Electrolyte solution and electrochemical surface modification methods

Abstract

An aqueous electrolyte solution including a concentration of citric acid in the range of about 1.6 g/L to about 982 g/L and an effective concentration of ammonium bifluoride (ABF), and being substantially free of a strong acid. Methods of treating the surface of a non-ferrous metal workpiece include exposing the surface to a bath of an aqueous electrolyte solution including a concentration of citric acid less than or equal to about 300 g/L and a concentration of ammonium bifluoride greater than or equal to about 10 g/L, and having no more than about 3.35 g/L of a strong acid, controlling the temperature of the bath to be greater than or equal to about 54° C., connecting the workpiece to the anode of a DC power supply and immersing a cathode of the DC power supply in the bath, and applying a current across the bath.

1 - 14 . (canceled) 
     
     
         15 . An aqueous electrolyte solution consisting essentially of:
 a weak acid;   a fluoride salt; and   no more than 3.35 g/L of a strong acid.   
     
     
         16 . The aqueous electrolyte solution as claimed in  claim 15 , wherein the weak acid is a carboxylic acid. 
     
     
         17 . The aqueous electrolyte solution as claimed in  claim 16 , wherein the carboxylic acid is selected from the group consisting of acetic acid, butyric acid, capric acid, caproic acid, caprylic acid, citric acid, enanthic acid, formic acid, lauric acid, palmitic acid, pelargonic acid, propionic acid, stearic acid, valeric acid, and combinations thereof. 
     
     
         18 . The aqueous electrolyte solution of  claim 17 , wherein the carboxylic acid is citric acid. 
     
     
         19 . The aqueous electrolyte solution of  claim 15 , wherein the fluoride salt is selected from the group consisting of alkali metal fluorides, alkali earth metal fluorides, silicate etching compounds, and combinations thereof. 
     
     
         20 . The aqueous electrolyte solution of  claim 19 , wherein the fluoride salt is selected from among silicate etching compounds. 
     
     
         21 . The aqueous electrolyte solution of  claim 19 , wherein the fluoride salt is selected from among alkali metal fluorides. 
     
     
         22 . The aqueous electrolyte solution of  claim 19 , wherein the fluoride salt is selected from among alkali earth metal fluorides. 
     
     
         23 . The aqueous electrolyte solution of  claim 15 , wherein the fluoride salt is ammonium biflouride. 
     
     
         24 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the weak acid is in the range of from about 1.665 g/L to about 982 g/L. 
     
     
         25 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the fluoride salt is in the range of from about 2 g/L to about 360 g/L. 
     
     
         26 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the weak acid is in the range of from about 1.665 g/L to about 982 g/L and the concentration of the fluoride salt is in the range of from about 2 g/L to about 360 g/L. 
     
     
         27 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the weak acid is less than or equal to about 300 g/L. 
     
     
         28 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the fluoride salt is greater than or equal to about 10 g/L. 
     
     
         29 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the weak acid is less than or equal to about 300 g/L and the concentration of the fluoride salt is greater than or equal to about 10 g/L. 
     
     
         30 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the weak acid is less than or equal to about 600 g/L. 
     
     
         31 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the fluoride salt is greater than or equal to about 60 g/L. 
     
     
         32 . The aqueous electrolyte solution of  claim 15 , wherein the concentration of the weak acid is less than or equal to about 600 g/L and the concentration of the fluoride salt is greater than or equal to about 60 g/L. 
     
     
         33 . The aqueous electrolyte solution of  claim 18 , wherein the concentration of the weak acid is less than or equal to about 60 g/L.