Trivalent chromium plating solution and plating method using the same

Abstract

Provided is hard trivalent chromium plating solution having improved covering power. The trivalent chromium plating solution comprises a trivalent chromium compound comprising a compound of formula (1) below; wherein Cr 2 (SO 4 ) n (OH) 6-2n ( n<3)   (1).

1 . A trivalent chromium plating solution comprising:
 a trivalent chromium compound comprising a compound of formula (1) below;
   wherein Cr 2 (SO 4 ) n (OH) 6-2n  ( n< 3)   (1).
 
   
     
     
         2 . The plating solution of  claim 1 , wherein the plating solution further comprising:
 a complexing agent suppressing a polymerization reaction of the trivalent chromium compound in the plating solution;   a conductivity agent increasing electrical conductivity of trivalent chromium ions;   a buffer agent stabilizing a hydrogen ion index of the plating solution;   a plating activating agent increasing adhesive power and capability of forming a plated layer;   a wetting agent removing a pitting phenomenon which occurs on a plated surface; and   a hydrogen ion index adjusting agent adjusting the hydrogen ion index of the plating solution,   
     
     
         3 . The plating solution of  claim 1 , wherein the trivalent chromium compound is added in an amount of 0.4 to 1.3 mol/L. 
     
     
         4 . The plating solution of  claim 2 , wherein the complexing agent is at least one selected from the group consisted of a formic acid, alkali metal formate and ammonium formate and is added in an amount of 0.05 to 2 mol/L. 
     
     
         5 . The plating solution of  claim 3 , wherein the conductivity agent is sodium sulfate and is added in an amount of 0.1 to 0.8 mol/L. 
     
     
         6 . The plating solution of  claim 4 , wherein the buffer agent comprises boric acid and aluminium sulfate, wherein the boric acid is added in an amount of 0.08 to 1 mol/L, and the aluminium sulfate is added in an amount of 0.05 to 0.2 mol/L. 
     
     
         7 . The plating solution of  claim 5 , wherein the plating activating agent is carbamide and is added in an amount of 0.1 to 1.2 mol/L. 
     
     
         8 . The plating solution of  claim 6 , wherein the wetting agent is sodium lauryl sulfate and is added in an amount of 0.01 to 1 g/L. 
     
     
         9 . The plating solution of  claim 7 , wherein the hydrogen ion index adjusting agent may be at least one selected from the group consisted of a sulfuric acid (H 2 SO 4 ), sodium hydroxide (NaOH), and sodium carbonate (Na 2 CO 3 ). 
     
     
         10 . The plating solution of  claim 1 , having a hydrogen ion index of 1.1 to 3.5. 
     
     
         11 . A plating method comprising:
 preparing a trivalent chromium plating solution in a plating bath;   immersing an object to be plated in the trivalent chromium plating solution; and   applying a negative potential to the object to be plated and applying a positive potential to an insoluble anode after installing the insoluble anode in the plating bath,   wherein the trivalent chromium plating solution comprises:
 a trivalent chromium compound comprising a compound of formula (1) below; 
 a complexing agent suppressing a polymerization reaction of the trivalent chromium compound in the plating solution; 
 a conductivity agent increasing electrical conductivity of trivalent chromium ions; 
 a buffer agent stabilizing a hydrogen ion index of the plating solution; 
 a plating activating additive increasing adhesive power and capability of forming a plated layer; 
 a wetting agent removing a pitting phenomenon which occurs on a plated surface; and 
 a hydrogen ion index adjusting agent adjusting the hydrogen ion index of the plating solution,
   wherein Cr 2 (SO 4 ) n (OH) 6-2n  ( n< 3)   (1).
 
 
   
     
     
         12 . The plating method of  claim 11 , wherein the insoluble anode is a titanium-manganese dioxide anode (TMDA), a dimensionally stable anode (DSA) having iridium oxide (IrO 2 ) or ruthenium oxide (RuO 2 ) formed on a porous titanium plate, or a platinized titanium anode. 
     
     
         13 . The plating method of  claim 11 , wherein in the applying of the negative potential and the applying of the positive potential, a current density is 15 to 30 A/dm 2 . 
     
     
         14 . The plating method of  claim 11 , wherein the plating bath is maintained at a temperature of 20 to 60° C.