Aircraft Paint

 - September 21, 2006, 11:46 AM

Exterior paint has always been a statement. In ancient times, sailors painted eyes on the bows of ships so they might find their way easily. Even today, it is a custom Chinese boat builders still follow. During World War II, “nose art” was common on military aircraft. Perhaps the best known was the Memphis Belle, a B-17 that bore the name and a scantily clad image of the belle herself.

Originally, the idea of paint on an airplane was not so much cosmetic as practical. It protected the skin of the airplane, primarily from corrosion. Exterior paint remains the protective coating on an expensive investment, but it has also become
a visual element. In either case, it is a challenge to those who create the design and to those who apply it.

The exterior paint on the typical business jet is hardly flamboyant, most often off-white with a couple of stripes, the airborne equivalent of a banker’s basic blue suit, but less exciting. There are some notable exceptions, but not many.

Ken Norris, manager of the Cimarron Aircraft paint shop in El Reno, Okla., recalls a client who insisted that his airplane be painted to resemble an architectural blueprint. It didn’t happen. Another customer, a film producer, wanted his King Air painted gloss black, in its entirety. That did happen.

Certainly, there is much from which the customer can choose. One paint facility reports that while Matterhorn White is by far the most popular color for the airplane as a whole, its mixing shop can create more than 6,000 different striping and trim colors, with such evocative names as Aloha Red, Eruption and Afterburner.
There are a number of specialty paints. The best known are the so-called “flip-flop” and metallic.

DuPont calls its flip-flop product Chromalusion. The House of Kolor in Picayune, Miss., calls its version Kameleon Kolors. Paint shop managers generally agree that for striping, logos or accent trim, such paints are appropriate. While some owners have opted for an entire aircraft done in such specialty paint, designers and painters urge against it because, apart from being incredibly expensive, specialty paint is difficult to apply and less durable than more conventional paint.

A 2.5-gallon kit of conventional paint (solvent, pigment and binders) costs about $250 for an off-white. A gallon of flip-flop may exceed $3,500 for a single gallon kit. This would put the price of paint alone for an entire Citation V at about $28,000, pushing the total cost to somewhere toward $100,000.

David Tidwell, manager of completions and modifications at Midcoast Aviation, said he gets few requests for the flip-flop but a number of requests for a “split-base” metallic paint scheme in which the bottom half of the fuselage is done in metallic and the top in a standard off-white base coat.

Ed Kirby, former paint shop manager at Bizjet in Tulsa, Okla., is no fan of metallics. “You can never get metallic paint from two different batches to match. And it’s almost impossible to get an even finish from one end of the airplane to the other, even with all the paint from the same batch,” he added.

Paint shop supervisors agree that applying metallic paint is difficult at best. The paint pots require constant agitation to keep the metallic particles in suspension, and even differences in the thickness of the paint application may change the appearance. And later it becomes virtually impossible to match the original paint if a small touchup or repainting of a damaged portion of skin is necessary.

Metallics also require post-application work. The tiny metallic particles tend to “stand on end,” creating a faintly rough surface that in most cases requires a clear-coat to create a glossy look, according to Tidwell. Midcoast generally does not apply a clear coat to the entire aircraft, said Tidwell, as it tends to yellow with time and ultraviolet exposure.

As to the cost of stripping and repainting a used airplane, it is a consideration, though not exactly a deal-breaker. Stripping, prepping and repainting a GIV may run well beyond $110,000. For a Falcon 50, count on something in the neighborhood of $85,000, which pays for a white fill primer, base color and two stripes.

Paint’s Paint, Right? Wrong
For those who do not paint airplanes, the process may seem relatively simple: roll the airplane into a hangar, break out the spray gun and spritz on a couple of coats. After all, paint’s paint, right? Wrong. Not all paint is created equal; the right equipment makes a difference; and the skills of the designers, layout specialists and painters are critical.

The process begins with the designer. It is there the client expresses a desire, and the designer explains what’s actually possible. Then, ideally, the two find some happy middle ground.

White and tones of off-white remain the most popular colors, but the traditional colored stripes seem to have given way to slightly more creative designs. Stripes might be of three or four different colors that in some cases expand and curve into a “wind-whipped” spray of curls. A few “bold” individuals have opted for accent stripes in flip-flop or metallic.

