Oil-impregnated nanoporous oxide coating for inhibiting aluminum corrosion

Abstract

A process includes means for depositing an anti-corrosion coating filled with liquid oil on an aluminum substrate. Aluminum is anodized and then treated with a thin hydrophobic sub-coating. The pores created through anodization are then impregnated with liquid oil. Oil penetration is maximized and residual air is minimized by first filling the pores with a filling solution, replacing the filling solution with an exchange fluid, and then replacing the exchange fluid with perfluorinated oil. The oil gives the surface coating anti-wetting properties and self-healing properties, thereby protecting the aluminum substrate underneath from corrosion.

We claim: 
     
         1 . A coating, comprising an inner layer containing aluminum oxide; an outer layer containing aluminum oxide; and a plurality of nanopores distributed throughout said outer layer, each nanopore of said plurality of nanopores having a respective lumen which contains a quantity of liquid oil. 
     
     
         2 . The coating of  claim 1 , wherein said quantity of liquid oil is sufficient to fill each respective lumen, whereby each respective lumen is substantially free of air. 
     
     
         3 . The coating of  claim 1 , wherein each of said plurality of nanopores has a sidewall which terminates at a dead-end. 
     
     
         4 . The coating of  claim 1 , wherein said liquid oil is water-repellant. 
     
     
         5 . The coating of  claim 1 , wherein said liquid oil is water immiscible. 
     
     
         6 . The coating of  claim 1 , wherein said liquid oil is anti-corrosive. 
     
     
         7 . The coating of  claim 1 , wherein said liquid oil is a perfluorinated oil. 
     
     
         8 . The coating of  claim 1 , wherein said outer layer has a pair of surfaces, one surface being in contact with said inner layer and another surface being opposite said one surface. 
     
     
         9 . The coating of  claim 8 , wherein said another surface of said outer layer has non-wetting properties. 
     
     
         10 . The coating of  claim 1 , further comprising a hydrophobic coating layer provided on said sidewall of each nanopore of said plurality of nanopores. 
     
     
         11 . The coating of  claim 10 , wherein said liquid oil is adapted to fill surface defects in said hydrophobic coating. 
     
     
         12 . A process for applying a liquid oil to a coating layer having nanopores, said process comprising the steps of:
 providing said nanopores with a filling solution having low surface tension;   replacing said filling solution with an exchange fluid that is miscible with both said exchange fluid and said liquid oil; and   replacing said exchange fluid with said liquid oil, such that said nanopores contain only said liquid oil.   
     
     
         13 . The process of  claim 12 , wherein said nanopores of said coating layer are completely filled with said liquid oil. 
     
     
         14 . The process of  claim 12 , wherein said filling solution has a low Henry's constant. 
     
     
         15 . The process of  claim 12 , wherein said process is conducted in a liquid environment. 
     
     
         16 . The process of  claim 12 , wherein said liquid oil is a perfluorinated oil. 
     
     
         17 . The process of  claim 12 , wherein said filling solution is ethanol. 
     
     
         18 . A method for forming a coating on a surface of a metal substrate, said method comprising the steps of:
 anodizing said substrate in oxalic acid to form an oxide layer having a plurality of nanopores, each nanopore having a sidewall; and   filling said plurality of nanopores with a liquid oil.   
     
     
         19 . The method of  claim 18 , further comprising the step of coating the sidewall of each nanopore of said plurality of nanopores with a hydrophobic coating material. 
     
     
         20 . The method of  claim 18 , wherein said metal substrate is aluminum. 
     
     
         21 . The method of  claim 18 , wherein said liquid oil is a perfluorinated oil. 
     
     
         22 . The method of  claim 18 , wherein filling said nanopores with said liquid oil further comprises the steps of:
 providing said nanopores with a filling solution having low surface tension;   replacing said filling solution with an exchange fluid that is miscible with both said exchange fluid and said liquid oil; and   replacing said exchange fluid with said liquid oil, such that said nanopores contain only said liquid oil.   
     
     
         23 . The process of  claim 22 , wherein said nanopores are completely filled with said liquid oil. 
     
     
         24 . The process of  claim 22 , wherein said filling solution has a low Henry's constant. 
     
     
         25 . The process of  claim 22 , wherein said process is conducted in a liquid environment. 
     
     
         26 . The process of  claim 22 , wherein said liquid oil is a perfluorinated oil. 
     
     
         27 . The process of  claim 22 , wherein said filling solution is ethanol.