Vacuum impregnation seals porosity and leak paths in metal castings and powdered metal parts that form during the casting or molding process. The process is done by filling the pores with a sealant under pressure to stop fluids or gases from leaking under pressure. Vacuum impregnation stops casting porosity and allows manufacturers to use parts that would otherwise be scrapped.

 The vacuum impregnation process seals internal leak paths to make it leak free and suitable for use. In the course of sealing castings against porosity, the parts would be processed through the following four stations:

  1. Impregnation Chamber: The operator would seal the chamber and draw a vacuum. This would remove air in the porosity and leak path in the casting wall. Parts would then be covered with sealant, and positive pressure applied. More energy would be required to penetrate the porosity with sealant than to evacuate the air. The operator would then release the pressure and drain the chamber.
  2. Excess Sealant Recovery: The operator would remove excess sealant through gravity, rotation or centrifugal force.
  3. Wash/Rinse Station: The operator would wash residual sealant from the part's internal passages, taps, pockets and features.
  4. Cure Station: The operator would polymerize the impregnated sealant in the leak path.


Vacuum impregnation should be done prior to final assembly. Specifically, for metal castings, vacuum impregnation should be done after final machining. Final machining may expose any porosity, creating a leak path. These paths can cause fluids and gases to leak from the casting, causing it to be non-conforming and unusable.


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