Casting Impregnation

Definition - What does Casting Impregnation mean?

Casting impregnation is the process of removing air from the pores of leakage paths in a casting and replacing it with resin that is specifically formulated to cure in the pores so that the casting becomes pressure tight.

It is a method of sealing porous materials without impacting the functional or dimensional characteristics of the material. The impregnation processes can provide:

  • Sealing
  • Reduced moisture and internal corrosion
  • Enhanced integrity

Corrosionpedia explains Casting Impregnation

Casting impregnation permanently seals micro- or macroporosity voids for pressure tightness and blocks corrosion and fungus growth. It also can improve the machinability of powder metallurgy parts. The impregnating resins act as a lubricant to eliminate machining chatter and prolong tool life.

Casting impregnation is important because when parts are created by casting metal, tiny defects are nearly impossible to avoid. Whether those defects involve porosity of the surface, bubbles or other types of incursions, they can negatively impact a part's performance under operating conditions.

The method chosen depends on a part's requirements, specifications and sealant that will be used. Methods include:

  • Dry Vacuum/Pressure (DVP): The DVP cycle requires two separate tanks, one for processing the part and the other for storing the sealant. This process is best used for metal parts that contain extremely small, microscopic pores that may be invisible to the naked eye.
  • Wet Vacuum/Pressure (VP): This cycle requires only one tank that contains the desired sealant.
  • Wet Vacuum (WV): This cycle is the quickest impregnation method. It requires only one tank with the desired sealant.

In applications, powder metallurgy (PM) components are sealed prior to plating and to reduce internal corrosion. Die castings and permanent molds are routinely sealed for life using acrylic resins. Porosity sealing improves the life of cutting tools by ten to one hundred times.

Impregnation is not only effective for preventing leaks, it is also an excellent pre-treatment for surface finishes. It is the preferred method for ensuring pressure-tight components in failsafe applications. It is used to improve the quality of their base castings, conserve resources and reduce scrap. Applicable industries include:

  • Aviation
  • Automotive
  • Food processing
  • Oil and gas

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