Processes and systems for formation of high voltage, anodic oxide on a valve metal anode

Abstract

Processes and systems for formation of high voltage, anodic oxide on a valve metal anode. The processes generally includes immersing a valve metal anode in an electrolyte forming bath comprised of a formation electrolyte, performing an anodization step; and maintaining or regulating the temperature of the formation electrolyte accurately at a temperature at or below 40° C. during the anodization step. The anodization firstly under constant current until a target potential is reached and secondly under constant potential at the target potential until the current falls below a predetermined termination current level. The systems generally include a tank configured to receive one or more anodes in an electrolyte forming bath comprised of a formation electrolyte; and a subsystem for cooling and maintaining the formation electrolyte at the desire processing temperature. The systems may further include electronic controls for monitoring and adjusting system or process parameters.

1 . A process for forming a high voltage, anodic oxide on a valve metal anode, comprising: 
 immersing a valve metal anode in an electrolyte forming bath comprising a formation electrolyte,    performing an anodization step; and    maintaining the temperature of the formation electrolyte in the forming bath accurately at a temperature at or below 40° C. during performance of the anodization step.    
   
   
       2 . A process for forming a high voltage, anodic oxide on a valve metal anode, comprising: 
 immersing a valve metal anode in an electrolyte forming bath comprising a formation electrolyte,    performing an anodization step under a constant current until a target potential is reached and then at the target potential until the current falls below a predetermined termination current level; and    maintaining the temperature of the formation electrolyte in the forming bath accurately at a temperature at or below 40° C. during performance of the anodization step.    
   
   
       3 . A process for forming a high voltage, anodic oxide on a valve metal anode, comprising: 
 immersing a valve metal anode in an electrolyte forming bath comprising a formation electrolyte,    performing an anodization step under a constant current until a target potential is reached and then at the target potential until the current falls below a predetermined termination current level;    circulating a flow of formation electrolyte from the forming bath through heat exchanger to provide a cooled flow of formation electrolyte; and    maintaining the temperature of the formation electrolyte in the forming bath accurately at a temperature at or below 40° C. during performance of the anodization step with the introduction of the cooled flow of formation electrolyte into the forming bath.    
   
   
       4 . A process for forming a high voltage, anodic oxide on a valve metal anode, comprising: 
 providing an electrolyte forming tank configured to receive one or more anodes, the tank containing an electrolyte forming bath comprising a formation electrolyte;    providing an electrolyte circulation subsystem for circulating and cooling the formation electrolyte;    immersing one or more anodes in the formation electrolyte;    circulating formation electrolyte from the forming bath through the circulation subsystem to provide a cooled flow of formation electrolyte;    applying an electrical potential to the one or more anodes, the electrical potential being ramped up to a target voltage under constant current until a target potential is reached;    continuing application of the electrical potential to the one or more anodes at the target potential until the current falls below a predetermined termination current level;    regulating the flow rate and temperature of the cooled flow of formation electrolyte so that the temperature of the formation electrolyte in the forming tank is accurately, maintained at a temperature at or below 40° C. during application of the electrical potential.    
   
   
       5 . A process according to  claim 4 , wherein the tank is further configured with a plurality of anode formation slots and wherein at least one anode is immersed in at least one of the plurality of anode formation slots.  
   
   
       6 . A process according to  claim 1 , wherein the temperature of the formation electrolyte is maintained accurately at or below 30° C.  
   
   
       7 . A process according to  claim 1 , wherein the temperature of the formation electrolyte is maintained accurately at or below 20° C.  
   
   
       8 . A process according to  claim 1 , wherein the temperature of the formation electrolyte is maintained accurately at a temperature at or below 10° C.  
   
   
       9 . A process according to  claim 1 , wherein the temperature of the formation electrolyte is maintained at a temperature between or below 10°-40° C.  
   
   
       10 . A process according to  claim 1 , wherein the temperature of the formation electrolyte is maintained at a temperature between 0°-40° C.  
   
   
       11 . A process according to  claim 1 , further comprising: 
 removing the anode from the electrolyte forming bath;    heat treating the anode;    re-immersing the anode in the formation electrolyte; and    performing a second anodization step while maintaining the temperature of the formation electrolyte in the forming bath accurately at a temperature at or below 40° C. during performance of the second anodization step.    
   
