Method for passivating a surface of a workpiece and apparatus for passivating workpieces

Abstract

In order to create a method for passivating a surface of a workpiece, said method enabling a complete and sufficient passivation of the surface of the workpiece in narrow cavities of the workpiece, even in the case of workpieces with complex geometry, it is proposed that the method comprises the following:introducing at least one workpiece into a treatment chamber;providing a passivating agent in the treatment chamber;cyclically changing the pressure in the treatment chamber while the passivating agent is located in the treatment chamber.

1 . A method for passivating a surface of a workpiece, comprising the following:
 introducing at least one workpiece into a treatment chamber;   providing a passivating agent in the treatment chamber;   cyclically changing the pressure in the treatment chamber while the passivating agent is located in the treatment chamber.   
     
     
         2 . The method in accordance with  claim 1 , wherein the maximum pressure is lower than the ambient pressure during the cyclical changing of the pressure in the treatment chamber. 
     
     
         3 . The method in accordance with  claim 1 , wherein the minimum pressure is less than half the maximum pressure during the cyclical changing of the pressure in the treatment chamber. 
     
     
         4 . The method in accordance with  claim 1 , wherein the minimum pressure is less than the vapor pressure of the passivating agent during the cyclical changing of the pressure in the treatment chamber. 
     
     
         5 . The method in accordance with  claim 1 , wherein the average cycle time of the changing of the pressure in the treatment chamber is at least one of i) at least 1 s and ii) at most 30 s. 
     
     
         6 . The method in accordance with  claim 1 , wherein the treatment chamber is connected to a negative pressure source during the changing of the pressure at least at times. 
     
     
         7 . The method in accordance with  claim 6 , wherein the negative pressure source comprises a vacuum pump. 
     
     
         8 . The method in accordance with  claim 6 , wherein the negative pressure source comprises a negative pressure store. 
     
     
         9 . The method in accordance with  claim 8 , wherein the negative pressure store is provided with a heat exchanger. 
     
     
         10 . The method in accordance with  claim 1 , wherein the passivating agent comprises at least one of i) phosphoric acid and ii) nitric acid. 
     
     
         11 . The method in accordance with  claim 10 , wherein the passivating agent contains phosphoric acid in a concentration of at least one of i) at least 1.5% by volume and ii) at most 3% by volume. 
     
     
         12 . The method in accordance with  claim 1 , wherein at least one of i) the passivating agent and ii) the at least one workpiece is/are acted upon with ultrasound during the changing of the pressure. 
     
     
         13 . The method in accordance with  claim 1 , wherein a workpiece to be passivated is introduced into a plurality of passivation stations one after the other, which contain different passivating agents. 
     
     
         14 . An apparatus for passivating workpieces, comprising
 a treatment chamber for accommodating at least one workpiece and a bath of a passivating agent; and   a pressure changing apparatus for cyclically changing the pressure in the treatment chamber while passivating agent is located in the treatment chamber.   
     
     
         15 . The apparatus in accordance with  claim 14 , wherein the apparatus comprises at least two treatment chambers, wherein a workpiece is treatable with a passivating agent in the first treatment chamber and a workpiece is rinsable with a rinsing liquid in the second treatment chamber simultaneously.