Apparatus and process to regenerate a trivalent chromium bath

Abstract

A process and apparatus for regenerating a plating bath comprising trivalent chromium cations (a trivalent chromium bath). The bath can be continuously, or more preferably, periodically with an ion exchange resin, preferably a cation exchange resin. A useful apparatus comprises a plating tank containing a trivalent chromium plating bath in communication with an ion exchange bed continuing ion exchange resin.

What is claimed is: 
     
       1. In the process to regenerate a plating bath comprising a plating tank having therein trivalent chromium cations and containing contaminating amounts of hexavalent chromium ion, which comprises the steps of contacting the bath with a cationic ion-exchange resin to regenerate the bath, and recycling the regenerated plating bath to the plating tank, the improvement which comprises the ion-exchange resin being substantially selective to exchange metal cations, and less selective for trivalent chromium cations than for hexavalent chromium cations, and the cationic exchange resin being substantially stable upon exposure to the plating bath. 
     
     
       2. The process of claim 1 further comprising the step of periodically regenerating the ion-exchange resin. 
     
     
       3. The process as recited in claim 1 further comprising the steps of: plating at least one article in a plating tank containing the trivalent chromium plating bath; and   passing the bath from the tank to a bed comprising a cationic exchange resin.   
     
     
       4. The process as recited in claim 1 wherein the bath is continuously contacted with the cationic exchange resin. 
     
     
       5. The process as recited in claim 1 wherein the bath is periodically contacted with the cationic exchange resin. 
     
     
       6. The process as recited in claim 1 wherein the cationic exchange resin is a polymer comprising a functionalized styrenic backbone. 
     
     
       7. The process as recited in claim 1 wherein the pH of the plating bath is from 1.0 to 5.0. .Iadd. 
     
     
       8.  A method for removing hexavalent chromium cations from a bath comprising trivalent chromium cations and hexavalent chromium cations comprising the step of contacting said bath with an ion exchange resin that selectively removes metallic cations including said hexavalent chromium cations, and wherein said resin is substantially stable upon exposure to said bath. .Iaddend..Iadd.9. The method of claim 8, wherein said bath further comprises metallic impurities. .Iaddend..Iadd.10. The method of claim 9, wherein said metallic impurities are removed from said bath by said ion exchange resin. .Iaddend..Iadd.11. The method of claim 8, wherein said ion exchange resin is a cation exchange resin. .Iaddend..Iadd.12. The method of claim 11, wherein said cation exchange resin selectively removes divalent metallic cations. .Iaddend..Iadd.13. The method of claim 8, wherein said bath is a plating bath. .Iaddend..Iadd.14. The method of claim 8, wherein said ion exchange resin is a polystyrene based cationic exchange resin having at least one acidic 
     
     
        functional group. .Iaddend..Iadd.15.  The method of claim 14, wherein said acidic functional group is an iminodiacetate functional group. 
     
     
        .Iaddend..Iadd.16.  The method of claim 8, wherein said ion exchange resin is a resin in the hydrogen or sodium ion form. .Iaddend..Iadd.17. The method of claim 8, further comprising the step of regenerating the resin with acid after said contacting step. .Iaddend..Iadd.18. A method for removing at least one metallic cation impurity from a bath comprising trivalent chromium cations comprising the step of contacting said bath with an ion exchange resin that selectively removes said metallic cation impurity, and wherein said resin is substantially stable upon exposure to said bath. .Iaddend..Iadd.19. The method of claim 18, wherein said metallic cation impurity is hexavalent chromium cations. .Iaddend..Iadd.20. The method of claim 18, wherein said metallic impurity comprises at least metallic impurity selected from the group consisting of zinc cations, copper cations, nickel cations, iron cations, lead cations, manganese cations, and cobalt cations. .Iaddend..Iadd.21. The method of claim 18, wherein said ion exchange resin is a cation exchange resin. .Iaddend..Iadd.22. The method of claim 18, wherein said ion exchange resin is a resin in the hydrogen or sodium ion form. .Iaddend..Iadd.23. The method of claim 18, further comprising the step of regenerating the resin 
     
     
        with acid after said contacting step. .Iaddend..Iadd.24.  A method for removing at least one metallic cation impurity from a bath comprising trivalent chromium cations comprising the step of contacting said bath with a cation exchange resin that is capable of selectively removing hexavalent chromium cations, and wherein said resin is substantially 
     
     
        stable upon exposure to said bath. .Iaddend..Iadd.25.  The method of claim 24, wherein said metallic cation impurity is hexavalent chromium cations. .Iaddend..Iadd.26. The method of claim 24, wherein said metallic impurity comprises at least metallic impurity selected from the group consisting of zinc cations, copper cations, nickel cations, iron cations, lead cations, manganese cations, and cobalt cations. .Iaddend..Iadd.27. The method of claim 24, wherein said bath is a plating bath. .Iaddend..Iadd.28. The method of claim 24, wherein said ion exchange resin is a polystyrene based cationic exchange resin having at least one acidic functional group. .Iaddend..Iadd.29. The method of claim 24, wherein said ion exchange resin is a resin in the hydrogen or sodium ion form. .Iaddend..Iadd.30. The method of claim 24, further comprising the step of regenerating the resin with acid after said contacting step. .Iaddend.