   
       12 . A process according to  claim 4 , further comprising: 
 removing the one or more anodes from the electrolyte forming bath;    heat treating the one or more anodes;    re-immersing the one or more anodes in the formation electrolyte;    circulating formation electrolyte from the forming bath through the circulation subsystem to provide a cooled flow of formation electrolyte;    applying an electrical potential to the one or more anodes, the electrical potential being ramped up to a target voltage under constant current until a target potential;    continuing application of the electrical potential at the target potential until the current falls below a predetermined termination current level; and    regulating the flow rate and temperature of the cooled flow of formation electrolyte so that the temperature of the formation electrolyte in the forming tank is accurately maintained at a temperature at or below 40° C. during the application of electrical potential.    
   
   
       13 . A process according to  claim 1 , wherein the anode is a tantalum anode.  
   
   
       14 . A tantalum anode formed by a process according to any one of claims  1 ,  2 ,  3  or  4 .  
   
   
       15 . An electrolytic bath system comprising; 
 a tank configured to receive one or more anodes, the tank containing an electrolyte forming bath comprising a formation electrolyte, the tank being configured with an inlet and an outlet;    an electrolyte circulation subsystem connected in flow through communication with the tank, the subsystem being configured to receive a flow of electrolyte from the outlet, to lower the temperature of the flow of electrolyte, and to return the flow of electrolyte to the inlet.    
   
   
       16 . A electrolytic bath system, comprising 
 a tank having a lower level and an upper level in flow-through communication with the lower level, the lower level having an inlet configured to receive a flow of electrolyte into the tank, the upper level having an outlet configured to discharge a flow of electrolyte from the tank, the upper level being configured with a plurality of anode formation slots, the slots being sized to receive at least one anode, the slots each having an opening through which electrolyte flows from the lower level into the upper level;    an electrolyte circulation subsystem, the subsystem being connected to the inlet and the outlet.    
   
   
       17 . A bath system according to  claim 15 , wherein the electrolyte circulation subsystem comprises a heat exchanger coupled to a refrigeration unit and at least one pump for circulating electrolyte between the tank and the circulation subsystem.  
   
   
       18 . A bath system according to  claim 15 , wherein the electrolyte circulation subsystem comprises: a heat exchanger; a refrigeration unit coupled to the heat exchanger; at least one pump for circulating electrolyte between the tank and the circulation subsystem; and at least one pump or blower for circulating a cooling fluid through the refrigeration unit.  
   
   
       19 . A bath system according to  claim 15 , wherein the tank is an enclosed housing configured with a lid and the system further comprises a vacuum unit for inducing reduced pressure within the tank.  
   
   
       20 . A bath system according to  claim 15 , wherein the system further comprises a vacuum unit configured to create a vacuum within the tank.  
   
   
       21 . A bath system according to  claim 15 , wherein the system further comprises a vacuum unit configured to create a pressure differential capable of forcing electrolyte into pore or interstices of anodes.  
   
   
       22 . A bath system according to  claim 15 , wherein the tank further comprises a plurality of fins or a plurality of fan for dissipating heat.  
   
   
       23 . A bath system according to  claim 15 , wherein the system further comprises a electronic controller.  
   
   
       24 . A bath system according to  claim 15 , wherein the system further comprises a electronic controller, the controller being equipped and configured to regulate either electrolyte circulation rate or heat transfer rate or both.  
   
   
       25 . A bath system according to  claim 15 , wherein the system further comprises a electronic controller, the controller being equipped and configured to regulate electrolyte circulation rate, heat transfer, and cooling fluid circulation rate.  
   
   
       26 . The electrolytic bath system, comprising: 
 a tank containing an electrolyte forming bath comprised of a formation electrolyte, the tank being configured to receive one or more anodes, the tank having interior and exterior walls spaced to define a plenum through which a cooling fluid can be circulated, an inlet for receiving the cooling fluid into the plenum and an outlet from which the cooling fluid exits the plenum; and a cooling fluid circulation subsystem connected in flow-through communication with the inlet and the outlet.    
   
   
       27 . A bath system according to  claim 18 , wherein the heat exchanger comprises a fluid-filled wall portion of the tank containing the forming electrolyte.