Method and composition for metal finishing

Abstract

The present invention describes a composition and method to control dimensional growth during an anodizing process. Potassium permanganate has been discovered, when added to an anodizing solution containing at least one acid, to minimize dimensional change. This novel composition and method were found to be safer, quicker and less expensive than the conventional method of anodizing aluminum. In addition, the novel composition and method were found to have superior properties to aluminum anodized by the conventional method with respect to durability and corrosion resistance. In addition to anodizing, the novel solution described herein is capable of several other uses including the removal of organic and metal contaminants from solution, producing black electroless nickel on a substrate, producing a bright nickel coating on a substrate such as aluminum, and cleaning and activating aluminum for plating.

What is claimed is: 
     
         1 . A method of controlling dimensional growth in an anodizing process for aluminum, magnesium or alloys thereof comprising:
 providing an anodizing solution comprising:
 an acid solution formed from at least one acid selected from the group consisting of sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid, citric acid, boric acid, carboxylic acid, carbonic acid and combinations thereof diluted with deionized water; and 
 at least one oxidizing agent selected from the group consisting of potassium permanganate, sodium permanganate, hydrogen permanganate, lithium permanganate, sodium orthovanadate and combinations thereof; 
 wherein the at least one acid is present in the anodizing solution at a concentration of between about 10% w/v to about 20% w/v; 
 wherein the at least one oxidizing agent is present in the anodizing solution at a concentration of between about 0.01% w/v to about 0.05% w/v; 
   placing a metal substrate into the anodizing solution wherein the metal substrate is aluminum, magnesium or alloys thereof;   anodizing the metal substrate by applying a voltage for a specified amount of time; and   removing the anodized metal substrate from the anodizing solution.   
     
     
         2 . The method of  claim 1 , further comprising adding an amount of phosphoric acid to the anodizing solution. 
     
     
         3 . The method of  claim 2 , wherein the phosphoric acid is present in the anodizing solution at a concentration of about 0.04% w/v. 
     
     
         4 . The method of  claim 1 , further comprising cleaning the metal specimen prior to placement in the cooled solution. 
     
     
         5 . The method of  claim 1 , further comprising cooling the solution to room temperature prior to adding the oxidizing agent. 
     
     
         6 . The method of  claim 1 , further comprising cooling the anodizing solution to about 60° F. prior to placing the metal substrate in the anodizing solution. 
     
     
         7 . The method of  claim 1 , wherein the acid is sulfuric acid. 
     
     
         8 . The method of  claim 1 , wherein the oxidizing agent is potassium permanganate. 
     
     
         9 . The method of  claim 1 , wherein the voltage is applied at a temperature of between about 60° F. to about 75° F. 
     
     
         10 . The method of  claim 1 , wherein the voltage is direct current (DC). 
     
     
         11 . The method of  claim 10 , wherein the voltage is applied at about 15 V. 
     
     
         12 . The method of  claim 11 , wherein the voltage is held constant. 
     
     
         13 . The method of  claim 1 , wherein the metal substrate is anodized for between about 20 to about 30 minutes.