Bright rhodium electrodeposition

Abstract

Disclosed is an electroplating solution for obtaining bright white rhodium electrodeposits, said solution containing rhodium in the form of a soluble sulfate or phosphate compound, together with an excess quantity of sulfuric acid, phosphoric acid, or mixtures of the two; the improvement of which is the addition of one or more nitrogen-containing heterocyclic organic compounds, in which at least one nitrogen is incorporated into a six-membered aromatic ring.

1 . An electroplating solution for the deposition of rhodium; said solution containing rhodium in the form of a soluble sulfate or phosphate, together with an excess of sulfuric acid, phosphoric acid, or mixtures of the two; 
 the improvement of which comprises the addition of one or more nitrogen-containing heterocyclic organic compounds, in which at least one nitrogen is incorporated into a six-membered aromatic ring.    
   
   
       2 . The electroplating solution of  claim 1 , wherein rhodium is in the form of rhodium sulfate.  
   
   
       3 . The electroplating solution of  claim 1 , wherein the rhodium is in the form of rhodium phosphate.  
   
   
       4 . The electroplating solution of claims  1 ,  2  or  3 , wherein the electrolyte is sulfuric acid.  
   
   
       5 . The electroplating solution of claims  1 ,  2  or  3 , wherein the electrolyte is phosphoric acid.  
   
   
       6 . The electroplating solution of claims  1 ,  2  or  3 , wherein the electrolyte is a mixture of sulfuric and phosphoric acids.  
   
   
       7 . The electroplating solution of claims  1 ,  2  or  3 , wherein the nitrogen-containing heterocyclic organic compound is pyridine or a derivative thereof.  
   
   
       8 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is nicotinic acid.  
   
   
       9 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is isonicotinic acid.  
   
   
       10 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is nicotinamide.  
   
   
       11 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is pyridine 3-sulfonic acid.  
   
   
       12 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is 3-pyridylacrylic acid.  
   
   
       13 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is 2-aminopyridine.  
   
   
       14 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is 3-aminopyridine.  
   
   
       15 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is picoline.  
   
   
       16 . The electroplating solution of  claim 7 , wherein the nitrogen containing heterocyclic organic compound is picolinic acid.  
   
   
       17 . The electroplating solution of claims  1 ,  2  or  3 , wherein the nitrogen-containing heterocyclic organic compound is pyrimidine or a derivative thereof.  
   
   
       18 . The electroplating solution of  claim 17 , wherein the nitrogen containing heterocyclic organic compound is 2-aminopyrimidine.  
   
   
       19 . The electroplating solution of claims  1 ,  2  or  3 , wherein the nitrogen-containing heterocyclic organic compound is pyridazine or a derivative thereof.  
   
   
       20 . The electroplating solution of  claim 19 , wherein the nitrogen containing heterocyclic organic compound is 3,6-dihydroxypyridazine.  
   
   
       21 . The electroplating solution of claims  1 ,  2  or  3 , wherein the nitrogen-containing heterocyclic organic compound is pyrazine or a derivative thereof.  
   
   
       22 . The electroplating solution of  claim 21 , wherein the nitrogen containing heterocyclic organic compound is pyrazinamide.  
   
   
       23 . An electroplating process comprising the steps of: 
 (a) immersing a substrate in an electroplating solution containing rhodium in the form of a soluble sulfate or phosphate, together with an excess of sulfuric acid, phosphoric acid, or mixtures of the two; wherein the solution further comprises one or more nitrogen-containing heterocyclic organic compounds, in which at least one nitrogen is incorporated into a six-membered aromatic ring; and    (b) applying a cathodic current to the substrate for the purpose of obtaining a bright and white deposit of rhodium thereon.    
   
   
       24 . The electroplating process of  claim 23 , wherein rhodium is in the form of rhodium sulfate.  
   
   
       25 . The electroplating process of  claim 23 , wherein the rhodium is in the form of rhodium phosphate.  
   
   
       26 . The electroplating process of claims  23 ,  24  or  25 , wherein the electrolyte is sulfuric acid.  
   
   
       27 . The electroplating process of claims  23 ,  24  or  25 , wherein the electrolyte is phosphoric acid.  
   
   
       28 . The electroplating process of claims  23 ,  24  or  25 , wherein the electrolyte is a mixture of sulfuric and phosphoric acids.  
   
   
       29 . The electroplating process of claims  23 ,  24  or  25 , wherein the nitrogen-containing heterocyclic organic compound is pyridine or a derivative thereof.  
   
   
       30 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is nicotinic acid.  
   
   
       31 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is isonicotinic acid.  
   
   
       32 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is nicotinamide.  
   
   
       33 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is pyridine 3-sulfonic acid.  
   
   
       34 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is 3-pyridylacrylic acid.  
   
   
       35 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is 2-aminopyridine.  
   
   
       36 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is 3-aminopyridine.  
   
   
       37 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is picoline.  
   
   
       38 . The electroplating process of  claim 29 , wherein the nitrogen containing heterocyclic organic compound is picolinic acid.  
   
   
       39 . The electroplating process of claims  23 ,  24  or  25 , wherein the nitrogen-containing heterocyclic organic compound is pyrimidine or a derivative thereof.  
   
   
       40 . The electroplating process of  claim 39 , wherein the nitrogen containing heterocyclic organic compound is 2-aminopyrimidine.  
   
   
       41 . The electroplating process of claims  23 ,  24  or  25 , wherein the nitrogen-containing heterocyclic organic compound is pyridazine or a derivative thereof.  
   
   
       42 . The electroplating process of  claim 41 , wherein the nitrogen containing heterocyclic organic compound is 3,6-dihydroxypyridazine.  
   
   
       43 . The electroplating process of claims  23 ,  24  or  25 , wherein the nitrogen-containing heterocyclic organic compound is pyrazine or a derivative thereof.  
   
   
       44 . The electroplating process of  claim 43 , wherein the nitrogen containing heterocyclic organic compound is pyrazinamide.