Anti-corrosive coating for metal surfaces
View Patent ↗A protective coating for a metal substrate is provided that is light, durable, galvanically protective, and easily applied at the site of manufacture. The coating has at least two layers, one of which is a galvanizing layer and one of which is a micro-composite of a galvanic metal and a non-conducting material, such as polymer. Such coatings are useful for example to protect pipes or other metal surfaces in corrosive environments. Methods of producing the coating are provided, including methods that use advanced spraying techniques to provide very thin but consistent layers. Using the advanced spraying methods the composite layer can be created by co-spraying the galvanic metal and the nonconductive material onto the surface of the galvanic coating. Optionally, an outer coat of insulating material can be applied to provide further protection to the surface.
1. A coated metal surface, comprising:
(a) a metal substrate;
(b) a metallic layer in direct contact with the substrate and continuously adhered to the substrate, said metallic layer comprising a first anodic metal wherein the metallic layer is 25 to 200 μm thick;
(c) a composite layer in direct contact with the metallic layer, said composite layer consisting essentially of a matrix of a first dielectric polymeric material and second anodic metal, wherein the second anodic metal is substantially electrically connected to the metal substrate and wherein the composite layer is 5 to 200 μm thick; and
(d) a dielectric topcoat in contact with the composite layer, comprising a second dielectric material wherein the topcoat is 5 to 200 μm thick.
2. The coated metal surface of claim 1 , wherein the metal substrate comprises iron.
3. The coated metal surface of claim 1 , wherein the metal substrate comprises a structure selected from the group consisting of a pipe, a pipe fitting, a pipe valve, a pump component, a pipe fixture, and an appurtenance to a pipe.
4. The coated metal surface of claim 3 , wherein the structure is for the conveyance from a source point to a delivery point of at least one of: freshwater, wastewater, and fuel gas.
5. The coated metal surface of claim 1 , wherein the second anodic metal is the first anodic metal.
6. The coated metal surface of claim 1 , wherein at least one of the first anodic metal and the second anodic metal comprises tellurium.
7. The coated metal surface of claim 1 , wherein each of the first anodic metal and the second anodic metal are independently selected from the group consisting of: zinc, aluminum, magnesium, indium, gallium, and alloys thereof.
8. The coated metal surface of claim 5 , wherein the first anodic metal and the second anodic metal comprise an aluminum-zinc alloy.
9. The coated metal surface of claim 8 , wherein the aluminum: zinc ratio is about 85:15 w/w.
10. The coated metal surface of claim 5 , wherein the first anodic metal and the second anodic metal are selected from the group consisting of: indium, an indium alloy, and an aluminum-silicon alloy.
11. The coated metal surface of claim 10 , wherein the first anodic metal and the second anodic metal comprise an aluminum-silicon alloy wherein the aluminum: silicon ratio is about 88:12 w/w.
12. The coated metal surface of claim 1 , wherein the first dielectric material is the second dielectric material.
13. The coated metal surface of claim 12 , wherein the dielectric material is selected from the group consisting of: epoxy, polyethylene, polypropylene, nylon, polytetrafluoroethylene, ethylene methacrylate acid copolymer, polyurethane, and silicone.
14. The coated metal surface of claim 1 , wherein the composite layer is the product of the process comprising thermally spraying the first dielectric material on the metallic layer and simultaneously thermally spraying the second anodic metal on the metallic layer.
15. A coated metal surface, comprising:
(a) a metal substrate;
(b) a metallic layer in direct contact with the substrate and continuously adhered to the substrate, said metallic layer comprising a first anodic metal wherein the metallic layer is 25 to 200 μm thick; and
(c) a composite layer in direct contact with the metallic layer, said composite layer consisting essentially of a matrix of a first dielectric polymeric material and a second anodic metal, wherein the second anodic metal is substantially electrically connected to the metal substrate and wherein the composite layer is 5 to 200 μm thick.
16. A coated iron surface, comprising:
(a) a substrate consisting essentially of iron alloy;
(b) 25 to 200 μm thick metallic layer coating the surface, said metallic layer consisting essentially of an anodic metal;
(c) 5 to 200 μm thick composite layer coating the metallic layer, said composite layer consisting essentially of the product of the process comprising: simultaneously thermally spraying a metal component and dielectric polymeric component on the metallic layer, wherein the metal component is the anodic metal and wherein the dielectric polymeric component is a first dielectric polymeric material; and
(d) 5 to 200 μm thick topcoat consisting essentially of the first dielectric polymeric material;
wherein the metallic layer is substantially electrically connected to the surface, and the metal component is substantially electrically connected to the surface.
17. A process of coating a metal surface, comprising:
(a) adhering 25 to 200 μm thick metallic layer comprising an anodic metal directly to a metal substrate;
(b) applying 5 to 200 μm thick composite layer consisting essentially of a second anodic metal and a first dielectric polymeric material to the metallic layer, the application of the composite layer comprising spraying the first dielectric polymeric material on the metallic layer and spraying the second anodic metal on the metallic layer; and
(c) applying 5 to 200 μm thick topcoat to the composite layer, said topcoat comprising a second dielectric material;
wherein the second anodic metal is substantially electrically connected to the metal substrate.
18. The process of claim 17 , further comprising heating at least one of the second anodic metal and the first dielectric material.
19. The process of claim 18 , wherein at least one of spraying the first dielectric material and spraying the second anodic metal comprises thermal spraying.
20. The process of claim 17 , wherein at least one of spraying the first dielectric material and spraying the second anodic metal comprises cold spraying.
21. The process of claim 17 , further comprising mixing the first dielectric material and the second anodic metal prior to spraying.
22. The process of claim 19 , wherein the first dielectric material comprises a thermoplastic polymer.
23. The process of claim 17 , wherein the first dielectric material is sprayed simultaneously as the second anodic metal is sprayed.
24. The process of claim 18 , further comprising heating the second anodic metal and the first dielectric material upon contact with the metallic layer.
25. The process of claim 17 , wherein the first anodic metal and the second anodic metal are the same, and wherein the first dielectric material and the second dielectric material are the same.
26. The process of claim 17 , further comprising heating the substrate to approximately the fusion temperature of the first anodic metal.
27. A process of coating a metal surface, comprising:
(a) adhering 25 to 200 μm thick metallic layer comprising an anodic metal directly to a metal substrate; and
(b) applying 5 to 200 μm thick composite layer consisting essentially of a second anodic metal and a first dielectric polymeric material to the metallic layer, the application of the composite layer comprising spraying the first dielectric polymeric material on the metallic layer and spraying the second anodic metal on the metallic layer;
wherein the second anodic metal is substantially electrically connected to the metal substrate.