Jointing compounds and sealants

Jointing compounds are used for protection at joints where they act by excluding dirt and moisture, and by providing a reservoir of soluble passivators which act as inhibitors. Sealants are applied to joints to prevent the escape of fluids, such as fuel, but they also exclude moisture. Jointing compounds are required to remain flexible so as to allow easy disassembly of parts.

Various synthetic resins are used for this purpose. The compounds harden sufficiently at edges to take paint, but they remain tacky within the joint so that flexure does not cause cracking. Sealants of the type now being specified are also elastomeric, and the most popular are polysulphide sealants containing corrosion inhibitors. The inhibitive sealants are very effective when used in faying surfaces and butt joints, for wet installation of fasteners and over fastener patterns. They are also effective in insulating dissimilar metals.