Molecular coating on metal surfaces
A coated metal surface is disclosed, with a chemically-bonded film of long-chain organic groups. Such coating may be hydrophobic, and therefore repel the presence of water. This allows the surface to resist corrosion and surface oxidation, without diminishing the desired metallic characteristics of the surface. Further disclosed are methods for applying and coating on various substrates. Such coating may be advantageously applied to protect metals from corrosive environments such as air, water, chemicals, and bodily fluids.
1. A method for creating a hydrophobic coating on a metal substrate, comprising the steps of:
cleaning a surface of the metal substrate;
activating the surface by exposing it to an oxidizing agent;
providing a plurality of organic molecular groups, each organic molecular group having a long-chain structure comprising a carbon backbone of at least 10 carbon atoms and a single carboxyl group;
providing conditions wherein at least a portion of the plurality of organic molecular groups is selectively bound to the surface,
wherein said portion of the organic molecular groups are bound to the metal surface by a chemical bond between the surface and the carboxyl group; and
wherein the substrate after hydrophobic coating is electrically conductive.
2. The method of claim 1 , wherein the organic molecular groups are fatty acid groups.
3. The method of claim 2 , wherein the carbon backbone comprises at least 12 and no more than 20 carbon atoms.
4. The method of claim 1 , wherein the cleaning step comprises the step of etching of the surface.
5. The method of claim 4 , wherein the etching step comprises the step of electrochemical etching of the surface.
6. The method of claim 5 , wherein the electrochemical etching step is conducted within a range of temperatures between about 40° C. and about 70° C.
7. The method of claim 1 , wherein the surface of the metal substrate comprises at least 50 percent by weight of a Group VIIIB element.
8. The method of claim 7 , wherein the Group VIIIB element is selected from the group consisting of iron and nickel.
9. The method of claim 1 , wherein surface of the metal substrate comprises at least 50 percent by weight of an element selected from the group consisting of zinc, aluminum, titanium, and tin.
10. The method of claim 1 , wherein the cleaning step comprises the step of exposing the substrate to a surfactant.
11. The method of claim 1 , wherein the oxidizing agent comprises a metal peroxide.
12. The method of claim 1 , wherein the binding step comprises the step of exposing the metal substrate to a solution comprising the organic molecular groups and an aprotic solvent.
13. The method of claim 1 , wherein the binding step comprises the step of maintaining a temperature at the surface of between about 85° C. to about 150° C. for a predetermined period of time while the binding takes place.
14. The method of claim 13 , wherein the temperature is between about 110° C. to about 125° C.
15. The method of claim 1 , wherein none of the plurality of organic molecular groups contains a cross-link to any other of the plurality of organic molecular groups.
16. The method of claim 1 , further comprising the step, performed after said step of providing conditions, of washing the surface to remove the portion of the organic molecular groups, if any, which remain unbound to the surface.
17. The method of claim 8 , wherein the Group VIIIB element is nickel.