ASETSDefense 2011: Sustainable Surface Engineering for Aerospace and Defense focused on environmental safety and occupational health (ESOH) and life-cycle cost issues relevant to surface engineering technologies used in the production and sustainment of aerospace and defense systems, including aircraft, vehicles, ships, and electronics. Workshop sessions assessed alternatives to hexavalent chromium (Cr6+, chromate), beryllium (Be), cadmium (Cd), and volatile organic compounds (VOCs). Other sessions highlighted alternative technologies used to protect light metals and electronics, new accelerated corrosion test methods, and coating removal technologies. Sponsored by SERDP and ESTCP, the workshop held in New Orleans, February 7-10, 2011, attracted more than 240 engineers representing DoD, prime contractors, and suppliers.
A special side meeting on February 6 covered computational and database methods for materials design and corrosion prediction, especially for galvanic corrosion. Both the Office of Naval Research (ONR) and Naval Air Systems Command (NAVAIR) have developed a vision for a predictive galvanic corrosion technology integrated with software to design corrosion out of new systems. At the same time, original equipment manufacturers (OEMs) such as Boeing have been developing both engineering and basic science approaches. In the last few years new computational models have become commercially available for materials development and galvanic protection, databases have been developed that can provide the data for input to those models, and a new approach to galvanic data acquisition is being developed to replace the galvanic series that has been used for the last half century. Briefings were provided by ONR, NAVAIR, the Marine Corps, Boeing, Elsyca, and Questek.
The workshop itself opened with presentations discussing how domestic initiatives such as the OSD-ATL Cr6+ Minimization Memorandum and international regulations such as REACH are affecting DoD operations and the supply chain and how DoD and suppliers can effectively respond to these regulations. Presenters from the Services and OEMs in the United States and Europe described current issues related to surface protection being created by REACH, such as loss of critical materials from the supply chain and very short lead times for finding and qualifying alternatives. They described efforts to address these concerns in the short term and to develop a long-term approach.
Presentations then focused on solutions to the issues DoD is facing with respect to surface protection on weapons systems. Representatives from Hill AFB announced that low hydrogen embrittlement (LHE) ZnNi electroplate with a Cr3+ sealer was equal to or better than the currently used Cd plating with a Cr6+ sealer in all of their performance tests. Since it has met the qualification requirements as an alternative to Cd plating, Hill AFB intends to install a full-scale ZnNi plating line and move all production to the new process. In the area of paints and primers, advances have been made in low temperature and UV curable powder-coat and e-coating technologies that allow for expanded use on new materials and new applications. These coatings are free of VOCs, and increasing their applications across DoD will result in environmental and cost benefits, while improving performance.
Progress on alternatives to hard chrome plating such as high velocity oxygen fueled (HVOF) coatings and electroplated nanophase Co-P coatings was also discussed. HVOF coatings continue to be used as an alternative to hard chrome plating on aircraft landing gear components. Nanophase Co-P coatings provide protection similar to hard chrome and can be applied using the same equipment, but they are significantly less harmful to workers and the environment. Two very different technologies have now demonstrated performance superior to hard chrome for gun barrels, an application where previous coatings had failed. One of these is an explosively clad Ta-W liner, and the other is an electromagnetically enhanced physical vapor-deposited (PVD) coating.
Several new initiatives that are focused on developing tests to better qualify alternative coatings were presented. One such project is developing an accelerated dynamic corrosion test protocol intended to provide a reliable prediction of how a coating will perform in service, without the need for extensive atmospheric exposure and service testing. Another project is developing a standard method to evaluate hydrogen re-embrittlement in materials exposed to new alterative chemicals. A better test for hydrogen re-embrittlement would enable more alternative materials to be implemented into DoD maintenance processes since the current methods of evaluation are not accurate and rule out alternatives unnecessarily.
To facilitate implementation of new surface engineering technologies, NAVAIR has recently released a Non-Chromate Coatings Engineering Circular that defines how Cr6+ alternatives should be transitioned into Naval aircraft. ESTCP has funded a new project on non-chrome primers that adopts a similar approach (WP-201132). Led by Craig Matzdorf of NAVAIR, this project is intended to be an overarching effort to evaluate nonchrome primers currently on the market and develop test protocols for qualifying new coatings. Its purpose is to bring alternatives into production as soon as possible for low-risk applications, while developing the data and experience needed for more difficult situations.
For the full workshop report and briefings, visit https://www.serdp-estcp.org/asetsdefense. A database of engineering data and reports, authorizations, and implementations related to alternative technologies is also available on the ASETSDefense web site at http://db.asetsdefense.org. New information is continually being added to this database.