Finishing touches

| December 12, 2008

Robots like this one at a Peterbilt plant reduce the cost and weight of the finish by applying a more even and consistent layer than would be possible by a handheld spray gun, making it possible to minimize the thickness of each coating.

Differences in weather, style, body type and affordability dictate how people dress. Similar factors should determine your choice of paint and how it’s applied when it’s time to “dress” your new truck.

After picking the color, the biggest decision you’ll face is whether to apply a single coat (also called a monocoat) or a basecoat plus a clearcoat. The clearcoat is an additional layer of finish that helps protect the paint even though it bears no pigment – that is, no color-producing material. It protects the paint against road chemicals, truck wash chemicals, etc., as well as against the sun’s ultraviolet rays. UV is particularly damaging in that it can alter the shade of the original color.

Price can be a factor, as some truck makers charge extra for a basecoat plus clearcoat, says Joe Wood, fleet segment manager for DuPont Coating Solutions. Others don’t. Volvo, for example, offers only basecoat/clearcoat finishes, says spokesman Jim McNamara.

“On most colors, the truck owner can expect a 30 percent to 45 percent increase in color and gloss retention when they utilize a basecoat/clearcoat system,” Wood says.

That’s a consideration especially if you are going to keep the truck a long time.

Two other factors in making the coating decision are where you operate and what color you’ve chosen.

“In a benign environment, you don’t need basecoat/clearcoat,” Wood says, “but it also depends on the color family. Those bright yellows, reds and white do better when it comes to color and glaze protection. On the other hand, when using medium and ABF [Freight System] green, and anything metallic, use basecoat/clearcoat.”

The extra layer of UV protection makes clearcoat a better choice when running, say, from Florida to Arizona, but it may be better for wintry climes such as Wisconsin’s, too. “Any vehicle that will be used in a harsh chemical environment should have basecoat/clearcoat,” Wood says.

Basecoat/clearcoat also is “easier to clean and easier to deal with,” Wood says. So if you often take the truck through a wash where chemicals are used, or simply can’t wash it regularly by any means, the two-stage finish will hold up much better.

Long before your choice is made, the truck manufacturer makes a critical choice in coating technology that could affect your finish, say Wood and John Lewis of PPG Industries.

“There are two main technologies used today: two-part polyurethanes and one-part melamine paint chemistries,” Wood says. The more commonly used polyurethanes are superior, he says, as they “deliver the ultimate in overall performance, including color and gloss retention, flexibility, chip performance, chemical resistance and scratch and mar performance.” The temperature at which the paint is baked also is lower, which helps protect parts of the cab.

Polyurethane also is more flexible, a desirable quality on thermoplastic cab parts where one-part melamine is more likely to crack.

“Polyurethane topcoats give excellent gloss, UV resistance, chemical resistance, durability and a vast array of color choices,” Lewis says. “Primers include a wider range of chemistries, epoxy primers being the most popular since they offer the best corrosion protection.”

For some truck manufacturers, choosing the coating may come down to a “price/value equation,” Lewis says. The overall system being used also affects the warranty the paint manufacturer gives to the truck maker, which in turn affects the buyer’s warranty on the finish.

“Most truck makers offer glamour color options within their basecoat/clearcoat options,” Wood says. This would include treatments such as metal flake finishes. Two-tone paint schemes are also available with some truck makers.

The finish process in its entirety has become complex. Volvo’s, for example, involves four sequences totaling 51 steps. Part of the Volvo process is something called “e-coat,” short for “electro-deposition coating,” used by most truck manufacturers.

After aggressive cleaning of the metal in six steps, the cab structure is dipped into a tank of epoxy primer and then subjected to a powerful electrical charge. The primer is formulated so that it is attracted to the metal because of the charge. Increasing voltage is then applied in three stages to draw the primer tightly to the metal and into all the nooks and crannies.

The remaining steps include sanding the primer, then applying the paint by dipping the structure into a tank and rotating it 360 degrees. This is done so air bubbles won’t get trapped in the nooks and crannies and crowd out the primer. The final steps involve applying, scuffing up, cleaning, and baking repeated layers of primer, paint and, ultimately, a protective clearcoat.


Paint: A work in progress
Truck-finish engineers don’t quite get the cliché “about as exciting as watching paint dry.” They’ve been watching paint dry for a long time and are excited to get better results every year. Here are observations from three original equipment manufacturers about developments in this field.

DAIMLER TRUCKS NORTH AMERICA (FREIGHTLINER, WESTERN STAR, STERLING). Angela Plaxton, manager of coating technology:

“Improvements for heavy truck finishes have been centered around appearance and durability. The texture or orange peel (smoothness) of the finish has improved significantly, so much so that the OEMs are able to raise our requirements because smoother finishes are now achievable.

“Overall durability of the clear coat products has improved as well. The latest clear coats can take quite a beating and still look good. They are also tougher and do not allow minor damage to get into the color coat, making repairs easier. Also, more robotic painting and the ability of some paint manufacturers to adapt the paint to our systems has made a huge difference in the finish level from the factory. Robots allow us to consistently paint the same color every time.”

NAVISTAR (INTERNATIONAL). Tom Barkimer, chief engineer for materials engineering:

“The major effort has been to improve durability, particularly corrosion protection. Newer de-icers are much more aggressive than common salt. But there has not been all that much change to the BC/CC (basecoat/clearcoat) topcoat system itself.

“Navistar already had outstanding durability in the topcoat, as durability of BC/CC urethane is already very good. We expect 10 years’ minimum durability.

“Improved control of the film thickness has improved durability, in particular UV durability. The UV protection for a BC/CC system is generally in the top clearcoat layer, and it is critical that the clearcoat be applied to a minimum film thickness in order to achieve complete UV protection.

“Also, Navistar is in the process of installing rotary atomizers in many of our truck plants in order to improve the paint transfer efficiency and surface appearance.”

KENWORTH. Marilyn Santangelo, assistant general manager for operations:

“DuPont [also the supplier for sister company Peterbilt] has replaced the industry paint standard (Imron Polyurethane 5000 and 6000 paint systems) with the Imron Elite single-stage and basecoat/clearcoat systems. The new finishes are easier to apply, require less rework and perform better in the field.

“The introduction of paint robots and the consistency they bring to the paint application process brought a huge positive shift in paint quality. We experienced an immediate improvement in the consistency of the paint film build or thickness because, for a given product configuration, the paint robots can repeatedly apply the same amount of paint, accurate within several milligrams. Also, the addition of paint robots virtually eliminated defects common with manual painting such as thin paint, runs and sags.”

Choosing a color
Color preference is subjective, but Joe Wood of DuPont offers some objective points about color that might influence your choice.

Paint color and durability are related, so color matters when you decide how important it is to get a basecoat/clearcoat finish. Bright, vivid colors such as reds and yellows hold their colors and prevent glaze better even when applied as a single coat.

Color also can reinforce image and marketing strategy, Wood says. Consider UPS’ Big Brown and its “What can Brown do for you?” mantra or distinctive and memorable fleet colors such as Schneider orange and ABF Freight System green.

“Appearance is critical for anyone who hauls food,” Wood says. “The ultimate customer really associates brand with the color. Imagine how you’d react if you saw an old beat-up gray truck delivering Boar’s Head instead of one of their brightly painted [black and red] trucks.”

You could exploit a similar strategy in marketing yourself. This especially is true if you haul a certain commodity such as grain or a single vendor’s colorful product, or consistently pull a trailer with a customer’s colorful logo on it.

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