Patent Publication Number: US-2021164122-A1

Title: Treating anodized alloy substrates

Description:
BACKGROUND 
     Substrates of alloys may be anodized to provide an oxidized layer on their surfaces. The anodization improves their corrosion resistance, appearance, hardness, wear resistance, glue-ability, paint adhesion, and other properties. The anodized alloy substrates find use in various applications. For example, an anodized aluminum alloy substrate is used for making casings of electronic devices, such as smartphones, tablet computers, and laptop computers. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The following detailed description references the figures, wherein: 
         FIG. 1  illustrates a method for treating an anodized alloy substrate, according to an example implementation of the present subject matter. 
         FIG. 2  illustrates a treatment of an alloy substrate, according to an example implementation of the present subject matter. 
         FIG. 3  illustrates a method for treatment of an aluminum alloy substrate, according to an example implementation of the present subject matter. 
         FIG. 4  illustrates a method for treatment of an alloy substrate, according to an example implementation of the present subject matter. 
     
    
    
     DETAILED DESCRIPTION 
     Alloy substrates, such as aluminum alloy substrates, may be anodized to form an oxidized layer on the surface. Anodization involves placing an alloy substrate as an electrode in an electrolyte and applying an electric potential between the alloy substrate and another electrode. For example, anodization of an aluminum alloy substrate may involve placing the aluminum alloy substrate as an anode in an acidic electrolyte and applying electric potential between the aluminum alloy substrate and another electrode, which acts as the cathode. 
     Some alloys, such as aluminum 6013 (Al 6013) alloy, upon anodizing, become colored and develop a reflective surface. The colored and reflective surface renders these alloys unsuitable for use in various applications, such as in casings of electronic devices. Sometimes, such alloys which become colored and reflective upon anodization have superior properties. For example, the Al 6013 has a higher tensile strength compared to other aluminum alloys, such as Al 6063, that are used for making the casings of electronic devices. Therefore, despite superior strength, the alloy may have limited use in various applications, owing to the colored and reflective surface. 
     The present subject matter relates to treating anodized alloy substrates, one example being an anodized aluminum substrate. Implementations of the present subject matter enhance, the whiteness of the anodized alloy substrates and also make them substantially non-reflective. 
     In accordance with an example implementation of the present subject an anodized alloy substrate is immersed in a titanium salt solution. The immersion in the titanium salt solution deposits titanium ions in a surface of the anodized alloy substrate to form a processed substrate. The processed substrate is then anodized to form a finished substrate. The anodization oxidizes the titanium ions in the surface to titanium dioxide particles. 
     In an example, the anodized alloy substrate includes a plurality of pores in its surface. The titanium ions from the titanium salt solution get deposited in the plurality of pores. 
     Further, in an example, the alloy substrate is an aluminum alloy substrate. After depositing titanium ions in the surface of the aluminum alloy substrate, the aluminum alloy substrate is baked to form a baked substrate. The baked substrate can then be anodized to form a finished aluminum alloy substrate. 
     The, deposition of titanium dioxide particles in the oxidized layer enhances the whiteness of the anodized alloy substrate and also makes it substantially non-reflective, As would be noted, the present subject can be used for treating anodized alloy substrates, such as an anodized substrate of Al 6013, to render them suitable for making casings of electronic devices. Further, since the anodized alloy substrate is anodized after deposition of titanium ions, the present subject matter provides a simple and effective method of providing titanium dioxide particles in the surface of the anodized alloy substrate. 
     The following description refers to the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the following description to refer to the same or similar parts. While several examples are described in the description, modifications, adaptations, and other implementations are possible, Accordingly, the following detailed description does not limit the disclosed examples. Instead, the proper scope of the disclosed examples may be defined by the appended claims. 
     Example implementations of the present subject matter are described with regard to depositing titanium dioxide particles in an anodized aluminum alloy substrate. Although not described, it will be understood that the implementations of the present subject matter can be used with other anodized alloy substrates. 
       FIG. 1  illustrates a method  100  for treating an anodized alloy substrate, according to an example implementation of the present subject matter. 
     At block  102 , an anodized alloy substrate is immersed in a titanium salt solution. The alloy substrate that is anodized may be, for example, an aluminum alloy substrate. The aluminum alloy may be a 2000, 3000, 5000, 6000, or 7000 series aluminum alloy. In an example, the alloy substrate is an Al 6013 alloy substrate. The immersion of the anodized alloy substrate in the titanium salt solution results in deposition of titanium ions from the titanium salt solution onto or in a surface of the anodized alloy substrate. 
