Fusion-bonded epoxy (FBE) is an epoxy-based powder coating that is used to protect various sizes of steel pipes used in pipeline construction and on a wide variety of piping connections, valves, etc. from deterioration due to corrosion. FBE coatings are thermoset polymer coatings. They come under the category of ‘protective coatings’ in paint and coating nomenclature. The name ‘fusion-bonded epoxy’ is derived from the way of resin crosslinking and the method of application. FBE coatings are in the form of dry powder at normal atmospheric temperatures.
The resin and hardener parts in the dry powder remain unreacted at normal storage conditions. At typical coating temperatures, in the range of 180 °C to 250 °C (360 °F to 480 °F), the contents of the powder melt and transform to a liquid form. The liquid FBE film wets and flows onto the steel surface on which it is applied, and soon becomes a solid coating by chemical crosslinking, assisted by heat. This process is known as fusion bonding. The chemical crosslinking reaction taking place in this case is irreversible, which means once the curing takes place, the coating application of further heating will not “melt” the coating, and thus it is known as a “thermoset” coating.