Since 9/11, customers seem to be of two minds. There are those who want no identifying markings on the aircraft beyond the N number. Others, however, make a point of having a U.S. flag flying on the tail.

Some international operators, however, have had the U.S. flag removed or declined to have it applied in response to the threat of international terrorism and kidnapping as a growth industry in some parts of the third world.

For a long time, paint was just paint. Regardless of brand, it consisted of about two-thirds volatile organic compounds (VOCs) that thinned it to a viscosity that allowed it to flow easily through a paint gun and then dry quickly. The other one-third was color pigment and binding agent, referred to as “solids.” The proportions remained standard, and solvents from one manufacturer worked equally with the pigment and binder of another. Paint shops knew the properties of conventional paints well and had become comfortable with their use. Then came high-solids paint (HSP).

In a world increasingly concerned with environmental dangers, various government agencies demanded a reduction in the release of dangerous VOCs. High-solids paint was, in fact, created in direct response to federal requirements set by the Environmental Protection Agency’s National Emissions Standards for Hazardous Air Pollutants (NESHAP) and was quickly adopted by the industry.

In HSPs, fully two-thirds of the volume is pigment and binder solids and one-third VOCs. Although more difficult to apply, the mixture results in less VOC-laden overspray remaining in the air to be filtered and disposed of later.

But while high-solids may have been a partial solution to environmental concerns, the new paint has brought with it new challenges. Unlike conventional paint, the VOC from one manufacturer may not be used with the pigment/binder of another manufacturer. And its heavy viscosity makes it more difficult to apply, requiring greater skill on the part of the painter to achieve the smooth, high-gloss finish that customers expect.

Chad Doyle, president of Jim Miller Aircraft Painting in Uvalde, Texas, said his company is “still pretty much shooting conventional paint,” and for good reason. “We just get a better finish.”

Doyle explained that when blended as recommended by the manufacturers, the relatively dense mixture of high solids cannot be as finely atomized as conventional paint. And if the amount of VOCs in high solids is increased to more finely atomize the paint for a smoother finish, “you end up releasing the same amount of VOCs in overspray that you would if you used conventional paint.”

Nevertheless, it seems high-solids paint is here to stay, and most paint shops have learned to work with it to their own satisfaction, and apparently to the satisfaction of their customers.

At the Dassault Falcon Jet facility in Wilmington, Del., the recently opened paint shop works exclusively with high-solids paint. Delaware environmental regulations require it, but John Rahilly, v-p of sales and marketing for Falcon factory service centers, believes that, properly applied, high solids now have the glossy “wet look” they didn’t have five or six years ago. “Properly mixed and applied, they look as good as the high-VOC conventional paints,” he said.

It also helps that manufacturers today are more willing to provide hands-on training to teach painters how to use new products and how to improve their expertise with old ones.

While some shops seem to have moved almost exclusively to high-solids and others have chosen to remain with conventional high VOC paint, most seem inclined to use either where regulations permit.

At Duncan Aviation, designer Mike Minchow said the paint shops at the company’s Lincoln, Neb. headquarters facility and the Battle Creek, Mich. center are using both high solids and high VOCs, “depending on the customer and the situation.”

Doug Bohac, the Lincoln paint shop manager, conceded that high-solids paint is more difficult work with, but it meets Environmental Protection Agency recommendations with regard to a reduction in VOC emissions. On the other hand, he is convinced that conventional paint lays down more smoothly and gives a nicer finish.

To reduce the amount of VOCs released during painting with high solids or conventional paint, there are several weapons of choice. The high-volume, low-pressure spray gun is a standard item.

The electrostatic spray gun makes it a still more efficient process. The electrostatic technology is similar to the effect of rubbing an inflated balloon on a fuzzy wool sweater to give it a positive electron charge and then “sticking” the balloon to a wall that has a negative charge. The electrostatic paint pot creates a positive charge that is transferred to the paint, while the aircraft is grounded, giving it a negative charge. The result is a negatively charged surface that attracts the positively charged paint particles.

Regulatory Issues Changing the Face of Painting
Paint shops are feeling the result of increasing government scrutiny and environmental concerns.

