Anti-corrosive oil-impregnated nanoporous oxide coating for stainless steel

A method of forming a protective, anti-corrosive coating on a stainless steel substrate adapted for exposure to vapor and wet conditions, said method comprising the steps of:

• a) anodizing said stainless steel substrate so as to form an oxide layer on an exterior surface thereof, said oxide layer including a plurality of nanopores having walls, at least some of said nanopores of said plurality of nanopores having a sidewall extending through said oxide layer to a dead end thereof, whereby said at least some of said nanopores exhibit a high aspect ratio, said oxide layer having an outer surface including said plurality of nanopores, which are distributed throughout said oxide layer such that each nanopore of said plurality of nanopores is isolated from every other nanopore of said plurality of nanopores by said oxide layer, including said outer surface thereof;
• b) annealing said stainless steel substrate, including said oxide layer thereof, to create a metal oxide film on said outer surface of said oxide layer, said metal oxide film being insoluble in water and adapted to protect said stainless steel substrate from corrosive media to which said stainless steel substrate is exposable;
• c) selecting a liquid oil that is water-immiscible and that has anti-corrosive properties;
• d) selecting a hydrophobic chemical that also has oleophilic properties, said hydrophobic chemical having a high chemical affinity to said liquid oil;
• e) applying an amount of said hydrophobic chemical to said metal oxide film and to said plurality of nanopores, including said at least some of said nanopores, so as to coat said metal oxide film and said walls of said plurality of nanopores, including said sidewall of each nanopore of said at least some of said nanopores, with a layer of said hydrophobic chemical, said layer of said hydrophobic chemical having a negligible effect on the dimensions and morphology of said plurality of nanopores, including said at least some of said nanopores;
• f) providing said plurality of nanopores, including said at least some of said nanopores, with an alcohol component in a quantity sufficient to fill said plurality of nanopores, including said at least some of said nanopores, with said alcohol component;
• g) selecting an oil solvent providing a high solubility to said liquid oil;
• h) providing said plurality of nanopores, including said at least some of said nanopores, with said oil solvent in a quantity sufficient to replace said alcohol component in said plurality of nanopores, including said at least some of said nanopores;
• and
• i) providing said metal oxide film and said plurality of nanopores, including said at least some of said nanopores, with said liquid oil in a quantity sufficient to replace said oil solvent in said plurality of nanopores, including said at least some of said nanopores, said quantity of said liquid oil being sufficient to completely fill said plurality of nanopores, including said at least some of said nanopores, with said liquid oil, whereby said plurality of nanopores, including said at least some of said nanopores, contain only said liquid oil, which cooperates with said metal oxide film to form said protective, anti-corrosive coating on said stainless steel substrate, and which exhibits self-healable properties as a result of the prior performance of step e) and hence the application of said hydrophobic chemical to said metal oxide film and to said plurality of nanopores, including said at least some of said nanopores, whereby said liquid oil is sufficiently flowable to fill damaged areas of said stainless steel substrate.