Electrolytic solution, electrolysis case, electropolishing system, and electropolishing method using these

Abstract

In an electropolishing method passing large current, an electrolytic solution is given a viscosity by reacting an organic acid (a phosphoric acid solution or a mixed solution of phosphoric acid and sulfuric acid) with a silicon dioxide as a gelling agent, the electrolytic solution is continuously introduced to an electrolysis case and concurrently the first introduced electrolytic solution is discharged to progress the electropolishing. The electrolysis case has a cathode at a specific height from a lower open end of a frame in a specific size and depth, an introduction port on the cathode for introducing the electrolytic solution with specific viscosity, and a discharge port for discharging the solution from the frame. It is possible to shorten the distance of the cathode in the electrolysis case from the open end corresponding to the work-piece surface, and control the resistant of the electrolytic solution, so that the large current can be passed and the operation time can be reduced.

1 . An electrolytic solution given a specific viscosity by reacting inorganic acid with gelling agent. 
     
     
         2 . The electrolytic solution according to  claim 1 , wherein
 the inorganic acid is phosphoric acid or a mixed solution of the phosphoric acid and sulfuric acid, and   the gelling agent is silicon dioxide.   
     
     
         3 . The electrolytic solution according to  claim 2 , comprising:
 500 mL/L to 1000 mL/L of 85% phosphoric acid;   0 mL/L to 500 mL/L of 98% sulfuric acid;   0 mL/L to 500 mL/L of water; and   100 g/L to 200 g/L of silicon dioxide.   
     
     
         4 . The electrolytic solution according to  claim 3 , further comprising 0.001% to 0.01% of surface active agent. 
     
     
         5 . An electrolysis case comprising:
 a case frame;   a cathode placed at a specific height from a lower open end of the case frame;   an introduction port for introducing an electrolytic solution with a specific viscosity into a space between a work-piece at the lower open end and the cathode; and,   a discharge port for discharging the electrolytic solution introduced in the case frame from the case frame.   
     
     
         6 . The electrolysis case according to  claim 5 , wherein
 the cathode is made of a net,   the introduction port introduces the electrolytic solution with the specific viscosity into the space between the workpiece at the lower open end and the cathode through a guide pipe, the guide pipe provided with small holes facing to the meshes of the net and arranged along the net, and   the discharge port uses the mesh.   
     
     
         7 . The electrolysis case according to  claim 6 , wherein
 the space between the lower open end of the case frame and the cathode is filled with a holding member for holding the electrolytic solution with the specific viscosity.   
     
     
         8 . An electropolishing system comprising:
 an electrolysis case according to  claim 5 ;
 an electrolytic solution tank for holding the electrolytic solution; 
   a pump for pumping out the electrolytic solution from the electrolytic solution tank at a specific discharge rate;   a flow control valve for controlling the flow rate of the pumped-out electrolytic solution at a specific flow rate per unit volume of the electrolysis case, and then feeding the electrolytic solution to the introduction port; and   a direct current source for applying negative voltage on the cathode of the electrolysis case and positive voltage on the work.   
     
     
         9 . An electropolishing method comprising steps of:
 placing a bottom end of a case frame of an electrolysis case provided with the cathode at a specific height from a lower open end of the case frame so as to face a surface of a work-piece;   continuously introducing an electrolytic solution with a specific viscosity to a space between the work-piece and the cathode, while discharging the prior introduced electrolytic solution;   passing a specific current by applying a specific positive voltage on the work and a specific negative voltage on the cathode; and   electropolishing an object area on the work-piece by moving a frame position on the work-piece.   
     
     
         10 . The electropolishing method according to  claim 9 , wherein
 the step of introducing the electrolytic solution to the space between the work-piece and the cathode is done at a specific flow rate per unit volume of the space between the work and the cathode.   
     
     
         11 . An electropolishing system comprising:
 an electrolysis case according to  claim 6 ;
 an electrolytic solution tank for holding the electrolytic solution; 
   a pump for pumping out the electrolytic solution from the electrolytic solution tank at a specific discharge rate;   a flow control valve for controlling the flow rate of the pumped-out electrolytic solution at a specific flow rate per unit volume of the electrolysis case, and then feeding the electrolytic solution to the introduction port; and
 a direct current source for applying negative voltage on the cathode of the electrolysis case and positive voltage on the work. 
   
     
     
         12 . An electropolishing system comprising:
 an electrolysis case according to  claim 7 ;
 an electrolytic solution tank for holding the electrolytic solution; 
   a pump for pumping out the electrolytic solution from the electrolytic solution tank at a specific discharge rate;   a flow control valve for controlling the flow rate of the pumped-out electrolytic solution at a specific flow rate per unit volume of the electrolysis case, and then feeding the electrolytic solution to the introduction port; and
 a direct current source for applying negative voltage on the cathode of the electrolysis case and positive voltage on the work.