Galvanic Corrosion Prediction for Aircraft Structures

ABSTRACT:The objective of this work is to develop a tool to quantitatively predict corrosion between carbon fiber composite (CFC) and 7050 Al, as used in remotely piloted aircraft (RPAs). Phase I showed that the dominant corrosion mechanism for this material mix is pitting. Therefore, this effort will introduce computational analysis of both galvanic and pitting corrosion rates on aluminum in structures joining CFC and aluminum in configurations typical of RPAs, wetted by water ingress or condensation. It will incorporate time-dependent changes in electrochemical properties and assess the effects of non-uniform electrolyte layers. The program will deliver to USAF a Rationalized Toolset that incorporates the knowledge gained during the program to permit accurate analysis and reduction of galvanic/pitting corrosion in airframes. It will also deliver a package of Recommended Corrosion Prediction Practices for material and process engineers, and a Recommended Corrosion Design Practices Document for designers. These tools will permit designers to minimize corrosion in RPA structures at the design stage, and maintainers to predict and manage corrosion in sustainment.BENEFIT:Since corrosion costs USAF about $4.5 billion per year (a quarter of the maintenance budget), the benefits of corrosion reduction are very large, especially when reduced corrosion is built in during the design phase. The tools developed and transitioned to USAF and OEMs by this project will make it possible for USAF to begin to move away from the find and fix approach to corrosion, to a less expensive and safer predict and manage approach. Since lightweighting, using composite structures and lightweight alloys has become so important for performance and energy savings, this approach is applicable, not just to military RPAs, but to all military and commercial aircraft and vehicles.