Published: Jan 2012
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ORGANIC COATINGS ARE PRIMARILY APPLIED TO aircraft for environmental protection and appearance. Reference  concludes, “The rate controlling parameter for the corrosion of aircraft alloys, excluding the mechanical damage factor, is the degradation time of the protective coating system.” This clearly indicates the importance of the coating system's durability and its ability to control corrosion and erosion. Relative to appearance, commercial aircraft benefit from the aesthetic characteristics of the coating system, while military aircraft rely on camouflage properties to minimize enemy detection and tracking during mission operations. To meet operational requirements, aircraft coating systems traditionally consist of a primer and a topcoat. Primers inhibit corrosion of the substrate and enhance adhesion of subsequent topcoats, while topcoats are applied for appearance and to enhance overall durability of the coating system. Self-priming topcoats, which perform as both primer and topcoat in a single coating, have recently been introduced [2,3]. In addition, specialty coatings are strategically applied to perform various functions such as protection against rain erosion, chafing, immersion in fuel, and high temperature. References [4–6] provide more detail on the formulation and properties of aircraft coatings. A number of factors affect the performance of aircraft coatings, including the substrate material, the aircraft's operational environment, and flight conditions. Aircraft structures and skins are manufactured from numerous metallic alloys and polymeric composites with a variety of pre-paint treatments, thus complicating the adhesion and corrosion inhibition characteristics of the coating system. Environmental conditions also can vary dramatically (arctic, tropical, marine, industrial, desert, etc.). Skin temperatures during flight can range from −54 to 177°C (−65 to 350°F) while ground conditions may be relatively benign or highly corrosive. Aircraft type and mission also play important roles in coating system performance. A commuter aircraft that hops from island to island in the tropics sees frequent pressurization and depressurization along with high temperature, humidity, and salt water. In contrast, a military tactical aircraft may fly far fewer hours but will experience extreme structural loads during flight conditions. These flight conditions place environmental and mechanical stresses on the aircraft coating system. Therefore, selection of appropriate test and evaluation procedures is an essential component for determining acceptable coatings for aircraft application .
Hegedus, Charles R.
Air Products and Chemicals, Allentown, PA
Spadafora, Stephen J.
NAVAIR Fellow/Head, Naval Air Systems Command, Patuxent River, MD
Eng, Anthony T.
Materials Engineer, Naval Surface Warfare Center, Philadelphia, PA
Pulley, David F.
Chemical Engineer, Naval Air Systems Command, Patuxent River, MD
Hirst, Donald J.
Materials Engineering Technician, Naval Air Systems Command, Patuxent River, MD