Method for anodizing aluminum-copper alloy

Abstract

An anodization method includes steps of providing an object formed of an aluminum-copper alloy, providing an anodizing bath comprising a basic silicate solution, providing an AC power supply including a first electrode and a second electrode, placing the first electrode in contact with the anodizing bath, connecting the second electrode to the object, placing the object in the anodizing bath, applying a voltage to the first and second electrodes to maintain a current density of about 10 mA/cm 2 or less to form an anodized coating on the object, removing the object from the bath, and sealing the anodized coating on the object.

1 . An anodization method comprising the steps of:
 providing an object formed of an aluminum-copper alloy;   providing an anodizing bath comprising a basic silicate solution;   providing an AC power supply including a first electrode and a second electrode;   placing the first electrode in contact with the anodizing bath;   connecting the second electrode to the object;   placing the object in the anodizing bath;   applying a voltage to the first and second electrodes to maintain a current density of about 10 mA/cm 2  or less to form an anodized coating on the object;   removing the object from the bath; and   sealing the anodized coating on the object.   
   
   
       2 . The anodization method of  claim 1  wherein said step of applying a voltage to the first and second electrodes comprises the step of applying a DC voltage having an AC component to the first and second electrodes. 
   
   
       3 . The anodization method of  claim 1  including the additional steps of:
 providing a DC power supply; and   connecting the DC power supply in series with the AC power supply;   and wherein said step of applying a voltage comprises the step of applying a DC voltage having an AC component to the first and second electrodes.   
   
   
       4 . The anodization method of  claim 2  wherein said step of applying a voltage having an AC component comprises the step of applying a voltage having a ratio of DC:AC components of about 5:1. 
   
   
       5 . The anodization method of  claim 2  including the additional step of chilling the anodizing bath to about 4° C. 
   
   
       6 . The anodization method of  claim 2  wherein said step of providing an object formed of an aluminum-copper alloy comprises the step of providing an object formed of aluminum-copper alloy plate. 
   
   
       7 . The anodization method of  claim 6  wherein said object formed of aluminum-alloy copper plate is a plate of series 2000 aluminum alloy. 
   
   
       8 . The anodization method of  claim 6  wherein said step of providing a plate of series 2000 aluminum alloy comprises the step of providing a plate formed from an alloy selected from the group consisting of AA2219, AA 2024 and AA2014. 
   
   
       9 . The anodization method of  claim 1  wherein said step of applying a voltage to the first and second electrodes to maintain a current density of about 10 mA/cm 2  or less to form an anodized coating on the object comprises the step of:
 increasing the voltage to maintain given current density of less than about 10 mA/cm 2  or less until the DC component of the voltage reaches about 320 V.   
   
   
       10 . The anodization method of  claim 1  wherein said applying a voltage to the first and second electrodes to maintain a current density of about 10 mA/cm 2  or less to form an anodized coating on the object comprises the steps of:
 increasing the voltage to maintain given current density of about 10 mA/cm 2  or less until the DC component of the voltage reaches about 300 V.   
   
   
       11 . The anodization method of  claim 1  wherein said step of sealing the anodized coating on the object comprises the step of coating the anodized coating with a para-p-xylylene polymer. 
   
   
       12 . The anodization method of  claim 11  wherein said para-p-xylylene polymer comprises Parylene HT. 
   
   
       13 . The anodization method of  claim 1  wherein said basic silicate solution comprises sodium silicate and has a pH of about 13. 
   
   
       14 . The anodization method of  claim 2  wherein aluminum-alloy copper comprises a series 2000 aluminum alloy. 
   
   
       15 . An anodization method comprising the steps of:
 providing an object formed of a 2000 series aluminum-copper alloy plate;   providing an anodizing bath comprising a sodium silicate solution and a potassium hydroxide solution having a pH of about 13;   providing an AC power supply including a first electrode and a second electrode;   placing the first electrode in the anodizing bath;   connecting the second electrode to the object;   placing the object in the anodizing bath;   cooling the anodizing bath to about 4° C.;   applying a DC voltage having an AC component to the first and second electrodes to maintain a current density of about 10 mA/cm 2  or less to form an anodized coating on the object;   removing the object from the bath; and   sealing the anodized coating on the object with a coating of Parylene HT.