Corrosion protection of buried metallic conductors

Abstract

A method for protecting a conductive metal from corrosion, including coating the conductive metal with a water impermeable carbonaceous conductive material to protect the conductive metal from corrosion.

The invention claimed is: 
     
         1 . A corrosion-protected electrically conductive assembly, the assembly comprising:
 a conductive metal element; and   a coating on the conductive metal element, wherein the coating is highly water impermeable for protecting the conductive metal element from corrosion, and is electrically conductive for conducting a current from the conductive metal element;   wherein the coating comprises a conductive carbonaceous material dispersed in a polymeric binder and the polymeric binder comprises at least one of a styrene acrylic copolymer, a crosslinked styrene acrylic copolymer, a styrene butadiene polymer, a carboxylated styrene butadiene co-polymer, a two-part precursor of a chemically cross-linked polymer, a nonionic polychloroprene, an anionic polychloroprene, a cationic polychloroprene, a polybutadiene, a butadiene acrylonitrile, a polyvinyl polymer, a co-polymer of polyethylene, polypropylene and/or polyvinyl acetate, a polyethylene, and an epoxy polymer.   
     
     
         2 . The assembly of  claim 1 , wherein the coating has a thickness of at least 0.01 inches. 
     
     
         3 . The assembly of  claim 1 , wherein the coating has an electrical resistivity of less than 10,000 ohm-cm and a water permeability of less than 10-5 cm/second. 
     
     
         4 . The assembly of  claim 1 , wherein the coating is essentially free of metal particles. 
     
     
         5 . The assembly of  claim 1 , wherein the conductive metal element is a rigid structure. 
     
     
         6 . The assembly of  claim 5 , wherein the conductive metal element is an embedded steel pylon. 
     
     
         7 . The assembly of  claim 5 , wherein the rigid structure is a pylon, a ground rod, or rebar. 
     
     
         8 . The assembly of  claim 7 , wherein the rigid structure is a pylon, and the pylon is an electrical power transmission tower or a communications tower. 
     
     
         9 . The assembly of  claim 1 , wherein the conductive metal grounding element is a wire, cable, or metal strap. 
     
     
         10 . The assembly of  claim 1 , wherein the conductive metal grounding element is a wire or a cable and the assembly is wound onto a spool. 
     
     
         11 . The assembly of  claim 1 , wherein the carbonaceous material makes up at least 35% of the coating by weight. 
     
     
         12 . The assembly of  claim 11 , wherein the carbonaceous material makes up between 60% and 90% of the coating by weight. 
     
     
         13 . An electrically grounded and corrosion-protected installation, comprising:
 a conductive metal element having at least a portion that is buried in the earth; and   a coating on the portion of the conductive metal element that is buried in the earth;   wherein the coating is highly water impermeable for protecting the conductive metal element from corrosion, and is electrically conductive for conducting a grounding current from the conductive metal element to a surrounding grounding medium;   wherein the coating comprises a conductive carbonaceous material dispersed in a polymeric binder, and the polymeric binder comprises at least one of a styrene acrylic copolymer, a crosslinked styrene acrylic copolymer, a styrene butadiene polymer, a carboxylated styrene butadiene co-polymer, a two-part precursor of a chemically cross-linked polymer, a nonionic polychloroprene, an anionic polychloroprene, a cationic polychloroprene, a polybutadiene, a butadiene acrylonitrile, a polyvinyl polymer, a co-polymer of polyethylene, polypropylene and/or polyvinyl acetate, a polyethylene, and an epoxy polymer.   
     
     
         14 . The installation of  claim 13 , wherein the conductive metal element is part of a rigid structure and comprises a lower portion that is buried in the earth and an upper portion that is above the lower portion. 
     
     
         15 . The installation of  claim 13 , further comprising an electrically conductive backfill surrounding the portion that is buried in the earth. 
     
     
         16 . The installation of  claim 13 , wherein the conductive metal element is entirely buried in the earth. 
     
     
         17 . The installation of  claim 16 , wherein the conductive metal element is a wire, cable, or strap. 
     
     
         18 . The installation of  claim 13 , wherein the conductive metal element comprises a copper conductor. 
     
     
         19 . The installation of  claim 13 , wherein the conductive metal element is a part of an electrical power transmission tower or a communications tower. 
     
     
         20 . A coating for a conductive metal element, the coating comprising:
 a polymeric binder comprising at least one of a styrene acrylic copolymer, a crosslinked styrene acrylic copolymer, a styrene butadiene polymer, a carboxylated styrene butadiene co-polymer, a two-part precursor of a chemically cross-linked polymer, a nonionic polychloroprene, an anionic polychloroprene, a cationic polychloroprene, a polybutadiene, a butadiene acrylonitrile, a polyvinyl polymer, a co-polymer of polyethylene, polypropylene and/or polyvinyl acetate, a polyethylene, and an epoxy polymer; and   a conductive carbonaceous material dispersed in the polymeric binder;   wherein the coating is water impermeable for protecting the conductive metal element from corrosion and electrically conductive for conducting a grounding current from the conductive metal element to a surrounding grounding medium.   
     
     
         21 . The coating of  claim 20 , wherein the coating has a thickness of at least 0.01 inches. 
     
     
         22 . The coating of  claim 20 , wherein the coating has an electrical resistivity of less than 10,000 ohm-cm and a water permeability of less than 10.5 cm/second. 
     
     
         23 . The coating of  claim 20 , wherein the coating is essentially free of metal particles. 
     
     
         24 . The assembly of  claim 20 , wherein the carbonaceous material makes up at least 35% of the coating by weight. 
     
     
         25 . The assembly of  claim 24 , wherein the carbonaceous material makes up between 60% and 90% of the coating by weight.