Trivalent chromium electroplating solution and an electroplating process with the solution

Abstract

A trivalent chromium electroplating solution in accordance with the present invention contains at least one trivalent chromium salt for electroplating a chromium coating layer on a workpiece. By using the low toxic trivalent chromium to substitute highly toxic hexavalent chromium, an electroplating process of the present trivalent chromium electroplating solution has less pollution.

1 . A trivalent chromium electroplating solution comprising an aqueous solution added with trivalent chromium salt, a complex agent, conductive salt, a buffering agent, and an additive,
 wherein the additive is a mixture of ammonium bromide, sodium bromide, and potassium bromide.   
     
     
         2 . The trivalent chromium electroplating solution as claimed in  claim 1 , wherein the additive is of 0.01 to 0.25 mole/L in the trivalent chromium electroplating solution. 
     
     
         3 . The trivalent chromium electroplating solution as claimed in  claim 1 , wherein the buffering agent is a mixture comprising boric acid, aluminum salt, dissolvable salts of boric acid, and aluminum salt; and
 the boric acid and the dissolvable salt are of 0.1-0.8 mole/L in the trivalent chromium electroplating solution.   
     
     
         4 . The trivalent chromium electroplating solution as claimed in  claim 3 , wherein the aluminum salt is selected from the group consisting of aluminum chloride, aluminum sulfate, and hydrates of aluminum chloride and aluminum sulfate; and
 the aluminum salt and the hydrates of the aluminum chloride and aluminum sulfate are of 0.1-0.6 mole/L in the trivalent chromium electroplating solution.   
     
     
         5 . The trivalent chromium electroplating solution as claimed in  claim 1 , wherein the complex agent is selected from the group consisting of urea (carbamide), glycine (aminoacetic acid), formic acid, dissoluble salts of acids, and dissoluble salts of urea. 
     
     
         6 . The trivalent chromium electroplating solution as claimed in  claim 5 , wherein the urea and a dissoluble salt of the urea are of 0.2-4.2 mole/L in the trivalent chromium electroplating solution. 
     
     
         7 . The trivalent chromium electroplating solution as claimed in  claim 5 , wherein the glycine and a dissoluble salt of glycine are of 0.1-2.8 mole/L in the trivalent chromium electroplating solution. 
     
     
         8 . The trivalent chromium electroplating solution as claimed in  claim 5 , wherein hydroxyacetic acid and/or a dissoluble salt of hydroxyacetic acid are of 0.1-2.8 mole/L in the trivalent chromium electroplating solution. 
     
     
         9 . The trivalent chromium electroplating solution as claimed in  claim 5 , wherein the formic acid and a dissoluble salt of formic acid are of 0.1-1.4 mole/L in the trivalent chromium electroplating solution. 
     
     
         10 . The trivalent chromium electroplating solution as claimed in  claim 1 , wherein the conductive salt is a mixture having at least two components selected from the group consisting of ammonium chloride, sodium chloride, potassium chloride, magnesium chloride, ammonium sulfate, sodium sulfate, potassium sulfate, and magnesium sulfate. 
     
     
         11 . The trivalent chromium electroplating solution as claimed in  claim 10 , wherein the conductive salt is of 1.0-3.0 mole/L in the trivalent chromium electroplating solution. 
     
     
         12 . The trivalent chromium electroplating solution as claimed in  claim 1 , wherein the trivalent chromium salt is selected from the group consisting of chromium chloride, chromium sulfate, and hydrates of the foregoing components; and
 the trivalent chromium salt and a hydrate of the trivalent chromium salt are of 0.2-1.4 mole/L in the trivalent chromium electroplating solution.   
     