     At block  104 , the processed substrate is anodized to form a finished substrate. The anodization oxidizes the titanium ions to titanium dioxide (TiO 2 ) particles. Therefore, the finished substrate includes titanium dioxide particles in its surface. While it is explained that the titanium dioxide particles are present in the oxidized layer in the description and claims, it is to be understood that the titanium dioxide particles may be present on the oxidized layer as well. Further, the portions of the specification teaching the presence of titanium dioxide particles in the oxidized layer are intended to cover the presence titanium dioxide particles on the oxidized layer as well. 
       FIG. 2  illustrates a treatment of an alloy substrate  200 , according to an example it of the present subject matter. 
     The alloy substrate  200  may be anodized to form an anodized alloy substrate  202 . The anodized alloy substrate  202  may also be referred to as a first processed substrate  202 . The anodization may be performed at a voltage in a range of about 10-120 V for a time period in a range of about 3-20 minutes. In an example, the anodizing solution includes a titanium salt. 
     The first processed substrate  202  includes an oxidized layer  204  as a result of the anodization. The first processed substrate  202  also includes a residual alloy portion  206 , which is the portion of the alloy substrate  200  that remains un-oxidized after the anodization. 
     The anodization causes the formation of a plurality of pores in the oxidized layer  204 . For example, the oxidized layer  204  includes pores  208 - 1 ,  208 - 2 , and  208 - 3 . In an example, each of the plurality of pores have a diameter, i.e., size, in a range of about 5-30 nm. 
     Titanium ions are deposited in the plurality of pores in the surface of the fiat processed substrate  202  to form a second processed substrate  210 , similar to the processed substrate explained with reference to  FIG. 1 . The deposition of the titanium ions can be performed by immersing the first processed substrate  202  in a titanium salt solution. When the first processed substrate  202  is immersed in the titanium salt solution, titanium ions in the titanium salt solution enter the plurality of pores. As illustrated, the second processed substrate  210  includes titanium ions, such as titanium ions  212 ,  214 , and  216  in the pores  208 - 1 ,  208 - 2 , and  208 - 3 , respectively. 
     The titanium salt solution at include at least one titanium salt selected from the group consisting of titanium acetate, titanium carbonate, titanium nitrate, titanium phosphate, titanium sulfate, titanium chloride, and combinations thereof. In an example, the titanium salt solution includes the at least one titanium salt in a weight percentage range of about 3-15%. The titanium salt solution may have a pH in a range of 2-4. Further, in an example, the titanium salt solution is maintained at a temperature in the range of about 30-50° C. 
     Upon depositing the titanium ions in the plurality of pores, the second processed substrate  210  is anodized to form a finished substrate  218 , The anodization of the second processed substrate  210  results in the oxidation of the titanium ions to titanium dioxide particles. Therefore, the finished substrate  218  includes titanium dioxide particles in its plurality of pores. For example, as illustrated, the finished substrate  218  includes titanium dioxide particles, such as titanium dioxide particles  220 ,  222 , and  224  in the pores  208 - 1 ,  208 - 2 , and  208 - 3 , respectively The anodization of the second processed substrate may be performed at a voltage in a range of about 10-120 V for a time period in a range of about 10-30 minutes. 
     In an example, the thickness of the residual alloy portion  206  in the finished substrate  218  is in a range of about 0.12 mm. Further, an outer layer  226  including the plurality of pores and the TiO 2  particles span a thickness in a range of about 10-300 nm, and the remainder of the oxidized layer  204  (portion of the oxidized layer excluding the outer layer  226 ) may have a thickness in a range of about 5-15 μm. 
     As will be understood, the anodization enables an efficient oxidation of the titanium ions to titanium dioxide particles. Therefore, the present subject matter provides a simple, effective, and efficient method of forming titanium dioxide particles in an alloy substrate. The anodization also enables formation of a uniform layer of titanium dioxide particles in the oxidized layer  204 . 
     As mentioned earlier, in an example, the alloy, substrate  200  can be an aluminum alloy substrate, Further, the alloy substrate  200  may be baked after depositing titanium ions in its surface. 
       FIG. 3  illustrates a method  300  for treating an aluminum alloy substrate according to an example implementation of the present subject matter. 
     At block  302 , an aluminum substrate is anodized to form a first processed substrate, such as the first processed substrate  202 . The first processed substrate includes a plurality of pores in its surface. 
