Electrodeposition baths containing a mixture of boron-containing compounds and chlorhexidine

Abstract

Disclosed is an electrodeposition bath comprising a mixture of (i) at least one boron-containing compounds and (ii) chlorhexidine for controlling the growth of microorganisms in the electrodeposition bath. The combination of (i) and (ii) at a low concentration provides better control of microbes than does either (i) or (ii) at higher concentrations.

1 . An improved process for electrodeposition of a coating, the improvement comprising use of an aqueous electrodeposition bath comprising: (a) an aqueous carrier having dispersed therein (i) a film forming binder comprising an epoxy-amine adduct and (ii) a blocked polyisocyanate crosslinking agent, (b) an effective amount (an amount sufficient to retard the growth of microorganisms in the electrodeposition bath) of a biocide that is a combination of (1) at least one boron-containing compound selected from boric acid, boric acid equivalents, or combinations thereof and (2) 1,6-bis [5-(p-chlorophenyl) biguanidino] hexane (chorhexidine), wherein the pH of the electrodeposition bath is 7 or less. 
     
     
         2 . The process of  claim 1 , wherein said boron-containing compound comprises boric acid salts, boric acid esters, boron oxide, and mixtures thereof. 
     
     
         3 . The process of  claim 1 , wherein said boron-containing compound comprises boric acid. 
     
     
         4 . The electrodeposition bath of  claim 1 , wherein the amount of boron-containing compound is present in an amount sufficient to provide an amount of boron in the range of from greater than 0.3% to less than 2.0% of the total weight of the bath. 
     
     
         5 . The electrodeposition bath of claim1, wherein the 1,6-bis [5-(p-chlorophenyl) biguanidino] hexane is present in the bath in an amount ranging from greater than 0.01% to 0.2% of the total weight of the bath. 
     
     
         6 . An improved process for depositing a coating by electrodeposition, wherein the improvement comprises use of an aqueous electrodeposition bath comprising: (a) an aqueous carrier having dispersed therein (i) a film forming binder comprising an epoxy-amine adduct and (ii) a blocked polyisocyanate crosslinking agent, (b) an effective amount (an amount sufficient to retard the growth of microorganisms in the electrodeposition bath) of a biocide that is a combination of (1) at least one boron-containing compound selected from boric acid, boric acid equivalents, or combinations thereof and (2) 1,6-bis [5-(p-chlorophenyl) biguanidino]hexane (chorhexidine), wherein the pH of the electrodeposition bath is greater than 7.