| What impregnants are used?
There are several main types of impregnants: (a) Polyester and Methacrylate Resins, which best meet the requirements set forth for impregnants. Impco Resins are specially formulated 100% solids, polyester and methacrylate resins designed for the impregnation of all types of ferrous and non-ferrous alloy castings. Impco Resins are among the few that are not inhibited by copper base alloys. (b) Epoxies; these are one or two part resins which have short pot life, are highly viscous and are expensive while normally requiring extended cure cycles and solvent washes. (c) Anaerobic Materials; these materials solidify in the absence of oxygen giving difficulty in impregnation since a full vacuum cannot be used. Their pot life is very unstable and their cost is 5-10 times the cost of polyester resins. (d) Phenolic Resins, Linseed Oil, Tung Oil; these are obsolete and are not 100% solids. They require prolonged bake-curing within an oven. Some also have a tendency to discolor and stain processed parts. (e) Sodium Silicate; these water glass materials are not only very brittle but when reduced to the proper dilution for impregnating purposes have only 20-25% solids content with the resulting lack of guarantee in the permanency of seal. However, sodium silicate materials have their purpose and are used primarily for low cost sealing of micro-porosity and sealing of cast iron parts where rusting augments the sealing material.
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