Cosmetic defect reduction in anodized parts

Abstract

A system and process for reducing cosmetic defects such as black lines, and otherwise improving the final cosmetic appearance of anodized parts is disclosed. The process can include degreasing an aluminum or other metal part in a neutral to low alkaline solution having a mild detergent, chemically polishing the metal part with a specialized solution having one or more additives at an increased temperature for a reduced amount of time, and anodizing the metal part at a reduced voltage and for a reduced amount of time. An activating step can also be performed as part of the overall process. Tap water rinse, deionized water rinse, desmut, seal and bake procedures can also be performed on the metal part.

What is claimed is: 
     
         1 . A system adapted for the manufacture of anodized metal parts, the system comprising:
 a degreasing station adapted to degrease a separate metal part, said degreasing station having an alkaline solution with a mild detergent, wherein the alkaline solution has a pH that ranges from about 8 to 9;   a chemical polishing station adapted to chemically polish the degreased metal part at a temperature that ranges from about 105 to 115 degrees C. and for a period of about 15 to 30 seconds, said chemical polishing station having a chemical polishing solution with one or more specialized additives; and   an anodizing station adapted to anodize the chemically polished part for about 15 to 20 minutes and at a voltage that ranges from about 12.5 to 14.5 volts.   
     
     
         2 . The system of  claim 1 , wherein said system is adapted to be used on aluminum parts. 
     
     
         3 . The system of  claim 1 , further including:
 an activation station adapted to activate the metal part between the degreasing and chemically polishing steps.   
     
     
         4 . The system of  claim 1 , further including:
 one or more rinsing stations adapted to rinse the metal part with tap water after the part has been processed through the degreasing station.   
     
     
         5 . The system of  claim 1 , further including:
 one or more deionized rinsing stations adapted to rinse the metal part with deionized water after the part has been processed through the chemical polishing station.   
     
     
         6 . The system of  claim 1 , further including:
 a de-smutting station adapted to de-smut the anodized metal part in a nitric acid solution at a temperature of about 25 degrees C. and for a period of about 30 seconds.   
     
     
         7 . The system of  claim 1 , further including:
 a sealing station adapted to seal the anodized metal part using an acetate solution that is applied at a temperature that ranges from about 92 to 96 degrees C. and for a period of about 15 minutes.   
     
     
         8 . The system of  claim 1 , further including:
 a baking station adapted to bake the sealed metal part at a temperature that ranges from about 85-90 degrees C. and for a period of about 10 to 15 minutes.   
     
     
         9 . The system of  claim 1 , wherein the chemical polishing solution comprises by weight about 76-82% phosphoric acid, 18-20% sulfuric acid, 1-5% nitric acid, 1-1.5% corrosion inhibiting additive, 1-1.5% buffering agent, and a trace amount of fatty alcohol ehyoxyl compound. 
     
     
         10 . A method of manufacturing a metal part having an aesthetically pleasing surface finish, comprising:
 degreasing the metal part in an alkaline solution having a mild detergent, wherein the alkaline solution has a pH that ranges from about 8 to 9;   chemically polishing the degreased metal part at a temperature that ranges from about 105 to 115 degrees C. and for a period of about 15 to 30 seconds, wherein said chemical polishing is accomplished using a solution having one or more specialized additives; and   anodizing the chemically polished part for about 15 to 20 minutes and at a voltage that ranges from about 12.5 to 14.5 volts.   
     
     
         11 . The method of  claim 10 , wherein the metal part is aluminum. 
     
     
         12 . The method of  claim 10 , wherein the metal part is designed to be used for a computing device. 
     
     
         13 . The method of  claim 10 , further including the step of:
 activating the degreased metal part between the degreasing and chemically polishing steps.   
     
     
         14 . The method of  claim 10 , further including the step of:
 rinsing the degreased metal part with tap water after the degreasing step.   
     
     
         15 . The method of  claim 10 , further including the step of:
 rinsing the degreased metal part with deionized water after the chemically polishing step.   
     
     
         16 . The method of  claim 10 , further including the step of:
 de-smutting the anodized metal part in a nitric acid solution at a temperature of about 25 degrees C. and for a period of about 30 seconds.   
     
     
         17 . The method of  claim 10 , further including the steps of:
 sealing the anodized metal part using an acetate solution that is applied at a temperature that ranges from about 92 to 96 degrees C. and for a period of about 15 minutes; and   baking the sealed metal part at a temperature that ranges from about 85-90 degrees C. and for a period of about 10 to 15 minutes.   
     
     
         18 . A computing device, comprising:
 a processor;   one or more input components coupled to the processor;   one or more output components coupled to the processor; and   an outer housing including at least one anodized metal component, wherein said at least one anodized metal component has been degreased in an alkaline solution having mild detergent and a pH that ranges from about 8 to 9, chemically polished at a temperature that ranges from about 105 to 115 degrees C. and for a period of about 15 to 30 seconds using a solution having one or more specialized additives, and anodized for about 15 to 20 minutes and at a voltage that ranges from about 12.5 to 14.5 volts.   
     
     
         19 . The computing device of  claim 18 , wherein said at least one anodized metal component comprises anodized aluminum. 
     
     
         20 . The computing device of  claim 18 , wherein said outer housing includes one or more microstructure defects that are not made readily apparent as a result of the anodization process.