The U.S. Naval Research Laboratory’s (NRL) Center for Corrosion Science and Engineering has developed a safer and user-friendly topcoat that was recently applied onto the exterior of Navy and Marine Corps aircraft.

The topcoat, which is a one-component (1K) polysiloxane based on organosilane polymers, is a new technology that is free of harmful isocyanates and other hazardous air polluting (HAP) chemicals.

Isocyanates and HAPs are found in two-component (2K) polyurethane topcoats currently used on U.S. Department of Defense (DoD) and commercial aircraft, according to NRL Officials.

Recent Applications

Erick Iezzi, a senior research chemist at NRL, recently applied the new topcoat with Naval Air Warfare Center – Aircraft Division engineers onto a U.S. Navy F/A-18 Hornet located at Naval Air Station Patuxent River in Maryland. Additionally, the 1K topcoat was applied on Marine Corps UH-1Y Venom and AH-1Z Viper helicopters located at Marine Corps Air Station New River in Jacksonville, North Carolina, and at Marine Corps Base Camp in Pendleton, California.

The 1K polysiloxane topcoat on these aircraft is scheduled for an evaluation period of one to two years.

“We're very proud of this achievement,” Iezzi said.  “Polyurethane topcoats have existed for several decades, yet within a few years we've been able develop an environmentally friendly alternative that provides similar laboratory performance and is easy for painters to use.”

Technical Features

According to the U.S. Occupational Safety and Health Administration (OSHA), exposure to isocyanates can result in irritation of the skin and mucous membranes, chest tightness, and difficulty breathing. HAPs are classified as potential human carcinogens. Isocyanate exposure can also cause sensitization, resulting in severe asthma attacks upon subsequent exposures at even low levels.

Replacing isocyanates with polysiloxane provides a safer coating for painters and anyone conducting maintenance in nearby areas, according to NRL. The new 1K topcoat also contains lower levels of volatile organic compounds, which negatively impact air quality when released during spray applications.

The 1K polysiloxane topcoat requires no metering or mixing of components because all chemicals are in a single container, thereby reducing time of preparation and providing a more homogeneous color on aircraft. The container is also resealable for future use, which reduces the generation of hazardous waste and disposal costs.

Patented Technology

Iezzi and other NRL chemists previously developed coatings for surface ships, but the requirements for aircraft coatings are more demanding. “Developing a new high-performance topcoat for aircraft is more difficult than for ships,” Iezzi said.  “Aircraft have aluminum skin, which means the coating must provide greater flexibility, especially at cold temperatures during high-altitude flight. An aircraft topcoat must also retain a camouflage appearance for longer periods of time.”

The polymers and polysiloxane coating technology are covered by U.S. patents, which are partially exclusively licensed by NCP Coatings, Inc. of Niles, Michigan. NCP produces the camouflage topcoat for demonstrations and field validation. The company is also using this technology to develop semi- and high-gloss formulations for aircraft.

The topcoat applications were coordinated with the Naval Air Systems Command and sponsored by the DoD’s Environmental Security Technology Certification Program, with contributing funds from the U.S. Office of Naval Research.

The NRL provides advanced scientific capabilities required to bolster the nation’s position of global naval leadership. With more than 2,500 personnel scientists, engineers and support staff, it has served the U.S. Navy and the country for nearly 100 years.