The objective of this project is to reduce the cost, time, and risk of implementing alternatives to hexavalent chromium and other toxic materials. The project will demonstrate and formalize for the Department of Defense (DoD) and the supply chain a cheaper, faster, more certain, and more efficient methodology for evaluating corrosion performance and implementing alternatives to hexavalent chromium, cadmium and other environmentally hazardous substance containing coating systems. The approach utilizes the growing capability for corrosion analysis and prediction to reduce the dependence on extensive corrosion testing to find and validate the best alternatives.
Corrdesa has formulated a Model/Downselect/Test (MDT) approach that combines computational analysis and prediction with testing to replace hexavalent chrome on commercial products within the short timelines permitted by restriction of hazardous substances, Registration, Evaluation, Authorization and Restriction of Chemicals Authorization and other environmental regulations. The method is in commercial use, but must be modified for use by DoD.
This project will link with a new Naval Air Systems Command (NAVAIR) four-year Office of Secretary of Defense (OSD) program on landing gear, and draw on data being produced in ESTCP WP18-5087 to develop a Cyclic Relative Humidity (CRH) test method that provides more realistic data than the American Society for Testing and Materials B117.
The approach will combine one-dimensional (1D), two-dimensional (2D) and full three-dimensional (3D) corrosion models. The 1D model is a well-known method of predicting galvanic corrosion (now incorporated into the new MIL-STD-889D to be issued this year) that the project team has commercialized as Corrosion Djinn®. For complex components and variable environments, the project team has developed workflows using full 3D Computer-Aided Engineering (CAE). To fill the gap between simple galvanic coupling that can be used without training, and full-scale CAE that only a computational expert can use, the project team has developed a 2D approach that is usable by M&P engineers. All three approaches use the same electrochemical database of materials and coatings.
In Year 1 the project team will demonstrate the approach with Naval Air Warfare Center Aircraft Division (NAWC-AD) for a difficult Cr6 replacement problem: non-chromate conversion/passivation treatments. Since almost all corrosion-prone components are painted, during Year 1 the project team will evaluate an electrochemical methodology for predicting the long-term degradation of painted system performance. The program has a Go-No-Go decision at the end of the year.
In Year 2 the project team will formalize the MDT methodology and verify it by comparison with NAVAIR data, linking it directly with a new four-year NAVAIR OSD Landing Gear program and the NAVAIR-led ESTCP WP18-5087 to develop CRH testing. During the year the project team will also formalize the organic coating degradation approach, linking it to prediction of galvanic and wide-area corrosion rates.
In Year 3 the MDT methodology will be linked with the prediction software and organic degradation prediction method, and transferred to an research testing development and evaluation server at NAWC-AD for evaluation.
Corrosion testing is one of the most time-consuming, uncertain and expensive requirements in finding and qualifying alternatives to chromates and other toxic corrosion control materials. Corrosion modeling and prediction is not at the point where it can replace qualification corrosion testing, but it can complement and eliminate a great deal of pre-qualification testing, especially for downselection and “what-if” analysis of damage tolerance and the effects of different coating stackups and environments. This will significantly reduce the time, cost, and risk of replacing corrosion control materials such as chromates, Cd, etc., while improving the outcome and freeing up limited resources for other problems.