In the case of used aircraft, the regulations begin with the stripping of old paint, which requires agents that are not friendly to the planet’s carbon-based life forms. The residue from the stripping must be trapped, filtered and the remaining semi-solids disposed of in compliance with federal, state and local regulations.

No matter what system of shop ventilation is used–downdraft, side-draft, up-draft– or what kind of paint and paint application system is employed, paint shops must meet EPA standards with regard to VOC emissions, and many states and municipalities have issued guidelines far more strict than those of the EPA.

While Jim Miller Aircraft Painting meets EPA standards, explained Doyle, it must also work within environmental guidelines set by the state of Texas and the municipal governments of the Dallas-Fort Worth area. “After the first two or three high-ozone days,” he said, “local regulations kick in and the amount of VOCs that can be released is reduced.”

Environmental regulations also result in mounds of paperwork. “We have to document the time we started emitting VOCs, how long we sprayed and how much we sprayed in an hour,” said Doyle. “I have one guy whose only job is to document this process.”

Painters and paint shop managers are well aware of the byproducts of paint application, most of which are health hazards and, to be more specific, cancer-causing agents. The list is long. There are solvents such as xylene, methyl ethyl ketone, methyl isobutyl ketone and toluene, all materials on the EPA 17 list targeted for reduction or elimination.

Compliance is neither easy nor inexpensive. At Midcoast Aviation’s newest paint bay, a triple-stage, downdraft tacky filter process is used and the cost of replacing the three filters in each of its three bay booths is more than $36,000 a year. And there is the additional cost of disposal of the residue.

Not all the regulations are environmental in nature. There is also the matter of RVSM. Painters are trained to apply coats in thicknesses of five to seven millimeters, but the challenge is greater on areas surrounding RVSM sensors. Here, the paint thickness must be within exacting limits for any particular aircraft or group of aircraft types. If a stripe or accent or logo falls within those RVSM sensor frame areas, perhaps as close as six inches from the port, raised edges must be milled down to the same thickness as the surrounding paint, with no edge that might distort the airflow across the port.

The paint bay is a key to control of temperature, humidity, air movement and barometric pressure–all factors that can affect paint application, drying and curing.
There are paint shops with side-draft ventilation, downdraft ventilation and updraft ventilation. Said Doyle, “They all seem to be pretty much the same as far as the final product is concerned.”

But there are advocates for each. The downdraft system in the newer paint facility at Dassault Falcon Jet’s Little Rock, Ark. completion center has the vote of paint department manager Alan Tompkins. “We’ve had a lot of good luck with it, cleaner finishes and savings in our waste-water treatment costs.”

The isocyanates in modern paints are there as a curing agent and react with resins to produce what the general public knows as polyurethane and its characteristic glossy “wet look” finish. But these isocyanates break down in air that contains too much moisture and the result is a flat or hazy finish, referred to by painters as “blush.” This may also happen if the humidity is allowed to rise before the paint is sufficiently dried, or “cured” in paint-speak.

At a higher temperature, assuming a constant humidity level, paint will dry more quickly. But perhaps too quickly, which can result in “flash-over” drying that leaves a skim of dry paint under which the remaining paint continues to dry. As it does, gases emitted during the drying process force their way up through the skim in the form of thousands of tiny pinholes, or what painters refer to as “solvent pop” or “orange peel finish.”

This may also occur if the initial base coat is not allowed to dry sufficiently before the second base coat is applied. Paint shops avoid this by adjusting the amount of additives in the paint.

Ideally, the temperature in a paint bay should range from 75 to 80 degrees F, with the humidity maintained at 30 or 50 percent.

Humidity and temperature controls are particularly important for shops in hot, humid geographical regions. The new paint shop at Dassault Falcon Jet’s Little Rock, Ark. completion center is an example. The controls ensure optimum painting conditions, even on days when the outside temperature reach more than 100 degrees F and the humidity shoots well past the 70-percent mark. At the same time, the controls will allow an increase in temperature to about 120 degrees F to reduce the pre-delivery curing time.

On the other hand, some shops seem to be ideally placed with regard to temperature and humidity. Jim Miller in Uvalde, Texas, where the weather is fairly uniformly warm and dry, is one such example.