     
         13 . An electroplating process for using a trivalent chromium electroplating solution comprising:
 (a) degreasing, wherein a prepared workpiece is degreased with a degreasing agent to remove oil and dirt from the surface of the workpiece;   (b) washing, wherein the prepared workpiece is washed to remove the degreasing agent and to keep the cleaned surface of the workpiece;   (c) surface activating, wherein the workpiece is dipped into one of acid and alkaline solution to activate the surface by adding oxidant or providing electricity so as to enhance the binding efficiency of the surface of the workpiece;   (d) trivalent chromium electroplating, wherein the workpiece, auxiliary electrodes, and the trivalent chromium electroplating solution are set in a tank and a fixed current is applied across between the workpiece and auxiliary electrodes by an additional power supply to start electroplating operation; and   (e) drying.   
     
     
         14 . The electroplating process as claimed in  claim 13 , wherein the auxiliary electrodes are made of material selected from the group comprising plantized titanium mesh, titanium plate, platinum, graphite, and stainless steel. 
     
     
         15 . The electroplating process as claimed in  claim 13 , wherein the fixed current provided by the additional power supply has a range from 5 to 95 ampere per square decimeter. 
     
     
         16 . The operational method as claimed in  claim 13 , wherein the temperature for a surface treatment of the workpiece is in a range of 1 to 60° C. 
     
     
         17 . The electroplating process as claimed in  claim 13 , wherein the trivalent chromium electroplating solution comprises an aqua solution added with trivalent chromium salt, a complex agent, conductive salt, a buffering agent, and an additive,
 wherein the additive is a mixture of ammonium bromide, sodium bromide and potassium bromide.   
     
     
         18 . The electroplating process as claimed in  claim 17 , wherein the trivalent chromium salt is selected from the group consisting of chromium chloride, chromium sulfate, and hydrates of the foregoing components; and
 the trivalent chromium salt and a hydrate of the trivalent chromium salt are of 0.2-1.4 mole/L in the trivalent chromium electroplating solution.   
     
     
         19 . The trivalent chromium electroplating solution as claimed in  claim 1 , wherein the buffering agent is a mixture comprising boric acid, aluminum salt, dissolvable salts of boric acid and aluminum salt; and
 one of the boric acid and the dissolvable salt is of 0.1-0.8 mole/L in the trivalent chromium electroplating solution.   
     
     
         20 . The trivalent chromium electroplating solution as claimed in  claim 3 , wherein the aluminum salt is selected from the group consisting of aluminum chloride, aluminum sulfate, and hydrates of aluminum chloride and aluminum sulfate; and
 one of the aluminum salt and the hydrates of the aluminum chloride and aluminum sulfate is of 0.1-0.6 mole/L in the trivalent chromium electroplating solution.   
     
     
         21 . The trivalent chromium electroplating solution as claimed in  claim 5 , wherein one of the urea and a dissoluble salt of the urea is of 0.2-4.2 mole/L in the trivalent chromium electroplating solution. 
     
     
         22 . The trivalent chromium electroplating solution as claimed in  claim 5 , wherein one of the glycine and a dissoluble salt of glycine is of 0.1-2.8 mole/L in the trivalent chromium electroplating solution. 
     
     
         23 . The trivalent chromium electroplating solution as claimed in  claim 5 , wherein one of the formic acid and a dissoluble salt of formic acid is of 0.1-1.4 mole/L in the trivalent chromium electroplating solution. 
     
     
         24 . The trivalent chromium electroplating solution as claimed in  claim 1 , wherein the trivalent chromium salt is selected from the group consisting of chromium chloride, chromium sulfate, and hydrates of the foregoing components;
 one of the trivalent chromium salt and a hydrate of the trivalent chromium salt is of 0.2-1.4 mole/L in the trivalent chromium electroplating solution.   
     
     
         25 . The electroplating process as claimed in  claim 17 , wherein the trivalent chromium salt is selected from the group consisting of chromium chloride, chromium sulfate, and hydrates of the foregoing components;
 one of the trivalent chromium salt and a hydrate of the trivalent chromium salt is of 0.2-1.4 mole/L in the trivalent chromium electroplating solution.