Pretreatment Compositions and Methods For Coating A Metal Substrate

Abstract

Disclosed are pretreatment compositions and associated methods for treating metal substrates with pretreatment compositions, including ferrous substrates, such as cold rolled steel and electrogalvanized steel. The pretreatment composition includes: (a) a group IIIB and/or IVB metal; (b) free fluorine; (c) a source of aluminum ions; and (d) water. The methods include contacting the metal substrates with the pretreatment composition.

1 . A pretreatment composition for treating a metal substrate comprising:
 (a) a group IIIB and/or IVB metal;   (b) an electropositive metal;   (c) free fluorine;   (d) a source of aluminum ions; and   (e) water,   wherein the source of aluminum ions is supplied in an amount sufficient to maintain the level of free fluorine in the composition to no less than 0.1 ppm and no more than 750 ppm.   
     
     
         2 . The pretreatment composition of  claim 1 , wherein the source of aluminum ions comprises a water soluble aluminum compound comprising one or more of aluminum sulfate, ammonium aluminum sulfate, potassium aluminum sulfate, sodium aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate, aluminum citrate, aluminum bromide, aluminum bromate, aluminum lactate, aluminum chlorate, aluminum tartrate, aluminum thiocyanate, aluminum hydroxychloride, aluminum formate, aluminum hydroxyacetate, aluminum malate, aluminum succinate, aluminum gluconate, aluminum glutamate, aluminum glycinate, aluminum fumarate, and their respective hydrated forms. 
     
     
         3 . The pretreatment composition of  claim 1 , wherein the source of aluminum ions comprises one or more of aluminum oxide, aluminum hydroxide, aluminum ferricyanide, aluminum phosphate, aluminum silicate, aluminum-containing clays, aluminum-containing zeolites, aluminum soaps and salts of aluminum-containing fatty acids. 
     
     
         4 . The pretreatment composition of  claim 1 , wherein the source of aluminum ions is complexed with an organic compound. 
     
     
         5 . The pretreatment composition of  claim 4 , wherein the organic compound comprises one or more of a polycarboxylic acid or an aminopolycarboxylic acid. 
     
     
         6 . The pretreatment composition of  claim 1 , wherein the group IIIB and/or IVB metal is present in the pretreatment composition in an amount of at least 100 ppm metal. 
     
     
         7 . The pretreatment composition of  claim 1 , wherein the electropositive metal is included in the pretreatment composition in an amount of at least 1 ppm of total metal measured as elemental metal. 
     
     
         8 . The pretreatment composition of  claim 1 , wherein the pretreatment composition is substantially free of phosphate ions. 
     
     
         9 . The pretreatment composition of  claim 1 , wherein the pretreatment composition is substantially free of chromate and/or zinc phosphate. 
     
     
         10 . A method for treating a metal substrate comprising contacting the substrate with a pretreatment composition comprising:
 (i) a group IIIB and/or IVB metal;   (ii) an electropositive metal;   (iii) free fluorine;   (iv) a source of aluminum ions; and   (v) water,   wherein the source of aluminum ions is supplied in an amount sufficient to maintain the level of free fluorine in the pretreatment composition to no less than 0.1 ppm and no more than 750 ppm.   
     
     
         11 . The method of  claim 10 , further comprising cleaning the metal substrate prior to the contacting step. 
     
     
         12 . The method of  claim 10 , wherein the source of aluminum ions (iv) comprises a water soluble aluminum compound comprising one or more of aluminum sulfate, ammonium aluminum sulfate, potassium aluminum sulfate, sodium aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum acetate, aluminum citrate, aluminum bromide, aluminum bromate, aluminum lactate, aluminum chlorate, aluminum tartrate, aluminum thiocyanate, aluminum hydroxychloride, aluminum formate, aluminum hydroxyacetate, aluminum malate, aluminum succinate, aluminum gluconate, aluminum glutamate, aluminum glycinate, aluminum fumarate, and their respective hydrated forms. 
     
     
         13 . The method of  claim 10 , wherein the source of aluminum ions (iv) comprises one or more of aluminum oxide, aluminum hydroxide, aluminum ferricyanide, aluminum phosphate, aluminum silicate, aluminum-containing clays, aluminum-containing zeolites, aluminum soaps and salts of aluminum-containing fatty acids. 
     
     
         14 . The method of  claim 10 , wherein the group IIIB and/or IVB metal (i) is present in the pretreatment composition in an amount of at least 100 ppm metal. 
     
     
         15 . The method of  claim 10 , wherein the electropositive metal (ii) is included in the pretreatment composition in an amount of at least 1 ppm of total metal measured as elemental metal. 
     
     
         16 . The method of  claim 10 , wherein the source of aluminum ions is complexed with an organic compound. 
     
     
         17 . The method of  claim 16 , wherein the organic compound comprises one or more of a polycarboxylic acid or an aminopolycarboxylic acid. 
     
     
         18 . The method of  claim 10 , further comprising contacting the pretreated substrate with a coating composition comprising a film-forming resin, wherein the contacting comprises an electrocoating step wherein an electrodepositable composition is deposited onto the pretreated substrate by electrodeposition. 
     
     
         19 . A metal substrate treated according to the method of  claim 10 .