Shop environmental control systems also maintain a positive interior pressure to keep dust and other impurities at bay.

Good Painters Are Born, not Made
Those in the aircraft exterior paint business usually agree there is some truth to the statement that good painters are born, not made.

Some in the business say that while anyone can be taught the mechanics of painting an airplane, it is impossible to teach someone to be good at it.

Tompkins at Falcon Jet said having five guys applying paint is like watching an orchestra. “If one guy is out of tune, the entire thing is ruined.” Tompkins said of the 50 people in a paint shop, perhaps a dozen are top-notch painters who share two common characteristics–“aptitude and attitude.”

Midcoast uses a team of six to paint a large business jet, consisting of four painters and two assistants, most of whom have been working together for years. “We have everybody dancing together, spraying the same mixture, at the same pressure, from the same [type] of spray guns, from the same pressure pot,” said a Midcoast supervisor.

At Lufthansa Technik in Hamburg, Germany, the focus is primarily on widebody executive/VIP aircraft, as large as a Boeing 747-400. “For a 747,” said aircraft paint sales manager Stefan Schreiber, “we may have 12 people painting at once from six platforms, one painter and one driver on each platform.”

For smaller aircraft, the technique is relatively simple. At Raytheon, the shop will apply paint to a Hawker Horizon starting at the nose, with one painter on each side of the airplane. They will work toward the tail, applying paint first to the lower half of the fuselage. At the tail, they will work back toward the nose on the upper half of the fuselage. The wings and tail surfaces are painted separately.

Duncan’s Bohac said, “Painting an airplane is an art. I have two layout guys who prep the airplane for painting, and I’d put them up against anyone in the world.”
What is more surprising are the conditions under which the paint crews work with such precision, wrapped in special suits, wearing masks to protect themselves from the toxic VOCs, and spending anywhere from four to six hours dragging a heavy spray gun around an airplane.

The painter, said Tompkins, is part monkey, “climbing across scaffolding three stories high, lugging a two-pound spray gun with a garden hose trailing behind it, wearing a hood with air being pumped into it, and all the time putting on a perfect coat of paint.”

A good aircraft exterior paint job, at the end of the day, is a combination of many elements–good product, good equipment and, most of all, good people, said Cimarron’s Norris. “If the airplane costs $14 million, don’t you think the owner is going to want that reflected in the first thing he sees?”

The Atomizer Does the Trick
Raytheon Aircraft has recently incorporated the Aerobell 3312 rotary atomizer into its arsenal. The device uses a rotating spray head that spins at some 40,000 rpm, breaking up and atomizing the paint into extremely fine particles. The technology isn’t new. In fact, it has been used for perhaps a decade to apply fine finish coats to cabin interior pieces, such as cabinetry, trim and bulkheads.

According to Raytheon paint shop manager Tim Dies, the result is an incredibly smooth finish, with minimal overspray and a reduction in the overall amount of paint required. Dies said the atomized paint emission is so fine that “You can see the paint going onto the surface, but the particles are so fine you can’t see the paint coming out of the nozzle.”

Most modern business jets have a relatively small percentage of composite materials incorporated into the airframe, radar fairings, tail surfaces, access panels and so on. But the fuselages of Raytheon’s Premier I and the new Hawker Horizon are all composite construction. According to Raytheon’s painters, the technique for painting composite materials is similar to that for aluminum, with some exceptions. With composites, a mold-release agent has to be cleaned off before the primer is applied. And while the primer sticks better to composites because they are naturally rough in texture, a more viscous primer/fill is required to fill the tiny pinholes and other blemishes that are by nature part of a composite surface.

Is aluminum then more receptive to a good coat of paint? Not necessarily. Primer and paint do not adhere well to aluminum in its natural state and for that reason an etching agent is normally applied as a first step.

As far as paint shops are concerned, composite materials have another undesirable characteristic in that as they age there is a certain amount of shrink-back. In terms of safety, it is not worth considering. In terms of cosmetics, it results in a very faint weave pattern that is transferred to the paint.

