Aqueous stripping composition for electrolytically removing a metal deposit from a substrate

Abstract

The present invention relates to an aqueous stripping composition for electrolytically removing a metal deposit from a substrate, the composition comprising(i) nitrate anions,(ii) one or more than one carboxylic acid and/or salts thereof, and(iii) one or more than one kind of halogen anions,wherein in the aqueous stripping composition (i) is the only nitrogen-containing species. The present invention furthermore relates to a respective use thereof and a respective method utilizing said aqueous stripping composition.

1 . An aqueous stripping composition for electrolytically removing a metal deposit from a substrate, the composition comprising
 (i) nitrate anions,   (ii) one or more than one carboxylic acid and/or salts thereof, and   (iii) one or more than one kind of halogen anions,   
       wherein in the aqueous stripping composition (i) is the only nitrogen-containing species. 
     
     
         2 . The composition of  claim 1 , wherein (i) has a concentration ranging from 10 mmol/L to 2600 mmol/L, based on the total volume of the aqueous stripping composition, preferably from 100 mmol/L to 2000 mmol/L, more preferably from 200 mmol/L to 1600 mmol/L, even more preferably from 300 mmol/L to 1400 mmol/L, yet even more preferably from 400 mmol/L to 1200 mmol/L, most preferably from 500 mmol/L to 900 mmol/L, yet most preferably from 550 mmol/L to 750 mmol/L. 
     
     
         3 . The composition of  claim 1 or 2 , wherein (ii) has a total concentration ranging from 25 mmol/L to 3000 mmol/L, based on the total volume of the aqueous stripping composition, preferably from 70 mmol/L to 2000 mmol/L, more preferably from 120 mmol/L to 1500 mmol/L, even more preferably from 230 mmol/L to 1000 mmol/L, yet even more preferably from 300 mmol/L to 900 mmol/L, most preferably from 370 mmol/L to 800 mmol/L, even most preferably from 450 mmol/L to 700 mmol/L. 
     
     
         4 . The composition of any one of  claims 1 to 3 , wherein (i) to (iii) has a molar ratio of 1 or more, based on the total concentration of (iii), preferably of 1.1 or more, more preferably of 1.3 or more, even more preferably of 1.5 or more, most preferably of 2 or more. 
     
     
         5 . The composition of any one of  claims 1 to 4 , wherein (ii) to (iii) have a molar ratio of 1 or more, based on the individual total concentration of (ii) and (iii), preferably of 1.3 or more, more preferably of 1.5 or more, even more preferably of 1.7 or more, most preferably of 1.8 or more. 
     
     
         6 . The composition of any one of  claims 1 to 5 , wherein (ii) comprises only monocarboxylic acids and/or salts thereof. 
     
     
         7 . The composition of any one of  claims 1 to 6 , wherein (ii) comprises two or more than two, preferably two, carboxylic acids and/or salts thereof. 
     
     
         8 . The composition of any one of  claims 1 to 7 , wherein (ii) comprises formic acid, acetic acid, and/or salts thereof, preferably acetic acid and/or salts thereof. 
     
     
         9 . The composition of any one of  claims 1 to 8 , wherein (ii) comprises at least one hydroxy carboxylic acid and/or salts thereof. 
     
     
         10 . The composition of  claim 9 , wherein (ii) comprises citric acid, gluconic acid, heptagluconic acid, and/or salts thereof, most preferably gluconic acid and/or salts thereof. 
     
     
         11 . The composition of any one of  claims 1 to 10 , wherein (ii) comprises
 (ii-a) a first mono-carboxylic acid and/or salts thereof, preferably a C1-C4 mono-carboxylic acid and/or salts thereof, more preferably formic acid, acetic acid, and/or salts thereof, most preferably acetic acid and/or salts thereof,   
       and additionally
 (ii-b) a second mono-carboxylic acid and/or salts thereof, preferably a C5-C14 mono-carboxylic acid and/or salts thereof, more preferably a C5-C14 hydroxy-monocarboxylic acid and/or salts thereof, most preferably gluconic acid, heptagluconic acid, and/or salts thereof. 
 
     
     
         12 . Use of an aqueous stripping composition as defined in anyone of  claims 1 to 11  for electrolytically removing partly or fully a metal deposit comprising palladium, copper, nickel, chromium, and/or alloys comprising at least one thereof from a substrate, wherein the substrate is different from the metal deposit. 
     
     
         13 . A method for removing partly or fully a metal deposit from a substrate, the method comprising the steps
 (a) providing as an anode the substrate comprising the metal deposit, the metal deposit comprising palladium, copper, nickel, chromium, and/or alloys comprising at least one thereof,   (b) providing an aqueous stripping composition comprising
 (i) nitrate anions, 
 (ii) one or more than one carboxylic acid and/or salts thereof, and 
 (iii) one or more than one kind of halogen anions, 
 wherein in the aqueous stripping composition (i) is the only nitrogen-containing species, 
   (c) providing at least one cathode,   (d) contacting the substrate with the aqueous stripping composition and applying an electrical current to the anode and the at least one cathode such that the metal deposit is partly or fully removed from the substrate,   
       wherein the substrate is different from the metal deposit. 
     
     
         14 . The method of  claim 13 , wherein the substrate comprises iron, preferably is a stainless-steel substrate. 
     
     
         15 . The method of  claim 13 or 14 , wherein at least one of palladium, copper, nickel, and chromium from the metal deposit is simultaneously deposited onto the at least one cathode, preferably the metal deposit comprises at least copper and during step (d) copper is simultaneously deposited onto the at least one cathode.