Electrocoat composition and process replacing phosphate pretreatment

Abstract

An electrically conductive substrate is electrocoated with an aqueous electrodeposition coating composition comprising a cathodically electrodepositable binder, the binder comprising an amine-functional phosphorylated resin and at least one additional coating layer, such as a second primer layer, a topcoat layer, or both.

1 . A method of coating a metal automotive vehicle body, comprising:
 (a) cleaning the metal automotive vehicle body;   (b) placing the cleaned metal automotive vehicle body into an aqueous electrocoat coating composition comprising an amine-functional phosphorylated resin.;   (c) connecting the metal automotive vehicle body as a cathode in an electric circuit and passing a current through the aqueous electrocoat coating composition to deposit an electrocoat coating layer onto the metal automotive vehicle body; and   (d) applying a further coating layer over the electrocoat coating layer.   
     
     
         2 . A method according to  claim 1 , wherein the further coating layer is a primer coating layer. 
     
     
         3 . A method according to  claim 1 , wherein the further coating layer is a topcoat coating layer. 
     
     
         4 . A method according to  claim 1 , wherein the electrocoat coating layer is cured before step (d). 
     
     
         5 . A method according to  claim 1 , wherein the electrocoat coating layer and the further coating layer are cured together after step (d). 
     
     
         6 . A method according to  claim 2 , further comprising
 (e) applying a topcoat layer over the primer coating layer layer.   
     
     
         7 . A method according to  claim 6 , wherein the topcoat layer comprises a basecoat/clearcoat composite coating. 
     
     
         8 . A method according to  claim 6 , wherein the primer layer is cured before applying the topcoat layer. 
     
     
         9 . A method according to  claim 6 , wherein the primer layer and the topcoat layer are cured together. 
     
     
         10 . A method according to  claim 6 , wherein the electrocoat coating layer, the primer layer, and the topcoat layer are cured together. 
     
     
         11 . A method according to  claim 1 , wherein the metal automotive vehicle body is free of a phosphate pre-treatment. 
     
     
         12 . A method according to  claim 1 , wherein the phosphorylated resin comprises a phosphate ester of a polyepoxide resin, a phosphonic acid ester of a polyepoxide resin, or a combination thereof. 
     
     
         13 . A method according to  claim 1 , wherein the phosphorylated resin comprises a diphosphate ester of a polyepoxide resin, a diphosphonic acid ester of a polyepoxide resin, or a combination thereof. 
     
     
         14 . A method according to  claim 1 , wherein the phosphorylated resin comprises, on average, more than one phosphorous atom per molecule. 
     
     
         15 . A method according to  claim 1 , wherein the phosphorylated resin is an epoxy resin. 
     
     
         16 . A method according to  claim 1 , wherein the phosphorylated epoxy resin is at least about 5 weight percent of electrocoat coating binder.