Environmental effects of ground and flight environments, including temperature extremes, damage by chemical fluids, moisture, and so forth, affect the durability of polymer-matrix composites. This article provides information on corrosion control methods in aircraft structures. It discusses the design considerations for sealants in joints. The article describes the common methods to seal aircraft structures: fay surface, fillet, butt joint, channel, brush, and form-in-place seals. It discusses the surface preparation and application method of primer and topcoat systems. Primer and paint application equipment as well as sealant application equipment are reviewed.