In high temperature applications, an embedded process is employed to attach the fin to the tube wall. In this process, a groove is actually cut into the tube, the fin strip inserted, and the tube material then “plowed” back against the fin to bond it to the tube. Separation of the fin and tube due to corrosion or temperature differentials are not a factor with the fin type. Since the fin does not employ a “foot”, this leaves the tube totally exposed to airside corrosion factors. In addition, due to the groove cut into the tube, a thicker tube wall thickness must be used to avoid over-pressuring the tube. The embedded fin is normally used for services greater than 170 °C and less than 400 °C. Poor atmospheric corrosion resistance is disadvantage of embedded fins
The extruded fin is produced by inserting the tube into an aluminum sleeve and then extruding the fins from the aluminum sleeve. Since the tube is totally covered by the aluminum sleeve, the tube wall is protected from outside corrosion, and the bond between the fin and the tube remains tight. The extruded fin tube is good for tube wall temperature up to 300 °C. This is the most expensive fin tube to produce. In extruded fin, both atmospheric corrosion resistance and mechanical resistance are excellent.