Conductive organic coatings

Abstract

A metal object is coated by applying the following layers in sequence to at least part of the surface of the metal object: (a) a chemical conversion layer, (b) a conductive organic layer having a thickness of 1 to 10 microns and containing at least an organic binder and an electrically conductive substance, (c) an electrodeposition lacquer having a thickness of 25 to 35 microns, and (d) at least one layer of topcoat. No filler is applied between the electrodeposition layer and the at least one layer of topcoat.

1 . A process for coating a metal object, said process comprising applying the following layers in sequence to at least part of the surface of the metal object: 
 (a) a chemical conversion layer;    (b) a conductive organic layer having a thickness of 1 to 10 μm and containing at least an organic binder and an electrically conductive substance;    (c) an electrodeposition lacquer having a thickness of 25 to 35 μm; and    (d) at least one layer of topcoat;    wherein no filler is applied between the electrodeposition layer (c) and the at least one layer of topcoat (d).    
     
     
         2 . A process according to  claim 1 , wherein the conductive organic layer (b) is obtained by applying a coating agent comprising: 
 (i) 10 to 30 wt. % of an organic binder which cures at a temperature of 140 to 159° C.;    (ii) 30 to 60 wt. % of a powder of an electrically conductive substance;    (iii) 10 to 40 wt. % of water; and    (iv) 0 to 30 wt. % of one or more other active and/or auxiliary substances, wherein the amounts of (i)-(iv) total 100 wt. %,    to the metal surface provided with the chemical conversion layer (a), and curing at a peak metal temperature in the range 130 to 159° C.    
     
     
         3 . A process according to  claim 1 , wherein the conductive organic layer (b) is obtained by applying a coating agent comprising: 
 (i) 5 to 40 wt. % of an organic binder containing: 
 (aa) at least one epoxide resin;  
 (ab) at least one hardener selected from the group consisting of cyanoguanidine, benzoguanamine and plasticized urea resin;  
 (ac) at least one amine adduct selected from the group consisting of polyoxyalkylenetriamine and epoxide resin/amine adducts;  
   (ii) 0 to 15 wt. % of at least one anti-corrosion pigment;    (iii) 40 to 70 wt % of at least one conductive pigment selected from the group consisting of powdered zinc, aluminum, graphite, molybdenum sulphide, carbon black and iron phosphide; and    (iv) 0 to 45 wt. % of a solvent;    and 0 to 50 wt. % of other active or auxiliary substances, wherein. the proportions of the components total 100%,    to the metal surface provided with the chemical conversion layer (a), and curing at a peak metal temperature in the range 160 to 260° C.    
     
     
         4 . A process according to  claim 1 , wherein the chemical conversion layer is formed by a method selected from the group consisting of phosphatizing, chromatizing, and conversion treatment using chromium-free treatment agents.  
     
     
         5 . A process according to  claim 1 , wherein the metal object is a metal strip comprised of galvanized steel.  
     
     
         6 . A process according to  claim 1 , wherein both a basecoat and a clear coat are applied to the electrodeposition lacquer.  
     
     
         7 . A process according to  claim 1 , wherein the conductive organic layer is comprised of at least one conductive pigment in powdered form selected from the group consisting of zinc, aluminum, graphite, molybdenum sulphide, carbon black and iron phosphide.  
     
     
         8 . A process according to  claim 1 , wherein the conductive organic layer is comprised of iron phosphide in powdered form having an average particle size of not more than 10 microns.  
     
     
         9 . A process according to  claim 1 , wherein the conductive organic layer has a thickness of between 5 and 9 microns.  
     
     
         10 . A process according to  claim 1 , wherein the organic binder is comprised of at least one epoxide resin in hardened form.  
     
     
         11 . A process according to  claim 1 , wherein the organic binder additionally contains at least one anti-corrosion pigment.  
     
     
         12 . A metal object which has, on the metal surface, a coating system comprising the following individual layers: 
 (a) a chemical conversion layer;    (b) a conductive organic layer having a thickness of 1 to 10 μm and containing at least an organic binder and an electrically conductive substance;    (c) an electrodeposition lacquer having a thickness of 25 to 35 μm;    (d) at least one layer of topcoat,    wherein no filler is present between the electrodeposition lacquer (c) and the at least one layer of topcoat (d).    
     
     
         13 . A metal object according to  claim 12 , wherein the metal object is a metal strip comprised of galvanized steel.  
     
     
         14 . A metal object according to  claim 12 , wherein both a basecoat and a clear coat are present on top of the electrodeposition lacquer.  
     
     
         15 . A metal object according to  claim 12 , wherein the conductive organic layer is comprised of at least one conductive pigment in powdered form selected from the group consisting of zinc, aluminum, graphite, molybdenum sulphide, carbon black and iron phosphide.  
     
     
         16 . A metal object according to  claim 12 , wherein the conductive organic layer is comprised of iron phosphide in powdered form having an average particle size of not more than 10 microns.  
     
     
         17 . A metal object according to  claim 12 , wherein the conductive organic layer has a thickness of between 5 and 9 microns.  
     
     
         18 . A metal object according to  claim 12 , wherein the organic binder is comprised of at least one epoxide resin in hardened form.  
     
     
         19 . A metal according to  claim 12 , wherein the organic binder additionally contains at least one anti-corrosion pigment.