Anodizing Valve Metals By Controlled Power

Abstract

The present invention is directed to a method for anodizing valve metal structures to a target formation voltage with a controlled power source.

1 . A method for anodizing a valve metal anode to a target formation voltage, comprising the steps of: 
 a) providing the valve metal anode in an anodizing electrolyte;    b) interconnecting a power supply that generates an output from a source voltage and a source current to provide an output power;    c) subjecting the anode to the output power; and    d) regulating the power output so that the difference between the output power and a desired power value is adjusted toward zero until the target formation voltage is reached.    
   
   
       2 . The method of  claim 1  including turning off the power supply for a predetermined time between successive intervals of the anode being subjected to the output power.  
   
   
       3 . The method of  claim 1  including providing the output power applied to the anode based on one of the group consisting of constant power, an increasing linear power, a decreasing linear power, a linearly varied power within each pulse and between pulses—increasingly and/or decreasingly, a non-linearly varied power within each pulse and between pulses—increasingly and/or decreasingly, a varied increasing power and a varied decreasing power.  
   
   
       4 . The method of  claim 1  further comprising the step of turning off the current and holding the voltage for a period of time sufficient to allow the anodizing electrolyte to diffuse from the anode.  
   
   
       5 . The method of  claim 1  including providing the electrolyte having a conductivity of about 10 μS/cm to about 50,000 μS/cm at 40° C.  
   
   
       6 . The method of  claim 1  wherein the anodizing electrolyte comprises an aqueous solution of ethylene glycol or an aqueous solution of polyethylene glycol and H 3 PO 4 .  
   
   
       7 . The method of  claim 1  wherein the anode is a valve metal selected from the group consisting of tantalum, aluminum, niobium, titanium, zirconium, hafnium, and alloys thereof.  
   
   
       8 . The method of  claim 1  including pulsing the output power.  
   
   
       9 . The method of  claim 1  including forming the anode to over 200 volts.  
   
   
       10 . The method of  claim 1  including providing the output power at below 50 Watts.  
   
   
       11 . The method of  claim 1  including providing the output power at below 30 Watts.  
   
   
       12 . The method of  claim 1  including providing the output power at below 10 Watts.  
   
   
       13 . The method of  claim 1  including agitating the anodizing electrolyte.  
   
   
       14 . The method of  claim 1  further including the step of limiting the current applied to the anode.  
   
   
       15 . The method of  claim 1  including adjusting the output power by (a) measuring the source voltage and the source current to calculate a measured power level, (b) comparing the measured power level to a desired power level and (c) adjusting the source voltage and the source current so the measured output power is at or near the desired power level.  
   
   
       16 . An anodized valve metal structure characterized as having been anodized in an electrolyte to a target formation voltage by an anodization protocol that subjects the valve metal structure to an adjustable output power from a power supply, wherein the output power was constantly adjusted so that the difference between the output power and a desired power value approached zero until a target formation voltage was reached.  
   
   
       17 . The valve metal structure of  claim 16  wherein the valve metal structure was not subjected to a current for a predetermined time frame.  
   
   
       18 . The valve metal structure of  claim 16  wherein the output power is based on one of the group consisting of a constant power, an increasing linear power, a decreasing linear power, a linearly varied power within each pulse and between pulses—increasingly and/or decreasingly, a non-linearly varied power within each pulse and between pulses—increasingly and/or decreasingly, a varied increasing power and a varied decreasing power.  
   
   
       19 . The valve metal structure of  claim 16  wherein the electrolyte had a conductivity of about 10 μS/cm to about 50,000 μS/cm at 40° C.  
   
   
       20 . The valve metal structure of  claim 16  wherein the valve metal is selected from one of the group consisting of tantalum, aluminum, niobium, titanium, zirconium, hafnium, and alloys thereof.  
   
   
       21 . The valve metal structure of  claim 16  wherein the output power was pulsed.  
   
   
       22 . The valve metal structure of  claim 16  characterized as being anodized to over 200 V.  
   
   
       23 . The valve metal structure of  claim 16  wherein the anodizing electrolyte was agitated.  
   
   
       24 . The valve metal structure of  claim 16  wherein the output power was obtained by (a) measuring the source voltage and the source current to calculate a measure output power, (b) comparing the measured output power to a desired power level and (c) adjusting the source voltage and the source current so the measured output power is at or near the desired power level.