Definition - What does Faying Surfaces mean?
Faying surfaces are the contacting surfaces or faces of two similar or dissimilar materials placed in tight contact to form a joint. They are mating surfaces that contain a sealant in between them during any assembly process so that there is no gap or crevice left between them.
They are used in engineering fastening and joint development of different members to form a strong structure. To prevent corrosion between the two surfaces, primers or sealing agents are used to provide an air- or moisture-tight joint.
Corrosionpedia explains Faying Surfaces
In engineering fabrication, especially in assembly workshops, joints are essential in creating intricate structures. However, poorly installed joints can be points of failure in structures; they are prone to corrosion attack. One common type of corrosion encountered with joints is crevice corrosion, which develops from gaps between two materials. Moisture is the main initiator of any metallic corrosion, thus preventing it from becoming trapped between the faying surfaces is the first concern in joint formation.
Developing a smooth surface is also essential, but in most cases crevices develop on these faying surfaces; most fabricators use sand blasting to provide a clean and even surface. However, sealing or coating attempts are made to minimize and avoid the occurrence of gaps; the environment of the two surfaces also matters a lot when making the joint.