Seam sealants are chemical coating compositions used today in the OEM automotive industry

Automotive industry

The automotive industry designs, develops, manufactures, markets, and sells motor vehicles, and is one of the world's most important economic sectors by revenue....

 primarily for the purpose of seals against air leaks and to waterproof sheetmetal overlaps that occur in the assembly of a vehicle. Such overlaps are typically decorative rather than structurally supportive. Accordingly, they are usually only spot welded

Spot welding

Spot welding is a process in which contacting metal surfaces are joined by the heat obtained from resistance to electric current flow. Work-pieces are held together under pressure exerted by electrodes. Typically the sheets are in the thickness range...

 and this process results in a closure that is not air or water tight.

Seam sealants are sprayed or extruded over the joined edges of these overlaps, and they then either cure to a flexible waterproof "seal" by drying (dehydrating) in the case of water borne compositions, or thermoset irreversibly to a flexible adherent seam seal by going through an oven

Oven

An oven is a thermally insulated chamber used for the heating, baking or drying of a substance. It is most commonly used for cooking. Kilns, and furnaces are special-purpose ovens...

 bake in the case of plasticized polyvinylchloride compositions. Most interior seam seals are not visible after the vehicle is finished, because they are covered by carpeting, interior roof headliner

Headliner

A headliner is a composite material that is adhered to the inside roof of automobiles or yachts. It typically consists of a face fabric with nonwoven or foam backing. Headliners consist of multilayered composite materials that bring together multiple functionalities, including the requested look,...

, or decorative trim panels. Exterior seam seals are always painted over and are referred to as "coach joint seals."