Raytheon has developed a new paint specifically for composite surfaces to solve this problem. “We’ve now painted 15 Premier Is with the new paint and we’ve had positive results,” said paint shop manager Brenda Ives. The new paint is going on all new Premier Is now and Ives said it will be applied later to the Horizon.

Doug Bohac at Duncan noted that in terms of coatings, work continues by various paint manufacturers to produce a primer that does not contain zinc chromate, a pigment added to primer to prevent corrosion and a known carcinogen that is high on the EPA’s hit list.

Start-up Introduces Water-based Exterior Paint
Will a water-based aircraft exterior paint become the new standard for the business aviation industry? Debrina Woods, founder and president of Palm Beach Gardens, Fla.-based Innovative Coatings Worldwide, thinks so. The company is the exclusive worldwide distributor for the paint, which is manufactured by AquaSurTech of Montreal.

“They’ve been making it for about 25 years and it’s the paint of choice of architects for buildings all over the world,” said Woods.

The AST D45/AMS product offers a number of advantages over conventional VOC and high-solid paints, said Woods. It contains no carcinogens and no chromates; cleans with cold water and mild detergent; has an adhesion rating of five and adheres to alloys, aluminum, titanium and composites; is applied in a recommended coating as thin as 1.28 mil and can cut dry weight by up to 80 percent. It has a drying time between coats of just 15 minutes. While it can be applied most efficiently with the standard high-volume, low-pressure gun, it can be mixed and applied with any existing equipment.

With a retail price of about $300 a gallon, it’s not inexpensive, but Woods points out that a single gallon covers 600 sq ft on a new surface.

“We’ve already done some demonstrations and the guys with the guns love it,” said Woods. She added that the product has also undergone successful review and testing for both Kerzner International–for applications to the Atlantic II project on the Palm Island project in Dubai–and NASSL in Orlando. Woods is currently selecting a number of independent aviation paint shops to do seven F-16 fighters as part of a test program for a European customer.

AquaSurTech had always main- tained a relatively low industry profile and has only recently become interested in seeing its product applied in aviation, said Woods. “It’s a proven product everywhere else, and now we’re going to introduce it to aviation.”

Caring for the New Paint
When the paint has been applied and dried and the airplane is delivered to its owner, there is the question of how to retain that new-paint gloss and shine.

Most paint shops are only too well aware of the labor, skill and dedication that went into painting the airplane. And they know that how long the colors remain bright and fresh will depend to a great degree on how well the owner cares for the finish. With that in mind, they advise:

• If possible, avoid flying through rain for the first 30 days, after which the paint should be thoroughly cured. Some paint shops like to stretch that to 90 days.

• Do not wash the airplane for the first 30 days, and do not allow water–not even dew–to stand on the airplane as impurities in the water may soak into the paint to create a permanent stain.

• Do not wax the airplane until after the first year of service. Use only wax approved
for aircraft paint. (Some owners are now using wax that contains Teflon.)

• To maintain the quality of the paint: keep the airplane hangared as much as possible as ultraviolet rays will break down the paint and salt air can quickly dull the finish and encourage corrosion; wash only with warm water and a mild detergent solution; use isopropyl alcohol to remove any exhaust soot, grease and oils and wipe the area down afterwards with a soft cloth dampened in water; repair any chipped paint with the kit supplied by the painter as chipped areas only become larger and eventually result in corrosion.

A good exterior paint job, well cared for, should last five to seven years, and under ideal conditions as long as 10 years. Some owners will budget for a new paint job every five years, said Ed Kirby, former paint shop manager of Tulsa, Okla.-based BizJet. “But a lot of people have discovered that with proper care, it will keep that new-paint look for a lot longer.”

Letting Robots Do the Work
By its nature, painting aircraft is a labor-intensive process, costly and time-consuming. Raytheon Aircraft believes that is going to change. According to director of flight test and completions Gary Pickett, the Wichita-based company is looking to robotics as the key. “It’s already being used on military aircraft, and we’re looking at how to transfer that technology to business aviation. It’s in our capital planning.”

Pickett said there are numerous advantages to a robotic paint process, including “consistency, a reduction in the volume of paint required and significantly reduced overspray.” And he pointed out that unlike the human version, a robotic machine can operate 24/7, “as long as you have a product in front of it.”