In order to properly seal casting porosity, parts must be clean and dry. The porosity must be free of any contaminants that might preclude the sealant from penetrating. If any residual contaminants are present, then the following problems may occur.
- Risk of Contamination
Residual fluids and solids on the part can contaminate the sealant. The impurity of sealant can inhibit the sealing of future parts. Vacuum impregnation is a controlled process. Sealant contamination will cause the vacuum impregnation process to not be controlled.
- Risk of Parts Not Being Properly Sealed
The vacuum cycle may not fully remove part debris and fluids. These will go into the porosity once the vacuum is released. As a result, the sealant will not be able to properly seal the porosity. The parts may not pass leak test since the porosity is not properly sealed due to the contamination.
- Increase TAKT time
Any residual fluids will need to be boiled off in the vacuum chamber. When water boils, it expands to approximately 1,700 times. That expansion means there is more volume for the vacuum pump to evacuate from the vessel, which takes time. In addition, if the water is in the part’s porosity, then the evaporation process could take several seconds more than evaporating from the surface. A few additional seconds may not sound like a lot of time. But this additional time compounds and can cause production delays with large production volumes.
How to Solve Casting Cleanliness?
The most effective way to clean castings is through vapor degreasing and the most environmentally conscious vapor degreasing process is vacuum vapor degreasing. Vacuum vapor degreasing is a relatively new form of vapor degreasing that removes contamination from the parts surface while being performed in an airless environment. Vacuum vapor degreasing is done prior to the casting impregnation process.
Vacuum Vapor Degreasing improves vacuum impregnation by allowing for efficient and effective sealing of porosity. When applied under vacuum, the solvent vapors travel unimpeded to the part surface and even help draw out contaminants from the porosity. The process not only removes contaminants, but dries the parts without fear of oxidation.