Multilayered
"Many people think, 'Oh, it's just primer,'" said PPG's Jeff Griffin. But there are actually several kinds of primer, as illustrated here. Primer refers to self-etching primer and epoxy primer, which are "strictly for corrosion protection and adhesion to bare metal," according to Griffin. Some body shops-including ours-don't perform this step. PPG recommends it whenever large patches of bare metal are exposed. Primer surfacer is there to fill in small scratches and imperfections. "It's the finishing step of the bodywork process," according to Griffin. "Primer Sealer" is a kind of "insurance policy," he continued. "It helps deal with sand-throughs and provides a uniform color to apply the topcoat to." What else does Griffin want us to know? "First and foremost, obey your local regulations. Second, use a two-component primer with a hardener. It's more durable." Third, preparation is critical. And last? "Treat the primer step as important-or more so-than the basecoat and clearcoat. It'll perform better and give you better paint adhesion and long-term durability.."
Although the Camaro's right fender only needed scuffing, spots that need body filler must also be taken down to bare metal. Be careful when sanding plastic or urethane pieces; the paint comes off very quickly, especially at the edges. | 
Hard-to-reach spots should be prepped by hand. | 
Jose uses lightweight body glaze on small areas, then sands it with 80-grit paper on a DA (dual-action sander). Larger areas, like the driver's door, require regular-weight filler, which Jose knocked down with a long-block and 150-grit. |
The idea here, according to Jose, is to get a nice thick layer of primer on the car. The gun is set to spray a 4-inch-wide pattern. The primer we used, PPG NCP 280, is very thick, according to our gunman. It took two coats to completely cover the car and give us enough material for sanding. | 
Our stock steel hood was rusted through. Luckily, we had a fiberglass lid from an '82 Z28, so on it went. Prep is essentially the same as the car's metal panels. | 
Our primer of choice for this project was PPG's NCP 280. Although it's a mainly a filler primer, PPG's Jeff Griffin says that this product does have corrosion protection properties. It's also a two-component primer, as it gets mixed 2:1 with the NCX 285 hardener. Studio Auto Body likes it because it's thick, requiring only two coats, in this case. According to Studio's Jeremiah Becker, PPG primer is glossy rather than flat, which gives the impression that the car is painted, allowing you to look down the body and check for straightness. "It's better to see wavy primer than wavy paint," he concluded. |
The look of our new primer coat isn't important. What's important is that there's lots of it. A thick coat fills scratches and other small imperfections, and also provides enough material for the next sanding stage. | | |