Methods and Compositions for Acid Treatment of a Metal Surface

Abstract

The invention relates to compositions and methods that are useful in etching a metal surface. In particular, the invention relates to novel acid compositions and methods of using such compositions in etching a metal surface, preferably an aluminum surface prior to anodizing to dissolve impurities, imperfections, scale, and oxide. The compositions are effective in maintaining their etching capacity and in removing smut produced by the etching of a surface as well as in general cleaning.

What is claimed is: 
     
         1 . A method of etching aluminum, said method comprising contacting said aluminum with a composition consisting essentially of:
 (a) about 20 to about 80 grams per liter of ammonium bifluoride;   (b) a surfactant; and   (c) water.   
     
     
         2 . The method according to  claim 1 , wherein said etching is performed at a temperature of about 100 to about 125° F. 
     
     
         3 . The method according to  claim 1 , wherein said etching is performed at a temperature of about 115° F. 
     
     
         4 . The method according to  claim 1 , wherein said etching is performed without bath cooling. 
     
     
         5 . The method according to  claim 1 , wherein said etching is performed in about 0.5 to about 10 minutes. 
     
     
         6 . The method according to  claim 5 , wherein said etching is performed in about 1 to about 3 minutes. 
     
     
         7 . The method according to  claim 1 , wherein said etching is performed at a pH of about 2 to about 5. 
     
     
         8 . The method according to  claim 1 , further comprising rinsing the etched aluminum. 
     
     
         9 . The method according to  claim 1 , wherein said aluminum is an aluminum alloy. 
     
     
         10 . The method according to  claim 1 , wherein the etched aluminum is resistant to pitting. 
     
     
         11 . The method according to  claim 1 , wherein the etched aluminum has a uniform matte finish when analyzed using a reflectometer at a 60° angle. 
     
     
         12 . The method according to  claim 1 , wherein extrusion lines on said etched aluminum are removed or minimized 
     
     
         13 . The method according to  claim 1 , which results in a significant reduction of waste products from the aluminum etching process. 
     
     
         14 . The method according to  claim 1 , which results in a reduction of water consumption in the aluminum etching process. 
     
     
         15 . The method according to  claim 1 , wherein said etching removes about 0.5 to 1.5 gr/ft 2  of aluminum. 
     
     
         16 . The method according to  claim 1 , wherein said composition further consists essentially of a grain refiner. 
     
     
         17 . The method according to  claim 1 , wherein said composition further consists essentially of an organic acid. 
     
     
         18 . The method according to  claim 1 , wherein said composition further consists essentially of an inorganic acid. 
     
     
         19 . A method of etching aluminum, said method comprising contacting said aluminum with a composition consisting of:
 (a) about 20 to about 80 grams per liter of ammonium bifluoride;   (b) a surfactant; and   (c) water.   
     
     
         20 . The method according to  claim 19 , wherein said etching is performed at a temperature of about 100 to about 125° F. 
     
     
         21 . The method according to  claim 19 , wherein said etching is performed at a temperature of about 115° F. 
     
     
         22 . The method according to  claim 19 , wherein said etching is performed without bath cooling. 
     
     
         23 . The method according to  claim 19 , wherein said etching removes about 0.5 to 1.5 gr/ft 2  of aluminum.