| How does impregnation improve product quality?
When Porosity in a casting causes problems, "bad" castings are often sorted out by testing and inspection. "Good" castings are as porous as the "bad" castings but the porosity is blind and not completely inter-connected. Subsequent mechanical or thermal shock or stress often breaks the thin membrane which keeps the blind porosity from being continuous, thus causing a "leaker". Impregnation fills porosity from both sides preventing leaks even if the membrane does break. Therefore, impregnation salvages castings and improves quality, while inspection only sorts out leakers.
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