Nonchrome Corrosion Protection for Conductive Coatings

Conductive coatings are required for military (and civilian) aircraft to control electrostatic discharge and provide protection against lightning strikes. These coatings, typically based upon polyurethane or epoxy polymers, rely upon silver, nickel, copper or carbon particles for electrical conductivity and are applied over an aluminum or composite substrate and a chromate-containing primer for corrosion protection. While chromate inhibitors are effective in reducing corrosion, they are toxic and the current trend is to replace them for health and environmental reasons. There is a need for nonchrome based primers that protect both the aluminum and composite material airframe substrates and inhibit corrosion within conductive coatings. Inhibitrol Inc proposes to undertake studies addressing these problems and to evaluate the use of tobacco extracts, comminuted tobacco leaf and dust as additives for conductive coatings since studies show these materials to be highly effective corrosion inhibitors. In some situations, tobacco extracts can be as effective as chromates in preventing corrosion but without the toxicity issues of chromates, as shown in independent toxicity studies. The use of tobacco dust/leaf has several advantages, including absence of toxicity, derived from a renewable source, low cost and demonstrated efficacy for many metals in a wide variety of media.