Certain important materials such as cast metal, powdered metal, plastic, and ceramic provide component parts that have inherent microporosity. These sub-surface pores occur naturally during processing of the part. They are generally the result of crystal formation and shrinkage or gas inclusions. Many times these parts are used in critical assemblies that must be pressure tight to be functional. However, upon machining of the part small pores are uncovered that can provide a gas or fluid leakage path.
As a result, the demand for porosity sealants and processes has grown significantly in recent years, particularly in the automotive industries. Low viscosity porosity sealants are commonly used to fill tiny imperfections and microporosity. These modern materials have become important design tools, and associated processes, such as vacuum impregnation, have become critical technologies in the manufacture of these parts.
This article will define the materials and processes that are commonly used to seal parts against porosity, and it will explore the use of modern anaerobic sealants in detail.