What is the difference between car primer and topcoat?
2 Answers
The differences between car primer and topcoat are: 1. Different composition: Primer consists of four parts: resin, filler, solvent, and additives; topcoat is composed of three parts: clear coat, color coat, and primer. 2. Different functions: Primer is the first layer of the paint system, used to level the paint surface, support the topcoat, provide fullness, and reduce costs; topcoat is the final coating layer, which increases the thickness of the paint film by adding layers of topcoat or applying thick coats. 3. Different roles: Topcoat has scratch resistance, gloss hardness, transparency feel, aging resistance, and yellowing resistance; primer fills the capillary pores in the steel plate, making it easier to apply paint on the surface, supports the topcoat to ensure it adheres tightly to the car surface, and helps reduce costs and save energy.
After repairing cars, I realized primer and topcoat are completely different. Primer acts like a foundation, directly applied to the metal frame—it's extremely viscous with anti-rust properties, leaving a rough texture after spraying. The topcoat is the shiny exterior we usually see, consisting of two layers: base color paint for pigmentation and clear coat on top for UV protection and scratch resistance. Once my car got scratched, revealing the gray primer beneath the damaged topcoat. Repainting required sanding the primer layer first, then reapplying three layers of topcoat—a huge hassle. When changing colors with wraps, never apply them directly over primer, or peeling the wrap might take the entire paint layer with it.
