System for Electrocoating Conductive Substrates

Abstract

The present invention is directed towards an electrocoating system for electrocoating a substrate ( 500 ), the system comprising a tank ( 100 ) configured to hold an electrodepositable coating composition; at least one pump ( 200 ) in fluid communication with the tank, at least one return conduit ( 210 ) connecting the tank with an inlet of the pump, at least one recirculating pipe ( 300 ) comprising a first end in fluid communication with an outlet of the pump and a second end having at least one aperture, and the at least one recirculating pipe comprising at least one external electrode ( 400 ) positioned at least partially outside of the tank. Also disclosed herein are methods of coating substrates, systems for coating a substrate, and coated substrates.

What is claimed is: 
     
         1 . An electrocoating system for electrocoating a substrate, the system comprising a tank configured to hold an electrodepositable coating composition; at least one pump in fluid communication with the tank, at least one return conduit connecting the tank with an inlet of the pump, at least one recirculating pipe comprising a first end in fluid communication with an outlet of the pump and a second end having at least one aperture, and the at least one recirculating pipe comprising at least one external electrode positioned at least partially outside of the tank, wherein:
 the substrate has a first surface and a second surface;   the pump is configured to receive the electrodepositable coating composition from the return conduit and deliver the electrodepositable coating composition into the tank through the recirculating pipe;   the external electrode is configured to provide an electric charge to the electrodepositable coating composition; and   the recirculating pipe is configured to extend into the interior of the tank and position the aperture of the second end to deliver at least a portion of the electrically charged electrodepositable coating composition to the first surface of the substrate.   
     
     
         2 . The electrocoating system of  claim 1 , wherein the external electrode comprises at least 50% of the recirculating pipe. 
     
     
         3 . The electrocoating system of  claim 1 , wherein the external electrode has an internal surface configured to contact the electrodepositable coating composition, and the electrocoating system is configured such that a ratio of a total combined surface area of the external electrode based on the surface area of the external surface area of the external electrode to a surface area of the first surface of the substrate is from 1:7 to 1:1. 
     
     
         4 . The electrocoating system of  claim 1 , wherein the external electrode comprises a section of the recirculating pipe located outside of the tank. 
     
     
         5 . The electrocoating system of  claim 1 , wherein the second end of the recirculating pipe comprises at least one nozzle comprising the aperture. 
     
     
         6 . The electrocoating system of  claim 1 , wherein the second end of the recirculating pipe is branched and comprises at least two apertures configured to deliver at least a portion of the electrodepositable coating composition charged by the external electrode to different surface sections of the first surface of the substrate. 
     
     
         7 . The electrocoating system of  claim 1 , wherein the recirculating pipe comprises a plurality of apertures configured to deliver the electrodepositable coating composition charged by the external electrode to different sections of the first surface of the substrate. 
     
     
         8 . The electrocoating system of  claim 1 , wherein the electrocoating system comprises a plurality of recirculating pipes configured to deliver the electrodepositable coating composition charged by the external electrode to different sections of the first surface of the substrate. 
     
     
         9 . The electrocoating system of  claim 8 , wherein the plurality of recirculating pipes is positioned equidistant along a length of the tank. 
     
     
         10 . The electrocoating system of  claim 1 , further comprising at least one internal electrode positioned inside the tank. 
     
     
         11 . The electrocoating system of  claim 10 , wherein the recirculating pipe comprises a plurality of the internal electrodes positioned along a length of the tank. 
     
     
         12 . The electrocoating system of  claim 11 , wherein the plurality of internal electrodes is positioned equidistant along the length of the tank. 
     
     
         13 . The electrocoating system of  claim 10 , wherein the electrocoating system is configured such that a ratio of a total combined surface area of the internal electrode to the surface area of the second surface of the substrate is from 1:7 to 1:1. 
     
     
         14 . The electrocoating system of  claim 1 , further comprising at least one power source to provide an electrical current to the electrocoating system, wherein the power source is electrically coupled to the external electrode and the substrate, wherein the substrate comprises a counter-electrode to the external electrode. 
     
     
         15 . The electrocoating system of  claim 10 , further comprising at least one power source to provide an electrical current to the electrocoating system, wherein the power source is electrically coupled to the external electrode, the internal electrode, and the substrate, wherein the substrate comprises a counter-electrode to the external electrode and the internal electrode. 
     
     
         16 . The electrocoating system of  claim 1 , wherein the tank, the return conduit, the pump and the recirculating pipe are directly coupled to form at least one continuous and uninterrupted loop configured for constrained flow of the electrodepositable coating composition through the return conduit, pump and recirculating pipe. 
     
     
         17 . The electrocoating system of  claim 1 , wherein the tank comprises a base portion and at least one side wall extending up from the base portion. 
     
     
         18 . The electrocoating system of  claim 1 , wherein the substrate comprises an open-polygon cross-sectional shape. 
     
     
         19 . The electrocoating system of  claim 1 , wherein the substrate comprises a rectangular cross-sectional shape. 
     
     
         20 . The electrocoating system of  claim 1 , wherein the substrate is a container. 
     
     
         21 . The electrocoating system of  claim 1 , wherein the substrate has a cross-sectional area of at least 40 m 2 . 
     
     
         22 . A method for coating a substrate comprising electrophoretically applying a coating deposited from an electrodepositable coating composition to at least a portion of the substrate using the electrocoating system of  claim 1 . 
     
     
         23 . The method of  claim 22 , wherein the electrodepositable coating composition comprises a cationic film-forming resin comprising sulphonium groups. 
     
     
         24 . The method of  claim 22 , wherein the method further comprises applying a topcoat coating composition to at least a portion of the substrate coated with the coating deposited from the electrodepositable coating composition. 
     
     
         25 . The method of  claim 22 , wherein the method further comprises pretreating the substrate with a pretreatment composition prior to applying the coating deposited from the electrodepositable coating composition. 
     
     
         26 . The method of  claim 22 , wherein the method further comprises priming the substrate with a priming composition prior to applying the coating deposited from the electrodepositable coating composition. 
     
     
         27 . The method of  claim 22 , wherein the substrate comprises an open-polygon cross-sectional shape or a rectangular cross-sectional shape. 
     
     
         28 . The method of  claim 22 , wherein the substrate is a container. 
     
     
         29 . A substrate coated by the method of  claim 22 . 
     
     
         30 . A system for coating a substrate comprising the electrocoating system of  claim 1 , and further comprising at least one of:
 a pretreatment system for pretreating the substrate prior to processing the substrate in the electrocoating system;   a priming system for priming the substrate prior to processing the substrate in the electrocoating system; and/or   a topcoat system for applying a topcoat coating to the substrate after processing the substrate in the electrocoating system.