Castings are impregnated for a variety of reasons, the most common being to retain gases or fluids under pressure. Examples of these would be air regulators, gas meters, pumps, gear housings, valves, fuel systems parts, refrigerant compressor housings, cylinder heads and liners, automotive housings, brake parts, and aircraft housings. These parts can hold pressure up to the burst strength of the casting. Powder metal parts and plastic injection molded components are also impregnated for these reasons.

Powder metal parts and castings are also impregnated in preparation for other metal finishing operations, such as plating or painting. Acids and other cleaning agents that are used in these operations may be absorbed into the pores and remain there during the rest of the operation. Later, these fluids emerge from the pores, causing pits, blisters, or other blemishes on the surface. Out gassing of air from the porosity during paint curing can also cause blistering. Sealing the porosity prior to this can eliminate this problem.

Impregnation can enhance the machinability of powder metal parts and improve tooling life. By filling the porosity with resin, the tool has an uninterrupted cut, thus eliminating tool chatter. A tremendous increase in tool life is possible.

Impregnation is also occasionally done to prevent internal corrosion. By sealing the pores, corrosive fluids cannot enter the porosity, which would later cause internal corrosion.