Environmentally durable metal honeycomb structure

A method of forming an environmentally durable, corrosion resistant honeycomb core structure from aluminum metal comprising the steps of:

• preparing a polymer receptive oxide coating on both surfaces of an aluminum foil by anodization of said aluminum foil in phosphoric acid said anodization taking place at a temperature in the range of about 75.degree. F. to 160.degree. F. for 0.1 to 30 minutes at a potential of from 5 to 50 volts with phosphoric acid concentration of 5% to 50%;
• applying a thin coating of an organic resin primer to said surfaces;
• curing said primer to a coherent film to form a primed aluminum foil;
• emplacing an adhesive on said primed aluminum foil, said adhesive being placed in locations chosen to form node bonds in a honeycomb structure;
• stacking said foil;
• curing said adhesive to form bonds between adjacent layers of primed aluminum foil to form a bonded stack of aluminum foil layers;
• expanding said stack to form honeycomb cells therein forming a honeycomb core;
• and
• bonding a face sheet to opposed end edge surfaces of said core with an adhesive which wets the surfaces of said primed aluminum foil to form fillets extending into said honeycomb cells;
• whereby a honeycomb core panel assembly is formed having all metal surfaces of said core coated with corrosion resistant, organic coating to render said core environmentally stable and resistant to corrosion.