A Novel Bio-Applique for Corrosion Protection

Traditional coatings used by the military to camouflage and protect aluminum alloys contain organic solvents (VOCs) and toxic metal corrosion inhibitors (chromates). Gases emitted during application and wastes generated when stripping the metal for recoating create hazardous working conditions and pollute the environment. Appliqués (thin film fluoropolymers with a pressure sensitive adhesive) provide an environmentally friendly and inexpensive alternative coating system that is easy to apply and maintain. Provided these impermeable coverings remain intact and properly bonded, they effectively prevent the substrate metal from corroding. However, if the appliqué is damaged, moisture and oxygen can permeate to the metal and initiate corrosion. Providing additional protection with a chromate-containing primer or conversion layer would defeat the attractiveness of the appliqué technology. Instead it is proposed to incorporate a biological system into the appliqué that will protect exposed metal against all types of corrosion. In effect, the biological system will secrete corrosion inhibitors and antimicrobials in a manner designed to emulate the "inhibition-on-demand" characteristics of chromate inhibitors. The biological system will be safe and environmentally friendly. This proposal provides detailed information on the functioning of the biological system and describes an experimental program to demonstrate its effectiveness. (P-040410)