Ecologically Benign Corrosion Protection by Stratified Coatings

Military aircraft are largely constructed from special aluminum alloys, which typically have secondary precipitate phases that substantially improve mechanical strength. However, these regions also promote corrosion in such common environmental conditionsas acid rain, saltwater, and thermal cycling. The problem is significant enough that the U.S. Air Force expends approximately $1 billion per year on cor-rosion-related maintenance for its aluminum-skinned aircraft. The hexavalent chromate compounds thathave traditionally been used in conversion coatings are being phased out because of potential hazards to the environment and personnel. Advanced multilayer coatings incorporating less hazardous ions with superior corrosion inhibiting properties have beendemonstrated in Phase I. In Phase II, the team of No-madics, Inc. and Oklahoma State University proposes to adapt these coatings to spray methods compati-ble with current depot capabilities. Industries benefiting from this technology include thecommercial aerospace industry and other industries utilizing aluminum alloys. The proposed technology has demonstrated corrosion protection in an environmentally friendly formula-tion. The Air Force and other branches of the military will immediatelybenefit from this technology. Further, applications exist for commercial and private aviation, as well as other industries that have a need to protect aluminum that will be exposed to the elements.