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.."