System for nickel-free zinc phosphate pretreatment

Abstract

Disclosed is a substrate pretreatment system, comprising (a) an activating rinse for treating at least a portion of a substrate comprising a dispersion of metal phosphate particles having a D 90 particle size of no greater than 10 μm, wherein the metal phosphate comprises divalent or trivalent metals or combinations thereof; and (b) a pretreatment composition for treating at least a portion of the substrate treated with the activating rinse, comprising zinc ions and phosphate ions, wherein the pretreatment composition is substantially free of nickel. Methods of treating a substrate with the substrate pretreatment system also are disclosed. Substrates treated with the substrate pretreatment system also are disclosed.

1 . A substrate pretreatment system, comprising:
 a) an activating rinse for treating at least a portion of a substrate comprising a dispersion of metal phosphate particles having a D90 particle size of no greater than 10 □m, wherein the metal phosphate comprises divalent or trivalent metals or combinations thereof; and   b) a pretreatment composition for treating at least a portion of the substrate treated with the activating rinse, comprising zinc ions and phosphate ions, wherein the pretreatment composition is substantially free of nickel.   
     
     
         2 . The pretreatment system of  claim 1 , wherein the activating rinse further comprises a metal sulfate salt, wherein the sulfate of the metal sulfate salt is present in an amount of 5 ppm to 5000 ppm based on a total weight of the activating rinse. 
     
     
         3 . The pretreatment system of  claim 1 , wherein the D 90  particle size is measured from a sample of the activating rinse that has been sonicated. 
     
     
         4 . The pretreatment system of  claim 1 , wherein the metal phosphate particles have a D 90  particle size of no more than 1 μm. 
     
     
         5 . The pretreatment system of  claim 4 , wherein the D 90  particle size is measured from a sample of the activating rinse that has been sonicated. 
     
     
         6 . The pretreatment system of  claim 1 , wherein the metal phosphate particles have a D 90  particle size of 50 nm to 500 nm. 
     
     
         7 . The pretreatment system of  claim 1 , wherein the divalent or trivalent metals of the metal phosphate in the activating rinse comprise zinc, iron or a combination thereof. 
     
     
         8 . The pretreatment system of  claim 1 , wherein the pretreatment composition is used in a pretreatment bath having a temperature of 20° C. to 60° C. 
     
     
         9 . The pretreatment system of  claim 1 , wherein the metal of the metal sulfate salt comprises nickel, copper, zinc, iron, magnesium, cobalt, aluminum or combinations thereof. 
     
     
         10 . The pretreatment system of  claim 1 , wherein the metal of the metal sulfate salt comprises nickel, cobalt or combinations thereof. 
     
     
         11 . A substrate treated with the pretreatment system of  claim 1 . 
     
     
         12 . The substrate of  claim 11 , wherein the phosphate coating formed from the pretreatment composition comprises metal/zinc phosphate crystals having an average crystal size of 0.4 μm to 2 μm as measured by a scanning electron microscope at 10,000× magnification. 
     
     
         13 . The substrate of  claim 11 , wherein the phosphate coating formed from the pretreatment composition comprises metal/zinc crystals having an average crystal size of 0.7 μm to 1.5 μm as measured by a scanning electron microscope at 10,000× magnification. 
     
     
         14 . The substrate of  claim 11 , wherein the phosphate coating has a weight of 0.5 to 4 g/m 2  as measured by the weigh-strip-weigh method. 
     
     
         15 . The substrate of  claim 11 , wherein the phosphate coating has a weight of 4.4 g/m 2  or less and an exposed adhesion value of 6 or greater. 
     
     
         16 . The substrate of  claim 11 , wherein the D 90  particle size is measured from a sample of the activating rinse that has been sonicated. 
     
     
         17 . The substrate of  claim 11 , further comprising an electrodeposited layer. 
     
     
         18 . A method of treating a substrate comprising:
 a) contacting at least a portion of a surface of the substrate with an activating rinse comprising a dispersion of metal phosphate particles having a D 90  particle size of no greater than 10 μm, wherein the metal phosphate comprises divalent or trivalent metals or combinations thereof; and   b) contacting at least a portion of the surface that has been contacted with the activating rinse with a pretreatment composition comprising zinc ions and phosphate ions, wherein the pretreatment composition is substantially free of nickel.   
     
     
         19 . The method of  claim 18 , wherein the (b) contacting comprises immersing the substrate in a bath comprising the pretreatment composition, wherein the bath temperature is 20° C. to 60° C. 
     
     
         20 . The method of  claim 18 , wherein the metal of the metal sulfate salt comprises nickel, copper, zinc, iron, magnesium, cobalt, aluminum or combinations thereof. 
     
     
         21 . The method of  claim 18 , wherein the metal of the metal sulfate salt comprises nickel, cobalt or combinations thereof. 
     
     
         22 . The method of  claim 18 , wherein the activating rinse further comprises a metal sulfate salt. 
     
     
         23 . The substrate of  claim 18 , wherein the D 90  particle size is measured from a sample of the activating rinse that has been sonicated.