an environmentally durable , aluminum honeycomb structure is obtained by surface treatment and application of a polymeric film forming substance to the aluminum foil used in manufacture of honeycomb core prior to application of the adhesive and expanding the stacked and bonded core whereby the cells of the honeycomb core structure are formed . by application of a polymeric film forming substance before bonding , all surfaces of the honeycomb core are protected from corrosion and other environmental degradations . the presence of a polymeric film forming substance on honeycomb core surfaces aids in the formation of strong core - to - face sheet bonds by improving the fillet configuration and thereby the strength obtained in face sheet - to - core bonding .