to within DE of &lt;1 of any given color target. 
       FIG. 6B  illustrates a sealed dyed part  610  subsequent to the dyed part  600  being exposed to the hydrothermal sealing process, in accordance with some embodiments. As shown in  FIG. 6B , the hydrated material  222  fills in the pore structures  212 , thereby also sealing the dye particles  602  within the pore structures  212 . As the metal oxide layer  206  is highly porous, the pore structures  212  should be sealed such as to permanently lock in the dyed color of the dyed part  600 . In some examples, this is particularly true of sulfuric acid anodizing performed in accordance with Type II anodizing of Mil A 8625. Indeed, this type of anodic oxide coatings are mesoporous (i.e., ˜10 11  pores per square centimeter, ˜20 nm diameter of good wettability and very high aspect ratio). 
       FIG. 6C  illustrates a dehydrated dyed part  620  formed by exposing the sealed dyed part  610  to a dehydration process, in accordance with some embodiments. In some examples, the dehydration process includes exposing the sealed dyed part  610  to at least one of heat or vacuum pressure. The dehydrated dyed part  620  includes dehydrated material  232 , such as γ-alumina (Al 2 O 3 ) that is formed from dehydrating boehmite (γ-AlOOH). The dehydrated material  232  plugs the openings  218  of the pore structures  212  such as to prevent external contaminants from reaching the metal substrate  204 . Although  FIG. 6C  illustrates that the dehydrated dyed part  620  includes dehydrated material  232  that extends through the entire length of the pore structures  212 , in other examples, the dehydrated material  232  may only extend partially through the entire length of the pore structures (i.e., not the entire length). 
     In some embodiments, during the dehydration process, the hydrated material  222  (e.g., aluminum oxide hydroxides) that is closer to the external surface  202  may be preferentially dehydrated relative to hydrated material  222  that is closer to the bottom surface  214  of the pore structures  212 . In other words, when subjecting the hydrothermally sealed part  230  to the dehydration process, the aluminum oxide hydroxide that is present near the external surface  202  is more likely to be converted to aluminum oxide (Al 2 O 3 ). Therefore, the concentration of dehydrated material  232  included within the pore structures  212  may taper off towards the bottom surfaces  214  of the pore structures  212 . 
     According to some embodiments, the pore structures  212  of the dehydrated dyed part  620  may include any combination of dye particles  602 , hydrated material  222 , or dehydrated material  232 . According to some examples, the dye particles  602  can include grey or black dye particles. The dye particles  602  may be distributed within the pore structures  212 . In some examples, the dye particles  602  are uniformly distributed in the pore structures  212 . By uniformly distributing the dye particles  602 , the metal oxide layer  206  is imparted with a uniform deep grey or black color. 
     In some examples, the color of the metal oxide layer  206  can be characterized according to L*a*b* color-opponent dimension values. The L* color opponent dimension value is one variable in an L*a*b* color space. In general, L* corresponds to an amount of lightness. L*=0 represents the darkest black while L*=100 represents white. By implementing dark dyed particles, such as black, the L* value of the metal oxide layer is less than L*=40, Consequently, when the hydrated material  222  is dissolved by external contaminants, there is a more noticeable light iridescence effect due to the difference in color between the exterior surface  202  of the metal oxide layer  206  and the surface of the hydrated material  222 . Conversely, because the dye particles  602  are generally distributed closer towards the bottom surfaces  214  of the pore structures  212 , if the metal oxide layer  206  does not include dark color dye particles  602 , then the difference in color between the external surface  202  of the metal oxide layer  206  and the hydrated material  222  is less noticeable. Thus, it may be preferable to prevent dissolution of the hydrated material  222  of the metallic surfaces of the portable electronic devices  102 ,  104 ,  106 ,  108  that are dyed in dark colors. 
       FIG. 7A  illustrates a schematic diagram of a cross-sectional view of a conventional sealed part  700 , in accordance with some embodiments. In some examples, the sealed part  700  illustrated in  FIG. 7A  is subsequent to exposure to external contaminants. In particular,  FIG. 7A  illustrates an exaggerated iridescence effect when visible light ray  710  is incident upon the external surface  702  of the sealed part  700 . As illustrated in  FIG. 7A , the sealed part  700  includes a hydrothermal seal that is comprised of hydrated material  720 . In particular, the sealed part  700  includes: R1=an amount of hydrated material which was previously dissolved from within the pore structures, and R2=an amount of hydrated material that remains within the pore structures. Consequently, when visible light ray  710  is incident upon the external surface  702  of the sealed part  700  at angle θ 1 , the visible light ray  710  is reflected by the external surface  702  of the metal oxide layer  706  according to angle θ 2  as reflected light ray  712 - a  and a remaining amount of the visible light ray  710  is reflected by the upper surface  722  of the hydrated material  720  that remains within the pore structures  712  according to angle θ 3  as reflected light ray  712 - b . Indeed, there is a positive causation between the intensity of the light iridescent effect and the difference in respective heights between the external surface  702  and the upper surface  722 . For example, the greater the difference in respective heights, the greater the light iridescent effect. 
