Accelerated sulfuric acid and boric sulfuric acid anodize process

Abstract

The process of anodizing aluminum or an aluminum alloy in an aqueous solution of about 60 g/L to about 100 g/L sulfuric acid and optionally about 0.1 g/L to about 10.7 g/L boric acid, maintained between a temperature of about 70 ° F. to about 90° F. An aluminum object is immersed in the acid bath, where it acts as an anode. A voltage of 6 V to 16 V is applied to the object at a current density, which varies with the alloy. The object is maintained in the anodizing conditions until an aluminum oxide coating is achieved with a weight of about 30 to about 800 mg/ft 2 .

What is claimed is:  
     
         1 . A method of anodizing an aluminum or aluminum alloy object comprising 
 maintaining an acid bath around the object of between about 60 g/L and about 100 g/L sulfuric acid and a temperature of between about 70° F. and about 90° F.;    applying a voltage of about 6 V to about 16 V across the object thereby providing a coating of aluminum oxide to the object; and    maintaining said voltage until the aluminum oxide has a coating weight of between about 30 mg/ft 2  and about 800 mg/ft 2 .    
     
     
         2 . The method of  claim 1 , wherein the acid bath further comprises between about 0.1 g/L and about 16.5 g/L boric acid.  
     
     
         3 . The method of  claim 1 , wherein the voltage is applied by ramping the voltage upward at a rate of between about 1 V/min and about 10 V/min.  
     
     
         4 . The method of  claim 1 , wherein the bath temperature is maintained between about 75° F. and about 85° F.  
     
     
         5 . The method of  claim 4 , wherein the bath temperature is maintained at about 80° F.  
     
     
         6 . The method of  claim 1 , wherein the sulfuric acid concentration of the bath is maintained between 75 g/L and 100 g/L.  
     
     
         7 . The method of  claim 6 , wherein the sulfuric acid concentration of the bath is maintained between 90 g/L and 100 g/L.  
     
     
         8 . The method of  claim 1 , further comprising the steps of degreasing, cleaning, and deoxidizing the aluminum object prior to the step of maintaining the acid bath around the object.  
     
     
         9 . The method of  claim 1 , further comprising the step of sealing the aluminum object after anodizing.  
     
     
         10 . A process for anodizing aluminum at an accelerated rate while maintaining fatigue resistance of the metal comprising 
 providing an anodizing bath of between about 60 g/L and about 100 g/L sulfuric acid and a temperature of between about 70° F. and about 90° F.;    immersing the object into the anodizing bath;    applying a voltage of about 6V to about 16V across the object thereby providing a coating of aluminum oxide to the object; and    maintaining said voltage for a period of about 5 to about 8 minutes.    
     
     
         11 . The process of  claim 10 , wherein the anodizing bath further comprises between about 0.1 g/L and about 10.7 g/L boric acid.  
     
     
         12 . The process of  claim 10 , wherein the voltage is applied by ramping the voltage upward at a rate of between about 1 V/min and about 10 V/min.  
     
     
         13 . An aluminum alloy article, anodized according to the process of  claim 1.