Ionic liquid for pickling stainless steel and method for pickling stainless steel by using same

Abstract

Disclosed are an ionic liquid for pickling a stainless steel capable of rapidly removing oxide scale from the stainless steel at room temperature without using nitric acid or hydrofluoric acid and a method for pickling a stainless steel by using the same. The method for pickling a stainless steel according to an embodiment includes performing electrolytic pickling treatment by immersing a stainless steel in a pickling solution including an ionic liquid, wherein the ionic liquid comprises at least one of an imidazolium cation, a betainium cation, a sulfonium cation, a piperidinium cation, a phosphonium cation, an ammonium cation, a pyridium cation, a pyrrolidinium cation, and a morpholinium cation, as a cationic functional group, and at least one of a halide anion, a sulfonate anion, an alkylsulfate anion, a phosphinate anion, a salicylate anion, a nitrate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, and a bistriflimide anion, as an anionic functional group.

1 . An ionic liquid for pickling a stainless steel comprising:
 at least one of an imidazolium cation, a betainium cation, a sulfonium cation, a piperidinium cation, a phosphonium cation, an ammonium cation, a pyridium cation, a pyrrolidinium cation, and a morpholinium cation, as a cationic functional group, and   at least one of a halide anion, a sulfonate anion, an alkylsulfate anion, a phosphinate anion, a salicylate anion, a nitrate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, and a bistriflimide anion, as an anionic functional group.   
     
     
         2 . The ionic liquid according to  claim 1 , wherein the ionic liquid is represented by one of the compounds (a) to (c) below: 
       
         
           
           
               
               
           
         
       
     
     
         3 . A method for pickling a stainless steel, the method comprising:
 performing electrolytic pickling treatment by immersing a stainless steel in a pickling solution including an ionic liquid,   wherein the ionic liquid comprises at least one of an imidazolium cation, a betainium cation, a sulfonium cation, a piperidinium cation, a phosphonium cation, an ammonium cation, a pyridium cation, a pyrrolidinium cation, and a morpholinium cation, as a cationic functional group, and   at least one of a halide anion, a sulfonate anion, an alkylsulfate anion, a phosphinate anion, a salicylate anion, a nitrate anion, a tetrafluoroborate anion, a hexafluorophosphate anion, and a bistriflimide anion, as an anionic functional group.   
     
     
         4 . The method according to  claim 3 , wherein the ionic liquid is represented by one of the compounds (a) to (c) below: 
       
         
           
           
               
               
           
         
       
     
     
         5 . The method according to  claim 3 , wherein the ionic liquid is contained in the pickling solution in a concentration of 2 M or less. 
     
     
         6 . The method according to  claim 3 , wherein the pickling solution is a solution prepared by adding an ionic liquid to a hydrochloric acid solution having a concentration of 1 M or less or a neutral solution including at least one of sodium chloride, potassium chloride, magnesium chloride, sodium sulfate, and potassium sulfate. 
     
     
         7 . The method according to  claim 3 , wherein a temperature of the pickling solution is from 15 to 25° C. 
     
     
         8 . The method according to  claim 3 , wherein the electrolytic pickling treatment is performed by applying a current density of 0.5 to 1.3 A/cm 2  while maintaining a surface potential of the stainless steel in the range of −1.5 to 1.5 V using an Ag/AgCl electrode as a reference electrode. 
     
     
         9 . The method according to  claim 3 , wherein a time taken to completely remove the oxide scale is 1 minute or less.