Hydrophobic coatings for metals incorporating anodic and rare-earth oxides and methods of applying same

Abstract

A hydrophobic coating and a method for applying such a coating to a surface of a metallic substrate. The method can include anodizing a nanoporous layer of anodic metal oxide on the surface; cathodizing yttrium oxide nanoparticles onto the surface; applying a hydrophobic ceramic coating composition to the surface by an application method selected from the group consisting of: flowing, dipping, and spraying; and heating the coated surface at a cure temperature from about 150° C. to about 300° C. for at least 2 hours.

1 . A hydrophobic, coated substrate comprising:
 a metallic substrate having a surface;   a nanoporous layer of anodic metal oxide formed on the surface; and   a hydrophobic ceramic coating bonded to the nanoporous layer.   
     
     
         2 . The substrate of  claim 1 , wherein the metallic substrate comprises a metal selected from the group consisting of: aluminum, titanium, and stainless steel. 
     
     
         3 . The substrate of  claim 2 , wherein the metal is aluminum. 
     
     
         4 . The substrate of  claim 3 , wherein the anodic metal oxide comprises anodic aluminum oxide. 
     
     
         5 . The substrate of  claim 1 , wherein the nanoporous layer of anodic metal oxide comprises nanopipettes having an average diameter from about 10 nm to about 100 nm and an average length from about 100 nm to about 10 μm 
     
     
         6 . The substrate of claim  55 , wherein the average diameter is from about 20 nm to about 50 nm and the average length is from about 1.5 μm to about 8 μm. 
     
     
         7 . The substrate of  claim 6 , further comprising yttrium oxide nanoparticles having a mean particle size of about 10 nm, embedded in the nanopipettes. 
     
     
         8 . The substrate of  claim 1 , wherein the hydrophobic ceramic coating comprises:
 a yttrium compound;   a dispersion of yttrium oxide nanoparticles;   a water-soluble polymer; and   a solvent solution of de-ionized water and a water-soluble alcohol.   
     
     
         9 . The substrate of  claim 8 , wherein the yttrium oxide nanoparticles have a mean particle size of about 10 nm and are in an amount ranging from about 2 percent to about 10 percent by weight of the dispersion. 
     
     
         10 . The substrate of  claim 9 , wherein the yttrium oxide nanoparticles are in an amount of about 5 percent by weight of the dispersion. 
     
     
         11 . A hydrophobic, coated substrate comprising:
 a metallic substrate having a surface;   a nanoporous layer of anodic metal oxide formed on the surface;   yttrium oxide nanoparticles embedded in the nanoporous layer; and   a hydrophobic ceramic coating bonded to the nanoporous layer.   
     
     
         12 . The substrate of  claim 11 , wherein the metallic substrate comprises a metal selected from the group consisting of: aluminum, titanium, and stainless steel. 
     
     
         13 . The substrate of  claim 12 , wherein the metal is aluminum. 
     
     
         14 . The substrate of  claim 13 , wherein the anodic metal oxide comprises anodic aluminum oxide. 
     
     
         15 . The substrate of  claim 11 , wherein the nanoporous layer of anodic metal oxide comprises nanopipettes having an average diameter from about 10 nm to about 100 nm and an average length from about 100 nm to about 10 μm 
     
     
         16 . The substrate of  claim 15 , wherein the average diameter is from about 20 nm to about 50 nm and the average length is from about 1.5 μm to about 8 μm. 
     
     
         17 . The substrate of  claim 16 , wherein the yttrium oxide nanoparticles have a mean particle size of about 10 nm and are embedded in the nanopipettes. 
     
     
         18 . The substrate of  claim 11 , wherein the hydrophobic ceramic coating comprises:
 yttrium acetate;   a dispersion of yttrium oxide nanoparticles in an amount ranging from about 0.1 percent to about 5 percent by weight of the hydrophobic ceramic coating;   polyvinyl alcohol in an amount from about 1 percent to about 5 percent by weight of the hydrophobic ceramic coating; and   a solvent solution of de-ionized water and isopropyl alcohol in a ratio of about 2:1.   
     
     
         19 . The substrate of  claim 18 , wherein the yttrium oxide nanoparticles in the dispersion have a mean particle size of about 10 nm. 
     
     
         20 . The substrate of  claim 19 , wherein the yttrium oxide nanoparticles in the dispersion are in an amount ranging from about 0.5 percent to about 1 percent by weight of the hydrophobic ceramic coating.