Consider it a small-scale version of the epic Man vs. Nature struggle. Automotive engineers keep trying to figure out ways to keep vehicle exteriors looking like new, but the relentless pounding of the natural elements keeps beating them down. Enter Decoma International Inc. (Concord, Ontario, Canada) with two new treatments for exterior parts that promise to keep them looking better longer.
Hardcoat for Plastics
Decoma’s LexaMar division (Boyne City, MI) has developed a proprietary hardcoat technology for polycarbonate exterior trim parts like roof panels, appliqués and cowl screens that it says will increase durability over traditional applications by as much as threefold. The technology is built into a new synchronous manufacturing process that combines parts-cleaning with an automatic coating system that continually monitors the chemical mixture and adjusts it as necessary. Decoma says its new process provides more consistent control of the hardcoat resin formulation resulting in trim components with better weather resistance, and a high-gloss abrasion-resistant finish.
The company has installed a new line to process parts using the new technology with a capacity of up to 50,000 parts/day. It already has contracts for several upcoming vehicle programs. Industry sources say the next generation Corvette will be among the vehicles to use this coating.
Anodizing for Aluminum
According to Dave Clark, general manager of Decoma’s Anotech subsidiary, anodized aluminum has a lot of advantages when it comes to exterior trim components like garnishes and moldings. He points out that “for a bright finish, there is a real cost advantage compared to chrome and chrome-plated parts, and the customer often can’t tell the difference.” Further, anodized aluminum can be easily processed to allow it to readily take most any color, and can be laser etched or sand blasted to add texture—areas where its chromed or painted counterparts can’t compete. But one problem with anodized aluminum exterior parts is that they are susceptible to significantly high or low pH levels, like those found in acid rain and in the alkali-rich solutions used in many touchless car washes. These pH levels can cause a blue mold-like patina to form on the part which, needless to say, detracts from its appeal.
To combat this phenomenon Anotech switched from a pre-sealant composed of nickel to one made out of lithium. Its testing indicated that the lithium is significantly more resistant to extreme pH levels, but parts still discolored over time after repeated runs through touchless car washes.
A more complete answer was needed. After more research, Anotech’s technical team hit upon a weatherable acrylic urethane created by PPG Industries (Pittsburgh, PA), but never introduced by PPG to the automotive industry. Encapsulating parts with the urethane proved to be exactly what was needed to stop the coating degradation.
“In the end, we needed an organic coating solution to combat the organic problem of extreme pH levels,” explains Gary Chevalier, assistant general manager, Anotech. “The coating is incredibly resistant to alkali attacks,” he says, “We hit it with a [highly alkali] pH of 14 for two hours and it did great.”
Though it is not ready to make any concrete announcements, Anotech revealed that the encapsulation material will be used on some upcoming production vehicles. The coating is applied with a waterborne e-coating process that boasts a near-100% transfer efficiency rate. Chevalier thinks that, now that the discoloration problem has been solved, more automakers will take advantage of cost-effective anodized aluminum without worrying about getting the blues.