Aircraft paint is probably one of the most underappreciated technologies in aviation. Everyone oohs and aahs over today’s jet engines and the electronics that dominate modern flight decks. But paint? Passengers think of it as a pretty face, not realizing its implications for safety, fuel efficiency and aerodynamics.
Paint protects the exterior surfaces of an airplane from the elements. An aircraft hurtling through the air at 500 miles per hour or more is exposed to high levels of ultraviolet (UV) exposure, rapid and extreme temperature cycling, expansions and contractions of the outer skin, high wind velocities, and the effects of air, rain, and manmade chemicals. Aircraft paint has to stand up to this environment, be flexible, adhesive and durable, maintaining gloss and vibrancy for the five- to 10-year interval between refinishings. It must also be as eco-friendly as possible. And it has to look good.
Typical fuselage paint must be able to withstand temperature swings of well over 100 °F, says Mark Cancilla, PPG Industries global platform director, aerospace coatings. In a matter of minutes the temperature around the aircraft’s exterior falls from ground levels to perhaps minus 60 °F at altitude. Temperature requirements typically range from minus 60 °F to 160 °F, he says. There are also high air velocities and changes in humidity to deal with. “Of course, the effects of UV light are also much greater at 40,000 feet, and so the exterior topcoat must be able to survive this to maintain the integrity of the livery colors,” he says. They also must resist chemicals such as deicing fluids, hydraulic fluids and industrial-strength cleaners.
Coatings for structural elements inside an airplane face a different set of challenges. These coatings must protect the aircraft from corrosion—in some cases for the duration—as some areas are difficult to reach for maintenance after the aircraft is assembled. Coatings for areas such as the insides of fuel tanks may need to last 25 or even 50 years, says Andreas Ossenkopf, director of aviation for Mankiewicz, a paint manufacturer headquartered in Germany. Structural components paints must resist chemicals such as hydraulic fluids and prevent the corrosion of aluminum from contact with water electrolytes as well as aggressive media, he adds.
Interior cabin coatings also must meet strict standards for flammability, smoke and toxicity, Ossenkopf says. And cabin coatings must be functional, durable and pleasing to the eye. Mankiewicz has delivered exterior, cabin, and structural element coatings to the aviation industry for decades, the company says.
AkzoNobel, a paint manufacturer based in Amsterdam, points out that aerospace is a qualification-driven market. Coating systems must pass the stringent specification testing requirements set out by the aviation authorities and aircraft manufacturers before they can be used in the market. It often takes years for products to go from development through qualification to commercial application on aircraft, explains Maud.