       FIG. 7B  illustrates a schematic diagram of a cross-sectional view of a dehydrated plugged part  750 , in accordance with some embodiments. As described herein, the dehydrated plugged part  750  may include a plug that plugs the openings of the pore structures  722 . The plug includes dehydrated material—e.g., the dehydrated material  752 —that is included within the pore structures  722  of the dehydrated plugged part  750 . In some examples, the dehydrated plugged part  750  is represented in  FIG. 7B  subsequent to exposure to external contaminants over prolonged usage. As illustrated in  FIG. 7B , the dehydrated plugged part  750  includes dehydrated material  752  that plugs the pore structures  722 . In contrast to the sealed part  700 , there is little or no difference in height between the upper surface  754  of the dehydrated material  752  and the external surface  702  of the metal oxide layer  706 . Beneficially, when the visible light ray  710  is incident upon the external surface  702  of the sealed part  700 , the visible light ray  710  is not reflected as multiple light rays by the metal oxide layer  706  and the dehydrated material  752 , thereby preventing the light interference effect. Instead the visible light ray  710  is reflected as reflected light ray  712 . 
       FIG. 8  illustrates a method  800  for forming plugs in a metal part, in accordance with some embodiments. As illustrated in  FIG. 8 , the method  800  can optionally begin at step  802 , where a surface of a part—e.g., a metal substrate  204 —is optionally processed. In some examples, the surface of the metal substrate  204  is subject to a cleaning process, a texturizing process, or a polishing process. In particular, the texturizing process can be beneficial in providing a roughened external surface that can promote growth of the metal oxide layer  206  at those roughened regions. 
     At step  804 , an anodization step is performed on the metal substrate  204 . During the anodization process, a metal oxide layer  206  is formed from the metal substrate  204 . In some examples, the metal oxide layer  206  may be formed through a thermal oxidation process or an electrolytic anodization process. 
     At step  806 , the metal oxide layer  206  is optionally colored as a result of a dyeing process. During the dyeing process, the anodized part—e.g., the anodized part  210 —is exposed to a dye solution bath. The anodized part  210  is submerged within the dye solution bath. 
     At step  808 , the pore structures  212  of the anodized part  210  are sealed via a sealing process according to some embodiments to form the hydrothermally sealed part  230 . In some instances, sealing the pore structures  212  may be preferable in that sealing closes the pore structures such that dye particles are retained within the metal oxide layer  206 . In some examples, the pore structures  212  the aluminum oxide is hydrated during the sealing process. As a result, the aluminum oxide is converted to aluminum oxide hydroxide. Moreover, this process of hydrating the aluminum oxide hydrates the pore walls  216  of the pore structures  212 , thereby increasing the structural integrity of the metal oxide layer  206 . 
     At step  810 , the hydrothermally sealed part  230  is exposed to a dehydration process, to form a dehydrated part  240 . In some examples, the dehydration process includes subjecting the hydrothermally sealed part  230  to a sufficient amount of heat and/or vacuum pressure. During the dehydration process, the hydrated material (e.g., aluminum oxide hydroxide, etc.) is dehydrated to form Al 2 O 3 . The dehydrated material plugs the openings  218  of the pore structures  212 . 
     At step  812 , the dehydrated part  240  is optionally exposed to a rehydration process to form the rehydrated part  250 . 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a computer readable medium for controlling manufacturing operations or as computer readable code on a computer readable medium for controlling a manufacturing line. The computer readable medium is any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20190124
Publication Date: 20220426
Grant Date: 20220426
Priority Date: 20180927
Inventors: CURRAN, JAMES A.
LI, HOISHUN
DIXON, NATHANIEL A.
Assignee: APPLE INC
CPC Classifications: [{"code": "C25D11/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/714", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/24942", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B1/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "B32B2307/752", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B33/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K5/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/24273", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/7265", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B15/043", "inventive": true, "first": true, "tree": "[]"}, {"code": "B32B3/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B15/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B15/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B2311/24", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/0243", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B5/147", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24339", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2457/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B5/145", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B2307/402", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "Y10T428/249956", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/243", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24331", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/402", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/7265", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B15/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B15/20", "inventive": true, "first": false, "tree": "[]"}, {"code": "C25D11/16", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/752", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/0243", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B15/043", "inventive": true, "first": true, "tree": "[]"}, {"code": "C25D11/18", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B5/145", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B5/147", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "B32B2457/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2311/24", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/24339", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/714", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B3/30", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/24331", "inventive": false, "first": false, "tree": "[]"}, {"code": "H05K5/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T428/24273", "inventive": false, "first": false, "tree": "[]"}, {"code": "C25D11/243", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B33/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "B32B2307/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/249956", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T428/24942", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 69947096