     At block  304 , the first processed substrate is contacted with a titanium salt solution to form a second processed substrate, such as the second processed substrate  210 . The contacting can be performed, for example, by immersing the first processed substrate in the titanium salt solution. The titanium salt solution can be the titanium salt solution explained with reference to  FIG. 2 . 
     At block  306 , the second processed substrate is baked to form a baked substrate. In an example, the baking of the second processed substrate may be performed at a temperature in a range of about 105-110° C. for a time period in a range of about 10-15 minutes. The baking of the second processed substrate enables the entry of a higher number of titanium ions in the plurality of pores. 
     At block  308 , the baked substrate is anodized to form a finished aluminum substrate. The finished aluminum substrate includes titanium dioxide particles in the plurality of pores. 
     The finished substrate can be sealed and subsequently baked. Further, prior to anodizing, the alloy substrate may be pre-treated. The pre-treatment, sealing, and baking are explained with reference to  FIG. 4 . 
       FIG. 4  illustrates a method  400  for treatment of an alloy substrate, according to an example implementation of the present subject matter. 
     At block  402 , an alloy substrate, such as the alloy substrate  200 , is cleaned using an alkaline solution. The alkaline solution can include bases, such as sodium hydroxide, potassium hydroxide and ammonia. 
     At block  404 , the cleaned, alloy substrate is neutralized using an acidic solution. The neutralization neutralizes the bases on the surface of the alloy substrate. The acidic solution used for the neutralization can be, for example, hydrochloric acid and nitric acid. 
     At block  406 , the alloy substrate is chemically polished. In an example, the polishing can be performed using phosphoric acid, nitric acid, sulfuric acid, or a combination thereof. 
     At block  408 , the alloy substrate is anodized, as explained with reference to  FIG. 2 . In an example, the anodization is, performed at a voltage in a range of about 10-120 V for a time period in a range of about 3-20 minutes. The anodization of the ahoy substrate forms an anodized alloy substrate, such as the anodized alloy substrate  202 . 
     At block  410 , the anodized alloy substrate washed using water. 
     At block  412 , the anodized substrate is immersed in a titanium salt solution, as explained with reference to  FIGS. 1 and 2 . The immersion in the titanium salt solution results in the formation of a processed substrate, such as the second processed substrate  210 , having titanium ions in a plurality of pores in the surface of the anodized substrate. 
     At block  414 , the processed substrate is anodized, as explained with reference to  FIGS. 1 and 2 . The anodization of the processed substrate converts it into a finished substrate, which includes titanium dioxide particles in the plurality of pores. 
     At block  416 , the finished substrate is sealed to form a sealed alloy substrate. The sealing of the finished substrate seals the plurality of pores, prevents the anodized alloy surface from being sticky, and makes it non-absorbent to dirt, grease, oil, stains, and the like. In an example, the sealing is performed in a solution including 0.6-5.0 wt. of nickel acetate and nickel fluoride as sealing agents at a temperature of 25-95° C. for a time period of 10-20 minutes. 
     At block  418 , the sealed alloy substrate is baked. In an example, the baking is performed at a temperature in a range of about 105-110° C. for a time period in a range of about 20-40 minutes. 
     In an implementation, as explained with reference to  FIG. 3 , the processed substrate is baked before being anodized at block  414 . The baking of the processed substrate may be performed at a temperature in a range of about 105-110° C. for a time period in a range of about 10-15 minutes. The baking of the processed substrate enables the entry of a higher number of titanium ions the plurality of pores. 
     The present subject matter provides a simple, effective, and efficient method of providing titanium dioxide particles in the oxidized layer on an anodized alloy substrate, thereby making it white and substantially non-reflective. Therefore, the present subject matter can be used for alloys, such as Al 6013, that have a high tensile strength, but have a yellowish and reflective appearance post anodization to render them suitable for applications like casings for electronic devices. Further, the anodization of the anodized alloy substrate after immersion in the titanium salt solution provides an efficient method of oxidizing titanium ions on the anodized alloy substrate. This anodization also provides a uniform layer of titanium dioxide particles in the oxidized layer. Therefore, present subject matter provides a simple, efficient, and effective method of providing titanium dioxide particles in an anodized alloy substrate. Still further, the steps involved in the method, such as sealing and baking, are performed at less aggressive temperature conditions, such as below 110° C., and at normal pressure. Therefore, the methods of the present subject matter can be performed in a simple cost-effective manner. 
     Although implementations of treating anodized alloy substrates have been described in language specific to structural features and/or methods, it is to be understood that the present subject matter is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed and explained as example implementations.