Metal substrates including metal oxide nanoporous thin films and methods of making the same

Abstract

The present disclosure is directed to a metal-containing apparatus including a substrate member constructed of a metal that is highly resistant to pitting corrosion and wear in aggressive media. An exemplary metal-containing apparatus is a plate heat exchanger. The metal includes an oxidation layer on the surface thereof and a thin metal oxide nanoporous film on top of the oxidation layer. The nanoporous film is highly compliant and is comprised of oxygen and aluminum, titanium, silicon, zirconium and combinations thereof.

We Claim: 
     
         1 . A method of making a metal-containing apparatus, the method comprising:
 providing a substrate material constructed of a metal;   introducing an oxidized layer on a surface of the substrate material, the oxidized layer having a thickness of less than about 200 nanometers;   providing a sol comprising nanoparticulate γ-AlOOH, TiO 2 , SiO 2 , ZrO 2 , or a mixture thereof, the nanoparticulates having a primary particle size of from about 1.5 nanometers to about 50 nanometers;   contacting the sol with the oxidized layer to provide at least one layer of the sol onto the oxidized layer;   heating the at least one layer at a temperature of from about 60° C. to about 100° C. for a time period of from about 15 minutes to about 2 hours to produce at least one dry layer; and thermally sintering the at least about one dry layer to produce a nanoporous film comprising oxygen and aluminum, titanium, silicon, zirconium or a combination thereof, the nanoporous film having a thickness of less than about 1 micrometer and a porosity of from about 26% to about 80%.   
     
     
         2 . The method of  claim 1 , wherein the oxidized layer is introduced onto the substrate using a heating process, a basic solution, or a hydrogen peroxide solution. 
     
     
         3 . The method of  claim 1 , wherein the sol is contacted with the oxidized layer utilizing a process selected from the group consisting of dipping, draining, spraying, electro-deposition, spinning, and combinations thereof. 
     
     
         4 . The method of  claim 1 , wherein the substrate material is constructed of a metal selected from the group consisting of stainless steel, carbon steel, and aluminum. 
     
     
         5 . The method of  claim 1 , wherein the nanoporous film has a thickness of from about 0.01 micrometers to about 1 micrometer. 
     
     
         6 . The method of  claim 1 , wherein the nanoporous film has a porosity of about 26%. 
     
     
         7 . The method of  claim 1 , wherein the sol comprises nanoparticulate TiO 2  having a primary particle size of from about 3 nanometers to about 8 nanometers. 
     
     
         8 . The method of  claim 1 , wherein the sol comprises nanoparticulate SiO 2  having a primary particle size of from about 1.4 nanometers to about 8 nanometers. 
     
     
         9 . The method of  claim 1 , wherein the sol comprises a mixture of nanoparticulate SiO 2  having a primary particle size of from about 1.5 nanometers to about 8 nanometers and nanoparticulate TiO 2  having a primary particle size of from about 3 nanometers to about 8 nanometers. 
     
     
         10 . The method of  claim 1 , wherein the sol comprises nanoparticulate ZrO 2  having a primary particle size of from about 3 nanometers to about 8 nanometers. 
     
     
         11 . The method of  claim 1 , further including a second nanoporous film on top of the first nanoporous film, the second nanoporous film comprising oxygen and an element selected from the group consisting of aluminum, titanium, silicon, zirconium and combinations thereof, the second nanoporous film having a thickness of less than about 1 micrometer and having a porosity of from about 26% to about 80%. 
     
     
         12 . The method of  claim 11 , wherein the second nanoporous film comprises zirconium dioxide. 
     
     
         13 . The method of  claim 11 , wherein the second nanoporous film has a thickness of from about 0.01 micrometers to about 1.0 micrometers.