The U.S. Department of Defense has chosen a new environmentally benign, corrosion-resistant coating for military aircraft and other weapons systems as a top project of 2012.

The Missouri University of Science and Technology project was selected as a 2012 Project of the Year for the Weapon Systems and Platforms program within the Defense Department's Strategic Environmental Research and Development Program.

The Missouri project, "Rare-Earth Corrosion Protection Mechanisms," uses rare-earth elements, rather than hexavalent chromium, for corrosion resistance.

Missouri University of Science and Technology

Drs. Bill Fahrenholtz (left) and Matt O'Keefe used Missouri S&T's focused ion beam technology to analyze rare-earth compounds that could be used in aircraft coatings.

The project was one of four selected by the program for helping the agency "achieve its mission while improving its environmental performance," the program reported.

'Significant Scientific Achievement'

The project teamed up university researchers with scientists from Deft Inc. of Irvine, CA, to understand the corrosion-protection mechanisms for rare-earth-based coatings for use on military aircraft. Rare-earth compounds are believed to be less harmful to the environment than conventional coating materials, the researchers said.

Most coating systems used for military aircraft contain hexavalent chromium, a toxic and carcinogenic substance. In 2009, the Pentagon adopted a policy to eliminate the use of compounds containing hexavalent chromium.

The Missouri S&T and Deft team "have made fundamental discoveries in understanding how rare-earth compounds containing cerium or praseodymium inhibit corrosion," DOD's research program reports.

The university team was led by Dr. Bill Fahrenholtz, Curators' Professor of ceramic engineering and a senior investigator in Missouri S&T's Materials Research Center, and Dr. Matt O'Keefe, professor of metallurgical engineering and the center's director. The Deft team was led by Dr. Eric Morris and Rich Albers, a chemist who develops paint formulations.

U.S. Air Force/Senior Airman Brett Clashman (left); DOD SERDP
Two coating systems were tested. Researchers say they may benefit several systems, including the Air Force's F-15 Eagle (left).

"Not only does the research of Dr. Fahrenholtz and his team represent a significant scientific achievement, it also exemplifies a highly successful collaborative effort between a university and private industry," the program said in an announcement about the award.

Protection without Toxins

"The results of this project will provide direction for further development of rare-earth compounds as surface treatments and coatings for the military that will reduce the use of toxic ... compounds while providing corrosion protection," the program said.

Two specific coating systems were examined: cerium-based conversion coatings (CeCCs) and epoxy polyamide primers containing praseodymium-based inhibitors. Before the project began, both coating systems demonstrated corrosion protection that could meet current U.S. military requirements for aircraft.

One of the coatings investigated in this project was a primer that contains a corrosion inhibitor based on praseodymium oxide. The corrosion inhibitor was developed at Missouri S&T as part of the thesis research of Morris under the guidance of Dr. Jim Stoffer and the late Dr. Tom O'Keefe.

Stoffer and O'Keefe began research on rare-earth coatings at Missouri S&T in the mid-1980s through an effort funded by McDonnell-Douglas, which later merged with Boeing. After completing his Ph.D. at Missouri S&T, Morris was hired by Deft, which also licensed the rare-earth inhibitor technology developed at S&T.

The resulting rare-earth primer is now used on several military aircraft, including F-15 fighters and Apache helicopters. The primer was cited by R&D Magazine in its 2006 R&D 100 listing of that year's most technologically significant achievements.